linux-kernel - Re: [PATCH 6/6] Use one zonelist that is filtered by nodemask

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Message-ID: <Pine.LNX.4.64.0711090924210.14572@schroedinger.engr.sgi.com>
Date:	Fri, 9 Nov 2007 09:26:01 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Lee Schermerhorn <Lee.Schermerhorn@...com>
cc:	Nishanth Aravamudan <nacc@...ibm.com>, Mel Gorman <mel@...net.ie>,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, rientjes@...gle.com,
	kamezawa.hiroyu@...fujitsu.com
Subject: Re: [PATCH 6/6] Use one zonelist that is filtered by nodemask

On Fri, 9 Nov 2007, Lee Schermerhorn wrote:

> > On the other hand, if we call alloc_pages() with GFP_THISNODE set, there
> > is no nid to base the allocation on, so we "fallback" to numa_node_id()
> > [ almost like the nid had been specified as -1 ].
> > 
> > So I guess this is logical -- but I wonder, do we have any callers of
> > alloc_pages(GFP_THISNODE) ? It seems like an odd thing to do, when
> > alloc_pages_node() exists?
> 
> I don't know if we have any current callers that do this, but absent any
> documentation specifying otherwise, Mel's implementation matches what
> I'd expect the behavior to be if I DID call alloc_pages with 'THISNODE.
> However, we could specify that THISNODE is ignored in __alloc_pages()
> and recommend the use of alloc_pages_node() passing numa_node_id() as
> the nid parameter to achieve the behavior.  This would eliminate the
> check for 'THISNODE in __alloc_pages().  Just mask it off before calling
> down to __alloc_pages_internal().
> 
> Does this make sense?

I like consistency. If someone absolutely wants a local page then 
specifying GFP_THISNODE to __alloc_pages is okay. Leave as is I guess. 

What happens though if an MPOL_BIND policy is in effect? The node used 
must then be the nearest node from the policy mask....


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