1 /*
   2  * Copyright (c) 2005, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "aot/aotLoader.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "code/codeCache.hpp"
  31 #include "gc/parallel/gcTaskManager.hpp"
  32 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
  33 #include "gc/parallel/parMarkBitMap.inline.hpp"
  34 #include "gc/parallel/pcTasks.hpp"
  35 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
  36 #include "gc/parallel/psCompactionManager.inline.hpp"
  37 #include "gc/parallel/psMarkSweep.hpp"
  38 #include "gc/parallel/psMarkSweepDecorator.hpp"
  39 #include "gc/parallel/psOldGen.hpp"
  40 #include "gc/parallel/psParallelCompact.inline.hpp"
  41 #include "gc/parallel/psPromotionManager.inline.hpp"
  42 #include "gc/parallel/psScavenge.hpp"
  43 #include "gc/parallel/psYoungGen.hpp"
  44 #include "gc/shared/gcCause.hpp"
  45 #include "gc/shared/gcHeapSummary.hpp"
  46 #include "gc/shared/gcId.hpp"
  47 #include "gc/shared/gcLocker.inline.hpp"
  48 #include "gc/shared/gcTimer.hpp"
  49 #include "gc/shared/gcTrace.hpp"
  50 #include "gc/shared/gcTraceTime.inline.hpp"
  51 #include "gc/shared/isGCActiveMark.hpp"
  52 #include "gc/shared/referencePolicy.hpp"
  53 #include "gc/shared/referenceProcessor.hpp"
  54 #include "gc/shared/spaceDecorator.hpp"
  55 #include "gc/shared/weakProcessor.hpp"
  56 #include "logging/log.hpp"
  57 #include "memory/resourceArea.hpp"
  58 #include "oops/instanceKlass.inline.hpp"
  59 #include "oops/instanceMirrorKlass.inline.hpp"
  60 #include "oops/methodData.hpp"
  61 #include "oops/objArrayKlass.inline.hpp"
  62 #include "oops/oop.inline.hpp"
  63 #include "runtime/atomic.hpp"
  64 #include "runtime/safepoint.hpp"
  65 #include "runtime/vmThread.hpp"
  66 #include "services/management.hpp"
  67 #include "services/memTracker.hpp"
  68 #include "services/memoryService.hpp"
  69 #include "utilities/align.hpp"
  70 #include "utilities/debug.hpp"
  71 #include "utilities/events.hpp"
  72 #include "utilities/formatBuffer.hpp"
  73 #include "utilities/stack.inline.hpp"
  74 
  75 #include <math.h>
  76 
  77 // All sizes are in HeapWords.
  78 const size_t ParallelCompactData::Log2RegionSize  = 16; // 64K words
  79 const size_t ParallelCompactData::RegionSize      = (size_t)1 << Log2RegionSize;
  80 const size_t ParallelCompactData::RegionSizeBytes =
  81   RegionSize << LogHeapWordSize;
  82 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
  83 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
  84 const size_t ParallelCompactData::RegionAddrMask       = ~RegionAddrOffsetMask;
  85 
  86 const size_t ParallelCompactData::Log2BlockSize   = 7; // 128 words
  87 const size_t ParallelCompactData::BlockSize       = (size_t)1 << Log2BlockSize;
  88 const size_t ParallelCompactData::BlockSizeBytes  =
  89   BlockSize << LogHeapWordSize;
  90 const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
  91 const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
  92 const size_t ParallelCompactData::BlockAddrMask       = ~BlockAddrOffsetMask;
  93 
  94 const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
  95 const size_t ParallelCompactData::Log2BlocksPerRegion =
  96   Log2RegionSize - Log2BlockSize;
  97 
  98 const ParallelCompactData::RegionData::region_sz_t
  99 ParallelCompactData::RegionData::dc_shift = 27;
 100 
 101 const ParallelCompactData::RegionData::region_sz_t
 102 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
 103 
 104 const ParallelCompactData::RegionData::region_sz_t
 105 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
 106 
 107 const ParallelCompactData::RegionData::region_sz_t
 108 ParallelCompactData::RegionData::los_mask = ~dc_mask;
 109 
 110 const ParallelCompactData::RegionData::region_sz_t
 111 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
 112 
 113 const ParallelCompactData::RegionData::region_sz_t
 114 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
 115 
 116 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
 117 
 118 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
 119 
 120 double PSParallelCompact::_dwl_mean;
 121 double PSParallelCompact::_dwl_std_dev;
 122 double PSParallelCompact::_dwl_first_term;
 123 double PSParallelCompact::_dwl_adjustment;
 124 #ifdef  ASSERT
 125 bool   PSParallelCompact::_dwl_initialized = false;
 126 #endif  // #ifdef ASSERT
 127 
 128 void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
 129                        HeapWord* destination)
 130 {
 131   assert(src_region_idx != 0, "invalid src_region_idx");
 132   assert(partial_obj_size != 0, "invalid partial_obj_size argument");
 133   assert(destination != NULL, "invalid destination argument");
 134 
 135   _src_region_idx = src_region_idx;
 136   _partial_obj_size = partial_obj_size;
 137   _destination = destination;
 138 
 139   // These fields may not be updated below, so make sure they're clear.
 140   assert(_dest_region_addr == NULL, "should have been cleared");
 141   assert(_first_src_addr == NULL, "should have been cleared");
 142 
 143   // Determine the number of destination regions for the partial object.
 144   HeapWord* const last_word = destination + partial_obj_size - 1;
 145   const ParallelCompactData& sd = PSParallelCompact::summary_data();
 146   HeapWord* const beg_region_addr = sd.region_align_down(destination);
 147   HeapWord* const end_region_addr = sd.region_align_down(last_word);
 148 
 149   if (beg_region_addr == end_region_addr) {
 150     // One destination region.
 151     _destination_count = 1;
 152     if (end_region_addr == destination) {
 153       // The destination falls on a region boundary, thus the first word of the
 154       // partial object will be the first word copied to the destination region.
 155       _dest_region_addr = end_region_addr;
 156       _first_src_addr = sd.region_to_addr(src_region_idx);
 157     }
 158   } else {
 159     // Two destination regions.  When copied, the partial object will cross a
 160     // destination region boundary, so a word somewhere within the partial
 161     // object will be the first word copied to the second destination region.
 162     _destination_count = 2;
 163     _dest_region_addr = end_region_addr;
 164     const size_t ofs = pointer_delta(end_region_addr, destination);
 165     assert(ofs < _partial_obj_size, "sanity");
 166     _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
 167   }
 168 }
 169 
 170 void SplitInfo::clear()
 171 {
 172   _src_region_idx = 0;
 173   _partial_obj_size = 0;
 174   _destination = NULL;
 175   _destination_count = 0;
 176   _dest_region_addr = NULL;
 177   _first_src_addr = NULL;
 178   assert(!is_valid(), "sanity");
 179 }
 180 
 181 #ifdef  ASSERT
 182 void SplitInfo::verify_clear()
 183 {
 184   assert(_src_region_idx == 0, "not clear");
 185   assert(_partial_obj_size == 0, "not clear");
 186   assert(_destination == NULL, "not clear");
 187   assert(_destination_count == 0, "not clear");
 188   assert(_dest_region_addr == NULL, "not clear");
 189   assert(_first_src_addr == NULL, "not clear");
 190 }
 191 #endif  // #ifdef ASSERT
 192 
 193 
 194 void PSParallelCompact::print_on_error(outputStream* st) {
 195   _mark_bitmap.print_on_error(st);
 196 }
 197 
 198 #ifndef PRODUCT
 199 const char* PSParallelCompact::space_names[] = {
 200   "old ", "eden", "from", "to  "
 201 };
 202 
 203 void PSParallelCompact::print_region_ranges() {
 204   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 205     return;
 206   }
 207   Log(gc, compaction) log;
 208   ResourceMark rm;
 209   LogStream ls(log.trace());
 210   Universe::print_on(&ls);
 211   log.trace("space  bottom     top        end        new_top");
 212   log.trace("------ ---------- ---------- ---------- ----------");
 213 
 214   for (unsigned int id = 0; id < last_space_id; ++id) {
 215     const MutableSpace* space = _space_info[id].space();
 216     log.trace("%u %s "
 217               SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
 218               SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
 219               id, space_names[id],
 220               summary_data().addr_to_region_idx(space->bottom()),
 221               summary_data().addr_to_region_idx(space->top()),
 222               summary_data().addr_to_region_idx(space->end()),
 223               summary_data().addr_to_region_idx(_space_info[id].new_top()));
 224   }
 225 }
 226 
 227 void
 228 print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
 229 {
 230 #define REGION_IDX_FORMAT        SIZE_FORMAT_W(7)
 231 #define REGION_DATA_FORMAT       SIZE_FORMAT_W(5)
 232 
 233   ParallelCompactData& sd = PSParallelCompact::summary_data();
 234   size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
 235   log_develop_trace(gc, compaction)(
 236       REGION_IDX_FORMAT " " PTR_FORMAT " "
 237       REGION_IDX_FORMAT " " PTR_FORMAT " "
 238       REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
 239       REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
 240       i, p2i(c->data_location()), dci, p2i(c->destination()),
 241       c->partial_obj_size(), c->live_obj_size(),
 242       c->data_size(), c->source_region(), c->destination_count());
 243 
 244 #undef  REGION_IDX_FORMAT
 245 #undef  REGION_DATA_FORMAT
 246 }
 247 
 248 void
 249 print_generic_summary_data(ParallelCompactData& summary_data,
 250                            HeapWord* const beg_addr,
 251                            HeapWord* const end_addr)
 252 {
 253   size_t total_words = 0;
 254   size_t i = summary_data.addr_to_region_idx(beg_addr);
 255   const size_t last = summary_data.addr_to_region_idx(end_addr);
 256   HeapWord* pdest = 0;
 257 
 258   while (i < last) {
 259     ParallelCompactData::RegionData* c = summary_data.region(i);
 260     if (c->data_size() != 0 || c->destination() != pdest) {
 261       print_generic_summary_region(i, c);
 262       total_words += c->data_size();
 263       pdest = c->destination();
 264     }
 265     ++i;
 266   }
 267 
 268   log_develop_trace(gc, compaction)("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
 269 }
 270 
 271 void
 272 PSParallelCompact::print_generic_summary_data(ParallelCompactData& summary_data,
 273                                               HeapWord* const beg_addr,
 274                                               HeapWord* const end_addr) {
 275   ::print_generic_summary_data(summary_data,beg_addr, end_addr);
 276 }
 277 
 278 void
 279 print_generic_summary_data(ParallelCompactData& summary_data,
 280                            SpaceInfo* space_info)
 281 {
 282   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 283     return;
 284   }
 285 
 286   for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
 287     const MutableSpace* space = space_info[id].space();
 288     print_generic_summary_data(summary_data, space->bottom(),
 289                                MAX2(space->top(), space_info[id].new_top()));
 290   }
 291 }
 292 
 293 void
 294 print_initial_summary_data(ParallelCompactData& summary_data,
 295                            const MutableSpace* space) {
 296   if (space->top() == space->bottom()) {
 297     return;
 298   }
 299 
 300   const size_t region_size = ParallelCompactData::RegionSize;
 301   typedef ParallelCompactData::RegionData RegionData;
 302   HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
 303   const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
 304   const RegionData* c = summary_data.region(end_region - 1);
 305   HeapWord* end_addr = c->destination() + c->data_size();
 306   const size_t live_in_space = pointer_delta(end_addr, space->bottom());
 307 
 308   // Print (and count) the full regions at the beginning of the space.
