[Mesa-dev] [PATCH 1/3] util/disc_cache: use LRU eviction rather than random eviction

[Grazvydas Ignotas]

On Mon, Mar 6, 2017 at 6:17 PM, Alan Swanson <reiver at improbability.net> wrote:
> Still using random selection of two-character subdirectory in which
> to check cache files rather than scanning entire cache.
> ---
>  src/util/disk_cache.c | 77 +++++++++++++++++++++++----------------------------
>  1 file changed, 34 insertions(+), 43 deletions(-)
>
> diff --git a/src/util/disk_cache.c b/src/util/disk_cache.c
> index 31a9336582..28f8ea4054 100644
> --- a/src/util/disk_cache.c
> +++ b/src/util/disk_cache.c
> @@ -438,30 +438,30 @@ 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;
> +   struct stat sb;
> +   char *tmp, *lru_name = NULL;
> +   time_t lru_atime = 0;
>     char *filename;
>
>     dir = opendir(dir_path);
>     if (dir == NULL)
>        return NULL;
>
> -   count = 0;
> -
>     while (1) {
>        entry = readdir(dir);
>        if (entry == NULL)
> @@ -469,39 +469,28 @@ 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++;
> +      if (fstatat(dirfd(dir), entry->d_name, &sb, 0) == 0) {
> +         if (!lru_atime || (sb.st_atime < lru_atime)) {
> +            tmp = realloc(lru_name, strlen(entry->d_name) + 1);
> +            if (tmp) {
> +               lru_name = tmp;
> +               memcpy(lru_name, entry->d_name,
> +                      strlen(entry->d_name) + 1);

Maybe avoid the double strlen()?
Either way, FWIW:
Reviewed-by: Grazvydas Ignotas <notasas at gmail.com>

Gražvydas