1 /*
   2  * Copyright (c) 2005, 2025, 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 "classfile/classLoaderDataGraph.hpp"
  26 #include "classfile/javaClasses.inline.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "code/codeCache.hpp"
  31 #include "compiler/oopMap.hpp"
  32 #include "gc/parallel/objectStartArray.inline.hpp"
  33 #include "gc/parallel/parallelArguments.hpp"
  34 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
  35 #include "gc/parallel/parMarkBitMap.inline.hpp"
  36 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
  37 #include "gc/parallel/psCompactionManager.inline.hpp"
  38 #include "gc/parallel/psOldGen.hpp"
  39 #include "gc/parallel/psParallelCompact.inline.hpp"
  40 #include "gc/parallel/psPromotionManager.inline.hpp"
  41 #include "gc/parallel/psRootType.hpp"
  42 #include "gc/parallel/psScavenge.hpp"
  43 #include "gc/parallel/psStringDedup.hpp"
  44 #include "gc/parallel/psYoungGen.hpp"
  45 #include "gc/shared/classUnloadingContext.hpp"
  46 #include "gc/shared/fullGCForwarding.inline.hpp"
  47 #include "gc/shared/gcCause.hpp"
  48 #include "gc/shared/gcHeapSummary.hpp"
  49 #include "gc/shared/gcId.hpp"
  50 #include "gc/shared/gcLocker.hpp"
  51 #include "gc/shared/gcTimer.hpp"
  52 #include "gc/shared/gcTrace.hpp"
  53 #include "gc/shared/gcTraceTime.inline.hpp"
  54 #include "gc/shared/gcVMOperations.hpp"
  55 #include "gc/shared/isGCActiveMark.hpp"
  56 #include "gc/shared/oopStorage.inline.hpp"
  57 #include "gc/shared/oopStorageSet.inline.hpp"
  58 #include "gc/shared/oopStorageSetParState.inline.hpp"
  59 #include "gc/shared/preservedMarks.inline.hpp"
  60 #include "gc/shared/referencePolicy.hpp"
  61 #include "gc/shared/referenceProcessor.hpp"
  62 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
  63 #include "gc/shared/spaceDecorator.hpp"
  64 #include "gc/shared/strongRootsScope.hpp"
  65 #include "gc/shared/taskTerminator.hpp"
  66 #include "gc/shared/weakProcessor.inline.hpp"
  67 #include "gc/shared/workerPolicy.hpp"
  68 #include "gc/shared/workerThread.hpp"
  69 #include "gc/shared/workerUtils.hpp"
  70 #include "logging/log.hpp"
  71 #include "memory/iterator.inline.hpp"
  72 #include "memory/memoryReserver.hpp"
  73 #include "memory/metaspaceUtils.hpp"
  74 #include "memory/resourceArea.hpp"
  75 #include "memory/universe.hpp"
  76 #include "nmt/memTracker.hpp"
  77 #include "oops/access.inline.hpp"
  78 #include "oops/instanceClassLoaderKlass.inline.hpp"
  79 #include "oops/instanceKlass.inline.hpp"
  80 #include "oops/instanceMirrorKlass.inline.hpp"
  81 #include "oops/methodData.hpp"
  82 #include "oops/objArrayKlass.inline.hpp"
  83 #include "oops/oop.inline.hpp"
  84 #include "runtime/atomic.hpp"
  85 #include "runtime/handles.inline.hpp"
  86 #include "runtime/java.hpp"
  87 #include "runtime/safepoint.hpp"
  88 #include "runtime/threads.hpp"
  89 #include "runtime/vmThread.hpp"
  90 #include "services/memoryService.hpp"
  91 #include "utilities/align.hpp"
  92 #include "utilities/debug.hpp"
  93 #include "utilities/events.hpp"
  94 #include "utilities/formatBuffer.hpp"
  95 #include "utilities/macros.hpp"
  96 #include "utilities/stack.inline.hpp"
  97 #if INCLUDE_JVMCI
  98 #include "jvmci/jvmci.hpp"
  99 #endif
 100 
 101 #include <math.h>
 102 
 103 // All sizes are in HeapWords.
 104 const size_t ParallelCompactData::Log2RegionSize  = 16; // 64K words
 105 const size_t ParallelCompactData::RegionSize      = (size_t)1 << Log2RegionSize;
 106 static_assert(ParallelCompactData::RegionSize >= BitsPerWord, "region-start bit word-aligned");
 107 const size_t ParallelCompactData::RegionSizeBytes =
 108   RegionSize << LogHeapWordSize;
 109 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
 110 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
 111 const size_t ParallelCompactData::RegionAddrMask       = ~RegionAddrOffsetMask;
 112 
 113 const ParallelCompactData::RegionData::region_sz_t
 114 ParallelCompactData::RegionData::dc_shift = 27;
 115 
 116 const ParallelCompactData::RegionData::region_sz_t
 117 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
 118 
 119 const ParallelCompactData::RegionData::region_sz_t
 120 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
 121 
 122 const ParallelCompactData::RegionData::region_sz_t
 123 ParallelCompactData::RegionData::los_mask = ~dc_mask;
 124 
 125 const ParallelCompactData::RegionData::region_sz_t
 126 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
 127 
 128 const ParallelCompactData::RegionData::region_sz_t
 129 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
 130 
 131 bool ParallelCompactData::RegionData::is_clear() {
 132   return (_destination == nullptr) &&
 133          (_source_region == 0) &&
 134          (_partial_obj_addr == nullptr) &&
 135          (_partial_obj_size == 0) &&
 136          (_dc_and_los == 0) &&
 137          (_shadow_state == 0);
 138 }
 139 
 140 #ifdef ASSERT
 141 void ParallelCompactData::RegionData::verify_clear() {
 142   assert(_destination == nullptr, "inv");
 143   assert(_source_region == 0, "inv");
 144   assert(_partial_obj_addr == nullptr, "inv");
 145   assert(_partial_obj_size == 0, "inv");
 146   assert(_dc_and_los == 0, "inv");
 147   assert(_shadow_state == 0, "inv");
 148 }
 149 #endif
 150 
 151 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
 152 
 153 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
 154 ReferenceProcessor* PSParallelCompact::_ref_processor = nullptr;
 155 
 156 void SplitInfo::record(size_t split_region_idx, HeapWord* split_point, size_t preceding_live_words) {
 157   assert(split_region_idx != 0, "precondition");
 158 
 159   // Obj denoted by split_point will be deferred to the next space.
 160   assert(split_point != nullptr, "precondition");
 161 
 162   const ParallelCompactData& sd = PSParallelCompact::summary_data();
 163 
 164   PSParallelCompact::RegionData* split_region_ptr = sd.region(split_region_idx);
 165   assert(preceding_live_words < split_region_ptr->data_size(), "inv");
 166 
 167   HeapWord* preceding_destination = split_region_ptr->destination();
 168   assert(preceding_destination != nullptr, "inv");
 169 
 170   // How many regions does the preceding part occupy
 171   uint preceding_destination_count;
 172   if (preceding_live_words == 0) {
 173     preceding_destination_count = 0;
 174   } else {
 175     // -1 so that the ending address doesn't fall on the region-boundary
 176     if (sd.region_align_down(preceding_destination) ==
 177         sd.region_align_down(preceding_destination + preceding_live_words - 1)) {
 178       preceding_destination_count = 1;
 179     } else {
 180       preceding_destination_count = 2;
 181     }
 182   }
 183 
 184   _split_region_idx = split_region_idx;
 185   _split_point = split_point;
 186   _preceding_live_words = preceding_live_words;
 187   _preceding_destination = preceding_destination;
 188   _preceding_destination_count = preceding_destination_count;
 189 }
 190 
 191 void SplitInfo::clear()
 192 {
 193   _split_region_idx = 0;
 194   _split_point = nullptr;
 195   _preceding_live_words = 0;
 196   _preceding_destination = nullptr;
 197   _preceding_destination_count = 0;
 198   assert(!is_valid(), "sanity");
 199 }
 200 
 201 #ifdef  ASSERT
 202 void SplitInfo::verify_clear()
 203 {
 204   assert(_split_region_idx == 0, "not clear");
 205   assert(_split_point == nullptr, "not clear");
 206   assert(_preceding_live_words == 0, "not clear");
 207   assert(_preceding_destination == nullptr, "not clear");
 208   assert(_preceding_destination_count == 0, "not clear");
 209 }
 210 #endif  // #ifdef ASSERT
 211 
 212 
 213 void PSParallelCompact::print_on_error(outputStream* st) {
 214   _mark_bitmap.print_on_error(st);
 215 }
 216 
 217 ParallelCompactData::ParallelCompactData() :
 218   _heap_start(nullptr),
 219   DEBUG_ONLY(_heap_end(nullptr) COMMA)
 220   _region_vspace(nullptr),
 221   _reserved_byte_size(0),
 222   _region_data(nullptr),
 223   _region_count(0) {}
 224 
 225 bool ParallelCompactData::initialize(MemRegion reserved_heap)
 226 {
 227   _heap_start = reserved_heap.start();
 228   const size_t heap_size = reserved_heap.word_size();
 229   DEBUG_ONLY(_heap_end = _heap_start + heap_size;)
 230 
 231   assert(region_align_down(_heap_start) == _heap_start,
 232          "region start not aligned");
 233 
 234   return initialize_region_data(heap_size);
 235 }
 236 
 237 PSVirtualSpace*
 238 ParallelCompactData::create_vspace(size_t count, size_t element_size)
 239 {
 240   const size_t raw_bytes = count * element_size;
 241   const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
 242   const size_t granularity = os::vm_allocation_granularity();
 243   const size_t rs_align = MAX2(page_sz, granularity);
 244 
 245   _reserved_byte_size = align_up(raw_bytes, rs_align);
 246 
 247   ReservedSpace rs = MemoryReserver::reserve(_reserved_byte_size,
 248                                              rs_align,
 249                                              page_sz);
 250 
 251   if (!rs.is_reserved()) {
 252     // Failed to reserve memory.
 253     return nullptr;
 254   }
 255 
 256   os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, rs.base(),
 257                        rs.size(), page_sz);
 258 
 259   MemTracker::record_virtual_memory_tag((address)rs.base(), mtGC);
 260 
 261   PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
 262 
 263   if (!vspace->expand_by(_reserved_byte_size)) {
 264     // Failed to commit memory.
 265 
 266     delete vspace;
 267 
 268     // Release memory reserved in the space.
 269     MemoryReserver::release(rs);
 270 
 271     return nullptr;
 272   }
 273 
 274   return vspace;
 275 }
 276 
 277 bool ParallelCompactData::initialize_region_data(size_t heap_size)
 278 {
 279   assert(is_aligned(heap_size, RegionSize), "precondition");
 280 
 281   const size_t count = heap_size >> Log2RegionSize;
 282   _region_vspace = create_vspace(count, sizeof(RegionData));
 283   if (_region_vspace != nullptr) {
 284     _region_data = (RegionData*)_region_vspace->reserved_low_addr();
 285     _region_count = count;
 286     return true;
 287   }
 288   return false;
 289 }
 290 
 291 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
 292   assert(beg_region <= _region_count, "beg_region out of range");
 293   assert(end_region <= _region_count, "end_region out of range");
 294 
 295   const size_t region_cnt = end_region - beg_region;
 296   memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
 297 }
 298 
 299 void
 300 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
 301 {
 302   assert(is_region_aligned(beg), "not RegionSize aligned");
 303   assert(is_region_aligned(end), "not RegionSize aligned");
 304 
 305   size_t cur_region = addr_to_region_idx(beg);
 306   const size_t end_region = addr_to_region_idx(end);
 307   HeapWord* addr = beg;
 308   while (cur_region < end_region) {
 309     _region_data[cur_region].set_destination(addr);
 310     _region_data[cur_region].set_destination_count(0);
 311     _region_data[cur_region].set_source_region(cur_region);
 312 
 313     // Update live_obj_size so the region appears completely full.
