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SubjectRe: [PATCH 11/16] sched: add latency tracing for -deadline tasks.
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On Fri, 2012-04-06 at 09:14 +0200, Juri Lelli wrote:
> From: Dario Faggioli <raistlin@linux.it>
>
> It is very likely that systems that wants/needs to use the new
> SCHED_DEADLINE policy also want to have the scheduling latency of
> the -deadline tasks under control.
>
> For this reason a new version of the scheduling wakeup latency,
> called "wakeup_dl", is introduced.
>
> As a consequence of applying this patch there will be three wakeup
> latency tracer:
> * "wakeup", that deals with all tasks in the system;
> * "wakeup_rt", that deals with -rt and -deadline tasks only;
> * "wakeup_dl", that deals with -deadline tasks only.
>
> Signed-off-by: Dario Faggioli <raistlin@linux.it>
> Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
> ---
> kernel/trace/trace_sched_wakeup.c | 41 ++++++++++++++++++++++++++++++++++++-
> kernel/trace/trace_selftest.c | 30 ++++++++++++++++----------
> 2 files changed, 58 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
> index e4a70c0..9c9b1be 100644
> --- a/kernel/trace/trace_sched_wakeup.c
> +++ b/kernel/trace/trace_sched_wakeup.c
> @@ -27,6 +27,7 @@ static int wakeup_cpu;
> static int wakeup_current_cpu;
> static unsigned wakeup_prio = -1;
> static int wakeup_rt;
> +static int wakeup_dl;
>
> static arch_spinlock_t wakeup_lock =
> (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
> @@ -420,6 +421,17 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
> if ((wakeup_rt && !rt_task(p)) ||
> p->prio >= wakeup_prio ||
> p->prio >= current->prio)

I don't think you meant to keep both if statements. Look above and
below ;-)

> + /*
> + * Semantic is like this:
> + * - wakeup tracer handles all tasks in the system, independently
> + * from their scheduling class;
> + * - wakeup_rt tracer handles tasks belonging to sched_dl and
> + * sched_rt class;
> + * - wakeup_dl handles tasks belonging to sched_dl class only.
> + */
> + if ((wakeup_dl && !dl_task(p)) ||
> + (wakeup_rt && !dl_task(p) && !rt_task(p)) ||
> + (p->prio >= wakeup_prio || p->prio >= current->prio))
> return;

Anyway, perhaps this should be broken up, as we don't want the double
test, that is, wakeup_rt and wakeup_dl are both checked. Perhaps do:

if (wakeup_dl && !dl_task(p))
return;
else if (wakeup_rt && !dl_task(p) && !rt_task(p))
return;

if (p->prio >= wakeup_prio || p->prio >= current->prio)
return;


-- Steve

>
> pc = preempt_count();
> @@ -431,7 +443,7 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
> arch_spin_lock(&wakeup_lock);
>
> /* check for races. */
> - if (!tracer_enabled || p->prio >= wakeup_prio)
> + if (!tracer_enabled || (!dl_task(p) && p->prio >= wakeup_prio))
> goto out_locked;
>
> /* reset the trace */
> @@ -539,16 +551,25 @@ static int __wakeup_tracer_init(struct trace_array *tr)
>




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