1 /* 2 * Copyright (c) 2001, 2014, 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/gcHeapSummary.hpp" 29 #include "gc_implementation/shared/gcTimer.hpp" 30 #include "gc_implementation/shared/gcTraceTime.hpp" 31 #include "gc_implementation/shared/gcTrace.hpp" 32 #include "gc_implementation/shared/spaceDecorator.hpp" 33 #include "memory/defNewGeneration.inline.hpp" 34 #include "memory/gcLocker.inline.hpp" 35 #include "memory/genCollectedHeap.hpp" 36 #include "memory/genOopClosures.inline.hpp" 37 #include "memory/genRemSet.hpp" 38 #include "memory/generationSpec.hpp" 39 #include "memory/iterator.hpp" 40 #include "memory/referencePolicy.hpp" 41 #include "memory/space.inline.hpp" 42 #include "oops/instanceRefKlass.hpp" 43 #include "oops/oop.inline.hpp" 44 #include "runtime/atomic.inline.hpp" 45 #include "runtime/java.hpp" 46 #include "runtime/prefetch.inline.hpp" 47 #include "runtime/thread.inline.hpp" 48 #include "utilities/copy.hpp" 49 #include "utilities/globalDefinitions.hpp" 50 #include "utilities/stack.inline.hpp" 51 52 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC 53 54 // 55 // DefNewGeneration functions. 56 57 // Methods of protected closure types. 58 59 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) { 60 assert(g->level() == 0, "Optimized for youngest gen."); 61 } 62 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 63 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded(); 64 } 65 66 DefNewGeneration::KeepAliveClosure:: 67 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 68 GenRemSet* rs = GenCollectedHeap::heap()->rem_set(); 69 _rs = (CardTableRS*)rs; 70 } 71 72 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 73 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 74 75 76 DefNewGeneration::FastKeepAliveClosure:: 77 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 78 DefNewGeneration::KeepAliveClosure(cl) { 79 _boundary = g->reserved().end(); 80 } 81 82 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 83 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 84 85 DefNewGeneration::EvacuateFollowersClosure:: 86 EvacuateFollowersClosure(GenCollectedHeap* gch, int level, 87 ScanClosure* cur, ScanClosure* older) : 88 _gch(gch), _level(level), 89 _scan_cur_or_nonheap(cur), _scan_older(older) 90 {} 91 92 void DefNewGeneration::EvacuateFollowersClosure::do_void() { 93 do { 94 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap, 95 _scan_older); 96 } while (!_gch->no_allocs_since_save_marks(_level)); 97 } 98 99 DefNewGeneration::FastEvacuateFollowersClosure:: 100 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level, 101 DefNewGeneration* gen, 102 FastScanClosure* cur, FastScanClosure* older) : 103 _gch(gch), _level(level), _gen(gen), 104 _scan_cur_or_nonheap(cur), _scan_older(older) 105 {} 106 107 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 108 do { 109 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap, 110 _scan_older); 111 } while (!_gch->no_allocs_since_save_marks(_level)); 112 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan"); 113 } 114 115 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 116 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 117 { 118 assert(_g->level() == 0, "Optimized for youngest generation"); 119 _boundary = _g->reserved().end(); 120 } 121 122 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); } 123 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); } 124 125 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 126 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 127 { 128 assert(_g->level() == 0, "Optimized for youngest generation"); 129 _boundary = _g->reserved().end(); 130 } 131 132 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); } 133 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); } 134 135 void KlassScanClosure::do_klass(Klass* klass) { 136 #ifndef PRODUCT 137 if (TraceScavenge) { 138 ResourceMark rm; 139 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s", 140 klass, 141 klass->external_name(), 142 klass->has_modified_oops() ? "true" : "false"); 143 } 144 #endif 145 146 // If the klass has not been dirtied we know that there's 147 // no references into the young gen and we can skip it. 148 if (klass->has_modified_oops()) { 149 if (_accumulate_modified_oops) { 150 klass->accumulate_modified_oops(); 151 } 152 153 // Clear this state since we're going to scavenge all the metadata. 