From: Andres Freund <andres@anarazel.de>
To: Ralf Hildebrandt <Ralf.Hildebrandt@charite.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Costly Context Switches
Date: Sun, 12 Dec 2010 20:07:07 +0100 [thread overview]
Message-ID: <201012122007.07372.andres@anarazel.de> (raw)
In-Reply-To: <20101212151112.GE26583@charite.de>
On Sunday 12 December 2010 16:11:12 Ralf Hildebrandt wrote:
> I recently made a parallel installation of dovecot-2.0 on my mailbox
> server, which is running dovecot-1.2 without any problems whatsoever.
>
> Using dovecot-2.0 on the same hardware, same kernel, with the same users
> and same mailboxes and usage behaviour results in an immense increase in
> the load numbers.
>
> Switching back to 1.2 results in a immediate decrease of the load back
> to "normal" numbers.
>
> This is mainly due to a 10-20 fold increase of the number of context
> switches. The same problem has been reported independently by Cor
> Bosman of XS4All, on different hardware (64bit instead of 32bit, real
> hardware instead of virtual hardware).
>
> So, now the kernel related question: How can I find out WHY the
> context switches are happening? Are there any "in kernel" statistics I
> could look at?
"strace" or "perf trace syscall-counts" would be a good start.
Andres
next prev parent reply other threads:[~2010-12-12 19:17 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-12 15:11 Costly Context Switches Ralf Hildebrandt
2010-12-12 19:07 ` Andres Freund [this message]
2010-12-13 13:51 ` Arnaldo Carvalho de Melo
2010-12-13 14:00 ` Ralf Hildebrandt
2010-12-13 14:25 ` Andres Freund
2010-12-13 14:29 ` Arnaldo Carvalho de Melo
2010-12-13 14:30 ` Andres Freund
2010-12-13 14:36 ` Arnaldo Carvalho de Melo
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