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 52 // 53 // DefNewGeneration functions. 54 55 // Methods of protected closure types. 56 57 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) { 58 assert(g->level() == 0, "Optimized for youngest gen."); 59 } 60 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 61 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded(); 62 } 63 64 DefNewGeneration::KeepAliveClosure:: 65 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 66 GenRemSet* rs = GenCollectedHeap::heap()->rem_set(); 67 _rs = (CardTableRS*)rs; 68 } 69 70 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 71 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 72 73 74 DefNewGeneration::FastKeepAliveClosure:: 75 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 76 DefNewGeneration::KeepAliveClosure(cl) { 77 _boundary = g->reserved().end(); 78 } 79 80 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 81 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 82 83 DefNewGeneration::EvacuateFollowersClosure:: 84 EvacuateFollowersClosure(GenCollectedHeap* gch, int level, 85 ScanClosure* cur, ScanClosure* older) : 86 _gch(gch), _level(level), 87 _scan_cur_or_nonheap(cur), _scan_older(older) 88 {} 89 90 void DefNewGeneration::EvacuateFollowersClosure::do_void() { 91 do { 92 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap, 93 _scan_older); 94 } while (!_gch->no_allocs_since_save_marks(_level)); 95 } 96 97 DefNewGeneration::FastEvacuateFollowersClosure:: 98 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level, 99 DefNewGeneration* gen, 100 FastScanClosure* cur, FastScanClosure* older) : 101 _gch(gch), _level(level), _gen(gen), 102 _scan_cur_or_nonheap(cur), _scan_older(older) 103 {} 104 105 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 106 do { 107 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap, 108 _scan_older); 109 } while (!_gch->no_allocs_since_save_marks(_level)); 110 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan"); 111 } 112 113 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 114 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 115 { 116 assert(_g->level() == 0, "Optimized for youngest generation"); 117 _boundary = _g->reserved().end(); 118 } 119 120 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); } 121 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); } 122 123 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 124 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 125 { 126 assert(_g->level() == 0, "Optimized for youngest generation"); 127 _boundary = _g->reserved().end(); 128 } 129 130 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); } 131 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); } 132 133 void KlassScanClosure::do_klass(Klass* klass) { 134 #ifndef PRODUCT 135 if (TraceScavenge) { 136 ResourceMark rm; 137 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s", 138 p2i(klass), 139 klass->external_name(), 140 klass->has_modified_oops() ? "true" : "false"); 141 } 142 #endif 143 144 // If the klass has not been dirtied we know that there's 145 // no references into the young gen and we can skip it. 146 if (klass->has_modified_oops()) { 147 if (_accumulate_modified_oops) { 148 klass->accumulate_modified_oops(); 149 } 150 151 // Clear this state since we're going to scavenge all the metadata. 152 klass->clear_modified_oops(); 153 154 // Tell the closure which Klass is being scanned so that it can be dirtied 155 // if oops are left pointing into the young gen. 156 _scavenge_closure->set_scanned_klass(klass); 157 158 klass->oops_do(_scavenge_closure); 159 160 _scavenge_closure->set_scanned_klass(NULL); 161 } 162 } 163 164 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 165 _g(g) 166 { 167 assert(_g->level() == 0, "Optimized for youngest generation"); 168 _boundary = _g->reserved().end(); 169 } 170 171 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); } 172 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); } 173 174 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); } 175 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); } 176 177 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure, 178 KlassRemSet* klass_rem_set) 179 : _scavenge_closure(scavenge_closure), 180 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {} 181 182 183 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 