@@ -509,6 +509,18 @@ static void armpmu_disable(struct pmu *pmu)
armpmu->stop(armpmu);
}
+/*
+ * In heterogeneous systems, events are specific to a particular
+ * microarchitecture, and aren't suitable for another. Thus, only match CPUs of
+ * the same microarchitecture.
+ */
+static int armpmu_filter_match(struct perf_event *event)
+{
+ struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
+ unsigned int cpu = smp_processor_id();
+ return cpumask_test_cpu(cpu, &armpmu->supported_cpus);
+}
+
#ifdef CONFIG_PM_RUNTIME
static int armpmu_runtime_resume(struct device *dev)
{
@@ -549,6 +561,7 @@ static void armpmu_init(struct arm_pmu *armpmu)
.start = armpmu_start,
.stop = armpmu_stop,
.read = armpmu_read,
+ .filter_match = armpmu_filter_match,
};
}
Different CPU microarchitectures implement different PMU events, and thus events which can be scheduled on one microarchitecture cannot be scheduled on another, and vice-versa. Some archicted events behave differently across microarchitectures, and thus cannot be meaningfully summed. Due to this, we reject the scheduling of an event on a CPU of a different microarchitecture to that the event targets. When the core perf code is scheduling events and encounters an event which cannot be scheduled, it stops attempting to schedule events. As the perf core periodically rotates the list of events, for some proportion of the time events which are unschedulable will block events which are schedulable, resulting in low utilisation of the hardware counters. This patch implements a pmu::filter_match callback such that we can detect and skip such events while scheduling early, before they can block the schedulable events. This prevents the low HW counter utilisation issue. Signed-off-by: Mark Rutland <mark.rutland@arm.com> --- arch/arm/kernel/perf_event.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)