1 /* 2 * Copyright (c) 2014, 2019, Red Hat, Inc. All rights reserved. 3 * 4 * This code is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU General Public License version 2 only, as 6 * published by the Free Software Foundation. 7 * 8 * This code is distributed in the hope that it will be useful, but WITHOUT 9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 11 * version 2 for more details (a copy is included in the LICENSE file that 12 * accompanied this code). 13 * 14 * You should have received a copy of the GNU General Public License version 15 * 2 along with this work; if not, write to the Free Software Foundation, 16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 17 * 18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 19 * or visit www.oracle.com if you need additional information or have any 20 * questions. 21 * 22 */ 23 24 #include "precompiled.hpp" 25 26 #include "code/codeCache.hpp" 27 #include "gc/shared/gcTraceTime.inline.hpp" 28 #include "gc/shenandoah/shenandoahBrooksPointer.hpp" 29 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp" 30 #include "gc/shenandoah/shenandoahCollectionSet.hpp" 31 #include "gc/shenandoah/shenandoahFreeSet.hpp" 32 #include "gc/shenandoah/shenandoahPhaseTimings.hpp" 33 #include "gc/shenandoah/shenandoahMarkCompact.hpp" 34 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp" 35 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 36 #include "gc/shenandoah/shenandoahHeuristics.hpp" 37 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp" 38 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp" 39 #include "gc/shenandoah/shenandoahTraversalGC.hpp" 40 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp" 41 #include "gc/shenandoah/shenandoahUtils.hpp" 42 #include "gc/shenandoah/shenandoahVerifier.hpp" 43 #include "gc/shenandoah/shenandoahVMOperations.hpp" 44 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp" 45 #include "memory/metaspace.hpp" 46 #include "oops/oop.inline.hpp" 47 #include "runtime/thread.hpp" 48 #include "utilities/copy.hpp" 49 #include "utilities/growableArray.hpp" 50 #include "gc/shared/workgroup.hpp" 51 52 void ShenandoahMarkCompact::initialize(GCTimer* gc_timer) { 53 _gc_timer = gc_timer; 54 } 55 56 void ShenandoahMarkCompact::do_it(GCCause::Cause gc_cause) { 57 ShenandoahHeap* heap = ShenandoahHeap::heap(); 58 59 if (ShenandoahVerify) { 60 heap->verifier()->verify_before_fullgc(); 61 } 62 63 if (VerifyBeforeGC) { 64 Universe::verify(); 65 } 66 67 heap->set_full_gc_in_progress(true); 68 69 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at a safepoint"); 70 assert(Thread::current()->is_VM_thread(), "Do full GC only while world is stopped"); 71 72 { 73 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps); 74 heap->pre_full_gc_dump(_gc_timer); 75 } 76 77 { 78 ShenandoahGCPhase prepare_phase(ShenandoahPhaseTimings::full_gc_prepare); 79 // Full GC is supposed to recover from any GC state: 80 81 // a0. Remember if we have forwarded objects 82 bool has_forwarded_objects = heap->has_forwarded_objects(); 83 84 // a1. Cancel evacuation, if in progress 85 if (heap->is_evacuation_in_progress()) { 86 heap->set_evacuation_in_progress(false); 87 } 88 assert(!heap->is_evacuation_in_progress(), "sanity"); 89 90 // a2. Cancel update-refs, if in progress 91 if (heap->is_update_refs_in_progress()) { 92 heap->set_update_refs_in_progress(false); 93 } 94 assert(!heap->is_update_refs_in_progress(), "sanity"); 95 96 // a3. Cancel concurrent traversal GC, if in progress 97 if (heap->is_concurrent_traversal_in_progress()) { 98 heap->traversal_gc()->reset(); 99 