Allow vm_space to merge ranges

src/kernel/main.cpp

@@ -78,6 +78,7 @@ kernel_main(kernel_args *header)
 			memory::page_offset - memory::kernel_offset,
 			heap);
 	k_space.reserve(0xffffff0000100000, 0x100000);
+	k_space.reserve(0xffffff0000200000, 0x100000);
 
 	initrd::disk ird(header->initrd, heap);
 	log::info(logs::boot, "initrd loaded with %d files.", ird.files().count());

src/libraries/kutil/include/kutil/avl_tree.h

@@ -150,6 +150,64 @@ private:
 		return existing;
 	}
 
+	static node_type * remove(node_type *existing, node_type *subtrahend, allocator &alloc)
+	{
+		if (existing == nullptr)
+			return existing;
+
+		if (existing == subtrahend) {
+			if (!existing->m_left || !existing->m_right) {
+				// At least one child is null
+				node_type *temp = existing->m_left ?
+					existing->m_left : existing->m_right;
+
+				if (temp == nullptr) {
+					// Both were null
+					temp = existing;
+					existing = nullptr;
+				} else {
+					*existing = *temp;
+				}
+
+				alloc.free(temp);
+			} else {
+				// Both children exist, find next node
+				node_type *temp = existing->m_right;
+				while (temp->m_left)
+					temp = temp->m_left;
+
+				*existing = *temp;
+				existing->m_right = remove(existing->m_right, temp, alloc);
+			}
+		} else if (existing->compare(subtrahend) < 0) {
+			existing->m_left = remove(existing->m_left, subtrahend, alloc);
+		} else {
+			existing->m_right = remove(existing->m_right, subtrahend, alloc);
+		}
+
+		if (!existing)
+			return nullptr;
+
+		int balance = existing->update_height();
+		if (balance > 1) {
+			int left_balance = existing->m_left->update_height();
+
+			if (left_balance < 0)
+				existing->m_left = rotate_left(existing->m_left);
+
+			return rotate_right(existing);
+		} else if (balance < -1) {
+			int right_balance = existing->m_right->update_height();
+
+			if (right_balance > 0)
+				existing->m_right = rotate_right(existing->m_right);
+
+			return rotate_left(existing);
+		}
+
+		return existing;
+	}
+
 	int m_height;
 	node_type *m_left;
 	node_type *m_right;
@@ -162,10 +220,21 @@ public:
 	using item_type = T;
 	using node_type = avl_node<T>;
 
-	inline void insert(node_type *addend) { m_root = node_type::insert(m_root, addend); }
 	inline node_type * root() { return m_root; }
+	inline unsigned count() const { return m_count; }
+
+	inline void remove(node_type *subtrahend, allocator &alloc) {
+		m_root = node_type::remove(m_root, subtrahend, alloc);
+		m_count--;
+	}
+
+	inline void insert(node_type *addend) {
+		m_root = node_type::insert(m_root, addend);
+		m_count++;
+	}
 
 private:
+	unsigned m_count {0};
 	node_type *m_root;
 };
 

src/libraries/kutil/include/kutil/slab_allocator.h

@@ -12,24 +12,36 @@ namespace kutil {
 /// A slab allocator for small structures kept in a linked list
 template <typename T, size_t N = memory::frame_size>
 class slab_allocator :
-	public linked_list<T>
+	public linked_list<T>,
+	public allocator
 {
 public:
 	using item_type = list_node<T>;
 
 	/// Default constructor.
-	/// \arg chunk_size The size of chunk to allocate, in bytes. 0 means default.
 	/// \arg alloc      The allocator to use to allocate chunks. Defaults to malloc().
 	slab_allocator(allocator &alloc) :
-		m_alloc(alloc)
+		m_alloc(alloc) {}
+
+	/// Allocator interface implementation
+	virtual void * allocate(size_t size) override
 	{
+		kassert(size == sizeof(T), "Asked slab allocator for wrong size");
+		if (size != sizeof(T)) return 0;
+		return pop();
+	}
+
+	/// Allocator interface implementation
+	virtual void free(void *p) override
+	{
+		push(static_cast<item_type*>(p));
 	}
 
 	/// Get an item from the cache. May allocate a new chunk if the cache is empty.
 	/// \returns  An allocated element
 	inline item_type * pop()
 	{
-		if (this->empty()) this->allocate();
+		if (this->empty()) this->allocate_chunk();
 		kassert(!this->empty(), "Slab allocator is empty after allocate()");
 		item_type *item = this->pop_front();
 		kutil::memset(item, 0, sizeof(item_type));
@@ -43,7 +55,8 @@ public:
 		this->push_front(item);
 	}
 
-	void allocate()
+private:
+	void allocate_chunk()
 	{
 		constexpr unsigned count = N / sizeof(item_type);
 
@@ -53,7 +66,6 @@ public:
 			this->push_back(&items[i]);
 	}
 
-private:
 	allocator& m_alloc;
 };
 

src/libraries/kutil/include/kutil/vm_space.h

@@ -66,8 +66,10 @@ private:
 	using tree_type = kutil::avl_tree<vm_range>;
 
 	node_type * split_out(node_type* node, uintptr_t start, size_t size, vm_state state);
+	node_type * consolidate(node_type* needle);
 