184 size_t initial_size, 185 int level, 186 const char* policy) 187 : Generation(rs, initial_size, level), 188 _promo_failure_drain_in_progress(false), 189 _should_allocate_from_space(false) 190 { 191 MemRegion cmr((HeapWord*)_virtual_space.low(), 192 (HeapWord*)_virtual_space.high()); 193 Universe::heap()->barrier_set()->resize_covered_region(cmr); 194 195 _eden_space = new ContiguousSpace(); 196 _from_space = new ContiguousSpace(); 197 _to_space = new ContiguousSpace(); 198 199 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) 200 vm_exit_during_initialization("Could not allocate a new gen space"); 201 202 // Compute the maximum eden and survivor space sizes. These sizes 203 // are computed assuming the entire reserved space is committed. 204 // These values are exported as performance counters. 205 uintx alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 206 uintx size = _virtual_space.reserved_size(); 207 _max_survivor_size = compute_survivor_size(size, alignment); 208 _max_eden_size = size - (2*_max_survivor_size); 209 210 // allocate the performance counters 211 GenCollectorPolicy* gcp = (GenCollectorPolicy*) GenCollectedHeap::heap()->collector_policy(); 212 213 // Generation counters -- generation 0, 3 subspaces 214 _gen_counters = new GenerationCounters("new", 0, 3, 215 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space); 216 _gc_counters = new CollectorCounters(policy, 0); 217 218 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 219 _gen_counters); 220 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 221 _gen_counters); 222 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 223 _gen_counters); 224 225 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 226 update_counters(); 227 _old_gen = NULL; 228 _tenuring_threshold = MaxTenuringThreshold; 229 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 230 231 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 232 } 233 234 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 235 bool clear_space, 236 bool mangle_space) { 237 uintx alignment = 238 GenCollectedHeap::heap()->collector_policy()->space_alignment(); 239 240 // If the spaces are being cleared (only done at heap initialization 241 // currently), the survivor spaces need not be empty. 242 // Otherwise, no care is taken for used areas in the survivor spaces 243 // so check. 244 assert(clear_space || (to()->is_empty() && from()->is_empty()), 245 "Initialization of the survivor spaces assumes these are empty"); 246 247 // Compute sizes 248 uintx size = _virtual_space.committed_size(); 249 uintx survivor_size = compute_survivor_size(size, alignment); 250 uintx eden_size = size - (2*survivor_size); 251 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 252 253 if (eden_size < minimum_eden_size) { 254 // May happen due to 64Kb rounding, if so adjust eden size back up 255 minimum_eden_size = align_size_up(minimum_eden_size, alignment); 256 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 257 uintx unaligned_survivor_size = 258 align_size_down(maximum_survivor_size, alignment); 259 survivor_size = MAX2(unaligned_survivor_size, alignment); 260 eden_size = size - (2*survivor_size); 261 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 262 assert(eden_size >= minimum_eden_size, "just checking"); 263 } 264 265 char *eden_start = _virtual_space.low(); 266 char *from_start = eden_start + eden_size; 267 char *to_start = from_start + survivor_size; 268 char *to_end = to_start + survivor_size; 269 270 assert(to_end == _virtual_space.high(), "just checking"); 271 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment"); 272 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment"); 273 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment"); 274 275 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 276 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 277 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 278 279 // A minimum eden size implies that there is a part of eden that 280 // is being used and that affects the initialization of any 281 // newly formed eden. 282 bool live_in_eden = minimum_eden_size > 0; 283 284 // If not clearing the spaces, do some checking to verify that 285 // the space are already mangled. 