Re: [PATCH RFC 0/2] sched: Introduce idle SMT priority for asymmetric capacity systems

[Mete Durlu]

Hi again,

> > > What you describe really fit into the prefered core that Shrikanth
> > > Hegde has developped
> >
> > I agree, but Shrikanth's solution can not bring some of the
> > behavior changes required. cpu_preferred_mask can help
> > direct task placement away from low capacity cores but idle
> > core first approach still places tasks to fully idle low
> > capacity cores. This patches proposal tries to move tasks
> > first to the idle SMT siblings.
>
> We have compute capacity to decide which CPU is better than others.
> The capacity of SMT CPU has also been somewhat random, but we should
> find a way to fix this instead of adding a threshold to decide whether
> to pack or spread tasks onto idle cores. With correct per CPU
> capacity, we can easily decide if an idle low core is better or not
> than the sibling of an already busy high core.
After thinking about this a bit more, I have decided to work
on a different approach rather than trying to integrate
into Shrikanth's vCPU backoff or trying to expand this series.

I'll come back with another series after I become more familiar
with how the SMT capacities are calculated and incorporated in
the decision making process. My gut says the real challenge is
going to be finding a way to benefit all architectures that
configure asymmetric capacities but I'll give it a shot.

Thanks for the valuable comments and guidance.
-Mete