mm: move zone->pages_scanned into a vmstat counter
zone->pages_scanned is a write-intensive cache line during page reclaim
and it's also updated during page free. Move the counter into vmstat to
take advantage of the per-cpu updates and do not update it in the free
paths unless necessary.
On a small UMA machine running tiobench the difference is marginal. On
a 4-node machine the overhead is more noticable. Note that automatic
NUMA balancing was disabled for this test as otherwise the system CPU
overhead is unpredictable.
3.16.0-rc3 3.16.0-rc3 3.16.0-rc3
vanillarearrange-v5 vmstat-v5
User 746.94 759.78 774.56
System 65336.22 58350.98 32847.27
Elapsed 27553.52 27282.02 27415.04
Note that the overhead reduction will vary depending on where exactly
pages are allocated and freed.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index ed0876b..0bd77f73 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -143,6 +143,7 @@
NR_SHMEM, /* shmem pages (included tmpfs/GEM pages) */
NR_DIRTIED, /* page dirtyings since bootup */
NR_WRITTEN, /* page writings since bootup */
+ NR_PAGES_SCANNED, /* pages scanned since last reclaim */
#ifdef CONFIG_NUMA
NUMA_HIT, /* allocated in intended node */
NUMA_MISS, /* allocated in non intended node */
@@ -480,7 +481,6 @@
/* Fields commonly accessed by the page reclaim scanner */
spinlock_t lru_lock;
- unsigned long pages_scanned; /* since last reclaim */
struct lruvec lruvec;
/* Evictions & activations on the inactive file list */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b7381d1..daa0160 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -680,9 +680,12 @@
int migratetype = 0;
int batch_free = 0;
int to_free = count;
+ unsigned long nr_scanned;
spin_lock(&zone->lock);
- zone->pages_scanned = 0;
+ nr_scanned = zone_page_state(zone, NR_PAGES_SCANNED);
+ if (nr_scanned)
+ __mod_zone_page_state(zone, NR_PAGES_SCANNED, -nr_scanned);
while (to_free) {
struct page *page;
@@ -731,8 +734,11 @@
unsigned int order,
int migratetype)
{
+ unsigned long nr_scanned;
spin_lock(&zone->lock);
- zone->pages_scanned = 0;
+ nr_scanned = zone_page_state(zone, NR_PAGES_SCANNED);
+ if (nr_scanned)
+ __mod_zone_page_state(zone, NR_PAGES_SCANNED, -nr_scanned);
__free_one_page(page, pfn, zone, order, migratetype);
if (unlikely(!is_migrate_isolate(migratetype)))
@@ -3248,7 +3254,7 @@
K(zone_page_state(zone, NR_BOUNCE)),
K(zone_page_state(zone, NR_FREE_CMA_PAGES)),
K(zone_page_state(zone, NR_WRITEBACK_TEMP)),
- zone->pages_scanned,
+ K(zone_page_state(zone, NR_PAGES_SCANNED)),
(!zone_reclaimable(zone) ? "yes" : "no")
);
printk("lowmem_reserve[]:");
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5fec1ba..9c8222b4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -174,7 +174,8 @@
bool zone_reclaimable(struct zone *zone)
{
- return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
+ return zone_page_state(zone, NR_PAGES_SCANNED) <
+ zone_reclaimable_pages(zone) * 6;
}
static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru)
@@ -1508,7 +1509,7 @@
__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
if (global_reclaim(sc)) {
- zone->pages_scanned += nr_scanned;
+ __mod_zone_page_state(zone, NR_PAGES_SCANNED, nr_scanned);
if (current_is_kswapd())
__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned);
else
@@ -1698,7 +1699,7 @@
nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
&nr_scanned, sc, isolate_mode, lru);
if (global_reclaim(sc))
- zone->pages_scanned += nr_scanned;
+ __mod_zone_page_state(zone, NR_PAGES_SCANNED, nr_scanned);
reclaim_stat->recent_scanned[file] += nr_taken;
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 8267f77..e574e883 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -763,6 +763,7 @@
"nr_shmem",
"nr_dirtied",
"nr_written",
+ "nr_pages_scanned",
#ifdef CONFIG_NUMA
"numa_hit",
@@ -1067,7 +1068,7 @@
min_wmark_pages(zone),
low_wmark_pages(zone),
high_wmark_pages(zone),
- zone->pages_scanned,
+ zone_page_state(zone, NR_PAGES_SCANNED),
zone->spanned_pages,
zone->present_pages,
zone->managed_pages);