[PATCH v2 1/7] sched/deadline: fix try to pull pinned dl tasks in pull algorithm

[PATCH v2 1/7] sched/deadline: fix try to pull pinned dl tasks in pull algorithm

[Wanpeng Li]

Function pick_next_earliest_dl_task is used to pick earliest and pushable
dl task from overloaded cpus in pull algorithm, however, it traverses
runqueue rbtree instead of pushable task rbtree which is also ordered by
tasks' deadlines. This will result in getting no candidates from overloaded
cpus if all the dl tasks on the overloaded cpus are pinned. This patch fix
it by traversing pushable task rbtree which is also ordered by tasks'
deadlines.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
 kernel/sched/deadline.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 890ce95..f09f3ad 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1230,6 +1230,33 @@ next_node:
 	return NULL;
 }
 
+/*
+ * Return the earliest pushable rq's task, which is suitable to be executed
+ * on the cpu, NULL otherwse
+ */
+static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq,
+									int cpu)
+{
+	struct rb_node *next_node = rq->dl.pushable_dl_tasks_leftmost;
+	struct task_struct *p = NULL;
+
+	if (!has_pushable_dl_tasks(rq))
+		return NULL;
+
+next_node:
+	if (next_node) {
+		p = rb_entry(next_node, struct task_struct, pushable_dl_tasks);
+
+		if (pick_dl_task(rq, p, cpu))
+			return p;
+
+		next_node = rb_next(next_node);
+		goto next_node;
+	}
+
+	return NULL;
+}
+
 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
 
 static int find_later_rq(struct task_struct *task)
@@ -1514,7 +1541,7 @@ static int pull_dl_task(struct rq *this_rq)
 		if (src_rq->dl.dl_nr_running <= 1)
 			goto skip;
 
-		p = pick_next_earliest_dl_task(src_rq, this_cpu);
+		p = pick_earliest_pushable_dl_task(src_rq, this_cpu);
 
 		/*
 		 * We found a task to be pulled if:
-- 
1.9.1

[PATCH v2 2/7] sched/deadline: make init_sched_dl_class() __init

[Wanpeng Li]

It's a bootstrap function, make init_sched_dl_class() __init.

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 f09f3ad..4303af2 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1686,7 +1686,7 @@ static void rq_offline_dl(struct rq *rq)
 	cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu);
 }
 
-void init_sched_dl_class(void)
+void __init init_sched_dl_class(void)
 {
 	unsigned int i;
 
-- 
1.9.1

[tip:sched/core] sched/deadline: Make init_sched_dl_class() __init

[tip-bot for Wanpeng Li]

Commit-ID:  a6c0e746fb8f4ea6508f274314378325a6e1ec9b
Gitweb:     http://git.kernel.org/tip/a6c0e746fb8f4ea6508f274314378325a6e1ec9b
Author:     Wanpeng Li <wanpeng.li@linux.intel.com>
AuthorDate: Wed, 13 May 2015 14:01:02 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 19 Jun 2015 10:06:46 +0200

sched/deadline: Make init_sched_dl_class() __init

It's a bootstrap function, make init_sched_dl_class() __init.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1431496867-4194-2-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 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 9cbe1c7..1c4bc31 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1685,7 +1685,7 @@ static void rq_offline_dl(struct rq *rq)
 	cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu);
 }
 
-void init_sched_dl_class(void)
+void __init init_sched_dl_class(void)
 {
 	unsigned int i;
 
--
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[PATCH v2 3/7] sched/deadline: reduce rq lock contention by eliminating locking of non-feasible target

[Wanpeng Li]

This patch adds check that prevents futile attempts to move dl tasks to
a CPU with active tasks of equal or earlier deadline. The same behavior as
commit 80e3d87b2c55 ("sched/rt: Reduce rq lock contention by eliminating
locking of non-feasible target") for rt class.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
v1 -> v2:
 * add check in find_lock_later_rq()

 kernel/sched/deadline.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 4303af2..e49b1e6 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1012,7 +1012,9 @@ select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
 	    (p->nr_cpus_allowed > 1)) {
 		int target = find_later_rq(p);
 
-		if (target != -1)
+		if (target != -1 &&
+				dl_time_before(p->dl.deadline,
+					cpu_rq(target)->dl.earliest_dl.curr))
 			cpu = target;
 	}
 	rcu_read_unlock();
@@ -1360,6 +1362,17 @@ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
 
 		later_rq = cpu_rq(cpu);
 
