Messages in this thread | | | Date | Tue, 16 Oct 2012 09:51:03 +0900 | From | Kamezawa Hiroyuki <> | Subject | Re: [PATCH] doc: describe memcg swappiness more precisely memory.swappiness==0 |
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(2012/10/16 7:07), Michal Hocko wrote: > And a follow up for memcg.swappiness documentation which is more > specific about spwappiness==0 meaning. > --- > From 1bc3a94fea728107ed108edd42df464b908cd067 Mon Sep 17 00:00:00 2001 > From: Michal Hocko <mhocko@suse.cz> > Date: Mon, 15 Oct 2012 11:43:56 +0200 > Subject: [PATCH] doc: describe memcg swappiness more precisely > > since fe35004f (mm: avoid swapping out with swappiness==0) memcg reclaim > stopped swapping out anon pages completely when 0 value is used. > Although this is somehow expected it hasn't been done for a really long > time this way and so it is probably better to be explicit about the > effect. Moreover global reclaim swapps out even when swappiness is 0 > to prevent from OOM killer. > > Signed-off-by: Michal Hocko <mhocko@suse.cz>
Nice :) Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> --- > Documentation/cgroups/memory.txt | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt > index c07f7b4..71c4da4 100644 > --- a/Documentation/cgroups/memory.txt > +++ b/Documentation/cgroups/memory.txt > @@ -466,6 +466,10 @@ Note: > 5.3 swappiness > > Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only. > +Please note that unlike the global swappiness, memcg knob set to 0 > +really prevents from any swapping even if there is a swap storage > +available. This might lead to memcg OOM killer if there are no file > +pages to reclaim. > > Following cgroups' swappiness can't be changed. > - root cgroup (uses /proc/sys/vm/swappiness). >
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