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

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Leo Yan <leo.yan@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>,
	James Clark <james.clark@arm.com>,
	linux-perf-users <linux-perf-users@vger.kernel.org>,
	leo.yan@linaro.com, German Gomez <German.Gomez@arm.com>,
	John Garry <john.garry@huawei.com>, Will Deacon <will@kernel.org>,
	Mathieu Poirier <mathieu.poirier@linaro.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>,
	Arnaldo Carvalho de Melo <acme@redhat.com>,
	Ravi Bangoria <ravi.bangoria@linux.ibm.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] perf: arm-spe: Fix perf report --mem-mode
Date: Sat, 9 Apr 2022 12:12:37 -0300	[thread overview]
Message-ID: <YlGiZRZlrBCmO+YG@kernel.org> (raw)
In-Reply-To: <20220409095941.GA1000846@leoy-ThinkPad-X240s>

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@arm.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@arm.com>
> > 
> > Acked-by: Namhyung Kim <namhyung@kernel.org>
> 
> Tested-by: Leo Yan <leo.yan@linaro.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