Re: [PATCH 0/4] sched/fair: Avoid unnecessary migrations within SMT domains

[Ricardo Neri]

On Thu, Aug 25, 2022 at 03:55:25PM -0700, Ricardo Neri wrote:
> Intel processors that support Intel Turbo Boost Max 3.0 use asym_packing
> to assign higher priorities to CPUs with higher maximum frequencies. It
> artificially assigns, however, a lower priority to the higher-numbered
> SMT siblings to ensure that they are used last.
> 
> This results in unnecessary task migrations within the SMT domains.
> 
> On processors with a mixture of higher-frequency SMT cores and lower-
> frequency non-SMT cores (such as Intel hybrid processors), a lower-
> priority CPU pulls tasks from the higher-priority cores if more than one
> SMT sibling is busy.
> 
> Do not use different priorities for each SMT sibling. Instead, tweak the
> asym_packing load balancer to recognize SMT cores with more than one
> busy sibling and let lower-priority CPUs pull tasks.
> 
> Removing these artificial priorities avoids superfluous migrations and
> lets lower-priority cores inspect all SMT siblings for the busiest queue.

Hello. I'd like to know if there are any comments on these patches. This
patchset is a requisite for the IPC classes of tasks patchset [1].

Thanks in advance!
Ricardo

[1]. https://lore.kernel.org/lkml/20220909231205.14009-5-ricardo.neri-calderon@xxxxxxxxxxxxxxx/T/