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    Subject[PATCH v3 21/50] perf pmu: Switch to io_dir__readdir
    From
    Avoid DIR allocations when scanning sysfs by using io_dir for the
    readdir implementation, that allocates about 1kb on the stack.

    Signed-off-by: Ian Rogers <irogers@google.com>
    ---
    tools/perf/util/pmu.c | 48 +++++++++++++++++-------------------------
    tools/perf/util/pmus.c | 30 ++++++++++----------------
    2 files changed, 30 insertions(+), 48 deletions(-)

    diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
    index a967d25e899b..91ae0ce06ef0 100644
    --- a/tools/perf/util/pmu.c
    +++ b/tools/perf/util/pmu.c
    @@ -12,6 +12,7 @@
    #include <stdbool.h>
    #include <dirent.h>
    #include <api/fs/fs.h>
    +#include <api/io_dir.h>
    #include <locale.h>
    #include <fnmatch.h>
    #include <math.h>
    @@ -184,19 +185,17 @@ static void perf_pmu_format__load(const struct perf_pmu *pmu, struct perf_pmu_fo
    */
    int perf_pmu__format_parse(struct perf_pmu *pmu, int dirfd, bool eager_load)
    {
    - struct dirent *evt_ent;
    - DIR *format_dir;
    + struct io_dirent64 *evt_ent;
    + struct io_dir format_dir;
    int ret = 0;

    - format_dir = fdopendir(dirfd);
    - if (!format_dir)
    - return -EINVAL;
    + io_dir__init(&format_dir, dirfd);

    - while ((evt_ent = readdir(format_dir)) != NULL) {
    + while ((evt_ent = io_dir__readdir(&format_dir)) != NULL) {
    struct perf_pmu_format *format;
    char *name = evt_ent->d_name;

    - if (!strcmp(name, ".") || !strcmp(name, ".."))
    + if (io_dir__is_dir(&format_dir, evt_ent))
    continue;

    format = perf_pmu__new_format(&pmu->format, name);
    @@ -223,7 +222,7 @@ int perf_pmu__format_parse(struct perf_pmu *pmu, int dirfd, bool eager_load)
    }
    }

    - closedir(format_dir);
    + close(format_dir.dirfd);
    return ret;
    }

    @@ -599,8 +598,8 @@ static inline bool pmu_alias_info_file(const char *name)
    static int pmu_aliases_parse(struct perf_pmu *pmu)
    {
    char path[PATH_MAX];
    - struct dirent *evt_ent;
    - DIR *event_dir;
    + struct io_dirent64 *evt_ent;
    + struct io_dir event_dir;
    size_t len;
    int fd, dir_fd;

    @@ -615,13 +614,9 @@ static int pmu_aliases_parse(struct perf_pmu *pmu)
    return 0;
    }

    - event_dir = fdopendir(dir_fd);
    - if (!event_dir){
    - close (dir_fd);
    - return -EINVAL;
    - }
    + io_dir__init(&event_dir, dir_fd);

    - while ((evt_ent = readdir(event_dir))) {
    + while ((evt_ent = io_dir__readdir(&event_dir))) {
    char *name = evt_ent->d_name;
    FILE *file;

    @@ -651,7 +646,6 @@ static int pmu_aliases_parse(struct perf_pmu *pmu)
    fclose(file);
    }

    - closedir(event_dir);
    close (dir_fd);
    pmu->sysfs_aliases_loaded = true;
    return 0;
    @@ -1879,10 +1873,9 @@ static void perf_pmu__del_caps(struct perf_pmu *pmu)
    */
    int perf_pmu__caps_parse(struct perf_pmu *pmu)
    {
    - struct stat st;
    char caps_path[PATH_MAX];
    - DIR *caps_dir;
    - struct dirent *evt_ent;
    + struct io_dir caps_dir;
    + struct io_dirent64 *evt_ent;
    int caps_fd;

    if (pmu->caps_initialized)
    @@ -1893,24 +1886,21 @@ int perf_pmu__caps_parse(struct perf_pmu *pmu)
    if (!perf_pmu__pathname_scnprintf(caps_path, sizeof(caps_path), pmu->name, "caps"))
    return -1;

