On Mon, 3 Apr 2000, Richard Wackerbarth wrote:
> On Mon, 03 Apr 2000, Donn Miller wrote:
>
> > I think we ought to re-examine the definition of load average. By
> > load, we mean an actual load on the cpu, and waiting processes aren't
> > really exerting a cpu load. So, by that reasoning I say waiting
> > processes don't count.
>
> I think you have an incorrect (incomplete) definition.
>
> Traditionally, the load was the number of processes WANTING to run.
> Tasks which are waiting for "user" I/O are excluded.
> However, tasks waiting to be swapped in should be counted.
This sounds to me like the right approach from point of view of a program
like sendmail that reacts to load average. If you get in to a position in
which the system is spending all of its time accessing the disc (so that
the number of processes actually USING the CPU is quite low 'cos they are
all waiting for pages to be swapped back in) is launching off yet more
work /really/ the right thing to do? If all it does is result in even more
thrashing then couldn't that actually *cut* the load average as calculated
using the first of those definitions and push the system even further into
the quagmire?
OK, so you could easily argue that load average is a far from perfect
measure for something of this sort but the second definition does sound
more useful IMHO...it gives a better measure of the number of processes
which can't yet complete their next chunk of work because of limited
system resources.
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