Re: [PATCH v5 10/15] perf jevents: Generate metrics and events as separate tables

John Garry
2023-01-30T16:08:07Z

On 26/01/2023 23:36, Ian Rogers wrote:
> @@ -660,7 +763,29 @@ 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)
> {
> - return (struct pmu_metrics_table *)perf_pmu__find_events_table(pmu);
> + const struct pmu_metrics_table *table = NULL;
> + char *cpuid = perf_pmu__getcpuid(pmu);
> + int 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->metric_table;
> + break;
> + }
> + }
> + free(cpuid);
> + return table;
> }

This is almost identical to generated perf_pmu__find_events_table(),
except we return a pmu_metrics_table * (instead of a pmu_events_table *)
and also return the metric table member (instead of event table). But
the definitions are:

/* Struct used to make the PMU event table implementation opaque to
callers. */
struct pmu_events_table {
const struct compact_pmu_event *entries;
size_t length;
};

/* Struct used to make the PMU metric table implementation opaque to
callers. */
struct pmu_metrics_table {
const struct compact_pmu_event *entries;
size_t length;
};

Those structs are defined to be the same thing, so I am failing to see
the point in a) separate structure types b) why so much duplication

As for b), I know that they are generated and the python code may be
simpler this way (is it?), but still...

Thanks,
John