 314     size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
 315     _region_data[cur_region].set_live_obj_size(live_size);
 316 
 317     ++cur_region;
 318     addr += RegionSize;
 319   }
 320 }
 321 
 322 // The total live words on src_region would overflow the target space, so find
 323 // the overflowing object and record the split point. The invariant is that an
 324 // obj should not cross space boundary.
 325 HeapWord* ParallelCompactData::summarize_split_space(size_t src_region,
 326                                                      SplitInfo& split_info,
 327                                                      HeapWord* const destination,
 328                                                      HeapWord* const target_end,
 329                                                      HeapWord** target_next) {
 330   assert(destination <= target_end, "sanity");
 331   assert(destination + _region_data[src_region].data_size() > target_end,
 332     "region should not fit into target space");
 333   assert(is_region_aligned(target_end), "sanity");
 334 
 335   size_t partial_obj_size = _region_data[src_region].partial_obj_size();
 336 
 337   if (destination + partial_obj_size > target_end) {
 338     assert(partial_obj_size > 0, "inv");
 339     // The overflowing obj is from a previous region.
 340     //
 341     // source-regions:
 342     //
 343     // ***************
 344     // |     A|AA    |
 345     // ***************
 346     //       ^
 347     //       | split-point
 348     //
 349     // dest-region:
 350     //
 351     // ********
 352     // |~~~~A |
 353     // ********
 354     //       ^^
 355     //       || target-space-end
 356     //       |
 357     //       | destination
 358     //
 359     // AAA would overflow target-space.
 360     //
 361     HeapWord* overflowing_obj = _region_data[src_region].partial_obj_addr();
 362     size_t split_region = addr_to_region_idx(overflowing_obj);
 363 
 364     // The number of live words before the overflowing object on this split region
 365     size_t preceding_live_words;
 366     if (is_region_aligned(overflowing_obj)) {
 367       preceding_live_words = 0;
 368     } else {
 369       // Words accounted by the overflowing object on the split region
 370       size_t overflowing_size = pointer_delta(region_align_up(overflowing_obj), overflowing_obj);
 371       preceding_live_words = region(split_region)->data_size() - overflowing_size;
 372     }
 373 
 374     split_info.record(split_region, overflowing_obj, preceding_live_words);
 375 
 376     // The [overflowing_obj, src_region_start) part has been accounted for, so
 377     // must move back the new_top, now that this overflowing obj is deferred.
 378     HeapWord* new_top = destination - pointer_delta(region_to_addr(src_region), overflowing_obj);
 379 
 380     // If the overflowing obj was relocated to its original destination,
 381     // those destination regions would have their source_region set. Now that
 382     // this overflowing obj is relocated somewhere else, reset the
 383     // source_region.
 384     {
 385       size_t range_start = addr_to_region_idx(region_align_up(new_top));
 386       size_t range_end = addr_to_region_idx(region_align_up(destination));
 387       for (size_t i = range_start; i < range_end; ++i) {
 388         region(i)->set_source_region(0);
 389       }
 390     }
 391 
 392     // Update new top of target space
 393     *target_next = new_top;
 394 
 395     return overflowing_obj;
 396   }
 397 
 398   // Obj-iteration to locate the overflowing obj
 399   HeapWord* region_start = region_to_addr(src_region);
 400   HeapWord* region_end = region_start + RegionSize;
 401   HeapWord* cur_addr = region_start + partial_obj_size;
 402   size_t live_words = partial_obj_size;
 403 
 404   while (true) {
 405     assert(cur_addr < region_end, "inv");
 406     cur_addr = PSParallelCompact::mark_bitmap()->find_obj_beg(cur_addr, region_end);
 407     // There must be an overflowing obj in this region
 408     assert(cur_addr < region_end, "inv");
 409 
 410     oop obj = cast_to_oop(cur_addr);
 411     size_t obj_size = obj->size();
 412     if (destination + live_words + obj_size > target_end) {
 413       // Found the overflowing obj
 414       split_info.record(src_region, cur_addr, live_words);
 415       *target_next = destination + live_words;
 416       return cur_addr;
 417     }
 418 
 419     live_words += obj_size;
 420     cur_addr += obj_size;
 421   }
 422 }
 423 
 424 size_t ParallelCompactData::live_words_in_space(const MutableSpace* space,
 425                                                 HeapWord** full_region_prefix_end) {
 426   size_t cur_region = addr_to_region_idx(space->bottom());
 427   const size_t end_region = addr_to_region_idx(region_align_up(space->top()));
 428   size_t live_words = 0;
 429   if (full_region_prefix_end == nullptr) {
 430     for (/* empty */; cur_region < end_region; ++cur_region) {
 431       live_words += _region_data[cur_region].data_size();
 432     }
 433   } else {
 434     bool first_set = false;
 435     for (/* empty */; cur_region < end_region; ++cur_region) {
 436       size_t live_words_in_region = _region_data[cur_region].data_size();
 437       if (!first_set && live_words_in_region < RegionSize) {
 438         *full_region_prefix_end = region_to_addr(cur_region);
 439         first_set = true;
 440       }
 441       live_words += live_words_in_region;
 442     }
 443     if (!first_set) {
 444       // All regions are full of live objs.
 445       assert(is_region_aligned(space->top()), "inv");
 446       *full_region_prefix_end = space->top();
 447     }
 448     assert(*full_region_prefix_end != nullptr, "postcondition");
 449     assert(is_region_aligned(*full_region_prefix_end), "inv");
 450     assert(*full_region_prefix_end >= space->bottom(), "in-range");
 451     assert(*full_region_prefix_end <= space->top(), "in-range");
 452   }
 453   return live_words;
 454 }
 455 
 456 bool ParallelCompactData::summarize(SplitInfo& split_info,
 457                                     HeapWord* source_beg, HeapWord* source_end,
 458                                     HeapWord** source_next,
 459                                     HeapWord* target_beg, HeapWord* target_end,
 460                                     HeapWord** target_next)
 461 {
 462   HeapWord* const source_next_val = source_next == nullptr ? nullptr : *source_next;
 463   log_develop_trace(gc, compaction)(
 464       "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
 465       "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
 466       p2i(source_beg), p2i(source_end), p2i(source_next_val),
 467       p2i(target_beg), p2i(target_end), p2i(*target_next));
 468 
 469   size_t cur_region = addr_to_region_idx(source_beg);
 470   const size_t end_region = addr_to_region_idx(region_align_up(source_end));
 471 
 472   HeapWord *dest_addr = target_beg;
 473   for (/* empty */; cur_region < end_region; cur_region++) {
 474     size_t words = _region_data[cur_region].data_size();
 475 
 476     // Skip empty ones
 477     if (words == 0) {
 478       continue;
 479     }
 480 
 481     if (split_info.is_split(cur_region)) {
 482       assert(words > split_info.preceding_live_words(), "inv");
 483       words -= split_info.preceding_live_words();
 484     }
 485 
 486     _region_data[cur_region].set_destination(dest_addr);
 487 
 488     // If cur_region does not fit entirely into the target space, find a point
 489     // at which the source space can be 'split' so that part is copied to the
 490     // target space and the rest is copied elsewhere.
 491     if (dest_addr + words > target_end) {
 492       assert(source_next != nullptr, "source_next is null when splitting");
 493       *source_next = summarize_split_space(cur_region, split_info, dest_addr,
 494                                            target_end, target_next);
 495       return false;
 496     }
 497 
 498     uint destination_count = split_info.is_split(cur_region)
 499                              ? split_info.preceding_destination_count()
 500                              : 0;
 501 
 502     HeapWord* const last_addr = dest_addr + words - 1;
 503     const size_t dest_region_1 = addr_to_region_idx(dest_addr);
 504     const size_t dest_region_2 = addr_to_region_idx(last_addr);
 505 
 506     // Initially assume that the destination regions will be the same and
 507     // adjust the value below if necessary.  Under this assumption, if
 508     // cur_region == dest_region_2, then cur_region will be compacted
 509     // completely into itself.
 510     destination_count += cur_region == dest_region_2 ? 0 : 1;
 511     if (dest_region_1 != dest_region_2) {
 512       // Destination regions differ; adjust destination_count.
 513       destination_count += 1;
 514       // Data from cur_region will be copied to the start of dest_region_2.
 515       _region_data[dest_region_2].set_source_region(cur_region);
 516     } else if (is_region_aligned(dest_addr)) {
 517       // Data from cur_region will be copied to the start of the destination
 518       // region.
 519       _region_data[dest_region_1].set_source_region(cur_region);
 520     }
 521 
 522     _region_data[cur_region].set_destination_count(destination_count);
 523     dest_addr += words;
 524   }
 525 
 526   *target_next = dest_addr;
 527   return true;
 528 }
 529 
 530 #ifdef ASSERT
 531 void ParallelCompactData::verify_clear() {
 532   for (uint cur_idx = 0; cur_idx < region_count(); ++cur_idx) {
 533     if (!region(cur_idx)->is_clear()) {
 534       log_warning(gc)("Uncleared Region: %u", cur_idx);
 535       region(cur_idx)->verify_clear();
 536     }
 537   }
 538 }
 539 #endif  // #ifdef ASSERT
 540 
 541 STWGCTimer          PSParallelCompact::_gc_timer;
 542 ParallelOldTracer   PSParallelCompact::_gc_tracer;
 543 elapsedTimer        PSParallelCompact::_accumulated_time;
 544 unsigned int        PSParallelCompact::_maximum_compaction_gc_num = 0;
 545 CollectorCounters*  PSParallelCompact::_counters = nullptr;
 546 ParMarkBitMap       PSParallelCompact::_mark_bitmap;
 547 ParallelCompactData PSParallelCompact::_summary_data;
 548 
 549 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
 550 
 551 class PCAdjustPointerClosure: public BasicOopIterateClosure {
 552   template <typename T>
 553   void do_oop_work(T* p) { PSParallelCompact::adjust_pointer(p); }
 554 
 555 public:
 556   virtual void do_oop(oop* p)                { do_oop_work(p); }
 557   virtual void do_oop(narrowOop* p)          { do_oop_work(p); }
 558 
 559   virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
 560 };
 561 
 562 static PCAdjustPointerClosure pc_adjust_pointer_closure;
 563 
 564 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
 565 
 566 void PSParallelCompact::post_initialize() {
 567   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 568   _span_based_discoverer.set_span(heap->reserved_region());
 569   _ref_processor =
 570     new ReferenceProcessor(&_span_based_discoverer,
 571                            ParallelGCThreads,   // mt processing degree
 572                            ParallelGCThreads,   // mt discovery degree
 573                            false,               // concurrent_discovery
 574                            &_is_alive_closure); // non-header is alive closure
 575 
 576   _counters = new CollectorCounters("Parallel full collection pauses", 1);
 577 
 578   // Initialize static fields in ParCompactionManager.
 579   ParCompactionManager::initialize(mark_bitmap());
 580 }
 581 
 582 bool PSParallelCompact::initialize_aux_data() {
 583   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 584   MemRegion mr = heap->reserved_region();
 585   assert(mr.byte_size() != 0, "heap should be reserved");
 586 
 587   initialize_space_info();
 588 
 589   if (!_mark_bitmap.initialize(mr)) {
 590     vm_shutdown_during_initialization(
 591       err_msg("Unable to allocate %zuKB bitmaps for parallel "
 592       "garbage collection for the requested %zuKB heap.",
 593       _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
 594     return false;
 595   }
 596 
 597   if (!_summary_data.initialize(mr)) {
 598     vm_shutdown_during_initialization(
 599       err_msg("Unable to allocate %zuKB card tables for parallel "
 600       "garbage collection for the requested %zuKB heap.",
 601       _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
 602     return false;
 603   }
 604 
 605   return true;
 606 }
 607 
 608 void PSParallelCompact::initialize_space_info()
 609 {
 610   memset(&_space_info, 0, sizeof(_space_info));
 611 
 612   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 613   PSYoungGen* young_gen = heap->young_gen();
 614 
 615   _space_info[old_space_id].set_space(heap->old_gen()->object_space());
 616   _space_info[eden_space_id].set_space(young_gen->eden_space());
 617   _space_info[from_space_id].set_space(young_gen->from_space());
 618   _space_info[to_space_id].set_space(young_gen->to_space());
 619 
 620   _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
 621 }
 622 
 623 void
 624 PSParallelCompact::clear_data_covering_space(SpaceId id)
 625 {
 626   // At this point, top is the value before GC, new_top() is the value that will
 627   // be set at the end of GC.  The marking bitmap is cleared to top; nothing
 628   // should be marked above top.  The summary data is cleared to the larger of
 629   // top & new_top.
