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Commit 744ed144 authored by Shaohua Li's avatar Shaohua Li Committed by Linus Torvalds
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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: default avatarShaohua 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d8505dee

mm/internal.h

+9 −0
Original line number Diff line number Diff line
@@ -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:

 */

mm/swap.c

+79 −11
Original line number Diff line number Diff line
@@ -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

 */

void activate_page(struct page *page)

static void __activate_page(struct page *page, void *arg)

{

	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);

	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);

		__count_vm_event(PGACTIVATE);



	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))

		__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)

mm/vmscan.c

+4 −2
Original line number Diff line number Diff line
@@ -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);