1 /* 2 * Copyright (c) 2001, 2013, 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/java.hpp" 45 #include "runtime/thread.inline.hpp" 46 #include "utilities/copy.hpp" 47 #include "utilities/stack.inline.hpp" 48 49 // 50 // DefNewGeneration functions. 51 52 // Methods of protected closure types. 53 54 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) { 55 assert(g->level() == 0, "Optimized for youngest gen."); 56 } 57 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 58 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded(); 59 } 60 61 DefNewGeneration::KeepAliveClosure:: 62 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 63 GenRemSet* rs = GenCollectedHeap::heap()->rem_set(); 64 assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind."); 65 _rs = (CardTableRS*)rs; 66 } 67 68 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 69 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 70 71 72 DefNewGeneration::FastKeepAliveClosure:: 73 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 74 DefNewGeneration::KeepAliveClosure(cl) { 75 _boundary = g->reserved().end(); 76 } 77 78 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 79 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 80 81 DefNewGeneration::EvacuateFollowersClosure:: 82 EvacuateFollowersClosure(GenCollectedHeap* gch, int level, 83 ScanClosure* cur, ScanClosure* older) : 84 _gch(gch), _level(level), 85 _scan_cur_or_nonheap(cur), _scan_older(older) 86 {} 87 88 void DefNewGeneration::EvacuateFollowersClosure::do_void() { 89 do { 90 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap, 91 _scan_older); 92 } while (!_gch->no_allocs_since_save_marks(_level)); 93 } 94 95 DefNewGeneration::FastEvacuateFollowersClosure:: 96 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level, 97 DefNewGeneration* gen, 98 FastScanClosure* cur, FastScanClosure* older) : 99 _gch(gch), _level(level), _gen(gen), 100 _scan_cur_or_nonheap(cur), _scan_older(older) 101 {} 102 103 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 104 do { 105 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap, 106 _scan_older); 107 } while (!_gch->no_allocs_since_save_marks(_level)); 108 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan"); 109 } 110 111 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 112 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 113 { 114 assert(_g->level() == 0, "Optimized for youngest generation"); 115 _boundary = _g->reserved().end(); 116 } 117 118 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); } 119 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); } 120 121 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 122 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 123 { 124 assert(_g->level() == 0, "Optimized for youngest generation"); 125 _boundary = _g->reserved().end(); 126 } 127 128 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); } 129 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); } 130 131 void KlassScanClosure::do_klass(Klass* klass) { 132 #ifndef PRODUCT 133 if (TraceScavenge) { 134 ResourceMark rm; 135 gclog_or_tty->print_cr("KlassScanClosure::do_klass %p, %s, dirty: %s", 136 klass, 137 klass->external_name(), 138 klass->has_modified_oops() ? "true" : "false"); 139 } 140 #endif 141 142 // If the klass has not been dirtied we know that there's 143 // no references into the young gen and we can skip it. 144 if (klass->has_modified_oops()) { 145 if (_accumulate_modified_oops) { 146 klass->accumulate_modified_oops(); 147 } 148 149 // Clear this state since we're going to scavenge all the metadata. 150 klass->clear_modified_oops(); 151 152 // Tell the closure which Klass is being scanned so that it can be dirtied 153 // if oops are left pointing into the young gen. 154 _scavenge_closure->set_scanned_klass(klass); 155 156 klass->oops_do(_scavenge_closure); 157 158 _scavenge_closure->set_scanned_klass(NULL); 159 } 160 } 161 162 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 163 _g(g) 164 { 165 assert(_g->level() == 0, "Optimized for youngest generation"); 166 _boundary = _g->reserved().end(); 167 } 168 169 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); } 170 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); } 171 172 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); } 173 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); } 174 175 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure, 176 KlassRemSet* klass_rem_set) 177 : _scavenge_closure(scavenge_closure), 178 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {} 179 180 181 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 