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/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 #if INCLUDE_ALL_GCS 52 #include "gc_implementation/parNew/parOopClosures.hpp" 53 #endif 54 55 // 56 // DefNewGeneration functions. 57 58 // Methods of protected closure types. 59 60 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) { 61 assert(g->level() == 0, "Optimized for youngest gen."); 62 } 63 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 64 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded(); 65 } 66 67 DefNewGeneration::KeepAliveClosure:: 68 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 69 GenRemSet* rs = GenCollectedHeap::heap()->rem_set(); 70 _rs = (CardTableRS*)rs; 71 } 72 73 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 74 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 75 76 77 DefNewGeneration::FastKeepAliveClosure:: 78 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 79 DefNewGeneration::KeepAliveClosure(cl) { 80 _boundary = g->reserved().end(); 81 } 82 83 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 84 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 85 86 DefNewGeneration::EvacuateFollowersClosure:: 87 EvacuateFollowersClosure(GenCollectedHeap* gch, int level, 88 ScanClosure* cur, ScanClosure* older) : 89 _gch(gch), _level(level), 90 _scan_cur_or_nonheap(cur), _scan_older(older) 91 {} 92 93 void DefNewGeneration::EvacuateFollowersClosure::do_void() { 94 do { 95 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap, 96 _scan_older); 97 } while (!_gch->no_allocs_since_save_marks(_level)); 98 } 99 100 DefNewGeneration::FastEvacuateFollowersClosure:: 101 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level, 102 DefNewGeneration* gen, 103 FastScanClosure* cur, FastScanClosure* older) : 104 _gch(gch), _level(level), _gen(gen), 105 _scan_cur_or_nonheap(cur), _scan_older(older) 106 {} 107 108 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 109 do { 110 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap, 111 _scan_older); 112 } while (!_gch->no_allocs_since_save_marks(_level)); 113 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan"); 114 } 115 116 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 117 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 118 { 119 assert(_g->level() == 0, "Optimized for youngest generation"); 120 _boundary = _g->reserved().end(); 121 } 122 123 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); } 124 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); } 125 126 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 127 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 128 { 129 assert(_g->level() == 0, "Optimized for youngest generation"); 130 _boundary = _g->reserved().end(); 131 } 132 133 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); } 134 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); } 135 136 void KlassScanClosure::do_klass(Klass* klass) { 137 #ifndef PRODUCT 138 if (TraceScavenge) { 139 ResourceMark rm; 140 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s", 141 p2i(klass), 142 klass->external_name(), 143 klass->has_modified_oops() ? "true" : "false"); 144 } 145 #endif 146 147 // If the klass has not been dirtied we know that there's 148 // no references into the young gen and we can skip it. 149 if (klass->has_modified_oops()) { 150 if (_accumulate_modified_oops) { 151 klass->accumulate_modified_oops(); 152 } 153 154 // Clear this state since we're going to scavenge all the metadata. 155 klass->clear_modified_oops(); 156 157 // Tell the closure which Klass is being scanned so that it can be dirtied 158 // if oops are left pointing into the young gen. 159 _scavenge_closure->set_scanned_klass(klass); 160 161 klass->oops_do(_scavenge_closure); 162 163 _scavenge_closure->set_scanned_klass(NULL); 164 } 165 } 166 167 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 168 _g(g) 169 { 170 assert(_g->level() == 0, "Optimized for youngest generation"); 171 _boundary = _g->reserved().end(); 172 } 173 174 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); } 175 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); } 176 177 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); } 178 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); } 179 180 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure, 181 KlassRemSet* klass_rem_set) 