 309   size_t full_region_count = 0;
 310   size_t i = summary_data.addr_to_region_idx(space->bottom());
 311   while (i < end_region && summary_data.region(i)->data_size() == region_size) {
 312     ParallelCompactData::RegionData* c = summary_data.region(i);
 313     log_develop_trace(gc, compaction)(
 314         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 315         i, p2i(c->destination()),
 316         c->partial_obj_size(), c->live_obj_size(),
 317         c->data_size(), c->source_region(), c->destination_count());
 318     ++full_region_count;
 319     ++i;
 320   }
 321 
 322   size_t live_to_right = live_in_space - full_region_count * region_size;
 323 
 324   double max_reclaimed_ratio = 0.0;
 325   size_t max_reclaimed_ratio_region = 0;
 326   size_t max_dead_to_right = 0;
 327   size_t max_live_to_right = 0;
 328 
 329   // Print the 'reclaimed ratio' for regions while there is something live in
 330   // the region or to the right of it.  The remaining regions are empty (and
 331   // uninteresting), and computing the ratio will result in division by 0.
 332   while (i < end_region && live_to_right > 0) {
 333     c = summary_data.region(i);
 334     HeapWord* const region_addr = summary_data.region_to_addr(i);
 335     const size_t used_to_right = pointer_delta(space->top(), region_addr);
 336     const size_t dead_to_right = used_to_right - live_to_right;
 337     const double reclaimed_ratio = double(dead_to_right) / live_to_right;
 338 
 339     if (reclaimed_ratio > max_reclaimed_ratio) {
 340             max_reclaimed_ratio = reclaimed_ratio;
 341             max_reclaimed_ratio_region = i;
 342             max_dead_to_right = dead_to_right;
 343             max_live_to_right = live_to_right;
 344     }
 345 
 346     ParallelCompactData::RegionData* c = summary_data.region(i);
 347     log_develop_trace(gc, compaction)(
 348         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d"
 349         "%12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
 350         i, p2i(c->destination()),
 351         c->partial_obj_size(), c->live_obj_size(),
 352         c->data_size(), c->source_region(), c->destination_count(),
 353         reclaimed_ratio, dead_to_right, live_to_right);
 354 
 355 
 356     live_to_right -= c->data_size();
 357     ++i;
 358   }
 359 
 360   // Any remaining regions are empty.  Print one more if there is one.
 361   if (i < end_region) {
 362     ParallelCompactData::RegionData* c = summary_data.region(i);
 363     log_develop_trace(gc, compaction)(
 364         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 365          i, p2i(c->destination()),
 366          c->partial_obj_size(), c->live_obj_size(),
 367          c->data_size(), c->source_region(), c->destination_count());
 368   }
 369 
 370   log_develop_trace(gc, compaction)("max:  " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
 371                                     max_reclaimed_ratio_region, max_dead_to_right, max_live_to_right, max_reclaimed_ratio);
 372 }
 373 
 374 void
 375 print_initial_summary_data(ParallelCompactData& summary_data,
 376                            SpaceInfo* space_info) {
 377   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 378     return;
 379   }
 380 
 381   unsigned int id = PSParallelCompact::old_space_id;
 382   const MutableSpace* space;
 383   do {
 384     space = space_info[id].space();
 385     print_initial_summary_data(summary_data, space);
 386   } while (++id < PSParallelCompact::eden_space_id);
 387 
 388   do {
 389     space = space_info[id].space();
 390     print_generic_summary_data(summary_data, space->bottom(), space->top());
 391   } while (++id < PSParallelCompact::last_space_id);
 392 }
 393 #endif  // #ifndef PRODUCT
 394 
 395 #ifdef  ASSERT
 396 size_t add_obj_count;
 397 size_t add_obj_size;
 398 size_t mark_bitmap_count;
 399 size_t mark_bitmap_size;
 400 #endif  // #ifdef ASSERT
 401 
 402 ParallelCompactData::ParallelCompactData()
 403 {
 404   _region_start = 0;
 405 
 406   _region_vspace = 0;
 407   _reserved_byte_size = 0;
 408   _region_data = 0;
 409   _region_count = 0;
 410 
 411   _block_vspace = 0;
 412   _block_data = 0;
 413   _block_count = 0;
 414 }
 415 
 416 bool ParallelCompactData::initialize(MemRegion covered_region)
 417 {
 418   _region_start = covered_region.start();
 419   const size_t region_size = covered_region.word_size();
 420   DEBUG_ONLY(_region_end = _region_start + region_size;)
 421 
 422   assert(region_align_down(_region_start) == _region_start,
 423          "region start not aligned");
 424   assert((region_size & RegionSizeOffsetMask) == 0,
 425          "region size not a multiple of RegionSize");
 426 
 427   bool result = initialize_region_data(region_size) && initialize_block_data();
 428   return result;
 429 }
 430 
 431 PSVirtualSpace*
 432 ParallelCompactData::create_vspace(size_t count, size_t element_size)
 433 {
 434   const size_t raw_bytes = count * element_size;
 435   const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
 436   const size_t granularity = os::vm_allocation_granularity();
 437   _reserved_byte_size = align_up(raw_bytes, MAX2(page_sz, granularity));
 438 
 439   const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
 440     MAX2(page_sz, granularity);
 441   ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0);
 442   os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, page_sz, rs.base(),
 443                        rs.size());
 444 
 445   MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
 446 
 447   PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
 448   if (vspace != 0) {
 449     if (vspace->expand_by(_reserved_byte_size)) {
 450       return vspace;
 451     }
 452     delete vspace;
 453     // Release memory reserved in the space.
 454     rs.release();
 455   }
 456 
 457   return 0;
 458 }
 459 
 460 bool ParallelCompactData::initialize_region_data(size_t region_size)
 461 {
 462   const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
 463   _region_vspace = create_vspace(count, sizeof(RegionData));
 464   if (_region_vspace != 0) {
 465     _region_data = (RegionData*)_region_vspace->reserved_low_addr();
 466     _region_count = count;
 467     return true;
 468   }
 469   return false;
 470 }
 471 
 472 bool ParallelCompactData::initialize_block_data()
 473 {
 474   assert(_region_count != 0, "region data must be initialized first");
 475   const size_t count = _region_count << Log2BlocksPerRegion;
 476   _block_vspace = create_vspace(count, sizeof(BlockData));
 477   if (_block_vspace != 0) {
 478     _block_data = (BlockData*)_block_vspace->reserved_low_addr();
 479     _block_count = count;
 480     return true;
 481   }
 482   return false;
 483 }
 484 
 485 void ParallelCompactData::clear()
 486 {
 487   memset(_region_data, 0, _region_vspace->committed_size());
 488   memset(_block_data, 0, _block_vspace->committed_size());
 489 }
 490 
 491 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
 492   assert(beg_region <= _region_count, "beg_region out of range");
 493   assert(end_region <= _region_count, "end_region out of range");
 494   assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize");
 495 
 496   const size_t region_cnt = end_region - beg_region;
 497   memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
 498 
 499   const size_t beg_block = beg_region * BlocksPerRegion;
 500   const size_t block_cnt = region_cnt * BlocksPerRegion;
 501   memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData));
 502 }
 503 
 504 HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
 505 {
 506   const RegionData* cur_cp = region(region_idx);
 507   const RegionData* const end_cp = region(region_count() - 1);
 508 
 509   HeapWord* result = region_to_addr(region_idx);
 510   if (cur_cp < end_cp) {
 511     do {
 512       result += cur_cp->partial_obj_size();
 513     } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
 514   }
 515   return result;
 516 }
 517 
 518 void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
 519 {
 520   const size_t obj_ofs = pointer_delta(addr, _region_start);
 521   const size_t beg_region = obj_ofs >> Log2RegionSize;
 522   const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
 523 
 524   DEBUG_ONLY(Atomic::inc(&add_obj_count);)
 525   DEBUG_ONLY(Atomic::add(len, &add_obj_size);)
 526 
 527   if (beg_region == end_region) {
 528     // All in one region.
 529     _region_data[beg_region].add_live_obj(len);
 530     return;
 531   }
 532 
 533   // First region.
 534   const size_t beg_ofs = region_offset(addr);
 535   _region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
 536 
 537   Klass* klass = ((oop)addr)->klass();
 538   // Middle regions--completely spanned by this object.
 539   for (size_t region = beg_region + 1; region < end_region; ++region) {
 540     _region_data[region].set_partial_obj_size(RegionSize);
 541     _region_data[region].set_partial_obj_addr(addr);
 542   }
 543 
 544   // Last region.
 545   const size_t end_ofs = region_offset(addr + len - 1);
 546   _region_data[end_region].set_partial_obj_size(end_ofs + 1);
 547   _region_data[end_region].set_partial_obj_addr(addr);
 548 }
 549 
 550 void
 551 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
 552 {
 553   assert(region_offset(beg) == 0, "not RegionSize aligned");
 554   assert(region_offset(end) == 0, "not RegionSize aligned");
 555 
 556   size_t cur_region = addr_to_region_idx(beg);
 557   const size_t end_region = addr_to_region_idx(end);
 558   HeapWord* addr = beg;
 559   while (cur_region < end_region) {
 560     _region_data[cur_region].set_destination(addr);
 561     _region_data[cur_region].set_destination_count(0);
 562     _region_data[cur_region].set_source_region(cur_region);
 563     _region_data[cur_region].set_data_location(addr);
 564 
 565     // Update live_obj_size so the region appears completely full.
