Date: Tue, 3 Aug 2010 08:52:16 +0530
From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: linux-mm@kvack.org,
        "nishimura@mxp.nes.nec.co.jp" <nishimura@mxp.nes.nec.co.jp>,
        vgoyal@redhat.com, m-ikeda@ds.jp.nec.com, gthelen@google.com,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH -mm 1/5] quick lookup memcg by ID
Message-ID: <20100803032216.GC3863@balbir.in.ibm.com>
Reply-To: balbir@linux.vnet.ibm.com
References: <20100802191113.05c982e4.kamezawa.hiroyu@jp.fujitsu.com>
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* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-02 19:13:04]:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.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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