Re: [PATCH v1 6/7] perf pmu-events: Remember the events and metrics table

[Adrian Hunter <adrian.hunter@intel.com>]

On 7/10/23 05:13, Ian Rogers wrote:
> strcmp_cpuid_str performs regular expression comparisons. Avoid
> repeated computation of the table by remembering the table in a
> static.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/pmu-events/jevents.py | 48 +++++++++++++++++++-------------
>  1 file changed, 28 insertions(+), 20 deletions(-)
> 
> diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py
> index fd009752b427..8d8d5088c53c 100755
> --- a/tools/perf/pmu-events/jevents.py
> +++ b/tools/perf/pmu-events/jevents.py
> @@ -978,28 +978,32 @@ int pmu_metrics_table__for_each_metric(const struct pmu_metrics_table *table,
>  
>  const struct pmu_events_table *perf_pmu__find_events_table(struct perf_pmu *pmu)
>  {
> -        const struct pmu_events_table *table = NULL;
> -        char *cpuid = perf_pmu__getcpuid(pmu);
> +        static const struct pmu_events_table *table;
>          size_t i;
>  
> -        /* on some platforms which uses cpus map, cpuid can be NULL for
> -         * PMUs other than CORE PMUs.
> -         */
> -        if (!cpuid)
> -                return NULL;
> -
> -        i = 0;
> -        for (;;) {
> -                const struct pmu_events_map *map = &pmu_events_map[i++];
> -                if (!map->arch)
> -                        break;
> -
> -                if (!strcmp_cpuid_str(map->cpuid, cpuid)) {
> -                        table = &map->event_table;
> -                        break;
> +        if (!table) {
> +                char *cpuid = perf_pmu__getcpuid(pmu);

Seems to assume the function is never called with a pmu
that would give a different result for perf_pmu__getcpuid(pmu)

> +
> +                /*
> +                 * On some platforms which uses cpus map, cpuid can be NULL for
> +                 * PMUs other than CORE PMUs.
> +                 */
> +                if (!cpuid)
> +                        return NULL;
> +
> +                i = 0;
> +                for (;;) {
> +                        const struct pmu_events_map *map = &pmu_events_map[i++];
> +                        if (!map->arch)
> +                                break;
> +
> +                        if (!strcmp_cpuid_str(map->cpuid, cpuid)) {
> +                                table = &map->event_table;
> +                                break;
> +                        }
>                  }
> +                free(cpuid);
>          }
> -        free(cpuid);
>          if (!pmu)
>                  return table;
>  
> @@ -1015,13 +1019,17 @@ const struct pmu_events_table *perf_pmu__find_events_table(struct perf_pmu *pmu)
>  
>  const struct pmu_metrics_table *perf_pmu__find_metrics_table(struct perf_pmu *pmu)
>  {
> -        const struct pmu_metrics_table *table = NULL;
> -        char *cpuid = perf_pmu__getcpuid(pmu);
> +        static const struct pmu_metrics_table *table;
> +        char *cpuid;
>          int i;
>  
> +        if (table)
> +                return table;

Ditto

> +
>          /* on some platforms which uses cpus map, cpuid can be NULL for
>           * PMUs other than CORE PMUs.
>           */
> +        cpuid = perf_pmu__getcpuid(pmu);
>          if (!cpuid)
>                  return NULL;
>