 566     size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
 567     _region_data[cur_region].set_live_obj_size(live_size);
 568 
 569     ++cur_region;
 570     addr += RegionSize;
 571   }
 572 }
 573 
 574 // Find the point at which a space can be split and, if necessary, record the
 575 // split point.
 576 //
 577 // If the current src region (which overflowed the destination space) doesn't
 578 // have a partial object, the split point is at the beginning of the current src
 579 // region (an "easy" split, no extra bookkeeping required).
 580 //
 581 // If the current src region has a partial object, the split point is in the
 582 // region where that partial object starts (call it the split_region).  If
 583 // split_region has a partial object, then the split point is just after that
 584 // partial object (a "hard" split where we have to record the split data and
 585 // zero the partial_obj_size field).  With a "hard" split, we know that the
 586 // partial_obj ends within split_region because the partial object that caused
 587 // the overflow starts in split_region.  If split_region doesn't have a partial
 588 // obj, then the split is at the beginning of split_region (another "easy"
 589 // split).
 590 HeapWord*
 591 ParallelCompactData::summarize_split_space(size_t src_region,
 592                                            SplitInfo& split_info,
 593                                            HeapWord* destination,
 594                                            HeapWord* target_end,
 595                                            HeapWord** target_next)
 596 {
 597   assert(destination <= target_end, "sanity");
 598   assert(destination + _region_data[src_region].data_size() > target_end,
 599     "region should not fit into target space");
 600   assert(is_region_aligned(target_end), "sanity");
 601 
 602   size_t split_region = src_region;
 603   HeapWord* split_destination = destination;
 604   size_t partial_obj_size = _region_data[src_region].partial_obj_size();
 605 
 606   if (destination + partial_obj_size > target_end) {
 607     // The split point is just after the partial object (if any) in the
 608     // src_region that contains the start of the object that overflowed the
 609     // destination space.
 610     //
 611     // Find the start of the "overflow" object and set split_region to the
 612     // region containing it.
 613     HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
 614     split_region = addr_to_region_idx(overflow_obj);
 615 
 616     // Clear the source_region field of all destination regions whose first word
 617     // came from data after the split point (a non-null source_region field
 618     // implies a region must be filled).
 619     //
 620     // An alternative to the simple loop below:  clear during post_compact(),
 621     // which uses memcpy instead of individual stores, and is easy to
 622     // parallelize.  (The downside is that it clears the entire RegionData
 623     // object as opposed to just one field.)
 624     //
 625     // post_compact() would have to clear the summary data up to the highest
 626     // address that was written during the summary phase, which would be
 627     //
 628     //         max(top, max(new_top, clear_top))
 629     //
 630     // where clear_top is a new field in SpaceInfo.  Would have to set clear_top
 631     // to target_end.
 632     const RegionData* const sr = region(split_region);
 633     const size_t beg_idx =
 634       addr_to_region_idx(region_align_up(sr->destination() +
 635                                          sr->partial_obj_size()));
 636     const size_t end_idx = addr_to_region_idx(target_end);
 637 
 638     log_develop_trace(gc, compaction)("split:  clearing source_region field in [" SIZE_FORMAT ", " SIZE_FORMAT ")", beg_idx, end_idx);
 639     for (size_t idx = beg_idx; idx < end_idx; ++idx) {
 640       _region_data[idx].set_source_region(0);
 641     }
 642 
 643     // Set split_destination and partial_obj_size to reflect the split region.
 644     split_destination = sr->destination();
 645     partial_obj_size = sr->partial_obj_size();
 646   }
 647 
 648   // The split is recorded only if a partial object extends onto the region.
 649   if (partial_obj_size != 0) {
 650     _region_data[split_region].set_partial_obj_size(0);
 651     split_info.record(split_region, partial_obj_size, split_destination);
 652   }
 653 
 654   // Setup the continuation addresses.
 655   *target_next = split_destination + partial_obj_size;
 656   HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
 657 
 658   if (log_develop_is_enabled(Trace, gc, compaction)) {
 659     const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
 660     log_develop_trace(gc, compaction)("%s split:  src=" PTR_FORMAT " src_c=" SIZE_FORMAT " pos=" SIZE_FORMAT,
 661                                       split_type, p2i(source_next), split_region, partial_obj_size);
 662     log_develop_trace(gc, compaction)("%s split:  dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT " tn=" PTR_FORMAT,
 663                                       split_type, p2i(split_destination),
 664                                       addr_to_region_idx(split_destination),
 665                                       p2i(*target_next));
 666 
 667     if (partial_obj_size != 0) {
 668       HeapWord* const po_beg = split_info.destination();
 669       HeapWord* const po_end = po_beg + split_info.partial_obj_size();
 670       log_develop_trace(gc, compaction)("%s split:  po_beg=" PTR_FORMAT " " SIZE_FORMAT " po_end=" PTR_FORMAT " " SIZE_FORMAT,
 671                                         split_type,
 672                                         p2i(po_beg), addr_to_region_idx(po_beg),
 673                                         p2i(po_end), addr_to_region_idx(po_end));
 674     }
 675   }
 676 
 677   return source_next;
 678 }
 679 
 680 bool ParallelCompactData::summarize(SplitInfo& split_info,
 681                                     HeapWord* source_beg, HeapWord* source_end,
 682                                     HeapWord** source_next,
 683                                     HeapWord* target_beg, HeapWord* target_end,
 684                                     HeapWord** target_next)
 685 {
 686   HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
 687   log_develop_trace(gc, compaction)(
 688       "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
 689       "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
 690       p2i(source_beg), p2i(source_end), p2i(source_next_val),
 691       p2i(target_beg), p2i(target_end), p2i(*target_next));
 692 
 693   size_t cur_region = addr_to_region_idx(source_beg);
 694   const size_t end_region = addr_to_region_idx(region_align_up(source_end));
 695 
 696   HeapWord *dest_addr = target_beg;
 697   while (cur_region < end_region) {
 698     // The destination must be set even if the region has no data.
 699     _region_data[cur_region].set_destination(dest_addr);
 700 
 701     size_t words = _region_data[cur_region].data_size();
 702     if (words > 0) {
 703       // If cur_region does not fit entirely into the target space, find a point
 704       // at which the source space can be 'split' so that part is copied to the
 705       // target space and the rest is copied elsewhere.
 706       if (dest_addr + words > target_end) {
 707         assert(source_next != NULL, "source_next is NULL when splitting");
 708         *source_next = summarize_split_space(cur_region, split_info, dest_addr,
 709                                              target_end, target_next);
 710         return false;
 711       }
 712 
 713       // Compute the destination_count for cur_region, and if necessary, update
 714       // source_region for a destination region.  The source_region field is
 715       // updated if cur_region is the first (left-most) region to be copied to a
 716       // destination region.
 717       //
 718       // The destination_count calculation is a bit subtle.  A region that has
 719       // data that compacts into itself does not count itself as a destination.
 720       // This maintains the invariant that a zero count means the region is
 721       // available and can be claimed and then filled.
 722       uint destination_count = 0;
 723       if (split_info.is_split(cur_region)) {
 724         // The current region has been split:  the partial object will be copied
 725         // to one destination space and the remaining data will be copied to
 726         // another destination space.  Adjust the initial destination_count and,
 727         // if necessary, set the source_region field if the partial object will
 728         // cross a destination region boundary.
 729         destination_count = split_info.destination_count();
 730         if (destination_count == 2) {
 731           size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
 732           _region_data[dest_idx].set_source_region(cur_region);
 733         }
 734       }
 735 
 736       HeapWord* const last_addr = dest_addr + words - 1;
 737       const size_t dest_region_1 = addr_to_region_idx(dest_addr);
 738       const size_t dest_region_2 = addr_to_region_idx(last_addr);
 739 
 740       // Initially assume that the destination regions will be the same and
 741       // adjust the value below if necessary.  Under this assumption, if
 742       // cur_region == dest_region_2, then cur_region will be compacted
 743       // completely into itself.
 744       destination_count += cur_region == dest_region_2 ? 0 : 1;
 745       if (dest_region_1 != dest_region_2) {
 746         // Destination regions differ; adjust destination_count.
 747         destination_count += 1;
 748         // Data from cur_region will be copied to the start of dest_region_2.
 749         _region_data[dest_region_2].set_source_region(cur_region);
 750       } else if (region_offset(dest_addr) == 0) {
 751         // Data from cur_region will be copied to the start of the destination
 752         // region.
 753         _region_data[dest_region_1].set_source_region(cur_region);
 754       }
 755 
 756       _region_data[cur_region].set_destination_count(destination_count);
 757       _region_data[cur_region].set_data_location(region_to_addr(cur_region));
 758       dest_addr += words;
 759     }
 760 
 761     ++cur_region;
 762   }
 763 
 764   *target_next = dest_addr;
 765   return true;
 766 }
 767 
 768 HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr, ParCompactionManager* cm) {
 769   assert(addr != NULL, "Should detect NULL oop earlier");
 770   assert(ParallelScavengeHeap::heap()->is_in(addr), "not in heap");
 771   assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked");
 772 
 773   // Region covering the object.
 774   RegionData* const region_ptr = addr_to_region_ptr(addr);
 775   HeapWord* result = region_ptr->destination();
 776 
 777   // If the entire Region is live, the new location is region->destination + the
 778   // offset of the object within in the Region.
 779 
 780   // Run some performance tests to determine if this special case pays off.  It
 781   // is worth it for pointers into the dense prefix.  If the optimization to
 782   // avoid pointer updates in regions that only point to the dense prefix is
 783   // ever implemented, this should be revisited.
 784   if (region_ptr->data_size() == RegionSize) {
 785     result += region_offset(addr);
 786     return result;
 787   }
 788 
 789   // Otherwise, the new location is region->destination + block offset + the
 790   // number of live words in the Block that are (a) to the left of addr and (b)
 791   // due to objects that start in the Block.
 792 
 793   // Fill in the block table if necessary.  This is unsynchronized, so multiple
 794   // threads may fill the block table for a region (harmless, since it is
 795   // idempotent).
