1 /* 2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "gc_implementation/concurrentMarkSweep/cmsLockVerifier.hpp" 27 #include "gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp" 28 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp" 29 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp" 30 #include "gc_implementation/shared/liveRange.hpp" 31 #include "gc_implementation/shared/spaceDecorator.hpp" 32 #include "gc_interface/collectedHeap.inline.hpp" 33 #include "memory/allocation.inline.hpp" 34 #include "memory/blockOffsetTable.inline.hpp" 35 #include "memory/resourceArea.hpp" 36 #include "memory/space.inline.hpp" 37 #include "memory/universe.inline.hpp" 38 #include "oops/oop.inline.hpp" 39 #include "runtime/globals.hpp" 40 #include "runtime/handles.inline.hpp" 41 #include "runtime/init.hpp" 42 #include "runtime/java.hpp" 43 #include "runtime/orderAccess.inline.hpp" 44 #include "runtime/vmThread.hpp" 45 #include "utilities/copy.hpp" 46 47 ///////////////////////////////////////////////////////////////////////// 48 //// CompactibleFreeListSpace 49 ///////////////////////////////////////////////////////////////////////// 50 51 // highest ranked free list lock rank 52 int CompactibleFreeListSpace::_lockRank = Mutex::leaf + 3; 53 54 // Defaults are 0 so things will break badly if incorrectly initialized. 55 size_t CompactibleFreeListSpace::IndexSetStart = 0; 56 size_t CompactibleFreeListSpace::IndexSetStride = 0; 57 58 size_t MinChunkSize = 0; 59 60 void CompactibleFreeListSpace::set_cms_values() { 61 // Set CMS global values 62 assert(MinChunkSize == 0, "already set"); 63 64 // MinChunkSize should be a multiple of MinObjAlignment and be large enough 65 // for chunks to contain a FreeChunk. 66 size_t min_chunk_size_in_bytes = align_size_up(sizeof(FreeChunk), MinObjAlignmentInBytes); 67 MinChunkSize = min_chunk_size_in_bytes / BytesPerWord; 68 69 assert(IndexSetStart == 0 && IndexSetStride == 0, "already set"); 70 IndexSetStart = MinChunkSize; 71 IndexSetStride = MinObjAlignment; 72 } 73 74 // Constructor 75 CompactibleFreeListSpace::CompactibleFreeListSpace(BlockOffsetSharedArray* bs, 76 MemRegion mr, bool use_adaptive_freelists, 77 FreeBlockDictionary<FreeChunk>::DictionaryChoice dictionaryChoice) : 78 _dictionaryChoice(dictionaryChoice), 79 _adaptive_freelists(use_adaptive_freelists), 80 _bt(bs, mr), 81 // free list locks are in the range of values taken by _lockRank 82 // This range currently is [_leaf+2, _leaf+3] 83 // Note: this requires that CFLspace c'tors 84 // are called serially in the order in which the locks are 85 // are acquired in the program text. This is true today. 86 _freelistLock(_lockRank--, "CompactibleFreeListSpace._lock", true, 87 Monitor::_safepoint_check_sometimes), 88 _parDictionaryAllocLock(Mutex::leaf - 1, // == rank(ExpandHeap_lock) - 1 89 "CompactibleFreeListSpace._dict_par_lock", true, 90 Monitor::_safepoint_check_never), 91 _rescan_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord * 92 CMSRescanMultiple), 93 _marking_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord * 94 CMSConcMarkMultiple), 95 _collector(NULL), 96 _preconsumptionDirtyCardClosure(NULL) 97 { 98 assert(sizeof(FreeChunk) / BytesPerWord <= MinChunkSize, 99 "FreeChunk is larger than expected"); 100 _bt.set_space(this); 101 initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle); 102 // We have all of "mr", all of which we place in the dictionary 103 // as one big chunk. We'll need to decide here which of several 104 // possible alternative dictionary implementations to use. For 105 // now the choice is easy, since we have only one working 106 // implementation, namely, the simple binary tree (splaying 107 // temporarily disabled). 108 switch (dictionaryChoice) { 109 case FreeBlockDictionary<FreeChunk>::dictionaryBinaryTree: 110 _dictionary = new AFLBinaryTreeDictionary(mr); 111 break; 112 case FreeBlockDictionary<FreeChunk>::dictionarySplayTree: 113 case FreeBlockDictionary<FreeChunk>::dictionarySkipList: 114 default: 115 warning("dictionaryChoice: selected option not understood; using" 116 " default BinaryTreeDictionary implementation instead."); 117 } 118 assert(_dictionary != NULL, "CMS dictionary initialization"); 119 // The indexed free lists are initially all empty and are lazily 120 // filled in on demand. Initialize the array elements to NULL. 121 initializeIndexedFreeListArray(); 122 123 // Not using adaptive free lists assumes that allocation is first 124 // from the linAB's. Also a cms perm gen which can be compacted 125 // has to have the klass's klassKlass allocated at a lower 126 // address in the heap than the klass so that the klassKlass is 127 // moved to its new location before the klass is moved. 128 // Set the _refillSize for the linear allocation blocks 129 if (!use_adaptive_freelists) { 130 FreeChunk* fc = _dictionary->get_chunk(mr.word_size(), 131 FreeBlockDictionary<FreeChunk>::atLeast); 132 // The small linAB initially has all the space and will allocate 133 // a chunk of any size. 134 HeapWord* addr = (HeapWord*) fc; 135 _smallLinearAllocBlock.set(addr, fc->size() , 136 1024*SmallForLinearAlloc, fc->size()); 137 // Note that _unallocated_block is not updated here. 138 // Allocations from the linear allocation block should 139 // update it. 140 } else { 141 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, 142 SmallForLinearAlloc); 143 } 144 // CMSIndexedFreeListReplenish should be at least 1 145 CMSIndexedFreeListReplenish = MAX2((uintx)1, CMSIndexedFreeListReplenish); 146 _promoInfo.setSpace(this); 147 if (UseCMSBestFit) { 148 _fitStrategy = FreeBlockBestFitFirst; 149 } else { 150 _fitStrategy = FreeBlockStrategyNone; 151 } 152 check_free_list_consistency(); 153 154 // Initialize locks for parallel case. 155 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { 156 _indexedFreeListParLocks[i] = new Mutex(Mutex::leaf - 1, // == ExpandHeap_lock - 1 157 "a freelist par lock", true, Mutex::_safepoint_check_sometimes); 158 DEBUG_ONLY( 159 _indexedFreeList[i].set_protecting_lock(_indexedFreeListParLocks[i]); 160 ) 161 } 162 _dictionary->set_par_lock(&_parDictionaryAllocLock); 163 } 164 165 // Like CompactibleSpace forward() but always calls cross_threshold() to 166 // update the block offset table. Removed initialize_threshold call because 167 // CFLS does not use a block offset array for contiguous spaces. 168 HeapWord* CompactibleFreeListSpace::forward(oop q, size_t size, 169 CompactPoint* cp, HeapWord* compact_top) { 170 // q is alive 171 // First check if we should switch compaction space 172 assert(this == cp->space, "'this' should be current compaction space."); 173 size_t compaction_max_size = pointer_delta(end(), compact_top); 174 assert(adjustObjectSize(size) == cp->space->adjust_object_size_v(size), 175 "virtual adjustObjectSize_v() method is not correct"); 176 size_t adjusted_size = adjustObjectSize(size); 177 assert(compaction_max_size >= MinChunkSize || compaction_max_size == 0, 178 "no small fragments allowed"); 179 assert(minimum_free_block_size() == MinChunkSize, 180 "for de-virtualized reference below"); 181 // Can't leave a nonzero size, residual fragment smaller than MinChunkSize 182 if (adjusted_size + MinChunkSize > compaction_max_size && 183 adjusted_size != compaction_max_size) { 184 do { 185 // switch to next compaction space 186 cp->space->set_compaction_top(compact_top); 187 cp->space = cp->space->next_compaction_space(); 188 if (cp->space == NULL) { 189 cp->gen = GenCollectedHeap::heap()->young_gen(); 190 assert(cp->gen != NULL, "compaction must succeed"); 191 cp->space = cp->gen->first_compaction_space(); 192 assert(cp->space != NULL, "generation must have a first compaction space"); 193 } 194 compact_top = cp->space->bottom(); 195 cp->space->set_compaction_top(compact_top); 196 // The correct adjusted_size may not be the same as that for this method 197 // (i.e., cp->space may no longer be "this" so adjust the size again. 198 // Use the virtual method which is not used above to save the virtual 199 // dispatch. 200 adjusted_size = cp->space->adjust_object_size_v(size); 201 compaction_max_size = pointer_delta(cp->space->end(), compact_top); 202 assert(cp->space->minimum_free_block_size() == 0, "just checking"); 203 } while (adjusted_size > compaction_max_size); 204 } 205 206 // store the forwarding pointer into the mark word 207 if ((HeapWord*)q != compact_top) { 208 q->forward_to(oop(compact_top)); 209 assert(q->is_gc_marked(), "encoding the pointer should preserve the mark"); 210 } else { 211 // if the object isn't moving we can just set the mark to the default 212 // mark and handle it specially later on. 213 q->init_mark(); 214 assert(q->forwardee() == NULL, "should be forwarded to NULL"); 215 } 216 217 compact_top += adjusted_size; 218 219 // we need to update the offset table so that the beginnings of objects can be 220 // found during scavenge. Note that we are updating the offset table based on 221 // where the object will be once the compaction phase finishes. 222 223 // Always call cross_threshold(). A contiguous space can only call it when 224 // the compaction_top exceeds the current threshold but not for an 225 // non-contiguous space. 226 cp->threshold = 227 cp->space->cross_threshold(compact_top - adjusted_size, compact_top); 228 return compact_top; 229 } 230 231 // A modified copy of OffsetTableContigSpace::cross_threshold() with _offsets -> _bt 232 // and use of single_block instead of alloc_block. The name here is not really 233 // appropriate - maybe a more general name could be invented for both the 234 // contiguous and noncontiguous spaces. 235 236 HeapWord* CompactibleFreeListSpace::cross_threshold(HeapWord* start, HeapWord* the_end) { 237 _bt.single_block(start, the_end); 238 return end(); 239 } 240 241 // Initialize them to NULL. 242 void CompactibleFreeListSpace::initializeIndexedFreeListArray() { 243 for (size_t i = 0; i < IndexSetSize; i++) { 244 // Note that on platforms where objects are double word aligned, 245 // the odd array elements are not used. It is convenient, however, 246 // to map directly from the object size to the array element. 247 _indexedFreeList[i].reset(IndexSetSize); 248 _indexedFreeList[i].set_size(i); 249 assert(_indexedFreeList[i].count() == 0, "reset check failed"); 250 assert(_indexedFreeList[i].head() == NULL, "reset check failed"); 251 assert(_indexedFreeList[i].tail() == NULL, "reset check failed"); 252 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed"); 253 } 254 } 255 256 void CompactibleFreeListSpace::resetIndexedFreeListArray() { 257 for (size_t i = 1; i < IndexSetSize; i++) { 258 assert(_indexedFreeList[i].size() == (size_t) i, 259 "Indexed free list sizes are incorrect"); 260 _indexedFreeList[i].reset(IndexSetSize); 261 assert(_indexedFreeList[i].count() == 0, "reset check failed"); 262 assert(_indexedFreeList[i].head() == NULL, "reset check failed"); 263 assert(_indexedFreeList[i].tail() == NULL, "reset check failed"); 264 assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed"); 265 } 266 } 267 268 void CompactibleFreeListSpace::reset(MemRegion mr) { 269 resetIndexedFreeListArray(); 270 dictionary()->reset(); 271 if (BlockOffsetArrayUseUnallocatedBlock) { 272 assert(end() == mr.end(), "We are compacting to the bottom of CMS gen"); 273 // Everything's allocated until proven otherwise. 274 _bt.set_unallocated_block(end()); 275 } 276 if (!mr.is_empty()) { 277 assert(mr.word_size() >= MinChunkSize, "Chunk size is too small"); 278 _bt.single_block(mr.start(), mr.word_size()); 279 FreeChunk* fc = (FreeChunk*) mr.start(); 280 fc->set_size(mr.word_size()); 281 if (mr.word_size() >= IndexSetSize ) { 282 returnChunkToDictionary(fc); 283 } else { 284 _bt.verify_not_unallocated((HeapWord*)fc, fc->size()); 285 _indexedFreeList[mr.word_size()].return_chunk_at_head(fc); 286 } 287 coalBirth(mr.word_size()); 288 } 289 _promoInfo.reset(); 290 _smallLinearAllocBlock._ptr = NULL; 291 _smallLinearAllocBlock._word_size = 0; 292 } 293 294 void CompactibleFreeListSpace::reset_after_compaction() { 295 // Reset the space to the new reality - one free chunk. 296 MemRegion mr(compaction_top(), end()); 297 reset(mr); 298 // Now refill the linear allocation block(s) if possible. 299 if (_adaptive_freelists) { 300 refillLinearAllocBlocksIfNeeded(); 301 } else { 302 // Place as much of mr in the linAB as we can get, 303 // provided it was big enough to go into the dictionary. 304 FreeChunk* fc = dictionary()->find_largest_dict(); 305 if (fc != NULL) { 306 assert(fc->size() == mr.word_size(), 307 "Why was the chunk broken up?"); 308 removeChunkFromDictionary(fc); 309 HeapWord* addr = (HeapWord*) fc; 310 _smallLinearAllocBlock.set(addr, fc->size() , 311 1024*SmallForLinearAlloc, fc->size()); 312 // Note that _unallocated_block is not updated here. 313 } 314 } 315 } 316 317 // Walks the entire dictionary, returning a coterminal 318 // chunk, if it exists. Use with caution since it involves 319 // a potentially complete walk of a potentially large tree. 320 FreeChunk* CompactibleFreeListSpace::find_chunk_at_end() { 321 322 assert_lock_strong(&_freelistLock); 323 324 return dictionary()->find_chunk_ends_at(end()); 325 } 326 327 328 #ifndef PRODUCT 329 void CompactibleFreeListSpace::initializeIndexedFreeListArrayReturnedBytes() { 330 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { 331 _indexedFreeList[i].allocation_stats()->set_returned_bytes(0); 332 } 333 } 334 335 size_t CompactibleFreeListSpace::sumIndexedFreeListArrayReturnedBytes() { 336 size_t sum = 0; 337 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { 338 sum += _indexedFreeList[i].allocation_stats()->returned_bytes(); 339 } 340 return sum; 341 } 342 343 size_t CompactibleFreeListSpace::totalCountInIndexedFreeLists() const { 344 size_t count = 0; 345 for (size_t i = IndexSetStart; i < IndexSetSize; i++) { 346 debug_only( 347 ssize_t total_list_count = 0; 348 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL; 349 fc = fc->next()) { 350 total_list_count++; 351 } 352 assert(total_list_count == _indexedFreeList[i].count(), 353 "Count in list is incorrect"); 354 ) 355 count += _indexedFreeList[i].count(); 356 } 357 return count; 358 } 359 360 size_t CompactibleFreeListSpace::totalCount() { 361 size_t num = totalCountInIndexedFreeLists(); 362 num += dictionary()->total_count(); 363 if (_smallLinearAllocBlock._word_size != 0) { 364 num++; 365 } 366 return num; 367 } 368 #endif 369 370 bool CompactibleFreeListSpace::is_free_block(const HeapWord* p) const { 371 FreeChunk* fc = (FreeChunk*) p; 372 return fc->is_free(); 373 } 374 375 size_t CompactibleFreeListSpace::used() const { 376 return capacity() - free(); 377 } 378 379 size_t CompactibleFreeListSpace::free() const { 380 // "MT-safe, but not MT-precise"(TM), if you will: i.e. 381 // if you do this while the structures are in flux you 382 // may get an approximate answer only; for instance 383 // because there is concurrent allocation either 384 // directly by mutators or for promotion during a GC. 385 // It's "MT-safe", however, in the sense that you are guaranteed 386 // not to crash and burn, for instance, because of walking 387 // pointers that could disappear as you were walking them. 388 // The approximation is because the various components 389 // that are read below are not read atomically (and 390 // further the computation of totalSizeInIndexedFreeLists() 391 // is itself a non-atomic computation. The normal use of 392 // this is during a resize operation at the end of GC 393 // and at that time you are guaranteed to get the 394 // correct actual value. However, for instance, this is 395 // also read completely asynchronously by the "perf-sampler" 396 // that supports jvmstat, and you are apt to see the values 397 // flicker in such cases. 