linux-kernel - Re: [PATCH] perf: arm-spe: Fix perf report --mem-mode

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Message-ID: <YlGiZRZlrBCmO+YG@kernel.org>
Date:   Sat, 9 Apr 2022 12:12:37 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Namhyung Kim <namhyung@...nel.org>,
        James Clark <james.clark@....com>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        leo.yan@...aro.com, German Gomez <German.Gomez@....com>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf: arm-spe: Fix perf report --mem-mode

Em Sat, Apr 09, 2022 at 05:59:41PM +0800, Leo Yan escreveu:
> On Fri, Apr 08, 2022 at 11:13:09AM -0700, Namhyung Kim wrote:
> > Hello,
> > 
> > On Fri, Apr 8, 2022 at 7:41 AM James Clark <james.clark@....com> wrote:
> > >
> > > Since commit bb30acae4c4d ("perf report: Bail out --mem-mode if mem info
> > > is not available") "perf mem report" and "perf report --mem-mode" don't
> > > allow opening the file unless one of the events has PERF_SAMPLE_DATA_SRC
> > > set.
> > >
> > > SPE doesn't have this set even though synthetic memory data is generated
> > > after it is decoded. Fix this issue by setting DATA_SRC on SPE events.
> > > This has no effect on the data collected because the SPE driver doesn't
> > > do anything with that flag and doesn't generate samples.
> > >
> > > Fixes: bb30acae4c4d ("perf report: Bail out --mem-mode if mem info is not available")
> > > Signed-off-by: James Clark <james.clark@....com>
> > 
> > Acked-by: Namhyung Kim <namhyung@...nel.org>
> 
> Tested-by: Leo Yan <leo.yan@...aro.org>
> 
> It's a bit awkward that after the commit bb30acae4c4d we cannot be
> backward compatible and any old perf data file will be failed to
> support by 'perf mem report' tool.

oh well, I think we should put in place a mechanism to run perf record
before some change, then make sure that a new perf is able to process
it after a rebuild.

If its something unsurmountable, then a proper explanation should be
done with a workaround to process those older files, even if pointing
out  to the perf version that is able to process the old file.

Anyway, applying this pa tch.

- ARnaldo