1 /* 2 * Copyright (c) 2001, 2012, 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/shared/collectorCounters.hpp" 27 #include "gc_implementation/shared/gcPolicyCounters.hpp" 28 #include "gc_implementation/shared/spaceDecorator.hpp" 29 #include "memory/defNewGeneration.inline.hpp" 30 #include "memory/gcLocker.inline.hpp" 31 #include "memory/genCollectedHeap.hpp" 32 #include "memory/genOopClosures.inline.hpp" 33 #include "memory/genRemSet.hpp" 34 #include "memory/generationSpec.hpp" 35 #include "memory/iterator.hpp" 36 #include "memory/referencePolicy.hpp" 37 #include "memory/space.inline.hpp" 38 #include "oops/instanceRefKlass.hpp" 39 #include "oops/oop.inline.hpp" 40 #include "runtime/java.hpp" 41 #include "runtime/thread.inline.hpp" 42 #include "utilities/copy.hpp" 43 #include "utilities/stack.inline.hpp" 44 45 // 46 // DefNewGeneration functions. 47 48 // Methods of protected closure types. 49 50 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) { 51 assert(g->level() == 0, "Optimized for youngest gen."); 52 } 53 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 54 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded(); 55 } 56 57 DefNewGeneration::KeepAliveClosure:: 58 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 59 GenRemSet* rs = GenCollectedHeap::heap()->rem_set(); 60 assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind."); 61 _rs = (CardTableRS*)rs; 62 } 63 64 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 65 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 66 67 68 DefNewGeneration::FastKeepAliveClosure:: 69 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 70 DefNewGeneration::KeepAliveClosure(cl) { 71 _boundary = g->reserved().end(); 72 } 73 74 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 75 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 76 77 DefNewGeneration::EvacuateFollowersClosure:: 78 EvacuateFollowersClosure(GenCollectedHeap* gch, int level, 79 ScanClosure* cur, ScanClosure* older) : 80 _gch(gch), _level(level), 81 _scan_cur_or_nonheap(cur), _scan_older(older) 82 {} 83 84 void DefNewGeneration::EvacuateFollowersClosure::do_void() { 85 do { 86 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap, 87 _scan_older); 88 } while (!_gch->no_allocs_since_save_marks(_level)); 89 } 90 91 DefNewGeneration::FastEvacuateFollowersClosure:: 92 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level, 93 DefNewGeneration* gen, 94 FastScanClosure* cur, FastScanClosure* older) : 95 _gch(gch), _level(level), _gen(gen), 96 _scan_cur_or_nonheap(cur), _scan_older(older) 97 {} 98 99 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 100 do { 101 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap, 102 _scan_older); 103 } while (!_gch->no_allocs_since_save_marks(_level)); 104 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan"); 105 } 106 107 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 108 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 109 { 110 assert(_g->level() == 0, "Optimized for youngest generation"); 111 _boundary = _g->reserved().end(); 112 } 113 114 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); } 115 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); } 116 117 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 118 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 119 { 120 assert(_g->level() == 0, "Optimized for youngest generation"); 121 _boundary = _g->reserved().end(); 122 } 123 124 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); } 125 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); } 126 127 void KlassScanClosure::do_klass(Klass* klass) { 128 #ifndef PRODUCT 129 if (TraceScavenge) { 130 ResourceMark rm; 131 gclog_or_tty->print_cr("KlassScanClosure::do_klass %p, %s, dirty: %s", 132 klass, 133 klass->external_name(), 134 klass->has_modified_oops() ? "true" : "false"); 135 } 136 #endif 137 138 // If the klass has not been dirtied we know that there's 139 // no references into the young gen and we can skip it. 140 if (klass->has_modified_oops()) { 141 if (_accumulate_modified_oops) { 142 klass->accumulate_modified_oops(); 143 } 144 145 // Clear this state since we're going to scavenge all the metadata. 