linux-kernel - Re: [PATCH v2] perf sched timehist: Improve error message when analyzing wrong file

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Date:   Wed, 30 Nov 2016 14:31:36 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     David Ahern <dsahern@...il.com>
Cc:     acme@...nel.org, mingo@...nel.org, peterz@...radead.org,
        jolsa@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] perf sched timehist: Improve error message when
 analyzing wrong file

On 11/30/16, David Ahern <dsahern@...il.com> wrote:
> Arnaldo reported an unhelpful error message when running perf sched
> timehist on a file that did not contain sched tracepoints:
>
>     [root@...et ~]# perf sched timehist
>     No trace sample to read. Did you call 'perf record -R'?
>
>     [root@...et ~]# perf evlist -v
>     cycles:ppp: size: 112, { sample_period, sample_freq }: 4000,
> sample_type: IP|TID|TIME|CALLCHAIN|CPU|PERIOD, disabled: 1, inherit: 1,
> mmap: 1, comm: 1, freq: 1, task: 1, precise_ip: 3, sample_id_all: 1,
> exclude_guest: 1, mmap2: 1, comm_exec: 1
>
> Change the has_traces check to look for the sched_switch event. Analysis
> for perf sched timehist requires at least this event.
>
> Now when analyzing a file without sched tracepoints you get:
>
>     root@...-vbox:/tmp$ perf sched timehist
>     No sched_switch events found. Have you run 'perf sched record'?
>
> Signed-off-by: David Ahern <dsahern@...il.com>

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung


> ---
>  tools/perf/builtin-sched.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index 870d94cd20ba..84c39f177bef 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -2629,8 +2629,12 @@ static int perf_sched__timehist(struct perf_sched
> *sched)
>  	if (perf_session__set_tracepoints_handlers(session, handlers))
>  		goto out;
>
> -	if (!perf_session__has_traces(session, "record -R"))
> +	/* sched_switch event at a minimum needs to exist */
> +	if (!perf_evlist__find_tracepoint_by_name(session->evlist,
> +						  "sched:sched_switch")) {
> +		pr_err("No sched_switch events found. Have you run 'perf sched
> record'?\n");
>  		goto out;
> +	}
>
>  	if (sched->show_migrations &&
>  	    perf_session__set_tracepoints_handlers(session, migrate_handlers))
> --
> 2.7.4 (Apple Git-66)
>
>


-- 
Thanks,
Namhyung Kim