398 assert(_dictionary != NULL, "No _dictionary?"); 399 return (_dictionary->total_chunk_size(DEBUG_ONLY(freelistLock())) + 400 totalSizeInIndexedFreeLists() + 401 _smallLinearAllocBlock._word_size) * HeapWordSize; 402 } 403 404 size_t CompactibleFreeListSpace::max_alloc_in_words() const { 405 assert(_dictionary != NULL, "No _dictionary?"); 406 assert_locked(); 407 size_t res = _dictionary->max_chunk_size(); 408 res = MAX2(res, MIN2(_smallLinearAllocBlock._word_size, 409 (size_t) SmallForLinearAlloc - 1)); 410 // XXX the following could potentially be pretty slow; 411 // should one, pessimistically for the rare cases when res 412 // calculated above is less than IndexSetSize, 413 // just return res calculated above? My reasoning was that 414 // those cases will be so rare that the extra time spent doesn't 415 // really matter.... 416 // Note: do not change the loop test i >= res + IndexSetStride 417 // to i > res below, because i is unsigned and res may be zero. 418 for (size_t i = IndexSetSize - 1; i >= res + IndexSetStride; 419 i -= IndexSetStride) { 420 if (_indexedFreeList[i].head() != NULL) { 421 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList"); 422 return i; 423 } 424 } 425 return res; 426 } 427 428 void LinearAllocBlock::print_on(outputStream* st) const { 429 st->print_cr(" LinearAllocBlock: ptr = " PTR_FORMAT ", word_size = " SIZE_FORMAT 430 ", refillsize = " SIZE_FORMAT ", allocation_size_limit = " SIZE_FORMAT, 431 p2i(_ptr), _word_size, _refillSize, _allocation_size_limit); 432 } 433 434 void CompactibleFreeListSpace::print_on(outputStream* st) const { 435 st->print_cr("COMPACTIBLE FREELIST SPACE"); 436 st->print_cr(" Space:"); 437 Space::print_on(st); 438 439 st->print_cr("promoInfo:"); 440 _promoInfo.print_on(st); 441 442 st->print_cr("_smallLinearAllocBlock"); 443 _smallLinearAllocBlock.print_on(st); 444 445 // dump_memory_block(_smallLinearAllocBlock->_ptr, 128); 446 447 st->print_cr(" _fitStrategy = %s, _adaptive_freelists = %s", 448 _fitStrategy?"true":"false", _adaptive_freelists?"true":"false"); 449 } 450 451 void CompactibleFreeListSpace::print_indexed_free_lists(outputStream* st) 452 const { 453 reportIndexedFreeListStatistics(); 454 gclog_or_tty->print_cr("Layout of Indexed Freelists"); 455 gclog_or_tty->print_cr("---------------------------"); 456 AdaptiveFreeList<FreeChunk>::print_labels_on(st, "size"); 457 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { 458 _indexedFreeList[i].print_on(gclog_or_tty); 459 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL; 460 fc = fc->next()) { 461 gclog_or_tty->print_cr("\t[" PTR_FORMAT "," PTR_FORMAT ") %s", 462 p2i(fc), p2i((HeapWord*)fc + i), 463 fc->cantCoalesce() ? "\t CC" : ""); 464 } 465 } 466 } 467 468 void CompactibleFreeListSpace::print_promo_info_blocks(outputStream* st) 469 const { 470 _promoInfo.print_on(st); 471 } 472 473 void CompactibleFreeListSpace::print_dictionary_free_lists(outputStream* st) 474 const { 475 _dictionary->report_statistics(); 476 st->print_cr("Layout of Freelists in Tree"); 477 st->print_cr("---------------------------"); 478 _dictionary->print_free_lists(st); 479 } 480 481 class BlkPrintingClosure: public BlkClosure { 482 const CMSCollector* _collector; 483 const CompactibleFreeListSpace* _sp; 484 const CMSBitMap* _live_bit_map; 485 const bool _post_remark; 486 outputStream* _st; 487 public: 488 BlkPrintingClosure(const CMSCollector* collector, 489 const CompactibleFreeListSpace* sp, 490 const CMSBitMap* live_bit_map, 491 outputStream* st): 492 _collector(collector), 493 _sp(sp), 494 _live_bit_map(live_bit_map), 495 _post_remark(collector->abstract_state() > CMSCollector::FinalMarking), 496 _st(st) { } 497 size_t do_blk(HeapWord* addr); 498 }; 499 500 size_t BlkPrintingClosure::do_blk(HeapWord* addr) { 501 size_t sz = _sp->block_size_no_stall(addr, _collector); 502 assert(sz != 0, "Should always be able to compute a size"); 503 if (_sp->block_is_obj(addr)) { 504 const bool dead = _post_remark && !_live_bit_map->isMarked(addr); 505 _st->print_cr(PTR_FORMAT ": %s object of size " SIZE_FORMAT "%s", 506 p2i(addr), 507 dead ? "dead" : "live", 508 sz, 509 (!dead && CMSPrintObjectsInDump) ? ":" : "."); 510 if (CMSPrintObjectsInDump && !dead) { 511 oop(addr)->print_on(_st); 512 _st->print_cr("--------------------------------------"); 513 } 514 } else { // free block 515 _st->print_cr(PTR_FORMAT ": free block of size " SIZE_FORMAT "%s", 516 p2i(addr), sz, CMSPrintChunksInDump ? ":" : "."); 517 if (CMSPrintChunksInDump) { 518 ((FreeChunk*)addr)->print_on(_st); 519 _st->print_cr("--------------------------------------"); 520 } 521 } 522 return sz; 523 } 524 525 void CompactibleFreeListSpace::dump_at_safepoint_with_locks(CMSCollector* c, 526 outputStream* st) { 527 st->print_cr("\n========================="); 528 st->print_cr("Block layout in CMS Heap:"); 529 st->print_cr("========================="); 530 BlkPrintingClosure bpcl(c, this, c->markBitMap(), st); 531 blk_iterate(&bpcl); 532 533 st->print_cr("\n======================================="); 534 st->print_cr("Order & Layout of Promotion Info Blocks"); 535 st->print_cr("======================================="); 536 print_promo_info_blocks(st); 537 538 st->print_cr("\n==========================="); 539 st->print_cr("Order of Indexed Free Lists"); 540 st->print_cr("========================="); 541 print_indexed_free_lists(st); 542 543 st->print_cr("\n================================="); 544 st->print_cr("Order of Free Lists in Dictionary"); 545 st->print_cr("================================="); 546 print_dictionary_free_lists(st); 547 } 548 549 550 void CompactibleFreeListSpace::reportFreeListStatistics() const { 551 assert_lock_strong(&_freelistLock); 552 assert(PrintFLSStatistics != 0, "Reporting error"); 553 _dictionary->report_statistics(); 554 if (PrintFLSStatistics > 1) { 555 reportIndexedFreeListStatistics(); 556 size_t total_size = totalSizeInIndexedFreeLists() + 557 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock())); 558 gclog_or_tty->print(" free=" SIZE_FORMAT " frag=%1.4f\n", total_size, flsFrag()); 559 } 560 } 561 562 void CompactibleFreeListSpace::reportIndexedFreeListStatistics() const { 563 assert_lock_strong(&_freelistLock); 564 gclog_or_tty->print("Statistics for IndexedFreeLists:\n" 565 "--------------------------------\n"); 566 size_t total_size = totalSizeInIndexedFreeLists(); 567 size_t free_blocks = numFreeBlocksInIndexedFreeLists(); 568 gclog_or_tty->print("Total Free Space: " SIZE_FORMAT "\n", total_size); 569 gclog_or_tty->print("Max Chunk Size: " SIZE_FORMAT "\n", maxChunkSizeInIndexedFreeLists()); 570 gclog_or_tty->print("Number of Blocks: " SIZE_FORMAT "\n", free_blocks); 571 if (free_blocks != 0) { 572 gclog_or_tty->print("Av. Block Size: " SIZE_FORMAT "\n", total_size/free_blocks); 573 } 574 } 575 576 size_t CompactibleFreeListSpace::numFreeBlocksInIndexedFreeLists() const { 577 size_t res = 0; 578 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { 579 debug_only( 580 ssize_t recount = 0; 581 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL; 582 fc = fc->next()) { 583 recount += 1; 584 } 585 assert(recount == _indexedFreeList[i].count(), 586 "Incorrect count in list"); 587 ) 588 res += _indexedFreeList[i].count(); 589 } 590 return res; 591 } 592 593 size_t CompactibleFreeListSpace::maxChunkSizeInIndexedFreeLists() const { 594 for (size_t i = IndexSetSize - 1; i != 0; i -= IndexSetStride) { 595 if (_indexedFreeList[i].head() != NULL) { 596 assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList"); 597 return (size_t)i; 598 } 599 } 600 return 0; 601 } 602 603 void CompactibleFreeListSpace::set_end(HeapWord* value) { 604 HeapWord* prevEnd = end(); 605 assert(prevEnd != value, "unnecessary set_end call"); 606 assert(prevEnd == NULL || !BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(), 607 "New end is below unallocated block"); 608 _end = value; 609 if (prevEnd != NULL) { 610 // Resize the underlying block offset table. 611 _bt.resize(pointer_delta(value, bottom())); 612 if (value <= prevEnd) { 613 assert(!BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(), 614 "New end is below unallocated block"); 615 } else { 616 // Now, take this new chunk and add it to the free blocks. 617 // Note that the BOT has not yet been updated for this block. 618 size_t newFcSize = pointer_delta(value, prevEnd); 619 // XXX This is REALLY UGLY and should be fixed up. XXX 620 if (!_adaptive_freelists && _smallLinearAllocBlock._ptr == NULL) { 621 // Mark the boundary of the new block in BOT 622 _bt.mark_block(prevEnd, value); 623 // put it all in the linAB 624 MutexLockerEx x(parDictionaryAllocLock(), 625 Mutex::_no_safepoint_check_flag); 626 _smallLinearAllocBlock._ptr = prevEnd; 627 _smallLinearAllocBlock._word_size = newFcSize; 628 repairLinearAllocBlock(&_smallLinearAllocBlock); 629 // Births of chunks put into a LinAB are not recorded. Births 630 // of chunks as they are allocated out of a LinAB are. 631 } else { 632 // Add the block to the free lists, if possible coalescing it 633 // with the last free block, and update the BOT and census data. 634 addChunkToFreeListsAtEndRecordingStats(prevEnd, newFcSize); 635 } 636 } 637 } 638 } 639 640 class FreeListSpace_DCTOC : public Filtering_DCTOC { 641 CompactibleFreeListSpace* _cfls; 642 CMSCollector* _collector; 643 protected: 644 // Override. 645 #define walk_mem_region_with_cl_DECL(ClosureType) \ 646 virtual void walk_mem_region_with_cl(MemRegion mr, \ 647 HeapWord* bottom, HeapWord* top, \ 648 ClosureType* cl); \ 649 void walk_mem_region_with_cl_par(MemRegion mr, \ 650 HeapWord* bottom, HeapWord* top, \ 651 ClosureType* cl); \ 652 void walk_mem_region_with_cl_nopar(MemRegion mr, \ 653 HeapWord* bottom, HeapWord* top, \ 654 ClosureType* cl) 655 walk_mem_region_with_cl_DECL(ExtendedOopClosure); 656 walk_mem_region_with_cl_DECL(FilteringClosure); 657 658 public: 659 FreeListSpace_DCTOC(CompactibleFreeListSpace* sp, 660 CMSCollector* collector, 661 ExtendedOopClosure* cl, 662 CardTableModRefBS::PrecisionStyle precision, 663 HeapWord* boundary) : 664 Filtering_DCTOC(sp, cl, precision, boundary), 665 _cfls(sp), _collector(collector) {} 666 }; 667 668 // We de-virtualize the block-related calls below, since we know that our 669 // space is a CompactibleFreeListSpace. 670 671 #define FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \ 672 void FreeListSpace_DCTOC::walk_mem_region_with_cl(MemRegion mr, \ 673 HeapWord* bottom, \ 674 HeapWord* top, \ 675 ClosureType* cl) { \ 676 bool is_par = GenCollectedHeap::heap()->n_par_threads() > 0; \ 677 if (is_par) { \ 678 assert(GenCollectedHeap::heap()->n_par_threads() == \ 679 GenCollectedHeap::heap()->workers()->active_workers(), "Mismatch"); \ 680 walk_mem_region_with_cl_par(mr, bottom, top, cl); \ 681 } else { \ 682 walk_mem_region_with_cl_nopar(mr, bottom, top, cl); \ 683 } \ 684 } \ 685 void FreeListSpace_DCTOC::walk_mem_region_with_cl_par(MemRegion mr, \ 686 HeapWord* bottom, \ 687 HeapWord* top, \ 688 ClosureType* cl) { \ 689 /* Skip parts that are before "mr", in case "block_start" sent us \ 690 back too far. */ \ 691 HeapWord* mr_start = mr.start(); \ 692 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \ 693 HeapWord* next = bottom + bot_size; \ 694 while (next < mr_start) { \ 695 bottom = next; \ 696 bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \ 697 next = bottom + bot_size; \ 698 } \ 699 \ 700 while (bottom < top) { \ 701 if (_cfls->CompactibleFreeListSpace::block_is_obj(bottom) && \ 702 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \ 703 oop(bottom)) && \ 704 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \ 705 size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \ 706 bottom += _cfls->adjustObjectSize(word_sz); \ 707 } else { \ 708 bottom += _cfls->CompactibleFreeListSpace::block_size(bottom); \ 709 } \ 710 } \ 711 } \ 712 void FreeListSpace_DCTOC::walk_mem_region_with_cl_nopar(MemRegion mr, \ 713 HeapWord* bottom, \ 714 HeapWord* top, \ 715 ClosureType* cl) { \ 716 /* Skip parts that are before "mr", in case "block_start" sent us \ 717 back too far. */ \ 718 HeapWord* mr_start = mr.start(); \ 719 size_t bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \ 720 HeapWord* next = bottom + bot_size; \ 721 while (next < mr_start) { \ 722 bottom = next; \ 723 bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \ 724 next = bottom + bot_size; \ 725 } \ 726 \ 727 while (bottom < top) { \ 728 if (_cfls->CompactibleFreeListSpace::block_is_obj_nopar(bottom) && \ 729 !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \ 730 oop(bottom)) && \ 731 !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \ 732 size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \ 733 bottom += _cfls->adjustObjectSize(word_sz); \ 734 } else { \ 735 bottom += _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \ 736 } \ 737 } \ 738 } 739 740 // (There are only two of these, rather than N, because the split is due 741 // only to the introduction of the FilteringClosure, a local part of the 742 // impl of this abstraction.) 743 FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(ExtendedOopClosure) 744 FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure) 745 746 DirtyCardToOopClosure* 747 CompactibleFreeListSpace::new_dcto_cl(ExtendedOopClosure* cl, 748 CardTableModRefBS::PrecisionStyle precision, 749 HeapWord* boundary) { 750 return new FreeListSpace_DCTOC(this, _collector, cl, precision, boundary); 751 } 752 753 754 // Note on locking for the space iteration functions: 755 // since the collector's iteration activities are concurrent with 756 // allocation activities by mutators, absent a suitable mutual exclusion 757 // mechanism the iterators may go awry. For instance a block being iterated 758 // may suddenly be allocated or divided up and part of it allocated and 759 // so on. 760 761 // Apply the given closure to each block in the space. 