Re: [PATCH v1 17/40] perf evsel: Modify group pmu name for software events

["Liang, Kan" <kan.liang@linux.intel.com>]

On 2023-04-26 3:00 a.m., Ian Rogers wrote:
> If we have a group of {cycles,faults} then we need the faults software
> event to appear to be on the same PMU as cycles so that we don't split
> the group in parse_events__sort_events_and_fix_groups. This case is
> relatively easy as cycles is the leader and will have a PMU name. In
> the reverse case, {faults,cycles} we still need faults to appear to
> have the PMU name of cycles but the old behavior is just to return
> "cpu". For hybrid this fails as cycles will be on "cpu_core" or
> "cpu_atom", causing faults to be split into a different group.
> 
> Change the behavior for software events so that the whole group is
> searched for the named PMU.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>

Thanks,
Kan

> ---
>  tools/perf/util/evsel.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 1cd04b5998d2..63522322e118 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -829,23 +829,26 @@ bool evsel__name_is(struct evsel *evsel, const char *name)
>  
>  const char *evsel__group_pmu_name(const struct evsel *evsel)
>  {
> -	const struct evsel *leader;
> +	struct evsel *leader, *pos;
>  
>  	/* If the pmu_name is set use it. pmu_name isn't set for CPU and software events. */
>  	if (evsel->pmu_name)
>  		return evsel->pmu_name;
>  	/*
>  	 * Software events may be in a group with other uncore PMU events. Use
> -	 * the pmu_name of the group leader to avoid breaking the software event
> -	 * out of the group.
> +	 * the pmu_name of the first non-software event to avoid breaking the
> +	 * software event out of the group.
>  	 *
>  	 * Aux event leaders, like intel_pt, expect a group with events from
>  	 * other PMUs, so substitute the AUX event's PMU in this case.
>  	 */
>  	leader  = evsel__leader(evsel);
> -	if ((evsel->core.attr.type == PERF_TYPE_SOFTWARE || evsel__is_aux_event(leader)) &&
> -	    leader->pmu_name) {
> -		return leader->pmu_name;
> +	if (evsel->core.attr.type == PERF_TYPE_SOFTWARE || evsel__is_aux_event(leader)) {
> +		/* Starting with the leader, find the first event with a named PMU. */
> +		for_each_group_evsel(pos, leader) {
> +			if (pos->pmu_name)
> +				return pos->pmu_name;
> +		}
>  	}
>  
>  	return "cpu";