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Date: Sat, 15 Aug 2015 17:21:07 +0900
From: Byungchul Park <byungchul.park@....com>
To: "T. Zhou" <t.s.zhou@...mail.com>
Cc: mingo@...nel.org, peterz@...radead.org,
linux-kernel@...r.kernel.org, yuyang.du@...el.com
Subject: Re: [PATCH 2/2] sched: make task_move_group_fair simple by using
switched_to(from)_fair
On Fri, Aug 14, 2015 at 10:50:34PM +0800, T. Zhou wrote:
> Hi,
>
> On Thu, Aug 13, 2015 at 07:49:19PM +0900, byungchul.park@....com wrote:
> > +static inline int need_vruntime_adjust(struct task_struct *p, int queued)
> > +{
> > + struct sched_entity *se = &p->se;
> > +
> > + /*
> > + * When !queued, vruntime of the task has usually NOT been normalized.
> > + * But there are some cases where it has already been normalized:
> > + *
> > + * - Moving a forked child which is waiting for being woken up by
> > + * wake_up_new_task().
> > + * - Moving a task which has been woken up by try_to_wake_up() and
> > + * waiting for actually being woken up by sched_ttwu_pending().
> > + */
> > + if (queued)
> > + return 0;
> > +
> > + if (!se->sum_exec_runtime || p->state == TASK_WAKING)
> > + return 0;
> > +
> > + if (p->state != TASK_RUNNING)
> > + return 1;
> > +
> > + return 0;
> > +}
>
> Original switched_from/to_fair() do not include the following check.
>
> if (!se->sum_exec_runtime || p->state == TASK_WAKING)
> return 0;
>
> I guess you're sure this check will always fail in switched_from/to_fair() case
hello,
i wanted to introduce a function for checking necessity of adjusting
vruntime in general which may be also used in future. :)
thanks,
byungchul
>
> Thanks
> > static void switched_from_fair(struct rq *rq, struct task_struct *p)
> > {
> > struct sched_entity *se = &p->se;
> > @@ -7918,7 +7943,7 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p)
> > * have normalized the vruntime, if it's !queued, then only when
> > * the task is sleeping will it still have non-normalized vruntime.
> > */
> > - if (!task_on_rq_queued(p) && p->state != TASK_RUNNING) {
> > + if (need_vruntime_adjust(p, task_on_rq_queued(p))) {
> > /*
> > * Fix up our vruntime so that the current sleep doesn't
> > * cause 'unlimited' sleep bonus.
> > @@ -7939,7 +7964,6 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p)
> > static void switched_to_fair(struct rq *rq, struct task_struct *p)
> > {
> > struct sched_entity *se = &p->se;
> > -
> > #ifdef CONFIG_FAIR_GROUP_SCHED
> > /*
> > * Since the real-depth could have been changed (only FAIR
> > @@ -7964,7 +7988,7 @@ static void switched_to_fair(struct rq *rq, struct task_struct *p)
> > * has non-normalized vruntime, if it's !queued, then it still has
> > * normalized vruntime.
> > */
> > - if (p->state != TASK_RUNNING)
> > + if (need_vruntime_adjust(p, task_on_rq_queued(p)))
> > se->vruntime += cfs_rq_of(se)->min_vruntime;
> > return;
> > }
> > @@ -8014,55 +8038,9 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
> > #ifdef CONFIG_FAIR_GROUP_SCHED
> > static void task_move_group_fair(struct task_struct *p, int queued)
> > {
> > - struct sched_entity *se = &p->se;
> > - struct cfs_rq *cfs_rq;
> > -
> > - /*
> > - * If the task was not on the rq at the time of this cgroup movement
> > - * it must have been asleep, sleeping tasks keep their ->vruntime
> > - * absolute on their old rq until wakeup (needed for the fair sleeper
> > - * bonus in place_entity()).
> > - *
> > - * If it was on the rq, we've just 'preempted' it, which does convert
> > - * ->vruntime to a relative base.
> > - *
> > - * Make sure both cases convert their relative position when migrating
> > - * to another cgroup's rq. This does somewhat interfere with the
> > - * fair sleeper stuff for the first placement, but who cares.
> > - */
> > - /*
> > - * When !queued, vruntime of the task has usually NOT been normalized.
> > - * But there are some cases where it has already been normalized:
> > - *
> > - * - Moving a forked child which is waiting for being woken up by
> > - * wake_up_new_task().
> > - * - Moving a task which has been woken up by try_to_wake_up() and
> > - * waiting for actually being woken up by sched_ttwu_pending().
> > - *
> > - * To prevent boost or penalty in the new cfs_rq caused by delta
> > - * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
> > - */
> > - if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING))
> > - queued = 1;
> > -
> > - cfs_rq = cfs_rq_of(se);
> > - if (!queued)
> > - se->vruntime -= cfs_rq->min_vruntime;
> > -
> > -#ifdef CONFIG_SMP
> > - /* synchronize task with its prev cfs_rq */
> > - detach_entity_load_avg(cfs_rq, se);
> > -#endif
> > + switched_from_fair(task_rq(p), p);
> > set_task_rq(p, task_cpu(p));
> > - se->depth = se->parent ? se->parent->depth + 1 : 0;
> > - cfs_rq = cfs_rq_of(se);
> > - if (!queued)
> > - se->vruntime += cfs_rq->min_vruntime;
> > -
> > -#ifdef CONFIG_SMP
> > - /* Virtually synchronize task with its new cfs_rq */
> > - attach_entity_load_avg(cfs_rq, se);
> > -#endif
> > + switched_to_fair(task_rq(p), p);
> > }
> >
> > void free_fair_sched_group(struct task_group *tg)
>
> --
> Tao
> --
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