Commit e4b4da140648d83f953837d4233dd87cb31f3ca4
2012-01-27T18:28:02
cache: Simplify locking mechanics The object cache is mostly IO-bound, so it makes no sense to have a lock per node.
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diff --git a/src/cache.c b/src/cache.c
index 6ba4d21..8150ec3 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -13,8 +13,6 @@
int git_cache_init(git_cache *cache, size_t size, git_cached_obj_freeptr free_ptr)
{
- size_t i;
-
if (size < 8)
size = 8;
@@ -25,20 +23,19 @@ int git_cache_init(git_cache *cache, size_t size, git_cached_obj_freeptr free_pt
size |= size >> 4;
size |= size >> 8;
size |= size >> 16;
+ size++;
- cache->size_mask = size;
+ cache->size_mask = size - 1;
cache->lru_count = 0;
cache->free_obj = free_ptr;
- cache->nodes = git__malloc((size + 1) * sizeof(cache_node));
+ git_mutex_init(&cache->lock);
+
+ cache->nodes = git__malloc(size * sizeof(git_cached_obj *));
if (cache->nodes == NULL)
return GIT_ENOMEM;
- for (i = 0; i < (size + 1); ++i) {
- git_mutex_init(&cache->nodes[i].lock);
- cache->nodes[i].ptr = NULL;
- }
-
+ memset(cache->nodes, 0x0, size * sizeof(git_cached_obj *));
return GIT_SUCCESS;
}
@@ -47,10 +44,8 @@ void git_cache_free(git_cache *cache)
size_t i;
for (i = 0; i < (cache->size_mask + 1); ++i) {
- if (cache->nodes[i].ptr)
- git_cached_obj_decref(cache->nodes[i].ptr, cache->free_obj);
-
- git_mutex_free(&cache->nodes[i].lock);
+ if (cache->nodes[i] != NULL)
+ git_cached_obj_decref(cache->nodes[i], cache->free_obj);
}
git__free(cache->nodes);
@@ -59,53 +54,54 @@ void git_cache_free(git_cache *cache)
void *git_cache_get(git_cache *cache, const git_oid *oid)
{
uint32_t hash;
- cache_node *node = NULL;
- void *result = NULL;
+ git_cached_obj *node = NULL, *result = NULL;
memcpy(&hash, oid->id, sizeof(hash));
- node = &cache->nodes[hash & cache->size_mask];
- git_mutex_lock(&node->lock);
+ git_mutex_lock(&cache->lock);
{
- if (node->ptr && git_cached_obj_compare(node->ptr, oid) == 0) {
- git_cached_obj_incref(node->ptr);
- result = node->ptr;
+ node = cache->nodes[hash & cache->size_mask];
+
+ if (node != NULL && git_oid_cmp(&node->oid, oid) == 0) {
+ git_cached_obj_incref(node);
+ result = node;
}
}
- git_mutex_unlock(&node->lock);
+ git_mutex_unlock(&cache->lock);
return result;
}
-void *git_cache_try_store(git_cache *cache, void *entry)
+void *git_cache_try_store(git_cache *cache, void *_entry)
{
+ git_cached_obj *entry = _entry;
uint32_t hash;
- const git_oid *oid;
- cache_node *node = NULL;
- oid = &((git_cached_obj*)entry)->oid;
- memcpy(&hash, oid->id, sizeof(hash));
- node = &cache->nodes[hash & cache->size_mask];
+ memcpy(&hash, &entry->oid, sizeof(hash));
/* increase the refcount on this object, because
* the cache now owns it */
git_cached_obj_incref(entry);
- git_mutex_lock(&node->lock);
-
- if (node->ptr == NULL) {
- node->ptr = entry;
- } else if (git_cached_obj_compare(node->ptr, oid) == 0) {
- git_cached_obj_decref(entry, cache->free_obj);
- entry = node->ptr;
- } else {
- git_cached_obj_decref(node->ptr, cache->free_obj);
- node->ptr = entry;
+
+ git_mutex_lock(&cache->lock);
+ {
+ git_cached_obj *node = cache->nodes[hash & cache->size_mask];
+
+ if (node == NULL) {
+ cache->nodes[hash & cache->size_mask] = entry;
+ } else if (git_oid_cmp(&node->oid, &entry->oid) == 0) {
+ git_cached_obj_decref(entry, cache->free_obj);
+ entry = node;
+ } else {
+ git_cached_obj_decref(node, cache->free_obj);
+ cache->nodes[hash & cache->size_mask] = entry;
+ }
}
+ git_mutex_unlock(&cache->lock);
/* increase the refcount again, because we are
* returning it to the user */
git_cached_obj_incref(entry);
- git_mutex_unlock(&node->lock);
return entry;
}
diff --git a/src/cache.h b/src/cache.h
index 8c885d9..688f145 100644
--- a/src/cache.h
+++ b/src/cache.h
@@ -23,42 +23,32 @@ typedef struct {
} git_cached_obj;
typedef struct {
- git_cached_obj *ptr;
+ git_cached_obj **nodes;
git_mutex lock;
-} cache_node;
-
-typedef struct {
- cache_node *nodes;
unsigned int lru_count;
size_t size_mask;
git_cached_obj_freeptr free_obj;
} git_cache;
-
int git_cache_init(git_cache *cache, size_t size, git_cached_obj_freeptr free_ptr);
void git_cache_free(git_cache *cache);
void *git_cache_try_store(git_cache *cache, void *entry);
void *git_cache_get(git_cache *cache, const git_oid *oid);
-
-GIT_INLINE(int) git_cached_obj_compare(git_cached_obj *obj, const git_oid *oid)
-{
- return git_oid_cmp(&obj->oid, oid);
-}
-
-GIT_INLINE(void) git_cached_obj_incref(git_cached_obj *obj)
+GIT_INLINE(void) git_cached_obj_incref(void *_obj)
{
+ git_cached_obj *obj = _obj;
git_atomic_inc(&obj->refcount);
}
-GIT_INLINE(void) git_cached_obj_decref(git_cached_obj *obj, git_cached_obj_freeptr free_obj)
+GIT_INLINE(void) git_cached_obj_decref(void *_obj, git_cached_obj_freeptr free_obj)
{
+ git_cached_obj *obj = _obj;
+
if (git_atomic_dec(&obj->refcount) == 0)
free_obj(obj);
}
-
-
#endif