linux-kernel - Re: [PATCH v7 2/2] perf cs-etm: Split --dump-raw-trace by AUX records

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Date:   Tue, 29 Jun 2021 13:08:09 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     James Clark <james.clark@....com>
Cc:     Leo Yan <leo.yan@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Coresight ML <coresight@...ts.linaro.org>,
        Al Grant <al.grant@....com>,
        Branislav Rankov <branislav.rankov@....com>,
        Denis Nikitin <denik@...omium.org>,
        "Suzuki K. Poulose" <suzuki.poulose@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mike Leach <mike.leach@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-perf-users@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 2/2] perf cs-etm: Split --dump-raw-trace by AUX records

On Tue, 29 Jun 2021 at 02:52, James Clark <james.clark@....com> wrote:
>
>
>
> On 28/06/2021 21:01, Mathieu Poirier wrote:
> > 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?
>
> From my point of view, this one is final. It looks like both Leo and I have tested
> it with and without his snapshot changes and it's working as expected in both cases.
>

Very well - I will start working on it once I'm through with the
ultrasoc patchset.

> Thanks
> James
>
> >
> > Thanks,
> > Mathieu
> >
> >> Cool, looking forward for the patches :)
> >>
> >> Leo