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/serial/defNewGeneration.inline.hpp" 27 #include "gc/shared/collectorCounters.hpp" 28 #include "gc/shared/gcHeapSummary.hpp" 29 #include "gc/shared/gcLocker.inline.hpp" 30 #include "gc/shared/gcPolicyCounters.hpp" 31 #include "gc/shared/gcTimer.hpp" 32 #include "gc/shared/gcTrace.hpp" 33 #include "gc/shared/gcTraceTime.hpp" 34 #include "gc/shared/genCollectedHeap.hpp" 35 #include "gc/shared/genOopClosures.inline.hpp" 36 #include "gc/shared/genRemSet.hpp" 37 #include "gc/shared/generationSpec.hpp" 38 #include "gc/shared/referencePolicy.hpp" 39 #include "gc/shared/space.inline.hpp" 40 #include "gc/shared/spaceDecorator.hpp" 41 #include "gc/shared/strongRootsScope.hpp" 42 #include "memory/iterator.hpp" 43 #include "oops/instanceRefKlass.hpp" 44 #include "oops/oop.inline.hpp" 45 #include "runtime/atomic.inline.hpp" 46 #include "runtime/java.hpp" 47 #include "runtime/prefetch.inline.hpp" 48 #include "runtime/thread.inline.hpp" 49 #include "utilities/copy.hpp" 50 #include "utilities/globalDefinitions.hpp" 51 #include "utilities/stack.inline.hpp" 52 #if INCLUDE_ALL_GCS 53 #include "gc/cms/parOopClosures.hpp" 54 #endif 55 56 // 57 // DefNewGeneration functions. 58 59 // Methods of protected closure types. 60 61 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) { 62 assert(g->level() == 0, "Optimized for youngest gen."); 63 } 64 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 65 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded(); 66 } 67 68 DefNewGeneration::KeepAliveClosure:: 69 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 70 GenRemSet* rs = GenCollectedHeap::heap()->rem_set(); 71 _rs = (CardTableRS*)rs; 72 } 73 74 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 75 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 76 77 78 DefNewGeneration::FastKeepAliveClosure:: 79 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 80 DefNewGeneration::KeepAliveClosure(cl) { 81 _boundary = g->reserved().end(); 82 } 83 84 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 85 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 86 87 DefNewGeneration::EvacuateFollowersClosure:: 88 EvacuateFollowersClosure(GenCollectedHeap* gch, int level, 89 ScanClosure* cur, ScanClosure* older) : 90 _gch(gch), _level(level), 91 _scan_cur_or_nonheap(cur), _scan_older(older) 92 {} 93 94 void DefNewGeneration::EvacuateFollowersClosure::do_void() { 95 do { 96 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap, 97 _scan_older); 98 } while (!_gch->no_allocs_since_save_marks(_level)); 99 } 100 101 DefNewGeneration::FastEvacuateFollowersClosure:: 102 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level, 103 DefNewGeneration* gen, 104 FastScanClosure* cur, FastScanClosure* older) : 105 _gch(gch), _level(level), _gen(gen), 106 _scan_cur_or_nonheap(cur), _scan_older(older) 107 {} 108 109 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 110 do { 111 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap, 112 _scan_older); 113 } while (!_gch->no_allocs_since_save_marks(_level)); 114 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan"); 115 } 116 117 ScanClosure::ScanClosure(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 ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); } 125 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); } 126 127 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 128 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 129 { 130 assert(_g->level() == 0, "Optimized for youngest generation"); 131 _boundary = _g->reserved().end(); 132 } 133 134 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); } 135 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); } 136 137 void KlassScanClosure::do_klass(Klass* klass) { 138 #ifndef PRODUCT 139 if (TraceScavenge) { 140 ResourceMark rm; 141 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s", 142 p2i(klass), 143 klass->external_name(), 144 klass->has_modified_oops() ? "true" : "false"); 145 } 146 #endif 147 148 // If the klass has not been dirtied we know that there's 149 // no references into the young gen and we can skip it. 150 if (klass->has_modified_oops()) { 151 if (_accumulate_modified_oops) { 152 klass->accumulate_modified_oops(); 153 } 154 155 // Clear this state since we're going to scavenge all the metadata. 