From 744ed1442757767ffede5008bb13e0805085902e Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Thu, 13 Jan 2011 15:47:34 -0800 Subject: [PATCH] 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 Cc: Andi Kleen Cc: Minchan Kim Cc: KOSAKI Motohiro Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/internal.h | 9 ++++++ mm/swap.c | 90 ++++++++++++++++++++++++++++++++++++++++++++------- mm/vmscan.c | 6 ++-- 3 files changed, 92 insertions(+), 13 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 69488205723d..4c98630f0f77 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -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: */ diff --git a/mm/swap.c b/mm/swap.c index ab498ea04ae3..bbc1ce9f9460 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -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); + int file = page_is_file_cache(page); + int lru = page_lru_base_type(page); + bool putback = !PageLRU(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); + /* 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); + 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); + } +} - update_page_reclaim_stat(zone, page, file, 1); +/* 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) diff --git a/mm/vmscan.c b/mm/vmscan.c index 47a50962ce81..99999a9b2b0b 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -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); -- 2.20.1