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

[Mete Durlu <meted@linux.ibm.com>]

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