146 klass->clear_modified_oops(); 147 148 // Tell the closure which Klass is being scanned so that it can be dirtied 149 // if oops are left pointing into the young gen. 150 _scavenge_closure->set_scanned_klass(klass); 151 152 klass->oops_do(_scavenge_closure); 153 154 _scavenge_closure->set_scanned_klass(NULL); 155 } 156 } 157 158 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 159 _g(g) 160 { 161 assert(_g->level() == 0, "Optimized for youngest generation"); 162 _boundary = _g->reserved().end(); 163 } 164 165 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); } 166 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); } 167 168 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); } 169 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); } 170 171 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure, 172 KlassRemSet* klass_rem_set) 173 : _scavenge_closure(scavenge_closure), 174 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {} 175 176 177 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 178 size_t initial_size, 179 int level, 180 const char* policy) 181 : Generation(rs, initial_size, level), 182 _promo_failure_drain_in_progress(false), 183 _should_allocate_from_space(false) 184 { 185 MemRegion cmr((HeapWord*)_virtual_space.low(), 186 (HeapWord*)_virtual_space.high()); 187 Universe::heap()->barrier_set()->resize_covered_region(cmr); 188 189 if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) { 190 _eden_space = new ConcEdenSpace(this); 191 } else { 192 _eden_space = new EdenSpace(this); 193 } 194 _from_space = new ContiguousSpace(); 195 _to_space = new ContiguousSpace(); 196 197 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) 198 vm_exit_during_initialization("Could not allocate a new gen space"); 199 200 // Compute the maximum eden and survivor space sizes. These sizes 201 // are computed assuming the entire reserved space is committed. 202 // These values are exported as performance counters. 203 uintx alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment(); 204 uintx size = _virtual_space.reserved_size(); 205 _max_survivor_size = compute_survivor_size(size, alignment); 206 _max_eden_size = size - (2*_max_survivor_size); 207 208 // allocate the performance counters 209 210 // Generation counters -- generation 0, 3 subspaces 211 _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space); 212 _gc_counters = new CollectorCounters(policy, 0); 213 214 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 215 _gen_counters); 216 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 217 _gen_counters); 218 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 219 _gen_counters); 220 221 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 222 update_counters(); 223 _next_gen = NULL; 224 _tenuring_threshold = MaxTenuringThreshold; 225 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 226 } 227 228 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 229 bool clear_space, 230 bool mangle_space) { 231 uintx alignment = 232 GenCollectedHeap::heap()->collector_policy()->min_alignment(); 233 234 // If the spaces are being cleared (only done at heap initialization 235 // currently), the survivor spaces need not be empty. 236 // Otherwise, no care is taken for used areas in the survivor spaces 237 // so check. 238 assert(clear_space || (to()->is_empty() && from()->is_empty()), 239 "Initialization of the survivor spaces assumes these are empty"); 240 241 // Compute sizes 242 uintx size = _virtual_space.committed_size(); 243 uintx survivor_size = compute_survivor_size(size, alignment); 244 uintx eden_size = size - (2*survivor_size); 245 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 246 247 if (eden_size < minimum_eden_size) { 248 // May happen due to 64Kb rounding, if so adjust eden size back up 249 minimum_eden_size = align_size_up(minimum_eden_size, alignment); 250 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 251 uintx unaligned_survivor_size = 252 align_size_down(maximum_survivor_size, alignment); 253 survivor_size = MAX2(unaligned_survivor_size, alignment); 254 eden_size = size - (2*survivor_size); 255 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 256 assert(eden_size >= minimum_eden_size, "just checking"); 257 } 258 259 char *eden_start = _virtual_space.low(); 260 char *from_start = eden_start + eden_size; 261 char *to_start = from_start + survivor_size; 262 char *to_end = to_start + survivor_size; 263 264 assert(to_end == _virtual_space.high(), "just checking"); 265 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment"); 266 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment"); 267 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment"); 268 269 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 270 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 271 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 272 273 // A minimum eden size implies that there is a part of eden that 274 // is being used and that affects the initialization of any 275 // newly formed eden. 276 bool live_in_eden = minimum_eden_size > 0; 277 278 // If not clearing the spaces, do some checking to verify that 279 // the space are already mangled. 