Re: 2.6.8-rc2-mm2 performance improvements (scheduler?)

[Peter Williams]

Andrew Morton wrote:
> "Martin J. Bligh" <mbligh@xxxxxxxxxxx> wrote:
>
> > SDET 8  (see disclaimer)
> >                            Throughput    Std. Dev
> >                     2.6.7       100.0%         0.2%
> >                 2.6.8-rc2       100.2%         1.0%
> >             2.6.8-rc2-mm2       117.4%         0.9%
> >
> > SDET 16  (see disclaimer)
> >                            Throughput    Std. Dev
> >                     2.6.7       100.0%         0.3%
> >                 2.6.8-rc2        99.5%         0.3%
> >             2.6.8-rc2-mm2       118.5%         0.6%
>
>
> hum, interesting.  Can Con's changes affect the inter-node and inter-cpu
> balancing decisions, or is this all due to caching effects, reduced context
> switching etc?

One candidate for the cause of this improvement is the replacement of 
the active/expired array mechanism with a single array.  I believe that 
one of the short comings of the active/expired array mechanism is that 
it can lead to excessive queuing (possibly even starvation) of tasks 
that aren't considered "interactive".

> I don't expect we'll be merging a new CPU scheduler into mainline any time
> soon, but we should work to understand where this improvement came from,
> and see if we can get the mainline scheduler to catch up.

Peter
--
Peter Williams                                   pwil3058@xxxxxxxxxxxxxx

"Learning, n. The kind of ignorance distinguishing the studious."
 -- Ambrose Bierce

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