From: Glauber Costa <glommer@parallels.com>
To: Michal Hocko <mhocko@suse.cz>
Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
linux-mm@kvack.org, devel@openvz.org,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Mel Gorman <mgorman@suse.de>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC 1/4] memcg: provide root figures from system totals
Date: Tue, 2 Oct 2012 13:15:43 +0400 [thread overview]
Message-ID: <506AB0BF.9030400@parallels.com> (raw)
In-Reply-To: <20121001170046.GC24860@dhcp22.suse.cz>
On 10/01/2012 09:00 PM, Michal Hocko wrote:
> On Tue 25-09-12 12:52:50, Glauber Costa wrote:
>> > For the root memcg, there is no need to rely on the res_counters.
> This is true only if there are no children groups but once there is at
> least one we have to move global statistics into root res_counter and
> start using it since then. This is a tricky part because it has to be
> done atomically so that we do not miss anything.
>
Why can't we shortcut it all the time?
It makes a lot of sense to use the root cgroup as the sum of everything,
IOW, global counters. Otherwise you are left in a situation where you
had global statistics, and all of a sudden, when a group is created, you
start having just a subset of that, excluding the tasks in root.
If we can always assume root will have the sum of *all* tasks, including
the ones in root, we should never need to rely on root res_counters.
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WARNING: multiple messages have this Message-ID (diff)
From: Glauber Costa <glommer@parallels.com>
To: Michal Hocko <mhocko@suse.cz>
Cc: <linux-kernel@vger.kernel.org>, <cgroups@vger.kernel.org>,
<linux-mm@kvack.org>, <devel@openvz.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Mel Gorman <mgorman@suse.de>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC 1/4] memcg: provide root figures from system totals
Date: Tue, 2 Oct 2012 13:15:43 +0400 [thread overview]
Message-ID: <506AB0BF.9030400@parallels.com> (raw)
In-Reply-To: <20121001170046.GC24860@dhcp22.suse.cz>
On 10/01/2012 09:00 PM, Michal Hocko wrote:
> On Tue 25-09-12 12:52:50, Glauber Costa wrote:
>> > For the root memcg, there is no need to rely on the res_counters.
> This is true only if there are no children groups but once there is at
> least one we have to move global statistics into root res_counter and
> start using it since then. This is a tricky part because it has to be
> done atomically so that we do not miss anything.
>
Why can't we shortcut it all the time?
It makes a lot of sense to use the root cgroup as the sum of everything,
IOW, global counters. Otherwise you are left in a situation where you
had global statistics, and all of a sudden, when a group is created, you
start having just a subset of that, excluding the tasks in root.
If we can always assume root will have the sum of *all* tasks, including
the ones in root, we should never need to rely on root res_counters.
next prev parent reply other threads:[~2012-10-02 9:15 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-25 8:52 [RFC 0/4] bypass charges if memcg is not used Glauber Costa
2012-09-25 8:52 ` Glauber Costa
[not found] ` <1348563173-8952-1-git-send-email-glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-09-25 8:52 ` [RFC 1/4] memcg: provide root figures from system totals Glauber Costa
2012-09-25 8:52 ` Glauber Costa
2012-09-25 8:52 ` Glauber Costa
[not found] ` <1348563173-8952-2-git-send-email-glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-10-01 17:00 ` Michal Hocko
2012-10-01 17:00 ` Michal Hocko
2012-10-01 17:00 ` Michal Hocko
2012-10-02 9:15 ` Glauber Costa [this message]
2012-10-02 9:15 ` Glauber Costa
[not found] ` <506AB0BF.9030400-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-10-02 9:34 ` Michal Hocko
2012-10-02 9:34 ` Michal Hocko
2012-10-02 9:34 ` Michal Hocko
2012-09-25 8:52 ` [RFC 2/4] memcg: make it suck faster Glauber Costa
2012-09-25 8:52 ` Glauber Costa
2012-09-25 8:52 ` Glauber Costa
[not found] ` <1348563173-8952-3-git-send-email-glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-09-25 21:02 ` Andrew Morton
2012-09-25 21:02 ` Andrew Morton
2012-09-25 21:02 ` Andrew Morton
2012-09-26 8:53 ` Glauber Costa
2012-09-26 8:53 ` Glauber Costa
2012-09-26 9:03 ` Daniel P. Berrange
2012-09-26 9:03 ` Daniel P. Berrange
2012-09-25 8:52 ` [RFC 3/4] memcg: do not call page_cgroup_init at system_boot Glauber Costa
2012-09-25 8:52 ` Glauber Costa
2012-09-25 8:52 ` Glauber Costa
2012-09-25 8:52 ` [RFC 4/4] memcg: do not walk all the way to the root for memcg Glauber Costa
2012-09-25 8:52 ` Glauber Costa
2012-09-25 8:52 ` Glauber Costa
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