280 if (!clear_space) { 281 // Must check mangling before the spaces are reshaped. Otherwise, 282 // the bottom or end of one space may have moved into another 283 // a failure of the check may not correctly indicate which space 284 // is not properly mangled. 285 if (ZapUnusedHeapArea) { 286 HeapWord* limit = (HeapWord*) _virtual_space.high(); 287 eden()->check_mangled_unused_area(limit); 288 from()->check_mangled_unused_area(limit); 289 to()->check_mangled_unused_area(limit); 290 } 291 } 292 293 // Reset the spaces for their new regions. 294 eden()->initialize(edenMR, 295 clear_space && !live_in_eden, 296 SpaceDecorator::Mangle); 297 // If clear_space and live_in_eden, we will not have cleared any 298 // portion of eden above its top. This can cause newly 299 // expanded space not to be mangled if using ZapUnusedHeapArea. 300 // We explicitly do such mangling here. 301 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 302 eden()->mangle_unused_area(); 303 } 304 from()->initialize(fromMR, clear_space, mangle_space); 305 to()->initialize(toMR, clear_space, mangle_space); 306 307 // Set next compaction spaces. 308 eden()->set_next_compaction_space(from()); 309 // The to-space is normally empty before a compaction so need 310 // not be considered. The exception is during promotion 311 // failure handling when to-space can contain live objects. 312 from()->set_next_compaction_space(NULL); 313 } 314 315 void DefNewGeneration::swap_spaces() { 316 ContiguousSpace* s = from(); 317 _from_space = to(); 318 _to_space = s; 319 eden()->set_next_compaction_space(from()); 320 // The to-space is normally empty before a compaction so need 321 // not be considered. The exception is during promotion 322 // failure handling when to-space can contain live objects. 323 from()->set_next_compaction_space(NULL); 324 325 if (UsePerfData) { 326 CSpaceCounters* c = _from_counters; 327 _from_counters = _to_counters; 328 _to_counters = c; 329 } 330 } 331 332 bool DefNewGeneration::expand(size_t bytes) { 333 MutexLocker x(ExpandHeap_lock); 334 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 335 bool success = _virtual_space.expand_by(bytes); 336 if (success && ZapUnusedHeapArea) { 337 // Mangle newly committed space immediately because it 338 // can be done here more simply that after the new 339 // spaces have been computed. 340 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 341 MemRegion mangle_region(prev_high, new_high); 342 SpaceMangler::mangle_region(mangle_region); 343 } 344 345 // Do not attempt an expand-to-the reserve size. The 346 // request should properly observe the maximum size of 347 // the generation so an expand-to-reserve should be 348 // unnecessary. Also a second call to expand-to-reserve 349 // value potentially can cause an undue expansion. 350 // For example if the first expand fail for unknown reasons, 351 // but the second succeeds and expands the heap to its maximum 352 // value. 353 if (GC_locker::is_active()) { 354 if (PrintGC && Verbose) { 355 gclog_or_tty->print_cr("Garbage collection disabled, " 356 "expanded heap instead"); 357 } 358 } 359 360 return success; 361 } 362 363 364 void DefNewGeneration::compute_new_size() { 365 // This is called after a gc that includes the following generation 366 // (which is required to exist.) So from-space will normally be empty. 367 // Note that we check both spaces, since if scavenge failed they revert roles. 368 // If not we bail out (otherwise we would have to relocate the objects) 369 if (!from()->is_empty() || !to()->is_empty()) { 370 return; 371 } 372 373 int next_level = level() + 1; 374 GenCollectedHeap* gch = GenCollectedHeap::heap(); 375 assert(next_level < gch->_n_gens, 376 "DefNewGeneration cannot be an oldest gen"); 377 378 Generation* next_gen = gch->_gens[next_level]; 379 size_t old_size = next_gen->capacity(); 380 size_t new_size_before = _virtual_space.committed_size(); 381 size_t min_new_size = spec()->init_size(); 382 size_t max_new_size = reserved().byte_size(); 383 assert(min_new_size <= new_size_before && 384 new_size_before <= max_new_size, 385 "just checking"); 386 // All space sizes must be multiples of Generation::GenGrain. 