blob: 35dd57e992827f12a2645f9a7b5265c994690406 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/mm/vmscan.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 *
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
12 */
13
Mitchel Humpherysb1de0d12014-06-06 14:38:30 -070014#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15
Linus Torvalds1da177e2005-04-16 15:20:36 -070016#include <linux/mm.h>
17#include <linux/module.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090018#include <linux/gfp.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070019#include <linux/kernel_stat.h>
20#include <linux/swap.h>
21#include <linux/pagemap.h>
22#include <linux/init.h>
23#include <linux/highmem.h>
Anton Vorontsov70ddf632013-04-29 15:08:31 -070024#include <linux/vmpressure.h>
Andrew Mortone129b5c2006-09-27 01:50:00 -070025#include <linux/vmstat.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070026#include <linux/file.h>
27#include <linux/writeback.h>
28#include <linux/blkdev.h>
29#include <linux/buffer_head.h> /* for try_to_release_page(),
30 buffer_heads_over_limit */
31#include <linux/mm_inline.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070032#include <linux/backing-dev.h>
33#include <linux/rmap.h>
34#include <linux/topology.h>
35#include <linux/cpu.h>
36#include <linux/cpuset.h>
Mel Gorman3e7d3442011-01-13 15:45:56 -080037#include <linux/compaction.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070038#include <linux/notifier.h>
39#include <linux/rwsem.h>
Rafael J. Wysocki248a0302006-03-22 00:09:04 -080040#include <linux/delay.h>
Yasunori Goto3218ae12006-06-27 02:53:33 -070041#include <linux/kthread.h>
Nigel Cunningham7dfb7102006-12-06 20:34:23 -080042#include <linux/freezer.h>
Balbir Singh66e17072008-02-07 00:13:56 -080043#include <linux/memcontrol.h>
Keika Kobayashi873b4772008-07-25 01:48:52 -070044#include <linux/delayacct.h>
Lee Schermerhornaf936a12008-10-18 20:26:53 -070045#include <linux/sysctl.h>
KOSAKI Motohiro929bea72011-04-14 15:22:12 -070046#include <linux/oom.h>
Linus Torvalds268bb0c2011-05-20 12:50:29 -070047#include <linux/prefetch.h>
Mitchel Humpherysb1de0d12014-06-06 14:38:30 -070048#include <linux/printk.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070049
50#include <asm/tlbflush.h>
51#include <asm/div64.h>
52
53#include <linux/swapops.h>
Rafael Aquini117aad12013-09-30 13:45:16 -070054#include <linux/balloon_compaction.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070055
Nick Piggin0f8053a2006-03-22 00:08:33 -080056#include "internal.h"
57
Mel Gorman33906bc2010-08-09 17:19:16 -070058#define CREATE_TRACE_POINTS
59#include <trace/events/vmscan.h>
60
Linus Torvalds1da177e2005-04-16 15:20:36 -070061struct scan_control {
KOSAKI Motohiro22fba332009-12-14 17:59:10 -080062 /* How many pages shrink_list() should reclaim */
63 unsigned long nr_to_reclaim;
64
Linus Torvalds1da177e2005-04-16 15:20:36 -070065 /* This context's GFP mask */
Al Viro6daa0e22005-10-21 03:18:50 -040066 gfp_t gfp_mask;
Linus Torvalds1da177e2005-04-16 15:20:36 -070067
Johannes Weineree814fe2014-08-06 16:06:19 -070068 /* Allocation order */
Andy Whitcroft5ad333e2007-07-17 04:03:16 -070069 int order;
Balbir Singh66e17072008-02-07 00:13:56 -080070
Johannes Weineree814fe2014-08-06 16:06:19 -070071 /*
72 * Nodemask of nodes allowed by the caller. If NULL, all nodes
73 * are scanned.
74 */
75 nodemask_t *nodemask;
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -070076
KOSAKI Motohiro5f53e762010-05-24 14:32:37 -070077 /*
Johannes Weinerf16015f2012-01-12 17:17:52 -080078 * The memory cgroup that hit its limit and as a result is the
79 * primary target of this reclaim invocation.
80 */
81 struct mem_cgroup *target_mem_cgroup;
Balbir Singh66e17072008-02-07 00:13:56 -080082
Johannes Weineree814fe2014-08-06 16:06:19 -070083 /* Scan (total_size >> priority) pages at once */
84 int priority;
85
86 unsigned int may_writepage:1;
87
88 /* Can mapped pages be reclaimed? */
89 unsigned int may_unmap:1;
90
91 /* Can pages be swapped as part of reclaim? */
92 unsigned int may_swap:1;
93
Johannes Weiner241994ed2015-02-11 15:26:06 -080094 /* Can cgroups be reclaimed below their normal consumption range? */
95 unsigned int may_thrash:1;
96
Johannes Weineree814fe2014-08-06 16:06:19 -070097 unsigned int hibernation_mode:1;
98
99 /* One of the zones is ready for compaction */
100 unsigned int compaction_ready:1;
101
102 /* Incremented by the number of inactive pages that were scanned */
103 unsigned long nr_scanned;
104
105 /* Number of pages freed so far during a call to shrink_zones() */
106 unsigned long nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107};
108
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
110
111#ifdef ARCH_HAS_PREFETCH
112#define prefetch_prev_lru_page(_page, _base, _field) \
113 do { \
114 if ((_page)->lru.prev != _base) { \
115 struct page *prev; \
116 \
117 prev = lru_to_page(&(_page->lru)); \
118 prefetch(&prev->_field); \
119 } \
120 } while (0)
121#else
122#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
123#endif
124
125#ifdef ARCH_HAS_PREFETCHW
126#define prefetchw_prev_lru_page(_page, _base, _field) \
127 do { \
128 if ((_page)->lru.prev != _base) { \
129 struct page *prev; \
130 \
131 prev = lru_to_page(&(_page->lru)); \
132 prefetchw(&prev->_field); \
133 } \
134 } while (0)
135#else
136#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
137#endif
138
139/*
140 * From 0 .. 100. Higher means more swappy.
141 */
142int vm_swappiness = 60;
Wang Sheng-Huid0480be2014-08-06 16:07:07 -0700143/*
144 * The total number of pages which are beyond the high watermark within all
145 * zones.
146 */
147unsigned long vm_total_pages;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148
149static LIST_HEAD(shrinker_list);
150static DECLARE_RWSEM(shrinker_rwsem);
151
Andrew Mortonc255a452012-07-31 16:43:02 -0700152#ifdef CONFIG_MEMCG
Johannes Weiner89b5fae2012-01-12 17:17:50 -0800153static bool global_reclaim(struct scan_control *sc)
154{
Johannes Weinerf16015f2012-01-12 17:17:52 -0800155 return !sc->target_mem_cgroup;
Johannes Weiner89b5fae2012-01-12 17:17:50 -0800156}
Tejun Heo97c93412015-05-22 18:23:36 -0400157
158/**
159 * sane_reclaim - is the usual dirty throttling mechanism operational?
160 * @sc: scan_control in question
161 *
162 * The normal page dirty throttling mechanism in balance_dirty_pages() is
163 * completely broken with the legacy memcg and direct stalling in
164 * shrink_page_list() is used for throttling instead, which lacks all the
165 * niceties such as fairness, adaptive pausing, bandwidth proportional
166 * allocation and configurability.
167 *
168 * This function tests whether the vmscan currently in progress can assume
169 * that the normal dirty throttling mechanism is operational.
170 */
171static bool sane_reclaim(struct scan_control *sc)
172{
173 struct mem_cgroup *memcg = sc->target_mem_cgroup;
174
175 if (!memcg)
176 return true;
177#ifdef CONFIG_CGROUP_WRITEBACK
Linus Torvalds69234ac2015-11-05 14:51:32 -0800178 if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
Tejun Heo97c93412015-05-22 18:23:36 -0400179 return true;
180#endif
181 return false;
182}
KAMEZAWA Hiroyuki91a45472008-02-07 00:14:29 -0800183#else
Johannes Weiner89b5fae2012-01-12 17:17:50 -0800184static bool global_reclaim(struct scan_control *sc)
185{
186 return true;
187}
Tejun Heo97c93412015-05-22 18:23:36 -0400188
189static bool sane_reclaim(struct scan_control *sc)
190{
191 return true;
192}
KAMEZAWA Hiroyuki91a45472008-02-07 00:14:29 -0800193#endif
194
Johannes Weinera1c3bfb2014-01-29 14:05:41 -0800195static unsigned long zone_reclaimable_pages(struct zone *zone)
Lisa Du6e543d52013-09-11 14:22:36 -0700196{
Alexandru Moised031a152015-11-05 18:48:08 -0800197 unsigned long nr;
Lisa Du6e543d52013-09-11 14:22:36 -0700198
199 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
200 zone_page_state(zone, NR_INACTIVE_FILE);
201
202 if (get_nr_swap_pages() > 0)
203 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
204 zone_page_state(zone, NR_INACTIVE_ANON);
205
206 return nr;
207}
208
209bool zone_reclaimable(struct zone *zone)
210{
Mel Gorman0d5d8232014-08-06 16:07:16 -0700211 return zone_page_state(zone, NR_PAGES_SCANNED) <
212 zone_reclaimable_pages(zone) * 6;
Lisa Du6e543d52013-09-11 14:22:36 -0700213}
214
Hugh Dickins4d7dcca2012-05-29 15:07:08 -0700215static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru)
KOSAKI Motohiroc9f299d2009-01-07 18:08:16 -0800216{
Hugh Dickinsc3c787e2012-05-29 15:06:52 -0700217 if (!mem_cgroup_disabled())
Hugh Dickins4d7dcca2012-05-29 15:07:08 -0700218 return mem_cgroup_get_lru_size(lruvec, lru);
KOSAKI Motohiroa3d8e052009-01-07 18:08:19 -0800219
Konstantin Khlebnikov074291f2012-05-29 15:07:00 -0700220 return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru);
KOSAKI Motohiroc9f299d2009-01-07 18:08:16 -0800221}
222
Linus Torvalds1da177e2005-04-16 15:20:36 -0700223/*
Glauber Costa1d3d4432013-08-28 10:18:04 +1000224 * Add a shrinker callback to be called from the vm.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225 */
Glauber Costa1d3d4432013-08-28 10:18:04 +1000226int register_shrinker(struct shrinker *shrinker)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700227{
Glauber Costa1d3d4432013-08-28 10:18:04 +1000228 size_t size = sizeof(*shrinker->nr_deferred);
229
230 /*
231 * If we only have one possible node in the system anyway, save
232 * ourselves the trouble and disable NUMA aware behavior. This way we
233 * will save memory and some small loop time later.
234 */
235 if (nr_node_ids == 1)
236 shrinker->flags &= ~SHRINKER_NUMA_AWARE;
237
238 if (shrinker->flags & SHRINKER_NUMA_AWARE)
239 size *= nr_node_ids;
240
241 shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
242 if (!shrinker->nr_deferred)
243 return -ENOMEM;
244
Rusty Russell8e1f9362007-07-17 04:03:17 -0700245 down_write(&shrinker_rwsem);
246 list_add_tail(&shrinker->list, &shrinker_list);
247 up_write(&shrinker_rwsem);
Glauber Costa1d3d4432013-08-28 10:18:04 +1000248 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700249}
Rusty Russell8e1f9362007-07-17 04:03:17 -0700250EXPORT_SYMBOL(register_shrinker);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251
252/*
253 * Remove one
254 */
Rusty Russell8e1f9362007-07-17 04:03:17 -0700255void unregister_shrinker(struct shrinker *shrinker)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700256{
257 down_write(&shrinker_rwsem);
258 list_del(&shrinker->list);
259 up_write(&shrinker_rwsem);
Andrew Vaginae393322013-10-16 13:46:46 -0700260 kfree(shrinker->nr_deferred);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700261}
Rusty Russell8e1f9362007-07-17 04:03:17 -0700262EXPORT_SYMBOL(unregister_shrinker);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700263
264#define SHRINK_BATCH 128
Glauber Costa1d3d4432013-08-28 10:18:04 +1000265
Vladimir Davydovcb731d62015-02-12 14:58:54 -0800266static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
267 struct shrinker *shrinker,
268 unsigned long nr_scanned,
269 unsigned long nr_eligible)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270{
Glauber Costa1d3d4432013-08-28 10:18:04 +1000271 unsigned long freed = 0;
272 unsigned long long delta;
273 long total_scan;
Vladimir Davydovd5bc5fd2014-04-03 14:47:32 -0700274 long freeable;
Glauber Costa1d3d4432013-08-28 10:18:04 +1000275 long nr;
276 long new_nr;
277 int nid = shrinkctl->nid;
278 long batch_size = shrinker->batch ? shrinker->batch
279 : SHRINK_BATCH;
280
Vladimir Davydovd5bc5fd2014-04-03 14:47:32 -0700281 freeable = shrinker->count_objects(shrinker, shrinkctl);
282 if (freeable == 0)
Glauber Costa1d3d4432013-08-28 10:18:04 +1000283 return 0;
284
285 /*
286 * copy the current shrinker scan count into a local variable
287 * and zero it so that other concurrent shrinker invocations
288 * don't also do this scanning work.
289 */
290 nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
291
292 total_scan = nr;
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800293 delta = (4 * nr_scanned) / shrinker->seeks;
Vladimir Davydovd5bc5fd2014-04-03 14:47:32 -0700294 delta *= freeable;
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800295 do_div(delta, nr_eligible + 1);
Glauber Costa1d3d4432013-08-28 10:18:04 +1000296 total_scan += delta;
297 if (total_scan < 0) {
Pintu Kumar8612c662014-12-10 15:42:58 -0800298 pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n",
Dave Chinnera0b02132013-08-28 10:18:16 +1000299 shrinker->scan_objects, total_scan);
Vladimir Davydovd5bc5fd2014-04-03 14:47:32 -0700300 total_scan = freeable;
Glauber Costa1d3d4432013-08-28 10:18:04 +1000301 }
302
303 /*
304 * We need to avoid excessive windup on filesystem shrinkers
305 * due to large numbers of GFP_NOFS allocations causing the
306 * shrinkers to return -1 all the time. This results in a large
307 * nr being built up so when a shrink that can do some work
308 * comes along it empties the entire cache due to nr >>>
Vladimir Davydovd5bc5fd2014-04-03 14:47:32 -0700309 * freeable. This is bad for sustaining a working set in
Glauber Costa1d3d4432013-08-28 10:18:04 +1000310 * memory.
311 *
312 * Hence only allow the shrinker to scan the entire cache when
313 * a large delta change is calculated directly.
314 */
Vladimir Davydovd5bc5fd2014-04-03 14:47:32 -0700315 if (delta < freeable / 4)
316 total_scan = min(total_scan, freeable / 2);
Glauber Costa1d3d4432013-08-28 10:18:04 +1000317
318 /*
319 * Avoid risking looping forever due to too large nr value:
320 * never try to free more than twice the estimate number of
321 * freeable entries.
322 */
Vladimir Davydovd5bc5fd2014-04-03 14:47:32 -0700323 if (total_scan > freeable * 2)
324 total_scan = freeable * 2;
Glauber Costa1d3d4432013-08-28 10:18:04 +1000325
326 trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800327 nr_scanned, nr_eligible,
328 freeable, delta, total_scan);
Glauber Costa1d3d4432013-08-28 10:18:04 +1000329
Vladimir Davydov0b1fb402014-01-23 15:53:22 -0800330 /*
331 * Normally, we should not scan less than batch_size objects in one
332 * pass to avoid too frequent shrinker calls, but if the slab has less
333 * than batch_size objects in total and we are really tight on memory,
334 * we will try to reclaim all available objects, otherwise we can end
335 * up failing allocations although there are plenty of reclaimable
336 * objects spread over several slabs with usage less than the
337 * batch_size.
338 *
339 * We detect the "tight on memory" situations by looking at the total
340 * number of objects we want to scan (total_scan). If it is greater
Vladimir Davydovd5bc5fd2014-04-03 14:47:32 -0700341 * than the total number of objects on slab (freeable), we must be
Vladimir Davydov0b1fb402014-01-23 15:53:22 -0800342 * scanning at high prio and therefore should try to reclaim as much as
343 * possible.
344 */
345 while (total_scan >= batch_size ||
Vladimir Davydovd5bc5fd2014-04-03 14:47:32 -0700346 total_scan >= freeable) {
Dave Chinnera0b02132013-08-28 10:18:16 +1000347 unsigned long ret;
Vladimir Davydov0b1fb402014-01-23 15:53:22 -0800348 unsigned long nr_to_scan = min(batch_size, total_scan);
Glauber Costa1d3d4432013-08-28 10:18:04 +1000349
Vladimir Davydov0b1fb402014-01-23 15:53:22 -0800350 shrinkctl->nr_to_scan = nr_to_scan;
Dave Chinnera0b02132013-08-28 10:18:16 +1000351 ret = shrinker->scan_objects(shrinker, shrinkctl);
352 if (ret == SHRINK_STOP)
353 break;
354 freed += ret;
Glauber Costa1d3d4432013-08-28 10:18:04 +1000355
Vladimir Davydov0b1fb402014-01-23 15:53:22 -0800356 count_vm_events(SLABS_SCANNED, nr_to_scan);
357 total_scan -= nr_to_scan;
Glauber Costa1d3d4432013-08-28 10:18:04 +1000358
359 cond_resched();
360 }
361
362 /*
363 * move the unused scan count back into the shrinker in a
364 * manner that handles concurrent updates. If we exhausted the
365 * scan, there is no need to do an update.
366 */
367 if (total_scan > 0)
368 new_nr = atomic_long_add_return(total_scan,
369 &shrinker->nr_deferred[nid]);
370 else
371 new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
372
Dave Hansendf9024a2014-06-04 16:08:07 -0700373 trace_mm_shrink_slab_end(shrinker, nid, freed, nr, new_nr, total_scan);
Glauber Costa1d3d4432013-08-28 10:18:04 +1000374 return freed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375}
376
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800377/**
Vladimir Davydovcb731d62015-02-12 14:58:54 -0800378 * shrink_slab - shrink slab caches
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800379 * @gfp_mask: allocation context
380 * @nid: node whose slab caches to target
Vladimir Davydovcb731d62015-02-12 14:58:54 -0800381 * @memcg: memory cgroup whose slab caches to target
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800382 * @nr_scanned: pressure numerator
383 * @nr_eligible: pressure denominator
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384 *
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800385 * Call the shrink functions to age shrinkable caches.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386 *
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800387 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
388 * unaware shrinkers will receive a node id of 0 instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700389 *
Vladimir Davydovcb731d62015-02-12 14:58:54 -0800390 * @memcg specifies the memory cgroup to target. If it is not NULL,
391 * only shrinkers with SHRINKER_MEMCG_AWARE set will be called to scan
392 * objects from the memory cgroup specified. Otherwise all shrinkers
393 * are called, and memcg aware shrinkers are supposed to scan the
394 * global list then.
395 *
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800396 * @nr_scanned and @nr_eligible form a ratio that indicate how much of
397 * the available objects should be scanned. Page reclaim for example
398 * passes the number of pages scanned and the number of pages on the
399 * LRU lists that it considered on @nid, plus a bias in @nr_scanned
400 * when it encountered mapped pages. The ratio is further biased by
401 * the ->seeks setting of the shrink function, which indicates the
402 * cost to recreate an object relative to that of an LRU page.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700403 *
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800404 * Returns the number of reclaimed slab objects.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700405 */
Vladimir Davydovcb731d62015-02-12 14:58:54 -0800406static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
407 struct mem_cgroup *memcg,
408 unsigned long nr_scanned,
409 unsigned long nr_eligible)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700410{
411 struct shrinker *shrinker;
Dave Chinner24f7c6b2013-08-28 10:17:56 +1000412 unsigned long freed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413
Vladimir Davydovcb731d62015-02-12 14:58:54 -0800414 if (memcg && !memcg_kmem_is_active(memcg))
415 return 0;
416
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800417 if (nr_scanned == 0)
418 nr_scanned = SWAP_CLUSTER_MAX;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700419
Minchan Kimf06590b2011-05-24 17:11:11 -0700420 if (!down_read_trylock(&shrinker_rwsem)) {
Dave Chinner24f7c6b2013-08-28 10:17:56 +1000421 /*
422 * If we would return 0, our callers would understand that we
423 * have nothing else to shrink and give up trying. By returning
424 * 1 we keep it going and assume we'll be able to shrink next
425 * time.
426 */
427 freed = 1;
Minchan Kimf06590b2011-05-24 17:11:11 -0700428 goto out;
429 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700430
431 list_for_each_entry(shrinker, &shrinker_list, list) {
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800432 struct shrink_control sc = {
433 .gfp_mask = gfp_mask,
434 .nid = nid,
Vladimir Davydovcb731d62015-02-12 14:58:54 -0800435 .memcg = memcg,
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800436 };
Vladimir Davydovec970972014-01-23 15:53:23 -0800437
Vladimir Davydovcb731d62015-02-12 14:58:54 -0800438 if (memcg && !(shrinker->flags & SHRINKER_MEMCG_AWARE))
439 continue;
440
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800441 if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
442 sc.nid = 0;
Dave Chinneracf92b42011-07-08 14:14:35 +1000443
Vladimir Davydovcb731d62015-02-12 14:58:54 -0800444 freed += do_shrink_slab(&sc, shrinker, nr_scanned, nr_eligible);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445 }
Johannes Weiner6b4f7792014-12-12 16:56:13 -0800446
Linus Torvalds1da177e2005-04-16 15:20:36 -0700447 up_read(&shrinker_rwsem);
Minchan Kimf06590b2011-05-24 17:11:11 -0700448out:
449 cond_resched();
Dave Chinner24f7c6b2013-08-28 10:17:56 +1000450 return freed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700451}
452
Vladimir Davydovcb731d62015-02-12 14:58:54 -0800453void drop_slab_node(int nid)
454{
455 unsigned long freed;
456
457 do {
458 struct mem_cgroup *memcg = NULL;
459
460 freed = 0;
461 do {
462 freed += shrink_slab(GFP_KERNEL, nid, memcg,
463 1000, 1000);
464 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
465 } while (freed > 10);
466}
467
468void drop_slab(void)
469{
470 int nid;
471
472 for_each_online_node(nid)
473 drop_slab_node(nid);
474}
475
Linus Torvalds1da177e2005-04-16 15:20:36 -0700476static inline int is_page_cache_freeable(struct page *page)
477{
Johannes Weinerceddc3a2009-09-21 17:03:00 -0700478 /*
479 * A freeable page cache page is referenced only by the caller
480 * that isolated the page, the page cache radix tree and
481 * optional buffer heads at page->private.
482 */
Johannes Weineredcf4742009-09-21 17:02:59 -0700483 return page_count(page) - page_has_private(page) == 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700484}
485
Tejun Heo703c2702015-05-22 17:13:44 -0400486static int may_write_to_inode(struct inode *inode, struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700487{
Christoph Lameter930d9152006-01-08 01:00:47 -0800488 if (current->flags & PF_SWAPWRITE)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700489 return 1;
Tejun Heo703c2702015-05-22 17:13:44 -0400490 if (!inode_write_congested(inode))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700491 return 1;
Tejun Heo703c2702015-05-22 17:13:44 -0400492 if (inode_to_bdi(inode) == current->backing_dev_info)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700493 return 1;
494 return 0;
495}
496
497/*
498 * We detected a synchronous write error writing a page out. Probably
499 * -ENOSPC. We need to propagate that into the address_space for a subsequent
500 * fsync(), msync() or close().
501 *
502 * The tricky part is that after writepage we cannot touch the mapping: nothing
503 * prevents it from being freed up. But we have a ref on the page and once
504 * that page is locked, the mapping is pinned.
505 *
506 * We're allowed to run sleeping lock_page() here because we know the caller has
507 * __GFP_FS.
508 */
509static void handle_write_error(struct address_space *mapping,
510 struct page *page, int error)
511{
Jens Axboe7eaceac2011-03-10 08:52:07 +0100512 lock_page(page);
Guillaume Chazarain3e9f45b2007-05-08 00:23:25 -0700513 if (page_mapping(page) == mapping)
514 mapping_set_error(mapping, error);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700515 unlock_page(page);
516}
517
Christoph Lameter04e62a22006-06-23 02:03:38 -0700518/* possible outcome of pageout() */
519typedef enum {
520 /* failed to write page out, page is locked */
521 PAGE_KEEP,
522 /* move page to the active list, page is locked */
523 PAGE_ACTIVATE,
524 /* page has been sent to the disk successfully, page is unlocked */
525 PAGE_SUCCESS,
526 /* page is clean and locked */
527 PAGE_CLEAN,
528} pageout_t;
529
Linus Torvalds1da177e2005-04-16 15:20:36 -0700530/*
Andrew Morton1742f192006-03-22 00:08:21 -0800531 * pageout is called by shrink_page_list() for each dirty page.
532 * Calls ->writepage().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700533 */
Andy Whitcroftc661b072007-08-22 14:01:26 -0700534static pageout_t pageout(struct page *page, struct address_space *mapping,
KOSAKI Motohiro7d3579e2010-10-26 14:21:42 -0700535 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536{
537 /*
538 * If the page is dirty, only perform writeback if that write
539 * will be non-blocking. To prevent this allocation from being
540 * stalled by pagecache activity. But note that there may be
541 * stalls if we need to run get_block(). We could test
542 * PagePrivate for that.
543 *
Al Viro81742022014-04-03 03:17:43 -0400544 * If this process is currently in __generic_file_write_iter() against
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545 * this page's queue, we can perform writeback even if that
546 * will block.
547 *
548 * If the page is swapcache, write it back even if that would
549 * block, for some throttling. This happens by accident, because
550 * swap_backing_dev_info is bust: it doesn't reflect the
551 * congestion state of the swapdevs. Easy to fix, if needed.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700552 */
553 if (!is_page_cache_freeable(page))
554 return PAGE_KEEP;
555 if (!mapping) {
556 /*
557 * Some data journaling orphaned pages can have
558 * page->mapping == NULL while being dirty with clean buffers.
