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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>
This commit is contained in:
Mel Gorman 2014-08-06 16:07:16 -07:00 committed by Linus Torvalds
parent 3484b2de94
commit 0d5d823ab4
4 changed files with 16 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/mmzone.h
View File

@ -143,6 +143,7 @@ enum zone_stat_item {
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 @@ struct zone {
/* 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 */

12
mm/page_alloc.c
View File

@ -680,9 +680,12 @@ static void free_pcppages_bulk(struct zone *zone, int count,
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 @@ static void free_one_page(struct zone *zone,
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 @@ void show_free_areas(unsigned int filter)
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[]:");

7
mm/vmscan.c
View File

@ -174,7 +174,8 @@ static unsigned long zone_reclaimable_pages(struct zone *zone)
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 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
__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 @@ static void shrink_active_list(unsigned long nr_to_scan,
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;

3
mm/vmstat.c
View File

@ -763,6 +763,7 @@ const char * const vmstat_text[] = {
"nr_shmem",
"nr_dirtied",
"nr_written",
"nr_pages_scanned",
#ifdef CONFIG_NUMA
"numa_hit",
@ -1067,7 +1068,7 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
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);