From f817ed48535ac6510ebae7c4116f24a5f9268834 Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Wed, 7 Jan 2009 18:07:53 -0800 Subject: memcg: move all acccounting to parent at rmdir() This patch provides a function to move account information of a page between mem_cgroups and rewrite force_empty to make use of this. This moving of page_cgroup is done under - lru_lock of source/destination mem_cgroup is held. - lock_page_cgroup() is held. Then, a routine which touches pc->mem_cgroup without lock_page_cgroup() should confirm pc->mem_cgroup is still valid or not. Typical code can be following. (while page is not under lock_page()) mem = pc->mem_cgroup; mz = page_cgroup_zoneinfo(pc) spin_lock_irqsave(&mz->lru_lock); if (pc->mem_cgroup == mem) ...../* some list handling */ spin_unlock_irqrestore(&mz->lru_lock); Of course, better way is lock_page_cgroup(pc); .... unlock_page_cgroup(pc); But you should confirm the nest of lock and avoid deadlock. If you treats page_cgroup from mem_cgroup's LRU under mz->lru_lock, you don't have to worry about what pc->mem_cgroup points to. moved pages are added to head of lru, not to tail. Expected users of this routine is: - force_empty (rmdir) - moving tasks between cgroup (for moving account information.) - hierarchy (maybe useful.) force_empty(rmdir) uses this move_account and move pages to its parent. This "move" will not cause OOM (I added "oom" parameter to try_charge().) If the parent is busy (not enough memory), force_empty calls try_to_free_page() and reduce usage. Purpose of this behavior is - Fix "forget all" behavior of force_empty and avoid leak of accounting. - By "moving first, free if necessary", keep pages on memory as much as possible. Adding a switch to change behavior of force_empty to - free first, move if necessary - free all, if there is mlocked/busy pages, return -EBUSY. is under consideration. (I'll add if someone requtests.) This patch also removes memory.force_empty file, a brutal debug-only interface. Reviewed-by: Daisuke Nishimura Tested-by: Daisuke Nishimura Signed-off-by: KAMEZAWA Hiroyuki Cc: Balbir Singh Cc: Paul Menage Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/controllers/memory.txt | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) (limited to 'Documentation') diff --git a/Documentation/controllers/memory.txt b/Documentation/controllers/memory.txt index 1c07547d3f8..58f32c166fa 100644 --- a/Documentation/controllers/memory.txt +++ b/Documentation/controllers/memory.txt @@ -207,12 +207,6 @@ exceeded. The memory.stat file gives accounting information. Now, the number of caches, RSS and Active pages/Inactive pages are shown. -The memory.force_empty gives an interface to drop *all* charges by force. - -# echo 1 > memory.force_empty - -will drop all charges in cgroup. Currently, this is maintained for test. - 4. Testing Balbir posted lmbench, AIM9, LTP and vmmstress results [10] and [11]. @@ -242,8 +236,10 @@ reclaimed. A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a cgroup might have some charge associated with it, even though all -tasks have migrated away from it. Such charges are automatically dropped at -rmdir() if there are no tasks. +tasks have migrated away from it. +Such charges are moved to its parent as much as possible and freed if parent +is full. Both of RSS and CACHES are moved to parent. +If both of them are busy, rmdir() returns -EBUSY. 5. TODO -- cgit v1.2.3