 796   if (!region_ptr->blocks_filled()) {
 797     PSParallelCompact::fill_blocks(addr_to_region_idx(addr));
 798     region_ptr->set_blocks_filled();
 799   }
 800 
 801   HeapWord* const search_start = block_align_down(addr);
 802   const size_t block_offset = addr_to_block_ptr(addr)->offset();
 803 
 804   const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
 805   const size_t live = bitmap->live_words_in_range(cm, search_start, oop(addr));
 806   result += block_offset + live;
 807   DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result));
 808   return result;
 809 }
 810 
 811 #ifdef ASSERT
 812 void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
 813 {
 814   const size_t* const beg = (const size_t*)vspace->committed_low_addr();
 815   const size_t* const end = (const size_t*)vspace->committed_high_addr();
 816   for (const size_t* p = beg; p < end; ++p) {
 817     assert(*p == 0, "not zero");
 818   }
 819 }
 820 
 821 void ParallelCompactData::verify_clear()
 822 {
 823   verify_clear(_region_vspace);
 824   verify_clear(_block_vspace);
 825 }
 826 #endif  // #ifdef ASSERT
 827 
 828 STWGCTimer          PSParallelCompact::_gc_timer;
 829 ParallelOldTracer   PSParallelCompact::_gc_tracer;
 830 elapsedTimer        PSParallelCompact::_accumulated_time;
 831 unsigned int        PSParallelCompact::_total_invocations = 0;
 832 unsigned int        PSParallelCompact::_maximum_compaction_gc_num = 0;
 833 jlong               PSParallelCompact::_time_of_last_gc = 0;
 834 CollectorCounters*  PSParallelCompact::_counters = NULL;
 835 ParMarkBitMap       PSParallelCompact::_mark_bitmap;
 836 ParallelCompactData PSParallelCompact::_summary_data;
 837 
 838 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
 839 
 840 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
 841 
 842 void PSParallelCompact::post_initialize() {
 843   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 844   MemRegion mr = heap->reserved_region();
 845   _ref_processor =
 846     new ReferenceProcessor(mr,            // span
 847                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 848                            ParallelGCThreads, // mt processing degree
 849                            true,              // mt discovery
 850                            ParallelGCThreads, // mt discovery degree
 851                            true,              // atomic_discovery
 852                            &_is_alive_closure); // non-header is alive closure
 853   _counters = new CollectorCounters("PSParallelCompact", 1);
 854 
 855   // Initialize static fields in ParCompactionManager.
 856   ParCompactionManager::initialize(mark_bitmap());
 857 }
 858 
 859 bool PSParallelCompact::initialize() {
 860   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 861   MemRegion mr = heap->reserved_region();
 862 
 863   // Was the old gen get allocated successfully?
 864   if (!heap->old_gen()->is_allocated()) {
 865     return false;
 866   }
 867 
 868   initialize_space_info();
 869   initialize_dead_wood_limiter();
 870 
 871   if (!_mark_bitmap.initialize(mr)) {
 872     vm_shutdown_during_initialization(
 873       err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
 874       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 875       _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
 876     return false;
 877   }
 878 
 879   if (!_summary_data.initialize(mr)) {
 880     vm_shutdown_during_initialization(
 881       err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
 882       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 883       _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
 884     return false;
 885   }
 886 
 887   return true;
 888 }
 889 
 890 void PSParallelCompact::initialize_space_info()
 891 {
 892   memset(&_space_info, 0, sizeof(_space_info));
 893 
 894   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 895   PSYoungGen* young_gen = heap->young_gen();
 896 
 897   _space_info[old_space_id].set_space(heap->old_gen()->object_space());
 898   _space_info[eden_space_id].set_space(young_gen->eden_space());
 899   _space_info[from_space_id].set_space(young_gen->from_space());
 900   _space_info[to_space_id].set_space(young_gen->to_space());
 901 
 902   _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
 903 }
 904 
 905 void PSParallelCompact::initialize_dead_wood_limiter()
 906 {
 907   const size_t max = 100;
 908   _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
 909   _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
 910   _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
 911   DEBUG_ONLY(_dwl_initialized = true;)
 912   _dwl_adjustment = normal_distribution(1.0);
 913 }
 914 
 915 void
 916 PSParallelCompact::clear_data_covering_space(SpaceId id)
 917 {
 918   // At this point, top is the value before GC, new_top() is the value that will
 919   // be set at the end of GC.  The marking bitmap is cleared to top; nothing
 920   // should be marked above top.  The summary data is cleared to the larger of
 921   // top & new_top.
 922   MutableSpace* const space = _space_info[id].space();
 923   HeapWord* const bot = space->bottom();
 924   HeapWord* const top = space->top();
 925   HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
 926 
 927   const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
 928   const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top));
 929   _mark_bitmap.clear_range(beg_bit, end_bit);
 930 
 931   const size_t beg_region = _summary_data.addr_to_region_idx(bot);
 932   const size_t end_region =
 933     _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
 934   _summary_data.clear_range(beg_region, end_region);
 935 
 936   // Clear the data used to 'split' regions.
 937   SplitInfo& split_info = _space_info[id].split_info();
 938   if (split_info.is_valid()) {
 939     split_info.clear();
 940   }
 941   DEBUG_ONLY(split_info.verify_clear();)
 942 }
 943 
 944 void PSParallelCompact::pre_compact()
 945 {
 946   // Update the from & to space pointers in space_info, since they are swapped
 947   // at each young gen gc.  Do the update unconditionally (even though a
 948   // promotion failure does not swap spaces) because an unknown number of young
 949   // collections will have swapped the spaces an unknown number of times.
 950   GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
 951   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 952   _space_info[from_space_id].set_space(heap->young_gen()->from_space());
 953   _space_info[to_space_id].set_space(heap->young_gen()->to_space());
 954 
 955   DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
 956   DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
 957 
 958   // Increment the invocation count
 959   heap->increment_total_collections(true);
 960 
 961   // We need to track unique mark sweep invocations as well.
 962   _total_invocations++;
 963 
 964   heap->print_heap_before_gc();
 965   heap->trace_heap_before_gc(&_gc_tracer);
 966 
 967   // Fill in TLABs
 968   heap->accumulate_statistics_all_tlabs();
 969   heap->ensure_parsability(true);  // retire TLABs
 970 
 971   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 972     HandleMark hm;  // Discard invalid handles created during verification
 973     Universe::verify("Before GC");
 974   }
 975 
 976   // Verify object start arrays
 977   if (VerifyObjectStartArray &&
 978       VerifyBeforeGC) {
 979     heap->old_gen()->verify_object_start_array();
 980   }
 981 
 982   DEBUG_ONLY(mark_bitmap()->verify_clear();)
 983   DEBUG_ONLY(summary_data().verify_clear();)
 984 
 985   // Have worker threads release resources the next time they run a task.
 986   gc_task_manager()->release_all_resources();
 987 
 988   ParCompactionManager::reset_all_bitmap_query_caches();
 989 }
 990 
 991 void PSParallelCompact::post_compact()
 992 {
 993   GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
 994 
 995   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
 996     // Clear the marking bitmap, summary data and split info.
 997     clear_data_covering_space(SpaceId(id));
 998     // Update top().  Must be done after clearing the bitmap and summary data.
 999     _space_info[id].publish_new_top();
1000   }
1001 
1002   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1003   MutableSpace* const from_space = _space_info[from_space_id].space();
1004   MutableSpace* const to_space   = _space_info[to_space_id].space();
1005 
1006   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1007   bool eden_empty = eden_space->is_empty();
1008   if (!eden_empty) {
1009     eden_empty = absorb_live_data_from_eden(heap->size_policy(),
1010                                             heap->young_gen(), heap->old_gen());
1011   }
1012 
1013   // Update heap occupancy information which is used as input to the soft ref
1014   // clearing policy at the next gc.
1015   Universe::update_heap_info_at_gc();
1016 
1017   bool young_gen_empty = eden_empty && from_space->is_empty() &&
1018     to_space->is_empty();
1019 
1020   ModRefBarrierSet* modBS = barrier_set_cast<ModRefBarrierSet>(heap->barrier_set());
1021   MemRegion old_mr = heap->old_gen()->reserved();
1022   if (young_gen_empty) {
1023     modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
1024   } else {
1025     modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1026   }
1027 
1028   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1029   ClassLoaderDataGraph::purge();
1030   MetaspaceAux::verify_metrics();
1031 
1032   CodeCache::gc_epilogue();
1033   JvmtiExport::gc_epilogue();
1034 
1035 #if COMPILER2_OR_JVMCI
1036   DerivedPointerTable::update_pointers();
1037 #endif
1038 
1039   ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->num_q());
1040 
1041   ref_processor()->enqueue_discovered_references(NULL, &pt);
1042 
1043   pt.print_enqueue_phase();
1044 
1045   if (ZapUnusedHeapArea) {
1046     heap->gen_mangle_unused_area();
1047   }
1048 
1049   // Update time of last GC
1050   reset_millis_since_last_gc();
1051 }
1052 
1053 HeapWord*
1054 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1055                                                     bool maximum_compaction)
1056 {
1057   const size_t region_size = ParallelCompactData::RegionSize;
1058   const ParallelCompactData& sd = summary_data();
1059 
1060   const MutableSpace* const space = _space_info[id].space();
1061   HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1062   const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1063   const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1064 
1065   // Skip full regions at the beginning of the space--they are necessarily part
1066   // of the dense prefix.
1067   size_t full_count = 0;
1068   const RegionData* cp;
1069   for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1070     ++full_count;
1071   }
1072 
1073   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1074   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1075   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1076   if (maximum_compaction || cp == end_cp || interval_ended) {
1077     _maximum_compaction_gc_num = total_invocations();
1078     return sd.region_to_addr(cp);
1079   }
1080 
1081   HeapWord* const new_top = _space_info[id].new_top();
1082   const size_t space_live = pointer_delta(new_top, space->bottom());
1083   const size_t space_used = space->used_in_words();
1084   const size_t space_capacity = space->capacity_in_words();
1085 
1086   const double cur_density = double(space_live) / space_capacity;
1087   const double deadwood_density =
1088     (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1089   const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1090 
1091   if (TraceParallelOldGCDensePrefix) {
1092     tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1093                   cur_density, deadwood_density, deadwood_goal);
1094     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1095                   "space_cap=" SIZE_FORMAT,
1096                   space_live, space_used,
1097                   space_capacity);
1098   }
1099 
1100   // XXX - Use binary search?
