linux-kernel - Re: [patch 5/9] Convert anon_vma lock to rw

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Date:	Wed, 2 Apr 2008 19:50:58 +0200
From:	Andrea Arcangeli <andrea@...ranet.com>
To:	Christoph Lameter <clameter@....com>
Cc:	Hugh Dickins <hugh@...itas.com>, Robin Holt <holt@....com>,
	Avi Kivity <avi@...ranet.com>, Izik Eidus <izike@...ranet.com>,
	kvm-devel@...ts.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	general@...ts.openfabrics.org,
	Steve Wise <swise@...ngridcomputing.com>,
	Roland Dreier <rdreier@...co.com>,
	Kanoj Sarcar <kanojsarcar@...oo.com>, steiner@....com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com
Subject: Re: [patch 5/9] Convert anon_vma lock to rw_sem and refcount

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!
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