linux-kernel - Re: [PATCH v1 2/2] perf metricgroup: Don't early exit if no CPUID table exists

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Message-ID: <20260206104543.GE3529712@e132581.arm.com>
Date: Fri, 6 Feb 2026 10:45:43 +0000
From: Leo Yan <leo.yan@....com>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	James Clark <james.clark@...aro.org>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] perf metricgroup: Don't early exit if no CPUID
 table exists

On Thu, Feb 05, 2026 at 10:36:03AM -0800, Ian Rogers wrote:
> The failure to find a table of metrics with a CPUID shouldn't early
> exit as the metric code will now also consider the default table.
> When searching for a metric or metric group,
> pmu_metrics_table__for_each_metric considers all tables and so the
> caller doesn't need to switch the table to do this.
> 
> Fixes: c7adeb0974f1 ("perf jevents: Add set of common metrics based on default ones")
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/metricgroup.c | 18 +++++-------------
>  1 file changed, 5 insertions(+), 13 deletions(-)
> 
> diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> index 40a1e14de418..46bf4dfeebc8 100644
> --- a/tools/perf/util/metricgroup.c
> +++ b/tools/perf/util/metricgroup.c
> @@ -1562,8 +1562,6 @@ int metricgroup__parse_groups(struct evlist *perf_evlist,
>  {
>  	const struct pmu_metrics_table *table = pmu_metrics_table__find();
>  
> -	if (!table)
> -		return -EINVAL;
>  	if (hardware_aware_grouping)
>  		pr_debug("Use hardware aware grouping instead of traditional metric grouping method\n");
>  
> @@ -1601,22 +1599,16 @@ static int metricgroup__has_metric_or_groups_callback(const struct pmu_metric *p
>  
>  bool metricgroup__has_metric_or_groups(const char *pmu, const char *metric_or_groups)
>  {
> -	const struct pmu_metrics_table *tables[2] = {
> -		pmu_metrics_table__find(),
> -		pmu_metrics_table__default(),
> -	};
> +	const struct pmu_metrics_table *table = pmu_metrics_table__find();

Here should be:

  const struct pmu_metrics_table *table = pmu_metrics_table__default();

With this change, the default metrics can work on my side:

 Performance counter stats for 'sleep 1':

                 1      context-switches                 #    434.8 cs/sec  cs_per_second     
                 0      cpu-migrations                   #      0.0 migrations/sec  migrations_per_second
                70      page-faults                      #  30439.1 faults/sec  page_faults_per_second
              2.30 msec task-clock                       #      0.0 CPUs  CPUs_utilized       
             17398      armv8_pmuv3_0/branch-misses/     #      4.3 %  branch_miss_rate       
            401746      armv8_pmuv3_0/branches/          #    174.7 M/sec  branch_frequency   
           1778245      armv8_pmuv3_0/cpu-cycles/        #      0.8 GHz  cycles_frequency     
           2341698      armv8_pmuv3_0/instructions/      #      1.3 instructions  insn_per_cycle
            680491      armv8_pmuv3_0/stalled-cycles-frontend/ #     0.38 frontend_cycles_idle      
            380360      armv8_pmuv3_0/stalled-cycles-backend/ #     0.21 backend_cycles_idle       
            380360      armv8_pmuv3_0/stalled-cycles-backend/ #     0.29 stalled_cycles_per_instruction

With above change:

Tested-by: Leo Yan <leo.yan@....com>


>  	struct metricgroup__has_metric_data data = {
>  		.pmu = pmu,
>  		.metric_or_groups = metric_or_groups,
>  	};
>  
> -	for (size_t i = 0; i < ARRAY_SIZE(tables); i++) {
> -		if (pmu_metrics_table__for_each_metric(tables[i],
> -							metricgroup__has_metric_or_groups_callback,
> -							&data))
> -			return true;
> -	}
> -	return false;
> +	return pmu_metrics_table__for_each_metric(table,
> +						  metricgroup__has_metric_or_groups_callback,
> +						  &data)
> +		? true : false;
>  }
>  
>  static int metricgroup__topdown_max_level_callback(const struct pmu_metric *pm,
> -- 
> 2.53.0.rc2.204.g2597b5adb4-goog
> 
>