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

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Date:	Wed, 15 Jun 2011 13:54:25 -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 01:47:33PM -0700, Linus Torvalds wrote:
> 
> 
> "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:
> >
> >It would be much lower risk to make the current code always use softirq
> >if !RCU_BOOST -- last time I attempted the revert, it was quite hairy.
> 
> I don't care if it's a real revert or not, but I want the threads gone. Entirely. Not just the patch that uses softirqs for some things, and threads for the callbacks. No, I don't want the threads to show up or exist at all.
> 
> And to be sure, I'd like the code to set up and use the threads to actually compile away statically, so that there clearly isn't some way it's partially enabled.

Yes, the kthread creation will happen only if RCU_BOOST=y.  Otherwise,
there will be no RCU kthreads at all.

							Thanx, Paul
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