1 /* 2 * Copyright (c) 2001, 2023, 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/cardTableRS.hpp" 27 #include "gc/serial/defNewGeneration.inline.hpp" 28 #include "gc/serial/serialGcRefProcProxyTask.hpp" 29 #include "gc/serial/serialHeap.inline.hpp" 30 #include "gc/serial/serialStringDedup.inline.hpp" 31 #include "gc/serial/tenuredGeneration.hpp" 32 #include "gc/shared/adaptiveSizePolicy.hpp" 33 #include "gc/shared/ageTable.inline.hpp" 34 #include "gc/shared/collectorCounters.hpp" 35 #include "gc/shared/continuationGCSupport.inline.hpp" 36 #include "gc/shared/gcArguments.hpp" 37 #include "gc/shared/gcHeapSummary.hpp" 38 #include "gc/shared/gcLocker.hpp" 39 #include "gc/shared/gcPolicyCounters.hpp" 40 #include "gc/shared/gcTimer.hpp" 41 #include "gc/shared/gcTrace.hpp" 42 #include "gc/shared/gcTraceTime.inline.hpp" 43 #include "gc/shared/generationSpec.hpp" 44 #include "gc/shared/preservedMarks.inline.hpp" 45 #include "gc/shared/referencePolicy.hpp" 46 #include "gc/shared/referenceProcessorPhaseTimes.hpp" 47 #include "gc/shared/space.inline.hpp" 48 #include "gc/shared/spaceDecorator.inline.hpp" 49 #include "gc/shared/strongRootsScope.hpp" 50 #include "gc/shared/weakProcessor.hpp" 51 #include "logging/log.hpp" 52 #include "memory/iterator.inline.hpp" 53 #include "memory/resourceArea.hpp" 54 #include "oops/instanceRefKlass.hpp" 55 #include "oops/oop.inline.hpp" 56 #include "runtime/java.hpp" 57 #include "runtime/javaThread.hpp" 58 #include "runtime/prefetch.inline.hpp" 59 #include "runtime/threads.hpp" 60 #include "utilities/align.hpp" 61 #include "utilities/copy.hpp" 62 #include "utilities/globalDefinitions.hpp" 63 #include "utilities/stack.inline.hpp" 64 65 class ScavengeHelper { 66 DefNewGeneration* _young_gen; 67 HeapWord* _young_gen_end; 68 public: 69 ScavengeHelper(DefNewGeneration* young_gen) : 70 _young_gen(young_gen), 71 _young_gen_end(young_gen->reserved().end()) {} 72 73 bool is_in_young_gen(void* p) const { 74 return p < _young_gen_end; 75 } 76 77 template <typename T, typename Func> 78 void try_scavenge(T* p, Func&& f) { 79 T heap_oop = RawAccess<>::oop_load(p); 80 // Should we copy the obj? 81 if (!CompressedOops::is_null(heap_oop)) { 82 oop obj = CompressedOops::decode_not_null(heap_oop); 83 if (is_in_young_gen(obj)) { 84 assert(!_young_gen->to()->is_in_reserved(obj), "Scanning field twice?"); 85 oop new_obj = obj->is_forwarded() ? obj->forwardee() 86 : _young_gen->copy_to_survivor_space(obj); 87 RawAccess<IS_NOT_NULL>::oop_store(p, new_obj); 88 89 // callback 90 f(new_obj); 91 } 92 } 93 } 94 }; 95 96 class InHeapScanClosure : public BasicOopIterateClosure { 97 ScavengeHelper _helper; 98 protected: 99 bool is_in_young_gen(void* p) const { 100 return _helper.is_in_young_gen(p); 101 } 102 103 template <typename T, typename Func> 104 void try_scavenge(T* p, Func&& f) { 105 _helper.try_scavenge(p, f); 106 } 107 108 InHeapScanClosure(DefNewGeneration* young_gen) : 109 BasicOopIterateClosure(young_gen->ref_processor()), 110 _helper(young_gen) {} 111 }; 112 113 class OffHeapScanClosure : public OopClosure { 114 ScavengeHelper _helper; 115 protected: 116 bool is_in_young_gen(void* p) const { 117 return _helper.is_in_young_gen(p); 118 } 119 120 template <typename T, typename Func> 121 void try_scavenge(T* p, Func&& f) { 122 _helper.try_scavenge(p, f); 123 } 124 125 OffHeapScanClosure(DefNewGeneration* young_gen) : _helper(young_gen) {} 126 }; 127 128 class OldGenScanClosure : public InHeapScanClosure { 129 CardTableRS* _rs; 130 131 template <typename T> 132 void do_oop_work(T* p) { 133 assert(!is_in_young_gen(p), "precondition"); 134 135 try_scavenge(p, [&] (oop new_obj) { 136 // If p points to a younger generation, mark the card. 137 if (is_in_young_gen(new_obj)) { 138 _rs->inline_write_ref_field_gc(p); 139 } 140 }); 141 } 142 public: 143 OldGenScanClosure(DefNewGeneration* g) : InHeapScanClosure(g), 144 _rs(SerialHeap::heap()->rem_set()) {} 145 146 void do_oop(oop* p) { do_oop_work(p); } 147 void do_oop(narrowOop* p) { do_oop_work(p); } 148 }; 149 150 class PromoteFailureClosure : public InHeapScanClosure { 151 template <typename T> 152 void do_oop_work(T* p) { 153 assert(is_in_young_gen(p), "promote-fail objs must be in young-gen"); 154 assert(!SerialHeap::heap()->young_gen()->to()->is_in_reserved(p), "must not be in to-space"); 155 156 try_scavenge(p, [] (auto) {}); 157 } 158 public: 159 PromoteFailureClosure(DefNewGeneration* g) : InHeapScanClosure(g) {} 160 161 void do_oop(oop* p) { do_oop_work(p); } 162 void do_oop(narrowOop* p) { do_oop_work(p); } 163 }; 164 165 class YoungGenScanClosure : public InHeapScanClosure { 166 template <typename T> 167 void do_oop_work(T* p) { 168 assert(SerialHeap::heap()->young_gen()->to()->is_in_reserved(p), "precondition"); 169 170 try_scavenge(p, [] (auto) {}); 171 } 172 public: 173 YoungGenScanClosure(DefNewGeneration* g) : InHeapScanClosure(g) {} 174 175 void