Re: [PATCH v3 07/20] sched/fair: Select preferred CPU at wakeup when possible

[Shrikanth Hegde <sshegde@linux.ibm.com>]

Hi Ilya, Thank you very much for reviewing the patch series.

On 6/8/26 10:09 PM, Ilya Leoshkevich wrote:
> 
> 
> On 6/4/26 07:14, K Prateek Nayak wrote:
>> Hello Shrikanth,
>>
>>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>>> index 29fbb5287cfc..a704285ac55a 100644
>>> --- a/kernel/sched/fair.c
>>> +++ b/kernel/sched/fair.c
>>> @@ -7743,7 +7743,8 @@ static inline int 
>>> sched_balance_find_dst_cpu(struct sched_domain *sd, struct tas
>>>   {
>>>       int new_cpu = cpu;
>>> -    if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr))
>>> +    if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr) &&
>>
>> Doesn't this mean we have no CPUs in this sd that fits the affinity
>> requirements?
>>
>>> +        cpu_preferred(prev_cpu))
>>
>> There is no point in going down the function if the affinity constraints
>> aren't met since we are traversing the hierarchy top-down and none of
>> the groups / child domains will satisfy the affinity requirements.
>>
>> Since the CPU returned here is again checked for is_cpu_allowed(), we'll
>> eventually hit the select_fallback_rq() path anyways so the check for
>> cpu_preferred(prev_cpu) seems unnecessary unless I'm missing something.
> 
> Do we need to add is_cpu_allowed() check to sched_exec()?
> Or is the existing cpu_active() check enough?
> 

sched_exec
	select_task_rq
	if (!is_cpu_allowed()
		select_fallback_rq

That is going to select based on preferred state and its affinity mask.

So, i think we are good there.