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

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Date:   Tue, 13 Dec 2016 07:32:02 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...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

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?

- Arnaldo 

> 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