Messages in this thread | | | Date | Thu, 13 Nov 2008 06:18:56 +0530 | From | Balbir Singh <> | Subject | Re: [RFC][PATCH 1/6] memcg: free all at rmdir |
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Andrew Morton wrote: > 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?
We do that for the force_empty() interface we have. Although we don't differentiate between cache and RSS at the moment.
-- Balbir
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