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SubjectRe: [PATCH v7 2/2] perf cs-etm: Split --dump-raw-trace by AUX records
On Mon, Jun 28, 2021 at 08:08:02PM +0800, Leo Yan wrote:
> On Mon, Jun 28, 2021 at 11:38:34AM +0100, James Clark wrote:
>
> [...]
>
> > >> static int cs_etm__process_auxtrace_event(struct perf_session *session,
> > >> union perf_event *event,
> > >> struct perf_tool *tool __maybe_unused)
> > >> @@ -2462,7 +2478,8 @@ static int cs_etm__process_auxtrace_event(struct perf_session *session,
> > >> cs_etm__dump_event(etm, buffer);
> > >> auxtrace_buffer__put_data(buffer);
> > >> }
> > >> - }
> > >> + } else if (dump_trace)
> > >> + dump_queued_data(etm, &event->auxtrace);
> > >
> > > IIUC, in the function cs_etm__process_auxtrace_event(), since
> > > "etm->data_queued" is always true, below flow will never run:
> > >
> > > if (!etm->data_queued) {
> > > ......
> > >
> > > if (dump_trace)
> > > if (auxtrace_buffer__get_data(buffer, fd)) {
> > > cs_etm__dump_event(etm, buffer);
> > > auxtrace_buffer__put_data(buffer);
> > > }
> > > }
> > >
> > > If so, it's better to use a new patch to polish the code.
> > >
> >
> > Hi Leo,
> >
> > I think this is not true in piped mode because there is no auxtrace index.
> > In that mode, events are processed only in file order and cs_etm__process_auxtrace_event()
> > is called for each buffer.
> >
> > You can reproduce this with something like this:
> >
> > ./perf record -o - ls > stdio.data
> > cat stdio.data | ./perf report -i -
>
> You are right! I tried these two commands with cs_etm event, just as
> you said, in this case, the AUX trace data is not queued; so the flow
> for "if (!etm->data_queued)" should be kept. If so, I am very fine
> for current change. Thanks for sharing the knowledge.
>
> > There are some other Coresight features that don't work as expected in this mode, like
> > sorting timestamps between CPUs. The aux split patchset won't work either because random
> > access isn't possible. And the TRBE patch that I'm working on now won't work, because it
> > also requires the random access to lookup the flags on the AUX record to configure the
> > decoder for unformatted trace.
>

There is a lot of things happening in this area. Based on the above should I
still plan to review this set or should I wait for another revision?

Thanks,
Mathieu

> Cool, looking forward for the patches :)
>
> Leo

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