lkml.org 
[lkml]   [2022]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] sched/core: use correct cpu_capacity in wake_affine_weight()
From


On 2022/11/16 19:00, Vincent Guittot wrote:
> On Wed, 16 Nov 2022 at 10:12, Honglei Wang <wanghonglei@didiglobal.com> wrote:
>>
>> It seems make more sense to do the load weight calculation with
>> respective cpu_capacity.
>>
>> Signed-off-by: Honglei Wang <wanghonglei@didiglobal.com>
>> ---
>> 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 e4a0b8bd941c..a9f75040969b 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -6262,13 +6262,13 @@ wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
>> this_eff_load += task_load;
>> if (sched_feat(WA_BIAS))
>> this_eff_load *= 100;
>> - this_eff_load *= capacity_of(prev_cpu);
>> + this_eff_load *= capacity_of(this_cpu);
>>
>> prev_eff_load = cpu_load(cpu_rq(prev_cpu));
>> prev_eff_load -= task_load;
>> if (sched_feat(WA_BIAS))
>> prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
>> - prev_eff_load *= capacity_of(this_cpu);
>> + prev_eff_load *= capacity_of(prev_cpu);
>
> we want to test :
> (cpu_load(this_rq) + task_h_load(p) ) / capacity_of(this_cpu) <
> cpu_load(prev_rq) / capacity_of(prev_cpu)
>
> but instead of doing expensive division, we do the below which gives
> the same result
> (cpu_load(this_rq) + task_h_load(p) ) * capacity_of(prev_cpu) <
> cpu_load(prev_rq) * capacity_of(this_cpu)
>
>

ha, I misunderstand the strategy, thanks for coaching, Vincent.

>>
>> /*
>> * If sync, adjust the weight of prev_eff_load such that if
>> --
>> 2.14.1
>>

\
 
 \ /
  Last update: 2022-11-16 12:28    [W:0.053 / U:0.152 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site