linux-kernel - Re: [RFC][PATCH 1/5] memcg: change for softlimit.

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Message-ID: <20090828144539.GN4889@balbir.in.ibm.com>
Date:	Fri, 28 Aug 2009 20:15:39 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>
Subject: Re: [RFC][PATCH 1/5] memcg: change for softlimit.

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-08-28 23:29:09]:

> Balbir Singh wrote:
> > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-08-28
> > 16:35:23]:
> >
> 
> >>
> >> Current soft-limit RB-tree will be easily broken i.e. not-sorted
> >> correctly
> >> if used under use_hierarchy=1.
> >>
> >
> > Not true, I think the sorted-ness is delayed and is seen when we pick
> > a tree for reclaim. Think of it as being lazy :)
> >
> plz explain how enexpectedly unsorted RB-tree can work sanely.
> 
>

There are two checks built-in

1. In the reclaim path (we see how much to reclaim, compared to the
soft limit)
2. In the dequeue path where we check if we really are over soft limit

I did lot of testing with the time based approach and found no broken
cases, I;ve been testing it with the mmotm (event based approach and I
am yet to see a broken case so far).

 

-- 
	Balbir
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