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

[Grazvydas Ignotas]

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];
 
    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
-- 
2.7.4