linux-kernel - Re: [PATCH v2 2/5] perf arm-spe: Calculate meta data size

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Message-ID: <ZvZNSr51YgWvc6tu@google.com>
Date: Thu, 26 Sep 2024 23:14:34 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Leo Yan <leo.yan@....com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
	James Clark <james.clark@...aro.org>,
	Mike Leach <mike.leach@...aro.org>, Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>, Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/5] perf arm-spe: Calculate meta data size

On Sat, Sep 14, 2024 at 10:54:55PM +0100, Leo Yan wrote:
> The metadata is designed to contain a header and per CPU information.
> 
> The arm_spe_find_cpus() function is introduced to identify how many CPUs
> support ARM SPE. Based on the CPU number, calculates the metadata size.
> 
> Signed-off-by: Leo Yan <leo.yan@....com>
> ---
>  tools/perf/arch/arm64/util/arm-spe.c | 35 +++++++++++++++++++++++++---
>  1 file changed, 32 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/arch/arm64/util/arm-spe.c b/tools/perf/arch/arm64/util/arm-spe.c
> index c2d5c8ca4900..15478989ef30 100644
> --- a/tools/perf/arch/arm64/util/arm-spe.c
> +++ b/tools/perf/arch/arm64/util/arm-spe.c
> @@ -37,11 +37,40 @@ struct arm_spe_recording {
>  	bool			*wrapped;
>  };
>  
> +static struct perf_cpu_map *arm_spe_find_cpus(struct evlist *evlist)

Please add a comment that it returns a new cpu map, and caller should
release the reference after use.

> +{
> +	struct perf_cpu_map *event_cpus = evlist->core.user_requested_cpus;
> +	struct perf_cpu_map *online_cpus = perf_cpu_map__new_online_cpus();
> +	struct perf_cpu_map *intersect_cpus;
> +
> +	/* cpu map is not "any" CPU , we have specific CPUs to work with */
> +	if (!perf_cpu_map__has_any_cpu(event_cpus)) {
> +		intersect_cpus = perf_cpu_map__intersect(event_cpus, online_cpus);
> +		perf_cpu_map__put(online_cpus);
> +	/* Event can be "any" CPU so count all CPUs. */
> +	} else {
> +		intersect_cpus = online_cpus;
> +	}
> +
> +	return intersect_cpus;
> +}
> +
>  static size_t
>  arm_spe_info_priv_size(struct auxtrace_record *itr __maybe_unused,
> -		       struct evlist *evlist __maybe_unused)
> +		       struct evlist *evlist)
>  {
> -	return ARM_SPE_AUXTRACE_V1_PRIV_SIZE;
> +	struct perf_cpu_map *cpu_map = arm_spe_find_cpus(evlist);
> +	size_t size;
> +
> +	if (!cpu_map)
> +		return 0;
> +
> +	size = ARM_SPE_AUXTRACE_PRIV_MAX +
> +	       ARM_SPE_CPU_PRIV_MAX * perf_cpu_map__nr(cpu_map);
> +	size *= sizeof(u64);
> +
> +	perf_cpu_map__put(cpu_map);
> +	return size;
>  }
>  
>  static int arm_spe_info_fill(struct auxtrace_record *itr,
> @@ -53,7 +82,7 @@ static int arm_spe_info_fill(struct auxtrace_record *itr,
>  			container_of(itr, struct arm_spe_recording, itr);
>  	struct perf_pmu *arm_spe_pmu = sper->arm_spe_pmu;
>  
> -	if (priv_size != ARM_SPE_AUXTRACE_V1_PRIV_SIZE)
> +	if (priv_size != arm_spe_info_priv_size(itr, session->evlist))
>  		return -EINVAL;
>  
>  	if (!session->evlist->core.nr_mmaps)
> -- 
> 2.34.1
>