do_oop(oop* p) { do_oop_work(p); } 176 void do_oop(narrowOop* p) { do_oop_work(p); } 177 }; 178 179 class RootScanClosure : public OffHeapScanClosure { 180 template <typename T> 181 void do_oop_work(T* p) { 182 assert(!SerialHeap::heap()->is_in_reserved(p), "outside the heap"); 183 184 try_scavenge(p, [] (auto) {}); 185 } 186 public: 187 RootScanClosure(DefNewGeneration* g) : OffHeapScanClosure(g) {} 188 189 void do_oop(oop* p) { do_oop_work(p); } 190 void do_oop(narrowOop* p) { do_oop_work(p); } 191 }; 192 193 class CLDScanClosure: public CLDClosure { 194 195 class CLDOopClosure : public OffHeapScanClosure { 196 ClassLoaderData* _scanned_cld; 197 198 template <typename T> 199 void do_oop_work(T* p) { 200 assert(!SerialHeap::heap()->is_in_reserved(p), "outside the heap"); 201 202 try_scavenge(p, [&] (oop new_obj) { 203 assert(_scanned_cld != nullptr, "inv"); 204 if (is_in_young_gen(new_obj) && !_scanned_cld->has_modified_oops()) { 205 _scanned_cld->record_modified_oops(); 206 } 207 }); 208 } 209 210 public: 211 CLDOopClosure(DefNewGeneration* g) : OffHeapScanClosure(g), 212 _scanned_cld(nullptr) {} 213 214 void set_scanned_cld(ClassLoaderData* cld) { 215 assert(cld == nullptr || _scanned_cld == nullptr, "Must be"); 216 _scanned_cld = cld; 217 } 218 219 void do_oop(oop* p) { do_oop_work(p); } 220 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 221 }; 222 223 CLDOopClosure _oop_closure; 224 public: 225 CLDScanClosure(DefNewGeneration* g) : _oop_closure(g) {} 226 227 void do_cld(ClassLoaderData* cld) { 228 // If the cld has not been dirtied we know that there's 229 // no references into the young gen and we can skip it. 230 if (cld->has_modified_oops()) { 231 232 // Tell the closure which CLD is being scanned so that it can be dirtied 233 // if oops are left pointing into the young gen. 234 _oop_closure.set_scanned_cld(cld); 235 236 // Clean the cld since we're going to scavenge all the metadata. 237 cld->oops_do(&_oop_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true); 238 239 _oop_closure.set_scanned_cld(nullptr); 240 } 241 } 242 }; 243 244 class IsAliveClosure: public BoolObjectClosure { 245 HeapWord* _young_gen_end; 246 public: 247 IsAliveClosure(DefNewGeneration* g): _young_gen_end(g->reserved().end()) {} 248 249 bool do_object_b(oop p) { 250 return cast_from_oop<HeapWord*>(p) >= _young_gen_end || p->is_forwarded(); 251 } 252 }; 253 254 class AdjustWeakRootClosure: public OffHeapScanClosure { 255 template <class T> 256 void do_oop_work(T* p) { 257 DEBUG_ONLY(SerialHeap* heap = SerialHeap::heap();) 258 assert(!heap->is_in_reserved(p), "outside the heap"); 259 260 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p); 261 if (is_in_young_gen(obj)) { 262 assert(!heap->young_gen()->to()->is_in_reserved(obj), "inv"); 263 assert(obj->is_forwarded(), "forwarded before weak-root-processing"); 264 oop new_obj = obj->forwardee(); 265 RawAccess<IS_NOT_NULL>::oop_store(p, new_obj); 266 } 267 } 268 public: 269 AdjustWeakRootClosure(DefNewGeneration* g): OffHeapScanClosure(g) {} 270 271 void do_oop(oop* p) { do_oop_work(p); } 272 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 273 }; 274 275 class KeepAliveClosure: public OopClosure { 276 DefNewGeneration* _young_gen; 277 HeapWord* _young_gen_end; 278 CardTableRS* _rs; 279 280 bool is_in_young_gen(void* p) const { 281 return p < _young_gen_end; 282 } 283 284 template <class T> 285 void do_oop_work(T* p) { 286 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p); 287 288 if (is_in_young_gen(obj)) { 289 oop new_obj = obj->is_forwarded() ? obj->forwardee() 290 : _young_gen->copy_to_survivor_space(obj); 291 RawAccess<IS_NOT_NULL>::oop_store(p, new_obj); 292 293 if (is_in_young_gen(new_obj) && !is_in_young_gen(p)) { 294 _rs->inline_write_ref_field_gc(p); 295 } 296 } 297 } 298 public: 299 KeepAliveClosure(DefNewGeneration* g) : 300 _young_gen(g), 301 _young_gen_end(g->reserved().end()), 302 _rs(SerialHeap::heap()->rem_set()) {} 303 304 void do_oop(oop* p) { do_oop_work(p); } 305 void do_oop(narrowOop* p) { do_oop_work(p); } 306 }; 307 308 class FastEvacuateFollowersClosure: public VoidClosure { 309 SerialHeap* _heap; 310 YoungGenScanClosure* _young_cl; 311 OldGenScanClosure* _old_cl; 312 public: 313 FastEvacuateFollowersClosure(SerialHeap* heap, 314 YoungGenScanClosure* young_cl, 315 OldGenScanClosure* old_cl) : 316 _heap(heap), _young_cl(young_cl), _old_cl(old_cl) 317 {} 318 319 void do_void() { 320 do { 321 _heap->oop_since_save_marks_iterate(_young_cl, _old_cl); 322 } while (!