linux-kernel - Re: [PATCH 15/19] mm: numa: Add fault driven placement and migration

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Message-ID: <20121107104940.GU8218@suse.de>
Date:	Wed, 7 Nov 2012 10:49:40 +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 15/19] mm: numa: Add fault driven placement and migration

On Tue, Nov 06, 2012 at 02:41:13PM -0500, Rik van Riel wrote:
> On 11/06/2012 04:14 AM, Mel Gorman wrote:
> >From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> >
> >NOTE: This patch is based on "sched, numa, mm: Add fault driven
> >	placement and migration policy" but as it throws away all the policy
> >	to just leave a basic foundation I had to drop the signed-offs-by.
> >
> >This patch creates a bare-bones method for setting PTEs pte_numa in the
> >context of the scheduler that when faulted later will be faulted onto the
> >node the CPU is running on.  In itself this does nothing useful but any
> >placement policy will fundamentally depend on receiving hints on placement
> >from fault context and doing something intelligent about it.
> >
> >Signed-off-by: Mel Gorman <mgorman@...e.de>
> 
> Excellent basis for implementing a smarter NUMA
> policy.
> 
> Not sure if such a policy should be implemented
> as a replacement for this patch, or on top of it...
> 

I'm expecting on top of it. As a POC, I'm looking at implementing the CPU
Follows Memory algorithm (mostly from autonuma) on top of this but using the
home-node logic from schednuma to handle how processes get scheduled. MORON
will need to relax to take the home node into account to avoid fighting
the home-node decisions. task_numa_fault() determines if the home node
needs to change based on statistics it gathers from faults. So far I am
keeping within the framework but it is still a WIP.

> Either way, thank you for cleaning up all of the
> NUMA base code, while I was away at conferences
> and stuck in airports :)
> 

My pleasure. Thanks a lot for reviewing this!

-- 
Mel Gorman
SUSE Labs
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