linux-kernel - Re: Race condition between putback_lru_page and mem_cgroup_move

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Message-Id: <1218108434.6086.29.camel@lts-notebook>
Date:	Thu, 07 Aug 2008 07:27:14 -0400
From:	Lee Schermerhorn <Lee.Schermerhorn@...com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	balbir@...ux.vnet.ibm.com, MinChan Kim <minchan.kim@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm <linux-mm@...ck.org>, Rik van Riel <riel@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Race condition between putback_lru_page and
	mem_cgroup_move_list

On Thu, 2008-08-07 at 20:00 +0900, KOSAKI Motohiro wrote:
> Hi
> 
> > If you mean the "active/inactive list transition" in
> > shrink_[in]active_list(), these are already batched under zone lru_lock
> > with batch size determined by the 'release pages' pvec.  So, I think
> > we're OK here.
> 
> No.
> 
> AFAIK shrink_inactive_list batched zone->lru_lock, 
> but it doesn't batched mz->lru_lock.
> 
> then, spin_lock_irqsave is freqently called.

Ah, I see what you mean.  Yes, the mem cgroup zone lru_lock will be
cycled frequently as each back of pages is put back during reclaim.  So,
you'd like to eliminate the mz lru_lock, move the mem cgroup zone info
under the corresponding zone lru_lock and move the page between memcg
lists atomically with adding to global lru lists?  

Lee

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