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    SubjectRe: [PATCH 2/5] perf lock: Add lock contention tracepoints record support
    On Tue, May 31, 2022 at 11:58 PM Namhyung Kim <namhyung@kernel.org> wrote:
    >
    > When LOCKDEP and LOCK_STAT events are not available, it falls back to
    > record the new lock contention tracepoints.
    >
    > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
    > ---
    > tools/perf/builtin-lock.c | 70 +++++++++++++++++++++++++++++++++++----
    > 1 file changed, 63 insertions(+), 7 deletions(-)
    >
    > diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
    > index 23a33ac15e68..3e3320b8cede 100644
    > --- a/tools/perf/builtin-lock.c
    > +++ b/tools/perf/builtin-lock.c
    > @@ -495,6 +495,12 @@ struct trace_lock_handler {
    >
    > int (*release_event)(struct evsel *evsel,
    > struct perf_sample *sample);
    > +
    > + int (*contention_begin_event)(struct evsel *evsel,
    > + struct perf_sample *sample);
    > +
    > + int (*contention_end_event)(struct evsel *evsel,
    > + struct perf_sample *sample);

    Would it make sense to add a comment here about LOCKDEP and LOCK_STAT?
    It could be confusing if the handler isn't called on different
    kernels.

    Thanks,
    Ian

    > };
    >
    > static struct lock_seq_stat *get_seq(struct thread_stat *ts, u64 addr)
    > @@ -822,6 +828,20 @@ static int evsel__process_lock_release(struct evsel *evsel, struct perf_sample *
    > return 0;
    > }
    >
    > +static int evsel__process_contention_begin(struct evsel *evsel, struct perf_sample *sample)
    > +{
    > + if (trace_handler->contention_begin_event)
    > + return trace_handler->contention_begin_event(evsel, sample);
    > + return 0;
    > +}
    > +
    > +static int evsel__process_contention_end(struct evsel *evsel, struct perf_sample *sample)
    > +{
    > + if (trace_handler->contention_end_event)
    > + return trace_handler->contention_end_event(evsel, sample);
    > + return 0;
    > +}
    > +
    > static void print_bad_events(int bad, int total)
    > {
    > /* Output for debug, this have to be removed */
    > @@ -1023,6 +1043,11 @@ static const struct evsel_str_handler lock_tracepoints[] = {
    > { "lock:lock_release", evsel__process_lock_release, }, /* CONFIG_LOCKDEP */
    > };
    >
    > +static const struct evsel_str_handler contention_tracepoints[] = {
    > + { "lock:contention_begin", evsel__process_contention_begin, },
    > + { "lock:contention_end", evsel__process_contention_end, },
    > +};
    > +
    > static bool force;
    >
    > static int __cmd_report(bool display_info)
    > @@ -1086,20 +1111,41 @@ static int __cmd_record(int argc, const char **argv)
    > "record", "-R", "-m", "1024", "-c", "1", "--synth", "task",
    > };
    > unsigned int rec_argc, i, j, ret;
    > + unsigned int nr_tracepoints;
    > const char **rec_argv;
    > + bool has_lock_stat = true;
    >
    > for (i = 0; i < ARRAY_SIZE(lock_tracepoints); i++) {
    > if (!is_valid_tracepoint(lock_tracepoints[i].name)) {
    > - pr_err("tracepoint %s is not enabled. "
    > - "Are CONFIG_LOCKDEP and CONFIG_LOCK_STAT enabled?\n",
    > - lock_tracepoints[i].name);
    > - return 1;
    > + pr_debug("tracepoint %s is not enabled. "
    > + "Are CONFIG_LOCKDEP and CONFIG_LOCK_STAT enabled?\n",
    > + lock_tracepoints[i].name);
    > + has_lock_stat = false;
    > + break;
    > + }
    > + }
    > +
    > + if (has_lock_stat)
    > + goto setup_args;
    > +
    > + for (i = 0; i < ARRAY_SIZE(contention_tracepoints); i++) {
    > + if (!is_valid_tracepoint(contention_tracepoints[i].name)) {
    > + pr_err("tracepoint %s is not enabled.\n",
    > + contention_tracepoints[i].name);
    > + return 1;
    > }
    > }
    >
    > +setup_args:
    > rec_argc = ARRAY_SIZE(record_args) + argc - 1;
    > +
    > + if (has_lock_stat)
    > + nr_tracepoints = ARRAY_SIZE(lock_tracepoints);
    > + else
    > + nr_tracepoints = ARRAY_SIZE(contention_tracepoints);
    > +
    > /* factor of 2 is for -e in front of each tracepoint */
    > - rec_argc += 2 * ARRAY_SIZE(lock_tracepoints);
    > + rec_argc += 2 * nr_tracepoints;
    >
    > rec_argv = calloc(rec_argc + 1, sizeof(char *));
    > if (!rec_argv)
    > @@ -1108,9 +1154,19 @@ static int __cmd_record(int argc, const char **argv)
    > for (i = 0; i < ARRAY_SIZE(record_args); i++)
    > rec_argv[i] = strdup(record_args[i]);
    >
    > - for (j = 0; j < ARRAY_SIZE(lock_tracepoints); j++) {
    > + for (j = 0; j < nr_tracepoints; j++) {
    > + const char *ev_name;
    > +
    > + if (has_lock_stat)
    > + ev_name = strdup(lock_tracepoints[j].name);
    > + else
    > + ev_name = strdup(contention_tracepoints[j].name);
    > +
    > + if (!ev_name)
    > + return -ENOMEM;
    > +
    > rec_argv[i++] = "-e";
    > - rec_argv[i++] = strdup(lock_tracepoints[j].name);
    > + rec_argv[i++] = ev_name;
    > }
    >
    > for (j = 1; j < (unsigned int)argc; j++, i++)
    > --
    > 2.36.1.255.ge46751e96f-goog
    >

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