+		if (!dl_time_before(task->dl.deadline,
+					later_rq->dl.earliest_dl.curr)) {
+			/*
+			 * Target rq has tasks of equal or earlier deadline,
+			 * retrying does not release any lock and is unlikely
+			 * to yield a different result.
+			 */
+			later_rq = NULL;
+			break;
+		}
+
 		/* Retry if something changed. */
 		if (double_lock_balance(rq, later_rq)) {
 			if (unlikely(task_rq(task) != rq ||
-- 
1.9.1

[tip:sched/core] sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target

[tip-bot for Wanpeng Li]

Commit-ID:  9d514262425691dddf942edea8bc9919e66fe140
Gitweb:     http://git.kernel.org/tip/9d514262425691dddf942edea8bc9919e66fe140
Author:     Wanpeng Li <wanpeng.li@linux.intel.com>
AuthorDate: Wed, 13 May 2015 14:01:03 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 19 Jun 2015 10:06:46 +0200

sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target

This patch adds a check that prevents futile attempts to move DL tasks
to a CPU with active tasks of equal or earlier deadline. The same
behavior as commit 80e3d87b2c55 ("sched/rt: Reduce rq lock contention
by eliminating locking of non-feasible target") for rt class.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1431496867-4194-3-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/deadline.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 1c4bc31..98f7871 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1012,7 +1012,9 @@ select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
 	    (p->nr_cpus_allowed > 1)) {
 		int target = find_later_rq(p);
 
-		if (target != -1)
+		if (target != -1 &&
+				dl_time_before(p->dl.deadline,
+					cpu_rq(target)->dl.earliest_dl.curr))
 			cpu = target;
 	}
 	rcu_read_unlock();
@@ -1359,6 +1361,17 @@ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
 
 		later_rq = cpu_rq(cpu);
 
+		if (!dl_time_before(task->dl.deadline,
+					later_rq->dl.earliest_dl.curr)) {
+			/*
+			 * Target rq has tasks of equal or earlier deadline,
+			 * retrying does not release any lock and is unlikely
+			 * to yield a different result.
+			 */
+			later_rq = NULL;
+			break;
+		}
+
 		/* Retry if something changed. */
 		if (double_lock_balance(rq, later_rq)) {
 			if (unlikely(task_rq(task) != rq ||
--
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[PATCH v2 4/7] sched/deadline: reschedule if stop task slip in after pull operations

[Wanpeng Li]

pull_dl_task can drop (and re-acquire) rq->lock, this means a stop task
can slip in, in which case we need to reschedule. This patch add the
reschedule when the scenario occurs.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
 kernel/sched/deadline.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index e49b1e6..7d4c4fc 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1750,7 +1750,13 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
 	if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
 		return;
 
-	if (pull_dl_task(rq))
+	/*
+	 * pull_dl_task() can drop (and re-acquire) rq->lock; this
+	 * means a stop task can slip in, in which case we need to
+	 * reschedule.
+	 */
+	if (pull_dl_task(rq) ||
+		(rq->stop && task_on_rq_queued(rq->stop)))
 		resched_curr(rq);
 }
 
@@ -1797,6 +1803,14 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
 			pull_dl_task(rq);
 
 		/*
+		 * pull_dl_task() can drop (and re-acquire) rq->lock; this
+		 * means a stop task can slip in, in which case we need to
+		 * reschedule.
+		 */
+		if (rq->stop && task_on_rq_queued(rq->stop))
+			resched_curr(rq);
+
+		/*
 		 * If we now have a earlier deadline task than p,
 		 * then reschedule, provided p is still on this
 		 * runqueue.
-- 
1.9.1

Re: [PATCH v2 4/7] sched/deadline: reschedule if stop task slip in after pull operations

[Peter Zijlstra]

On Wed, May 13, 2015 at 02:01:04PM +0800, Wanpeng Li wrote:
> pull_dl_task can drop (and re-acquire) rq->lock, this means a stop task
> can slip in, in which case we need to reschedule. This patch add the
> reschedule when the scenario occurs.
> 
> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
> ---
>  kernel/sched/deadline.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index e49b1e6..7d4c4fc 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1750,7 +1750,13 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
>  	if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
>  		return;
>  
> -	if (pull_dl_task(rq))
> +	/*
> +	 * pull_dl_task() can drop (and re-acquire) rq->lock; this
> +	 * means a stop task can slip in, in which case we need to
> +	 * reschedule.
> +	 */
> +	if (pull_dl_task(rq) ||
> +		(rq->stop && task_on_rq_queued(rq->stop)))
>  		resched_curr(rq);

But, the waking of the stop task will already have done the preemption
check and won (obviously). So the wakeup should already have done the
resched_curr().

