Re: [PATCH v2 4/7] sched/fair: Introduce sched_smt_siblings_idle()

[Dietmar Eggemann <dietmar.eggemann@arm.com>]

On 12/12/2022 18:54, Ricardo Neri wrote:
> On Tue, Dec 06, 2022 at 07:03:37PM +0100, Dietmar Eggemann wrote:
>> On 22/11/2022 21:35, Ricardo Neri wrote:

[...]

>>> +bool sched_smt_siblings_idle(int cpu)
>>> +{
>>> +	return is_core_idle(cpu);
>>> +}
>>
>> Nitpick: Can we not just have one exported function for both use-cases:
>> NUMA and x86 ITMT?
> 
> By adding a new function I intend to preserve the inlinig of is_core_idle()
> in update_numa_stats() (via numa_idle_core(), which is also inline). Do you
> think there is no value?

OK. It's only used in NUMA balancing (task_numa_fault() -> ... ->
update_numa_stats()). I can't see that this will have a noticeable perf
impact but only benchmark can really tell.

A `static inline bool sched_is_core_idle(int cpu)` via
include/linux/sched/topology.h might work? We have similar functions
(like sched_core_cookie_match()` but in the private scheduler header
file kernel/sched/sched.h though.

> A downside of having the new function is that now the code is duplicated
> in update_numa_stats() and sched_smt_siblings_idle().
> 
> I can take your suggestion if losing the inline is OK.

I doubt that it will have an impact but can't be sure.

[...]