_heap->no_allocs_since_save_marks()); 323 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan"); 324 } 325 }; 326 327 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 328 size_t initial_size, 329 size_t min_size, 330 size_t max_size, 331 const char* policy) 332 : Generation(rs, initial_size), 333 _preserved_marks_set(false /* in_c_heap */), 334 _promo_failure_drain_in_progress(false), 335 _should_allocate_from_space(false), 336 _string_dedup_requests() 337 { 338 MemRegion cmr((HeapWord*)_virtual_space.low(), 339 (HeapWord*)_virtual_space.high()); 340 GenCollectedHeap* gch = GenCollectedHeap::heap(); 341 342 gch->rem_set()->resize_covered_region(cmr); 343 344 _eden_space = new ContiguousSpace(); 345 _from_space = new ContiguousSpace(); 346 _to_space = new ContiguousSpace(); 347 348 // Compute the maximum eden and survivor space sizes. These sizes 349 // are computed assuming the entire reserved space is committed. 350 // These values are exported as performance counters. 351 uintx size = _virtual_space.reserved_size(); 352 _max_survivor_size = compute_survivor_size(size, SpaceAlignment); 353 _max_eden_size = size - (2*_max_survivor_size); 354 355 // allocate the performance counters 356 357 // Generation counters -- generation 0, 3 subspaces 358 _gen_counters = new GenerationCounters("new", 0, 3, 359 min_size, max_size, &_virtual_space); 360 _gc_counters = new CollectorCounters(policy, 0); 361 362 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 363 _gen_counters); 364 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 365 _gen_counters); 366 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 367 _gen_counters); 368 369 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 370 update_counters(); 371 _old_gen = nullptr; 372 _tenuring_threshold = MaxTenuringThreshold; 373 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 374 375 _ref_processor = nullptr; 376 377 _gc_timer = new STWGCTimer(); 378 379 _gc_tracer = new DefNewTracer(); 380 } 381 382 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 383 bool clear_space, 384 bool mangle_space) { 385 // If the spaces are being cleared (only done at heap initialization 386 // currently), the survivor spaces need not be empty. 387 // Otherwise, no care is taken for used areas in the survivor spaces 388 // so check. 389 assert(clear_space || (to()->is_empty() && from()->is_empty()), 390 "Initialization of the survivor spaces assumes these are empty"); 391 392 // Compute sizes 393 uintx size = _virtual_space.committed_size(); 394 uintx survivor_size = compute_survivor_size(size, SpaceAlignment); 395 uintx eden_size = size - (2*survivor_size); 396 if (eden_size > max_eden_size()) { 397 // Need to reduce eden_size to satisfy the max constraint. The delta needs 398 // to be 2*SpaceAlignment aligned so that both survivors are properly 399 // aligned. 400 uintx eden_delta = align_up(eden_size - max_eden_size(), 2*SpaceAlignment); 401 eden_size -= eden_delta; 402 survivor_size += eden_delta/2; 403 } 404 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 405 406 if (eden_size < minimum_eden_size) { 407 // May happen due to 64Kb rounding, if so adjust eden size back up 408 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment); 409 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 410 uintx unaligned_survivor_size = 411 align_down(maximum_survivor_size, SpaceAlignment); 412 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment); 413 eden_size = size - (2*survivor_size); 414 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 415 assert(eden_size >= minimum_eden_size, "just checking"); 416 } 417 418 char *eden_start = _virtual_space.low(); 419 char *from_start = eden_start + eden_size; 420 char *to_start = from_start + survivor_size; 421 char *to_end = to_start + survivor_size; 422 423 assert(to_end == _virtual_space.high(), "just checking"); 424 assert(Space::is_aligned(eden_start), "checking alignment"); 425 assert(Space::is_aligned(from_start), "checking alignment"); 426 assert(Space::is_aligned(to_start), "checking alignment"); 427 428 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 429 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 430 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 431 432 // A minimum eden size implies that there is a part of eden that 433 // is being used and that affects the initialization of any 434 // newly formed eden. 435 bool live_in_eden = minimum_eden_size > 0; 436 437 // If not clearing the spaces, do some checking to verify that 438 // the space are already mangled. 439 if (!clear_space) { 440 // Must check mangling before the spaces are reshaped. Otherwise, 441 // the bottom or end of one space may have moved into another 442 // a failure of the check may not correctly indicate which space 443 // is not properly mangled. 444 if (ZapUnusedHeapArea) { 445 HeapWord* limit = (HeapWord*) _virtual_space.high(); 446 eden()->check_mangled_unused_area(limit); 447 from()->check_mangled_unused_area(limit); 448 to()->check_mangled_unused_area(limit); 449 } 450 } 451 452 // Reset the spaces for their new regions. 453 eden()->initialize(edenMR, 454 clear_space && !live_in_eden, 455 SpaceDecorator::Mangle); 456 // If clear_space and live_in_eden, we will not have cleared any 457 // portion of eden above its top. This can cause newly 458 // expanded space not to be mangled if using ZapUnusedHeapArea. 