387 size_t alignment = Generation::GenGrain; 388 389 // Compute desired new generation size based on NewRatio and 390 // NewSizeThreadIncrease 391 size_t desired_new_size = old_size/NewRatio; 392 int threads_count = Threads::number_of_non_daemon_threads(); 393 size_t thread_increase_size = threads_count * NewSizeThreadIncrease; 394 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment); 395 396 // Adjust new generation size 397 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 398 assert(desired_new_size <= max_new_size, "just checking"); 399 400 bool changed = false; 401 if (desired_new_size > new_size_before) { 402 size_t change = desired_new_size - new_size_before; 403 assert(change % alignment == 0, "just checking"); 404 if (expand(change)) { 405 changed = true; 406 } 407 // If the heap failed to expand to the desired size, 408 // "changed" will be false. If the expansion failed 409 // (and at this point it was expected to succeed), 410 // ignore the failure (leaving "changed" as false). 411 } 412 if (desired_new_size < new_size_before && eden()->is_empty()) { 413 // bail out of shrinking if objects in eden 414 size_t change = new_size_before - desired_new_size; 415 assert(change % alignment == 0, "just checking"); 416 _virtual_space.shrink_by(change); 417 changed = true; 418 } 419 if (changed) { 420 // The spaces have already been mangled at this point but 421 // may not have been cleared (set top = bottom) and should be. 422 // Mangling was done when the heap was being expanded. 423 compute_space_boundaries(eden()->used(), 424 SpaceDecorator::Clear, 425 SpaceDecorator::DontMangle); 426 MemRegion cmr((HeapWord*)_virtual_space.low(), 427 (HeapWord*)_virtual_space.high()); 428 Universe::heap()->barrier_set()->resize_covered_region(cmr); 429 if (Verbose && PrintGC) { 430 size_t new_size_after = _virtual_space.committed_size(); 431 size_t eden_size_after = eden()->capacity(); 432 size_t survivor_size_after = from()->capacity(); 433 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->" 434 SIZE_FORMAT "K [eden=" 435 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 436 new_size_before/K, new_size_after/K, 437 eden_size_after/K, survivor_size_after/K); 438 if (WizardMode) { 439 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]", 440 thread_increase_size/K, threads_count); 441 } 442 gclog_or_tty->cr(); 443 } 444 } 445 } 446 447 void DefNewGeneration::object_iterate_since_last_GC(ObjectClosure* cl) { 448 // $$$ This may be wrong in case of "scavenge failure"? 449 eden()->object_iterate(cl); 450 } 451 452 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) { 453 assert(false, "NYI -- are you sure you want to call this?"); 454 } 455 456 457 size_t DefNewGeneration::capacity() const { 458 return eden()->capacity() 459 + from()->capacity(); // to() is only used during scavenge 460 } 461 462 463 size_t DefNewGeneration::used() const { 464 return eden()->used() 465 + from()->used(); // to() is only used during scavenge 466 } 467 468 469 size_t DefNewGeneration::free() const { 470 return eden()->free() 471 + from()->free(); // to() is only used during scavenge 472 } 473 474 size_t DefNewGeneration::max_capacity() const { 475 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment(); 476 const size_t reserved_bytes = reserved().byte_size(); 477 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 478 } 479 480 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 481 return eden()->free(); 482 } 483 484 size_t DefNewGeneration::capacity_before_gc() const { 485 return eden()->capacity(); 486 } 487 488 size_t DefNewGeneration::contiguous_available() const { 489 return eden()->free(); 490 } 491 492 493 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); } 494 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 495 496 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 497 eden()->object_iterate(blk); 498 from()->object_iterate(blk); 499 } 500 501 502 void DefNewGeneration::space_iterate(SpaceClosure* blk, 503 bool usedOnly) { 504 blk->do_space(eden()); 505 blk->do_space(from()); 506 blk->do_space(to()); 507 } 508 509 // The last collection bailed out, we are running out of heap space, 510 // so we try to allocate the from-space, too. 511 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 512 HeapWord* result = NULL; 513 if (Verbose && PrintGCDetails) { 514 gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):" 515 " will_fail: %s" 516 " heap_lock: %s" 517 " free: " SIZE_FORMAT, 518 size, 519 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 520 "true" : "false", 521 