runtime/Collector.h

   1 /*
   2  *  Copyright (C) 1999-2000 Harri Porten (porten@kde.org)
   3  *  Copyright (C) 2001 Peter Kelly (pmk@post.com)
   4  *  Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
   5  *
   6  *  This library is free software; you can redistribute it and/or
   7  *  modify it under the terms of the GNU Lesser General Public
   8  *  License as published by the Free Software Foundation; either
   9  *  version 2 of the License, or (at your option) any later version.
  10  *
  11  *  This library is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  *  Lesser General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU Lesser General Public
  17  *  License along with this library; if not, write to the Free Software
  18  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  19  *
  20  */
  21
  22 #ifndef Collector_h
  23 #define Collector_h
  24
  25 #include <stddef.h>
  26 #include <string.h>
  27 #include <wtf/HashCountedSet.h>
  28 #include <wtf/HashSet.h>
  29 #include <wtf/Noncopyable.h>
  30 #include <wtf/OwnPtr.h>
  31 #include <wtf/StdLibExtras.h>
  32 #include <wtf/Threading.h>
  33
  34 #if ENABLE(JSC_MULTIPLE_THREADS)
  35 #include <pthread.h>
  36 #endif
  37
  38 #if OS(SYMBIAN)
  39 #include <wtf/symbian/BlockAllocatorSymbian.h>
  40 #endif
  41
  42 #define ASSERT_CLASS_FITS_IN_CELL(class) COMPILE_ASSERT(sizeof(class) <= CELL_SIZE, class_fits_in_cell)
  43
  44 namespace JSC {
  45
  46     class CollectorBlock;
  47     class JSCell;
  48     class JSGlobalData;
  49     class JSValue;
  50     class MarkedArgumentBuffer;
  51     class MarkStack;
  52
  53     enum OperationInProgress { NoOperation, Allocation, Collection };
  54
  55     class LiveObjectIterator;
  56
  57     struct CollectorHeap {
  58         size_t nextBlock;
  59         size_t nextCell;
  60         CollectorBlock** blocks;
  61
  62         void* nextNumber;
  63
  64         size_t numBlocks;
  65         size_t usedBlocks;
  66
  67         size_t extraCost;
  68         bool didShrink;
  69
  70         OperationInProgress operationInProgress;
  71     };
  72
  73     class Heap : public Noncopyable {
  74     public:
  75         class Thread;
  76
  77         void destroy();
  78
  79         void* allocateNumber(size_t);
  80         void* allocate(size_t);
  81
  82         bool isBusy(); // true if an allocation or collection is in progress
  83         void collectAllGarbage();
  84
  85         static const size_t minExtraCost = 256;
  86         static const size_t maxExtraCost = 1024 * 1024;
  87
  88         void reportExtraMemoryCost(size_t cost);
  89
  90         size_t objectCount() const;
  91         struct Statistics {
  92             size_t size;
  93             size_t free;
  94         };
  95         Statistics statistics() const;
  96
  97         void protect(JSValue);
  98         // Returns true if the value is no longer protected by any protect pointers
  99         // (though it may still be alive due to heap/stack references).
 100         bool unprotect(JSValue);
 101
 102         static Heap* heap(JSValue); // 0 for immediate values
 103         static Heap* heap(JSCell*);
 104
 105         size_t globalObjectCount();
 106         size_t protectedObjectCount();
 107         size_t protectedGlobalObjectCount();
 108         HashCountedSet<const char*>* protectedObjectTypeCounts();
 109         HashCountedSet<const char*>* objectTypeCounts();
 110
 111         void registerThread(); // Only needs to be called by clients that can use the same heap from multiple threads.