459 // We explicitly do such mangling here. 460 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 461 eden()->mangle_unused_area(); 462 } 463 from()->initialize(fromMR, clear_space, mangle_space); 464 to()->initialize(toMR, clear_space, mangle_space); 465 466 // Set next compaction spaces. 467 eden()->set_next_compaction_space(from()); 468 // The to-space is normally empty before a compaction so need 469 // not be considered. The exception is during promotion 470 // failure handling when to-space can contain live objects. 471 from()->set_next_compaction_space(nullptr); 472 } 473 474 void DefNewGeneration::swap_spaces() { 475 ContiguousSpace* s = from(); 476 _from_space = to(); 477 _to_space = s; 478 eden()->set_next_compaction_space(from()); 479 // The to-space is normally empty before a compaction so need 480 // not be considered. The exception is during promotion 481 // failure handling when to-space can contain live objects. 482 from()->set_next_compaction_space(nullptr); 483 484 if (UsePerfData) { 485 CSpaceCounters* c = _from_counters; 486 _from_counters = _to_counters; 487 _to_counters = c; 488 } 489 } 490 491 bool DefNewGeneration::expand(size_t bytes) { 492 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 493 bool success = _virtual_space.expand_by(bytes); 494 if (success && ZapUnusedHeapArea) { 495 // Mangle newly committed space immediately because it 496 // can be done here more simply that after the new 497 // spaces have been computed. 498 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 499 MemRegion mangle_region(prev_high, new_high); 500 SpaceMangler::mangle_region(mangle_region); 501 } 502 503 // Do not attempt an expand-to-the reserve size. The 504 // request should properly observe the maximum size of 505 // the generation so an expand-to-reserve should be 506 // unnecessary. Also a second call to expand-to-reserve 507 // value potentially can cause an undue expansion. 508 // For example if the first expand fail for unknown reasons, 509 // but the second succeeds and expands the heap to its maximum 510 // value. 511 if (GCLocker::is_active()) { 512 log_debug(gc)("Garbage collection disabled, expanded heap instead"); 513 } 514 515 return success; 516 } 517 518 size_t DefNewGeneration::calculate_thread_increase_size(int threads_count) const { 519 size_t thread_increase_size = 0; 520 // Check an overflow at 'threads_count * NewSizeThreadIncrease'. 521 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) { 522 thread_increase_size = threads_count * NewSizeThreadIncrease; 523 } 524 return thread_increase_size; 525 } 526 527 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate, 528 size_t new_size_before, 529 size_t alignment, 530 size_t thread_increase_size) const { 531 size_t desired_new_size = new_size_before; 532 533 if (NewSizeThreadIncrease > 0 && thread_increase_size > 0) { 534 535 // 1. Check an overflow at 'new_size_candidate + thread_increase_size'. 536 if (new_size_candidate <= max_uintx - thread_increase_size) { 537 new_size_candidate += thread_increase_size; 538 539 // 2. Check an overflow at 'align_up'. 540 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1)); 541 if (new_size_candidate <= aligned_max) { 542 desired_new_size = align_up(new_size_candidate, alignment); 543 } 544 } 545 } 546 547 return desired_new_size; 548 } 549 550 void DefNewGeneration::compute_new_size() { 551 // This is called after a GC that includes the old generation, so from-space 552 // will normally be empty. 553 // Note that we check both spaces, since if scavenge failed they revert roles. 554 // If not we bail out (otherwise we would have to relocate the objects). 555 if (!from()->is_empty() || !to()->is_empty()) { 556 return; 557 } 558 559 GenCollectedHeap* gch = GenCollectedHeap::heap(); 560 561 size_t old_size = gch->old_gen()->capacity(); 562 size_t new_size_before = _virtual_space.committed_size(); 563 size_t min_new_size = initial_size(); 564 size_t max_new_size = reserved().byte_size(); 565 assert(min_new_size <= new_size_before && 566 new_size_before <= max_new_size, 567 "just checking"); 568 // All space sizes must be multiples of Generation::GenGrain. 569 size_t alignment = Generation::GenGrain; 570 571 int threads_count = Threads::number_of_non_daemon_threads(); 572 size_t thread_increase_size = calculate_thread_increase_size(threads_count); 573 574 size_t new_size_candidate = old_size / NewRatio; 575 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease 576 // and reverts to previous value if any overflow happens 577 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, 578 alignment, thread_increase_size); 579 580 // Adjust new generation size 581 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size); 582 assert(desired_new_size <= max_new_size, "just checking"); 583 584 bool changed = false; 585 if (desired_new_size > new_size_before) { 586 size_t change = desired_new_size - new_size_before; 587 assert(change % alignment == 0, "just checking"); 588 if (expand(change)) { 589 changed = true; 590 } 591 // If the heap failed to expand to the desired size, 592 // "changed" will be false. If the expansion failed 593 // (and at this point it was expected to succeed), 594 // ignore the failure (leaving "changed" as false). 