memcg: implement memory thresholds
It allows to register multiple memory and memsw thresholds and gets
notifications when it crosses.
To register a threshold application need:
- create an eventfd;
- open memory.usage_in_bytes or memory.memsw.usage_in_bytes;
- write string like "<event_fd> <memory.usage_in_bytes> <threshold>" to
cgroup.event_control.
Application will be notified through eventfd when memory usage crosses
threshold in any direction.
It's applicable for root and non-root cgroup.
It uses stats to track memory usage, simmilar to soft limits. It checks
if we need to send event to userspace on every 100 page in/out. I guess
it's good compromise between performance and accuracy of thresholds.
[akpm@linux-foundation.org: coding-style fixes]
[nishimura@mxp.nes.nec.co.jp: fix documentation merge issue]
Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Dan Malek <dan@embeddedalley.com>
Cc: Vladislav Buzov <vbuzov@embeddedalley.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Alexander Shishkin <virtuoso@slind.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5a41d93..649df43 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6,6 +6,10 @@
* Copyright 2007 OpenVZ SWsoft Inc
* Author: Pavel Emelianov <xemul@openvz.org>
*
+ * Memory thresholds
+ * Copyright (C) 2009 Nokia Corporation
+ * Author: Kirill A. Shutemov
+ *
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
@@ -35,6 +39,8 @@
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/spinlock.h>
+#include <linux/eventfd.h>
+#include <linux/sort.h>
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/vmalloc.h>
@@ -58,6 +64,7 @@
#endif
#define SOFTLIMIT_EVENTS_THRESH (1000)
+#define THRESHOLDS_EVENTS_THRESH (100)
/*
* Statistics for memory cgroup.
@@ -74,6 +81,8 @@
MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
MEM_CGROUP_STAT_SOFTLIMIT, /* decrements on each page in/out.
used by soft limit implementation */
+ MEM_CGROUP_STAT_THRESHOLDS, /* decrements on each page in/out.
+ used by threshold implementation */
MEM_CGROUP_STAT_NSTATS,
};
@@ -177,6 +186,23 @@
static struct mem_cgroup_tree soft_limit_tree __read_mostly;
+struct mem_cgroup_threshold {
+ struct eventfd_ctx *eventfd;
+ u64 threshold;
+};
+
+struct mem_cgroup_threshold_ary {
+ /* An array index points to threshold just below usage. */
+ atomic_t current_threshold;
+ /* Size of entries[] */
+ unsigned int size;
+ /* Array of thresholds */
+ struct mem_cgroup_threshold entries[0];
+};
+
+static bool mem_cgroup_threshold_check(struct mem_cgroup *mem);
+static void mem_cgroup_threshold(struct mem_cgroup *mem);
+
/*
* The memory controller data structure. The memory controller controls both
* page cache and RSS per cgroup. We would eventually like to provide
@@ -228,6 +254,15 @@
/* set when res.limit == memsw.limit */
bool memsw_is_minimum;
+ /* protect arrays of thresholds */
+ struct mutex thresholds_lock;
+
+ /* thresholds for memory usage. RCU-protected */
+ struct mem_cgroup_threshold_ary *thresholds;
+
+ /* thresholds for mem+swap usage. RCU-protected */
+ struct mem_cgroup_threshold_ary *memsw_thresholds;
+
/*
* Should we move charges of a task when a task is moved into this
* mem_cgroup ? And what type of charges should we move ?
@@ -549,6 +584,8 @@
__mem_cgroup_stat_add_safe(cpustat,
MEM_CGROUP_STAT_PGPGOUT_COUNT, 1);
__mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_SOFTLIMIT, -1);
+ __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_THRESHOLDS, -1);
+
put_cpu();
}
@@ -1576,6 +1613,8 @@
if (page && mem_cgroup_soft_limit_check(mem))
mem_cgroup_update_tree(mem, page);
done:
+ if (mem_cgroup_threshold_check(mem))
+ mem_cgroup_threshold(mem);
return 0;
nomem:
css_put(&mem->css);
@@ -2148,6 +2187,8 @@
if (mem_cgroup_soft_limit_check(mem))
mem_cgroup_update_tree(mem, page);
+ if (mem_cgroup_threshold_check(mem))
+ mem_cgroup_threshold(mem);
/* at swapout, this memcg will be accessed to record to swap */
if (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
css_put(&mem->css);
@@ -3232,12 +3273,277 @@
return 0;
}
+static bool mem_cgroup_threshold_check(struct mem_cgroup *mem)
+{
+ bool ret = false;
+ int cpu;
+ s64 val;
+ struct mem_cgroup_stat_cpu *cpustat;
+
+ cpu = get_cpu();
+ cpustat = &mem->stat.cpustat[cpu];
+ val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_THRESHOLDS);
+ if (unlikely(val < 0)) {
+ __mem_cgroup_stat_set_safe(cpustat, MEM_CGROUP_STAT_THRESHOLDS,
+ THRESHOLDS_EVENTS_THRESH);
+ ret = true;
+ }
+ put_cpu();
+ return ret;
+}
+
+static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
+{
+ struct mem_cgroup_threshold_ary *t;
+ u64 usage;
+ int i;
+
+ rcu_read_lock();
+ if (!swap)
+ t = rcu_dereference(memcg->thresholds);
+ else
+ t = rcu_dereference(memcg->memsw_thresholds);
+
+ if (!t)
+ goto unlock;
+
+ usage = mem_cgroup_usage(memcg, swap);
+
+ /*
+ * current_threshold points to threshold just below usage.
