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Date: Wed, 2 Apr 2008 19:50:58 +0200
From: Andrea Arcangeli <andrea@qumranet.com>
To: Christoph Lameter <clameter@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>, Robin Holt <holt@sgi.com>,
       Avi Kivity <avi@qumranet.com>, Izik Eidus <izike@qumranet.com>,
       kvm-devel@lists.sourceforge.net,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, general@lists.openfabrics.org,
       Steve Wise <swise@opengridcomputing.com>,
       Roland Dreier <rdreier@cisco.com>, Kanoj Sarcar <kanojsarcar@yahoo.com>,
       steiner@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       daniel.blueman@quadrics.com
Subject: Re: [patch 5/9] Convert anon_vma lock to rw_sem and refcount
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References: <20080401205531.986291575@sgi.com> <20080401205636.777127252@sgi.com>
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On Tue, Apr 01, 2008 at 01:55:36PM -0700, Christoph Lameter wrote:
>   This results in f.e. the Aim9 brk performance test to got down by 10-15%.

I guess it's more likely because of overscheduling for small crtitical
sections, did you counted the total number of context switches? I
guess there will be a lot more with your patch applied. That
regression is a showstopper and it is the reason why I've suggested
before to add a CONFIG_XPMEM or CONFIG_MMU_NOTIFIER_SLEEP config
option to make the VM locks sleep capable only when XPMEM=y
(PREEMPT_RT will enable it too). Thanks for doing the benchmark work!