[tip:perf/core] perf report: Document +field style argument support for --field option

[tip-bot for Changbin Du]

Commit-ID:  d35fa1e75fdb308ae8a1a3efffe7ddedbd6051e2
Gitweb:     http://git.kernel.org/tip/d35fa1e75fdb308ae8a1a3efffe7ddedbd6051e2
Author:     Changbin Du <changbin.du@xxxxxxxxx>
AuthorDate: Mon, 13 Mar 2017 16:32:52 +0800
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Mon, 13 Mar 2017 11:44:44 -0300

perf report: Document +field style argument support for --field option

Commit 2f3f9bcf000b ("perf tools: Add +field argument support for
--field option") by Jiri Olsa <jolsa@xxxxxxxxxx> introduced +field style
argument support for --field option.

This is useful but not updated documentation.  This add a little
description there.

Signed-off-by: Changbin Du <changbin.du@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20170313083252.23644-1-changbin.du@xxxxxxxxx
[ Slightly improved the phrase structure ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/Documentation/perf-report.txt | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/perf/Documentation/perf-report.txt b/tools/perf/Documentation/perf-report.txt
index 33f9190..672b149a 100644
--- a/tools/perf/Documentation/perf-report.txt
+++ b/tools/perf/Documentation/perf-report.txt
@@ -173,6 +173,9 @@ OPTIONS
 	By default, every sort keys not specified in -F will be appended
 	automatically.
 
+	If the keys starts with a prefix '+', then it will append the specified
+        field(s) to the default field order. For example: perf report -F +period,sample.
+
 -p::
 --parent=<regex>::
         A regex filter to identify parent. The parent is a caller of this