+ * If it's not true, a threshold was crossed after last
+ * call of __mem_cgroup_threshold().
+ */
+ i = atomic_read(&t->current_threshold);
+
+ /*
+ * Iterate backward over array of thresholds starting from
+ * current_threshold and check if a threshold is crossed.
+ * If none of thresholds below usage is crossed, we read
+ * only one element of the array here.
+ */
+ for (; i >= 0 && unlikely(t->entries[i].threshold > usage); i--)
+ eventfd_signal(t->entries[i].eventfd, 1);
+
+ /* i = current_threshold + 1 */
+ i++;
+
+ /*
+ * Iterate forward over array of thresholds starting from
+ * current_threshold+1 and check if a threshold is crossed.
+ * If none of thresholds above usage is crossed, we read
+ * only one element of the array here.
+ */
+ for (; i < t->size && unlikely(t->entries[i].threshold <= usage); i++)
+ eventfd_signal(t->entries[i].eventfd, 1);
+
+ /* Update current_threshold */
+ atomic_set(&t->current_threshold, i - 1);
+unlock:
+ rcu_read_unlock();
+}
+
+static void mem_cgroup_threshold(struct mem_cgroup *memcg)
+{
+ __mem_cgroup_threshold(memcg, false);
+ if (do_swap_account)
+ __mem_cgroup_threshold(memcg, true);
+}
+
+static int compare_thresholds(const void *a, const void *b)
+{
+ const struct mem_cgroup_threshold *_a = a;
+ const struct mem_cgroup_threshold *_b = b;
+
+ return _a->threshold - _b->threshold;
+}
+
+static int mem_cgroup_register_event(struct cgroup *cgrp, struct cftype *cft,
+ struct eventfd_ctx *eventfd, const char *args)
+{
+ struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+ struct mem_cgroup_threshold_ary *thresholds, *thresholds_new;
+ int type = MEMFILE_TYPE(cft->private);
+ u64 threshold, usage;
+ int size;
+ int i, ret;
+
+ ret = res_counter_memparse_write_strategy(args, &threshold);
+ if (ret)
+ return ret;
+
+ mutex_lock(&memcg->thresholds_lock);
+ if (type == _MEM)
+ thresholds = memcg->thresholds;
+ else if (type == _MEMSWAP)
+ thresholds = memcg->memsw_thresholds;
+ else
+ BUG();
+
+ usage = mem_cgroup_usage(memcg, type == _MEMSWAP);
+
+ /* Check if a threshold crossed before adding a new one */
+ if (thresholds)
+ __mem_cgroup_threshold(memcg, type == _MEMSWAP);
+
+ if (thresholds)
+ size = thresholds->size + 1;
+ else
+ size = 1;
+
+ /* Allocate memory for new array of thresholds */
+ thresholds_new = kmalloc(sizeof(*thresholds_new) +
+ size * sizeof(struct mem_cgroup_threshold),
+ GFP_KERNEL);
+ if (!thresholds_new) {
+ ret = -ENOMEM;
+ goto unlock;
+ }
+ thresholds_new->size = size;
+
+ /* Copy thresholds (if any) to new array */
+ if (thresholds)
+ memcpy(thresholds_new->entries, thresholds->entries,
+ thresholds->size *
+ sizeof(struct mem_cgroup_threshold));
+ /* Add new threshold */
+ thresholds_new->entries[size - 1].eventfd = eventfd;
+ thresholds_new->entries[size - 1].threshold = threshold;
+
+ /* Sort thresholds. Registering of new threshold isn't time-critical */
+ sort(thresholds_new->entries, size,
+ sizeof(struct mem_cgroup_threshold),
+ compare_thresholds, NULL);
+
+ /* Find current threshold */
+ atomic_set(&thresholds_new->current_threshold, -1);
+ for (i = 0; i < size; i++) {
+ if (thresholds_new->entries[i].threshold < usage) {
+ /*
+ * thresholds_new->current_threshold will not be used
+ * until rcu_assign_pointer(), so it's safe to increment
+ * it here.
