Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity

[Juri Lelli]

On 11/07/16 16:16, Xunlei Pang wrote:
> On 2016/07/11 at 16:01, luca abeni wrote:
> > Hello,
> >
> > On Mon, 11 Jul 2016 13:03:56 +0800
> > Xunlei Pang  wrote:
> >
> >> On 2016/07/08 at 19:28, Juri Lelli wrote:
> > [...]
> >>> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
> >>> sched_dl_entity *dl_se, return;
> >>>  
> >>>   /*
> >>> +  * Use the scheduling parameters of the top pi-waiter task,
> >>> +  * if we have one from which we can inherit a deadline.
> >>> +  */
> >>> + if (dl_se->dl_boosted &&
> >>> + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
> >>> + dl_prio(pi_task->normal_prio))
> >>> + pi_se = _task->dl;
> >>> +
> >>> + /*
> >>>* We use the regular wall clock time to set deadlines in
> >>> the
> >>>* future; in fact, we must consider execution overheads
> >>> (time
> >>>* spent on hardirq context, etc.).
> >>> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
> >>> struct task_struct *p) static void switched_to_dl(struct rq *rq,
> >>> struct task_struct *p) {
> >>>   if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> >>> - setup_new_dl_entity(>dl, >dl);
> >>> + setup_new_dl_entity(>dl);  
> >> I'm curious why we even call setup_new_dl_entity() for non-queued
> >> cases? It seems more reasonable to do it when it really gets queued.
> >> We can see that enqueue_task_dl()->update_dl_entity() also has the
> >> same update logic as switched_to_dl().
> > I wondered the same when removing the dl_new field from
> > sched_dl_entity... But then I realised that enqueue_dl_entity() does
> > not always invoke update_dl_entity() or replenish_dl_entity()... For
> > example, when a task switches from SCHED_OTHER (or RT) to -deadline due
> > to sched_setattr() (or similar) these functions are not invoked.
> 
> Yeah, but for wake-up cases it does, as ENQUEUE_WAKEUP is set.
> What I meant is, can we only update for queued tasks in switched_to_dl()?
> 

Looks sensible to do. I think we can use the already present
task_on_rq_queued() check in there. I'll put together a v4 ASAP (if Luca
doesn't have already something).

Thanks,

- Juri

Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity

[Juri Lelli]

On 11/07/16 16:16, Xunlei Pang wrote:
> On 2016/07/11 at 16:01, luca abeni wrote:
> > Hello,
> >
> > On Mon, 11 Jul 2016 13:03:56 +0800
> > Xunlei Pang  wrote:
> >
> >> On 2016/07/08 at 19:28, Juri Lelli wrote:
> > [...]
> >>> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
> >>> sched_dl_entity *dl_se, return;
> >>>  
> >>>   /*
> >>> +  * Use the scheduling parameters of the top pi-waiter task,
> >>> +  * if we have one from which we can inherit a deadline.
> >>> +  */
> >>> + if (dl_se->dl_boosted &&
> >>> + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
> >>> + dl_prio(pi_task->normal_prio))
> >>> + pi_se = _task->dl;
> >>> +
> >>> + /*
> >>>* We use the regular wall clock time to set deadlines in
> >>> the
> >>>* future; in fact, we must consider execution overheads
> >>> (time
> >>>* spent on hardirq context, etc.).
> >>> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
> >>> struct task_struct *p) static void switched_to_dl(struct rq *rq,
> >>> struct task_struct *p) {
> >>>   if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> >>> - setup_new_dl_entity(>dl, >dl);
> >>> + setup_new_dl_entity(>dl);  
> >> I'm curious why we even call setup_new_dl_entity() for non-queued
> >> cases? It seems more reasonable to do it when it really gets queued.
> >> We can see that enqueue_task_dl()->update_dl_entity() also has the
> >> same update logic as switched_to_dl().
> > I wondered the same when removing the dl_new field from
> > sched_dl_entity... But then I realised that enqueue_dl_entity() does
> > not always invoke update_dl_entity() or replenish_dl_entity()... For
> > example, when a task switches from SCHED_OTHER (or RT) to -deadline due
> > to sched_setattr() (or similar) these functions are not invoked.
> 
> Yeah, but for wake-up cases it does, as ENQUEUE_WAKEUP is set.
> What I meant is, can we only update for queued tasks in switched_to_dl()?
> 

Looks sensible to do. I think we can use the already present
task_on_rq_queued() check in there. I'll put together a v4 ASAP (if Luca
doesn't have already something).