heap->set_concurrent_traversal_in_progress(false); 100 } 101 102 // b. Cancel concurrent mark, if in progress 103 if (heap->is_concurrent_mark_in_progress()) { 104 heap->concurrent_mark()->cancel(); 105 heap->stop_concurrent_marking(); 106 } 107 assert(!heap->is_concurrent_mark_in_progress(), "sanity"); 108 109 // c. Reset the bitmaps for new marking 110 heap->reset_mark_bitmap(); 111 assert(heap->marking_context()->is_bitmap_clear(), "sanity"); 112 assert(!heap->marking_context()->is_complete(), "sanity"); 113 114 // d. Abandon reference discovery and clear all discovered references. 115 ReferenceProcessor* rp = heap->ref_processor(); 116 rp->disable_discovery(); 117 rp->abandon_partial_discovery(); 118 rp->verify_no_references_recorded(); 119 120 // e. Set back forwarded objects bit back, in case some steps above dropped it. 121 heap->set_has_forwarded_objects(has_forwarded_objects); 122 } 123 124 heap->make_parsable(true); 125 126 OrderAccess::fence(); 127 128 phase1_mark_heap(); 129 130 // Once marking is done, which may have fixed up forwarded objects, we can drop it. 131 // Coming out of Full GC, we would not have any forwarded objects. 132 // This also prevents read barrier from kicking in while adjusting pointers in phase3. 133 heap->set_has_forwarded_objects(false); 134 135 heap->set_full_gc_move_in_progress(true); 136 137 // Setup workers for the rest 138 OrderAccess::fence(); 139 140 // Initialize worker slices 141 ShenandoahHeapRegionSet** worker_slices = NEW_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, heap->max_workers(), mtGC); 142 for (uint i = 0; i < heap->max_workers(); i++) { 143 worker_slices[i] = new ShenandoahHeapRegionSet(); 144 } 145 146 { 147 // The rest of code performs region moves, where region status is undefined 148 // until all phases run together. 149 ShenandoahHeapLocker lock(heap->lock()); 150 151 phase2_calculate_target_addresses(worker_slices); 152 153 OrderAccess::fence(); 154 155 phase3_update_references(); 156 157 phase4_compact_objects(worker_slices); 158 } 159 160 // Resize metaspace 161 MetaspaceGC::compute_new_size(); 162 163 // Free worker slices 164 for (uint i = 0; i < heap->max_workers(); i++) { 165 delete worker_slices[i]; 166 } 167 FREE_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, worker_slices); 168 169 JvmtiExport::gc_epilogue(); 170 171 heap->set_full_gc_move_in_progress(false); 172 heap->set_full_gc_in_progress(false); 173 174 if (ShenandoahVerify) { 175 heap->verifier()->verify_after_fullgc(); 176 } 177 178 if (VerifyAfterGC) { 179 Universe::verify(); 180 } 181 182 { 183 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps); 184 heap->post_full_gc_dump(_gc_timer); 185 } 186 } 187 188 class ShenandoahPrepareForMarkClosure: public ShenandoahHeapRegionClosure { 189 private: 190 ShenandoahMarkingContext* const _ctx; 191 192 public: 193 ShenandoahPrepareForMarkClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {} 194 195 void heap_region_do(ShenandoahHeapRegion *r) { 196 _ctx->capture_top_at_mark_start(r); 197 r->clear_live_data(); 198 r->set_concurrent_iteration_safe_limit(r->top()); 199 } 200 }; 201 202 void ShenandoahMarkCompact::phase1_mark_heap() { 203 GCTraceTime(Info, gc, phases) time("Phase 1: Mark live objects", _gc_timer); 204 ShenandoahGCPhase mark_phase(ShenandoahPhaseTimings::full_gc_mark); 205 206 ShenandoahHeap* heap = ShenandoahHeap::heap(); 207 208 ShenandoahPrepareForMarkClosure cl; 209 heap->heap_region_iterate(&cl); 210 211 ShenandoahConcurrentMark* cm = heap->concurrent_mark(); 212 213 heap->set_process_references(heap->heuristics()->can_process_references()); 214 