559 */
David Howells266cf652009-04-03 16:42:36 +0100560 if (page_has_private(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700561 if (try_to_free_buffers(page)) {
562 ClearPageDirty(page);
Mitchel Humpherysb1de0d12014-06-06 14:38:30 -0700563 pr_info("%s: orphaned page\n", __func__);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700564 return PAGE_CLEAN;
565 }
566 }
567 return PAGE_KEEP;
568 }
569 if (mapping->a_ops->writepage == NULL)
570 return PAGE_ACTIVATE;
Tejun Heo703c2702015-05-22 17:13:44 -0400571 if (!may_write_to_inode(mapping->host, sc))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700572 return PAGE_KEEP;
573
574 if (clear_page_dirty_for_io(page)) {
575 int res;
576 struct writeback_control wbc = {
577 .sync_mode = WB_SYNC_NONE,
578 .nr_to_write = SWAP_CLUSTER_MAX,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700579 .range_start = 0,
580 .range_end = LLONG_MAX,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700581 .for_reclaim = 1,
582 };
583
584 SetPageReclaim(page);
585 res = mapping->a_ops->writepage(page, &wbc);
586 if (res < 0)
587 handle_write_error(mapping, page, res);
Zach Brown994fc28c2005-12-15 14:28:17 -0800588 if (res == AOP_WRITEPAGE_ACTIVATE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589 ClearPageReclaim(page);
590 return PAGE_ACTIVATE;
591 }
Andy Whitcroftc661b072007-08-22 14:01:26 -0700592
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593 if (!PageWriteback(page)) {
594 /* synchronous write or broken a_ops? */
595 ClearPageReclaim(page);
596 }
yalin wang3aa23852016-01-14 15:18:30 -0800597 trace_mm_vmscan_writepage(page);
Andrew Mortone129b5c2006-09-27 01:50:00 -0700598 inc_zone_page_state(page, NR_VMSCAN_WRITE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700599 return PAGE_SUCCESS;
600 }
601
602 return PAGE_CLEAN;
603}
604
Andrew Mortona649fd92006-10-17 00:09:36 -0700605/*
Nick Piggine2867812008-07-25 19:45:30 -0700606 * Same as remove_mapping, but if the page is removed from the mapping, it
607 * gets returned with a refcount of 0.
Andrew Mortona649fd92006-10-17 00:09:36 -0700608 */
Johannes Weinera5289102014-04-03 14:47:51 -0700609static int __remove_mapping(struct address_space *mapping, struct page *page,
610 bool reclaimed)
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800611{
Greg Thelenc4843a72015-05-22 17:13:16 -0400612 unsigned long flags;
613 struct mem_cgroup *memcg;
614
Nick Piggin28e4d962006-09-25 23:31:23 -0700615 BUG_ON(!PageLocked(page));
616 BUG_ON(mapping != page_mapping(page));
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800617
Greg Thelenc4843a72015-05-22 17:13:16 -0400618 memcg = mem_cgroup_begin_page_stat(page);
619 spin_lock_irqsave(&mapping->tree_lock, flags);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800620 /*
Nick Piggin0fd0e6b2006-09-27 01:50:02 -0700621 * The non racy check for a busy page.
622 *
623 * Must be careful with the order of the tests. When someone has
624 * a ref to the page, it may be possible that they dirty it then
625 * drop the reference. So if PageDirty is tested before page_count
626 * here, then the following race may occur:
627 *
628 * get_user_pages(&page);
629 * [user mapping goes away]
630 * write_to(page);
631 * !PageDirty(page) [good]
632 * SetPageDirty(page);
633 * put_page(page);
634 * !page_count(page) [good, discard it]
635 *
636 * [oops, our write_to data is lost]
637 *
638 * Reversing the order of the tests ensures such a situation cannot
639 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
640 * load is not satisfied before that of page->_count.
641 *
642 * Note that if SetPageDirty is always performed via set_page_dirty,
643 * and thus under tree_lock, then this ordering is not required.
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800644 */
Nick Piggine2867812008-07-25 19:45:30 -0700645 if (!page_freeze_refs(page, 2))
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800646 goto cannot_free;
Nick Piggine2867812008-07-25 19:45:30 -0700647 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
648 if (unlikely(PageDirty(page))) {
649 page_unfreeze_refs(page, 2);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800650 goto cannot_free;
Nick Piggine2867812008-07-25 19:45:30 -0700651 }
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800652
653 if (PageSwapCache(page)) {
654 swp_entry_t swap = { .val = page_private(page) };
Johannes Weiner0a31bc92014-08-08 14:19:22 -0700655 mem_cgroup_swapout(page, swap);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800656 __delete_from_swap_cache(page);
Greg Thelenc4843a72015-05-22 17:13:16 -0400657 spin_unlock_irqrestore(&mapping->tree_lock, flags);
658 mem_cgroup_end_page_stat(memcg);
Johannes Weiner0a31bc92014-08-08 14:19:22 -0700659 swapcache_free(swap);
Nick Piggine2867812008-07-25 19:45:30 -0700660 } else {
Linus Torvalds6072d132010-12-01 13:35:19 -0500661 void (*freepage)(struct page *);
Johannes Weinera5289102014-04-03 14:47:51 -0700662 void *shadow = NULL;
Linus Torvalds6072d132010-12-01 13:35:19 -0500663
664 freepage = mapping->a_ops->freepage;
Johannes Weinera5289102014-04-03 14:47:51 -0700665 /*
666 * Remember a shadow entry for reclaimed file cache in
667 * order to detect refaults, thus thrashing, later on.
668 *
669 * But don't store shadows in an address space that is
670 * already exiting. This is not just an optizimation,
671 * inode reclaim needs to empty out the radix tree or
672 * the nodes are lost. Don't plant shadows behind its
673 * back.
674 */
675 if (reclaimed && page_is_file_cache(page) &&
676 !mapping_exiting(mapping))
677 shadow = workingset_eviction(mapping, page);
Greg Thelenc4843a72015-05-22 17:13:16 -0400678 __delete_from_page_cache(page, shadow, memcg);
679 spin_unlock_irqrestore(&mapping->tree_lock, flags);
680 mem_cgroup_end_page_stat(memcg);
Linus Torvalds6072d132010-12-01 13:35:19 -0500681
682 if (freepage != NULL)
683 freepage(page);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800684 }
685
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800686 return 1;
687
688cannot_free:
Greg Thelenc4843a72015-05-22 17:13:16 -0400689 spin_unlock_irqrestore(&mapping->tree_lock, flags);
690 mem_cgroup_end_page_stat(memcg);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800691 return 0;
692}
693
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694/*
Nick Piggine2867812008-07-25 19:45:30 -0700695 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
696 * someone else has a ref on the page, abort and return 0. If it was
697 * successfully detached, return 1. Assumes the caller has a single ref on
698 * this page.
699 */
700int remove_mapping(struct address_space *mapping, struct page *page)
701{
Johannes Weinera5289102014-04-03 14:47:51 -0700702 if (__remove_mapping(mapping, page, false)) {
Nick Piggine2867812008-07-25 19:45:30 -0700703 /*
704 * Unfreezing the refcount with 1 rather than 2 effectively
705 * drops the pagecache ref for us without requiring another
706 * atomic operation.
707 */
708 page_unfreeze_refs(page, 1);
709 return 1;
710 }
711 return 0;
712}
713
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700714/**
715 * putback_lru_page - put previously isolated page onto appropriate LRU list
716 * @page: page to be put back to appropriate lru list
717 *
718 * Add previously isolated @page to appropriate LRU list.
719 * Page may still be unevictable for other reasons.
720 *
721 * lru_lock must not be held, interrupts must be enabled.
722 */
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700723void putback_lru_page(struct page *page)
724{
Vlastimil Babka0ec3b742013-09-11 14:22:26 -0700725 bool is_unevictable;
Lee Schermerhornbbfd28e2008-10-18 20:26:40 -0700726 int was_unevictable = PageUnevictable(page);
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700727
Sasha Levin309381fea2014-01-23 15:52:54 -0800728 VM_BUG_ON_PAGE(PageLRU(page), page);
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700729
730redo:
731 ClearPageUnevictable(page);
732
Hugh Dickins39b5f292012-10-08 16:33:18 -0700733 if (page_evictable(page)) {
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700734 /*
735 * For evictable pages, we can use the cache.
736 * In event of a race, worst case is we end up with an
737 * unevictable page on [in]active list.
738 * We know how to handle that.
739 */
Vlastimil Babka0ec3b742013-09-11 14:22:26 -0700740 is_unevictable = false;
Mel Gormanc53954a2013-07-03 15:02:34 -0700741 lru_cache_add(page);
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700742 } else {
743 /*
744 * Put unevictable pages directly on zone's unevictable
745 * list.
746 */
Vlastimil Babka0ec3b742013-09-11 14:22:26 -0700747 is_unevictable = true;
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700748 add_page_to_unevictable_list(page);
Johannes Weiner6a7b9542009-10-26 16:50:00 -0700749 /*
Minchan Kim21ee9f32011-10-31 17:09:28 -0700750 * When racing with an mlock or AS_UNEVICTABLE clearing
751 * (page is unlocked) make sure that if the other thread
752 * does not observe our setting of PG_lru and fails
Hugh Dickins24513262012-01-20 14:34:21 -0800753 * isolation/check_move_unevictable_pages,
Minchan Kim21ee9f32011-10-31 17:09:28 -0700754 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
Johannes Weiner6a7b9542009-10-26 16:50:00 -0700755 * the page back to the evictable list.
756 *
Minchan Kim21ee9f32011-10-31 17:09:28 -0700757 * The other side is TestClearPageMlocked() or shmem_lock().
Johannes Weiner6a7b9542009-10-26 16:50:00 -0700758 */
759 smp_mb();
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700760 }
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700761
762 /*
763 * page's status can change while we move it among lru. If an evictable
764 * page is on unevictable list, it never be freed. To avoid that,
765 * check after we added it to the list, again.
766 */
Vlastimil Babka0ec3b742013-09-11 14:22:26 -0700767 if (is_unevictable && page_evictable(page)) {
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700768 if (!isolate_lru_page(page)) {
769 put_page(page);
770 goto redo;
771 }
772 /* This means someone else dropped this page from LRU
773 * So, it will be freed or putback to LRU again. There is
774 * nothing to do here.
775 */
776 }
777
Vlastimil Babka0ec3b742013-09-11 14:22:26 -0700778 if (was_unevictable && !is_unevictable)
Lee Schermerhornbbfd28e2008-10-18 20:26:40 -0700779 count_vm_event(UNEVICTABLE_PGRESCUED);
Vlastimil Babka0ec3b742013-09-11 14:22:26 -0700780 else if (!was_unevictable && is_unevictable)
Lee Schermerhornbbfd28e2008-10-18 20:26:40 -0700781 count_vm_event(UNEVICTABLE_PGCULLED);
782
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700783 put_page(page); /* drop ref from isolate */
784}
785
Johannes Weinerdfc8d632010-03-05 13:42:19 -0800786enum page_references {
787 PAGEREF_RECLAIM,
788 PAGEREF_RECLAIM_CLEAN,
Johannes Weiner645747462010-03-05 13:42:22 -0800789 PAGEREF_KEEP,
Johannes Weinerdfc8d632010-03-05 13:42:19 -0800790 PAGEREF_ACTIVATE,
791};
792
793static enum page_references page_check_references(struct page *page,
794 struct scan_control *sc)
795{
Johannes Weiner645747462010-03-05 13:42:22 -0800796 int referenced_ptes, referenced_page;
Johannes Weinerdfc8d632010-03-05 13:42:19 -0800797 unsigned long vm_flags;
Johannes Weinerdfc8d632010-03-05 13:42:19 -0800798
Johannes Weinerc3ac9a82012-05-29 15:06:25 -0700799 referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
800 &vm_flags);
Johannes Weiner645747462010-03-05 13:42:22 -0800801 referenced_page = TestClearPageReferenced(page);
Johannes Weinerdfc8d632010-03-05 13:42:19 -0800802
Johannes Weinerdfc8d632010-03-05 13:42:19 -0800803 /*
804 * Mlock lost the isolation race with us. Let try_to_unmap()
805 * move the page to the unevictable list.
806 */
807 if (vm_flags & VM_LOCKED)
808 return PAGEREF_RECLAIM;
809
Johannes Weiner645747462010-03-05 13:42:22 -0800810 if (referenced_ptes) {
Michal Hockoe48982732012-05-29 15:06:45 -0700811 if (PageSwapBacked(page))
Johannes Weiner645747462010-03-05 13:42:22 -0800812 return PAGEREF_ACTIVATE;
813 /*
814 * All mapped pages start out with page table
815 * references from the instantiating fault, so we need
816 * to look twice if a mapped file page is used more
817 * than once.
818 *
819 * Mark it and spare it for another trip around the
820 * inactive list. Another page table reference will
821 * lead to its activation.
822 *
823 * Note: the mark is set for activated pages as well
824 * so that recently deactivated but used pages are
825 * quickly recovered.
826 */
827 SetPageReferenced(page);
828
Konstantin Khlebnikov34dbc672012-01-10 15:06:59 -0800829 if (referenced_page || referenced_ptes > 1)
Johannes Weiner645747462010-03-05 13:42:22 -0800830 return PAGEREF_ACTIVATE;
831
Konstantin Khlebnikovc909e992012-01-10 15:07:03 -0800832 /*
833 * Activate file-backed executable pages after first usage.
834 */
835 if (vm_flags & VM_EXEC)
836 return PAGEREF_ACTIVATE;
837
Johannes Weiner645747462010-03-05 13:42:22 -0800838 return PAGEREF_KEEP;
839 }
Johannes Weinerdfc8d632010-03-05 13:42:19 -0800840
841 /* Reclaim if clean, defer dirty pages to writeback */
KOSAKI Motohiro2e302442010-10-26 14:21:46 -0700842 if (referenced_page && !PageSwapBacked(page))
Johannes Weiner645747462010-03-05 13:42:22 -0800843 return PAGEREF_RECLAIM_CLEAN;
844
845 return PAGEREF_RECLAIM;
Johannes Weinerdfc8d632010-03-05 13:42:19 -0800846}
847
Mel Gormane2be15f2013-07-03 15:01:57 -0700848/* Check if a page is dirty or under writeback */
849static void page_check_dirty_writeback(struct page *page,
850 bool *dirty, bool *writeback)
851{
Mel Gormanb4597222013-07-03 15:02:05 -0700852 struct address_space *mapping;
853
Mel Gormane2be15f2013-07-03 15:01:57 -0700854 /*
855 * Anonymous pages are not handled by flushers and must be written
856 * from reclaim context. Do not stall reclaim based on them
857 */
858 if (!page_is_file_cache(page)) {
859 *dirty = false;
860 *writeback = false;
861 return;
862 }
863
864 /* By default assume that the page flags are accurate */
865 *dirty = PageDirty(page);
866 *writeback = PageWriteback(page);
Mel Gormanb4597222013-07-03 15:02:05 -0700867
868 /* Verify dirty/writeback state if the filesystem supports it */
869 if (!page_has_private(page))
870 return;
871
872 mapping = page_mapping(page);
873 if (mapping && mapping->a_ops->is_dirty_writeback)
874 mapping->a_ops->is_dirty_writeback(page, dirty, writeback);
Mel Gormane2be15f2013-07-03 15:01:57 -0700875}
876
Nick Piggine2867812008-07-25 19:45:30 -0700877/*
Andrew Morton1742f192006-03-22 00:08:21 -0800878 * shrink_page_list() returns the number of reclaimed pages
Linus Torvalds1da177e2005-04-16 15:20:36 -0700879 */
Andrew Morton1742f192006-03-22 00:08:21 -0800880static unsigned long shrink_page_list(struct list_head *page_list,
Konstantin Khlebnikov6a18adb2012-05-29 15:06:59 -0700881 struct zone *zone,
Mel Gormanf84f6e22011-10-31 17:07:51 -0700882 struct scan_control *sc,
Minchan Kim02c6de82012-10-08 16:31:55 -0700883 enum ttu_flags ttu_flags,
Mel Gorman8e950282013-07-03 15:02:02 -0700884 unsigned long *ret_nr_dirty,
Mel Gormand43006d2013-07-03 15:01:50 -0700885 unsigned long *ret_nr_unqueued_dirty,
Mel Gorman8e950282013-07-03 15:02:02 -0700886 unsigned long *ret_nr_congested,
Minchan Kim02c6de82012-10-08 16:31:55 -0700887 unsigned long *ret_nr_writeback,
Mel Gormanb1a6f212013-07-03 15:01:58 -0700888 unsigned long *ret_nr_immediate,
Minchan Kim02c6de82012-10-08 16:31:55 -0700889 bool force_reclaim)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890{
891 LIST_HEAD(ret_pages);
Mel Gormanabe4c3b2010-08-09 17:19:31 -0700892 LIST_HEAD(free_pages);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700893 int pgactivate = 0;
Mel Gormand43006d2013-07-03 15:01:50 -0700894 unsigned long nr_unqueued_dirty = 0;
Mel Gorman0e093d992010-10-26 14:21:45 -0700895 unsigned long nr_dirty = 0;
896 unsigned long nr_congested = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -0800897 unsigned long nr_reclaimed = 0;
Mel Gorman92df3a72011-10-31 17:07:56 -0700898 unsigned long nr_writeback = 0;
Mel Gormanb1a6f212013-07-03 15:01:58 -0700899 unsigned long nr_immediate = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700900
901 cond_resched();
902
Linus Torvalds1da177e2005-04-16 15:20:36 -0700903 while (!list_empty(page_list)) {
904 struct address_space *mapping;
905 struct page *page;
906 int may_enter_fs;
Minchan Kim02c6de82012-10-08 16:31:55 -0700907 enum page_references references = PAGEREF_RECLAIM_CLEAN;
Mel Gormane2be15f2013-07-03 15:01:57 -0700908 bool dirty, writeback;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700909
910 cond_resched();
911
912 page = lru_to_page(page_list);
913 list_del(&page->lru);
914
Nick Piggin529ae9a2008-08-02 12:01:03 +0200915 if (!trylock_page(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700916 goto keep;
917
Sasha Levin309381fea2014-01-23 15:52:54 -0800918 VM_BUG_ON_PAGE(PageActive(page), page);
919 VM_BUG_ON_PAGE(page_zone(page) != zone, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700920
921 sc->nr_scanned++;
Christoph Lameter80e43422006-02-11 17:55:53 -0800922
Hugh Dickins39b5f292012-10-08 16:33:18 -0700923 if (unlikely(!page_evictable(page)))
Nick Pigginb291f002008-10-18 20:26:44 -0700924 goto cull_mlocked;
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700925
Johannes Weinera6dc60f82009-03-31 15:19:30 -0700926 if (!sc->may_unmap && page_mapped(page))
Christoph Lameter80e43422006-02-11 17:55:53 -0800927 goto keep_locked;
928
Linus Torvalds1da177e2005-04-16 15:20:36 -0700929 /* Double the slab pressure for mapped and swapcache pages */
930 if (page_mapped(page) || PageSwapCache(page))
931 sc->nr_scanned++;
932
Andy Whitcroftc661b072007-08-22 14:01:26 -0700933 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
934 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
935
Mel Gorman283aba92013-07-03 15:01:51 -0700936 /*
Mel Gormane2be15f2013-07-03 15:01:57 -0700937 * The number of dirty pages determines if a zone is marked
938 * reclaim_congested which affects wait_iff_congested. kswapd
939 * will stall and start writing pages if the tail of the LRU
940 * is all dirty unqueued pages.
941 */
942 page_check_dirty_writeback(page, &dirty, &writeback);
943 if (dirty || writeback)
944 nr_dirty++;
945
946 if (dirty && !writeback)
947 nr_unqueued_dirty++;
948
Mel Gormand04e8ac2013-07-03 15:02:03 -0700949 /*
950 * Treat this page as congested if the underlying BDI is or if
951 * pages are cycling through the LRU so quickly that the
952 * pages marked for immediate reclaim are making it to the
953 * end of the LRU a second time.
954 */
Mel Gormane2be15f2013-07-03 15:01:57 -0700955 mapping = page_mapping(page);
Jamie Liu1da58ee2014-12-10 15:43:20 -0800956 if (((dirty || writeback) && mapping &&
Tejun Heo703c2702015-05-22 17:13:44 -0400957 inode_write_congested(mapping->host)) ||
Mel Gormand04e8ac2013-07-03 15:02:03 -0700958 (writeback && PageReclaim(page)))
Mel Gormane2be15f2013-07-03 15:01:57 -0700959 nr_congested++;
960
961 /*
Mel Gorman283aba92013-07-03 15:01:51 -0700962 * If a page at the tail of the LRU is under writeback, there
963 * are three cases to consider.
964 *
965 * 1) If reclaim is encountering an excessive number of pages
966 * under writeback and this page is both under writeback and
967 * PageReclaim then it indicates that pages are being queued
968 * for IO but are being recycled through the LRU before the
969 * IO can complete. Waiting on the page itself risks an
970 * indefinite stall if it is impossible to writeback the
971 * page due to IO error or disconnected storage so instead
Mel Gormanb1a6f212013-07-03 15:01:58 -0700972 * note that the LRU is being scanned too quickly and the
973 * caller can stall after page list has been processed.
Mel Gorman283aba92013-07-03 15:01:51 -0700974 *
Tejun Heo97c93412015-05-22 18:23:36 -0400975 * 2) Global or new memcg reclaim encounters a page that is
Michal Hockoecf5fc62015-08-04 14:36:58 -0700976 * not marked for immediate reclaim, or the caller does not
977 * have __GFP_FS (or __GFP_IO if it's simply going to swap,
978 * not to fs). In this case mark the page for immediate
Tejun Heo97c93412015-05-22 18:23:36 -0400979 * reclaim and continue scanning.
Mel Gorman283aba92013-07-03 15:01:51 -0700980 *
Michal Hockoecf5fc62015-08-04 14:36:58 -0700981 * Require may_enter_fs because we would wait on fs, which
982 * may not have submitted IO yet. And the loop driver might
Mel Gorman283aba92013-07-03 15:01:51 -0700983 * enter reclaim, and deadlock if it waits on a page for
984 * which it is needed to do the write (loop masks off
985 * __GFP_IO|__GFP_FS for this reason); but more thought
986 * would probably show more reasons.
987 *
Hugh Dickins7fadc822015-09-08 15:03:46 -0700988 * 3) Legacy memcg encounters a page that is already marked
Mel Gorman283aba92013-07-03 15:01:51 -0700989 * PageReclaim. memcg does not have any dirty pages
990 * throttling so we could easily OOM just because too many
991 * pages are in writeback and there is nothing else to
992 * reclaim. Wait for the writeback to complete.
993 */
Andy Whitcroftc661b072007-08-22 14:01:26 -0700994 if (PageWriteback(page)) {
Mel Gorman283aba92013-07-03 15:01:51 -0700995 /* Case 1 above */
996 if (current_is_kswapd() &&
997 PageReclaim(page) &&
Johannes Weiner57054652014-10-09 15:28:17 -0700998 test_bit(ZONE_WRITEBACK, &zone->flags)) {
Mel Gormanb1a6f212013-07-03 15:01:58 -0700999 nr_immediate++;
1000 goto keep_locked;
Mel Gorman283aba92013-07-03 15:01:51 -07001001
1002 /* Case 2 above */
Tejun Heo97c93412015-05-22 18:23:36 -04001003 } else if (sane_reclaim(sc) ||
Michal Hockoecf5fc62015-08-04 14:36:58 -07001004 !PageReclaim(page) || !may_enter_fs) {
Hugh Dickinsc3b94f42012-07-31 16:45:59 -07001005 /*
1006 * This is slightly racy - end_page_writeback()
1007 * might have just cleared PageReclaim, then
1008 * setting PageReclaim here end up interpreted
1009 * as PageReadahead - but that does not matter
1010 * enough to care. What we do want is for this
1011 * page to have PageReclaim set next time memcg
1012 * reclaim reaches the tests above, so it will
1013 * then wait_on_page_writeback() to avoid OOM;
1014 * and it's also appropriate in global reclaim.
1015 */
1016 SetPageReclaim(page);
Michal Hockoe62e3842012-07-31 16:45:55 -07001017 nr_writeback++;
Hugh Dickinsc3b94f42012-07-31 16:45:59 -07001018 goto keep_locked;
Mel Gorman283aba92013-07-03 15:01:51 -07001019
1020 /* Case 3 above */
1021 } else {
Hugh Dickins7fadc822015-09-08 15:03:46 -07001022 unlock_page(page);
Mel Gorman283aba92013-07-03 15:01:51 -07001023 wait_on_page_writeback(page);
Hugh Dickins7fadc822015-09-08 15:03:46 -07001024 /* then go back and try same page again */
1025 list_add_tail(&page->lru, page_list);
1026 continue;
Michal Hockoe62e3842012-07-31 16:45:55 -07001027 }
Andy Whitcroftc661b072007-08-22 14:01:26 -07001028 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001029
Minchan Kim02c6de82012-10-08 16:31:55 -07001030 if (!force_reclaim)
1031 references = page_check_references(page, sc);
1032
Johannes Weinerdfc8d632010-03-05 13:42:19 -08001033 switch (references) {
1034 case PAGEREF_ACTIVATE:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001035 goto activate_locked;
Johannes Weiner645747462010-03-05 13:42:22 -08001036 case PAGEREF_KEEP:
1037 goto keep_locked;
Johannes Weinerdfc8d632010-03-05 13:42:19 -08001038 case PAGEREF_RECLAIM:
1039 case PAGEREF_RECLAIM_CLEAN:
1040 ; /* try to reclaim the page below */
1041 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001042
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043 /*
1044 * Anonymous process memory has backing store?
1045 * Try to allocate it some swap space here.
1046 */
Nick Pigginb291f002008-10-18 20:26:44 -07001047 if (PageAnon(page) && !PageSwapCache(page)) {
Hugh Dickins63eb6b932008-11-19 15:36:37 -08001048 if (!(sc->gfp_mask & __GFP_IO))
1049 goto keep_locked;
Shaohua Li5bc7b8a2013-04-29 15:08:36 -07001050 if (!add_to_swap(page, page_list))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001051 goto activate_locked;
Hugh Dickins63eb6b932008-11-19 15:36:37 -08001052 may_enter_fs = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001053
Mel Gormane2be15f2013-07-03 15:01:57 -07001054 /* Adding to swap updated mapping */
1055 mapping = page_mapping(page);
1056 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001057
1058 /*
1059 * The page is mapped into the page tables of one or more
1060 * processes. Try to unmap it here.
1061 */
1062 if (page_mapped(page) && mapping) {
Mel Gorman72b252a2015-09-04 15:47:32 -07001063 switch (try_to_unmap(page,
1064 ttu_flags|TTU_BATCH_FLUSH)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001065 case SWAP_FAIL:
1066 goto activate_locked;
1067 case SWAP_AGAIN:
1068 goto keep_locked;
Nick Pigginb291f002008-10-18 20:26:44 -07001069 case SWAP_MLOCK:
1070 goto cull_mlocked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001071 case SWAP_SUCCESS:
1072 ; /* try to free the page below */
1073 }
1074 }
1075
1076 if (PageDirty(page)) {
Mel Gormanee728862011-10-31 17:07:38 -07001077 /*
1078 * Only kswapd can writeback filesystem pages to
Mel Gormand43006d2013-07-03 15:01:50 -07001079 * avoid risk of stack overflow but only writeback
1080 * if many dirty pages have been encountered.
