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    SubjectRe: [PATCH 11/16] sched: add latency tracing for -deadline tasks.
    On 04/11/2012 11:03 PM, Steven Rostedt wrote:
    > 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 ;-)
    >

    Ouch! Forgot to cut something! :-(

    >> + /*
    >> + * 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;

    Yes, way better.

    Thanks!

    - Juri

    >>
    >> 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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