perf stat: Merge uncore events by default for hybrid platform

On a hybrid platform, by default 'perf stat' aggregates and reports the
event counts per PMU. For example,

# perf stat -e cycles -a true

Performance counter stats for 'system wide':

1,400,445 cpu_core/cycles/
680,881 cpu_atom/cycles/

0.001770773 seconds time elapsed

But for uncore events that's not a suitable method. Uncore has nothing
to do with hybrid. So for uncore events, we aggregate event counts from
all PMUs and report the counts without PMUs.

Before:

# perf stat -e arb/event=0x81,umask=0x1/,arb/event=0x84,umask=0x1/ -a true

Performance counter stats for 'system wide':

2,058 uncore_arb_0/event=0x81,umask=0x1/
2,028 uncore_arb_1/event=0x81,umask=0x1/
0 uncore_arb_0/event=0x84,umask=0x1/
0 uncore_arb_1/event=0x84,umask=0x1/

0.000614498 seconds time elapsed

After:

# perf stat -e arb/event=0x81,umask=0x1/,arb/event=0x84,umask=0x1/ -a true

Performance counter stats for 'system wide':

3,996 arb/event=0x81,umask=0x1/
0 arb/event=0x84,umask=0x1/

0.000630046 seconds time elapsed

Of course, we also keep the '--no-merge' working for uncore events.

# perf stat -e arb/event=0x81,umask=0x1/,arb/event=0x84,umask=0x1/ --no-merge true

Performance counter stats for 'system wide':

1,952 uncore_arb_0/event=0x81,umask=0x1/
1,921 uncore_arb_1/event=0x81,umask=0x1/
0 uncore_arb_0/event=0x84,umask=0x1/
0 uncore_arb_1/event=0x84,umask=0x1/

0.000575536 seconds time elapsed

Signed-off-by: Jin Yao <[e-mail]>
Acked-by: Jiri Olsa <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-stat.c

···
 
 	evlist__check_cpu_maps(evsel_list);
 
-	if (perf_pmu__has_hybrid())
-		stat_config.no_merge = true;
-
 	/*
 	 * Initialize thread_map with comm names,
 	 * so we could print it out on output.

tools/perf/util/stat-display.c

···
 	}
 }
 
+static bool is_uncore(struct evsel *evsel)
+{
+	struct perf_pmu *pmu = evsel__find_pmu(evsel);
+
+	return pmu && pmu->is_uncore;
+}
+
+static bool hybrid_uniquify(struct evsel *evsel)
+{
+	return perf_pmu__has_hybrid() && !is_uncore(evsel);
+}
+
 static bool collect_data(struct perf_stat_config *config, struct evsel *counter,
 			    void (*cb)(struct perf_stat_config *config, struct evsel *counter, void *data,
 				       bool first),
···
 	if (counter->merged_stat)
 		return false;
 	cb(config, counter, data, true);
-	if (config->no_merge)
+	if (config->no_merge || hybrid_uniquify(counter))
 		uniquify_event_name(counter);
 	else if (counter->auto_merge_stats)
 		collect_all_aliases(config, counter, cb, data);