Subject: Re: High load average on disk I/O on 2.6.17-rc3
From: Arjan van de Ven <arjan@infradead.org>
To: "Martin J. Bligh" <mbligh@mbligh.org>
Cc: Andrew Morton <akpm@osdl.org>, Jason Schoonover <jasons@pioneer-pra.com>,
       linux-kernel@vger.kernel.org
In-Reply-To: <445F548A.703@mbligh.org>
References: <200605051010.19725.jasons@pioneer-pra.com>
	 <20060507095039.089ad37c.akpm@osdl.org>  <445F548A.703@mbligh.org>
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Date: Mon, 08 May 2006 16:55:48 +0200
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On Mon, 2006-05-08 at 07:24 -0700, Martin J. Bligh wrote:
> > It's pretty harmless though.  The "load average" thing just means that the
> > extra pdflush threads are twiddling thumbs waiting on some disk I/O -
> > they'll later exit and clean themselves up.  They won't be consuming
> > significant resources.
> 
> If they're waiting on disk I/O, they shouldn't be runnable, and thus
> should not be counted as part of the load average, surely?

yes they are, since at least a decade. "load average" != "cpu
utilisation" by any means. It's "tasks waiting for a hardware resource
to become available". CPU is one such resource (runnable) but disk is
another. There are more ... 

think of load as "if I bought faster hardware this would improve"


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