diff options
| -rw-r--r-- | src/util/disk_cache.c | 77 |
1 files changed, 34 insertions, 43 deletions
diff --git a/src/util/disk_cache.c b/src/util/disk_cache.c index c71f039ee6d..931e308cd53 100644 --- a/src/util/disk_cache.c +++ b/src/util/disk_cache.c @@ -466,30 +466,29 @@ make_cache_file_directory(struct disk_cache *cache, const cache_key key) free(dir); } -/* Given a directory path and predicate function, count all entries in - * that directory for which the predicate returns true. Then choose a - * random entry from among those counted. +/* Given a directory path and predicate function, find the entry with + * the oldest access time in that directory for which the predicate + * returns true. * * Returns: A malloc'ed string for the path to the chosen file, (or * NULL on any error). The caller should free the string when * finished. */ static char * -choose_random_file_matching(const char *dir_path, - bool (*predicate)(const struct dirent *, - const char *dir_path)) +choose_lru_file_matching(const char *dir_path, + bool (*predicate)(const struct dirent *, + const char *dir_path)) { DIR *dir; struct dirent *entry; - unsigned int count, victim; char *filename; + char *lru_name = NULL; + time_t lru_atime = 0; dir = opendir(dir_path); if (dir == NULL) return NULL; - count = 0; - while (1) { entry = readdir(dir); if (entry == NULL) @@ -497,39 +496,29 @@ choose_random_file_matching(const char *dir_path, if (!predicate(entry, dir_path)) continue; - count++; - } - - if (count == 0) { - closedir(dir); - return NULL; - } - - victim = rand() % count; - - rewinddir(dir); - count = 0; - - while (1) { - entry = readdir(dir); - if (entry == NULL) - break; - if (!predicate(entry, dir_path)) - continue; - if (count == victim) - break; - - count++; + struct stat sb; + if (fstatat(dirfd(dir), entry->d_name, &sb, 0) == 0) { + if (!lru_atime || (sb.st_atime < lru_atime)) { + size_t len = strlen(entry->d_name) + 1; + char *tmp = realloc(lru_name, len); + if (tmp) { + lru_name = tmp; + memcpy(lru_name, entry->d_name, len); + lru_atime = sb.st_atime; + } + } + } } - if (entry == NULL) { + if (lru_name == NULL) { closedir(dir); return NULL; } - if (asprintf(&filename, "%s/%s", dir_path, entry->d_name) < 0) + if (asprintf(&filename, "%s/%s", dir_path, lru_name) < 0) filename = NULL; + free(lru_name); closedir(dir); return filename; @@ -561,12 +550,12 @@ is_regular_non_tmp_file(const struct dirent *entry, const char *path) /* Returns the size of the deleted file, (or 0 on any error). */ static size_t -unlink_random_file_from_directory(const char *path) +unlink_lru_file_from_directory(const char *path) { struct stat sb; char *filename; - filename = choose_random_file_matching(path, is_regular_non_tmp_file); + filename = choose_lru_file_matching(path, is_regular_non_tmp_file); if (filename == NULL) return 0; @@ -630,7 +619,7 @@ is_two_character_sub_directory(const struct dirent *entry, const char *path) } static void -evict_random_item(struct disk_cache *cache) +evict_lru_item(struct disk_cache *cache) { const char hex[] = "0123456789abcde"; char *dir_path; @@ -640,6 +629,7 @@ evict_random_item(struct disk_cache *cache) /* With a reasonably-sized, full cache, (and with keys generated * from a cryptographic hash), we can choose two random hex digits * and reasonably expect the directory to exist with a file in it. + * Provides pseudo-LRU eviction to reduce checking all cache files. */ a = rand() % 16; b = rand() % 16; @@ -647,7 +637,7 @@ evict_random_item(struct disk_cache *cache) if (asprintf(&dir_path, "%s/%c%c", cache->path, hex[a], hex[b]) < 0) return; - size = unlink_random_file_from_directory(dir_path); + size = unlink_lru_file_from_directory(dir_path); free(dir_path); @@ -657,18 +647,19 @@ evict_random_item(struct disk_cache *cache) } /* In the case where the random choice of directory didn't find - * something, we choose randomly from the existing directories. + * something, we choose the least recently accessed from the + * existing directories. * * Really, the only reason this code exists is to allow the unit * tests to work, (which use an artificially-small cache to be able * to force a single cached item to be evicted). */ - dir_path = choose_random_file_matching(cache->path, - is_two_character_sub_directory); + dir_path = choose_lru_file_matching(cache->path, + is_two_character_sub_directory); if (dir_path == NULL) return; - size = unlink_random_file_from_directory(dir_path); + size = unlink_lru_file_from_directory(dir_path); free(dir_path); @@ -863,7 +854,7 @@ cache_put(void *job, int thread_index) * else first. */ if (*dc_job->cache->size + dc_job->size > dc_job->cache->max_size) - evict_random_item(dc_job->cache); + evict_lru_item(dc_job->cache); /* Create CRC of the data and store at the start of the file. We will * read this when restoring the cache and use it to check for corruption. |