    - if (stat(caps_path, &st) < 0) {
    + caps_fd = open(caps_path, O_CLOEXEC | O_DIRECTORY | O_RDONLY);
    + if (caps_fd == -1) {
    pmu->caps_initialized = true;
    return 0; /* no error if caps does not exist */
    }

    - caps_dir = opendir(caps_path);
    - if (!caps_dir)
    - return -EINVAL;
    -
    - caps_fd = dirfd(caps_dir);
    + io_dir__init(&caps_dir, caps_fd);

    - while ((evt_ent = readdir(caps_dir)) != NULL) {
    + while ((evt_ent = io_dir__readdir(&caps_dir)) != NULL) {
    char *name = evt_ent->d_name;
    char value[128];
    FILE *file;
    int fd;

    - if (!strcmp(name, ".") || !strcmp(name, ".."))
    + if (io_dir__is_dir(&caps_dir, evt_ent))
    continue;

    fd = openat(caps_fd, name, O_RDONLY);
    @@ -1932,7 +1922,7 @@ int perf_pmu__caps_parse(struct perf_pmu *pmu)
    fclose(file);
    }

    - closedir(caps_dir);
    + close(caps_fd);

    pmu->caps_initialized = true;
    return pmu->nr_caps;
    diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
    index ce4931461741..65b23b98666b 100644
    --- a/tools/perf/util/pmus.c
    +++ b/tools/perf/util/pmus.c
    @@ -3,10 +3,10 @@
    #include <linux/list_sort.h>
    #include <linux/string.h>
    #include <linux/zalloc.h>
    +#include <api/io_dir.h>
    #include <subcmd/pager.h>
    #include <sys/types.h>
    #include <ctype.h>
    -#include <dirent.h>
    #include <pthread.h>
    #include <string.h>
    #include <unistd.h>
    @@ -184,8 +184,8 @@ static int pmus_cmp(void *priv __maybe_unused,
    static void pmu_read_sysfs(bool core_only)
    {
    int fd;
    - DIR *dir;
    - struct dirent *dent;
    + struct io_dir dir;
    + struct io_dirent64 *dent;

    if (read_sysfs_all_pmus || (core_only && read_sysfs_core_pmus))
    return;
    @@ -194,13 +194,9 @@ static void pmu_read_sysfs(bool core_only)
    if (fd < 0)
    return;

    - dir = fdopendir(fd);
    - if (!dir) {
    - close(fd);
    - return;
    - }
    + io_dir__init(&dir, fd);

    - while ((dent = readdir(dir))) {
    + while ((dent = io_dir__readdir(&dir)) != NULL) {
    if (!strcmp(dent->d_name, ".") || !strcmp(dent->d_name, ".."))
    continue;
    if (core_only && !is_pmu_core(dent->d_name))
    @@ -209,7 +205,7 @@ static void pmu_read_sysfs(bool core_only)
    perf_pmu__find2(fd, dent->d_name);
    }

    - closedir(dir);
    + close(fd);
    if (list_empty(&core_pmus)) {
    if (!perf_pmu__create_placeholder_core_pmu(&core_pmus))
    pr_err("Failure to set up any core PMUs\n");
    @@ -563,8 +559,8 @@ bool perf_pmus__supports_extended_type(void)
    char *perf_pmus__default_pmu_name(void)
    {
    int fd;
    - DIR *dir;
    - struct dirent *dent;
    + struct io_dir dir;
    + struct io_dirent64 *dent;
    char *result = NULL;

    if (!list_empty(&core_pmus))
    @@ -574,13 +570,9 @@ char *perf_pmus__default_pmu_name(void)
    if (fd < 0)
    return strdup("cpu");

    - dir = fdopendir(fd);
    - if (!dir) {
    - close(fd);
    - return strdup("cpu");
    - }
    + io_dir__init(&dir, fd);

    - while ((dent = readdir(dir))) {
    + while ((dent = io_dir__readdir(&dir)) != NULL) {
    if (!strcmp(dent->d_name, ".") || !strcmp(dent->d_name, ".."))
    continue;
    if (is_pmu_core(dent->d_name)) {
    @@ -589,7 +581,7 @@ char *perf_pmus__default_pmu_name(void)
    }
    }

    - closedir(dir);
    + close(fd);
    return result ?: strdup("cpu");
    }

    --
    2.42.0.758.gaed0368e0e-goog
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