On Thu, Jan 28, 2016 at 01:20:28PM +0000, 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 <wangn...@huawei.com>
> Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
> Cc: Jiri Olsa <jo...@kernel.org>
> Cc: Jérémie Galarneau <jeremie.galarn...@efficios.com>
> Cc: Zefan Li <lize...@huawei.com>
> Cc: pi3or...@163.com
> ---
>
> v1 -> v2: Free evsel->priv, destroy evlist
> (even 'perf report' doesn't destroy evlist created by
> perf_session__open)
Acked-by: Jiri Olsa <jo...@kernel.org>
Arnaldo,
we're missing perf_evlist__delete in report command
I remember there were several cleanups skipped intentionaly,
but I dont think this one is the case.. also report TUI provides
the 's' key to load new data file.. which makes this leak
important
however even with this patch I can see perf report getting
more memory every time it reloads the data.. either there's
something else, or I'm looking at it wrong ;-)
thanks,
jirka
---
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 2bf537f190a0..7a4a27a6f053 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -970,12 +970,14 @@ repeat:
ret = __cmd_report(&report);
if (ret == K_SWITCH_INPUT_DATA) {
+ perf_evlist__delete(session->evlist);
perf_session__delete(session);
goto repeat;
} else
ret = 0;
error:
+ perf_evlist__delete(session->evlist);
perf_session__delete(session);
return ret;
}
