* [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task()
@ 2017-02-15 5:11 Byungchul Park
2017-02-15 5:22 ` Byungchul Park
2017-02-15 10:47 ` Juri Lelli
0 siblings, 2 replies; 11+ messages in thread
From: Byungchul Park @ 2017-02-15 5:11 UTC (permalink / raw)
To: peterz, mingo; +Cc: linux-kernel, juri.lelli, kernel-team
Once pick_next_pushable_dl_task(rq) return 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 a redundant condition and make code simpler.
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] 11+ messages in thread
* Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-02-15 5:11 [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task() Byungchul Park
@ 2017-02-15 5:22 ` Byungchul Park
2017-02-15 10:47 ` Juri Lelli
1 sibling, 0 replies; 11+ messages in thread
From: Byungchul Park @ 2017-02-15 5:22 UTC (permalink / raw)
To: peterz, mingo; +Cc: linux-kernel, juri.lelli, kernel-team
On Wed, Feb 15, 2017 at 02:11:51PM +0900, Byungchul Park wrote:
> Once pick_next_pushable_dl_task(rq) return 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 a redundant condition and make code simpler.
Furthermore, unnecessary one branch and unnecessary 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 [flat|nested] 11+ messages in thread
* Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-02-15 5:11 [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task() Byungchul Park
2017-02-15 5:22 ` Byungchul Park
@ 2017-02-15 10:47 ` Juri Lelli
2017-02-15 11:37 ` Peter Zijlstra
2017-02-15 14:25 ` Steven Rostedt
1 sibling, 2 replies; 11+ messages in thread
From: Juri Lelli @ 2017-02-15 10:47 UTC (permalink / raw)
To: Byungchul Park
Cc: peterz, mingo, linux-kernel, juri.lelli, kernel-team,
Steven Rostedt, Luca Abeni
[+Steve, Luca]
Hi,
On 15/02/17 14:11, Byungchul Park wrote:
> Once pick_next_pushable_dl_task(rq) return 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 a redundant condition and make code simpler.
>
> 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) {
Seems a sensible optimization to me. Actually, we are doing the same for
rt.c; Steve, Peter, do you think we should optimize that as well?
Thanks,
- Juri
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-02-15 10:47 ` Juri Lelli
@ 2017-02-15 11:37 ` Peter Zijlstra
2017-02-15 14:25 ` Steven Rostedt
1 sibling, 0 replies; 11+ messages in thread
From: Peter Zijlstra @ 2017-02-15 11:37 UTC (permalink / raw)
To: Juri Lelli
Cc: Byungchul Park, mingo, linux-kernel, juri.lelli, kernel-team,
Steven Rostedt, Luca Abeni
On Wed, Feb 15, 2017 at 10:47:49AM +0000, Juri Lelli wrote:
> [+Steve, Luca]
>
> Hi,
>
> On 15/02/17 14:11, Byungchul Park wrote:
> > Once pick_next_pushable_dl_task(rq) return 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 a redundant condition and make code simpler.
> >
> > 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) {
>
> Seems a sensible optimization to me. Actually, we are doing the same for
> rt.c; Steve, Peter, do you think we should optimize that as well?
>
If correct (and I've not spend brain cycles on that) yes. We should keep
this push-pull muck synced between rt and deadline as much as possible.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-02-15 10:47 ` Juri Lelli
2017-02-15 11:37 ` Peter Zijlstra
@ 2017-02-15 14:25 ` Steven Rostedt
2017-02-15 14:45 ` Juri Lelli
1 sibling, 1 reply; 11+ messages in thread
From: Steven Rostedt @ 2017-02-15 14:25 UTC (permalink / raw)
To: Juri Lelli
Cc: Byungchul Park, peterz, mingo, linux-kernel, juri.lelli,
kernel-team, Luca Abeni
On Wed, 15 Feb 2017 10:47:49 +0000
Juri Lelli <juri.lelli@arm.com> wrote:
> [+Steve, Luca]
>
> Hi,
>
> On 15/02/17 14:11, Byungchul Park wrote:
> > Once pick_next_pushable_dl_task(rq) return 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 a redundant condition and make code simpler.
> >
> > 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) {
>
> Seems a sensible optimization to me. Actually, we are doing the same for
> rt.c; Steve, Peter, do you think we should optimize that as well?
>
Are we doing the same for push_rt_task()? I don't see it, and I don't
see it in tip/sched/core either. What I have is:
if (task_cpu(next_task) == rq->cpu && task == next_task) {
But that said, I believe this patch is correct, and we should change
rt.c as well.
task = pick_next_pushable_dl_task(rq);
Which 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. Then if task == next_task, then task_cpu(next_task)
must be rq->cpu as well.
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Mind fixing rt.c if it hasn't been fixed already.
