linux-kernel - Re: [PATCH -mm 1/5] quick lookup memcg by ID

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Message-ID: <20100803032216.GC3863@balbir.in.ibm.com>
Date:	Tue, 3 Aug 2010 08:52:16 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	linux-mm@...ck.org,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	vgoyal@...hat.com, m-ikeda@...jp.nec.com, gthelen@...gle.com,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -mm 1/5] quick lookup memcg by ID

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2010-08-02 19:13:04]:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
> Now, memory cgroup has an ID per cgroup and make use of it at
>  - hierarchy walk,
>  - swap recording.
> 
> This patch is for making more use of it. The final purpose is
> to replace page_cgroup->mem_cgroup's pointer to an unsigned short.
> 
> This patch caches a pointer of memcg in an array. By this, we
> don't have to call css_lookup() which requires radix-hash walk.
> This saves some amount of memory footprint at lookup memcg via id.
>

It is a memory versus speed tradeoff, but if the number of created
cgroups is low, it might not be all that slow, besides we do that for
swap_cgroup anyway - no?
 

-- 
	Three Cheers,
	Balbir
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