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Date: Tue, 06 Nov 2012 14:19:18 -0500
From: Rik van Riel <riel@redhat.com>
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To: Mel Gorman <mgorman@suse.de>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Andrea Arcangeli <aarcange@redhat.com>, Ingo Molnar <mingo@kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>, Hugh Dickins <hughd@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux-MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 14/19] mm: mempolicy: Add MPOL_MF_LAZY
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On 11/06/2012 04:14 AM, Mel Gorman wrote:
> From: Lee Schermerhorn <lee.schermerhorn@hp.com>
>
> NOTE: Once again there is a lot of patch stealing and the end result
> 	is sufficiently different that I had to drop the signed-offs.
> 	Will re-add if the original authors are ok with that.
>
> This patch adds another mbind() flag to request "lazy migration".  The
> flag, MPOL_MF_LAZY, modifies MPOL_MF_MOVE* such that the selected
> pages are marked PROT_NONE. The pages will be migrated in the fault
> path on "first touch", if the policy dictates at that time.
>
> "Lazy Migration" will allow testing of migrate-on-fault via mbind().
> Also allows applications to specify that only subsequently touched
> pages be migrated to obey new policy, instead of all pages in range.
> This can be useful for multi-threaded applications working on a
> large shared data area that is initialized by an initial thread
> resulting in all pages on one [or a few, if overflowed] nodes.
> After PROT_NONE, the pages in regions assigned to the worker threads
> will be automatically migrated local to the threads on 1st touch.
>
> Signed-off-by: Mel Gorman <mgorman@suse.de>

Reviewed-by: Rik van Riel <riel@redhat.com>