-	slab_allocator<node_type> m_alloc;
+	slab_allocator<node_type> m_slab;
+	allocator &m_alloc;
 	tree_type m_ranges;
 };
 

src/libraries/kutil/vm_space.cpp

@@ -1,16 +1,18 @@
 #include <algorithm>
 #include "kutil/logger.h"
+#include "kutil/vector.h"
 #include "kutil/vm_space.h"
 
 namespace kutil {
 
 using node_type = kutil::avl_node<vm_range>;
-
+using node_vec = kutil::vector<node_type*>;
 
 vm_space::vm_space(uintptr_t start, size_t size, allocator &alloc) :
+	m_slab(alloc),
 	m_alloc(alloc)
 {
-	node_type *node = m_alloc.pop();
+	node_type *node = m_slab.pop();
 	node->address = start;
 	node->size = size;
 	node->state = vm_state::none;
@@ -23,8 +25,8 @@ vm_space::vm_space(uintptr_t start, size_t size, allocator &alloc) :
 inline static bool
 overlaps(node_type *node, uintptr_t start, size_t size)
 {
-	return start <= node->end() &&
+	return start < node->end() &&
-		   (start + size) >= node->address;
+		   (start + size) > node->address;
 }
 
 static node_type *
@@ -46,7 +48,7 @@ node_type *
 vm_space::split_out(node_type *node, uintptr_t start, size_t size, vm_state state)
 {
 	// No cross-boundary splits allowed for now
-	bool contained = 
+	bool contained =
 		start >= node->address &&
 		start+size <= node->end();
 
@@ -59,23 +61,32 @@ vm_space::split_out(node_type *node, uintptr_t start, size_t size, vm_state stat
 	if (state == old_state)
 		return node;
 
+	node->state = state;
+
 	log::debug(logs::vmem, "Splitting out region %016llx-%016llx[%d] from %016llx-%016llx[%d]",
 			start, start+size, state, node->address, node->end(), old_state);
 
+	bool do_consolidate = false;
 	if (node->address < start) {
 		// Split off rest into new node
 		size_t leading = start - node->address;
 
-		node_type *next = m_alloc.pop();
+		node_type *next = m_slab.pop();
 		next->state = state;
 		next->address = start;
 		next->size = node->size - leading;
+
 		node->size = leading;
+		node->state = old_state;
+
+		log::debug(logs::vmem,
+			"   leading region %016llx-%016llx[%d]",
+			node->address, node->address + node->size, node->state);
 
 		m_ranges.insert(next);
 		node = next;
 	} else {
-		// TODO: check if this can merge with prev node
+		do_consolidate = true;
 	}
 
 	if (node->end() > start + size) {
@@ -83,27 +94,79 @@ vm_space::split_out(node_type *node, uintptr_t start, size_t size, vm_state stat
 		size_t trailing =  node->size - size;
 		node->size -= trailing;
 
-		node_type *next = m_alloc.pop();
+		node_type *next = m_slab.pop();
 		next->state = old_state;
 		next->address = node->end();
 		next->size = trailing;
 
+		log::debug(logs::vmem,
+			"   tailing region %016llx-%016llx[%d]",
+			next->address, next->address + next->size, next->state);
+
 		m_ranges.insert(next);
 	} else {
-		// TODO: check if this can merge with next node
+		do_consolidate = true;
 	}
 
+	if (do_consolidate)
+		node = consolidate(node);
+
 	return node;
 }
 
+inline void gather(node_type *node, node_vec &vec)
+{
+	if (node) {
+		gather(node->left(), vec);
+		vec.append(node);
+		gather(node->right(), vec);
+	}
+}
+
+node_type *
+vm_space::consolidate(node_type *needle)
+{
+	node_vec nodes(m_ranges.count(), m_alloc);
+	gather(m_ranges.root(), nodes);
+
+	node_type *prev = nullptr;
+	for (auto *node : nodes) {
+		log::debug(logs::vmem,
+			"* Existing region %016llx-%016llx[%d]",
+			node->address, node->address + node->size, node->state);
+
+		if (prev && node->address == prev->end() && node->state == prev->state) {
+			log::debug(logs::vmem,
+				"Joining regions %016llx-%016llx[%d] %016llx-%016llx[%d]",
+				prev->address, prev->address + prev->size, prev->state,
+				node->address, node->address + node->size, node->state);
+
+			prev->size += node->size;
+			if (needle == node)
+				needle = prev;
+			m_ranges.remove(node, m_slab);
+		} else {
+			prev = node;
+		}
+	}
+
+	return needle;
+}
+
 uintptr_t
 vm_space::reserve(uintptr_t start, size_t size)
 {
 	log::debug(logs::vmem, "Reserving region %016llx-%016llx", start, start+size);
 
 	node_type *node = find_overlapping(m_ranges.root(), start, size);
-	if (!node || node->state != vm_state::none)
+	if (!node) {
+		log::debug(logs::vmem, "  found no match");
 		return 0;
+	} else if (node->state != vm_state::none) {
+		log::debug(logs::vmem, "  found wrong state %016llx-%016llx[%d]",
+			node->address, node->address + node->size, node->state);
+		return 0;
+	}
 
 	node = split_out(node, start, size, vm_state::reserved);
 	return node ? start : 0;