 630   MutableSpace* const space = _space_info[id].space();
 631   HeapWord* const bot = space->bottom();
 632   HeapWord* const top = space->top();
 633   HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
 634 
 635   _mark_bitmap.clear_range(bot, top);
 636 
 637   const size_t beg_region = _summary_data.addr_to_region_idx(bot);
 638   const size_t end_region =
 639     _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
 640   _summary_data.clear_range(beg_region, end_region);
 641 
 642   // Clear the data used to 'split' regions.
 643   SplitInfo& split_info = _space_info[id].split_info();
 644   if (split_info.is_valid()) {
 645     split_info.clear();
 646   }
 647   DEBUG_ONLY(split_info.verify_clear();)
 648 }
 649 
 650 void PSParallelCompact::pre_compact()
 651 {
 652   // Update the from & to space pointers in space_info, since they are swapped
 653   // at each young gen gc.  Do the update unconditionally (even though a
 654   // promotion failure does not swap spaces) because an unknown number of young
 655   // collections will have swapped the spaces an unknown number of times.
 656   GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
 657   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 658   _space_info[from_space_id].set_space(heap->young_gen()->from_space());
 659   _space_info[to_space_id].set_space(heap->young_gen()->to_space());
 660 
 661   // Increment the invocation count
 662   heap->increment_total_collections(true);
 663 
 664   CodeCache::on_gc_marking_cycle_start();
 665 
 666   heap->print_heap_before_gc();
 667   heap->trace_heap_before_gc(&_gc_tracer);
 668 
 669   // Fill in TLABs
 670   heap->ensure_parsability(true);  // retire TLABs
 671 
 672   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 673     Universe::verify("Before GC");
 674   }
 675 
 676   DEBUG_ONLY(mark_bitmap()->verify_clear();)
 677   DEBUG_ONLY(summary_data().verify_clear();)
 678 }
 679 
 680 void PSParallelCompact::post_compact()
 681 {
 682   GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
 683   ParCompactionManager::remove_all_shadow_regions();
 684 
 685   CodeCache::on_gc_marking_cycle_finish();
 686   CodeCache::arm_all_nmethods();
 687 
 688   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
 689     // Clear the marking bitmap, summary data and split info.
 690     clear_data_covering_space(SpaceId(id));
 691     {
 692       MutableSpace* space = _space_info[id].space();
 693       HeapWord* top = space->top();
 694       HeapWord* new_top = _space_info[id].new_top();
 695       if (ZapUnusedHeapArea && new_top < top) {
 696         space->mangle_region(MemRegion(new_top, top));
 697       }
 698       // Update top().  Must be done after clearing the bitmap and summary data.
 699       space->set_top(new_top);
 700     }
 701   }
 702 
 703 #ifdef ASSERT
 704   {
 705     mark_bitmap()->verify_clear();
 706     summary_data().verify_clear();
 707   }
 708 #endif
 709 
 710   ParCompactionManager::flush_all_string_dedup_requests();
 711 
 712   MutableSpace* const eden_space = _space_info[eden_space_id].space();
 713   MutableSpace* const from_space = _space_info[from_space_id].space();
 714   MutableSpace* const to_space   = _space_info[to_space_id].space();
 715 
 716   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 717   bool eden_empty = eden_space->is_empty();
 718 
 719   // Update heap occupancy information which is used as input to the soft ref
 720   // clearing policy at the next gc.
 721   Universe::heap()->update_capacity_and_used_at_gc();
 722 
 723   bool young_gen_empty = eden_empty && from_space->is_empty() &&
 724     to_space->is_empty();
 725 
 726   PSCardTable* ct = heap->card_table();
 727   MemRegion old_mr = heap->old_gen()->committed();
 728   if (young_gen_empty) {
 729     ct->clear_MemRegion(old_mr);
 730   } else {
 731     ct->dirty_MemRegion(old_mr);
 732   }
 733 
 734   {
 735     // Delete metaspaces for unloaded class loaders and clean up loader_data graph
 736     GCTraceTime(Debug, gc, phases) t("Purge Class Loader Data", gc_timer());
 737     ClassLoaderDataGraph::purge(true /* at_safepoint */);
 738     DEBUG_ONLY(MetaspaceUtils::verify();)
 739   }
 740 
 741   // Need to clear claim bits for the next mark.
 742   ClassLoaderDataGraph::clear_claimed_marks();
 743 
 744   heap->prune_scavengable_nmethods();
 745 
 746 #if COMPILER2_OR_JVMCI
 747   DerivedPointerTable::update_pointers();
 748 #endif
 749 
 750   // Signal that we have completed a visit to all live objects.
 751   Universe::heap()->record_whole_heap_examined_timestamp();
 752 }
 753 
 754 HeapWord* PSParallelCompact::compute_dense_prefix_for_old_space(MutableSpace* old_space,
 755                                                                 HeapWord* full_region_prefix_end) {
 756   const size_t region_size = ParallelCompactData::RegionSize;
 757   const ParallelCompactData& sd = summary_data();
 758 
 759   // Iteration starts with the region *after* the full-region-prefix-end.
 760   const RegionData* const start_region = sd.addr_to_region_ptr(full_region_prefix_end);
 761   // If final region is not full, iteration stops before that region,
 762   // because fill_dense_prefix_end assumes that prefix_end <= top.
 763   const RegionData* const end_region = sd.addr_to_region_ptr(old_space->top());
 764   assert(start_region <= end_region, "inv");
 765 
 766   size_t max_waste = old_space->capacity_in_words() * (MarkSweepDeadRatio / 100.0);
 767   const RegionData* cur_region = start_region;
 768   for (/* empty */; cur_region < end_region; ++cur_region) {
 769     assert(region_size >= cur_region->data_size(), "inv");
 770     size_t dead_size = region_size - cur_region->data_size();
 771     if (max_waste < dead_size) {
 772       break;
 773     }
 774     max_waste -= dead_size;
 775   }
 776 
 777   HeapWord* const prefix_end = sd.region_to_addr(cur_region);
 778   assert(sd.is_region_aligned(prefix_end), "postcondition");
 779   assert(prefix_end >= full_region_prefix_end, "in-range");
 780   assert(prefix_end <= old_space->top(), "in-range");
 781   return prefix_end;
 782 }
 783 
 784 void PSParallelCompact::fill_dense_prefix_end(SpaceId id) {
 785   // Comparing two sizes to decide if filling is required:
 786   //
 787   // The size of the filler (min-obj-size) is 2 heap words with the default
 788   // MinObjAlignment, since both markword and klass take 1 heap word.
 789   // With +UseCompactObjectHeaders, the minimum filler size is only one word,
 790   // because the Klass* gets encoded in the mark-word.
 791   //
 792   // The size of the gap (if any) right before dense-prefix-end is
 793   // MinObjAlignment.
 794   //
 795   // Need to fill in the gap only if it's smaller than min-obj-size, and the
 796   // filler obj will extend to next region.
 797 
 798   if (MinObjAlignment >= checked_cast<int>(CollectedHeap::min_fill_size())) {
 799     return;
 800   }
 801 
 802   assert(!UseCompactObjectHeaders, "Compact headers can allocate small objects");
 803   assert(CollectedHeap::min_fill_size() == 2, "inv");
 804   HeapWord* const dense_prefix_end = dense_prefix(id);
 805   assert(_summary_data.is_region_aligned(dense_prefix_end), "precondition");
 806   assert(dense_prefix_end <= space(id)->top(), "precondition");
 807   if (dense_prefix_end == space(id)->top()) {
 808     // Must not have single-word gap right before prefix-end/top.
 809     return;
 810   }
 811   RegionData* const region_after_dense_prefix = _summary_data.addr_to_region_ptr(dense_prefix_end);
 812 
 813   if (region_after_dense_prefix->partial_obj_size() != 0 ||
 814       _mark_bitmap.is_marked(dense_prefix_end)) {
 815     // The region after the dense prefix starts with live bytes.
 816     return;
 817   }
 818 
 819   HeapWord* block_start = start_array(id)->block_start_reaching_into_card(dense_prefix_end);
 820   if (block_start == dense_prefix_end - 1) {
 821     assert(!_mark_bitmap.is_marked(block_start), "inv");
 822     // There is exactly one heap word gap right before the dense prefix end, so we need a filler object.
 823     // The filler object will extend into region_after_dense_prefix.
 824     const size_t obj_len = 2; // min-fill-size
 825     HeapWord* const obj_beg = dense_prefix_end - 1;
 826     CollectedHeap::fill_with_object(obj_beg, obj_len);
 827     _mark_bitmap.mark_obj(obj_beg);
 828     _summary_data.addr_to_region_ptr(obj_beg)->add_live_obj(1);
 829     region_after_dense_prefix->set_partial_obj_size(1);
 830     region_after_dense_prefix->set_partial_obj_addr(obj_beg);
 831     assert(start_array(id) != nullptr, "sanity");
 832     start_array(id)->update_for_block(obj_beg, obj_beg + obj_len);
 833   }
 834 }
 835 
 836 bool PSParallelCompact::check_maximum_compaction(size_t total_live_words,
 837                                                  MutableSpace* const old_space,
 838                                                  HeapWord* full_region_prefix_end) {
 839 
 840   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 841 
 842   // Check System.GC
 843   bool is_max_on_system_gc = UseMaximumCompactionOnSystemGC
 844                           && GCCause::is_user_requested_gc(heap->gc_cause());
 845 
 846   // Check if all live objs are larger than old-gen.
 847   const bool is_old_gen_overflowing = (total_live_words > old_space->capacity_in_words());
 848 
 849   // JVM flags
 850   const uint total_invocations = heap->total_full_collections();
 851   assert(total_invocations >= _maximum_compaction_gc_num, "sanity");
 852   const size_t gcs_since_max = total_invocations - _maximum_compaction_gc_num;
 853   const bool is_interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
 854 
 855   // If all regions in old-gen are full
 856   const bool is_region_full =
 857     full_region_prefix_end >= _summary_data.region_align_down(old_space->top());
 858 
 859   if (is_max_on_system_gc || is_old_gen_overflowing || is_interval_ended || is_region_full) {
 860     _maximum_compaction_gc_num = total_invocations;
 861     return true;
 862   }
 863 
 864   return false;
 865 }
 866 
 867 void PSParallelCompact::summary_phase()
 868 {
 869   GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
 870 
 871   MutableSpace* const old_space = _space_info[old_space_id].space();
 872   {
 873     size_t total_live_words = 0;
 874     HeapWord* full_region_prefix_end = nullptr;
 875     {
 876       // old-gen
 877       size_t live_words = _summary_data.live_words_in_space(old_space,
 878                                                             &full_region_prefix_end);
 879       total_live_words += live_words;
 880     }
 881     // young-gen
 882     for (uint i = eden_space_id; i < last_space_id; ++i) {
 883       const MutableSpace* space = _space_info[i].space();
 884       size_t live_words = _summary_data.live_words_in_space(space);
 885       total_live_words += live_words;
 886       _space_info[i].set_new_top(space->bottom() + live_words);
 887       _space_info[i].set_dense_prefix(space->bottom());
 888     }
 889 
 890     bool maximum_compaction = check_maximum_compaction(total_live_words,
 891                                                        old_space,
 892                                                        full_region_prefix_end);
 893     HeapWord* dense_prefix_end = maximum_compaction
 894                                  ? full_region_prefix_end
 895                                  : compute_dense_prefix_for_old_space(old_space,
 896                                                                       full_region_prefix_end);
 897     SpaceId id = old_space_id;
 898     _space_info[id].set_dense_prefix(dense_prefix_end);
 899 
 900     if (dense_prefix_end != old_space->bottom()) {
 901       fill_dense_prefix_end(id);
 902       _summary_data.summarize_dense_prefix(old_space->bottom(), dense_prefix_end);
 903     }
 904 
 905     // Compacting objs in [dense_prefix_end, old_space->top())
 906     _summary_data.summarize(_space_info[id].split_info(),
 907                             dense_prefix_end, old_space->top(), nullptr,
 908                             dense_prefix_end, old_space->end(),
 909                             _space_info[id].new_top_addr());
 910   }
 911 
 912   // Summarize the remaining spaces in the young gen.  The initial target space
 913   // is the old gen.  If a space does not fit entirely into the target, then the
 914   // remainder is compacted into the space itself and that space becomes the new
 915   // target.
