diff options
| author | Kan Liang <kan.liang@linux.intel.com> | 2023-10-25 13:16:19 -0700 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2023-10-27 15:05:08 +0200 |
| commit | 571d91dcadfa3cef499010b4eddb9b58b0da4d24 (patch) | |
| tree | 1ae541b3ac838cf76949c40a9b41740a54d93740 /Documentation/ABI/testing/sysfs-bus-event_source-devices-caps | |
| parent | 744940f1921c8feb90e3c4bcc1e153fdd6e10fe2 (diff) | |
perf: Add branch stack counters
Currently, the additional information of a branch entry is stored in a
u64 space. With more and more information added, the space is running
out. For example, the information of occurrences of events will be added
for each branch.
Two places were suggested to append the counters.
https://lore.kernel.org/lkml/20230802215814.GH231007@hirez.programming.kicks-ass.net/
One place is right after the flags of each branch entry. It changes the
existing struct perf_branch_entry. The later ARCH specific
implementation has to be really careful to consistently pick
the right struct.
The other place is right after the entire struct perf_branch_stack.
The disadvantage is that the pointer of the extra space has to be
recorded. The common interface perf_sample_save_brstack() has to be
updated.
The latter is much straightforward, and should be easily understood and
maintained. It is implemented in the patch.
Add a new branch sample type, PERF_SAMPLE_BRANCH_COUNTERS, to indicate
the event which is recorded in the branch info.
The "u64 counters" may store the occurrences of several events. The
information regarding the number of events/counters and the width of
each counter should be exposed via sysfs as a reference for the perf
tool. Define the branch_counter_nr and branch_counter_width ABI here.
The support will be implemented later in the Intel-specific patch.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20231025201626.3000228-1-kan.liang@linux.intel.com
Diffstat (limited to 'Documentation/ABI/testing/sysfs-bus-event_source-devices-caps')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-event_source-devices-caps | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-event_source-devices-caps b/Documentation/ABI/testing/sysfs-bus-event_source-devices-caps index 8757dcf41c08..a5f506f7d481 100644 --- a/Documentation/ABI/testing/sysfs-bus-event_source-devices-caps +++ b/Documentation/ABI/testing/sysfs-bus-event_source-devices-caps @@ -16,3 +16,9 @@ Description: 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. |