182 : _scavenge_closure(scavenge_closure), 183 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {} 184 185 186 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 187 size_t initial_size, 188 int level, 189 const char* policy) 190 : Generation(rs, initial_size, level), 191 _promo_failure_drain_in_progress(false), 192 _should_allocate_from_space(false) 193 { 194 MemRegion cmr((HeapWord*)_virtual_space.low(), 195 (HeapWord*)_virtual_space.high()); 196 GenCollectedHeap* gch = GenCollectedHeap::heap(); 197 198 gch->barrier_set()->resize_covered_region(cmr); 199 200 _eden_space = new ContiguousSpace(); 201 _from_space = new ContiguousSpace(); 202 _to_space = new ContiguousSpace(); 203 204 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) 205 vm_exit_during_initialization("Could not allocate a new gen space"); 206 207 // Compute the maximum eden and survivor space sizes. These sizes 208 // are computed assuming the entire reserved space is committed. 209 // These values are exported as performance counters. 210 uintx alignment = gch->collector_policy()->space_alignment(); 211 uintx size = _virtual_space.reserved_size(); 212 _max_survivor_size = compute_survivor_size(size, alignment); 213 _max_eden_size = size - (2*_max_survivor_size); 214 215 // allocate the performance counters 216 GenCollectorPolicy* gcp = (GenCollectorPolicy*)gch->collector_policy(); 217 218 // Generation counters -- generation 0, 3 subspaces 219 _gen_counters = new GenerationCounters("new", 0, 3, 220 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space); 221 _gc_counters = new CollectorCounters(policy, 0); 222 223 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 224 _gen_counters); 225 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 226 _gen_counters); 227 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 228 _gen_counters); 229 230 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 231 update_counters(); 232 _old_gen = NULL; 233 _tenuring_threshold = MaxTenuringThreshold; 234 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 235 236 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 237 } 238 239 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 240 bool clear_space, 241 bool mangle_space) { 242 uintx alignment = 243 GenCollectedHeap::heap()->collector_policy()->space_alignment(); 244 245 // If the spaces are being cleared (only done at heap initialization 246 // currently), the survivor spaces need not be empty. 247 // Otherwise, no care is taken for used areas in the survivor spaces 248 // so check. 249 assert(clear_space || (to()->is_empty() && from()->is_empty()), 250 "Initialization of the survivor spaces assumes these are empty"); 251 252 // Compute sizes 253 uintx size = _virtual_space.committed_size(); 254 uintx survivor_size = compute_survivor_size(size, alignment); 255 uintx eden_size = size - (2*survivor_size); 256 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 257 258 if (eden_size < minimum_eden_size) { 259 // May happen due to 64Kb rounding, if so adjust eden size back up 260 minimum_eden_size = align_size_up(minimum_eden_size, alignment); 261 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 262 uintx unaligned_survivor_size = 263 align_size_down(maximum_survivor_size, alignment); 264 survivor_size = MAX2(unaligned_survivor_size, alignment); 265 eden_size = size - (2*survivor_size); 266 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 267 assert(eden_size >= minimum_eden_size, "just checking"); 268 } 269 270 char *eden_start = _virtual_space.low(); 271 char *from_start = eden_start + eden_size; 272 char *to_start = from_start + survivor_size; 273 char *to_end = to_start + survivor_size; 274 275 assert(to_end == _virtual_space.high(), "just checking"); 276 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment"); 277 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment"); 278 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment"); 279 280 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 281 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 282 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 283 284 // A minimum eden size implies that there is a part of eden that 285 // is being used and that affects the initialization of any 286 // newly formed eden. 287 bool live_in_eden = minimum_eden_size > 0; 288 289 // If not clearing the spaces, do some checking to verify that 290 // the space are already mangled. 