156 klass->clear_modified_oops(); 157 158 // Tell the closure which Klass is being scanned so that it can be dirtied 159 // if oops are left pointing into the young gen. 160 _scavenge_closure->set_scanned_klass(klass); 161 162 klass->oops_do(_scavenge_closure); 163 164 _scavenge_closure->set_scanned_klass(NULL); 165 } 166 } 167 168 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 169 _g(g) 170 { 171 assert(_g->level() == 0, "Optimized for youngest generation"); 172 _boundary = _g->reserved().end(); 173 } 174 175 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); } 176 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); } 177 178 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); } 179 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); } 180 181 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure, 182 KlassRemSet* klass_rem_set) 183 : _scavenge_closure(scavenge_closure), 184 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {} 185 186 187 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 188 size_t initial_size, 189 int level, 190 const char* policy) 191 : Generation(rs, initial_size, level), 192 _promo_failure_drain_in_progress(false), 193 _should_allocate_from_space(false) 194 { 195 MemRegion cmr((HeapWord*)_virtual_space.low(), 196 (HeapWord*)_virtual_space.high()); 197 GenCollectedHeap* gch = GenCollectedHeap::heap(); 198 199 gch->barrier_set()->resize_covered_region(cmr); 200 201 _eden_space = new ContiguousSpace(); 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 = gch->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*)gch->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 _old_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 == 1, "DefNewGeneration must be a young gen"); 388 389 Generation* old_gen = gch->old_gen(); 390 size_t old_size = old_gen->capacity(); 391 size_t new_size_before = _virtual_space.committed_size(); 392 size_t min_new_size = spec()->init_size(); 393 size_t max_new_size = reserved().byte_size(); 394 assert(min_new_size <= new_size_before && 395 new_size_before <= max_new_size, 396 "just checking"); 397 // All space sizes must be multiples of Generation::GenGrain. 398 size_t alignment = Generation::GenGrain; 399 400 // Compute desired new generation size based on NewRatio and 401 // NewSizeThreadIncrease 402 size_t desired_new_size = old_size/NewRatio; 403 int threads_count = Threads::number_of_non_daemon_threads(); 404 size_t thread_increase_size = threads_count * NewSizeThreadIncrease; 405 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment); 406 407 // Adjust new generation size 408 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 409 assert(desired_new_size <= max_new_size, "just checking"); 410 411 bool changed = false; 412 if (desired_new_size > new_size_before) { 413 size_t change = desired_new_size - new_size_before; 414 assert(change % alignment == 0, "just checking"); 415 if (expand(change)) { 416 changed = true; 417 } 418 // If the heap failed to expand to the desired size, 419 // "changed" will be false. If the expansion failed 420 // (and at this point it was expected to succeed), 421 // ignore the failure (leaving "changed" as false). 422 } 423 if (desired_new_size < new_size_before && eden()->is_empty()) { 424 // bail out of shrinking if objects in eden 425 size_t change = new_size_before - desired_new_size; 426 assert(change % alignment == 0, "just checking"); 427 _virtual_space.shrink_by(change); 428 changed = true; 429 } 430 if (changed) { 431 // The spaces have already been mangled at this point but 432 // may not have been cleared (set top = bottom) and should be. 433 // Mangling was done when the heap was being expanded. 434 compute_space_boundaries(eden()->used(), 435 SpaceDecorator::Clear, 436 SpaceDecorator::DontMangle); 437 MemRegion cmr((HeapWord*)_virtual_space.low(), 438 (HeapWord*)_virtual_space.high()); 439 gch->barrier_set()->resize_covered_region(cmr); 440 if (Verbose && PrintGC) { 441 size_t new_size_after = _virtual_space.committed_size(); 442 size_t eden_size_after = eden()->capacity(); 443 size_t survivor_size_after = from()->capacity(); 444 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->" 445 SIZE_FORMAT "K [eden=" 446 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 447 new_size_before/K, new_size_after/K, 448 eden_size_after/K, survivor_size_after/K); 449 if (WizardMode) { 450 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]", 451 thread_increase_size/K, threads_count); 452 } 453 gclog_or_tty->cr(); 454 } 455 } 456 } 457 458 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) { 459 assert(false, "NYI -- are you sure you want to call this?"); 460 } 461 462 463 size_t DefNewGeneration::capacity() const { 464 return eden()->capacity() 465 + from()->capacity(); // to() is only used during scavenge 466 } 467 468 469 size_t DefNewGeneration::used() const { 470 return eden()->used() 471 + from()->used(); // to() is only used during scavenge 