Subject: Re: REGRESSION: Performance regressions from switching
 anon_vma->lock to mutex
From: Tim Chen <tim.c.chen@linux.intel.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andi Kleen <ak@linux.intel.com>, Shaohua Li <shaohua.li@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@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>
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Date: Wed, 15 Jun 2011 11:43:18 -0700
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On Wed, 2011-06-15 at 18:45 +0200, Peter Zijlstra wrote:
> On Wed, 2011-06-15 at 09:18 -0700, Andi Kleen wrote:
> 
> > And in general it looks like blind conversion from spinlock to mutex
> > is a bad idea right now.
> 
> For 4 socket machines, maybe. On 2 sockets I cannot reproduce anything.
> 
> I wonder if its the fairness thing, the mutex spinners aren't fifo fair
> like the ticket locks are. It could be significant with larger socket
> count since their cacheline arbitration is more sucky.
> 
> 
> 

Peter,

Wonder if you can provide the profile on your run so I can compare with
what I got on 4 sockets?

Thanks.

Tim

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