Source/JavaScriptCore/runtime/MarkedSpace.cpp

   1 /*
   2  *  Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
   3  *  Copyright (C) 2007 Eric Seidel <eric@webkit.org>
   4  *
   5  *  This library is free software; you can redistribute it and/or
   6  *  modify it under the terms of the GNU Lesser General Public
   7  *  License as published by the Free Software Foundation; either
   8  *  version 2 of the License, or (at your option) any later version.
   9  *
  10  *  This library is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  *  Lesser General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU Lesser General Public
  16  *  License along with this library; if not, write to the Free Software
  17  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  18  *
  19  */
  20
  21 #include "config.h"
  22 #include "MarkedSpace.h"
  23
  24 #include "CollectorHeapIterator.h"
  25 #include "JSCell.h"
  26 #include "JSGlobalData.h"
  27 #include "JSLock.h"
  28
  29 using std::max;
  30
  31 namespace JSC {
  32
  33 class Structure;
  34
  35 // tunable parameters
  36
  37 const size_t GROWTH_FACTOR = 2;
  38 const size_t LOW_WATER_FACTOR = 4;
  39 const size_t ALLOCATIONS_PER_COLLECTION = 3600;
  40 // This value has to be a macro to be used in max() without introducing
  41 // a PIC branch in Mach-O binaries, see <rdar://problem/5971391>.
  42 #define MIN_ARRAY_SIZE (static_cast<size_t>(14))
  43
  44 MarkedSpace::MarkedSpace(JSGlobalData* globalData)
  45     : m_globalData(globalData)
  46 {
  47     memset(&m_heap, 0, sizeof(CollectorHeap));
  48     allocateBlock();
  49 }
  50
  51 void MarkedSpace::destroy()
  52 {
  53     clearMarkBits(); // Make sure weak pointers appear dead during destruction.
  54
  55     while (m_heap.usedBlocks)
  56         freeBlock(0);
  57     fastFree(m_heap.blocks);
  58
  59     memset(&m_heap, 0, sizeof(CollectorHeap));
  60 }
  61
  62 NEVER_INLINE MarkedBlock* MarkedSpace::allocateBlock()
  63 {
  64     PageAllocationAligned allocation = PageAllocationAligned::allocate(BLOCK_SIZE, BLOCK_SIZE, OSAllocator::JSGCHeapPages);
  65     MarkedBlock* block = static_cast<MarkedBlock*>(allocation.base());
  66     if (!block)
  67         CRASH();
  68
  69     // Initialize block.
  70
  71     block->heap = &globalData()->heap;
  72     clearMarkBits(block);
  73
  74     Structure* dummyMarkableCellStructure = globalData()->dummyMarkableCellStructure.get();
  75     for (size_t i = 0; i < HeapConstants::cellsPerBlock; ++i)
  76         new (&block->cells[i]) JSCell(dummyMarkableCellStructure);
  77
  78     // Add block to blocks vector.
  79
  80     size_t numBlocks = m_heap.numBlocks;
  81     if (m_heap.usedBlocks == numBlocks) {
  82         static const size_t maxNumBlocks = ULONG_MAX / sizeof(PageAllocationAligned) / GROWTH_FACTOR;
  83         if (numBlocks > maxNumBlocks)
  84             CRASH();
  85         numBlocks = max(MIN_ARRAY_SIZE, numBlocks * GROWTH_FACTOR);
  86         m_heap.numBlocks = numBlocks;
  87         m_heap.blocks = static_cast<PageAllocationAligned*>(fastRealloc(m_heap.blocks, numBlocks * sizeof(PageAllocationAligned)));
  88     }
  89     m_heap.blocks[m_heap.usedBlocks++] = allocation;
  90
  91     return block;
  92 }
  93
  94 NEVER_INLINE void MarkedSpace::freeBlock(size_t block)
  95 {
  96     ObjectIterator it(m_heap, block, 0);
  97     ObjectIterator end(m_heap, block + 1, 0);
  98     for ( ; it != end; ++it)
  99         (*it)->~JSCell();
 100     m_heap.blocks[block].deallocate();
 101
 102     // swap with the last block so we compact as we go
 103     m_heap.blocks[block] = m_heap.blocks[m_heap.usedBlocks - 1];
 104     m_heap.usedBlocks--;
 105
 106     if (m_heap.numBlocks > MIN_ARRAY_SIZE && m_heap.usedBlocks < m_heap.numBlocks / LOW_WATER_FACTOR) {
 107         m_heap.numBlocks = m_heap.numBlocks / GROWTH_FACTOR;
 108         m_heap.blocks = static_cast<PageAllocationAligned*>(fastRealloc(m_heap.blocks, m_heap.numBlocks * sizeof(PageAllocationAligned)));
 109     }
 110 }
 111
 112 void* MarkedSpace::allocate(size_t s)
 113 {
 114     ASSERT(globalData()->identifierTable == wtfThreadData().currentIdentifierTable());
 115     typedef HeapConstants::Block Block;
 116     typedef HeapConstants::Cell Cell;
 117
 118     ASSERT(JSLock::lockCount() > 0);
 119     ASSERT(JSLock::currentThreadIsHoldingLock());
 120     ASSERT_UNUSED(s, s <= HeapConstants::cellSize);
 121
 122     // Fast case: find the next garbage cell and recycle it.
