linux-kernel - Re: REGRESSION: Performance regressions from switching anon

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Message-ID: <BANLkTin3onK+43LxODfbu-sdm-pFut0TKw@mail.gmail.com>
Date:	Fri, 17 Jun 2011 09:46:00 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Tim Chen <tim.c.chen@...ux.intel.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Shaohua Li <shaohua.li@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	David Miller <davem@...emloft.net>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Russell King <rmk@....linux.org.uk>,
	Paul Mundt <lethal@...ux-sh.org>,
	Jeff Dike <jdike@...toit.com>,
	Richard Weinberger <richard@....at>,
	"Luck, Tony" <tony.luck@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>, Nick Piggin <npiggin@...nel.dk>,
	Namhyung Kim <namhyung@...il.com>,
	"Shi, Alex" <alex.shi@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: REGRESSION: Performance regressions from switching anon_vma->lock
 to mutex

On Fri, Jun 17, 2011 at 4:28 AM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
>
> Something like so? Compiles and runs the benchmark in question.

Oh, and can you do this with a commit log and sign-off, and I'll put
it in my "anon_vma-locking" branch that I have. I'm not going to
actually merge that branch into mainline until I've seen a few more
acks or more testing by Tim.

But if Tim's numbers hold up (-32% to +15% performance by just the
first one, and +15% isn't actually an improvement since tmpfs
read-ahead should have gotten us to +66%), I think we have to do this
just to avoid the performance regression.

                                     Linus
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