linux-kernel - Re: [PATCH -mm 3/5] memcg scalable file stat accounting method

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Message-Id: <20100804102527.d3bb4afc.nishimura@mxp.nes.nec.co.jp>
Date:	Wed, 4 Aug 2010 10:25:27 +0900
From:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	linux-mm@...ck.org,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	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>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Subject: Re: [PATCH -mm 3/5] memcg scalable file stat accounting method

On Wed, 4 Aug 2010 10:11:50 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:

> On Wed, 4 Aug 2010 09:55:13 +0900
> Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:
> 
> > > @@ -1074,7 +1075,49 @@ static unsigned int get_swappiness(struc
> > >  	return swappiness;
> > >  }
> > >  
> > > -/* A routine for testing mem is not under move_account */
> > > +static void mem_cgroup_start_move(struct mem_cgroup *mem)
> > > +{
> > > +	int cpu;
> > > +	/* for fast checking in mem_cgroup_update_file_stat() etc..*/
> > > +	spin_lock(&mc.lock);
> > > +	for_each_possible_cpu(cpu)
> > > +		per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) += 1;
> > > +	spin_unlock(&mc.lock);
> > > +
> > > +	synchronize_rcu();
> > > +}
> > > +
> > > +static void mem_cgroup_end_move(struct mem_cgroup *mem)
> > > +{
> > > +	int cpu;
> > > +
> > > +	if (!mem)
> > > +		return;
> > Is this check necessary?
> > 
> 
> Yes, I hit NULL here.
> That happens migration=off case, IIRC.
> 
Ah, you're right.
Thank you for your clarification.

Daisuke Nishimura.
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