 916   SpaceId dst_space_id = old_space_id;
 917   HeapWord* dst_space_end = old_space->end();
 918   HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
 919   for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
 920     const MutableSpace* space = _space_info[id].space();
 921     const size_t live = pointer_delta(_space_info[id].new_top(),
 922                                       space->bottom());
 923     const size_t available = pointer_delta(dst_space_end, *new_top_addr);
 924 
 925     if (live > 0 && live <= available) {
 926       // All the live data will fit.
 927       bool done = _summary_data.summarize(_space_info[id].split_info(),
 928                                           space->bottom(), space->top(),
 929                                           nullptr,
 930                                           *new_top_addr, dst_space_end,
 931                                           new_top_addr);
 932       assert(done, "space must fit into old gen");
 933 
 934       // Reset the new_top value for the space.
 935       _space_info[id].set_new_top(space->bottom());
 936     } else if (live > 0) {
 937       // Attempt to fit part of the source space into the target space.
 938       HeapWord* next_src_addr = nullptr;
 939       bool done = _summary_data.summarize(_space_info[id].split_info(),
 940                                           space->bottom(), space->top(),
 941                                           &next_src_addr,
 942                                           *new_top_addr, dst_space_end,
 943                                           new_top_addr);
 944       assert(!done, "space should not fit into old gen");
 945       assert(next_src_addr != nullptr, "sanity");
 946 
 947       // The source space becomes the new target, so the remainder is compacted
 948       // within the space itself.
 949       dst_space_id = SpaceId(id);
 950       dst_space_end = space->end();
 951       new_top_addr = _space_info[id].new_top_addr();
 952       done = _summary_data.summarize(_space_info[id].split_info(),
 953                                      next_src_addr, space->top(),
 954                                      nullptr,
 955                                      space->bottom(), dst_space_end,
 956                                      new_top_addr);
 957       assert(done, "space must fit when compacted into itself");
 958       assert(*new_top_addr <= space->top(), "usage should not grow");
 959     }
 960   }
 961 }
 962 
 963 // This method should contain all heap-specific policy for invoking a full
 964 // collection.  invoke_no_policy() will only attempt to compact the heap; it
 965 // will do nothing further.  If we need to bail out for policy reasons, scavenge
 966 // before full gc, or any other specialized behavior, it needs to be added here.
 967 //
 968 // Note that this method should only be called from the vm_thread while at a
 969 // safepoint.
 970 //
 971 // Note that the all_soft_refs_clear flag in the soft ref policy
 972 // may be true because this method can be called without intervening
 973 // activity.  For example when the heap space is tight and full measure
 974 // are being taken to free space.
 975 bool PSParallelCompact::invoke(bool clear_all_soft_refs) {
 976   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 977   assert(Thread::current() == (Thread*)VMThread::vm_thread(),
 978          "should be in vm thread");
 979 
 980   SvcGCMarker sgcm(SvcGCMarker::FULL);
 981   IsSTWGCActiveMark mark;
 982 
 983   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 984   clear_all_soft_refs = clear_all_soft_refs
 985                      || heap->soft_ref_policy()->should_clear_all_soft_refs();
 986 
 987   return PSParallelCompact::invoke_no_policy(clear_all_soft_refs);
 988 }
 989 
 990 // This method contains no policy. You should probably
 991 // be calling invoke() instead.
 992 bool PSParallelCompact::invoke_no_policy(bool clear_all_soft_refs) {
 993   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
 994   assert(ref_processor() != nullptr, "Sanity");
 995 
 996   if (GCLocker::check_active_before_gc()) {
 997     return false;
 998   }
 999 
1000   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1001 
1002   GCIdMark gc_id_mark;
1003   _gc_timer.register_gc_start();
1004   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1005 
1006   GCCause::Cause gc_cause = heap->gc_cause();
1007   PSYoungGen* young_gen = heap->young_gen();
1008   PSOldGen* old_gen = heap->old_gen();
1009   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1010 
1011   // The scope of casr should end after code that can change
1012   // SoftRefPolicy::_should_clear_all_soft_refs.
1013   ClearedAllSoftRefs casr(clear_all_soft_refs,
1014                           heap->soft_ref_policy());
1015 
1016   // Make sure data structures are sane, make the heap parsable, and do other
1017   // miscellaneous bookkeeping.
1018   pre_compact();
1019 
1020   const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
1021 
1022   {
1023     const uint active_workers =
1024       WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
1025                                         ParallelScavengeHeap::heap()->workers().active_workers(),
1026                                         Threads::number_of_non_daemon_threads());
1027     ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
1028 
1029     GCTraceCPUTime tcpu(&_gc_tracer);
1030     GCTraceTime(Info, gc) tm("Pause Full", nullptr, gc_cause, true);
1031 
1032     heap->pre_full_gc_dump(&_gc_timer);
1033 
1034     TraceCollectorStats tcs(counters());
1035     TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause, "end of major GC");
1036 
1037     if (log_is_enabled(Debug, gc, heap, exit)) {
1038       accumulated_time()->start();
1039     }
1040 
1041     // Let the size policy know we're starting
1042     size_policy->major_collection_begin();
1043 
1044 #if COMPILER2_OR_JVMCI
1045     DerivedPointerTable::clear();
1046 #endif
1047 
1048     ref_processor()->start_discovery(clear_all_soft_refs);
1049 
1050     ClassUnloadingContext ctx(1 /* num_nmethod_unlink_workers */,
1051                               false /* unregister_nmethods_during_purge */,
1052                               false /* lock_nmethod_free_separately */);
1053 
1054     marking_phase(&_gc_tracer);
1055 
1056     summary_phase();
1057 
1058 #if COMPILER2_OR_JVMCI
1059     assert(DerivedPointerTable::is_active(), "Sanity");
1060     DerivedPointerTable::set_active(false);
1061 #endif
1062 
1063     forward_to_new_addr();
1064 
1065     adjust_pointers();
1066 
1067     compact();
1068 
1069     ParCompactionManager::_preserved_marks_set->restore(&ParallelScavengeHeap::heap()->workers());
1070 
1071     ParCompactionManager::verify_all_region_stack_empty();
1072 
1073     // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
1074     // done before resizing.
1075     post_compact();
1076 
1077     // Let the size policy know we're done
1078     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1079 
1080     if (UseAdaptiveSizePolicy) {
1081       log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1082       log_trace(gc, ergo)("old_gen_capacity: %zu young_gen_capacity: %zu",
1083                           old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1084 
1085       // Don't check if the size_policy is ready here.  Let
1086       // the size_policy check that internally.
1087       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1088           AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1089         // Swap the survivor spaces if from_space is empty. The
1090         // resize_young_gen() called below is normally used after
1091         // a successful young GC and swapping of survivor spaces;
1092         // otherwise, it will fail to resize the young gen with
1093         // the current implementation.
1094         if (young_gen->from_space()->is_empty()) {
1095           young_gen->from_space()->clear(SpaceDecorator::Mangle);
1096           young_gen->swap_spaces();
1097         }
1098 
1099         // Calculate optimal free space amounts
1100         assert(young_gen->max_gen_size() >
1101           young_gen->from_space()->capacity_in_bytes() +
1102           young_gen->to_space()->capacity_in_bytes(),
1103           "Sizes of space in young gen are out-of-bounds");
1104 
1105         size_t young_live = young_gen->used_in_bytes();
1106         size_t eden_live = young_gen->eden_space()->used_in_bytes();
1107         size_t old_live = old_gen->used_in_bytes();
1108         size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1109         size_t max_old_gen_size = old_gen->max_gen_size();
1110         size_t max_eden_size = young_gen->max_gen_size() -
1111           young_gen->from_space()->capacity_in_bytes() -
1112           young_gen->to_space()->capacity_in_bytes();
1113 
1114         // Used for diagnostics
1115         size_policy->clear_generation_free_space_flags();
1116 
1117         size_policy->compute_generations_free_space(young_live,
1118                                                     eden_live,
1119                                                     old_live,
1120                                                     cur_eden,
1121                                                     max_old_gen_size,
1122                                                     max_eden_size,
1123                                                     true /* full gc*/);
1124 
1125         size_policy->check_gc_overhead_limit(eden_live,
1126                                              max_old_gen_size,
1127                                              max_eden_size,
1128                                              true /* full gc*/,
1129                                              gc_cause,
1130                                              heap->soft_ref_policy());
1131 
1132         size_policy->decay_supplemental_growth(true /* full gc*/);
1133 
1134         heap->resize_old_gen(
1135           size_policy->calculated_old_free_size_in_bytes());
1136 
1137         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1138                                size_policy->calculated_survivor_size_in_bytes());
1139       }
1140 
1141       log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1142     }
1143 
1144     if (UsePerfData) {
1145       PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1146       counters->update_counters();
1147       counters->update_old_capacity(old_gen->capacity_in_bytes());
1148       counters->update_young_capacity(young_gen->capacity_in_bytes());
1149     }
1150 
1151     heap->resize_all_tlabs();
1152 
1153     // Resize the metaspace capacity after a collection
1154     MetaspaceGC::compute_new_size();
1155 
1156     if (log_is_enabled(Debug, gc, heap, exit)) {
1157       accumulated_time()->stop();
1158     }
1159 
1160     heap->print_heap_change(pre_gc_values);
1161 
1162     // Track memory usage and detect low memory
1163     MemoryService::track_memory_usage();
1164     heap->update_counters();
1165 
1166     heap->post_full_gc_dump(&_gc_timer);
1167   }
1168 
1169   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1170     Universe::verify("After GC");
1171   }
1172 
1173   heap->print_heap_after_gc();
1174   heap->trace_heap_after_gc(&_gc_tracer);
1175 
1176   AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
1177 
1178   _gc_timer.register_gc_end();
1179 
1180   _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1181   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1182 
1183   return true;
1184 }
1185 
1186 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
1187 private:
1188   uint _worker_id;
1189 
1190 public:
1191   PCAddThreadRootsMarkingTaskClosure(uint worker_id) : _worker_id(worker_id) { }
1192   void do_thread(Thread* thread) {
1193     assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1194 
1195     ResourceMark rm;
1196 
1197     ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(_worker_id);
1198 
1199     MarkingNMethodClosure mark_and_push_in_blobs(&cm->_mark_and_push_closure,
1200                                                  !NMethodToOopClosure::FixRelocations,
1201                                                  true /* keepalive nmethods */);
1202 
1203     thread->oops_do(&cm->_mark_and_push_closure, &mark_and_push_in_blobs);
1204 
1205     // Do the real work
1206     cm->follow_marking_stacks();
1207   }
1208 };
1209 