762 void CompactibleFreeListSpace::blk_iterate_careful(BlkClosureCareful* cl) { 763 assert_lock_strong(freelistLock()); 764 HeapWord *cur, *limit; 765 for (cur = bottom(), limit = end(); cur < limit; 766 cur += cl->do_blk_careful(cur)); 767 } 768 769 // Apply the given closure to each block in the space. 770 void CompactibleFreeListSpace::blk_iterate(BlkClosure* cl) { 771 assert_lock_strong(freelistLock()); 772 HeapWord *cur, *limit; 773 for (cur = bottom(), limit = end(); cur < limit; 774 cur += cl->do_blk(cur)); 775 } 776 777 // Apply the given closure to each oop in the space. 778 void CompactibleFreeListSpace::oop_iterate(ExtendedOopClosure* cl) { 779 assert_lock_strong(freelistLock()); 780 HeapWord *cur, *limit; 781 size_t curSize; 782 for (cur = bottom(), limit = end(); cur < limit; 783 cur += curSize) { 784 curSize = block_size(cur); 785 if (block_is_obj(cur)) { 786 oop(cur)->oop_iterate(cl); 787 } 788 } 789 } 790 791 // NOTE: In the following methods, in order to safely be able to 792 // apply the closure to an object, we need to be sure that the 793 // object has been initialized. We are guaranteed that an object 794 // is initialized if we are holding the Heap_lock with the 795 // world stopped. 796 void CompactibleFreeListSpace::verify_objects_initialized() const { 797 if (is_init_completed()) { 798 assert_locked_or_safepoint(Heap_lock); 799 if (Universe::is_fully_initialized()) { 800 guarantee(SafepointSynchronize::is_at_safepoint(), 801 "Required for objects to be initialized"); 802 } 803 } // else make a concession at vm start-up 804 } 805 806 // Apply the given closure to each object in the space 807 void CompactibleFreeListSpace::object_iterate(ObjectClosure* blk) { 808 assert_lock_strong(freelistLock()); 809 NOT_PRODUCT(verify_objects_initialized()); 810 HeapWord *cur, *limit; 811 size_t curSize; 812 for (cur = bottom(), limit = end(); cur < limit; 813 cur += curSize) { 814 curSize = block_size(cur); 815 if (block_is_obj(cur)) { 816 blk->do_object(oop(cur)); 817 } 818 } 819 } 820 821 // Apply the given closure to each live object in the space 822 // The usage of CompactibleFreeListSpace 823 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows 824 // objects in the space with references to objects that are no longer 825 // valid. For example, an object may reference another object 826 // that has already been sweep up (collected). This method uses 827 // obj_is_alive() to determine whether it is safe to apply the closure to 828 // an object. See obj_is_alive() for details on how liveness of an 829 // object is decided. 830 831 void CompactibleFreeListSpace::safe_object_iterate(ObjectClosure* blk) { 832 assert_lock_strong(freelistLock()); 833 NOT_PRODUCT(verify_objects_initialized()); 834 HeapWord *cur, *limit; 835 size_t curSize; 836 for (cur = bottom(), limit = end(); cur < limit; 837 cur += curSize) { 838 curSize = block_size(cur); 839 if (block_is_obj(cur) && obj_is_alive(cur)) { 840 blk->do_object(oop(cur)); 841 } 842 } 843 } 844 845 void CompactibleFreeListSpace::object_iterate_mem(MemRegion mr, 846 UpwardsObjectClosure* cl) { 847 assert_locked(freelistLock()); 848 NOT_PRODUCT(verify_objects_initialized()); 849 assert(!mr.is_empty(), "Should be non-empty"); 850 // We use MemRegion(bottom(), end()) rather than used_region() below 851 // because the two are not necessarily equal for some kinds of 852 // spaces, in particular, certain kinds of free list spaces. 853 // We could use the more complicated but more precise: 854 // MemRegion(used_region().start(), round_to(used_region().end(), CardSize)) 855 // but the slight imprecision seems acceptable in the assertion check. 856 assert(MemRegion(bottom(), end()).contains(mr), 857 "Should be within used space"); 858 HeapWord* prev = cl->previous(); // max address from last time 859 if (prev >= mr.end()) { // nothing to do 860 return; 861 } 862 // This assert will not work when we go from cms space to perm 863 // space, and use same closure. Easy fix deferred for later. XXX YSR 864 // assert(prev == NULL || contains(prev), "Should be within space"); 865 866 bool last_was_obj_array = false; 867 HeapWord *blk_start_addr, *region_start_addr; 868 if (prev > mr.start()) { 869 region_start_addr = prev; 870 blk_start_addr = prev; 871 // The previous invocation may have pushed "prev" beyond the 872 // last allocated block yet there may be still be blocks 873 // in this region due to a particular coalescing policy. 874 // Relax the assertion so that the case where the unallocated 875 // block is maintained and "prev" is beyond the unallocated 876 // block does not cause the assertion to fire. 877 assert((BlockOffsetArrayUseUnallocatedBlock && 878 (!is_in(prev))) || 879 (blk_start_addr == block_start(region_start_addr)), "invariant"); 880 } else { 881 region_start_addr = mr.start(); 882 blk_start_addr = block_start(region_start_addr); 883 } 884 HeapWord* region_end_addr = mr.end(); 885 MemRegion derived_mr(region_start_addr, region_end_addr); 886 while (blk_start_addr < region_end_addr) { 887 const size_t size = block_size(blk_start_addr); 888 if (block_is_obj(blk_start_addr)) { 889 last_was_obj_array = cl->do_object_bm(oop(blk_start_addr), derived_mr); 890 } else { 891 last_was_obj_array = false; 892 } 893 blk_start_addr += size; 894 } 895 if (!last_was_obj_array) { 896 assert((bottom() <= blk_start_addr) && (blk_start_addr <= end()), 897 "Should be within (closed) used space"); 898 assert(blk_start_addr > prev, "Invariant"); 899 cl->set_previous(blk_start_addr); // min address for next time 900 } 901 } 902 903 // Callers of this iterator beware: The closure application should 904 // be robust in the face of uninitialized objects and should (always) 905 // return a correct size so that the next addr + size below gives us a 906 // valid block boundary. [See for instance, 907 // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful() 908 // in ConcurrentMarkSweepGeneration.cpp.] 909 HeapWord* 910 CompactibleFreeListSpace::object_iterate_careful_m(MemRegion mr, 911 ObjectClosureCareful* cl) { 912 assert_lock_strong(freelistLock()); 913 // Can't use used_region() below because it may not necessarily 914 // be the same as [bottom(),end()); although we could 915 // use [used_region().start(),round_to(used_region().end(),CardSize)), 916 // that appears too cumbersome, so we just do the simpler check 917 // in the assertion below. 918 assert(!mr.is_empty() && MemRegion(bottom(),end()).contains(mr), 919 "mr should be non-empty and within used space"); 920 HeapWord *addr, *end; 921 size_t size; 922 for (addr = block_start_careful(mr.start()), end = mr.end(); 923 addr < end; addr += size) { 924 FreeChunk* fc = (FreeChunk*)addr; 925 if (fc->is_free()) { 926 // Since we hold the free list lock, which protects direct 927 // allocation in this generation by mutators, a free object 928 // will remain free throughout this iteration code. 929 size = fc->size(); 930 } else { 931 // Note that the object need not necessarily be initialized, 932 // because (for instance) the free list lock does NOT protect 933 // object initialization. The closure application below must 934 // therefore be correct in the face of uninitialized objects. 935 size = cl->do_object_careful_m(oop(addr), mr); 936 if (size == 0) { 937 // An unparsable object found. Signal early termination. 938 return addr; 939 } 940 } 941 } 942 return NULL; 943 } 944 945 946 HeapWord* CompactibleFreeListSpace::block_start_const(const void* p) const { 947 NOT_PRODUCT(verify_objects_initialized()); 948 return _bt.block_start(p); 949 } 950 951 HeapWord* CompactibleFreeListSpace::block_start_careful(const void* p) const { 952 return _bt.block_start_careful(p); 953 } 954 955 size_t CompactibleFreeListSpace::block_size(const HeapWord* p) const { 956 NOT_PRODUCT(verify_objects_initialized()); 957 // This must be volatile, or else there is a danger that the compiler 958 // will compile the code below into a sometimes-infinite loop, by keeping 959 // the value read the first time in a register. 960 while (true) { 961 // We must do this until we get a consistent view of the object. 962 if (FreeChunk::indicatesFreeChunk(p)) { 963 volatile FreeChunk* fc = (volatile FreeChunk*)p; 964 size_t res = fc->size(); 965 966 // Bugfix for systems with weak memory model (PPC64/IA64). The 967 // block's free bit was set and we have read the size of the 968 // block. Acquire and check the free bit again. If the block is 969 // still free, the read size is correct. 970 OrderAccess::acquire(); 971 972 // If the object is still a free chunk, return the size, else it 973 // has been allocated so try again. 974 if (FreeChunk::indicatesFreeChunk(p)) { 975 assert(res != 0, "Block size should not be 0"); 976 return res; 977 } 978 } else { 979 // must read from what 'p' points to in each loop. 980 Klass* k = ((volatile oopDesc*)p)->klass_or_null(); 981 if (k != NULL) { 982 assert(k->is_klass(), "Should really be klass oop."); 983 oop o = (oop)p; 984 assert(o->is_oop(true /* ignore mark word */), "Should be an oop."); 985 986 // Bugfix for systems with weak memory model (PPC64/IA64). 987 // The object o may be an array. Acquire to make sure that the array 988 // size (third word) is consistent. 989 OrderAccess::acquire(); 990 991 size_t res = o->size_given_klass(k); 992 res = adjustObjectSize(res); 993 assert(res != 0, "Block size should not be 0"); 994 return res; 995 } 996 } 997 } 998 } 999 1000 // TODO: Now that is_parsable is gone, we should combine these two functions. 1001 // A variant of the above that uses the Printezis bits for 1002 // unparsable but allocated objects. This avoids any possible 1003 // stalls waiting for mutators to initialize objects, and is 1004 // thus potentially faster than the variant above. However, 1005 // this variant may return a zero size for a block that is 1006 // under mutation and for which a consistent size cannot be 1007 // inferred without stalling; see CMSCollector::block_size_if_printezis_bits(). 1008 size_t CompactibleFreeListSpace::block_size_no_stall(HeapWord* p, 1009 const CMSCollector* c) 1010 const { 1011 assert(MemRegion(bottom(), end()).contains(p), "p not in space"); 1012 // This must be volatile, or else there is a danger that the compiler 1013 // will compile the code below into a sometimes-infinite loop, by keeping 1014 // the value read the first time in a register. 1015 DEBUG_ONLY(uint loops = 0;) 1016 while (true) { 1017 // We must do this until we get a consistent view of the object. 1018 if (FreeChunk::indicatesFreeChunk(p)) { 1019 volatile FreeChunk* fc = (volatile FreeChunk*)p; 1020 size_t res = fc->size(); 1021 1022 // Bugfix for systems with weak memory model (PPC64/IA64). The 1023 // free bit of the block was set and we have read the size of 1024 // the block. Acquire and check the free bit again. If the 1025 // block is still free, the read size is correct. 1026 OrderAccess::acquire(); 1027 1028 if (FreeChunk::indicatesFreeChunk(p)) { 1029 assert(res != 0, "Block size should not be 0"); 1030 assert(loops == 0, "Should be 0"); 1031 return res; 1032 } 1033 } else { 1034 // must read from what 'p' points to in each loop. 1035 Klass* k = ((volatile oopDesc*)p)->klass_or_null(); 1036 // We trust the size of any object that has a non-NULL 1037 // klass and (for those in the perm gen) is parsable 1038 // -- irrespective of its conc_safe-ty. 1039 if (k != NULL) { 1040 assert(k->is_klass(), "Should really be klass oop."); 1041 oop o = (oop)p; 1042 assert(o->is_oop(), "Should be an oop"); 1043 1044 // Bugfix for systems with weak memory model (PPC64/IA64). 1045 // The object o may be an array. Acquire to make sure that the array 1046 // size (third word) is consistent. 1047 OrderAccess::acquire(); 1048 1049 size_t res = o->size_given_klass(k); 1050 res = adjustObjectSize(res); 1051 assert(res != 0, "Block size should not be 0"); 1052 return res; 1053 } else { 1054 // May return 0 if P-bits not present. 1055 return c->block_size_if_printezis_bits(p); 1056 } 1057 } 1058 assert(loops == 0, "Can loop at most once"); 1059 DEBUG_ONLY(loops++;) 1060 } 1061 } 1062 1063 size_t CompactibleFreeListSpace::block_size_nopar(const HeapWord* p) const { 1064 NOT_PRODUCT(verify_objects_initialized()); 1065 assert(MemRegion(bottom(), end()).contains(p), "p not in space"); 1066 FreeChunk* fc = (FreeChunk*)p; 1067 if (fc->is_free()) { 1068 return fc->size(); 1069 } else { 1070 // Ignore mark word because this may be a recently promoted 1071 // object whose mark word is used to chain together grey 1072 // objects (the last one would have a null value). 1073 assert(oop(p)->is_oop(true), "Should be an oop"); 1074 return adjustObjectSize(oop(p)->size()); 1075 } 1076 } 1077 1078 // This implementation assumes that the property of "being an object" is 1079 // stable. But being a free chunk may not be (because of parallel 1080 // promotion.) 1081 bool CompactibleFreeListSpace::block_is_obj(const HeapWord* p) const { 1082 FreeChunk* fc = (FreeChunk*)p; 1083 assert(is_in_reserved(p), "Should be in space"); 1084 // When doing a mark-sweep-compact of the CMS generation, this 1085 // assertion may fail because prepare_for_compaction() uses 1086 // space that is garbage to maintain information on ranges of 1087 // live objects so that these live ranges can be moved as a whole. 1088 // Comment out this assertion until that problem can be solved 1089 // (i.e., that the block start calculation may look at objects 1090 // at address below "p" in finding the object that contains "p" 1091 // and those objects (if garbage) may have been modified to hold 1092 // live range information. 1093 // assert(CollectedHeap::use_parallel_gc_threads() || _bt.block_start(p) == p, 1094 // "Should be a block boundary"); 1095 if (FreeChunk::indicatesFreeChunk(p)) return false; 1096 Klass* k = oop(p)->klass_or_null(); 1097 if (k != NULL) { 1098 // Ignore mark word because it may have been used to 1099 // chain together promoted objects (the last one 1100 // would have a null value). 1101 assert(oop(p)->is_oop(true), "Should be an oop"); 1102 return true; 1103 } else { 1104 return false; // Was not an object at the start of collection. 1105 } 1106 } 1107 1108 // Check if the object is alive. This fact is checked either by consulting 1109 // the main marking bitmap in the sweeping phase or, if it's a permanent 1110 // generation and we're not in the sweeping phase, by checking the 1111 // perm_gen_verify_bit_map where we store the "deadness" information if 1112 // we did not sweep the perm gen in the most recent previous GC cycle. 