linux-kernel - Re: [PATCH 4/4] perf mem amd: Scan all PMUs instead of just core ones

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Message-ID: <CAP-5=fVm4_BhZTx2OpR+FYo4GD3ZTFiiY1NR_4_XnDX6XHuhLQ@mail.gmail.com>
Date:   Tue, 13 Jun 2023 08:34:35 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Ravi Bangoria <ravi.bangoria@....com>
Cc:     acme@...nel.org, jolsa@...nel.org, namhyung@...nel.org,
        mark.rutland@....com, peterz@...radead.org,
        adrian.hunter@...el.com, kan.liang@...ux.intel.com,
        james.clark@....com, alisaidi@...zon.com, leo.yan@...aro.org,
        maddy@...ux.ibm.com, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org, sandipan.das@....com,
        ananth.narayan@....com, santosh.shukla@....com
Subject: Re: [PATCH 4/4] perf mem amd: Scan all PMUs instead of just core ones

On Tue, Jun 13, 2023 at 2:56 AM Ravi Bangoria <ravi.bangoria@....com> wrote:
>
> Scanning only core PMUs is not sufficient on AMD since perf mem on
> AMD uses IBS OP PMU, which is independent of core PMU.
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
> ---
>  tools/perf/arch/x86/util/mem-events.c |  5 +++++
>  tools/perf/util/mem-events.c          | 16 ++++++++++++----
>  tools/perf/util/mem-events.h          |  1 +
>  3 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/arch/x86/util/mem-events.c b/tools/perf/arch/x86/util/mem-events.c
> index a8a782bcb121..43af872e89a6 100644
> --- a/tools/perf/arch/x86/util/mem-events.c
> +++ b/tools/perf/arch/x86/util/mem-events.c
> @@ -91,3 +91,8 @@ char *perf_mem_events__name(int i, char *pmu_name)
>
>         return (char *)e->name;
>  }
> +
> +bool perf_mem_events__via_core_pmus(void)
> +{
> +       return !x86__is_amd_cpu();
> +}
> diff --git a/tools/perf/util/mem-events.c b/tools/perf/util/mem-events.c
> index be15aadb6b14..0c04f883d634 100644
> --- a/tools/perf/util/mem-events.c
> +++ b/tools/perf/util/mem-events.c
> @@ -109,6 +109,14 @@ static bool perf_mem_event__supported(const char *mnt, char *sysfs_name)
>         return !stat(path, &st);
>  }
>
> +bool __weak perf_mem_events__via_core_pmus(void)
> +{
> +       return true;
> +}
> +
> +#define perf_mem_scan_next_pmu(pmu) \
> +       (perf_mem_events__via_core_pmus() ? perf_pmus__scan_core(pmu) : perf_pmus__scan(pmu))
> +
>  int perf_mem_events__init(void)
>  {
>         const char *mnt = sysfs__mount();
> @@ -130,7 +138,7 @@ int perf_mem_events__init(void)
>                 if (!e->tag)
>                         continue;
>
> -               while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
> +               while ((pmu = perf_mem_scan_next_pmu(pmu)) != NULL) {
>                         scnprintf(sysfs_name, sizeof(sysfs_name), e->sysfs_name, pmu->name);
>                         e->supported |= perf_mem_event__supported(mnt, sysfs_name);
>                 }
> @@ -165,7 +173,7 @@ static void perf_mem_events__print_unsupport_hybrid(struct perf_mem_event *e,
>         char sysfs_name[100];
>         struct perf_pmu *pmu = NULL;
>
> -       while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
> +       while ((pmu = perf_mem_scan_next_pmu(pmu)) != NULL) {

It was my mistake to optimize this, I think we can just go back to:
perf_pmus__scan(pmu)
which would remove a lot of the weak/macros etc. here. We can have a
comment as to why this is scan not scan_core, because of AMD. I plan
to further improve overhead of PMUs so I'm not worried about losing
the small performance win from this.

Thanks,
Ian

>                 scnprintf(sysfs_name, sizeof(sysfs_name), e->sysfs_name,
>                           pmu->name);
>                 if (!perf_mem_event__supported(mnt, sysfs_name)) {
> @@ -188,7 +196,7 @@ int perf_mem_events__record_args(const char **rec_argv, int *argv_nr,
>                 if (!e->record)
>                         continue;
>
> -               if (perf_pmus__num_core_pmus() == 1) {
> +               if (perf_pmus__num_mem_pmus() == 1) {
>                         if (!e->supported) {
>                                 pr_err("failed: event '%s' not supported\n",
>                                        perf_mem_events__name(j, NULL));
> @@ -203,7 +211,7 @@ int perf_mem_events__record_args(const char **rec_argv, int *argv_nr,
>                                 return -1;
>                         }
>
> -                       while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
> +                       while ((pmu = perf_mem_scan_next_pmu(pmu)) != NULL) {
>                                 rec_argv[i++] = "-e";
>                                 s = perf_mem_events__name(j, pmu->name);
>                                 if (s) {
> diff --git a/tools/perf/util/mem-events.h b/tools/perf/util/mem-events.h
> index 12372309d60e..d650eb311113 100644
> --- a/tools/perf/util/mem-events.h
> +++ b/tools/perf/util/mem-events.h
> @@ -36,6 +36,7 @@ enum {
>  extern unsigned int perf_mem_events__loads_ldlat;
>
>  int perf_mem_events__parse(const char *str);
> +bool perf_mem_events__via_core_pmus(void);
>  int perf_mem_events__init(void);
>
>  char *perf_mem_events__name(int i, char *pmu_name);
> --
> 2.40.1
>