Re: [PATCH 2/4] sched/fair: Move avg_scan_cost calculations under SIS_PROP
From: Li, Aubrey
Date: Wed Dec 09 2020 - 00:30:22 EST
On 2020/12/9 0:03, Vincent Guittot wrote:
> On Tue, 8 Dec 2020 at 16:35, Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote:
>>
>> As noted by Vincent Guittot, avg_scan_costs are calculated for SIS_PROP
>> even if SIS_PROP is disabled. Move the time calculations under a SIS_PROP
>> check and while we are at it, exclude the cost of initialising the CPU
>> mask from the average scan cost.
>>
>> Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
>> ---
>> kernel/sched/fair.c | 14 ++++++++------
>> 1 file changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index ac7b34e7372b..5c41875aec23 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -6153,6 +6153,8 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
>> if (!this_sd)
>> return -1;
>
> Just noticed while reviewing the patch that the above related to
> this_sd can also go under sched_feat(SIS_PROP)
>
>>
>> + cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
>> +
>> if (sched_feat(SIS_PROP)) {
>> u64 avg_cost, avg_idle, span_avg;
>>
>> @@ -6168,11 +6170,9 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
>> nr = div_u64(span_avg, avg_cost);
>> else
>> nr = 4;
>> - }
>> -
>> - time = cpu_clock(this);
>>
>> - cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
>> + time = cpu_clock(this);
>> + }
>>
>> for_each_cpu_wrap(cpu, cpus, target) {
>> if (!--nr)
nr is the key of this throttling mechanism, need to be placed under sched_feat(SIS_PROP) as well.
Thanks,
-Aubrey