Re: [PATCH v3 16/35] perf pmu: Remove perf_pmu__hybrid_mounted

["Liang, Kan" <kan.liang@linux.intel.com>]

On 2023-05-24 6:18 p.m., Ian Rogers wrote:
> perf_pmu__hybrid_mounted is used to detect whether cpu_core or
> cpu_atom is mounted with a non-empty cpus file by
> pmu_lookup. pmu_lookup will attempt to read the cpus file too and so
> the check can be folded into this.
> 
> Checking hybrid_mounted in pmu_is_uncore is redundant as the next
> cpumask read will fail returning false.
> 
> Reduce the scope of perf_pmu__find_hybrid_pmu by making it static.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/util/pmu-hybrid.c | 15 +--------------
>  tools/perf/util/pmu-hybrid.h |  3 ---
>  tools/perf/util/pmu.c        | 26 ++++++++++++++------------
>  3 files changed, 15 insertions(+), 29 deletions(-)
> 
> diff --git a/tools/perf/util/pmu-hybrid.c b/tools/perf/util/pmu-hybrid.c
> index bc4cb0738c35..7fe943dd3217 100644
> --- a/tools/perf/util/pmu-hybrid.c
> +++ b/tools/perf/util/pmu-hybrid.c
> @@ -18,20 +18,7 @@
>  
>  LIST_HEAD(perf_pmu__hybrid_pmus);
>  
> -bool perf_pmu__hybrid_mounted(const char *name)
> -{
> -	int cpu;
> -	char pmu_name[PATH_MAX];
> -	struct perf_pmu pmu = {.name = pmu_name};
> -
> -	if (strncmp(name, "cpu_", 4))
> -		return false;
> -
> -	strlcpy(pmu_name, name, sizeof(pmu_name));
> -	return perf_pmu__scan_file(&pmu, "cpus", "%u", &cpu) > 0;
> -}
> -
> -struct perf_pmu *perf_pmu__find_hybrid_pmu(const char *name)
> +static struct perf_pmu *perf_pmu__find_hybrid_pmu(const char *name)
>  {
>  	struct perf_pmu *pmu;
>  
> diff --git a/tools/perf/util/pmu-hybrid.h b/tools/perf/util/pmu-hybrid.h
> index 206b94931531..8dbcae935020 100644
> --- a/tools/perf/util/pmu-hybrid.h
> +++ b/tools/perf/util/pmu-hybrid.h
> @@ -13,9 +13,6 @@ extern struct list_head perf_pmu__hybrid_pmus;
>  #define perf_pmu__for_each_hybrid_pmu(pmu)	\
>  	list_for_each_entry(pmu, &perf_pmu__hybrid_pmus, hybrid_list)
>  
> -bool perf_pmu__hybrid_mounted(const char *name);
> -
> -struct perf_pmu *perf_pmu__find_hybrid_pmu(const char *name);
>  bool perf_pmu__is_hybrid(const char *name);
>  
>  static inline int perf_pmu__hybrid_pmu_num(void)
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index cd94abe7a87a..e9f3e6a777c0 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -617,9 +617,6 @@ static bool pmu_is_uncore(int dirfd, const char *name)
>  {
>  	int fd;
>  
> -	if (perf_pmu__hybrid_mounted(name))
> -		return false;
> -
>  	fd = perf_pmu__pathname_fd(dirfd, name, "cpumask", O_PATH);
>  	if (fd < 0)
>  		return false;
> @@ -900,6 +897,16 @@ static int pmu_max_precise(int dirfd, struct perf_pmu *pmu)
>  	return max_precise;
>  }
>  
> +/**
> + * perf_pmu__skip_empty_cpus() - should pmu_lookup skip the named PMU if the
> + *      cpus or cpumask file isn't present?
> + * @name: Name of PMU.
> + */
> +static bool perf_pmu__skip_empty_cpus(const char *name)
> +{
> +	return !strcmp(name, "cpu_core") || !strcmp(name, "cpu_atom");

Can we use the below to replace?
return !strncmp(name, "cpu_", 4);

Otherwise, anytime a new core PMU name is introduced, I have to patch
the function.

Thanks,
Kan

> +}
> +
>  static struct perf_pmu *pmu_lookup(int dirfd, const char *lookup_name)
>  {
>  	struct perf_pmu *pmu;
> @@ -907,15 +914,8 @@ static struct perf_pmu *pmu_lookup(int dirfd, const char *lookup_name)
>  	LIST_HEAD(aliases);
>  	__u32 type;
>  	char *name = pmu_find_real_name(lookup_name);
> -	bool is_hybrid = perf_pmu__hybrid_mounted(name);
>  	char *alias_name;
>  
> -	/*
> -	 * Check pmu name for hybrid and the pmu may be invalid in sysfs
> -	 */
> -	if (!strncmp(name, "cpu_", 4) && !is_hybrid)
> -		return NULL;
> -
>  	/*
>  	 * The pmu data we store & need consists of the pmu
>  	 * type value and format definitions. Load both right
> @@ -935,8 +935,10 @@ static struct perf_pmu *pmu_lookup(int dirfd, const char *lookup_name)
>  		return NULL;
>  
>  	pmu->cpus = pmu_cpumask(dirfd, name);
> -	pmu->name = strdup(name);
> +	if (!pmu->cpus && perf_pmu__skip_empty_cpus(name))
> +		goto err;
>  
> +	pmu->name = strdup(name);
>  	if (!pmu->name)
>  		goto err;
>  
> @@ -967,7 +969,7 @@ static struct perf_pmu *pmu_lookup(int dirfd, const char *lookup_name)
>  	list_splice(&aliases, &pmu->aliases);
>  	list_add_tail(&pmu->list, &pmus);
>  
> -	if (is_hybrid)
> +	if (!strcmp(name, "cpu_core") || !strcmp(name, "cpu_atom"))
>  		list_add_tail(&pmu->hybrid_list, &perf_pmu__hybrid_pmus);
>  	else
>  		INIT_LIST_HEAD(&pmu->hybrid_list);