Heap_lock->is_locked() ? "locked" : "unlocked", 522 from()->free()); 523 } 524 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) { 525 if (Heap_lock->owned_by_self() || 526 (SafepointSynchronize::is_at_safepoint() && 527 Thread::current()->is_VM_thread())) { 528 // If the Heap_lock is not locked by this thread, this will be called 529 // again later with the Heap_lock held. 530 result = from()->allocate(size); 531 } else if (PrintGC && Verbose) { 532 gclog_or_tty->print_cr(" Heap_lock is not owned by self"); 533 } 534 } else if (PrintGC && Verbose) { 535 gclog_or_tty->print_cr(" should_allocate_from_space: NOT"); 536 } 537 if (PrintGC && Verbose) { 538 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object"); 539 } 540 return result; 541 } 542 543 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 544 bool is_tlab, 545 bool parallel) { 546 // We don't attempt to expand the young generation (but perhaps we should.) 547 return allocate(size, is_tlab); 548 } 549 550 void DefNewGeneration::adjust_desired_tenuring_threshold() { 551 // Set the desired survivor size to half the real survivor space 552 _tenuring_threshold = 553 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize); 554 } 555 556 void DefNewGeneration::collect(bool full, 557 bool clear_all_soft_refs, 558 size_t size, 559 bool is_tlab) { 560 assert(full || size > 0, "otherwise we don't want to collect"); 561 GenCollectedHeap* gch = GenCollectedHeap::heap(); 562 _next_gen = gch->next_gen(this); 563 assert(_next_gen != NULL, 564 "This must be the youngest gen, and not the only gen"); 565 566 // If the next generation is too full to accomodate promotion 567 // from this generation, pass on collection; let the next generation 568 // do it. 569 if (!collection_attempt_is_safe()) { 570 if (Verbose && PrintGCDetails) { 571 gclog_or_tty->print(" :: Collection attempt not safe :: "); 572 } 573 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 574 return; 575 } 576 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 577 578 init_assuming_no_promotion_failure(); 579 580 TraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, gclog_or_tty); 581 // Capture heap used before collection (for printing). 582 size_t gch_prev_used = gch->used(); 583 584 SpecializationStats::clear(); 585 586 // These can be shared for all code paths 587 IsAliveClosure is_alive(this); 588 ScanWeakRefClosure scan_weak_ref(this); 589 590 age_table()->clear(); 591 to()->clear(SpaceDecorator::Mangle); 592 593 gch->rem_set()->prepare_for_younger_refs_iterate(false); 594 595 assert(gch->no_allocs_since_save_marks(0), 596 "save marks have not been newly set."); 597 598 // Not very pretty. 599 CollectorPolicy* cp = gch->collector_policy(); 600 601 FastScanClosure fsc_with_no_gc_barrier(this, false); 602 FastScanClosure fsc_with_gc_barrier(this, true); 603 604 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier, 605 gch->rem_set()->klass_rem_set()); 606 607 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 608 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this, 609 &fsc_with_no_gc_barrier, 610 &fsc_with_gc_barrier); 611 612 assert(gch->no_allocs_since_save_marks(0), 613 "save marks have not been newly set."); 614 615 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; 616 617 gch->gen_process_strong_roots(_level, 618 true, // Process younger gens, if any, 619 // as strong roots. 620 true, // activate StrongRootsScope 621 true, // is scavenging 622 SharedHeap::ScanningOption(so), 623 &fsc_with_no_gc_barrier, 624 true, // walk *all* scavengable nmethods 625 &fsc_with_gc_barrier, 626 &klass_scan_closure); 627 628 // "evacuate followers". 629 evacuate_followers.do_void(); 630 631 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 632 ReferenceProcessor* rp = ref_processor(); 633 rp->setup_policy(clear_all_soft_refs); 634 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 635 NULL); 636 if (!promotion_failed()) { 637 // Swap the survivor spaces. 638 eden()->clear(SpaceDecorator::Mangle); 639 from()->clear(SpaceDecorator::Mangle); 640 if (ZapUnusedHeapArea) { 641 // This is now done here because of the piece-meal mangling which 642 // can check for valid mangling at intermediate points in the 643 // collection(s). When a minor collection fails to collect 644 // sufficient space resizing of the young generation can occur 645 // an redistribute the spaces in the young generation. Mangle 646 // here so that unzapped regions don't get distributed to 647 // other spaces. 