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Date: Sat, 18 Jun 2011 10:08:18 +0200
From: Ingo Molnar <mingo@elte.hu>
Subject: Re: REGRESSION: Performance regressions from switching
 anon_vma->lock to mutex
Message-ID: <20110618080818.GA10351@elte.hu>
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To: Andi Kleen <ak@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Tim Chen <tim.c.chen@linux.intel.com>, Shaohua Li <shaohua.li@intel.com>, Andrew Morton <akpm@linux-foundation.org>, Hugh Dickins <hughd@google.com>, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, David Miller <davem@davemloft.net>, Martin Schwidefsky <schwidefsky@de.ibm.com>, Russell King <rmk@arm.linux.org.uk>, Paul Mundt <lethal@linux-sh.org>, Jeff Dike <jdike@addtoit.com>, Richard Weinberger <richard@nod.at>, "Luck, Tony" <tony.luck@intel.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Mel Gorman <mel@csn.ul.ie>, Nick Piggin <npiggin@kernel.dk>, Namhyung Kim <namhyung@gmail.com>, "Shi, Alex" <alex.shi@intel.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "Rafael J. Wysocki" <rjw@sisk.pl>


* Andi Kleen <ak@linux.intel.com> wrote:

> On Fri, Jun 17, 2011 at 09:46:00AM -0700, Linus Torvalds wrote:
> > On Fri, Jun 17, 2011 at 4:28 AM, Peter Zijlstra <a.p.zijlstra@chello.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.
> 
> You could also add the mutex "optimize caching protocol" 
> patch I posted earlier to that branch.
> 
> It didn't actually improve Tim's throughput number, but it made the 
> CPU consumption of the mutex go down.

Why have you ignored the negative feedback for that patch:

  http://marc.info/?i=20110617190705.GA26824@elte.hu

and why have you resent this patch without addressing that feedback?

Thanks,

	Ingo

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