linux-kernel - Re: ext3 IO latency measurements (was: Linux 2.6.29)

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Message-ID: <20090326090939.GA8993@elte.hu>
Date:	Thu, 26 Mar 2009 10:09:39 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jan Kara <jack@...e.cz>, Oleg Nesterov <oleg@...hat.com>,
	Roland McGrath <roland@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Theodore Tso <tytso@....edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arjan van de Ven <arjan@...radead.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Nick Piggin <npiggin@...e.de>,
	Jens Axboe <jens.axboe@...cle.com>,
	David Rees <drees76@...il.com>, Jesper Krogh <jesper@...gh.cc>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: ext3 IO latency measurements (was: Linux 2.6.29)


* Ingo Molnar <mingo@...e.hu> wrote:

> Oh, and while at it - also a job control complaint. I tried to 
> Ctrl-C the above script:
> 
> file # 858 (253560 bytes), reading it took: 0.06 seconds.
> file # 859 (253560 bytes), reading it took: 0.02 seconds.
> file # 860 (253560 bytes), reading it took: 5.53 seconds.
> file # 861 (253560 bytes), reading it took: 3.70 seconds.
> file # 862 (253560 bytes), reading it took: 0.88 seconds.
> file # 863 (253560 bytes), reading it took: 0.04 seconds.
> file # 864 (253560 bytes), reading it took: ^C0.69 seconds.
> file # 865 (253560 bytes), reading it took: ^C0.49 seconds.
> file # 866 (253560 bytes), reading it took: ^C0.01 seconds.
> file # 867 (253560 bytes), reading it took: ^C0.02 seconds.
> file # 868 (253560 bytes), reading it took: ^C^C0.01 seconds.
> file # 869 (253560 bytes), reading it took: ^C^C0.04 seconds.
> file # 870 (253560 bytes), reading it took: ^C^C^C0.03 seconds.
> file # 871 (253560 bytes), reading it took: ^C0.02 seconds.
> file # 872 (253560 bytes), reading it took: ^C^C0.02 seconds.
> file # 873 (253560 bytes), reading it took: 
> ^C^C^C^Caldebaran:~/linux/linux/test-files/src> 
> 
> I had to hit Ctrl-C numerous times before Bash would honor it. 
> This to is a very common thing on large SMP systems. [...]

It happened when i tried to Ctrl-C the compile job as well:

Thu Mar 26 11:04:05 CET 2009
Thu Mar 26 11:06:30 CET 2009
^CThu Mar 26 11:07:55 CET 2009
^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^Caldebaran:/home/mingo/linux/linux> 

a single Ctrl-C is rarely enough to stop busy Bash shell scripts on 
Linux. Why?

	Ingo
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