154 klass->clear_modified_oops(); 155 156 // Tell the closure which Klass is being scanned so that it can be dirtied 157 // if oops are left pointing into the young gen. 158 _scavenge_closure->set_scanned_klass(klass); 159 160 klass->oops_do(_scavenge_closure); 161 162 _scavenge_closure->set_scanned_klass(NULL); 163 } 164 } 165 166 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 167 _g(g) 168 { 169 assert(_g->level() == 0, "Optimized for youngest generation"); 170 _boundary = _g->reserved().end(); 171 } 172 173 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); } 174 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); } 175 176 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); } 177 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); } 178 179 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure, 180 KlassRemSet* klass_rem_set) 181 : _scavenge_closure(scavenge_closure), 182 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {} 183 184 185 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 186 size_t initial_size, 187 int level, 188 const char* policy) 189 : Generation(rs, initial_size, level), 190 _promo_failure_drain_in_progress(false), 191 _should_allocate_from_space(false) 192 { 193 MemRegion cmr((HeapWord*)_virtual_space.low(), 194 (HeapWord*)_virtual_space.high()); 195 Universe::heap()->barrier_set()->resize_covered_region(cmr); 196 197 if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) { 198 _eden_space = new ConcEdenSpace(this); 199 } else { 200 _eden_space = new EdenSpace(this); 201 } 202 _from_space = new ContiguousSpace(); 203 _to_space = new ContiguousSpace(); 204 205 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) 206 vm_exit_during_initialization("Could not allocate a new gen space"); 207 208 // Compute the maximum eden and survivor space sizes. These sizes 209 // are computed assuming the entire reserved space is committed. 210 // These values are exported as performance counters. 211 uintx alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 212 uintx size = _virtual_space.reserved_size(); 213 _max_survivor_size = compute_survivor_size(size, alignment); 214 _max_eden_size = size - (2*_max_survivor_size); 215 216 // allocate the performance counters 217 GenCollectorPolicy* gcp = (GenCollectorPolicy*) GenCollectedHeap::heap()->collector_policy(); 218 219 // Generation counters -- generation 0, 3 subspaces 220 _gen_counters = new GenerationCounters("new", 0, 3, 221 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space); 222 _gc_counters = new CollectorCounters(policy, 0); 223 224 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 225 _gen_counters); 226 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 227 _gen_counters); 228 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 229 _gen_counters); 230 231 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 232 update_counters(); 233 _next_gen = NULL; 234 _tenuring_threshold = MaxTenuringThreshold; 235 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 236 237 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 238 } 239 240 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 241 bool clear_space, 242 bool mangle_space) { 243 uintx alignment = 244 GenCollectedHeap::heap()->collector_policy()->space_alignment(); 245 246 // If the spaces are being cleared (only done at heap initialization 247 // currently), the survivor spaces need not be empty. 248 // Otherwise, no care is taken for used areas in the survivor spaces 249 // so check. 250 assert(clear_space || (to()->is_empty() && from()->is_empty()), 251 "Initialization of the survivor spaces assumes these are empty"); 252 253 // Compute sizes 254 uintx size = _virtual_space.committed_size(); 255 uintx survivor_size = compute_survivor_size(size, alignment); 256 uintx eden_size = size - (2*survivor_size); 257 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 258 259 if (eden_size < minimum_eden_size) { 260 // May happen due to 64Kb rounding, if so adjust eden size back up 261 minimum_eden_size = align_size_up(minimum_eden_size, alignment); 262 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 263 uintx unaligned_survivor_size = 264 align_size_down(maximum_survivor_size, alignment); 265 survivor_size = MAX2(unaligned_survivor_size, alignment); 266 eden_size = size - (2*survivor_size); 267 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 268 assert(eden_size >= minimum_eden_size, "just checking"); 269 } 270 271 char *eden_start = _virtual_space.low(); 272 char *from_start = eden_start + eden_size; 273 char *to_start = from_start + survivor_size; 274 char *to_end = to_start + survivor_size; 275 276 assert(to_end == _virtual_space.high(), "just checking"); 277 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment"); 278 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment"); 279 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment"); 280 281 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 282 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 283 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 284 285 // A minimum eden size implies that there is a part of eden that 286 // is being used and that affects the initialization of any 287 // newly formed eden. 288 bool live_in_eden = minimum_eden_size > 0; 289 290 // If not clearing the spaces, do some checking to verify that 291 // the space are already mangled. 