1210 void steal_marking_work(TaskTerminator& terminator, uint worker_id) {
1211   assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1212 
1213   ParCompactionManager* cm =
1214     ParCompactionManager::gc_thread_compaction_manager(worker_id);
1215 
1216   do {
1217     ScannerTask task;
1218     if (ParCompactionManager::steal(worker_id, task)) {
1219       cm->follow_contents(task, true);
1220     }
1221     cm->follow_marking_stacks();
1222   } while (!terminator.offer_termination());
1223 }
1224 
1225 class MarkFromRootsTask : public WorkerTask {
1226   StrongRootsScope _strong_roots_scope; // needed for Threads::possibly_parallel_threads_do
1227   OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_set_par_state;
1228   TaskTerminator _terminator;
1229   uint _active_workers;
1230 
1231 public:
1232   MarkFromRootsTask(uint active_workers) :
1233       WorkerTask("MarkFromRootsTask"),
1234       _strong_roots_scope(active_workers),
1235       _terminator(active_workers, ParCompactionManager::marking_stacks()),
1236       _active_workers(active_workers) {}
1237 
1238   virtual void work(uint worker_id) {
1239     ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1240     cm->create_marking_stats_cache();
1241     {
1242       CLDToOopClosure cld_closure(&cm->_mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
1243       ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
1244 
1245       // Do the real work
1246       cm->follow_marking_stacks();
1247     }
1248 
1249     {
1250       PCAddThreadRootsMarkingTaskClosure closure(worker_id);
1251       Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &closure);
1252     }
1253 
1254     // Mark from OopStorages
1255     {
1256       _oop_storage_set_par_state.oops_do(&cm->_mark_and_push_closure);
1257       // Do the real work
1258       cm->follow_marking_stacks();
1259     }
1260 
1261     if (_active_workers > 1) {
1262       steal_marking_work(_terminator, worker_id);
1263     }
1264   }
1265 };
1266 
1267 class ParallelCompactRefProcProxyTask : public RefProcProxyTask {
1268   TaskTerminator _terminator;
1269 
1270 public:
1271   ParallelCompactRefProcProxyTask(uint max_workers)
1272     : RefProcProxyTask("ParallelCompactRefProcProxyTask", max_workers),
1273       _terminator(_max_workers, ParCompactionManager::marking_stacks()) {}
1274 
1275   void work(uint worker_id) override {
1276     assert(worker_id < _max_workers, "sanity");
1277     ParCompactionManager* cm = (_tm == RefProcThreadModel::Single) ? ParCompactionManager::get_vmthread_cm() : ParCompactionManager::gc_thread_compaction_manager(worker_id);
1278     BarrierEnqueueDiscoveredFieldClosure enqueue;
1279     ParCompactionManager::FollowStackClosure complete_gc(cm, (_tm == RefProcThreadModel::Single) ? nullptr : &_terminator, worker_id);
1280     _rp_task->rp_work(worker_id, PSParallelCompact::is_alive_closure(), &cm->_mark_and_push_closure, &enqueue, &complete_gc);
1281   }
1282 
1283   void prepare_run_task_hook() override {
1284     _terminator.reset_for_reuse(_queue_count);
1285   }
1286 };
1287 
1288 static void flush_marking_stats_cache(const uint num_workers) {
1289   for (uint i = 0; i < num_workers; ++i) {
1290     ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(i);
1291     cm->flush_and_destroy_marking_stats_cache();
1292   }
1293 }
1294 
1295 void PSParallelCompact::marking_phase(ParallelOldTracer *gc_tracer) {
1296   // Recursively traverse all live objects and mark them
1297   GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
1298 
1299   uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1300 
1301   ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
1302   {
1303     GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
1304 
1305     MarkFromRootsTask task(active_gc_threads);
1306     ParallelScavengeHeap::heap()->workers().run_task(&task);
1307   }
1308 
1309   // Process reference objects found during marking
1310   {
1311     GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
1312 
1313     ReferenceProcessorStats stats;
1314     ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
1315 
1316     ref_processor()->set_active_mt_degree(active_gc_threads);
1317     ParallelCompactRefProcProxyTask task(ref_processor()->max_num_queues());
1318     stats = ref_processor()->process_discovered_references(task, pt);
1319 
1320     gc_tracer->report_gc_reference_stats(stats);
1321     pt.print_all_references();
1322   }
1323 
1324   {
1325     GCTraceTime(Debug, gc, phases) tm("Flush Marking Stats", &_gc_timer);
1326 
1327     flush_marking_stats_cache(active_gc_threads);
1328   }
1329 
1330   // This is the point where the entire marking should have completed.
1331   ParCompactionManager::verify_all_marking_stack_empty();
1332 
1333   {
1334     GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
1335     WeakProcessor::weak_oops_do(&ParallelScavengeHeap::heap()->workers(),
1336                                 is_alive_closure(),
1337                                 &do_nothing_cl,
1338                                 1);
1339   }
1340 
1341   {
1342     GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
1343 
1344     ClassUnloadingContext* ctx = ClassUnloadingContext::context();
1345 
1346     bool unloading_occurred;
1347     {
1348       CodeCache::UnlinkingScope scope(is_alive_closure());
1349 
1350       // Follow system dictionary roots and unload classes.
1351       unloading_occurred = SystemDictionary::do_unloading(&_gc_timer);
1352 
1353       // Unload nmethods.
1354       CodeCache::do_unloading(unloading_occurred);
1355     }
1356 
1357     {
1358       GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
1359       // Release unloaded nmethod's memory.
1360       ctx->purge_nmethods();
1361     }
1362     {
1363       GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", &_gc_timer);
1364       ParallelScavengeHeap::heap()->prune_unlinked_nmethods();
1365     }
1366     {
1367       GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
1368       ctx->free_nmethods();
1369     }
1370 
1371     // Prune dead klasses from subklass/sibling/implementor lists.
1372     Klass::clean_weak_klass_links(unloading_occurred);
1373 
1374     // Clean JVMCI metadata handles.
1375     JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
1376   }
1377 
1378   {
1379     GCTraceTime(Debug, gc, phases) tm("Report Object Count", &_gc_timer);
1380     _gc_tracer.report_object_count_after_gc(is_alive_closure(), &ParallelScavengeHeap::heap()->workers());
1381   }
1382 #if TASKQUEUE_STATS
1383   ParCompactionManager::print_and_reset_taskqueue_stats();
1384 #endif
1385 }
1386 
1387 template<typename Func>
1388 void PSParallelCompact::adjust_in_space_helper(SpaceId id, volatile uint* claim_counter, Func&& on_stripe) {
1389   MutableSpace* sp = PSParallelCompact::space(id);
1390   HeapWord* const bottom = sp->bottom();
1391   HeapWord* const top = sp->top();
1392   if (bottom == top) {
1393     return;
1394   }
1395 
1396   const uint num_regions_per_stripe = 2;
1397   const size_t region_size = ParallelCompactData::RegionSize;
1398   const size_t stripe_size = num_regions_per_stripe * region_size;
1399 
1400   while (true) {
1401     uint counter = Atomic::fetch_then_add(claim_counter, num_regions_per_stripe);
1402     HeapWord* cur_stripe = bottom + counter * region_size;
1403     if (cur_stripe >= top) {
1404       break;
1405     }
1406     HeapWord* stripe_end = MIN2(cur_stripe + stripe_size, top);
1407     on_stripe(cur_stripe, stripe_end);
1408   }
1409 }
1410 
1411 void PSParallelCompact::adjust_in_old_space(volatile uint* claim_counter) {
1412   // Regions in old-space shouldn't be split.
1413   assert(!_space_info[old_space_id].split_info().is_valid(), "inv");
1414 
1415   auto scan_obj_with_limit = [&] (HeapWord* obj_start, HeapWord* left, HeapWord* right) {
1416     assert(mark_bitmap()->is_marked(obj_start), "inv");
1417     oop obj = cast_to_oop(obj_start);
1418     return obj->oop_iterate_size(&pc_adjust_pointer_closure, MemRegion(left, right));
1419   };
1420 
1421   adjust_in_space_helper(old_space_id, claim_counter, [&] (HeapWord* stripe_start, HeapWord* stripe_end) {
1422     assert(_summary_data.is_region_aligned(stripe_start), "inv");
1423     RegionData* cur_region = _summary_data.addr_to_region_ptr(stripe_start);
1424     HeapWord* obj_start;
1425     if (cur_region->partial_obj_size() != 0) {
1426       obj_start = cur_region->partial_obj_addr();
1427       obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1428     } else {
1429       obj_start = stripe_start;
1430     }
1431 
1432     while (obj_start < stripe_end) {
1433       obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1434       if (obj_start >= stripe_end) {
1435         break;
1436       }
1437       obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1438     }
1439   });
1440 }
1441 
1442 void PSParallelCompact::adjust_in_young_space(SpaceId id, volatile uint* claim_counter) {
1443   adjust_in_space_helper(id, claim_counter, [](HeapWord* stripe_start, HeapWord* stripe_end) {
1444     HeapWord* obj_start = stripe_start;
1445     while (obj_start < stripe_end) {
1446       obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1447       if (obj_start >= stripe_end) {
1448         break;
1449       }
1450       oop obj = cast_to_oop(obj_start);
1451       obj_start += obj->oop_iterate_size(&pc_adjust_pointer_closure);
1452     }
1453   });
1454 }
1455 
1456 void PSParallelCompact::adjust_pointers_in_spaces(uint worker_id, volatile uint* claim_counters) {
1457   auto start_time = Ticks::now();
1458   adjust_in_old_space(&claim_counters[0]);
1459   for (uint id = eden_space_id; id < last_space_id; ++id) {
1460     adjust_in_young_space(SpaceId(id), &claim_counters[id]);
1461   }
1462   log_trace(gc, phases)("adjust_pointers_in_spaces worker %u: %.3f ms", worker_id, (Ticks::now() - start_time).seconds() * 1000);
1463 }
1464 
1465 class PSAdjustTask final : public WorkerTask {
1466   SubTasksDone                               _sub_tasks;
1467   WeakProcessor::Task                        _weak_proc_task;
1468   OopStorageSetStrongParState<false, false>  _oop_storage_iter;
1469   uint                                       _nworkers;
1470   volatile uint _claim_counters[PSParallelCompact::last_space_id] = {};
1471 
1472   enum PSAdjustSubTask {
1473     PSAdjustSubTask_code_cache,
1474 
1475     PSAdjustSubTask_num_elements
1476   };
1477 
1478 public:
1479   PSAdjustTask(uint nworkers) :
1480     WorkerTask("PSAdjust task"),
1481     _sub_tasks(PSAdjustSubTask_num_elements),
1482     _weak_proc_task(nworkers),
1483     _nworkers(nworkers) {
1484 
1485     ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
1486     if (nworkers > 1) {
1487       Threads::change_thread_claim_token();
1488     }
1489   }
1490 
1491   ~PSAdjustTask() {
1492     Threads::assert_all_threads_claimed();
1493   }
1494 
1495   void work(uint worker_id) {
1496     ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1497     cm->preserved_marks()->adjust_during_full_gc();
1498     {
1499       // adjust pointers in all spaces
1500       PSParallelCompact::adjust_pointers_in_spaces(worker_id, _claim_counters);
1501     }
1502     {
1503       ResourceMark rm;
1504       Threads::possibly_parallel_oops_do(_nworkers > 1, &pc_adjust_pointer_closure, nullptr);
1505     }
1506     _oop_storage_iter.oops_do(&pc_adjust_pointer_closure);
1507     {
1508       CLDToOopClosure cld_closure(&pc_adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
1509       ClassLoaderDataGraph::cld_do(&cld_closure);
1510     }
1511     {
1512       AlwaysTrueClosure always_alive;
1513       _weak_proc_task.work(worker_id, &always_alive, &pc_adjust_pointer_closure);
1514     }
1515     if (_sub_tasks.try_claim_task(PSAdjustSubTask_code_cache)) {
1516       NMethodToOopClosure adjust_code(&pc_adjust_pointer_closure, NMethodToOopClosure::FixRelocations);
1517       CodeCache::nmethods_do(&adjust_code);
1518     }
1519     _sub_tasks.all_tasks_claimed();
1520   }
1521 };
1522 
1523 void PSParallelCompact::adjust_pointers() {
1524   // Adjust the pointers to reflect the new locations
1525   GCTraceTime(Info, gc, phases) tm("Adjust Pointers", &_gc_timer);
1526   uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1527   PSAdjustTask task(nworkers);
1528   ParallelScavengeHeap::heap()->workers().run_task(&task);
1529 }
1530 
1531 // Split [start, end) evenly for a number of workers and return the
1532 // range for worker_id.
