From 08e552c69c6930d64722de3ec18c51844d06ee28 Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Wed, 7 Jan 2009 18:08:01 -0800 Subject: memcg: synchronized LRU A big patch for changing memcg's LRU semantics. Now, - page_cgroup is linked to mem_cgroup's its own LRU (per zone). - LRU of page_cgroup is not synchronous with global LRU. - page and page_cgroup is one-to-one and statically allocated. - To find page_cgroup is on what LRU, you have to check pc->mem_cgroup as - lru = page_cgroup_zoneinfo(pc, nid_of_pc, zid_of_pc); - SwapCache is handled. And, when we handle LRU list of page_cgroup, we do following. pc = lookup_page_cgroup(page); lock_page_cgroup(pc); .....................(1) mz = page_cgroup_zoneinfo(pc); spin_lock(&mz->lru_lock); .....add to LRU spin_unlock(&mz->lru_lock); unlock_page_cgroup(pc); But (1) is spin_lock and we have to be afraid of dead-lock with zone->lru_lock. So, trylock() is used at (1), now. Without (1), we can't trust "mz" is correct. This is a trial to remove this dirty nesting of locks. This patch changes mz->lru_lock to be zone->lru_lock. Then, above sequence will be written as spin_lock(&zone->lru_lock); # in vmscan.c or swap.c via global LRU mem_cgroup_add/remove/etc_lru() { pc = lookup_page_cgroup(page); mz = page_cgroup_zoneinfo(pc); if (PageCgroupUsed(pc)) { ....add to LRU } spin_lock(&zone->lru_lock); # in vmscan.c or swap.c via global LRU This is much simpler. (*) We're safe even if we don't take lock_page_cgroup(pc). Because.. 1. When pc->mem_cgroup can be modified. - at charge. - at account_move(). 2. at charge the PCG_USED bit is not set before pc->mem_cgroup is fixed. 3. at account_move() the page is isolated and not on LRU. Pros. - easy for maintenance. - memcg can make use of laziness of pagevec. - we don't have to duplicated LRU/Active/Unevictable bit in page_cgroup. - LRU status of memcg will be synchronized with global LRU's one. - # of locks are reduced. - account_move() is simplified very much. Cons. - may increase cost of LRU rotation. (no impact if memcg is not configured.) Signed-off-by: KAMEZAWA Hiroyuki Cc: Li Zefan Cc: Balbir Singh Cc: Pavel Emelyanov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index f63b20dd771..45983af1de3 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -512,7 +512,6 @@ redo: lru = LRU_UNEVICTABLE; add_page_to_unevictable_list(page); } - mem_cgroup_move_lists(page, lru); /* * page's status can change while we move it among lru. If an evictable @@ -547,7 +546,6 @@ void putback_lru_page(struct page *page) lru = !!TestClearPageActive(page) + page_is_file_cache(page); lru_cache_add_lru(page, lru); - mem_cgroup_move_lists(page, lru); put_page(page); } #endif /* CONFIG_UNEVICTABLE_LRU */ @@ -813,6 +811,7 @@ int __isolate_lru_page(struct page *page, int mode, int file) return ret; ret = -EBUSY; + if (likely(get_page_unless_zero(page))) { /* * Be careful not to clear PageLRU until after we're @@ -821,6 +820,7 @@ int __isolate_lru_page(struct page *page, int mode, int file) */ ClearPageLRU(page); ret = 0; + mem_cgroup_del_lru(page); } return ret; @@ -1134,7 +1134,6 @@ static unsigned long shrink_inactive_list(unsigned long max_scan, SetPageLRU(page); lru = page_lru(page); add_page_to_lru_list(zone, page, lru); - mem_cgroup_move_lists(page, lru); if (PageActive(page) && scan_global_lru(sc)) { int file = !!page_is_file_cache(page); zone->recent_rotated[file]++; @@ -1263,7 +1262,7 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone, ClearPageActive(page); list_move(&page->lru, &zone->lru[lru].list); - mem_cgroup_move_lists(page, lru); + mem_cgroup_add_lru_list(page, lru); pgmoved++; if (!pagevec_add(&pvec, page)) { __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); @@ -2408,6 +2407,7 @@ retry: __dec_zone_state(zone, NR_UNEVICTABLE); list_move(&page->lru, &zone->lru[l].list); + mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); __inc_zone_state(zone, NR_INACTIVE_ANON + l); __count_vm_event(UNEVICTABLE_PGRESCUED); } else { @@ -2416,6 +2416,7 @@ retry: */ SetPageUnevictable(page); list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); + mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); if (page_evictable(page, NULL)) goto retry; } -- cgit v1.2.3