So why?

Re: [PATCH v2 4/7] sched/deadline: reschedule if stop task slip in after pull operations

[Wanpeng Li]

On 5/29/15 10:16 PM, Peter Zijlstra wrote:
> On Wed, May 13, 2015 at 02:01:04PM +0800, Wanpeng Li wrote:
>> pull_dl_task can drop (and re-acquire) rq->lock, this means a stop task
>> can slip in, in which case we need to reschedule. This patch add the
>> reschedule when the scenario occurs.
>>
>> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
>> ---
>>   kernel/sched/deadline.c | 16 +++++++++++++++-
>>   1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
>> index e49b1e6..7d4c4fc 100644
>> --- a/kernel/sched/deadline.c
>> +++ b/kernel/sched/deadline.c
>> @@ -1750,7 +1750,13 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
>>   	if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
>>   		return;
>>   
>> -	if (pull_dl_task(rq))
>> +	/*
>> +	 * pull_dl_task() can drop (and re-acquire) rq->lock; this
>> +	 * means a stop task can slip in, in which case we need to
>> +	 * reschedule.
>> +	 */
>> +	if (pull_dl_task(rq) ||
>> +		(rq->stop && task_on_rq_queued(rq->stop)))
>>   		resched_curr(rq);
> But, the waking of the stop task will already have done the preemption
> check and won (obviously). So the wakeup should already have done the
> resched_curr().

Indeed, thanks for your pointing out. :)

>
> So why?
>
> --
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> Please read the FAQ at  http://www.tux.org/lkml/

[PATCH v2 5/7] sched/deadline: drop duplicate init_sched_dl_class declaration

[Wanpeng Li]

There are two init_sched_dl_class declarations, this patch drop 
the duplicated one.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
v1 -> v2:
 * trim the changelog

 kernel/sched/sched.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index d854555..d62b288 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1290,7 +1290,6 @@ extern void update_max_interval(void);
 extern void init_sched_dl_class(void);
 extern void init_sched_rt_class(void);
 extern void init_sched_fair_class(void);
-extern void init_sched_dl_class(void);
 
 extern void resched_curr(struct rq *rq);
 extern void resched_cpu(int cpu);
-- 
1.9.1

[tip:sched/core] sched/deadline: Drop duplicate init_sched_dl_class() declaration

[tip-bot for Wanpeng Li]

Commit-ID:  178a4d23e4e6a0a90b086dad86697676b49db60a
Gitweb:     http://git.kernel.org/tip/178a4d23e4e6a0a90b086dad86697676b49db60a
Author:     Wanpeng Li <wanpeng.li@linux.intel.com>
AuthorDate: Wed, 13 May 2015 14:01:05 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 19 Jun 2015 10:06:47 +0200

sched/deadline: Drop duplicate init_sched_dl_class() declaration

There are two init_sched_dl_class() declarations, this patch drops
the duplicate.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1431496867-4194-5-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/sched.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index d854555..d62b288 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1290,7 +1290,6 @@ extern void update_max_interval(void);
 extern void init_sched_dl_class(void);
 extern void init_sched_rt_class(void);
 extern void init_sched_fair_class(void);
-extern void init_sched_dl_class(void);
 
 extern void resched_curr(struct rq *rq);
 extern void resched_cpu(int cpu);
--
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[PATCH v2 6/7] sched/core: remove superfluous resetting of dl_throttled flag

[Wanpeng Li]

Resetting dl_throttled flag in rt_mutex_setprio (for a task that is going
to be boosted) is superfluous, as the natural place to do so is in
replenish_dl_entity(). If the task was on the runqueue and it is boosted
by a DL task, it will be enqueued back with ENQUEUE_REPLENISH flag set,
which can guarantee that dl_throttled is reset in replenish_dl_entity().

This patch drops the resetting of throttled status in function
rt_mutex_setprio().

