perf pmus: Check if we can encode the PMU number in perf_event_attr.type

In some architectures we can't encode the PMU number in
perf_event_attr.type and thus can't just ask for the same event in
multiple CPUs (and thus PMUs), that is what we want in hybrid systems
but we can't when that encoding isn't understood by the kernel, such as
in ARM64's big.LITTLE.

If that is the case, fallback to the previous behaviour till we find a
better solution to have consistent output accross architectures with
hybrid CPU configurations.

Co-developed-with: Ian Rogers <irogers@google.com>
Cc: James Clark <james.clark@arm.com>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/linux-perf-users/ZIzYgImv61OGK1wA@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
index a2032c1b7644fbf216434863685553d105d242c0..d891d72c824ec3b610fcb0c6209461557461ee01 100644 (file)
--- a/tools/perf/util/pmus.c
+++ b/tools/perf/util/pmus.c
@@ -4,6 +4,7 @@
 #include <subcmd/pager.h>
 #include <sys/types.h>
 #include <dirent.h>
+#include <pthread.h>
 #include <string.h>
 #include <unistd.h>
 #include "debug.h"
@@ -492,9 +493,35 @@ int perf_pmus__num_core_pmus(void)
        return count;
 }
 
+static bool __perf_pmus__supports_extended_type(void)
+{
+       struct perf_pmu *pmu = NULL;
+
+       if (perf_pmus__num_core_pmus() <= 1)
+               return false;
+
+       while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
+               if (!is_event_supported(PERF_TYPE_HARDWARE, PERF_COUNT_HW_CPU_CYCLES | ((__u64)pmu->type << PERF_PMU_TYPE_SHIFT)))
+                       return false;
+       }
+
+       return true;
+}
+
+static bool perf_pmus__do_support_extended_type;
+
+static void perf_pmus__init_supports_extended_type(void)
+{
+       perf_pmus__do_support_extended_type = __perf_pmus__supports_extended_type();
+}
+
 bool perf_pmus__supports_extended_type(void)
 {
-       return perf_pmus__num_core_pmus() > 1;
+       static pthread_once_t extended_type_once = PTHREAD_ONCE_INIT;
+
+       pthread_once(&extended_type_once, perf_pmus__init_supports_extended_type);
+
+       return perf_pmus__do_support_extended_type;
 }
 
 struct perf_pmu *evsel__find_pmu(const struct evsel *evsel)