1101   HeapWord* dense_prefix = sd.region_to_addr(cp);
1102   const RegionData* full_cp = cp;
1103   const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1104   while (cp < end_cp) {
1105     HeapWord* region_destination = cp->destination();
1106     const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1107     if (TraceParallelOldGCDensePrefix && Verbose) {
1108       tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1109                     "dp=" PTR_FORMAT " " "cdw=" SIZE_FORMAT_W(8),
1110                     sd.region(cp), p2i(region_destination),
1111                     p2i(dense_prefix), cur_deadwood);
1112     }
1113 
1114     if (cur_deadwood >= deadwood_goal) {
1115       // Found the region that has the correct amount of deadwood to the left.
1116       // This typically occurs after crossing a fairly sparse set of regions, so
1117       // iterate backwards over those sparse regions, looking for the region
1118       // that has the lowest density of live objects 'to the right.'
1119       size_t space_to_left = sd.region(cp) * region_size;
1120       size_t live_to_left = space_to_left - cur_deadwood;
1121       size_t space_to_right = space_capacity - space_to_left;
1122       size_t live_to_right = space_live - live_to_left;
1123       double density_to_right = double(live_to_right) / space_to_right;
1124       while (cp > full_cp) {
1125         --cp;
1126         const size_t prev_region_live_to_right = live_to_right -
1127           cp->data_size();
1128         const size_t prev_region_space_to_right = space_to_right + region_size;
1129         double prev_region_density_to_right =
1130           double(prev_region_live_to_right) / prev_region_space_to_right;
1131         if (density_to_right <= prev_region_density_to_right) {
1132           return dense_prefix;
1133         }
1134         if (TraceParallelOldGCDensePrefix && Verbose) {
1135           tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1136                         "pc_d2r=%10.8f", sd.region(cp), density_to_right,
1137                         prev_region_density_to_right);
1138         }
1139         dense_prefix -= region_size;
1140         live_to_right = prev_region_live_to_right;
1141         space_to_right = prev_region_space_to_right;
1142         density_to_right = prev_region_density_to_right;
1143       }
1144       return dense_prefix;
1145     }
1146 
1147     dense_prefix += region_size;
1148     ++cp;
1149   }
1150 
1151   return dense_prefix;
1152 }
1153 
1154 #ifndef PRODUCT
1155 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1156                                                  const SpaceId id,
1157                                                  const bool maximum_compaction,
1158                                                  HeapWord* const addr)
1159 {
1160   const size_t region_idx = summary_data().addr_to_region_idx(addr);
1161   RegionData* const cp = summary_data().region(region_idx);
1162   const MutableSpace* const space = _space_info[id].space();
1163   HeapWord* const new_top = _space_info[id].new_top();
1164 
1165   const size_t space_live = pointer_delta(new_top, space->bottom());
1166   const size_t dead_to_left = pointer_delta(addr, cp->destination());
1167   const size_t space_cap = space->capacity_in_words();
1168   const double dead_to_left_pct = double(dead_to_left) / space_cap;
1169   const size_t live_to_right = new_top - cp->destination();
1170   const size_t dead_to_right = space->top() - addr - live_to_right;
1171 
1172   tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1173                 "spl=" SIZE_FORMAT " "
1174                 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1175                 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
1176                 " ratio=%10.8f",
1177                 algorithm, p2i(addr), region_idx,
1178                 space_live,
1179                 dead_to_left, dead_to_left_pct,
1180                 dead_to_right, live_to_right,
1181                 double(dead_to_right) / live_to_right);
1182 }
1183 #endif  // #ifndef PRODUCT
1184 
1185 // Return a fraction indicating how much of the generation can be treated as
1186 // "dead wood" (i.e., not reclaimed).  The function uses a normal distribution
1187 // based on the density of live objects in the generation to determine a limit,
1188 // which is then adjusted so the return value is min_percent when the density is
1189 // 1.
1190 //
1191 // The following table shows some return values for a different values of the
1192 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1193 // min_percent is 1.
1194 //
1195 //                          fraction allowed as dead wood
1196 //         -----------------------------------------------------------------
1197 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1198 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1199 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1200 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1201 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1202 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1203 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1204 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1205 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1206 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1207 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1208 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1209 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1210 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1211 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1212 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1213 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1214 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1215 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1216 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1217 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1218 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1219 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1220 
1221 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1222 {
1223   assert(_dwl_initialized, "uninitialized");
1224 
1225   // The raw limit is the value of the normal distribution at x = density.
1226   const double raw_limit = normal_distribution(density);
1227 
1228   // Adjust the raw limit so it becomes the minimum when the density is 1.
1229   //
1230   // First subtract the adjustment value (which is simply the precomputed value
1231   // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1232   // Then add the minimum value, so the minimum is returned when the density is
1233   // 1.  Finally, prevent negative values, which occur when the mean is not 0.5.
1234   const double min = double(min_percent) / 100.0;
1235   const double limit = raw_limit - _dwl_adjustment + min;
1236   return MAX2(limit, 0.0);
1237 }
1238 
1239 ParallelCompactData::RegionData*
1240 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1241                                            const RegionData* end)
1242 {
1243   const size_t region_size = ParallelCompactData::RegionSize;
1244   ParallelCompactData& sd = summary_data();
1245   size_t left = sd.region(beg);
1246   size_t right = end > beg ? sd.region(end) - 1 : left;
1247 
1248   // Binary search.
1249   while (left < right) {
1250     // Equivalent to (left + right) / 2, but does not overflow.
1251     const size_t middle = left + (right - left) / 2;
1252     RegionData* const middle_ptr = sd.region(middle);
1253     HeapWord* const dest = middle_ptr->destination();
1254     HeapWord* const addr = sd.region_to_addr(middle);
1255     assert(dest != NULL, "sanity");
1256     assert(dest <= addr, "must move left");
1257 
1258     if (middle > left && dest < addr) {
1259       right = middle - 1;
1260     } else if (middle < right && middle_ptr->data_size() == region_size) {
1261       left = middle + 1;
1262     } else {
1263       return middle_ptr;
1264     }
1265   }
1266   return sd.region(left);
1267 }
1268 
1269 ParallelCompactData::RegionData*
1270 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1271                                           const RegionData* end,
1272                                           size_t dead_words)
1273 {
1274   ParallelCompactData& sd = summary_data();
1275   size_t left = sd.region(beg);
1276   size_t right = end > beg ? sd.region(end) - 1 : left;
1277 
1278   // Binary search.
1279   while (left < right) {
1280     // Equivalent to (left + right) / 2, but does not overflow.
1281     const size_t middle = left + (right - left) / 2;
1282     RegionData* const middle_ptr = sd.region(middle);
1283     HeapWord* const dest = middle_ptr->destination();
1284     HeapWord* const addr = sd.region_to_addr(middle);
1285     assert(dest != NULL, "sanity");
1286     assert(dest <= addr, "must move left");
1287 
1288     const size_t dead_to_left = pointer_delta(addr, dest);
1289     if (middle > left && dead_to_left > dead_words) {
1290       right = middle - 1;
1291     } else if (middle < right && dead_to_left < dead_words) {
1292       left = middle + 1;
1293     } else {
1294       return middle_ptr;
1295     }
1296   }
1297   return sd.region(left);
1298 }
1299 
1300 // The result is valid during the summary phase, after the initial summarization
1301 // of each space into itself, and before final summarization.
1302 inline double
1303 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1304                                    HeapWord* const bottom,
1305                                    HeapWord* const top,
1306                                    HeapWord* const new_top)
1307 {
1308   ParallelCompactData& sd = summary_data();
1309 
1310   assert(cp != NULL, "sanity");
1311   assert(bottom != NULL, "sanity");
1312   assert(top != NULL, "sanity");
1313   assert(new_top != NULL, "sanity");
1314   assert(top >= new_top, "summary data problem?");
1315   assert(new_top > bottom, "space is empty; should not be here");
1316   assert(new_top >= cp->destination(), "sanity");
1317   assert(top >= sd.region_to_addr(cp), "sanity");
1318 
1319   HeapWord* const destination = cp->destination();
1320   const size_t dense_prefix_live  = pointer_delta(destination, bottom);
1321   const size_t compacted_region_live = pointer_delta(new_top, destination);
1322   const size_t compacted_region_used = pointer_delta(top,
1323                                                      sd.region_to_addr(cp));
1324   const size_t reclaimable = compacted_region_used - compacted_region_live;
1325 
1326   const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1327   return double(reclaimable) / divisor;
1328 }
1329 
1330 // Return the address of the end of the dense prefix, a.k.a. the start of the
1331 // compacted region.  The address is always on a region boundary.
1332 //
1333 // Completely full regions at the left are skipped, since no compaction can
1334 // occur in those regions.  Then the maximum amount of dead wood to allow is
1335 // computed, based on the density (amount live / capacity) of the generation;
1336 // the region with approximately that amount of dead space to the left is
1337 // identified as the limit region.  Regions between the last completely full
1338 // region and the limit region are scanned and the one that has the best
1339 // (maximum) reclaimed_ratio() is selected.
1340 HeapWord*
1341 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1342                                         bool maximum_compaction)
1343 {
1344   const size_t region_size = ParallelCompactData::RegionSize;
1345   const ParallelCompactData& sd = summary_data();
1346 
1347   const MutableSpace* const space = _space_info[id].space();
1348   HeapWord* const top = space->top();
1349   HeapWord* const top_aligned_up = sd.region_align_up(top);
1350   HeapWord* const new_top = _space_info[id].new_top();
1351   HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1352   HeapWord* const bottom = space->bottom();
1353   const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1354   const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1355   const RegionData* const new_top_cp =
1356     sd.addr_to_region_ptr(new_top_aligned_up);
1357 
1358   // Skip full regions at the beginning of the space--they are necessarily part
1359   // of the dense prefix.
1360   const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1361   assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1362          space->is_empty(), "no dead space allowed to the left");
1363   assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1364          "region must have dead space");
1365 
1366   // The gc number is saved whenever a maximum compaction is done, and used to
1367   // determine when the maximum compaction interval has expired.  This avoids
1368   // successive max compactions for different reasons.