291 if (!clear_space) { 292 // Must check mangling before the spaces are reshaped. Otherwise, 293 // the bottom or end of one space may have moved into another 294 // a failure of the check may not correctly indicate which space 295 // is not properly mangled. 296 if (ZapUnusedHeapArea) { 297 HeapWord* limit = (HeapWord*) _virtual_space.high(); 298 eden()->check_mangled_unused_area(limit); 299 from()->check_mangled_unused_area(limit); 300 to()->check_mangled_unused_area(limit); 301 } 302 } 303 304 // Reset the spaces for their new regions. 305 eden()->initialize(edenMR, 306 clear_space && !live_in_eden, 307 SpaceDecorator::Mangle); 308 // If clear_space and live_in_eden, we will not have cleared any 309 // portion of eden above its top. This can cause newly 310 // expanded space not to be mangled if using ZapUnusedHeapArea. 311 // We explicitly do such mangling here. 312 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 313 eden()->mangle_unused_area(); 314 } 315 from()->initialize(fromMR, clear_space, mangle_space); 316 to()->initialize(toMR, clear_space, mangle_space); 317 318 // Set next compaction spaces. 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 } 325 326 void DefNewGeneration::swap_spaces() { 327 ContiguousSpace* s = from(); 328 _from_space = to(); 329 _to_space = s; 330 eden()->set_next_compaction_space(from()); 331 // The to-space is normally empty before a compaction so need 332 // not be considered. The exception is during promotion 333 // failure handling when to-space can contain live objects. 334 from()->set_next_compaction_space(NULL); 335 336 if (UsePerfData) { 337 CSpaceCounters* c = _from_counters; 338 _from_counters = _to_counters; 339 _to_counters = c; 340 } 341 } 342 343 bool DefNewGeneration::expand(size_t bytes) { 344 MutexLocker x(ExpandHeap_lock); 345 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 346 bool success = _virtual_space.expand_by(bytes); 347 if (success && ZapUnusedHeapArea) { 348 // Mangle newly committed space immediately because it 349 // can be done here more simply that after the new 350 // spaces have been computed. 351 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 352 MemRegion mangle_region(prev_high, new_high); 353 SpaceMangler::mangle_region(mangle_region); 354 } 355 356 // Do not attempt an expand-to-the reserve size. The 357 // request should properly observe the maximum size of 358 // the generation so an expand-to-reserve should be 359 // unnecessary. Also a second call to expand-to-reserve 360 // value potentially can cause an undue expansion. 361 // For example if the first expand fail for unknown reasons, 362 // but the second succeeds and expands the heap to its maximum 363 // value. 364 if (GC_locker::is_active()) { 365 if (PrintGC && Verbose) { 366 gclog_or_tty->print_cr("Garbage collection disabled, " 367 "expanded heap instead"); 368 } 369 } 370 371 return success; 372 } 373 374 375 void DefNewGeneration::compute_new_size() { 376 // This is called after a gc that includes the following generation 377 // (which is required to exist.) So from-space will normally be empty. 378 // Note that we check both spaces, since if scavenge failed they revert roles. 379 // If not we bail out (otherwise we would have to relocate the objects) 380 if (!from()->is_empty() || !to()->is_empty()) { 381 return; 382 } 383 384 int next_level = level() + 1; 385 GenCollectedHeap* gch = GenCollectedHeap::heap(); 386 assert(next_level == 1, "DefNewGeneration must be a young gen"); 387 388 Generation* old_gen = gch->old_gen(); 389 size_t old_size = old_gen->capacity(); 390 size_t new_size_before = _virtual_space.committed_size(); 391 size_t min_new_size = spec()->init_size(); 392 size_t max_new_size = reserved().byte_size(); 393 assert(min_new_size <= new_size_before && 394 new_size_before <= max_new_size, 395 "just checking"); 396 // All space sizes must be multiples of Generation::GenGrain. 