 112
 113         static bool isCellMarked(const JSCell*);
 114         static void markCell(JSCell*);
 115
 116         void markConservatively(MarkStack&, void* start, void* end);
 117
 118         HashSet<MarkedArgumentBuffer*>& markListSet() { if (!m_markListSet) m_markListSet = new HashSet<MarkedArgumentBuffer*>; return *m_markListSet; }
 119
 120         JSGlobalData* globalData() const { return m_globalData; }
 121         static bool isNumber(JSCell*);
 122
 123         LiveObjectIterator primaryHeapBegin();
 124         LiveObjectIterator primaryHeapEnd();
 125
 126     private:
 127         void reset();
 128         void sweep();
 129         static CollectorBlock* cellBlock(const JSCell*);
 130         static size_t cellOffset(const JSCell*);
 131
 132         friend class JSGlobalData;
 133         Heap(JSGlobalData*);
 134         ~Heap();
 135
 136         NEVER_INLINE CollectorBlock* allocateBlock();
 137         NEVER_INLINE void freeBlock(size_t);
 138         NEVER_INLINE void freeBlockPtr(CollectorBlock*);
 139         void freeBlocks();
 140         void resizeBlocks();
 141         void growBlocks(size_t neededBlocks);
 142         void shrinkBlocks(size_t neededBlocks);
 143         void clearMarkBits();
 144         void clearMarkBits(CollectorBlock*);
 145         size_t markedCells(size_t startBlock = 0, size_t startCell = 0) const;
 146
 147         void recordExtraCost(size_t);
 148
 149         void addToStatistics(Statistics&) const;
 150
 151         void markRoots();
 152         void markProtectedObjects(MarkStack&);
 153         void markCurrentThreadConservatively(MarkStack&);
 154         void markCurrentThreadConservativelyInternal(MarkStack&);
 155         void markOtherThreadConservatively(MarkStack&, Thread*);
 156         void markStackObjectsConservatively(MarkStack&);
 157
 158         typedef HashCountedSet<JSCell*> ProtectCountSet;
 159
 160         CollectorHeap m_heap;
 161
 162         ProtectCountSet m_protectedValues;
 163
 164         HashSet<MarkedArgumentBuffer*>* m_markListSet;
 165
 166 #if ENABLE(JSC_MULTIPLE_THREADS)
 167         void makeUsableFromMultipleThreads();
 168
 169         static void unregisterThread(void*);
 170         void unregisterThread();
 171
 172         Mutex m_registeredThreadsMutex;
 173         Thread* m_registeredThreads;
 174         pthread_key_t m_currentThreadRegistrar;
 175 #endif
 176
 177 #if OS(SYMBIAN)
 178         // Allocates collector blocks with correct alignment
 179         WTF::AlignedBlockAllocator m_blockallocator;
 180 #endif
 181
 182         JSGlobalData* m_globalData;
 183     };
 184
 185     // tunable parameters
 186     template<size_t bytesPerWord> struct CellSize;
 187
 188     // cell size needs to be a power of two for certain optimizations in collector.cpp
 189 #if USE(JSVALUE32)
 190     template<> struct CellSize<sizeof(uint32_t)> { static const size_t m_value = 32; };
 191 #else
 192     template<> struct CellSize<sizeof(uint32_t)> { static const size_t m_value = 64; };
 193 #endif
 194     template<> struct CellSize<sizeof(uint64_t)> { static const size_t m_value = 64; };
 195
 196     const size_t BLOCK_SIZE = 64 * 1024; // 64k
 197
 198     // derived constants
 199     const size_t BLOCK_OFFSET_MASK = BLOCK_SIZE - 1;
 200     const size_t BLOCK_MASK = ~BLOCK_OFFSET_MASK;
 201     const size_t MINIMUM_CELL_SIZE = CellSize<sizeof(void*)>::m_value;
 202     const size_t CELL_ARRAY_LENGTH = (MINIMUM_CELL_SIZE / sizeof(double)) + (MINIMUM_CELL_SIZE % sizeof(double) != 0 ? sizeof(double) : 0);
 203     const size_t CELL_SIZE = CELL_ARRAY_LENGTH * sizeof(double);
 204     const size_t SMALL_CELL_SIZE = CELL_SIZE / 2;
 205     const size_t CELL_MASK = CELL_SIZE - 1;
 206     const size_t CELL_ALIGN_MASK = ~CELL_MASK;
 207     const size_t CELLS_PER_BLOCK = (BLOCK_SIZE - sizeof(Heap*)) * 8 * CELL_SIZE / (8 * CELL_SIZE + 1) / CELL_SIZE; // one bitmap byte can represent 8 cells.