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
v1 -> v2:
 * rewrite patch subject and changelog

 kernel/sched/core.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 355f953..a9fd4916 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3087,7 +3087,6 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
 		if (!dl_prio(p->normal_prio) ||
 		    (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) {
 			p->dl.dl_boosted = 1;
-			p->dl.dl_throttled = 0;
 			enqueue_flag = ENQUEUE_REPLENISH;
 		} else
 			p->dl.dl_boosted = 0;
-- 
1.9.1

[tip:sched/core] sched: Remove superfluous resetting of the p-> dl_throttled flag

[tip-bot for Wanpeng Li]

Commit-ID:  6713c3aa7f63626c0cecf9c509fb48d885b2dd12
Gitweb:     http://git.kernel.org/tip/6713c3aa7f63626c0cecf9c509fb48d885b2dd12
Author:     Wanpeng Li <wanpeng.li@linux.intel.com>
AuthorDate: Wed, 13 May 2015 14:01:06 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 19 Jun 2015 10:06:47 +0200

sched: Remove superfluous resetting of the p->dl_throttled flag

Resetting the p->dl_throttled flag in rt_mutex_setprio() (for a task that is going
to be boosted) is superfluous, as the natural place to do so is in
replenish_dl_entity().

If the task was on the runqueue and it is boosted by a DL task, it will be enqueued
back with ENQUEUE_REPLENISH flag set, which can guarantee that dl_throttled is
reset in replenish_dl_entity().

This patch drops the resetting of throttled status in function rt_mutex_setprio().

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1431496867-4194-6-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/core.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1428c7c..10338ce 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3099,7 +3099,6 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
 		if (!dl_prio(p->normal_prio) ||
 		    (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) {
 			p->dl.dl_boosted = 1;
-			p->dl.dl_throttled = 0;
 			enqueue_flag = ENQUEUE_REPLENISH;
 		} else
 			p->dl.dl_boosted = 0;
--
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[PATCH v2 7/7] sched/rt: reschedule if stop/dl task slip in after pull operations

[Wanpeng Li]

pull_rt_task() can drop (and re-acquire) rq->lock, this means a dl 
or stop task can slip in, in which case need to reschedule. This 
patch add the reschedule when the scenario occurs.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
 kernel/sched/rt.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 560d2fa..8c948bf 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2136,7 +2136,14 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p)
 	if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
 		return;
 
-	if (pull_rt_task(rq))
+	/*
+	 * pull_rt_task() can drop (and re-acquire) rq->lock; this
+	 * means a dl or stop task can slip in, in which case we need
+	 * to reschedule.
+	 */
+	if (pull_rt_task(rq) ||
+		(unlikely((rq->stop && task_on_rq_queued(rq->stop)) ||
+			rq->dl.dl_nr_running)))
 		resched_curr(rq);
 }
 
@@ -2197,6 +2204,16 @@ prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
 		 */
 		if (oldprio < p->prio)
 			pull_rt_task(rq);
+
+		/*
+		 * pull_rt_task() can drop (and re-acquire) rq->lock; this
+		 * means a dl or stop task can slip in, in which case we need
+		 * to reschedule.
+		 */
+		if (unlikely((rq->stop && task_on_rq_queued(rq->stop)) ||
+			rq->dl.dl_nr_running))
+			resched_curr(rq);
+
 		/*
 		 * If there's a higher priority task waiting to run
 		 * then reschedule. Note, the above pull_rt_task
-- 
1.9.1

Re: [PATCH v2 7/7] sched/rt: reschedule if stop/dl task slip in after pull operations

[Peter Zijlstra]

On Wed, May 13, 2015 at 02:01:07PM +0800, Wanpeng Li wrote:
> pull_rt_task() can drop (and re-acquire) rq->lock, this means a dl 
> or stop task can slip in, in which case need to reschedule. This 
> patch add the reschedule when the scenario occurs.
> 
> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
> ---
>  kernel/sched/rt.c | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 560d2fa..8c948bf 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -2136,7 +2136,14 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p)
>  	if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
>  		return;
>  
> -	if (pull_rt_task(rq))
> +	/*
> +	 * pull_rt_task() can drop (and re-acquire) rq->lock; this
> +	 * means a dl or stop task can slip in, in which case we need
> +	 * to reschedule.
> +	 */
> +	if (pull_rt_task(rq) ||
> +		(unlikely((rq->stop && task_on_rq_queued(rq->stop)) ||
> +			rq->dl.dl_nr_running)))
>  		resched_curr(rq);
>  }

Same as before; why is the normal wakeup preemption check not working?

