On 25/05/16 16:01, Vincent Guittot wrote: > The cfs_rq->avg.last_update_time is initialize to 0 with the main effect > that the 1st sched_entity that will be attached, will keep its > last_update_time set to 0 and will attached once again during the > enqueue. > Initialize cfs_rq->avg.last_update_time to 1 instead. > > Signed-off-by: Vincent Guittot <vincent.guit...@linaro.org> > --- > > v2: > - rq_clock_task(rq_of(cfs_rq)) can't be used because lock is not held > > kernel/sched/fair.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 218f8e8..3724656 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -8586,6 +8586,14 @@ void init_tg_cfs_entry(struct task_group *tg, struct > cfs_rq *cfs_rq, > se->depth = parent->depth + 1; > } > > + /* > + * Set last_update_time to something different from 0 to make > + * sure the 1st sched_entity will not be attached twice: once > + * when attaching the task to the group and one more time when > + * enqueueing the task. > + */ > + tg->cfs_rq[cpu]->avg.last_update_time = 1; > + > se->my_q = cfs_rq; > /* guarantee group entities always have weight */ > update_load_set(&se->load, NICE_0_LOAD);
So why not setting the last_update_time value for those cfs_rq's when we have the lock? E.g. in task_move_group_fair() or attach_task_cfs_rq(). @@ -8490,12 +8493,20 @@ void init_cfs_rq(struct cfs_rq *cfs_rq) #ifdef CONFIG_FAIR_GROUP_SCHED static void task_move_group_fair(struct task_struct *p) { +#ifdef CONFIG_SMP + struct cfs_rq *cfs_rq = NULL; +#endif + detach_task_cfs_rq(p); set_task_rq(p, task_cpu(p)); #ifdef CONFIG_SMP /* Tell se's cfs_rq has been changed -- migrated */ p->se.avg.last_update_time = 0; + + cfs_rq = cfs_rq_of(&p->se); + if (!cfs_rq->avg.last_update_time) + cfs_rq->avg.last_update_time = rq_clock_task(rq_of(cfs_rq)); #endif or @@ -8423,6 +8423,9 @@ static void attach_task_cfs_rq(struct task_struct *p) se->depth = se->parent ? se->parent->depth + 1 : 0; #endif + if (!cfs_rq->avg.last_update_time) + cfs_rq->avg.last_update_time = rq_clock_task(rq_of(cfs_rq)); + /* Synchronize task with its cfs_rq */ attach_entity_load_avg(cfs_rq, se);