648 to()->mangle_unused_area(); 649 } 650 swap_spaces(); 651 652 assert(to()->is_empty(), "to space should be empty now"); 653 654 adjust_desired_tenuring_threshold(); 655 656 // A successful scavenge should restart the GC time limit count which is 657 // for full GC's. 658 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 659 size_policy->reset_gc_overhead_limit_count(); 660 if (PrintGC && !PrintGCDetails) { 661 gch->print_heap_change(gch_prev_used); 662 } 663 assert(!gch->incremental_collection_failed(), "Should be clear"); 664 } else { 665 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 666 _promo_failure_scan_stack.clear(true); // Clear cached segments. 667 668 remove_forwarding_pointers(); 669 if (PrintGCDetails) { 670 gclog_or_tty->print(" (promotion failed) "); 671 } 672 // Add to-space to the list of space to compact 673 // when a promotion failure has occurred. In that 674 // case there can be live objects in to-space 675 // as a result of a partial evacuation of eden 676 // and from-space. 677 swap_spaces(); // For uniformity wrt ParNewGeneration. 678 from()->set_next_compaction_space(to()); 679 gch->set_incremental_collection_failed(); 680 681 // Inform the next generation that a promotion failure occurred. 682 _next_gen->promotion_failure_occurred(); 683 684 // Reset the PromotionFailureALot counters. 685 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();) 686 } 687 // set new iteration safe limit for the survivor spaces 688 from()->set_concurrent_iteration_safe_limit(from()->top()); 689 to()->set_concurrent_iteration_safe_limit(to()->top()); 690 SpecializationStats::print(); 691 692 // We need to use a monotonically non-deccreasing time in ms 693 // or we will see time-warp warnings and os::javaTimeMillis() 694 // does not guarantee monotonicity. 695 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 696 update_time_of_last_gc(now); 697 } 698 699 class RemoveForwardPointerClosure: public ObjectClosure { 700 public: 701 void do_object(oop obj) { 702 obj->init_mark(); 703 } 704 }; 705 706 void DefNewGeneration::init_assuming_no_promotion_failure() { 707 _promotion_failed = false; 708 from()->set_next_compaction_space(NULL); 709 } 710 711 void DefNewGeneration::remove_forwarding_pointers() { 712 RemoveForwardPointerClosure rspc; 713 eden()->object_iterate(&rspc); 714 from()->object_iterate(&rspc); 715 716 // Now restore saved marks, if any. 717 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(), 718 "should be the same"); 719 while (!_objs_with_preserved_marks.is_empty()) { 720 oop obj = _objs_with_preserved_marks.pop(); 721 markOop m = _preserved_marks_of_objs.pop(); 722 obj->set_mark(m); 723 } 724 _objs_with_preserved_marks.clear(true); 725 _preserved_marks_of_objs.clear(true); 726 } 727 728 void DefNewGeneration::preserve_mark(oop obj, markOop m) { 729 assert(promotion_failed() && m->must_be_preserved_for_promotion_failure(obj), 730 "Oversaving!"); 731 _objs_with_preserved_marks.push(obj); 732 _preserved_marks_of_objs.push(m); 733 } 734 735 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { 736 if (m->must_be_preserved_for_promotion_failure(obj)) { 737 preserve_mark(obj, m); 738 } 739 } 740 741 void DefNewGeneration::handle_promotion_failure(oop old) { 742 if (PrintPromotionFailure && !_promotion_failed) { 743 gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ", 744 old->size()); 745 } 746 _promotion_failed = true; 747 preserve_mark_if_necessary(old, old->mark()); 748 // forward to self 749 old->forward_to(old); 750 751 _promo_failure_scan_stack.push(old); 752 753 if (!_promo_failure_drain_in_progress) { 754 // prevent recursion in copy_to_survivor_space() 755 _promo_failure_drain_in_progress = true; 756 drain_promo_failure_scan_stack(); 757 _promo_failure_drain_in_progress = false; 758 } 759 } 760 761 oop DefNewGeneration::copy_to_survivor_space(oop old) { 762 assert(is_in_reserved(old) && !old->is_forwarded(), 763 "shouldn't be scavenging this oop"); 764 size_t s = old->size(); 765 oop obj = NULL; 766 767 // Try allocating obj in to-space (unless too old) 768 if (old->age() < tenuring_threshold()) { 769 obj = (oop) to()->allocate(s); 770 } 771 772 // Otherwise try allocating obj tenured 773 if (obj == NULL) { 774 obj = _next_gen->promote(old, s); 775 if (obj == NULL) { 776 handle_promotion_failure(old); 777 return old; 778 } 779 } else { 780 // Prefetch beyond obj 781 const intx interval = PrefetchCopyIntervalInBytes; 782 Prefetch::write(obj, interval); 783 784 // Copy obj 785 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 786 787 // Increment age if obj still in new generation 788 obj->incr_age(); 789 age_table()->add(obj, s); 790 } 791 792 // Done, insert forward pointer to obj in this header 793 old->forward_to(obj); 794 795 return obj; 796 } 797 798 void DefNewGeneration::drain_promo_failure_scan_stack() { 799 while (!