Mel Gormanee728862011-10-31 17:07:38 -07001081 */
Mel Gormanf84f6e22011-10-31 17:07:51 -07001082 if (page_is_file_cache(page) &&
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07001083 (!current_is_kswapd() ||
Johannes Weiner57054652014-10-09 15:28:17 -07001084 !test_bit(ZONE_DIRTY, &zone->flags))) {
Mel Gorman49ea7eb2011-10-31 17:07:59 -07001085 /*
1086 * Immediately reclaim when written back.
1087 * Similar in principal to deactivate_page()
1088 * except we already have the page isolated
1089 * and know it's dirty
1090 */
1091 inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
1092 SetPageReclaim(page);
1093
Mel Gormanee728862011-10-31 17:07:38 -07001094 goto keep_locked;
1095 }
1096
Johannes Weinerdfc8d632010-03-05 13:42:19 -08001097 if (references == PAGEREF_RECLAIM_CLEAN)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001098 goto keep_locked;
Andrew Morton4dd4b922008-03-24 12:29:52 -07001099 if (!may_enter_fs)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001100 goto keep_locked;
Christoph Lameter52a83632006-02-01 03:05:28 -08001101 if (!sc->may_writepage)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001102 goto keep_locked;
1103
Mel Gormand950c942015-09-04 15:47:35 -07001104 /*
1105 * Page is dirty. Flush the TLB if a writable entry
1106 * potentially exists to avoid CPU writes after IO
1107 * starts and then write it out here.
1108 */
1109 try_to_unmap_flush_dirty();
KOSAKI Motohiro7d3579e2010-10-26 14:21:42 -07001110 switch (pageout(page, mapping, sc)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001111 case PAGE_KEEP:
1112 goto keep_locked;
1113 case PAGE_ACTIVATE:
1114 goto activate_locked;
1115 case PAGE_SUCCESS:
KOSAKI Motohiro7d3579e2010-10-26 14:21:42 -07001116 if (PageWriteback(page))
Mel Gorman41ac1992012-05-29 15:06:19 -07001117 goto keep;
KOSAKI Motohiro7d3579e2010-10-26 14:21:42 -07001118 if (PageDirty(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001119 goto keep;
KOSAKI Motohiro7d3579e2010-10-26 14:21:42 -07001120
Linus Torvalds1da177e2005-04-16 15:20:36 -07001121 /*
1122 * A synchronous write - probably a ramdisk. Go
1123 * ahead and try to reclaim the page.
1124 */
Nick Piggin529ae9a2008-08-02 12:01:03 +02001125 if (!trylock_page(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001126 goto keep;
1127 if (PageDirty(page) || PageWriteback(page))
1128 goto keep_locked;
1129 mapping = page_mapping(page);
1130 case PAGE_CLEAN:
1131 ; /* try to free the page below */
1132 }
1133 }
1134
1135 /*
1136 * If the page has buffers, try to free the buffer mappings
1137 * associated with this page. If we succeed we try to free
1138 * the page as well.
1139 *
1140 * We do this even if the page is PageDirty().
1141 * try_to_release_page() does not perform I/O, but it is
1142 * possible for a page to have PageDirty set, but it is actually
1143 * clean (all its buffers are clean). This happens if the
1144 * buffers were written out directly, with submit_bh(). ext3
Lee Schermerhorn894bc312008-10-18 20:26:39 -07001145 * will do this, as well as the blockdev mapping.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001146 * try_to_release_page() will discover that cleanness and will
1147 * drop the buffers and mark the page clean - it can be freed.
1148 *
1149 * Rarely, pages can have buffers and no ->mapping. These are
1150 * the pages which were not successfully invalidated in
1151 * truncate_complete_page(). We try to drop those buffers here
1152 * and if that worked, and the page is no longer mapped into
1153 * process address space (page_count == 1) it can be freed.
1154 * Otherwise, leave the page on the LRU so it is swappable.
1155 */
David Howells266cf652009-04-03 16:42:36 +01001156 if (page_has_private(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001157 if (!try_to_release_page(page, sc->gfp_mask))
1158 goto activate_locked;
Nick Piggine2867812008-07-25 19:45:30 -07001159 if (!mapping && page_count(page) == 1) {
1160 unlock_page(page);
1161 if (put_page_testzero(page))
1162 goto free_it;
1163 else {
1164 /*
1165 * rare race with speculative reference.
1166 * the speculative reference will free
1167 * this page shortly, so we may
1168 * increment nr_reclaimed here (and
1169 * leave it off the LRU).
1170 */
1171 nr_reclaimed++;
1172 continue;
1173 }
1174 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001175 }
1176
Johannes Weinera5289102014-04-03 14:47:51 -07001177 if (!mapping || !__remove_mapping(mapping, page, true))
Christoph Lameter49d2e9c2006-01-08 01:00:48 -08001178 goto keep_locked;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001179
Nick Piggina978d6f2008-10-18 20:26:58 -07001180 /*
1181 * At this point, we have no other references and there is
1182 * no way to pick any more up (removed from LRU, removed
1183 * from pagecache). Can use non-atomic bitops now (and
1184 * we obviously don't have to worry about waking up a process
1185 * waiting on the page lock, because there are no references.
1186 */
1187 __clear_page_locked(page);
Nick Piggine2867812008-07-25 19:45:30 -07001188free_it:
Andrew Morton05ff5132006-03-22 00:08:20 -08001189 nr_reclaimed++;
Mel Gormanabe4c3b2010-08-09 17:19:31 -07001190
1191 /*
1192 * Is there need to periodically free_page_list? It would
1193 * appear not as the counts should be low
1194 */
1195 list_add(&page->lru, &free_pages);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001196 continue;
1197
Nick Pigginb291f002008-10-18 20:26:44 -07001198cull_mlocked:
Hugh Dickins63d6c5a2009-01-06 14:39:38 -08001199 if (PageSwapCache(page))
1200 try_to_free_swap(page);
Nick Pigginb291f002008-10-18 20:26:44 -07001201 unlock_page(page);
Jaewon Kimc54839a2015-09-08 15:02:21 -07001202 list_add(&page->lru, &ret_pages);
Nick Pigginb291f002008-10-18 20:26:44 -07001203 continue;
1204
Linus Torvalds1da177e2005-04-16 15:20:36 -07001205activate_locked:
Rik van Riel68a223942008-10-18 20:26:23 -07001206 /* Not a candidate for swapping, so reclaim swap space. */
1207 if (PageSwapCache(page) && vm_swap_full())
Hugh Dickinsa2c43ee2009-01-06 14:39:36 -08001208 try_to_free_swap(page);
Sasha Levin309381fea2014-01-23 15:52:54 -08001209 VM_BUG_ON_PAGE(PageActive(page), page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001210 SetPageActive(page);
1211 pgactivate++;
1212keep_locked:
1213 unlock_page(page);
1214keep:
1215 list_add(&page->lru, &ret_pages);
Sasha Levin309381fea2014-01-23 15:52:54 -08001216 VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001217 }
Mel Gormanabe4c3b2010-08-09 17:19:31 -07001218
Johannes Weiner747db952014-08-08 14:19:24 -07001219 mem_cgroup_uncharge_list(&free_pages);
Mel Gorman72b252a2015-09-04 15:47:32 -07001220 try_to_unmap_flush();
Mel Gormanb745bc82014-06-04 16:10:22 -07001221 free_hot_cold_page_list(&free_pages, true);
Mel Gormanabe4c3b2010-08-09 17:19:31 -07001222
Linus Torvalds1da177e2005-04-16 15:20:36 -07001223 list_splice(&ret_pages, page_list);
Christoph Lameterf8891e52006-06-30 01:55:45 -07001224 count_vm_events(PGACTIVATE, pgactivate);
Johannes Weiner0a31bc92014-08-08 14:19:22 -07001225
Mel Gorman8e950282013-07-03 15:02:02 -07001226 *ret_nr_dirty += nr_dirty;
1227 *ret_nr_congested += nr_congested;
Mel Gormand43006d2013-07-03 15:01:50 -07001228 *ret_nr_unqueued_dirty += nr_unqueued_dirty;
Mel Gorman92df3a72011-10-31 17:07:56 -07001229 *ret_nr_writeback += nr_writeback;
Mel Gormanb1a6f212013-07-03 15:01:58 -07001230 *ret_nr_immediate += nr_immediate;
Andrew Morton05ff5132006-03-22 00:08:20 -08001231 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001232}
1233
Minchan Kim02c6de82012-10-08 16:31:55 -07001234unsigned long reclaim_clean_pages_from_list(struct zone *zone,
1235 struct list_head *page_list)
1236{
1237 struct scan_control sc = {
1238 .gfp_mask = GFP_KERNEL,
1239 .priority = DEF_PRIORITY,
1240 .may_unmap = 1,
1241 };
Mel Gorman8e950282013-07-03 15:02:02 -07001242 unsigned long ret, dummy1, dummy2, dummy3, dummy4, dummy5;
Minchan Kim02c6de82012-10-08 16:31:55 -07001243 struct page *page, *next;
1244 LIST_HEAD(clean_pages);
1245
1246 list_for_each_entry_safe(page, next, page_list, lru) {
Rafael Aquini117aad12013-09-30 13:45:16 -07001247 if (page_is_file_cache(page) && !PageDirty(page) &&
1248 !isolated_balloon_page(page)) {
Minchan Kim02c6de82012-10-08 16:31:55 -07001249 ClearPageActive(page);
1250 list_move(&page->lru, &clean_pages);
1251 }
1252 }
1253
1254 ret = shrink_page_list(&clean_pages, zone, &sc,
Mel Gorman8e950282013-07-03 15:02:02 -07001255 TTU_UNMAP|TTU_IGNORE_ACCESS,
1256 &dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true);
Minchan Kim02c6de82012-10-08 16:31:55 -07001257 list_splice(&clean_pages, page_list);
Christoph Lameter83da7512014-04-18 15:07:10 -07001258 mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret);
Minchan Kim02c6de82012-10-08 16:31:55 -07001259 return ret;
1260}
1261
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001262/*
1263 * Attempt to remove the specified page from its LRU. Only take this page
1264 * if it is of the appropriate PageActive status. Pages which are being
1265 * freed elsewhere are also ignored.
1266 *
1267 * page: page to consider
1268 * mode: one of the LRU isolation modes defined above
1269 *
1270 * returns 0 on success, -ve errno on failure.
1271 */
Konstantin Khlebnikovf3fd4a62012-05-29 15:06:54 -07001272int __isolate_lru_page(struct page *page, isolate_mode_t mode)
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001273{
1274 int ret = -EINVAL;
1275
1276 /* Only take pages on the LRU. */
1277 if (!PageLRU(page))
1278 return ret;
1279
Minchan Kime46a2872012-10-08 16:33:48 -07001280 /* Compaction should not handle unevictable pages but CMA can do so */
1281 if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
Lee Schermerhorn894bc312008-10-18 20:26:39 -07001282 return ret;
1283
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001284 ret = -EBUSY;
KAMEZAWA Hiroyuki08e552c2009-01-07 18:08:01 -08001285
Mel Gormanc8244932012-01-12 17:19:38 -08001286 /*
1287 * To minimise LRU disruption, the caller can indicate that it only
1288 * wants to isolate pages it will be able to operate on without
1289 * blocking - clean pages for the most part.
1290 *
1291 * ISOLATE_CLEAN means that only clean pages should be isolated. This
1292 * is used by reclaim when it is cannot write to backing storage
1293 *
1294 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1295 * that it is possible to migrate without blocking
1296 */
1297 if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
1298 /* All the caller can do on PageWriteback is block */
1299 if (PageWriteback(page))
1300 return ret;
1301
1302 if (PageDirty(page)) {
1303 struct address_space *mapping;
1304
1305 /* ISOLATE_CLEAN means only clean pages */
1306 if (mode & ISOLATE_CLEAN)
1307 return ret;
1308
1309 /*
1310 * Only pages without mappings or that have a
1311 * ->migratepage callback are possible to migrate
1312 * without blocking
1313 */
1314 mapping = page_mapping(page);
1315 if (mapping && !mapping->a_ops->migratepage)
1316 return ret;
1317 }
1318 }
Minchan Kim39deaf82011-10-31 17:06:51 -07001319
Minchan Kimf80c0672011-10-31 17:06:55 -07001320 if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
1321 return ret;
1322
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001323 if (likely(get_page_unless_zero(page))) {
1324 /*
1325 * Be careful not to clear PageLRU until after we're
1326 * sure the page is not being freed elsewhere -- the
1327 * page release code relies on it.
1328 */
1329 ClearPageLRU(page);
1330 ret = 0;
1331 }
1332
1333 return ret;
1334}
1335
Christoph Lameter49d2e9c2006-01-08 01:00:48 -08001336/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001337 * zone->lru_lock is heavily contended. Some of the functions that
1338 * shrink the lists perform better by taking out a batch of pages
1339 * and working on them outside the LRU lock.
1340 *
1341 * For pagecache intensive workloads, this function is the hottest
1342 * spot in the kernel (apart from copy_*_user functions).
1343 *
1344 * Appropriate locks must be held before calling this function.
1345 *
1346 * @nr_to_scan: The number of pages to look through on the list.
Konstantin Khlebnikov5dc35972012-05-29 15:06:58 -07001347 * @lruvec: The LRU vector to pull pages from.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001348 * @dst: The temp list to put pages on to.
Hugh Dickinsf6260122012-01-12 17:20:06 -08001349 * @nr_scanned: The number of pages that were scanned.
Rik van Rielfe2c2a12012-03-21 16:33:51 -07001350 * @sc: The scan_control struct for this reclaim session
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001351 * @mode: One of the LRU isolation modes
Konstantin Khlebnikov3cb99452012-05-29 15:06:53 -07001352 * @lru: LRU list id for isolating
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353 *
1354 * returns how many pages were moved onto *@dst.
1355 */
Andrew Morton69e05942006-03-22 00:08:19 -08001356static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
Konstantin Khlebnikov5dc35972012-05-29 15:06:58 -07001357 struct lruvec *lruvec, struct list_head *dst,
Rik van Rielfe2c2a12012-03-21 16:33:51 -07001358 unsigned long *nr_scanned, struct scan_control *sc,
Konstantin Khlebnikov3cb99452012-05-29 15:06:53 -07001359 isolate_mode_t mode, enum lru_list lru)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001360{
Hugh Dickins75b00af2012-05-29 15:07:09 -07001361 struct list_head *src = &lruvec->lists[lru];
Andrew Morton69e05942006-03-22 00:08:19 -08001362 unsigned long nr_taken = 0;
Wu Fengguangc9b02d92006-03-22 00:08:23 -08001363 unsigned long scan;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001364
Vladimir Davydov0b802f12015-09-08 15:02:18 -07001365 for (scan = 0; scan < nr_to_scan && nr_taken < nr_to_scan &&
1366 !list_empty(src); scan++) {
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001367 struct page *page;
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001368 int nr_pages;
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001369
Linus Torvalds1da177e2005-04-16 15:20:36 -07001370 page = lru_to_page(src);
1371 prefetchw_prev_lru_page(page, src, flags);
1372
Sasha Levin309381fea2014-01-23 15:52:54 -08001373 VM_BUG_ON_PAGE(!PageLRU(page), page);
Nick Piggin8d438f92006-03-22 00:07:59 -08001374
Konstantin Khlebnikovf3fd4a62012-05-29 15:06:54 -07001375 switch (__isolate_lru_page(page, mode)) {
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001376 case 0:
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001377 nr_pages = hpage_nr_pages(page);
1378 mem_cgroup_update_lru_size(lruvec, lru, -nr_pages);
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001379 list_move(&page->lru, dst);
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001380 nr_taken += nr_pages;
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001381 break;
Nick Piggin46453a62006-03-22 00:07:58 -08001382
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001383 case -EBUSY:
1384 /* else it is being freed elsewhere */
1385 list_move(&page->lru, src);
1386 continue;
1387
1388 default:
1389 BUG();
1390 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001391 }
1392
Hugh Dickinsf6260122012-01-12 17:20:06 -08001393 *nr_scanned = scan;
Hugh Dickins75b00af2012-05-29 15:07:09 -07001394 trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan,
1395 nr_taken, mode, is_file_lru(lru));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001396 return nr_taken;
1397}
1398
Nick Piggin62695a82008-10-18 20:26:09 -07001399/**
1400 * isolate_lru_page - tries to isolate a page from its LRU list
1401 * @page: page to isolate from its LRU list
1402 *
1403 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1404 * vmstat statistic corresponding to whatever LRU list the page was on.
1405 *
1406 * Returns 0 if the page was removed from an LRU list.
1407 * Returns -EBUSY if the page was not on an LRU list.
1408 *
1409 * The returned page will have PageLRU() cleared. If it was found on
Lee Schermerhorn894bc312008-10-18 20:26:39 -07001410 * the active list, it will have PageActive set. If it was found on
1411 * the unevictable list, it will have the PageUnevictable bit set. That flag
1412 * may need to be cleared by the caller before letting the page go.
Nick Piggin62695a82008-10-18 20:26:09 -07001413 *
1414 * The vmstat statistic corresponding to the list on which the page was
1415 * found will be decremented.
1416 *
1417 * Restrictions:
1418 * (1) Must be called with an elevated refcount on the page. This is a
1419 * fundamentnal difference from isolate_lru_pages (which is called
1420 * without a stable reference).
1421 * (2) the lru_lock must not be held.
1422 * (3) interrupts must be enabled.
1423 */
1424int isolate_lru_page(struct page *page)
1425{
1426 int ret = -EBUSY;
1427
Sasha Levin309381fea2014-01-23 15:52:54 -08001428 VM_BUG_ON_PAGE(!page_count(page), page);
Konstantin Khlebnikov0c917312011-05-24 17:12:21 -07001429
Nick Piggin62695a82008-10-18 20:26:09 -07001430 if (PageLRU(page)) {
1431 struct zone *zone = page_zone(page);
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001432 struct lruvec *lruvec;
Nick Piggin62695a82008-10-18 20:26:09 -07001433
1434 spin_lock_irq(&zone->lru_lock);
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001435 lruvec = mem_cgroup_page_lruvec(page, zone);
Konstantin Khlebnikov0c917312011-05-24 17:12:21 -07001436 if (PageLRU(page)) {
Lee Schermerhorn894bc312008-10-18 20:26:39 -07001437 int lru = page_lru(page);
Konstantin Khlebnikov0c917312011-05-24 17:12:21 -07001438 get_page(page);
Nick Piggin62695a82008-10-18 20:26:09 -07001439 ClearPageLRU(page);
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001440 del_page_from_lru_list(page, lruvec, lru);
1441 ret = 0;
Nick Piggin62695a82008-10-18 20:26:09 -07001442 }
1443 spin_unlock_irq(&zone->lru_lock);
1444 }
1445 return ret;
1446}
1447
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001448/*
Fengguang Wud37dd5d2012-12-18 14:23:28 -08001449 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1450 * then get resheduled. When there are massive number of tasks doing page
1451 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1452 * the LRU list will go small and be scanned faster than necessary, leading to
1453 * unnecessary swapping, thrashing and OOM.
Rik van Riel35cd7812009-09-21 17:01:38 -07001454 */
1455static int too_many_isolated(struct zone *zone, int file,
1456 struct scan_control *sc)
1457{
1458 unsigned long inactive, isolated;
1459
1460 if (current_is_kswapd())
1461 return 0;
1462
Tejun Heo97c93412015-05-22 18:23:36 -04001463 if (!sane_reclaim(sc))
Rik van Riel35cd7812009-09-21 17:01:38 -07001464 return 0;
1465
1466 if (file) {
1467 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1468 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1469 } else {
1470 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1471 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1472 }
1473
Fengguang Wu3cf23842012-12-18 14:23:31 -08001474 /*
1475 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1476 * won't get blocked by normal direct-reclaimers, forming a circular
1477 * deadlock.
1478 */
Mel Gormand0164ad2015-11-06 16:28:21 -08001479 if ((sc->gfp_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS))
Fengguang Wu3cf23842012-12-18 14:23:31 -08001480 inactive >>= 3;
1481
Rik van Riel35cd7812009-09-21 17:01:38 -07001482 return isolated > inactive;
1483}
1484
Mel Gorman66635622010-08-09 17:19:30 -07001485static noinline_for_stack void
Hugh Dickins75b00af2012-05-29 15:07:09 -07001486putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list)
Mel Gorman66635622010-08-09 17:19:30 -07001487{
Konstantin Khlebnikov27ac81d2012-05-29 15:07:00 -07001488 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1489 struct zone *zone = lruvec_zone(lruvec);
Hugh Dickins3f797682012-01-12 17:20:07 -08001490 LIST_HEAD(pages_to_free);
Mel Gorman66635622010-08-09 17:19:30 -07001491
Mel Gorman66635622010-08-09 17:19:30 -07001492 /*
1493 * Put back any unfreeable pages.
1494 */
Mel Gorman66635622010-08-09 17:19:30 -07001495 while (!list_empty(page_list)) {
Hugh Dickins3f797682012-01-12 17:20:07 -08001496 struct page *page = lru_to_page(page_list);
Mel Gorman66635622010-08-09 17:19:30 -07001497 int lru;
Hugh Dickins3f797682012-01-12 17:20:07 -08001498
Sasha Levin309381fea2014-01-23 15:52:54 -08001499 VM_BUG_ON_PAGE(PageLRU(page), page);
Mel Gorman66635622010-08-09 17:19:30 -07001500 list_del(&page->lru);
Hugh Dickins39b5f292012-10-08 16:33:18 -07001501 if (unlikely(!page_evictable(page))) {
Mel Gorman66635622010-08-09 17:19:30 -07001502 spin_unlock_irq(&zone->lru_lock);
1503 putback_lru_page(page);
1504 spin_lock_irq(&zone->lru_lock);
1505 continue;
1506 }
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001507
1508 lruvec = mem_cgroup_page_lruvec(page, zone);
1509
Linus Torvalds7a608572011-01-17 14:42:19 -08001510 SetPageLRU(page);
Mel Gorman66635622010-08-09 17:19:30 -07001511 lru = page_lru(page);
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001512 add_page_to_lru_list(page, lruvec, lru);
1513
Mel Gorman66635622010-08-09 17:19:30 -07001514 if (is_active_lru(lru)) {
1515 int file = is_file_lru(lru);
Rik van Riel9992af12011-01-13 15:47:13 -08001516 int numpages = hpage_nr_pages(page);
1517 reclaim_stat->recent_rotated[file] += numpages;
Mel Gorman66635622010-08-09 17:19:30 -07001518 }
Hugh Dickins2bcf8872012-01-12 17:19:56 -08001519 if (put_page_testzero(page)) {
1520 __ClearPageLRU(page);
1521 __ClearPageActive(page);
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001522 del_page_from_lru_list(page, lruvec, lru);
Hugh Dickins2bcf8872012-01-12 17:19:56 -08001523
1524 if (unlikely(PageCompound(page))) {
1525 spin_unlock_irq(&zone->lru_lock);
Johannes Weiner747db952014-08-08 14:19:24 -07001526 mem_cgroup_uncharge(page);
Hugh Dickins2bcf8872012-01-12 17:19:56 -08001527 (*get_compound_page_dtor(page))(page);
1528 spin_lock_irq(&zone->lru_lock);
1529 } else
1530 list_add(&page->lru, &pages_to_free);
Mel Gorman66635622010-08-09 17:19:30 -07001531 }
1532 }
Mel Gorman66635622010-08-09 17:19:30 -07001533
Hugh Dickins3f797682012-01-12 17:20:07 -08001534 /*
1535 * To save our caller's stack, now use input list for pages to free.
1536 */
1537 list_splice(&pages_to_free, page_list);
Mel Gorman66635622010-08-09 17:19:30 -07001538}
1539
1540/*
NeilBrown399ba0b2014-06-04 16:07:42 -07001541 * If a kernel thread (such as nfsd for loop-back mounts) services
1542 * a backing device by writing to the page cache it sets PF_LESS_THROTTLE.
1543 * In that case we should only throttle if the backing device it is
1544 * writing to is congested. In other cases it is safe to throttle.