292 if (!clear_space) { 293 // Must check mangling before the spaces are reshaped. Otherwise, 294 // the bottom or end of one space may have moved into another 295 // a failure of the check may not correctly indicate which space 296 // is not properly mangled. 297 if (ZapUnusedHeapArea) { 298 HeapWord* limit = (HeapWord*) _virtual_space.high(); 299 eden()->check_mangled_unused_area(limit); 300 from()->check_mangled_unused_area(limit); 301 to()->check_mangled_unused_area(limit); 302 } 303 } 304 305 // Reset the spaces for their new regions. 306 eden()->initialize(edenMR, 307 clear_space && !live_in_eden, 308 SpaceDecorator::Mangle); 309 // If clear_space and live_in_eden, we will not have cleared any 310 // portion of eden above its top. This can cause newly 311 // expanded space not to be mangled if using ZapUnusedHeapArea. 312 // We explicitly do such mangling here. 313 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 314 eden()->mangle_unused_area(); 315 } 316 from()->initialize(fromMR, clear_space, mangle_space); 317 to()->initialize(toMR, clear_space, mangle_space); 318 319 // Set next compaction spaces. 320 eden()->set_next_compaction_space(from()); 321 // The to-space is normally empty before a compaction so need 322 // not be considered. The exception is during promotion 323 // failure handling when to-space can contain live objects. 324 from()->set_next_compaction_space(NULL); 325 } 326 327 void DefNewGeneration::swap_spaces() { 328 ContiguousSpace* s = from(); 329 _from_space = to(); 330 _to_space = s; 331 eden()->set_next_compaction_space(from()); 332 // The to-space is normally empty before a compaction so need 333 // not be considered. The exception is during promotion 334 // failure handling when to-space can contain live objects. 335 from()->set_next_compaction_space(NULL); 336 337 if (UsePerfData) { 338 CSpaceCounters* c = _from_counters; 339 _from_counters = _to_counters; 340 _to_counters = c; 341 } 342 } 343 344 bool DefNewGeneration::expand(size_t bytes) { 345 MutexLocker x(ExpandHeap_lock); 346 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 347 bool success = _virtual_space.expand_by(bytes); 348 if (success && ZapUnusedHeapArea) { 349 // Mangle newly committed space immediately because it 350 // can be done here more simply that after the new 351 // spaces have been computed. 352 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 353 MemRegion mangle_region(prev_high, new_high); 354 SpaceMangler::mangle_region(mangle_region); 355 } 356 357 // Do not attempt an expand-to-the reserve size. The 358 // request should properly observe the maximum size of 359 // the generation so an expand-to-reserve should be 360 // unnecessary. Also a second call to expand-to-reserve 361 // value potentially can cause an undue expansion. 362 // For example if the first expand fail for unknown reasons, 363 // but the second succeeds and expands the heap to its maximum 364 // value. 365 if (GC_locker::is_active()) { 366 if (PrintGC && Verbose) { 367 gclog_or_tty->print_cr("Garbage collection disabled, " 368 "expanded heap instead"); 369 } 370 } 371 372 return success; 373 } 374 375 376 void DefNewGeneration::compute_new_size() { 377 // This is called after a gc that includes the following generation 378 // (which is required to exist.) So from-space will normally be empty. 379 // Note that we check both spaces, since if scavenge failed they revert roles. 380 // If not we bail out (otherwise we would have to relocate the objects) 381 if (!from()->is_empty() || !to()->is_empty()) { 382 return; 383 } 384 385 int next_level = level() + 1; 386 GenCollectedHeap* gch = GenCollectedHeap::heap(); 387 assert(next_level < gch->_n_gens, 388 "DefNewGeneration cannot be an oldest gen"); 389 390 Generation* next_gen = gch->get_gen(next_level); 391 size_t old_size = next_gen->capacity(); 392 size_t new_size_before = _virtual_space.committed_size(); 393 size_t min_new_size = spec()->init_size(); 394 size_t max_new_size = reserved().byte_size(); 395 assert(min_new_size <= new_size_before && 396 new_size_before <= max_new_size, 397 "just checking"); 398 // All space sizes must be multiples of Generation::GenGrain. 