595 } 596 if (desired_new_size < new_size_before && eden()->is_empty()) { 597 // bail out of shrinking if objects in eden 598 size_t change = new_size_before - desired_new_size; 599 assert(change % alignment == 0, "just checking"); 600 _virtual_space.shrink_by(change); 601 changed = true; 602 } 603 if (changed) { 604 // The spaces have already been mangled at this point but 605 // may not have been cleared (set top = bottom) and should be. 606 // Mangling was done when the heap was being expanded. 607 compute_space_boundaries(eden()->used(), 608 SpaceDecorator::Clear, 609 SpaceDecorator::DontMangle); 610 MemRegion cmr((HeapWord*)_virtual_space.low(), 611 (HeapWord*)_virtual_space.high()); 612 gch->rem_set()->resize_covered_region(cmr); 613 614 log_debug(gc, ergo, heap)( 615 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 616 new_size_before/K, _virtual_space.committed_size()/K, 617 eden()->capacity()/K, from()->capacity()/K); 618 log_trace(gc, ergo, heap)( 619 " [allowed " SIZE_FORMAT "K extra for %d threads]", 620 thread_increase_size/K, threads_count); 621 } 622 } 623 624 void DefNewGeneration::ref_processor_init() { 625 assert(_ref_processor == nullptr, "a reference processor already exists"); 626 assert(!_reserved.is_empty(), "empty generation?"); 627 _span_based_discoverer.set_span(_reserved); 628 _ref_processor = new ReferenceProcessor(&_span_based_discoverer); // a vanilla reference processor 629 } 630 631 size_t DefNewGeneration::capacity() const { 632 return eden()->capacity() 633 + from()->capacity(); // to() is only used during scavenge 634 } 635 636 637 size_t DefNewGeneration::used() const { 638 return eden()->used() 639 + from()->used(); // to() is only used during scavenge 640 } 641 642 643 size_t DefNewGeneration::free() const { 644 return eden()->free() 645 + from()->free(); // to() is only used during scavenge 646 } 647 648 size_t DefNewGeneration::max_capacity() const { 649 const size_t reserved_bytes = reserved().byte_size(); 650 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment); 651 } 652 653 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 654 return eden()->free(); 655 } 656 657 size_t DefNewGeneration::capacity_before_gc() const { 658 return eden()->capacity(); 659 } 660 661 size_t DefNewGeneration::contiguous_available() const { 662 return eden()->free(); 663 } 664 665 666 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 667 eden()->object_iterate(blk); 668 from()->object_iterate(blk); 669 } 670 671 672 void DefNewGeneration::space_iterate(SpaceClosure* blk, 673 bool usedOnly) { 674 blk->do_space(eden()); 675 blk->do_space(from()); 676 blk->do_space(to()); 677 } 678 679 // The last collection bailed out, we are running out of heap space, 680 // so we try to allocate the from-space, too. 681 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 682 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc(); 683 684 // If the Heap_lock is not locked by this thread, this will be called 685 // again later with the Heap_lock held. 686 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread())); 687 688 HeapWord* result = nullptr; 689 if (do_alloc) { 690 result = from()->allocate(size); 691 } 692 693 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s", 694 size, 695 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 696 "true" : "false", 697 Heap_lock->is_locked() ? "locked" : "unlocked", 698 from()->free(), 699 should_try_alloc ? "" : " should_allocate_from_space: NOT", 700 do_alloc ? " Heap_lock is not owned by self" : "", 701 result == nullptr ? "null" : "object"); 702 703 return result; 704 } 705 706 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, bool is_tlab) { 707 // We don't attempt to expand the young generation (but perhaps we should.) 