[PATCH 11/17] perf evswitch: Add hint when not finding specified on/off events

Arnaldo Carvalho de Melo
2019-08-16T20:17:59Z

If the user specifies a on or off switch event and it isn't in the
perf.data file, provide a hint about how to see the events in the
perf.data evlist:

# perf script --switch-on=syscall:sys_enter_nanosleep --switch-off=syscalls:sys_exit_nanosleep
ERROR: event_on event not found (syscall:sys_enter_nanosleep)
HINT: use 'perf evlist' to see the available event names
#
# perf evlist
sched:sched_kthread_stop
sched:sched_kthread_stop_ret
sched:sched_waking
sched:sched_wakeup
sched:sched_wakeup_new
sched:sched_switch
sched:sched_migrate_task
sched:sched_process_free
sched:sched_process_exit
sched:sched_wait_task
sched:sched_process_wait
sched:sched_process_fork
sched:sched_process_exec
sched:sched_stat_wait
sched:sched_stat_sleep
sched:sched_stat_iowait
sched:sched_stat_blocked
sched:sched_stat_runtime
sched:sched_pi_setprio
sched:sched_move_numa
sched:sched_stick_numa
sched:sched_swap_numa
sched:sched_wake_idle_without_ipi
syscalls:sys_enter_clock_nanosleep
syscalls:sys_exit_clock_nanosleep
syscalls:sys_enter_nanosleep
syscalls:sys_exit_nanosleep
# Tip: use 'perf evlist --trace-fields' to show fields for tracepoint events
#
# perf script --switch-on=syscalls:sys_enter_nanosleep --switch-off=syscalls:sys_exit_nanosleep
sleep 20919 [001] 109866.144411: sched:sched_stat_runtime: comm=sleep pid=20919 runtime=521249 [ns] vruntime=202919398131 [ns]
sleep 20919 [001] 109866.144412: sched:sched_switch: sleep:20919 [120] S ==> swapper/1:0 [120]
swapper 0 [001] 109867.144568: sched:sched_waking: comm=sleep pid=20919 prio=120 target_cpu=001
swapper 0 [001] 109867.144586: sched:sched_wakeup: sleep:20919 [120] success=1 CPU:001
#

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: William Cohen <wcohen@redhat.com>
Link: https://lkml.kernel.org/n/tip-iijjvdlyad973oskdq8gmi5w@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/evswitch.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/evswitch.c b/tools/perf/util/evswitch.c
index 71daed615a2c..3ba72f743d3c 100644
--- a/tools/perf/util/evswitch.c
+++ b/tools/perf/util/evswitch.c
@@ -33,7 +33,9 @@ bool evswitch__discard(struct evswitch *evswitch, struct evsel *evsel)

static int evswitch__fprintf_enoent(FILE *fp, const char *evtype, const char *evname)
{
- return fprintf(fp, "ERROR: switch-%s event not found (%s)\n", evtype, evname);
+ int printed = fprintf(fp, "ERROR: switch-%s event not found (%s)\n", evtype, evname);
+
+ return printed += fprintf(fp, "HINT: use 'perf evlist' to see the available event names\n");
}

int evswitch__init(struct evswitch *evswitch, struct evlist *evlist, FILE *fp)
--
2.21.0