Messages in this thread | | | Date | Thu, 13 Nov 2008 05:53:49 +0530 | From | Balbir Singh <> | Subject | Re: [RFC][PATCH 1/6] memcg: free all at rmdir |
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Andrew Morton wrote: > On Wed, 12 Nov 2008 12:26:56 +0900 > KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote: > >> +5.1 on_rmdir >> +set behavior of memcg at rmdir (Removing cgroup) default is "drop". >> + >> +5.1.1 drop >> + #echo on_rmdir drop > memory.attribute >> + This is default. All pages on the memcg will be freed. >> + If pages are locked or too busy, they will be moved up to the parent. >> + Useful when you want to drop (large) page caches used in this memcg. >> + But some of in-use page cache can be dropped by this. >> + >> +5.1.2 keep >> + #echo on_rmdir keep > memory.attribute >> + All pages on the memcg will be moved to its parent. >> + Useful when you don't want to drop page caches used in this memcg. >> + You can keep page caches from some library or DB accessed by this >> + memcg on memory. > > Would it not be more useful to implement a per-memcg version of > /proc/sys/vm/drop_caches? (One without drop_caches' locking bug, > hopefully). > > If we do this then we can make the above "keep" behaviour non-optional, > and the operator gets to choose whether or not to drop the caches > before doing the rmdir. > > Plus, we get a new per-memcg drop_caches capability. And it's a nicer > interface, and it doesn't have the obvious races which on_rmdir has, > etc. >
Andrew, I suspect that will not be easy, since we don't track address spaces that belong to a particular memcg. If page cache ends up being shared across memcg's, dropping them would impact both mem cgroups.
-- Balbir
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