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

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Message-ID: <20090828160340.GU4889@balbir.in.ibm.com>
Date:	Fri, 28 Aug 2009 21:33:40 +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> [2009-08-29 00:21:50]:

> > tof unmap_vmas, exit_mmap, etc so that we don't have to keep
> > additional data structures around.
> >
> We can't. We uncharge when page->mapcount goes down to 0.
> This is unknown until page_remove_rmap() decrement page->mapcount
> by "atomic" ops.
> 
> My first version allocated memcg_batch_info on stack ...and..
> I had to pass an extra argument to page_remove_rmap() etc....
> That was very ugly ;(
> Now, I adds per-task memcg_batch_info to task struct.
> Because it will be always used at exit() and make exit() path
> much faster, it's not very costly.
>

Aaah.. I see that makes a lot of sense. Thanks for the clarification. 

-- 
	Balbir
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