diff options
| author | Krzysztof Łopatowski <krzysztof.m.lopatowski@gmail.com> | 2025-02-06 12:33:15 +0100 |
|---|---|---|
| committer | Namhyung Kim <namhyung@kernel.org> | 2025-02-19 13:55:59 -0800 |
| commit | 4bac7fb5862740087825eda3ed6168e91da8b7e6 (patch) | |
| tree | 8d58716be83fe1892389f1d868089a4fcf933022 /tools/perf | |
| parent | 6353255e7cfab568058580424fa0967bf4504fe5 (diff) | |
| download | ath-4bac7fb5862740087825eda3ed6168e91da8b7e6.tar.gz | |
perf tools: Improve startup time by reducing unnecessary stat() calls
When testing perf trace on NixOS, I noticed significant startup delays:
- `ls`: ~2ms
- `strace ls`: ~10ms
- `perf trace ls`: ~550ms
Profiling showed that 51% of the time is spent reading files,
26% in loading BPF programs, and 11% in `newfstatat`.
This patch optimizes module path exploration by avoiding `stat()` calls
unless necessary. For filesystems that do not implement `d_type`
(DT_UNKNOWN), it falls back to the old behavior.
See `readdir(3)` for details.
This reduces `perf trace ls` time to ~500ms.
A more thorough startup optimization based on command parameters would
be ideal, but that is a larger effort.
Signed-off-by: Krzysztof Łopatowski <krzysztof.m.lopatowski@gmail.com>
Acked-by: Howard Chu <howardchu95@gmail.com>
Link: https://lore.kernel.org/r/20250206113314.335376-2-krzysztof.m.lopatowski@gmail.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Diffstat (limited to 'tools/perf')
| -rw-r--r-- | tools/perf/util/machine.c | 18 |
1 files changed, 12 insertions, 6 deletions
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index d96cbfd97ad8f..316f0879e5e08 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -1339,7 +1339,7 @@ static int maps__set_module_path(struct maps *maps, const char *path, struct kmo static int maps__set_modules_path_dir(struct maps *maps, const char *dir_name, int depth) { - struct dirent *dent; + const struct dirent *dent; DIR *dir = opendir(dir_name); int ret = 0; @@ -1350,14 +1350,20 @@ static int maps__set_modules_path_dir(struct maps *maps, const char *dir_name, i while ((dent = readdir(dir)) != NULL) { char path[PATH_MAX]; - struct stat st; + unsigned char d_type = dent->d_type; - /*sshfs might return bad dent->d_type, so we have to stat*/ path__join(path, sizeof(path), dir_name, dent->d_name); - if (stat(path, &st)) - continue; - if (S_ISDIR(st.st_mode)) { + if (d_type == DT_UNKNOWN) { + struct stat st; + + if (stat(path, &st)) + continue; + if (S_ISDIR(st.st_mode)) + d_type = DT_DIR; + } + + if (d_type == DT_DIR) { if (!strcmp(dent->d_name, ".") || !strcmp(dent->d_name, "..")) continue; |