 123
 124     do {
 125         ASSERT(m_heap.nextBlock < m_heap.usedBlocks);
 126         Block* block = m_heap.collectorBlock(m_heap.nextBlock);
 127         do {
 128             ASSERT(m_heap.nextCell < HeapConstants::cellsPerBlock);
 129             if (!block->marked.get(m_heap.nextCell)) { // Always false for the last cell in the block
 130                 Cell* cell = &block->cells[m_heap.nextCell];
 131
 132                 JSCell* imp = reinterpret_cast<JSCell*>(cell);
 133                 imp->~JSCell();
 134
 135                 ++m_heap.nextCell;
 136                 return cell;
 137             }
 138             m_heap.nextCell = block->marked.nextPossiblyUnset(m_heap.nextCell);
 139         } while (m_heap.nextCell != HeapConstants::cellsPerBlock);
 140         m_heap.nextCell = 0;
 141         m_heap.waterMark += BLOCK_SIZE;
 142     } while (++m_heap.nextBlock != m_heap.usedBlocks);
 143
 144     if (m_heap.waterMark < m_heap.highWaterMark)
 145         return &allocateBlock()->cells[m_heap.nextCell++];
 146
 147     return 0;
 148 }
 149
 150 void MarkedSpace::resizeBlocks()
 151 {
 152     size_t usedCellCount = markedCells();
 153     size_t minCellCount = usedCellCount + max(ALLOCATIONS_PER_COLLECTION, usedCellCount);
 154     size_t minBlockCount = (minCellCount + HeapConstants::cellsPerBlock - 1) / HeapConstants::cellsPerBlock;
 155
 156     size_t maxCellCount = 1.25f * minCellCount;
 157     size_t maxBlockCount = (maxCellCount + HeapConstants::cellsPerBlock - 1) / HeapConstants::cellsPerBlock;
 158
 159     if (m_heap.usedBlocks < minBlockCount)
 160         growBlocks(minBlockCount);
 161     else if (m_heap.usedBlocks > maxBlockCount)
 162         shrinkBlocks(maxBlockCount);
 163 }
 164
 165 void MarkedSpace::growBlocks(size_t neededBlocks)
 166 {
 167     ASSERT(m_heap.usedBlocks < neededBlocks);
 168     while (m_heap.usedBlocks < neededBlocks)
 169         allocateBlock();
 170 }
 171
 172 void MarkedSpace::shrinkBlocks(size_t neededBlocks)
 173 {
 174     ASSERT(m_heap.usedBlocks > neededBlocks);
 175
 176     // Clear the always-on last bit, so isEmpty() isn't fooled by it.
 177     for (size_t i = 0; i < m_heap.usedBlocks; ++i)
 178         m_heap.collectorBlock(i)->marked.clear(HeapConstants::cellsPerBlock - 1);
 179
 180     for (size_t i = 0; i != m_heap.usedBlocks && m_heap.usedBlocks != neededBlocks; ) {
 181         if (m_heap.collectorBlock(i)->marked.isEmpty()) {
 182             freeBlock(i);
 183         } else
 184             ++i;
 185     }
 186
 187     // Reset the always-on last bit.
 188     for (size_t i = 0; i < m_heap.usedBlocks; ++i)
 189         m_heap.collectorBlock(i)->marked.set(HeapConstants::cellsPerBlock - 1);
 190 }
 191
 192 bool MarkedSpace::containsSlowCase(const void* x)
 193 {
 194     uintptr_t xAsBits = reinterpret_cast<uintptr_t>(x);
 195     xAsBits &= CELL_ALIGN_MASK;
 196
 197     uintptr_t offset = xAsBits & BLOCK_OFFSET_MASK;
 198     const size_t lastCellOffset = sizeof(CollectorCell) * (CELLS_PER_BLOCK - 1);
 199     if (offset > lastCellOffset)
 200         return false;
 201
 202     MarkedBlock* blockAddr = reinterpret_cast<MarkedBlock*>(xAsBits - offset);
 203     size_t usedBlocks = m_heap.usedBlocks;
 204     for (size_t block = 0; block < usedBlocks; block++) {
 205         if (m_heap.collectorBlock(block) != blockAddr)
 206             continue;
 207
 208         // x is a pointer into the heap. Now, verify that the cell it
 209         // points to is live. (If the cell is dead, we must not mark it,
 210         // since that would revive it in a zombie state.)