heap->set_unload_classes(heap->heuristics()->can_unload_classes()); 215 216 ReferenceProcessor* rp = heap->ref_processor(); 217 // enable ("weak") refs discovery 218 rp->enable_discovery(true /*verify_no_refs*/); 219 rp->setup_policy(true); // forcefully purge all soft references 220 rp->set_active_mt_degree(heap->workers()->active_workers()); 221 222 cm->update_roots(ShenandoahPhaseTimings::full_gc_roots); 223 cm->mark_roots(ShenandoahPhaseTimings::full_gc_roots); 224 cm->finish_mark_from_roots(/* full_gc = */ true); 225 226 heap->mark_complete_marking_context(); 227 } 228 229 class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure { 230 private: 231 ShenandoahHeap* const _heap; 232 GrowableArray<ShenandoahHeapRegion*>& _empty_regions; 233 int _empty_regions_pos; 234 ShenandoahHeapRegion* _to_region; 235 ShenandoahHeapRegion* _from_region; 236 HeapWord* _compact_point; 237 238 public: 239 ShenandoahPrepareForCompactionObjectClosure(GrowableArray<ShenandoahHeapRegion*>& empty_regions, ShenandoahHeapRegion* to_region) : 240 _heap(ShenandoahHeap::heap()), 241 _empty_regions(empty_regions), 242 _empty_regions_pos(0), 243 _to_region(to_region), 244 _from_region(NULL), 245 _compact_point(to_region->bottom()) {} 246 247 void set_from_region(ShenandoahHeapRegion* from_region) { 248 _from_region = from_region; 249 } 250 251 void finish_region() { 252 assert(_to_region != NULL, "should not happen"); 253 _to_region->set_new_top(_compact_point); 254 } 255 256 bool is_compact_same_region() { 257 return _from_region == _to_region; 258 } 259 260 int empty_regions_pos() { 261 return _empty_regions_pos; 262 } 263 264 void do_object(oop p) { 265 assert(_from_region != NULL, "must set before work"); 266 assert(_heap->complete_marking_context()->is_marked(p), "must be marked"); 267 assert(!_heap->complete_marking_context()->allocated_after_mark_start((HeapWord*) p), "must be truly marked"); 268 269 size_t obj_size = p->size() + ShenandoahBrooksPointer::word_size(); 270 if (_compact_point + obj_size > _to_region->end()) { 271 finish_region(); 272 273 // Object doesn't fit. Pick next empty region and start compacting there. 274 ShenandoahHeapRegion* new_to_region; 275 if (_empty_regions_pos < _empty_regions.length()) { 276 new_to_region = _empty_regions.at(_empty_regions_pos); 277 _empty_regions_pos++; 278 } else { 279 // Out of empty region? Compact within the same region. 280 new_to_region = _from_region; 281 } 282 283 assert(new_to_region != _to_region, "must not reuse same to-region"); 284 assert(new_to_region != NULL, "must not be NULL"); 285 _to_region = new_to_region; 286 _compact_point = _to_region->bottom(); 287 } 288 289 // Object fits into current region, record new location: 290 assert(_compact_point + obj_size <= _to_region->end(), "must fit"); 291 shenandoah_assert_not_forwarded(NULL, p); 292 ShenandoahBrooksPointer::set_raw(p, _compact_point + ShenandoahBrooksPointer::word_size()); 293 _compact_point += obj_size; 294 } 295 }; 296 297 class ShenandoahPrepareForCompactionTask : public AbstractGangTask { 298 private: 299 ShenandoahHeap* const _heap; 300 ShenandoahHeapRegionSet** const _worker_slices; 301 ShenandoahRegionIterator _heap_regions; 302 303 ShenandoahHeapRegion* next_from_region(ShenandoahHeapRegionSet* slice) { 304 ShenandoahHeapRegion* from_region = _heap_regions.next(); 305 306 while (from_region != NULL && (!from_region->is_move_allowed() || from_region->is_humongous())) { 307 from_region = _heap_regions.next(); 308 } 309 310 if (from_region != NULL) { 311 assert(slice != NULL, "sanity"); 312 assert(!from_region->is_humongous(), "this path cannot handle humongous