 208
 209     const size_t BITMAP_SIZE = (CELLS_PER_BLOCK + 7) / 8;
 210     const size_t BITMAP_WORDS = (BITMAP_SIZE + 3) / sizeof(uint32_t);
 211
 212     struct CollectorBitmap {
 213         uint32_t bits[BITMAP_WORDS];
 214         bool get(size_t n) const { return !!(bits[n >> 5] & (1 << (n & 0x1F))); }
 215         void set(size_t n) { bits[n >> 5] |= (1 << (n & 0x1F)); }
 216         void clear(size_t n) { bits[n >> 5] &= ~(1 << (n & 0x1F)); }
 217         void clearAll() { memset(bits, 0, sizeof(bits)); }
 218         size_t count(size_t startCell = 0)
 219         {
 220             size_t result = 0;
 221             for ( ; (startCell & 0x1F) != 0; ++startCell) {
 222                 if (get(startCell))
 223                     ++result;
 224             }
 225             for (size_t i = startCell >> 5; i < BITMAP_WORDS; ++i)
 226                 result += WTF::bitCount(bits[i]);
 227             return result;
 228         }
 229         size_t isEmpty() // Much more efficient than testing count() == 0.
 230         {
 231             for (size_t i = 0; i < BITMAP_WORDS; ++i)
 232                 if (bits[i] != 0)
 233                     return false;
 234             return true;
 235         }
 236     };
 237
 238     struct CollectorCell {
 239         double memory[CELL_ARRAY_LENGTH];
 240     };
 241
 242     class CollectorBlock {
 243     public:
 244         CollectorCell cells[CELLS_PER_BLOCK];
 245         CollectorBitmap marked;
 246         Heap* heap;
 247     };
 248
 249     struct HeapConstants {
 250         static const size_t cellSize = CELL_SIZE;
 251         static const size_t cellsPerBlock = CELLS_PER_BLOCK;
 252         typedef CollectorCell Cell;
 253         typedef CollectorBlock Block;
 254     };
 255
 256     inline CollectorBlock* Heap::cellBlock(const JSCell* cell)
 257     {
 258         return reinterpret_cast<CollectorBlock*>(reinterpret_cast<uintptr_t>(cell) & BLOCK_MASK);
 259     }
 260
 261     inline size_t Heap::cellOffset(const JSCell* cell)
 262     {
 263         return (reinterpret_cast<uintptr_t>(cell) & BLOCK_OFFSET_MASK) / CELL_SIZE;
 264     }
 265
 266     inline bool Heap::isCellMarked(const JSCell* cell)
 267     {
 268         return cellBlock(cell)->marked.get(cellOffset(cell));
 269     }
 270
 271     inline void Heap::markCell(JSCell* cell)
 272     {
 273         cellBlock(cell)->marked.set(cellOffset(cell));
 274     }
 275
 276     inline void Heap::reportExtraMemoryCost(size_t cost)
 277     {
 278         if (cost > minExtraCost)
 279             recordExtraCost(cost);
 280     }
 281
 282     inline void* Heap::allocateNumber(size_t s)
 283     {
 284         if (void* result = m_heap.nextNumber) {
 285             m_heap.nextNumber = 0;
 286             return result;
 287         }
 288
 289         void* result = allocate(s);
 290         m_heap.nextNumber = static_cast<char*>(result) + (CELL_SIZE / 2);
 291         return result;
 292     }
 293
 294 } // namespace JSC
 295
 296 #endif /* Collector_h */