1369   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1370   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1371   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1372     total_invocations() == HeapFirstMaximumCompactionCount;
1373   if (maximum_compaction || full_cp == top_cp || interval_ended) {
1374     _maximum_compaction_gc_num = total_invocations();
1375     return sd.region_to_addr(full_cp);
1376   }
1377 
1378   const size_t space_live = pointer_delta(new_top, bottom);
1379   const size_t space_used = space->used_in_words();
1380   const size_t space_capacity = space->capacity_in_words();
1381 
1382   const double density = double(space_live) / double(space_capacity);
1383   const size_t min_percent_free = MarkSweepDeadRatio;
1384   const double limiter = dead_wood_limiter(density, min_percent_free);
1385   const size_t dead_wood_max = space_used - space_live;
1386   const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1387                                       dead_wood_max);
1388 
1389   if (TraceParallelOldGCDensePrefix) {
1390     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1391                   "space_cap=" SIZE_FORMAT,
1392                   space_live, space_used,
1393                   space_capacity);
1394     tty->print_cr("dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
1395                   "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1396                   density, min_percent_free, limiter,
1397                   dead_wood_max, dead_wood_limit);
1398   }
1399 
1400   // Locate the region with the desired amount of dead space to the left.
1401   const RegionData* const limit_cp =
1402     dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1403 
1404   // Scan from the first region with dead space to the limit region and find the
1405   // one with the best (largest) reclaimed ratio.
1406   double best_ratio = 0.0;
1407   const RegionData* best_cp = full_cp;
1408   for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1409     double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1410     if (tmp_ratio > best_ratio) {
1411       best_cp = cp;
1412       best_ratio = tmp_ratio;
1413     }
1414   }
1415 
1416   return sd.region_to_addr(best_cp);
1417 }
1418 
1419 void PSParallelCompact::summarize_spaces_quick()
1420 {
1421   for (unsigned int i = 0; i < last_space_id; ++i) {
1422     const MutableSpace* space = _space_info[i].space();
1423     HeapWord** nta = _space_info[i].new_top_addr();
1424     bool result = _summary_data.summarize(_space_info[i].split_info(),
1425                                           space->bottom(), space->top(), NULL,
1426                                           space->bottom(), space->end(), nta);
1427     assert(result, "space must fit into itself");
1428     _space_info[i].set_dense_prefix(space->bottom());
1429   }
1430 }
1431 
1432 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1433 {
1434   HeapWord* const dense_prefix_end = dense_prefix(id);
1435   const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1436   const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1437   if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1438     // Only enough dead space is filled so that any remaining dead space to the
1439     // left is larger than the minimum filler object.  (The remainder is filled
1440     // during the copy/update phase.)
1441     //
1442     // The size of the dead space to the right of the boundary is not a
1443     // concern, since compaction will be able to use whatever space is
1444     // available.
1445     //
1446     // Here '||' is the boundary, 'x' represents a don't care bit and a box
1447     // surrounds the space to be filled with an object.
1448     //
1449     // In the 32-bit VM, each bit represents two 32-bit words:
1450     //                              +---+
1451     // a) beg_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1452     //    end_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1453     //                              +---+
1454     //
1455     // In the 64-bit VM, each bit represents one 64-bit word:
1456     //                              +------------+
1457     // b) beg_bits:  ...  x   x   x | 0   ||   0 | x  x  ...
1458     //    end_bits:  ...  x   x   1 | 0   ||   0 | x  x  ...
1459     //                              +------------+
1460     //                          +-------+
1461     // c) beg_bits:  ...  x   x | 0   0 | ||   0   x  x  ...
1462     //    end_bits:  ...  x   1 | 0   0 | ||   0   x  x  ...
1463     //                          +-------+
1464     //                      +-----------+
1465     // d) beg_bits:  ...  x | 0   0   0 | ||   0   x  x  ...
1466     //    end_bits:  ...  1 | 0   0   0 | ||   0   x  x  ...
1467     //                      +-----------+
1468     //                          +-------+
1469     // e) beg_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1470     //    end_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1471     //                          +-------+
1472 
1473     // Initially assume case a, c or e will apply.
1474     size_t obj_len = CollectedHeap::min_fill_size();
1475     HeapWord* obj_beg = dense_prefix_end - obj_len;
1476 
1477 #ifdef  _LP64
1478     if (MinObjAlignment > 1) { // object alignment > heap word size
1479       // Cases a, c or e.
1480     } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1481       // Case b above.
1482       obj_beg = dense_prefix_end - 1;
1483     } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1484                _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1485       // Case d above.
1486       obj_beg = dense_prefix_end - 3;
1487       obj_len = 3;
1488     }
1489 #endif  // #ifdef _LP64
1490 
1491     CollectedHeap::fill_with_object(obj_beg, obj_len);
1492     _mark_bitmap.mark_obj(obj_beg, obj_len);
1493     _summary_data.add_obj(obj_beg, obj_len);
1494     assert(start_array(id) != NULL, "sanity");
1495     start_array(id)->allocate_block(obj_beg);
1496   }
1497 }
1498 
1499 void
1500 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1501 {
1502   assert(id < last_space_id, "id out of range");
1503   assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom(),
1504          "should have been reset in summarize_spaces_quick()");
1505 
1506   const MutableSpace* space = _space_info[id].space();
1507   if (_space_info[id].new_top() != space->bottom()) {
1508     HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1509     _space_info[id].set_dense_prefix(dense_prefix_end);
1510 
1511 #ifndef PRODUCT
1512     if (TraceParallelOldGCDensePrefix) {
1513       print_dense_prefix_stats("ratio", id, maximum_compaction,
1514                                dense_prefix_end);
1515       HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1516       print_dense_prefix_stats("density", id, maximum_compaction, addr);
1517     }
1518 #endif  // #ifndef PRODUCT
1519 
1520     // Recompute the summary data, taking into account the dense prefix.  If
1521     // every last byte will be reclaimed, then the existing summary data which
1522     // compacts everything can be left in place.
1523     if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1524       // If dead space crosses the dense prefix boundary, it is (at least
1525       // partially) filled with a dummy object, marked live and added to the
1526       // summary data.  This simplifies the copy/update phase and must be done
1527       // before the final locations of objects are determined, to prevent
1528       // leaving a fragment of dead space that is too small to fill.
1529       fill_dense_prefix_end(id);
1530 
1531       // Compute the destination of each Region, and thus each object.
1532       _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1533       _summary_data.summarize(_space_info[id].split_info(),
1534                               dense_prefix_end, space->top(), NULL,
1535                               dense_prefix_end, space->end(),
1536                               _space_info[id].new_top_addr());
1537     }
1538   }
1539 
1540   if (log_develop_is_enabled(Trace, gc, compaction)) {
1541     const size_t region_size = ParallelCompactData::RegionSize;
1542     HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1543     const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1544     const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1545     HeapWord* const new_top = _space_info[id].new_top();
1546     const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1547     const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1548     log_develop_trace(gc, compaction)(
1549         "id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1550         "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1551         "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1552         id, space->capacity_in_words(), p2i(dense_prefix_end),
1553         dp_region, dp_words / region_size,
1554         cr_words / region_size, p2i(new_top));
1555   }
1556 }
1557 
1558 #ifndef PRODUCT
1559 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1560                                           HeapWord* dst_beg, HeapWord* dst_end,
1561                                           SpaceId src_space_id,
1562                                           HeapWord* src_beg, HeapWord* src_end)
1563 {
1564   log_develop_trace(gc, compaction)(
1565       "Summarizing %d [%s] into %d [%s]:  "
1566       "src=" PTR_FORMAT "-" PTR_FORMAT " "
1567       SIZE_FORMAT "-" SIZE_FORMAT " "
1568       "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1569       SIZE_FORMAT "-" SIZE_FORMAT,
1570       src_space_id, space_names[src_space_id],
1571       dst_space_id, space_names[dst_space_id],
1572       p2i(src_beg), p2i(src_end),
1573       _summary_data.addr_to_region_idx(src_beg),
1574       _summary_data.addr_to_region_idx(src_end),
1575       p2i(dst_beg), p2i(dst_end),
1576       _summary_data.addr_to_region_idx(dst_beg),
1577       _summary_data.addr_to_region_idx(dst_end));
1578 }
1579 #endif  // #ifndef PRODUCT
1580 
1581 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1582                                       bool maximum_compaction)
1583 {
1584   GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
1585 
1586 #ifdef  ASSERT
1587   if (TraceParallelOldGCMarkingPhase) {
1588     tty->print_cr("add_obj_count=" SIZE_FORMAT " "
1589                   "add_obj_bytes=" SIZE_FORMAT,
1590                   add_obj_count, add_obj_size * HeapWordSize);
1591     tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
1592                   "mark_bitmap_bytes=" SIZE_FORMAT,
1593                   mark_bitmap_count, mark_bitmap_size * HeapWordSize);
1594   }
1595 #endif  // #ifdef ASSERT
1596 
1597   // Quick summarization of each space into itself, to see how much is live.
1598   summarize_spaces_quick();
1599 
1600   log_develop_trace(gc, compaction)("summary phase:  after summarizing each space to self");
1601   NOT_PRODUCT(print_region_ranges());
1602   NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1603 
1604   // The amount of live data that will end up in old space (assuming it fits).
1605   size_t old_space_total_live = 0;
1606   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1607     old_space_total_live += pointer_delta(_space_info[id].new_top(),
1608                                           _space_info[id].space()->bottom());
1609   }
1610 
1611   MutableSpace* const old_space = _space_info[old_space_id].space();
1612   const size_t old_capacity = old_space->capacity_in_words();
1613   if (old_space_total_live > old_capacity) {
1614     // XXX - should also try to expand
1615     maximum_compaction = true;
1616   }
1617 
1618   // Old generations.
1619   summarize_space(old_space_id, maximum_compaction);
1620 
1621   // Summarize the remaining spaces in the young gen.  The initial target space
1622   // is the old gen.  If a space does not fit entirely into the target, then the
1623   // remainder is compacted into the space itself and that space becomes the new
1624   // target.
1625   SpaceId dst_space_id = old_space_id;
1626   HeapWord* dst_space_end = old_space->end();
1627   HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1628   for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1629     const MutableSpace* space = _space_info[id].space();
1630     const size_t live = pointer_delta(_space_info[id].new_top(),
1631                                       space->bottom());
1632     const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1633 
1634     NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1635                                   SpaceId(id), space->bottom(), space->top());)
1636     if (live > 0 && live <= available) {
1637       // All the live data will fit.
1638       bool done = _summary_data.summarize(_space_info[id].split_info(),
1639                                           space->bottom(), space->top(),
1640                                           NULL,
1641                                           *new_top_addr, dst_space_end,
1642                                           new_top_addr);
1643       assert(done, "space must fit into old gen");
1644 
1645       // Reset the new_top value for the space.
