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perf record: Introduce --switch-output-event
Now we can use it with --overwrite to have a flight recorder mode that
gets snapshot requests from arbitrary events that are processed in the
side band thread together with the PERF_RECORD_BPF_EVENT processing.
Example:
To collect scheduler events until a recvmmsg syscall happens, system
wide:
[root@five a]# rm -f perf.data.2020042717*
[root@five a]# perf record --overwrite -e sched:*switch,syscalls:*recvmmsg --switch-output-event syscalls:sys_enter_recvmmsg
[ perf record: dump data: Woken up 1 times ]
[ perf record: Dump perf.data.2020042717585458 ]
[ perf record: dump data: Woken up 1 times ]
[ perf record: Dump perf.data.2020042717590235 ]
[ perf record: dump data: Woken up 1 times ]
[ perf record: Dump perf.data.2020042717590398 ]
^C[ perf record: Woken up 1 times to write data ]
[ perf record: Dump perf.data.2020042717590511 ]
[ perf record: Captured and wrote 7.244 MB perf.data.<timestamp> ]
So in the above case we had 3 snapshots, the fourth was forced by
control+C:
[root@five a]# ls -la
total 20440
drwxr-xr-x. 2 root root 4096 Apr 27 17:59 .
dr-xr-x---. 12 root root 4096 Apr 27 17:46 ..
-rw-------. 1 root root 3936125 Apr 27 17:58 perf.data.2020042717585458
-rw-------. 1 root root 5074869 Apr 27 17:59 perf.data.2020042717590235
-rw-------. 1 root root 4291037 Apr 27 17:59 perf.data.2020042717590398
-rw-------. 1 root root 7617037 Apr 27 17:59 perf.data.2020042717590511
[root@five a]#
One can make this more precise by adding the switch output event to the
main -e events list, as since this is done asynchronously, a few events
after the signal event will appear in the snapshots, as can be seen
with:
[root@five a]# rm -f perf.data.20200427175*
[root@five a]# perf record --overwrite -e sched:*switch,syscalls:*recvmmsg --switch-output-event syscalls:sys_enter_recvmmsg
[ perf record: dump data: Woken up 1 times ]
[ perf record: Dump perf.data.2020042718024203 ]
[ perf record: dump data: Woken up 1 times ]
[ perf record: Dump perf.data.2020042718024301 ]
[ perf record: dump data: Woken up 1 times ]
[ perf record: Dump perf.data.2020042718024484 ]
^C[ perf record: Woken up 1 times to write data ]
[ perf record: Dump perf.data.2020042718024562 ]
[ perf record: Captured and wrote 7.337 MB perf.data.<timestamp> ]
[root@five a]# perf script -i perf.data.2020042718024203 | tail -15
PacerThread 148586 [005] 122.830729: sched:sched_switch: prev_comm=PacerThread prev_pid=148586...
swapper 0 [000] 122.833588: sched:sched_switch: prev_comm=swapper/0 prev_pid=...
NetworkManager 1251 [000] 122.833619: syscalls:sys_enter_recvmmsg: fd: 0x0000001c, mmsg: 0x7ffe83054a1...
swapper 0 [002] 122.833624: sched:sched_switch: prev_comm=swapper/2 prev_pid=...
swapper 0 [003] 122.833624: sched:sched_switch: prev_comm=swapper/3 prev_pid=...
NetworkManager 1251 [000] 122.833626: syscalls:sys_exit_recvmmsg: 0x1
kworker/3:3-eve 158946 [003] 122.833628: sched:sched_switch: prev_comm=kworker/3:3 prev_pid=15894...
swapper 0 [004] 122.833641: sched:sched_switch: prev_comm=swapper/4 prev_pid=...
NetworkManager 1251 [000] 122.833642: sched:sched_switch: prev_comm=NetworkManage...
perf 228273 [002] 122.833645: sched:sched_switch: prev_comm=perf prev_pid=22827...
swapper 0 [011] 122.833646: sched:sched_switch: prev_comm=swapper/1...
swapper 0 [002] 122.833648: sched:sched_switch: prev_comm=swapper/...
kworker/0:2-eve 207387 [000] 122.833648: sched:sched_switch: prev_comm=kworker/0:2 prev_pid=20738...
kworker/2:3-eve 232038 [002] 122.833652: sched:sched_switch: prev_comm=kworker/2:3 prev_pid=23203...
perf 235825 [003] 122.833653: sched:sched_switch: prev_comm=perf prev_pid=23582...
