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| Started by | Byungchul Park <byungchul.park@lge.com> |
|---|---|
| First post | 2017-05-12 03:10 +0200 |
| Last post | 2017-05-23 10:50 +0200 |
| Articles | 4 — 3 participants |
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[RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task() Byungchul Park <byungchul.park@lge.com> - 2017-05-12 03:10 +0200
Re: [RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task() Byungchul Park <byungchul.park@lge.com> - 2017-05-18 04:10 +0200
Re: [RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task() Juri Lelli <juri.lelli@arm.com> - 2017-05-18 10:20 +0200
[tip:sched/core] sched/deadline: Remove unnecessary condition in push_dl_task() tip-bot for Byungchul Park <tipbot@zytor.com> - 2017-05-23 10:50 +0200
| From | Byungchul Park <byungchul.park@lge.com> |
|---|---|
| Date | 2017-05-12 03:10 +0200 |
| Subject | [RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task() |
| Message-ID | <tG7fH-5uI-5@gated-at.bofh.it> |
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. Remove the redundant condition and make code simpler.
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>
Reviewed-by: Juri Lelli <juri.lelli@arm.com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.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
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| From | Byungchul Park <byungchul.park@lge.com> |
|---|---|
| Date | 2017-05-18 04:10 +0200 |
| Subject | Re: [RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task() |
| Message-ID | <tIj34-32b-9@gated-at.bofh.it> |
| In reply to | #1640099 |
On Fri, May 12, 2017 at 10:05:59AM +0900, Byungchul Park wrote:
> 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. Remove the redundant condition and make code simpler.
>
> By this patch, unnecessary one branch and two LOAD operations in 'if'
> statement can be avoided.
+cc rostedt@goodmis.org
+cc juri.lelli@arm.com
+cc bristot@redhat.com
>
> Signed-off-by: Byungchul Park <byungchul.park@lge.com>
> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> Reviewed-by: Juri Lelli <juri.lelli@arm.com>
> Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.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
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| From | Juri Lelli <juri.lelli@arm.com> |
|---|---|
| Date | 2017-05-18 10:20 +0200 |
| Subject | Re: [RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task() |
| Message-ID | <tIoP7-7E3-11@gated-at.bofh.it> |
| In reply to | #1643739 |
Hi, On 18/05/17 11:00, Byungchul Park wrote: > On Fri, May 12, 2017 at 10:05:59AM +0900, Byungchul Park wrote: > > 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. Remove the redundant condition and make code simpler. > > > > By this patch, unnecessary one branch and two LOAD operations in 'if' > > statement can be avoided. > > +cc rostedt@goodmis.org > +cc juri.lelli@arm.com > +cc bristot@redhat.com > > > > > Signed-off-by: Byungchul Park <byungchul.park@lge.com> > > Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org> > > Reviewed-by: Juri Lelli <juri.lelli@arm.com> It looked, and still looks, good to me. :) Thanks, - Juri
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| From | tip-bot for Byungchul Park <tipbot@zytor.com> |
|---|---|
| Date | 2017-05-23 10:50 +0200 |
| Subject | [tip:sched/core] sched/deadline: Remove unnecessary condition in push_dl_task() |
| Message-ID | <tKdFV-Jg-45@gated-at.bofh.it> |
| In reply to | #1640099 |
Commit-ID: a776b968e52895a350d636e6e7fdcb3b10846fa4
Gitweb: http://git.kernel.org/tip/a776b968e52895a350d636e6e7fdcb3b10846fa4
Author: Byungchul Park <byungchul.park@lge.com>
AuthorDate: Fri, 12 May 2017 10:05:59 +0900
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 23 May 2017 10:01:33 +0200
sched/deadline: Remove unnecessary condition in push_dl_task()
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. Remove the redundant condition and make the code simpler.
This way one unnecessary branch and two LOAD operations can be avoided.
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Juri Lelli <juri.lelli@arm.com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: <kernel-team@lge.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/1494551159-22367-1-git-send-email-byungchul.park@lge.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 a2ce590..df6c291 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1533,7 +1533,7 @@ retry:
* 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.
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