1113 bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const { 1114 assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(), 1115 "Else races are possible"); 1116 assert(block_is_obj(p), "The address should point to an object"); 1117 1118 // If we're sweeping, we use object liveness information from the main bit map 1119 // for both perm gen and old gen. 1120 // We don't need to lock the bitmap (live_map or dead_map below), because 1121 // EITHER we are in the middle of the sweeping phase, and the 1122 // main marking bit map (live_map below) is locked, 1123 // OR we're in other phases and perm_gen_verify_bit_map (dead_map below) 1124 // is stable, because it's mutated only in the sweeping phase. 1125 // NOTE: This method is also used by jmap where, if class unloading is 1126 // off, the results can return "false" for legitimate perm objects, 1127 // when we are not in the midst of a sweeping phase, which can result 1128 // in jmap not reporting certain perm gen objects. This will be moot 1129 // if/when the perm gen goes away in the future. 1130 if (_collector->abstract_state() == CMSCollector::Sweeping) { 1131 CMSBitMap* live_map = _collector->markBitMap(); 1132 return live_map->par_isMarked((HeapWord*) p); 1133 } 1134 return true; 1135 } 1136 1137 bool CompactibleFreeListSpace::block_is_obj_nopar(const HeapWord* p) const { 1138 FreeChunk* fc = (FreeChunk*)p; 1139 assert(is_in_reserved(p), "Should be in space"); 1140 assert(_bt.block_start(p) == p, "Should be a block boundary"); 1141 if (!fc->is_free()) { 1142 // Ignore mark word because it may have been used to 1143 // chain together promoted objects (the last one 1144 // would have a null value). 1145 assert(oop(p)->is_oop(true), "Should be an oop"); 1146 return true; 1147 } 1148 return false; 1149 } 1150 1151 // "MT-safe but not guaranteed MT-precise" (TM); you may get an 1152 // approximate answer if you don't hold the freelistlock when you call this. 1153 size_t CompactibleFreeListSpace::totalSizeInIndexedFreeLists() const { 1154 size_t size = 0; 1155 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { 1156 debug_only( 1157 // We may be calling here without the lock in which case we 1158 // won't do this modest sanity check. 1159 if (freelistLock()->owned_by_self()) { 1160 size_t total_list_size = 0; 1161 for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL; 1162 fc = fc->next()) { 1163 total_list_size += i; 1164 } 1165 assert(total_list_size == i * _indexedFreeList[i].count(), 1166 "Count in list is incorrect"); 1167 } 1168 ) 1169 size += i * _indexedFreeList[i].count(); 1170 } 1171 return size; 1172 } 1173 1174 HeapWord* CompactibleFreeListSpace::par_allocate(size_t size) { 1175 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); 1176 return allocate(size); 1177 } 1178 1179 HeapWord* 1180 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlockRemainder(size_t size) { 1181 return getChunkFromLinearAllocBlockRemainder(&_smallLinearAllocBlock, size); 1182 } 1183 1184 HeapWord* CompactibleFreeListSpace::allocate(size_t size) { 1185 assert_lock_strong(freelistLock()); 1186 HeapWord* res = NULL; 1187 assert(size == adjustObjectSize(size), 1188 "use adjustObjectSize() before calling into allocate()"); 1189 1190 if (_adaptive_freelists) { 1191 res = allocate_adaptive_freelists(size); 1192 } else { // non-adaptive free lists 1193 res = allocate_non_adaptive_freelists(size); 1194 } 1195 1196 if (res != NULL) { 1197 // check that res does lie in this space! 1198 assert(is_in_reserved(res), "Not in this space!"); 1199 assert(is_aligned((void*)res), "alignment check"); 1200 1201 FreeChunk* fc = (FreeChunk*)res; 1202 fc->markNotFree(); 1203 assert(!fc->is_free(), "shouldn't be marked free"); 1204 assert(oop(fc)->klass_or_null() == NULL, "should look uninitialized"); 1205 // Verify that the block offset table shows this to 1206 // be a single block, but not one which is unallocated. 1207 _bt.verify_single_block(res, size); 1208 _bt.verify_not_unallocated(res, size); 1209 // mangle a just allocated object with a distinct pattern. 1210 debug_only(fc->mangleAllocated(size)); 1211 } 1212 1213 return res; 1214 } 1215 1216 HeapWord* CompactibleFreeListSpace::allocate_non_adaptive_freelists(size_t size) { 1217 HeapWord* res = NULL; 1218 // try and use linear allocation for smaller blocks 1219 if (size < _smallLinearAllocBlock._allocation_size_limit) { 1220 // if successful, the following also adjusts block offset table 1221 res = getChunkFromSmallLinearAllocBlock(size); 1222 } 1223 // Else triage to indexed lists for smaller sizes 1224 if (res == NULL) { 1225 if (size < SmallForDictionary) { 1226 res = (HeapWord*) getChunkFromIndexedFreeList(size); 1227 } else { 1228 // else get it from the big dictionary; if even this doesn't 1229 // work we are out of luck. 1230 res = (HeapWord*)getChunkFromDictionaryExact(size); 1231 } 1232 } 1233 1234 return res; 1235 } 1236 1237 HeapWord* CompactibleFreeListSpace::allocate_adaptive_freelists(size_t size) { 1238 assert_lock_strong(freelistLock()); 1239 HeapWord* res = NULL; 1240 assert(size == adjustObjectSize(size), 1241 "use adjustObjectSize() before calling into allocate()"); 1242 1243 // Strategy 1244 // if small 1245 // exact size from small object indexed list if small 1246 // small or large linear allocation block (linAB) as appropriate 1247 // take from lists of greater sized chunks 1248 // else 1249 // dictionary 1250 // small or large linear allocation block if it has the space 1251 // Try allocating exact size from indexTable first 1252 if (size < IndexSetSize) { 1253 res = (HeapWord*) getChunkFromIndexedFreeList(size); 1254 if(res != NULL) { 1255 assert(res != (HeapWord*)_indexedFreeList[size].head(), 1256 "Not removed from free list"); 1257 // no block offset table adjustment is necessary on blocks in 1258 // the indexed lists. 1259 1260 // Try allocating from the small LinAB 1261 } else if (size < _smallLinearAllocBlock._allocation_size_limit && 1262 (res = getChunkFromSmallLinearAllocBlock(size)) != NULL) { 1263 // if successful, the above also adjusts block offset table 1264 // Note that this call will refill the LinAB to 1265 // satisfy the request. This is different that 1266 // evm. 1267 // Don't record chunk off a LinAB? smallSplitBirth(size); 1268 } else { 1269 // Raid the exact free lists larger than size, even if they are not 1270 // overpopulated. 1271 res = (HeapWord*) getChunkFromGreater(size); 1272 } 1273 } else { 1274 // Big objects get allocated directly from the dictionary. 1275 res = (HeapWord*) getChunkFromDictionaryExact(size); 1276 if (res == NULL) { 1277 // Try hard not to fail since an allocation failure will likely 1278 // trigger a synchronous GC. Try to get the space from the 1279 // allocation blocks. 1280 res = getChunkFromSmallLinearAllocBlockRemainder(size); 1281 } 1282 } 1283 1284 return res; 1285 } 1286 1287 // A worst-case estimate of the space required (in HeapWords) to expand the heap 1288 // when promoting obj. 1289 size_t CompactibleFreeListSpace::expansionSpaceRequired(size_t obj_size) const { 1290 // Depending on the object size, expansion may require refilling either a 1291 // bigLAB or a smallLAB plus refilling a PromotionInfo object. MinChunkSize 1292 // is added because the dictionary may over-allocate to avoid fragmentation. 1293 size_t space = obj_size; 1294 if (!_adaptive_freelists) { 1295 space = MAX2(space, _smallLinearAllocBlock._refillSize); 1296 } 1297 space += _promoInfo.refillSize() + 2 * MinChunkSize; 1298 return space; 1299 } 1300 1301 FreeChunk* CompactibleFreeListSpace::getChunkFromGreater(size_t numWords) { 1302 FreeChunk* ret; 1303 1304 assert(numWords >= MinChunkSize, "Size is less than minimum"); 1305 assert(linearAllocationWouldFail() || bestFitFirst(), 1306 "Should not be here"); 1307 1308 size_t i; 1309 size_t currSize = numWords + MinChunkSize; 1310 assert(currSize % MinObjAlignment == 0, "currSize should be aligned"); 1311 for (i = currSize; i < IndexSetSize; i += IndexSetStride) { 1312 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i]; 1313 if (fl->head()) { 1314 ret = getFromListGreater(fl, numWords); 1315 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk"); 1316 return ret; 1317 } 1318 } 1319 1320 currSize = MAX2((size_t)SmallForDictionary, 1321 (size_t)(numWords + MinChunkSize)); 1322 1323 /* Try to get a chunk that satisfies request, while avoiding 1324 fragmentation that can't be handled. */ 1325 { 1326 ret = dictionary()->get_chunk(currSize); 1327 if (ret != NULL) { 1328 assert(ret->size() - numWords >= MinChunkSize, 1329 "Chunk is too small"); 1330 _bt.allocated((HeapWord*)ret, ret->size()); 1331 /* Carve returned chunk. */ 1332 (void) splitChunkAndReturnRemainder(ret, numWords); 1333 /* Label this as no longer a free chunk. */ 1334 assert(ret->is_free(), "This chunk should be free"); 1335 ret->link_prev(NULL); 1336 } 1337 assert(ret == NULL || ret->is_free(), "Should be returning a free chunk"); 1338 return ret; 1339 } 1340 ShouldNotReachHere(); 1341 } 1342 1343 bool CompactibleFreeListSpace::verifyChunkInIndexedFreeLists(FreeChunk* fc) const { 1344 assert(fc->size() < IndexSetSize, "Size of chunk is too large"); 1345 return _indexedFreeList[fc->size()].verify_chunk_in_free_list(fc); 1346 } 1347 1348 bool CompactibleFreeListSpace::verify_chunk_is_linear_alloc_block(FreeChunk* fc) const { 1349 assert((_smallLinearAllocBlock._ptr != (HeapWord*)fc) || 1350 (_smallLinearAllocBlock._word_size == fc->size()), 1351 "Linear allocation block shows incorrect size"); 1352 return ((_smallLinearAllocBlock._ptr == (HeapWord*)fc) && 1353 (_smallLinearAllocBlock._word_size == fc->size())); 1354 } 1355 1356 // Check if the purported free chunk is present either as a linear 1357 // allocation block, the size-indexed table of (smaller) free blocks, 1358 // or the larger free blocks kept in the binary tree dictionary. 1359 bool CompactibleFreeListSpace::verify_chunk_in_free_list(FreeChunk* fc) const { 1360 if (verify_chunk_is_linear_alloc_block(fc)) { 1361 return true; 1362 } else if (fc->size() < IndexSetSize) { 1363 return verifyChunkInIndexedFreeLists(fc); 1364 } else { 1365 return dictionary()->verify_chunk_in_free_list(fc); 1366 } 1367 } 1368 1369 #ifndef PRODUCT 1370 void CompactibleFreeListSpace::assert_locked() const { 1371 CMSLockVerifier::assert_locked(freelistLock(), parDictionaryAllocLock()); 1372 } 1373 1374 void CompactibleFreeListSpace::assert_locked(const Mutex* lock) const { 1375 CMSLockVerifier::assert_locked(lock); 1376 } 1377 #endif 1378 1379 FreeChunk* CompactibleFreeListSpace::allocateScratch(size_t size) { 1380 // In the parallel case, the main thread holds the free list lock 1381 // on behalf the parallel threads. 1382 FreeChunk* fc; 1383 { 1384 // If GC is parallel, this might be called by several threads. 1385 // This should be rare enough that the locking overhead won't affect 1386 // the sequential code. 1387 MutexLockerEx x(parDictionaryAllocLock(), 1388 Mutex::_no_safepoint_check_flag); 1389 fc = getChunkFromDictionary(size); 1390 } 1391 if (fc != NULL) { 1392 fc->dontCoalesce(); 1393 assert(fc->is_free(), "Should be free, but not coalescable"); 1394 // Verify that the block offset table shows this to 1395 // be a single block, but not one which is unallocated. 1396 _bt.verify_single_block((HeapWord*)fc, fc->size()); 1397 _bt.verify_not_unallocated((HeapWord*)fc, fc->size()); 1398 } 1399 return fc; 1400 } 1401 1402 oop CompactibleFreeListSpace::promote(oop obj, size_t obj_size) { 1403 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in"); 1404 assert_locked(); 1405 1406 // if we are tracking promotions, then first ensure space for 1407 // promotion (including spooling space for saving header if necessary). 1408 // then allocate and copy, then track promoted info if needed. 1409 // When tracking (see PromotionInfo::track()), the mark word may 1410 // be displaced and in this case restoration of the mark word 1411 // occurs in the (oop_since_save_marks_)iterate phase. 1412 if (_promoInfo.tracking() && !_promoInfo.ensure_spooling_space()) { 1413 return NULL; 1414 } 1415 // Call the allocate(size_t, bool) form directly to avoid the 1416 // additional call through the allocate(size_t) form. Having 1417 // the compile inline the call is problematic because allocate(size_t) 1418 // is a virtual method. 1419 HeapWord* res = allocate(adjustObjectSize(obj_size)); 1420 if (res != NULL) { 1421 Copy::aligned_disjoint_words((HeapWord*)obj, res, obj_size); 1422 // if we should be tracking promotions, do so. 1423 if (_promoInfo.tracking()) { 1424 _promoInfo.track((PromotedObject*)res); 1425 } 1426 } 1427 return oop(res); 1428 } 1429 1430 HeapWord* 1431 CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlock(size_t size) { 1432 assert_locked(); 1433 assert(size >= MinChunkSize, "minimum chunk size"); 1434 assert(size < _smallLinearAllocBlock._allocation_size_limit, 1435 "maximum from smallLinearAllocBlock"); 1436 return getChunkFromLinearAllocBlock(&_smallLinearAllocBlock, size); 1437 } 1438 1439 HeapWord* 1440 CompactibleFreeListSpace::getChunkFromLinearAllocBlock(LinearAllocBlock *blk, 1441 size_t size) { 1442 assert_locked(); 1443 assert(size >= MinChunkSize, "too small"); 1444 HeapWord* res = NULL; 1445 // Try to do linear allocation from blk, making sure that 1446 if (blk->_word_size == 0) { 1447 // We have probably been unable to fill this either in the prologue or 1448 // when it was exhausted at the last linear allocation. Bail out until 1449 // next time. 1450 assert(blk->_ptr == NULL, "consistency check"); 1451 return NULL; 1452 } 1453 assert(blk->_word_size != 0 && blk->_ptr != NULL, "consistency check"); 1454 res = getChunkFromLinearAllocBlockRemainder(blk, size); 1455 if (res != NULL) return res; 1456 1457 // about to exhaust this linear allocation block 1458 if (blk->_word_size == size) { // exactly satisfied 1459 res = blk->_ptr; 1460 _bt.allocated(res, blk->_word_size); 1461 } else if (size + MinChunkSize <= blk->_refillSize) { 1462 size_t sz = blk->_word_size; 1463 // Update _unallocated_block if the size is such that chunk would be 1464 // returned to the indexed free list. All other chunks in the indexed 1465 // free lists are allocated from the dictionary so that _unallocated_block 1466 // has already been adjusted for them. Do it here so that the cost 1467 // for all chunks added back to the indexed free lists. 1468 if (sz < SmallForDictionary) { 1469 _bt.allocated(blk->_ptr, sz); 1470 } 1471 // Return the chunk that isn't big enough, and then refill below. 1472 addChunkToFreeLists(blk->_ptr, sz); 1473 split_birth(sz); 1474 // Don't keep statistics on adding back chunk from a LinAB. 1475 } else { 1476 // A refilled block would not satisfy the request. 