Thanks,

- Juri

Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity

[luca abeni]

On Mon, 11 Jul 2016 16:16:20 +0800
Xunlei Pang  wrote:

> On 2016/07/11 at 16:01, luca abeni wrote:
> > Hello,
> >
> > On Mon, 11 Jul 2016 13:03:56 +0800
> > Xunlei Pang  wrote:
> >  
> >> On 2016/07/08 at 19:28, Juri Lelli wrote:  
> > [...]  
> >>> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
> >>> sched_dl_entity *dl_se, return;
> >>>  
> >>>   /*
> >>> +  * Use the scheduling parameters of the top pi-waiter
> >>> task,
> >>> +  * if we have one from which we can inherit a deadline.
> >>> +  */
> >>> + if (dl_se->dl_boosted &&
> >>> + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se)))
> >>> &&
> >>> + dl_prio(pi_task->normal_prio))
> >>> + pi_se = _task->dl;
> >>> +
> >>> + /*
> >>>* We use the regular wall clock time to set deadlines in
> >>> the
> >>>* future; in fact, we must consider execution overheads
> >>> (time
> >>>* spent on hardirq context, etc.).
> >>> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
> >>> struct task_struct *p) static void switched_to_dl(struct rq *rq,
> >>> struct task_struct *p) {
> >>>   if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> >>> - setup_new_dl_entity(>dl, >dl);
> >>> + setup_new_dl_entity(>dl);
> >> I'm curious why we even call setup_new_dl_entity() for non-queued
> >> cases? It seems more reasonable to do it when it really gets
> >> queued. We can see that enqueue_task_dl()->update_dl_entity() also
> >> has the same update logic as switched_to_dl().  
> > I wondered the same when removing the dl_new field from
> > sched_dl_entity... But then I realised that enqueue_dl_entity() does
> > not always invoke update_dl_entity() or replenish_dl_entity()... For
> > example, when a task switches from SCHED_OTHER (or RT) to -deadline
> > due to sched_setattr() (or similar) these functions are not
> > invoked.  
> 
> Yeah, but for wake-up cases it does, as ENQUEUE_WAKEUP is set.
> What I meant is, can we only update for queued tasks in
> switched_to_dl()?

Uhm... Looking at this code again, I am not sure anymore about it...
(switched_to_dl() is invoked after enqueue enqueue_task_dl()?)

Maybe the best thing to do is to move the
"if (dl_time_before(p->dl.deadline, rq_clock(rq)))"
check in enqueue_dl_entity() (Juri, what do you think)? I'll try this
approach in the next days.



Thanks,
Luca

Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity

[luca abeni]

On Mon, 11 Jul 2016 16:16:20 +0800
Xunlei Pang  wrote:

> On 2016/07/11 at 16:01, luca abeni wrote:
> > Hello,
> >
> > On Mon, 11 Jul 2016 13:03:56 +0800
> > Xunlei Pang  wrote:
> >  
> >> On 2016/07/08 at 19:28, Juri Lelli wrote:  
> > [...]  
> >>> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
> >>> sched_dl_entity *dl_se, return;
> >>>  
> >>>   /*
> >>> +  * Use the scheduling parameters of the top pi-waiter
> >>> task,
> >>> +  * if we have one from which we can inherit a deadline.
> >>> +  */
> >>> + if (dl_se->dl_boosted &&
> >>> + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se)))
> >>> &&
> >>> + dl_prio(pi_task->normal_prio))
> >>> + pi_se = _task->dl;
> >>> +
> >>> + /*
> >>>* We use the regular wall clock time to set deadlines in
> >>> the
> >>>* future; in fact, we must consider execution overheads
> >>> (time
> >>>* spent on hardirq context, etc.).
> >>> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
> >>> struct task_struct *p) static void switched_to_dl(struct rq *rq,
> >>> struct task_struct *p) {
> >>>   if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> >>> - setup_new_dl_entity(>dl, >dl);
> >>> + setup_new_dl_entity(>dl);
> >> I'm curious why we even call setup_new_dl_entity() for non-queued
> >> cases? It seems more reasonable to do it when it really gets
> >> queued. We can see that enqueue_task_dl()->update_dl_entity() also
> >> has the same update logic as switched_to_dl().  
> > I wondered the same when removing the dl_new field from
> > sched_dl_entity... But then I realised that enqueue_dl_entity() does
> > not always invoke update_dl_entity() or replenish_dl_entity()... For
> > example, when a task switches from SCHED_OTHER (or RT) to -deadline
> > due to sched_setattr() (or similar) these functions are not
> > invoked.  
> 
> Yeah, but for wake-up cases it does, as ENQUEUE_WAKEUP is set.
> What I meant is, can we only update for queued tasks in
> switched_to_dl()?

Uhm... Looking at this code again, I am not sure anymore about it...
(switched_to_dl() is invoked after enqueue enqueue_task_dl()?)

Maybe the best thing to do is to move the
"if (dl_time_before(p->dl.deadline, rq_clock(rq)))"
check in enqueue_dl_entity() (Juri, what do you think)? I'll try this
approach in the next days.



Thanks,
Luca

Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity

[Xunlei Pang]

On 2016/07/11 at 16:01, luca abeni wrote:
> Hello,
>
> On Mon, 11 Jul 2016 13:03:56 +0800
> Xunlei Pang  wrote:
>
>> On 2016/07/08 at 19:28, Juri Lelli wrote:
> [...]
>>> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
>>> sched_dl_entity *dl_se, return;
>>>  
>>> /*
>>> +* Use the scheduling parameters of the top pi-waiter task,
>>> +* if we have one from which we can inherit a deadline.
>>> +*/
>>> +   if (dl_se->dl_boosted &&
>>> +   (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
>>> +   dl_prio(pi_task->normal_prio))
>>> +   pi_se = _task->dl;
>>> +
>>> +   /*
>>>  * We use the regular wall clock time to set deadlines in
>>> the
>>>  * future; in fact, we must consider execution overheads
>>> (time
>>>  * spent on hardirq context, etc.).
>>> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
>>> struct task_struct *p) static void switched_to_dl(struct rq *rq,
>>> struct task_struct *p) {
>>> if (dl_time_before(p->dl.deadline, rq_clock(rq)))
>>> -   setup_new_dl_entity(>dl, >dl);
>>> +   setup_new_dl_entity(>dl);  
>> I'm curious why we even call setup_new_dl_entity() for non-queued
>> cases? It seems more reasonable to do it when it really gets queued.
>> We can see that enqueue_task_dl()->update_dl_entity() also has the
>> same update logic as switched_to_dl().
> I wondered the same when removing the dl_new field from
> sched_dl_entity... But then I realised that enqueue_dl_entity() does
> not always invoke update_dl_entity() or replenish_dl_entity()... For
> example, when a task switches from SCHED_OTHER (or RT) to -deadline due
> to sched_setattr() (or similar) these functions are not invoked.

Yeah, but for wake-up cases it does, as ENQUEUE_WAKEUP is set.
What I meant is, can we only update for queued tasks in switched_to_dl()?