708 return allocate(size, is_tlab); 709 } 710 711 void DefNewGeneration::adjust_desired_tenuring_threshold() { 712 // Set the desired survivor size to half the real survivor space 713 size_t const survivor_capacity = to()->capacity() / HeapWordSize; 714 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 715 716 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size); 717 718 if (UsePerfData) { 719 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters(); 720 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold); 721 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize); 722 } 723 724 age_table()->print_age_table(_tenuring_threshold); 725 } 726 727 void DefNewGeneration::collect(bool full, 728 bool clear_all_soft_refs, 729 size_t size, 730 bool is_tlab) { 731 assert(full || size > 0, "otherwise we don't want to collect"); 732 733 SerialHeap* heap = SerialHeap::heap(); 734 735 // If the next generation is too full to accommodate promotion 736 // from this generation, pass on collection; let the next generation 737 // do it. 738 if (!collection_attempt_is_safe()) { 739 log_trace(gc)(":: Collection attempt not safe ::"); 740 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 741 return; 742 } 743 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 744 _gc_timer->register_gc_start(); 745 _gc_tracer->report_gc_start(heap->gc_cause(), _gc_timer->gc_start()); 746 _ref_processor->start_discovery(clear_all_soft_refs); 747 748 _old_gen = heap->old_gen(); 749 750 init_assuming_no_promotion_failure(); 751 752 GCTraceTime(Trace, gc, phases) tm("DefNew", nullptr, heap->gc_cause()); 753 754 heap->trace_heap_before_gc(_gc_tracer); 755 756 // These can be shared for all code paths 757 IsAliveClosure is_alive(this); 758 759 age_table()->clear(); 760 to()->clear(SpaceDecorator::Mangle); 761 // The preserved marks should be empty at the start of the GC. 762 _preserved_marks_set.init(1); 763 764 assert(heap->no_allocs_since_save_marks(), 765 "save marks have not been newly set."); 766 767 YoungGenScanClosure young_gen_cl(this); 768 OldGenScanClosure old_gen_cl(this); 769 770 FastEvacuateFollowersClosure evacuate_followers(heap, 771 &young_gen_cl, 772 &old_gen_cl); 773 774 assert(heap->no_allocs_since_save_marks(), 775 "save marks have not been newly set."); 776 777 { 778 StrongRootsScope srs(0); 779 RootScanClosure root_cl{this}; 780 CLDScanClosure cld_scan_closure{this}; 781 782 heap->young_process_roots(&root_cl, 783 &old_gen_cl, 784 &cld_scan_closure); 785 } 786 787 // "evacuate followers". 788 evacuate_followers.do_void(); 789 790 { 791 // Reference processing 792 KeepAliveClosure keep_alive(this); 793 ReferenceProcessor* rp = ref_processor(); 794 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues()); 795 SerialGCRefProcProxyTask task(is_alive, keep_alive, evacuate_followers); 796 const ReferenceProcessorStats& stats = rp->process_discovered_references(task, pt); 797 _gc_tracer->report_gc_reference_stats(stats); 798 _gc_tracer->report_tenuring_threshold(tenuring_threshold()); 799 pt.print_all_references(); 800 } 801 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 802 803 { 804 AdjustWeakRootClosure cl{this}; 805 WeakProcessor::weak_oops_do(&is_alive, &cl); 806 } 807 808 // Verify that the usage of keep_alive didn't copy any objects. 809 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 810 811 _string_dedup_requests.flush(); 812 813 if (!_promotion_failed) { 814 // Swap the survivor spaces. 815 eden()->clear(SpaceDecorator::Mangle); 816 from()->clear(SpaceDecorator::Mangle); 817 if (ZapUnusedHeapArea) { 818 // This is now done here because of the piece-meal mangling which 819 // can check for valid mangling at intermediate points in the 820 // collection(s). When a young collection fails to collect 821 // sufficient space resizing of the young generation can occur 822 // an redistribute the spaces in the young generation. Mangle 823 // here so that unzapped regions don't get distributed to 824 // other spaces. 825 to()->mangle_unused_area(); 826 } 827 swap_spaces(); 828 829 assert(to()->is_empty(), "to space should be empty now"); 830 831 adjust_desired_tenuring_threshold(); 832 833 // A successful scavenge should restart the GC time limit count which is 834 // for full GC's. 835 AdaptiveSizePolicy* size_policy = heap->size_policy(); 836 size_policy->reset_gc_overhead_limit_count(); 837 assert(!heap->incremental_collection_failed(), "Should be clear"); 838 } else { 839 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 840 _promo_failure_scan_stack.clear(true); // Clear cached segments. 841 842 remove_forwarding_pointers(); 843 log_info(gc, promotion)("Promotion failed"); 844 // Add to-space to the list of space to compact 845 // when a promotion failure has occurred. In that 846 // case there can be live objects in to-space 847 // as a result of a partial evacuation of eden 848 // and from-space. 849 swap_spaces(); // For uniformity wrt ParNewGeneration. 850 from()->set_next_compaction_space(to()); 851 heap->set_incremental_collection_failed(); 852 853 // Inform the next generation that a promotion failure occurred. 854 _old_gen->promotion_failure_occurred(); 855 _gc_tracer->report_promotion_failed(_promotion_failed_info); 856 857 // Reset the PromotionFailureALot counters. 858 NOT_PRODUCT(heap->reset_promotion_should_fail();) 859 } 860 // We should have processed and cleared all the preserved marks. 