A new patch of libbabeltrace [1] reveals a object leak problem in
perf data CTF support: perf code never release event_class which is
allocated in add_event() and stored in evsel's private field.
If libbabeltrace has the above patch applied, leaking event_class
prevent writer being destroied and flushing metadata. For example:
$ ./perf record ls
Lowering default frequency rate to 500.
Please consider tweaking /proc/sys/kernel/perf_event_max_sample_rate.
perf.data
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.012 MB perf.data (12 samples) ]
$ ./perf data convert --to-ctf ./out.ctf
[ perf data convert: Converted 'perf.data' into CTF data './out.ctf' ]
[ perf data convert: Converted and wrote 0.000 MB (12 samples) ]
$ cat ./out.ctf/metadata
$ ls -l ./out.ctf/metadata
-rw-r----- 1 w00229757 mm 0 Jan 27 10:49 ./out.ctf/metadata
The correct result should be:
...
$ cat ./out.ctf/metadata
/* CTF 1.8 */
trace {
[SNIP]
$ ls -l ./out.ctf/metadata
-rw-r----- 1 w00229757 mm 2446 Jan 27 10:52 ./out.ctf/metadata
The full story is:
Patch [1] of babeltrace redesign reference counting scheme. In that
patch:
* writer <- trace (bt_ctf_writer_create)
* trace <- stream_class (bt_ctf_trace_add_stream_class)
* stream_class <- event_class (bt_ctf_stream_class_add_event_class)
('<-' means 'is a parent of')
Holding of event_class causes reference count of corresponding
'writer' increases through parent chain. Perf expect 'writer' is
released (so metadata is flushed) through bt_ctf_writer_put() in
ctf_writer__cleanup(). However, since it never release event_class,
the reference of 'writer' won't be reduced, so bt_ctf_writer_put()
won't lead releasing of writer.
Before this CTF patch, !(writer <- trace). Even event_class leak,
writer is able to be released.
[1]
https://github.com/efficios/babeltrace/commit/e6a8e8e4744633807083a077ff9f101eb97d9801
Signed-off-by: Wang Nan <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Jérémie Galarneau <[email protected]>
Cc: Zefan Li <[email protected]>
Cc: [email protected]
---
tools/perf/util/data-convert-bt.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/tools/perf/util/data-convert-bt.c
b/tools/perf/util/data-convert-bt.c
index 34cd1e4..b722e57 100644
--- a/tools/perf/util/data-convert-bt.c
+++ b/tools/perf/util/data-convert-bt.c
@@ -858,6 +858,23 @@ static int setup_events(struct ctf_writer *cw, struct
perf_session *session)
return 0;
}
+static void cleanup_events(struct perf_session *session)
+{
+ struct perf_evlist *evlist = session->evlist;
+ struct perf_evsel *evsel;
+
+ evlist__for_each(evlist, evsel) {
+ struct evsel_priv *priv;
+
+ priv = evsel->priv;
+ bt_ctf_event_class_put(priv->event_class);
+ zfree(&evsel->priv);
+ }
+
+ perf_evlist__delete(evlist);
+ session->evlist = NULL;
+}
+
static int setup_streams(struct ctf_writer *cw, struct perf_session *session)
{
struct ctf_stream **stream;
@@ -1171,6 +1188,7 @@ int bt_convert__perf2ctf(const char *input, const char
*path, bool force)
(double) c.events_size / 1024.0 / 1024.0,
c.events_count);
+ cleanup_events(session);
perf_session__delete(session);
ctf_writer__cleanup(cw);
--
1.8.3.4
