From: Linus Torvalds <torvalds@linux-foundation.org>
To: paulmck@linux.vnet.ibm.com
Cc: Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
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>
Subject: Re: [GIT PULL] Re: REGRESSION: Performance regressions from switching anon_vma->lock to mutex
Date: Wed, 15 Jun 2011 14:27:42 -0700 [thread overview]
Message-ID: <75bf3621-4ab8-4c16-8301-5bb82d14d703@email.android.com> (raw)
In-Reply-To: <20110615211517.GI2267@linux.vnet.ibm.com>
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
>
> The time will still be consumed, but in softirq
>context, though of course with many fewer context switches.
So the problem with threads goes way beyond just the context switches, or even just the problem with tracing.
Threads change the batching behavior, for example. That is *especially* true with background threads or with realtime threads. Both end up having high priority -either because they are realtime, or because they've been sleeping and thus have been building up extra priority that way.
So when you wake up such a thread, suddenly you get preemption behaviour, or you get the semaphores deciding to break out of their busy loops due to need_resched being set etc.
In contrast, softirqs don't have those kinds of side effects. They have a much smaller effect on system behavior and just run the code we ask them to.
Linus
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next prev parent reply other threads:[~2011-06-15 21:28 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-15 0:29 Tim Chen
2011-06-15 0:36 ` Andi Kleen
2011-06-17 19:07 ` Ingo Molnar
2011-06-15 1:21 ` Linus Torvalds
2011-06-15 3:42 ` Linus Torvalds
2011-06-15 1:26 ` Shaohua Li
2011-06-15 11:52 ` Peter Zijlstra
2011-06-15 12:49 ` Peter Zijlstra
2011-06-15 16:18 ` Andi Kleen
2011-06-15 16:45 ` Peter Zijlstra
2011-06-15 16:47 ` Andi Kleen
2011-06-15 18:43 ` Tim Chen
2011-06-15 20:32 ` Peter Zijlstra
2011-06-15 20:57 ` Andi Kleen
2011-06-15 21:12 ` Tim Chen
2011-06-15 21:37 ` Peter Zijlstra
2011-06-15 21:51 ` Linus Torvalds
2011-06-15 22:19 ` Andi Kleen
2011-06-16 0:16 ` Linus Torvalds
2011-06-16 20:14 ` Andi Kleen
2011-06-16 20:37 ` Linus Torvalds
2011-06-17 0:24 ` Andi Kleen
2011-06-17 9:13 ` Ingo Molnar
2011-06-15 22:15 ` Andi Kleen
2011-06-16 1:08 ` Tim Chen
2011-06-16 1:50 ` Linus Torvalds
2011-06-16 20:26 ` Tim Chen
2011-06-16 20:47 ` Linus Torvalds
2011-06-16 21:05 ` Linus Torvalds
2011-06-16 21:06 ` Linus Torvalds
2011-06-16 21:26 ` Linus Torvalds
2011-06-17 3:58 ` Linus Torvalds
2011-06-17 11:28 ` Peter Zijlstra
2011-06-17 11:54 ` Peter Zijlstra
2011-06-17 16:36 ` Linus Torvalds
2011-06-17 17:41 ` Hugh Dickins
2011-06-17 17:55 ` Peter Zijlstra
2011-06-17 18:01 ` Linus Torvalds
2011-06-17 18:18 ` Peter Zijlstra
2011-06-17 18:32 ` Peter Zijlstra
2011-06-17 18:39 ` Linus Torvalds
2011-06-17 18:41 ` Linus Torvalds
2011-06-17 20:19 ` Tim Chen
2011-06-17 22:20 ` Hugh Dickins
2011-06-18 4:47 ` Linus Torvalds
2011-06-17 19:53 ` [PATCH] mm, memory-failure: Fix spinlock vs mutex order Peter Zijlstra
2011-06-17 20:04 ` Andi Kleen
2011-06-17 16:46 ` REGRESSION: Performance regressions from switching anon_vma->lock to mutex Linus Torvalds
2011-06-17 17:28 ` Linus Torvalds
2011-06-17 19:40 ` Andi Kleen
2011-06-18 8:08 ` Ingo Molnar
2011-06-17 18:22 ` Tim Chen
2011-06-17 19:05 ` Ray Lee
2011-06-16 22:00 ` Andi Kleen
2011-06-15 10:36 ` Peter Zijlstra
2011-06-15 10:58 ` Peter Zijlstra
2011-06-15 11:41 ` Peter Zijlstra
2011-06-15 19:11 ` Linus Torvalds
2011-06-15 19:24 ` Andrew Morton
2011-06-15 20:16 ` Ingo Molnar
2011-06-15 20:55 ` Linus Torvalds
2011-06-15 20:12 ` [GIT PULL] " Ingo Molnar
2011-06-15 20:29 ` Paul E. McKenney
2011-06-15 20:47 ` Linus Torvalds
2011-06-15 20:54 ` Paul E. McKenney
2011-06-15 21:05 ` Linus Torvalds
2011-06-15 21:15 ` Paul E. McKenney
2011-06-15 21:27 ` Linus Torvalds [this message]
2011-06-16 7:03 ` Ingo Molnar
2011-06-16 17:16 ` Paul E. McKenney
2011-06-16 20:25 ` Ingo Molnar
2011-06-16 21:01 ` Frederic Weisbecker
2011-06-16 23:02 ` Ingo Molnar
2011-06-17 15:19 ` Frederic Weisbecker
2011-06-16 21:02 ` Andi Kleen
2011-06-16 22:21 ` Benjamin Herrenschmidt
2011-06-16 22:38 ` Ingo Molnar
2011-06-16 22:47 ` Andi Kleen
2011-06-16 22:58 ` Ingo Molnar
2011-06-17 0:45 ` Paul E. McKenney
2011-06-17 9:43 ` Ingo Molnar
2011-06-17 16:48 ` Paul E. McKenney
2011-06-16 23:37 ` Paul E. McKenney
2011-06-15 20:13 ` Tim Chen
2011-06-15 20:17 ` Ingo Molnar
2011-06-15 20:21 ` Tim Chen
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