#ifndef MarkedBlock_h
#define MarkedBlock_h
+#include "CardSet.h"
+#include "HeapBlock.h"
+
#include <wtf/Bitmap.h>
+#include <wtf/DataLog.h>
+#include <wtf/DoublyLinkedList.h>
+#include <wtf/HashFunctions.h>
#include <wtf/PageAllocationAligned.h>
#include <wtf/StdLibExtras.h>
+#include <wtf/Vector.h>
+
+// Set to log state transitions of blocks.
+#define HEAP_LOG_BLOCK_STATE_TRANSITIONS 0
+
+#if HEAP_LOG_BLOCK_STATE_TRANSITIONS
+#define HEAP_LOG_BLOCK_STATE_TRANSITION(block) do { \
+ dataLog( \
+ "%s:%d %s: block %s = %p, %d\n", \
+ __FILE__, __LINE__, __FUNCTION__, \
+ #block, (block), (block)->m_state); \
+ } while (false)
+#else
+#define HEAP_LOG_BLOCK_STATE_TRANSITION(block) ((void)0)
+#endif
namespace JSC {
-
+
class Heap;
class JSCell;
- class JSGlobalData;
typedef uintptr_t Bits;
- static const size_t KB = 1024;
-
- class MarkedBlock {
+ static const size_t MB = 1024 * 1024;
+
+ bool isZapped(const JSCell*);
+
+ // A marked block is a page-aligned container for heap-allocated objects.
+ // Objects are allocated within cells of the marked block. For a given
+ // marked block, all cells have the same size. Objects smaller than the
+ // cell size may be allocated in the marked block, in which case the
+ // allocation suffers from internal fragmentation: wasted space whose
+ // size is equal to the difference between the cell size and the object
+ // size.
+
+ class MarkedBlock : public HeapBlock {
+ friend class WTF::DoublyLinkedListNode<MarkedBlock>;
public:
- static const size_t atomSize = sizeof(double); // Ensures natural alignment for all built-in types.
+ // Ensure natural alignment for native types whilst recognizing that the smallest
+ // object the heap will commonly allocate is four words.
+ static const size_t atomSize = 4 * sizeof(void*);
+ static const size_t atomShift = 5;
+ static const size_t blockSize = 64 * KB;
+ static const size_t blockMask = ~(blockSize - 1); // blockSize must be a power of two.
- static MarkedBlock* create(JSGlobalData*, size_t cellSize);
+ static const size_t atomsPerBlock = blockSize / atomSize; // ~0.4% overhead
+ static const size_t atomMask = atomsPerBlock - 1;
+ static const int cardShift = 8; // This is log2 of bytes per card.
+ static const size_t bytesPerCard = 1 << cardShift;
+ static const int cardCount = blockSize / bytesPerCard;
+ static const int cardMask = cardCount - 1;
+
+ struct FreeCell {
+ FreeCell* next;
+ };
+
+ struct FreeList {
+ FreeCell* head;
+ size_t bytes;
+
+ FreeList();
+ FreeList(FreeCell*, size_t);
+ };
+
+ struct VoidFunctor {
+ typedef void ReturnType;
+ void returnValue() { }
+ };
+
+ static MarkedBlock* create(Heap*, size_t cellSize, bool cellsNeedDestruction);
+ static MarkedBlock* recycle(MarkedBlock*, Heap*, size_t cellSize, bool cellsNeedDestruction);
static void destroy(MarkedBlock*);
static bool isAtomAligned(const void*);
static size_t firstAtom();
Heap* heap() const;
-
- void setPrev(MarkedBlock*);
- void setNext(MarkedBlock*);
- MarkedBlock* prev() const;
- MarkedBlock* next() const;
void* allocate();
- void reset();
- void sweep();
-
- bool isEmpty();
+
+ enum SweepMode { SweepOnly, SweepToFreeList };
+ FreeList sweep(SweepMode = SweepOnly);
+
+ // While allocating from a free list, MarkedBlock temporarily has bogus
+ // cell liveness data. To restore accurate cell liveness data, call one
+ // of these functions:
+ void didConsumeFreeList(); // Call this once you've allocated all the items in the free list.
