Re: [PATCH 2/2] perf parse-events: Remove "not supported" hybrid cache events

[Ian Rogers <irogers@google.com>]

On Wed, Sep 21, 2022 at 6:47 PM <zhengjun.xing@linux.intel.com> wrote:
>
> From: Zhengjun Xing <zhengjun.xing@linux.intel.com>
>
> By default, we create two hybrid cache events, one is for cpu_core, and
> another is for cpu_atom. But Some hybrid hardware cache events are only
> available on one CPU PMU. For example, the 'L1-dcache-load-misses' is only
> available on cpu_core, while the 'L1-icache-loads' is only available on
> cpu_atom. We need to remove "not supported" hybrid cache events. By
> extending is_event_supported() to global API and using it to check if the
> hybrid cache events are supported before being created, we can remove the
> "not supported" hybrid cache events.
>
> Before:
>
>  # ./perf stat -e L1-dcache-load-misses,L1-icache-loads -a sleep 1
>
>  Performance counter stats for 'system wide':
>
>             52,570      cpu_core/L1-dcache-load-misses/
>    <not supported>      cpu_atom/L1-dcache-load-misses/
>    <not supported>      cpu_core/L1-icache-loads/
>          1,471,817      cpu_atom/L1-icache-loads/
>
>        1.004915229 seconds time elapsed
>
> After:
>
>  # ./perf stat -e L1-dcache-load-misses,L1-icache-loads -a sleep 1
>
>  Performance counter stats for 'system wide':
>
>             54,510      cpu_core/L1-dcache-load-misses/
>          1,441,286      cpu_atom/L1-icache-loads/
>
>        1.005114281 seconds time elapsed
>
> Fixes: 30def61f64ba ("perf parse-events: Create two hybrid cache events")
> Signed-off-by: Zhengjun Xing <zhengjun.xing@linux.intel.com>
> Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
> ---
>  tools/perf/util/parse-events-hybrid.c | 8 +++++++-
>  tools/perf/util/print-events.c        | 2 +-
>  tools/perf/util/print-events.h        | 3 ++-
>  3 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/util/parse-events-hybrid.c b/tools/perf/util/parse-events-hybrid.c
> index 284f8eabd3b9..cf2e1c2e968f 100644
> --- a/tools/perf/util/parse-events-hybrid.c
> +++ b/tools/perf/util/parse-events-hybrid.c
> @@ -14,6 +14,7 @@
>  #include "pmu.h"
>  #include "pmu-hybrid.h"
>  #include "perf.h"
> +#include "print-events.h"
>
>  static void config_hybrid_attr(struct perf_event_attr *attr,
>                                int type, int pmu_type)
> @@ -48,13 +49,18 @@ static int create_event_hybrid(__u32 config_type, int *idx,
>         __u64 config = attr->config;
>
>         config_hybrid_attr(attr, config_type, pmu->type);
> +
> +       if (attr->type == PERF_TYPE_HW_CACHE
> +           && !is_event_supported(attr->type, attr->config))
> +               goto out;

A comment to explain this would be useful.

> +
>         evsel = parse_events__add_event_hybrid(list, idx, attr, name, metric_id,
>                                                pmu, config_terms);
>         if (evsel)
>                 evsel->pmu_name = strdup(pmu->name);
>         else
>                 return -ENOMEM;

For consistency should this use the "goto" pattern now? You can also
handle the ENOMEM case for strdup.

> -
> +out:
>         attr->type = type;
>         attr->config = config;
>         return 0;
> diff --git a/tools/perf/util/print-events.c b/tools/perf/util/print-events.c
> index 04050d4f6db8..fa5cc94cfcfe 100644
> --- a/tools/perf/util/print-events.c
> +++ b/tools/perf/util/print-events.c
> @@ -239,7 +239,7 @@ void print_sdt_events(const char *subsys_glob, const char *event_glob,
>         strlist__delete(sdtlist);
>  }
>
> -static bool is_event_supported(u8 type, u64 config)
> +bool is_event_supported(u8 type, u64 config)

This makes me tempted to say this function should be in parse-events.c.

Thanks,
Ian

>  {
>         bool ret = true;
>         int open_return;
> diff --git a/tools/perf/util/print-events.h b/tools/perf/util/print-events.h
> index 1da9910d83a6..ad2902fd0507 100644
> --- a/tools/perf/util/print-events.h
> +++ b/tools/perf/util/print-events.h
> @@ -1,14 +1,15 @@
>  /* SPDX-License-Identifier: GPL-2.0 */
>  #ifndef __PERF_PRINT_EVENTS_H
>  #define __PERF_PRINT_EVENTS_H
> -
>  #include <stdbool.h>
> +#include <linux/types.h>
>
>  struct event_symbol;
>
>  void print_events(const char *event_glob, bool name_only, bool quiet_flag,
>                   bool long_desc, bool details_flag, bool deprecated,
>                   const char *pmu_name);
> +bool is_event_supported(u8 type, u64 config);
>  int print_hwcache_events(const char *event_glob, bool name_only);
>  void print_sdt_events(const char *subsys_glob, const char *event_glob,
>                       bool name_only);
> --
> 2.25.1
>