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

From: Ian Rogers
Date: Wed Sep 21 2022 - 23:22:11 EST


On Wed, Sep 21, 2022 at 6:47 PM <zhengjun.xing@xxxxxxxxxxxxxxx> wrote:
>
> From: Zhengjun Xing <zhengjun.xing@xxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxx>
> Reviewed-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> ---
> 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
>