Re: Hybrid PMU issues on aarch64. was: Re: perf test failures in linux-next on s390

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Fri, Jun 16, 2023 at 01:53:41PM -0300, Arnaldo Carvalho de Melo escreveu:
> > presumably with the #ifdef you just get 1 PMU - shame. I think rather
> > than do an #ifdef we can do something like call is_event_supported:
> > https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/util/print-events.c?h=perf-tools-next#n232
> > so:
> > 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) {
> >     return is_event_supported(PERF_TYPE_HARDWARE,
> > PERF_COUNT_HW_CPU_CYCLES | ((__u64)pmu->type << PERF_PMU_TYPE_SHIFT);
> >  }
> > return false;
> > }
> > We probably don't want to do this for each call of
> > perf_pmus__supports_extended_type so you could use a static and
> > pthread_once, etc.
> > 
> > This would mean if this regression is introduced elsewhere than ARM it
> > will self heal. It will also mean that when ARM support extended types
> > in the kernel, they will get the normal heterogeneous behavior.
> 
> That looks better, I'll try it when I get back to my office.

End result, Ack?


diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
index a2032c1b7644..d891d72c824e 100644
--- 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)
diff --git a/tools/perf/util/print-events.c b/tools/perf/util/print-events.c
index 7a5f87392720..a7566edc86a3 100644
--- a/tools/perf/util/print-events.c
+++ b/tools/perf/util/print-events.c
@@ -229,7 +229,7 @@ void print_sdt_events(const struct print_callbacks *print_cb, void *print_state)
 	strlist__delete(sdtlist);
 }
 
-static bool is_event_supported(u8 type, u64 config)
+bool is_event_supported(u8 type, u64 config)
 {
 	bool ret = true;
 	int open_return;
diff --git a/tools/perf/util/print-events.h b/tools/perf/util/print-events.h
index e75a3d7e3fe3..d7fab411e75c 100644
--- a/tools/perf/util/print-events.h
+++ b/tools/perf/util/print-events.h
@@ -3,6 +3,7 @@
 #define __PERF_PRINT_EVENTS_H
 
 #include <linux/perf_event.h>
+#include <linux/types.h>
 #include <stdbool.h>
 
 struct event_symbol;
@@ -36,5 +37,6 @@ void print_symbol_events(const struct print_callbacks *print_cb, void *print_sta
 			 unsigned int max);
 void print_tool_events(const struct print_callbacks *print_cb, void *print_state);
 void print_tracepoint_events(const struct print_callbacks *print_cb, void *print_state);
+bool is_event_supported(u8 type, u64 config);
 
 #endif /* __PERF_PRINT_EVENTS_H */