[PATCH RFC V2 2/5] perf/documentation: Add description for period

[kan.liang@intel.com]

From: Kan Liang <kan.liang@intel.com>

'period' param is not defined in
/sys/bus/event_sources/devices/<pmu>/format/*

Signed-off-by: Kan Liang <kan.liang@intel.com>
---
 tools/perf/Documentation/perf-record.txt | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 9b9d9d0..5b47b2c 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -45,6 +45,14 @@ OPTIONS
           param1 and param2 are defined as formats for the PMU in:
           /sys/bus/event_sources/devices/<pmu>/format/*
 
+	  There are also some params which are not defined in .../<pmu>/format/*.
+	  These params can be used to set event defaults.
+	  Here is a list of the params.
+	  - 'period': Set event sampling period
+
+	  Note: If user explicitly sets options which conflict with the params,
+	  the value set by the params will be overridden.
+
         - a hardware breakpoint event in the form of '\mem:addr[/len][:access]'
           where addr is the address in memory you want to break in.
           Access is the memory access type (read, write, execute) it can
-- 
1.8.3.1