linux-kernel - Re: [PATCH v13 6/7] mm, oom, docs: describe the cgroup-aware OOM killer

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Date:   Fri, 1 Dec 2017 17:01:49 +0000
From:   Roman Gushchin <guro@...com>
To:     Michal Hocko <mhocko@...nel.org>
CC:     <linux-mm@...r.kernel.org>, Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Tejun Heo <tj@...nel.org>, <kernel-team@...com>,
        <cgroups@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH v13 6/7] mm, oom, docs: describe the cgroup-aware OOM
 killer

On Fri, Dec 01, 2017 at 09:41:54AM +0100, Michal Hocko wrote:
> On Thu 30-11-17 15:28:23, Roman Gushchin wrote:
> > @@ -1229,6 +1252,41 @@ to be accessed repeatedly by other cgroups, it may make sense to use
> >  POSIX_FADV_DONTNEED to relinquish the ownership of memory areas
> >  belonging to the affected files to ensure correct memory ownership.
> >  
> > +OOM Killer
> > +~~~~~~~~~~
> > +
> > +Cgroup v2 memory controller implements a cgroup-aware OOM killer.
> > +It means that it treats cgroups as first class OOM entities.
> 
> This should mention groupoom mount option to enable this functionality.
> 
> Other than that looks ok to me
> Acked-by: Michal Hocko <mhocko@...e.com>
> -- 
> Michal Hocko
> SUSE Labs


>From 1d9c87128897ee7f27f9651d75b80f73985373e8 Mon Sep 17 00:00:00 2001
From: Roman Gushchin <guro@...com>
Date: Fri, 1 Dec 2017 15:34:59 +0000
Subject: [PATCH] mm, oom, docs: document groupoom mount option

Add a note that cgroup-aware OOM logic is disabled by default
and describe how to enable it.

Signed-off-by: Roman Gushchin <guro@...com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Vladimir Davydov <vdavydov.dev@...il.com>
Cc: Tejun Heo <tj@...nel.org>
Cc: kernel-team@...com
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org
---
 Documentation/cgroup-v2.txt | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
index c80a147f94b7..ff8e92db636d 100644
--- a/Documentation/cgroup-v2.txt
+++ b/Documentation/cgroup-v2.txt
@@ -1049,6 +1049,9 @@ PAGE_SIZE multiple when read back.
 	and will never kill the unkillable task, even if memory.oom_group
 	is set.
 
+	If cgroup-aware OOM killer is not enabled, ENOTSUPP error
+	is returned on attempt to access the file.
+
   memory.events
 	A read-only flat-keyed file which exists on non-root cgroups.
 	The following entries are defined.  Unless specified
@@ -1258,6 +1261,12 @@ OOM Killer
 Cgroup v2 memory controller implements a cgroup-aware OOM killer.
 It means that it treats cgroups as first class OOM entities.
 
+Cgroup-aware OOM logic is turned off by default and requires
+passing the "groupoom" option on mounting cgroupfs. It can also
+by remounting cgroupfs with the following command::
+
+  # mount -o remount,groupoom $MOUNT_POINT
+
 Under OOM conditions the memory controller tries to make the best
 choice of a victim, looking for a memory cgroup with the largest
 memory footprint, considering leaf cgroups and cgroups with the
-- 
2.14.3