From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f46.google.com (mail-ee0-f46.google.com [74.125.83.46]) by kanga.kvack.org (Postfix) with ESMTP id 092466B008A for ; Thu, 17 Apr 2014 08:57:05 -0400 (EDT) Received: by mail-ee0-f46.google.com with SMTP id t10so644372eei.19 for ; Thu, 17 Apr 2014 05:57:05 -0700 (PDT) Received: from zene.cmpxchg.org (zene.cmpxchg.org. [2a01:238:4224:fa00:ca1f:9ef3:caee:a2bd]) by mx.google.com with ESMTPS id m49si35254678eeo.71.2014.04.17.05.57.03 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Thu, 17 Apr 2014 05:57:04 -0700 (PDT) Date: Thu, 17 Apr 2014 08:56:57 -0400 From: Johannes Weiner Subject: Re: [patch] mm: memcontrol: remove hierarchy restrictions for swappiness and oom_control Message-ID: <20140417125657.GA23470@cmpxchg.org> References: <1397682798-22906-1-git-send-email-hannes@cmpxchg.org> <20140416143425.c2b6f511cf4c6cd7336134b3@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140416143425.c2b6f511cf4c6cd7336134b3@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Michal Hocko , Tejun Heo , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org On Wed, Apr 16, 2014 at 02:34:25PM -0700, Andrew Morton wrote: > On Wed, 16 Apr 2014 17:13:18 -0400 Johannes Weiner wrote: > > > Per-memcg swappiness and oom killing can currently not be tweaked on a > > memcg that is part of a hierarchy, but not the root of that hierarchy. > > Users have complained that they can't configure this when they turned > > on hierarchy mode. In fact, with hierarchy mode becoming the default, > > this restriction disables the tunables entirely. > > > > But there is no good reason for this restriction. The settings for > > swappiness and OOM killing are taken from whatever memcg whose limit > > triggered reclaim and OOM invocation, regardless of its position in > > the hierarchy tree. > > > > Allow setting swappiness on any group. The knob on the root memcg > > already reads the global VM swappiness, make it writable as well. > > > > Allow disabling the OOM killer on any non-root memcg. > > Documentation/cgroups/memory.txt needs updates? Yes, that makes sense, thanks. How about this? --- Subject: [patch] mm: memcontrol: remove hierarchy restrictions for swappiness and oom_control fix Update Documentation/cgroups/memory.txt Signed-off-by: Johannes Weiner --- diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index 2622115276aa..1829c65f8371 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -535,17 +535,15 @@ Note: 5.3 swappiness -Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only. +Similar to /proc/sys/vm/swappiness, but only affecting reclaim that is +triggered by this cgroup's hard limit. The tunable in the root cgroup +corresponds to the global swappiness setting. + 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). -- a cgroup which uses hierarchy and it has other cgroup(s) below it. -- a cgroup which uses hierarchy and not the root of hierarchy. - 5.4 failcnt A memory cgroup provides memory.failcnt and memory.memsw.failcnt files. @@ -754,7 +752,6 @@ You can disable the OOM-killer by writing "1" to memory.oom_control file, as: #echo 1 > memory.oom_control -This operation is only allowed to the top cgroup of a sub-hierarchy. If OOM-killer is disabled, tasks under cgroup will hang/sleep in memory cgroup's OOM-waitqueue when they request accountable memory. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org