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Date: Tue, 28 Apr 2020 11:48:39 +0200
From: Jiri Olsa <jolsa@...hat.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Clark Williams <williams@...hat.com>,
linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Song Liu <songliubraving@...com>,
Wang Nan <wangnan0@...wei.com>
Subject: Re: [PATCH 7/7] perf record: Introduce --switch-output-event
On Mon, Apr 27, 2020 at 06:19:35PM -0300, Arnaldo Carvalho de Melo wrote:
SNIP
> ---
> tools/perf/Documentation/perf-record.txt | 13 ++++++++
> tools/perf/builtin-record.c | 40 +++++++++++++++++++++---
> 2 files changed, 49 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index 6e8b4649307c..561ef55743e2 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -556,6 +556,19 @@ overhead. You can still switch them on with:
>
> --switch-output --no-no-buildid --no-no-buildid-cache
>
> +--switch-output-event::
> +Events that will cause the switch of the perf.data file, auto-selecting
> +--switch-output=signal, the results are similar as internally the side band
> +thread will also send a SIGUSR2 to the main one.
> +
> +Uses the same syntax as --event, it will just not be recorded, serving only to
> +switch the perf.data file as soon as the --switch-output event is processed by
> +a separate sideband thread.
> +
> +This sideband thread is also used to other purposes, like processing the
> +PERF_RECORD_BPF_EVENT records as they happen, asking the kernel for extra BPF
> +information, etc.
first I thought we should follow the --switch-output 'xxx' way,
but then you need to specify an event, so I guess --switch-output-event
is better
> +
> --switch-max-files=N::
>
> When rotating perf.data with --switch-output, only keep N files.
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index ed2244847400..8ff5eaec26e9 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -87,6 +87,7 @@ struct record {
> struct evlist *evlist;
> struct perf_session *session;
> struct evlist *sb_evlist;
> + pthread_t thread_id;
> int realtime_prio;
> bool no_buildid;
> bool no_buildid_set;
> @@ -1436,6 +1437,13 @@ static int record__synthesize(struct record *rec, bool tail)
> return err;
> }
>
> +static int record__process_signal_event(union perf_event *event __maybe_unused, void *data)
> +{
> + struct record *rec = data;
> + pthread_kill(rec->thread_id, SIGUSR2);
> + return 0;
> +}
> +
> static int __cmd_record(struct record *rec, int argc, const char **argv)
> {
> int err;
> @@ -1580,12 +1588,24 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
> goto out_child;
> }
>
> - if (!opts->no_bpf_event) {
> - rec->sb_evlist = evlist__new();
> + if (rec->sb_evlist != NULL) {
> + /*
> + * We get here if --switch-output-event populated the
> + * sb_evlist, so associate a callback that will send a SIGUSR2
> + * to the main thread.
> + */
> + evlist__set_cb(rec->sb_evlist, record__process_signal_event, rec);
> + rec->thread_id = pthread_self();
> + }
>
> + if (!opts->no_bpf_event) {
> if (rec->sb_evlist == NULL) {
> - pr_err("Couldn't create side band evlist.\n.");
> - goto out_child;
> + rec->sb_evlist = evlist__new();
> +
> + if (rec->sb_evlist == NULL) {
> + pr_err("Couldn't create side band evlist.\n.");
> + goto out_child;
> + }
> }
>
> if (evlist__add_bpf_sb_event(rec->sb_evlist, &session->header.env)) {
it's getting bigger, I wonder we should put all the sb_* setup in
separated functions like sb_start/sb_stop
> @@ -2179,10 +2199,19 @@ static int switch_output_setup(struct record *rec)
> };
> unsigned long val;
>
> + /*
> + * If we're using --switch-output-events, then we imply its
> + * --switch-output=signal, as we'll send a SIGUSR2 from the side band
> + * thread to its parent.
> + */
> + if (rec->sb_evlist != NULL)
> + goto do_signal;
> +
> if (!s->set)
> return 0;
hum, it looks like this jump is not necessay and can be avoided
by some bool checks.. could we add some bool when --switch-output-event
is used, so we don't depend on wether rec->sb_evlist was allocated for
whatever reason?
jirka
>
> if (!strcmp(s->str, "signal")) {
> +do_signal:
> s->signal = true;
> pr_debug("switch-output with SIGUSR2 signal\n");
> goto enabled;
> @@ -2440,6 +2469,9 @@ static struct option __record_options[] = {
> &record.switch_output.set, "signal or size[BKMG] or time[smhd]",
> "Switch output when receiving SIGUSR2 (signal) or cross a size or time threshold",
> "signal"),
> + OPT_CALLBACK(0, "switch-output-event", &record.sb_evlist, "switch output event",
> + "switch output event selector. use 'perf list' to list available events",
> + parse_events_option_new_evlist),
> OPT_INTEGER(0, "switch-max-files", &record.switch_output.num_files,
> "Limit number of switch output generated files"),
> OPT_BOOLEAN(0, "dry-run", &dry_run,
> --
> 2.21.1
>
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