+ void zapFreeList(const FreeList&); // Call this to undo the free list.
void clearMarks();
size_t markCount();
+ bool markCountIsZero(); // Faster than markCount().
size_t cellSize();
+ bool cellsNeedDestruction();
size_t size();
size_t capacity();
- bool contains(const void*);
- size_t atomNumber(const void*);
bool isMarked(const void*);
bool testAndSetMarked(const void*);
+ bool isLive(const JSCell*);
+ bool isLiveCell(const void*);
void setMarked(const void*);
- template <typename Functor> void forEach(Functor&);
+#if ENABLE(GGC)
+ void setDirtyObject(const void* atom)
+ {
+ ASSERT(MarkedBlock::blockFor(atom) == this);
+ m_cards.markCardForAtom(atom);
+ }
+
+ uint8_t* addressOfCardFor(const void* atom)
+ {
+ ASSERT(MarkedBlock::blockFor(atom) == this);
+ return &m_cards.cardForAtom(atom);
+ }
+
+ static inline size_t offsetOfCards()
+ {
+ return OBJECT_OFFSETOF(MarkedBlock, m_cards);
+ }
+
+ static inline size_t offsetOfMarks()
+ {
+ return OBJECT_OFFSETOF(MarkedBlock, m_marks);
+ }
+
+ typedef Vector<JSCell*, 32> DirtyCellVector;
+ inline void gatherDirtyCells(DirtyCellVector&);
+ template <int size> inline void gatherDirtyCellsWithSize(DirtyCellVector&);
+#endif
+
+ template <typename Functor> void forEachCell(Functor&);
private:
- static const size_t blockSize = 16 * KB;
- static const size_t blockMask = ~(blockSize - 1); // blockSize must be a power of two.
+ static const size_t atomAlignmentMask = atomSize - 1; // atomSize must be a power of two.
- static const size_t atomMask = ~(atomSize - 1); // atomSize must be a power of two.
-
- static const size_t atomsPerBlock = blockSize / atomSize;
+ enum BlockState { New, FreeListed, Allocated, Marked, Zapped };
+ template<bool destructorCallNeeded> FreeList sweepHelper(SweepMode = SweepOnly);
typedef char Atom[atomSize];
- MarkedBlock(const PageAllocationAligned&, JSGlobalData*, size_t cellSize);
+ MarkedBlock(PageAllocationAligned&, Heap*, size_t cellSize, bool cellsNeedDestruction);
Atom* atoms();
+ size_t atomNumber(const void*);
+ void callDestructor(JSCell*);
+ template<BlockState, SweepMode, bool destructorCallNeeded> FreeList specializedSweep();
+
+#if ENABLE(GGC)
+ CardSet<bytesPerCard, blockSize> m_cards;
+#endif
- size_t m_nextAtom;
- size_t m_endAtom; // This is a fuzzy end. Always test for < m_endAtom.
size_t m_atomsPerCell;
- WTF::Bitmap<blockSize / atomSize> m_marks;
- PageAllocationAligned m_allocation;
+ size_t m_endAtom; // This is a fuzzy end. Always test for < m_endAtom.
+#if ENABLE(PARALLEL_GC)
+ WTF::Bitmap<atomsPerBlock, WTF::BitmapAtomic> m_marks;
+#else
+ WTF::Bitmap<atomsPerBlock, WTF::BitmapNotAtomic> m_marks;
+#endif
+ bool m_cellsNeedDestruction;
+ BlockState m_state;
Heap* m_heap;
- MarkedBlock* m_prev;
- MarkedBlock* m_next;
};
+ inline MarkedBlock::FreeList::FreeList()
+ : head(0)
+ , bytes(0)
+ {
+ }
+
+ inline MarkedBlock::FreeList::FreeList(FreeCell* head, size_t bytes)
+ : head(head)
+ , bytes(bytes)
+ {
+ }
+
inline size_t MarkedBlock::firstAtom()
{
return WTF::roundUpToMultipleOf<atomSize>(sizeof(MarkedBlock)) / atomSize;
inline bool MarkedBlock::isAtomAligned(const void* p)
{
- return !((intptr_t)(p) & ~atomMask);
+ return !(reinterpret_cast<Bits>(p) & atomAlignmentMask);
}
inline MarkedBlock* MarkedBlock::blockFor(const void* p)
{
- return reinterpret_cast<MarkedBlock*>(reinterpret_cast<uintptr_t>(p) & blockMask);
+ return reinterpret_cast<MarkedBlock*>(reinterpret_cast<Bits>(p) & blockMask);
}
inline Heap* MarkedBlock::heap() const
return m_heap;
}
- inline void MarkedBlock::setPrev(MarkedBlock* prev)
+ inline void MarkedBlock::didConsumeFreeList()
{
- m_prev = prev;
- }
+ HEAP_LOG_BLOCK_STATE_TRANSITION(this);
- inline void MarkedBlock::setNext(MarkedBlock* next)
- {
- m_next = next;
+ ASSERT(m_state == FreeListed);
+ m_state = Allocated;
}
- inline MarkedBlock* MarkedBlock::prev() const
+ inline void MarkedBlock::clearMarks()
{
- return m_prev;
- }
+ HEAP_LOG_BLOCK_STATE_TRANSITION(this);
- inline MarkedBlock* MarkedBlock::next() const
- {
- return m_next;
+ ASSERT(m_state != New && m_state != FreeListed);
+ m_marks.clearAll();
+
+ // This will become true at the end of the mark phase. We set it now to
+ // avoid an extra pass to do so later.
