linux-kernel - Re: unresponsiveness on linux desktop during file copy

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Message-ID: <4A0FD0AD.4030402@gmail.com>
Date:	Sun, 17 May 2009 02:54:05 -0600
From:	Robert Hancock <hancockrwd@...il.com>
To:	Satish Eerpini <eerpini@...il.com>
CC:	Mark Knecht <markknecht@...il.com>, Rik van Riel <riel@...hat.com>,
	Ray Lee <ray-lk@...rabbit.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: unresponsiveness on linux desktop during file copy

Satish Eerpini wrote:
>> Do you believe this was working better on an earlier kernel? If so you
>> might drop back and see if these commands work better. If so that
>> would suggest a regression of some type.
> 
> I remember good performance with 2.6.26.x series, ... but I could not
> try that out, ,... things on a 2.6.27.23 kernel seem no better :
> 
> Linux 2.6.27.23 (satish) 	05/16/2009
> 
> 12:11:18 PM     CPU     %user     %nice   %system   %iowait    %steal     %idle
> 12:11:21 PM     all      0.00      0.00      3.92     75.65      0.00     20.42
> 12:11:24 PM     all      0.00      0.00      3.55     67.85      0.00     28.59
> 12:11:27 PM     all      0.16      0.00      4.51     45.09      0.00     50.24
> 12:11:30 PM     all      0.00      0.00      3.59     44.77      0.00     51.63
> 12:11:33 PM     all      0.16      0.00      5.25     82.51      0.00     12.08
> Average:        all      0.06      0.00      4.17     63.24      0.00     32.53
> 
> the average disk speed was about 10.5 MB/s, indeed the average IOWAIT
> is more than that in the latest kernel, I will see if I can test it on
> a 2.6.26.x kernel or earlier one and send you guys the stats.

High iowait during a file copy with no other activity is entirely 
normal. If you have a core that has nothing to do but wait for IO to 
complete, you'll get iowait time. This isn't indicating a problem.
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