Date: Thu, 15 Nov 2012 13:01:23 -0800 (PST)
From: David Rientjes <rientjes@google.com>
To: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
cc: Andrew Morton <akpm@linux-foundation.org>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Michal Hocko <mhocko@suse.cz>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [patch 2/4] mm, oom: cleanup pagefault oom handler
In-Reply-To: <50A4AB9E.4030106@jp.fujitsu.com>
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References: <alpine.DEB.2.00.1211140111190.32125@chino.kir.corp.google.com> <alpine.DEB.2.00.1211140113020.32125@chino.kir.corp.google.com> <50A4AB9E.4030106@jp.fujitsu.com>
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On Thu, 15 Nov 2012, Kamezawa Hiroyuki wrote:

> > @@ -708,15 +671,17 @@ out:
> > 
> >   /*
> >    * The pagefault handler calls here because it is out of memory, so kill a
> > - * memory-hogging task.  If a populated zone has ZONE_OOM_LOCKED set, a
> > parallel
> > - * oom killing is already in progress so do nothing.  If a task is found
> > with
> > - * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit.
> > + * memory-hogging task.  If any populated zone has ZONE_OOM_LOCKED set, a
> > + * parallel oom killing is already in progress so do nothing.
> >    */
> >   void pagefault_out_of_memory(void)
> >   {
> > -	if (try_set_system_oom()) {
> > +	struct zonelist *zonelist = node_zonelist(first_online_node,
> > +						  GFP_KERNEL);
> 
> 
> why GFP_KERNEL ? not GFP_HIGHUSER_MOVABLE ?
> 

The usual way to get a zonelist consisting of all zones ordered by 
preferring a node is node_zonelist(nid, GFP_KERNEL), but there's no 
difference between using GFP_KERNEL, GFP_HIGHUSER_MOVABLE, or even 0.  I 
simply duplicated what the sysrq trigger was doing, but you could also do 
&first_online_pgdat->node_zonelists[0], it's really just a matter of 
preference.
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