linux-kernel - Re: [RFC PATCH] mm/migration: Remove anon vma locking from try_to

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Message-ID: <50BA52B6.2010009@redhat.com>
Date:	Sat, 01 Dec 2012 13:55:50 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Turner <pjt@...gle.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Christoph Lameter <cl@...ux.com>, Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Johannes Weiner <hannes@...xchg.org>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [RFC PATCH] mm/migration: Remove anon vma locking from try_to_unmap()
 use

On 12/01/2012 01:38 PM, Linus Torvalds wrote:
> On Sat, Dec 1, 2012 at 4:26 AM, Ingo Molnar <mingo@...nel.org> wrote:
>>
>>
>> So as a quick concept hack I wrote the patch attached below.
>> (It's not signed off, see the patch description text for the
>> reason.)
>
> Well, it confirms that anon_vma locking is a big problem, but as
> outlined in my other email it's completely incorrect from an actual
> behavior standpoint.
>
> Btw, I think the anon_vma lock could be made a spinlock

The anon_vma lock used to be a spinlock, and was turned into a
mutex by Peter, as part of an effort to make more of the VM
preemptible.

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