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mm: batch activate_page() to reduce lock contention 

The zone->lru_lock is heavily contented in workload where activate_page()
is frequently used.  We could do batch activate_page() to reduce the lock
contention.  The batched pages will be added into zone list when the pool
is full or page reclaim is trying to drain them.

For example, in a 4 socket 64 CPU system, create a sparse file and 64
processes, processes shared map to the file.  Each process read access the
whole file and then exit.  The process exit will do unmap_vmas() and cause
a lot of activate_page() call.  In such workload, we saw about 58% total
time reduction with below patch.  Other workloads with a lot of
activate_page also benefits a lot too.

I tested some microbenchmarks:
case-anon-cow-rand-mt		0.58%
case-anon-cow-rand		-3.30%
case-anon-cow-seq-mt		-0.51%
case-anon-cow-seq		-5.68%
case-anon-r-rand-mt		0.23%
case-anon-r-rand		0.81%
case-anon-r-seq-mt		-0.71%
case-anon-r-seq			-1.99%
case-anon-rx-rand-mt		2.11%
case-anon-rx-seq-mt		3.46%
case-anon-w-rand-mt		-0.03%
case-anon-w-rand		-0.50%
case-anon-w-seq-mt		-1.08%
case-anon-w-seq			-0.12%
case-anon-wx-rand-mt		-5.02%
case-anon-wx-seq-mt		-1.43%
case-fork			1.65%
case-fork-sleep			-0.07%
case-fork-withmem		1.39%
case-hugetlb			-0.59%
case-lru-file-mmap-read-mt	-0.54%
case-lru-file-mmap-read		0.61%
case-lru-file-mmap-read-rand	-2.24%
case-lru-file-readonce		-0.64%
case-lru-file-readtwice		-11.69%
case-lru-memcg			-1.35%
case-mmap-pread-rand-mt		1.88%
case-mmap-pread-rand		-15.26%
case-mmap-pread-seq-mt		0.89%
case-mmap-pread-seq		-69.72%
case-mmap-xread-rand-mt		0.71%
case-mmap-xread-seq-mt		0.38%

The most significent are:
case-lru-file-readtwice		-11.69%
case-mmap-pread-rand		-15.26%
case-mmap-pread-seq		-69.72%

which use activate_page a lot.  others are basically variations because
each run has slightly difference.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Shaohua Li 2011-01-13 15:47:34 -08:00 committed by Linus Torvalds
parent d8505dee1a
commit 744ed14427
3 changed files with 94 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
mm/internal.h
View File

@ -39,6 +39,15 @@ static inline void __put_page(struct page *page)
extern unsigned long highest_memmap_pfn;
#ifdef CONFIG_SMP
extern int putback_active_lru_page(struct zone *zone, struct page *page);
#else
static inline int putback_active_lru_page(struct zone *zone, struct page *page)
{
return 0;
}
#endif
/*
* in mm/vmscan.c:
*/

94
mm/swap.c
View File

@ -271,27 +271,94 @@ static void update_page_reclaim_stat(struct zone *zone, struct page *page,
}
/*
* FIXME: speed this up?
* A page will go to active list either by activate_page or putback_lru_page.
* In the activate_page case, the page hasn't active bit set. The page might
* not in LRU list because it's isolated before it gets a chance to be moved to
* active list. The window is small because pagevec just stores several pages.
* For such case, we do nothing for such page.
* In the putback_lru_page case, the page isn't in lru list but has active
* bit set
*/
static void __activate_page(struct page *page, void *arg)
{
struct zone *zone = page_zone(page);
int file = page_is_file_cache(page);
int lru = page_lru_base_type(page);
bool putback = !PageLRU(page);
/* The page is isolated before it's moved to active list */
if (!PageLRU(page) && !PageActive(page))
return;
if ((PageLRU(page) && PageActive(page)) || PageUnevictable(page))
return;
if (!putback)
del_page_from_lru_list(zone, page, lru);
else
SetPageLRU(page);
SetPageActive(page);
lru += LRU_ACTIVE;
add_page_to_lru_list(zone, page, lru);
if (putback)
return;
__count_vm_event(PGACTIVATE);
update_page_reclaim_stat(zone, page, file, 1);
}
#ifdef CONFIG_SMP
static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
static void activate_page_drain(int cpu)
{
struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
if (pagevec_count(pvec))
pagevec_lru_move_fn(pvec, __activate_page, NULL);
}
void activate_page(struct page *page)
{
if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
page_cache_get(page);
if (!pagevec_add(pvec, page))
pagevec_lru_move_fn(pvec, __activate_page, NULL);
put_cpu_var(activate_page_pvecs);
}
}
/* Caller should hold zone->lru_lock */
int putback_active_lru_page(struct zone *zone, struct page *page)
{
struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
if (!pagevec_add(pvec, page)) {
spin_unlock_irq(&zone->lru_lock);
pagevec_lru_move_fn(pvec, __activate_page, NULL);
spin_lock_irq(&zone->lru_lock);
}
put_cpu_var(activate_page_pvecs);
return 1;
}
#else
static inline void activate_page_drain(int cpu)
{
}
void activate_page(struct page *page)
{
struct zone *zone = page_zone(page);
spin_lock_irq(&zone->lru_lock);
if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
int file = page_is_file_cache(page);
int lru = page_lru_base_type(page);
del_page_from_lru_list(zone, page, lru);
SetPageActive(page);
lru += LRU_ACTIVE;
add_page_to_lru_list(zone, page, lru);
__count_vm_event(PGACTIVATE);
update_page_reclaim_stat(zone, page, file, 1);
}
if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page))
__activate_page(page, NULL);
spin_unlock_irq(&zone->lru_lock);
}
#endif
/*
* Mark a page as having seen activity.
@ -390,6 +457,7 @@ static void drain_cpu_pagevecs(int cpu)
pagevec_move_tail(pvec);
local_irq_restore(flags);
}
activate_page_drain(cpu);
}
void lru_add_drain(void)

6
mm/vmscan.c
View File

@ -1271,14 +1271,16 @@ putback_lru_pages(struct zone *zone, struct scan_control *sc,
spin_lock_irq(&zone->lru_lock);
continue;
}
SetPageLRU(page);
lru = page_lru(page);
add_page_to_lru_list(zone, page, lru);
if (is_active_lru(lru)) {
int file = is_file_lru(lru);
int numpages = hpage_nr_pages(page);
reclaim_stat->recent_rotated[file] += numpages;
if (putback_active_lru_page(zone, page))
continue;
}
SetPageLRU(page);
add_page_to_lru_list(zone, page, lru);
if (!pagevec_add(&pvec, page)) {
spin_unlock_irq(&zone->lru_lock);
__pagevec_release(&pvec);