472 } 473 474 475 size_t DefNewGeneration::free() const { 476 return eden()->free() 477 + from()->free(); // to() is only used during scavenge 478 } 479 480 size_t DefNewGeneration::max_capacity() const { 481 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 482 const size_t reserved_bytes = reserved().byte_size(); 483 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 484 } 485 486 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 487 return eden()->free(); 488 } 489 490 size_t DefNewGeneration::capacity_before_gc() const { 491 return eden()->capacity(); 492 } 493 494 size_t DefNewGeneration::contiguous_available() const { 495 return eden()->free(); 496 } 497 498 499 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); } 500 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 501 502 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 503 eden()->object_iterate(blk); 504 from()->object_iterate(blk); 505 } 506 507 508 void DefNewGeneration::space_iterate(SpaceClosure* blk, 509 bool usedOnly) { 510 blk->do_space(eden()); 511 blk->do_space(from()); 512 blk->do_space(to()); 513 } 514 515 // The last collection bailed out, we are running out of heap space, 516 // so we try to allocate the from-space, too. 517 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 518 HeapWord* result = NULL; 519 if (Verbose && PrintGCDetails) { 520 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):" 521 " will_fail: %s" 522 " heap_lock: %s" 523 " free: " SIZE_FORMAT, 524 size, 525 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 526 "true" : "false", 527 Heap_lock->is_locked() ? "locked" : "unlocked", 528 from()->free()); 529 } 530 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) { 531 if (Heap_lock->owned_by_self() || 532 (SafepointSynchronize::is_at_safepoint() && 533 Thread::current()->is_VM_thread())) { 534 // If the Heap_lock is not locked by this thread, this will be called 535 // again later with the Heap_lock held. 536 result = from()->allocate(size); 537 } else if (PrintGC && Verbose) { 538 gclog_or_tty->print_cr(" Heap_lock is not owned by self"); 539 } 540 } else if (PrintGC && Verbose) { 541 gclog_or_tty->print_cr(" should_allocate_from_space: NOT"); 542 } 543 if (PrintGC && Verbose) { 544 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object"); 545 } 546 return result; 547 } 548 549 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 550 bool is_tlab, 551 bool parallel) { 552 // We don't attempt to expand the young generation (but perhaps we should.) 553 return allocate(size, is_tlab); 554 } 555 556 void DefNewGeneration::adjust_desired_tenuring_threshold() { 557 // Set the desired survivor size to half the real survivor space 558 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters(); 559 _tenuring_threshold = 560 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters); 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 _old_gen = gch->old_gen(); 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 // These can be shared for all code paths 598 IsAliveClosure is_alive(this); 599 ScanWeakRefClosure scan_weak_ref(this); 600 601 age_table()->clear(); 602 to()->clear(SpaceDecorator::Mangle); 603 604 gch->rem_set()->prepare_for_younger_refs_iterate(false); 605 606 assert(gch->no_allocs_since_save_marks(0), 607 "save marks have not been newly set."); 608 609 // Not very pretty. 610 CollectorPolicy* cp = gch->collector_policy(); 611 612 FastScanClosure fsc_with_no_gc_barrier(this, false); 613 FastScanClosure fsc_with_gc_barrier(this, true); 614 615 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier, 616 gch->rem_set()->klass_rem_set()); 617 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure, 618 &fsc_with_no_gc_barrier, 619 false); 620 621 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 622 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this, 623 &fsc_with_no_gc_barrier, 624 &fsc_with_gc_barrier); 625 626 assert(gch->no_allocs_since_save_marks(0), 627 "save marks have not been newly set."); 628 629 { 630 // SerialGC runs with n_workers == 0. 631 StrongRootsScope srs(0); 632 633 gch->gen_process_roots(&srs, 634 _level, 635 true, // Process younger gens, if any, 636 // as strong roots. 637 GenCollectedHeap::SO_ScavengeCodeCache, 638 GenCollectedHeap::StrongAndWeakRoots, 639 &fsc_with_no_gc_barrier, 640 &fsc_with_gc_barrier, 641 &cld_scan_closure); 642 } 643 644 // "evacuate followers". 645 evacuate_followers.do_void(); 646 647 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 648 ReferenceProcessor* rp = ref_processor(); 649 rp->setup_policy(clear_all_soft_refs); 650 const ReferenceProcessorStats& stats = 651 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 652 NULL, _gc_timer, gc_tracer.gc_id()); 653 gc_tracer.report_gc_reference_stats(stats); 654 655 if (!