Re: [PATCH 5/5] sched/fair: narrow the sched_use_asym_prio checking scenario

[kuiliang Shi]

On 1/26/24 8:06 AM, Ricardo Neri wrote:
> On Thu, Jan 25, 2024 at 05:35:32PM +0800, kuiliang Shi wrote:
>>
>>
>> On 1/23/24 4:47 PM, Shrikanth Hegde wrote:
>>>
>>>
>>> On 1/17/24 2:27 PM, alexs@xxxxxxxxxx wrote:
>>>> From: Alex Shi <alexs@xxxxxxxxxx>
>>>>
>>>> Current function doesn't match it's comments, in fact, core_idle
>>>> checking is only meaningful with non-SMT.
>>>> So make the function right.
>>>>
>>>> Signed-off-by: Alex Shi <alexs@xxxxxxxxxx>
>>>> To: Valentin Schneider <vschneid@xxxxxxxxxx>
>>>> To: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
>>>> To: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
>>>> To: Ingo Molnar <mingo@xxxxxxxxxx>
>>>> ---
>>>>  kernel/sched/fair.c | 4 ++--
>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>>>> index 96163ab69ae0..0a321f639c79 100644
>>>> --- a/kernel/sched/fair.c
>>>> +++ b/kernel/sched/fair.c
>>>> @@ -9741,8 +9741,8 @@ group_type group_classify(unsigned int imbalance_pct,
>>>>   */
>>>>  static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
>>>>  {
>>>> -	return (!sched_smt_active()) ||
>>>> -		(sd->flags & SD_SHARE_CPUCAPACITY) || is_core_idle(cpu);
>>>> +	return	(sd->flags & SD_SHARE_CPUCAPACITY) ||
>>>> +		(!sched_smt_active() && is_core_idle(cpu));
>>>>  }
>>>
>>> This seems wrong. This would always return false for higher than SMT domains 
>>> if smt is active. 
>>>
>>
>> yes, thanks for point out.
>>
>>> Was this meant to be sched_smt_active() && is_core_idle(cpu)? 
>>
>> In theory, yes, it should like this. But I have no ASYM device to test. :(
> 
> This would not work with !SMT and asym_packing.
> 
> I can test your patches on asym_packing + SMT systems if you post a new
> version.
> 

Hi Neri,

Thanks a lot for generous offer! I don't know if my understanding right, but I try my best to have a best guessing in V2 patch for you. :)

Many thanks for the help!

Best regards
Alex