182 size_t initial_size, 183 int level, 184 const char* policy) 185 : Generation(rs, initial_size, level), 186 _promo_failure_drain_in_progress(false), 187 _should_allocate_from_space(false) 188 { 189 MemRegion cmr((HeapWord*)_virtual_space.low(), 190 (HeapWord*)_virtual_space.high()); 191 Universe::heap()->barrier_set()->resize_covered_region(cmr); 192 193 if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) { 194 _eden_space = new ConcEdenSpace(this); 195 } else { 196 _eden_space = new EdenSpace(this); 197 } 198 _from_space = new ContiguousSpace(); 199 _to_space = new ContiguousSpace(); 200 201 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) 202 vm_exit_during_initialization("Could not allocate a new gen space"); 203 204 // Compute the maximum eden and survivor space sizes. These sizes 205 // are computed assuming the entire reserved space is committed. 206 // These values are exported as performance counters. 207 uintx alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment(); 208 uintx size = _virtual_space.reserved_size(); 209 _max_survivor_size = compute_survivor_size(size, alignment); 210 _max_eden_size = size - (2*_max_survivor_size); 211 212 // allocate the performance counters 213 214 // Generation counters -- generation 0, 3 subspaces 215 _gen_counters = new GenerationCounters("new", 0, 3, &_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 _next_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()->min_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* next_gen = gch->_gens[next_level]; 385 size_t old_size = next_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()->min_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(%u):" 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(os::elapsed_counter()); 566 DefNewTracer gc_tracer; 567 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); 568 569 _next_gen = gch->next_gen(this); 570 assert(_next_gen != NULL, 571 "This must be the youngest gen, and not the only gen"); 572 573 // If the next generation is too full to accommodate promotion 574 // from this generation, pass on collection; let the next generation 575 // do it. 576 if (!collection_attempt_is_safe()) { 577 if (Verbose && PrintGCDetails) { 578 gclog_or_tty->print(" :: Collection attempt not safe :: "); 579 } 580 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 581 return; 582 } 583 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 584 585 init_assuming_no_promotion_failure(); 586 587 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL); 588 // Capture heap used before collection (for printing). 589 size_t gch_prev_used = gch->used(); 590 591 gch->trace_heap_before_gc(&gc_tracer); 592 593 SpecializationStats::clear(); 594 595 // These can be shared for all code paths 596 IsAliveClosure is_alive(this); 597 ScanWeakRefClosure scan_weak_ref(this); 598 599 age_table()->clear(); 600 to()->clear(SpaceDecorator::Mangle); 601 602 gch->rem_set()->prepare_for_younger_refs_iterate(false); 603 604 assert(gch->no_allocs_since_save_marks(0), 605 "save marks have not been newly set."); 606 607 // Not very pretty. 608 CollectorPolicy* cp = gch->collector_policy(); 609 610 FastScanClosure fsc_with_no_gc_barrier(this, false); 611 FastScanClosure fsc_with_gc_barrier(this, true); 612 613 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier, 614 gch->rem_set()->klass_rem_set()); 615 616 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 617 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this, 618 &fsc_with_no_gc_barrier, 619 &fsc_with_gc_barrier); 620 621 assert(gch->no_allocs_since_save_marks(0), 622 "save marks have not been newly set."); 623 624 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; 625 626 gch->gen_process_strong_roots(_level, 627 true, // Process younger gens, if any, 628 // as strong roots. 629 true, // activate StrongRootsScope 630 true, // is scavenging 631 SharedHeap::ScanningOption(so), 632 &fsc_with_no_gc_barrier, 633 true, // walk *all* scavengable nmethods 634 &fsc_with_gc_barrier, 635 &klass_scan_closure); 636 637 // "evacuate followers". 638 evacuate_followers.do_void(); 639 640 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 641 ReferenceProcessor* rp = ref_processor(); 642 rp->setup_policy(clear_all_soft_refs); 643 const ReferenceProcessorStats& stats = 644 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 645 NULL, _gc_timer); 646 gc_tracer.report_gc_reference_stats(stats); 647 648 if (!_promotion_failed) { 649 // Swap the survivor spaces. 