Re: [PATCH v9 1/7] perf pmu: "Compat" supports regular expression matching identifiers

[Ian Rogers]

On Mon, Sep 18, 2023 at 4:52 AM Jing Zhang <renyu.zj@xxxxxxxxxxxxxxxxx> wrote:
>
> The jevent "Compat" is used for uncore PMU alias or metric definitions.
>
> The same PMU driver has different PMU identifiers due to different
> hardware versions and types, but they may have some common PMU event.
> Since a Compat value can only match one identifier, when adding the
> same event alias to PMUs with different identifiers, each identifier
> needs to be defined once, which is not streamlined enough.
>
> So let "Compat" support using regular expression to match identifiers
> for uncore PMU alias. For example, if the "Compat" value is set to
> "43401|43c01", it would be able to match PMU identifiers such as "43401"
> or "43c01", which correspond to CMN600_r0p0 or CMN700_r0p0.
>
> Signed-off-by: Jing Zhang <renyu.zj@xxxxxxxxxxxxxxxxx>
> ---
>  tools/perf/util/pmu.c | 23 +++++++++++++++++++++--
>  tools/perf/util/pmu.h |  1 +
>  2 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index e215985..7e2242f 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -28,6 +28,7 @@
>  #include "strbuf.h"
>  #include "fncache.h"
>  #include "util/evsel_config.h"
> +#include <regex.h>
>
>  struct perf_pmu perf_pmu__fake = {
>         .name = "fake",
> @@ -875,6 +876,24 @@ static bool pmu_uncore_alias_match(const char *pmu_name, const char *name)
>         return res;
>  }
>
> +bool pmu_uncore_identifier_match(const char *compat, const char *id)
> +{
> +       regex_t re;
> +       regmatch_t pmatch[1];
> +       int match;
> +
> +       if (regcomp(&re, compat, REG_EXTENDED) != 0) {
> +               /* Warn unable to generate match particular string. */
> +               pr_info("Invalid regular expression %s\n", compat);
> +               return false;
> +       }
> +
> +       match = !regexec(&re, id, 1, pmatch, 0);

I wonder if we can make the regular expressions like
"^(434|436|43c|43a)" more like "(434|436|43c|43a).*", so that we fully
match the id string, by here doing:

if (match) {
  /* Ensure a full match. */
  match = pmatch[0].rm_so == 0 && pmatch[0].rm_eo == strlen(id);
}

I think longer term we can use jevents.py to generate a pmu-events.l,
which would have a contents something like:

(434|436|43c|43a).*  { return PMU_....;}

That should make the matching faster but may add some restrictions
onto the regular expression.

Thanks,
Ian

> +       regfree(&re);
> +
> +       return match;
> +}
> +
>  static int pmu_add_cpu_aliases_map_callback(const struct pmu_event *pe,
>                                         const struct pmu_events_table *table __maybe_unused,
>                                         void *vdata)
> @@ -915,8 +934,8 @@ static int pmu_add_sys_aliases_iter_fn(const struct pmu_event *pe,
>         if (!pe->compat || !pe->pmu)
>                 return 0;
>
> -       if (!strcmp(pmu->id, pe->compat) &&
> -           pmu_uncore_alias_match(pe->pmu, pmu->name)) {
> +       if (pmu_uncore_alias_match(pe->pmu, pmu->name) &&
> +                       pmu_uncore_identifier_match(pe->compat, pmu->id)) {
>                 perf_pmu__new_alias(pmu,
>                                 pe->name,
>                                 pe->desc,
> diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
> index bd5d804..fc155ce 100644
> --- a/tools/perf/util/pmu.h
> +++ b/tools/perf/util/pmu.h
> @@ -240,6 +240,7 @@ void pmu_add_cpu_aliases_table(struct perf_pmu *pmu,
>  char *perf_pmu__getcpuid(struct perf_pmu *pmu);
>  const struct pmu_events_table *pmu_events_table__find(void);
>  const struct pmu_metrics_table *pmu_metrics_table__find(void);
> +bool pmu_uncore_identifier_match(const char *compat, const char *id);
>
>  int perf_pmu__convert_scale(const char *scale, char **end, double *sval);
>
> --
> 1.8.3.1
>