linux-kernel - Re: [PATCH 1/2] perf data: Show error message when ctf setup failed

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Date:	Mon, 13 Apr 2015 16:30:59 -0400
From:	Jérémie Galarneau 
	<jeremie.galarneau@...icios.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Alexandre Montplaisir <alexmonthy@...populi.im>,
	He Kuang <hekuang@...wei.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Jiri Olsa <jolsa@...nel.org>, acme@...nel.org,
	a.p.zijlstra@...llo.nl, mingo@...hat.com,
	Wang Nan <wangnan0@...wei.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] perf data: Show error message when ctf setup failed

On Fri, Apr 10, 2015 at 8:37 AM, Jiri Olsa <jolsa@...hat.com> wrote:
> On Fri, Apr 10, 2015 at 02:05:45PM +0200, Jiri Olsa wrote:
>
> SNIP
>
>> > >>I tested by using babeltrace binary and it works.
>> > >>
>> > >>After receiving your reply, I test on the latest tracecompass. A
>> > >>folder named 'ctf' is showed instead of the expected file
>> > >>'ctf-data', this folder only contains the raw metadata and
>> > >>perf-stream files but not analysed.
>> > >CC-ing Alexandre from tracecompass devel ^^^
>> >
>> > Hi,
>> >
>> > I just came back from vacation, sorry for not replying earlier!
>> >
>> > I managed to compile perf with CTF support, but by using Babeltrace's commit
>> > 5584a48. It fails to compile against current master, because of private
>> > headers getting exposed. I reported that to the BT maintainers.
>>
>> there's fix in babeltrace tree already
>>
>> >
>> > Then it seems there's another bug with Trace Compass's current master, trace
>> > validation cannot fail, and any file will get imported with no errors. We
>> > will look into this.
>> > But the root of the problem was that the converted CTF trace was not being
>> > recognized as valid. This is because some events define "stream_id = 0;",
>> > and others don't specify a stream_id at all. It seems quite random, see the
>> > full metadata here: http://pastebin.com/pACgV5JU
>> >
>> > Is there a reason why some events specify a stream_id and some don't?
>>
>> hum, that seems like a bug.. I'll check
>>
>
> ok, found the problem.. the "stream_id" event_class's attribute is created
> only when the instance of the event (not event_class) is created
>
> so you'll see the stream_id attribute only for events, that
> we actually got data for.. the rest is without, because
> their instance was never created
>
> seems to me like libbabeltrace bug, unless the application should
> take care about stream_id attribute.. but it's not the case for
> the rest of the 'internal' attributes.. Jeremie?

According to the spec, the stream_id attribute can be left unspecified
if only one stream is defined. However, is seems Babeltrace's CTF-Writer
will leave the stream_id out of the event's declaration even when
multiple streams are defined.

I'll submit a fix.

Thanks.
Jérémie

>
> anyway, I made a attached workaround and it all works nicely again,
> tracecompass is happy and shows the data properly
>
> I put all the pending ctf changes (plus the workaround) into:
>   git://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
>   perf/ctf branch
>
> jirka
>
>
> ---
> diff --git a/tools/perf/util/data-convert-bt.c b/tools/perf/util/data-convert-bt.c
> index 977cc3f98d8f..d7f03dcb1700 100644
> --- a/tools/perf/util/data-convert-bt.c
> +++ b/tools/perf/util/data-convert-bt.c
> @@ -803,6 +803,7 @@ static int add_generic_types(struct ctf_writer *cw, struct perf_evsel *evsel,
>  static int add_event(struct ctf_writer *cw, struct perf_evsel *evsel)
>  {
>         struct bt_ctf_event_class *event_class;
> +       struct bt_ctf_event *event;
>         struct evsel_priv *priv;
>         const char *name = perf_evsel__name(evsel);
>         int ret;
> @@ -833,6 +834,14 @@ static int add_event(struct ctf_writer *cw, struct perf_evsel *evsel)
>         if (!priv)
>                 goto err;
>
> +       event = bt_ctf_event_create(event_class);
> +       if (!event) {
> +               pr_err("Failed to create an CTF event\n");
> +               goto err;
> +       }
> +
> +       bt_ctf_event_put(event);
> +
>         priv->event_class = event_class;
>         evsel->priv       = priv;
>         return 0;



-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com
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