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Date: Wed, 4 Aug 2010 10:11:50 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: linux-mm@kvack.org,
        "balbir@linux.vnet.ibm.com" <balbir@linux.vnet.ibm.com>,
        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 3/5] memcg scalable file stat accounting method
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On Wed, 4 Aug 2010 09:55:13 +0900
Daisuke Nishimura <nishimura@mxp.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.

Thanks,
-Kame

> Thanks,
> Daisuke Nishimura.
> 
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