perf tools: Keep group information

Add a few of group-related field in struct perf_{evlist,evsel} so that
the group information in a evlist can be known easily.  It only counts
groups which have more than 1 members since leader-only groups are
treated as non-group events.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1358845787-1350-2-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index cbf4232..c9031eb 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -74,6 +74,7 @@
 	bool 			needs_swap;
 	/* parse modifier helper */
 	int			exclude_GH;
+	int			nr_members;
 	struct perf_evsel	*leader;
 	char			*group_name;
 };
@@ -259,4 +260,9 @@
 int perf_evsel__open_strerror(struct perf_evsel *evsel,
 			      struct perf_target *target,
 			      int err, char *msg, size_t size);
+
+static inline int perf_evsel__group_idx(struct perf_evsel *evsel)
+{
+	return evsel->idx - evsel->leader->idx;
+}
 #endif /* __PERF_EVSEL_H */