linux-kernel - Re: [PATCH] memcg: implement low limits

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Date:	Wed, 27 Feb 2013 14:39:36 +0400
From:	Roman Gushchin <klamm@...dex-team.ru>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Johannes Weiner-Arquette <hannes@...xchg.org>,
	"bsingharora@...il.com" <bsingharora@...il.com>,
	"kamezawa.hiroyu@...fujitsu.com" <kamezawa.hiroyu@...fujitsu.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>,
	"mel@....ul.ie" <mel@....ul.ie>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Ying Han <yinghan@...gle.com>
Subject: Re: [PATCH] memcg: implement low limits

27.02.2013, 13:41, "Michal Hocko" <mhocko@...e.cz>:
> Let me restate what I have already mentioned in the private
> communication.
>
> We already have soft limit which can be implemented to achieve the
> same/similar functionality and in fact this is a long term objective (at
> least for me). I hope I will be able to post my code soon. The last post
> by Ying Hand (cc-ing her) was here:
> http://comments.gmane.org/gmane.linux.kernel.mm/83499
>
> To be honest I do not like introduction of a new limit because we have
> two already and the situation would get over complicated.

I think, there are three different tasks:
1) keeping cgroups below theirs hard limit to avoid direct reclaim (for performance reasons),
2) cgroup's prioritization during global reclaim,
3) granting some amount of memory to a selected cgroup (and protecting it from reclaim without significant reasons)

IMHO, combining them all in one limit will simplify a kernel code, but will also make a user's (or administrator's) 
life much more complicated. Introducing low limits can make the situation simpler.

>
> More comments on the code bellow.

Thank you very much!
I'll address them in an other letter.

--
Regards,
Roman
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