On 20 June 2016 at 13:35, Dietmar Eggemann <dietmar.eggem...@arm.com> wrote:
>
>
> On 17/06/16 17:18, Peter Zijlstra wrote:
>> On Fri, Jun 17, 2016 at 06:02:39PM +0200, Peter Zijlstra wrote:
>>> So yes, ho-humm, how to go about doing that bestest. Lemme have a play.
>>
>> This is what I came up with, not entirely pretty, but I suppose it'll
>> have to do.
>>
>> ---
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -724,6 +724,7 @@ void post_init_entity_util_avg(struct sc
>> struct cfs_rq *cfs_rq = cfs_rq_of(se);
>> struct sched_avg *sa = &se->avg;
>> long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
>> + u64 now = cfs_rq_clock_task(cfs_rq);
>>
>> if (cap > 0) {
>> if (cfs_rq->avg.util_avg != 0) {
>> @@ -738,7 +739,20 @@ void post_init_entity_util_avg(struct sc
>> sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
>> }
>>
>> - update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, false);
>> + if (entity_is_task(se)) {
>> + struct task_struct *p = task_of(se);
>> + if (p->sched_class != &fair_sched_class) {
>> + /*
>> + * For !fair tasks do attach_entity_load_avg()
>> + * followed by detach_entity_load_avg() as per
>> + * switched_from_fair().
>> + */
>> + se->avg.last_update_time = now;
>> + return;
>> + }
>> + }
>> +
>> + update_cfs_rq_load_avg(now, cfs_rq, false);
>> attach_entity_load_avg(cfs_rq, se);
>> }
>>
>>
>
> Doesn't a sleeping !fair_sched_class task which switches to fair uses
> try_to_wake_up() rather than wake_up_new_task() so it won't go through
> post_init_entity_util_avg()?
It will go through wake_up_new_task and post_init_entity_util_avg
during its fork which is enough to set last_update_time. Then, it will
use the switched_to_fair if the task becomes a fair one
