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

[Martin Bligh]

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.
>
> Userspace does not care whether there are 2 or 20 pdflush threads waiting
> for IO. However, when the network/disks can no longer keep up, userspace
> processes will end up going to sleep in writeback or reclaim -- *that* is
> when we start feeling the load.

Personally I'd be far happier having separated counters for both. Then
we can see what the real bottleneck is. Whilst we're at it, on a per-cpu
and per-elevator-queue basis ;-)

M.
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