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 --- include/linux/page_cgroup.h | 17 ----------------- 1 file changed, 17 deletions(-) (limited to 'include/linux/page_cgroup.h') diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h index d754b2dfbf2d..602cc1fdee90 100644 --- a/include/linux/page_cgroup.h +++ b/include/linux/page_cgroup.h @@ -26,10 +26,6 @@ enum { PCG_LOCK, /* page cgroup is locked */ PCG_CACHE, /* charged as cache */ PCG_USED, /* this object is in use. */ - /* flags for LRU placement */ - PCG_ACTIVE, /* page is active in this cgroup */ - PCG_FILE, /* page is file system backed */ - PCG_UNEVICTABLE, /* page is unevictableable */ }; #define TESTPCGFLAG(uname, lname) \ @@ -50,19 +46,6 @@ TESTPCGFLAG(Cache, CACHE) TESTPCGFLAG(Used, USED) CLEARPCGFLAG(Used, USED) -/* LRU management flags (from global-lru definition) */ -TESTPCGFLAG(File, FILE) -SETPCGFLAG(File, FILE) -CLEARPCGFLAG(File, FILE) - -TESTPCGFLAG(Active, ACTIVE) -SETPCGFLAG(Active, ACTIVE) -CLEARPCGFLAG(Active, ACTIVE) - -TESTPCGFLAG(Unevictable, UNEVICTABLE) -SETPCGFLAG(Unevictable, UNEVICTABLE) -CLEARPCGFLAG(Unevictable, UNEVICTABLE) - static inline int page_cgroup_nid(struct page_cgroup *pc) { return page_to_nid(pc->page); -- cgit v1.2.3