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perf sched timehist: Improve error message when analyzing wrong file

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Arnaldo reported an unhelpful error message when running perf sched
timehist on a file that did not contain sched tracepoints:

    [root@jouet ~]# perf sched timehist
    No trace sample to read. Did you call 'perf record -R'?

    [root@jouet ~]# 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@f21-vbox:/tmp$ perf sched timehist
    No sched_switch events found. Have you run 'perf sched record'?

Signed-off-by: David Ahern <dsahern@gmail.com>
Reported-and-Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1480451988-43673-1-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
David Ahern 2016-11-29 13:39:48 -07:00 committed by Arnaldo Carvalho de Melo
parent 8ac1eb7bab
commit f45bf8d393
1 changed files with 5 additions and 1 deletions
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6
tools/perf/builtin-sched.c
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@ -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))