1646       _space_info[id].set_new_top(space->bottom());
1647     } else if (live > 0) {
1648       // Attempt to fit part of the source space into the target space.
1649       HeapWord* next_src_addr = NULL;
1650       bool done = _summary_data.summarize(_space_info[id].split_info(),
1651                                           space->bottom(), space->top(),
1652                                           &next_src_addr,
1653                                           *new_top_addr, dst_space_end,
1654                                           new_top_addr);
1655       assert(!done, "space should not fit into old gen");
1656       assert(next_src_addr != NULL, "sanity");
1657 
1658       // The source space becomes the new target, so the remainder is compacted
1659       // within the space itself.
1660       dst_space_id = SpaceId(id);
1661       dst_space_end = space->end();
1662       new_top_addr = _space_info[id].new_top_addr();
1663       NOT_PRODUCT(summary_phase_msg(dst_space_id,
1664                                     space->bottom(), dst_space_end,
1665                                     SpaceId(id), next_src_addr, space->top());)
1666       done = _summary_data.summarize(_space_info[id].split_info(),
1667                                      next_src_addr, space->top(),
1668                                      NULL,
1669                                      space->bottom(), dst_space_end,
1670                                      new_top_addr);
1671       assert(done, "space must fit when compacted into itself");
1672       assert(*new_top_addr <= space->top(), "usage should not grow");
1673     }
1674   }
1675 
1676   log_develop_trace(gc, compaction)("Summary_phase:  after final summarization");
1677   NOT_PRODUCT(print_region_ranges());
1678   NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1679 }
1680 
1681 // This method should contain all heap-specific policy for invoking a full
1682 // collection.  invoke_no_policy() will only attempt to compact the heap; it
1683 // will do nothing further.  If we need to bail out for policy reasons, scavenge
1684 // before full gc, or any other specialized behavior, it needs to be added here.
1685 //
1686 // Note that this method should only be called from the vm_thread while at a
1687 // safepoint.
1688 //
1689 // Note that the all_soft_refs_clear flag in the collector policy
1690 // may be true because this method can be called without intervening
1691 // activity.  For example when the heap space is tight and full measure
1692 // are being taken to free space.
1693 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1694   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1695   assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1696          "should be in vm thread");
1697 
1698   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1699   GCCause::Cause gc_cause = heap->gc_cause();
1700   assert(!heap->is_gc_active(), "not reentrant");
1701 
1702   PSAdaptiveSizePolicy* policy = heap->size_policy();
1703   IsGCActiveMark mark;
1704 
1705   if (ScavengeBeforeFullGC) {
1706     PSScavenge::invoke_no_policy();
1707   }
1708 
1709   const bool clear_all_soft_refs =
1710     heap->soft_ref_policy()->should_clear_all_soft_refs();
1711 
1712   PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1713                                       maximum_heap_compaction);
1714 }
1715 
1716 // This method contains no policy. You should probably
1717 // be calling invoke() instead.
1718 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
1719   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
1720   assert(ref_processor() != NULL, "Sanity");
1721 
1722   if (GCLocker::check_active_before_gc()) {
1723     return false;
1724   }
1725 
1726   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1727 
1728   GCIdMark gc_id_mark;
1729   _gc_timer.register_gc_start();
1730   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1731 
1732   TimeStamp marking_start;
1733   TimeStamp compaction_start;
1734   TimeStamp collection_exit;
1735 
1736   GCCause::Cause gc_cause = heap->gc_cause();
1737   PSYoungGen* young_gen = heap->young_gen();
1738   PSOldGen* old_gen = heap->old_gen();
1739   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1740 
1741   // The scope of casr should end after code that can change
1742   // CollectorPolicy::_should_clear_all_soft_refs.
1743   ClearedAllSoftRefs casr(maximum_heap_compaction,
1744                           heap->soft_ref_policy());
1745 
1746   if (ZapUnusedHeapArea) {
1747     // Save information needed to minimize mangling
1748     heap->record_gen_tops_before_GC();
1749   }
1750 
1751   // Make sure data structures are sane, make the heap parsable, and do other
1752   // miscellaneous bookkeeping.
1753   pre_compact();
1754 
1755   PreGCValues pre_gc_values(heap);
1756 
1757   // Get the compaction manager reserved for the VM thread.
1758   ParCompactionManager* const vmthread_cm =
1759     ParCompactionManager::manager_array(gc_task_manager()->workers());
1760 
1761   {
1762     ResourceMark rm;
1763     HandleMark hm;
1764 
1765     // Set the number of GC threads to be used in this collection
1766     gc_task_manager()->set_active_gang();
1767     gc_task_manager()->task_idle_workers();
1768 
1769     GCTraceCPUTime tcpu;
1770     GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause, true);
1771 
1772     heap->pre_full_gc_dump(&_gc_timer);
1773 
1774     TraceCollectorStats tcs(counters());
1775     TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause);
1776 
1777     if (log_is_enabled(Debug, gc, heap, exit)) {
1778       accumulated_time()->start();
1779     }
1780 
1781     // Let the size policy know we're starting
1782     size_policy->major_collection_begin();
1783 
1784     CodeCache::gc_prologue();
1785 
1786 #if COMPILER2_OR_JVMCI
1787     DerivedPointerTable::clear();
1788 #endif
1789 
1790     ref_processor()->enable_discovery();
1791     ref_processor()->setup_policy(maximum_heap_compaction);
1792 
1793     bool marked_for_unloading = false;
1794 
1795     marking_start.update();
1796     marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
1797 
1798     bool max_on_system_gc = UseMaximumCompactionOnSystemGC
1799       && GCCause::is_user_requested_gc(gc_cause);
1800     summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
1801 
1802 #if COMPILER2_OR_JVMCI
1803     assert(DerivedPointerTable::is_active(), "Sanity");
1804     DerivedPointerTable::set_active(false);
1805 #endif
1806 
1807     // adjust_roots() updates Universe::_intArrayKlassObj which is
1808     // needed by the compaction for filling holes in the dense prefix.
1809     adjust_roots(vmthread_cm);
1810 
1811     compaction_start.update();
1812     compact();
1813 
1814     // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
1815     // done before resizing.
1816     post_compact();
1817 
1818     // Let the size policy know we're done
1819     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1820 
1821     if (UseAdaptiveSizePolicy) {
1822       log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1823       log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
1824                           old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1825 
1826       // Don't check if the size_policy is ready here.  Let
1827       // the size_policy check that internally.
1828       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1829           AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1830         // Swap the survivor spaces if from_space is empty. The
1831         // resize_young_gen() called below is normally used after
1832         // a successful young GC and swapping of survivor spaces;
1833         // otherwise, it will fail to resize the young gen with
1834         // the current implementation.
1835         if (young_gen->from_space()->is_empty()) {
1836           young_gen->from_space()->clear(SpaceDecorator::Mangle);
1837           young_gen->swap_spaces();
1838         }
1839 
1840         // Calculate optimal free space amounts
1841         assert(young_gen->max_size() >
1842           young_gen->from_space()->capacity_in_bytes() +
1843           young_gen->to_space()->capacity_in_bytes(),
1844           "Sizes of space in young gen are out-of-bounds");
1845 
1846         size_t young_live = young_gen->used_in_bytes();
1847         size_t eden_live = young_gen->eden_space()->used_in_bytes();
1848         size_t old_live = old_gen->used_in_bytes();
1849         size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1850         size_t max_old_gen_size = old_gen->max_gen_size();
1851         size_t max_eden_size = young_gen->max_size() -
1852           young_gen->from_space()->capacity_in_bytes() -
1853           young_gen->to_space()->capacity_in_bytes();
1854 
1855         // Used for diagnostics
1856         size_policy->clear_generation_free_space_flags();
1857 
1858         size_policy->compute_generations_free_space(young_live,
1859                                                     eden_live,
1860                                                     old_live,
1861                                                     cur_eden,
1862                                                     max_old_gen_size,
1863                                                     max_eden_size,
1864                                                     true /* full gc*/);
1865 
1866         size_policy->check_gc_overhead_limit(young_live,
1867                                              eden_live,
1868                                              max_old_gen_size,
1869                                              max_eden_size,
1870                                              true /* full gc*/,
1871                                              gc_cause,
1872                                              heap->soft_ref_policy());
1873 
1874         size_policy->decay_supplemental_growth(true /* full gc*/);
1875 
1876         heap->resize_old_gen(
1877           size_policy->calculated_old_free_size_in_bytes());
1878 
1879         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1880                                size_policy->calculated_survivor_size_in_bytes());
1881       }
1882 
1883       log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1884     }
1885 
1886     if (UsePerfData) {
1887       PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1888       counters->update_counters();
1889       counters->update_old_capacity(old_gen->capacity_in_bytes());
1890       counters->update_young_capacity(young_gen->capacity_in_bytes());
1891     }
1892 
1893     heap->resize_all_tlabs();
1894 
1895     // Resize the metaspace capacity after a collection
1896     MetaspaceGC::compute_new_size();
1897 
1898     if (log_is_enabled(Debug, gc, heap, exit)) {
1899       accumulated_time()->stop();
1900     }
1901 
1902     young_gen->print_used_change(pre_gc_values.young_gen_used());
1903     old_gen->print_used_change(pre_gc_values.old_gen_used());
1904     MetaspaceAux::print_metaspace_change(pre_gc_values.metadata_used());
1905 
1906     // Track memory usage and detect low memory
1907     MemoryService::track_memory_usage();
1908     heap->update_counters();
1909     gc_task_manager()->release_idle_workers();
1910 
1911     heap->post_full_gc_dump(&_gc_timer);
1912   }
1913 
1914 #ifdef ASSERT
1915   for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
1916     ParCompactionManager* const cm =
1917       ParCompactionManager::manager_array(int(i));
1918     assert(cm->marking_stack()->is_empty(),       "should be empty");
1919     assert(cm->region_stack()->is_empty(), "Region stack " SIZE_FORMAT " is not empty", i);
1920   }
1921 #endif // ASSERT
1922 
1923   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1924     HandleMark hm;  // Discard invalid handles created during verification
1925     Universe::verify("After GC");
1926   }
1927 
1928   // Re-verify object start arrays
1929   if (VerifyObjectStartArray &&
1930       VerifyAfterGC) {
1931     old_gen->verify_object_start_array();
1932   }
1933 
1934   if (ZapUnusedHeapArea) {
1935     old_gen->object_space()->check_mangled_unused_area_complete();
1936   }
1937 
1938   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1939 
1940   collection_exit.update();
1941 
1942   heap->print_heap_after_gc();
1943   heap->trace_heap_after_gc(&_gc_tracer);
1944 
1945   log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
1946                          marking_start.ticks(), compaction_start.ticks(),
1947                          collection_exit.ticks());
1948   gc_task_manager()->print_task_time_stamps();
1949 
1950 #ifdef TRACESPINNING
1951   ParallelTaskTerminator::print_termination_counts();
1952 #endif
1953 
1954   AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
1955 
1956   _gc_timer.register_gc_end();
1957 
1958   _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1959   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1960 
1961   return true;
1962 }
1963 
1964 bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
1965                                              PSYoungGen* young_gen,
1966                                              PSOldGen* old_gen) {
1967   MutableSpace* const eden_space = young_gen->eden_space();
1968   assert(!eden_space->is_empty(), "eden must be non-empty");
1969   assert(young_gen->virtual_space()->alignment() ==
1970          old_gen->virtual_space()->alignment(), "alignments do not match");
1971 
1972   if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
1973     return false;
1974   }
1975 
1976   // Both generations must be completely committed.