650 eden()->clear(SpaceDecorator::Mangle); 651 from()->clear(SpaceDecorator::Mangle); 652 if (ZapUnusedHeapArea) { 653 // This is now done here because of the piece-meal mangling which 654 // can check for valid mangling at intermediate points in the 655 // collection(s). When a minor collection fails to collect 656 // sufficient space resizing of the young generation can occur 657 // an redistribute the spaces in the young generation. Mangle 658 // here so that unzapped regions don't get distributed to 659 // other spaces. 660 to()->mangle_unused_area(); 661 } 662 swap_spaces(); 663 664 assert(to()->is_empty(), "to space should be empty now"); 665 666 adjust_desired_tenuring_threshold(); 667 668 // A successful scavenge should restart the GC time limit count which is 669 // for full GC's. 670 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 671 size_policy->reset_gc_overhead_limit_count(); 672 if (PrintGC && !PrintGCDetails) { 673 gch->print_heap_change(gch_prev_used); 674 } 675 assert(!gch->incremental_collection_failed(), "Should be clear"); 676 } else { 677 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 678 _promo_failure_scan_stack.clear(true); // Clear cached segments. 679 680 remove_forwarding_pointers(); 681 if (PrintGCDetails) { 682 gclog_or_tty->print(" (promotion failed) "); 683 } 684 // Add to-space to the list of space to compact 685 // when a promotion failure has occurred. In that 686 // case there can be live objects in to-space 687 // as a result of a partial evacuation of eden 688 // and from-space. 689 swap_spaces(); // For uniformity wrt ParNewGeneration. 690 from()->set_next_compaction_space(to()); 691 gch->set_incremental_collection_failed(); 692 693 // Inform the next generation that a promotion failure occurred. 694 _next_gen->promotion_failure_occurred(); 695 gc_tracer.report_promotion_failed(_promotion_failed_info); 696 697 // Reset the PromotionFailureALot counters. 698 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();) 699 } 700 // set new iteration safe limit for the survivor spaces 701 from()->set_concurrent_iteration_safe_limit(from()->top()); 702 to()->set_concurrent_iteration_safe_limit(to()->top()); 703 SpecializationStats::print(); 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(os::elapsed_counter()); 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 = " SIZE_FORMAT ") ", 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(s); 792 } 793 794 // Otherwise try allocating obj tenured 795 if (obj == NULL) { 796 obj = _next_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 (_next_gen == NULL) { 902 GenCollectedHeap* gch = GenCollectedHeap::heap(); 903 _next_gen = gch->next_gen(this); 904 assert(_next_gen != NULL, 905 "This must be the youngest gen, and not the only gen"); 906 } 907 return _next_gen->promotion_attempt_is_safe(used()); 908 } 909 910 void DefNewGeneration::gc_epilogue(bool full) { 911 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 912 913 assert(!GC_locker::is_active(), "We should not be executing here"); 914 // Check if the heap is approaching full after a collection has 915 // been done. Generally the young generation is empty at 916 // a minimum at the end of a collection. If it is not, then 917 // the heap is approaching full. 918 GenCollectedHeap* gch = GenCollectedHeap::heap(); 919 if (full) { 920 DEBUG_ONLY(seen_incremental_collection_failed = false;) 921 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 922 if (Verbose && PrintGCDetails) { 923 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 924 GCCause::to_string(gch->gc_cause())); 925 } 926 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 927 set_should_allocate_from_space(); // we seem to be running out of space 928 } else { 929 if (Verbose && PrintGCDetails) { 930 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 931 GCCause::to_string(gch->gc_cause())); 932 } 933 gch->clear_incremental_collection_failed(); // We just did a full collection 934 clear_should_allocate_from_space(); // if set 935 } 936 } else { 937 #ifdef ASSERT 938 // It is possible that incremental_collection_failed() == true 939 // here, because an attempted scavenge did not succeed. The policy 940 // is normally expected to cause a full collection which should 941 // clear that condition, so we should not be here twice in a row 942 // with incremental_collection_failed() == true without having done 943 // a full collection in between. 