1545 */
1546static int current_may_throttle(void)
1547{
1548 return !(current->flags & PF_LESS_THROTTLE) ||
1549 current->backing_dev_info == NULL ||
1550 bdi_write_congested(current->backing_dev_info);
1551}
1552
1553/*
Andrew Morton1742f192006-03-22 00:08:21 -08001554 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1555 * of reclaimed pages
Linus Torvalds1da177e2005-04-16 15:20:36 -07001556 */
Mel Gorman66635622010-08-09 17:19:30 -07001557static noinline_for_stack unsigned long
Konstantin Khlebnikov1a93be02012-05-29 15:07:01 -07001558shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07001559 struct scan_control *sc, enum lru_list lru)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001560{
1561 LIST_HEAD(page_list);
KOSAKI Motohiroe247dbc2010-08-09 17:19:28 -07001562 unsigned long nr_scanned;
Andrew Morton05ff5132006-03-22 00:08:20 -08001563 unsigned long nr_reclaimed = 0;
KOSAKI Motohiroe247dbc2010-08-09 17:19:28 -07001564 unsigned long nr_taken;
Mel Gorman8e950282013-07-03 15:02:02 -07001565 unsigned long nr_dirty = 0;
1566 unsigned long nr_congested = 0;
Mel Gormane2be15f2013-07-03 15:01:57 -07001567 unsigned long nr_unqueued_dirty = 0;
Mel Gorman92df3a72011-10-31 17:07:56 -07001568 unsigned long nr_writeback = 0;
Mel Gormanb1a6f212013-07-03 15:01:58 -07001569 unsigned long nr_immediate = 0;
Konstantin Khlebnikovf3fd4a62012-05-29 15:06:54 -07001570 isolate_mode_t isolate_mode = 0;
Konstantin Khlebnikov3cb99452012-05-29 15:06:53 -07001571 int file = is_file_lru(lru);
Konstantin Khlebnikov1a93be02012-05-29 15:07:01 -07001572 struct zone *zone = lruvec_zone(lruvec);
1573 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
KOSAKI Motohiro78dc5832009-06-16 15:31:40 -07001574
Rik van Riel35cd7812009-09-21 17:01:38 -07001575 while (unlikely(too_many_isolated(zone, file, sc))) {
KOSAKI Motohiro58355c72009-10-26 16:49:35 -07001576 congestion_wait(BLK_RW_ASYNC, HZ/10);
Rik van Riel35cd7812009-09-21 17:01:38 -07001577
1578 /* We are about to die and free our memory. Return now. */
1579 if (fatal_signal_pending(current))
1580 return SWAP_CLUSTER_MAX;
1581 }
1582
Linus Torvalds1da177e2005-04-16 15:20:36 -07001583 lru_add_drain();
Minchan Kimf80c0672011-10-31 17:06:55 -07001584
1585 if (!sc->may_unmap)
Hillf Danton61317282012-03-21 16:33:48 -07001586 isolate_mode |= ISOLATE_UNMAPPED;
Minchan Kimf80c0672011-10-31 17:06:55 -07001587 if (!sc->may_writepage)
Hillf Danton61317282012-03-21 16:33:48 -07001588 isolate_mode |= ISOLATE_CLEAN;
Minchan Kimf80c0672011-10-31 17:06:55 -07001589
Linus Torvalds1da177e2005-04-16 15:20:36 -07001590 spin_lock_irq(&zone->lru_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001591
Konstantin Khlebnikov5dc35972012-05-29 15:06:58 -07001592 nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
1593 &nr_scanned, sc, isolate_mode, lru);
Konstantin Khlebnikov95d918f2012-05-29 15:06:59 -07001594
1595 __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
1596 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1597
Johannes Weiner89b5fae2012-01-12 17:17:50 -08001598 if (global_reclaim(sc)) {
Mel Gorman0d5d8232014-08-06 16:07:16 -07001599 __mod_zone_page_state(zone, NR_PAGES_SCANNED, nr_scanned);
KOSAKI Motohirob35ea172009-09-21 17:01:36 -07001600 if (current_is_kswapd())
Hugh Dickins75b00af2012-05-29 15:07:09 -07001601 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned);
KOSAKI Motohiroe247dbc2010-08-09 17:19:28 -07001602 else
Hugh Dickins75b00af2012-05-29 15:07:09 -07001603 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned);
KOSAKI Motohiroe247dbc2010-08-09 17:19:28 -07001604 }
Hillf Dantond563c052012-03-21 16:34:02 -07001605 spin_unlock_irq(&zone->lru_lock);
KOSAKI Motohiroa7312862009-09-21 17:01:37 -07001606
Hillf Dantond563c052012-03-21 16:34:02 -07001607 if (nr_taken == 0)
Mel Gorman66635622010-08-09 17:19:30 -07001608 return 0;
KOSAKI Motohiroe247dbc2010-08-09 17:19:28 -07001609
Minchan Kim02c6de82012-10-08 16:31:55 -07001610 nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
Mel Gorman8e950282013-07-03 15:02:02 -07001611 &nr_dirty, &nr_unqueued_dirty, &nr_congested,
1612 &nr_writeback, &nr_immediate,
1613 false);
KOSAKI Motohiroe247dbc2010-08-09 17:19:28 -07001614
Hugh Dickins3f797682012-01-12 17:20:07 -08001615 spin_lock_irq(&zone->lru_lock);
1616
Konstantin Khlebnikov95d918f2012-05-29 15:06:59 -07001617 reclaim_stat->recent_scanned[file] += nr_taken;
Hillf Dantond563c052012-03-21 16:34:02 -07001618
Ying Han904249a2012-04-25 16:01:48 -07001619 if (global_reclaim(sc)) {
1620 if (current_is_kswapd())
1621 __count_zone_vm_events(PGSTEAL_KSWAPD, zone,
1622 nr_reclaimed);
1623 else
1624 __count_zone_vm_events(PGSTEAL_DIRECT, zone,
1625 nr_reclaimed);
1626 }
KOSAKI Motohiroe247dbc2010-08-09 17:19:28 -07001627
Konstantin Khlebnikov27ac81d2012-05-29 15:07:00 -07001628 putback_inactive_pages(lruvec, &page_list);
Hugh Dickins3f797682012-01-12 17:20:07 -08001629
Konstantin Khlebnikov95d918f2012-05-29 15:06:59 -07001630 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
Hugh Dickins3f797682012-01-12 17:20:07 -08001631
1632 spin_unlock_irq(&zone->lru_lock);
1633
Johannes Weiner747db952014-08-08 14:19:24 -07001634 mem_cgroup_uncharge_list(&page_list);
Mel Gormanb745bc82014-06-04 16:10:22 -07001635 free_hot_cold_page_list(&page_list, true);
Mel Gormane11da5b2010-10-26 14:21:40 -07001636
Mel Gorman92df3a72011-10-31 17:07:56 -07001637 /*
1638 * If reclaim is isolating dirty pages under writeback, it implies
1639 * that the long-lived page allocation rate is exceeding the page
1640 * laundering rate. Either the global limits are not being effective
1641 * at throttling processes due to the page distribution throughout
1642 * zones or there is heavy usage of a slow backing device. The
1643 * only option is to throttle from reclaim context which is not ideal
1644 * as there is no guarantee the dirtying process is throttled in the
1645 * same way balance_dirty_pages() manages.
1646 *
Mel Gorman8e950282013-07-03 15:02:02 -07001647 * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number
1648 * of pages under pages flagged for immediate reclaim and stall if any
1649 * are encountered in the nr_immediate check below.
Mel Gorman92df3a72011-10-31 17:07:56 -07001650 */
Mel Gorman918fc712013-07-08 16:00:25 -07001651 if (nr_writeback && nr_writeback == nr_taken)
Johannes Weiner57054652014-10-09 15:28:17 -07001652 set_bit(ZONE_WRITEBACK, &zone->flags);
Mel Gorman92df3a72011-10-31 17:07:56 -07001653
Mel Gormand43006d2013-07-03 15:01:50 -07001654 /*
Tejun Heo97c93412015-05-22 18:23:36 -04001655 * Legacy memcg will stall in page writeback so avoid forcibly
1656 * stalling here.
Mel Gormand43006d2013-07-03 15:01:50 -07001657 */
Tejun Heo97c93412015-05-22 18:23:36 -04001658 if (sane_reclaim(sc)) {
Mel Gormanb1a6f212013-07-03 15:01:58 -07001659 /*
Mel Gorman8e950282013-07-03 15:02:02 -07001660 * Tag a zone as congested if all the dirty pages scanned were
1661 * backed by a congested BDI and wait_iff_congested will stall.
1662 */
1663 if (nr_dirty && nr_dirty == nr_congested)
Johannes Weiner57054652014-10-09 15:28:17 -07001664 set_bit(ZONE_CONGESTED, &zone->flags);
Mel Gorman8e950282013-07-03 15:02:02 -07001665
1666 /*
Mel Gormanb1a6f212013-07-03 15:01:58 -07001667 * If dirty pages are scanned that are not queued for IO, it
1668 * implies that flushers are not keeping up. In this case, flag
Johannes Weiner57054652014-10-09 15:28:17 -07001669 * the zone ZONE_DIRTY and kswapd will start writing pages from
1670 * reclaim context.
Mel Gormanb1a6f212013-07-03 15:01:58 -07001671 */
1672 if (nr_unqueued_dirty == nr_taken)
Johannes Weiner57054652014-10-09 15:28:17 -07001673 set_bit(ZONE_DIRTY, &zone->flags);
Mel Gormanb1a6f212013-07-03 15:01:58 -07001674
1675 /*
Linus Torvaldsb738d762014-06-08 14:17:00 -07001676 * If kswapd scans pages marked marked for immediate
1677 * reclaim and under writeback (nr_immediate), it implies
1678 * that pages are cycling through the LRU faster than
Mel Gormanb1a6f212013-07-03 15:01:58 -07001679 * they are written so also forcibly stall.
1680 */
Linus Torvaldsb738d762014-06-08 14:17:00 -07001681 if (nr_immediate && current_may_throttle())
Mel Gormanb1a6f212013-07-03 15:01:58 -07001682 congestion_wait(BLK_RW_ASYNC, HZ/10);
Mel Gormane2be15f2013-07-03 15:01:57 -07001683 }
Mel Gormand43006d2013-07-03 15:01:50 -07001684
Mel Gorman8e950282013-07-03 15:02:02 -07001685 /*
1686 * Stall direct reclaim for IO completions if underlying BDIs or zone
1687 * is congested. Allow kswapd to continue until it starts encountering
1688 * unqueued dirty pages or cycling through the LRU too quickly.
1689 */
NeilBrown399ba0b2014-06-04 16:07:42 -07001690 if (!sc->hibernation_mode && !current_is_kswapd() &&
1691 current_may_throttle())
Mel Gorman8e950282013-07-03 15:02:02 -07001692 wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
1693
yalin wangba5e9572016-01-14 15:18:48 -08001694 trace_mm_vmscan_lru_shrink_inactive(zone, nr_scanned, nr_reclaimed,
1695 sc->priority, file);
Andrew Morton05ff5132006-03-22 00:08:20 -08001696 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001697}
1698
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001699/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001700 * This moves pages from the active list to the inactive list.
1701 *
1702 * We move them the other way if the page is referenced by one or more
1703 * processes, from rmap.
1704 *
1705 * If the pages are mostly unmapped, the processing is fast and it is
1706 * appropriate to hold zone->lru_lock across the whole operation. But if
1707 * the pages are mapped, the processing is slow (page_referenced()) so we
1708 * should drop zone->lru_lock around each page. It's impossible to balance
1709 * this, so instead we remove the pages from the LRU while processing them.
1710 * It is safe to rely on PG_active against the non-LRU pages in here because
1711 * nobody will play with that bit on a non-LRU page.
1712 *
1713 * The downside is that we have to touch page->_count against each page.
1714 * But we had to alter page->flags anyway.
1715 */
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001716
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001717static void move_active_pages_to_lru(struct lruvec *lruvec,
Wu Fengguang3eb41402009-06-16 15:33:13 -07001718 struct list_head *list,
Hugh Dickins2bcf8872012-01-12 17:19:56 -08001719 struct list_head *pages_to_free,
Wu Fengguang3eb41402009-06-16 15:33:13 -07001720 enum lru_list lru)
1721{
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001722 struct zone *zone = lruvec_zone(lruvec);
Wu Fengguang3eb41402009-06-16 15:33:13 -07001723 unsigned long pgmoved = 0;
Wu Fengguang3eb41402009-06-16 15:33:13 -07001724 struct page *page;
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001725 int nr_pages;
Wu Fengguang3eb41402009-06-16 15:33:13 -07001726
Wu Fengguang3eb41402009-06-16 15:33:13 -07001727 while (!list_empty(list)) {
1728 page = lru_to_page(list);
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001729 lruvec = mem_cgroup_page_lruvec(page, zone);
Wu Fengguang3eb41402009-06-16 15:33:13 -07001730
Sasha Levin309381fea2014-01-23 15:52:54 -08001731 VM_BUG_ON_PAGE(PageLRU(page), page);
Wu Fengguang3eb41402009-06-16 15:33:13 -07001732 SetPageLRU(page);
1733
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001734 nr_pages = hpage_nr_pages(page);
1735 mem_cgroup_update_lru_size(lruvec, lru, nr_pages);
Johannes Weiner925b7672012-01-12 17:18:15 -08001736 list_move(&page->lru, &lruvec->lists[lru]);
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001737 pgmoved += nr_pages;
Wu Fengguang3eb41402009-06-16 15:33:13 -07001738
Hugh Dickins2bcf8872012-01-12 17:19:56 -08001739 if (put_page_testzero(page)) {
1740 __ClearPageLRU(page);
1741 __ClearPageActive(page);
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001742 del_page_from_lru_list(page, lruvec, lru);
Hugh Dickins2bcf8872012-01-12 17:19:56 -08001743
1744 if (unlikely(PageCompound(page))) {
1745 spin_unlock_irq(&zone->lru_lock);
Johannes Weiner747db952014-08-08 14:19:24 -07001746 mem_cgroup_uncharge(page);
Hugh Dickins2bcf8872012-01-12 17:19:56 -08001747 (*get_compound_page_dtor(page))(page);
1748 spin_lock_irq(&zone->lru_lock);
1749 } else
1750 list_add(&page->lru, pages_to_free);
Wu Fengguang3eb41402009-06-16 15:33:13 -07001751 }
1752 }
1753 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1754 if (!is_active_lru(lru))
1755 __count_vm_events(PGDEACTIVATE, pgmoved);
1756}
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001757
Hugh Dickinsf6260122012-01-12 17:20:06 -08001758static void shrink_active_list(unsigned long nr_to_scan,
Konstantin Khlebnikov1a93be02012-05-29 15:07:01 -07001759 struct lruvec *lruvec,
Johannes Weinerf16015f2012-01-12 17:17:52 -08001760 struct scan_control *sc,
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07001761 enum lru_list lru)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001762{
KOSAKI Motohiro44c241f2009-09-21 17:01:35 -07001763 unsigned long nr_taken;
Hugh Dickinsf6260122012-01-12 17:20:06 -08001764 unsigned long nr_scanned;
Wu Fengguang6fe6b7e2009-06-16 15:33:05 -07001765 unsigned long vm_flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001766 LIST_HEAD(l_hold); /* The pages which were snipped off */
Wu Fengguang8cab4752009-06-16 15:33:12 -07001767 LIST_HEAD(l_active);
Christoph Lameterb69408e2008-10-18 20:26:14 -07001768 LIST_HEAD(l_inactive);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001769 struct page *page;
Konstantin Khlebnikov1a93be02012-05-29 15:07:01 -07001770 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
KOSAKI Motohiro44c241f2009-09-21 17:01:35 -07001771 unsigned long nr_rotated = 0;
Konstantin Khlebnikovf3fd4a62012-05-29 15:06:54 -07001772 isolate_mode_t isolate_mode = 0;
Konstantin Khlebnikov3cb99452012-05-29 15:06:53 -07001773 int file = is_file_lru(lru);
Konstantin Khlebnikov1a93be02012-05-29 15:07:01 -07001774 struct zone *zone = lruvec_zone(lruvec);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001775
1776 lru_add_drain();
Minchan Kimf80c0672011-10-31 17:06:55 -07001777
1778 if (!sc->may_unmap)
Hillf Danton61317282012-03-21 16:33:48 -07001779 isolate_mode |= ISOLATE_UNMAPPED;
Minchan Kimf80c0672011-10-31 17:06:55 -07001780 if (!sc->may_writepage)
Hillf Danton61317282012-03-21 16:33:48 -07001781 isolate_mode |= ISOLATE_CLEAN;
Minchan Kimf80c0672011-10-31 17:06:55 -07001782
Linus Torvalds1da177e2005-04-16 15:20:36 -07001783 spin_lock_irq(&zone->lru_lock);
Johannes Weiner925b7672012-01-12 17:18:15 -08001784
Konstantin Khlebnikov5dc35972012-05-29 15:06:58 -07001785 nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
1786 &nr_scanned, sc, isolate_mode, lru);
Johannes Weiner89b5fae2012-01-12 17:17:50 -08001787 if (global_reclaim(sc))
Mel Gorman0d5d8232014-08-06 16:07:16 -07001788 __mod_zone_page_state(zone, NR_PAGES_SCANNED, nr_scanned);
Johannes Weiner89b5fae2012-01-12 17:17:50 -08001789
Johannes Weinerb7c46d12009-09-21 17:02:56 -07001790 reclaim_stat->recent_scanned[file] += nr_taken;
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001791
Hugh Dickinsf6260122012-01-12 17:20:06 -08001792 __count_zone_vm_events(PGREFILL, zone, nr_scanned);
Konstantin Khlebnikov3cb99452012-05-29 15:06:53 -07001793 __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
KOSAKI Motohiroa7312862009-09-21 17:01:37 -07001794 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001795 spin_unlock_irq(&zone->lru_lock);
1796
Linus Torvalds1da177e2005-04-16 15:20:36 -07001797 while (!list_empty(&l_hold)) {
1798 cond_resched();
1799 page = lru_to_page(&l_hold);
1800 list_del(&page->lru);
Rik van Riel7e9cd482008-10-18 20:26:35 -07001801
Hugh Dickins39b5f292012-10-08 16:33:18 -07001802 if (unlikely(!page_evictable(page))) {
Lee Schermerhorn894bc312008-10-18 20:26:39 -07001803 putback_lru_page(page);
1804 continue;
1805 }
1806
Mel Gormancc715d92012-03-21 16:34:00 -07001807 if (unlikely(buffer_heads_over_limit)) {
1808 if (page_has_private(page) && trylock_page(page)) {
1809 if (page_has_private(page))
1810 try_to_release_page(page, 0);
1811 unlock_page(page);
1812 }
1813 }
1814
Johannes Weinerc3ac9a82012-05-29 15:06:25 -07001815 if (page_referenced(page, 0, sc->target_mem_cgroup,
1816 &vm_flags)) {
Rik van Riel9992af12011-01-13 15:47:13 -08001817 nr_rotated += hpage_nr_pages(page);
Wu Fengguang8cab4752009-06-16 15:33:12 -07001818 /*
1819 * Identify referenced, file-backed active pages and
1820 * give them one more trip around the active list. So
1821 * that executable code get better chances to stay in
1822 * memory under moderate memory pressure. Anon pages
1823 * are not likely to be evicted by use-once streaming
1824 * IO, plus JVM can create lots of anon VM_EXEC pages,
1825 * so we ignore them here.
1826 */
Wu Fengguang41e20982009-10-26 16:49:53 -07001827 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
Wu Fengguang8cab4752009-06-16 15:33:12 -07001828 list_add(&page->lru, &l_active);
1829 continue;
1830 }
1831 }
Rik van Riel7e9cd482008-10-18 20:26:35 -07001832
KOSAKI Motohiro5205e562009-09-21 17:01:44 -07001833 ClearPageActive(page); /* we are de-activating */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001834 list_add(&page->lru, &l_inactive);
1835 }
1836
Andrew Mortonb5557492009-01-06 14:40:13 -08001837 /*
Wu Fengguang8cab4752009-06-16 15:33:12 -07001838 * Move pages back to the lru list.
Andrew Mortonb5557492009-01-06 14:40:13 -08001839 */
Johannes Weiner2a1dc502008-12-01 03:00:35 +01001840 spin_lock_irq(&zone->lru_lock);
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001841 /*
Wu Fengguang8cab4752009-06-16 15:33:12 -07001842 * Count referenced pages from currently used mappings as rotated,
1843 * even though only some of them are actually re-activated. This
1844 * helps balance scan pressure between file and anonymous pages in
Jerome Marchand7c0db9e2014-08-06 16:08:01 -07001845 * get_scan_count.
Rik van Riel7e9cd482008-10-18 20:26:35 -07001846 */
Johannes Weinerb7c46d12009-09-21 17:02:56 -07001847 reclaim_stat->recent_rotated[file] += nr_rotated;
Rik van Riel556adec2008-10-18 20:26:34 -07001848
Hugh Dickinsfa9add62012-05-29 15:07:09 -07001849 move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru);
1850 move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE);
KOSAKI Motohiroa7312862009-09-21 17:01:37 -07001851 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
Christoph Lameterf8891e52006-06-30 01:55:45 -07001852 spin_unlock_irq(&zone->lru_lock);
Hugh Dickins2bcf8872012-01-12 17:19:56 -08001853
Johannes Weiner747db952014-08-08 14:19:24 -07001854 mem_cgroup_uncharge_list(&l_hold);
Mel Gormanb745bc82014-06-04 16:10:22 -07001855 free_hot_cold_page_list(&l_hold, true);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001856}
1857
Minchan Kim74e3f3c2010-10-26 14:21:31 -07001858#ifdef CONFIG_SWAP
Yaowei Bai42e2e452015-11-05 18:47:36 -08001859static bool inactive_anon_is_low_global(struct zone *zone)
KOSAKI Motohirof89eb902009-01-07 18:08:14 -08001860{
1861 unsigned long active, inactive;
1862
1863 active = zone_page_state(zone, NR_ACTIVE_ANON);
1864 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1865
Yaowei Bai29d06bb2015-11-05 18:47:17 -08001866 return inactive * zone->inactive_ratio < active;
KOSAKI Motohirof89eb902009-01-07 18:08:14 -08001867}
1868
KOSAKI Motohiro14797e22009-01-07 18:08:18 -08001869/**
1870 * inactive_anon_is_low - check if anonymous pages need to be deactivated
Konstantin Khlebnikovc56d5c72012-05-29 15:07:00 -07001871 * @lruvec: LRU vector to check
KOSAKI Motohiro14797e22009-01-07 18:08:18 -08001872 *
1873 * Returns true if the zone does not have enough inactive anon pages,
1874 * meaning some active anon pages need to be deactivated.
1875 */
Yaowei Bai42e2e452015-11-05 18:47:36 -08001876static bool inactive_anon_is_low(struct lruvec *lruvec)
KOSAKI Motohiro14797e22009-01-07 18:08:18 -08001877{
Minchan Kim74e3f3c2010-10-26 14:21:31 -07001878 /*
1879 * If we don't have swap space, anonymous page deactivation
1880 * is pointless.
1881 */
1882 if (!total_swap_pages)
Yaowei Bai42e2e452015-11-05 18:47:36 -08001883 return false;
Minchan Kim74e3f3c2010-10-26 14:21:31 -07001884
Hugh Dickinsc3c787e2012-05-29 15:06:52 -07001885 if (!mem_cgroup_disabled())
Konstantin Khlebnikovc56d5c72012-05-29 15:07:00 -07001886 return mem_cgroup_inactive_anon_is_low(lruvec);
Johannes Weinerf16015f2012-01-12 17:17:52 -08001887
Konstantin Khlebnikovc56d5c72012-05-29 15:07:00 -07001888 return inactive_anon_is_low_global(lruvec_zone(lruvec));
KOSAKI Motohiro14797e22009-01-07 18:08:18 -08001889}
Minchan Kim74e3f3c2010-10-26 14:21:31 -07001890#else
Yaowei Bai42e2e452015-11-05 18:47:36 -08001891static inline bool inactive_anon_is_low(struct lruvec *lruvec)
Minchan Kim74e3f3c2010-10-26 14:21:31 -07001892{
Yaowei Bai42e2e452015-11-05 18:47:36 -08001893 return false;
Minchan Kim74e3f3c2010-10-26 14:21:31 -07001894}
1895#endif
KOSAKI Motohiro14797e22009-01-07 18:08:18 -08001896
Rik van Riel56e49d22009-06-16 15:32:28 -07001897/**
1898 * inactive_file_is_low - check if file pages need to be deactivated
Konstantin Khlebnikovc56d5c72012-05-29 15:07:00 -07001899 * @lruvec: LRU vector to check
Rik van Riel56e49d22009-06-16 15:32:28 -07001900 *
1901 * When the system is doing streaming IO, memory pressure here
1902 * ensures that active file pages get deactivated, until more
1903 * than half of the file pages are on the inactive list.
1904 *
1905 * Once we get to that situation, protect the system's working
1906 * set from being evicted by disabling active file page aging.
1907 *
1908 * This uses a different ratio than the anonymous pages, because
1909 * the page cache uses a use-once replacement algorithm.
1910 */
Yaowei Bai42e2e452015-11-05 18:47:36 -08001911static bool inactive_file_is_low(struct lruvec *lruvec)
Rik van Riel56e49d22009-06-16 15:32:28 -07001912{
Johannes Weinere3790142013-02-22 16:35:19 -08001913 unsigned long inactive;
1914 unsigned long active;
Rik van Riel56e49d22009-06-16 15:32:28 -07001915
Johannes Weinere3790142013-02-22 16:35:19 -08001916 inactive = get_lru_size(lruvec, LRU_INACTIVE_FILE);
1917 active = get_lru_size(lruvec, LRU_ACTIVE_FILE);
1918
1919 return active > inactive;
Rik van Riel56e49d22009-06-16 15:32:28 -07001920}
1921
Yaowei Bai42e2e452015-11-05 18:47:36 -08001922static bool inactive_list_is_low(struct lruvec *lruvec, enum lru_list lru)
Rik van Rielb39415b2009-12-14 17:59:48 -08001923{
Hugh Dickins75b00af2012-05-29 15:07:09 -07001924 if (is_file_lru(lru))
Konstantin Khlebnikovc56d5c72012-05-29 15:07:00 -07001925 return inactive_file_is_low(lruvec);
Rik van Rielb39415b2009-12-14 17:59:48 -08001926 else
Konstantin Khlebnikovc56d5c72012-05-29 15:07:00 -07001927 return inactive_anon_is_low(lruvec);
Rik van Rielb39415b2009-12-14 17:59:48 -08001928}
1929
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001930static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
Konstantin Khlebnikov1a93be02012-05-29 15:07:01 -07001931 struct lruvec *lruvec, struct scan_control *sc)
Christoph Lameterb69408e2008-10-18 20:26:14 -07001932{
Rik van Rielb39415b2009-12-14 17:59:48 -08001933 if (is_active_lru(lru)) {
Hugh Dickins75b00af2012-05-29 15:07:09 -07001934 if (inactive_list_is_low(lruvec, lru))
Konstantin Khlebnikov1a93be02012-05-29 15:07:01 -07001935 shrink_active_list(nr_to_scan, lruvec, sc, lru);
Rik van Riel556adec2008-10-18 20:26:34 -07001936 return 0;
1937 }
1938
Konstantin Khlebnikov1a93be02012-05-29 15:07:01 -07001939 return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
Christoph Lameterb69408e2008-10-18 20:26:14 -07001940}
1941
Johannes Weiner9a265112013-02-22 16:32:17 -08001942enum scan_balance {
1943 SCAN_EQUAL,
1944 SCAN_FRACT,
1945 SCAN_ANON,
1946 SCAN_FILE,
1947};
1948
Linus Torvalds1da177e2005-04-16 15:20:36 -07001949/*
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001950 * Determine how aggressively the anon and file LRU lists should be
1951 * scanned. The relative value of each set of LRU lists is determined
1952 * by looking at the fraction of the pages scanned we did rotate back
1953 * onto the active list instead of evict.
1954 *
Wanpeng Libe7bd592012-06-14 20:41:02 +08001955 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
1956 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001957 */
Johannes Weiner02695172014-08-06 16:06:17 -07001958static void get_scan_count(struct lruvec *lruvec, int swappiness,
Johannes Weiner6b4f7792014-12-12 16:56:13 -08001959 struct scan_control *sc, unsigned long *nr,
1960 unsigned long *lru_pages)
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001961{
Konstantin Khlebnikov90126372012-05-29 15:07:01 -07001962 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
Johannes Weiner9a265112013-02-22 16:32:17 -08001963 u64 fraction[2];
1964 u64 denominator = 0; /* gcc */
Konstantin Khlebnikov90126372012-05-29 15:07:01 -07001965 struct zone *zone = lruvec_zone(lruvec);
Johannes Weiner9a265112013-02-22 16:32:17 -08001966 unsigned long anon_prio, file_prio;
1967 enum scan_balance scan_balance;
Johannes Weiner0bf14572014-04-08 16:04:10 -07001968 unsigned long anon, file;
Johannes Weiner9a265112013-02-22 16:32:17 -08001969 bool force_scan = false;
1970 unsigned long ap, fp;
1971 enum lru_list lru;
Suleiman Souhlal6f04f482014-06-04 16:06:44 -07001972 bool some_scanned;
1973 int pass;
KAMEZAWA Hiroyuki246e87a2011-05-26 16:25:34 -07001974
Johannes Weinerf11c0ca2011-10-31 17:07:27 -07001975 /*
1976 * If the zone or memcg is small, nr[l] can be 0. This
1977 * results in no scanning on this priority and a potential
1978 * priority drop. Global direct reclaim can go to the next
1979 * zone and tends to have no problems. Global kswapd is for
1980 * zone balancing and it needs to scan a minimum amount. When
1981 * reclaiming for a memcg, a priority drop can cause high
1982 * latencies, so it's better to scan a minimum amount there as
1983 * well.