286 if (!clear_space) { 287 // Must check mangling before the spaces are reshaped. Otherwise, 288 // the bottom or end of one space may have moved into another 289 // a failure of the check may not correctly indicate which space 290 // is not properly mangled. 291 if (ZapUnusedHeapArea) { 292 HeapWord* limit = (HeapWord*) _virtual_space.high(); 293 eden()->check_mangled_unused_area(limit); 294 from()->check_mangled_unused_area(limit); 295 to()->check_mangled_unused_area(limit); 296 } 297 } 298 299 // Reset the spaces for their new regions. 300 eden()->initialize(edenMR, 301 clear_space && !live_in_eden, 302 SpaceDecorator::Mangle); 303 // If clear_space and live_in_eden, we will not have cleared any 304 // portion of eden above its top. This can cause newly 305 // expanded space not to be mangled if using ZapUnusedHeapArea. 306 // We explicitly do such mangling here. 307 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 308 eden()->mangle_unused_area(); 309 } 310 from()->initialize(fromMR, clear_space, mangle_space); 311 to()->initialize(toMR, clear_space, mangle_space); 312 313 // Set next compaction spaces. 314 eden()->set_next_compaction_space(from()); 315 // The to-space is normally empty before a compaction so need 316 // not be considered. The exception is during promotion 317 // failure handling when to-space can contain live objects. 318 from()->set_next_compaction_space(NULL); 319 } 320 321 void DefNewGeneration::swap_spaces() { 322 ContiguousSpace* s = from(); 323 _from_space = to(); 324 _to_space = s; 325 eden()->set_next_compaction_space(from()); 326 // The to-space is normally empty before a compaction so need 327 // not be considered. The exception is during promotion 328 // failure handling when to-space can contain live objects. 329 from()->set_next_compaction_space(NULL); 330 331 if (UsePerfData) { 332 CSpaceCounters* c = _from_counters; 333 _from_counters = _to_counters; 334 _to_counters = c; 335 } 336 } 337 338 bool DefNewGeneration::expand(size_t bytes) { 339 MutexLocker x(ExpandHeap_lock); 340 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 341 bool success = _virtual_space.expand_by(bytes); 342 if (success && ZapUnusedHeapArea) { 343 // Mangle newly committed space immediately because it 344 // can be done here more simply that after the new 345 // spaces have been computed. 346 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 347 MemRegion mangle_region(prev_high, new_high); 348 SpaceMangler::mangle_region(mangle_region); 349 } 350 351 // Do not attempt an expand-to-the reserve size. The 352 // request should properly observe the maximum size of 353 // the generation so an expand-to-reserve should be 354 // unnecessary. Also a second call to expand-to-reserve 355 // value potentially can cause an undue expansion. 356 // For example if the first expand fail for unknown reasons, 357 // but the second succeeds and expands the heap to its maximum 358 // value. 359 if (GC_locker::is_active()) { 360 if (PrintGC && Verbose) { 361 gclog_or_tty->print_cr("Garbage collection disabled, " 362 "expanded heap instead"); 363 } 364 } 365 366 return success; 367 } 368 369 370 void DefNewGeneration::compute_new_size() { 371 // This is called after a gc that includes the following generation 372 // (which is required to exist.) So from-space will normally be empty. 373 // Note that we check both spaces, since if scavenge failed they revert roles. 374 // If not we bail out (otherwise we would have to relocate the objects) 375 if (!from()->is_empty() || !to()->is_empty()) { 376 return; 377 } 378 379 int next_level = level() + 1; 380 GenCollectedHeap* gch = GenCollectedHeap::heap(); 381 assert(next_level < gch->n_gens(), 382 "DefNewGeneration cannot be an oldest gen"); 383 384 Generation* old_gen = gch->old_gen(); 385 size_t old_size = old_gen->capacity(); 386 size_t new_size_before = _virtual_space.committed_size(); 387 size_t min_new_size = spec()->init_size(); 388 size_t max_new_size = reserved().byte_size(); 389 assert(min_new_size <= new_size_before && 390 new_size_before <= max_new_size, 391 "just checking"); 392 // All space sizes must be multiples of Generation::GenGrain. 