Messages in this thread | | | Date | Wed, 12 Nov 2008 16:46:37 -0800 | From | Andrew Morton <> | Subject | Re: [RFC][PATCH 1/6] memcg: free all at rmdir |
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On Thu, 13 Nov 2008 05:53:49 +0530 Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> 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. >
walk the LRUs?
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