399 size_t alignment = Generation::GenGrain; 400 401 // Compute desired new generation size based on NewRatio and 402 // NewSizeThreadIncrease 403 size_t desired_new_size = old_size/NewRatio; 404 int threads_count = Threads::number_of_non_daemon_threads(); 405 size_t thread_increase_size = threads_count * NewSizeThreadIncrease; 406 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment); 407 408 // Adjust new generation size 409 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 410 assert(desired_new_size <= max_new_size, "just checking"); 411 412 bool changed = false; 413 if (desired_new_size > new_size_before) { 414 size_t change = desired_new_size - new_size_before; 415 assert(change % alignment == 0, "just checking"); 416 if (expand(change)) { 417 changed = true; 418 } 419 // If the heap failed to expand to the desired size, 420 // "changed" will be false. If the expansion failed 421 // (and at this point it was expected to succeed), 422 // ignore the failure (leaving "changed" as false). 423 } 424 if (desired_new_size < new_size_before && eden()->is_empty()) { 425 // bail out of shrinking if objects in eden 426 size_t change = new_size_before - desired_new_size; 427 assert(change % alignment == 0, "just checking"); 428 _virtual_space.shrink_by(change); 429 changed = true; 430 } 431 if (changed) { 432 // The spaces have already been mangled at this point but 433 // may not have been cleared (set top = bottom) and should be. 434 // Mangling was done when the heap was being expanded. 435 compute_space_boundaries(eden()->used(), 436 SpaceDecorator::Clear, 437 SpaceDecorator::DontMangle); 438 MemRegion cmr((HeapWord*)_virtual_space.low(), 439 (HeapWord*)_virtual_space.high()); 440 Universe::heap()->barrier_set()->resize_covered_region(cmr); 441 if (Verbose && PrintGC) { 442 size_t new_size_after = _virtual_space.committed_size(); 443 size_t eden_size_after = eden()->capacity(); 444 size_t survivor_size_after = from()->capacity(); 445 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->" 446 SIZE_FORMAT "K [eden=" 447 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 448 new_size_before/K, new_size_after/K, 449 eden_size_after/K, survivor_size_after/K); 450 if (WizardMode) { 451 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]", 452 thread_increase_size/K, threads_count); 453 } 454 gclog_or_tty->cr(); 455 } 456 } 457 } 458 459 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) { 460 assert(false, "NYI -- are you sure you want to call this?"); 461 } 462 463 464 size_t DefNewGeneration::capacity() const { 465 return eden()->capacity() 466 + from()->capacity(); // to() is only used during scavenge 467 } 468 469 470 size_t DefNewGeneration::used() const { 471 return eden()->used() 472 + from()->used(); // to() is only used during scavenge 473 } 474 475 476 size_t DefNewGeneration::free() const { 477 return eden()->free() 478 + from()->free(); // to() is only used during scavenge 479 } 480 481 size_t DefNewGeneration::max_capacity() const { 482 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 483 const size_t reserved_bytes = reserved().byte_size(); 484 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 485 } 486 487 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 488 return eden()->free(); 489 } 490 491 size_t DefNewGeneration::capacity_before_gc() const { 492 return eden()->capacity(); 493 } 494 495 size_t DefNewGeneration::contiguous_available() const { 496 return eden()->free(); 497 } 498 499 500 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); } 501 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 502 503 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 504 eden()->object_iterate(blk); 505 from()->object_iterate(blk); 506 } 507 508 509 void DefNewGeneration::space_iterate(SpaceClosure* blk, 510 bool usedOnly) { 511 blk->do_space(eden()); 512 blk->do_space(from()); 513 blk->do_space(to()); 514 } 515 516 // The last collection bailed out, we are running out of heap space, 517 // so we try to allocate the from-space, too. 518 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 519 HeapWord* result = NULL; 520 if (Verbose && PrintGCDetails) { 521 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):" 522 " will_fail: %s" 523 " heap_lock: %s" 524 " free: " SIZE_FORMAT, 525 size, 526 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 527 "true" : "false", 528 Heap_lock->is_locked() ? "locked" : "unlocked", 529 from()->free()); 530 } 531 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) { 532 if (Heap_lock->owned_by_self() || 533 (SafepointSynchronize::is_at_safepoint() && 534 Thread::current()->is_VM_thread())) { 535 // If the Heap_lock is not locked by this thread, this will be called 536 // again later with the Heap_lock held. 537 result = from()->allocate(size); 538 } else if (PrintGC && Verbose) { 539 gclog_or_tty->print_cr(" Heap_lock is not owned by self"); 540 } 541 } else if (PrintGC && Verbose) { 542 gclog_or_tty->print_cr(" should_allocate_from_space: NOT"); 543 } 544 if (PrintGC && Verbose) { 545 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object"); 546 } 547 return result; 548 } 549 550 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 551 bool is_tlab, 552 bool parallel) { 553 // We don't attempt to expand the young generation (but perhaps we should.) 