From: Swapnil Sapkal <swapnil.sapkal@amd.com>

The live mode works similar to simple `perf stat` command, by profiling
the target and printing results on the terminal as soon as the target
finishes.

Example usage:

  # perf sched stats -- sleep 10

Signed-off-by: Swapnil Sapkal <swapnil.sapkal@amd.com>
Co-developed-by: Ravi Bangoria <ravi.bangoria@amd.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
---
 tools/perf/builtin-sched.c | 87 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 86 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index cd465644fce5..e888ae763eac 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -4319,6 +4319,91 @@ static int perf_sched__schedstat_report(struct perf_sched *sched)
 	return err;
 }
 
+static int process_synthesized_event_live(const struct perf_tool *tool __maybe_unused,
+					  union perf_event *event,
+					  struct perf_sample *sample __maybe_unused,
+					  struct machine *machine __maybe_unused)
+{
+	return perf_sched__process_schedstat(NULL, event);
+}
+
+static int perf_sched__schedstat_live(struct perf_sched *sched,
+				      int argc, const char **argv)
+{
+	struct evlist *evlist;
+	struct target *target;
+	int reset = 0;
+	int err = 0;
+
+	signal(SIGINT, sighandler);
+	signal(SIGCHLD, sighandler);
+	signal(SIGTERM, sighandler);
+
+	evlist = evlist__new();
+	if (!evlist)
+		return -ENOMEM;
+
+	/*
+	 * `perf sched schedstat` does not support workload profiling (-p pid)
+	 * since /proc/schedstat file contains cpu specific data only. Hence, a
+	 * profile target is either set of cpus or systemwide, never a process.
+	 * Note that, although `-- <workload>` is supported, profile data are
+	 * still cpu/systemwide.
+	 */
+	target = zalloc(sizeof(struct target));
+	if (cpu_list)
+		target->cpu_list = cpu_list;
+	else
+		target->system_wide = true;
+
+	if (argc) {
+		err = evlist__prepare_workload(evlist, target, argv, false, NULL);
+		if (err)
+			goto out_target;
+	}
+
+	if (cpu_list) {
+		user_requested_cpus = perf_cpu_map__new(cpu_list);
+		if (!user_requested_cpus)
+			goto out_target;
+	}
+
+	err = perf_event__synthesize_schedstat(&(sched->tool),
+					       process_synthesized_event_live,
+					       user_requested_cpus);
+	if (err < 0)
+		goto out_target;
+
+	err = enable_sched_schedstats(&reset);
+	if (err < 0)
+		goto out_target;
+
+	if (argc)
+		evlist__start_workload(evlist);
+
+	/* wait for signal */
+	pause();
+
+	if (reset) {
+		err = disable_sched_schedstat();
+		if (err < 0)
+			goto out_target;
+	}
+
+	err = perf_event__synthesize_schedstat(&(sched->tool),
+					       process_synthesized_event_live,
+					       user_requested_cpus);
+	if (err)
+		goto out_target;
+
+	setup_pager();
+	show_schedstat_data();
+	free_schedstat();
+out_target:
+	free(target);
+	return err;
+}
+
 static bool schedstat_events_exposed(void)
 {
 	/*
@@ -4640,7 +4725,7 @@ int cmd_sched(int argc, const char **argv)
 						     stats_usage, 0);
 			return perf_sched__schedstat_report(&sched);
 		}
-		usage_with_options(stats_usage, stats_options);
+		return perf_sched__schedstat_live(&sched, argc, argv);
 	} else {
 		usage_with_options(sched_usage, sched_options);
 	}
-- 
2.46.0