perf: sched map skips redundant lines with cpu filters

perf sched map supports cpu filter.
However, even with cpu filters active, any context switch currently
corresponds to a separate line.
As result, context switches on irrelevant cpus result to redundant lines,
which makes the output particlularly difficult to read on wide
architectures.

Fix it by skipping printing for irrelevant CPUs.

Example snippet of output before fix:

  *B0       1.461147 secs
   B0
   B0
   B0
  *G0       1.517139 secs

After fix:

  *B0       1.461147 secs
  *G0       1.517139 secs
Signed-off-by: Fernand Sieber <sieberf@amazon.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-and-tested-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240614073517.94974-1-sieberf@amazon.com

tools/perf/builtin-sched.c

@@ -1594,8 +1594,6 @@ static int map_switch_event(struct perf_sched *sched, struct evsel *evsel,
 
 	sched->curr_thread[this_cpu.cpu] = thread__get(sched_in);
 
-	printf("  ");
-
 	new_shortname = 0;
 	if (!tr->shortname[0]) {
 		if (!strcmp(thread__comm_str(sched_in), "swapper")) {
@@ -1622,6 +1620,11 @@ static int map_switch_event(struct perf_sched *sched, struct evsel *evsel,
 		new_shortname = 1;
 	}
 
+	if (sched->map.cpus && !perf_cpu_map__has(sched->map.cpus, this_cpu))
+		goto out;
+
+	printf("  ");
+
 	for (i = 0; i < cpus_nr; i++) {
 		struct perf_cpu cpu = {
 			.cpu = sched->map.comp ? sched->map.comp_cpus[i].cpu : i,
@@ -1656,9 +1659,6 @@ static int map_switch_event(struct perf_sched *sched, struct evsel *evsel,
 			color_fprintf(stdout, color, "   ");
 	}
 
-	if (sched->map.cpus && !perf_cpu_map__has(sched->map.cpus, this_cpu))
-		goto out;
-
 	timestamp__scnprintf_usec(timestamp, stimestamp, sizeof(stimestamp));
 	color_fprintf(stdout, color, "  %12s secs ", stimestamp);
 	if (new_shortname || tr->comm_changed || (verbose > 0 && thread__tid(sched_in))) {
@@ -1675,9 +1675,9 @@ static int map_switch_event(struct perf_sched *sched, struct evsel *evsel,
 	if (sched->map.comp && new_cpu)
 		color_fprintf(stdout, color, " (CPU %d)", this_cpu);
 
-out:
 	color_fprintf(stdout, color, "\n");
 
+out:
 	thread__put(sched_in);
 
 	return 0;