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Date: Sat, 01 Dec 2012 13:55:50 -0500
From: Rik van Riel <riel@redhat.com>
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To: Linus Torvalds <torvalds@linux-foundation.org>
CC: Ingo Molnar <mingo@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Paul Turner <pjt@google.com>,
        Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
        Christoph Lameter <cl@linux.com>, Mel Gorman <mgorman@suse.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Johannes Weiner <hannes@cmpxchg.org>, Hugh Dickins <hughd@google.com>
Subject: Re: [RFC PATCH] mm/migration: Remove anon vma locking from try_to_unmap()
 use
References: <1354305521-11583-1-git-send-email-mingo@kernel.org> <CA+55aFwjxm7OYuucHeE2WFr4p+jwr63t=kSdHndta_QkyFbyBQ@mail.gmail.com> <20121201094927.GA12366@gmail.com> <20121201122649.GA20322@gmail.com> <CA+55aFx8QtP0hg8qxn__4vHQuzH7QkhTN-4fwgOpM-A=KuBBjA@mail.gmail.com>
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On 12/01/2012 01:38 PM, Linus Torvalds wrote:
> On Sat, Dec 1, 2012 at 4:26 AM, Ingo Molnar <mingo@kernel.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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