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

[Arjan van de Ven <arjan@infradead.org>]

On Tue, 2006-05-09 at 11:57 +1000, Nick Piggin wrote:
> Arjan van de Ven wrote:
> 
> >>... 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.
> >
> 
> Perhaps kernel threads in D state should not contribute toward load avg

that would be a change from, well... a LONG time

The question is what "load" means; if you want to change that... then
there are even better metrics possible. Like
"number of processes wanting to run + number of busy spindles + number
of busy nics + number of VM zones that are below the problem
watermark" (where "busy" means "queue full")

or 50 million other definitions. If we're going to change the meaning,
we might as well give it a "real" meaning. 

(And even then it is NOT a good measure for determining if the machine
can perform more work, the graph I put in a previous mail is very real,
and in practice it seems the saturation line is easily 4x or 5x of the
"linear" point)

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