Re: [PATCH v5 1/3] sched/fair: Introduce the burstable CFS controller

[Benjamin Segall]

Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes:

> On Mon, May 24, 2021 at 08:42:03PM +0800, changhuaixin wrote:
>
>> >> static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
>> >> @@ -4651,6 +4666,9 @@ static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b,
>> >> 	if (cfs_b->quota == RUNTIME_INF)
>> >> 		amount = min_amount;
>> >> 	else {
>> >> +		if (!cfs_b->period_active)
>> >> +			__refill_cfs_bandwidth_runtime(cfs_b);
>> > 
>> > Why this call?
>> 
>> As the cfs bandwidth timer stops on idle with runtime unfilled, refill runtime when it restarts to make
>> use of the underrun when period timer stops. Another way to do this might be:
>> 
>>         throttled = !list_empty(&cfs_b->throttled_cfs_rq);
>>         cfs_b->nr_periods += overrun;
>> 
>> +       __refill_cfs_bandwidth_runtime(cfs_b);
>> +
>>         /*
>>          * idle depends on !throttled (for the case of a large deficit), and if
>>          * we're going inactive then everything else can be deferred
>>          */
>>         if (cfs_b->idle && !throttled)
>>                 goto out_deactivate;
>> 
>> -       __refill_cfs_bandwidth_runtime(cfs_b);
>> -
>>         if (!throttled) {
>> 
>
> Ben, do you have a preference?


I think I prefer the latter, possibly with a
/* Refill extra burst quota even if cfs_b->idle */