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

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Date:   Tue, 13 Dec 2016 19:49:44 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        David Ahern <dsahern@...il.com>,
        Andi Kleen <andi@...stfloor.org>,
        Minchan Kim <minchan@...nel.org>
Subject: Re: [PATCH 1/2] perf sched timehist: Fix --idle-hist when no
 callchains

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@...nel.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