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/*
* Copyright (C) 1999-2000 Harri Porten (porten@kde.org)
* Copyright (C) 2001 Peter Kelly (pmk@post.com)
* Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
#ifndef MarkedSpace_h
#define MarkedSpace_h
#include "MachineStackMarker.h"
#include "PageAllocationAligned.h"
#include <wtf/FixedArray.h>
#include <wtf/HashCountedSet.h>
#include <wtf/Noncopyable.h>
#include <wtf/Vector.h>
namespace JSC {
class CollectorBlock;
class Heap;
class JSCell;
class JSGlobalData;
class LiveObjectIterator;
class MarkStack;
class WeakGCHandle;
#if OS(WINCE) || OS(SYMBIAN) || PLATFORM(BREWMP)
const size_t BLOCK_SIZE = 64 * 1024; // 64k
#else
const size_t BLOCK_SIZE = 256 * 1024; // 256k
#endif
typedef HashCountedSet<JSCell*> ProtectCountSet;
struct CollectorHeap {
size_t nextBlock;
size_t nextCell;
PageAllocationAligned* blocks;
size_t numBlocks;
size_t usedBlocks;
CollectorBlock* collectorBlock(size_t index) const
{
return static_cast<CollectorBlock*>(blocks[index].base());
}
};
class MarkedSpace {
WTF_MAKE_NONCOPYABLE(MarkedSpace);
public:
MarkedSpace(JSGlobalData*);
void destroy(ProtectCountSet&);
void* allocate(size_t);
size_t objectCount() const;
struct Statistics {
size_t size;
size_t free;
};
Statistics statistics() const;
size_t size() const;
static Heap* heap(JSCell*);
static bool isCellMarked(const JSCell*);
static bool checkMarkCell(const JSCell*);
static void markCell(JSCell*);
WeakGCHandle* addWeakGCHandle(JSCell*);
void markConservatively(ConservativeSet&, void* start, void* end);
static bool isNumber(JSCell*);
LiveObjectIterator primaryHeapBegin();
LiveObjectIterator primaryHeapEnd();
JSGlobalData* globalData() { return m_globalData; }
static CollectorBlock* cellBlock(const JSCell*);
static size_t cellOffset(const JSCell*);
void reset();
void sweep();
NEVER_INLINE CollectorBlock* allocateBlock();
NEVER_INLINE void freeBlock(size_t);
void resizeBlocks();
void growBlocks(size_t neededBlocks);
void shrinkBlocks(size_t neededBlocks);
void clearMarkBits();
void clearMarkBits(CollectorBlock*);
size_t markedCells(size_t startBlock = 0, size_t startCell = 0) const;
void addToStatistics(Statistics&) const;
void markRoots();
private:
CollectorHeap m_heap;
JSGlobalData* m_globalData;
};
// tunable parameters
// derived constants
const size_t BLOCK_OFFSET_MASK = BLOCK_SIZE - 1;
const size_t BLOCK_MASK = ~BLOCK_OFFSET_MASK;
const size_t MINIMUM_CELL_SIZE = 64;
const size_t CELL_ARRAY_LENGTH = (MINIMUM_CELL_SIZE / sizeof(double)) + (MINIMUM_CELL_SIZE % sizeof(double) != 0 ? sizeof(double) : 0);
const size_t CELL_SIZE = CELL_ARRAY_LENGTH * sizeof(double);
const size_t SMALL_CELL_SIZE = CELL_SIZE / 2;
const size_t CELL_MASK = CELL_SIZE - 1;
const size_t CELL_ALIGN_MASK = ~CELL_MASK;
const size_t CELLS_PER_BLOCK = (BLOCK_SIZE - sizeof(MarkedSpace*)) * 8 * CELL_SIZE / (8 * CELL_SIZE + 1) / CELL_SIZE; // one bitmap byte can represent 8 cells.
const size_t BITMAP_SIZE = (CELLS_PER_BLOCK + 7) / 8;
const size_t BITMAP_WORDS = (BITMAP_SIZE + 3) / sizeof(uint32_t);
struct CollectorBitmap {
FixedArray<uint32_t, BITMAP_WORDS> bits;
bool get(size_t n) const { return !!(bits[n >> 5] & (1 << (n & 0x1F))); }
void set(size_t n) { bits[n >> 5] |= (1 << (n & 0x1F)); }
bool getset(size_t n)
{
unsigned i = (1 << (n & 0x1F));
uint32_t& b = bits[n >> 5];
bool r = !!(b & i);
b |= i;
return r;
}
void clear(size_t n) { bits[n >> 5] &= ~(1 << (n & 0x1F)); }
void clearAll() { memset(bits.data(), 0, sizeof(bits)); }
ALWAYS_INLINE void advanceToNextPossibleFreeCell(size_t& startCell)
{
if (!~bits[startCell >> 5])
startCell = (startCell & (~0x1F)) + 32;
else
++startCell;
}
size_t count(size_t startCell = 0)
{
size_t result = 0;
for ( ; (startCell & 0x1F) != 0; ++startCell) {
if (get(startCell))
++result;
}
for (size_t i = startCell >> 5; i < BITMAP_WORDS; ++i)
result += WTF::bitCount(bits[i]);
return result;
}
size_t isEmpty() // Much more efficient than testing count() == 0.
{
for (size_t i = 0; i < BITMAP_WORDS; ++i)
if (bits[i] != 0)
return false;
return true;
}
};
struct CollectorCell {
FixedArray<double, CELL_ARRAY_LENGTH> memory;
};
class CollectorBlock {
public:
FixedArray<CollectorCell, CELLS_PER_BLOCK> cells;
CollectorBitmap marked;
Heap* heap;
};
struct HeapConstants {
static const size_t cellSize = CELL_SIZE;
static const size_t cellsPerBlock = CELLS_PER_BLOCK;
typedef CollectorCell Cell;
typedef CollectorBlock Block;
};
inline CollectorBlock* MarkedSpace::cellBlock(const JSCell* cell)
{
return reinterpret_cast<CollectorBlock*>(reinterpret_cast<uintptr_t>(cell) & BLOCK_MASK);
}
inline size_t MarkedSpace::cellOffset(const JSCell* cell)
{
return (reinterpret_cast<uintptr_t>(cell) & BLOCK_OFFSET_MASK) / CELL_SIZE;
}
inline bool MarkedSpace::isCellMarked(const JSCell* cell)
{
return cellBlock(cell)->marked.get(cellOffset(cell));
}
inline bool MarkedSpace::checkMarkCell(const JSCell* cell)
{
return cellBlock(cell)->marked.getset(cellOffset(cell));
}
inline void MarkedSpace::markCell(JSCell* cell)
{
cellBlock(cell)->marked.set(cellOffset(cell));
}
} // namespace JSC
#endif // MarkedSpace_h
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