Re: [PATCH v5 2/3] sched/topology: Rework CPU capacity asymmetry detection

Dietmar Eggemann
2021-06-03T09:09:54Z

On 02/06/2021 21:48, Beata Michalska wrote:
> On Wed, Jun 02, 2021 at 07:17:12PM +0200, Dietmar Eggemann wrote:
>> On 27/05/2021 19:07, Beata Michalska wrote:
>>> On Thu, May 27, 2021 at 05:08:42PM +0200, Dietmar Eggemann wrote:
>>>> On 26/05/2021 23:40, Beata Michalska wrote:
>>>>> On Wed, May 26, 2021 at 08:17:41PM +0200, Dietmar Eggemann wrote:
>>>>>> On 26/05/2021 14:51, Beata Michalska wrote:
>>>>>>> On Wed, May 26, 2021 at 01:15:46PM +0100, Beata Michalska wrote:
>>>>>>>> On Wed, May 26, 2021 at 11:52:25AM +0200, Dietmar Eggemann wrote:
>>>>>>>>> On 25/05/2021 12:29, Beata Michalska wrote:
>>>>>>>>>> On Tue, May 25, 2021 at 10:53:07AM +0100, Valentin Schneider wrote:
>>>>>>>>>>> On 24/05/21 23:55, Beata Michalska wrote:
>>>>>>>>>>>> On Mon, May 24, 2021 at 07:01:04PM +0100, Valentin Schneider wrote:
>>>>>>>>>>>>> On 24/05/21 11:16, Beata Michalska wrote:

[...]

> So what I have done is :
>
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index 77e6f79235ad..ec4ae225687e 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -1324,6 +1324,7 @@ asym_cpu_capacity_classify(struct sched_domain *sd,
> if (!asym_cap_miss)
> sd_asym_flags |= SD_ASYM_CPUCAPACITY_FULL;
>
> + WARN_ONCE(cpu_smt_flags() & sd->flags, "Detected CPU capacity asymmetry on SMT level");
> leave:
> return sd_asym_flags;
> }
>
> Comment can be adjusted.
> This would sit in the classify function to nicely wrap asymmetry bits in one
> place. What do you think ?

... and you would need to pass in the sched domain pointer ;-)

Still prefer to check it in sd_init() since there is where we set the flags.

But you can't do 'cpu_smt_flags() & sd->flags'. MC level would hit too,
since it has SD_SHARE_PKG_RESOURCES as well.