perf record: Document --group option

The 'perf record --group' option lacks documentation and confuses users.
As -e/--event option already supports group spec, it should not be used
anymore.

Also add a short description of event group itself.

Reported-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1425266013-5034-1-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 4d668945dfe6..355c4f5569b5 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -55,6 +55,11 @@ OPTIONS
           If you want to profile write accesses in [0x1000~1008), just set
           'mem:0x1000/8:w'.
 
+        - a group of events surrounded by a pair of brace ("{event1,event2,...}").
+          Each event is separated by commas and the group should be quoted to
+          prevent the shell interpretation.  You also need to use --group on
+          "perf report" to view group events together.
+
 --filter=<filter>::
         Event filter.
 
@@ -104,6 +109,10 @@ OPTIONS
         specification with appended unit character - B/K/M/G. The
         size is rounded up to have nearest pages power of two value.
 
+--group::
+        Put all events in a single event group.  This precedes the --event
+        option and remains only for backward compatibility.  See --event.
+
 -g::
         Enables call-graph (stack chain/backtrace) recording.