linux-kernel - Re: [GIT PULL] Re: REGRESSION: Performance regressions from switching anon

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Message-ID: <20110615211517.GI2267@linux.vnet.ibm.com>
Date:	Wed, 15 Jun 2011 14:15:17 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	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: [GIT PULL] Re: REGRESSION: Performance regressions from
 switching anon_vma->lock to mutex

On Wed, Jun 15, 2011 at 02:05:46PM -0700, Linus Torvalds wrote:
> 
> 
> Ingo Molnar <mingo@...e.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..

I am putting together a patch that gets rid of the kthreads in the
!RCU_BOOST case.  The time will still be consumed, but in softirq
context, though of course with many fewer context switches.

							Thanx, Paul
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