linux-kernel - Re: [patch v3 -mm 1/3] memcg: integrate soft reclaim tighter with zone shrinking code

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Message-ID: <CAOS58YP6qXM_mXvsCtGSViOZTw=mwnfUS7cZGAES8F4w5mCQdA@mail.gmail.com>
Date:	Fri, 17 May 2013 10:45:54 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Michal Hocko <mhocko@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Cgroups <cgroups@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Ying Han <yinghan@...gle.com>, Hugh Dickins <hughd@...gle.com>,
	Glauber Costa <glommer@...allels.com>,
	Michel Lespinasse <walken@...gle.com>,
	Greg Thelen <gthelen@...gle.com>,
	Balbir Singh <bsingharora@...il.com>
Subject: Re: [patch v3 -mm 1/3] memcg: integrate soft reclaim tighter with
 zone shrinking code

Hello,

On Fri, May 17, 2013 at 10:27 AM, Johannes Weiner <hannes@...xchg.org> wrote:
>>Hmmm... if the iteration is the problem, it shouldn't be difficult to
>>build list of children which should be iterated.  Would that make it
>>acceptable?
>
> You mean, a separate structure that tracks which groups are in excess of the limit?  Like the current tree? :)

Heh, yeah, realized that after writing it but it can be something much
simpler. ie. just linked list of children with soft limit configured.

> Kidding aside, yes, that would be better, and an unsorted list would probably be enough for the global case.

Yeap.

> To support target reclaim soft limits later on, we could maybe propagate tags upwards the cgroup tree when a group is in excess so that reclaim can be smarter about which subtrees to test for soft limits and which to skip during the soft limit pass.  The no-softlimit-set-anywhere case is then only a single tag test in the root cgroup.
>
> But starting with the list would be simple enough, delete a bunch of code, come with the same performance improvements etc.

Thanks.

--
tejun
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