* [PATCH v2 1/2] sched/deadline: Remove unnecessary condition in push_dl_task()
@ 2017-02-16 2:05 Byungchul Park
2017-02-16 2:05 ` [PATCH v2 2/2] sched/rt: Remove unnecessary condition in push_rt_task() Byungchul Park
2017-02-16 2:34 ` [PATCH v2 1/2] sched/deadline: Remove unnecessary condition in push_dl_task() Steven Rostedt
0 siblings, 2 replies; 4+ messages in thread
From: Byungchul Park @ 2017-02-16 2:05 UTC (permalink / raw)
To: peterz, mingo; +Cc: linux-kernel, juri.lelli, rostedt, kernel-team
Once pick_next_pushable_dl_task(rq) returns a task, it guarantees that
the task's cpu is rq->cpu, so task_cpu(next_task) is always rq->cpu if
task == next_task. Remove the redundant condition and make code simpler.
pick_next_pushable_dl_task(rq) has BUG_ON(rq->cpu != task_cpu(task))
when it returns a task other than NULL, which means that task_cpu(task)
must be rq->cpu. So if task == next_task, then task_cpu(next_task) must
be rq->cpu as well.
By this patch, unnecessary one branch and two LOAD operations in 'if'
statement can be avoided.
Signed-off-by: Byungchul Park <byungchul.park@lge.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 27737f3..ad8d577 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1483,7 +1483,7 @@ static int push_dl_task(struct rq *rq)
* then possible that next_task has migrated.
*/
task = pick_next_pushable_dl_task(rq);
- if (task_cpu(next_task) == rq->cpu && task == next_task) {
+ if (task == next_task) {
/*
* The task is still there. We don't try
* again, some other cpu will pull it when ready.
--
1.9.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v2 2/2] sched/rt: Remove unnecessary condition in push_rt_task()
2017-02-16 2:05 [PATCH v2 1/2] sched/deadline: Remove unnecessary condition in push_dl_task() Byungchul Park
@ 2017-02-16 2:05 ` Byungchul Park
2017-02-16 2:36 ` Steven Rostedt
2017-02-16 2:34 ` [PATCH v2 1/2] sched/deadline: Remove unnecessary condition in push_dl_task() Steven Rostedt
1 sibling, 1 reply; 4+ messages in thread
From: Byungchul Park @ 2017-02-16 2:05 UTC (permalink / raw)
To: peterz, mingo; +Cc: linux-kernel, juri.lelli, rostedt, kernel-team
Once pick_next_pushable_task(rq) returns a task, it guarantees that
the task's cpu is rq->cpu, so task_cpu(next_task) is always rq->cpu if
task == next_task. Remove the redundant condition and make code simpler.
pick_next_pushable_task(rq) has BUG_ON(rq_cpu != task_cpu(task)) when
it returns a task other than NULL, which means that task_cpu(task) must
be rq->cpu. So if task == next_task, then task_cpu(next_task) must be
rq->cpu as well.
By this patch, unnecessary one branch and two LOAD operations in 'if'
statement can be avoided.
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
kernel/sched/rt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 4101f9d..5abd9a52 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1820,7 +1820,7 @@ static int push_rt_task(struct rq *rq)
* pushing.
*/
task = pick_next_pushable_task(rq);
- if (task_cpu(next_task) == rq->cpu && task == next_task) {
+ if (task == next_task) {
/*
* The task hasn't migrated, and is still the next
* eligible task, but we failed to find a run-queue
--
1.9.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2 1/2] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-02-16 2:05 [PATCH v2 1/2] sched/deadline: Remove unnecessary condition in push_dl_task() Byungchul Park
2017-02-16 2:05 ` [PATCH v2 2/2] sched/rt: Remove unnecessary condition in push_rt_task() Byungchul Park
@ 2017-02-16 2:34 ` Steven Rostedt
1 sibling, 0 replies; 4+ messages in thread
From: Steven Rostedt @ 2017-02-16 2:34 UTC (permalink / raw)
To: Byungchul Park; +Cc: peterz, mingo, linux-kernel, juri.lelli, kernel-team
On Thu, 16 Feb 2017 11:05:53 +0900
Byungchul Park <byungchul.park@lge.com> wrote:
> Once pick_next_pushable_dl_task(rq) returns a task, it guarantees that
> the task's cpu is rq->cpu, so task_cpu(next_task) is always rq->cpu if
> task == next_task. Remove the redundant condition and make code simpler.
>
> pick_next_pushable_dl_task(rq) has BUG_ON(rq->cpu != task_cpu(task))
> when it returns a task other than NULL, which means that task_cpu(task)
> must be rq->cpu. So if task == next_task, then task_cpu(next_task) must
> be rq->cpu as well.
>
> By this patch, unnecessary one branch and two LOAD operations in 'if'
> statement can be avoided.
>
> Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
-- Steve
> ---
> 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 27737f3..ad8d577 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1483,7 +1483,7 @@ static int push_dl_task(struct rq *rq)
> * then possible that next_task has migrated.
> */
> task = pick_next_pushable_dl_task(rq);
> - if (task_cpu(next_task) == rq->cpu && task == next_task) {
> + if (task == next_task) {
> /*
> * The task is still there. We don't try
> * again, some other cpu will pull it when ready.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2 2/2] sched/rt: Remove unnecessary condition in push_rt_task()
2017-02-16 2:05 ` [PATCH v2 2/2] sched/rt: Remove unnecessary condition in push_rt_task() Byungchul Park
@ 2017-02-16 2:36 ` Steven Rostedt
0 siblings, 0 replies; 4+ messages in thread
From: Steven Rostedt @ 2017-02-16 2:36 UTC (permalink / raw)
To: Byungchul Park; +Cc: peterz, mingo, linux-kernel, juri.lelli, kernel-team
On Thu, 16 Feb 2017 11:05:54 +0900
Byungchul Park <byungchul.park@lge.com> wrote:
> Once pick_next_pushable_task(rq) returns a task, it guarantees that
> the task's cpu is rq->cpu, so task_cpu(next_task) is always rq->cpu if
> task == next_task. Remove the redundant condition and make code simpler.
>
> pick_next_pushable_task(rq) has BUG_ON(rq_cpu != task_cpu(task)) when
> it returns a task other than NULL, which means that task_cpu(task) must
> be rq->cpu. So if task == next_task, then task_cpu(next_task) must be
> rq->cpu as well.
>
> By this patch, unnecessary one branch and two LOAD operations in 'if'
> statement can be avoided.
>
> Signed-off-by: Byungchul Park <byungchul.park@lge.com>
> ---
> kernel/sched/rt.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 4101f9d..5abd9a52 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1820,7 +1820,7 @@ static int push_rt_task(struct rq *rq)
> * pushing.
> */
> task = pick_next_pushable_task(rq);
> - if (task_cpu(next_task) == rq->cpu && task == next_task) {
> + if (task == next_task) {
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
-- Steve
> /*
> * The task hasn't migrated, and is still the next
> * eligible task, but we failed to find a run-queue
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-02-16 2:36 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-02-16 2:05 [PATCH v2 1/2] sched/deadline: Remove unnecessary condition in push_dl_task() Byungchul Park
2017-02-16 2:05 ` [PATCH v2 2/2] sched/rt: Remove unnecessary condition in push_rt_task() Byungchul Park
2017-02-16 2:36 ` Steven Rostedt
2017-02-16 2:34 ` [PATCH v2 1/2] sched/deadline: Remove unnecessary condition in push_dl_task() Steven Rostedt
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