_promotion_failed) { 656 // Swap the survivor spaces. 657 eden()->clear(SpaceDecorator::Mangle); 658 from()->clear(SpaceDecorator::Mangle); 659 if (ZapUnusedHeapArea) { 660 // This is now done here because of the piece-meal mangling which 661 // can check for valid mangling at intermediate points in the 662 // collection(s). When a minor collection fails to collect 663 // sufficient space resizing of the young generation can occur 664 // an redistribute the spaces in the young generation. Mangle 665 // here so that unzapped regions don't get distributed to 666 // other spaces. 667 to()->mangle_unused_area(); 668 } 669 swap_spaces(); 670 671 assert(to()->is_empty(), "to space should be empty now"); 672 673 adjust_desired_tenuring_threshold(); 674 675 // A successful scavenge should restart the GC time limit count which is 676 // for full GC's. 677 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 678 size_policy->reset_gc_overhead_limit_count(); 679 assert(!gch->incremental_collection_failed(), "Should be clear"); 680 } else { 681 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 682 _promo_failure_scan_stack.clear(true); // Clear cached segments. 683 684 remove_forwarding_pointers(); 685 if (PrintGCDetails) { 686 gclog_or_tty->print(" (promotion failed) "); 687 } 688 // Add to-space to the list of space to compact 689 // when a promotion failure has occurred. In that 690 // case there can be live objects in to-space 691 // as a result of a partial evacuation of eden 692 // and from-space. 693 swap_spaces(); // For uniformity wrt ParNewGeneration. 694 from()->set_next_compaction_space(to()); 695 gch->set_incremental_collection_failed(); 696 697 // Inform the next generation that a promotion failure occurred. 698 _old_gen->promotion_failure_occurred(); 699 gc_tracer.report_promotion_failed(_promotion_failed_info); 700 701 // Reset the PromotionFailureALot counters. 702 NOT_PRODUCT(gch->reset_promotion_should_fail();) 703 } 704 if (PrintGC && !PrintGCDetails) { 705 gch->print_heap_change(gch_prev_used); 706 } 707 // set new iteration safe limit for the survivor spaces 708 from()->set_concurrent_iteration_safe_limit(from()->top()); 709 to()->set_concurrent_iteration_safe_limit(to()->top()); 710 711 // We need to use a monotonically non-decreasing time in ms 712 // or we will see time-warp warnings and os::javaTimeMillis() 713 // does not guarantee monotonicity. 714 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 715 update_time_of_last_gc(now); 716 717 gch->trace_heap_after_gc(&gc_tracer); 718 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 719 720 _gc_timer->register_gc_end(); 721 722 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 723 } 724 725 class RemoveForwardPointerClosure: public ObjectClosure { 726 public: 727 void do_object(oop obj) { 728 obj->init_mark(); 729 } 730 }; 731 732 void DefNewGeneration::init_assuming_no_promotion_failure() { 733 _promotion_failed = false; 734 _promotion_failed_info.reset(); 735 from()->set_next_compaction_space(NULL); 736 } 737 738 void DefNewGeneration::remove_forwarding_pointers() { 739 RemoveForwardPointerClosure rspc; 740 eden()->object_iterate(&rspc); 741 from()->object_iterate(&rspc); 742 743 // Now restore saved marks, if any. 744 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(), 745 "should be the same"); 746 while (!_objs_with_preserved_marks.is_empty()) { 747 oop obj = _objs_with_preserved_marks.pop(); 748 markOop m = _preserved_marks_of_objs.pop(); 749 obj->set_mark(m); 750 } 751 _objs_with_preserved_marks.clear(true); 752 _preserved_marks_of_objs.clear(true); 753 } 754 755 void DefNewGeneration::preserve_mark(oop obj, markOop m) { 756 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj), 757 "Oversaving!"); 758 _objs_with_preserved_marks.push(obj); 759 _preserved_marks_of_objs.push(m); 760 } 761 762 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { 763 if (m->must_be_preserved_for_promotion_failure(obj)) { 764 preserve_mark(obj, m); 765 } 766 } 767 768 void DefNewGeneration::handle_promotion_failure(oop old) { 769 if (PrintPromotionFailure && !_promotion_failed) { 770 gclog_or_tty->print(" (promotion failure size = %d) ", 771 old->size()); 772 } 773 _promotion_failed = true; 774 _promotion_failed_info.register_copy_failure(old->size()); 775 preserve_mark_if_necessary(old, old->mark()); 776 // forward to self 777 old->forward_to(old); 778 779 _promo_failure_scan_stack.push(old); 780 781 if (!