393 size_t alignment = Generation::GenGrain; 394 395 // Compute desired new generation size based on NewRatio and 396 // NewSizeThreadIncrease 397 size_t desired_new_size = old_size/NewRatio; 398 int threads_count = Threads::number_of_non_daemon_threads(); 399 size_t thread_increase_size = threads_count * NewSizeThreadIncrease; 400 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment); 401 402 // Adjust new generation size 403 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 404 assert(desired_new_size <= max_new_size, "just checking"); 405 406 bool changed = false; 407 if (desired_new_size > new_size_before) { 408 size_t change = desired_new_size - new_size_before; 409 assert(change % alignment == 0, "just checking"); 410 if (expand(change)) { 411 changed = true; 412 } 413 // If the heap failed to expand to the desired size, 414 // "changed" will be false. If the expansion failed 415 // (and at this point it was expected to succeed), 416 // ignore the failure (leaving "changed" as false). 417 } 418 if (desired_new_size < new_size_before && eden()->is_empty()) { 419 // bail out of shrinking if objects in eden 420 size_t change = new_size_before - desired_new_size; 421 assert(change % alignment == 0, "just checking"); 422 _virtual_space.shrink_by(change); 423 changed = true; 424 } 425 if (changed) { 426 // The spaces have already been mangled at this point but 427 // may not have been cleared (set top = bottom) and should be. 428 // Mangling was done when the heap was being expanded. 429 compute_space_boundaries(eden()->used(), 430 SpaceDecorator::Clear, 431 SpaceDecorator::DontMangle); 432 MemRegion cmr((HeapWord*)_virtual_space.low(), 433 (HeapWord*)_virtual_space.high()); 434 Universe::heap()->barrier_set()->resize_covered_region(cmr); 435 if (Verbose && PrintGC) { 436 size_t new_size_after = _virtual_space.committed_size(); 437 size_t eden_size_after = eden()->capacity(); 438 size_t survivor_size_after = from()->capacity(); 439 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->" 440 SIZE_FORMAT "K [eden=" 441 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 442 new_size_before/K, new_size_after/K, 443 eden_size_after/K, survivor_size_after/K); 444 if (WizardMode) { 445 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]", 446 thread_increase_size/K, threads_count); 447 } 448 gclog_or_tty->cr(); 449 } 450 } 451 } 452 453 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) { 454 assert(false, "NYI -- are you sure you want to call this?"); 455 } 456 457 458 size_t DefNewGeneration::capacity() const { 459 return eden()->capacity() 460 + from()->capacity(); // to() is only used during scavenge 461 } 462 463 464 size_t DefNewGeneration::used() const { 465 return eden()->used() 466 + from()->used(); // to() is only used during scavenge 467 } 468 469 470 size_t DefNewGeneration::free() const { 471 return eden()->free() 472 + from()->free(); // to() is only used during scavenge 473 } 474 475 size_t DefNewGeneration::max_capacity() const { 476 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 477 const size_t reserved_bytes = reserved().byte_size(); 478 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 479 } 480 481 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 482 return eden()->free(); 483 } 484 485 size_t DefNewGeneration::capacity_before_gc() const { 486 return eden()->capacity(); 487 } 488 489 size_t DefNewGeneration::contiguous_available() const { 490 return eden()->free(); 491 } 492 493 494 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); } 495 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 496 497 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 498 eden()->object_iterate(blk); 499 from()->object_iterate(blk); 500 } 501 502 503 void DefNewGeneration::space_iterate(SpaceClosure* blk, 504 bool usedOnly) { 505 blk->do_space(eden()); 506 blk->do_space(from()); 507 blk->do_space(to()); 508 } 509 510 // The last collection bailed out, we are running out of heap space, 511 // so we try to allocate the from-space, too. 512 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 513 HeapWord* result = NULL; 514 if (Verbose && PrintGCDetails) { 515 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):" 516 " will_fail: %s" 517 " heap_lock: %s" 518 " free: " SIZE_FORMAT, 519 size, 520 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 521 "true" : "false", 522 Heap_lock->is_locked() ? "locked" : "unlocked", 523 from()->free()); 524 } 525 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) { 526 if (Heap_lock->owned_by_self() || 527 (SafepointSynchronize::is_at_safepoint() && 528 Thread::current()->is_VM_thread())) { 529 // If the Heap_lock is not locked by this thread, this will be called 530 // again later with the Heap_lock held. 531 result = from()->allocate(size); 532 } else if (PrintGC && Verbose) { 533 gclog_or_tty->print_cr(" Heap_lock is not owned by self"); 534 } 535 } else if (PrintGC && Verbose) { 536 gclog_or_tty->print_cr(" should_allocate_from_space: NOT"); 537 } 538 if (PrintGC && Verbose) { 539 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object"); 540 } 541 return result; 542 } 543 544 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 545 bool is_tlab, 546 bool parallel) { 547 // We don't attempt to expand the young generation (but perhaps we should.) 