Hi Jiri, What's your opinion on this patch? Thank you.
On 2016/1/27 19:21, Wang Nan wrote:
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 | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/tools/perf/util/data-convert-bt.c b/tools/perf/util/data-convert-bt.c index 34cd1e4..e553321 100644 --- a/tools/perf/util/data-convert-bt.c +++ b/tools/perf/util/data-convert-bt.c @@ -858,6 +858,19 @@ 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); + } +} + static int setup_streams(struct ctf_writer *cw, struct perf_session *session) { struct ctf_stream **stream; @@ -1171,6 +1184,7 @@ 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);
