-
-#define TwoPow(n) (1ull << n)
-
-class AllocationTableSizeClass {
-public:
- AllocationTableSizeClass(size_t size, size_t blockSize, unsigned log2BlockSize)
- : m_blockSize(blockSize)
- {
- ASSERT(blockSize == TwoPow(log2BlockSize));
-
- // Calculate the number of blocks needed to hold size.
- size_t blockMask = blockSize - 1;
- m_blockCount = (size + blockMask) >> log2BlockSize;
-
- // Align to the smallest power of two >= m_blockCount.
- m_blockAlignment = 1;
- while (m_blockAlignment < m_blockCount)
- m_blockAlignment += m_blockAlignment;
- }
-
- size_t blockSize() const { return m_blockSize; }
- size_t blockCount() const { return m_blockCount; }
- size_t blockAlignment() const { return m_blockAlignment; }
-
- size_t size()
- {
- return m_blockSize * m_blockCount;
- }
-
-private:
- size_t m_blockSize;
- size_t m_blockCount;
- size_t m_blockAlignment;
-};
-
-template<unsigned log2Entries>
-class AllocationTableLeaf {
- typedef uint64_t BitField;
-
-public:
- static const unsigned log2SubregionSize = 12; // 2^12 == pagesize
- static const unsigned log2RegionSize = log2SubregionSize + log2Entries;
-
- static const size_t subregionSize = TwoPow(log2SubregionSize);
- static const size_t regionSize = TwoPow(log2RegionSize);
- static const unsigned entries = TwoPow(log2Entries);
- COMPILE_ASSERT(entries <= (sizeof(BitField) * 8), AllocationTableLeaf_entries_fit_in_BitField);
-
- AllocationTableLeaf()
- : m_allocated(0)
- {
- }
-
- ~AllocationTableLeaf()
- {
- ASSERT(isEmpty());
- }
-
- size_t allocate(AllocationTableSizeClass& sizeClass)
- {
- ASSERT(sizeClass.blockSize() == subregionSize);
- ASSERT(!isFull());
-
- size_t alignment = sizeClass.blockAlignment();
- size_t count = sizeClass.blockCount();
- // Use this mask to check for spans of free blocks.
- BitField mask = ((1ull << count) - 1) << (alignment - count);
-
- // Step in units of alignment size.
- for (unsigned i = 0; i < entries; i += alignment) {
- if (!(m_allocated & mask)) {
- m_allocated |= mask;
- return (i + (alignment - count)) << log2SubregionSize;
- }
- mask <<= alignment;
- }
- return notFound;
- }
-
- void free(size_t location, AllocationTableSizeClass& sizeClass)
- {
- ASSERT(sizeClass.blockSize() == subregionSize);
-
- size_t entry = location >> log2SubregionSize;
- size_t count = sizeClass.blockCount();
- BitField mask = ((1ull << count) - 1) << entry;
-
- ASSERT((m_allocated & mask) == mask);
- m_allocated &= ~mask;
- }
-
- bool isEmpty()
- {
- return !m_allocated;
- }
-
- bool isFull()
- {
- return !~m_allocated;
- }
-
- static size_t size()
- {
- return regionSize;
- }
-
- static AllocationTableSizeClass classForSize(size_t size)
- {
- return AllocationTableSizeClass(size, subregionSize, log2SubregionSize);
- }
-
-#ifndef NDEBUG
- void dump(size_t parentOffset = 0, unsigned indent = 0)
- {
- for (unsigned i = 0; i < indent; ++i)
- fprintf(stderr, " ");
- fprintf(stderr, "%08x: [%016llx]\n", (int)parentOffset, m_allocated);
- }
-#endif
-
-private:
- BitField m_allocated;
-};
-
-
-template<class NextLevel>
-class LazyAllocationTable {
-public:
- static const unsigned log2RegionSize = NextLevel::log2RegionSize;
- static const unsigned entries = NextLevel::entries;
-
- LazyAllocationTable()
- : m_ptr(0)
- {
- }
-
- ~LazyAllocationTable()
- {
- ASSERT(isEmpty());
- }
-
- size_t allocate(AllocationTableSizeClass& sizeClass)
- {
- if (!m_ptr)
- m_ptr = new NextLevel();
- return m_ptr->allocate(sizeClass);
- }
-
- void free(size_t location, AllocationTableSizeClass& sizeClass)
- {
- ASSERT(m_ptr);
- m_ptr->free(location, sizeClass);
- if (m_ptr->isEmpty()) {
- delete m_ptr;
- m_ptr = 0;
- }
- }
-
- bool isEmpty()
- {
- return !m_ptr;
- }
-
- bool isFull()
- {
- return m_ptr && m_ptr->isFull();
- }
-
- static size_t size()
- {
- return NextLevel::size();
- }
-
-#ifndef NDEBUG
- void dump(size_t parentOffset = 0, unsigned indent = 0)
- {
- ASSERT(m_ptr);
- m_ptr->dump(parentOffset, indent);
- }
-#endif
-
- static AllocationTableSizeClass classForSize(size_t size)
- {
- return NextLevel::classForSize(size);
- }
-
-private:
- NextLevel* m_ptr;
-};
-
-template<class NextLevel, unsigned log2Entries>
-class AllocationTableDirectory {
- typedef uint64_t BitField;
-
-public:
- static const unsigned log2SubregionSize = NextLevel::log2RegionSize;
- static const unsigned log2RegionSize = log2SubregionSize + log2Entries;
-
- static const size_t subregionSize = TwoPow(log2SubregionSize);
- static const size_t regionSize = TwoPow(log2RegionSize);
- static const unsigned entries = TwoPow(log2Entries);
- COMPILE_ASSERT(entries <= (sizeof(BitField) * 8), AllocationTableDirectory_entries_fit_in_BitField);
-
- AllocationTableDirectory()
- : m_full(0)
- , m_hasSuballocation(0)
- {
- }
-
- ~AllocationTableDirectory()
- {
- ASSERT(isEmpty());
- }
-
- size_t allocate(AllocationTableSizeClass& sizeClass)
- {
- ASSERT(sizeClass.blockSize() <= subregionSize);
- ASSERT(!isFull());
-
- if (sizeClass.blockSize() < subregionSize) {
- BitField bit = 1;
- for (unsigned i = 0; i < entries; ++i, bit += bit) {
- if (m_full & bit)
- continue;
- size_t location = m_suballocations[i].allocate(sizeClass);
- if (location != notFound) {
- // If this didn't already have a subregion, it does now!
