Messages in this thread | | | From | Vincent Guittot <> | Date | Mon, 20 Jun 2016 14:35:30 +0200 | Subject | Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks |
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On 20 June 2016 at 13:35, Dietmar Eggemann <dietmar.eggemann@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
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