1477 return NULL; 1478 } 1479 1480 blk->_ptr = NULL; blk->_word_size = 0; 1481 refillLinearAllocBlock(blk); 1482 assert(blk->_ptr == NULL || blk->_word_size >= size + MinChunkSize, 1483 "block was replenished"); 1484 if (res != NULL) { 1485 split_birth(size); 1486 repairLinearAllocBlock(blk); 1487 } else if (blk->_ptr != NULL) { 1488 res = blk->_ptr; 1489 size_t blk_size = blk->_word_size; 1490 blk->_word_size -= size; 1491 blk->_ptr += size; 1492 split_birth(size); 1493 repairLinearAllocBlock(blk); 1494 // Update BOT last so that other (parallel) GC threads see a consistent 1495 // view of the BOT and free blocks. 1496 // Above must occur before BOT is updated below. 1497 OrderAccess::storestore(); 1498 _bt.split_block(res, blk_size, size); // adjust block offset table 1499 } 1500 return res; 1501 } 1502 1503 HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlockRemainder( 1504 LinearAllocBlock* blk, 1505 size_t size) { 1506 assert_locked(); 1507 assert(size >= MinChunkSize, "too small"); 1508 1509 HeapWord* res = NULL; 1510 // This is the common case. Keep it simple. 1511 if (blk->_word_size >= size + MinChunkSize) { 1512 assert(blk->_ptr != NULL, "consistency check"); 1513 res = blk->_ptr; 1514 // Note that the BOT is up-to-date for the linAB before allocation. It 1515 // indicates the start of the linAB. The split_block() updates the 1516 // BOT for the linAB after the allocation (indicates the start of the 1517 // next chunk to be allocated). 1518 size_t blk_size = blk->_word_size; 1519 blk->_word_size -= size; 1520 blk->_ptr += size; 1521 split_birth(size); 1522 repairLinearAllocBlock(blk); 1523 // Update BOT last so that other (parallel) GC threads see a consistent 1524 // view of the BOT and free blocks. 1525 // Above must occur before BOT is updated below. 1526 OrderAccess::storestore(); 1527 _bt.split_block(res, blk_size, size); // adjust block offset table 1528 _bt.allocated(res, size); 1529 } 1530 return res; 1531 } 1532 1533 FreeChunk* 1534 CompactibleFreeListSpace::getChunkFromIndexedFreeList(size_t size) { 1535 assert_locked(); 1536 assert(size < SmallForDictionary, "just checking"); 1537 FreeChunk* res; 1538 res = _indexedFreeList[size].get_chunk_at_head(); 1539 if (res == NULL) { 1540 res = getChunkFromIndexedFreeListHelper(size); 1541 } 1542 _bt.verify_not_unallocated((HeapWord*) res, size); 1543 assert(res == NULL || res->size() == size, "Incorrect block size"); 1544 return res; 1545 } 1546 1547 FreeChunk* 1548 CompactibleFreeListSpace::getChunkFromIndexedFreeListHelper(size_t size, 1549 bool replenish) { 1550 assert_locked(); 1551 FreeChunk* fc = NULL; 1552 if (size < SmallForDictionary) { 1553 assert(_indexedFreeList[size].head() == NULL || 1554 _indexedFreeList[size].surplus() <= 0, 1555 "List for this size should be empty or under populated"); 1556 // Try best fit in exact lists before replenishing the list 1557 if (!bestFitFirst() || (fc = bestFitSmall(size)) == NULL) { 1558 // Replenish list. 1559 // 1560 // Things tried that failed. 1561 // Tried allocating out of the two LinAB's first before 1562 // replenishing lists. 1563 // Tried small linAB of size 256 (size in indexed list) 1564 // and replenishing indexed lists from the small linAB. 1565 // 1566 FreeChunk* newFc = NULL; 1567 const size_t replenish_size = CMSIndexedFreeListReplenish * size; 1568 if (replenish_size < SmallForDictionary) { 1569 // Do not replenish from an underpopulated size. 1570 if (_indexedFreeList[replenish_size].surplus() > 0 && 1571 _indexedFreeList[replenish_size].head() != NULL) { 1572 newFc = _indexedFreeList[replenish_size].get_chunk_at_head(); 1573 } else if (bestFitFirst()) { 1574 newFc = bestFitSmall(replenish_size); 1575 } 1576 } 1577 if (newFc == NULL && replenish_size > size) { 1578 assert(CMSIndexedFreeListReplenish > 1, "ctl pt invariant"); 1579 newFc = getChunkFromIndexedFreeListHelper(replenish_size, false); 1580 } 1581 // Note: The stats update re split-death of block obtained above 1582 // will be recorded below precisely when we know we are going to 1583 // be actually splitting it into more than one pieces below. 1584 if (newFc != NULL) { 1585 if (replenish || CMSReplenishIntermediate) { 1586 // Replenish this list and return one block to caller. 1587 size_t i; 1588 FreeChunk *curFc, *nextFc; 1589 size_t num_blk = newFc->size() / size; 1590 assert(num_blk >= 1, "Smaller than requested?"); 1591 assert(newFc->size() % size == 0, "Should be integral multiple of request"); 1592 if (num_blk > 1) { 1593 // we are sure we will be splitting the block just obtained 1594 // into multiple pieces; record the split-death of the original 1595 splitDeath(replenish_size); 1596 } 1597 // carve up and link blocks 0, ..., num_blk - 2 1598 // The last chunk is not added to the lists but is returned as the 1599 // free chunk. 1600 for (curFc = newFc, nextFc = (FreeChunk*)((HeapWord*)curFc + size), 1601 i = 0; 1602 i < (num_blk - 1); 1603 curFc = nextFc, nextFc = (FreeChunk*)((HeapWord*)nextFc + size), 1604 i++) { 1605 curFc->set_size(size); 1606 // Don't record this as a return in order to try and 1607 // determine the "returns" from a GC. 1608 _bt.verify_not_unallocated((HeapWord*) fc, size); 1609 _indexedFreeList[size].return_chunk_at_tail(curFc, false); 1610 _bt.mark_block((HeapWord*)curFc, size); 1611 split_birth(size); 1612 // Don't record the initial population of the indexed list 1613 // as a split birth. 1614 } 1615 1616 // check that the arithmetic was OK above 1617 assert((HeapWord*)nextFc == (HeapWord*)newFc + num_blk*size, 1618 "inconsistency in carving newFc"); 1619 curFc->set_size(size); 1620 _bt.mark_block((HeapWord*)curFc, size); 1621 split_birth(size); 1622 fc = curFc; 1623 } else { 1624 // Return entire block to caller 1625 fc = newFc; 1626 } 1627 } 1628 } 1629 } else { 1630 // Get a free chunk from the free chunk dictionary to be returned to 1631 // replenish the indexed free list. 1632 fc = getChunkFromDictionaryExact(size); 1633 } 1634 // assert(fc == NULL || fc->is_free(), "Should be returning a free chunk"); 1635 return fc; 1636 } 1637 1638 FreeChunk* 1639 CompactibleFreeListSpace::getChunkFromDictionary(size_t size) { 1640 assert_locked(); 1641 FreeChunk* fc = _dictionary->get_chunk(size, 1642 FreeBlockDictionary<FreeChunk>::atLeast); 1643 if (fc == NULL) { 1644 return NULL; 1645 } 1646 _bt.allocated((HeapWord*)fc, fc->size()); 1647 if (fc->size() >= size + MinChunkSize) { 1648 fc = splitChunkAndReturnRemainder(fc, size); 1649 } 1650 assert(fc->size() >= size, "chunk too small"); 1651 assert(fc->size() < size + MinChunkSize, "chunk too big"); 1652 _bt.verify_single_block((HeapWord*)fc, fc->size()); 1653 return fc; 1654 } 1655 1656 FreeChunk* 1657 CompactibleFreeListSpace::getChunkFromDictionaryExact(size_t size) { 1658 assert_locked(); 1659 FreeChunk* fc = _dictionary->get_chunk(size, 1660 FreeBlockDictionary<FreeChunk>::atLeast); 1661 if (fc == NULL) { 1662 return fc; 1663 } 1664 _bt.allocated((HeapWord*)fc, fc->size()); 1665 if (fc->size() == size) { 1666 _bt.verify_single_block((HeapWord*)fc, size); 1667 return fc; 1668 } 1669 assert(fc->size() > size, "get_chunk() guarantee"); 1670 if (fc->size() < size + MinChunkSize) { 1671 // Return the chunk to the dictionary and go get a bigger one. 1672 returnChunkToDictionary(fc); 1673 fc = _dictionary->get_chunk(size + MinChunkSize, 1674 FreeBlockDictionary<FreeChunk>::atLeast); 1675 if (fc == NULL) { 1676 return NULL; 1677 } 1678 _bt.allocated((HeapWord*)fc, fc->size()); 1679 } 1680 assert(fc->size() >= size + MinChunkSize, "tautology"); 1681 fc = splitChunkAndReturnRemainder(fc, size); 1682 assert(fc->size() == size, "chunk is wrong size"); 1683 _bt.verify_single_block((HeapWord*)fc, size); 1684 return fc; 1685 } 1686 1687 void 1688 CompactibleFreeListSpace::returnChunkToDictionary(FreeChunk* chunk) { 1689 assert_locked(); 1690 1691 size_t size = chunk->size(); 1692 _bt.verify_single_block((HeapWord*)chunk, size); 1693 // adjust _unallocated_block downward, as necessary 1694 _bt.freed((HeapWord*)chunk, size); 1695 _dictionary->return_chunk(chunk); 1696 #ifndef PRODUCT 1697 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) { 1698 TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >* tc = TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::as_TreeChunk(chunk); 1699 TreeList<FreeChunk, AdaptiveFreeList<FreeChunk> >* tl = tc->list(); 1700 tl->verify_stats(); 1701 } 1702 #endif // PRODUCT 1703 } 1704 1705 void 1706 CompactibleFreeListSpace::returnChunkToFreeList(FreeChunk* fc) { 1707 assert_locked(); 1708 size_t size = fc->size(); 1709 _bt.verify_single_block((HeapWord*) fc, size); 1710 _bt.verify_not_unallocated((HeapWord*) fc, size); 1711 if (_adaptive_freelists) { 1712 _indexedFreeList[size].return_chunk_at_tail(fc); 1713 } else { 1714 _indexedFreeList[size].return_chunk_at_head(fc); 1715 } 1716 #ifndef PRODUCT 1717 if (CMSCollector::abstract_state() != CMSCollector::Sweeping) { 1718 _indexedFreeList[size].verify_stats(); 1719 } 1720 #endif // PRODUCT 1721 } 1722 1723 // Add chunk to end of last block -- if it's the largest 1724 // block -- and update BOT and census data. We would 1725 // of course have preferred to coalesce it with the 1726 // last block, but it's currently less expensive to find the 1727 // largest block than it is to find the last. 1728 void 1729 CompactibleFreeListSpace::addChunkToFreeListsAtEndRecordingStats( 1730 HeapWord* chunk, size_t size) { 1731 // check that the chunk does lie in this space! 1732 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!"); 1733 // One of the parallel gc task threads may be here 1734 // whilst others are allocating. 1735 Mutex* lock = &_parDictionaryAllocLock; 1736 FreeChunk* ec; 1737 { 1738 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag); 1739 ec = dictionary()->find_largest_dict(); // get largest block 1740 if (ec != NULL && ec->end() == (uintptr_t*) chunk) { 1741 // It's a coterminal block - we can coalesce. 1742 size_t old_size = ec->size(); 1743 coalDeath(old_size); 1744 removeChunkFromDictionary(ec); 1745 size += old_size; 1746 } else { 1747 ec = (FreeChunk*)chunk; 1748 } 1749 } 1750 ec->set_size(size); 1751 debug_only(ec->mangleFreed(size)); 1752 if (size < SmallForDictionary) { 1753 lock = _indexedFreeListParLocks[size]; 1754 } 1755 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag); 1756 addChunkAndRepairOffsetTable((HeapWord*)ec, size, true); 1757 // record the birth under the lock since the recording involves 1758 // manipulation of the list on which the chunk lives and 1759 // if the chunk is allocated and is the last on the list, 1760 // the list can go away. 1761 coalBirth(size); 1762 } 1763 1764 void 1765 CompactibleFreeListSpace::addChunkToFreeLists(HeapWord* chunk, 1766 size_t size) { 1767 // check that the chunk does lie in this space! 1768 assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!"); 1769 assert_locked(); 1770 _bt.verify_single_block(chunk, size); 1771 1772 FreeChunk* fc = (FreeChunk*) chunk; 1773 fc->set_size(size); 1774 debug_only(fc->mangleFreed(size)); 1775 if (size < SmallForDictionary) { 1776 returnChunkToFreeList(fc); 1777 } else { 1778 returnChunkToDictionary(fc); 1779 } 1780 } 1781 1782 void 1783 CompactibleFreeListSpace::addChunkAndRepairOffsetTable(HeapWord* chunk, 1784 size_t size, bool coalesced) { 1785 assert_locked(); 1786 assert(chunk != NULL, "null chunk"); 1787 if (coalesced) { 1788 // repair BOT 1789 _bt.single_block(chunk, size); 1790 } 1791 addChunkToFreeLists(chunk, size); 1792 } 1793 1794 // We _must_ find the purported chunk on our free lists; 1795 // we assert if we don't. 1796 void 1797 CompactibleFreeListSpace::removeFreeChunkFromFreeLists(FreeChunk* fc) { 1798 size_t size = fc->size(); 1799 assert_locked(); 1800 debug_only(verifyFreeLists()); 1801 if (size < SmallForDictionary) { 1802 removeChunkFromIndexedFreeList(fc); 1803 } else { 1804 removeChunkFromDictionary(fc); 1805 } 1806 _bt.verify_single_block((HeapWord*)fc, size); 1807 debug_only(verifyFreeLists()); 1808 } 1809 1810 void 1811 CompactibleFreeListSpace::removeChunkFromDictionary(FreeChunk* fc) { 1812 size_t size = fc->size(); 1813 assert_locked(); 1814 assert(fc != NULL, "null chunk"); 1815 _bt.verify_single_block((HeapWord*)fc, size); 1816 _dictionary->remove_chunk(fc); 1817 // adjust _unallocated_block upward, as necessary 1818 _bt.allocated((HeapWord*)fc, size); 1819 } 1820 1821 void 1822 CompactibleFreeListSpace::removeChunkFromIndexedFreeList(FreeChunk* fc) { 1823 assert_locked(); 1824 size_t size = fc->size(); 1825 _bt.verify_single_block((HeapWord*)fc, size); 1826 NOT_PRODUCT( 1827 if (FLSVerifyIndexTable) { 1828 verifyIndexedFreeList(size); 1829 } 1830 ) 1831 _indexedFreeList[size].remove_chunk(fc); 1832 NOT_PRODUCT( 1833 if (FLSVerifyIndexTable) { 1834 verifyIndexedFreeList(size); 1835 } 1836 ) 1837 } 1838 1839 FreeChunk* CompactibleFreeListSpace::bestFitSmall(size_t numWords) { 1840 /* A hint is the next larger size that has a surplus. 1841 Start search at a size large enough to guarantee that 1842 the excess is >= MIN_CHUNK. */ 1843 size_t start = align_object_size(numWords + MinChunkSize); 1844 if (start < IndexSetSize) { 1845 AdaptiveFreeList<FreeChunk>* it = _indexedFreeList; 1846 size_t hint = _indexedFreeList[start].hint(); 1847 while (hint < IndexSetSize) { 1848 assert(hint % MinObjAlignment == 0, "hint should be aligned"); 1849 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[hint]; 1850 if (fl->surplus() > 0 && fl->head() != NULL) { 1851 // Found a list with surplus, reset original hint 1852 // and split out a free chunk which is returned. 1853 _indexedFreeList[start].set_hint(hint); 1854 FreeChunk* res = getFromListGreater(fl, numWords); 1855 assert(res == NULL || res->is_free(), 1856 "Should be returning a free chunk"); 1857 return res; 1858 } 1859 hint = fl->hint(); /* keep looking */ 1860 } 1861 /* None found. */ 1862 it[start].set_hint(IndexSetSize); 1863 } 1864 return NULL; 1865 } 1866 1867 /* Requires fl->size >= numWords + MinChunkSize */ 1868 FreeChunk* CompactibleFreeListSpace::getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, 1869 size_t numWords) { 1870 FreeChunk *curr = fl->head(); 1871 size_t oldNumWords = curr->size(); 1872 assert(numWords >= MinChunkSize, "Word size is too small"); 1873 assert(curr != NULL, "List is empty"); 1874 assert(oldNumWords >= numWords + MinChunkSize, 1875 "Size of chunks in the list is too small"); 1876 1877 fl->remove_chunk(curr); 1878 // recorded indirectly by splitChunkAndReturnRemainder - 1879 // smallSplit(oldNumWords, numWords); 1880 FreeChunk* new_chunk = splitChunkAndReturnRemainder(curr, numWords); 1881 // Does anything have to be done for the remainder in terms of 1882 // fixing the card table? 