Re: [PATCH v2 7/7] sched/rt: reschedule if stop/dl task slip in after pull operations

[Wanpeng Li]

On 5/29/15 10:34 PM, Peter Zijlstra wrote:
> On Wed, May 13, 2015 at 02:01:07PM +0800, Wanpeng Li wrote:
>> pull_rt_task() can drop (and re-acquire) rq->lock, this means a dl
>> or stop task can slip in, in which case need to reschedule. This
>> patch add the reschedule when the scenario occurs.
>>
>> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
>> ---
>>   kernel/sched/rt.c | 19 ++++++++++++++++++-
>>   1 file changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
>> index 560d2fa..8c948bf 100644
>> --- a/kernel/sched/rt.c
>> +++ b/kernel/sched/rt.c
>> @@ -2136,7 +2136,14 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p)
>>   	if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
>>   		return;
>>   
>> -	if (pull_rt_task(rq))
>> +	/*
>> +	 * pull_rt_task() can drop (and re-acquire) rq->lock; this
>> +	 * means a dl or stop task can slip in, in which case we need
>> +	 * to reschedule.
>> +	 */
>> +	if (pull_rt_task(rq) ||
>> +		(unlikely((rq->stop && task_on_rq_queued(rq->stop)) ||
>> +			rq->dl.dl_nr_running)))
>>   		resched_curr(rq);
>>   }
> Same as before; why is the normal wakeup preemption check not working?

I will drop these two patches and send out v3. :)

Regards,
Wanpeng Li

> --
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Re: [PATCH v2 1/7] sched/deadline: fix try to pull pinned dl tasks in pull algorithm

[Wanpeng Li]

Ping Peterz for this patchset, :)
On Wed, May 13, 2015 at 02:01:01PM +0800, Wanpeng Li wrote:
>Function pick_next_earliest_dl_task is used to pick earliest and pushable
>dl task from overloaded cpus in pull algorithm, however, it traverses
>runqueue rbtree instead of pushable task rbtree which is also ordered by
>tasks' deadlines. This will result in getting no candidates from overloaded
>cpus if all the dl tasks on the overloaded cpus are pinned. This patch fix
>it by traversing pushable task rbtree which is also ordered by tasks'
>deadlines.
>
>Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
>---
> kernel/sched/deadline.c | 29 ++++++++++++++++++++++++++++-
> 1 file changed, 28 insertions(+), 1 deletion(-)
>
>diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
>index 890ce95..f09f3ad 100644
>--- a/kernel/sched/deadline.c
>+++ b/kernel/sched/deadline.c
>@@ -1230,6 +1230,33 @@ next_node:
> 	return NULL;
> }
> 
>+/*
>+ * Return the earliest pushable rq's task, which is suitable to be executed
>+ * on the cpu, NULL otherwse
>+ */
>+static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq,
>+									int cpu)
>+{
>+	struct rb_node *next_node = rq->dl.pushable_dl_tasks_leftmost;
>+	struct task_struct *p = NULL;
>+
>+	if (!has_pushable_dl_tasks(rq))
>+		return NULL;
>+
>+next_node:
>+	if (next_node) {
>+		p = rb_entry(next_node, struct task_struct, pushable_dl_tasks);
>+
>+		if (pick_dl_task(rq, p, cpu))
>+			return p;
>+
>+		next_node = rb_next(next_node);
>+		goto next_node;
>+	}
>+
>+	return NULL;
>+}
>+
> static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
> 
> static int find_later_rq(struct task_struct *task)
>@@ -1514,7 +1541,7 @@ static int pull_dl_task(struct rq *this_rq)
> 		if (src_rq->dl.dl_nr_running <= 1)
> 			goto skip;
> 
>-		p = pick_next_earliest_dl_task(src_rq, this_cpu);
>+		p = pick_earliest_pushable_dl_task(src_rq, this_cpu);
> 
> 		/*
> 		 * We found a task to be pulled if:
>-- 
>1.9.1

Re: [PATCH v2 1/7] sched/deadline: fix try to pull pinned dl tasks in pull algorithm

[Wanpeng Li]

