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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 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.

Cool, looking forward for the patches :)

Leo

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