 211         if (block < m_heap.nextBlock)
 212             return true;
 213
 214         size_t cellOffset = offset / CELL_SIZE;
 215
 216         if (block == m_heap.nextBlock && cellOffset < m_heap.nextCell)
 217             return true;
 218
 219         return blockAddr->marked.get(cellOffset);
 220     }
 221
 222     return false;
 223 }
 224
 225 void MarkedSpace::clearMarkBits()
 226 {
 227     for (size_t i = 0; i < m_heap.usedBlocks; ++i)
 228         clearMarkBits(m_heap.collectorBlock(i));
 229 }
 230
 231 void MarkedSpace::clearMarkBits(MarkedBlock* block)
 232 {
 233     // allocate assumes that the last cell in every block is marked.
 234     block->marked.clearAll();
 235     block->marked.set(HeapConstants::cellsPerBlock - 1);
 236 }
 237
 238 size_t MarkedSpace::markedCells(size_t startBlock, size_t startCell) const
 239 {
 240     ASSERT(startBlock <= m_heap.usedBlocks);
 241     ASSERT(startCell < HeapConstants::cellsPerBlock);
 242
 243     if (startBlock >= m_heap.usedBlocks)
 244         return 0;
 245
 246     size_t result = 0;
 247     result += m_heap.collectorBlock(startBlock)->marked.count(startCell);
 248     for (size_t i = startBlock + 1; i < m_heap.usedBlocks; ++i)
 249         result += m_heap.collectorBlock(i)->marked.count();
 250
 251     return result;
 252 }
 253
 254 void MarkedSpace::sweep()
 255 {
 256 #if !ENABLE(JSC_ZOMBIES)
 257     Structure* dummyMarkableCellStructure = globalData()->dummyMarkableCellStructure.get();
 258 #endif
 259
 260     DeadObjectIterator it(m_heap, 0, 0);
 261     DeadObjectIterator end(m_heap, m_heap.usedBlocks, 0);
 262     for ( ; it != end; ++it) {
 263         JSCell* cell = *it;
 264 #if ENABLE(JSC_ZOMBIES)
 265         if (!cell->isZombie()) {
 266             const ClassInfo* info = cell->classInfo();
 267             cell->~JSCell();
 268             new (cell) JSZombie(info, JSZombie::leakedZombieStructure());
 269             Heap::markCell(cell);
 270         }
 271 #else
 272         cell->~JSCell();
 273         // Callers of sweep assume it's safe to mark any cell in the heap.
 274         new (cell) JSCell(dummyMarkableCellStructure);
 275 #endif
 276     }
 277
 278     shrinkBlocks(0);
 279 }
 280
 281 size_t MarkedSpace::objectCount() const
 282 {
 283     return m_heap.nextBlock * HeapConstants::cellsPerBlock // allocated full blocks
 284            + m_heap.nextCell // allocated cells in current block
 285            + markedCells(m_heap.nextBlock, m_heap.nextCell) // marked cells in remainder of m_heap
 286            - m_heap.usedBlocks; // 1 cell per block is a dummy sentinel
 287 }
 288
 289 size_t MarkedSpace::size() const
 290 {
 291     return objectCount() * HeapConstants::cellSize;
 292 }
 293
 294 size_t MarkedSpace::capacity() const
 295 {
 296     return m_heap.usedBlocks * BLOCK_SIZE;
 297 }
 298
 299 void MarkedSpace::reset()
 300 {
 301     m_heap.nextCell = 0;
 302     m_heap.nextBlock = 0;
 303     m_heap.waterMark = 0;
 304 #if ENABLE(JSC_ZOMBIES)
 305     sweep();
 306 #endif
 307 }
 308
 309 LiveObjectIterator MarkedSpace::primaryHeapBegin()
 310 {
 311     return LiveObjectIterator(m_heap, 0, 0);
 312 }
 313
 314 LiveObjectIterator MarkedSpace::primaryHeapEnd()
 315 {
 316     return LiveObjectIterator(m_heap, m_heap.usedBlocks, 0);
 317 }
 318
 319 } // namespace JSC