- m_hasSuballocation |= bit;
- // Mirror the suballocation's full bit.
- if (m_suballocations[i].isFull())
- m_full |= bit;
- return (i * subregionSize) + location;
- }
- }
- return notFound;
- }
-
- // A block is allocated if either it is fully allocated or contains suballocations.
- BitField allocated = m_full | m_hasSuballocation;
-
- size_t alignment = sizeClass.blockAlignment();
- size_t count = sizeClass.blockCount();
- // Use this mask to check for spans of free blocks.
- BitField mask = ((1ull << count) - 1) << (alignment - count);
-
- // Step in units of alignment size.
- for (unsigned i = 0; i < entries; i += alignment) {
- if (!(allocated & mask)) {
- m_full |= mask;
- return (i + (alignment - count)) << log2SubregionSize;
- }
- mask <<= alignment;
- }
- return notFound;
- }
-
- void free(size_t location, AllocationTableSizeClass& sizeClass)
- {
- ASSERT(sizeClass.blockSize() <= subregionSize);
-
- size_t entry = location >> log2SubregionSize;
-
- if (sizeClass.blockSize() < subregionSize) {
- BitField bit = 1ull << entry;
- m_suballocations[entry].free(location & (subregionSize - 1), sizeClass);
- // Check if the suballocation is now empty.
- if (m_suballocations[entry].isEmpty())
- m_hasSuballocation &= ~bit;
- // No need to check, it clearly isn't full any more!
- m_full &= ~bit;
- } else {
- size_t count = sizeClass.blockCount();
- BitField mask = ((1ull << count) - 1) << entry;
- ASSERT((m_full & mask) == mask);
- ASSERT(!(m_hasSuballocation & mask));
- m_full &= ~mask;
- }
- }
-
- bool isEmpty()
- {
- return !(m_full | m_hasSuballocation);
- }
-
- bool isFull()
- {
- return !~m_full;
- }
-
- static size_t size()
- {
- return regionSize;
- }
-
- static AllocationTableSizeClass classForSize(size_t size)
- {
- if (size < subregionSize) {
- AllocationTableSizeClass sizeClass = NextLevel::classForSize(size);
- if (sizeClass.size() < NextLevel::size())
- return sizeClass;
- }
- return AllocationTableSizeClass(size, subregionSize, log2SubregionSize);
- }
-
-#ifndef NDEBUG
- void dump(size_t parentOffset = 0, unsigned indent = 0)
- {
- for (unsigned i = 0; i < indent; ++i)
- fprintf(stderr, " ");
- fprintf(stderr, "%08x: [", (int)parentOffset);
- for (unsigned i = 0; i < entries; ++i) {
- BitField bit = 1ull << i;
- char c = m_hasSuballocation & bit
- ? (m_full & bit ? 'N' : 'n')
- : (m_full & bit ? 'F' : '-');
- fprintf(stderr, "%c", c);
- }
- fprintf(stderr, "]\n");
-
- for (unsigned i = 0; i < entries; ++i) {
- BitField bit = 1ull << i;
- size_t offset = parentOffset | (subregionSize * i);
- if (m_hasSuballocation & bit)
- m_suballocations[i].dump(offset, indent + 1);
- }
- }
-#endif
-
-private:
- NextLevel m_suballocations[entries];
- // Subregions exist in one of four states:
- // (1) empty (both bits clear)
- // (2) fully allocated as a single allocation (m_full set)
- // (3) partially allocated through suballocations (m_hasSuballocation set)
- // (4) fully allocated through suballocations (both bits set)
- BitField m_full;
- BitField m_hasSuballocation;
-};
-
-typedef AllocationTableLeaf<6> PageTables256KB;
-typedef AllocationTableDirectory<PageTables256KB, 6> PageTables16MB;
-typedef AllocationTableDirectory<LazyAllocationTable<PageTables16MB>, 1> PageTables32MB;
-typedef AllocationTableDirectory<LazyAllocationTable<PageTables16MB>, 6> PageTables1GB;
-