2013-10-04 19:25:42

by Shawn Bohrer

Subject: [PATCH] sched/rt: Remove redundant nr_cpus_allowed test

From: Shawn Bohrer <[email protected]>

In 76854c7e8f3f4172fef091e78d88b3b751463ac6 "sched: Use
rt.nr_cpus_allowed to recover select_task_rq() cycles" an optimization
was added to select_task_rq_rt() that immediately returns when
p->nr_cpus_allowed == 1 at the beginning of the function. This makes
the latter p->nr_cpus_allowed > 1 check redundant and can be removed.

Signed-off-by: Shawn Bohrer <[email protected]>
---
kernel/sched/rt.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 01970c8..ceebfba 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1213,8 +1213,7 @@ select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)
*/
if (curr && unlikely(rt_task(curr)) &&
(curr->nr_cpus_allowed < 2 ||
- curr->prio <= p->prio) &&
- (p->nr_cpus_allowed > 1)) {
+ curr->prio <= p->prio)) {
int target = find_lowest_rq(p);

if (target != -1)
--
1.8.1.4

2013-10-04 19:34:05

by Steven Rostedt

Subject: Re: [PATCH] sched/rt: Remove redundant nr_cpus_allowed test

On Fri, 4 Oct 2013 14:24:53 -0500
Shawn Bohrer <[email protected]> wrote:

> From: Shawn Bohrer <[email protected]>
>
> In 76854c7e8f3f4172fef091e78d88b3b751463ac6 "sched: Use
> rt.nr_cpus_allowed to recover select_task_rq() cycles" an optimization
> was added to select_task_rq_rt() that immediately returns when
> p->nr_cpus_allowed == 1 at the beginning of the function. This makes
> the latter p->nr_cpus_allowed > 1 check redundant and can be removed.
>
> Signed-off-by: Shawn Bohrer <[email protected]>

Reviewed-by: Steven Rostedt <[email protected]>

-- Steve

> ---
> kernel/sched/rt.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 01970c8..ceebfba 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1213,8 +1213,7 @@ select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)
> */
> if (curr && unlikely(rt_task(curr)) &&
> (curr->nr_cpus_allowed < 2 ||
> - curr->prio <= p->prio) &&
> - (p->nr_cpus_allowed > 1)) {
> + curr->prio <= p->prio)) {
> int target = find_lowest_rq(p);
>
> if (target != -1)

2013-10-06 14:05:27

by tip-bot for Vasyl Gomonovych

Subject: [tip:sched/core] sched/rt: Remove redundant nr_cpus_allowed test

Commit-ID: 6bfa687c19b7ab8adee03f0d43c197c2945dd869
Gitweb: http://git.kernel.org/tip/6bfa687c19b7ab8adee03f0d43c197c2945dd869
Author: Shawn Bohrer <[email protected]>
AuthorDate: Fri, 4 Oct 2013 14:24:53 -0500
Committer: Ingo Molnar <[email protected]>
CommitDate: Sun, 6 Oct 2013 11:28:40 +0200

sched/rt: Remove redundant nr_cpus_allowed test

In 76854c7e8f3f4172fef091e78d88b3b751463ac6 ("sched: Use
rt.nr_cpus_allowed to recover select_task_rq() cycles") an
optimization was added to select_task_rq_rt() that immediately
returns when p->nr_cpus_allowed == 1 at the beginning of the
function.

This makes the latter p->nr_cpus_allowed > 1 check redundant,
which can now be removed.

Signed-off-by: Shawn Bohrer <[email protected]>
Reviewed-by: Steven Rostedt <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: [email protected]
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/sched/rt.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 01970c8..ceebfba 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1213,8 +1213,7 @@ select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)
*/
if (curr && unlikely(rt_task(curr)) &&
(curr->nr_cpus_allowed < 2 ||
- curr->prio <= p->prio) &&
- (p->nr_cpus_allowed > 1)) {
+ curr->prio <= p->prio)) {
int target = find_lowest_rq(p);

if (target != -1)