linux-kernel - Re: [patch 1/4] mm, oom: ensure sysrq+f always passes valid zonelist

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Date:	Wed, 14 Nov 2012 14:31:14 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch 1/4] mm, oom: ensure sysrq+f always passes valid zonelist

On Wed 14-11-12 03:03:02, David Rientjes wrote:
> On Wed, 14 Nov 2012, Michal Hocko wrote:
> 
> > > With hotpluggable and memoryless nodes, it's possible that node 0 will
> > > not be online, so use the first online node's zonelist rather than
> > > hardcoding node 0 to pass a zonelist with all zones to the oom killer.
> > 
> > Makes sense although I haven't seen a machine with no 0 node yet.
> 
> We routinely do testing with them, actually, just by physically removing 
> all memory described by the SRAT that maps to node 0.  You could do the 
> same thing by making all pxms that map to node 0 to be hotpluggable in 
> your memory affinity structure.  I've been bit by it one too many times so 
> I always keep in mind that no single node id is guaranteed to be online 
> (although at least one node is always online); hence, first_online_node is 
> the solution.

I thought that a boot cpu would be bound to a node0 or something similar.
Thanks for the clarification!

> > According to 13808910 this is indeed possible.
> > 
> > > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > Signed-off-by: David Rientjes <rientjes@...gle.com>
> > 
> > Reviewed-by: Michal Hocko <mhocko@...e.cz>
> > 
> 
> Thanks!

-- 
Michal Hocko
SUSE Labs
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