1533 static void split_regions_for_worker(size_t start, size_t end,
1534                                      uint worker_id, uint num_workers,
1535                                      size_t* worker_start, size_t* worker_end) {
1536   assert(start < end, "precondition");
1537   assert(num_workers > 0, "precondition");
1538   assert(worker_id < num_workers, "precondition");
1539 
1540   size_t num_regions = end - start;
1541   size_t num_regions_per_worker = num_regions / num_workers;
1542   size_t remainder = num_regions % num_workers;
1543   // The first few workers will get one extra.
1544   *worker_start = start + worker_id * num_regions_per_worker
1545                   + MIN2(checked_cast<size_t>(worker_id), remainder);
1546   *worker_end = *worker_start + num_regions_per_worker
1547                 + (worker_id < remainder ? 1 : 0);
1548 }
1549 
1550 void PSParallelCompact::forward_to_new_addr() {
1551   GCTraceTime(Info, gc, phases) tm("Forward", &_gc_timer);
1552   uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1553 
1554   struct ForwardTask final : public WorkerTask {
1555     uint _num_workers;
1556 
1557     explicit ForwardTask(uint num_workers) :
1558       WorkerTask("PSForward task"),
1559       _num_workers(num_workers) {}
1560 
1561     static void forward_objs_in_range(ParCompactionManager* cm,
1562                                       HeapWord* start,
1563                                       HeapWord* end,
1564                                       HeapWord* destination) {
1565       HeapWord* cur_addr = start;
1566       HeapWord* new_addr = destination;
1567 
1568       while (cur_addr < end) {
1569         cur_addr = mark_bitmap()->find_obj_beg(cur_addr, end);
1570         if (cur_addr >= end) {
1571           return;
1572         }
1573         assert(mark_bitmap()->is_marked(cur_addr), "inv");
1574         oop obj = cast_to_oop(cur_addr);
1575         if (new_addr != cur_addr) {
1576           cm->preserved_marks()->push_if_necessary(obj, obj->mark());
1577           FullGCForwarding::forward_to(obj, cast_to_oop(new_addr));
1578         }
1579         size_t obj_size = obj->size();
1580         new_addr += obj_size;
1581         cur_addr += obj_size;
1582       }
1583     }
1584 
1585     void work(uint worker_id) override {
1586       ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1587       for (uint id = old_space_id; id < last_space_id; ++id) {
1588         MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1589         HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1590         HeapWord* top = sp->top();
1591 
1592         if (dense_prefix_addr == top) {
1593           continue;
1594         }
1595 
1596         const SplitInfo& split_info = _space_info[SpaceId(id)].split_info();
1597 
1598         size_t dense_prefix_region = _summary_data.addr_to_region_idx(dense_prefix_addr);
1599         size_t top_region = _summary_data.addr_to_region_idx(_summary_data.region_align_up(top));
1600         size_t start_region;
1601         size_t end_region;
1602         split_regions_for_worker(dense_prefix_region, top_region,
1603                                  worker_id, _num_workers,
1604                                  &start_region, &end_region);
1605         for (size_t cur_region = start_region; cur_region < end_region; ++cur_region) {
1606           RegionData* region_ptr = _summary_data.region(cur_region);
1607           size_t partial_obj_size = region_ptr->partial_obj_size();
1608 
1609           if (partial_obj_size == ParallelCompactData::RegionSize) {
1610             // No obj-start
1611             continue;
1612           }
1613 
1614           HeapWord* region_start = _summary_data.region_to_addr(cur_region);
1615           HeapWord* region_end = region_start + ParallelCompactData::RegionSize;
1616 
1617           if (split_info.is_split(cur_region)) {
1618             // Part 1: will be relocated to space-1
1619             HeapWord* preceding_destination = split_info.preceding_destination();
1620             HeapWord* split_point = split_info.split_point();
1621             forward_objs_in_range(cm, region_start + partial_obj_size, split_point, preceding_destination + partial_obj_size);
1622 
1623             // Part 2: will be relocated to space-2
1624             HeapWord* destination = region_ptr->destination();
1625             forward_objs_in_range(cm, split_point, region_end, destination);
1626           } else {
1627             HeapWord* destination = region_ptr->destination();
1628             forward_objs_in_range(cm, region_start + partial_obj_size, region_end, destination + partial_obj_size);
1629           }
1630         }
1631       }
1632     }
1633   } task(nworkers);
1634 
1635   ParallelScavengeHeap::heap()->workers().run_task(&task);
1636   debug_only(verify_forward();)
1637 }
1638 
1639 #ifdef ASSERT
1640 void PSParallelCompact::verify_forward() {
1641   HeapWord* old_dense_prefix_addr = dense_prefix(SpaceId(old_space_id));
1642   RegionData* old_region = _summary_data.region(_summary_data.addr_to_region_idx(old_dense_prefix_addr));
1643   HeapWord* bump_ptr = old_region->partial_obj_size() != 0
1644                        ? old_dense_prefix_addr + old_region->partial_obj_size()
1645                        : old_dense_prefix_addr;
1646   SpaceId bump_ptr_space = old_space_id;
1647 
1648   for (uint id = old_space_id; id < last_space_id; ++id) {
1649     MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1650     HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1651     HeapWord* top = sp->top();
1652     HeapWord* cur_addr = dense_prefix_addr;
1653 
1654     while (cur_addr < top) {
1655       cur_addr = mark_bitmap()->find_obj_beg(cur_addr, top);
1656       if (cur_addr >= top) {
1657         break;
1658       }
1659       assert(mark_bitmap()->is_marked(cur_addr), "inv");
1660       assert(bump_ptr <= _space_info[bump_ptr_space].new_top(), "inv");
1661       // Move to the space containing cur_addr
1662       if (bump_ptr == _space_info[bump_ptr_space].new_top()) {
1663         bump_ptr = space(space_id(cur_addr))->bottom();
1664         bump_ptr_space = space_id(bump_ptr);
1665       }
1666       oop obj = cast_to_oop(cur_addr);
1667       if (cur_addr == bump_ptr) {
1668         assert(!FullGCForwarding::is_forwarded(obj), "inv");
1669       } else {
1670         assert(FullGCForwarding::forwardee(obj) == cast_to_oop(bump_ptr), "inv");
1671       }
1672       bump_ptr += obj->size();
1673       cur_addr += obj->size();
1674     }
1675   }
1676 }
1677 #endif
1678 
1679 // Helper class to print 8 region numbers per line and then print the total at the end.
1680 class FillableRegionLogger : public StackObj {
1681 private:
1682   Log(gc, compaction) log;
1683   static const int LineLength = 8;
1684   size_t _regions[LineLength];
1685   int _next_index;
1686   bool _enabled;
1687   size_t _total_regions;
1688 public:
1689   FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
1690   ~FillableRegionLogger() {
1691     log.trace("%zu initially fillable regions", _total_regions);
1692   }
1693 
1694   void print_line() {
1695     if (!_enabled || _next_index == 0) {
1696       return;
1697     }
1698     FormatBuffer<> line("Fillable: ");
1699     for (int i = 0; i < _next_index; i++) {
1700       line.append(" %7zu", _regions[i]);
1701     }
1702     log.trace("%s", line.buffer());
1703     _next_index = 0;
1704   }
1705 
1706   void handle(size_t region) {
1707     if (!_enabled) {
1708       return;
1709     }
1710     _regions[_next_index++] = region;
1711     if (_next_index == LineLength) {
1712       print_line();
1713     }
1714     _total_regions++;
1715   }
1716 };
1717 
1718 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
1719 {
1720   GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
1721 
1722   // Find the threads that are active
1723   uint worker_id = 0;
1724 
1725   // Find all regions that are available (can be filled immediately) and
1726   // distribute them to the thread stacks.  The iteration is done in reverse
1727   // order (high to low) so the regions will be removed in ascending order.
1728 
1729   const ParallelCompactData& sd = PSParallelCompact::summary_data();
1730 
1731   // id + 1 is used to test termination so unsigned  can
1732   // be used with an old_space_id == 0.
1733   FillableRegionLogger region_logger;
1734   for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
1735     SpaceInfo* const space_info = _space_info + id;
1736     HeapWord* const new_top = space_info->new_top();
1737 
1738     const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
1739     const size_t end_region =
1740       sd.addr_to_region_idx(sd.region_align_up(new_top));
1741 
1742     for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
1743       if (sd.region(cur)->claim_unsafe()) {
1744         ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1745         bool result = sd.region(cur)->mark_normal();
1746         assert(result, "Must succeed at this point.");
1747         cm->region_stack()->push(cur);
1748         region_logger.handle(cur);
1749         // Assign regions to tasks in round-robin fashion.
1750         if (++worker_id == parallel_gc_threads) {
1751           worker_id = 0;
1752         }
1753       }
1754     }
1755     region_logger.print_line();
1756   }
1757 }
1758 
1759 static void compaction_with_stealing_work(TaskTerminator* terminator, uint worker_id) {
1760   assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1761 
1762   ParCompactionManager* cm =
1763     ParCompactionManager::gc_thread_compaction_manager(worker_id);
1764 
1765   // Drain the stacks that have been preloaded with regions
1766   // that are ready to fill.
1767 
1768   cm->drain_region_stacks();
1769 
1770   guarantee(cm->region_stack()->is_empty(), "Not empty");
1771 
1772   size_t region_index = 0;
1773 
1774   while (true) {
1775     if (ParCompactionManager::steal(worker_id, region_index)) {
1776       PSParallelCompact::fill_and_update_region(cm, region_index);
1777       cm->drain_region_stacks();
1778     } else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
1779       // Fill and update an unavailable region with the help of a shadow region
1780       PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
1781       cm->drain_region_stacks();
1782     } else {
1783       if (terminator->offer_termination()) {
1784         break;
1785       }
1786       // Go around again.
1787     }
1788   }
1789 }
1790 
1791 class FillDensePrefixAndCompactionTask: public WorkerTask {
1792   uint _num_workers;
1793   TaskTerminator _terminator;
1794 
1795 public:
1796   FillDensePrefixAndCompactionTask(uint active_workers) :
1797       WorkerTask("FillDensePrefixAndCompactionTask"),
1798       _num_workers(active_workers),
1799       _terminator(active_workers, ParCompactionManager::region_task_queues()) {
1800   }
1801 
1802   virtual void work(uint worker_id) {
1803     {
1804       auto start = Ticks::now();
1805       PSParallelCompact::fill_dead_objs_in_dense_prefix(worker_id, _num_workers);
1806       log_trace(gc, phases)("Fill dense prefix by worker %u: %.3f ms", worker_id, (Ticks::now() - start).seconds() * 1000);
1807     }
1808     compaction_with_stealing_work(&_terminator, worker_id);
1809   }
1810 };
1811 
1812 void PSParallelCompact::fill_range_in_dense_prefix(HeapWord* start, HeapWord* end) {
1813 #ifdef ASSERT
1814   {
1815     assert(start < end, "precondition");
1816     assert(mark_bitmap()->find_obj_beg(start, end) == end, "precondition");
1817     HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1818     if (start != bottom) {
1819       HeapWord* obj_start = mark_bitmap()->find_obj_beg_reverse(bottom, start);
1820       HeapWord* after_obj = obj_start + cast_to_oop(obj_start)->size();
1821       assert(after_obj == start, "precondition");
1822     }
1823   }
1824 #endif
1825 
1826   CollectedHeap::fill_with_objects(start, pointer_delta(end, start));
1827   HeapWord* addr = start;
1828   do {
1829     size_t size = cast_to_oop(addr)->size();
1830     start_array(old_space_id)->update_for_block(addr, addr + size);
1831     addr += size;
1832   } while (addr < end);
1833 }
1834 
1835 void PSParallelCompact::fill_dead_objs_in_dense_prefix(uint worker_id, uint num_workers) {
1836   ParMarkBitMap* bitmap = mark_bitmap();
1837 
1838   HeapWord* const bottom = _space_info[old_space_id].space()->bottom();
1839   HeapWord* const prefix_end = dense_prefix(old_space_id);
1840 
1841   if (bottom == prefix_end) {
1842     return;
1843   }
1844 
1845   size_t bottom_region = _summary_data.addr_to_region_idx(bottom);
1846   size_t prefix_end_region = _summary_data.addr_to_region_idx(prefix_end);
1847 
1848   size_t start_region;
1849   size_t end_region;
1850   split_regions_for_worker(bottom_region, prefix_end_region,
1851                            worker_id, num_workers,
1852                            &start_region, &end_region);
1853 
1854   if (start_region == end_region) {
1855     return;
1856   }
1857 
1858   HeapWord* const start_addr = _summary_data.region_to_addr(start_region);
1859   HeapWord* const end_addr = _summary_data.region_to_addr(end_region);
1860 
1861   // Skip live partial obj (if any) from previous region.