554 return allocate(size, is_tlab); 555 } 556 557 void DefNewGeneration::adjust_desired_tenuring_threshold() { 558 // Set the desired survivor size to half the real survivor space 559 _tenuring_threshold = 560 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize); 561 } 562 563 void DefNewGeneration::collect(bool full, 564 bool clear_all_soft_refs, 565 size_t size, 566 bool is_tlab) { 567 assert(full || size > 0, "otherwise we don't want to collect"); 568 569 GenCollectedHeap* gch = GenCollectedHeap::heap(); 570 571 _gc_timer->register_gc_start(); 572 DefNewTracer gc_tracer; 573 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); 574 575 _next_gen = gch->next_gen(this); 576 577 // If the next generation is too full to accommodate promotion 578 // from this generation, pass on collection; let the next generation 579 // do it. 580 if (!collection_attempt_is_safe()) { 581 if (Verbose && PrintGCDetails) { 582 gclog_or_tty->print(" :: Collection attempt not safe :: "); 583 } 584 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 585 return; 586 } 587 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 588 589 init_assuming_no_promotion_failure(); 590 591 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id()); 592 // Capture heap used before collection (for printing). 593 size_t gch_prev_used = gch->used(); 594 595 gch->trace_heap_before_gc(&gc_tracer); 596 597 SpecializationStats::clear(); 598 599 // These can be shared for all code paths 600 IsAliveClosure is_alive(this); 601 ScanWeakRefClosure scan_weak_ref(this); 602 603 age_table()->clear(); 604 to()->clear(SpaceDecorator::Mangle); 605 606 gch->rem_set()->prepare_for_younger_refs_iterate(false); 607 608 assert(gch->no_allocs_since_save_marks(0), 609 "save marks have not been newly set."); 610 611 // Not very pretty. 612 CollectorPolicy* cp = gch->collector_policy(); 613 614 FastScanClosure fsc_with_no_gc_barrier(this, false); 615 FastScanClosure fsc_with_gc_barrier(this, true); 616 617 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier, 618 gch->rem_set()->klass_rem_set()); 619 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure, 620 &fsc_with_no_gc_barrier, 621 false); 622 623 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 624 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this, 625 &fsc_with_no_gc_barrier, 626 &fsc_with_gc_barrier); 627 628 assert(gch->no_allocs_since_save_marks(0), 629 "save marks have not been newly set."); 630 631 gch->gen_process_roots(_level, 632 true, // Process younger gens, if any, 633 // as strong roots. 634 true, // activate StrongRootsScope 635 SharedHeap::SO_ScavengeCodeCache, 636 GenCollectedHeap::StrongAndWeakRoots, 637 &fsc_with_no_gc_barrier, 638 &fsc_with_gc_barrier, 639 &cld_scan_closure); 640 641 // "evacuate followers". 642 evacuate_followers.do_void(); 643 644 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 645 ReferenceProcessor* rp = ref_processor(); 646 rp->setup_policy(clear_all_soft_refs); 647 const ReferenceProcessorStats& stats = 648 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 649 NULL, _gc_timer, gc_tracer.gc_id()); 650 gc_tracer.report_gc_reference_stats(stats); 651 652 if (!_promotion_failed) { 653 // Swap the survivor spaces. 654 eden()->clear(SpaceDecorator::Mangle); 655 from()->clear(SpaceDecorator::Mangle); 656 if (ZapUnusedHeapArea) { 657 // This is now done here because of the piece-meal mangling which 658 // can check for valid mangling at intermediate points in the 659 // collection(s). When a minor collection fails to collect 660 // sufficient space resizing of the young generation can occur 661 // an redistribute the spaces in the young generation. Mangle 662 // here so that unzapped regions don't get distributed to 663 // other spaces. 664 to()->mangle_unused_area(); 665 } 666 swap_spaces(); 667 668 assert(to()->is_empty(), "to space should be empty now"); 669 670 adjust_desired_tenuring_threshold(); 671 672 // A successful scavenge should restart the GC time limit count which is 673 // for full GC's. 674 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 675 size_policy->reset_gc_overhead_limit_count(); 676 assert(!gch->incremental_collection_failed(), "Should be clear"); 677 } else { 678 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 679 _promo_failure_scan_stack.clear(true); // Clear cached segments. 