548 return allocate(size, is_tlab); 549 } 550 551 void DefNewGeneration::adjust_desired_tenuring_threshold() { 552 // Set the desired survivor size to half the real survivor space 553 _tenuring_threshold = 554 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize); 555 } 556 557 void DefNewGeneration::collect(bool full, 558 bool clear_all_soft_refs, 559 size_t size, 560 bool is_tlab) { 561 assert(full || size > 0, "otherwise we don't want to collect"); 562 563 GenCollectedHeap* gch = GenCollectedHeap::heap(); 564 565 _gc_timer->register_gc_start(); 566 DefNewTracer gc_tracer; 567 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); 568 569 _old_gen = gch->old_gen(); 570 571 // If the next generation is too full to accommodate promotion 572 // from this generation, pass on collection; let the next generation 573 // do it. 574 if (!collection_attempt_is_safe()) { 575 if (Verbose && PrintGCDetails) { 576 gclog_or_tty->print(" :: Collection attempt not safe :: "); 577 } 578 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 579 return; 580 } 581 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 582 583 init_assuming_no_promotion_failure(); 584 585 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id()); 586 // Capture heap used before collection (for printing). 587 size_t gch_prev_used = gch->used(); 588 589 gch->trace_heap_before_gc(&gc_tracer); 590 591 // These can be shared for all code paths 592 IsAliveClosure is_alive(this); 593 ScanWeakRefClosure scan_weak_ref(this); 594 595 age_table()->clear(); 596 to()->clear(SpaceDecorator::Mangle); 597 598 gch->rem_set()->prepare_for_younger_refs_iterate(false); 599 600 assert(gch->no_allocs_since_save_marks(0), 601 "save marks have not been newly set."); 602 603 // Not very pretty. 604 CollectorPolicy* cp = gch->collector_policy(); 605 606 FastScanClosure fsc_with_no_gc_barrier(this, false); 607 FastScanClosure fsc_with_gc_barrier(this, true); 608 609 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier, 610 gch->rem_set()->klass_rem_set()); 611 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure, 612 &fsc_with_no_gc_barrier, 613 false); 614 615 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 616 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this, 617 &fsc_with_no_gc_barrier, 618 &fsc_with_gc_barrier); 619 620 assert(gch->no_allocs_since_save_marks(0), 621 "save marks have not been newly set."); 622 623 gch->gen_process_roots(_level, 624 true, // Process younger gens, if any, 625 // as strong roots. 626 true, // activate StrongRootsScope 627 GenCollectedHeap::SO_ScavengeCodeCache, 628 GenCollectedHeap::StrongAndWeakRoots, 629 &fsc_with_no_gc_barrier, 630 &fsc_with_gc_barrier, 631 &cld_scan_closure); 632 633 // "evacuate followers". 634 evacuate_followers.do_void(); 635 636 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 637 ReferenceProcessor* rp = ref_processor(); 638 rp->setup_policy(clear_all_soft_refs); 639 const ReferenceProcessorStats& stats = 640 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 641 NULL, _gc_timer, gc_tracer.gc_id()); 642 gc_tracer.report_gc_reference_stats(stats); 643 644 if (!_promotion_failed) { 645 // Swap the survivor spaces. 646 eden()->clear(SpaceDecorator::Mangle); 647 from()->clear(SpaceDecorator::Mangle); 648 if (ZapUnusedHeapArea) { 649 // This is now done here because of the piece-meal mangling which 650 // can check for valid mangling at intermediate points in the 651 // collection(s). When a minor collection fails to collect 652 // sufficient space resizing of the young generation can occur 653 // an redistribute the spaces in the young generation. Mangle 654 // here so that unzapped regions don't get distributed to 655 // other spaces. 