+ */
+ atomic_inc(&thresholds_new->current_threshold);
+ }
+ }
+
+ /*
+ * We need to increment refcnt to be sure that all thresholds
+ * will be unregistered before calling __mem_cgroup_free()
+ */
+ mem_cgroup_get(memcg);
+
+ if (type == _MEM)
+ rcu_assign_pointer(memcg->thresholds, thresholds_new);
+ else
+ rcu_assign_pointer(memcg->memsw_thresholds, thresholds_new);
+
+ /* To be sure that nobody uses thresholds before freeing it */
+ synchronize_rcu();
+
+ kfree(thresholds);
+unlock:
+ mutex_unlock(&memcg->thresholds_lock);
+
+ return ret;
+}
+
+static int mem_cgroup_unregister_event(struct cgroup *cgrp, struct cftype *cft,
+ struct eventfd_ctx *eventfd)
+{
+ struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+ struct mem_cgroup_threshold_ary *thresholds, *thresholds_new;
+ int type = MEMFILE_TYPE(cft->private);
+ u64 usage;
+ int size = 0;
+ int i, j, ret;
+
+ mutex_lock(&memcg->thresholds_lock);
+ if (type == _MEM)
+ thresholds = memcg->thresholds;
+ else if (type == _MEMSWAP)
+ thresholds = memcg->memsw_thresholds;
+ else
+ BUG();
+
+ /*
+ * Something went wrong if we trying to unregister a threshold
+ * if we don't have thresholds
+ */
+ BUG_ON(!thresholds);
+
+ usage = mem_cgroup_usage(memcg, type == _MEMSWAP);
+
+ /* Check if a threshold crossed before removing */
+ __mem_cgroup_threshold(memcg, type == _MEMSWAP);
+
+ /* Calculate new number of threshold */
+ for (i = 0; i < thresholds->size; i++) {
+ if (thresholds->entries[i].eventfd != eventfd)
+ size++;
+ }
+
+ /* Set thresholds array to NULL if we don't have thresholds */
+ if (!size) {
+ thresholds_new = NULL;
+ goto assign;
+ }
+
+ /* Allocate memory for new array of thresholds */
+ thresholds_new = kmalloc(sizeof(*thresholds_new) +
+ size * sizeof(struct mem_cgroup_threshold),
+ GFP_KERNEL);
+ if (!thresholds_new) {
+ ret = -ENOMEM;
+ goto unlock;
+ }
+ thresholds_new->size = size;
+
+ /* Copy thresholds and find current threshold */
+ atomic_set(&thresholds_new->current_threshold, -1);
+ for (i = 0, j = 0; i < thresholds->size; i++) {
+ if (thresholds->entries[i].eventfd == eventfd)
+ continue;
+
+ thresholds_new->entries[j] = thresholds->entries[i];
+ if (thresholds_new->entries[j].threshold < usage) {
+ /*
+ * thresholds_new->current_threshold will not be used
+ * until rcu_assign_pointer(), so it's safe to increment
+ * it here.
+ */
+ atomic_inc(&thresholds_new->current_threshold);
+ }
+ j++;
+ }
+
+assign:
+ if (type == _MEM)
+ rcu_assign_pointer(memcg->thresholds, thresholds_new);
+ else
+ rcu_assign_pointer(memcg->memsw_thresholds, thresholds_new);
+
+ /* To be sure that nobody uses thresholds before freeing it */
+ synchronize_rcu();
+
+ for (i = 0; i < thresholds->size - size; i++)
+ mem_cgroup_put(memcg);
+
+ kfree(thresholds);
+unlock:
+ mutex_unlock(&memcg->thresholds_lock);
+
+ return ret;
+}
static struct cftype mem_cgroup_files[] = {
{
.name = "usage_in_bytes",
.private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
.read_u64 = mem_cgroup_read,
+ .register_event = mem_cgroup_register_event,
+ .unregister_event = mem_cgroup_unregister_event,
},
{
.name = "max_usage_in_bytes",
@@ -3294,6 +3600,8 @@
.name = "memsw.usage_in_bytes",
.private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
.read_u64 = mem_cgroup_read,
+ .register_event = mem_cgroup_register_event,
+ .unregister_event = mem_cgroup_unregister_event,
},
{
.name = "memsw.max_usage_in_bytes",
@@ -3538,6 +3846,7 @@
mem->swappiness = get_swappiness(parent);
atomic_set(&mem->refcnt, 1);
mem->move_charge_at_immigrate = 0;
+ mutex_init(&mem->thresholds_lock);
return &mem->css;
free_out:
__mem_cgroup_free(mem);