| Message ID | 1473330112-28528-6-git-send-email-mark.rutland@arm.com |
|---|---|
| State | New |
| Headers | show |
On Thu, Sep 08, 2016 at 11:21:50AM +0100, Mark Rutland wrote: > 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> > --- > drivers/perf/arm_pmu.c | 21 +++++++++++++++++++++ > include/linux/perf/arm_pmu.h | 1 + > 2 files changed, 22 insertions(+) > > diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c > index ac83e1e..09e9944 100644 > --- a/drivers/perf/arm_pmu.c > +++ b/drivers/perf/arm_pmu.c > @@ -534,6 +534,25 @@ 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 struct device_attribute armpmu_cpumask_attr = > + __ATTR(cpus, S_IRUGO, armpmu_cpumask_show, NULL); You can use the DEVICE_ATTR macro for this. Will
On Fri, Sep 09, 2016 at 11:24:43AM +0100, Will Deacon wrote: > On Thu, Sep 08, 2016 at 11:21:50AM +0100, Mark Rutland wrote: > > +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 struct device_attribute armpmu_cpumask_attr = > > + __ATTR(cpus, S_IRUGO, armpmu_cpumask_show, NULL); > > You can use the DEVICE_ATTR macro for this. Ok. I've made use of this locally. I'll send an updated version of the patches shortly, once I've given this a spin on HW Mark.
diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c index ac83e1e..09e9944 100644 --- a/drivers/perf/arm_pmu.c +++ b/drivers/perf/arm_pmu.c @@ -534,6 +534,25 @@ 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 struct device_attribute armpmu_cpumask_attr = + __ATTR(cpus, S_IRUGO, armpmu_cpumask_show, NULL); + +static struct attribute *armpmu_common_attrs[] = { + &armpmu_cpumask_attr.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 +570,8 @@ 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 8030814..4040b90 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
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> --- drivers/perf/arm_pmu.c | 21 +++++++++++++++++++++ include/linux/perf/arm_pmu.h | 1 + 2 files changed, 22 insertions(+) -- 1.9.1