linux-kernel - Re: [06/44] numa: fix slab_node(MPOL

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Message-ID: <1291782782.5324.54.camel@edumazet-laptop>
Date:	Wed, 08 Dec 2010 05:33:02 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Lee Schermerhorn <Lee.Schermerhorn@...com>
Cc:	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	stable@...nel.org, stable-review@...nel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Mel Gorman <mel@....ul.ie>,
	Christoph Lameter <cl@...ux.com>
Subject: Re: [06/44] numa: fix slab_node(MPOL_BIND)

Le mardi 07 décembre 2010 à 22:03 -0500, Lee Schermerhorn a écrit :
> On Tue, 2010-12-07 at 16:04 -0800, Greg KH wrote:
> > 2.6.27-stable review patch.  If anyone has any objections, please let us know.
> > 
> > ------------------
> > 
> > From: Eric Dumazet <eric.dumazet@...il.com>
> > 
> > commit 800416f799e0723635ac2d720ad4449917a1481c upstream.
> > 

> > 
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -1404,7 +1404,7 @@ unsigned slab_node(struct mempolicy *pol
> >  		(void)first_zones_zonelist(zonelist, highest_zoneidx,
> >  							&policy->v.nodes,
> >  							&zone);
> > -		return zone->node;
> > +		return zone ? zone->node : numa_node_id();
> 
> I think this should be numa_mem_id().  Given the documented purpose of
> slab_node(), we want a node from which page allocation is likely to
> succeed.  numa_node_id() can return a memoryless node for, e.g.,  some
> configurations of some HP ia64 platforms.  numa_mem_id() was introduced
> to return that same node from which "local" mempolicy would allocate
> pages.

Hmm... numa_mem_id() was introduced in 2.6.35 as an optimization.

When I did this patch (to fix a bug), mm/mempolicy.c only contained
calls to numa_node_id() (and still is today)

By the way, anybody knows how I can emulate a memoryless node on a dual
node x86_64 machine (with memory present on both nodes) ?



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