Subject: Re: REGRESSION: Performance regressions from switching
 anon_vma->lock to mutex
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Tim Chen <tim.c.chen@linux.intel.com>
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 23:37:29 +0200
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On Wed, 2011-06-15 at 14:12 -0700, Tim Chen wrote:
> Thanks to Andi for providing the info.  We've used this workaround in
> our testing so it will not mask true kernel scaling bottlenecks.


http://programming.kicks-ass.net/sekrit/39-2.txt.bz2
http://programming.kicks-ass.net/sekrit/tip-2.txt.bz2

tip+sirq+linus is still slightly faster than .39 here, although removing
that sysconf() wreckage closed the gap considerably (needing to know the
number of cpus to optimize locking sounds like a trainwreck all of its
own, needing it _that_ often instead of just once at startup is even
worse).

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