regions"); 313 assert(from_region->is_move_allowed(), "only regions that can be moved in mark-compact"); 314 slice->add_region(from_region); 315 } 316 317 return from_region; 318 } 319 320 public: 321 ShenandoahPrepareForCompactionTask(ShenandoahHeapRegionSet** worker_slices) : 322 AbstractGangTask("Shenandoah Prepare For Compaction Task"), 323 _heap(ShenandoahHeap::heap()), _worker_slices(worker_slices) { 324 } 325 326 void work(uint worker_id) { 327 ShenandoahHeapRegionSet* slice = _worker_slices[worker_id]; 328 ShenandoahHeapRegion* from_region = next_from_region(slice); 329 // No work? 330 if (from_region == NULL) { 331 return; 332 } 333 334 // Sliding compaction. Walk all regions in the slice, and compact them. 335 // Remember empty regions and reuse them as needed. 336 ResourceMark rm; 337 GrowableArray<ShenandoahHeapRegion*> empty_regions((int)_heap->num_regions()); 338 ShenandoahPrepareForCompactionObjectClosure cl(empty_regions, from_region); 339 while (from_region != NULL) { 340 cl.set_from_region(from_region); 341 if (from_region->has_live()) { 342 _heap->marked_object_iterate(from_region, &cl); 343 } 344 345 // Compacted the region to somewhere else? From-region is empty then. 346 if (!cl.is_compact_same_region()) { 347 empty_regions.append(from_region); 348 } 349 from_region = next_from_region(slice); 350 } 351 cl.finish_region(); 352 353 // Mark all remaining regions as empty 354 for (int pos = cl.empty_regions_pos(); pos < empty_regions.length(); ++pos) { 355 ShenandoahHeapRegion* r = empty_regions.at(pos); 356 r->set_new_top(r->bottom()); 357 } 358 } 359 }; 360 361 void ShenandoahMarkCompact::calculate_target_humongous_objects() { 362 ShenandoahHeap* heap = ShenandoahHeap::heap(); 363 364 // Compute the new addresses for humongous objects. We need to do this after addresses 365 // for regular objects are calculated, and we know what regions in heap suffix are 366 // available for humongous moves. 367 // 368 // Scan the heap backwards, because we are compacting humongous regions towards the end. 369 // Maintain the contiguous compaction window in [to_begin; to_end), so that we can slide 370 // humongous start there. 371 // 372 // The complication is potential non-movable regions during the scan. If such region is 373 // detected, then sliding restarts towards that non-movable region. 374 375 size_t to_begin = heap->num_regions(); 376 size_t to_end = heap->num_regions(); 377 378 for (size_t c = heap->num_regions() - 1; c > 0; c--) { 379 ShenandoahHeapRegion *r = heap->get_region(c); 380 if (r->is_humongous_continuation() || (r->new_top() == r->bottom())) { 381 // To-region candidate: record this, and continue scan 382 to_begin = r->region_number(); 383 continue; 384 } 385 386 if (r->is_humongous_start() && r->is_move_allowed()) { 387 // From-region candidate: movable humongous region 388 oop old_obj = oop(r->bottom() + ShenandoahBrooksPointer::word_size()); 389 size_t words_size = old_obj->size() + ShenandoahBrooksPointer::word_size(); 390 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize); 391 392 size_t start = to_end - num_regions; 393 394 if (start >= to_begin && start != r->region_number()) { 395 // Fits into current window, and the move is non-trivial. Record the move then, and continue scan. 396 ShenandoahBrooksPointer::set_raw(old_obj, heap->get_region(start)->bottom() + ShenandoahBrooksPointer::word_size()); 397 to_end = start; 398 continue; 399 } 400 } 401 402 // Failed to fit. Scan starting from current region. 