1883 assert(new_chunk == NULL || new_chunk->is_free(), 1884 "Should be returning a free chunk"); 1885 return new_chunk; 1886 } 1887 1888 FreeChunk* 1889 CompactibleFreeListSpace::splitChunkAndReturnRemainder(FreeChunk* chunk, 1890 size_t new_size) { 1891 assert_locked(); 1892 size_t size = chunk->size(); 1893 assert(size > new_size, "Split from a smaller block?"); 1894 assert(is_aligned(chunk), "alignment problem"); 1895 assert(size == adjustObjectSize(size), "alignment problem"); 1896 size_t rem_sz = size - new_size; 1897 assert(rem_sz == adjustObjectSize(rem_sz), "alignment problem"); 1898 assert(rem_sz >= MinChunkSize, "Free chunk smaller than minimum"); 1899 FreeChunk* ffc = (FreeChunk*)((HeapWord*)chunk + new_size); 1900 assert(is_aligned(ffc), "alignment problem"); 1901 ffc->set_size(rem_sz); 1902 ffc->link_next(NULL); 1903 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads. 1904 // Above must occur before BOT is updated below. 1905 // adjust block offset table 1906 OrderAccess::storestore(); 1907 assert(chunk->is_free() && ffc->is_free(), "Error"); 1908 _bt.split_block((HeapWord*)chunk, chunk->size(), new_size); 1909 if (rem_sz < SmallForDictionary) { 1910 bool is_par = (GenCollectedHeap::heap()->n_par_threads() > 0); 1911 if (is_par) _indexedFreeListParLocks[rem_sz]->lock(); 1912 assert(!is_par || 1913 (GenCollectedHeap::heap()->n_par_threads() == 1914 GenCollectedHeap::heap()->workers()->active_workers()), "Mismatch"); 1915 returnChunkToFreeList(ffc); 1916 split(size, rem_sz); 1917 if (is_par) _indexedFreeListParLocks[rem_sz]->unlock(); 1918 } else { 1919 returnChunkToDictionary(ffc); 1920 split(size, rem_sz); 1921 } 1922 chunk->set_size(new_size); 1923 return chunk; 1924 } 1925 1926 void 1927 CompactibleFreeListSpace::sweep_completed() { 1928 // Now that space is probably plentiful, refill linear 1929 // allocation blocks as needed. 1930 refillLinearAllocBlocksIfNeeded(); 1931 } 1932 1933 void 1934 CompactibleFreeListSpace::gc_prologue() { 1935 assert_locked(); 1936 if (PrintFLSStatistics != 0) { 1937 gclog_or_tty->print("Before GC:\n"); 1938 reportFreeListStatistics(); 1939 } 1940 refillLinearAllocBlocksIfNeeded(); 1941 } 1942 1943 void 1944 CompactibleFreeListSpace::gc_epilogue() { 1945 assert_locked(); 1946 if (PrintGCDetails && Verbose && !_adaptive_freelists) { 1947 if (_smallLinearAllocBlock._word_size == 0) 1948 warning("CompactibleFreeListSpace(epilogue):: Linear allocation failure"); 1949 } 1950 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); 1951 _promoInfo.stopTrackingPromotions(); 1952 repairLinearAllocationBlocks(); 1953 // Print Space's stats 1954 if (PrintFLSStatistics != 0) { 1955 gclog_or_tty->print("After GC:\n"); 1956 reportFreeListStatistics(); 1957 } 1958 } 1959 1960 // Iteration support, mostly delegated from a CMS generation 1961 1962 void CompactibleFreeListSpace::save_marks() { 1963 assert(Thread::current()->is_VM_thread(), 1964 "Global variable should only be set when single-threaded"); 1965 // Mark the "end" of the used space at the time of this call; 1966 // note, however, that promoted objects from this point 1967 // on are tracked in the _promoInfo below. 1968 set_saved_mark_word(unallocated_block()); 1969 #ifdef ASSERT 1970 // Check the sanity of save_marks() etc. 1971 MemRegion ur = used_region(); 1972 MemRegion urasm = used_region_at_save_marks(); 1973 assert(ur.contains(urasm), 1974 err_msg(" Error at save_marks(): [" PTR_FORMAT "," PTR_FORMAT ")" 1975 " should contain [" PTR_FORMAT "," PTR_FORMAT ")", 1976 p2i(ur.start()), p2i(ur.end()), p2i(urasm.start()), p2i(urasm.end()))); 1977 #endif 1978 // inform allocator that promotions should be tracked. 1979 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); 1980 _promoInfo.startTrackingPromotions(); 1981 } 1982 1983 bool CompactibleFreeListSpace::no_allocs_since_save_marks() { 1984 assert(_promoInfo.tracking(), "No preceding save_marks?"); 1985 assert(GenCollectedHeap::heap()->n_par_threads() == 0, 1986 "Shouldn't be called if using parallel gc."); 1987 return _promoInfo.noPromotions(); 1988 } 1989 1990 #define CFLS_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 1991 \ 1992 void CompactibleFreeListSpace:: \ 1993 oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) { \ 1994 assert(GenCollectedHeap::heap()->n_par_threads() == 0, \ 1995 "Shouldn't be called (yet) during parallel part of gc."); \ 1996 _promoInfo.promoted_oops_iterate##nv_suffix(blk); \ 1997 /* \ 1998 * This also restores any displaced headers and removes the elements from \ 1999 * the iteration set as they are processed, so that we have a clean slate \ 2000 * at the end of the iteration. Note, thus, that if new objects are \ 2001 * promoted as a result of the iteration they are iterated over as well. \ 2002 */ \ 2003 assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); \ 2004 } 2005 2006 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DEFN) 2007 2008 bool CompactibleFreeListSpace::linearAllocationWouldFail() const { 2009 return _smallLinearAllocBlock._word_size == 0; 2010 } 2011 2012 void CompactibleFreeListSpace::repairLinearAllocationBlocks() { 2013 // Fix up linear allocation blocks to look like free blocks 2014 repairLinearAllocBlock(&_smallLinearAllocBlock); 2015 } 2016 2017 void CompactibleFreeListSpace::repairLinearAllocBlock(LinearAllocBlock* blk) { 2018 assert_locked(); 2019 if (blk->_ptr != NULL) { 2020 assert(blk->_word_size != 0 && blk->_word_size >= MinChunkSize, 2021 "Minimum block size requirement"); 2022 FreeChunk* fc = (FreeChunk*)(blk->_ptr); 2023 fc->set_size(blk->_word_size); 2024 fc->link_prev(NULL); // mark as free 2025 fc->dontCoalesce(); 2026 assert(fc->is_free(), "just marked it free"); 2027 assert(fc->cantCoalesce(), "just marked it uncoalescable"); 2028 } 2029 } 2030 2031 void CompactibleFreeListSpace::refillLinearAllocBlocksIfNeeded() { 2032 assert_locked(); 2033 if (_smallLinearAllocBlock._ptr == NULL) { 2034 assert(_smallLinearAllocBlock._word_size == 0, 2035 "Size of linAB should be zero if the ptr is NULL"); 2036 // Reset the linAB refill and allocation size limit. 2037 _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, SmallForLinearAlloc); 2038 } 2039 refillLinearAllocBlockIfNeeded(&_smallLinearAllocBlock); 2040 } 2041 2042 void 2043 CompactibleFreeListSpace::refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk) { 2044 assert_locked(); 2045 assert((blk->_ptr == NULL && blk->_word_size == 0) || 2046 (blk->_ptr != NULL && blk->_word_size >= MinChunkSize), 2047 "blk invariant"); 2048 if (blk->_ptr == NULL) { 2049 refillLinearAllocBlock(blk); 2050 } 2051 if (PrintMiscellaneous && Verbose) { 2052 if (blk->_word_size == 0) { 2053 warning("CompactibleFreeListSpace(prologue):: Linear allocation failure"); 2054 } 2055 } 2056 } 2057 2058 void 2059 CompactibleFreeListSpace::refillLinearAllocBlock(LinearAllocBlock* blk) { 2060 assert_locked(); 2061 assert(blk->_word_size == 0 && blk->_ptr == NULL, 2062 "linear allocation block should be empty"); 2063 FreeChunk* fc; 2064 if (blk->_refillSize < SmallForDictionary && 2065 (fc = getChunkFromIndexedFreeList(blk->_refillSize)) != NULL) { 2066 // A linAB's strategy might be to use small sizes to reduce 2067 // fragmentation but still get the benefits of allocation from a 2068 // linAB. 2069 } else { 2070 fc = getChunkFromDictionary(blk->_refillSize); 2071 } 2072 if (fc != NULL) { 2073 blk->_ptr = (HeapWord*)fc; 2074 blk->_word_size = fc->size(); 2075 fc->dontCoalesce(); // to prevent sweeper from sweeping us up 2076 } 2077 } 2078 2079 // Support for concurrent collection policy decisions. 2080 bool CompactibleFreeListSpace::should_concurrent_collect() const { 2081 // In the future we might want to add in fragmentation stats -- 2082 // including erosion of the "mountain" into this decision as well. 2083 return !adaptive_freelists() && linearAllocationWouldFail(); 2084 } 2085 2086 // Support for compaction 2087 void CompactibleFreeListSpace::prepare_for_compaction(CompactPoint* cp) { 2088 scan_and_forward(this, cp); 2089 // Prepare_for_compaction() uses the space between live objects 2090 // so that later phase can skip dead space quickly. So verification 2091 // of the free lists doesn't work after. 2092 } 2093 2094 void CompactibleFreeListSpace::adjust_pointers() { 2095 // In other versions of adjust_pointers(), a bail out 2096 // based on the amount of live data in the generation 2097 // (i.e., if 0, bail out) may be used. 2098 // Cannot test used() == 0 here because the free lists have already 2099 // been mangled by the compaction. 2100 2101 scan_and_adjust_pointers(this); 2102 // See note about verification in prepare_for_compaction(). 2103 } 2104 2105 void CompactibleFreeListSpace::compact() { 2106 scan_and_compact(this); 2107 } 2108 2109 // Fragmentation metric = 1 - [sum of (fbs**2) / (sum of fbs)**2] 2110 // where fbs is free block sizes 2111 double CompactibleFreeListSpace::flsFrag() const { 2112 size_t itabFree = totalSizeInIndexedFreeLists(); 2113 double frag = 0.0; 2114 size_t i; 2115 2116 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { 2117 double sz = i; 2118 frag += _indexedFreeList[i].count() * (sz * sz); 2119 } 2120 2121 double totFree = itabFree + 2122 _dictionary->total_chunk_size(DEBUG_ONLY(freelistLock())); 2123 if (totFree > 0) { 2124 frag = ((frag + _dictionary->sum_of_squared_block_sizes()) / 2125 (totFree * totFree)); 2126 frag = (double)1.0 - frag; 2127 } else { 2128 assert(frag == 0.0, "Follows from totFree == 0"); 2129 } 2130 return frag; 2131 } 2132 2133 void CompactibleFreeListSpace::beginSweepFLCensus( 2134 float inter_sweep_current, 2135 float inter_sweep_estimate, 2136 float intra_sweep_estimate) { 2137 assert_locked(); 2138 size_t i; 2139 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { 2140 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i]; 2141 if (PrintFLSStatistics > 1) { 2142 gclog_or_tty->print("size[" SIZE_FORMAT "] : ", i); 2143 } 2144 fl->compute_desired(inter_sweep_current, inter_sweep_estimate, intra_sweep_estimate); 2145 fl->set_coal_desired((ssize_t)((double)fl->desired() * CMSSmallCoalSurplusPercent)); 2146 fl->set_before_sweep(fl->count()); 2147 fl->set_bfr_surp(fl->surplus()); 2148 } 2149 _dictionary->begin_sweep_dict_census(CMSLargeCoalSurplusPercent, 2150 inter_sweep_current, 2151 inter_sweep_estimate, 2152 intra_sweep_estimate); 2153 } 2154 2155 void CompactibleFreeListSpace::setFLSurplus() { 2156 assert_locked(); 2157 size_t i; 2158 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { 2159 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i]; 2160 fl->set_surplus(fl->count() - 2161 (ssize_t)((double)fl->desired() * CMSSmallSplitSurplusPercent)); 2162 } 2163 } 2164 2165 void CompactibleFreeListSpace::setFLHints() { 2166 assert_locked(); 2167 size_t i; 2168 size_t h = IndexSetSize; 2169 for (i = IndexSetSize - 1; i != 0; i -= IndexSetStride) { 2170 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i]; 2171 fl->set_hint(h); 2172 if (fl->surplus() > 0) { 2173 h = i; 2174 } 2175 } 2176 } 2177 2178 void CompactibleFreeListSpace::clearFLCensus() { 2179 assert_locked(); 2180 size_t i; 2181 for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { 2182 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i]; 2183 fl->set_prev_sweep(fl->count()); 2184 fl->set_coal_births(0); 2185 fl->set_coal_deaths(0); 2186 fl->set_split_births(0); 2187 fl->set_split_deaths(0); 2188 } 2189 } 2190 2191 void CompactibleFreeListSpace::endSweepFLCensus(size_t sweep_count) { 2192 if (PrintFLSStatistics > 0) { 2193 HeapWord* largestAddr = (HeapWord*) dictionary()->find_largest_dict(); 2194 gclog_or_tty->print_cr("CMS: Large block " PTR_FORMAT, 2195 p2i(largestAddr)); 2196 } 2197 setFLSurplus(); 2198 setFLHints(); 2199 if (PrintGC && PrintFLSCensus > 0) { 2200 printFLCensus(sweep_count); 2201 } 2202 clearFLCensus(); 2203 assert_locked(); 2204 _dictionary->end_sweep_dict_census(CMSLargeSplitSurplusPercent); 2205 } 2206 2207 bool CompactibleFreeListSpace::coalOverPopulated(size_t size) { 2208 if (size < SmallForDictionary) { 2209 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size]; 2210 return (fl->coal_desired() < 0) || 2211 ((int)fl->count() > fl->coal_desired()); 2212 } else { 2213 return dictionary()->coal_dict_over_populated(size); 2214 } 2215 } 2216 2217 void CompactibleFreeListSpace::smallCoalBirth(size_t size) { 2218 assert(size < SmallForDictionary, "Size too large for indexed list"); 2219 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size]; 2220 fl->increment_coal_births(); 2221 fl->increment_surplus(); 2222 } 2223 2224 void CompactibleFreeListSpace::smallCoalDeath(size_t size) { 2225 assert(size < SmallForDictionary, "Size too large for indexed list"); 2226 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size]; 2227 fl->increment_coal_deaths(); 2228 fl->decrement_surplus(); 2229 } 2230 2231 void CompactibleFreeListSpace::coalBirth(size_t size) { 2232 if (size < SmallForDictionary) { 2233 smallCoalBirth(size); 2234 } else { 2235 dictionary()->dict_census_update(size, 2236 false /* split */, 2237 true /* birth */); 2238 } 2239 } 2240 2241 void CompactibleFreeListSpace::coalDeath(size_t size) { 2242 if(size < SmallForDictionary) { 2243 smallCoalDeath(size); 2244 } else { 2245 dictionary()->dict_census_update(size, 2246 false /* split */, 2247 false /* birth */); 2248 } 2249 } 2250 2251 void CompactibleFreeListSpace::smallSplitBirth(size_t size) { 2252 assert(size < SmallForDictionary, "Size too large for indexed list"); 2253 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size]; 2254 fl->increment_split_births(); 2255 fl->increment_surplus(); 2256 } 2257 2258 void CompactibleFreeListSpace::smallSplitDeath(size_t size) { 2259 assert(size < SmallForDictionary, "Size too large for indexed list"); 2260 AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size]; 2261 fl->increment_split_deaths(); 2262 fl->decrement_surplus(); 2263 } 2264 2265 void CompactibleFreeListSpace::split_birth(size_t size) { 2266 if (size < SmallForDictionary) { 2267 smallSplitBirth(size); 2268 } else { 2269 dictionary()->dict_census_update(size, 2270 true /* split */, 2271 true /* birth */); 2272 } 2273 } 2274 2275 void CompactibleFreeListSpace::splitDeath(size_t size) { 2276 if (size < SmallForDictionary) { 2277 smallSplitDeath(size); 2278 } else { 2279 dictionary()->dict_census_update(size, 2280 true /* split */, 2281 false /* birth */); 2282 } 2283 } 2284 2285 void CompactibleFreeListSpace::split(size_t from, size_t to1) { 2286 size_t to2 = from - to1; 2287 splitDeath(from); 2288 split_birth(to1); 2289 split_birth(to2); 2290 } 2291 2292 void CompactibleFreeListSpace::print() const { 2293 print_on(tty); 2294 } 2295 2296 void CompactibleFreeListSpace::prepare_for_verify() { 2297 assert_locked(); 2298 repairLinearAllocationBlocks(); 2299 // Verify that the SpoolBlocks look like free blocks of 2300 // appropriate sizes... To be done ... 