397 size_t alignment = Generation::GenGrain; 398 399 // Compute desired new generation size based on NewRatio and 400 // NewSizeThreadIncrease 401 size_t desired_new_size = old_size/NewRatio; 402 int threads_count = Threads::number_of_non_daemon_threads(); 403 size_t thread_increase_size = threads_count * NewSizeThreadIncrease; 404 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment); 405 406 // Adjust new generation size 407 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 408 assert(desired_new_size <= max_new_size, "just checking"); 409 410 bool changed = false; 411 if (desired_new_size > new_size_before) { 412 size_t change = desired_new_size - new_size_before; 413 assert(change % alignment == 0, "just checking"); 414 if (expand(change)) { 415 changed = true; 416 } 417 // If the heap failed to expand to the desired size, 418 // "changed" will be false. If the expansion failed 419 // (and at this point it was expected to succeed), 420 // ignore the failure (leaving "changed" as false). 421 } 422 if (desired_new_size < new_size_before && eden()->is_empty()) { 423 // bail out of shrinking if objects in eden 424 size_t change = new_size_before - desired_new_size; 425 assert(change % alignment == 0, "just checking"); 426 _virtual_space.shrink_by(change); 427 changed = true; 428 } 429 if (changed) { 430 // The spaces have already been mangled at this point but 431 // may not have been cleared (set top = bottom) and should be. 432 // Mangling was done when the heap was being expanded. 433 compute_space_boundaries(eden()->used(), 434 SpaceDecorator::Clear, 435 SpaceDecorator::DontMangle); 436 MemRegion cmr((HeapWord*)_virtual_space.low(), 437 (HeapWord*)_virtual_space.high()); 438 gch->barrier_set()->resize_covered_region(cmr); 439 if (Verbose && PrintGC) { 440 size_t new_size_after = _virtual_space.committed_size(); 441 size_t eden_size_after = eden()->capacity(); 442 size_t survivor_size_after = from()->capacity(); 443 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->" 444 SIZE_FORMAT "K [eden=" 445 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 446 new_size_before/K, new_size_after/K, 447 eden_size_after/K, survivor_size_after/K); 448 if (WizardMode) { 449 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]", 450 thread_increase_size/K, threads_count); 451 } 452 gclog_or_tty->cr(); 453 } 454 } 455 } 456 457 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) { 458 assert(false, "NYI -- are you sure you want to call this?"); 459 } 460 461 462 size_t DefNewGeneration::capacity() const { 463 return eden()->capacity() 464 + from()->capacity(); // to() is only used during scavenge 465 } 466 467 468 size_t DefNewGeneration::used() const { 469 return eden()->used() 470 + from()->used(); // to() is only used during scavenge 471 } 472 473 474 size_t DefNewGeneration::free() const { 475 return eden()->free() 476 + from()->free(); // to() is only used during scavenge 477 } 478 479 size_t DefNewGeneration::max_capacity() const { 480 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 481 const size_t reserved_bytes = reserved().byte_size(); 482 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 483 } 484 485 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 486 return eden()->free(); 487 } 488 489 size_t DefNewGeneration::capacity_before_gc() const { 490 return eden()->capacity(); 491 } 492 493 size_t DefNewGeneration::contiguous_available() const { 494 return eden()->free(); 495 } 496 497 498 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); } 499 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 500 501 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 502 eden()->object_iterate(blk); 503 from()->object_iterate(blk); 504 } 505 506 507 void DefNewGeneration::space_iterate(SpaceClosure* blk, 508 bool usedOnly) { 509 blk->do_space(eden()); 510 blk->do_space(from()); 511 blk->do_space(to()); 512 } 513 514 // The last collection bailed out, we are running out of heap space, 515 // so we try to allocate the from-space, too. 516 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 517 HeapWord* result = NULL; 518 if (Verbose && PrintGCDetails) { 519 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):" 520 " will_fail: %s" 521 " heap_lock: %s" 522 " free: " SIZE_FORMAT, 523 size, 524 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 525 "true" : "false", 526 Heap_lock->is_locked() ? "locked" : "unlocked", 527 from()->free()); 528 } 529 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) { 530 if (Heap_lock->owned_by_self() || 531 (SafepointSynchronize::is_at_safepoint() && 532 Thread::current()->is_VM_thread())) { 533 // If the Heap_lock is not locked by this thread, this will be called 534 // again later with the Heap_lock held. 535 result = from()->allocate(size); 536 } else if (PrintGC && Verbose) { 537 gclog_or_tty->print_cr(" Heap_lock is not owned by self"); 538 } 539 } else if (PrintGC && Verbose) { 540 gclog_or_tty->print_cr(" should_allocate_from_space: NOT"); 541 } 542 if (PrintGC && Verbose) { 543 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object"); 544 } 545 return result; 546 } 547 548 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 549 bool is_tlab, 550 bool parallel) { 551 // We don't attempt to expand the young generation (but perhaps we should.) 