perf pmu: Unbreak perf record for arm/arm64 with events with explicit PMU
Currently, perf record is broken on arm/arm64 systems when the PMU is
specified explicitly as part of the event, e.g.
$ ./perf record -e armv8_cortex_a53/cpu_cycles/u true
In such cases, perf record fails to open events unless
perf_event_paranoid is set to -1, even if the PMU in question supports
mode exclusion. Further, even when perf_event_paranoid is toggled, no
samples are recorded.
This is an unintended side effect of commit:
e3ba76deef23064f ("perf tools: Force uncore events to system wide monitoring)
... which assumes that if a PMU has an associated cpu_map, it is an
uncore PMU, and forces events for such PMUs to be system-wide.
This is not true for arm/arm64 systems, which can have heterogeneous
CPUs. To account for this, multiple CPU PMUs are exposed, each with a
"cpus" field under sysfs, which the perf tool parses into a cpu_map. ARM
PMUs do not have a "cpumask" file, and only have a "cpus" file. For the
gory details as to why, see commit:
7e3fcffe95544010 ("perf pmu: Support alternative sysfs cpumask")
Given all of this, we can instead identify uncore PMUs by explicitly
checking for a "cpumask" file, and restore arm/arm64 PMU support back to
a working state. This patch does so, adding a new perf_pmu::is_uncore
field, and splitting the existing cpumask parsing so that it can be
reused.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by Will Deacon <will.deacon@arm.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: 4.12+ <stable@vger.kernel.org>
Fixes: e3ba76deef23064f ("perf tools: Force uncore events to system wide monitoring)
Link: http://lkml.kernel.org/r/1507315102-5942-1-git-send-email-mark.rutland@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index ac16a9d..1c4d7b4 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -470,31 +470,10 @@ static void pmu_read_sysfs(void)
closedir(dir);
}
-static struct cpu_map *pmu_cpumask(const char *name)
+static struct cpu_map *__pmu_cpumask(const char *path)
{
- struct stat st;
- char path[PATH_MAX];
FILE *file;
struct cpu_map *cpus;
- const char *sysfs = sysfs__mountpoint();
- const char *templates[] = {
- "%s/bus/event_source/devices/%s/cpumask",
- "%s/bus/event_source/devices/%s/cpus",
- NULL
- };
- const char **template;
-
- if (!sysfs)
- return NULL;
-
- for (template = templates; *template; template++) {
- snprintf(path, PATH_MAX, *template, sysfs, name);
- if (stat(path, &st) == 0)
- break;
- }
-
- if (!*template)
- return NULL;
file = fopen(path, "r");
if (!file)
@@ -506,6 +485,51 @@ static struct cpu_map *pmu_cpumask(const char *name)
}
/*
+ * Uncore PMUs have a "cpumask" file under sysfs. CPU PMUs (e.g. on arm/arm64)
+ * may have a "cpus" file.
+ */
+#define CPUS_TEMPLATE_UNCORE "%s/bus/event_source/devices/%s/cpumask"
+#define CPUS_TEMPLATE_CPU "%s/bus/event_source/devices/%s/cpus"
+
+static struct cpu_map *pmu_cpumask(const char *name)
+{
+ char path[PATH_MAX];
+ struct cpu_map *cpus;
+ const char *sysfs = sysfs__mountpoint();
+ const char *templates[] = {
+ CPUS_TEMPLATE_UNCORE,
+ CPUS_TEMPLATE_CPU,
+ NULL
+ };
+ const char **template;
+
+ if (!sysfs)
+ return NULL;
+
+ for (template = templates; *template; template++) {
+ snprintf(path, PATH_MAX, *template, sysfs, name);
+ cpus = __pmu_cpumask(path);
+ if (cpus)
+ return cpus;
+ }
+
+ return NULL;
+}
+
+static bool pmu_is_uncore(const char *name)
+{
+ char path[PATH_MAX];
+ struct cpu_map *cpus;
+ const char *sysfs = sysfs__mountpoint();
+
+ snprintf(path, PATH_MAX, CPUS_TEMPLATE_UNCORE, sysfs, name);
+ cpus = __pmu_cpumask(path);
+ cpu_map__put(cpus);
+
+ return !!cpus;
+}
+
+/*
* Return the CPU id as a raw string.
*
* Each architecture should provide a more precise id string that
@@ -617,6 +641,8 @@ static struct perf_pmu *pmu_lookup(const char *name)
pmu->cpus = pmu_cpumask(name);
+ pmu->is_uncore = pmu_is_uncore(name);
+
INIT_LIST_HEAD(&pmu->format);
INIT_LIST_HEAD(&pmu->aliases);
list_splice(&format, &pmu->format);