linux-kernel - Re: 2.6.36 io bring the system to its knees

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Date:	Sun, 07 Nov 2010 13:08:20 +0100
From:	Jens Axboe <axboe@...nel.dk>
To:	dave b <db.pub.mail@...il.com>
CC:	Sanjoy Mahajan <sanjoy@...n.edu>,
	Dave Chinner <david@...morbit.com>,
	Jesper Juhl <jj@...osbits.net>,
	Chris Mason <chris.mason@...cle.com>,
	Ingo Molnar <mingo@...e.hu>, Pekka Enberg <penberg@...nel.org>,
	Aidar Kultayev <the.aidar@...il.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Nick Piggin <npiggin@...e.de>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>, Ted Ts'o <tytso@....edu>,
	Corrado Zoccolo <czoccolo@...il.com>,
	Shaohua Li <shaohua.li@...el.com>,
	Steven Barrett <damentz@...il.com>
Subject: Re: 2.6.36 io bring the system to its knees

On 2010-11-06 15:10, dave b wrote:
> I now personally have thought that this problem is the kernel not
> keeping track of reads vs writers properly  or not providing enough
> time to reading processes as writing ones which look like they are
> blocking the system....
> 
> If you want to do a simple test do an unlimited dd  (or two dd's of a
> limited size, say 10gb) and a find /
> Tell me how it goes :) ( the system will stall)
> (obviously stop the dd after some time :) ).
> 
> http://article.gmane.org/gmane.linux.kernel.device-mapper.dm-crypt/4561
> iirc can reproduce this on plain ext3.

As already mentioned, ext3 is just not a good choice for this sort of
thing. Did you have atimes enabled?

-- 
Jens Axboe

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