[PATCH 02/17] perf script: Allow specifying event to switch on processing of other events

Arnaldo Carvalho de Melo
2019-08-16T20:17:29Z

Sometime we want to only consider events after something happens, so
allow discarding events till such events is found, e.g.:

Record all scheduler tracepoints and the sys_enter_nanosleep syscall
event for the 'sleep 1' workload:

# perf record -e sched:*,syscalls:sys_enter_nanosleep sleep 1
[ perf record: Woken up 31 times to write data ]
[ perf record: Captured and wrote 0.032 MB perf.data (10 samples) ]
#

So we have these events in the generated perf data file:

# 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_nanosleep
# Tip: use 'perf evlist --trace-fields' to show fields for tracepoint events
#

Then show all of the events that actually took place in this 'perf record' session:

# perf script
:13637 13637 [002] 108237.581529: sched:sched_waking: comm=perf pid=13638 prio=120 target_cpu=001
:13637 13637 [002] 108237.581537: sched:sched_wakeup: perf:13638 [120] success=1 CPU:001
sleep 13638 [001] 108237.581992: sched:sched_process_exec: filename=/usr/bin/sleep pid=13638 old_pid=13638
sleep 13638 [001] 108237.582286: syscalls:sys_enter_nanosleep: rqtp: 0x7fff1948ac40, rmtp: 0x00000000
sleep 13638 [001] 108237.582289: sched:sched_stat_runtime: comm=sleep pid=13638 runtime=578104 [ns] vruntime=202889459556 [ns]
sleep 13638 [001] 108237.582291: sched:sched_switch: sleep:13638 [120] S ==> swapper/1:0 [120]
swapper 0 [001] 108238.582428: sched:sched_waking: comm=sleep pid=13638 prio=120 target_cpu=001
swapper 0 [001] 108238.582458: sched:sched_wakeup: sleep:13638 [120] success=1 CPU:001
sleep 13638 [001] 108238.582698: sched:sched_stat_runtime: comm=sleep pid=13638 runtime=173915 [ns] vruntime=202889633471 [ns]
sleep 13638 [001] 108238.582782: sched:sched_process_exit: comm=sleep pid=13638 prio=120
#

Now lets see only the ones that took place after a certain "marker":

# perf script --switch-on syscalls:sys_enter_nanosleep
sleep 13638 [001] 108237.582289: sched:sched_stat_runtime: comm=sleep pid=13638 runtime=578104 [ns] vruntime=202889459556 [ns]
sleep 13638 [001] 108237.582291: sched:sched_switch: sleep:13638 [120] S ==> swapper/1:0 [120]
swapper 0 [001] 108238.582428: sched:sched_waking: comm=sleep pid=13638 prio=120 target_cpu=001
swapper 0 [001] 108238.582458: sched:sched_wakeup: sleep:13638 [120] success=1 CPU:001
sleep 13638 [001] 108238.582698: sched:sched_stat_runtime: comm=sleep pid=13638 runtime=173915 [ns] vruntime=202889633471 [ns]
sleep 13638 [001] 108238.582782: sched:sched_process_exit: comm=sleep pid=13638 prio=120
#

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-f1oo0ufdhrkx6nhy2lj1ierm@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/Documentation/perf-script.txt | 3 +++
tools/perf/builtin-script.c | 26 ++++++++++++++++++++++++
2 files changed, 29 insertions(+)

diff --git a/tools/perf/Documentation/perf-script.txt b/tools/perf/Documentation/perf-script.txt
index caaab28f8400..9936819aae1c 100644
--- a/tools/perf/Documentation/perf-script.txt
+++ b/tools/perf/Documentation/perf-script.txt
@@ -417,6 +417,9 @@ include::itrace.txt[]
For itrace only show specified functions and their callees for
itrace. Multiple functions can be separated by comma.

+--switch-on EVENT_NAME::
+ Only consider events after this event is found.
+
SEE ALSO
--------
linkperf:perf-record[1], linkperf:perf-script-perl[1],
diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index 31a529ec139f..d0bc7ccaf7bf 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -1616,6 +1616,11 @@ static int perf_sample__fprintf_synth(struct perf_sample *sample,
return 0;
}

+struct evswitch {
+ struct evsel *on;
+ bool discarding;
+};
+
struct perf_script {
struct perf_tool tool;
struct perf_session *session;
@@ -1628,6 +1633,7 @@ struct perf_script {
bool show_bpf_events;
bool allocated;
bool per_event_dump;
+ struct evswitch evswitch;
struct perf_cpu_map *cpus;
struct perf_thread_map *threads;
int name_width;
@@ -1805,6 +1811,13 @@ static void process_event(struct perf_script *script,
if (!show_event(sample, evsel, thread, al))
return;

+ if (script->evswitch.on && script->evswitch.discarding) {
+ if (script->evswitch.on != evsel)
+ return;
+
+ script->evswitch.discarding = false;
+ }
+
++es->samples;

perf_sample__fprintf_start(sample, thread, evsel,
@@ -3395,6 +3408,7 @@ int cmd_script(int argc, const char **argv)
struct utsname uts;
char *script_path = NULL;
const char **__argv;
+ const char *event_switch_on = NULL;
int i, j, err = 0;
struct perf_script script = {
.tool = {
@@ -3538,6 +3552,8 @@ int cmd_script(int argc, const char **argv)
"file", "file saving guest os /proc/kallsyms"),
OPT_STRING(0, "guestmodules", &symbol_conf.default_guest_modules,
"file", "file saving guest os /proc/modules"),
+ OPT_STRING(0, "switch-on", &event_switch_on,
+ "event", "Consider events from the first ocurrence of this event"),
OPT_END()
};
const char * const script_subcommands[] = { "record", "report", NULL };
@@ -3862,6 +3878,16 @@ int cmd_script(int argc, const char **argv)
script.range_num);
}

+ if (event_switch_on) {
+ script.evswitch.on = perf_evlist__find_evsel_by_str(session->evlist, event_switch_on);
+ if (script.evswitch.on == NULL) {
+ fprintf(stderr, "switch-on event not found (%s)\n", event_switch_on);
+ err = -ENOENT;
+ goto out_delete;
+ }
+ script.evswitch.discarding = true;
+ }
+
err = __cmd_script(&script);

flush_scripting();
--
2.21.0