Re: High load average on disk I/O on 2.6.17-rc3

[Arjan van de Ven]

On Mon, 2006-05-08 at 17:22 +0200, Erik Mouw wrote:
> On Mon, May 08, 2006 at 04:55:48PM +0200, Arjan van de Ven wrote:
> > 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 ... 
> 
> ... except that any kernel < 2.6 didn't account tasks waiting for disk
> IO.

they did. It was "D" state, which counted into load average.



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