656 to()->mangle_unused_area(); 657 } 658 swap_spaces(); 659 660 assert(to()->is_empty(), "to space should be empty now"); 661 662 adjust_desired_tenuring_threshold(); 663 664 // A successful scavenge should restart the GC time limit count which is 665 // for full GC's. 666 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 667 size_policy->reset_gc_overhead_limit_count(); 668 assert(!gch->incremental_collection_failed(), "Should be clear"); 669 } else { 670 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 671 _promo_failure_scan_stack.clear(true); // Clear cached segments. 672 673 remove_forwarding_pointers(); 674 if (PrintGCDetails) { 675 gclog_or_tty->print(" (promotion failed) "); 676 } 677 // Add to-space to the list of space to compact 678 // when a promotion failure has occurred. In that 679 // case there can be live objects in to-space 680 // as a result of a partial evacuation of eden 681 // and from-space. 682 swap_spaces(); // For uniformity wrt ParNewGeneration. 683 from()->set_next_compaction_space(to()); 684 gch->set_incremental_collection_failed(); 685 686 // Inform the next generation that a promotion failure occurred. 687 _old_gen->promotion_failure_occurred(); 688 gc_tracer.report_promotion_failed(_promotion_failed_info); 689 690 // Reset the PromotionFailureALot counters. 691 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();) 692 } 693 if (PrintGC && !PrintGCDetails) { 694 gch->print_heap_change(gch_prev_used); 695 } 696 // set new iteration safe limit for the survivor spaces 697 from()->set_concurrent_iteration_safe_limit(from()->top()); 698 to()->set_concurrent_iteration_safe_limit(to()->top()); 699 700 // We need to use a monotonically non-decreasing time in ms 701 // or we will see time-warp warnings and os::javaTimeMillis() 702 // does not guarantee monotonicity. 703 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 704 update_time_of_last_gc(now); 705 706 gch->trace_heap_after_gc(&gc_tracer); 707 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 708 709 _gc_timer->register_gc_end(); 710 711 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 712 } 713 714 class RemoveForwardPointerClosure: public ObjectClosure { 715 public: 716 void do_object(oop obj) { 717 obj->init_mark(); 718 } 719 }; 720 721 void DefNewGeneration::init_assuming_no_promotion_failure() { 722 _promotion_failed = false; 723 _promotion_failed_info.reset(); 724 from()->set_next_compaction_space(NULL); 725 } 726 727 void DefNewGeneration::remove_forwarding_pointers() { 728 RemoveForwardPointerClosure rspc; 729 eden()->object_iterate(&rspc); 730 from()->object_iterate(&rspc); 731 732 // Now restore saved marks, if any. 733 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(), 734 "should be the same"); 735 while (!_objs_with_preserved_marks.is_empty()) { 736 oop obj = _objs_with_preserved_marks.pop(); 737 markOop m = _preserved_marks_of_objs.pop(); 738 obj->set_mark(m); 739 } 740 _objs_with_preserved_marks.clear(true); 741 _preserved_marks_of_objs.clear(true); 742 } 743 744 void DefNewGeneration::preserve_mark(oop obj, markOop m) { 745 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj), 746 "Oversaving!"); 747 _objs_with_preserved_marks.push(obj); 748 _preserved_marks_of_objs.push(m); 749 } 750 751 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { 752 if (m->must_be_preserved_for_promotion_failure(obj)) { 753 preserve_mark(obj, m); 754 } 755 } 756 757 void DefNewGeneration::handle_promotion_failure(oop old) { 758 if (PrintPromotionFailure && !_promotion_failed) { 759 gclog_or_tty->print(" (promotion failure size = %d) ", 760 old->size()); 761 } 762 _promotion_failed = true; 763 _promotion_failed_info.register_copy_failure(old->size()); 764 preserve_mark_if_necessary(old, old->mark()); 765 // forward to self 766 old->forward_to(old); 767 768 _promo_failure_scan_stack.push(old); 769 770 if (!