1984 */
Vladimir Davydov90cbc252015-02-11 15:25:55 -08001985 if (current_is_kswapd()) {
1986 if (!zone_reclaimable(zone))
1987 force_scan = true;
1988 if (!mem_cgroup_lruvec_online(lruvec))
1989 force_scan = true;
1990 }
Johannes Weiner89b5fae2012-01-12 17:17:50 -08001991 if (!global_reclaim(sc))
Johannes Weinera4d3e9e2011-09-14 16:21:52 -07001992 force_scan = true;
Shaohua Li76a33fc2010-05-24 14:32:36 -07001993
1994 /* If we have no swap space, do not bother scanning anon pages. */
Shaohua Liec8acf22013-02-22 16:34:38 -08001995 if (!sc->may_swap || (get_nr_swap_pages() <= 0)) {
Johannes Weiner9a265112013-02-22 16:32:17 -08001996 scan_balance = SCAN_FILE;
Shaohua Li76a33fc2010-05-24 14:32:36 -07001997 goto out;
1998 }
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001999
Johannes Weiner10316b32013-02-22 16:32:14 -08002000 /*
2001 * Global reclaim will swap to prevent OOM even with no
2002 * swappiness, but memcg users want to use this knob to
2003 * disable swapping for individual groups completely when
2004 * using the memory controller's swap limit feature would be
2005 * too expensive.
2006 */
Johannes Weiner02695172014-08-06 16:06:17 -07002007 if (!global_reclaim(sc) && !swappiness) {
Johannes Weiner9a265112013-02-22 16:32:17 -08002008 scan_balance = SCAN_FILE;
Johannes Weiner10316b32013-02-22 16:32:14 -08002009 goto out;
2010 }
2011
2012 /*
2013 * Do not apply any pressure balancing cleverness when the
2014 * system is close to OOM, scan both anon and file equally
2015 * (unless the swappiness setting disagrees with swapping).
2016 */
Johannes Weiner02695172014-08-06 16:06:17 -07002017 if (!sc->priority && swappiness) {
Johannes Weiner9a265112013-02-22 16:32:17 -08002018 scan_balance = SCAN_EQUAL;
Johannes Weiner10316b32013-02-22 16:32:14 -08002019 goto out;
2020 }
2021
Johannes Weiner11d16c22013-02-22 16:32:15 -08002022 /*
Johannes Weiner62376252014-05-06 12:50:07 -07002023 * Prevent the reclaimer from falling into the cache trap: as
2024 * cache pages start out inactive, every cache fault will tip
2025 * the scan balance towards the file LRU. And as the file LRU
2026 * shrinks, so does the window for rotation from references.
2027 * This means we have a runaway feedback loop where a tiny
2028 * thrashing file LRU becomes infinitely more attractive than
2029 * anon pages. Try to detect this based on file LRU size.
2030 */
2031 if (global_reclaim(sc)) {
Jerome Marchand2ab051e2014-08-06 16:08:03 -07002032 unsigned long zonefile;
2033 unsigned long zonefree;
Johannes Weiner62376252014-05-06 12:50:07 -07002034
Jerome Marchand2ab051e2014-08-06 16:08:03 -07002035 zonefree = zone_page_state(zone, NR_FREE_PAGES);
2036 zonefile = zone_page_state(zone, NR_ACTIVE_FILE) +
2037 zone_page_state(zone, NR_INACTIVE_FILE);
2038
2039 if (unlikely(zonefile + zonefree <= high_wmark_pages(zone))) {
Johannes Weiner62376252014-05-06 12:50:07 -07002040 scan_balance = SCAN_ANON;
2041 goto out;
2042 }
2043 }
2044
2045 /*
Johannes Weiner7c5bd702013-02-22 16:32:10 -08002046 * There is enough inactive page cache, do not reclaim
2047 * anything from the anonymous working set right now.
2048 */
2049 if (!inactive_file_is_low(lruvec)) {
Johannes Weiner9a265112013-02-22 16:32:17 -08002050 scan_balance = SCAN_FILE;
Johannes Weiner7c5bd702013-02-22 16:32:10 -08002051 goto out;
2052 }
2053
Johannes Weiner9a265112013-02-22 16:32:17 -08002054 scan_balance = SCAN_FRACT;
2055
Johannes Weiner7c5bd702013-02-22 16:32:10 -08002056 /*
KOSAKI Motohiro58c37f62010-08-09 17:19:51 -07002057 * With swappiness at 100, anonymous and file have the same priority.
2058 * This scanning priority is essentially the inverse of IO cost.
2059 */
Johannes Weiner02695172014-08-06 16:06:17 -07002060 anon_prio = swappiness;
Hugh Dickins75b00af2012-05-29 15:07:09 -07002061 file_prio = 200 - anon_prio;
KOSAKI Motohiro58c37f62010-08-09 17:19:51 -07002062
2063 /*
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002064 * OK, so we have swap space and a fair amount of page cache
2065 * pages. We use the recently rotated / recently scanned
2066 * ratios to determine how valuable each cache is.
2067 *
2068 * Because workloads change over time (and to avoid overflow)
2069 * we keep these statistics as a floating average, which ends
2070 * up weighing recent references more than old ones.
2071 *
2072 * anon in [0], file in [1]
2073 */
Jerome Marchand2ab051e2014-08-06 16:08:03 -07002074
2075 anon = get_lru_size(lruvec, LRU_ACTIVE_ANON) +
2076 get_lru_size(lruvec, LRU_INACTIVE_ANON);
2077 file = get_lru_size(lruvec, LRU_ACTIVE_FILE) +
2078 get_lru_size(lruvec, LRU_INACTIVE_FILE);
2079
Konstantin Khlebnikov90126372012-05-29 15:07:01 -07002080 spin_lock_irq(&zone->lru_lock);
KOSAKI Motohiro6e901572009-01-07 18:08:15 -08002081 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
KOSAKI Motohiro6e901572009-01-07 18:08:15 -08002082 reclaim_stat->recent_scanned[0] /= 2;
2083 reclaim_stat->recent_rotated[0] /= 2;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002084 }
2085
KOSAKI Motohiro6e901572009-01-07 18:08:15 -08002086 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
KOSAKI Motohiro6e901572009-01-07 18:08:15 -08002087 reclaim_stat->recent_scanned[1] /= 2;
2088 reclaim_stat->recent_rotated[1] /= 2;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002089 }
2090
2091 /*
Rik van Riel00d80892008-11-19 15:36:44 -08002092 * The amount of pressure on anon vs file pages is inversely
2093 * proportional to the fraction of recently scanned pages on
2094 * each list that were recently referenced and in active use.
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002095 */
Satoru Moriyafe350042012-05-29 15:06:47 -07002096 ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
KOSAKI Motohiro6e901572009-01-07 18:08:15 -08002097 ap /= reclaim_stat->recent_rotated[0] + 1;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002098
Satoru Moriyafe350042012-05-29 15:06:47 -07002099 fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
KOSAKI Motohiro6e901572009-01-07 18:08:15 -08002100 fp /= reclaim_stat->recent_rotated[1] + 1;
Konstantin Khlebnikov90126372012-05-29 15:07:01 -07002101 spin_unlock_irq(&zone->lru_lock);
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002102
Shaohua Li76a33fc2010-05-24 14:32:36 -07002103 fraction[0] = ap;
2104 fraction[1] = fp;
2105 denominator = ap + fp + 1;
2106out:
Suleiman Souhlal6f04f482014-06-04 16:06:44 -07002107 some_scanned = false;
2108 /* Only use force_scan on second pass. */
2109 for (pass = 0; !some_scanned && pass < 2; pass++) {
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002110 *lru_pages = 0;
Suleiman Souhlal6f04f482014-06-04 16:06:44 -07002111 for_each_evictable_lru(lru) {
2112 int file = is_file_lru(lru);
2113 unsigned long size;
2114 unsigned long scan;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002115
Suleiman Souhlal6f04f482014-06-04 16:06:44 -07002116 size = get_lru_size(lruvec, lru);
2117 scan = size >> sc->priority;
Johannes Weiner9a265112013-02-22 16:32:17 -08002118
Suleiman Souhlal6f04f482014-06-04 16:06:44 -07002119 if (!scan && pass && force_scan)
2120 scan = min(size, SWAP_CLUSTER_MAX);
Johannes Weiner9a265112013-02-22 16:32:17 -08002121
Suleiman Souhlal6f04f482014-06-04 16:06:44 -07002122 switch (scan_balance) {
2123 case SCAN_EQUAL:
2124 /* Scan lists relative to size */
2125 break;
2126 case SCAN_FRACT:
2127 /*
2128 * Scan types proportional to swappiness and
2129 * their relative recent reclaim efficiency.
2130 */
2131 scan = div64_u64(scan * fraction[file],
2132 denominator);
2133 break;
2134 case SCAN_FILE:
2135 case SCAN_ANON:
2136 /* Scan one type exclusively */
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002137 if ((scan_balance == SCAN_FILE) != file) {
2138 size = 0;
Suleiman Souhlal6f04f482014-06-04 16:06:44 -07002139 scan = 0;
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002140 }
Suleiman Souhlal6f04f482014-06-04 16:06:44 -07002141 break;
2142 default:
2143 /* Look ma, no brain */
2144 BUG();
2145 }
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002146
2147 *lru_pages += size;
Suleiman Souhlal6f04f482014-06-04 16:06:44 -07002148 nr[lru] = scan;
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002149
Johannes Weiner9a265112013-02-22 16:32:17 -08002150 /*
Suleiman Souhlal6f04f482014-06-04 16:06:44 -07002151 * Skip the second pass and don't force_scan,
2152 * if we found something to scan.
Johannes Weiner9a265112013-02-22 16:32:17 -08002153 */
Suleiman Souhlal6f04f482014-06-04 16:06:44 -07002154 some_scanned |= !!scan;
Johannes Weiner9a265112013-02-22 16:32:17 -08002155 }
Shaohua Li76a33fc2010-05-24 14:32:36 -07002156 }
Wu Fengguang6e08a362009-06-16 15:32:29 -07002157}
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002158
Mel Gorman72b252a2015-09-04 15:47:32 -07002159#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
2160static void init_tlb_ubc(void)
2161{
2162 /*
2163 * This deliberately does not clear the cpumask as it's expensive
2164 * and unnecessary. If there happens to be data in there then the
2165 * first SWAP_CLUSTER_MAX pages will send an unnecessary IPI and
2166 * then will be cleared.
2167 */
2168 current->tlb_ubc.flush_required = false;
2169}
2170#else
2171static inline void init_tlb_ubc(void)
2172{
2173}
2174#endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
2175
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002176/*
2177 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2178 */
Johannes Weiner02695172014-08-06 16:06:17 -07002179static void shrink_lruvec(struct lruvec *lruvec, int swappiness,
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002180 struct scan_control *sc, unsigned long *lru_pages)
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002181{
2182 unsigned long nr[NR_LRU_LISTS];
Mel Gormane82e0562013-07-03 15:01:44 -07002183 unsigned long targets[NR_LRU_LISTS];
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002184 unsigned long nr_to_scan;
2185 enum lru_list lru;
2186 unsigned long nr_reclaimed = 0;
2187 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
2188 struct blk_plug plug;
Mel Gorman1a501902014-06-04 16:10:49 -07002189 bool scan_adjusted;
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002190
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002191 get_scan_count(lruvec, swappiness, sc, nr, lru_pages);
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002192
Mel Gormane82e0562013-07-03 15:01:44 -07002193 /* Record the original scan target for proportional adjustments later */
2194 memcpy(targets, nr, sizeof(nr));
2195
Mel Gorman1a501902014-06-04 16:10:49 -07002196 /*
2197 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
2198 * event that can occur when there is little memory pressure e.g.
2199 * multiple streaming readers/writers. Hence, we do not abort scanning
2200 * when the requested number of pages are reclaimed when scanning at
2201 * DEF_PRIORITY on the assumption that the fact we are direct
2202 * reclaiming implies that kswapd is not keeping up and it is best to
2203 * do a batch of work at once. For memcg reclaim one check is made to
2204 * abort proportional reclaim if either the file or anon lru has already
2205 * dropped to zero at the first pass.
2206 */
2207 scan_adjusted = (global_reclaim(sc) && !current_is_kswapd() &&
2208 sc->priority == DEF_PRIORITY);
2209
Mel Gorman72b252a2015-09-04 15:47:32 -07002210 init_tlb_ubc();
2211
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002212 blk_start_plug(&plug);
2213 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
2214 nr[LRU_INACTIVE_FILE]) {
Mel Gormane82e0562013-07-03 15:01:44 -07002215 unsigned long nr_anon, nr_file, percentage;
2216 unsigned long nr_scanned;
2217
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002218 for_each_evictable_lru(lru) {
2219 if (nr[lru]) {
2220 nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
2221 nr[lru] -= nr_to_scan;
2222
2223 nr_reclaimed += shrink_list(lru, nr_to_scan,
2224 lruvec, sc);
2225 }
2226 }
Mel Gormane82e0562013-07-03 15:01:44 -07002227
2228 if (nr_reclaimed < nr_to_reclaim || scan_adjusted)
2229 continue;
2230
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002231 /*
Mel Gormane82e0562013-07-03 15:01:44 -07002232 * For kswapd and memcg, reclaim at least the number of pages
Mel Gorman1a501902014-06-04 16:10:49 -07002233 * requested. Ensure that the anon and file LRUs are scanned
Mel Gormane82e0562013-07-03 15:01:44 -07002234 * proportionally what was requested by get_scan_count(). We
2235 * stop reclaiming one LRU and reduce the amount scanning
2236 * proportional to the original scan target.
2237 */
2238 nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
2239 nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
2240
Mel Gorman1a501902014-06-04 16:10:49 -07002241 /*
2242 * It's just vindictive to attack the larger once the smaller
2243 * has gone to zero. And given the way we stop scanning the
2244 * smaller below, this makes sure that we only make one nudge
2245 * towards proportionality once we've got nr_to_reclaim.
2246 */
2247 if (!nr_file || !nr_anon)
2248 break;
2249
Mel Gormane82e0562013-07-03 15:01:44 -07002250 if (nr_file > nr_anon) {
2251 unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
2252 targets[LRU_ACTIVE_ANON] + 1;
2253 lru = LRU_BASE;
2254 percentage = nr_anon * 100 / scan_target;
2255 } else {
2256 unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
2257 targets[LRU_ACTIVE_FILE] + 1;
2258 lru = LRU_FILE;
2259 percentage = nr_file * 100 / scan_target;
2260 }
2261
2262 /* Stop scanning the smaller of the LRU */
2263 nr[lru] = 0;
2264 nr[lru + LRU_ACTIVE] = 0;
2265
2266 /*
2267 * Recalculate the other LRU scan count based on its original
2268 * scan target and the percentage scanning already complete
2269 */
2270 lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
2271 nr_scanned = targets[lru] - nr[lru];
2272 nr[lru] = targets[lru] * (100 - percentage) / 100;
2273 nr[lru] -= min(nr[lru], nr_scanned);
2274
2275 lru += LRU_ACTIVE;
2276 nr_scanned = targets[lru] - nr[lru];
2277 nr[lru] = targets[lru] * (100 - percentage) / 100;
2278 nr[lru] -= min(nr[lru], nr_scanned);
2279
2280 scan_adjusted = true;
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002281 }
2282 blk_finish_plug(&plug);
2283 sc->nr_reclaimed += nr_reclaimed;
2284
2285 /*
2286 * Even if we did not try to evict anon pages at all, we want to
2287 * rebalance the anon lru active/inactive ratio.
2288 */
2289 if (inactive_anon_is_low(lruvec))
2290 shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
2291 sc, LRU_ACTIVE_ANON);
2292
2293 throttle_vm_writeout(sc->gfp_mask);
2294}
2295
Mel Gorman23b9da52012-05-29 15:06:20 -07002296/* Use reclaim/compaction for costly allocs or under memory pressure */
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07002297static bool in_reclaim_compaction(struct scan_control *sc)
Mel Gorman23b9da52012-05-29 15:06:20 -07002298{
Kirill A. Shutemovd84da3f2012-12-11 16:00:31 -08002299 if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
Mel Gorman23b9da52012-05-29 15:06:20 -07002300 (sc->order > PAGE_ALLOC_COSTLY_ORDER ||
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07002301 sc->priority < DEF_PRIORITY - 2))
Mel Gorman23b9da52012-05-29 15:06:20 -07002302 return true;
2303
2304 return false;
2305}
2306
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002307/*
Mel Gorman23b9da52012-05-29 15:06:20 -07002308 * Reclaim/compaction is used for high-order allocation requests. It reclaims
2309 * order-0 pages before compacting the zone. should_continue_reclaim() returns
2310 * true if more pages should be reclaimed such that when the page allocator
2311 * calls try_to_compact_zone() that it will have enough free pages to succeed.
2312 * It will give up earlier than that if there is difficulty reclaiming pages.
Mel Gorman3e7d3442011-01-13 15:45:56 -08002313 */
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002314static inline bool should_continue_reclaim(struct zone *zone,
Mel Gorman3e7d3442011-01-13 15:45:56 -08002315 unsigned long nr_reclaimed,
2316 unsigned long nr_scanned,
2317 struct scan_control *sc)
2318{
2319 unsigned long pages_for_compaction;
2320 unsigned long inactive_lru_pages;
2321
2322 /* If not in reclaim/compaction mode, stop */
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07002323 if (!in_reclaim_compaction(sc))
Mel Gorman3e7d3442011-01-13 15:45:56 -08002324 return false;
2325
Mel Gorman28765922011-02-25 14:44:20 -08002326 /* Consider stopping depending on scan and reclaim activity */
2327 if (sc->gfp_mask & __GFP_REPEAT) {
2328 /*
2329 * For __GFP_REPEAT allocations, stop reclaiming if the
2330 * full LRU list has been scanned and we are still failing
2331 * to reclaim pages. This full LRU scan is potentially
2332 * expensive but a __GFP_REPEAT caller really wants to succeed
2333 */
2334 if (!nr_reclaimed && !nr_scanned)
2335 return false;
2336 } else {
2337 /*
2338 * For non-__GFP_REPEAT allocations which can presumably
2339 * fail without consequence, stop if we failed to reclaim
2340 * any pages from the last SWAP_CLUSTER_MAX number of
2341 * pages that were scanned. This will return to the
2342 * caller faster at the risk reclaim/compaction and
2343 * the resulting allocation attempt fails
2344 */
2345 if (!nr_reclaimed)
2346 return false;
2347 }
Mel Gorman3e7d3442011-01-13 15:45:56 -08002348
2349 /*
2350 * If we have not reclaimed enough pages for compaction and the
2351 * inactive lists are large enough, continue reclaiming
2352 */
2353 pages_for_compaction = (2UL << sc->order);
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002354 inactive_lru_pages = zone_page_state(zone, NR_INACTIVE_FILE);
Shaohua Liec8acf22013-02-22 16:34:38 -08002355 if (get_nr_swap_pages() > 0)
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002356 inactive_lru_pages += zone_page_state(zone, NR_INACTIVE_ANON);
Mel Gorman3e7d3442011-01-13 15:45:56 -08002357 if (sc->nr_reclaimed < pages_for_compaction &&
2358 inactive_lru_pages > pages_for_compaction)
2359 return true;
2360
2361 /* If compaction would go ahead or the allocation would succeed, stop */
Vlastimil Babkaebff3982014-12-10 15:43:22 -08002362 switch (compaction_suitable(zone, sc->order, 0, 0)) {
Mel Gorman3e7d3442011-01-13 15:45:56 -08002363 case COMPACT_PARTIAL:
2364 case COMPACT_CONTINUE:
2365 return false;
2366 default:
2367 return true;
2368 }
2369}
2370
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002371static bool shrink_zone(struct zone *zone, struct scan_control *sc,
2372 bool is_classzone)
Johannes Weinerf16015f2012-01-12 17:17:52 -08002373{
Vladimir Davydovcb731d62015-02-12 14:58:54 -08002374 struct reclaim_state *reclaim_state = current->reclaim_state;
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002375 unsigned long nr_reclaimed, nr_scanned;
Johannes Weiner2344d7e2014-08-06 16:06:15 -07002376 bool reclaimable = false;
Johannes Weinerf16015f2012-01-12 17:17:52 -08002377
Johannes Weiner56600482012-01-12 17:17:59 -08002378 do {
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002379 struct mem_cgroup *root = sc->target_mem_cgroup;
2380 struct mem_cgroup_reclaim_cookie reclaim = {
2381 .zone = zone,
2382 .priority = sc->priority,
2383 };
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002384 unsigned long zone_lru_pages = 0;
Andrew Morton694fbc02013-09-24 15:27:37 -07002385 struct mem_cgroup *memcg;
Johannes Weiner56600482012-01-12 17:17:59 -08002386
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002387 nr_reclaimed = sc->nr_reclaimed;
2388 nr_scanned = sc->nr_scanned;
Konstantin Khlebnikovf9be23d2012-05-29 15:07:02 -07002389
Andrew Morton694fbc02013-09-24 15:27:37 -07002390 memcg = mem_cgroup_iter(root, NULL, &reclaim);
2391 do {
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002392 unsigned long lru_pages;
Vladimir Davydovcb731d62015-02-12 14:58:54 -08002393 unsigned long scanned;
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002394 struct lruvec *lruvec;
Johannes Weiner02695172014-08-06 16:06:17 -07002395 int swappiness;
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002396
Johannes Weiner241994ed2015-02-11 15:26:06 -08002397 if (mem_cgroup_low(root, memcg)) {
2398 if (!sc->may_thrash)
2399 continue;
2400 mem_cgroup_events(memcg, MEMCG_LOW, 1);
2401 }
2402
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002403 lruvec = mem_cgroup_zone_lruvec(zone, memcg);
Johannes Weiner02695172014-08-06 16:06:17 -07002404 swappiness = mem_cgroup_swappiness(memcg);
Vladimir Davydovcb731d62015-02-12 14:58:54 -08002405 scanned = sc->nr_scanned;
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002406
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002407 shrink_lruvec(lruvec, swappiness, sc, &lru_pages);
2408 zone_lru_pages += lru_pages;
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002409
Vladimir Davydovcb731d62015-02-12 14:58:54 -08002410 if (memcg && is_classzone)
2411 shrink_slab(sc->gfp_mask, zone_to_nid(zone),
2412 memcg, sc->nr_scanned - scanned,
2413 lru_pages);
2414
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002415 /*
Michal Hockoa394cb82013-02-22 16:32:30 -08002416 * Direct reclaim and kswapd have to scan all memory
2417 * cgroups to fulfill the overall scan target for the
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002418 * zone.
Michal Hockoa394cb82013-02-22 16:32:30 -08002419 *
2420 * Limit reclaim, on the other hand, only cares about
2421 * nr_to_reclaim pages to be reclaimed and it will
2422 * retry with decreasing priority if one round over the
2423 * whole hierarchy is not sufficient.
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002424 */
Michal Hockoa394cb82013-02-22 16:32:30 -08002425 if (!global_reclaim(sc) &&
2426 sc->nr_reclaimed >= sc->nr_to_reclaim) {
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002427 mem_cgroup_iter_break(root, memcg);
2428 break;
2429 }
Johannes Weiner241994ed2015-02-11 15:26:06 -08002430 } while ((memcg = mem_cgroup_iter(root, memcg, &reclaim)));
Anton Vorontsov70ddf632013-04-29 15:08:31 -07002431
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002432 /*
2433 * Shrink the slab caches in the same proportion that
2434 * the eligible LRU pages were scanned.
2435 */
Vladimir Davydovcb731d62015-02-12 14:58:54 -08002436 if (global_reclaim(sc) && is_classzone)
2437 shrink_slab(sc->gfp_mask, zone_to_nid(zone), NULL,
2438 sc->nr_scanned - nr_scanned,
2439 zone_lru_pages);
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002440
Vladimir Davydovcb731d62015-02-12 14:58:54 -08002441 if (reclaim_state) {
2442 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2443 reclaim_state->reclaimed_slab = 0;
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002444 }
2445
Anton Vorontsov70ddf632013-04-29 15:08:31 -07002446 vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
2447 sc->nr_scanned - nr_scanned,
2448 sc->nr_reclaimed - nr_reclaimed);
2449
Johannes Weiner2344d7e2014-08-06 16:06:15 -07002450 if (sc->nr_reclaimed - nr_reclaimed)
2451 reclaimable = true;
2452
Johannes Weiner9b4f98c2013-02-22 16:32:19 -08002453 } while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed,
2454 sc->nr_scanned - nr_scanned, sc));
Johannes Weiner2344d7e2014-08-06 16:06:15 -07002455
2456 return reclaimable;
Johannes Weinerf16015f2012-01-12 17:17:52 -08002457}
2458
Vlastimil Babka53853e22014-10-09 15:27:02 -07002459/*
2460 * Returns true if compaction should go ahead for a high-order request, or
2461 * the high-order allocation would succeed without compaction.
2462 */
Johannes Weiner0b064962014-08-06 16:06:12 -07002463static inline bool compaction_ready(struct zone *zone, int order)
Mel Gormanfe4b1b22012-01-12 17:19:45 -08002464{
2465 unsigned long balance_gap, watermark;
2466 bool watermark_ok;
2467
Mel Gormanfe4b1b22012-01-12 17:19:45 -08002468 /*
2469 * Compaction takes time to run and there are potentially other
2470 * callers using the pages just freed. Continue reclaiming until
2471 * there is a buffer of free pages available to give compaction
2472 * a reasonable chance of completing and allocating the page
2473 */
Jianyu Zhan4be89a32014-06-04 16:10:38 -07002474 balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP(
2475 zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO));
Johannes Weiner0b064962014-08-06 16:06:12 -07002476 watermark = high_wmark_pages(zone) + balance_gap + (2UL << order);
Mel Gormane2b19192015-11-06 16:28:09 -08002477 watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0);
Mel Gormanfe4b1b22012-01-12 17:19:45 -08002478
2479 /*
2480 * If compaction is deferred, reclaim up to a point where
2481 * compaction will have a chance of success when re-enabled
2482 */
Johannes Weiner0b064962014-08-06 16:06:12 -07002483 if (compaction_deferred(zone, order))
Mel Gormanfe4b1b22012-01-12 17:19:45 -08002484 return watermark_ok;
2485
Vlastimil Babka53853e22014-10-09 15:27:02 -07002486 /*
2487 * If compaction is not ready to start and allocation is not likely
2488 * to succeed without it, then keep reclaiming.