680 681 remove_forwarding_pointers(); 682 if (PrintGCDetails) { 683 gclog_or_tty->print(" (promotion failed) "); 684 } 685 // Add to-space to the list of space to compact 686 // when a promotion failure has occurred. In that 687 // case there can be live objects in to-space 688 // as a result of a partial evacuation of eden 689 // and from-space. 690 swap_spaces(); // For uniformity wrt ParNewGeneration. 691 from()->set_next_compaction_space(to()); 692 gch->set_incremental_collection_failed(); 693 694 // Inform the next generation that a promotion failure occurred. 695 _next_gen->promotion_failure_occurred(); 696 gc_tracer.report_promotion_failed(_promotion_failed_info); 697 698 // Reset the PromotionFailureALot counters. 699 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();) 700 } 701 if (PrintGC && !PrintGCDetails) { 702 gch->print_heap_change(gch_prev_used); 703 } 704 // set new iteration safe limit for the survivor spaces 705 from()->set_concurrent_iteration_safe_limit(from()->top()); 706 to()->set_concurrent_iteration_safe_limit(to()->top()); 707 SpecializationStats::print(); 708 709 // We need to use a monotonically non-decreasing time in ms 710 // or we will see time-warp warnings and os::javaTimeMillis() 711 // does not guarantee monotonicity. 712 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 713 update_time_of_last_gc(now); 714 715 gch->trace_heap_after_gc(&gc_tracer); 716 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 717 718 _gc_timer->register_gc_end(); 719 720 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 721 } 722 723 class RemoveForwardPointerClosure: public ObjectClosure { 724 public: 725 void do_object(oop obj) { 726 obj->init_mark(); 727 } 728 }; 729 730 void DefNewGeneration::init_assuming_no_promotion_failure() { 731 _promotion_failed = false; 732 _promotion_failed_info.reset(); 733 from()->set_next_compaction_space(NULL); 734 } 735 736 void DefNewGeneration::remove_forwarding_pointers() { 737 RemoveForwardPointerClosure rspc; 738 eden()->object_iterate(&rspc); 739 from()->object_iterate(&rspc); 740 741 // Now restore saved marks, if any. 742 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(), 743 "should be the same"); 744 while (!_objs_with_preserved_marks.is_empty()) { 745 oop obj = _objs_with_preserved_marks.pop(); 746 markOop m = _preserved_marks_of_objs.pop(); 747 obj->set_mark(m); 748 } 749 _objs_with_preserved_marks.clear(true); 750 _preserved_marks_of_objs.clear(true); 751 } 752 753 void DefNewGeneration::preserve_mark(oop obj, markOop m) { 754 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj), 755 "Oversaving!"); 756 _objs_with_preserved_marks.push(obj); 757 _preserved_marks_of_objs.push(m); 758 } 759 760 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { 761 if (m->must_be_preserved_for_promotion_failure(obj)) { 762 preserve_mark(obj, m); 763 } 764 } 765 766 void DefNewGeneration::handle_promotion_failure(oop old) { 767 if (PrintPromotionFailure && !_promotion_failed) { 768 gclog_or_tty->print(" (promotion failure size = %d) ", 769 old->size()); 770 } 771 _promotion_failed = true; 772 _promotion_failed_info.register_copy_failure(old->size()); 773 preserve_mark_if_necessary(old, old->mark()); 774 // forward to self 775 old->forward_to(old); 776 777 _promo_failure_scan_stack.push(old); 778 779 if (!_promo_failure_drain_in_progress) { 780 // prevent recursion in copy_to_survivor_space() 781 _promo_failure_drain_in_progress = true; 782 drain_promo_failure_scan_stack(); 783 _promo_failure_drain_in_progress = false; 784 } 785 } 786 787 oop DefNewGeneration::copy_to_survivor_space(oop old) { 788 assert(is_in_reserved(old) && !old->is_forwarded(), 789 "shouldn't be scavenging this oop"); 790 size_t s = old->size(); 791 oop obj = NULL; 792 793 // Try allocating obj in to-space (unless too old) 794 if (old->age() < tenuring_threshold()) { 795 obj = (oop) to()->allocate_aligned(s); 796 } 797 798 // Otherwise try allocating obj tenured 799 if (obj == NULL) { 800 obj = _next_gen->promote(old, s); 801 if (obj == NULL) { 802 handle_promotion_failure(old); 803 return old; 804 } 805 } else { 806 // Prefetch beyond obj 807 const intx interval = PrefetchCopyIntervalInBytes; 808 Prefetch::write(obj, interval); 809 810 // Copy obj 811 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 812 813 // Increment age if obj still in new generation 814 obj->incr_age(); 815 age_table()->add(obj, s); 816 } 817 818 // Done, insert forward pointer to obj in this header 819 old->forward_to(obj); 820 821 return obj; 822 } 823 824 void DefNewGeneration::drain_promo_failure_scan_stack() { 825 while (!