linux-kernel - Re: [PATCH 18/19] sched, numa: Per task memory placement for big processes

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Message-ID: <5018547B.4020000@redhat.com>
Date:	Tue, 31 Jul 2012 17:56:11 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	mingo@...nel.org, oleg@...hat.com, pjt@...gle.com,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	tglx@...utronix.de, Lee.Schermerhorn@...com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 18/19] sched, numa: Per task memory placement for big
 processes

On 07/31/2012 03:12 PM, Peter Zijlstra wrote:
> Probability says that the task faulting on a page after we protect it,
> is most likely to be the task that uses that page most.
>
> To decrease the likelyhood of acting on a false relation, we only
> migrate a page when two consecutive samples are from the same task.
>
> I'm still not entirely convinced this scheme is sound, esp. for things
> like virtualization and n:m threading solutions in general the
> compute<->task relation is fundamentally untrue.

Again, we may need some additional code on top in the future,
eg. something like Andrea's policy that tries grouping related
tasks/threads together, but this looks like a very good way
to start.

We can introduce complexity if it is needed. Simplicity is good.

Acked-by: Rik van Riel

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