_promo_failure_drain_in_progress) { 782 // prevent recursion in copy_to_survivor_space() 783 _promo_failure_drain_in_progress = true; 784 drain_promo_failure_scan_stack(); 785 _promo_failure_drain_in_progress = false; 786 } 787 } 788 789 oop DefNewGeneration::copy_to_survivor_space(oop old) { 790 assert(is_in_reserved(old) && !old->is_forwarded(), 791 "shouldn't be scavenging this oop"); 792 size_t s = old->size(); 793 oop obj = NULL; 794 795 // Try allocating obj in to-space (unless too old) 796 if (old->age() < tenuring_threshold()) { 797 obj = (oop) to()->allocate_aligned(s); 798 } 799 800 // Otherwise try allocating obj tenured 801 if (obj == NULL) { 802 obj = _old_gen->promote(old, s); 803 if (obj == NULL) { 804 handle_promotion_failure(old); 805 return old; 806 } 807 } else { 808 // Prefetch beyond obj 809 const intx interval = PrefetchCopyIntervalInBytes; 810 Prefetch::write(obj, interval); 811 812 // Copy obj 813 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 814 815 // Increment age if obj still in new generation 816 obj->incr_age(); 817 age_table()->add(obj, s); 818 } 819 820 // Done, insert forward pointer to obj in this header 821 old->forward_to(obj); 822 823 return obj; 824 } 825 826 void DefNewGeneration::drain_promo_failure_scan_stack() { 827 while (!_promo_failure_scan_stack.is_empty()) { 828 oop obj = _promo_failure_scan_stack.pop(); 829 obj->oop_iterate(_promo_failure_scan_stack_closure); 830 } 831 } 832 833 void DefNewGeneration::save_marks() { 834 eden()->set_saved_mark(); 835 to()->set_saved_mark(); 836 from()->set_saved_mark(); 837 } 838 839 840 void DefNewGeneration::reset_saved_marks() { 841 eden()->reset_saved_mark(); 842 to()->reset_saved_mark(); 843 from()->reset_saved_mark(); 844 } 845 846 847 bool DefNewGeneration::no_allocs_since_save_marks() { 848 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 849 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 850 return to()->saved_mark_at_top(); 851 } 852 853 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 854 \ 855 void DefNewGeneration:: \ 856 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 857 cl->set_generation(this); \ 858 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 859 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 860 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 861 cl->reset_generation(); \ 862 save_marks(); \ 863 } 864 865 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 866 867 #undef DefNew_SINCE_SAVE_MARKS_DEFN 868 869 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 870 size_t max_alloc_words) { 871 if (requestor == this || _promotion_failed) return; 872 assert(requestor->level() > level(), "DefNewGeneration must be youngest"); 873 874 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 875 if (to_space->top() > to_space->bottom()) { 876 trace("to_space not empty when contribute_scratch called"); 877 } 878 */ 879 880 ContiguousSpace* to_space = to(); 881 assert(to_space->end() >= to_space->top(), "pointers out of order"); 882 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 883 if (free_words >= MinFreeScratchWords) { 884 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 885 sb->num_words = free_words; 886 sb->next = list; 887 list = sb; 888 } 889 } 890 891 void DefNewGeneration::reset_scratch() { 892 // If contributing scratch in to_space, mangle all of 893 // to_space if ZapUnusedHeapArea. This is needed because 894 // top is not maintained while using to-space as scratch. 895 if (ZapUnusedHeapArea) { 896 to()->mangle_unused_area_complete(); 897 } 898 } 899 900 bool DefNewGeneration::collection_attempt_is_safe() { 901 if (!to()->is_empty()) { 902 if (Verbose && PrintGCDetails) { 903 gclog_or_tty->print(" :: to is not empty :: "); 904 } 905 return false; 906 } 907 if (_old_gen == NULL) { 908 GenCollectedHeap* gch = GenCollectedHeap::heap(); 909 _old_gen = gch->old_gen(); 910 } 911 return _old_gen->promotion_attempt_is_safe(used()); 912 } 913 914 void DefNewGeneration::gc_epilogue(bool full) { 915 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 916 917 assert(!GC_locker::is_active(), "We should not be executing here"); 918 // Check if the heap is approaching full after a collection has 919 // been done. Generally the young generation is empty at 920 // a minimum at the end of a collection. If it is not, then 921 // the heap is approaching full. 922 GenCollectedHeap* gch = GenCollectedHeap::heap(); 923 if (full) { 924 DEBUG_ONLY(seen_incremental_collection_failed = false;) 925 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 926 if (Verbose && PrintGCDetails) { 927 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 928 GCCause::to_string(gch->gc_cause())); 929 } 930 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 931 set_should_allocate_from_space(); // we seem to be running out of space 932 } else { 933 if (Verbose && PrintGCDetails) { 934 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 935 GCCause::to_string(gch->gc_cause())); 936 } 937 gch->clear_incremental_collection_failed(); // We just did a full collection 938 clear_should_allocate_from_space(); // if set 939 } 940 } else { 941 #ifdef ASSERT 942 // It is possible that incremental_collection_failed() == true 943 // here, because an attempted scavenge did not succeed. The policy 944 // is normally expected to cause a full collection which should 945 // clear that condition, so we should not be here twice in a row 946 // with incremental_collection_failed() == true without having done 947 // a full collection in between. 948 if (!seen_incremental_collection_failed && 949 gch->incremental_collection_failed()) { 950 if (Verbose && PrintGCDetails) { 951 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 952 GCCause::to_string(gch->gc_cause())); 953 } 954 seen_incremental_collection_failed = true; 955 } else if (seen_incremental_collection_failed) { 956 if (Verbose && PrintGCDetails) { 957 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 958 GCCause::to_string(gch->gc_cause())); 959 } 960 assert(gch->gc_cause() == GCCause::_scavenge_alot || 961 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 962 !gch->incremental_collection_failed(), 963 "Twice in a row"); 964 seen_incremental_collection_failed = false; 965 } 966 #endif // ASSERT 967 } 968 969 if (ZapUnusedHeapArea) { 970 eden()->check_mangled_unused_area_complete(); 971 from()->check_mangled_unused_area_complete(); 972 to()->check_mangled_unused_area_complete(); 973 } 974 975 if (!CleanChunkPoolAsync) { 976 Chunk::clean_chunk_pool(); 977 } 978 979 // update the generation and space performance counters 980 update_counters(); 981 gch->collector_policy()->counters()->update_counters(); 982 } 983 984 void DefNewGeneration::record_spaces_top() { 985 assert(ZapUnusedHeapArea, "Not mangling unused space"); 986 eden()->set_top_for_allocations(); 987 to()->set_top_for_allocations(); 988 from()->set_top_for_allocations(); 989 } 990 991 void DefNewGeneration::ref_processor_init() { 992 Generation::ref_processor_init(); 993 } 994 995 996 void DefNewGeneration::update_counters() { 997 if (UsePerfData) { 998 _eden_counters->update_all(); 999 _from_counters->update_all(); 1000 _to_counters->update_all(); 1001 _gen_counters->update_all(); 1002 } 1003 } 1004 1005 void DefNewGeneration::verify() { 1006 eden()->verify(); 1007 from()->verify(); 1008 to()->verify(); 1009 } 1010 1011 void DefNewGeneration::print_on(outputStream* st) const { 1012 Generation::print_on(st); 1013 st->print(" eden"); 1014 eden()->print_on(st); 1015 st->print(" from"); 1016 from()->print_on(st); 1017 st->print(" to "); 1018 to()->print_on(st); 1019 } 1020 1021 1022 const char* DefNewGeneration::name() const { 1023 return "def new generation"; 1024 } 1025 1026 // Moved from inline file as they are not called inline 1027 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 1028 return eden(); 1029 } 1030 1031 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 1032 // This is the slow-path allocation for the DefNewGeneration. 1033 // Most allocations are fast-path in compiled code. 1034 // We try to allocate from the eden. If that works, we are happy. 1035 // Note that since DefNewGeneration supports lock-free allocation, we 1036 // have to use it here, as well. 1037 HeapWord* result = eden()->par_allocate(word_size); 1038 if (result != NULL) { 1039 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1040 _old_gen->sample_eden_chunk(); 1041 } 1042 } else { 1043 // If the eden is full and the last collection bailed out, we are running 1044 // out of heap space, and we try to allocate the from-space, too. 1045 // allocate_from_space can't be inlined because that would introduce a 1046 // circular dependency at compile time. 1047 result = allocate_from_space(word_size); 1048 } 1049 return result; 1050 } 1051 1052 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1053 bool is_tlab) { 1054 HeapWord* res = eden()->par_allocate(word_size); 1055 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1056 _old_gen->sample_eden_chunk(); 1057 } 1058 return res; 1059 } 1060 1061 size_t DefNewGeneration::tlab_capacity() const { 1062 return eden()->capacity(); 1063 } 1064 1065 size_t DefNewGeneration::tlab_used() const { 1066 return eden()->used(); 1067 } 1068 1069 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1070 return unsafe_max_alloc_nogc(); 1071 }