linux-kernel - Re: [PATCH 26/31] sched: numa: Make mempolicy home-node aware

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Message-ID: <20121114185017.GQ8218@suse.de>
Date:	Wed, 14 Nov 2012 18:50:17 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Rik van Riel <riel@...hat.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Hugh Dickins <hughd@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 26/31] sched: numa: Make mempolicy home-node aware

On Wed, Nov 14, 2012 at 01:22:33PM -0500, Rik van Riel wrote:
> On 11/13/2012 06:12 AM, Mel Gorman wrote:
> >From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> >
> >Add another layer of fallback policy to make the home node concept
> >useful from a memory allocation PoV.
> >
> >This changes the mpol order to:
> >
> >  - vma->vm_ops->get_policy	[if applicable]
> >  - vma->vm_policy		[if applicable]
> >  - task->mempolicy
> >  - tsk_home_node() preferred	[NEW]
> >  - default_policy
> 
> Why is the home node policy not the default policy?
> 

hmm, it effectively is if there is no other policy set. The changelog is
a bit misleading. In V3, this will be dropped entirely. It was not clear
that doing a remote alloc for home nodes was a good idea. Instead memory
is always allocated locally to the faulting process as normal and
migrated later if necessary.

-- 
Mel Gorman
SUSE Labs
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