[PATCH v2] perf cgroup: simplify arguments if track multiple events for a cgroup

[weiping zhang <zhangweiping@didichuxing.com>]

if use -G with one cgroup and -e with multiple events, only the first
event has correct cgroup setting, all events from the second will track
system-wide events.

if user want track multiple events for a specific cgroup, user must give
parameters like follow:
$ perf stat -e e1 -e e2 -e e3 -G test,test,test
this patch simplify this case, just type one cgroup, like following:
$ perf stat -e e1 -e e2 -e e3 -G test

$ mkdir -p /sys/fs/cgroup/perf_event/test
$ perf stat -e cycles -e cache-misses  -a -I 1000 -G test

before:
     1.001007226      <not counted>      cycles                    test
     1.001007226              7,506      cache-misses

after:
     1.000834097      <not counted>      cycles                    test
     1.000834097      <not counted>      cache-misses              test

Signed-off-by: weiping zhang <zhangweiping@didichuxing.com>
---
 tools/perf/Documentation/perf-record.txt |  3 ++-
 tools/perf/Documentation/perf-stat.txt   |  3 ++-
 tools/perf/util/cgroup.c                 | 17 ++++++++++++++++-
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 5a626ef..0fe9850 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -308,7 +308,8 @@ can be provided. Each cgroup is applied to the corresponding event, i.e., first
 to first event, second cgroup to second event and so on. It is possible to provide
 an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must have
 corresponding events, i.e., they always refer to events defined earlier on the command
-line.
+line. If user want track multiple events for a specific cgroup, user can use -e e1 -e e2
+-G foo,foo or just use -e e1 -e e2 -G foo.
 
 -b::
 --branch-any::
diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 823fce7..a234b3c 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -118,7 +118,8 @@ can be provided. Each cgroup is applied to the corresponding event, i.e., first
 to first event, second cgroup to second event and so on. It is possible to provide
 an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must have
 corresponding events, i.e., they always refer to events defined earlier on the command
-line.
+line. If user want track multiple events for a specific cgroup, user can use -e e1 -e e2
+-G foo,foo or just use -e e1 -e e2 -G foo.
 
 -o file::
 --output file::
diff --git a/tools/perf/util/cgroup.c b/tools/perf/util/cgroup.c
index d9ffc1e..38aaeb2 100644
--- a/tools/perf/util/cgroup.c
+++ b/tools/perf/util/cgroup.c
@@ -154,9 +154,11 @@ int parse_cgroups(const struct option *opt __maybe_unused, const char *str,
 		  int unset __maybe_unused)
 {
 	struct perf_evlist *evlist = *(struct perf_evlist **)opt->value;
+	struct perf_evsel *counter;
+	struct cgroup_sel *cgrp = NULL;
 	const char *p, *e, *eos = str + strlen(str);
 	char *s;
-	int ret;
+	int ret, i;
 
 	if (list_empty(&evlist->entries)) {
 		fprintf(stderr, "must define events before cgroups\n");
@@ -185,5 +187,18 @@ int parse_cgroups(const struct option *opt __maybe_unused, const char *str,
 			break;
 		str = p+1;
 	}
+	/* for the case one cgroup combine to multiple events */
+	i = 0;
+	if (nr_cgroups == 1) {
+		evlist__for_each_entry(evlist, counter) {
+			if (i == 0)
+				cgrp = counter->cgrp;
+			else {
+				counter->cgrp = cgrp;
+				refcount_inc(&cgrp->refcnt);
+			}
+			i++;
+		}
+	}
 	return 0;
 }
-- 
2.9.4