_promo_failure_scan_stack.is_empty()) { 826 oop obj = _promo_failure_scan_stack.pop(); 827 obj->oop_iterate(_promo_failure_scan_stack_closure); 828 } 829 } 830 831 void DefNewGeneration::save_marks() { 832 eden()->set_saved_mark(); 833 to()->set_saved_mark(); 834 from()->set_saved_mark(); 835 } 836 837 838 void DefNewGeneration::reset_saved_marks() { 839 eden()->reset_saved_mark(); 840 to()->reset_saved_mark(); 841 from()->reset_saved_mark(); 842 } 843 844 845 bool DefNewGeneration::no_allocs_since_save_marks() { 846 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 847 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 848 return to()->saved_mark_at_top(); 849 } 850 851 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 852 \ 853 void DefNewGeneration:: \ 854 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 855 cl->set_generation(this); \ 856 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 857 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 858 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 859 cl->reset_generation(); \ 860 save_marks(); \ 861 } 862 863 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 864 865 #undef DefNew_SINCE_SAVE_MARKS_DEFN 866 867 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 868 size_t max_alloc_words) { 869 if (requestor == this || _promotion_failed) return; 870 assert(requestor->level() > level(), "DefNewGeneration must be youngest"); 871 872 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 873 if (to_space->top() > to_space->bottom()) { 874 trace("to_space not empty when contribute_scratch called"); 875 } 876 */ 877 878 ContiguousSpace* to_space = to(); 879 assert(to_space->end() >= to_space->top(), "pointers out of order"); 880 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 881 if (free_words >= MinFreeScratchWords) { 882 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 883 sb->num_words = free_words; 884 sb->next = list; 885 list = sb; 886 } 887 } 888 889 void DefNewGeneration::reset_scratch() { 890 // If contributing scratch in to_space, mangle all of 891 // to_space if ZapUnusedHeapArea. This is needed because 892 // top is not maintained while using to-space as scratch. 893 if (ZapUnusedHeapArea) { 894 to()->mangle_unused_area_complete(); 895 } 896 } 897 898 bool DefNewGeneration::collection_attempt_is_safe() { 899 if (!to()->is_empty()) { 900 if (Verbose && PrintGCDetails) { 901 gclog_or_tty->print(" :: to is not empty :: "); 902 } 903 return false; 904 } 905 if (_next_gen == NULL) { 906 GenCollectedHeap* gch = GenCollectedHeap::heap(); 907 _next_gen = gch->next_gen(this); 908 } 909 return _next_gen->promotion_attempt_is_safe(used()); 910 } 911 912 void DefNewGeneration::gc_epilogue(bool full) { 913 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 914 915 assert(!GC_locker::is_active(), "We should not be executing here"); 916 // Check if the heap is approaching full after a collection has 917 // been done. Generally the young generation is empty at 918 // a minimum at the end of a collection. If it is not, then 919 // the heap is approaching full. 920 GenCollectedHeap* gch = GenCollectedHeap::heap(); 921 if (full) { 922 DEBUG_ONLY(seen_incremental_collection_failed = false;) 923 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 924 if (Verbose && PrintGCDetails) { 925 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 926 GCCause::to_string(gch->gc_cause())); 927 } 928 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 929 set_should_allocate_from_space(); // we seem to be running out of space 930 } else { 931 if (Verbose && PrintGCDetails) { 932 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 933 GCCause::to_string(gch->gc_cause())); 934 } 935 gch->clear_incremental_collection_failed(); // We just did a full collection 936 clear_should_allocate_from_space(); // if set 937 } 938 } else { 939 #ifdef ASSERT 940 // It is possible that incremental_collection_failed() == true 941 // here, because an attempted scavenge did not succeed. The policy 942 // is normally expected to cause a full collection which should 943 // clear that condition, so we should not be here twice in a row 944 // with incremental_collection_failed() == true without having done 945 // a full collection in between. 