552 return allocate(size, is_tlab); 553 } 554 555 void DefNewGeneration::adjust_desired_tenuring_threshold() { 556 // Set the desired survivor size to half the real survivor space 557 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters(); 558 _tenuring_threshold = 559 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters); 560 } 561 562 void DefNewGeneration::collect(bool full, 563 bool clear_all_soft_refs, 564 size_t size, 565 bool is_tlab) { 566 assert(full || size > 0, "otherwise we don't want to collect"); 567 568 GenCollectedHeap* gch = GenCollectedHeap::heap(); 569 570 _gc_timer->register_gc_start(); 571 DefNewTracer gc_tracer; 572 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); 573 574 _old_gen = gch->old_gen(); 575 576 // If the next generation is too full to accommodate promotion 577 // from this generation, pass on collection; let the next generation 578 // do it. 579 if (!collection_attempt_is_safe()) { 580 if (Verbose && PrintGCDetails) { 581 gclog_or_tty->print(" :: Collection attempt not safe :: "); 582 } 583 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 584 return; 585 } 586 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 587 588 init_assuming_no_promotion_failure(); 589 590 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id()); 591 // Capture heap used before collection (for printing). 592 size_t gch_prev_used = gch->used(); 593 594 gch->trace_heap_before_gc(&gc_tracer); 595 596 // These can be shared for all code paths 597 IsAliveClosure is_alive(this); 598 ScanWeakRefClosure scan_weak_ref(this); 599 600 age_table()->clear(); 601 to()->clear(SpaceDecorator::Mangle); 602 603 gch->rem_set()->prepare_for_younger_refs_iterate(false); 604 605 assert(gch->no_allocs_since_save_marks(0), 606 "save marks have not been newly set."); 607 608 // Not very pretty. 609 CollectorPolicy* cp = gch->collector_policy(); 610 611 FastScanClosure fsc_with_no_gc_barrier(this, false); 612 FastScanClosure fsc_with_gc_barrier(this, true); 613 614 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier, 615 gch->rem_set()->klass_rem_set()); 616 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure, 617 &fsc_with_no_gc_barrier, 618 false); 619 620 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 621 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this, 622 &fsc_with_no_gc_barrier, 623 &fsc_with_gc_barrier); 624 625 assert(gch->no_allocs_since_save_marks(0), 626 "save marks have not been newly set."); 627 628 gch->gen_process_roots(_level, 629 true, // Process younger gens, if any, 630 // as strong roots. 631 true, // activate StrongRootsScope 632 GenCollectedHeap::SO_ScavengeCodeCache, 633 GenCollectedHeap::StrongAndWeakRoots, 634 &fsc_with_no_gc_barrier, 635 &fsc_with_gc_barrier, 636 &cld_scan_closure); 637 638 // "evacuate followers". 639 evacuate_followers.do_void(); 640 641 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 642 ReferenceProcessor* rp = ref_processor(); 643 rp->setup_policy(clear_all_soft_refs); 644 const ReferenceProcessorStats& stats = 645 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 646 NULL, _gc_timer, gc_tracer.gc_id()); 647 gc_tracer.report_gc_reference_stats(stats); 648 649 if (!_promotion_failed) { 650 // Swap the survivor spaces. 651 eden()->clear(SpaceDecorator::Mangle); 652 from()->clear(SpaceDecorator::Mangle); 653 if (ZapUnusedHeapArea) { 654 // This is now done here because of the piece-meal mangling which 655 // can check for valid mangling at intermediate points in the 656 // collection(s). When a minor collection fails to collect 657 // sufficient space resizing of the young generation can occur 658 // an redistribute the spaces in the young generation. Mangle 659 // here so that unzapped regions don't get distributed to 660 // other spaces. 