[PATCH v2 1/6] sched/rt: check if curr can be pushed/pulled somewhere else in advance

[PATCH v2 1/6] sched/rt: check if curr can be pushed/pulled somewhere else in advance

[Wanpeng Li]

This patch checks if current can be pushed/pulled somewhere else 
in advance to make logic clear, the same behavior as rt class.

- If current can't be migrated, useless to reschedule, let's hope 
  task can move out.
- If task is migratable, so let's not schedule it and see if it 
  can be pushed or pulled somewhere else.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
 kernel/sched/rt.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index d024e6c..a0b51aa 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1351,16 +1351,22 @@ out:
 
 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
 {
-	if (rq->curr->nr_cpus_allowed == 1)
+	/*
+	 * Current can't be migrated, useless to reschedule,
+	 * let's hope p can move out.
+	 */
+	if (rq->curr->nr_cpus_allowed == 1 ||
+		!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
 		return;
 
+	/*
+	 * p is migratable, so let's not schedule it and
+	 * see if it is pushed or pulled somewhere else.
+	 */
 	if (p->nr_cpus_allowed != 1
 	    && cpupri_find(&rq->rd->cpupri, p, NULL))
 		return;
 
-	if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
-		return;
-
 	/*
 	 * There appears to be other cpus that can accept
 	 * current and none to run 'p', so lets reschedule
-- 
1.9.1

[PATCH v2 2/6] sched/deadline: fix artificial overrun introduced by yield_task_dl

[Wanpeng Li]

The yield semantic of deadline class is to reduce remaining runtime to 
zero, and then update_curr_dl() will stop it. However, comsumed bandwidth 
is reduced from the budget of yield task again even if it has already been 
set to zero which leads to artificial overrun. This patch fix it by make 
sure we don't steal some more time from the task that yielded in update_curr_dl().

Suggested-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
v1 -> v2:
 * make sure we don't steal some more time from the task 
   that yielded in update_curr_dl().

 kernel/sched/deadline.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 2e31a30..db6ad38 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -633,7 +633,7 @@ static void update_curr_dl(struct rq *rq)
 
 	sched_rt_avg_update(rq, delta_exec);
 
-	dl_se->runtime -= delta_exec;
+	dl_se->runtime -= dl_se->dl_yielded ? 0 : delta_exec;
 	if (dl_runtime_exceeded(rq, dl_se)) {
 		__dequeue_task_dl(rq, curr, 0);
 		if (likely(start_dl_timer(dl_se, curr->dl.dl_boosted)))
-- 
1.9.1

[PATCH v2 3/6] sched/dl: add deadline rq status print

[Wanpeng Li]

This patch add deadline rq status print.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
 kernel/sched/deadline.c | 9 +++++++++
 kernel/sched/debug.c    | 7 +++++++
 kernel/sched/sched.h    | 1 +
 3 files changed, 17 insertions(+)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index db6ad38..4c5fdf5 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1727,3 +1727,12 @@ const struct sched_class dl_sched_class = {
 	.switched_from		= switched_from_dl,
 	.switched_to		= switched_to_dl,
 };
+
+#ifdef CONFIG_SCHED_DEBUG
+extern void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq);
+
+void print_dl_stats(struct seq_file *m, int cpu)
+{
+	print_dl_rq(m, cpu, &cpu_rq(cpu)->dl);
+}
+#endif /* CONFIG_SCHED_DEBUG */
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index ce33780..eeb6046 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -261,6 +261,12 @@ void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq)
 #undef P
 }
 
+void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq)
+{
+	SEQ_printf(m, "\ndl_rq[%d]:\n", cpu);
+	SEQ_printf(m, "  .%-30s: %ld\n", "dl_nr_running", dl_rq->dl_nr_running);
+}
+
 extern __read_mostly int sched_clock_running;
 
 static void print_cpu(struct seq_file *m, int cpu)
@@ -329,6 +335,7 @@ do {									\
 	spin_lock_irqsave(&sched_debug_lock, flags);
 	print_cfs_stats(m, cpu);
 	print_rt_stats(m, cpu);
+	print_dl_stats(m, cpu);
 
 	print_rq(m, rq, cpu);
 	spin_unlock_irqrestore(&sched_debug_lock, flags);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index ec3917c..3c6cac6 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1532,6 +1532,7 @@ extern struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq);
 extern struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq);
 extern void print_cfs_stats(struct seq_file *m, int cpu);
 extern void print_rt_stats(struct seq_file *m, int cpu);
+extern void print_dl_stats(struct seq_file *m, int cpu);
 
 extern void init_cfs_rq(struct cfs_rq *cfs_rq);
 extern void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq);
-- 
1.9.1

[PATCH v2 4/6] sched/dl: push task away if the deadline is equal to curr during wakeup

[Wanpeng Li]

This patch pushes task away if the dealine of the task is equal 
to current during wake up. The same behavior as rt class.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
 kernel/sched/deadline.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 4c5fdf5..1c09751 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1511,7 +1511,7 @@ static void task_woken_dl(struct rq *rq, struct task_struct *p)
 	    p->nr_cpus_allowed > 1 &&
 	    dl_task(rq->curr) &&
 	    (rq->curr->nr_cpus_allowed < 2 ||
-	     dl_entity_preempt(&rq->curr->dl, &p->dl))) {
+	     !dl_entity_preempt(&p->dl, &rq->curr->dl))) {
 		push_dl_tasks(rq);
 	}
 }
-- 
1.9.1

[PATCH v2 5/6] sched/deadline: reschedule from switched_from_dl() after a successful pull

[Wanpeng Li]

In switched_from_dl() we have to issue a resched if we successfully 
pulled some task from other cpus. This patch also aligns the behavior 
with -rt.