_promo_failure_drain_in_progress) { 771 // prevent recursion in copy_to_survivor_space() 772 _promo_failure_drain_in_progress = true; 773 drain_promo_failure_scan_stack(); 774 _promo_failure_drain_in_progress = false; 775 } 776 } 777 778 oop DefNewGeneration::copy_to_survivor_space(oop old) { 779 assert(is_in_reserved(old) && !old->is_forwarded(), 780 "shouldn't be scavenging this oop"); 781 size_t s = old->size(); 782 oop obj = NULL; 783 784 // Try allocating obj in to-space (unless too old) 785 if (old->age() < tenuring_threshold()) { 786 obj = (oop) to()->allocate_aligned(s); 787 } 788 789 // Otherwise try allocating obj tenured 790 if (obj == NULL) { 791 obj = _old_gen->promote(old, s); 792 if (obj == NULL) { 793 handle_promotion_failure(old); 794 return old; 795 } 796 } else { 797 // Prefetch beyond obj 798 const intx interval = PrefetchCopyIntervalInBytes; 799 Prefetch::write(obj, interval); 800 801 // Copy obj 802 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 803 804 // Increment age if obj still in new generation 805 obj->incr_age(); 806 age_table()->add(obj, s); 807 } 808 809 // Done, insert forward pointer to obj in this header 810 old->forward_to(obj); 811 812 return obj; 813 } 814 815 void DefNewGeneration::drain_promo_failure_scan_stack() { 816 while (!_promo_failure_scan_stack.is_empty()) { 817 oop obj = _promo_failure_scan_stack.pop(); 818 obj->oop_iterate(_promo_failure_scan_stack_closure); 819 } 820 } 821 822 void DefNewGeneration::save_marks() { 823 eden()->set_saved_mark(); 824 to()->set_saved_mark(); 825 from()->set_saved_mark(); 826 } 827 828 829 void DefNewGeneration::reset_saved_marks() { 830 eden()->reset_saved_mark(); 831 to()->reset_saved_mark(); 832 from()->reset_saved_mark(); 833 } 834 835 836 bool DefNewGeneration::no_allocs_since_save_marks() { 837 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 838 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 839 return to()->saved_mark_at_top(); 840 } 841 842 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 843 \ 844 void DefNewGeneration:: \ 845 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 846 cl->set_generation(this); \ 847 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 848 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 849 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 850 cl->reset_generation(); \ 851 save_marks(); \ 852 } 853 854 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 855 856 #undef DefNew_SINCE_SAVE_MARKS_DEFN 857 858 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 859 size_t max_alloc_words) { 860 if (requestor == this || _promotion_failed) return; 861 assert(requestor->level() > level(), "DefNewGeneration must be youngest"); 862 863 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 864 if (to_space->top() > to_space->bottom()) { 865 trace("to_space not empty when contribute_scratch called"); 866 } 867 */ 868 869 ContiguousSpace* to_space = to(); 870 assert(to_space->end() >= to_space->top(), "pointers out of order"); 871 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 872 if (free_words >= MinFreeScratchWords) { 873 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 874 sb->num_words = free_words; 875 sb->next = list; 876 list = sb; 877 } 878 } 879 880 void DefNewGeneration::reset_scratch() { 881 // If contributing scratch in to_space, mangle all of 882 // to_space if ZapUnusedHeapArea. This is needed because 883 // top is not maintained while using to-space as scratch. 884 if (ZapUnusedHeapArea) { 885 to()->mangle_unused_area_complete(); 886 } 887 } 888 889 bool DefNewGeneration::collection_attempt_is_safe() { 890 if (!to()->is_empty()) { 891 if (Verbose && PrintGCDetails) { 892 gclog_or_tty->print(" :: to is not empty :: "); 893 } 894 return false; 895 } 896 if (_old_gen == NULL) { 897 GenCollectedHeap* gch = GenCollectedHeap::heap(); 898 _old_gen = gch->old_gen(); 899 } 900 return _old_gen->promotion_attempt_is_safe(used()); 901 } 902 903 void DefNewGeneration::gc_epilogue(bool full) { 904 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 905 906 assert(!GC_locker::is_active(), "We should not be executing here"); 907 // Check if the heap is approaching full after a collection has 908 // been done. Generally the young generation is empty at 909 // a minimum at the end of a collection. If it is not, then 910 // the heap is approaching full. 911 GenCollectedHeap* gch = GenCollectedHeap::heap(); 912 if (full) { 913 DEBUG_ONLY(seen_incremental_collection_failed = false;) 914 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 915 if (Verbose && PrintGCDetails) { 916 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 917 GCCause::to_string(gch->gc_cause())); 918 } 919 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 920 set_should_allocate_from_space(); // we seem to be running out of space 921 } else { 922 if (Verbose && PrintGCDetails) { 923 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 924 GCCause::to_string(gch->gc_cause())); 925 } 926 gch->clear_incremental_collection_failed(); // We just did a full collection 927 clear_should_allocate_from_space(); // if set 928 } 929 } else { 930 #ifdef ASSERT 931 // It is possible that incremental_collection_failed() == true 932 // here, because an attempted scavenge did not succeed. The policy 933 // is normally expected to cause a full collection which should 934 // clear that condition, so we should not be here twice in a row 935 // with incremental_collection_failed() == true without having done 936 // a full collection in between. 