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| author | Mark Rutland <mark.rutland@arm.com> | 2016-09-09 14:08:30 +0100 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2016-09-09 14:51:51 +0100 |
| commit | 48538b5863d8e8f8d567fc9a1d27a68623e0a0ff (patch) | |
| tree | bf2feca2a3cd582ed4d0f52b16ed83e1350321f5 | |
| parent | 1589680da6f7df30d8a592eebee16478f3e34a2c (diff) | |
| download | lwn-48538b5863d8e8f8d567fc9a1d27a68623e0a0ff.tar.gz lwn-48538b5863d8e8f8d567fc9a1d27a68623e0a0ff.zip | |
drivers/perf: arm_pmu: expose a cpumask in sysfs
In systems with heterogeneous CPUs, there are multiple logical CPU PMUs,
each of which covers a subset of CPUs in the system. In some cases
userspace needs to know which CPUs a given logical PMU covers, so we'd
like to expose a cpumask under sysfs, similar to what is done for uncore
PMUs.
Unfortunately, prior to commit 00e727bb389359c8 ("perf stat: Balance
opening and reading events"), perf stat only correctly handled a cpumask
holding a single CPU, and only when profiling in system-wide mode. In
other cases, the presence of a cpumask file could cause perf stat to
behave erratically.
Thus, exposing a cpumask file would break older perf binaries in cases
where they would otherwise work.
To avoid this issue while still providing userspace with the information
it needs, this patch exposes a differently-named file (cpus) under
sysfs. New tools can look for this and operate correctly, while older
tools will not be adversely affected by its presence.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
| -rw-r--r-- | drivers/perf/arm_pmu.c | 20 | ||||
| -rw-r--r-- | include/linux/perf/arm_pmu.h | 1 |
2 files changed, 21 insertions, 0 deletions
diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c index 60c065eb638d..c36913ad3a09 100644 --- a/drivers/perf/arm_pmu.c +++ b/drivers/perf/arm_pmu.c @@ -534,6 +534,24 @@ static int armpmu_filter_match(struct perf_event *event) return cpumask_test_cpu(cpu, &armpmu->supported_cpus); } +static ssize_t armpmu_cpumask_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct arm_pmu *armpmu = to_arm_pmu(dev_get_drvdata(dev)); + return cpumap_print_to_pagebuf(true, buf, &armpmu->supported_cpus); +} + +static DEVICE_ATTR(cpus, S_IRUGO, armpmu_cpumask_show, NULL); + +static struct attribute *armpmu_common_attrs[] = { + &dev_attr_cpus.attr, + NULL, +}; + +static struct attribute_group armpmu_common_attr_group = { + .attrs = armpmu_common_attrs, +}; + static void armpmu_init(struct arm_pmu *armpmu) { atomic_set(&armpmu->active_events, 0); @@ -551,6 +569,8 @@ static void armpmu_init(struct arm_pmu *armpmu) .filter_match = armpmu_filter_match, .attr_groups = armpmu->attr_groups, }; + armpmu->attr_groups[ARMPMU_ATTR_GROUP_COMMON] = + &armpmu_common_attr_group; } /* Set at runtime when we know what CPU type we are. */ diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h index 268bc63f1358..dc1f2f30c961 100644 --- a/include/linux/perf/arm_pmu.h +++ b/include/linux/perf/arm_pmu.h @@ -78,6 +78,7 @@ struct pmu_hw_events { }; enum armpmu_attr_groups { + ARMPMU_ATTR_GROUP_COMMON, ARMPMU_ATTR_GROUP_EVENTS, ARMPMU_ATTR_GROUP_FORMATS, ARMPMU_NR_ATTR_GROUPS |