661 to()->mangle_unused_area(); 662 } 663 swap_spaces(); 664 665 assert(to()->is_empty(), "to space should be empty now"); 666 667 adjust_desired_tenuring_threshold(); 668 669 // A successful scavenge should restart the GC time limit count which is 670 // for full GC's. 671 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 672 size_policy->reset_gc_overhead_limit_count(); 673 assert(!gch->incremental_collection_failed(), "Should be clear"); 674 } else { 675 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 676 _promo_failure_scan_stack.clear(true); // Clear cached segments. 677 678 remove_forwarding_pointers(); 679 if (PrintGCDetails) { 680 gclog_or_tty->print(" (promotion failed) "); 681 } 682 // Add to-space to the list of space to compact 683 // when a promotion failure has occurred. In that 684 // case there can be live objects in to-space 685 // as a result of a partial evacuation of eden 686 // and from-space. 687 swap_spaces(); // For uniformity wrt ParNewGeneration. 688 from()->set_next_compaction_space(to()); 689 gch->set_incremental_collection_failed(); 690 691 // Inform the next generation that a promotion failure occurred. 692 _old_gen->promotion_failure_occurred(); 693 gc_tracer.report_promotion_failed(_promotion_failed_info); 694 695 // Reset the PromotionFailureALot counters. 696 NOT_PRODUCT(gch->reset_promotion_should_fail();) 697 } 698 if (PrintGC && !PrintGCDetails) { 699 gch->print_heap_change(gch_prev_used); 700 } 701 // set new iteration safe limit for the survivor spaces 702 from()->set_concurrent_iteration_safe_limit(from()->top()); 703 to()->set_concurrent_iteration_safe_limit(to()->top()); 704 705 // We need to use a monotonically non-decreasing time in ms 706 // or we will see time-warp warnings and os::javaTimeMillis() 707 // does not guarantee monotonicity. 708 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 709 update_time_of_last_gc(now); 710 711 gch->trace_heap_after_gc(&gc_tracer); 712 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 713 714 _gc_timer->register_gc_end(); 715 716 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 717 } 718 719 class RemoveForwardPointerClosure: public ObjectClosure { 720 public: 721 void do_object(oop obj) { 722 obj->init_mark(); 723 } 724 }; 725 726 void DefNewGeneration::init_assuming_no_promotion_failure() { 727 _promotion_failed = false; 728 _promotion_failed_info.reset(); 729 from()->set_next_compaction_space(NULL); 730 } 731 732 void DefNewGeneration::remove_forwarding_pointers() { 733 RemoveForwardPointerClosure rspc; 734 eden()->object_iterate(&rspc); 735 from()->object_iterate(&rspc); 736 737 // Now restore saved marks, if any. 738 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(), 739 "should be the same"); 740 while (!_objs_with_preserved_marks.is_empty()) { 741 oop obj = _objs_with_preserved_marks.pop(); 742 markOop m = _preserved_marks_of_objs.pop(); 743 obj->set_mark(m); 744 } 745 _objs_with_preserved_marks.clear(true); 746 _preserved_marks_of_objs.clear(true); 747 } 748 749 void DefNewGeneration::preserve_mark(oop obj, markOop m) { 750 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj), 751 "Oversaving!"); 752 _objs_with_preserved_marks.push(obj); 753 _preserved_marks_of_objs.push(m); 754 } 755 756 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { 757 if (m->must_be_preserved_for_promotion_failure(obj)) { 758 preserve_mark(obj, m); 759 } 760 } 761 762 void DefNewGeneration::handle_promotion_failure(oop old) { 763 if (PrintPromotionFailure && !_promotion_failed) { 764 gclog_or_tty->print(" (promotion failure size = %d) ", 765 old->size()); 766 } 767 _promotion_failed = true; 768 _promotion_failed_info.register_copy_failure(old->size()); 769 preserve_mark_if_necessary(old, old->mark()); 770 // forward to self 771 old->forward_to(old); 772 773 _promo_failure_scan_stack.push(old); 774 775 if (!