[root@five a]#
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lore.kernel.org/lkml/20200429131106.27974-8-acme@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo
parent
636eb4d001
commit
899e5ffbf2
@ -556,6 +556,19 @@ overhead. You can still switch them on with:
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--switch-output --no-no-buildid --no-no-buildid-cache
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--switch-output-event::
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Events that will cause the switch of the perf.data file, auto-selecting
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--switch-output=signal, the results are similar as internally the side band
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thread will also send a SIGUSR2 to the main one.
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Uses the same syntax as --event, it will just not be recorded, serving only to
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switch the perf.data file as soon as the --switch-output event is processed by
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a separate sideband thread.
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This sideband thread is also used to other purposes, like processing the
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PERF_RECORD_BPF_EVENT records as they happen, asking the kernel for extra BPF
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information, etc.
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--switch-max-files=N::
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When rotating perf.data with --switch-output, only keep N files.
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@ -88,7 +88,9 @@ struct record {
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struct evlist *evlist;
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struct perf_session *session;
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struct evlist *sb_evlist;
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pthread_t thread_id;
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int realtime_prio;
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bool switch_output_event_set;
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bool no_buildid;
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bool no_buildid_set;
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bool no_buildid_cache;
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@ -1437,6 +1439,13 @@ static int record__synthesize(struct record *rec, bool tail)
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return err;
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}
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static int record__process_signal_event(union perf_event *event __maybe_unused, void *data)
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{
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struct record *rec = data;
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pthread_kill(rec->thread_id, SIGUSR2);
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return 0;
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}
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static int __cmd_record(struct record *rec, int argc, const char **argv)
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{
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int err;
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@ -1581,13 +1590,25 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
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goto out_child;
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}
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if (rec->sb_evlist != NULL) {
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/*
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* We get here if --switch-output-event populated the
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* sb_evlist, so associate a callback that will send a SIGUSR2
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* to the main thread.
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*/
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evlist__set_cb(rec->sb_evlist, record__process_signal_event, rec);
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rec->thread_id = pthread_self();
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}
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if (!opts->no_bpf_event) {
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if (rec->sb_evlist == NULL) {
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rec->sb_evlist = evlist__new();
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if (rec->sb_evlist == NULL) {
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pr_err("Couldn't create side band evlist.\n.");
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goto out_child;
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}
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}
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if (evlist__add_bpf_sb_event(rec->sb_evlist, &session->header.env)) {
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pr_err("Couldn't ask for PERF_RECORD_BPF_EVENT side band events.\n.");
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@ -2180,10 +2201,19 @@ static int switch_output_setup(struct record *rec)
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};
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unsigned long val;
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/*
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* If we're using --switch-output-events, then we imply its
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* --switch-output=signal, as we'll send a SIGUSR2 from the side band
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* thread to its parent.
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*/
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if (rec->switch_output_event_set)
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goto do_signal;
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if (!s->set)
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return 0;
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if (!strcmp(s->str, "signal")) {
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do_signal:
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s->signal = true;
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pr_debug("switch-output with SIGUSR2 signal\n");
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goto enabled;
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@ -2441,6 +2471,9 @@ static struct option __record_options[] = {
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&record.switch_output.set, "signal or size[BKMG] or time[smhd]",
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"Switch output when receiving SIGUSR2 (signal) or cross a size or time threshold",
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"signal"),
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OPT_CALLBACK_SET(0, "switch-output-event", &record.sb_evlist, &record.switch_output_event_set, "switch output event",
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"switch output event selector. use 'perf list' to list available events",
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parse_events_option_new_evlist),
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OPT_INTEGER(0, "switch-max-files", &record.switch_output.num_files,
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"Limit number of switch output generated files"),
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OPT_BOOLEAN(0, "dry-run", &dry_run,
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