* [RESEND PATCH v3] sched/rt: Remove unnecessary condition in push_rt_task()
@ 2017-05-12 1:05 Byungchul Park
2017-05-18 2:01 ` Byungchul Park
2017-05-23 8:44 ` [tip:sched/core] " tip-bot for Byungchul Park
0 siblings, 2 replies; 3+ messages in thread
From: Byungchul Park @ 2017-05-12 1:05 UTC (permalink / raw)
To: peterz; +Cc: linux-kernel, kernel-team
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. 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/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] 3+ messages in thread
* Re: [RESEND PATCH v3] sched/rt: Remove unnecessary condition in push_rt_task()
2017-05-12 1:05 [RESEND PATCH v3] sched/rt: Remove unnecessary condition in push_rt_task() Byungchul Park
@ 2017-05-18 2:01 ` Byungchul Park
2017-05-23 8:44 ` [tip:sched/core] " tip-bot for Byungchul Park
1 sibling, 0 replies; 3+ messages in thread
From: Byungchul Park @ 2017-05-18 2:01 UTC (permalink / raw)
To: peterz; +Cc: linux-kernel, kernel-team, rostedt, juri.lelli, bristot
On Fri, May 12, 2017 at 10:05:43AM +0900, Byungchul Park wrote:
> 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. 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/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 [flat|nested] 3+ messages in thread
* [tip:sched/core] sched/rt: Remove unnecessary condition in push_rt_task()
2017-05-12 1:05 [RESEND PATCH v3] sched/rt: Remove unnecessary condition in push_rt_task() Byungchul Park
2017-05-18 2:01 ` Byungchul Park
@ 2017-05-23 8:44 ` tip-bot for Byungchul Park
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot for Byungchul Park @ 2017-05-23 8:44 UTC (permalink / raw)
To: linux-tip-commits
Cc: hpa, linux-kernel, peterz, byungchul.park, mingo, bristot,
torvalds, kernel-team, tglx, rostedt, juri.lelli
Commit-ID: de16b91effdbf5aeff8346b99bcd0991a5362db9
Gitweb: http://git.kernel.org/tip/de16b91effdbf5aeff8346b99bcd0991a5362db9
Author: Byungchul Park <byungchul.park@lge.com>
AuthorDate: Fri, 12 May 2017 10:05:43 +0900
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 23 May 2017 10:01:33 +0200
sched/rt: Remove unnecessary condition in push_rt_task()
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. 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/1494551143-22219-1-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
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 979b734..c18b500 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1819,7 +1819,7 @@ retry:
* 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
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2017-05-12 1:05 [RESEND PATCH v3] sched/rt: Remove unnecessary condition in push_rt_task() Byungchul Park
2017-05-18 2:01 ` Byungchul Park
2017-05-23 8:44 ` [tip:sched/core] " tip-bot for Byungchul Park
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