2013-03-14 09:48:58

by Peter Zijlstra

Subject: [PATCH] sched,trace: Allow tracing the preemption decision on wakeup

Thomas noted that we do the wakeup preemption check after the wakeup
trace point, this means the tracepoint cannot test/report this decision;
which is rather important for latency sensitive workloads. Therefore
move the tracepoint after doing the preemption check.

Suggested-by: Thomas Gleixner <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
---
kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b36635e..849deb9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1288,8 +1288,8 @@ static void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
static void
ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
{
- trace_sched_wakeup(p, true);
check_preempt_curr(rq, p, wake_flags);
+ trace_sched_wakeup(p, true);

p->state = TASK_RUNNING;
#ifdef CONFIG_SMP

2013-03-14 12:00:48

by Steven Rostedt

Subject: Re: [PATCH] sched,trace: Allow tracing the preemption decision on wakeup

On Thu, 2013-03-14 at 10:48 +0100, Peter Zijlstra wrote:
> Thomas noted that we do the wakeup preemption check after the wakeup
> trace point, this means the tracepoint cannot test/report this decision;
> which is rather important for latency sensitive workloads. Therefore
> move the tracepoint after doing the preemption check.
>
> Suggested-by: Thomas Gleixner <[email protected]>
> Signed-off-by: Peter Zijlstra <[email protected]>

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

> ---
> kernel/sched/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index b36635e..849deb9 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1288,8 +1288,8 @@ static void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
> static void
> ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
> {
> - trace_sched_wakeup(p, true);
> check_preempt_curr(rq, p, wake_flags);
> + trace_sched_wakeup(p, true);
>
> p->state = TASK_RUNNING;
> #ifdef CONFIG_SMP
>

2013-03-14 15:43:23

by Paul Turner

Subject: Re: [PATCH] sched,trace: Allow tracing the preemption decision on wakeup

Yeah -- this one is a real no brainer to move; looks good :)

On Thu, Mar 14, 2013 at 5:00 AM, Steven Rostedt <[email protected]> wrote:
> On Thu, 2013-03-14 at 10:48 +0100, Peter Zijlstra wrote:
>> Thomas noted that we do the wakeup preemption check after the wakeup
>> trace point, this means the tracepoint cannot test/report this decision;
>> which is rather important for latency sensitive workloads. Therefore
>> move the tracepoint after doing the preemption check.
>>
>> Suggested-by: Thomas Gleixner <[email protected]>
>> Signed-off-by: Peter Zijlstra <[email protected]>
>
> Acked-by: Steven Rostedt <[email protected]>
>
>> ---
>> kernel/sched/core.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index b36635e..849deb9 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -1288,8 +1288,8 @@ static void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
>> static void
>> ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
>> {
>> - trace_sched_wakeup(p, true);
>> check_preempt_curr(rq, p, wake_flags);
>> + trace_sched_wakeup(p, true);
>>
>> p->state = TASK_RUNNING;
>> #ifdef CONFIG_SMP
>>
>
>

2013-03-18 11:10:48

by tip-bot for Vasyl Gomonovych

Subject: [tip:sched/core] sched/tracing: Allow tracing the preemption decision on wakeup

Commit-ID: a8d7ad52a7befbde896276d05c75c90fed48b5bf
Gitweb: http://git.kernel.org/tip/a8d7ad52a7befbde896276d05c75c90fed48b5bf
Author: Peter Zijlstra <[email protected]>
AuthorDate: Thu, 14 Mar 2013 10:48:39 +0100
Committer: Ingo Molnar <[email protected]>
CommitDate: Mon, 18 Mar 2013 10:18:08 +0100

sched/tracing: Allow tracing the preemption decision on wakeup

Thomas noted that we do the wakeup preemption check after the
wakeup trace point, this means the tracepoint cannot test/report
this decision; which is rather important for latency sensitive
workloads. Therefore move the tracepoint after doing the
preemption check.

Suggested-by: Thomas Gleixner <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Acked-by: Paul Turner <[email protected]>
Cc: Mike Galbraith <[email protected]>
Link: http://lkml.kernel.org/r/1363254519.26965.9.camel@laptop
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b36635e..849deb9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1288,8 +1288,8 @@ static void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
static void
ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
{
- trace_sched_wakeup(p, true);
check_preempt_curr(rq, p, wake_flags);
+ trace_sched_wakeup(p, true);

p->state = TASK_RUNNING;
#ifdef CONFIG_SMP