403 to_begin = r->region_number(); 404 to_end = r->region_number(); 405 } 406 } 407 408 class ShenandoahEnsureHeapActiveClosure: public ShenandoahHeapRegionClosure { 409 private: 410 ShenandoahHeap* const _heap; 411 412 public: 413 ShenandoahEnsureHeapActiveClosure() : _heap(ShenandoahHeap::heap()) {} 414 void heap_region_do(ShenandoahHeapRegion* r) { 415 if (r->is_trash()) { 416 r->recycle(); 417 } 418 if (r->is_cset()) { 419 r->make_regular_bypass(); 420 } 421 if (r->is_empty_uncommitted()) { 422 r->make_committed_bypass(); 423 } 424 assert (r->is_committed(), "only committed regions in heap now, see region " SIZE_FORMAT, r->region_number()); 425 426 // Record current region occupancy: this communicates empty regions are free 427 // to the rest of Full GC code. 428 r->set_new_top(r->top()); 429 } 430 }; 431 432 class ShenandoahTrashImmediateGarbageClosure: public ShenandoahHeapRegionClosure { 433 private: 434 ShenandoahHeap* const _heap; 435 ShenandoahMarkingContext* const _ctx; 436 437 public: 438 ShenandoahTrashImmediateGarbageClosure() : 439 _heap(ShenandoahHeap::heap()), 440 _ctx(ShenandoahHeap::heap()->complete_marking_context()) {} 441 442 void heap_region_do(ShenandoahHeapRegion* r) { 443 if (r->is_humongous_start()) { 444 oop humongous_obj = oop(r->bottom() + ShenandoahBrooksPointer::word_size()); 445 if (!_ctx->is_marked(humongous_obj)) { 446 assert(!r->has_live(), 447 "Region " SIZE_FORMAT " is not marked, should not have live", r->region_number()); 448 _heap->trash_humongous_region_at(r); 449 } else { 450 assert(r->has_live(), 451 "Region " SIZE_FORMAT " should have live", r->region_number()); 452 } 453 } else if (r->is_humongous_continuation()) { 454 // If we hit continuation, the non-live humongous starts should have been trashed already 455 assert(r->humongous_start_region()->has_live(), 456 "Region " SIZE_FORMAT " should have live", r->region_number()); 457 } else if (r->is_regular()) { 458 if (!r->has_live()) { 459 r->make_trash_immediate(); 460 } 461 } 462 } 463 }; 464 465 void ShenandoahMarkCompact::phase2_calculate_target_addresses(ShenandoahHeapRegionSet** worker_slices) { 466 GCTraceTime(Info, gc, phases) time("Phase 2: Compute new object addresses", _gc_timer); 467 ShenandoahGCPhase calculate_address_phase(ShenandoahPhaseTimings::full_gc_calculate_addresses); 468 469 ShenandoahHeap* heap = ShenandoahHeap::heap(); 470 471 { 472 // Trash the immediately collectible regions before computing addresses 473 ShenandoahTrashImmediateGarbageClosure tigcl; 474 heap->heap_region_iterate(&tigcl); 475 476 // Make sure regions are in good state: committed, active, clean. 477 // This is needed because we are potentially sliding the data through them. 478 ShenandoahEnsureHeapActiveClosure ecl; 479 heap->heap_region_iterate(&ecl); 480 } 481 482 // Compute the new addresses for regular objects 483 { 484 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_regular); 485 ShenandoahPrepareForCompactionTask prepare_task(worker_slices); 486 heap->workers()->run_task(&prepare_task); 487 } 488 489 // Compute the new addresses for humongous objects 490 { 491 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_humong); 492 calculate_target_humongous_objects(); 493 } 494 } 495 496 class ShenandoahAdjustPointersClosure : public MetadataVisitingOopIterateClosure { 497 private: 498 ShenandoahHeap* const _heap; 499 ShenandoahMarkingContext* const _ctx; 500 501 template <class T> 502 inline void do_oop_work(T* p) { 503 T o = RawAccess<>::oop_load(p); 504 if (!CompressedOops::is_null(o)) { 505 oop obj = CompressedOops::decode_not_null(o); 506 assert(_ctx->is_marked(obj), "must be marked"); 507 oop forw = oop(ShenandoahBrooksPointer::get_raw(obj)); 508 RawAccess<IS_NOT_NULL>::oop_store(p, forw); 