1 What: /sys/bus/event_source/devices/ 1 What: /sys/bus/event_source/devices/<dev>/caps
2 Date: May 2022 2 Date: May 2022
3 KernelVersion: 5.19 3 KernelVersion: 5.19
4 Contact: Linux kernel mailing list <linu 4 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
5 Description: 5 Description:
6 Attribute group to describe th 6 Attribute group to describe the capabilities exposed
7 for a particular pmu. Each att 7 for a particular pmu. Each attribute of this group can
8 expose information specific to 8 expose information specific to a PMU, say pmu_name, so that
9 userspace can understand some 9 userspace can understand some of the feature which the
10 platform specific PMU supports 10 platform specific PMU supports.
11 11
12 One of the example available c 12 One of the example available capability in supported platform
13 like Intel is pmu_name, which 13 like Intel is pmu_name, which exposes underlying CPU name known
14 to the PMU driver. 14 to the PMU driver.
15 15
16 Example output in powerpc: 16 Example output in powerpc:
17 grep . /sys/bus/event_source/d 17 grep . /sys/bus/event_source/devices/cpu/caps/*
18 /sys/bus/event_source/devices/ 18 /sys/bus/event_source/devices/cpu/caps/pmu_name:POWER9
19 19
20 The "branch_counter_nr" in the 20 The "branch_counter_nr" in the supported platform exposes the
21 maximum number of counters whi 21 maximum number of counters which can be shown in the u64 counters
22 of PERF_SAMPLE_BRANCH_COUNTERS 22 of PERF_SAMPLE_BRANCH_COUNTERS, while the "branch_counter_width"
23 exposes the width of each coun 23 exposes the width of each counter. Both of them can be used by
24 the perf tool to parse the log 24 the perf tool to parse the logged counters in each branch.
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