-- Steve
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-02-15 14:25 ` Steven Rostedt
@ 2017-02-15 14:45 ` Juri Lelli
2017-02-15 14:55 ` Steven Rostedt
2017-02-16 2:17 ` Byungchul Park
0 siblings, 2 replies; 11+ messages in thread
From: Juri Lelli @ 2017-02-15 14:45 UTC (permalink / raw)
To: Steven Rostedt
Cc: Byungchul Park, peterz, mingo, linux-kernel, juri.lelli,
kernel-team, Luca Abeni
On 15/02/17 09:25, Steven Rostedt wrote:
> On Wed, 15 Feb 2017 10:47:49 +0000
> Juri Lelli <juri.lelli@arm.com> wrote:
>
> > [+Steve, Luca]
> >
> > Hi,
> >
> > On 15/02/17 14:11, Byungchul Park wrote:
> > > Once pick_next_pushable_dl_task(rq) return 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 a redundant condition and make code simpler.
> > >
> > > 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) {
> >
> > Seems a sensible optimization to me. Actually, we are doing the same for
> > rt.c; Steve, Peter, do you think we should optimize that as well?
> >
>
> Are we doing the same for push_rt_task()? I don't see it, and I don't
> see it in tip/sched/core either. What I have is:
>
> if (task_cpu(next_task) == rq->cpu && task == next_task) {
Sorry, bad wording on my side. I meant the are currently checking the
same conditions both for DL and for RT, and we should probably optimize
RT as well if we are going to take this patch.
>
> But that said, I believe this patch is correct, and we should change
> rt.c as well.
>
That's what I meant. :)
>
> task = pick_next_pushable_dl_task(rq);
>
> Which 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. Then if task == next_task, then task_cpu(next_task)
> must be rq->cpu as well.
Right.
>
> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
>
You can also add mine
Reviewed-by: Juri Lelli <juri.lelli@arm.com>
> Mind fixing rt.c if it hasn't been fixed already.
>
> -- Steve
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-02-15 14:45 ` Juri Lelli
@ 2017-02-15 14:55 ` Steven Rostedt
2017-02-16 2:17 ` Byungchul Park
1 sibling, 0 replies; 11+ messages in thread
From: Steven Rostedt @ 2017-02-15 14:55 UTC (permalink / raw)
To: Juri Lelli
Cc: Byungchul Park, peterz, mingo, linux-kernel, juri.lelli,
kernel-team, Luca Abeni
On Wed, 15 Feb 2017 14:45:03 +0000
Juri Lelli <juri.lelli@arm.com> wrote:
> >
> > task = pick_next_pushable_dl_task(rq);
> >
> > Which 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. Then if task == next_task, then task_cpu(next_task)
> > must be rq->cpu as well.
>
> Right.
Perhaps my comment should also be added in the change log.
-- Steve
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-02-15 14:45 ` Juri Lelli
2017-02-15 14:55 ` Steven Rostedt
@ 2017-02-16 2:17 ` Byungchul Park
2017-02-16 2:31 ` Steven Rostedt
1 sibling, 1 reply; 11+ messages in thread
From: Byungchul Park @ 2017-02-16 2:17 UTC (permalink / raw)
To: Juri Lelli
Cc: Steven Rostedt, peterz, mingo, linux-kernel, juri.lelli,
kernel-team, Luca Abeni
On Wed, Feb 15, 2017 at 02:45:03PM +0000, Juri Lelli wrote:
> On 15/02/17 09:25, Steven Rostedt wrote:
> > On Wed, 15 Feb 2017 10:47:49 +0000
> > Juri Lelli <juri.lelli@arm.com> wrote:
> >
> > > [+Steve, Luca]
> > >
> > > Hi,
> > >
> > > On 15/02/17 14:11, Byungchul Park wrote:
> > > > Once pick_next_pushable_dl_task(rq) return 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 a redundant condition and make code simpler.
> > > >
> > > > 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) {
> > >
> > > Seems a sensible optimization to me. Actually, we are doing the same for
> > > rt.c; Steve, Peter, do you think we should optimize that as well?
> > >
> >
> > Are we doing the same for push_rt_task()? I don't see it, and I don't
> > see it in tip/sched/core either. What I have is:
> >
> > if (task_cpu(next_task) == rq->cpu && task == next_task) {
>
> Sorry, bad wording on my side. I meant the are currently checking the
> same conditions both for DL and for RT, and we should probably optimize
> RT as well if we are going to take this patch.
>
> >
> > But that said, I believe this patch is correct, and we should change
> > rt.c as well.
> >
>
> That's what I meant. :)
>
> >
> > task = pick_next_pushable_dl_task(rq);
> >
> > Which 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. Then if task == next_task, then task_cpu(next_task)
> > must be rq->cpu as well.
>
> Right.
>
> >
> > Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> >
>
> You can also add mine
>
> Reviewed-by: Juri Lelli <juri.lelli@arm.com>
Juri and steven, thank you very much for reviewing it.
I'm not sure and familiar with... Should I add your 'reviewed by' into
my patches by myself?
>
> > Mind fixing rt.c if it hasn't been fixed already.
