linux-kernel - Re: [RFC][PATCH 2/5] memcg: uncharge in batched manner

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Message-ID: <20090828151011.GS4889@balbir.in.ibm.com>
Date:	Fri, 28 Aug 2009 20:40:11 +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 2/5] memcg: uncharge in batched manner

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-08-28 13:24:38]:

> 
> In massive parallel enviroment, res_counter can be a performance bottleneck.
> This patch is a trial for reducing lock contention.
> One strong techinque to reduce lock contention is reducing calls by
> batching some amount of calls int one.
> 
> Considering charge/uncharge chatacteristic,
> 	- charge is done one by one via demand-paging.
> 	- uncharge is done by
> 		- in chunk at munmap, truncate, exit, execve...
> 		- one by one via vmscan/paging.
> 
> It seems we hace a chance to batched-uncharge.
> This patch is a base patch for batched uncharge. For avoiding
> scattering memcg's structure, this patch adds memcg batch uncharge
> information to the task. please see start/end usage in next patch.
>

Overall it is a very good idea, can't we do the uncharge at the poin
tof unmap_vmas, exit_mmap, etc so that we don't have to keep
additional data structures around. 

-- 
	Balbir
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