From: Ingo Molnar <mingo@elte.hu>
To: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Cc: Matthew Wilcox <matthew@wil.cx>,
LKML <linux-kernel@vger.kernel.org>,
Alexander Viro <viro@ftp.linux.org.uk>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: AIM7 40% regression with 2.6.26-rc1
Date: Tue, 6 May 2008 13:44:49 +0200 [thread overview]
Message-ID: <20080506114449.GC32591@elte.hu> (raw)
In-Reply-To: <1210052904.3453.30.camel@ymzhang>
* Zhang, Yanmin <yanmin_zhang@linux.intel.com> wrote:
> Comparing with kernel 2.6.25, AIM7 (use tmpfs) has more than 40% with
> 2.6.26-rc1 on my 8-core stoakley, 16-core tigerton, and Itanium
> Montecito. Bisect located below patch.
>
> 64ac24e738823161693bf791f87adc802cf529ff is first bad commit
> commit 64ac24e738823161693bf791f87adc802cf529ff
> Author: Matthew Wilcox <matthew@wil.cx>
> Date: Fri Mar 7 21:55:58 2008 -0500
>
> Generic semaphore implementation
>
> After I manually reverted the patch against 2.6.26-rc1 while fixing
> lots of conflictions/errors, aim7 regression became less than 2%.
hm, which exact semaphore would that be due to?
My first blind guess would be the BKL - there's not much other semaphore
use left in the core kernel otherwise that would affect AIM7 normally.
The VFS still makes frequent use of the BKL and AIM7 is very VFS
intense. Getting rid of that BKL use from the VFS might be useful to
performance anyway.
Could you try to check that it's indeed the BKL?
Easiest way to check it would be to run AIM7 it on
sched-devel.git/latest and do scheduler tracing via:
http://people.redhat.com/mingo/sched-devel.git/readme-tracer.txt
by doing:
echo stacktrace > /debug/tracing/iter_ctl
you could get exact backtraces of all scheduling points in the trace. If
the BKL's down() shows up in those traces then it's definitely the BKL
that causes this. The backtraces will also tell us exactly which BKL use
is the most frequent one.
To keep tracing overhead low on SMP i'd also suggest to only trace a
single CPU, via:
echo 1 > /debug/tracing/tracing_cpumask
Ingo
next prev parent reply other threads:[~2008-05-06 11:45 UTC|newest]
Thread overview: 140+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-06 5:48 AIM7 40% regression with 2.6.26-rc1 Zhang, Yanmin
2008-05-06 11:18 ` Matthew Wilcox
2008-05-06 11:44 ` Ingo Molnar [this message]
2008-05-06 12:09 ` Matthew Wilcox
2008-05-06 16:23 ` Matthew Wilcox
2008-05-06 16:36 ` Linus Torvalds
2008-05-06 16:42 ` Matthew Wilcox
2008-05-06 16:39 ` Alan Cox
2008-05-06 16:51 ` Matthew Wilcox
2008-05-06 16:45 ` Alan Cox
2008-05-06 17:42 ` Linus Torvalds
2008-05-06 20:28 ` Linus Torvalds
2008-05-06 16:44 ` J. Bruce Fields
2008-05-06 17:21 ` Andrew Morton
2008-05-06 17:31 ` Matthew Wilcox
2008-05-06 17:49 ` Ingo Molnar
2008-05-06 18:07 ` Andrew Morton
2008-05-11 11:11 ` Matthew Wilcox
2008-05-06 17:39 ` Ingo Molnar
2008-05-07 6:49 ` Zhang, Yanmin
2008-05-06 17:45 ` Linus Torvalds
2008-05-07 16:38 ` Matthew Wilcox
2008-05-07 16:55 ` Linus Torvalds
2008-05-07 17:08 ` Linus Torvalds
2008-05-07 17:16 ` Andrew Morton
2008-05-07 17:27 ` Linus Torvalds
2008-05-07 17:22 ` Ingo Molnar
2008-05-07 17:25 ` Ingo Molnar
2008-05-07 17:31 ` Linus Torvalds
2008-05-07 17:47 ` Linus Torvalds
2008-05-07 17:49 ` Ingo Molnar
2008-05-07 18:02 ` Linus Torvalds
2008-05-07 18:17 ` Ingo Molnar
2008-05-07 18:27 ` Linus Torvalds
2008-05-07 18:43 ` Ingo Molnar
2008-05-07 19:01 ` Linus Torvalds
2008-05-07 19:09 ` Ingo Molnar
2008-05-07 19:24 ` Matthew Wilcox
2008-05-07 19:44 ` Linus Torvalds
2008-05-07 20:00 ` Oi. NFS people. Read this Matthew Wilcox
