linux-kernel - Re: [PATCH v3 6/7] sched/topology: Introduce SD metaflag for flags needing

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Date:   Thu, 02 Jul 2020 19:46:57 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
        vincent.guittot@...aro.org, morten.rasmussen@....com
Subject: Re: [PATCH v3 6/7] sched/topology: Introduce SD metaflag for flags needing > 1 groups


On 02/07/20 19:29, Dietmar Eggemann wrote:
> On 01/07/2020 21:06, Valentin Schneider wrote:
>
> [...]
>
>> @@ -105,16 +122,18 @@ SD_FLAG(SD_SERIALIZE,           8, SDF_SHARED_PARENT)
>>   * Place busy tasks earlier in the domain
>>   *
>>   * SHARED_CHILD: Usually set on the SMT level. Technically could be set further
>> - * up, but currently assumed to be set from the base domain upwards (see
>> - * update_top_cache_domain()).
>> + *               up, but currently assumed to be set from the base domain
>> + *               upwards (see update_top_cache_domain()).
>>   */
>> -SD_FLAG(SD_ASYM_PACKING,        9, SDF_SHARED_CHILD)
>> +SD_FLAG(SD_ASYM_PACKING,        9, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
>>
>>  /*
>>   * Prefer to place tasks in a sibling domain
>>   *
>>   * Set up until domains start spanning NUMA nodes. Close to being a SHARED_CHILD
>>   * flag, but cleared below domains with SD_ASYM_CPUCAPACITY.
>> + *
>> + * NEEDS_GROUPS: Load balancing flag.
>>   */
>>  SD_FLAG(SD_PREFER_SIBLING,      10, 0)
>
> Related to my comment in [PATCH v3 5/7], maybe you wanted to add
> SDF_NEEDS_GROUPS for SD_PREFER_SIBLING as well ? This comment
> 'NEEDS_GROUPS: Load balancing flag.' makes me wondering.
>
> Currently, SD_PREFER_SIBLING isn't in SD_DEGENERATE_GROUPS_MASK=0xaef.
>

You're right, that's a fail from my end. Thanks (and sorry)!

> [...]