_promo_failure_drain_in_progress) { 776 // prevent recursion in copy_to_survivor_space() 777 _promo_failure_drain_in_progress = true; 778 drain_promo_failure_scan_stack(); 779 _promo_failure_drain_in_progress = false; 780 } 781 } 782 783 oop DefNewGeneration::copy_to_survivor_space(oop old) { 784 assert(is_in_reserved(old) && !old->is_forwarded(), 785 "shouldn't be scavenging this oop"); 786 size_t s = old->size(); 787 oop obj = NULL; 788 789 // Try allocating obj in to-space (unless too old) 790 if (old->age() < tenuring_threshold()) { 791 obj = (oop) to()->allocate_aligned(s); 792 } 793 794 // Otherwise try allocating obj tenured 795 if (obj == NULL) { 796 obj = _old_gen->promote(old, s); 797 if (obj == NULL) { 798 handle_promotion_failure(old); 799 return old; 800 } 801 } else { 802 // Prefetch beyond obj 803 const intx interval = PrefetchCopyIntervalInBytes; 804 Prefetch::write(obj, interval); 805 806 // Copy obj 807 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 808 809 // Increment age if obj still in new generation 810 obj->incr_age(); 811 age_table()->add(obj, s); 812 } 813 814 // Done, insert forward pointer to obj in this header 815 old->forward_to(obj); 816 817 return obj; 818 } 819 820 void DefNewGeneration::drain_promo_failure_scan_stack() { 821 while (!_promo_failure_scan_stack.is_empty()) { 822 oop obj = _promo_failure_scan_stack.pop(); 823 obj->oop_iterate(_promo_failure_scan_stack_closure); 824 } 825 } 826 827 void DefNewGeneration::save_marks() { 828 eden()->set_saved_mark(); 829 to()->set_saved_mark(); 830 from()->set_saved_mark(); 831 } 832 833 834 void DefNewGeneration::reset_saved_marks() { 835 eden()->reset_saved_mark(); 836 to()->reset_saved_mark(); 837 from()->reset_saved_mark(); 838 } 839 840 841 bool DefNewGeneration::no_allocs_since_save_marks() { 842 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 843 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 844 return to()->saved_mark_at_top(); 845 } 846 847 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 848 \ 849 void DefNewGeneration:: \ 850 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 851 cl->set_generation(this); \ 852 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 853 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 854 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 855 cl->reset_generation(); \ 856 save_marks(); \ 857 } 858 859 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 860 861 #undef DefNew_SINCE_SAVE_MARKS_DEFN 862 863 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 864 size_t max_alloc_words) { 865 if (requestor == this || _promotion_failed) return; 866 assert(requestor->level() > level(), "DefNewGeneration must be youngest"); 867 868 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 869 if (to_space->top() > to_space->bottom()) { 870 trace("to_space not empty when contribute_scratch called"); 871 } 872 */ 873 874 ContiguousSpace* to_space = to(); 875 assert(to_space->end() >= to_space->top(), "pointers out of order"); 876 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 877 if (free_words >= MinFreeScratchWords) { 878 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 879 sb->num_words = free_words; 880 sb->next = list; 881 list = sb; 882 } 883 } 884 885 void DefNewGeneration::reset_scratch() { 886 // If contributing scratch in to_space, mangle all of 887 // to_space if ZapUnusedHeapArea. This is needed because 888 // top is not maintained while using to-space as scratch. 889 if (ZapUnusedHeapArea) { 890 to()->mangle_unused_area_complete(); 891 } 892 } 893 894 bool DefNewGeneration::collection_attempt_is_safe() { 895 if (!to()->is_empty()) { 896 if (Verbose && PrintGCDetails) { 897 gclog_or_tty->print(" :: to is not empty :: "); 898 } 899 return false; 900 } 901 if (_old_gen == NULL) { 902 GenCollectedHeap* gch = GenCollectedHeap::heap(); 903 _old_gen = gch->old_gen(); 904 } 905 return _old_gen->promotion_attempt_is_safe(used()); 906 } 907 908 void DefNewGeneration::gc_epilogue(bool full) { 909 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 910 911 assert(!GC_locker::is_active(), "We should not be executing here"); 912 // Check if the heap is approaching full after a collection has 913 // been done. Generally the young generation is empty at 914 // a minimum at the end of a collection. If it is not, then 915 // the heap is approaching full. 916 GenCollectedHeap* gch = GenCollectedHeap::heap(); 917 if (full) { 918 DEBUG_ONLY(seen_incremental_collection_failed = false;) 919 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 920 if (Verbose && PrintGCDetails) { 921 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 922 GCCause::to_string(gch->gc_cause())); 923 } 924 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 925 set_should_allocate_from_space(); // we seem to be running out of space 926 } else { 927 if (Verbose && PrintGCDetails) { 928 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 929 GCCause::to_string(gch->gc_cause())); 930 } 931 gch->clear_incremental_collection_failed(); // We just did a full collection 932 clear_should_allocate_from_space(); // if set 933 } 934 } else { 935 #ifdef ASSERT 936 // It is possible that incremental_collection_failed() == true 937 // here, because an attempted scavenge did not succeed. The policy 938 // is normally expected to cause a full collection which should 939 // clear that condition, so we should not be here twice in a row 940 // with incremental_collection_failed() == true without having done 941 // a full collection in between. 