[Mesa-dev] [PATCH] util/disk_cache: fix stored_keys index

[Timothy Arceri]

On 19/03/17 09:46, Grazvydas Ignotas wrote:
> It seems there is a bug because:
> - 20 bytes are compared, but only 1 byte stored_keys step is used
> - entries can overlap each other by 19 bytes
> - index_mmap is ~1.3M in size, but only first 64K is used
>
> With this fix for Deus Ex:
> - startup time (from launch to Feral logo): ~38s -> ~16s
> - disk_cache_has_key() hit rate: ~50% -> ~96%
>
> Signed-off-by: Grazvydas Ignotas <notasas at gmail.com>
> ---
>  src/util/disk_cache.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/src/util/disk_cache.c b/src/util/disk_cache.c
> index 7d10ba2..b88ef52 100644
> --- a/src/util/disk_cache.c
> +++ b/src/util/disk_cache.c
> @@ -1025,11 +1025,11 @@ disk_cache_put_key(struct disk_cache *cache, const cache_key key)
>  {
>     const uint32_t *key_chunk = (const uint32_t *) key;
>     int i = *key_chunk & CACHE_INDEX_KEY_MASK;
>     unsigned char *entry;
>
> -   entry = &cache->stored_keys[i + CACHE_KEY_SIZE];
> +   entry = &cache->stored_keys[i * CACHE_KEY_SIZE];

Yeah this is a bug. Patch pushed. Thanks!

>
>     memcpy(entry, key, CACHE_KEY_SIZE);
>  }
>
>  /* This function lets us test whether a given key was previously
> @@ -1044,11 +1044,11 @@ disk_cache_has_key(struct disk_cache *cache, const cache_key key)
>  {
>     const uint32_t *key_chunk = (const uint32_t *) key;
>     int i = *key_chunk & CACHE_INDEX_KEY_MASK;
>     unsigned char *entry;
>
> -   entry = &cache->stored_keys[i + CACHE_KEY_SIZE];
> +   entry = &cache->stored_keys[i * CACHE_KEY_SIZE];
>
>     return memcmp(entry, key, CACHE_KEY_SIZE) == 0;
>  }
>
>  void
>