Re: [PATCH 1/2] perf sched timehist: Fix --idle-hist when no callchains

Namhyung Kim
2016-12-13T10:51:03Z

Hi Arnaldo,

On Tue, Dec 13, 2016 at 07:32:02AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Dec 13, 2016 at 05:06:31PM +0900, Namhyung Kim escreveu:
> > When idle hist is enabled, the itr->last_thread should be set so that
> > it can find which thread run before idle task. But it was only set in
> > the save_idle_callchain(). This makes idle task doesn't show up in
> > the output when callchain is not recorded.
>
> It is important to provide a Fixes: tag so that I can check if the
> problem was introduced by some patch still not sent to Ingo, in which
> case I could try and merge them, is this the case here?

Yes,

Fixes: b50c3ab0f1cc ("perf sched timehist: Save callchain when entering idle")

Thanks,
Namhyung

>
> > Before:
> >
> > $ perf sched timehist --idle-hist
> > Samples do not have callchains.
> > time cpu task name wait time sch delay run time
> > [tid/pid] (msec) (msec) (msec)
> > --------------- ------ -------------------- --------- --------- ---------
> > 197731.753834 [0001] perf[27469] 0.000 0.000 0.000
> > 197731.753915 [0003] migration/3[23] 0.000 0.000 0.000
> > 197731.754335 [0002] firefox[17773/17739] 0.000 0.000 0.000
> > 197731.754486 [0001] sleep[27470] 0.000 0.000 0.000
> > 197731.754981 [0002] firefox[17773/17739] 0.000 0.000 0.000
> > 197731.755994 [0002] firefox[17773/17739] 0.000 0.000 0.000
> > ...
> >
> > After:
> >
> > 197731.753834 [0001] perf[27469] 0.000 0.000 0.000
> > 197731.753914 [0001] <idle> 0.000 0.000 0.079
> > 197731.753915 [0003] migration/3[23] 0.000 0.000 0.000
> > 197731.754335 [0002] firefox[17773/17739] 0.000 0.000 0.000
> > 197731.754486 [0001] sleep[27470] 0.000 0.000 0.000
> > 197731.754903 [0002] <idle> 0.047 0.000 0.567
> > 197731.754981 [0002] firefox[17773/17739] 0.000 0.000 0.567
> > 197731.755922 [0002] <idle> 0.078 0.000 0.941
> > 197731.755994 [0002] firefox[17773/17739] 0.000 0.000 0.941
> > 197731.756625 [0003] <idle> 0.123 0.000 2.709
> > ...
> >
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> > tools/perf/builtin-sched.c | 33 +++++++++++++++++----------------
> > 1 file changed, 17 insertions(+), 16 deletions(-)
> >
> > diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> > index 0750e938a656..405a91d0515f 100644
> > --- a/tools/perf/builtin-sched.c
> > +++ b/tools/perf/builtin-sched.c
> > @@ -2102,26 +2102,12 @@ static struct thread *get_idle_thread(int cpu)
> > return idle_threads[cpu];
> > }
> >
> > -static void save_idle_callchain(struct thread *thread,
> > +static void save_idle_callchain(struct idle_thread_runtime *itr,
> > struct perf_sample *sample)
> > {
> > - struct thread *idle;
> > - struct idle_thread_runtime *itr;
> > -
> > if (!symbol_conf.use_callchain || sample->callchain == NULL)
> > return;
> >
> > - idle = get_idle_thread(sample->cpu);
> > - if (idle == NULL) {
> > - pr_err("Failed to get idle thread for cpu %d.\n", sample->cpu);
> > - return;
> > - }
> > -
> > - itr = thread__priv(idle);
> > - if (itr == NULL)
> > - return;
> > -
> > - itr->last_thread = thread;
> > callchain_cursor__copy(&itr->cursor, &callchain_cursor);
> > }
> >
> > @@ -2179,9 +2165,24 @@ static struct thread *timehist_get_thread(struct perf_sched *sched,
> >
> > save_task_callchain(sched, sample, evsel, machine);
> > if (sched->idle_hist) {
> > + struct thread *idle;
> > + struct idle_thread_runtime *itr;
> > +
> > + idle = get_idle_thread(sample->cpu);
> > + if (idle == NULL) {
> > + pr_err("Failed to get idle thread for cpu %d.\n", sample->cpu);
> > + return NULL;
> > + }
> > +
> > + itr = thread__priv(idle);
> > + if (itr == NULL)
> > + return NULL;
> > +
> > + itr->last_thread = thread;
> > +
> > /* copy task callchain when entering to idle */
> > if (perf_evsel__intval(evsel, sample, "next_pid") == 0)
> > - save_idle_callchain(thread, sample);
> > + save_idle_callchain(itr, sample);
> > }
> > }
> >
> > --
> > 2.10.2