2489 */
Vlastimil Babkaebff3982014-12-10 15:43:22 -08002490 if (compaction_suitable(zone, order, 0, 0) == COMPACT_SKIPPED)
Mel Gormanfe4b1b22012-01-12 17:19:45 -08002491 return false;
2492
2493 return watermark_ok;
2494}
2495
Linus Torvalds1da177e2005-04-16 15:20:36 -07002496/*
2497 * This is the direct reclaim path, for page-allocating processes. We only
2498 * try to reclaim pages from zones which will satisfy the caller's allocation
2499 * request.
2500 *
Mel Gorman41858962009-06-16 15:32:12 -07002501 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2502 * Because:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002503 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2504 * allocation or
Mel Gorman41858962009-06-16 15:32:12 -07002505 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2506 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2507 * zone defense algorithm.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002508 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07002509 * If a zone is deemed to be full of pinned pages then just give it a light
2510 * scan then give up on it.
Johannes Weiner2344d7e2014-08-06 16:06:15 -07002511 *
2512 * Returns true if a zone was reclaimable.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002513 */
Johannes Weiner2344d7e2014-08-06 16:06:15 -07002514static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002515{
Mel Gormandd1a2392008-04-28 02:12:17 -07002516 struct zoneref *z;
Mel Gorman54a6eb52008-04-28 02:12:16 -07002517 struct zone *zone;
Andrew Morton0608f432013-09-24 15:27:41 -07002518 unsigned long nr_soft_reclaimed;
2519 unsigned long nr_soft_scanned;
Weijie Yang619d0d762014-04-07 15:36:59 -07002520 gfp_t orig_mask;
Weijie Yang9bbc04e2014-04-07 15:37:00 -07002521 enum zone_type requested_highidx = gfp_zone(sc->gfp_mask);
Johannes Weiner2344d7e2014-08-06 16:06:15 -07002522 bool reclaimable = false;
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08002523
Mel Gormancc715d92012-03-21 16:34:00 -07002524 /*
2525 * If the number of buffer_heads in the machine exceeds the maximum
2526 * allowed level, force direct reclaim to scan the highmem zone as
2527 * highmem pages could be pinning lowmem pages storing buffer_heads
2528 */
Weijie Yang619d0d762014-04-07 15:36:59 -07002529 orig_mask = sc->gfp_mask;
Mel Gormancc715d92012-03-21 16:34:00 -07002530 if (buffer_heads_over_limit)
2531 sc->gfp_mask |= __GFP_HIGHMEM;
2532
Mel Gormand4debc62010-08-09 17:19:29 -07002533 for_each_zone_zonelist_nodemask(zone, z, zonelist,
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002534 requested_highidx, sc->nodemask) {
2535 enum zone_type classzone_idx;
2536
Con Kolivasf3fe6512006-01-06 00:11:15 -08002537 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002538 continue;
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002539
2540 classzone_idx = requested_highidx;
2541 while (!populated_zone(zone->zone_pgdat->node_zones +
2542 classzone_idx))
2543 classzone_idx--;
2544
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08002545 /*
2546 * Take care memory controller reclaiming has small influence
2547 * to global LRU.
2548 */
Johannes Weiner89b5fae2012-01-12 17:17:50 -08002549 if (global_reclaim(sc)) {
Vladimir Davydov344736f2014-10-20 15:50:30 +04002550 if (!cpuset_zone_allowed(zone,
2551 GFP_KERNEL | __GFP_HARDWALL))
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08002552 continue;
Vladimir Davydov65ec02c2014-04-03 14:47:20 -07002553
Lisa Du6e543d52013-09-11 14:22:36 -07002554 if (sc->priority != DEF_PRIORITY &&
2555 !zone_reclaimable(zone))
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08002556 continue; /* Let kswapd poll it */
Johannes Weiner0b064962014-08-06 16:06:12 -07002557
2558 /*
2559 * If we already have plenty of memory free for
2560 * compaction in this zone, don't free any more.
2561 * Even though compaction is invoked for any
2562 * non-zero order, only frequent costly order
2563 * reclamation is disruptive enough to become a
2564 * noticeable problem, like transparent huge
2565 * page allocations.
2566 */
2567 if (IS_ENABLED(CONFIG_COMPACTION) &&
2568 sc->order > PAGE_ALLOC_COSTLY_ORDER &&
2569 zonelist_zone_idx(z) <= requested_highidx &&
2570 compaction_ready(zone, sc->order)) {
2571 sc->compaction_ready = true;
2572 continue;
Rik van Riele0887c12011-10-31 17:09:31 -07002573 }
Johannes Weiner0b064962014-08-06 16:06:12 -07002574
Andrew Morton0608f432013-09-24 15:27:41 -07002575 /*
2576 * This steals pages from memory cgroups over softlimit
2577 * and returns the number of reclaimed pages and
2578 * scanned pages. This works for global memory pressure
2579 * and balancing, not for a memcg's limit.
2580 */
2581 nr_soft_scanned = 0;
2582 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2583 sc->order, sc->gfp_mask,
2584 &nr_soft_scanned);
2585 sc->nr_reclaimed += nr_soft_reclaimed;
2586 sc->nr_scanned += nr_soft_scanned;
Johannes Weiner2344d7e2014-08-06 16:06:15 -07002587 if (nr_soft_reclaimed)
2588 reclaimable = true;
KAMEZAWA Hiroyukiac34a1a2011-06-27 16:18:12 -07002589 /* need some check for avoid more shrink_zone() */
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08002590 }
Nick Piggin408d8542006-09-25 23:31:27 -07002591
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002592 if (shrink_zone(zone, sc, zone_idx(zone) == classzone_idx))
Johannes Weiner2344d7e2014-08-06 16:06:15 -07002593 reclaimable = true;
2594
2595 if (global_reclaim(sc) &&
2596 !reclaimable && zone_reclaimable(zone))
2597 reclaimable = true;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002598 }
Mel Gormane0c23272011-10-31 17:09:33 -07002599
Vladimir Davydov65ec02c2014-04-03 14:47:20 -07002600 /*
Weijie Yang619d0d762014-04-07 15:36:59 -07002601 * Restore to original mask to avoid the impact on the caller if we
2602 * promoted it to __GFP_HIGHMEM.
2603 */
2604 sc->gfp_mask = orig_mask;
Minchan Kimd1908362010-09-22 13:05:01 -07002605
Johannes Weiner2344d7e2014-08-06 16:06:15 -07002606 return reclaimable;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002607}
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002608
Linus Torvalds1da177e2005-04-16 15:20:36 -07002609/*
2610 * This is the main entry point to direct page reclaim.
2611 *
2612 * If a full scan of the inactive list fails to free enough memory then we
2613 * are "out of memory" and something needs to be killed.
2614 *
2615 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2616 * high - the zone may be full of dirty or under-writeback pages, which this
Jens Axboe5b0830c2009-09-23 19:37:09 +02002617 * caller can't do much about. We kick the writeback threads and take explicit
2618 * naps in the hope that some of these pages can be written. But if the
2619 * allocating task holds filesystem locks which prevent writeout this might not
2620 * work, and the allocation attempt will fail.
Nishanth Aravamudana41f24e2008-04-29 00:58:25 -07002621 *
2622 * returns: 0, if no pages reclaimed
2623 * else, the number of pages reclaimed
Linus Torvalds1da177e2005-04-16 15:20:36 -07002624 */
Mel Gormandac1d272008-04-28 02:12:12 -07002625static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
Vladimir Davydov3115cd92014-04-03 14:47:22 -07002626 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002627{
Johannes Weiner241994ed2015-02-11 15:26:06 -08002628 int initial_priority = sc->priority;
Andrew Morton69e05942006-03-22 00:08:19 -08002629 unsigned long total_scanned = 0;
KOSAKI Motohiro22fba332009-12-14 17:59:10 -08002630 unsigned long writeback_threshold;
Johannes Weiner2344d7e2014-08-06 16:06:15 -07002631 bool zones_reclaimable;
Johannes Weiner241994ed2015-02-11 15:26:06 -08002632retry:
Keika Kobayashi873b4772008-07-25 01:48:52 -07002633 delayacct_freepages_start();
2634
Johannes Weiner89b5fae2012-01-12 17:17:50 -08002635 if (global_reclaim(sc))
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08002636 count_vm_event(ALLOCSTALL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002637
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07002638 do {
Anton Vorontsov70ddf632013-04-29 15:08:31 -07002639 vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
2640 sc->priority);
Balbir Singh66e17072008-02-07 00:13:56 -08002641 sc->nr_scanned = 0;
Johannes Weiner2344d7e2014-08-06 16:06:15 -07002642 zones_reclaimable = shrink_zones(zonelist, sc);
Mel Gormane0c23272011-10-31 17:09:33 -07002643
Balbir Singh66e17072008-02-07 00:13:56 -08002644 total_scanned += sc->nr_scanned;
KOSAKI Motohirobb21c7c2010-06-04 14:15:05 -07002645 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
Johannes Weiner0b064962014-08-06 16:06:12 -07002646 break;
2647
2648 if (sc->compaction_ready)
2649 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002650
2651 /*
Minchan Kim0e50ce32013-02-22 16:35:37 -08002652 * If we're getting trouble reclaiming, start doing
2653 * writepage even in laptop mode.
2654 */
2655 if (sc->priority < DEF_PRIORITY - 2)
2656 sc->may_writepage = 1;
2657
2658 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002659 * Try to write back as many pages as we just scanned. This
2660 * tends to cause slow streaming writers to write data to the
2661 * disk smoothly, at the dirtying rate, which is nice. But
2662 * that's undesirable in laptop mode, where we *want* lumpy
2663 * writeout. So in laptop mode, write out the whole world.
2664 */
KOSAKI Motohiro22fba332009-12-14 17:59:10 -08002665 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2666 if (total_scanned > writeback_threshold) {
Curt Wohlgemuth0e175a12011-10-07 21:54:10 -06002667 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
2668 WB_REASON_TRY_TO_FREE_PAGES);
Balbir Singh66e17072008-02-07 00:13:56 -08002669 sc->may_writepage = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002670 }
Johannes Weiner0b064962014-08-06 16:06:12 -07002671 } while (--sc->priority >= 0);
KOSAKI Motohirobb21c7c2010-06-04 14:15:05 -07002672
Keika Kobayashi873b4772008-07-25 01:48:52 -07002673 delayacct_freepages_end();
2674
KOSAKI Motohirobb21c7c2010-06-04 14:15:05 -07002675 if (sc->nr_reclaimed)
2676 return sc->nr_reclaimed;
2677
Mel Gorman0cee34f2012-01-12 17:19:49 -08002678 /* Aborted reclaim to try compaction? don't OOM, then */
Johannes Weiner0b064962014-08-06 16:06:12 -07002679 if (sc->compaction_ready)
Mel Gorman73350842012-01-12 17:19:33 -08002680 return 1;
2681
Johannes Weiner241994ed2015-02-11 15:26:06 -08002682 /* Untapped cgroup reserves? Don't OOM, retry. */
2683 if (!sc->may_thrash) {
2684 sc->priority = initial_priority;
2685 sc->may_thrash = 1;
2686 goto retry;
2687 }
2688
Johannes Weiner2344d7e2014-08-06 16:06:15 -07002689 /* Any of the zones still reclaimable? Don't OOM. */
2690 if (zones_reclaimable)
KOSAKI Motohirobb21c7c2010-06-04 14:15:05 -07002691 return 1;
2692
2693 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002694}
2695
Mel Gorman55150612012-07-31 16:44:35 -07002696static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)
2697{
2698 struct zone *zone;
2699 unsigned long pfmemalloc_reserve = 0;
2700 unsigned long free_pages = 0;
2701 int i;
2702 bool wmark_ok;
2703
2704 for (i = 0; i <= ZONE_NORMAL; i++) {
2705 zone = &pgdat->node_zones[i];
Nishanth Aravamudanf012a842015-06-24 16:56:39 -07002706 if (!populated_zone(zone) ||
2707 zone_reclaimable_pages(zone) == 0)
Mel Gorman675becc2014-06-04 16:07:35 -07002708 continue;
2709
Mel Gorman55150612012-07-31 16:44:35 -07002710 pfmemalloc_reserve += min_wmark_pages(zone);
2711 free_pages += zone_page_state(zone, NR_FREE_PAGES);
2712 }
2713
Mel Gorman675becc2014-06-04 16:07:35 -07002714 /* If there are no reserves (unexpected config) then do not throttle */
2715 if (!pfmemalloc_reserve)
2716 return true;
2717
Mel Gorman55150612012-07-31 16:44:35 -07002718 wmark_ok = free_pages > pfmemalloc_reserve / 2;
2719
2720 /* kswapd must be awake if processes are being throttled */
2721 if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
2722 pgdat->classzone_idx = min(pgdat->classzone_idx,
2723 (enum zone_type)ZONE_NORMAL);
2724 wake_up_interruptible(&pgdat->kswapd_wait);
2725 }
2726
2727 return wmark_ok;
2728}
2729
2730/*
2731 * Throttle direct reclaimers if backing storage is backed by the network
2732 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
2733 * depleted. kswapd will continue to make progress and wake the processes
Mel Gorman50694c22012-11-26 16:29:48 -08002734 * when the low watermark is reached.
2735 *
2736 * Returns true if a fatal signal was delivered during throttling. If this
2737 * happens, the page allocator should not consider triggering the OOM killer.
Mel Gorman55150612012-07-31 16:44:35 -07002738 */
Mel Gorman50694c22012-11-26 16:29:48 -08002739static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
Mel Gorman55150612012-07-31 16:44:35 -07002740 nodemask_t *nodemask)
2741{
Mel Gorman675becc2014-06-04 16:07:35 -07002742 struct zoneref *z;
Mel Gorman55150612012-07-31 16:44:35 -07002743 struct zone *zone;
Mel Gorman675becc2014-06-04 16:07:35 -07002744 pg_data_t *pgdat = NULL;
Mel Gorman55150612012-07-31 16:44:35 -07002745
2746 /*
2747 * Kernel threads should not be throttled as they may be indirectly
2748 * responsible for cleaning pages necessary for reclaim to make forward
2749 * progress. kjournald for example may enter direct reclaim while
2750 * committing a transaction where throttling it could forcing other
2751 * processes to block on log_wait_commit().
2752 */
2753 if (current->flags & PF_KTHREAD)
Mel Gorman50694c22012-11-26 16:29:48 -08002754 goto out;
2755
2756 /*
2757 * If a fatal signal is pending, this process should not throttle.
2758 * It should return quickly so it can exit and free its memory
2759 */
2760 if (fatal_signal_pending(current))
2761 goto out;
Mel Gorman55150612012-07-31 16:44:35 -07002762
Mel Gorman675becc2014-06-04 16:07:35 -07002763 /*
2764 * Check if the pfmemalloc reserves are ok by finding the first node
2765 * with a usable ZONE_NORMAL or lower zone. The expectation is that
2766 * GFP_KERNEL will be required for allocating network buffers when
2767 * swapping over the network so ZONE_HIGHMEM is unusable.
2768 *
2769 * Throttling is based on the first usable node and throttled processes
2770 * wait on a queue until kswapd makes progress and wakes them. There
2771 * is an affinity then between processes waking up and where reclaim
2772 * progress has been made assuming the process wakes on the same node.
2773 * More importantly, processes running on remote nodes will not compete
2774 * for remote pfmemalloc reserves and processes on different nodes
2775 * should make reasonable progress.
2776 */
2777 for_each_zone_zonelist_nodemask(zone, z, zonelist,
Michael S. Tsirkin17636fa2015-01-26 12:58:41 -08002778 gfp_zone(gfp_mask), nodemask) {
Mel Gorman675becc2014-06-04 16:07:35 -07002779 if (zone_idx(zone) > ZONE_NORMAL)
2780 continue;
2781
2782 /* Throttle based on the first usable node */
2783 pgdat = zone->zone_pgdat;
2784 if (pfmemalloc_watermark_ok(pgdat))
2785 goto out;
2786 break;
2787 }
2788
2789 /* If no zone was usable by the allocation flags then do not throttle */
2790 if (!pgdat)
Mel Gorman50694c22012-11-26 16:29:48 -08002791 goto out;
Mel Gorman55150612012-07-31 16:44:35 -07002792
Mel Gorman68243e72012-07-31 16:44:39 -07002793 /* Account for the throttling */
2794 count_vm_event(PGSCAN_DIRECT_THROTTLE);
2795
Mel Gorman55150612012-07-31 16:44:35 -07002796 /*
2797 * If the caller cannot enter the filesystem, it's possible that it
2798 * is due to the caller holding an FS lock or performing a journal
2799 * transaction in the case of a filesystem like ext[3|4]. In this case,
2800 * it is not safe to block on pfmemalloc_wait as kswapd could be
2801 * blocked waiting on the same lock. Instead, throttle for up to a
2802 * second before continuing.
2803 */
2804 if (!(gfp_mask & __GFP_FS)) {
2805 wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
2806 pfmemalloc_watermark_ok(pgdat), HZ);
Mel Gorman50694c22012-11-26 16:29:48 -08002807
2808 goto check_pending;
Mel Gorman55150612012-07-31 16:44:35 -07002809 }
2810
2811 /* Throttle until kswapd wakes the process */
2812 wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
2813 pfmemalloc_watermark_ok(pgdat));
Mel Gorman50694c22012-11-26 16:29:48 -08002814
2815check_pending:
2816 if (fatal_signal_pending(current))
2817 return true;
2818
2819out:
2820 return false;
Mel Gorman55150612012-07-31 16:44:35 -07002821}
2822
Mel Gormandac1d272008-04-28 02:12:12 -07002823unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
KAMEZAWA Hiroyuki327c0e92009-03-31 15:23:31 -07002824 gfp_t gfp_mask, nodemask_t *nodemask)
Balbir Singh66e17072008-02-07 00:13:56 -08002825{
Mel Gorman33906bc2010-08-09 17:19:16 -07002826 unsigned long nr_reclaimed;
Balbir Singh66e17072008-02-07 00:13:56 -08002827 struct scan_control sc = {
KOSAKI Motohiro22fba332009-12-14 17:59:10 -08002828 .nr_to_reclaim = SWAP_CLUSTER_MAX,
Johannes Weineree814fe2014-08-06 16:06:19 -07002829 .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
2830 .order = order,
2831 .nodemask = nodemask,
2832 .priority = DEF_PRIORITY,
2833 .may_writepage = !laptop_mode,
Johannes Weinera6dc60f82009-03-31 15:19:30 -07002834 .may_unmap = 1,
KOSAKI Motohiro2e2e4252009-04-21 12:24:57 -07002835 .may_swap = 1,
Balbir Singh66e17072008-02-07 00:13:56 -08002836 };
2837
Mel Gorman55150612012-07-31 16:44:35 -07002838 /*
Mel Gorman50694c22012-11-26 16:29:48 -08002839 * Do not enter reclaim if fatal signal was delivered while throttled.
2840 * 1 is returned so that the page allocator does not OOM kill at this
2841 * point.
Mel Gorman55150612012-07-31 16:44:35 -07002842 */
Mel Gorman50694c22012-11-26 16:29:48 -08002843 if (throttle_direct_reclaim(gfp_mask, zonelist, nodemask))
Mel Gorman55150612012-07-31 16:44:35 -07002844 return 1;
2845
Mel Gorman33906bc2010-08-09 17:19:16 -07002846 trace_mm_vmscan_direct_reclaim_begin(order,
2847 sc.may_writepage,
2848 gfp_mask);
2849
Vladimir Davydov3115cd92014-04-03 14:47:22 -07002850 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
Mel Gorman33906bc2010-08-09 17:19:16 -07002851
2852 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2853
2854 return nr_reclaimed;
Balbir Singh66e17072008-02-07 00:13:56 -08002855}
2856
Andrew Mortonc255a452012-07-31 16:43:02 -07002857#ifdef CONFIG_MEMCG
Balbir Singh66e17072008-02-07 00:13:56 -08002858
Johannes Weiner72835c82012-01-12 17:18:32 -08002859unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
Balbir Singh4e416952009-09-23 15:56:39 -07002860 gfp_t gfp_mask, bool noswap,
Ying Han0ae5e892011-05-26 16:25:25 -07002861 struct zone *zone,
2862 unsigned long *nr_scanned)
Balbir Singh4e416952009-09-23 15:56:39 -07002863{
2864 struct scan_control sc = {
KOSAKI Motohirob8f5c562010-08-10 18:03:02 -07002865 .nr_to_reclaim = SWAP_CLUSTER_MAX,
Johannes Weineree814fe2014-08-06 16:06:19 -07002866 .target_mem_cgroup = memcg,
Balbir Singh4e416952009-09-23 15:56:39 -07002867 .may_writepage = !laptop_mode,
2868 .may_unmap = 1,
2869 .may_swap = !noswap,
Balbir Singh4e416952009-09-23 15:56:39 -07002870 };
Konstantin Khlebnikovf9be23d2012-05-29 15:07:02 -07002871 struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
Johannes Weiner02695172014-08-06 16:06:17 -07002872 int swappiness = mem_cgroup_swappiness(memcg);
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002873 unsigned long lru_pages;
Ying Han0ae5e892011-05-26 16:25:25 -07002874
Balbir Singh4e416952009-09-23 15:56:39 -07002875 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2876 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
KOSAKI Motohirobdce6d92010-08-09 17:19:56 -07002877
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07002878 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
KOSAKI Motohirobdce6d92010-08-09 17:19:56 -07002879 sc.may_writepage,
2880 sc.gfp_mask);
2881
Balbir Singh4e416952009-09-23 15:56:39 -07002882 /*
2883 * NOTE: Although we can get the priority field, using it
2884 * here is not a good idea, since it limits the pages we can scan.
2885 * if we don't reclaim here, the shrink_zone from balance_pgdat
2886 * will pick up pages from other mem cgroup's as well. We hack
2887 * the priority and make it zero.
2888 */
Johannes Weiner6b4f7792014-12-12 16:56:13 -08002889 shrink_lruvec(lruvec, swappiness, &sc, &lru_pages);
KOSAKI Motohirobdce6d92010-08-09 17:19:56 -07002890
2891 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2892
Ying Han0ae5e892011-05-26 16:25:25 -07002893 *nr_scanned = sc.nr_scanned;
Balbir Singh4e416952009-09-23 15:56:39 -07002894 return sc.nr_reclaimed;
2895}
2896
Johannes Weiner72835c82012-01-12 17:18:32 -08002897unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
Johannes Weinerb70a2a22014-10-09 15:28:56 -07002898 unsigned long nr_pages,
KOSAKI Motohiroa7885eb2009-01-07 18:08:24 -08002899 gfp_t gfp_mask,
Johannes Weinerb70a2a22014-10-09 15:28:56 -07002900 bool may_swap)
Balbir Singh66e17072008-02-07 00:13:56 -08002901{
Balbir Singh4e416952009-09-23 15:56:39 -07002902 struct zonelist *zonelist;
KOSAKI Motohirobdce6d92010-08-09 17:19:56 -07002903 unsigned long nr_reclaimed;
Ying Han889976d2011-05-26 16:25:33 -07002904 int nid;
Balbir Singh66e17072008-02-07 00:13:56 -08002905 struct scan_control sc = {
Johannes Weinerb70a2a22014-10-09 15:28:56 -07002906 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
Johannes Weineree814fe2014-08-06 16:06:19 -07002907 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2908 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2909 .target_mem_cgroup = memcg,
2910 .priority = DEF_PRIORITY,
Balbir Singh66e17072008-02-07 00:13:56 -08002911 .may_writepage = !laptop_mode,
Johannes Weinera6dc60f82009-03-31 15:19:30 -07002912 .may_unmap = 1,
Johannes Weinerb70a2a22014-10-09 15:28:56 -07002913 .may_swap = may_swap,
Ying Hana09ed5e2011-05-24 17:12:26 -07002914 };
Balbir Singh66e17072008-02-07 00:13:56 -08002915
Ying Han889976d2011-05-26 16:25:33 -07002916 /*
2917 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2918 * take care of from where we get pages. So the node where we start the
2919 * scan does not need to be the current node.
2920 */
Johannes Weiner72835c82012-01-12 17:18:32 -08002921 nid = mem_cgroup_select_victim_node(memcg);
Ying Han889976d2011-05-26 16:25:33 -07002922
2923 zonelist = NODE_DATA(nid)->node_zonelists;
KOSAKI Motohirobdce6d92010-08-09 17:19:56 -07002924
2925 trace_mm_vmscan_memcg_reclaim_begin(0,
2926 sc.may_writepage,
2927 sc.gfp_mask);
2928
Vladimir Davydov3115cd92014-04-03 14:47:22 -07002929 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
KOSAKI Motohirobdce6d92010-08-09 17:19:56 -07002930
2931 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2932
2933 return nr_reclaimed;
Balbir Singh66e17072008-02-07 00:13:56 -08002934}
2935#endif
2936
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07002937static void age_active_anon(struct zone *zone, struct scan_control *sc)
Johannes Weinerf16015f2012-01-12 17:17:52 -08002938{
Johannes Weinerb95a2f22012-01-12 17:18:06 -08002939 struct mem_cgroup *memcg;
Johannes Weinerf16015f2012-01-12 17:17:52 -08002940
Johannes Weinerb95a2f22012-01-12 17:18:06 -08002941 if (!total_swap_pages)
2942 return;
2943
2944 memcg = mem_cgroup_iter(NULL, NULL, NULL);
2945 do {
Konstantin Khlebnikovc56d5c72012-05-29 15:07:00 -07002946 struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
Johannes Weinerb95a2f22012-01-12 17:18:06 -08002947
Konstantin Khlebnikovc56d5c72012-05-29 15:07:00 -07002948 if (inactive_anon_is_low(lruvec))
Konstantin Khlebnikov1a93be02012-05-29 15:07:01 -07002949 shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07002950 sc, LRU_ACTIVE_ANON);
Johannes Weinerb95a2f22012-01-12 17:18:06 -08002951
2952 memcg = mem_cgroup_iter(NULL, memcg, NULL);
2953 } while (memcg);
Johannes Weinerf16015f2012-01-12 17:17:52 -08002954}
2955
Johannes Weiner60cefed2012-11-29 13:54:23 -08002956static bool zone_balanced(struct zone *zone, int order,
2957 unsigned long balance_gap, int classzone_idx)
2958{
2959 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) +
Mel Gormane2b19192015-11-06 16:28:09 -08002960 balance_gap, classzone_idx))
Johannes Weiner60cefed2012-11-29 13:54:23 -08002961 return false;
2962
Vlastimil Babkaebff3982014-12-10 15:43:22 -08002963 if (IS_ENABLED(CONFIG_COMPACTION) && order && compaction_suitable(zone,
2964 order, 0, classzone_idx) == COMPACT_SKIPPED)
Johannes Weiner60cefed2012-11-29 13:54:23 -08002965 return false;
2966
2967 return true;
2968}
2969
Mel Gorman1741c872011-01-13 15:46:21 -08002970/*
Zlatko Calusic4ae0a482012-12-23 15:12:54 +01002971 * pgdat_balanced() is used when checking if a node is balanced.
