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    SubjectRe: [PATCH v3 1/7] perf pmu: Use file system cache to optimize sysfs access
    On Fri, Oct 25, 2019 at 11:14:11AM -0700, Andi Kleen wrote:

    SNIP

    > if (pmu_aliases_parse(path, head))
    > return -1;
    > @@ -525,7 +524,6 @@ static int pmu_alias_terms(struct perf_pmu_alias *alias,
    > */
    > static int pmu_type(const char *name, __u32 *type)
    > {
    > - struct stat st;
    > char path[PATH_MAX];
    > FILE *file;
    > int ret = 0;
    > @@ -537,7 +535,7 @@ static int pmu_type(const char *name, __u32 *type)
    > snprintf(path, PATH_MAX,
    > "%s" EVENT_SOURCE_DEVICE_PATH "%s/type", sysfs, name);
    >
    > - if (stat(path, &st) < 0)
    > + if (access(path, R_OK) < 0)

    why not file_available call in here?

    jirka

    > return -1;
    >
    > file = fopen(path, "r");
    > @@ -628,14 +626,11 @@ static struct perf_cpu_map *pmu_cpumask(const char *name)
    > static bool pmu_is_uncore(const char *name)
    > {
    > char path[PATH_MAX];
    > - struct perf_cpu_map *cpus;
    > - const char *sysfs = sysfs__mountpoint();
    > + const char *sysfs;
    >
    > + sysfs = sysfs__mountpoint();
    > snprintf(path, PATH_MAX, CPUS_TEMPLATE_UNCORE, sysfs, name);

    SNIP

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