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Subject: Re: [GIT PULL] Re: REGRESSION: Performance regressions from switching anon_vma->lock to mutex
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Wed, 15 Jun 2011 14:05:46 -0700
To: Ingo Molnar <mingo@elte.hu>
CC: Peter Zijlstra <peterz@infradead.org>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Tim Chen <tim.c.chen@linux.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>,
        Tony Luck <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>, ak@linux.intel.com,
        shaohua.li@intel.com, alex.shi@intel.com, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, "Rafael J. Wysocki" <rjw@sisk.pl>
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Ingo Molnar <mingo@elte.hu> wrote:
>
>I have this fix queued up currently:
>
>  09223371deac: rcu: Use softirq to address performance regression

I really don't think that is even close to enough.

It still does all the callbacks in the threads, and according to Peter, about half the rcu time in the threads remained..

        Linus