Regards,
Xunlei

>
>
>   Luca
>
>> If so, for already queued and boosted cases, rt_mutex_setprio() will
>> call enqueue_task() with ENQUEUE_REPLENISH set, so enqueue_dl_entity()
>> ->replenish_dl_entity() will advance p->dl.deadline beforehand, see
>> code: replenish_dl_entity():
>> if (dl_se->dl_deadline == 0) {
>> dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
>> dl_se->runtime = pi_se->dl_runtime;
>> }
>>
>> IOW, we don't need to handle !dl boosted cases in
>> setup_new_dl_entity().
>>
>> Regards,
>> Xunlei
>>
>>>  
>>> if (task_on_rq_queued(p) && rq->curr != p) {
>>>  #ifdef CONFIG_SMP  

Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity

[Xunlei Pang]

On 2016/07/11 at 16:01, luca abeni wrote:
> Hello,
>
> On Mon, 11 Jul 2016 13:03:56 +0800
> Xunlei Pang  wrote:
>
>> On 2016/07/08 at 19:28, Juri Lelli wrote:
> [...]
>>> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
>>> sched_dl_entity *dl_se, return;
>>>  
>>> /*
>>> +* Use the scheduling parameters of the top pi-waiter task,
>>> +* if we have one from which we can inherit a deadline.
>>> +*/
>>> +   if (dl_se->dl_boosted &&
>>> +   (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
>>> +   dl_prio(pi_task->normal_prio))
>>> +   pi_se = _task->dl;
>>> +
>>> +   /*
>>>  * We use the regular wall clock time to set deadlines in
>>> the
>>>  * future; in fact, we must consider execution overheads
>>> (time
>>>  * spent on hardirq context, etc.).
>>> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
>>> struct task_struct *p) static void switched_to_dl(struct rq *rq,
>>> struct task_struct *p) {
>>> if (dl_time_before(p->dl.deadline, rq_clock(rq)))
>>> -   setup_new_dl_entity(>dl, >dl);
>>> +   setup_new_dl_entity(>dl);  
>> I'm curious why we even call setup_new_dl_entity() for non-queued
>> cases? It seems more reasonable to do it when it really gets queued.
>> We can see that enqueue_task_dl()->update_dl_entity() also has the
>> same update logic as switched_to_dl().
> I wondered the same when removing the dl_new field from
> sched_dl_entity... But then I realised that enqueue_dl_entity() does
> not always invoke update_dl_entity() or replenish_dl_entity()... For
> example, when a task switches from SCHED_OTHER (or RT) to -deadline due
> to sched_setattr() (or similar) these functions are not invoked.

Yeah, but for wake-up cases it does, as ENQUEUE_WAKEUP is set.
What I meant is, can we only update for queued tasks in switched_to_dl()?

Regards,
Xunlei

>
>
>   Luca
>
>> If so, for already queued and boosted cases, rt_mutex_setprio() will
>> call enqueue_task() with ENQUEUE_REPLENISH set, so enqueue_dl_entity()
>> ->replenish_dl_entity() will advance p->dl.deadline beforehand, see
>> code: replenish_dl_entity():
>> if (dl_se->dl_deadline == 0) {
>> dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
>> dl_se->runtime = pi_se->dl_runtime;
>> }
>>
>> IOW, we don't need to handle !dl boosted cases in
>> setup_new_dl_entity().
>>
>> Regards,
>> Xunlei
>>
>>>  
>>> if (task_on_rq_queued(p) && rq->curr != p) {
>>>  #ifdef CONFIG_SMP  

Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity

[luca abeni]

Hello,

On Mon, 11 Jul 2016 13:03:56 +0800
Xunlei Pang  wrote:

> On 2016/07/08 at 19:28, Juri Lelli wrote:
[...]
> > @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
> > sched_dl_entity *dl_se, return;
> >  
> > /*
> > +* Use the scheduling parameters of the top pi-waiter task,
> > +* if we have one from which we can inherit a deadline.
> > +*/
> > +   if (dl_se->dl_boosted &&
> > +   (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
> > +   dl_prio(pi_task->normal_prio))
> > +   pi_se = _task->dl;
> > +
> > +   /*
> >  * We use the regular wall clock time to set deadlines in
> > the
> >  * future; in fact, we must consider execution overheads
> > (time
> >  * spent on hardirq context, etc.).
> > @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
> > struct task_struct *p) static void switched_to_dl(struct rq *rq,
> > struct task_struct *p) {
> > if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> > -   setup_new_dl_entity(>dl, >dl);
> > +   setup_new_dl_entity(>dl);  
> 
> I'm curious why we even call setup_new_dl_entity() for non-queued
> cases? It seems more reasonable to do it when it really gets queued.
> We can see that enqueue_task_dl()->update_dl_entity() also has the
> same update logic as switched_to_dl().

