perf pmus: Avoid repeated sysfs scanning

perf_pmus__scan will process every directory in sysfs to see if it is
a PMU, attempting to add it if not already in the pmus list. Add two
booleans to record whether this scanning has been done for core or all
PMUs. Skip scanning in the event that scanning has already occurred.

Reviewed-by: Kan Liang <[email protected]>
Signed-off-by: Ian Rogers <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ali Saidi <[email protected]>
Cc: Athira Rajeev <[email protected]>
Cc: Dmitrii Dolgov <[email protected]>
Cc: Huacai Chen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jing Zhang <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: John Garry <[email protected]>
Cc: Kajol Jain <[email protected]>
Cc: Kang Minchul <[email protected]>
Cc: Leo Yan <[email protected]>
Cc: Madhavan Srinivasan <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mike Leach <[email protected]>
Cc: Ming Wang <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ravi Bangoria <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Sandipan Das <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Suzuki Poulouse <[email protected]>
Cc: Thomas Richter <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Xing Zhengjun <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 31 insertions, 2 deletions

diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
index de7fc36519c9..2c512345191d 100644
--- a/tools/perf/util/pmus.c
+++ b/tools/perf/util/pmus.c
@@ -14,6 +14,8 @@
 
 static LIST_HEAD(core_pmus);
 static LIST_HEAD(other_pmus);
+static bool read_sysfs_core_pmus;
+static bool read_sysfs_all_pmus;
 
 void perf_pmus__destroy(void)
 {
@@ -29,6 +31,8 @@ void perf_pmus__destroy(void)
 
 		perf_pmu__delete(pmu);
 	}
+	read_sysfs_core_pmus = false;
+	read_sysfs_all_pmus = false;
 }
 
 static struct perf_pmu *pmu_find(const char *name)
@@ -53,6 +57,7 @@ struct perf_pmu *perf_pmus__find(const char *name)
 {
 	struct perf_pmu *pmu;
 	int dirfd;
+	bool core_pmu;
 
 	/*
 	 * Once PMU is loaded it stays in the list,
@@ -63,8 +68,15 @@ struct perf_pmu *perf_pmus__find(const char *name)
 	if (pmu)
 		return pmu;
 
+	if (read_sysfs_all_pmus)
+		return NULL;
+
+	core_pmu = is_pmu_core(name);
+	if (core_pmu && read_sysfs_core_pmus)
+		return NULL;
+
 	dirfd = perf_pmu__event_source_devices_fd();
-	pmu = perf_pmu__lookup(is_pmu_core(name) ? &core_pmus : &other_pmus, dirfd, name);
+	pmu = perf_pmu__lookup(core_pmu ? &core_pmus : &other_pmus, dirfd, name);
 	close(dirfd);
 
 	return pmu;
@@ -73,6 +85,7 @@ struct perf_pmu *perf_pmus__find(const char *name)
 static struct perf_pmu *perf_pmu__find2(int dirfd, const char *name)
 {
 	struct perf_pmu *pmu;
+	bool core_pmu;
 
 	/*
 	 * Once PMU is loaded it stays in the list,
@@ -83,7 +96,14 @@ static struct perf_pmu *perf_pmu__find2(int dirfd, const char *name)
 	if (pmu)
 		return pmu;
 
-	return perf_pmu__lookup(is_pmu_core(name) ? &core_pmus : &other_pmus, dirfd, name);
+	if (read_sysfs_all_pmus)
+		return NULL;
+
+	core_pmu = is_pmu_core(name);
+	if (core_pmu && read_sysfs_core_pmus)
+		return NULL;
+
+	return perf_pmu__lookup(core_pmu ? &core_pmus : &other_pmus, dirfd, name);
 }
 
 /* Add all pmus in sysfs to pmu list: */
@@ -93,6 +113,9 @@ static void pmu_read_sysfs(bool core_only)
 	DIR *dir;
 	struct dirent *dent;
 
+	if (read_sysfs_all_pmus || (core_only && read_sysfs_core_pmus))
+		return;
+
 	fd = perf_pmu__event_source_devices_fd();
 	if (fd < 0)
 		return;
@@ -111,6 +134,12 @@ static void pmu_read_sysfs(bool core_only)
 	}
 
 	closedir(dir);
+	if (core_only) {
+		read_sysfs_core_pmus = true;
+	} else {
+		read_sysfs_core_pmus = true;
+		read_sysfs_all_pmus = true;
+	}
 }
 
 struct perf_pmu *perf_pmus__find_by_type(unsigned int type)