509 } 510 } 511 512 public: 513 ShenandoahAdjustPointersClosure() : 514 _heap(ShenandoahHeap::heap()), 515 _ctx(ShenandoahHeap::heap()->complete_marking_context()) {} 516 517 void do_oop(oop* p) { do_oop_work(p); } 518 void do_oop(narrowOop* p) { do_oop_work(p); } 519 }; 520 521 class ShenandoahAdjustPointersObjectClosure : public ObjectClosure { 522 private: 523 ShenandoahHeap* const _heap; 524 ShenandoahAdjustPointersClosure _cl; 525 526 public: 527 ShenandoahAdjustPointersObjectClosure() : 528 _heap(ShenandoahHeap::heap()) { 529 } 530 void do_object(oop p) { 531 assert(_heap->complete_marking_context()->is_marked(p), "must be marked"); 532 HeapWord* forw = ShenandoahBrooksPointer::get_raw(p); 533 p->oop_iterate(&_cl); 534 } 535 }; 536 537 class ShenandoahAdjustPointersTask : public AbstractGangTask { 538 private: 539 ShenandoahHeap* const _heap; 540 ShenandoahRegionIterator _regions; 541 542 public: 543 ShenandoahAdjustPointersTask() : 544 AbstractGangTask("Shenandoah Adjust Pointers Task"), 545 _heap(ShenandoahHeap::heap()) { 546 } 547 548 void work(uint worker_id) { 549 ShenandoahAdjustPointersObjectClosure obj_cl; 550 ShenandoahHeapRegion* r = _regions.next(); 551 while (r != NULL) { 552 if (!r->is_humongous_continuation() && r->has_live()) { 553 _heap->marked_object_iterate(r, &obj_cl); 554 } 555 r = _regions.next(); 556 } 557 } 558 }; 559 560 class ShenandoahAdjustRootPointersTask : public AbstractGangTask { 561 private: 562 ShenandoahRootProcessor* _rp; 563 564 public: 565 ShenandoahAdjustRootPointersTask(ShenandoahRootProcessor* rp) : 566 AbstractGangTask("Shenandoah Adjust Root Pointers Task"), 567 _rp(rp) {} 568 569 void work(uint worker_id) { 570 ShenandoahAdjustPointersClosure cl; 571 CLDToOopClosure adjust_cld_closure(&cl, ClassLoaderData::_claim_strong); 572 MarkingCodeBlobClosure adjust_code_closure(&cl, 573 CodeBlobToOopClosure::FixRelocations); 574 575 _rp->update_all_roots<AlwaysTrueClosure>(&cl, 576 &adjust_cld_closure, 577 &adjust_code_closure, NULL, worker_id); 578 } 579 }; 580 581 void ShenandoahMarkCompact::phase3_update_references() { 582 GCTraceTime(Info, gc, phases) time("Phase 3: Adjust pointers", _gc_timer); 583 ShenandoahGCPhase adjust_pointer_phase(ShenandoahPhaseTimings::full_gc_adjust_pointers); 584 585 ShenandoahHeap* heap = ShenandoahHeap::heap(); 586 587 WorkGang* workers = heap->workers(); 588 uint nworkers = workers->active_workers(); 589 { 590 #if COMPILER2_OR_JVMCI 591 DerivedPointerTable::clear(); 592 #endif 593 ShenandoahRootProcessor rp(heap, nworkers, ShenandoahPhaseTimings::full_gc_roots); 594 ShenandoahAdjustRootPointersTask task(&rp); 595 workers->run_task(&task); 596 #if COMPILER2_OR_JVMCI 597 DerivedPointerTable::update_pointers(); 598 #endif 599 } 600 601 ShenandoahAdjustPointersTask adjust_pointers_task; 602 workers->run_task(&adjust_pointers_task); 603 } 604 605 class ShenandoahCompactObjectsClosure : public ObjectClosure { 606 private: 607 ShenandoahHeap* const _heap; 608 uint const _worker_id; 609 610 public: 611 ShenandoahCompactObjectsClosure(uint worker_id) : 612 _heap(ShenandoahHeap::heap()), _worker_id(worker_id) {} 613 614 void do_object(oop p) { 615 assert(_heap->complete_marking_context()->is_marked(p), "must be marked"); 616 size_t size = (size_t)p->size(); 617 HeapWord* compact_to = ShenandoahBrooksPointer::get_raw(p); 618 HeapWord* compact_from = (HeapWord*) p; 619 if (compact_from != compact_to) { 620 Copy::aligned_conjoint_words(compact_from, compact_to, size); 621 } 622 oop new_obj = oop(compact_to); 623 ShenandoahBrooksPointer::initialize(new_obj); 624 } 625 }; 626 627 class