I wondered the same when removing the dl_new field from
sched_dl_entity... But then I realised that enqueue_dl_entity() does
not always invoke update_dl_entity() or replenish_dl_entity()... For
example, when a task switches from SCHED_OTHER (or RT) to -deadline due
to sched_setattr() (or similar) these functions are not invoked.


Luca

> If so, for already queued and boosted cases, rt_mutex_setprio() will
> call enqueue_task() with ENQUEUE_REPLENISH set, so enqueue_dl_entity()
> ->replenish_dl_entity() will advance p->dl.deadline beforehand, see
> code: replenish_dl_entity():
> if (dl_se->dl_deadline == 0) {
> dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
> dl_se->runtime = pi_se->dl_runtime;
> }
> 
> IOW, we don't need to handle !dl boosted cases in
> setup_new_dl_entity().
> 
> Regards,
> Xunlei
> 
> >  
> > if (task_on_rq_queued(p) && rq->curr != p) {
> >  #ifdef CONFIG_SMP  
> 

Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity

[luca abeni]

Hello,

On Mon, 11 Jul 2016 13:03:56 +0800
Xunlei Pang  wrote:

> On 2016/07/08 at 19:28, Juri Lelli wrote:
[...]
> > @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
> > sched_dl_entity *dl_se, return;
> >  
> > /*
> > +* Use the scheduling parameters of the top pi-waiter task,
> > +* if we have one from which we can inherit a deadline.
> > +*/
> > +   if (dl_se->dl_boosted &&
> > +   (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
> > +   dl_prio(pi_task->normal_prio))
> > +   pi_se = _task->dl;
> > +
> > +   /*
> >  * We use the regular wall clock time to set deadlines in
> > the
> >  * future; in fact, we must consider execution overheads
> > (time
> >  * spent on hardirq context, etc.).
> > @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
> > struct task_struct *p) static void switched_to_dl(struct rq *rq,
> > struct task_struct *p) {
> > if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> > -   setup_new_dl_entity(>dl, >dl);
> > +   setup_new_dl_entity(>dl);  
> 
> I'm curious why we even call setup_new_dl_entity() for non-queued
> cases? It seems more reasonable to do it when it really gets queued.
> We can see that enqueue_task_dl()->update_dl_entity() also has the
> same update logic as switched_to_dl().

I wondered the same when removing the dl_new field from
sched_dl_entity... But then I realised that enqueue_dl_entity() does
not always invoke update_dl_entity() or replenish_dl_entity()... For
example, when a task switches from SCHED_OTHER (or RT) to -deadline due
to sched_setattr() (or similar) these functions are not invoked.


Luca

> If so, for already queued and boosted cases, rt_mutex_setprio() will
> call enqueue_task() with ENQUEUE_REPLENISH set, so enqueue_dl_entity()
> ->replenish_dl_entity() will advance p->dl.deadline beforehand, see
> code: replenish_dl_entity():
> if (dl_se->dl_deadline == 0) {
> dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
> dl_se->runtime = pi_se->dl_runtime;
> }
> 
> IOW, we don't need to handle !dl boosted cases in
> setup_new_dl_entity().
> 
> Regards,
> Xunlei
> 
> >  
> > if (task_on_rq_queued(p) && rq->curr != p) {
> >  #ifdef CONFIG_SMP  
> 

Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity

[Xunlei Pang]