Suggested-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
v1 -> v2:
 * align the behaviour with -rt.

 kernel/sched/deadline.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 1c09751..2b23d50 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1623,8 +1623,11 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
 	 * this is the right place to try to pull some other one
 	 * from an overloaded cpu, if any.
 	 */
-	if (!rq->dl.dl_nr_running)
-		pull_dl_task(rq);
+	if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
+		return;
+
+	if (pull_dl_task(rq))
+		resched_curr(rq);
 #endif
 }
 
-- 
1.9.1

[PATCH v2 6/6] sched/dl: don't check CONFIG_SMP in switched_from_dl

[Wanpeng Li]

There are both UP and SMP version of pull_dl_task(), so don't need 
to check CONFIG_SMP in switched_from_dl();

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
 kernel/sched/deadline.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 2b23d50..c262eeb 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1617,7 +1617,6 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
 
 	__dl_clear_params(p);
 
-#ifdef CONFIG_SMP
 	/*
 	 * Since this might be the only -deadline task on the rq,
 	 * this is the right place to try to pull some other one
@@ -1628,7 +1627,6 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
 
 	if (pull_dl_task(rq))
 		resched_curr(rq);
-#endif
 }
 
 /*
-- 
1.9.1

Re: [PATCH v2 1/6] sched/rt: check if curr can be pushed/pulled somewhere else in advance

[Kirill Tkhai]

Hi,

В Чт, 30/10/2014 в 22:16 +0800, Wanpeng Li пишет:
> This patch checks if current can be pushed/pulled somewhere else 
> in advance to make logic clear, the same behavior as rt class.
> 
> - If current can't be migrated, useless to reschedule, let's hope 
>   task can move out.
> - If task is migratable, so let's not schedule it and see if it 
>   can be pushed or pulled somewhere else.

No functional changes, are they? So I'd suggest to change subject
on something connected with "cleanup".

Also, the description confuses. Please, write that code was cleaned
up, and that comments were added.

> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
> ---
>  kernel/sched/rt.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index d024e6c..a0b51aa 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1351,16 +1351,22 @@ out:
>  
>  static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
>  {
> -	if (rq->curr->nr_cpus_allowed == 1)
> +	/*
> +	 * Current can't be migrated, useless to reschedule,
> +	 * let's hope p can move out.
> +	 */
> +	if (rq->curr->nr_cpus_allowed == 1 ||
> +		!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
>  		return;

All conditions of multi-line if() should be aligned the same:

+	if (rq->curr->nr_cpus_allowed == 1 ||
+	    !cpupri_find(&rq->rd->cpupri, rq->curr, NULL))

>  
> +	/*
> +	 * p is migratable, so let's not schedule it and
> +	 * see if it is pushed or pulled somewhere else.
> +	 */
>  	if (p->nr_cpus_allowed != 1
>  	    && cpupri_find(&rq->rd->cpupri, p, NULL))
>  		return;
>  
> -	if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
> -		return;
> -
>  	/*
>  	 * There appears to be other cpus that can accept
>  	 * current and none to run 'p', so lets reschedule

Thanks,
Kirill

Re: [PATCH v2 1/6] sched/rt: check if curr can be pushed/pulled somewhere else in advance

[Wanpeng Li]

Hi Kirill,
On Thu, Oct 30, 2014 at 06:01:05PM +0300, Kirill Tkhai wrote:
>Hi,
>
>В Чт, 30/10/2014 в 22:16 +0800, Wanpeng Li пишет:
>> This patch checks if current can be pushed/pulled somewhere else 
>> in advance to make logic clear, the same behavior as rt class.
>> 
>> - If current can't be migrated, useless to reschedule, let's hope 
>>   task can move out.
>> - If task is migratable, so let's not schedule it and see if it 
>>   can be pushed or pulled somewhere else.
>
>No functional changes, are they? So I'd suggest to change subject
>on something connected with "cleanup".
>
>Also, the description confuses. Please, write that code was cleaned
>up, and that comments were added.
>

Ok.

>> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
>> ---
>>  kernel/sched/rt.c | 14 ++++++++++----
>>  1 file changed, 10 insertions(+), 4 deletions(-)
>> 
>> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
>> index d024e6c..a0b51aa 100644
>> --- a/kernel/sched/rt.c
>> +++ b/kernel/sched/rt.c
>> @@ -1351,16 +1351,22 @@ out:
>>  
>>  static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
>>  {
>> -	if (rq->curr->nr_cpus_allowed == 1)
>> +	/*
>> +	 * Current can't be migrated, useless to reschedule,
>> +	 * let's hope p can move out.
>> +	 */
>> +	if (rq->curr->nr_cpus_allowed == 1 ||
>> +		!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
>>  		return;
>
>All conditions of multi-line if() should be aligned the same:
>
>+	if (rq->curr->nr_cpus_allowed == 1 ||
>+	    !cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
>

I will update the patch in next version, thanks for your review.

Regards,
Wanpeng Li

>>  
>> +	/*
>> +	 * p is migratable, so let's not schedule it and
>> +	 * see if it is pushed or pulled somewhere else.
>> +	 */
>>  	if (p->nr_cpus_allowed != 1
>>  	    && cpupri_find(&rq->rd->cpupri, p, NULL))
>>  		return;
>>  
>> -	if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
>> -		return;
>> -
>>  	/*
>>  	 * There appears to be other cpus that can accept
>>  	 * current and none to run 'p', so lets reschedule
>
>Thanks,
>Kirill
>