perf pmus: Allow just core PMU scanning

Scanning all PMUs is expensive as all PMUs sysfs entries are loaded,
benchmarking shows more than 4x the cost:

```
$ perf bench internals pmu-scan -i 1000
Computing performance of sysfs PMU event scan for 1000 times
  Average core PMU scanning took: 989.231 usec (+- 1.535 usec)
  Average PMU scanning took: 4309.425 usec (+- 74.322 usec)
```

Add new perf_pmus__scan_core routine that scans just core
PMUs. Replace perf_pmus__scan calls with perf_pmus__scan_core when
non-core PMUs are being ignored.

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ali Saidi <alisaidi@amazon.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Dmitrii Dolgov <9erthalion6@gmail.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jing Zhang <renyu.zj@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kang Minchul <tegongkang@gmail.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Ming Wang <wangming01@loongson.cn>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20230527072210.2900565-30-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 29 insertions, 21 deletions

diff --git a/tools/perf/bench/pmu-scan.c b/tools/perf/bench/pmu-scan.c
index 51cae2d03353..c7d207f8e13c 100644
--- a/tools/perf/bench/pmu-scan.c
+++ b/tools/perf/bench/pmu-scan.c
@@ -22,6 +22,7 @@ struct pmu_scan_result {
 	int nr_aliases;
 	int nr_formats;
 	int nr_caps;
+	bool is_core;
 };
 
 static const struct option options[] = {
@@ -53,6 +54,7 @@ static int save_result(void)
 		r = results + nr_pmus;
 
 		r->name = strdup(pmu->name);
+		r->is_core = pmu->is_core;
 		r->nr_caps = pmu->nr_caps;
 
 		r->nr_aliases = 0;
@@ -72,7 +74,7 @@ static int save_result(void)
 	return 0;
 }
 
-static int check_result(void)
+static int check_result(bool core_only)
 {
 	struct pmu_scan_result *r;
 	struct perf_pmu *pmu;
@@ -81,6 +83,9 @@ static int check_result(void)
 
 	for (int i = 0; i < nr_pmus; i++) {
 		r = &results[i];
+		if (core_only && !r->is_core)
+			continue;
+
 		pmu = perf_pmus__find(r->name);
 		if (pmu == NULL) {
 			pr_err("Cannot find PMU %s\n", r->name);
@@ -130,7 +135,6 @@ static int run_pmu_scan(void)
 	struct timeval start, end, diff;
 	double time_average, time_stddev;
 	u64 runtime_us;
-	unsigned int i;
 	int ret;
 
 	init_stats(&stats);
@@ -142,26 +146,30 @@ static int run_pmu_scan(void)
 		return -1;
 	}
 
-	for (i = 0; i < iterations; i++) {
-		gettimeofday(&start, NULL);
-		perf_pmus__scan(NULL);
-		gettimeofday(&end, NULL);
-
-		timersub(&end, &start, &diff);
-		runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
-		update_stats(&stats, runtime_us);
-
-		ret = check_result();
-		perf_pmus__destroy();
-		if (ret < 0)
-			break;
+	for (int j = 0; j < 2; j++) {
+		bool core_only = (j == 0);
+
+		for (unsigned int i = 0; i < iterations; i++) {
+			gettimeofday(&start, NULL);
+			if (core_only)
+				perf_pmus__scan_core(NULL);
+			else
+				perf_pmus__scan(NULL);
+			gettimeofday(&end, NULL);
+			timersub(&end, &start, &diff);
+			runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
+			update_stats(&stats, runtime_us);
+
+			ret = check_result(core_only);
+			perf_pmus__destroy();
+			if (ret < 0)
+				break;
+		}
+		time_average = avg_stats(&stats);
+		time_stddev = stddev_stats(&stats);
+		pr_info("  Average%s PMU scanning took: %.3f usec (+- %.3f usec)\n",
+			core_only ? " core" : "", time_average, time_stddev);
 	}
-
-	time_average = avg_stats(&stats);
-	time_stddev = stddev_stats(&stats);
-	pr_info("  Average PMU scanning took: %.3f usec (+- %.3f usec)\n",
-		time_average, time_stddev);
-
 	delete_result();
 	return 0;
 }