* [RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task()
@ 2017-05-12 1:05 Byungchul Park
2017-05-18 2:00 ` Byungchul Park
2017-05-23 8:45 ` [tip:sched/core] " tip-bot for Byungchul Park
0 siblings, 2 replies; 4+ messages in thread
From: Byungchul Park @ 2017-05-12 1:05 UTC (permalink / raw)
To: peterz; +Cc: linux-kernel, kernel-team
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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-05-12 1:05 [RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task() Byungchul Park
@ 2017-05-18 2:00 ` Byungchul Park
2017-05-18 8:12 ` Juri Lelli
2017-05-23 8:45 ` [tip:sched/core] " tip-bot for Byungchul Park
1 sibling, 1 reply; 4+ messages in thread
From: Byungchul Park @ 2017-05-18 2:00 UTC (permalink / raw)
To: peterz; +Cc: linux-kernel, kernel-team, rostedt, juri.lelli, bristot
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
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-05-18 2:00 ` Byungchul Park
@ 2017-05-18 8:12 ` Juri Lelli
0 siblings, 0 replies; 4+ messages in thread
From: Juri Lelli @ 2017-05-18 8:12 UTC (permalink / raw)
To: Byungchul Park; +Cc: peterz, linux-kernel, kernel-team, rostedt, bristot
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
^ permalink raw reply [flat|nested] 4+ messages in thread
* [tip:sched/core] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-05-12 1:05 [RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task() Byungchul Park
2017-05-18 2:00 ` Byungchul Park
@ 2017-05-23 8:45 ` tip-bot for Byungchul Park
1 sibling, 0 replies; 4+ messages in thread
From: tip-bot for Byungchul Park @ 2017-05-23 8:45 UTC (permalink / raw)
To: linux-tip-commits
Cc: kernel-team, hpa, peterz, linux-kernel, rostedt, byungchul.park,
tglx, bristot, mingo, torvalds, juri.lelli
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.
^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-05-23 8:49 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-05-12 1:05 [RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task() Byungchul Park
2017-05-18 2:00 ` Byungchul Park
2017-05-18 8:12 ` Juri Lelli
2017-05-23 8:45 ` [tip:sched/core] " tip-bot for Byungchul Park
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).