| Message ID | 1453893665-20530-1-git-send-email-wangnan0@huawei.com |
|---|---|
| State | Superseded |
| Headers | show |
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 <wangnan0@huawei.com> > Cc: Arnaldo Carvalho de Melo <acme@redhat.com> > Cc: Jiri Olsa <jolsa@kernel.org> > Cc: Jérémie Galarneau <jeremie.galarneau@efficios.com> > Cc: Zefan Li <lizefan@huawei.com> > Cc: pi3orama@163.com > --- > 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); >
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);
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 <wangnan0@huawei.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Jérémie Galarneau <jeremie.galarneau@efficios.com> Cc: Zefan Li <lizefan@huawei.com> Cc: pi3orama@163.com --- tools/perf/util/data-convert-bt.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) -- 1.8.3.4