linux-kernel - Re: [PATCH] perf cs-etm: Delay decode of non-timeless data until cs_etm__flush

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Date:   Thu, 1 Jul 2021 15:33:15 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     James Clark <james.clark@....com>,
        Coresight ML <coresight@...ts.linaro.org>,
        Leo Yan <leo.yan@...aro.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>,
        Mike Leach <mike.leach@...aro.org>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.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] perf cs-etm: Delay decode of non-timeless data until cs_etm__flush_events()

On Thu, 1 Jul 2021 at 11:15, Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
>
> Em Mon, Jun 14, 2021 at 09:54:42AM -0600, Mathieu Poirier escreveu:
> > On Wed, Jun 09, 2021 at 04:04:20PM +0300, James Clark wrote:
> > > Currently, timeless mode starts the decode on PERF_RECORD_EXIT, and
> > > non-timeless mode starts decoding on the fist PERF_RECORD_AUX record.
> > >
> > > This can cause the "data has no samples!" error if the first
> > > PERF_RECORD_AUX record comes before the first (or any relevant)
> > > PERF_RECORD_MMAP2 record because the mmaps are required by the decoder
> > > to access the binary data.
> > >
> > > This change pushes the start of non-timeless decoding to the very end of
> > > parsing the file. The PERF_RECORD_EXIT event can't be used because it
> > > might not exist in system-wide or snapshot modes.
>
> <SNIP>
>
> > This looks good to me but I'd like to have other people testing it.
>
> So Leo reviewed and tested this, I'm taking your "looks good to me" as
> an Acked-by, as per Documentation/process/submitting-patches.rst.
>

Yes, please.  My goal here was to wait for other people to test this
code, which Leo did.

> - Arnaldo
>
> > Thanks,
> > Mathieu