_promo_failure_scan_stack.is_empty()) { 800 oop obj = _promo_failure_scan_stack.pop(); 801 obj->oop_iterate(_promo_failure_scan_stack_closure); 802 } 803 } 804 805 void DefNewGeneration::save_marks() { 806 eden()->set_saved_mark(); 807 to()->set_saved_mark(); 808 from()->set_saved_mark(); 809 } 810 811 812 void DefNewGeneration::reset_saved_marks() { 813 eden()->reset_saved_mark(); 814 to()->reset_saved_mark(); 815 from()->reset_saved_mark(); 816 } 817 818 819 bool DefNewGeneration::no_allocs_since_save_marks() { 820 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 821 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 822 return to()->saved_mark_at_top(); 823 } 824 825 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 826 \ 827 void DefNewGeneration:: \ 828 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 829 cl->set_generation(this); \ 830 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 831 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 832 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 833 cl->reset_generation(); \ 834 save_marks(); \ 835 } 836 837 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 838 839 #undef DefNew_SINCE_SAVE_MARKS_DEFN 840 841 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 842 size_t max_alloc_words) { 843 if (requestor == this || _promotion_failed) return; 844 assert(requestor->level() > level(), "DefNewGeneration must be youngest"); 845 846 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 847 if (to_space->top() > to_space->bottom()) { 848 trace("to_space not empty when contribute_scratch called"); 849 } 850 */ 851 852 ContiguousSpace* to_space = to(); 853 assert(to_space->end() >= to_space->top(), "pointers out of order"); 854 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 855 if (free_words >= MinFreeScratchWords) { 856 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 857 sb->num_words = free_words; 858 sb->next = list; 859 list = sb; 860 } 861 } 862 863 void DefNewGeneration::reset_scratch() { 864 // If contributing scratch in to_space, mangle all of 865 // to_space if ZapUnusedHeapArea. This is needed because 866 // top is not maintained while using to-space as scratch. 867 if (ZapUnusedHeapArea) { 868 to()->mangle_unused_area_complete(); 869 } 870 } 871 872 bool DefNewGeneration::collection_attempt_is_safe() { 873 if (!to()->is_empty()) { 874 if (Verbose && PrintGCDetails) { 875 gclog_or_tty->print(" :: to is not empty :: "); 876 } 877 return false; 878 } 879 if (_next_gen == NULL) { 880 GenCollectedHeap* gch = GenCollectedHeap::heap(); 881 _next_gen = gch->next_gen(this); 882 assert(_next_gen != NULL, 883 "This must be the youngest gen, and not the only gen"); 884 } 885 return _next_gen->promotion_attempt_is_safe(used()); 886 } 887 888 void DefNewGeneration::gc_epilogue(bool full) { 889 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 890 891 assert(!GC_locker::is_active(), "We should not be executing here"); 892 // Check if the heap is approaching full after a collection has 893 // been done. Generally the young generation is empty at 894 // a minimum at the end of a collection. If it is not, then 895 // the heap is approaching full. 896 GenCollectedHeap* gch = GenCollectedHeap::heap(); 897 if (full) { 898 DEBUG_ONLY(seen_incremental_collection_failed = false;) 899 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 900 if (Verbose && PrintGCDetails) { 901 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 902 GCCause::to_string(gch->gc_cause())); 903 } 904 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 905 set_should_allocate_from_space(); // we seem to be running out of space 906 } else { 907 if (Verbose && PrintGCDetails) { 908 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 909 GCCause::to_string(gch->gc_cause())); 910 } 911 gch->clear_incremental_collection_failed(); // We just did a full collection 912 clear_should_allocate_from_space(); // if set 913 } 914 } else { 915 #ifdef ASSERT 916 // It is possible that incremental_collection_failed() == true 917 // here, because an attempted scavenge did not succeed. The policy 918 // is normally expected to cause a full collection which should 919 // clear that condition, so we should not be here twice in a row 920 // with incremental_collection_failed() == true without having done 921 // a full collection in between. 