linux-kernel - Re: [PATCH] perf list: Skip the invalid hybrid pmu

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Date:   Tue, 6 Jul 2021 21:58:15 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Jin Yao <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH] perf list: Skip the invalid hybrid pmu

On Thu, Jun 10, 2021 at 01:16:46PM +0800, Jin Yao wrote:
> On hybrid platform, such as Alderlake, if atom CPUs are offlined,
> the kernel still exports the sysfs path '/sys/devices/cpu_atom/' for
> 'cpu_atom' pmu but the file '/sys/devices/cpu_atom/cpus' is empty,
> which indicates this is an invalid pmu.
> 
> The perf-list needs to check and skip the invalid hybrid pmu.
> 
> Before:
> 
>   # perf list
>   ...
>   branch-instructions OR cpu_atom/branch-instructions/ [Kernel PMU event]
>   branch-instructions OR cpu_core/branch-instructions/ [Kernel PMU event]
>   branch-misses OR cpu_atom/branch-misses/           [Kernel PMU event]
>   branch-misses OR cpu_core/branch-misses/           [Kernel PMU event]
>   bus-cycles OR cpu_atom/bus-cycles/                 [Kernel PMU event]
>   bus-cycles OR cpu_core/bus-cycles/                 [Kernel PMU event]
>   ...
> 
> The cpu_atom events are still displayed even if atom CPUs are offlined.
> 
> After:
> 
>   # perf list
>   ...
>   branch-instructions OR cpu_core/branch-instructions/ [Kernel PMU event]
>   branch-misses OR cpu_core/branch-misses/           [Kernel PMU event]
>   bus-cycles OR cpu_core/bus-cycles/                 [Kernel PMU event]
>   ...
> 
> Now only cpu_core events are displayed.
> 
> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
> ---
>  tools/perf/util/pmu-hybrid.c | 11 +++++++++++
>  tools/perf/util/pmu-hybrid.h |  2 ++
>  tools/perf/util/pmu.c        |  3 +++
>  3 files changed, 16 insertions(+)
> 
> diff --git a/tools/perf/util/pmu-hybrid.c b/tools/perf/util/pmu-hybrid.c
> index f51ccaac60ee..fcc1182f8fe5 100644
> --- a/tools/perf/util/pmu-hybrid.c
> +++ b/tools/perf/util/pmu-hybrid.c
> @@ -87,3 +87,14 @@ char *perf_pmu__hybrid_type_to_pmu(const char *type)
>  	free(pmu_name);
>  	return NULL;
>  }
> +
> +bool perf_pmu__is_invalid_hybrid(const char *name)
> +{
> +	if (strncmp(name, "cpu_", 4))
> +		return false;
> +
> +	if (perf_pmu__hybrid_mounted(name))
> +		return false;
> +
> +	return true;
> +}
> diff --git a/tools/perf/util/pmu-hybrid.h b/tools/perf/util/pmu-hybrid.h
> index 2b186c26a43e..8261a312c854 100644
> --- a/tools/perf/util/pmu-hybrid.h
> +++ b/tools/perf/util/pmu-hybrid.h
> @@ -30,4 +30,6 @@ static inline int perf_pmu__hybrid_pmu_num(void)
>  	return num;
>  }
>  
> +bool perf_pmu__is_invalid_hybrid(const char *name);
> +
>  #endif /* __PMU_HYBRID_H */
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index 88c8ecdc60b0..281670e9c4bd 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -1604,6 +1604,9 @@ void print_pmu_events(const char *event_glob, bool name_only, bool quiet_flag,
>  	pmu = NULL;
>  	j = 0;
>  	while ((pmu = perf_pmu__scan(pmu)) != NULL) {
> +		if (perf_pmu__is_invalid_hybrid(pmu->name))
> +			continue;

hum why not detect it in pmu_lookup early on
and not add that pmu at all?

thanks,
jirka

> +
>  		list_for_each_entry(alias, &pmu->aliases, list) {
>  			char *name = alias->desc ? alias->name :
>  				format_alias(buf, sizeof(buf), pmu, alias);
> -- 
> 2.17.1
>