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SubjectRe: [RFC/PATCH 0/3] sched: allow arch override of cpu power
Ingo Molnar wrote:
>
> * Nathan Lynch <ntl@pobox.com> wrote:
> > So it would be nice to have the scheduler slightly prefer primary
> > threads on POWER6 machines. These patches, which allow the
> > architecture to override the scheduler's CPU "power" calculation, are
> > one possible approach, but I'm open to others. Please note: these
> > seemed to have the desired effect on 2.6.25-rc kernels (2-3%
> > improvement in a kernbench-like make -j <nr_cores>), but I'm not
> > seeing this improvement with 2.6.26-rc kernels for some reason I am
> > still trying to track down.
>
> ok, i guess that discrepancy has to be tracked down before we can think
> about these patches - but the principle is OK.

Great. I'll keep trying to figure out what's going on there.


> One problem is that the whole cpu-power balancing code in sched.c is a
> bit ... unclear and under-documented. So any change to this area should
> begin at documenting the basics: what do the units mean exactly, how are
> they used in balancing and what is the desired effect.
>
> I'd not be surprised if there were a few buglets in this area, SMT is
> not at the forefront of testing at the moment. There's nothing
> spectacularly broken in it (i have a HT machine myself), but the
> concepts have bitrotten a bit. Patches - even if they just add comments
> - are welcome :-)

Okay, I'll have a look. Thanks Ingo.


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