922 if (!seen_incremental_collection_failed && 923 gch->incremental_collection_failed()) { 924 if (Verbose && PrintGCDetails) { 925 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 926 GCCause::to_string(gch->gc_cause())); 927 } 928 seen_incremental_collection_failed = true; 929 } else if (seen_incremental_collection_failed) { 930 if (Verbose && PrintGCDetails) { 931 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 932 GCCause::to_string(gch->gc_cause())); 933 } 934 assert(gch->gc_cause() == GCCause::_scavenge_alot || 935 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 936 !gch->incremental_collection_failed(), 937 "Twice in a row"); 938 seen_incremental_collection_failed = false; 939 } 940 #endif // ASSERT 941 } 942 943 if (ZapUnusedHeapArea) { 944 eden()->check_mangled_unused_area_complete(); 945 from()->check_mangled_unused_area_complete(); 946 to()->check_mangled_unused_area_complete(); 947 } 948 949 if (!CleanChunkPoolAsync) { 950 Chunk::clean_chunk_pool(); 951 } 952 953 // update the generation and space performance counters 954 update_counters(); 955 gch->collector_policy()->counters()->update_counters(); 956 } 957 958 void DefNewGeneration::record_spaces_top() { 959 assert(ZapUnusedHeapArea, "Not mangling unused space"); 960 eden()->set_top_for_allocations(); 961 to()->set_top_for_allocations(); 962 from()->set_top_for_allocations(); 963 } 964 965 966 void DefNewGeneration::update_counters() { 967 if (UsePerfData) { 968 _eden_counters->update_all(); 969 _from_counters->update_all(); 970 _to_counters->update_all(); 971 _gen_counters->update_all(); 972 } 973 } 974 975 void DefNewGeneration::verify() { 976 eden()->verify(); 977 from()->verify(); 978 to()->verify(); 979 } 980 981 void DefNewGeneration::print_on(outputStream* st) const { 982 Generation::print_on(st); 983 st->print(" eden"); 984 eden()->print_on(st); 985 st->print(" from"); 986 from()->print_on(st); 987 st->print(" to "); 988 to()->print_on(st); 989 } 990 991 992 const char* DefNewGeneration::name() const { 993 return "def new generation"; 994 } 995 996 // Moved from inline file as they are not called inline 997 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 998 return eden(); 999 } 1000 1001 HeapWord* DefNewGeneration::allocate(size_t word_size, 1002 bool is_tlab) { 1003 // This is the slow-path allocation for the DefNewGeneration. 1004 // Most allocations are fast-path in compiled code. 1005 // We try to allocate from the eden. If that works, we are happy. 1006 // Note that since DefNewGeneration supports lock-free allocation, we 1007 // have to use it here, as well. 1008 HeapWord* result = eden()->par_allocate(word_size); 1009 if (result != NULL) { 1010 return result; 1011 } 1012 do { 1013 HeapWord* old_limit = eden()->soft_end(); 1014 if (old_limit < eden()->end()) { 1015 // Tell the next generation we reached a limit. 1016 HeapWord* new_limit = 1017 next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size); 1018 if (new_limit != NULL) { 1019 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit); 1020 } else { 1021 assert(eden()->soft_end() == eden()->end(), 1022 "invalid state after allocation_limit_reached returned null"); 1023 } 1024 } else { 1025 // The allocation failed and the soft limit is equal to the hard limit, 1026 // there are no reasons to do an attempt to allocate 1027 assert(old_limit == eden()->end(), "sanity check"); 1028 break; 1029 } 1030 // Try to allocate until succeeded or the soft limit can't be adjusted 1031 result = eden()->par_allocate(word_size); 1032 } while (result == NULL); 1033 1034 // If the eden is full and the last collection bailed out, we are running 1035 // out of heap space, and we try to allocate the from-space, too. 1036 // allocate_from_space can't be inlined because that would introduce a 1037 // circular dependency at compile time. 1038 if (result == NULL) { 1039 result = allocate_from_space(word_size); 1040 } 1041 return result; 1042 } 1043 1044 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1045 bool is_tlab) { 1046 return eden()->par_allocate(word_size); 1047 } 1048 1049 void DefNewGeneration::gc_prologue(bool full) { 1050 // Ensure that _end and _soft_end are the same in eden space. 1051 eden()->set_soft_end(eden()->end()); 1052 } 1053 1054 size_t DefNewGeneration::tlab_capacity() const { 1055 return eden()->capacity(); 1056 } 1057 1058 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1059 return unsafe_max_alloc_nogc(); 1060 }