Ping,
On Tue, May 19, 2015 at 08:23:15AM +0800, Wanpeng Li wrote:
>Ping Peterz for this patchset, :)
>On Wed, May 13, 2015 at 02:01:01PM +0800, Wanpeng Li wrote:
>>Function pick_next_earliest_dl_task is used to pick earliest and pushable
>>dl task from overloaded cpus in pull algorithm, however, it traverses
>>runqueue rbtree instead of pushable task rbtree which is also ordered by
>>tasks' deadlines. This will result in getting no candidates from overloaded
>>cpus if all the dl tasks on the overloaded cpus are pinned. This patch fix
>>it by traversing pushable task rbtree which is also ordered by tasks'
>>deadlines.
>>
>>Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
>>---
>> kernel/sched/deadline.c | 29 ++++++++++++++++++++++++++++-
>> 1 file changed, 28 insertions(+), 1 deletion(-)
>>
>>diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
>>index 890ce95..f09f3ad 100644
>>--- a/kernel/sched/deadline.c
>>+++ b/kernel/sched/deadline.c
>>@@ -1230,6 +1230,33 @@ next_node:
>> 	return NULL;
>> }
>> 
>>+/*
>>+ * Return the earliest pushable rq's task, which is suitable to be executed
>>+ * on the cpu, NULL otherwse
>>+ */
>>+static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq,
>>+									int cpu)
>>+{
>>+	struct rb_node *next_node = rq->dl.pushable_dl_tasks_leftmost;
>>+	struct task_struct *p = NULL;
>>+
>>+	if (!has_pushable_dl_tasks(rq))
>>+		return NULL;
>>+
>>+next_node:
>>+	if (next_node) {
>>+		p = rb_entry(next_node, struct task_struct, pushable_dl_tasks);
>>+
>>+		if (pick_dl_task(rq, p, cpu))
>>+			return p;
>>+
>>+		next_node = rb_next(next_node);
>>+		goto next_node;
>>+	}
>>+
>>+	return NULL;
>>+}
>>+
>> static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
>> 
>> static int find_later_rq(struct task_struct *task)
>>@@ -1514,7 +1541,7 @@ static int pull_dl_task(struct rq *this_rq)
>> 		if (src_rq->dl.dl_nr_running <= 1)
>> 			goto skip;
>> 
>>-		p = pick_next_earliest_dl_task(src_rq, this_cpu);
>>+		p = pick_earliest_pushable_dl_task(src_rq, this_cpu);
>> 
>> 		/*
>> 		 * We found a task to be pulled if:
>>-- 
>>1.9.1

[tip:sched/core] sched/deadline: Optimize pull_dl_task()

[tip-bot for Wanpeng Li]

Commit-ID:  8b5e770ed7c05a65ffd2d33a83c14572696236dc
Gitweb:     http://git.kernel.org/tip/8b5e770ed7c05a65ffd2d33a83c14572696236dc
Author:     Wanpeng Li <wanpeng.li@linux.intel.com>
AuthorDate: Wed, 13 May 2015 14:01:01 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 19 Jun 2015 10:06:45 +0200

sched/deadline: Optimize pull_dl_task()

pull_dl_task() uses pick_next_earliest_dl_task() to select a migration
candidate; this is sub-optimal since the next earliest task -- as per
the regular runqueue -- might not be migratable at all. This could
result in iterating the entire runqueue looking for a task.

Instead iterate the pushable queue -- this queue only contains tasks
that have at least 2 cpus set in their cpus_allowed mask.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
[ Improved the changelog. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1431496867-4194-1-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/deadline.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 890ce95..9cbe1c7 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1230,6 +1230,32 @@ next_node:
 	return NULL;
 }
 
+/*
+ * Return the earliest pushable rq's task, which is suitable to be executed
+ * on the CPU, NULL otherwise:
+ */
+static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu)
+{
+	struct rb_node *next_node = rq->dl.pushable_dl_tasks_leftmost;
+	struct task_struct *p = NULL;
+
+	if (!has_pushable_dl_tasks(rq))
+		return NULL;
+
+next_node:
+	if (next_node) {
+		p = rb_entry(next_node, struct task_struct, pushable_dl_tasks);
+
+		if (pick_dl_task(rq, p, cpu))
+			return p;
+
+		next_node = rb_next(next_node);
+		goto next_node;
+	}
+
+	return NULL;
+}
+
 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
 
 static int find_later_rq(struct task_struct *task)
@@ -1514,7 +1540,7 @@ static int pull_dl_task(struct rq *this_rq)
 		if (src_rq->dl.dl_nr_running <= 1)
 			goto skip;
 
-		p = pick_next_earliest_dl_task(src_rq, this_cpu);
+		p = pick_earliest_pushable_dl_task(src_rq, this_cpu);
 
 		/*
 		 * We found a task to be pulled if:
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