On 2016/07/08 at 19:28, Juri Lelli wrote:
> setup_new_dl_entity() takes two parameters, but it only actually uses
> one of them, under a different name, to setup a new dl_entity, after:
>
>  2f9f3fdc928 "sched/deadline: Remove dl_new from struct sched_dl_entity"
>
> as we currently do
>
>  setup_new_dl_entity(>dl, >dl)
>
> However, before Luca's change we were doing
>
>  setup_new_dl_entity(dl_se, pi_se)
>
> in update_dl_entity() for a dl_se->new entity: we were using pi_se's
> parameters (the potential PI donor) for setting up a new entity.
>
> Restore this behaviour (as we want to correctly initialize parameters of
> a boosted task that enters DEADLINE) by removing the useless second
> parameter of setup_new_dl_entity() and retrieving the top waiter
> directly from inside that function.
>
> Cc: Ingo Molnar 
> Cc: Peter Zijlstra 
> Cc: Steven Rostedt 
> Cc: Luca Abeni 
> Signed-off-by: Juri Lelli 
>
> ---
>  Changes from v2:
>- optimize by calling rt_mutex_get_top_task only if the task is
>  boosted (as suggested by Steve)
>
>  Changes from v1:
>- Steve pointed out that we were actually using the second parameter
>  to permorm initialization
>- Luca confirmed that behavior is slightly changed w.r.t. before his
>  change
>- changelog updated and original behavior restored
> ---
>  kernel/sched/deadline.c | 16 +---
>  1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index fcb7f0217ff4..7aeb21963d3c 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -346,11 +346,12 @@ static void check_preempt_curr_dl(struct rq *rq, struct 
> task_struct *p,
>   * one, and to (try to!) reconcile itself with its own scheduling
>   * parameters.
>   */
> -static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
> -struct sched_dl_entity *pi_se)
> +static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
>  {
>   struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
>   struct rq *rq = rq_of_dl_rq(dl_rq);
> + struct task_struct *pi_task;
> + struct sched_dl_entity *pi_se = dl_se;
>  
>   WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
>  
> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct 
> sched_dl_entity *dl_se,
>   return;
>  
>   /*
> +  * Use the scheduling parameters of the top pi-waiter task,
> +  * if we have one from which we can inherit a deadline.
> +  */
> + if (dl_se->dl_boosted &&
> + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
> + dl_prio(pi_task->normal_prio))
> + pi_se = _task->dl;
> +
> + /*
>* We use the regular wall clock time to set deadlines in the
>* future; in fact, we must consider execution overheads (time
>* spent on hardirq context, etc.).
> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq, struct 
> task_struct *p)
>  static void switched_to_dl(struct rq *rq, struct task_struct *p)
>  {
>   if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> - setup_new_dl_entity(>dl, >dl);
> + setup_new_dl_entity(>dl);

I'm curious why we even call setup_new_dl_entity() for non-queued cases?
It seems more reasonable to do it when it really gets queued. We can see
that enqueue_task_dl()->update_dl_entity() also has the same update logic
as switched_to_dl().

If so, for already queued and boosted cases, rt_mutex_setprio() will call
enqueue_task() with ENQUEUE_REPLENISH set, so enqueue_dl_entity()
->replenish_dl_entity() will advance p->dl.deadline beforehand, see code:
replenish_dl_entity():
if (dl_se->dl_deadline == 0) {
dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
dl_se->runtime = pi_se->dl_runtime;
}

IOW, we don't need to handle !dl boosted cases in setup_new_dl_entity().

Regards,
Xunlei

>  
>   if (task_on_rq_queued(p) && rq->curr != p) {
>  #ifdef CONFIG_SMP

Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity

[Xunlei Pang]

