Added ObjectCache::objects_per_slab, which allowed to squash the TODO in

object_cache_reserve_internal().


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@35203 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/system/kernel/slab/HashedObjectCache.cpp

@@ -72,6 +72,8 @@ HashedObjectCache::Create(const char* name, size_t object_size,
 		cache->slab_size = max_c(16 * B_PAGE_SIZE, 8 * object_size);
 	cache->lower_boundary = __fls0(cache->object_size);
 
+	cache->objects_per_slab = cache->slab_size / cache->object_size;
+
 	return cache;
 }
 

src/system/kernel/slab/ObjectCache.h

@@ -47,6 +47,7 @@ struct ObjectCache : DoublyLinkedListLinkImpl<ObjectCache> {
 									// minimum number of free objects
 
 			size_t				slab_size;
+			size_t				objects_per_slab;
 			size_t				usage;
 			size_t				maximum;
 			uint32				flags;

src/system/kernel/slab/Slab.cpp

@@ -316,10 +316,7 @@ static status_t
 object_cache_reserve_internal(ObjectCache* cache, size_t objectCount,
 	uint32 flags, bool unlockWhileAllocating)
 {
-	size_t numBytes = objectCount * cache->object_size;
-	size_t slabCount = ((numBytes - 1) / cache->slab_size) + 1;
-		// TODO: This also counts the unusable space of each slab, which can
-		// sum up.
+	size_t slabCount = (objectCount - 1) / cache->objects_per_slab + 1;
 
 	while (slabCount > 0) {
 		slab* newSlab = cache->CreateSlab(flags, unlockWhileAllocating);

src/system/kernel/slab/SmallObjectCache.cpp

@@ -35,6 +35,9 @@ SmallObjectCache::Create(const char* name, size_t object_size,
 	else
 		cache->slab_size = B_PAGE_SIZE;
 
+	cache->objects_per_slab = (cache->slab_size - sizeof(slab))
+		/ cache->object_size;
+
 	return cache;
 }