1862   HeapWord* cur_addr;
1863   RegionData* start_region_ptr = _summary_data.region(start_region);
1864   if (start_region_ptr->partial_obj_size() != 0) {
1865     HeapWord* partial_obj_start = start_region_ptr->partial_obj_addr();
1866     assert(bitmap->is_marked(partial_obj_start), "inv");
1867     cur_addr = partial_obj_start + cast_to_oop(partial_obj_start)->size();
1868   } else {
1869     cur_addr = start_addr;
1870   }
1871 
1872   // end_addr is inclusive to handle regions starting with dead space.
1873   while (cur_addr <= end_addr) {
1874     // Use prefix_end to handle trailing obj in each worker region-chunk.
1875     HeapWord* live_start = bitmap->find_obj_beg(cur_addr, prefix_end);
1876     if (cur_addr != live_start) {
1877       // Only worker 0 handles proceeding dead space.
1878       if (cur_addr != start_addr || worker_id == 0) {
1879         fill_range_in_dense_prefix(cur_addr, live_start);
1880       }
1881     }
1882     if (live_start >= end_addr) {
1883       break;
1884     }
1885     assert(bitmap->is_marked(live_start), "inv");
1886     cur_addr = live_start + cast_to_oop(live_start)->size();
1887   }
1888 }
1889 
1890 void PSParallelCompact::compact() {
1891   GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
1892 
1893   uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1894 
1895   initialize_shadow_regions(active_gc_threads);
1896   prepare_region_draining_tasks(active_gc_threads);
1897 
1898   {
1899     GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
1900 
1901     FillDensePrefixAndCompactionTask task(active_gc_threads);
1902     ParallelScavengeHeap::heap()->workers().run_task(&task);
1903 
1904 #ifdef  ASSERT
1905     verify_filler_in_dense_prefix();
1906 
1907     // Verify that all regions have been processed.
1908     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1909       verify_complete(SpaceId(id));
1910     }
1911 #endif
1912   }
1913 }
1914 
1915 #ifdef  ASSERT
1916 void PSParallelCompact::verify_filler_in_dense_prefix() {
1917   HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1918   HeapWord* dense_prefix_end = dense_prefix(old_space_id);
1919   HeapWord* cur_addr = bottom;
1920   while (cur_addr < dense_prefix_end) {
1921     oop obj = cast_to_oop(cur_addr);
1922     oopDesc::verify(obj);
1923     if (!mark_bitmap()->is_marked(cur_addr)) {
1924       Klass* k = cast_to_oop(cur_addr)->klass();
1925       assert(k == Universe::fillerArrayKlass() || k == vmClasses::FillerObject_klass(), "inv");
1926     }
1927     cur_addr += obj->size();
1928   }
1929 }
1930 
1931 void PSParallelCompact::verify_complete(SpaceId space_id) {
1932   // All Regions served as compaction targets, from dense_prefix() to
1933   // new_top(), should be marked as filled and all Regions between new_top()
1934   // and top() should be available (i.e., should have been emptied).
1935   ParallelCompactData& sd = summary_data();
1936   SpaceInfo si = _space_info[space_id];
1937   HeapWord* new_top_addr = sd.region_align_up(si.new_top());
1938   HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
1939   const size_t beg_region = sd.addr_to_region_idx(si.dense_prefix());
1940   const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
1941   const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
1942 
1943   size_t cur_region;
1944   for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
1945     const RegionData* const c = sd.region(cur_region);
1946     assert(c->completed(), "region %zu not filled: destination_count=%u",
1947            cur_region, c->destination_count());
1948   }
1949 
1950   for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
1951     const RegionData* const c = sd.region(cur_region);
1952     assert(c->available(), "region %zu not empty: destination_count=%u",
1953            cur_region, c->destination_count());
1954   }
1955 }
1956 #endif  // #ifdef ASSERT
1957 
1958 // Return the SpaceId for the space containing addr.  If addr is not in the
1959 // heap, last_space_id is returned.  In debug mode it expects the address to be
1960 // in the heap and asserts such.
1961 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
1962   assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
1963 
1964   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1965     if (_space_info[id].space()->contains(addr)) {
1966       return SpaceId(id);
1967     }
1968   }
1969 
1970   assert(false, "no space contains the addr");
1971   return last_space_id;
1972 }
1973 
1974 // Skip over count live words starting from beg, and return the address of the
1975 // next live word. Callers must also ensure that there are enough live words in
1976 // the range [beg, end) to skip.
1977 HeapWord* PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
1978 {
1979   ParMarkBitMap* m = mark_bitmap();
1980   HeapWord* cur_addr = beg;
1981   while (true) {
1982     cur_addr = m->find_obj_beg(cur_addr, end);
1983     assert(cur_addr < end, "inv");
1984     size_t obj_size = cast_to_oop(cur_addr)->size();
1985     // Strictly greater-than
1986     if (obj_size > count) {
1987       return cur_addr + count;
1988     }
1989     count -= obj_size;
1990     cur_addr += obj_size;
1991   }
1992 }
1993 
1994 // On starting to fill a destination region (dest-region), we need to know the
1995 // location of the word that will be at the start of the dest-region after
1996 // compaction. A dest-region can have one or more source regions, but only the
1997 // first source-region contains this location. This location is retrieved by
1998 // calling `first_src_addr` on a dest-region.
1999 // Conversely, a source-region has a dest-region which holds the destination of
2000 // the first live word on this source-region, based on which the destination
2001 // for the rest of live words can be derived.
2002 //
2003 // Note:
2004 // There is some complication due to space-boundary-fragmentation (an obj can't
2005 // cross space-boundary) -- a source-region may be split and behave like two
2006 // distinct regions with their own dest-region, as depicted below.
2007 //
2008 // source-region: region-n
2009 //
2010 // **********************
2011 // |     A|A~~~~B|B     |
2012 // **********************
2013 //    n-1     n     n+1
2014 //
2015 // AA, BB denote two live objs. ~~~~ denotes unknown number of live objs.
2016 //
2017 // Assuming the dest-region for region-n is the final region before
2018 // old-space-end and its first-live-word is the middle of AA, the heap content
2019 // will look like the following after compaction:
2020 //
2021 // **************                  *************
2022 //      A|A~~~~ |                  |BB    |
2023 // **************                  *************
2024 //              ^                  ^
2025 //              | old-space-end    | eden-space-start
2026 //
2027 // Therefore, in this example, region-n will have two dest-regions:
2028 // 1. the final region in old-space
2029 // 2. the first region in eden-space.
2030 // To handle this special case, we introduce the concept of split-region, whose
2031 // contents are relocated to two spaces. `SplitInfo` captures all necessary
2032 // info about the split, the first part, spliting-point, and the second part.
2033 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2034                                             SpaceId src_space_id,
2035                                             size_t src_region_idx)
2036 {
2037   const size_t RegionSize = ParallelCompactData::RegionSize;
2038   const ParallelCompactData& sd = summary_data();
2039   assert(sd.is_region_aligned(dest_addr), "precondition");
2040 
2041   const RegionData* const src_region_ptr = sd.region(src_region_idx);
2042   assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2043 
2044   const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2045   HeapWord* const src_region_destination = src_region_ptr->destination();
2046 
2047   HeapWord* const region_start = sd.region_to_addr(src_region_idx);
2048   HeapWord* const region_end = sd.region_to_addr(src_region_idx) + RegionSize;
2049 
2050   // Identify the actual destination for the first live words on this region,
2051   // taking split-region into account.
2052   HeapWord* region_start_destination;
2053   const SplitInfo& split_info = _space_info[src_space_id].split_info();
2054   if (split_info.is_split(src_region_idx)) {
2055     // The second part of this split region; use the recorded split point.
2056     if (dest_addr == src_region_destination) {
2057       return split_info.split_point();
2058     }
2059     region_start_destination = split_info.preceding_destination();
2060   } else {
2061     region_start_destination = src_region_destination;
2062   }
2063 
2064   // Calculate the offset to be skipped
2065   size_t words_to_skip = pointer_delta(dest_addr, region_start_destination);
2066 
2067   HeapWord* result;
2068   if (partial_obj_size > words_to_skip) {
2069     result = region_start + words_to_skip;
2070   } else {
2071     words_to_skip -= partial_obj_size;
2072     result = skip_live_words(region_start + partial_obj_size, region_end, words_to_skip);
2073   }
2074 
2075   if (split_info.is_split(src_region_idx)) {
2076     assert(result < split_info.split_point(), "postcondition");
2077   } else {
2078     assert(result < region_end, "postcondition");
2079   }
2080 
2081   return result;
2082 }
2083 
2084 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2085                                                      SpaceId src_space_id,
2086                                                      size_t beg_region,
2087                                                      HeapWord* end_addr)
2088 {
2089   ParallelCompactData& sd = summary_data();
2090 
2091 #ifdef ASSERT
2092   MutableSpace* const src_space = _space_info[src_space_id].space();
2093   HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2094   assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2095          "src_space_id does not match beg_addr");
2096   assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2097          "src_space_id does not match end_addr");
2098 #endif // #ifdef ASSERT
2099 
2100   RegionData* const beg = sd.region(beg_region);
2101   RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2102 
2103   // Regions up to new_top() are enqueued if they become available.
2104   HeapWord* const new_top = _space_info[src_space_id].new_top();
2105   RegionData* const enqueue_end =
2106     sd.addr_to_region_ptr(sd.region_align_up(new_top));
2107 
2108   for (RegionData* cur = beg; cur < end; ++cur) {
2109     assert(cur->data_size() > 0, "region must have live data");
2110     cur->decrement_destination_count();
2111     if (cur < enqueue_end && cur->available() && cur->claim()) {
2112       if (cur->mark_normal()) {
2113         cm->push_region(sd.region(cur));
2114       } else if (cur->mark_copied()) {
2115         // Try to copy the content of the shadow region back to its corresponding
2116         // heap region if the shadow region is filled. Otherwise, the GC thread
2117         // fills the shadow region will copy the data back (see
2118         // MoveAndUpdateShadowClosure::complete_region).
2119         copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
2120         ParCompactionManager::push_shadow_region_mt_safe(cur->shadow_region());
2121         cur->set_completed();
2122       }
2123     }
2124   }
2125 }
2126 
2127 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2128                                           SpaceId& src_space_id,
2129                                           HeapWord*& src_space_top,
2130                                           HeapWord* end_addr)
2131 {
2132   ParallelCompactData& sd = PSParallelCompact::summary_data();
2133 
2134   size_t src_region_idx = 0;
2135 
2136   // Skip empty regions (if any) up to the top of the space.
2137   HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2138   RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2139   HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2140   const RegionData* const top_region_ptr = sd.addr_to_region_ptr(top_aligned_up);
2141 
2142   while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2143     ++src_region_ptr;
2144   }
2145 
2146   if (src_region_ptr < top_region_ptr) {
2147     // Found the first non-empty region in the same space.
2148     src_region_idx = sd.region(src_region_ptr);
2149     closure.set_source(sd.region_to_addr(src_region_idx));
2150     return src_region_idx;
2151   }
2152 
2153   // Switch to a new source space and find the first non-empty region.
