linux-kernel - Re: Finding what is stuck...

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Message-ID: <20080901170812.2c3b041b@infradead.org>
Date:	Mon, 1 Sep 2008 17:08:12 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	"J.A. Magallón" <jamagallon@....com>
Cc:	Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: Re: Finding what is stuck...

On Tue, 2 Sep 2008 02:04:47 +0200
"J.A. Magallón" <jamagallon@....com> wrote:

> Hi all...
> 
> I'm running 2.6.27-rc5-git2 on an Aspire One.
> The system is in general pretty responsive, but sometimes it just gets
> totally stuck. Even the mouse stops. 
> 
> It looks related to disk (SSD) access, but I'm not totally sure.
> Is there any way to find what is getting stuck ? I know that SSDs can
> be slow on write, I don't mind if the system is faster or slower
> (it's small :))), but if the speed is constant. That occasional
> pauses are strange, like if SSD flushing gets stuck on BKL
> (I know, no idea about what I talk...).
> 
> I'm using ext3 fs, noop iosched. But as I say, I'm not sure that the
> disk writes are the culprit.
> 
> Any idea about how to find this ?

Have you tried to run "latencytop"?
(you need to enable this in the kernel config as well)

it tends to (for me at least) point out very well where stalls happen,
or at least, what the system is doing when they happen.

(hint: make sure you do "make install" before running it)

-- 
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