linux-kernel - Re: [RFC PATCH 0/4]: affinity-on-next-touch

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Date:	Fri, 12 Jun 2009 14:30:06 +0200
From:	Brice Goglin <Brice.Goglin@...ia.fr>
To:	Stefan Lankes <lankes@...s.rwth-aachen.de>
CC:	'Andi Kleen' <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Lee.Schermerhorn@...com, linux-numa@...r.kernel.org,
	Boris Bierbaum <boris@...s.rwth-aachen.de>
Subject: Re: [RFC PATCH 0/4]: affinity-on-next-touch

Stefan Lankes wrote:
> He enables the support of migration-on-fault via cpusets (echo 1 >
> /dev/cpuset/migrate_on_fault).
> Afterwards, every process could initiate migration-on-fault via mbind(...,
> MPOL_MF_MOVE|MPOL_MF_LAZY).

So mbind(MPOL_MF_LAZY) is taking care of changing page protection so as
to generate page-faults on next-touch? (instead of your madvise)
Is it migrating the whole memory area? Or only single pages?

Then, what's happening with MPOL_MF_LAZY in the kernel? Is it actually
stored in the mempolicy? If so, couldn't another fault later cause
another migration?
Or is MPOL_MF_LAZY filtered out of the policy once the protection of all
PTE has been changed?
I don't see why we need a new mempolicy here. If we are migrating single
pages, migrate-on-next-touch looks like a page-attribute to me. There
should be nothing to store in a mempolicy/VMA/whatever.

Brice

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