2301 } 2302 2303 class VerifyAllBlksClosure: public BlkClosure { 2304 private: 2305 const CompactibleFreeListSpace* _sp; 2306 const MemRegion _span; 2307 HeapWord* _last_addr; 2308 size_t _last_size; 2309 bool _last_was_obj; 2310 bool _last_was_live; 2311 2312 public: 2313 VerifyAllBlksClosure(const CompactibleFreeListSpace* sp, 2314 MemRegion span) : _sp(sp), _span(span), 2315 _last_addr(NULL), _last_size(0), 2316 _last_was_obj(false), _last_was_live(false) { } 2317 2318 virtual size_t do_blk(HeapWord* addr) { 2319 size_t res; 2320 bool was_obj = false; 2321 bool was_live = false; 2322 if (_sp->block_is_obj(addr)) { 2323 was_obj = true; 2324 oop p = oop(addr); 2325 guarantee(p->is_oop(), "Should be an oop"); 2326 res = _sp->adjustObjectSize(p->size()); 2327 if (_sp->obj_is_alive(addr)) { 2328 was_live = true; 2329 p->verify(); 2330 } 2331 } else { 2332 FreeChunk* fc = (FreeChunk*)addr; 2333 res = fc->size(); 2334 if (FLSVerifyLists && !fc->cantCoalesce()) { 2335 guarantee(_sp->verify_chunk_in_free_list(fc), 2336 "Chunk should be on a free list"); 2337 } 2338 } 2339 if (res == 0) { 2340 gclog_or_tty->print_cr("Livelock: no rank reduction!"); 2341 gclog_or_tty->print_cr( 2342 " Current: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n" 2343 " Previous: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n", 2344 p2i(addr), res, was_obj ?"true":"false", was_live ?"true":"false", 2345 p2i(_last_addr), _last_size, _last_was_obj?"true":"false", _last_was_live?"true":"false"); 2346 _sp->print_on(gclog_or_tty); 2347 guarantee(false, "Seppuku!"); 2348 } 2349 _last_addr = addr; 2350 _last_size = res; 2351 _last_was_obj = was_obj; 2352 _last_was_live = was_live; 2353 return res; 2354 } 2355 }; 2356 2357 class VerifyAllOopsClosure: public OopClosure { 2358 private: 2359 const CMSCollector* _collector; 2360 const CompactibleFreeListSpace* _sp; 2361 const MemRegion _span; 2362 const bool _past_remark; 2363 const CMSBitMap* _bit_map; 2364 2365 protected: 2366 void do_oop(void* p, oop obj) { 2367 if (_span.contains(obj)) { // the interior oop points into CMS heap 2368 if (!_span.contains(p)) { // reference from outside CMS heap 2369 // Should be a valid object; the first disjunct below allows 2370 // us to sidestep an assertion in block_is_obj() that insists 2371 // that p be in _sp. Note that several generations (and spaces) 2372 // are spanned by _span (CMS heap) above. 2373 guarantee(!_sp->is_in_reserved(obj) || 2374 _sp->block_is_obj((HeapWord*)obj), 2375 "Should be an object"); 2376 guarantee(obj->is_oop(), "Should be an oop"); 2377 obj->verify(); 2378 if (_past_remark) { 2379 // Remark has been completed, the object should be marked 2380 _bit_map->isMarked((HeapWord*)obj); 2381 } 2382 } else { // reference within CMS heap 2383 if (_past_remark) { 2384 // Remark has been completed -- so the referent should have 2385 // been marked, if referring object is. 2386 if (_bit_map->isMarked(_collector->block_start(p))) { 2387 guarantee(_bit_map->isMarked((HeapWord*)obj), "Marking error?"); 2388 } 2389 } 2390 } 2391 } else if (_sp->is_in_reserved(p)) { 2392 // the reference is from FLS, and points out of FLS 2393 guarantee(obj->is_oop(), "Should be an oop"); 2394 obj->verify(); 2395 } 2396 } 2397 2398 template <class T> void do_oop_work(T* p) { 2399 T heap_oop = oopDesc::load_heap_oop(p); 2400 if (!oopDesc::is_null(heap_oop)) { 2401 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2402 do_oop(p, obj); 2403 } 2404 } 2405 2406 public: 2407 VerifyAllOopsClosure(const CMSCollector* collector, 2408 const CompactibleFreeListSpace* sp, MemRegion span, 2409 bool past_remark, CMSBitMap* bit_map) : 2410 _collector(collector), _sp(sp), _span(span), 2411 _past_remark(past_remark), _bit_map(bit_map) { } 2412 2413 virtual void do_oop(oop* p) { VerifyAllOopsClosure::do_oop_work(p); } 2414 virtual void do_oop(narrowOop* p) { VerifyAllOopsClosure::do_oop_work(p); } 2415 }; 2416 2417 void CompactibleFreeListSpace::verify() const { 2418 assert_lock_strong(&_freelistLock); 2419 verify_objects_initialized(); 2420 MemRegion span = _collector->_span; 2421 bool past_remark = (_collector->abstract_state() == 2422 CMSCollector::Sweeping); 2423 2424 ResourceMark rm; 2425 HandleMark hm; 2426 2427 // Check integrity of CFL data structures 2428 _promoInfo.verify(); 2429 _dictionary->verify(); 2430 if (FLSVerifyIndexTable) { 2431 verifyIndexedFreeLists(); 2432 } 2433 // Check integrity of all objects and free blocks in space 2434 { 2435 VerifyAllBlksClosure cl(this, span); 2436 ((CompactibleFreeListSpace*)this)->blk_iterate(&cl); // cast off const 2437 } 2438 // Check that all references in the heap to FLS 2439 // are to valid objects in FLS or that references in 2440 // FLS are to valid objects elsewhere in the heap 2441 if (FLSVerifyAllHeapReferences) 2442 { 2443 VerifyAllOopsClosure cl(_collector, this, span, past_remark, 2444 _collector->markBitMap()); 2445 CollectedHeap* ch = Universe::heap(); 2446 2447 // Iterate over all oops in the heap. Uses the _no_header version 2448 // since we are not interested in following the klass pointers. 2449 ch->oop_iterate_no_header(&cl); 2450 } 2451 2452 if (VerifyObjectStartArray) { 2453 // Verify the block offset table 2454 _bt.verify(); 2455 } 2456 } 2457 2458 #ifndef PRODUCT 2459 void CompactibleFreeListSpace::verifyFreeLists() const { 2460 if (FLSVerifyLists) { 2461 _dictionary->verify(); 2462 verifyIndexedFreeLists(); 2463 } else { 2464 if (FLSVerifyDictionary) { 2465 _dictionary->verify(); 2466 } 2467 if (FLSVerifyIndexTable) { 2468 verifyIndexedFreeLists(); 2469 } 2470 } 2471 } 2472 #endif 2473 2474 void CompactibleFreeListSpace::verifyIndexedFreeLists() const { 2475 size_t i = 0; 2476 for (; i < IndexSetStart; i++) { 2477 guarantee(_indexedFreeList[i].head() == NULL, "should be NULL"); 2478 } 2479 for (; i < IndexSetSize; i++) { 2480 verifyIndexedFreeList(i); 2481 } 2482 } 2483 2484 void CompactibleFreeListSpace::verifyIndexedFreeList(size_t size) const { 2485 FreeChunk* fc = _indexedFreeList[size].head(); 2486 FreeChunk* tail = _indexedFreeList[size].tail(); 2487 size_t num = _indexedFreeList[size].count(); 2488 size_t n = 0; 2489 guarantee(((size >= IndexSetStart) && (size % IndexSetStride == 0)) || fc == NULL, 2490 "Slot should have been empty"); 2491 for (; fc != NULL; fc = fc->next(), n++) { 2492 guarantee(fc->size() == size, "Size inconsistency"); 2493 guarantee(fc->is_free(), "!free?"); 2494 guarantee(fc->next() == NULL || fc->next()->prev() == fc, "Broken list"); 2495 guarantee((fc->next() == NULL) == (fc == tail), "Incorrect tail"); 2496 } 2497 guarantee(n == num, "Incorrect count"); 2498 } 2499 2500 #ifndef PRODUCT 2501 void CompactibleFreeListSpace::check_free_list_consistency() const { 2502 assert((TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::min_size() <= IndexSetSize), 2503 "Some sizes can't be allocated without recourse to" 2504 " linear allocation buffers"); 2505 assert((TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::min_size()*HeapWordSize == sizeof(TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >)), 2506 "else MIN_TREE_CHUNK_SIZE is wrong"); 2507 assert(IndexSetStart != 0, "IndexSetStart not initialized"); 2508 assert(IndexSetStride != 0, "IndexSetStride not initialized"); 2509 } 2510 #endif 2511 2512 void CompactibleFreeListSpace::printFLCensus(size_t sweep_count) const { 2513 assert_lock_strong(&_freelistLock); 2514 AdaptiveFreeList<FreeChunk> total; 2515 gclog_or_tty->print("end sweep# " SIZE_FORMAT "\n", sweep_count); 2516 AdaptiveFreeList<FreeChunk>::print_labels_on(gclog_or_tty, "size"); 2517 size_t total_free = 0; 2518 for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { 2519 const AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i]; 2520 total_free += fl->count() * fl->size(); 2521 if (i % (40*IndexSetStride) == 0) { 2522 AdaptiveFreeList<FreeChunk>::print_labels_on(gclog_or_tty, "size"); 2523 } 2524 fl->print_on(gclog_or_tty); 2525 total.set_bfr_surp( total.bfr_surp() + fl->bfr_surp() ); 2526 total.set_surplus( total.surplus() + fl->surplus() ); 2527 total.set_desired( total.desired() + fl->desired() ); 2528 total.set_prev_sweep( total.prev_sweep() + fl->prev_sweep() ); 2529 total.set_before_sweep(total.before_sweep() + fl->before_sweep()); 2530 total.set_count( total.count() + fl->count() ); 2531 total.set_coal_births( total.coal_births() + fl->coal_births() ); 2532 total.set_coal_deaths( total.coal_deaths() + fl->coal_deaths() ); 2533 total.set_split_births(total.split_births() + fl->split_births()); 2534 total.set_split_deaths(total.split_deaths() + fl->split_deaths()); 2535 } 2536 total.print_on(gclog_or_tty, "TOTAL"); 2537 gclog_or_tty->print_cr("Total free in indexed lists " 2538 SIZE_FORMAT " words", total_free); 2539 gclog_or_tty->print("growth: %8.5f deficit: %8.5f\n", 2540 (double)(total.split_births()+total.coal_births()-total.split_deaths()-total.coal_deaths())/ 2541 (total.prev_sweep() != 0 ? (double)total.prev_sweep() : 1.0), 2542 (double)(total.desired() - total.count())/(total.desired() != 0 ? (double)total.desired() : 1.0)); 2543 _dictionary->print_dict_census(); 2544 } 2545 2546 /////////////////////////////////////////////////////////////////////////// 2547 // CFLS_LAB 2548 /////////////////////////////////////////////////////////////////////////// 2549 2550 #define VECTOR_257(x) \ 2551 /* 1 2 3 4 5 6 7 8 9 1x 11 12 13 14 15 16 17 18 19 2x 21 22 23 24 25 26 27 28 29 3x 31 32 */ \ 2552 { x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \ 2553 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \ 2554 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \ 2555 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \ 2556 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \ 2557 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \ 2558 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \ 2559 x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \ 2560 x } 2561 2562 // Initialize with default setting for CMS, _not_ 2563 // generic OldPLABSize, whose static default is different; if overridden at the 2564 // command-line, this will get reinitialized via a call to 2565 // modify_initialization() below. 2566 AdaptiveWeightedAverage CFLS_LAB::_blocks_to_claim[] = 2567 VECTOR_257(AdaptiveWeightedAverage(OldPLABWeight, (float)CFLS_LAB::_default_dynamic_old_plab_size)); 2568 size_t CFLS_LAB::_global_num_blocks[] = VECTOR_257(0); 2569 uint CFLS_LAB::_global_num_workers[] = VECTOR_257(0); 2570 2571 CFLS_LAB::CFLS_LAB(CompactibleFreeListSpace* cfls) : 2572 _cfls(cfls) 2573 { 2574 assert(CompactibleFreeListSpace::IndexSetSize == 257, "Modify VECTOR_257() macro above"); 2575 for (size_t i = CompactibleFreeListSpace::IndexSetStart; 2576 i < CompactibleFreeListSpace::IndexSetSize; 2577 i += CompactibleFreeListSpace::IndexSetStride) { 2578 _indexedFreeList[i].set_size(i); 2579 _num_blocks[i] = 0; 2580 } 2581 } 2582 2583 static bool _CFLS_LAB_modified = false; 2584 2585 void CFLS_LAB::modify_initialization(size_t n, unsigned wt) { 2586 assert(!_CFLS_LAB_modified, "Call only once"); 2587 _CFLS_LAB_modified = true; 2588 for (size_t i = CompactibleFreeListSpace::IndexSetStart; 2589 i < CompactibleFreeListSpace::IndexSetSize; 2590 i += CompactibleFreeListSpace::IndexSetStride) { 2591 _blocks_to_claim[i].modify(n, wt, true /* force */); 2592 } 2593 } 2594 2595 HeapWord* CFLS_LAB::alloc(size_t word_sz) { 2596 FreeChunk* res; 2597 assert(word_sz == _cfls->adjustObjectSize(word_sz), "Error"); 2598 if (word_sz >= CompactibleFreeListSpace::IndexSetSize) { 2599 // This locking manages sync with other large object allocations. 2600 MutexLockerEx x(_cfls->parDictionaryAllocLock(), 2601 Mutex::_no_safepoint_check_flag); 2602 res = _cfls->getChunkFromDictionaryExact(word_sz); 2603 if (res == NULL) return NULL; 2604 } else { 2605 AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[word_sz]; 2606 if (fl->count() == 0) { 2607 // Attempt to refill this local free list. 2608 get_from_global_pool(word_sz, fl); 2609 // If it didn't work, give up. 2610 if (fl->count() == 0) return NULL; 2611 } 2612 res = fl->get_chunk_at_head(); 2613 assert(res != NULL, "Why was count non-zero?"); 2614 } 2615 res->markNotFree(); 2616 assert(!res->is_free(), "shouldn't be marked free"); 2617 assert(oop(res)->klass_or_null() == NULL, "should look uninitialized"); 2618 // mangle a just allocated object with a distinct pattern. 2619 debug_only(res->mangleAllocated(word_sz)); 2620 return (HeapWord*)res; 2621 } 2622 2623 // Get a chunk of blocks of the right size and update related 2624 // book-keeping stats 2625 void CFLS_LAB::get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl) { 2626 // Get the #blocks we want to claim 2627 size_t n_blks = (size_t)_blocks_to_claim[word_sz].average(); 2628 assert(n_blks > 0, "Error"); 2629 assert(ResizeOldPLAB || n_blks == OldPLABSize, "Error"); 2630 // In some cases, when the application has a phase change, 2631 // there may be a sudden and sharp shift in the object survival 2632 // profile, and updating the counts at the end of a scavenge 2633 // may not be quick enough, giving rise to large scavenge pauses 2634 // during these phase changes. It is beneficial to detect such 2635 // changes on-the-fly during a scavenge and avoid such a phase-change 2636 // pothole. The following code is a heuristic attempt to do that. 2637 // It is protected by a product flag until we have gained 2638 // enough experience with this heuristic and fine-tuned its behavior. 2639 // WARNING: This might increase fragmentation if we overreact to 2640 // small spikes, so some kind of historical smoothing based on 2641 // previous experience with the greater reactivity might be useful. 2642 // Lacking sufficient experience, CMSOldPLABResizeQuicker is disabled by 2643 // default. 2644 if (ResizeOldPLAB && CMSOldPLABResizeQuicker) { 2645 size_t multiple = _num_blocks[word_sz]/(CMSOldPLABToleranceFactor*CMSOldPLABNumRefills*n_blks); 2646 n_blks += CMSOldPLABReactivityFactor*multiple*n_blks; 2647 n_blks = MIN2(n_blks, CMSOldPLABMax); 2648 } 2649 assert(n_blks > 0, "Error"); 2650 _cfls->par_get_chunk_of_blocks(word_sz, n_blks, fl); 2651 // Update stats table entry for this block size 2652 _num_blocks[word_sz] += fl->count(); 2653 } 2654 2655 void CFLS_LAB::compute_desired_plab_size() { 2656 for (size_t i = CompactibleFreeListSpace::IndexSetStart; 2657 i < CompactibleFreeListSpace::IndexSetSize; 2658 i += CompactibleFreeListSpace::IndexSetStride) { 2659 assert((_global_num_workers[i] == 0) == (_global_num_blocks[i] == 0), 2660 "Counter inconsistency"); 2661 if (_global_num_workers[i] > 0) { 2662 // Need to smooth wrt historical average 2663 if (ResizeOldPLAB) { 2664 _blocks_to_claim[i].sample( 2665 MAX2(CMSOldPLABMin, 2666 MIN2(CMSOldPLABMax, 2667 _global_num_blocks[i]/(_global_num_workers[i]*CMSOldPLABNumRefills)))); 2668 } 2669 // Reset counters for next round 2670 _global_num_workers[i] = 0; 2671 _global_num_blocks[i] = 0; 2672 if (PrintOldPLAB) { 2673 gclog_or_tty->print_cr("[" SIZE_FORMAT "]: " SIZE_FORMAT, 2674 i, (size_t)_blocks_to_claim[i].average()); 2675 } 2676 } 2677 } 2678 } 2679 2680 // If this is changed in the future to allow parallel 2681 // access, one would need to take the FL locks and, 2682 // depending on how it is used, stagger access from 2683 // parallel threads to reduce contention. 