On 2016/07/08 at 19:28, Juri Lelli wrote:
> setup_new_dl_entity() takes two parameters, but it only actually uses
> one of them, under a different name, to setup a new dl_entity, after:
>
>  2f9f3fdc928 "sched/deadline: Remove dl_new from struct sched_dl_entity"
>
> as we currently do
>
>  setup_new_dl_entity(>dl, >dl)
>
> However, before Luca's change we were doing
>
>  setup_new_dl_entity(dl_se, pi_se)
>
> in update_dl_entity() for a dl_se->new entity: we were using pi_se's
> parameters (the potential PI donor) for setting up a new entity.
>
> Restore this behaviour (as we want to correctly initialize parameters of
> a boosted task that enters DEADLINE) by removing the useless second
> parameter of setup_new_dl_entity() and retrieving the top waiter
> directly from inside that function.
>
> Cc: Ingo Molnar 
> Cc: Peter Zijlstra 
> Cc: Steven Rostedt 
> Cc: Luca Abeni 
> Signed-off-by: Juri Lelli 
>
> ---
>  Changes from v2:
>- optimize by calling rt_mutex_get_top_task only if the task is
>  boosted (as suggested by Steve)
>
>  Changes from v1:
>- Steve pointed out that we were actually using the second parameter
>  to permorm initialization
>- Luca confirmed that behavior is slightly changed w.r.t. before his
>  change
>- changelog updated and original behavior restored
> ---
>  kernel/sched/deadline.c | 16 +---
>  1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index fcb7f0217ff4..7aeb21963d3c 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -346,11 +346,12 @@ static void check_preempt_curr_dl(struct rq *rq, struct 
> task_struct *p,
>   * one, and to (try to!) reconcile itself with its own scheduling
>   * parameters.
>   */
> -static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
> -struct sched_dl_entity *pi_se)
> +static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
>  {
>   struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
>   struct rq *rq = rq_of_dl_rq(dl_rq);
> + struct task_struct *pi_task;
> + struct sched_dl_entity *pi_se = dl_se;
>  
>   WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
>  
> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct 
> sched_dl_entity *dl_se,
>   return;
>  
>   /*
> +  * Use the scheduling parameters of the top pi-waiter task,
> +  * if we have one from which we can inherit a deadline.
> +  */
> + if (dl_se->dl_boosted &&
> + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
> + dl_prio(pi_task->normal_prio))
> + pi_se = _task->dl;
> +
> + /*
>* We use the regular wall clock time to set deadlines in the
>* future; in fact, we must consider execution overheads (time
>* spent on hardirq context, etc.).
> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq, struct 
> task_struct *p)
>  static void switched_to_dl(struct rq *rq, struct task_struct *p)
>  {
>   if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> - setup_new_dl_entity(>dl, >dl);
> + setup_new_dl_entity(>dl);

I'm curious why we even call setup_new_dl_entity() for non-queued cases?
It seems more reasonable to do it when it really gets queued. We can see
that enqueue_task_dl()->update_dl_entity() also has the same update logic
as switched_to_dl().

If so, for already queued and boosted cases, rt_mutex_setprio() will call
enqueue_task() with ENQUEUE_REPLENISH set, so enqueue_dl_entity()
->replenish_dl_entity() will advance p->dl.deadline beforehand, see code:
replenish_dl_entity():
if (dl_se->dl_deadline == 0) {
dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
dl_se->runtime = pi_se->dl_runtime;
}

IOW, we don't need to handle !dl boosted cases in setup_new_dl_entity().

Regards,
Xunlei

>  
>   if (task_on_rq_queued(p) && rq->curr != p) {
>  #ifdef CONFIG_SMP

[PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity

[Juri Lelli]

setup_new_dl_entity() takes two parameters, but it only actually uses
one of them, under a different name, to setup a new dl_entity, after:

 2f9f3fdc928 "sched/deadline: Remove dl_new from struct sched_dl_entity"

as we currently do

 setup_new_dl_entity(>dl, >dl)

However, before Luca's change we were doing

 setup_new_dl_entity(dl_se, pi_se)

in update_dl_entity() for a dl_se->new entity: we were using pi_se's
parameters (the potential PI donor) for setting up a new entity.

Restore this behaviour (as we want to correctly initialize parameters of
a boosted task that enters DEADLINE) by removing the useless second
parameter of setup_new_dl_entity() and retrieving the top waiter
directly from inside that function.

Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Luca Abeni 
Signed-off-by: Juri Lelli 

---
 Changes from v2:
   - optimize by calling rt_mutex_get_top_task only if the task is
 boosted (as suggested by Steve)

 Changes from v1:
   - Steve pointed out that we were actually using the second parameter
 to permorm initialization
   - Luca confirmed that behavior is slightly changed w.r.t. before his
 change
   - changelog updated and original behavior restored
---
 kernel/sched/deadline.c | 16 +---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index fcb7f0217ff4..7aeb21963d3c 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -346,11 +346,12 @@ static void check_preempt_curr_dl(struct rq *rq, struct 
task_struct *p,
  * one, and to (try to!) reconcile itself with its own scheduling
  * parameters.
  */
-static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
-  struct sched_dl_entity *pi_se)
+static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
 {
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rq *rq = rq_of_dl_rq(dl_rq);
+   struct task_struct *pi_task;
+   struct sched_dl_entity *pi_se = dl_se;
 
WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
 
@@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct 
sched_dl_entity *dl_se,
return;
 
/*
+* Use the scheduling parameters of the top pi-waiter task,
+* if we have one from which we can inherit a deadline.
+*/
+   if (dl_se->dl_boosted &&
+   (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
+   dl_prio(pi_task->normal_prio))
+   pi_se = _task->dl;
+
+   /*
 * We use the regular wall clock time to set deadlines in the
 * future; in fact, we must consider execution overheads (time
 * spent on hardirq context, etc.).
@@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq, struct 
task_struct *p)
 static void switched_to_dl(struct rq *rq, struct task_struct *p)
 {
if (dl_time_before(p->dl.deadline, rq_clock(rq)))
-   setup_new_dl_entity(>dl, >dl);
+   setup_new_dl_entity(>dl);
 
if (task_on_rq_queued(p) && rq->curr != p) {
 #ifdef CONFIG_SMP
-- 
2.7.4

[PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity

[Juri Lelli]

setup_new_dl_entity() takes two parameters, but it only actually uses
one of them, under a different name, to setup a new dl_entity, after:

 2f9f3fdc928 "sched/deadline: Remove dl_new from struct sched_dl_entity"

as we currently do

 setup_new_dl_entity(>dl, >dl)

However, before Luca's change we were doing

 setup_new_dl_entity(dl_se, pi_se)

in update_dl_entity() for a dl_se->new entity: we were using pi_se's
parameters (the potential PI donor) for setting up a new entity.

Restore this behaviour (as we want to correctly initialize parameters of
a boosted task that enters DEADLINE) by removing the useless second
parameter of setup_new_dl_entity() and retrieving the top waiter
directly from inside that function.

Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Luca Abeni 
Signed-off-by: Juri Lelli 

---
 Changes from v2:
   - optimize by calling rt_mutex_get_top_task only if the task is
 boosted (as suggested by Steve)

 Changes from v1:
   - Steve pointed out that we were actually using the second parameter
 to permorm initialization
   - Luca confirmed that behavior is slightly changed w.r.t. before his
 change
   - changelog updated and original behavior restored
---
 kernel/sched/deadline.c | 16 +---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index fcb7f0217ff4..7aeb21963d3c 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -346,11 +346,12 @@ static void check_preempt_curr_dl(struct rq *rq, struct 
task_struct *p,
  * one, and to (try to!) reconcile itself with its own scheduling
  * parameters.
  */
-static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
-  struct sched_dl_entity *pi_se)
+static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
 {
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rq *rq = rq_of_dl_rq(dl_rq);
+   struct task_struct *pi_task;
+   struct sched_dl_entity *pi_se = dl_se;
 
WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
 
@@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct 
sched_dl_entity *dl_se,
return;
 
/*
+* Use the scheduling parameters of the top pi-waiter task,
+* if we have one from which we can inherit a deadline.
+*/
+   if (dl_se->dl_boosted &&
+   (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
+   dl_prio(pi_task->normal_prio))
+   pi_se = _task->dl;
+
+   /*
 * We use the regular wall clock time to set deadlines in the
 * future; in fact, we must consider execution overheads (time
 * spent on hardirq context, etc.).
@@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq, struct 
task_struct *p)
 static void switched_to_dl(struct rq *rq, struct task_struct *p)
 {
if (dl_time_before(p->dl.deadline, rq_clock(rq)))
-   setup_new_dl_entity(>dl, >dl);
+   setup_new_dl_entity(>dl);
 
if (task_on_rq_queued(p) && rq->curr != p) {
 #ifdef CONFIG_SMP
-- 
2.7.4