[PATCH]sched/rt: Simplify pick_rt_task: remove next_prio() inheritance

[PATCH]sched/rt: Simplify pick_rt_task: remove next_prio() inheritance

[Kirill Tkhai]

Function next_prio() has been removed and pull_rt_task() is the only
user of pick_next_highest_task_rt() at the moment.

pull_rt_task is not interested in p->nr_cpus_allowed, its only interest
is the fact that cpu is allowed to execute p. If nr_cpus_allowed == 1,
cpu != task_cpu(p) and cpu is allowed then it means that task p is in
the middle of the migration techniques; the task waits until it is moved
by migration thread. So, lets pull it earlier.

Signed-off-by: Kirill V Tkhai <tkhai@yandex.ru>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: Ingo Molnar <mingo@kernel.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: linux-rt-users <linux-rt-users@vger.kernel.org>
---
 kernel/sched/rt.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 4e8f0f4..9aa2921 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1427,8 +1427,7 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
 {
 	if (!task_running(rq, p) &&
-	    (cpu < 0 || cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) &&
-	    (p->nr_cpus_allowed > 1))
+	    cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
 		return 1;
 	return 0;
 }

Re: [PATCH]sched/rt: Simplify pick_rt_task: remove next_prio() inheritance

[Steven Rostedt]

On Thu, 2013-01-31 at 18:56 +0400, Kirill Tkhai wrote:
> Function next_prio() has been removed and pull_rt_task() is the only
> user of pick_next_highest_task_rt() at the moment.
> 
> pull_rt_task is not interested in p->nr_cpus_allowed, its only interest
> is the fact that cpu is allowed to execute p. If nr_cpus_allowed == 1,
> cpu != task_cpu(p) and cpu is allowed then it means that task p is in
> the middle of the migration techniques; the task waits until it is moved
> by migration thread. So, lets pull it earlier.
> 
> Signed-off-by: Kirill V Tkhai <tkhai@yandex.ru>

Acked-by: Steven Rostedt <rostedt@goodmis.org>

-- Steve

> CC: Ingo Molnar <mingo@kernel.org>
> CC: Peter Zijlstra <peterz@infradead.org>
> CC: linux-rt-users <linux-rt-users@vger.kernel.org>
> ---
>  kernel/sched/rt.c |    3 +--
>  1 files changed, 1 insertions(+), 2 deletions(-)
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 4e8f0f4..9aa2921 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1427,8 +1427,7 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
>  static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
>  {
>  	if (!task_running(rq, p) &&
> -	    (cpu < 0 || cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) &&
> -	    (p->nr_cpus_allowed > 1))
> +	    cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
>  		return 1;
>  	return 0;
>  }

[tip:sched/core] sched/rt: Further simplify pick_rt_task()

[tip-bot for Kirill Tkhai]

Commit-ID:  60334caf37dc7c59120b21faa625534a6fffead0
Gitweb:     http://git.kernel.org/tip/60334caf37dc7c59120b21faa625534a6fffead0
Author:     Kirill Tkhai <tkhai@yandex.ru>
AuthorDate: Thu, 31 Jan 2013 18:56:17 +0400
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 3 Feb 2013 19:54:58 +0100

sched/rt: Further simplify pick_rt_task()

Function next_prio() has been removed and pull_rt_task() is the
only user of pick_next_highest_task_rt() at the moment.

pull_rt_task is not interested in p->nr_cpus_allowed, its only
interest is the fact that cpu is allowed to execute p. If
nr_cpus_allowed == 1, cpu != task_cpu(p) and cpu is allowed then
it means that task p is in the middle of the migration
techniques; the task waits until it is moved by migration
thread. So, lets pull it earlier.

Signed-off-by: Kirill V Tkhai <tkhai@yandex.ru>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
CC: linux-rt-users <linux-rt-users@vger.kernel.org>
Link: http://lkml.kernel.org/r/70871359644177@web16d.yandex.ru
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 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 94abca4..c25de14 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1427,8 +1427,7 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
 {
 	if (!task_running(rq, p) &&
-	    (cpu < 0 || cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) &&
-	    (p->nr_cpus_allowed > 1))
+	    cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
 		return 1;
 	return 0;
 }