2684 void CFLS_LAB::retire(int tid) { 2685 // We run this single threaded with the world stopped; 2686 // so no need for locks and such. 2687 NOT_PRODUCT(Thread* t = Thread::current();) 2688 assert(Thread::current()->is_VM_thread(), "Error"); 2689 for (size_t i = CompactibleFreeListSpace::IndexSetStart; 2690 i < CompactibleFreeListSpace::IndexSetSize; 2691 i += CompactibleFreeListSpace::IndexSetStride) { 2692 assert(_num_blocks[i] >= (size_t)_indexedFreeList[i].count(), 2693 "Can't retire more than what we obtained"); 2694 if (_num_blocks[i] > 0) { 2695 size_t num_retire = _indexedFreeList[i].count(); 2696 assert(_num_blocks[i] > num_retire, "Should have used at least one"); 2697 { 2698 // MutexLockerEx x(_cfls->_indexedFreeListParLocks[i], 2699 // Mutex::_no_safepoint_check_flag); 2700 2701 // Update globals stats for num_blocks used 2702 _global_num_blocks[i] += (_num_blocks[i] - num_retire); 2703 _global_num_workers[i]++; 2704 assert(_global_num_workers[i] <= ParallelGCThreads, "Too big"); 2705 if (num_retire > 0) { 2706 _cfls->_indexedFreeList[i].prepend(&_indexedFreeList[i]); 2707 // Reset this list. 2708 _indexedFreeList[i] = AdaptiveFreeList<FreeChunk>(); 2709 _indexedFreeList[i].set_size(i); 2710 } 2711 } 2712 if (PrintOldPLAB) { 2713 gclog_or_tty->print_cr("%d[" SIZE_FORMAT "]: " SIZE_FORMAT "/" SIZE_FORMAT "/" SIZE_FORMAT, 2714 tid, i, num_retire, _num_blocks[i], (size_t)_blocks_to_claim[i].average()); 2715 } 2716 // Reset stats for next round 2717 _num_blocks[i] = 0; 2718 } 2719 } 2720 } 2721 2722 // Used by par_get_chunk_of_blocks() for the chunks from the 2723 // indexed_free_lists. Looks for a chunk with size that is a multiple 2724 // of "word_sz" and if found, splits it into "word_sz" chunks and add 2725 // to the free list "fl". "n" is the maximum number of chunks to 2726 // be added to "fl". 2727 bool CompactibleFreeListSpace:: par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) { 2728 2729 // We'll try all multiples of word_sz in the indexed set, starting with 2730 // word_sz itself and, if CMSSplitIndexedFreeListBlocks, try larger multiples, 2731 // then try getting a big chunk and splitting it. 2732 { 2733 bool found; 2734 int k; 2735 size_t cur_sz; 2736 for (k = 1, cur_sz = k * word_sz, found = false; 2737 (cur_sz < CompactibleFreeListSpace::IndexSetSize) && 2738 (CMSSplitIndexedFreeListBlocks || k <= 1); 2739 k++, cur_sz = k * word_sz) { 2740 AdaptiveFreeList<FreeChunk> fl_for_cur_sz; // Empty. 2741 fl_for_cur_sz.set_size(cur_sz); 2742 { 2743 MutexLockerEx x(_indexedFreeListParLocks[cur_sz], 2744 Mutex::_no_safepoint_check_flag); 2745 AdaptiveFreeList<FreeChunk>* gfl = &_indexedFreeList[cur_sz]; 2746 if (gfl->count() != 0) { 2747 // nn is the number of chunks of size cur_sz that 2748 // we'd need to split k-ways each, in order to create 2749 // "n" chunks of size word_sz each. 2750 const size_t nn = MAX2(n/k, (size_t)1); 2751 gfl->getFirstNChunksFromList(nn, &fl_for_cur_sz); 2752 found = true; 2753 if (k > 1) { 2754 // Update split death stats for the cur_sz-size blocks list: 2755 // we increment the split death count by the number of blocks 2756 // we just took from the cur_sz-size blocks list and which 2757 // we will be splitting below. 2758 ssize_t deaths = gfl->split_deaths() + 2759 fl_for_cur_sz.count(); 2760 gfl->set_split_deaths(deaths); 2761 } 2762 } 2763 } 2764 // Now transfer fl_for_cur_sz to fl. Common case, we hope, is k = 1. 2765 if (found) { 2766 if (k == 1) { 2767 fl->prepend(&fl_for_cur_sz); 2768 } else { 2769 // Divide each block on fl_for_cur_sz up k ways. 2770 FreeChunk* fc; 2771 while ((fc = fl_for_cur_sz.get_chunk_at_head()) != NULL) { 2772 // Must do this in reverse order, so that anybody attempting to 2773 // access the main chunk sees it as a single free block until we 2774 // change it. 2775 size_t fc_size = fc->size(); 2776 assert(fc->is_free(), "Error"); 2777 for (int i = k-1; i >= 0; i--) { 2778 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz); 2779 assert((i != 0) || 2780 ((fc == ffc) && ffc->is_free() && 2781 (ffc->size() == k*word_sz) && (fc_size == word_sz)), 2782 "Counting error"); 2783 ffc->set_size(word_sz); 2784 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads. 2785 ffc->link_next(NULL); 2786 // Above must occur before BOT is updated below. 2787 OrderAccess::storestore(); 2788 // splitting from the right, fc_size == i * word_sz 2789 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */); 2790 fc_size -= word_sz; 2791 assert(fc_size == i*word_sz, "Error"); 2792 _bt.verify_not_unallocated((HeapWord*)ffc, word_sz); 2793 _bt.verify_single_block((HeapWord*)fc, fc_size); 2794 _bt.verify_single_block((HeapWord*)ffc, word_sz); 2795 // Push this on "fl". 2796 fl->return_chunk_at_head(ffc); 2797 } 2798 // TRAP 2799 assert(fl->tail()->next() == NULL, "List invariant."); 2800 } 2801 } 2802 // Update birth stats for this block size. 2803 size_t num = fl->count(); 2804 MutexLockerEx x(_indexedFreeListParLocks[word_sz], 2805 Mutex::_no_safepoint_check_flag); 2806 ssize_t births = _indexedFreeList[word_sz].split_births() + num; 2807 _indexedFreeList[word_sz].set_split_births(births); 2808 return true; 2809 } 2810 } 2811 return found; 2812 } 2813 } 2814 2815 FreeChunk* CompactibleFreeListSpace::get_n_way_chunk_to_split(size_t word_sz, size_t n) { 2816 2817 FreeChunk* fc = NULL; 2818 FreeChunk* rem_fc = NULL; 2819 size_t rem; 2820 { 2821 MutexLockerEx x(parDictionaryAllocLock(), 2822 Mutex::_no_safepoint_check_flag); 2823 while (n > 0) { 2824 fc = dictionary()->get_chunk(MAX2(n * word_sz, _dictionary->min_size()), 2825 FreeBlockDictionary<FreeChunk>::atLeast); 2826 if (fc != NULL) { 2827 break; 2828 } else { 2829 n--; 2830 } 2831 } 2832 if (fc == NULL) return NULL; 2833 // Otherwise, split up that block. 2834 assert((ssize_t)n >= 1, "Control point invariant"); 2835 assert(fc->is_free(), "Error: should be a free block"); 2836 _bt.verify_single_block((HeapWord*)fc, fc->size()); 2837 const size_t nn = fc->size() / word_sz; 2838 n = MIN2(nn, n); 2839 assert((ssize_t)n >= 1, "Control point invariant"); 2840 rem = fc->size() - n * word_sz; 2841 // If there is a remainder, and it's too small, allocate one fewer. 2842 if (rem > 0 && rem < MinChunkSize) { 2843 n--; rem += word_sz; 2844 } 2845 // Note that at this point we may have n == 0. 2846 assert((ssize_t)n >= 0, "Control point invariant"); 2847 2848 // If n is 0, the chunk fc that was found is not large 2849 // enough to leave a viable remainder. We are unable to 2850 // allocate even one block. Return fc to the 2851 // dictionary and return, leaving "fl" empty. 2852 if (n == 0) { 2853 returnChunkToDictionary(fc); 2854 return NULL; 2855 } 2856 2857 _bt.allocated((HeapWord*)fc, fc->size(), true /* reducing */); // update _unallocated_blk 2858 dictionary()->dict_census_update(fc->size(), 2859 true /*split*/, 2860 false /*birth*/); 2861 2862 // First return the remainder, if any. 2863 // Note that we hold the lock until we decide if we're going to give 2864 // back the remainder to the dictionary, since a concurrent allocation 2865 // may otherwise see the heap as empty. (We're willing to take that 2866 // hit if the block is a small block.) 2867 if (rem > 0) { 2868 size_t prefix_size = n * word_sz; 2869 rem_fc = (FreeChunk*)((HeapWord*)fc + prefix_size); 2870 rem_fc->set_size(rem); 2871 rem_fc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads. 2872 rem_fc->link_next(NULL); 2873 // Above must occur before BOT is updated below. 2874 assert((ssize_t)n > 0 && prefix_size > 0 && rem_fc > fc, "Error"); 2875 OrderAccess::storestore(); 2876 _bt.split_block((HeapWord*)fc, fc->size(), prefix_size); 2877 assert(fc->is_free(), "Error"); 2878 fc->set_size(prefix_size); 2879 if (rem >= IndexSetSize) { 2880 returnChunkToDictionary(rem_fc); 2881 dictionary()->dict_census_update(rem, true /*split*/, true /*birth*/); 2882 rem_fc = NULL; 2883 } 2884 // Otherwise, return it to the small list below. 2885 } 2886 } 2887 if (rem_fc != NULL) { 2888 MutexLockerEx x(_indexedFreeListParLocks[rem], 2889 Mutex::_no_safepoint_check_flag); 2890 _bt.verify_not_unallocated((HeapWord*)rem_fc, rem_fc->size()); 2891 _indexedFreeList[rem].return_chunk_at_head(rem_fc); 2892 smallSplitBirth(rem); 2893 } 2894 assert(n * word_sz == fc->size(), 2895 err_msg("Chunk size " SIZE_FORMAT " is not exactly splittable by " 2896 SIZE_FORMAT " sized chunks of size " SIZE_FORMAT, 2897 fc->size(), n, word_sz)); 2898 return fc; 2899 } 2900 2901 void CompactibleFreeListSpace:: par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t targetted_number_of_chunks, AdaptiveFreeList<FreeChunk>* fl) { 2902 2903 FreeChunk* fc = get_n_way_chunk_to_split(word_sz, targetted_number_of_chunks); 2904 2905 if (fc == NULL) { 2906 return; 2907 } 2908 2909 size_t n = fc->size() / word_sz; 2910 2911 assert((ssize_t)n > 0, "Consistency"); 2912 // Now do the splitting up. 2913 // Must do this in reverse order, so that anybody attempting to 2914 // access the main chunk sees it as a single free block until we 2915 // change it. 2916 size_t fc_size = n * word_sz; 2917 // All but first chunk in this loop 2918 for (ssize_t i = n-1; i > 0; i--) { 2919 FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz); 2920 ffc->set_size(word_sz); 2921 ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads. 2922 ffc->link_next(NULL); 2923 // Above must occur before BOT is updated below. 2924 OrderAccess::storestore(); 2925 // splitting from the right, fc_size == (n - i + 1) * wordsize 2926 _bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */); 2927 fc_size -= word_sz; 2928 _bt.verify_not_unallocated((HeapWord*)ffc, ffc->size()); 2929 _bt.verify_single_block((HeapWord*)ffc, ffc->size()); 2930 _bt.verify_single_block((HeapWord*)fc, fc_size); 2931 // Push this on "fl". 2932 fl->return_chunk_at_head(ffc); 2933 } 2934 // First chunk 2935 assert(fc->is_free() && fc->size() == n*word_sz, "Error: should still be a free block"); 2936 // The blocks above should show their new sizes before the first block below 2937 fc->set_size(word_sz); 2938 fc->link_prev(NULL); // idempotent wrt free-ness, see assert above 2939 fc->link_next(NULL); 2940 _bt.verify_not_unallocated((HeapWord*)fc, fc->size()); 2941 _bt.verify_single_block((HeapWord*)fc, fc->size()); 2942 fl->return_chunk_at_head(fc); 2943 2944 assert((ssize_t)n > 0 && (ssize_t)n == fl->count(), "Incorrect number of blocks"); 2945 { 2946 // Update the stats for this block size. 2947 MutexLockerEx x(_indexedFreeListParLocks[word_sz], 2948 Mutex::_no_safepoint_check_flag); 2949 const ssize_t births = _indexedFreeList[word_sz].split_births() + n; 2950 _indexedFreeList[word_sz].set_split_births(births); 2951 // ssize_t new_surplus = _indexedFreeList[word_sz].surplus() + n; 2952 // _indexedFreeList[word_sz].set_surplus(new_surplus); 2953 } 2954 2955 // TRAP 2956 assert(fl->tail()->next() == NULL, "List invariant."); 2957 } 2958 2959 void CompactibleFreeListSpace:: par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) { 2960 assert(fl->count() == 0, "Precondition."); 2961 assert(word_sz < CompactibleFreeListSpace::IndexSetSize, 2962 "Precondition"); 2963 2964 if (par_get_chunk_of_blocks_IFL(word_sz, n, fl)) { 2965 // Got it 2966 return; 2967 } 2968 2969 // Otherwise, we'll split a block from the dictionary. 2970 par_get_chunk_of_blocks_dictionary(word_sz, n, fl); 2971 } 2972 2973 // Set up the space's par_seq_tasks structure for work claiming 2974 // for parallel rescan. See CMSParRemarkTask where this is currently used. 2975 // XXX Need to suitably abstract and generalize this and the next 2976 // method into one. 2977 void 2978 CompactibleFreeListSpace:: 2979 initialize_sequential_subtasks_for_rescan(int n_threads) { 2980 // The "size" of each task is fixed according to rescan_task_size. 2981 assert(n_threads > 0, "Unexpected n_threads argument"); 2982 const size_t task_size = rescan_task_size(); 2983 size_t n_tasks = (used_region().word_size() + task_size - 1)/task_size; 2984 assert((n_tasks == 0) == used_region().is_empty(), "n_tasks incorrect"); 2985 assert(n_tasks == 0 || 2986 ((used_region().start() + (n_tasks - 1)*task_size < used_region().end()) && 2987 (used_region().start() + n_tasks*task_size >= used_region().end())), 2988 "n_tasks calculation incorrect"); 2989 SequentialSubTasksDone* pst = conc_par_seq_tasks(); 2990 assert(!pst->valid(), "Clobbering existing data?"); 2991 // Sets the condition for completion of the subtask (how many threads 2992 // need to finish in order to be done). 2993 pst->set_n_threads(n_threads); 2994 pst->set_n_tasks((int)n_tasks); 2995 } 2996 2997 // Set up the space's par_seq_tasks structure for work claiming 2998 // for parallel concurrent marking. See CMSConcMarkTask where this is currently used. 2999 void 3000 CompactibleFreeListSpace:: 3001 initialize_sequential_subtasks_for_marking(int n_threads, 3002 HeapWord* low) { 3003 // The "size" of each task is fixed according to rescan_task_size. 3004 assert(n_threads > 0, "Unexpected n_threads argument"); 3005 const size_t task_size = marking_task_size(); 3006 assert(task_size > CardTableModRefBS::card_size_in_words && 3007 (task_size % CardTableModRefBS::card_size_in_words == 0), 3008 "Otherwise arithmetic below would be incorrect"); 3009 MemRegion span = _gen->reserved(); 3010 if (low != NULL) { 3011 if (span.contains(low)) { 3012 // Align low down to a card boundary so that 3013 // we can use block_offset_careful() on span boundaries. 3014 HeapWord* aligned_low = (HeapWord*)align_size_down((uintptr_t)low, 3015 CardTableModRefBS::card_size); 3016 // Clip span prefix at aligned_low 3017 span = span.intersection(MemRegion(aligned_low, span.end())); 3018 } else if (low > span.end()) { 3019 span = MemRegion(low, low); // Null region 3020 } // else use entire span 3021 } 3022 assert(span.is_empty() || 3023 ((uintptr_t)span.start() % CardTableModRefBS::card_size == 0), 3024 "span should start at a card boundary"); 3025 size_t n_tasks = (span.word_size() + task_size - 1)/task_size; 3026 assert((n_tasks == 0) == span.is_empty(), "Inconsistency"); 3027 assert(n_tasks == 0 || 3028 ((span.start() + (n_tasks - 1)*task_size < span.end()) && 3029 (span.start() + n_tasks*task_size >= span.end())), 3030 "n_tasks calculation incorrect"); 3031 SequentialSubTasksDone* pst = conc_par_seq_tasks(); 3032 assert(!pst->valid(), "Clobbering existing data?"); 3033 // Sets the condition for completion of the subtask (how many threads 3034 // need to finish in order to be done). 3035 pst->set_n_threads(n_threads); 3036 pst->set_n_tasks((int)n_tasks); 3037 }