2972 *
2973 * For order-0, all zones must be balanced!
2974 *
2975 * For high-order allocations only zones that meet watermarks and are in a
2976 * zone allowed by the callers classzone_idx are added to balanced_pages. The
2977 * total of balanced pages must be at least 25% of the zones allowed by
2978 * classzone_idx for the node to be considered balanced. Forcing all zones to
2979 * be balanced for high orders can cause excessive reclaim when there are
2980 * imbalanced zones.
Mel Gorman1741c872011-01-13 15:46:21 -08002981 * The choice of 25% is due to
2982 * o a 16M DMA zone that is balanced will not balance a zone on any
2983 * reasonable sized machine
2984 * o On all other machines, the top zone must be at least a reasonable
Lucas De Marchi25985ed2011-03-30 22:57:33 -03002985 * percentage of the middle zones. For example, on 32-bit x86, highmem
Mel Gorman1741c872011-01-13 15:46:21 -08002986 * would need to be at least 256M for it to be balance a whole node.
2987 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2988 * to balance a node on its own. These seemed like reasonable ratios.
2989 */
Zlatko Calusic4ae0a482012-12-23 15:12:54 +01002990static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
Mel Gorman1741c872011-01-13 15:46:21 -08002991{
Jiang Liub40da042013-02-22 16:33:52 -08002992 unsigned long managed_pages = 0;
Zlatko Calusic4ae0a482012-12-23 15:12:54 +01002993 unsigned long balanced_pages = 0;
Mel Gorman1741c872011-01-13 15:46:21 -08002994 int i;
2995
Zlatko Calusic4ae0a482012-12-23 15:12:54 +01002996 /* Check the watermark levels */
2997 for (i = 0; i <= classzone_idx; i++) {
2998 struct zone *zone = pgdat->node_zones + i;
Mel Gorman1741c872011-01-13 15:46:21 -08002999
Zlatko Calusic4ae0a482012-12-23 15:12:54 +01003000 if (!populated_zone(zone))
3001 continue;
3002
Jiang Liub40da042013-02-22 16:33:52 -08003003 managed_pages += zone->managed_pages;
Zlatko Calusic4ae0a482012-12-23 15:12:54 +01003004
3005 /*
3006 * A special case here:
3007 *
3008 * balance_pgdat() skips over all_unreclaimable after
3009 * DEF_PRIORITY. Effectively, it considers them balanced so
3010 * they must be considered balanced here as well!
3011 */
Lisa Du6e543d52013-09-11 14:22:36 -07003012 if (!zone_reclaimable(zone)) {
Jiang Liub40da042013-02-22 16:33:52 -08003013 balanced_pages += zone->managed_pages;
Zlatko Calusic4ae0a482012-12-23 15:12:54 +01003014 continue;
3015 }
3016
3017 if (zone_balanced(zone, order, 0, i))
Jiang Liub40da042013-02-22 16:33:52 -08003018 balanced_pages += zone->managed_pages;
Zlatko Calusic4ae0a482012-12-23 15:12:54 +01003019 else if (!order)
3020 return false;
3021 }
3022
3023 if (order)
Jiang Liub40da042013-02-22 16:33:52 -08003024 return balanced_pages >= (managed_pages >> 2);
Zlatko Calusic4ae0a482012-12-23 15:12:54 +01003025 else
3026 return true;
Mel Gorman1741c872011-01-13 15:46:21 -08003027}
3028
Mel Gorman55150612012-07-31 16:44:35 -07003029/*
3030 * Prepare kswapd for sleeping. This verifies that there are no processes
3031 * waiting in throttle_direct_reclaim() and that watermarks have been met.
3032 *
3033 * Returns true if kswapd is ready to sleep
3034 */
3035static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
Mel Gormandc83edd2011-01-13 15:46:26 -08003036 int classzone_idx)
Mel Gormanf50de2d2009-12-14 17:58:53 -08003037{
Mel Gormanf50de2d2009-12-14 17:58:53 -08003038 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
3039 if (remaining)
Mel Gorman55150612012-07-31 16:44:35 -07003040 return false;
3041
3042 /*
Vlastimil Babka9e5e3662015-01-08 14:32:40 -08003043 * The throttled processes are normally woken up in balance_pgdat() as
3044 * soon as pfmemalloc_watermark_ok() is true. But there is a potential
3045 * race between when kswapd checks the watermarks and a process gets
3046 * throttled. There is also a potential race if processes get
3047 * throttled, kswapd wakes, a large process exits thereby balancing the
3048 * zones, which causes kswapd to exit balance_pgdat() before reaching
3049 * the wake up checks. If kswapd is going to sleep, no process should
3050 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
3051 * the wake up is premature, processes will wake kswapd and get
3052 * throttled again. The difference from wake ups in balance_pgdat() is
3053 * that here we are under prepare_to_wait().
Mel Gorman55150612012-07-31 16:44:35 -07003054 */
Vlastimil Babka9e5e3662015-01-08 14:32:40 -08003055 if (waitqueue_active(&pgdat->pfmemalloc_wait))
3056 wake_up_all(&pgdat->pfmemalloc_wait);
Mel Gormanf50de2d2009-12-14 17:58:53 -08003057
Zlatko Calusic4ae0a482012-12-23 15:12:54 +01003058 return pgdat_balanced(pgdat, order, classzone_idx);
Mel Gormanf50de2d2009-12-14 17:58:53 -08003059}
3060
Linus Torvalds1da177e2005-04-16 15:20:36 -07003061/*
Mel Gorman75485362013-07-03 15:01:42 -07003062 * kswapd shrinks the zone by the number of pages required to reach
3063 * the high watermark.
Mel Gormanb8e83b92013-07-03 15:01:45 -07003064 *
3065 * Returns true if kswapd scanned at least the requested number of pages to
Mel Gorman283aba92013-07-03 15:01:51 -07003066 * reclaim or if the lack of progress was due to pages under writeback.
3067 * This is used to determine if the scanning priority needs to be raised.
Mel Gorman75485362013-07-03 15:01:42 -07003068 */
Mel Gormanb8e83b92013-07-03 15:01:45 -07003069static bool kswapd_shrink_zone(struct zone *zone,
Mel Gorman7c954f62013-07-03 15:01:54 -07003070 int classzone_idx,
Mel Gorman75485362013-07-03 15:01:42 -07003071 struct scan_control *sc,
Mel Gorman2ab44f42013-07-03 15:01:47 -07003072 unsigned long *nr_attempted)
Mel Gorman75485362013-07-03 15:01:42 -07003073{
Mel Gorman7c954f62013-07-03 15:01:54 -07003074 int testorder = sc->order;
3075 unsigned long balance_gap;
Mel Gorman7c954f62013-07-03 15:01:54 -07003076 bool lowmem_pressure;
Mel Gorman75485362013-07-03 15:01:42 -07003077
3078 /* Reclaim above the high watermark. */
3079 sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone));
Mel Gorman7c954f62013-07-03 15:01:54 -07003080
3081 /*
3082 * Kswapd reclaims only single pages with compaction enabled. Trying
3083 * too hard to reclaim until contiguous free pages have become
3084 * available can hurt performance by evicting too much useful data
3085 * from memory. Do not reclaim more than needed for compaction.
3086 */
3087 if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
Vlastimil Babkaebff3982014-12-10 15:43:22 -08003088 compaction_suitable(zone, sc->order, 0, classzone_idx)
3089 != COMPACT_SKIPPED)
Mel Gorman7c954f62013-07-03 15:01:54 -07003090 testorder = 0;
3091
3092 /*
3093 * We put equal pressure on every zone, unless one zone has way too
3094 * many pages free already. The "too many pages" is defined as the
3095 * high wmark plus a "gap" where the gap is either the low
3096 * watermark or 1% of the zone, whichever is smaller.
3097 */
Jianyu Zhan4be89a32014-06-04 16:10:38 -07003098 balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP(
3099 zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO));
Mel Gorman7c954f62013-07-03 15:01:54 -07003100
3101 /*
3102 * If there is no low memory pressure or the zone is balanced then no
3103 * reclaim is necessary
3104 */
3105 lowmem_pressure = (buffer_heads_over_limit && is_highmem(zone));
3106 if (!lowmem_pressure && zone_balanced(zone, testorder,
3107 balance_gap, classzone_idx))
3108 return true;
3109
Johannes Weiner6b4f7792014-12-12 16:56:13 -08003110 shrink_zone(zone, sc, zone_idx(zone) == classzone_idx);
Mel Gorman75485362013-07-03 15:01:42 -07003111
Mel Gorman2ab44f42013-07-03 15:01:47 -07003112 /* Account for the number of pages attempted to reclaim */
3113 *nr_attempted += sc->nr_to_reclaim;
3114
Johannes Weiner57054652014-10-09 15:28:17 -07003115 clear_bit(ZONE_WRITEBACK, &zone->flags);
Mel Gorman283aba92013-07-03 15:01:51 -07003116
Mel Gorman7c954f62013-07-03 15:01:54 -07003117 /*
3118 * If a zone reaches its high watermark, consider it to be no longer
3119 * congested. It's possible there are dirty pages backed by congested
3120 * BDIs but as pressure is relieved, speculatively avoid congestion
3121 * waits.
3122 */
Lisa Du6e543d52013-09-11 14:22:36 -07003123 if (zone_reclaimable(zone) &&
Mel Gorman7c954f62013-07-03 15:01:54 -07003124 zone_balanced(zone, testorder, 0, classzone_idx)) {
Johannes Weiner57054652014-10-09 15:28:17 -07003125 clear_bit(ZONE_CONGESTED, &zone->flags);
3126 clear_bit(ZONE_DIRTY, &zone->flags);
Mel Gorman7c954f62013-07-03 15:01:54 -07003127 }
3128
Mel Gormanb8e83b92013-07-03 15:01:45 -07003129 return sc->nr_scanned >= sc->nr_to_reclaim;
Mel Gorman75485362013-07-03 15:01:42 -07003130}
3131
3132/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07003133 * For kswapd, balance_pgdat() will work across all this node's zones until
Mel Gorman41858962009-06-16 15:32:12 -07003134 * they are all at high_wmark_pages(zone).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003135 *
Mel Gorman0abdee22011-01-13 15:46:22 -08003136 * Returns the final order kswapd was reclaiming at
Linus Torvalds1da177e2005-04-16 15:20:36 -07003137 *
3138 * There is special handling here for zones which are full of pinned pages.
3139 * This can happen if the pages are all mlocked, or if they are all used by
3140 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
3141 * What we do is to detect the case where all pages in the zone have been
3142 * scanned twice and there has been zero successful reclaim. Mark the zone as
3143 * dead and from now on, only perform a short scan. Basically we're polling
3144 * the zone for when the problem goes away.
3145 *
3146 * kswapd scans the zones in the highmem->normal->dma direction. It skips
Mel Gorman41858962009-06-16 15:32:12 -07003147 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
3148 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
3149 * lower zones regardless of the number of free pages in the lower zones. This
3150 * interoperates with the page allocator fallback scheme to ensure that aging
3151 * of pages is balanced across the zones.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003152 */
Mel Gorman99504742011-01-13 15:46:20 -08003153static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
Mel Gormandc83edd2011-01-13 15:46:26 -08003154 int *classzone_idx)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003155{
Linus Torvalds1da177e2005-04-16 15:20:36 -07003156 int i;
Mel Gorman99504742011-01-13 15:46:20 -08003157 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
Andrew Morton0608f432013-09-24 15:27:41 -07003158 unsigned long nr_soft_reclaimed;
3159 unsigned long nr_soft_scanned;
Andrew Morton179e9632006-03-22 00:08:18 -08003160 struct scan_control sc = {
3161 .gfp_mask = GFP_KERNEL,
Johannes Weineree814fe2014-08-06 16:06:19 -07003162 .order = order,
Mel Gormanb8e83b92013-07-03 15:01:45 -07003163 .priority = DEF_PRIORITY,
Johannes Weineree814fe2014-08-06 16:06:19 -07003164 .may_writepage = !laptop_mode,
Johannes Weinera6dc60f82009-03-31 15:19:30 -07003165 .may_unmap = 1,
KOSAKI Motohiro2e2e4252009-04-21 12:24:57 -07003166 .may_swap = 1,
Andrew Morton179e9632006-03-22 00:08:18 -08003167 };
Christoph Lameterf8891e52006-06-30 01:55:45 -07003168 count_vm_event(PAGEOUTRUN);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003169
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07003170 do {
Mel Gorman2ab44f42013-07-03 15:01:47 -07003171 unsigned long nr_attempted = 0;
Mel Gormanb8e83b92013-07-03 15:01:45 -07003172 bool raise_priority = true;
Mel Gorman2ab44f42013-07-03 15:01:47 -07003173 bool pgdat_needs_compaction = (order > 0);
Mel Gormanb8e83b92013-07-03 15:01:45 -07003174
3175 sc.nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003176
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07003177 /*
3178 * Scan in the highmem->dma direction for the highest
3179 * zone which needs scanning
3180 */
3181 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
3182 struct zone *zone = pgdat->node_zones + i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003183
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07003184 if (!populated_zone(zone))
3185 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003186
Lisa Du6e543d52013-09-11 14:22:36 -07003187 if (sc.priority != DEF_PRIORITY &&
3188 !zone_reclaimable(zone))
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07003189 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003190
Rik van Riel556adec2008-10-18 20:26:34 -07003191 /*
3192 * Do some background aging of the anon list, to give
3193 * pages a chance to be referenced before reclaiming.
3194 */
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07003195 age_active_anon(zone, &sc);
Rik van Riel556adec2008-10-18 20:26:34 -07003196
Mel Gormancc715d92012-03-21 16:34:00 -07003197 /*
3198 * If the number of buffer_heads in the machine
3199 * exceeds the maximum allowed level and this node
3200 * has a highmem zone, force kswapd to reclaim from
3201 * it to relieve lowmem pressure.
3202 */
3203 if (buffer_heads_over_limit && is_highmem_idx(i)) {
3204 end_zone = i;
3205 break;
3206 }
3207
Johannes Weiner60cefed2012-11-29 13:54:23 -08003208 if (!zone_balanced(zone, order, 0, 0)) {
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07003209 end_zone = i;
Andrew Mortone1dbeda2006-12-06 20:32:01 -08003210 break;
Shaohua Li439423f2011-08-25 15:59:12 -07003211 } else {
Mel Gormand43006d2013-07-03 15:01:50 -07003212 /*
3213 * If balanced, clear the dirty and congested
3214 * flags
3215 */
Johannes Weiner57054652014-10-09 15:28:17 -07003216 clear_bit(ZONE_CONGESTED, &zone->flags);
3217 clear_bit(ZONE_DIRTY, &zone->flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003218 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07003219 }
Zlatko Calusicdafcb732013-02-22 16:32:34 -08003220
Mel Gormanb8e83b92013-07-03 15:01:45 -07003221 if (i < 0)
Andrew Mortone1dbeda2006-12-06 20:32:01 -08003222 goto out;
3223
Linus Torvalds1da177e2005-04-16 15:20:36 -07003224 for (i = 0; i <= end_zone; i++) {
3225 struct zone *zone = pgdat->node_zones + i;
3226
Mel Gorman2ab44f42013-07-03 15:01:47 -07003227 if (!populated_zone(zone))
3228 continue;
3229
Mel Gorman2ab44f42013-07-03 15:01:47 -07003230 /*
3231 * If any zone is currently balanced then kswapd will
3232 * not call compaction as it is expected that the
3233 * necessary pages are already available.
3234 */
3235 if (pgdat_needs_compaction &&
3236 zone_watermark_ok(zone, order,
3237 low_wmark_pages(zone),
3238 *classzone_idx, 0))
3239 pgdat_needs_compaction = false;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003240 }
3241
3242 /*
Mel Gormanb7ea3c42013-07-03 15:01:53 -07003243 * If we're getting trouble reclaiming, start doing writepage
3244 * even in laptop mode.
3245 */
3246 if (sc.priority < DEF_PRIORITY - 2)
3247 sc.may_writepage = 1;
3248
3249 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07003250 * Now scan the zone in the dma->highmem direction, stopping
3251 * at the last zone which needs scanning.
3252 *
3253 * We do this because the page allocator works in the opposite
3254 * direction. This prevents the page allocator from allocating
3255 * pages behind kswapd's direction of progress, which would
3256 * cause too much scanning of the lower zones.
3257 */
3258 for (i = 0; i <= end_zone; i++) {
3259 struct zone *zone = pgdat->node_zones + i;
3260
Con Kolivasf3fe6512006-01-06 00:11:15 -08003261 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003262 continue;
3263
Lisa Du6e543d52013-09-11 14:22:36 -07003264 if (sc.priority != DEF_PRIORITY &&
3265 !zone_reclaimable(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003266 continue;
3267
Linus Torvalds1da177e2005-04-16 15:20:36 -07003268 sc.nr_scanned = 0;
Balbir Singh4e416952009-09-23 15:56:39 -07003269
Andrew Morton0608f432013-09-24 15:27:41 -07003270 nr_soft_scanned = 0;
3271 /*
3272 * Call soft limit reclaim before calling shrink_zone.
3273 */
3274 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
3275 order, sc.gfp_mask,
3276 &nr_soft_scanned);
3277 sc.nr_reclaimed += nr_soft_reclaimed;
3278
Rik van Riel32a43302007-10-16 01:24:50 -07003279 /*
Mel Gorman7c954f62013-07-03 15:01:54 -07003280 * There should be no need to raise the scanning
3281 * priority if enough pages are already being scanned
3282 * that that high watermark would be met at 100%
3283 * efficiency.
Rik van Riel32a43302007-10-16 01:24:50 -07003284 */
Johannes Weiner6b4f7792014-12-12 16:56:13 -08003285 if (kswapd_shrink_zone(zone, end_zone,
3286 &sc, &nr_attempted))
Mel Gorman7c954f62013-07-03 15:01:54 -07003287 raise_priority = false;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003288 }
Mel Gorman55150612012-07-31 16:44:35 -07003289
3290 /*
3291 * If the low watermark is met there is no need for processes
3292 * to be throttled on pfmemalloc_wait as they should not be
3293 * able to safely make forward progress. Wake them
3294 */
3295 if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
3296 pfmemalloc_watermark_ok(pgdat))
Vlastimil Babkacfc51152015-02-11 15:25:12 -08003297 wake_up_all(&pgdat->pfmemalloc_wait);
Mel Gorman55150612012-07-31 16:44:35 -07003298
Linus Torvalds1da177e2005-04-16 15:20:36 -07003299 /*
Mel Gormanb8e83b92013-07-03 15:01:45 -07003300 * Fragmentation may mean that the system cannot be rebalanced
3301 * for high-order allocations in all zones. If twice the
3302 * allocation size has been reclaimed and the zones are still
3303 * not balanced then recheck the watermarks at order-0 to
3304 * prevent kswapd reclaiming excessively. Assume that a
3305 * process requested a high-order can direct reclaim/compact.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003306 */
Mel Gormanb8e83b92013-07-03 15:01:45 -07003307 if (order && sc.nr_reclaimed >= 2UL << order)
KOSAKI Motohiro73ce02e2009-01-06 14:40:33 -08003308 order = sc.order = 0;
3309
Mel Gormanb8e83b92013-07-03 15:01:45 -07003310 /* Check if kswapd should be suspending */
3311 if (try_to_freeze() || kthread_should_stop())
3312 break;
3313
3314 /*
Mel Gorman2ab44f42013-07-03 15:01:47 -07003315 * Compact if necessary and kswapd is reclaiming at least the
3316 * high watermark number of pages as requsted
3317 */
3318 if (pgdat_needs_compaction && sc.nr_reclaimed > nr_attempted)
3319 compact_pgdat(pgdat, order);
3320
3321 /*
Mel Gormanb8e83b92013-07-03 15:01:45 -07003322 * Raise priority if scanning rate is too low or there was no
3323 * progress in reclaiming pages
3324 */
3325 if (raise_priority || !sc.nr_reclaimed)
3326 sc.priority--;
Mel Gorman9aa41342013-07-03 15:01:48 -07003327 } while (sc.priority >= 1 &&
Mel Gormanb8e83b92013-07-03 15:01:45 -07003328 !pgdat_balanced(pgdat, order, *classzone_idx));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003329
Mel Gormanb8e83b92013-07-03 15:01:45 -07003330out:
Mel Gorman0abdee22011-01-13 15:46:22 -08003331 /*
Mel Gorman55150612012-07-31 16:44:35 -07003332 * Return the order we were reclaiming at so prepare_kswapd_sleep()
Mel Gorman0abdee22011-01-13 15:46:22 -08003333 * makes a decision on the order we were last reclaiming at. However,
3334 * if another caller entered the allocator slow path while kswapd
3335 * was awake, order will remain at the higher level
3336 */
Mel Gormandc83edd2011-01-13 15:46:26 -08003337 *classzone_idx = end_zone;
Mel Gorman0abdee22011-01-13 15:46:22 -08003338 return order;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003339}
3340
Mel Gormandc83edd2011-01-13 15:46:26 -08003341static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
KOSAKI Motohirof0bc0a62011-01-13 15:45:50 -08003342{
3343 long remaining = 0;
3344 DEFINE_WAIT(wait);
3345
3346 if (freezing(current) || kthread_should_stop())
3347 return;
3348
3349 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
3350
3351 /* Try to sleep for a short interval */
Mel Gorman55150612012-07-31 16:44:35 -07003352 if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
KOSAKI Motohirof0bc0a62011-01-13 15:45:50 -08003353 remaining = schedule_timeout(HZ/10);
3354 finish_wait(&pgdat->kswapd_wait, &wait);
3355 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
3356 }
3357
3358 /*
3359 * After a short sleep, check if it was a premature sleep. If not, then
3360 * go fully to sleep until explicitly woken up.
3361 */
Mel Gorman55150612012-07-31 16:44:35 -07003362 if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
KOSAKI Motohirof0bc0a62011-01-13 15:45:50 -08003363 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
3364
3365 /*
3366 * vmstat counters are not perfectly accurate and the estimated
3367 * value for counters such as NR_FREE_PAGES can deviate from the
3368 * true value by nr_online_cpus * threshold. To avoid the zone
3369 * watermarks being breached while under pressure, we reduce the
3370 * per-cpu vmstat threshold while kswapd is awake and restore
3371 * them before going back to sleep.
3372 */
3373 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
Aaditya Kumar1c7e7f62012-07-17 15:48:07 -07003374
Mel Gorman62997022012-10-08 16:32:47 -07003375 /*
3376 * Compaction records what page blocks it recently failed to
3377 * isolate pages from and skips them in the future scanning.
3378 * When kswapd is going to sleep, it is reasonable to assume
3379 * that pages and compaction may succeed so reset the cache.
3380 */
3381 reset_isolation_suitable(pgdat);
3382
Aaditya Kumar1c7e7f62012-07-17 15:48:07 -07003383 if (!kthread_should_stop())
3384 schedule();
3385
KOSAKI Motohirof0bc0a62011-01-13 15:45:50 -08003386 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
3387 } else {
3388 if (remaining)
3389 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
3390 else
3391 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
3392 }
3393 finish_wait(&pgdat->kswapd_wait, &wait);
3394}
3395
Linus Torvalds1da177e2005-04-16 15:20:36 -07003396/*
3397 * The background pageout daemon, started as a kernel thread
Rik van Riel4f98a2f2008-10-18 20:26:32 -07003398 * from the init process.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003399 *
3400 * This basically trickles out pages so that we have _some_
3401 * free memory available even if there is no other activity
3402 * that frees anything up. This is needed for things like routing
3403 * etc, where we otherwise might have all activity going on in
3404 * asynchronous contexts that cannot page things out.
3405 *
3406 * If there are applications that are active memory-allocators
3407 * (most normal use), this basically shouldn't matter.
3408 */
3409static int kswapd(void *p)
3410{
Mel Gorman215ddd62011-07-08 15:39:40 -07003411 unsigned long order, new_order;
Alex,Shid2ebd0f62011-10-31 17:08:39 -07003412 unsigned balanced_order;
Mel Gorman215ddd62011-07-08 15:39:40 -07003413 int classzone_idx, new_classzone_idx;
Alex,Shid2ebd0f62011-10-31 17:08:39 -07003414 int balanced_classzone_idx;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003415 pg_data_t *pgdat = (pg_data_t*)p;
3416 struct task_struct *tsk = current;
KOSAKI Motohirof0bc0a62011-01-13 15:45:50 -08003417
Linus Torvalds1da177e2005-04-16 15:20:36 -07003418 struct reclaim_state reclaim_state = {
3419 .reclaimed_slab = 0,
3420 };
Rusty Russella70f7302009-03-13 14:49:46 +10303421 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003422
Nick Piggincf40bd12009-01-21 08:12:39 +01003423 lockdep_set_current_reclaim_state(GFP_KERNEL);
3424
Rusty Russell174596a2009-01-01 10:12:29 +10303425 if (!cpumask_empty(cpumask))
Mike Travisc5f59f02008-04-04 18:11:10 -07003426 set_cpus_allowed_ptr(tsk, cpumask);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003427 current->reclaim_state = &reclaim_state;
3428
3429 /*
3430 * Tell the memory management that we're a "memory allocator",
3431 * and that if we need more memory we should get access to it
3432 * regardless (see "__alloc_pages()"). "kswapd" should
3433 * never get caught in the normal page freeing logic.
3434 *
3435 * (Kswapd normally doesn't need memory anyway, but sometimes
3436 * you need a small amount of memory in order to be able to
3437 * page out something else, and this flag essentially protects
3438 * us from recursively trying to free more memory as we're
3439 * trying to free the first piece of memory in the first place).
