(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@xxxxxxx> 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@xxxxxxx>
Nice :) Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
--- 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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