ShenandoahCompactObjectsTask : public AbstractGangTask { 628 private: 629 ShenandoahHeap* const _heap; 630 ShenandoahHeapRegionSet** const _worker_slices; 631 632 public: 633 ShenandoahCompactObjectsTask(ShenandoahHeapRegionSet** worker_slices) : 634 AbstractGangTask("Shenandoah Compact Objects Task"), 635 _heap(ShenandoahHeap::heap()), 636 _worker_slices(worker_slices) { 637 } 638 639 void work(uint worker_id) { 640 ShenandoahHeapRegionSetIterator slice(_worker_slices[worker_id]); 641 642 ShenandoahCompactObjectsClosure cl(worker_id); 643 ShenandoahHeapRegion* r = slice.next(); 644 while (r != NULL) { 645 assert(!r->is_humongous(), "must not get humongous regions here"); 646 if (r->has_live()) { 647 _heap->marked_object_iterate(r, &cl); 648 } 649 r->set_top(r->new_top()); 650 r = slice.next(); 651 } 652 } 653 }; 654 655 class ShenandoahPostCompactClosure : public ShenandoahHeapRegionClosure { 656 private: 657 ShenandoahHeap* const _heap; 658 size_t _live; 659 660 public: 661 ShenandoahPostCompactClosure() : _heap(ShenandoahHeap::heap()), _live(0) { 662 _heap->free_set()->clear(); 663 } 664 665 void heap_region_do(ShenandoahHeapRegion* r) { 666 assert (!r->is_cset(), "cset regions should have been demoted already"); 667 668 // Need to reset the complete-top-at-mark-start pointer here because 669 // the complete marking bitmap is no longer valid. This ensures 670 // size-based iteration in marked_object_iterate(). 671 // NOTE: See blurb at ShenandoahMCResetCompleteBitmapTask on why we need to skip 672 // pinned regions. 673 if (!r->is_pinned()) { 674 _heap->complete_marking_context()->reset_top_at_mark_start(r); 675 } 676 677 size_t live = r->used(); 678 679 // Make empty regions that have been allocated into regular 680 if (r->is_empty() && live > 0) { 681 r->make_regular_bypass(); 682 } 683 684 // Reclaim regular regions that became empty 685 if (r->is_regular() && live == 0) { 686 r->make_trash(); 687 } 688 689 // Recycle all trash regions 690 if (r->is_trash()) { 691 live = 0; 692 r->recycle(); 693 } 694 695 r->set_live_data(live); 696 r->reset_alloc_metadata_to_shared(); 697 _live += live; 698 } 699 700 size_t get_live() { 701 return _live; 702 } 703 }; 704 705 void ShenandoahMarkCompact::compact_humongous_objects() { 706 // Compact humongous regions, based on their fwdptr objects. 707 // 708 // This code is serial, because doing the in-slice parallel sliding is tricky. In most cases, 709 // humongous regions are already compacted, and do not require further moves, which alleviates 710 // sliding costs. We may consider doing this in parallel in future. 711 712 ShenandoahHeap* heap = ShenandoahHeap::heap(); 713 714 for (size_t c = heap->num_regions() - 1; c > 0; c--) { 715 ShenandoahHeapRegion* r = heap->get_region(c); 716 if (r->is_humongous_start()) { 717 oop old_obj = oop(r->bottom() + ShenandoahBrooksPointer::word_size()); 718 size_t words_size = old_obj->size() + ShenandoahBrooksPointer::word_size(); 719 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize); 720 721 size_t old_start = r->region_number(); 722 size_t old_end = old_start + num_regions - 1; 723 size_t new_start = heap->heap_region_index_containing(ShenandoahBrooksPointer::get_raw(old_obj)); 724 size_t new_end = new_start + num_regions - 1; 725 726 if (old_start == new_start) { 727 // No need to move the object, it stays at the same slot 728 continue; 729 } 730 731 assert (r->is_move_allowed(), "should be movable"); 732 733 Copy::aligned_conjoint_words(heap->get_region(old_start)->bottom(), 734 heap->get_region(new_start)->bottom(), 735 ShenandoahHeapRegion::region_size_words()*num_regions); 