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

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Message-ID: <48BD08B6.4040707@tuffmail.co.uk>
Date:	Tue, 02 Sep 2008 10:34:46 +0100
From:	Alan Jenkins <alan-jenkins@...fmail.co.uk>
To:	Jan Knutar <jknutar@....fi>
CC:	jamagallon@....com, linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Finding what is stuck...

Jan Knutar wrote:

> On Tuesday 02 September 2008, J.A. Magallón wrote:
>
>> 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.
>
> Are you hitting swap at all? Does it have swap?
>
> On my N810 tablet there can be a huge slowdown if it starts swapping.
> The first time it dips into swap is relatively painless when stuff gets
> written out sequentially, but after that when writes are mostly random
> the throughput drops to a few kilobytes per second, causing massive
> slowdown... The MMC/SD cards hate random write, and I expect SSDs are
> no better.
>
> iostat -x -k 10
> in a terminal is useful. Check the iowait and util% numbers after/during
> slowdown...

My experience on the EeePC is similar.  I didn't look into it much but I
think it helped a lot switching to the "noop" ioscheduler

(echo noop > /sys/block/sda/queue/scheduler)

as opposed to the default CFQ, if you haven't already done so.

Alan
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