Commit 6a211d7c9abbddee342c353092b681b21913b2dd
2014-08-26T15:12:43
Refactor git_cache to use an rwlock This significantly reduces contention when many threads are trying to read from the cache simultaneously.
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diff --git a/src/cache.c b/src/cache.c
index 36ce665..8dc9cbf 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -68,8 +68,8 @@ int git_cache_init(git_cache *cache)
{
memset(cache, 0, sizeof(*cache));
cache->map = git_oidmap_alloc();
- if (git_mutex_init(&cache->lock)) {
- giterr_set(GITERR_OS, "Failed to initialize cache mutex");
+ if (git_rwlock_init(&cache->lock)) {
+ giterr_set(GITERR_OS, "Failed to initialize cache rwlock");
return -1;
}
return 0;
@@ -94,19 +94,19 @@ static void clear_cache(git_cache *cache)
void git_cache_clear(git_cache *cache)
{
- if (git_mutex_lock(&cache->lock) < 0)
+ if (git_rwlock_wrlock(&cache->lock) < 0)
return;
clear_cache(cache);
- git_mutex_unlock(&cache->lock);
+ git_rwlock_wrunlock(&cache->lock);
}
void git_cache_free(git_cache *cache)
{
git_cache_clear(cache);
git_oidmap_free(cache->map);
- git_mutex_free(&cache->lock);
+ git_rwlock_free(&cache->lock);
git__memzero(cache, sizeof(*cache));
}
@@ -152,7 +152,7 @@ static void *cache_get(git_cache *cache, const git_oid *oid, unsigned int flags)
khiter_t pos;
git_cached_obj *entry = NULL;
- if (!git_cache__enabled || git_mutex_lock(&cache->lock) < 0)
+ if (!git_cache__enabled || git_rwlock_rdlock(&cache->lock) < 0)
return NULL;
pos = kh_get(oid, cache->map, oid);
@@ -166,7 +166,7 @@ static void *cache_get(git_cache *cache, const git_oid *oid, unsigned int flags)
}
}
- git_mutex_unlock(&cache->lock);
+ git_rwlock_rdunlock(&cache->lock);
return entry;
}
@@ -185,7 +185,7 @@ static void *cache_store(git_cache *cache, git_cached_obj *entry)
if (!cache_should_store(entry->type, entry->size))
return entry;
- if (git_mutex_lock(&cache->lock) < 0)
+ if (git_rwlock_wrlock(&cache->lock) < 0)
return entry;
/* soften the load on the cache */
@@ -227,7 +227,7 @@ static void *cache_store(git_cache *cache, git_cached_obj *entry)
}
}
- git_mutex_unlock(&cache->lock);
+ git_rwlock_wrunlock(&cache->lock);
return entry;
}
diff --git a/src/cache.h b/src/cache.h
index 53fbcf4..6971237 100644
--- a/src/cache.h
+++ b/src/cache.h
@@ -30,7 +30,7 @@ typedef struct {
typedef struct {
git_oidmap *map;
- git_mutex lock;
+ git_rwlock lock;
ssize_t used_memory;
} git_cache;