Commit b0f00855 authored by Yang Jihong's avatar Yang Jihong Committed by Arnaldo Carvalho de Melo
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perf sched: Fix record failure when CONFIG_SCHEDSTATS is not set 



The tracepoints trace_sched_stat_{wait, sleep, iowait} are not exposed to user
if CONFIG_SCHEDSTATS is not set, "perf sched record" records the three events.
As a result, the command fails.

Before:

  #perf sched record sleep 1
  event syntax error: 'sched:sched_stat_wait'
                       \___ unknown tracepoint

  Error:  File /sys/kernel/tracing/events/sched/sched_stat_wait not found.
  Hint:   Perhaps this kernel misses some CONFIG_ setting to enable this feature?.

  Run 'perf list' for a list of valid events

   Usage: perf record [<options>] [<command>]
      or: perf record [<options>] -- <command> [<options>]

      -e, --event <event>   event selector. use 'perf list' to list available events

Solution:
  Check whether schedstat tracepoints are exposed. If no, these events are not recorded.

After:
  # perf sched record sleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.163 MB perf.data (1091 samples) ]
  # perf sched report
  run measurement overhead: 4736 nsecs
  sleep measurement overhead: 9059979 nsecs
  the run test took 999854 nsecs
  the sleep test took 8945271 nsecs
  nr_run_events:        716
  nr_sleep_events:      785
  nr_wakeup_events:     0
  ...
  ------------------------------------------------------------

Fixes: 2a09b5de ("sched/fair: do not expose some tracepoints to user if CONFIG_SCHEDSTATS is not set")
Signed-off-by: default avatarYang Jihong <yangjihong1@huawei.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Yafang Shao <laoar.shao@gmail.com>
Link: http://lore.kernel.org/lkml/20210713112358.194693-1-yangjihong1@huawei.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 22a66551

tools/perf/builtin-sched.c

+29 −4
Original line number Diff line number Diff line
@@ -3335,6 +3335,16 @@ static void setup_sorting(struct perf_sched *sched, const struct option *options 
	sort_dimension__add("pid", &sched->cmp_pid);

}



static bool schedstat_events_exposed(void)

{

	/*

	 * Select "sched:sched_stat_wait" event to check

	 * whether schedstat tracepoints are exposed.

	 */

	return IS_ERR(trace_event__tp_format("sched", "sched_stat_wait")) ?

		false : true;

}



static int __cmd_record(int argc, const char **argv)

{

	unsigned int rec_argc, i, j;
@@ -3346,21 +3356,33 @@ static int __cmd_record(int argc, const char **argv) 
		"-m", "1024",

		"-c", "1",

		"-e", "sched:sched_switch",

		"-e", "sched:sched_stat_wait",

		"-e", "sched:sched_stat_sleep",

		"-e", "sched:sched_stat_iowait",

		"-e", "sched:sched_stat_runtime",

		"-e", "sched:sched_process_fork",

		"-e", "sched:sched_wakeup_new",

		"-e", "sched:sched_migrate_task",

	};



	/*

	 * The tracepoints trace_sched_stat_{wait, sleep, iowait}

	 * are not exposed to user if CONFIG_SCHEDSTATS is not set,

	 * to prevent "perf sched record" execution failure, determine

	 * whether to record schedstat events according to actual situation.

	 */

	const char * const schedstat_args[] = {

		"-e", "sched:sched_stat_wait",

		"-e", "sched:sched_stat_sleep",

		"-e", "sched:sched_stat_iowait",

	};

	unsigned int schedstat_argc = schedstat_events_exposed() ?

		ARRAY_SIZE(schedstat_args) : 0;



	struct tep_event *waking_event;



	/*

	 * +2 for either "-e", "sched:sched_wakeup" or

	 * "-e", "sched:sched_waking"

	 */

	rec_argc = ARRAY_SIZE(record_args) + 2 + argc - 1;

	rec_argc = ARRAY_SIZE(record_args) + 2 + schedstat_argc + argc - 1;

	rec_argv = calloc(rec_argc + 1, sizeof(char *));



	if (rec_argv == NULL)
@@ -3376,6 +3398,9 @@ static int __cmd_record(int argc, const char **argv) 
	else

		rec_argv[i++] = strdup("sched:sched_wakeup");



	for (j = 0; j < schedstat_argc; j++)

		rec_argv[i++] = strdup(schedstat_args[j]);



	for (j = 1; j < (unsigned int)argc; j++, i++)

		rec_argv[i] = argv[j];