3440 */
Christoph Lameter930d9152006-01-08 01:00:47 -08003441 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
Rafael J. Wysocki83144182007-07-17 04:03:35 -07003442 set_freezable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003443
Mel Gorman215ddd62011-07-08 15:39:40 -07003444 order = new_order = 0;
Alex,Shid2ebd0f62011-10-31 17:08:39 -07003445 balanced_order = 0;
Mel Gorman215ddd62011-07-08 15:39:40 -07003446 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
Alex,Shid2ebd0f62011-10-31 17:08:39 -07003447 balanced_classzone_idx = classzone_idx;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003448 for ( ; ; ) {
Jeff Liu6f6313d2012-12-11 16:02:48 -08003449 bool ret;
Christoph Lameter3e1d1d22005-06-24 23:13:50 -07003450
Mel Gorman215ddd62011-07-08 15:39:40 -07003451 /*
3452 * If the last balance_pgdat was unsuccessful it's unlikely a
3453 * new request of a similar or harder type will succeed soon
3454 * so consider going to sleep on the basis we reclaimed at
3455 */
Alex,Shid2ebd0f62011-10-31 17:08:39 -07003456 if (balanced_classzone_idx >= new_classzone_idx &&
3457 balanced_order == new_order) {
Mel Gorman215ddd62011-07-08 15:39:40 -07003458 new_order = pgdat->kswapd_max_order;
3459 new_classzone_idx = pgdat->classzone_idx;
3460 pgdat->kswapd_max_order = 0;
3461 pgdat->classzone_idx = pgdat->nr_zones - 1;
3462 }
3463
Mel Gorman99504742011-01-13 15:46:20 -08003464 if (order < new_order || classzone_idx > new_classzone_idx) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003465 /*
3466 * Don't sleep if someone wants a larger 'order'
Mel Gorman99504742011-01-13 15:46:20 -08003467 * allocation or has tigher zone constraints
Linus Torvalds1da177e2005-04-16 15:20:36 -07003468 */
3469 order = new_order;
Mel Gorman99504742011-01-13 15:46:20 -08003470 classzone_idx = new_classzone_idx;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003471 } else {
Alex,Shid2ebd0f62011-10-31 17:08:39 -07003472 kswapd_try_to_sleep(pgdat, balanced_order,
3473 balanced_classzone_idx);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003474 order = pgdat->kswapd_max_order;
Mel Gorman99504742011-01-13 15:46:20 -08003475 classzone_idx = pgdat->classzone_idx;
Alex,Shif0dfcde2011-10-31 17:08:45 -07003476 new_order = order;
3477 new_classzone_idx = classzone_idx;
Mel Gorman4d405022011-01-13 15:46:23 -08003478 pgdat->kswapd_max_order = 0;
Mel Gorman215ddd62011-07-08 15:39:40 -07003479 pgdat->classzone_idx = pgdat->nr_zones - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003480 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07003481
David Rientjes8fe23e02009-12-14 17:58:33 -08003482 ret = try_to_freeze();
3483 if (kthread_should_stop())
3484 break;
3485
3486 /*
3487 * We can speed up thawing tasks if we don't call balance_pgdat
3488 * after returning from the refrigerator
3489 */
Mel Gorman33906bc2010-08-09 17:19:16 -07003490 if (!ret) {
3491 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
Alex,Shid2ebd0f62011-10-31 17:08:39 -07003492 balanced_classzone_idx = classzone_idx;
3493 balanced_order = balance_pgdat(pgdat, order,
3494 &balanced_classzone_idx);
Mel Gorman33906bc2010-08-09 17:19:16 -07003495 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07003496 }
Takamori Yamaguchib0a8cc52012-11-08 15:53:39 -08003497
Johannes Weiner71abdc12014-06-06 14:35:35 -07003498 tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD);
Takamori Yamaguchib0a8cc52012-11-08 15:53:39 -08003499 current->reclaim_state = NULL;
Johannes Weiner71abdc12014-06-06 14:35:35 -07003500 lockdep_clear_current_reclaim_state();
3501
Linus Torvalds1da177e2005-04-16 15:20:36 -07003502 return 0;
3503}
3504
3505/*
3506 * A zone is low on free memory, so wake its kswapd task to service it.
3507 */
Mel Gorman99504742011-01-13 15:46:20 -08003508void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003509{
3510 pg_data_t *pgdat;
3511
Con Kolivasf3fe6512006-01-06 00:11:15 -08003512 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003513 return;
3514
Vladimir Davydov344736f2014-10-20 15:50:30 +04003515 if (!cpuset_zone_allowed(zone, GFP_KERNEL | __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003516 return;
Mel Gorman88f5acf2011-01-13 15:45:41 -08003517 pgdat = zone->zone_pgdat;
Mel Gorman99504742011-01-13 15:46:20 -08003518 if (pgdat->kswapd_max_order < order) {
Mel Gorman88f5acf2011-01-13 15:45:41 -08003519 pgdat->kswapd_max_order = order;
Mel Gorman99504742011-01-13 15:46:20 -08003520 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
3521 }
Con Kolivas8d0986e2005-09-13 01:25:07 -07003522 if (!waitqueue_active(&pgdat->kswapd_wait))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003523 return;
Johannes Weiner892f7952013-09-11 14:20:39 -07003524 if (zone_balanced(zone, order, 0, 0))
Mel Gorman88f5acf2011-01-13 15:45:41 -08003525 return;
3526
3527 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
Con Kolivas8d0986e2005-09-13 01:25:07 -07003528 wake_up_interruptible(&pgdat->kswapd_wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003529}
3530
Rafael J. Wysockic6f37f12009-05-24 22:16:31 +02003531#ifdef CONFIG_HIBERNATION
Linus Torvalds1da177e2005-04-16 15:20:36 -07003532/*
KOSAKI Motohiro7b517552009-12-14 17:59:12 -08003533 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07003534 * freed pages.
3535 *
3536 * Rather than trying to age LRUs the aim is to preserve the overall
3537 * LRU order by reclaiming preferentially
3538 * inactive > active > active referenced > active mapped
Linus Torvalds1da177e2005-04-16 15:20:36 -07003539 */
KOSAKI Motohiro7b517552009-12-14 17:59:12 -08003540unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003541{
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07003542 struct reclaim_state reclaim_state;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07003543 struct scan_control sc = {
KOSAKI Motohiro7b517552009-12-14 17:59:12 -08003544 .nr_to_reclaim = nr_to_reclaim,
Johannes Weineree814fe2014-08-06 16:06:19 -07003545 .gfp_mask = GFP_HIGHUSER_MOVABLE,
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07003546 .priority = DEF_PRIORITY,
Johannes Weineree814fe2014-08-06 16:06:19 -07003547 .may_writepage = 1,
3548 .may_unmap = 1,
3549 .may_swap = 1,
3550 .hibernation_mode = 1,
Linus Torvalds1da177e2005-04-16 15:20:36 -07003551 };
Ying Hana09ed5e2011-05-24 17:12:26 -07003552 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
KOSAKI Motohiro7b517552009-12-14 17:59:12 -08003553 struct task_struct *p = current;
3554 unsigned long nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003555
KOSAKI Motohiro7b517552009-12-14 17:59:12 -08003556 p->flags |= PF_MEMALLOC;
3557 lockdep_set_current_reclaim_state(sc.gfp_mask);
3558 reclaim_state.reclaimed_slab = 0;
3559 p->reclaim_state = &reclaim_state;
Andrew Morton69e05942006-03-22 00:08:19 -08003560
Vladimir Davydov3115cd92014-04-03 14:47:22 -07003561 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07003562
KOSAKI Motohiro7b517552009-12-14 17:59:12 -08003563 p->reclaim_state = NULL;
3564 lockdep_clear_current_reclaim_state();
3565 p->flags &= ~PF_MEMALLOC;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07003566
KOSAKI Motohiro7b517552009-12-14 17:59:12 -08003567 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003568}
Rafael J. Wysockic6f37f12009-05-24 22:16:31 +02003569#endif /* CONFIG_HIBERNATION */
Linus Torvalds1da177e2005-04-16 15:20:36 -07003570
Linus Torvalds1da177e2005-04-16 15:20:36 -07003571/* It's optimal to keep kswapds on the same CPUs as their memory, but
3572 not required for correctness. So if the last cpu in a node goes
3573 away, we get changed to run anywhere: as the first one comes back,
3574 restore their cpu bindings. */
Greg Kroah-Hartmanfcb35a92012-12-21 15:01:06 -08003575static int cpu_callback(struct notifier_block *nfb, unsigned long action,
3576 void *hcpu)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003577{
Yasunori Goto58c0a4a2007-10-16 01:25:40 -07003578 int nid;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003579
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07003580 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
Lai Jiangshan48fb2e22012-12-12 13:51:43 -08003581 for_each_node_state(nid, N_MEMORY) {
Mike Travisc5f59f02008-04-04 18:11:10 -07003582 pg_data_t *pgdat = NODE_DATA(nid);
Rusty Russella70f7302009-03-13 14:49:46 +10303583 const struct cpumask *mask;
3584
3585 mask = cpumask_of_node(pgdat->node_id);
Mike Travisc5f59f02008-04-04 18:11:10 -07003586
Rusty Russell3e597942009-01-01 10:12:24 +10303587 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003588 /* One of our CPUs online: restore mask */
Mike Travisc5f59f02008-04-04 18:11:10 -07003589 set_cpus_allowed_ptr(pgdat->kswapd, mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003590 }
3591 }
3592 return NOTIFY_OK;
3593}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003594
Yasunori Goto3218ae12006-06-27 02:53:33 -07003595/*
3596 * This kswapd start function will be called by init and node-hot-add.
3597 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3598 */
3599int kswapd_run(int nid)
3600{
3601 pg_data_t *pgdat = NODE_DATA(nid);
3602 int ret = 0;
3603
3604 if (pgdat->kswapd)
3605 return 0;
3606
3607 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
3608 if (IS_ERR(pgdat->kswapd)) {
3609 /* failure at boot is fatal */
3610 BUG_ON(system_state == SYSTEM_BOOTING);
Gavin Shand5dc0ad2012-10-08 16:29:27 -07003611 pr_err("Failed to start kswapd on node %d\n", nid);
3612 ret = PTR_ERR(pgdat->kswapd);
Xishi Qiud72515b2013-04-17 15:58:34 -07003613 pgdat->kswapd = NULL;
Yasunori Goto3218ae12006-06-27 02:53:33 -07003614 }
3615 return ret;
3616}
3617
David Rientjes8fe23e02009-12-14 17:58:33 -08003618/*
Jiang Liud8adde12012-07-11 14:01:52 -07003619 * Called by memory hotplug when all memory in a node is offlined. Caller must
Vladimir Davydovbfc8c902014-06-04 16:07:18 -07003620 * hold mem_hotplug_begin/end().
David Rientjes8fe23e02009-12-14 17:58:33 -08003621 */
3622void kswapd_stop(int nid)
3623{
3624 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
3625
Jiang Liud8adde12012-07-11 14:01:52 -07003626 if (kswapd) {
David Rientjes8fe23e02009-12-14 17:58:33 -08003627 kthread_stop(kswapd);
Jiang Liud8adde12012-07-11 14:01:52 -07003628 NODE_DATA(nid)->kswapd = NULL;
3629 }
David Rientjes8fe23e02009-12-14 17:58:33 -08003630}
3631
Linus Torvalds1da177e2005-04-16 15:20:36 -07003632static int __init kswapd_init(void)
3633{
Yasunori Goto3218ae12006-06-27 02:53:33 -07003634 int nid;
Andrew Morton69e05942006-03-22 00:08:19 -08003635
Linus Torvalds1da177e2005-04-16 15:20:36 -07003636 swap_setup();
Lai Jiangshan48fb2e22012-12-12 13:51:43 -08003637 for_each_node_state(nid, N_MEMORY)
Yasunori Goto3218ae12006-06-27 02:53:33 -07003638 kswapd_run(nid);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003639 hotcpu_notifier(cpu_callback, 0);
3640 return 0;
3641}
3642
3643module_init(kswapd_init)
Christoph Lameter9eeff232006-01-18 17:42:31 -08003644
3645#ifdef CONFIG_NUMA
3646/*
3647 * Zone reclaim mode
3648 *
3649 * If non-zero call zone_reclaim when the number of free pages falls below
3650 * the watermarks.
Christoph Lameter9eeff232006-01-18 17:42:31 -08003651 */
3652int zone_reclaim_mode __read_mostly;
3653
Christoph Lameter1b2ffb72006-02-01 03:05:34 -08003654#define RECLAIM_OFF 0
Fernando Luis Vazquez Cao7d034312008-07-29 22:33:41 -07003655#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
Christoph Lameter1b2ffb72006-02-01 03:05:34 -08003656#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
Zhihui Zhang95bbc0c2015-06-24 16:56:42 -07003657#define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */
Christoph Lameter1b2ffb72006-02-01 03:05:34 -08003658
Christoph Lameter9eeff232006-01-18 17:42:31 -08003659/*
Christoph Lametera92f7122006-02-01 03:05:32 -08003660 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3661 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3662 * a zone.
3663 */
3664#define ZONE_RECLAIM_PRIORITY 4
3665
Christoph Lameter9eeff232006-01-18 17:42:31 -08003666/*
Christoph Lameter96146342006-07-03 00:24:13 -07003667 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3668 * occur.
3669 */
3670int sysctl_min_unmapped_ratio = 1;
3671
3672/*
Christoph Lameter0ff38492006-09-25 23:31:52 -07003673 * If the number of slab pages in a zone grows beyond this percentage then
3674 * slab reclaim needs to occur.
3675 */
3676int sysctl_min_slab_ratio = 5;
3677
Mel Gorman90afa5d2009-06-16 15:33:20 -07003678static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3679{
3680 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3681 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3682 zone_page_state(zone, NR_ACTIVE_FILE);
3683
3684 /*
3685 * It's possible for there to be more file mapped pages than
3686 * accounted for by the pages on the file LRU lists because
3687 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3688 */
3689 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3690}
3691
3692/* Work out how many page cache pages we can reclaim in this reclaim_mode */
Alexandru Moised031a152015-11-05 18:48:08 -08003693static unsigned long zone_pagecache_reclaimable(struct zone *zone)
Mel Gorman90afa5d2009-06-16 15:33:20 -07003694{
Alexandru Moised031a152015-11-05 18:48:08 -08003695 unsigned long nr_pagecache_reclaimable;
3696 unsigned long delta = 0;
Mel Gorman90afa5d2009-06-16 15:33:20 -07003697
3698 /*
Zhihui Zhang95bbc0c2015-06-24 16:56:42 -07003699 * If RECLAIM_UNMAP is set, then all file pages are considered
Mel Gorman90afa5d2009-06-16 15:33:20 -07003700 * potentially reclaimable. Otherwise, we have to worry about
3701 * pages like swapcache and zone_unmapped_file_pages() provides
3702 * a better estimate
3703 */
Zhihui Zhang95bbc0c2015-06-24 16:56:42 -07003704 if (zone_reclaim_mode & RECLAIM_UNMAP)
Mel Gorman90afa5d2009-06-16 15:33:20 -07003705 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3706 else
3707 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3708
3709 /* If we can't clean pages, remove dirty pages from consideration */
3710 if (!(zone_reclaim_mode & RECLAIM_WRITE))
3711 delta += zone_page_state(zone, NR_FILE_DIRTY);
3712
3713 /* Watch for any possible underflows due to delta */
3714 if (unlikely(delta > nr_pagecache_reclaimable))
3715 delta = nr_pagecache_reclaimable;
3716
3717 return nr_pagecache_reclaimable - delta;
3718}
3719
Christoph Lameter0ff38492006-09-25 23:31:52 -07003720/*
Christoph Lameter9eeff232006-01-18 17:42:31 -08003721 * Try to free up some pages from this zone through reclaim.
3722 */
Andrew Morton179e9632006-03-22 00:08:18 -08003723static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
Christoph Lameter9eeff232006-01-18 17:42:31 -08003724{
Christoph Lameter7fb2d462006-03-22 00:08:22 -08003725 /* Minimum pages needed in order to stay on node */
Andrew Morton69e05942006-03-22 00:08:19 -08003726 const unsigned long nr_pages = 1 << order;
Christoph Lameter9eeff232006-01-18 17:42:31 -08003727 struct task_struct *p = current;
3728 struct reclaim_state reclaim_state;
Andrew Morton179e9632006-03-22 00:08:18 -08003729 struct scan_control sc = {
Andrew Morton62b726c2013-02-22 16:32:24 -08003730 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
Ming Lei21caf2f2013-02-22 16:34:08 -08003731 .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
Johannes Weinerbd2f6192009-03-31 15:19:38 -07003732 .order = order,
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07003733 .priority = ZONE_RECLAIM_PRIORITY,
Johannes Weineree814fe2014-08-06 16:06:19 -07003734 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
Zhihui Zhang95bbc0c2015-06-24 16:56:42 -07003735 .may_unmap = !!(zone_reclaim_mode & RECLAIM_UNMAP),
Johannes Weineree814fe2014-08-06 16:06:19 -07003736 .may_swap = 1,
Andrew Morton179e9632006-03-22 00:08:18 -08003737 };
Christoph Lameter9eeff232006-01-18 17:42:31 -08003738
Christoph Lameter9eeff232006-01-18 17:42:31 -08003739 cond_resched();
Christoph Lameterd4f77962006-02-24 13:04:22 -08003740 /*
Zhihui Zhang95bbc0c2015-06-24 16:56:42 -07003741 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
Christoph Lameterd4f77962006-02-24 13:04:22 -08003742 * and we also need to be able to write out pages for RECLAIM_WRITE
Zhihui Zhang95bbc0c2015-06-24 16:56:42 -07003743 * and RECLAIM_UNMAP.
Christoph Lameterd4f77962006-02-24 13:04:22 -08003744 */
3745 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
KOSAKI Motohiro76ca5422010-03-05 13:41:47 -08003746 lockdep_set_current_reclaim_state(gfp_mask);
Christoph Lameter9eeff232006-01-18 17:42:31 -08003747 reclaim_state.reclaimed_slab = 0;
3748 p->reclaim_state = &reclaim_state;
Christoph Lameterc84db232006-02-01 03:05:29 -08003749
Mel Gorman90afa5d2009-06-16 15:33:20 -07003750 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
Christoph Lameter0ff38492006-09-25 23:31:52 -07003751 /*
3752 * Free memory by calling shrink zone with increasing
3753 * priorities until we have enough memory freed.
3754 */
Christoph Lameter0ff38492006-09-25 23:31:52 -07003755 do {
Johannes Weiner6b4f7792014-12-12 16:56:13 -08003756 shrink_zone(zone, &sc, true);
Konstantin Khlebnikov9e3b2f82012-05-29 15:06:57 -07003757 } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
Christoph Lameter0ff38492006-09-25 23:31:52 -07003758 }
Christoph Lameterc84db232006-02-01 03:05:29 -08003759
Christoph Lameter9eeff232006-01-18 17:42:31 -08003760 p->reclaim_state = NULL;
Christoph Lameterd4f77962006-02-24 13:04:22 -08003761 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
KOSAKI Motohiro76ca5422010-03-05 13:41:47 -08003762 lockdep_clear_current_reclaim_state();
Rik van Riela79311c2009-01-06 14:40:01 -08003763 return sc.nr_reclaimed >= nr_pages;
Christoph Lameter9eeff232006-01-18 17:42:31 -08003764}
Andrew Morton179e9632006-03-22 00:08:18 -08003765
3766int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3767{
Andrew Morton179e9632006-03-22 00:08:18 -08003768 int node_id;
David Rientjesd773ed62007-10-16 23:26:01 -07003769 int ret;
Andrew Morton179e9632006-03-22 00:08:18 -08003770
3771 /*
Christoph Lameter0ff38492006-09-25 23:31:52 -07003772 * Zone reclaim reclaims unmapped file backed pages and
3773 * slab pages if we are over the defined limits.
Christoph Lameter34aa1332006-06-30 01:55:37 -07003774 *
Christoph Lameter96146342006-07-03 00:24:13 -07003775 * A small portion of unmapped file backed pages is needed for
3776 * file I/O otherwise pages read by file I/O will be immediately
3777 * thrown out if the zone is overallocated. So we do not reclaim
3778 * if less than a specified percentage of the zone is used by
3779 * unmapped file backed pages.
Andrew Morton179e9632006-03-22 00:08:18 -08003780 */
Mel Gorman90afa5d2009-06-16 15:33:20 -07003781 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3782 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
Mel Gormanfa5e0842009-06-16 15:33:22 -07003783 return ZONE_RECLAIM_FULL;
Andrew Morton179e9632006-03-22 00:08:18 -08003784
Lisa Du6e543d52013-09-11 14:22:36 -07003785 if (!zone_reclaimable(zone))
Mel Gormanfa5e0842009-06-16 15:33:22 -07003786 return ZONE_RECLAIM_FULL;
David Rientjesd773ed62007-10-16 23:26:01 -07003787
Andrew Morton179e9632006-03-22 00:08:18 -08003788 /*
David Rientjesd773ed62007-10-16 23:26:01 -07003789 * Do not scan if the allocation should not be delayed.
Andrew Morton179e9632006-03-22 00:08:18 -08003790 */
Mel Gormand0164ad2015-11-06 16:28:21 -08003791 if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC))
Mel Gormanfa5e0842009-06-16 15:33:22 -07003792 return ZONE_RECLAIM_NOSCAN;
Andrew Morton179e9632006-03-22 00:08:18 -08003793
3794 /*
3795 * Only run zone reclaim on the local zone or on zones that do not
3796 * have associated processors. This will favor the local processor
3797 * over remote processors and spread off node memory allocations
3798 * as wide as possible.
3799 */
Christoph Lameter89fa3022006-09-25 23:31:55 -07003800 node_id = zone_to_nid(zone);
Christoph Lameter37c07082007-10-16 01:25:36 -07003801 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
Mel Gormanfa5e0842009-06-16 15:33:22 -07003802 return ZONE_RECLAIM_NOSCAN;
David Rientjesd773ed62007-10-16 23:26:01 -07003803
Johannes Weiner57054652014-10-09 15:28:17 -07003804 if (test_and_set_bit(ZONE_RECLAIM_LOCKED, &zone->flags))
Mel Gormanfa5e0842009-06-16 15:33:22 -07003805 return ZONE_RECLAIM_NOSCAN;
3806
David Rientjesd773ed62007-10-16 23:26:01 -07003807 ret = __zone_reclaim(zone, gfp_mask, order);
Johannes Weiner57054652014-10-09 15:28:17 -07003808 clear_bit(ZONE_RECLAIM_LOCKED, &zone->flags);
David Rientjesd773ed62007-10-16 23:26:01 -07003809
Mel Gorman24cf725182009-06-16 15:33:23 -07003810 if (!ret)
3811 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3812
David Rientjesd773ed62007-10-16 23:26:01 -07003813 return ret;
Andrew Morton179e9632006-03-22 00:08:18 -08003814}
Christoph Lameter9eeff232006-01-18 17:42:31 -08003815#endif
Lee Schermerhorn894bc312008-10-18 20:26:39 -07003816
Lee Schermerhorn894bc312008-10-18 20:26:39 -07003817/*
3818 * page_evictable - test whether a page is evictable
3819 * @page: the page to test
Lee Schermerhorn894bc312008-10-18 20:26:39 -07003820 *
3821 * Test whether page is evictable--i.e., should be placed on active/inactive
Hugh Dickins39b5f292012-10-08 16:33:18 -07003822 * lists vs unevictable list.
Lee Schermerhorn894bc312008-10-18 20:26:39 -07003823 *
3824 * Reasons page might not be evictable:
Lee Schermerhornba9ddf42008-10-18 20:26:42 -07003825 * (1) page's mapping marked unevictable
Nick Pigginb291f002008-10-18 20:26:44 -07003826 * (2) page is part of an mlocked VMA
Lee Schermerhornba9ddf42008-10-18 20:26:42 -07003827 *
Lee Schermerhorn894bc312008-10-18 20:26:39 -07003828 */
Hugh Dickins39b5f292012-10-08 16:33:18 -07003829int page_evictable(struct page *page)
Lee Schermerhorn894bc312008-10-18 20:26:39 -07003830{
Hugh Dickins39b5f292012-10-08 16:33:18 -07003831 return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
Lee Schermerhorn894bc312008-10-18 20:26:39 -07003832}
Lee Schermerhorn89e004ea2008-10-18 20:26:43 -07003833
Hugh Dickins850465792012-01-20 14:34:19 -08003834#ifdef CONFIG_SHMEM
Lee Schermerhorn89e004ea2008-10-18 20:26:43 -07003835/**
Hugh Dickins24513262012-01-20 14:34:21 -08003836 * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
3837 * @pages: array of pages to check
3838 * @nr_pages: number of pages to check
Lee Schermerhorn89e004ea2008-10-18 20:26:43 -07003839 *
Hugh Dickins24513262012-01-20 14:34:21 -08003840 * Checks pages for evictability and moves them to the appropriate lru list.
Hugh Dickins850465792012-01-20 14:34:19 -08003841 *
3842 * This function is only used for SysV IPC SHM_UNLOCK.
Lee Schermerhorn89e004ea2008-10-18 20:26:43 -07003843 */
Hugh Dickins24513262012-01-20 14:34:21 -08003844void check_move_unevictable_pages(struct page **pages, int nr_pages)
Lee Schermerhorn89e004ea2008-10-18 20:26:43 -07003845{
Johannes Weiner925b7672012-01-12 17:18:15 -08003846 struct lruvec *lruvec;
Hugh Dickins24513262012-01-20 14:34:21 -08003847 struct zone *zone = NULL;
3848 int pgscanned = 0;
3849 int pgrescued = 0;
3850 int i;
Lee Schermerhorn89e004ea2008-10-18 20:26:43 -07003851
Hugh Dickins24513262012-01-20 14:34:21 -08003852 for (i = 0; i < nr_pages; i++) {
3853 struct page *page = pages[i];
3854 struct zone *pagezone;
Lee Schermerhornaf936a12008-10-18 20:26:53 -07003855
Hugh Dickins24513262012-01-20 14:34:21 -08003856 pgscanned++;
3857 pagezone = page_zone(page);
3858 if (pagezone != zone) {
3859 if (zone)
3860 spin_unlock_irq(&zone->lru_lock);
3861 zone = pagezone;
3862 spin_lock_irq(&zone->lru_lock);
Lee Schermerhorn89e004ea2008-10-18 20:26:43 -07003863 }
Hugh Dickinsfa9add62012-05-29 15:07:09 -07003864 lruvec = mem_cgroup_page_lruvec(page, zone);
Lee Schermerhorn89e004ea2008-10-18 20:26:43 -07003865
Hugh Dickins24513262012-01-20 14:34:21 -08003866 if (!PageLRU(page) || !PageUnevictable(page))
3867 continue;
3868
Hugh Dickins39b5f292012-10-08 16:33:18 -07003869 if (page_evictable(page)) {
Hugh Dickins24513262012-01-20 14:34:21 -08003870 enum lru_list lru = page_lru_base_type(page);
3871
Sasha Levin309381fea2014-01-23 15:52:54 -08003872 VM_BUG_ON_PAGE(PageActive(page), page);
Hugh Dickins24513262012-01-20 14:34:21 -08003873 ClearPageUnevictable(page);
Hugh Dickinsfa9add62012-05-29 15:07:09 -07003874 del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE);
3875 add_page_to_lru_list(page, lruvec, lru);
Hugh Dickins24513262012-01-20 14:34:21 -08003876 pgrescued++;
3877 }
Lee Schermerhorn89e004ea2008-10-18 20:26:43 -07003878 }
Hugh Dickins24513262012-01-20 14:34:21 -08003879
3880 if (zone) {
3881 __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
3882 __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
3883 spin_unlock_irq(&zone->lru_lock);
3884 }
Hugh Dickins850465792012-01-20 14:34:19 -08003885}
3886#endif /* CONFIG_SHMEM */