On Tue, Sep 08, 2015 at 01:38:08PM +0800, Wanpeng Li wrote: > On 9/8/15 1:28 PM, Byungchul Park wrote: > >On Tue, Sep 08, 2015 at 11:46:01AM +0800, Wanpeng Li wrote: > >>On 9/7/15 10:02 PM, Peter Zijlstra wrote: > >>>Please always Cc at least the person who wrote the lines you modify. > >>> > >>>On Mon, Sep 07, 2015 at 05:45:20PM +0800, Wanpeng Li wrote: > >>>>The sleeper task will be normalized when moved from fair_sched_class, in > >>>>order that vruntime will be adjusted either the task is running or > >>>>sleeping > >>>>when moved back. The nomalization in switch_to_fair for sleep task will > >>>>result in lose fair sleeper bonus in place_entity() once the vruntime - > >>>>cfs_rq->min_vruntime is big when moved from fair_sched_class. > >>>> > >>>>This patch fix it by adjusting vruntime just during migrating as original > >>>>codes since the vruntime of the task has usually NOT been normalized in > >>>>this case. > >>>Sorry, I cannot follow that at all. Maybe its me being sleep deprived, > >>>but could you try that again? > >>When changing away from the fair class while sleeping, relative > >>vruntime is calculated to handle the case sleep when moved from > >>fair_sched_class and running when moved to fair_sched_class. The > >i don't think relative vruntime is calculated to handle the special case > >you mentioned. i think the calculation is necessary for all cases detaching > > Please refer why the relative vruntime caculation is introduced to > switched_from_fair(): https://lkml.org/lkml/2011/1/17/129
hello, it is just a bug caused by not calculating a relative vruntime when detached a task from cfs_rq, which is necessary though. > > >a task from a cfs_rq. > > > >>absolute vruntime will be calculated in enqueue_entity() either the > >>task is running or sleeping when moved back. The fair sleeper bonus > >i think absolute vruntime is calculated in enqueue_entuty() only when the > >task is on rq. therefore in the case that the task is not on rq, > >switched_to_fair() has to calculate the absolute vruntime instread. > > Absolute vruntime is caculated in place_entity() which is called by > enqueue_entity() for DEQUEUE_SLEEP task. as you may know, place_entity() is not for calculating an absolute vruntime though.. anyway the important thing here is that, when a sleeping task is moved back to fair class, enqueue_entity() for DEQUEUE_SLEEP task won't be called. thanks, byungchul > > Regards, > Wanpeng Li > > > > >>should be gained in place_entity() if the task is still sleeping. > >>However, after recent commit ( 23ec30ddd7c1306: 'sched: add two > >>functions for att(det)aching a task to(from) a cfs_rq'), the > >>absolute vruntime will be calculated in switched_to_fair(), so the > >>max_vruntime() which is called in place_entity() will select the > >>absolute vruntime which is calculated in switched_to_fair() as the > >>se->vruntime and lose the fair sleeper bonus. > >please refer my another reply, and let me know if i missed something. > > > >thanks, > >byungchul > > > >>Regards, > >>Wanpeng Li > >> > >>>>Signed-off-by: Wanpeng Li <wanpeng...@hotmail.com> > >>>>--- > >>>> kernel/sched/fair.c | 11 +++++++---- > >>>> 1 files changed, 7 insertions(+), 4 deletions(-) > >>>> > >>>>diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > >>>>index d26d3b7..eb9aa35 100644 > >>>>--- a/kernel/sched/fair.c > >>>>+++ b/kernel/sched/fair.c > >>>>@@ -8005,9 +8005,6 @@ static void attach_task_cfs_rq(struct task_struct > >>>>*p) > >>>> /* Synchronize task with its cfs_rq */ > >>>> attach_entity_load_avg(cfs_rq, se); > >>>>- > >>>>- if (!vruntime_normalized(p)) > >>>>- se->vruntime += cfs_rq->min_vruntime; > >>>> } > >>>> static void switched_from_fair(struct rq *rq, struct task_struct *p) > >>>>@@ -8066,14 +8063,20 @@ void init_cfs_rq(struct cfs_rq *cfs_rq) > >>>> #ifdef CONFIG_FAIR_GROUP_SCHED > >>>> static void task_move_group_fair(struct task_struct *p) > >>>> { > >>>>+ struct sched_entity *se = &p->se; > >>>>+ struct cfs_rq *cfs_rq = cfs_rq_of(se); > >>>>+ > >>>> 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; > >>>>+ se->avg.last_update_time = 0; > >>>> #endif > >>>> attach_task_cfs_rq(p); > >>>>+ > >>>>+ if (!vruntime_normalized(p)) > >>>>+ se->vruntime += cfs_rq->min_vruntime; > >>>> } > >>>> void free_fair_sched_group(struct task_group *tg) > >>>>-- > >>>>1.7.1 > >>>> > >>-- > >>To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > >>the body of a message to majord...@vger.kernel.org > >>More majordomo info at http://vger.kernel.org/majordomo-info.html > >>Please read the FAQ at http://www.tux.org/lkml/ > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/