861 _preserved_marks_set.reclaim(); 862 863 heap->trace_heap_after_gc(_gc_tracer); 864 865 _gc_timer->register_gc_end(); 866 867 _gc_tracer->report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 868 } 869 870 void DefNewGeneration::init_assuming_no_promotion_failure() { 871 _promotion_failed = false; 872 _promotion_failed_info.reset(); 873 from()->set_next_compaction_space(nullptr); 874 } 875 876 void DefNewGeneration::remove_forwarding_pointers() { 877 assert(_promotion_failed, "precondition"); 878 879 // Will enter Full GC soon due to failed promotion. Must reset the mark word 880 // of objs in young-gen so that no objs are marked (forwarded) when Full GC 881 // starts. (The mark word is overloaded: `is_marked()` == `is_forwarded()`.) 882 struct ResetForwardedMarkWord : ObjectClosure { 883 void do_object(oop obj) override { 884 if (obj->is_forwarded()) { 885 obj->forward_safe_init_mark(); 886 } 887 } 888 } cl; 889 eden()->object_iterate(&cl); 890 from()->object_iterate(&cl); 891 892 restore_preserved_marks(); 893 } 894 895 void DefNewGeneration::restore_preserved_marks() { 896 _preserved_marks_set.restore(nullptr); 897 } 898 899 void DefNewGeneration::handle_promotion_failure(oop old) { 900 log_debug(gc, promotion)("Promotion failure size = " SIZE_FORMAT ") ", old->size()); 901 902 _promotion_failed = true; 903 _promotion_failed_info.register_copy_failure(old->size()); 904 _preserved_marks_set.get()->push_if_necessary(old, old->mark()); 905 906 ContinuationGCSupport::transform_stack_chunk(old); 907 908 old->forward_to_self(); 909 910 _promo_failure_scan_stack.push(old); 911 912 if (!_promo_failure_drain_in_progress) { 913 // prevent recursion in copy_to_survivor_space() 914 _promo_failure_drain_in_progress = true; 915 drain_promo_failure_scan_stack(); 916 _promo_failure_drain_in_progress = false; 917 } 918 } 919 920 oop DefNewGeneration::copy_to_survivor_space(oop old) { 921 assert(is_in_reserved(old) && !old->is_forwarded(), 922 "shouldn't be scavenging this oop"); 923 size_t s = old->size(); 924 oop obj = nullptr; 925 926 // Try allocating obj in to-space (unless too old) 927 if (old->age() < tenuring_threshold()) { 928 obj = cast_to_oop(to()->allocate(s)); 929 } 930 931 bool new_obj_is_tenured = false; 932 // Otherwise try allocating obj tenured 933 if (obj == nullptr) { 934 obj = _old_gen->promote(old, s); 935 if (obj == nullptr) { 936 handle_promotion_failure(old); 937 return old; 938 } 939 new_obj_is_tenured = true; 940 } else { 941 // Prefetch beyond obj 942 const intx interval = PrefetchCopyIntervalInBytes; 943 Prefetch::write(obj, interval); 944 945 // Copy obj 946 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s); 947 948 ContinuationGCSupport::transform_stack_chunk(obj); 949 950 // Increment age if obj still in new generation 951 obj->incr_age(); 952 age_table()->add(obj, s); 953 } 954 955 // Done, insert forward pointer to obj in this header 956 old->forward_to(obj); 957 958 if (SerialStringDedup::is_candidate_from_evacuation(obj, new_obj_is_tenured)) { 959 // Record old; request adds a new weak reference, which reference 960 // processing expects to refer to a from-space object. 961 _string_dedup_requests.add(old); 962 } 963 return obj; 964 } 965 966 void DefNewGeneration::drain_promo_failure_scan_stack() { 967 PromoteFailureClosure cl{this}; 968 while (!_promo_failure_scan_stack.is_empty()) { 969 oop obj = _promo_failure_scan_stack.pop(); 970 obj->oop_iterate(&cl); 971 } 972 } 973 974 void DefNewGeneration::save_marks() { 975 eden()->set_saved_mark(); 976 to()->set_saved_mark(); 977 from()->set_saved_mark(); 978 } 979 980 981 bool DefNewGeneration::no_allocs_since_save_marks() { 982 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 983 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 984 return to()->saved_mark_at_top(); 985 } 986 987 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 988 size_t max_alloc_words) { 989 if (requestor == this || _promotion_failed) { 990 return; 991 } 992 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 993 994 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 995 if (to_space->top() > to_space->bottom()) { 996 trace("to_space not empty when contribute_scratch called"); 997 } 998 */ 999 1000 ContiguousSpace* to_space = to(); 1001 assert(to_space->end() >= to_space->top(), "pointers out of order"); 1002 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 1003 if (free_words >= MinFreeScratchWords) { 1004 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 1005 sb->num_words = free_words; 1006 sb->next = list; 1007 list = sb; 1008 } 1009 } 1010 1011 void DefNewGeneration::reset_scratch() { 1012 // If contributing scratch in to_space, mangle all of 1013 // to_space if ZapUnusedHeapArea. This is needed because 1014 // top is not maintained while using to-space as scratch. 