2008-05-07 22:10 ` Trond Myklebust
2008-05-09 1:43 ` J. Bruce Fields
2008-05-08 3:24 ` AIM7 40% regression with 2.6.26-rc1 Zhang, Yanmin
2008-05-08 3:34 ` Linus Torvalds
2008-05-08 4:37 ` Zhang, Yanmin
2008-05-08 14:58 ` Linus Torvalds
2008-05-07 2:11 ` Zhang, Yanmin
2008-05-07 3:41 ` Zhang, Yanmin
2008-05-07 3:59 ` Andrew Morton
2008-05-07 4:46 ` Zhang, Yanmin
2008-05-07 6:26 ` Ingo Molnar
2008-05-07 6:28 ` Ingo Molnar
2008-05-07 7:05 ` Zhang, Yanmin
2008-05-07 11:00 ` Andi Kleen
2008-05-07 11:46 ` Matthew Wilcox
2008-05-07 12:21 ` Andi Kleen
2008-05-07 14:36 ` Linus Torvalds
2008-05-07 14:35 ` Alan Cox
2008-05-07 15:00 ` Linus Torvalds
2008-05-07 15:02 ` Linus Torvalds
2008-05-07 14:57 ` Andi Kleen
2008-05-07 15:31 ` Andrew Morton
2008-05-07 16:22 ` Matthew Wilcox
2008-05-07 15:19 ` Linus Torvalds
2008-05-07 17:14 ` Ingo Molnar
2008-05-08 2:44 ` Zhang, Yanmin
2008-05-08 3:29 ` Linus Torvalds
2008-05-08 4:08 ` Zhang, Yanmin
2008-05-08 4:17 ` Linus Torvalds
2008-05-08 12:01 ` [patch] speed up / fix the new generic semaphore code (fix AIM7 40% regression with 2.6.26-rc1) Ingo Molnar
2008-05-08 12:28 ` Ingo Molnar
2008-05-08 14:43 ` Ingo Molnar
2008-05-08 15:10 ` [git pull] scheduler fixes Ingo Molnar
2008-05-08 15:33 ` Adrian Bunk
2008-05-08 15:41 ` Ingo Molnar
2008-05-08 19:42 ` Adrian Bunk
2008-05-11 11:03 ` Matthew Wilcox
2008-05-11 11:14 ` Matthew Wilcox
2008-05-11 11:48 ` Matthew Wilcox
2008-05-11 12:50 ` Ingo Molnar
2008-05-11 12:52 ` Ingo Molnar
2008-05-11 13:02 ` Matthew Wilcox
2008-05-11 13:26 ` Matthew Wilcox
2008-05-11 14:00 ` Ingo Molnar
2008-05-11 14:18 ` Matthew Wilcox
2008-05-11 14:42 ` Ingo Molnar
2008-05-11 14:48 ` Matthew Wilcox
2008-05-11 15:19 ` Ingo Molnar
2008-05-11 15:29 ` Matthew Wilcox
2008-05-13 14:11 ` Ingo Molnar
2008-05-13 14:21 ` Matthew Wilcox
2008-05-13 14:42 ` Ingo Molnar
2008-05-13 15:28 ` Matthew Wilcox
2008-05-13 17:13 ` Ingo Molnar
2008-05-13 17:22 ` Linus Torvalds
2008-05-13 21:05 ` Ingo Molnar
2008-05-11 13:54 ` Ingo Molnar
2008-05-11 14:22 ` Matthew Wilcox
2008-05-11 14:32 ` Ingo Molnar
2008-05-11 14:46 ` Matthew Wilcox
2008-05-11 16:47 ` Linus Torvalds
2008-05-11 13:01 ` Ingo Molnar
2008-05-11 13:06 ` Matthew Wilcox
2008-05-11 13:45 ` Ingo Molnar
2008-05-11 14:10 ` Sven Wegener
2008-05-08 16:02 ` [patch] speed up / fix the new generic semaphore code (fix AIM7 40% regression with 2.6.26-rc1) Linus Torvalds
2008-05-08 18:30 ` Linus Torvalds
2008-05-08 20:19 ` Ingo Molnar
2008-05-08 20:27 ` Linus Torvalds
2008-05-08 21:45 ` Ingo Molnar
2008-05-08 22:02 ` Ingo Molnar
2008-05-08 22:55 ` Linus Torvalds
2008-05-08 23:07 ` Linus Torvalds
2008-05-08 23:14 ` Linus Torvalds
2008-05-08 23:16 ` Alan Cox
2008-05-08 23:33 ` Linus Torvalds
2008-05-08 23:27 ` Alan Cox
2008-05-09 6:50 ` Ingo Molnar
2008-05-09 8:29 ` Andi Kleen
2008-05-08 13:20 ` Matthew Wilcox
2008-05-08 15:01 ` Ingo Molnar
2008-05-08 13:56 ` Arjan van de Ven
2008-05-08 6:43 ` AIM7 40% regression with 2.6.26-rc1 Ingo Molnar
2008-05-08 6:48 ` Andrew Morton
2008-05-08 7:14 ` Zhang, Yanmin
2008-05-08 7:39 ` Ingo Molnar
2008-05-08 8:44 ` Zhang, Yanmin
2008-05-08 9:21 ` Ingo Molnar
2008-05-08 9:29 ` Ingo Molnar
2008-05-08 9:30 ` Zhang, Yanmin
2008-05-07 16:20 ` Ingo Molnar
2008-05-07 16:35 ` Linus Torvalds
2008-05-07 17:05 ` Ingo Molnar
2008-05-07 17:24 ` Linus Torvalds
2008-05-07 17:36 ` Ingo Molnar
2008-05-07 17:55 ` Linus Torvalds
2008-05-07 17:59 ` Matthew Wilcox
2008-05-07 18:17 ` Linus Torvalds
2008-05-07 18:49 ` Ingo Molnar
2008-05-07 13:59 ` Alan Cox
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