What: /sys/bus/event_source/devices//caps Date: May 2022 KernelVersion: 5.19 Contact: Linux kernel mailing list Description: Attribute group to describe the capabilities exposed for a particular pmu. Each attribute of this group can expose information specific to a PMU, say pmu_name, so that userspace can understand some of the feature which the platform specific PMU supports. One of the example available capability in supported platform like Intel is pmu_name, which exposes underlying CPU name known to the PMU driver. Example output in powerpc: grep . /sys/bus/event_source/devices/cpu/caps/* /sys/bus/event_source/devices/cpu/caps/pmu_name:POWER9 The "branch_counter_nr" in the supported platform exposes the maximum number of counters which can be shown in the u64 counters of PERF_SAMPLE_BRANCH_COUNTERS, while the "branch_counter_width" exposes the width of each counter. Both of them can be used by the perf tool to parse the logged counters in each branch.