942 if (!seen_incremental_collection_failed && 943 gch->incremental_collection_failed()) { 944 if (Verbose && PrintGCDetails) { 945 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 946 GCCause::to_string(gch->gc_cause())); 947 } 948 seen_incremental_collection_failed = true; 949 } else if (seen_incremental_collection_failed) { 950 if (Verbose && PrintGCDetails) { 951 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 952 GCCause::to_string(gch->gc_cause())); 953 } 954 assert(gch->gc_cause() == GCCause::_scavenge_alot || 955 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 956 !gch->incremental_collection_failed(), 957 "Twice in a row"); 958 seen_incremental_collection_failed = false; 959 } 960 #endif // ASSERT 961 } 962 963 if (ZapUnusedHeapArea) { 964 eden()->check_mangled_unused_area_complete(); 965 from()->check_mangled_unused_area_complete(); 966 to()->check_mangled_unused_area_complete(); 967 } 968 969 if (!CleanChunkPoolAsync) { 970 Chunk::clean_chunk_pool(); 971 } 972 973 // update the generation and space performance counters 974 update_counters(); 975 gch->collector_policy()->counters()->update_counters(); 976 } 977 978 void DefNewGeneration::record_spaces_top() { 979 assert(ZapUnusedHeapArea, "Not mangling unused space"); 980 eden()->set_top_for_allocations(); 981 to()->set_top_for_allocations(); 982 from()->set_top_for_allocations(); 983 } 984 985 void DefNewGeneration::ref_processor_init() { 986 Generation::ref_processor_init(); 987 } 988 989 990 void DefNewGeneration::update_counters() { 991 if (UsePerfData) { 992 _eden_counters->update_all(); 993 _from_counters->update_all(); 994 _to_counters->update_all(); 995 _gen_counters->update_all(); 996 } 997 } 998 999 void DefNewGeneration::verify() { 1000 eden()->verify(); 1001 from()->verify(); 1002 to()->verify(); 1003 } 1004 1005 void DefNewGeneration::print_on(outputStream* st) const { 1006 Generation::print_on(st); 1007 st->print(" eden"); 1008 eden()->print_on(st); 1009 st->print(" from"); 1010 from()->print_on(st); 1011 st->print(" to "); 1012 to()->print_on(st); 1013 } 1014 1015 1016 const char* DefNewGeneration::name() const { 1017 return "def new generation"; 1018 } 1019 1020 // Moved from inline file as they are not called inline 1021 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 1022 return eden(); 1023 } 1024 1025 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 1026 // This is the slow-path allocation for the DefNewGeneration. 1027 // Most allocations are fast-path in compiled code. 1028 // We try to allocate from the eden. If that works, we are happy. 1029 // Note that since DefNewGeneration supports lock-free allocation, we 1030 // have to use it here, as well. 1031 HeapWord* result = eden()->par_allocate(word_size); 1032 if (result != NULL) { 1033 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1034 _old_gen->sample_eden_chunk(); 1035 } 1036 } else { 1037 // If the eden is full and the last collection bailed out, we are running 1038 // out of heap space, and we try to allocate the from-space, too. 1039 // allocate_from_space can't be inlined because that would introduce a 1040 // circular dependency at compile time. 1041 result = allocate_from_space(word_size); 1042 } 1043 return result; 1044 } 1045 1046 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1047 bool is_tlab) { 1048 HeapWord* res = eden()->par_allocate(word_size); 1049 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1050 _old_gen->sample_eden_chunk(); 1051 } 1052 return res; 1053 } 1054 1055 size_t DefNewGeneration::tlab_capacity() const { 1056 return eden()->capacity(); 1057 } 1058 1059 size_t DefNewGeneration::tlab_used() const { 1060 return eden()->used(); 1061 } 1062 1063 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1064 return unsafe_max_alloc_nogc(); 1065 }