946 if (!seen_incremental_collection_failed && 947 gch->incremental_collection_failed()) { 948 if (Verbose && PrintGCDetails) { 949 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 950 GCCause::to_string(gch->gc_cause())); 951 } 952 seen_incremental_collection_failed = true; 953 } else if (seen_incremental_collection_failed) { 954 if (Verbose && PrintGCDetails) { 955 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 956 GCCause::to_string(gch->gc_cause())); 957 } 958 assert(gch->gc_cause() == GCCause::_scavenge_alot || 959 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 960 !gch->incremental_collection_failed(), 961 "Twice in a row"); 962 seen_incremental_collection_failed = false; 963 } 964 #endif // ASSERT 965 } 966 967 if (ZapUnusedHeapArea) { 968 eden()->check_mangled_unused_area_complete(); 969 from()->check_mangled_unused_area_complete(); 970 to()->check_mangled_unused_area_complete(); 971 } 972 973 if (!CleanChunkPoolAsync) { 974 Chunk::clean_chunk_pool(); 975 } 976 977 // update the generation and space performance counters 978 update_counters(); 979 gch->collector_policy()->counters()->update_counters(); 980 } 981 982 void DefNewGeneration::record_spaces_top() { 983 assert(ZapUnusedHeapArea, "Not mangling unused space"); 984 eden()->set_top_for_allocations(); 985 to()->set_top_for_allocations(); 986 from()->set_top_for_allocations(); 987 } 988 989 void DefNewGeneration::ref_processor_init() { 990 Generation::ref_processor_init(); 991 } 992 993 994 void DefNewGeneration::update_counters() { 995 if (UsePerfData) { 996 _eden_counters->update_all(); 997 _from_counters->update_all(); 998 _to_counters->update_all(); 999 _gen_counters->update_all(); 1000 } 1001 } 1002 1003 void DefNewGeneration::verify() { 1004 eden()->verify(); 1005 from()->verify(); 1006 to()->verify(); 1007 } 1008 1009 void DefNewGeneration::print_on(outputStream* st) const { 1010 Generation::print_on(st); 1011 st->print(" eden"); 1012 eden()->print_on(st); 1013 st->print(" from"); 1014 from()->print_on(st); 1015 st->print(" to "); 1016 to()->print_on(st); 1017 } 1018 1019 1020 const char* DefNewGeneration::name() const { 1021 return "def new generation"; 1022 } 1023 1024 // Moved from inline file as they are not called inline 1025 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 1026 return eden(); 1027 } 1028 1029 HeapWord* DefNewGeneration::allocate(size_t word_size, 1030 bool is_tlab) { 1031 // This is the slow-path allocation for the DefNewGeneration. 1032 // Most allocations are fast-path in compiled code. 1033 // We try to allocate from the eden. If that works, we are happy. 1034 // Note that since DefNewGeneration supports lock-free allocation, we 1035 // have to use it here, as well. 1036 HeapWord* result = eden()->par_allocate(word_size); 1037 if (result != NULL) { 1038 if (CMSEdenChunksRecordAlways && _next_gen != NULL) { 1039 _next_gen->sample_eden_chunk(); 1040 } 1041 return result; 1042 } 1043 do { 1044 HeapWord* old_limit = eden()->soft_end(); 1045 if (old_limit < eden()->end()) { 1046 // Tell the next generation we reached a limit. 1047 HeapWord* new_limit = 1048 next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size); 1049 if (new_limit != NULL) { 1050 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit); 1051 } else { 1052 assert(eden()->soft_end() == eden()->end(), 1053 "invalid state after allocation_limit_reached returned null"); 1054 } 1055 } else { 1056 // The allocation failed and the soft limit is equal to the hard limit, 1057 // there are no reasons to do an attempt to allocate 1058 assert(old_limit == eden()->end(), "sanity check"); 1059 break; 1060 } 1061 // Try to allocate until succeeded or the soft limit can't be adjusted 1062 result = eden()->par_allocate(word_size); 1063 } while (result == NULL); 1064 1065 // If the eden is full and the last collection bailed out, we are running 1066 // out of heap space, and we try to allocate the from-space, too. 1067 // allocate_from_space can't be inlined because that would introduce a 1068 // circular dependency at compile time. 1069 if (result == NULL) { 1070 result = allocate_from_space(word_size); 1071 } else if (CMSEdenChunksRecordAlways && _next_gen != NULL) { 1072 _next_gen->sample_eden_chunk(); 1073 } 1074 return result; 1075 } 1076 1077 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1078 bool is_tlab) { 1079 HeapWord* res = eden()->par_allocate(word_size); 1080 if (CMSEdenChunksRecordAlways && _next_gen != NULL) { 1081 _next_gen->sample_eden_chunk(); 1082 } 1083 return res; 1084 } 1085 1086 void DefNewGeneration::gc_prologue(bool full) { 1087 // Ensure that _end and _soft_end are the same in eden space. 1088 eden()->set_soft_end(eden()->end()); 1089 } 1090 1091 size_t DefNewGeneration::tlab_capacity() const { 1092 return eden()->capacity(); 1093 } 1094 1095 size_t DefNewGeneration::tlab_used() const { 1096 return eden()->used(); 1097 } 1098 1099 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1100 return unsafe_max_alloc_nogc(); 1101 }