+ m_state = Marked;
}
- inline void MarkedBlock::reset()
+ inline size_t MarkedBlock::markCount()
{
- m_nextAtom = firstAtom();
+ return m_marks.count();
}
- inline bool MarkedBlock::isEmpty()
+ inline bool MarkedBlock::markCountIsZero()
{
return m_marks.isEmpty();
}
- inline void MarkedBlock::clearMarks()
- {
- m_marks.clearAll();
- }
-
- inline size_t MarkedBlock::markCount()
+ inline size_t MarkedBlock::cellSize()
{
- return m_marks.count();
+ return m_atomsPerCell * atomSize;
}
- inline size_t MarkedBlock::cellSize()
+ inline bool MarkedBlock::cellsNeedDestruction()
{
- return m_atomsPerCell * atomSize;
+ return m_cellsNeedDestruction;
}
inline size_t MarkedBlock::size()
return m_allocation.size();
}
- inline bool MarkedBlock::contains(const void* p)
- {
- ASSERT(p && isAtomAligned(p) && atomNumber(p) < atomsPerBlock);
-
- // Even though we physically contain p, we only logically contain p if p
- // points to a live cell. (Claiming to contain a dead cell would trick the
- // conservative garbage collector into resurrecting the cell in a zombie state.)
- return isMarked(p);
- }
-
inline size_t MarkedBlock::atomNumber(const void* p)
{
- return (reinterpret_cast<uintptr_t>(p) - reinterpret_cast<uintptr_t>(this)) / atomSize;
+ return (reinterpret_cast<Bits>(p) - reinterpret_cast<Bits>(this)) / atomSize;
}
inline bool MarkedBlock::isMarked(const void* p)
inline bool MarkedBlock::testAndSetMarked(const void* p)
{
- return m_marks.testAndSet(atomNumber(p));
+ return m_marks.concurrentTestAndSet(atomNumber(p));
}
inline void MarkedBlock::setMarked(const void* p)
m_marks.set(atomNumber(p));
}
- template <typename Functor> inline void MarkedBlock::forEach(Functor& functor)
+ inline bool MarkedBlock::isLive(const JSCell* cell)
+ {
+ switch (m_state) {
+ case Allocated:
+ return true;
+ case Zapped:
+ if (isZapped(cell)) {
+ // Object dead in previous collection, not allocated since previous collection: mark bit should not be set.
+ ASSERT(!m_marks.get(atomNumber(cell)));
+ return false;
+ }
+
+ // Newly allocated objects: mark bit not set.
+ // Objects that survived prior collection: mark bit set.
+ return true;
+ case Marked:
+ return m_marks.get(atomNumber(cell));
+
+ case New:
+ case FreeListed:
+ ASSERT_NOT_REACHED();
+ return false;
+ }
+
+ ASSERT_NOT_REACHED();
+ return false;
+ }
+
+ inline bool MarkedBlock::isLiveCell(const void* p)
+ {
+ ASSERT(MarkedBlock::isAtomAligned(p));
+ size_t atomNumber = this->atomNumber(p);
+ size_t firstAtom = this->firstAtom();
+ if (atomNumber < firstAtom) // Filters pointers into MarkedBlock metadata.
+ return false;
+ if ((atomNumber - firstAtom) % m_atomsPerCell) // Filters pointers into cell middles.
+ return false;
+ if (atomNumber >= m_endAtom) // Filters pointers into invalid cells out of the range.