1015 if (ZapUnusedHeapArea) { 1016 to()->mangle_unused_area_complete(); 1017 } 1018 } 1019 1020 bool DefNewGeneration::collection_attempt_is_safe() { 1021 if (!to()->is_empty()) { 1022 log_trace(gc)(":: to is not empty ::"); 1023 return false; 1024 } 1025 if (_old_gen == nullptr) { 1026 GenCollectedHeap* gch = GenCollectedHeap::heap(); 1027 _old_gen = gch->old_gen(); 1028 } 1029 return _old_gen->promotion_attempt_is_safe(used()); 1030 } 1031 1032 void DefNewGeneration::gc_epilogue(bool full) { 1033 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 1034 1035 assert(!GCLocker::is_active(), "We should not be executing here"); 1036 // Check if the heap is approaching full after a collection has 1037 // been done. Generally the young generation is empty at 1038 // a minimum at the end of a collection. If it is not, then 1039 // the heap is approaching full. 1040 GenCollectedHeap* gch = GenCollectedHeap::heap(); 1041 if (full) { 1042 DEBUG_ONLY(seen_incremental_collection_failed = false;) 1043 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 1044 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 1045 GCCause::to_string(gch->gc_cause())); 1046 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 1047 set_should_allocate_from_space(); // we seem to be running out of space 1048 } else { 1049 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 1050 GCCause::to_string(gch->gc_cause())); 1051 gch->clear_incremental_collection_failed(); // We just did a full collection 1052 clear_should_allocate_from_space(); // if set 1053 } 1054 } else { 1055 #ifdef ASSERT 1056 // It is possible that incremental_collection_failed() == true 1057 // here, because an attempted scavenge did not succeed. The policy 1058 // is normally expected to cause a full collection which should 1059 // clear that condition, so we should not be here twice in a row 1060 // with incremental_collection_failed() == true without having done 1061 // a full collection in between. 1062 if (!seen_incremental_collection_failed && 1063 gch->incremental_collection_failed()) { 1064 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 1065 GCCause::to_string(gch->gc_cause())); 1066 seen_incremental_collection_failed = true; 1067 } else if (seen_incremental_collection_failed) { 1068 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 1069 GCCause::to_string(gch->gc_cause())); 1070 seen_incremental_collection_failed = false; 1071 } 1072 #endif // ASSERT 1073 } 1074 1075 if (ZapUnusedHeapArea) { 1076 eden()->check_mangled_unused_area_complete(); 1077 from()->check_mangled_unused_area_complete(); 1078 to()->check_mangled_unused_area_complete(); 1079 } 1080 1081 // update the generation and space performance counters 1082 update_counters(); 1083 gch->counters()->update_counters(); 1084 } 1085 1086 void DefNewGeneration::record_spaces_top() { 1087 assert(ZapUnusedHeapArea, "Not mangling unused space"); 1088 eden()->set_top_for_allocations(); 1089 to()->set_top_for_allocations(); 1090 from()->set_top_for_allocations(); 1091 } 1092 1093 void DefNewGeneration::update_counters() { 1094 if (UsePerfData) { 1095 _eden_counters->update_all(); 1096 _from_counters->update_all(); 1097 _to_counters->update_all(); 1098 _gen_counters->update_all(); 1099 } 1100 } 1101 1102 void DefNewGeneration::verify() { 1103 eden()->verify(); 1104 from()->verify(); 1105 to()->verify(); 1106 } 1107 1108 void DefNewGeneration::print_on(outputStream* st) const { 1109 Generation::print_on(st); 1110 st->print(" eden"); 1111 eden()->print_on(st); 1112 st->print(" from"); 1113 from()->print_on(st); 1114 st->print(" to "); 1115 to()->print_on(st); 1116 } 1117 1118 1119 const char* DefNewGeneration::name() const { 1120 return "def new generation"; 1121 } 1122 1123 // Moved from inline file as they are not called inline 1124 ContiguousSpace* DefNewGeneration::first_compaction_space() const { 1125 return eden(); 1126 } 1127 1128 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 1129 // This is the slow-path allocation for the DefNewGeneration. 1130 // Most allocations are fast-path in compiled code. 1131 // We try to allocate from the eden. If that works, we are happy. 1132 // Note that since DefNewGeneration supports lock-free allocation, we 1133 // have to use it here, as well. 1134 HeapWord* result = eden()->par_allocate(word_size); 1135 if (result == nullptr) { 1136 // If the eden is full and the last collection bailed out, we are running 1137 // out of heap space, and we try to allocate the from-space, too. 1138 // allocate_from_space can't be inlined because that would introduce a 1139 // circular dependency at compile time. 1140 result = allocate_from_space(word_size); 1141 } 1142 return result; 1143 } 1144 1145 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1146 bool is_tlab) { 1147 return eden()->par_allocate(word_size); 1148 } 1149 1150 size_t DefNewGeneration::tlab_capacity() const { 1151 return eden()->capacity(); 1152 } 1153 1154 size_t DefNewGeneration::tlab_used() const { 1155 return eden()->used(); 1156 } 1157 1158 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1159 return unsafe_max_alloc_nogc(); 1160 } --- EOF ---