Messages in this thread | | | From | Xuewen Yan <> | Date | Mon, 27 Feb 2023 09:51:55 +0800 | Subject | Re: [RFC PATCH] sched/fair: update the vruntime to be max vruntime when yield |
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Hi all
Looking forward to your comments.
Thanks!
On Wed, Feb 22, 2023 at 4:21 PM Xuewen Yan <xuewen.yan@unisoc.com> wrote: > > When task call the sched_yield, cfs would set the cfs's skip buddy. > If there is no other task call the sched_yield syscall, the task would > always be skiped when there are tasks in rq. As a result, the task's > vruntime would not be updated for long time, and the cfs's min_vruntime > is almost not updated. > When this scenario happens, when the yield task had wait for a long time, > and other tasks run a long time, once there is other task call the sched_yield, > the cfs's skip_buddy is covered, at this time, the first task can run normally, > but the task's vruntime is small, as a result, the task would always run, > because other task's vruntime is big. This would lead to other tasks can not > run for a long time. > In order to mitigate this, update the yield_task's vruntime to be cfs's max vruntime. > This way, the cfs's min vruntime can be updated as the process running. > > Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com> > --- > kernel/sched/fair.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index ff4dbbae3b10..a9ff1921fc07 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -670,7 +670,6 @@ static struct sched_entity *__pick_next_entity(struct sched_entity *se) > return __node_2_se(next); > } > > -#ifdef CONFIG_SCHED_DEBUG > struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) > { > struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root); > @@ -681,6 +680,7 @@ struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) > return __node_2_se(last); > } > > +#ifdef CONFIG_SCHED_DEBUG > /************************************************************** > * Scheduling class statistics methods: > */ > @@ -7751,8 +7751,18 @@ static void set_next_buddy(struct sched_entity *se) > > static void set_skip_buddy(struct sched_entity *se) > { > - for_each_sched_entity(se) > - cfs_rq_of(se)->skip = se; > + for_each_sched_entity(se) { > + struct sched_entity *last; > + struct cfs_rq *cfs_rq = cfs_rq_of(se); > + > + last = __pick_last_entity(cfs_rq); > + if (last) { > + se->vruntime = last->vruntime; > + update_min_vruntime(cfs_rq); > + } > + > + cfs_rq->skip = se; > + } > } > > /* > -- > 2.25.1 >
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