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

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Message-ID: <d3013ec4-8102-46a9-9e0d-e7253859ea38@email.android.com>
Date:	Wed, 15 Jun 2011 13:55:25 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	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>,
	Tony Luck <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>, ak@...ux.intel.com,
	shaohua.li@...el.com, alex.shi@...el.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: REGRESSION: Performance regressions from switching anon_vma->lock to mutex



Ingo Molnar <mingo@...e.hu> wrote:
>
>perf record -g will go a long way towards such a tool already - but i 
>think it would be useful to create a more top-alike view as well. 

perf record -g doesn't help when the issue is that we're recording a single process and the actual work is being done in another unrelated process that is just being woken up.

Sure, you can do a system wide recording, but that shows all kinds of unrelated noise and requires root permissions.

So those rcu threads really need to go.

      Linus
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