937 if (!seen_incremental_collection_failed && 938 gch->incremental_collection_failed()) { 939 if (Verbose && PrintGCDetails) { 940 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 941 GCCause::to_string(gch->gc_cause())); 942 } 943 seen_incremental_collection_failed = true; 944 } else if (seen_incremental_collection_failed) { 945 if (Verbose && PrintGCDetails) { 946 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 947 GCCause::to_string(gch->gc_cause())); 948 } 949 assert(gch->gc_cause() == GCCause::_scavenge_alot || 950 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 951 !gch->incremental_collection_failed(), 952 "Twice in a row"); 953 seen_incremental_collection_failed = false; 954 } 955 #endif // ASSERT 956 } 957 958 if (ZapUnusedHeapArea) { 959 eden()->check_mangled_unused_area_complete(); 960 from()->check_mangled_unused_area_complete(); 961 to()->check_mangled_unused_area_complete(); 962 } 963 964 if (!CleanChunkPoolAsync) { 965 Chunk::clean_chunk_pool(); 966 } 967 968 // update the generation and space performance counters 969 update_counters(); 970 gch->collector_policy()->counters()->update_counters(); 971 } 972 973 void DefNewGeneration::record_spaces_top() { 974 assert(ZapUnusedHeapArea, "Not mangling unused space"); 975 eden()->set_top_for_allocations(); 976 to()->set_top_for_allocations(); 977 from()->set_top_for_allocations(); 978 } 979 980 void DefNewGeneration::ref_processor_init() { 981 Generation::ref_processor_init(); 982 } 983 984 985 void DefNewGeneration::update_counters() { 986 if (UsePerfData) { 987 _eden_counters->update_all(); 988 _from_counters->update_all(); 989 _to_counters->update_all(); 990 _gen_counters->update_all(); 991 } 992 } 993 994 void DefNewGeneration::verify() { 995 eden()->verify(); 996 from()->verify(); 997 to()->verify(); 998 } 999 1000 void DefNewGeneration::print_on(outputStream* st) const { 1001 Generation::print_on(st); 1002 st->print(" eden"); 1003 eden()->print_on(st); 1004 st->print(" from"); 1005 from()->print_on(st); 1006 st->print(" to "); 1007 to()->print_on(st); 1008 } 1009 1010 1011 const char* DefNewGeneration::name() const { 1012 return "def new generation"; 1013 } 1014 1015 // Moved from inline file as they are not called inline 1016 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 1017 return eden(); 1018 } 1019 1020 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 1021 // This is the slow-path allocation for the DefNewGeneration. 1022 // Most allocations are fast-path in compiled code. 1023 // We try to allocate from the eden. If that works, we are happy. 1024 // Note that since DefNewGeneration supports lock-free allocation, we 1025 // have to use it here, as well. 1026 HeapWord* result = eden()->par_allocate(word_size); 1027 if (result != NULL) { 1028 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1029 _old_gen->sample_eden_chunk(); 1030 } 1031 } else { 1032 // If the eden is full and the last collection bailed out, we are running 1033 // out of heap space, and we try to allocate the from-space, too. 1034 // allocate_from_space can't be inlined because that would introduce a 1035 // circular dependency at compile time. 1036 result = allocate_from_space(word_size); 1037 } 1038 return result; 1039 } 1040 1041 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1042 bool is_tlab) { 1043 HeapWord* res = eden()->par_allocate(word_size); 1044 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1045 _old_gen->sample_eden_chunk(); 1046 } 1047 return res; 1048 } 1049 1050 size_t DefNewGeneration::tlab_capacity() const { 1051 return eden()->capacity(); 1052 } 1053 1054 size_t DefNewGeneration::tlab_used() const { 1055 return eden()->used(); 1056 } 1057 1058 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1059 return unsafe_max_alloc_nogc(); 1060 }