added initial slab code to the kernel. It is still unused, and there is still no VM interaction.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@20832 a95241bf-73f2-0310-859d-f6bbb57e9c96
2007-04-26 03:41:24 +00:00
parent 5f29df20b2
commit 81423c91c7
11 changed files with 1169 additions and 0 deletions
@@ -0,0 +1,104 @@
+/*
+ * Copyright 2007, Hugo Santos. All Rights Reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *      Hugo Santos, [email protected]
+ */
+
+#ifndef _SLAB_MERGED_STRATEGY_H_
+#define _SLAB_MERGED_STRATEGY_H_
+
+#include <slab/Strategy.h>
+
+
+namespace Private {
+	static inline const void *
+	LowerBoundary(void *object, size_t byteCount)
+	{
+		const uint8_t *null = (uint8_t *)NULL;
+		return null + ((((uint8_t *)object) - null) & ~(byteCount - 1));
+	}
+}
+
+
+// This slab strategy includes the ObjectLink at the end of each object and the
+// slab at the end of the allocated pages. It uses aligned allocations to
+// provide object to slab mapping with zero storage, thus there is only one
+// word of overhead per object. This is optimized for small objects.
+template<typename Backend>
+class MergedLinkCacheStrategy : public BaseCacheStrategy<Backend> {
+public:
+	typedef typename BaseCacheStrategy<Backend>::Slab Slab;
+	typedef cache_object_link Link;
+
+	MergedLinkCacheStrategy(base_cache *parent)
+		: BaseCacheStrategy<Backend>(parent) {}
+
+	static size_t RequiredSpace(size_t objectSize)
+	{
+		return objectSize + sizeof(Link);
+	}
+
+	void *Object(Link *link) const
+	{
+		return ((uint8_t *)link) - (fParent->object_size - sizeof(Link));
+	}
+
+	CacheObjectInfo ObjectInformation(void *object) const
+	{
+		Slab *slab = _SlabInPages(Private::LowerBoundary(object, _SlabSize()));
+		return CacheObjectInfo(slab, _Linkage(object));
+	}
+
+	BaseSlab *NewSlab(uint32_t flags)
+	{
+		typename Backend::AllocationID id;
+		void *pages;
+
+		size_t byteCount = _SlabSize();
+		if (byteCount > Backend::kMaximumAlignedLength)
+			byteCount = Backend::kMaximumAlignedLength;
+
+		// in order to save a pointer per object or a hash table to
+		// map objects to slabs we required this set of pages to be
+		// aligned in a (pageCount * PAGE_SIZE) boundary.
+		if (Backend::AllocatePages(fParent, &id, &pages, byteCount,
+				CACHE_ALIGN_TO_TOTAL | flags) < B_OK)
+			return NULL;
+
+		_SlabInPages(pages)->id = id;
+
+		return BaseCacheStrategy<Backend>::_ConstructSlab(_SlabInPages(pages),
+			pages, sizeof(Slab), _Linkage, this);
+	}
+
+	void ReturnSlab(BaseSlab *slab)
+	{
+		BaseCacheStrategy<Backend>::_DestructSlab(slab);
+	}
+
+private:
+	size_t _SlabSize() const
+	{
+		return BaseCacheStrategy<Backend>::SlabSize(sizeof(Slab));
+	}
+
+	Link *_Linkage(void *object) const
+	{
+		return (Link *)(((uint8_t *)object)
+			+ (fParent->object_size - sizeof(Link)));
+	}
+
+	Slab *_SlabInPages(const void *pages) const
+	{
+		return (Slab *)(((uint8_t *)pages) + _SlabSize() - sizeof(Slab));
+	}
+
+	static Link *_Linkage(void *_this, void *object)
+	{
+		return ((MergedLinkCacheStrategy *)_this)->_Linkage(object);
+	}
+};
+
+#endif