> >
> > -- Steve
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-02-16 2:17 ` Byungchul Park
@ 2017-02-16 2:31 ` Steven Rostedt
2017-02-16 2:33 ` Steven Rostedt
0 siblings, 1 reply; 11+ messages in thread
From: Steven Rostedt @ 2017-02-16 2:31 UTC (permalink / raw)
To: Byungchul Park
Cc: Juri Lelli, peterz, mingo, linux-kernel, juri.lelli, kernel-team,
Luca Abeni
On Thu, 16 Feb 2017 11:17:58 +0900
Byungchul Park <byungchul.park@lge.com> wrote:
> Juri and steven, thank you very much for reviewing it.
>
> I'm not sure and familiar with... Should I add your 'reviewed by' into
> my patches by myself?
>
No, it's the maintainer's job to add these tags when they take your
patch. If you were to resend the patch because of a minor change
(something a reviewer told you to make but still gave you their
reviewed-by tag), then you could add it. Or if you have a patch series
and resend a new series, you can add the reviewed-by tags to the
patches that were not changed. But if you were to change a patch, then
you need to ask the reviewer to give their tag again, because they need
to review the changes made before their tag should go on it.
Make sense?
-- Steve
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-02-16 2:31 ` Steven Rostedt
@ 2017-02-16 2:33 ` Steven Rostedt
2017-02-16 2:41 ` Byungchul Park
0 siblings, 1 reply; 11+ messages in thread
From: Steven Rostedt @ 2017-02-16 2:33 UTC (permalink / raw)
To: Byungchul Park
Cc: Juri Lelli, peterz, mingo, linux-kernel, juri.lelli, kernel-team,
Luca Abeni
On Wed, 15 Feb 2017 21:31:50 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> On Thu, 16 Feb 2017 11:17:58 +0900
> Byungchul Park <byungchul.park@lge.com> wrote:
>
>
> > Juri and steven, thank you very much for reviewing it.
> >
> > I'm not sure and familiar with... Should I add your 'reviewed by' into
> > my patches by myself?
> >
>
> No, it's the maintainer's job to add these tags when they take your
> patch. If you were to resend the patch because of a minor change
> (something a reviewer told you to make but still gave you their
> reviewed-by tag), then you could add it. Or if you have a patch series
> and resend a new series, you can add the reviewed-by tags to the
> patches that were not changed. But if you were to change a patch, then
> you need to ask the reviewer to give their tag again, because they need
> to review the changes made before their tag should go on it.
>
I just noticed that you sent a v2 of the patch we reviewed. Since you
didn't change it, you could have added our review-by tags. That makes
it a bit easier for maintainers to know.
-- Steve
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task()
2017-02-16 2:33 ` Steven Rostedt
@ 2017-02-16 2:41 ` Byungchul Park
0 siblings, 0 replies; 11+ messages in thread
From: Byungchul Park @ 2017-02-16 2:41 UTC (permalink / raw)
To: Steven Rostedt
Cc: Juri Lelli, peterz, mingo, linux-kernel, juri.lelli, kernel-team,
Luca Abeni
On Wed, Feb 15, 2017 at 09:33:35PM -0500, Steven Rostedt wrote:
> On Wed, 15 Feb 2017 21:31:50 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > On Thu, 16 Feb 2017 11:17:58 +0900
> > Byungchul Park <byungchul.park@lge.com> wrote:
> >
> >
> > > Juri and steven, thank you very much for reviewing it.
> > >
> > > I'm not sure and familiar with... Should I add your 'reviewed by' into
> > > my patches by myself?
> > >
> >
> > No, it's the maintainer's job to add these tags when they take your
> > patch. If you were to resend the patch because of a minor change
> > (something a reviewer told you to make but still gave you their
> > reviewed-by tag), then you could add it. Or if you have a patch series
> > and resend a new series, you can add the reviewed-by tags to the
> > patches that were not changed. But if you were to change a patch, then
> > you need to ask the reviewer to give their tag again, because they need
> > to review the changes made before their tag should go on it.
> >
>
> I just noticed that you sent a v2 of the patch we reviewed. Since you
> didn't change it, you could have added our review-by tags. That makes
> it a bit easier for maintainers to know.
I got it! Thank you very much for your kind explanation.
>
> -- Steve
^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2017-02-16 2:41 UTC | newest]
Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-02-15 5:11 [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task() Byungchul Park
2017-02-15 5:22 ` Byungchul Park
2017-02-15 10:47 ` Juri Lelli
2017-02-15 11:37 ` Peter Zijlstra
2017-02-15 14:25 ` Steven Rostedt
2017-02-15 14:45 ` Juri Lelli
2017-02-15 14:55 ` Steven Rostedt
2017-02-16 2:17 ` Byungchul Park
2017-02-16 2:31 ` Steven Rostedt
2017-02-16 2:33 ` Steven Rostedt
2017-02-16 2:41 ` Byungchul Park
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