2154   uint space_id = src_space_id + 1;
2155   assert(space_id < last_space_id, "not enough spaces");
2156 
2157   for (/* empty */; space_id < last_space_id; ++space_id) {
2158     HeapWord* bottom = _space_info[space_id].space()->bottom();
2159     HeapWord* top = _space_info[space_id].space()->top();
2160     // Skip empty space
2161     if (bottom == top) {
2162       continue;
2163     }
2164 
2165     // Identify the first region that contains live words in this space
2166     size_t cur_region = sd.addr_to_region_idx(bottom);
2167     size_t end_region = sd.addr_to_region_idx(sd.region_align_up(top));
2168 
2169     for (/* empty */ ; cur_region < end_region; ++cur_region) {
2170       RegionData* cur = sd.region(cur_region);
2171       if (cur->live_obj_size() > 0) {
2172         HeapWord* region_start_addr = sd.region_to_addr(cur_region);
2173 
2174         src_space_id = SpaceId(space_id);
2175         src_space_top = top;
2176         closure.set_source(region_start_addr);
2177         return cur_region;
2178       }
2179     }
2180   }
2181 
2182   ShouldNotReachHere();
2183 }
2184 
2185 HeapWord* PSParallelCompact::partial_obj_end(HeapWord* region_start_addr) {
2186   ParallelCompactData& sd = summary_data();
2187   assert(sd.is_region_aligned(region_start_addr), "precondition");
2188 
2189   // Use per-region partial_obj_size to locate the end of the obj, that extends
2190   // to region_start_addr.
2191   size_t start_region_idx = sd.addr_to_region_idx(region_start_addr);
2192   size_t end_region_idx = sd.region_count();
2193   size_t accumulated_size = 0;
2194   for (size_t region_idx = start_region_idx; region_idx < end_region_idx; ++region_idx) {
2195     size_t cur_partial_obj_size = sd.region(region_idx)->partial_obj_size();
2196     accumulated_size += cur_partial_obj_size;
2197     if (cur_partial_obj_size != ParallelCompactData::RegionSize) {
2198       break;
2199     }
2200   }
2201   return region_start_addr + accumulated_size;
2202 }
2203 
2204 // Use region_idx as the destination region, and evacuate all live objs on its
2205 // source regions to this destination region.
2206 void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
2207 {
2208   ParMarkBitMap* const bitmap = mark_bitmap();
2209   ParallelCompactData& sd = summary_data();
2210   RegionData* const region_ptr = sd.region(region_idx);
2211 
2212   // Get the source region and related info.
2213   size_t src_region_idx = region_ptr->source_region();
2214   SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2215   HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2216   HeapWord* dest_addr = sd.region_to_addr(region_idx);
2217 
2218   closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2219 
2220   // Adjust src_region_idx to prepare for decrementing destination counts (the
2221   // destination count is not decremented when a region is copied to itself).
2222   if (src_region_idx == region_idx) {
2223     src_region_idx += 1;
2224   }
2225 
2226   // source-region:
2227   //
2228   // **********
2229   // |   ~~~  |
2230   // **********
2231   //      ^
2232   //      |-- closure.source() / first_src_addr
2233   //
2234   //
2235   // ~~~ : live words
2236   //
2237   // destination-region:
2238   //
2239   // **********
2240   // |        |
2241   // **********
2242   // ^
2243   // |-- region-start
2244   if (bitmap->is_unmarked(closure.source())) {
2245     // An object overflows the previous destination region, so this
2246     // destination region should copy the remainder of the object or as much as
2247     // will fit.
2248     HeapWord* const old_src_addr = closure.source();
2249     {
2250       HeapWord* region_start = sd.region_align_down(closure.source());
2251       HeapWord* obj_start = bitmap->find_obj_beg_reverse(region_start, closure.source());
2252       HeapWord* obj_end;
2253       if (obj_start != closure.source()) {
2254         assert(bitmap->is_marked(obj_start), "inv");
2255         // Found the actual obj-start, try to find the obj-end using either
2256         // size() if this obj is completely contained in the current region.
2257         HeapWord* next_region_start = region_start + ParallelCompactData::RegionSize;
2258         HeapWord* partial_obj_start = (next_region_start >= src_space_top)
2259                                       ? nullptr
2260                                       : sd.addr_to_region_ptr(next_region_start)->partial_obj_addr();
2261         // This obj extends to next region iff partial_obj_addr of the *next*
2262         // region is the same as obj-start.
2263         if (partial_obj_start == obj_start) {
2264           // This obj extends to next region.
2265           obj_end = partial_obj_end(next_region_start);
2266         } else {
2267           // Completely contained in this region; safe to use size().
2268           obj_end = obj_start + cast_to_oop(obj_start)->size();
2269         }
2270       } else {
2271         // This obj extends to current region.
2272         obj_end = partial_obj_end(region_start);
2273       }
2274       size_t partial_obj_size = pointer_delta(obj_end, closure.source());
2275       closure.copy_partial_obj(partial_obj_size);
2276     }
2277 
2278     if (closure.is_full()) {
2279       decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2280       closure.complete_region(dest_addr, region_ptr);
2281       return;
2282     }
2283 
2284     // Finished copying without using up the current destination-region
2285     HeapWord* const end_addr = sd.region_align_down(closure.source());
2286     if (sd.region_align_down(old_src_addr) != end_addr) {
2287       assert(sd.region_align_up(old_src_addr) == end_addr, "only one region");
2288       // The partial object was copied from more than one source region.
2289       decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2290 
2291       // Move to the next source region, possibly switching spaces as well.  All
2292       // args except end_addr may be modified.
2293       src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2294     }
2295   }
2296 
2297   // Handle the rest obj-by-obj, where we know obj-start.
2298   do {
2299     HeapWord* cur_addr = closure.source();
2300     HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
2301                                     src_space_top);
2302     // To handle the case where the final obj in source region extends to next region.
2303     HeapWord* final_obj_start = (end_addr == src_space_top)
2304                                 ? nullptr
2305                                 : sd.addr_to_region_ptr(end_addr)->partial_obj_addr();
2306     // Apply closure on objs inside [cur_addr, end_addr)
2307     do {
2308       cur_addr = bitmap->find_obj_beg(cur_addr, end_addr);
2309       if (cur_addr == end_addr) {
2310         break;
2311       }
2312       size_t obj_size;
2313       if (final_obj_start == cur_addr) {
2314         obj_size = pointer_delta(partial_obj_end(end_addr), cur_addr);
2315       } else {
2316         // This obj doesn't extend into next region; size() is safe to use.
2317         obj_size = cast_to_oop(cur_addr)->size();
2318       }
2319       closure.do_addr(cur_addr, obj_size);
2320       cur_addr += obj_size;
2321     } while (cur_addr < end_addr && !closure.is_full());
2322 
2323     if (closure.is_full()) {
2324       decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2325       closure.complete_region(dest_addr, region_ptr);
2326       return;
2327     }
2328 
2329     decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2330 
2331     // Move to the next source region, possibly switching spaces as well.  All
2332     // args except end_addr may be modified.
2333     src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2334   } while (true);
2335 }
2336 
2337 void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
2338 {
2339   MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2340   fill_region(cm, cl, region_idx);
2341 }
2342 
2343 void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
2344 {
2345   // Get a shadow region first
2346   ParallelCompactData& sd = summary_data();
2347   RegionData* const region_ptr = sd.region(region_idx);
2348   size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
2349   // The InvalidShadow return value indicates the corresponding heap region is available,
2350   // so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
2351   // MoveAndUpdateShadowClosure to fill the acquired shadow region.
2352   if (shadow_region == ParCompactionManager::InvalidShadow) {
2353     MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2354     region_ptr->shadow_to_normal();
2355     return fill_region(cm, cl, region_idx);
2356   } else {
2357     MoveAndUpdateShadowClosure cl(mark_bitmap(), region_idx, shadow_region);
2358     return fill_region(cm, cl, region_idx);
2359   }
2360 }
2361 
2362 void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
2363 {
2364   Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
2365 }
2366 
2367 bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t &region_idx)
2368 {
2369   size_t next = cm->next_shadow_region();
2370   ParallelCompactData& sd = summary_data();
2371   size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
2372   uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2373 
2374   while (next < old_new_top) {
2375     if (sd.region(next)->mark_shadow()) {
2376       region_idx = next;
2377       return true;
2378     }
2379     next = cm->move_next_shadow_region_by(active_gc_threads);
2380   }
2381 
2382   return false;
2383 }
2384 
2385 // The shadow region is an optimization to address region dependencies in full GC. The basic
2386 // idea is making more regions available by temporally storing their live objects in empty
2387 // shadow regions to resolve dependencies between them and the destination regions. Therefore,
2388 // GC threads need not wait destination regions to be available before processing sources.
2389 //
2390 // A typical workflow would be:
2391 // After draining its own stack and failing to steal from others, a GC worker would pick an
2392 // unavailable region (destination count > 0) and get a shadow region. Then the worker fills
2393 // the shadow region by copying live objects from source regions of the unavailable one. Once
2394 // the unavailable region becomes available, the data in the shadow region will be copied back.
2395 // Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
2396 void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
2397 {
2398   const ParallelCompactData& sd = PSParallelCompact::summary_data();
2399 
2400   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2401     SpaceInfo* const space_info = _space_info + id;
2402     MutableSpace* const space = space_info->space();
2403 
2404     const size_t beg_region =
2405       sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
2406     const size_t end_region =
2407       sd.addr_to_region_idx(sd.region_align_down(space->end()));
2408 
2409     for (size_t cur = beg_region; cur < end_region; ++cur) {
2410       ParCompactionManager::push_shadow_region(cur);
2411     }
2412   }
2413 
2414   size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
2415   for (uint i = 0; i < parallel_gc_threads; i++) {
2416     ParCompactionManager *cm = ParCompactionManager::gc_thread_compaction_manager(i);
2417     cm->set_next_shadow_region(beg_region + i);
2418   }
2419 }
2420 
2421 void MoveAndUpdateClosure::copy_partial_obj(size_t partial_obj_size)
2422 {
2423   size_t words = MIN2(partial_obj_size, words_remaining());
2424 
2425   // This test is necessary; if omitted, the pointer updates to a partial object
2426   // that crosses the dense prefix boundary could be overwritten.
2427   if (source() != copy_destination()) {
2428     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2429     Copy::aligned_conjoint_words(source(), copy_destination(), words);
2430   }
2431   update_state(words);
2432 }
2433 
2434 void MoveAndUpdateClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2435   assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
2436   region_ptr->set_completed();
2437 }
2438 
2439 void MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
2440   assert(destination() != nullptr, "sanity");
2441   _source = addr;
2442 
2443   // The start_array must be updated even if the object is not moving.
2444   if (_start_array != nullptr) {
2445     _start_array->update_for_block(destination(), destination() + words);
2446   }
2447 
2448   // Avoid overflow
2449   words = MIN2(words, words_remaining());
2450   assert(words > 0, "inv");
2451 
2452   if (copy_destination() != source()) {
2453     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2454     assert(source() != destination(), "inv");
2455     assert(FullGCForwarding::is_forwarded(cast_to_oop(source())), "inv");
2456     assert(FullGCForwarding::forwardee(cast_to_oop(source())) == cast_to_oop(destination()), "inv");
2457     Copy::aligned_conjoint_words(source(), copy_destination(), words);
2458     cast_to_oop(copy_destination())->init_mark();
2459   }
2460 
2461   update_state(words);
2462 }
2463 
2464 void MoveAndUpdateShadowClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2465   assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
2466   // Record the shadow region index
2467   region_ptr->set_shadow_region(_shadow);
2468   // Mark the shadow region as filled to indicate the data is ready to be
2469   // copied back
2470   region_ptr->mark_filled();
2471   // Try to copy the content of the shadow region back to its corresponding
2472   // heap region if available; the GC thread that decreases the destination
2473   // count to zero will do the copying otherwise (see
2474   // PSParallelCompact::decrement_destination_counts).
2475   if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
2476     region_ptr->set_completed();
2477     PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
2478     ParCompactionManager::push_shadow_region_mt_safe(_shadow);
2479   }
2480 }