+ return false;
+
+ return isLive(static_cast<const JSCell*>(p));
+ }
+
+ template <typename Functor> inline void MarkedBlock::forEachCell(Functor& functor)
{
for (size_t i = firstAtom(); i < m_endAtom; i += m_atomsPerCell) {
- if (!m_marks.get(i))
+ JSCell* cell = reinterpret_cast_ptr<JSCell*>(&atoms()[i]);
+ if (!isLive(cell))
continue;
- functor(reinterpret_cast<JSCell*>(&atoms()[i]));
+
+ functor(cell);
}
}
+#if ENABLE(GGC)
+template <int _cellSize> void MarkedBlock::gatherDirtyCellsWithSize(DirtyCellVector& dirtyCells)
+{
+ if (m_cards.testAndClear(0)) {
+ char* ptr = reinterpret_cast<char*>(&atoms()[firstAtom()]);
+ const char* end = reinterpret_cast<char*>(this) + bytesPerCard;
+ while (ptr < end) {
+ JSCell* cell = reinterpret_cast<JSCell*>(ptr);
+ if (isMarked(cell))
+ dirtyCells.append(cell);
+ ptr += _cellSize;
+ }
+ }
+
+ const size_t cellOffset = firstAtom() * atomSize % _cellSize;
+ for (size_t i = 1; i < m_cards.cardCount; i++) {
+ if (!m_cards.testAndClear(i))
+ continue;
+ char* ptr = reinterpret_cast<char*>(this) + i * bytesPerCard + cellOffset;
+ char* end = reinterpret_cast<char*>(this) + (i + 1) * bytesPerCard;
+
+ while (ptr < end) {
+ JSCell* cell = reinterpret_cast<JSCell*>(ptr);
+ if (isMarked(cell))
+ dirtyCells.append(cell);
+ ptr += _cellSize;
+ }
+ }
+}
+
+void MarkedBlock::gatherDirtyCells(DirtyCellVector& dirtyCells)
+{
+ COMPILE_ASSERT((int)m_cards.cardCount == (int)cardCount, MarkedBlockCardCountsMatch);
+
+ ASSERT(m_state != New && m_state != FreeListed);
+
+ // This is an optimisation to avoid having to walk the set of marked
+ // blocks twice during GC.
+ m_state = Marked;
+
+ if (markCountIsZero())
+ return;
+
+ size_t cellSize = this->cellSize();
+ if (cellSize == 32) {
+ gatherDirtyCellsWithSize<32>(dirtyCells);
+ return;
+ }
+ if (cellSize == 64) {
+ gatherDirtyCellsWithSize<64>(dirtyCells);
+ return;
+ }
+
+ const size_t firstCellOffset = firstAtom() * atomSize % cellSize;
+
+ if (m_cards.testAndClear(0)) {
+ char* ptr = reinterpret_cast<char*>(this) + firstAtom() * atomSize;
+ char* end = reinterpret_cast<char*>(this) + bytesPerCard;
+ while (ptr < end) {
+ JSCell* cell = reinterpret_cast<JSCell*>(ptr);
+ if (isMarked(cell))
+ dirtyCells.append(cell);
+ ptr += cellSize;
+ }
+ }
+ for (size_t i = 1; i < m_cards.cardCount; i++) {
+ if (!m_cards.testAndClear(i))
+ continue;
+ char* ptr = reinterpret_cast<char*>(this) + firstCellOffset + cellSize * ((i * bytesPerCard + cellSize - 1 - firstCellOffset) / cellSize);
+ char* end = reinterpret_cast<char*>(this) + std::min((i + 1) * bytesPerCard, m_endAtom * atomSize);
+
+ while (ptr < end) {
+ JSCell* cell = reinterpret_cast<JSCell*>(ptr);
+ if (isMarked(cell))
+ dirtyCells.append(cell);
+ ptr += cellSize;
+ }
+ }
+}
+#endif
+
} // namespace JSC
-#endif // MarkedSpace_h
+namespace WTF {
+
+ struct MarkedBlockHash : PtrHash<JSC::MarkedBlock*> {
+ static unsigned hash(JSC::MarkedBlock* const& key)
+ {
+ // Aligned VM regions tend to be monotonically increasing integers,
+ // which is a great hash function, but we have to remove the low bits,
+ // since they're always zero, which is a terrible hash function!
+ return reinterpret_cast<JSC::Bits>(key) / JSC::MarkedBlock::blockSize;
+ }
+ };
+
+ template<> struct DefaultHash<JSC::MarkedBlock*> {
+ typedef MarkedBlockHash Hash;
+ };
+
+} // namespace WTF
+
+#endif // MarkedBlock_h
projects / apple / javascriptcore.git / blobdiff