perf Document: Sysfs event names must be lower or upper case

To avoid directory scans in perf it is going to be assumed that sysfs
event names are either lower or upper case.

Reviewed-by: Kan Liang <[email protected]>
Signed-off-by: Ian Rogers <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Bjorn Helgaas <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jing Zhang <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Ravi Bangoria <[email protected]>
Cc: Thomas Richter <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-event_source-devices-events b/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
index 77de58d03822..e7efeab2ee83 100644
--- a/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
+++ b/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
@@ -37,6 +37,12 @@ Description:	Per-pmu performance monitoring events specific to the running syste
 		performance monitoring event supported by the <pmu>. The name
 		of the file is the name of the event.
 
+		As performance monitoring event names are case
+		insensitive in the perf tool, the perf tool only looks
+		for lower or upper case event names in sysfs to avoid
+		scanning the directory. It is therefore required the
+		name of the event here is either lower or upper case.
+
 		File contents:
 
 			<term>[=<value>][,<term>[=<value>]]...