944 if (!seen_incremental_collection_failed && 945 gch->incremental_collection_failed()) { 946 if (Verbose && PrintGCDetails) { 947 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 948 GCCause::to_string(gch->gc_cause())); 949 } 950 seen_incremental_collection_failed = true; 951 } else if (seen_incremental_collection_failed) { 952 if (Verbose && PrintGCDetails) { 953 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 954 GCCause::to_string(gch->gc_cause())); 955 } 956 assert(gch->gc_cause() == GCCause::_scavenge_alot || 957 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 958 !gch->incremental_collection_failed(), 959 "Twice in a row"); 960 seen_incremental_collection_failed = false; 961 } 962 #endif // ASSERT 963 } 964 965 if (ZapUnusedHeapArea) { 966 eden()->check_mangled_unused_area_complete(); 967 from()->check_mangled_unused_area_complete(); 968 to()->check_mangled_unused_area_complete(); 969 } 970 971 if (!CleanChunkPoolAsync) { 972 Chunk::clean_chunk_pool(); 973 } 974 975 // update the generation and space performance counters 976 update_counters(); 977 gch->collector_policy()->counters()->update_counters(); 978 } 979 980 void DefNewGeneration::record_spaces_top() { 981 assert(ZapUnusedHeapArea, "Not mangling unused space"); 982 eden()->set_top_for_allocations(); 983 to()->set_top_for_allocations(); 984 from()->set_top_for_allocations(); 985 } 986 987 void DefNewGeneration::ref_processor_init() { 988 Generation::ref_processor_init(); 989 } 990 991 992 void DefNewGeneration::update_counters() { 993 if (UsePerfData) { 994 _eden_counters->update_all(); 995 _from_counters->update_all(); 996 _to_counters->update_all(); 997 _gen_counters->update_all(); 998 } 999 } 1000 1001 void DefNewGeneration::verify() { 1002 eden()->verify(); 1003 from()->verify(); 1004 to()->verify(); 1005 } 1006 1007 void DefNewGeneration::print_on(outputStream* st) const { 1008 Generation::print_on(st); 1009 st->print(" eden"); 1010 eden()->print_on(st); 1011 st->print(" from"); 1012 from()->print_on(st); 1013 st->print(" to "); 1014 to()->print_on(st); 1015 } 1016 1017 1018 const char* DefNewGeneration::name() const { 1019 return "def new generation"; 1020 } 1021 1022 // Moved from inline file as they are not called inline 1023 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 1024 return eden(); 1025 } 1026 1027 HeapWord* DefNewGeneration::allocate(size_t word_size, 1028 bool is_tlab) { 1029 // This is the slow-path allocation for the DefNewGeneration. 1030 // Most allocations are fast-path in compiled code. 1031 // We try to allocate from the eden. If that works, we are happy. 1032 // Note that since DefNewGeneration supports lock-free allocation, we 1033 // have to use it here, as well. 1034 HeapWord* result = eden()->par_allocate(word_size); 1035 if (result != NULL) { 1036 if (CMSEdenChunksRecordAlways && _next_gen != NULL) { 1037 _next_gen->sample_eden_chunk(); 1038 } 1039 return result; 1040 } 1041 do { 1042 HeapWord* old_limit = eden()->soft_end(); 1043 if (old_limit < eden()->end()) { 1044 // Tell the next generation we reached a limit. 1045 HeapWord* new_limit = 1046 next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size); 1047 if (new_limit != NULL) { 1048 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit); 1049 } else { 1050 assert(eden()->soft_end() == eden()->end(), 1051 "invalid state after allocation_limit_reached returned null"); 1052 } 1053 } else { 1054 // The allocation failed and the soft limit is equal to the hard limit, 1055 // there are no reasons to do an attempt to allocate 1056 assert(old_limit == eden()->end(), "sanity check"); 1057 break; 1058 } 1059 // Try to allocate until succeeded or the soft limit can't be adjusted 1060 result = eden()->par_allocate(word_size); 1061 } while (result == NULL); 1062 1063 // If the eden is full and the last collection bailed out, we are running 1064 // out of heap space, and we try to allocate the from-space, too. 1065 // allocate_from_space can't be inlined because that would introduce a 1066 // circular dependency at compile time. 1067 if (result == NULL) { 1068 result = allocate_from_space(word_size); 1069 } else if (CMSEdenChunksRecordAlways && _next_gen != NULL) { 1070 _next_gen->sample_eden_chunk(); 1071 } 1072 return result; 1073 } 1074 1075 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1076 bool is_tlab) { 1077 HeapWord* res = eden()->par_allocate(word_size); 1078 if (CMSEdenChunksRecordAlways && _next_gen != NULL) { 1079 _next_gen->sample_eden_chunk(); 1080 } 1081 return res; 1082 } 1083 1084 void DefNewGeneration::gc_prologue(bool full) { 1085 // Ensure that _end and _soft_end are the same in eden space. 1086 eden()->set_soft_end(eden()->end()); 1087 } 1088 1089 size_t DefNewGeneration::tlab_capacity() const { 1090 return eden()->capacity(); 1091 } 1092 1093 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1094 return unsafe_max_alloc_nogc(); 1095 }