On 31 October 2017 at 16:01, Peter Zijlstra <pet...@infradead.org> wrote:
> On Tue, Oct 31, 2017 at 12:14:11PM +0100, Vincent Guittot wrote:
>
>> > + if (runnable_sum >= 0) {
>> > + /*
>> > + * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
>> > + * the CPU is saturated running == runnable.
>> > + */
>> > + runnable_sum += se->avg.load_sum;
>> > + runnable_sum = min(runnable_sum, (long)LOAD_AVG_MAX);
>> > + } else {
>> > + /*
>> > + * Estimate the departing task's runnable by assuming all
>> > tasks
>> > + * are equally runnable.
>> > + *
>> > + * XXX: doesn't deal with multiple departures?
>>
>> Why this would not deal with multiple departures ?
>> we are using gcfs_rq->avg.load_sum that reflects the new state of the
>> gcfs_rq to evaluate the runnable_sum
>
> Ah, I figured the load_sum thing below reflected one average task worth
> of runnable.
>
>
>> > + /* runnable_sum can't be lower than running_sum */
>> > + running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT; /* XXX ? */
>>
>> running_sum is scaled by cpu's capacity but not load_sum
>>
>> I have made the shortcut of using SCHED_CAPACITY_SHIFT for capacity
>> but we might better use arch_scale_cpu_capacity(NULL, cpu) instead
>
> Ah, right. We should improve the comments thereabouts, I got totally
> lost trying to track that yesterday.
>
> Also; we should look at doing that invariant patch you're still sitting
> on.
Yes. I have to rebase and test lastest changes i did
