Re: [PATCH v2] perf report: Set PERF_SAMPLE_DATA_SRC bit for Arm SPE event

[Arnaldo Carvalho de Melo]

Em Thu, Apr 14, 2022 at 11:29:48AM +0100, James Clark escreveu:
> 
> 
> On 14/04/2022 02:27, Arnaldo Carvalho de Melo wrote:
> > Em Wed, Apr 13, 2022 at 05:23:17PM +0800, Leo Yan escreveu:
> >> 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 report result if the PERF_SAMPLE_DATA_SRC bit is missed in sample
> >> type.
> >>
> >> The commit ffab48705205 ("perf: arm-spe: Fix perf report --mem-mode")
> >> partially fixes the issue.  It adds PERF_SAMPLE_DATA_SRC bit for Arm SPE
> >> event, this allows the perf data file generated by kernel v5.18-rc1 or
> >> later version can be reported properly.
> >>
> >> On the other hand, perf tool still fails to be backward compatibility
> >> for a data file recorded by an older version's perf which contains Arm
> >> SPE trace data.  This patch is a workaround in reporting phase, when
> >> detects ARM SPE PMU event and without PERF_SAMPLE_DATA_SRC bit, it will
> >> force to set the bit in the sample type and give a warning info.
> >>
> >> Fixes: bb30acae4c4d ("perf report: Bail out --mem-mode if mem info is not available")
> >> Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
> >> Tested-by: German Gomez <german.gomez@xxxxxxx>
> >> ---
> >> v2: Change event name from "arm_spe_" to "arm_spe";
> >>     Add German's test tag.
> > 
> > Tentatively applied, would be great to have James' and Ravi's
> > Acked-by/Reviewed-by, which I'll add before pushing this out if provided
> > in time.
> > 
> > - Arnaldo
> >  
> >>  tools/perf/builtin-report.c | 16 ++++++++++++++++
> >>  1 file changed, 16 insertions(+)
> >>
> >> diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
> >> index 1ad75c7ba074..acb07a4a9b67 100644
> >> --- a/tools/perf/builtin-report.c
> >> +++ b/tools/perf/builtin-report.c
> >> @@ -353,6 +353,7 @@ static int report__setup_sample_type(struct report *rep)
> >>  	struct perf_session *session = rep->session;
> >>  	u64 sample_type = evlist__combined_sample_type(session->evlist);
> >>  	bool is_pipe = perf_data__is_pipe(session->data);
> >> +	struct evsel *evsel;
> >>  
> >>  	if (session->itrace_synth_opts->callchain ||
> >>  	    session->itrace_synth_opts->add_callchain ||
> >> @@ -407,6 +408,21 @@ static int report__setup_sample_type(struct report *rep)
> >>  	}
> >>  
> >>  	if (sort__mode == SORT_MODE__MEMORY) {
> >> +		/*
> >> +		 * FIXUP: prior to kernel 5.18, Arm SPE missed to set
> >> +		 * PERF_SAMPLE_DATA_SRC bit in sample type.  For backward
> >> +		 * compatibility, set the bit if it's an old perf data file.
> >> +		 */
> >> +		evlist__for_each_entry(session->evlist, evsel) {
> >> +			if (strstr(evsel->name, "arm_spe") &&
> >> +				!(sample_type & PERF_SAMPLE_DATA_SRC)) {
> >> +				ui__warning("PERF_SAMPLE_DATA_SRC bit is not set "
> >> +					    "for Arm SPE event.\n");
> 
> Looks ok to me. Personally I would remove the warning, otherwise people are going to start
> thinking that they need to do something about it or something bad has happened.
> 
> But because we've fixed it up there shouldn't really need to be a warning or any action.
> 
> I don't feel too strongly about this though, so I will leave it up to Leo to make the
> final decision:
> 
> Reviewed-by: James Clark <james.clark@xxxxxxx>

Thanks, collecting your review,

- Arnaldo