736 737 oop new_obj = oop(heap->get_region(new_start)->bottom() + ShenandoahBrooksPointer::word_size()); 738 ShenandoahBrooksPointer::initialize(new_obj); 739 740 { 741 for (size_t c = old_start; c <= old_end; c++) { 742 ShenandoahHeapRegion* r = heap->get_region(c); 743 r->make_regular_bypass(); 744 r->set_top(r->bottom()); 745 } 746 747 for (size_t c = new_start; c <= new_end; c++) { 748 ShenandoahHeapRegion* r = heap->get_region(c); 749 if (c == new_start) { 750 r->make_humongous_start_bypass(); 751 } else { 752 r->make_humongous_cont_bypass(); 753 } 754 755 // Trailing region may be non-full, record the remainder there 756 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask(); 757 if ((c == new_end) && (remainder != 0)) { 758 r->set_top(r->bottom() + remainder); 759 } else { 760 r->set_top(r->end()); 761 } 762 763 r->reset_alloc_metadata_to_shared(); 764 } 765 } 766 } 767 } 768 } 769 770 // This is slightly different to ShHeap::reset_next_mark_bitmap: 771 // we need to remain able to walk pinned regions. 772 // Since pinned region do not move and don't get compacted, we will get holes with 773 // unreachable objects in them (which may have pointers to unloaded Klasses and thus 774 // cannot be iterated over using oop->size(). The only way to safely iterate over those is using 775 // a valid marking bitmap and valid TAMS pointer. This class only resets marking 776 // bitmaps for un-pinned regions, and later we only reset TAMS for unpinned regions. 777 class ShenandoahMCResetCompleteBitmapTask : public AbstractGangTask { 778 private: 779 ShenandoahRegionIterator _regions; 780 781 public: 782 ShenandoahMCResetCompleteBitmapTask() : 783 AbstractGangTask("Parallel Reset Bitmap Task") { 784 } 785 786 void work(uint worker_id) { 787 ShenandoahHeapRegion* region = _regions.next(); 788 ShenandoahHeap* heap = ShenandoahHeap::heap(); 789 ShenandoahMarkingContext* const ctx = heap->complete_marking_context(); 790 while (region != NULL) { 791 if (heap->is_bitmap_slice_committed(region) && !region->is_pinned() && region->has_live()) { 792 ctx->clear_bitmap(region); 793 } 794 region = _regions.next(); 795 } 796 } 797 }; 798 799 void ShenandoahMarkCompact::phase4_compact_objects(ShenandoahHeapRegionSet** worker_slices) { 800 GCTraceTime(Info, gc, phases) time("Phase 4: Move objects", _gc_timer); 801 ShenandoahGCPhase compaction_phase(ShenandoahPhaseTimings::full_gc_copy_objects); 802 803 ShenandoahHeap* heap = ShenandoahHeap::heap(); 804 805 // Compact regular objects first 806 { 807 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_regular); 808 ShenandoahCompactObjectsTask compact_task(worker_slices); 809 heap->workers()->run_task(&compact_task); 810 } 811 812 // Compact humongous objects after regular object moves 813 { 814 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_humong); 815 compact_humongous_objects(); 816 } 817 818 // Reset complete bitmap. We're about to reset the complete-top-at-mark-start pointer 819 // and must ensure the bitmap is in sync. 820 { 821 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_reset_complete); 822 ShenandoahMCResetCompleteBitmapTask task; 823 heap->workers()->run_task(&task); 824 } 825 826 // Bring regions in proper states after the collection, and set heap properties. 827 { 828 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_rebuild); 829 830 ShenandoahPostCompactClosure post_compact; 831 heap->heap_region_iterate(&post_compact); 832 heap->set_used(post_compact.get_live()); 833 834 heap->collection_set()->clear(); 835 heap->free_set()->rebuild(); 836 } 837 838 heap->clear_cancelled_gc(); 839 }