1977   if (young_gen->virtual_space()->uncommitted_size() != 0) {
1978     return false;
1979   }
1980   if (old_gen->virtual_space()->uncommitted_size() != 0) {
1981     return false;
1982   }
1983 
1984   // Figure out how much to take from eden.  Include the average amount promoted
1985   // in the total; otherwise the next young gen GC will simply bail out to a
1986   // full GC.
1987   const size_t alignment = old_gen->virtual_space()->alignment();
1988   const size_t eden_used = eden_space->used_in_bytes();
1989   const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
1990   const size_t absorb_size = align_up(eden_used + promoted, alignment);
1991   const size_t eden_capacity = eden_space->capacity_in_bytes();
1992 
1993   if (absorb_size >= eden_capacity) {
1994     return false; // Must leave some space in eden.
1995   }
1996 
1997   const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
1998   if (new_young_size < young_gen->min_gen_size()) {
1999     return false; // Respect young gen minimum size.
2000   }
2001 
2002   log_trace(heap, ergo)(" absorbing " SIZE_FORMAT "K:  "
2003                         "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
2004                         "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
2005                         "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
2006                         absorb_size / K,
2007                         eden_capacity / K, (eden_capacity - absorb_size) / K,
2008                         young_gen->from_space()->used_in_bytes() / K,
2009                         young_gen->to_space()->used_in_bytes() / K,
2010                         young_gen->capacity_in_bytes() / K, new_young_size / K);
2011 
2012   // Fill the unused part of the old gen.
2013   MutableSpace* const old_space = old_gen->object_space();
2014   HeapWord* const unused_start = old_space->top();
2015   size_t const unused_words = pointer_delta(old_space->end(), unused_start);
2016 
2017   if (unused_words > 0) {
2018     if (unused_words < CollectedHeap::min_fill_size()) {
2019       return false;  // If the old gen cannot be filled, must give up.
2020     }
2021     CollectedHeap::fill_with_objects(unused_start, unused_words);
2022   }
2023 
2024   // Take the live data from eden and set both top and end in the old gen to
2025   // eden top.  (Need to set end because reset_after_change() mangles the region
2026   // from end to virtual_space->high() in debug builds).
2027   HeapWord* const new_top = eden_space->top();
2028   old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
2029                                         absorb_size);
2030   young_gen->reset_after_change();
2031   old_space->set_top(new_top);
2032   old_space->set_end(new_top);
2033   old_gen->reset_after_change();
2034 
2035   // Update the object start array for the filler object and the data from eden.
2036   ObjectStartArray* const start_array = old_gen->start_array();
2037   for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
2038     start_array->allocate_block(p);
2039   }
2040 
2041   // Could update the promoted average here, but it is not typically updated at
2042   // full GCs and the value to use is unclear.  Something like
2043   //
2044   // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
2045 
2046   size_policy->set_bytes_absorbed_from_eden(absorb_size);
2047   return true;
2048 }
2049 
2050 GCTaskManager* const PSParallelCompact::gc_task_manager() {
2051   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
2052     "shouldn't return NULL");
2053   return ParallelScavengeHeap::gc_task_manager();
2054 }
2055 
2056 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2057                                       bool maximum_heap_compaction,
2058                                       ParallelOldTracer *gc_tracer) {
2059   // Recursively traverse all live objects and mark them
2060   GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
2061 
2062   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2063   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2064   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2065   TaskQueueSetSuper* qset = ParCompactionManager::stack_array();
2066   ParallelTaskTerminator terminator(active_gc_threads, qset);
2067 
2068   ParCompactionManager::MarkAndPushClosure mark_and_push_closure(cm);
2069   ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
2070 
2071   // Need new claim bits before marking starts.
2072   ClassLoaderDataGraph::clear_claimed_marks();
2073 
2074   {
2075     GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
2076 
2077     ParallelScavengeHeap::ParStrongRootsScope psrs;
2078 
2079     GCTaskQueue* q = GCTaskQueue::create();
2080 
2081     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::universe));
2082     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jni_handles));
2083     // We scan the thread roots in parallel
2084     Threads::create_thread_roots_marking_tasks(q);
2085     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::object_synchronizer));
2086     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::management));
2087     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::system_dictionary));
2088     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::class_loader_data));
2089     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jvmti));
2090     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::code_cache));
2091 
2092     if (active_gc_threads > 1) {
2093       for (uint j = 0; j < active_gc_threads; j++) {
2094         q->enqueue(new StealMarkingTask(&terminator));
2095       }
2096     }
2097 
2098     gc_task_manager()->execute_and_wait(q);
2099   }
2100 
2101   // Process reference objects found during marking
2102   {
2103     GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
2104 
2105     ReferenceProcessorStats stats;
2106     ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->num_q());
2107     if (ref_processor()->processing_is_mt()) {
2108       RefProcTaskExecutor task_executor;
2109       stats = ref_processor()->process_discovered_references(
2110         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2111         &task_executor, &pt);
2112     } else {
2113       stats = ref_processor()->process_discovered_references(
2114         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
2115         &pt);
2116     }
2117 
2118     gc_tracer->report_gc_reference_stats(stats);
2119     pt.print_all_references();
2120   }
2121 
2122   // This is the point where the entire marking should have completed.
2123   assert(cm->marking_stacks_empty(), "Marking should have completed");
2124 
2125   {
2126     GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
2127     WeakProcessor::weak_oops_do(is_alive_closure(), &do_nothing_cl);
2128   }
2129 
2130   {
2131     GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
2132 
2133     // Follow system dictionary roots and unload classes.
2134     bool purged_class = SystemDictionary::do_unloading(is_alive_closure(), &_gc_timer);
2135 
2136     // Unload nmethods.
2137     CodeCache::do_unloading(is_alive_closure(), purged_class);
2138 
2139     // Prune dead klasses from subklass/sibling/implementor lists.
2140     Klass::clean_weak_klass_links(is_alive_closure());
2141   }
2142 
2143   {
2144     GCTraceTime(Debug, gc, phases) t("Scrub String Table", &_gc_timer);
2145     // Delete entries for dead interned strings.
2146     StringTable::unlink(is_alive_closure());
2147   }
2148 
2149   {
2150     GCTraceTime(Debug, gc, phases) t("Scrub Symbol Table", &_gc_timer);
2151     // Clean up unreferenced symbols in symbol table.
2152     SymbolTable::unlink();
2153   }
2154 
2155   _gc_tracer.report_object_count_after_gc(is_alive_closure());
2156 }
2157 
2158 void PSParallelCompact::adjust_roots(ParCompactionManager* cm) {
2159   // Adjust the pointers to reflect the new locations
2160   GCTraceTime(Info, gc, phases) tm("Adjust Roots", &_gc_timer);
2161 
2162   // Need new claim bits when tracing through and adjusting pointers.
2163   ClassLoaderDataGraph::clear_claimed_marks();
2164 
2165   PSParallelCompact::AdjustPointerClosure oop_closure(cm);
2166 
2167   // General strong roots.
2168   Universe::oops_do(&oop_closure);
2169   JNIHandles::oops_do(&oop_closure);   // Global (strong) JNI handles
2170   Threads::oops_do(&oop_closure, NULL);
2171   ObjectSynchronizer::oops_do(&oop_closure);
2172   Management::oops_do(&oop_closure);
2173   JvmtiExport::oops_do(&oop_closure);
2174   SystemDictionary::oops_do(&oop_closure);
2175   ClassLoaderDataGraph::oops_do(&oop_closure, true);
2176 
2177   // Now adjust pointers in remaining weak roots.  (All of which should
2178   // have been cleared if they pointed to non-surviving objects.)
2179   WeakProcessor::oops_do(&oop_closure);
2180 
2181   CodeBlobToOopClosure adjust_from_blobs(&oop_closure, CodeBlobToOopClosure::FixRelocations);
2182   CodeCache::blobs_do(&adjust_from_blobs);
2183   AOTLoader::oops_do(&oop_closure);
2184   StringTable::oops_do(&oop_closure);
2185   ref_processor()->weak_oops_do(&oop_closure);
2186   // Roots were visited so references into the young gen in roots
2187   // may have been scanned.  Process them also.
2188   // Should the reference processor have a span that excludes
2189   // young gen objects?
2190   PSScavenge::reference_processor()->weak_oops_do(&oop_closure);
2191 }
2192 
2193 // Helper class to print 8 region numbers per line and then print the total at the end.
2194 class FillableRegionLogger : public StackObj {
2195 private:
2196   Log(gc, compaction) log;
2197   static const int LineLength = 8;
2198   size_t _regions[LineLength];
2199   int _next_index;
2200   bool _enabled;
2201   size_t _total_regions;
2202 public:
2203   FillableRegionLogger() : _next_index(0), _total_regions(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)) { }
2204   ~FillableRegionLogger() {
2205     log.trace(SIZE_FORMAT " initially fillable regions", _total_regions);
2206   }
2207 
2208   void print_line() {
2209     if (!_enabled || _next_index == 0) {
2210       return;
2211     }
2212     FormatBuffer<> line("Fillable: ");
2213     for (int i = 0; i < _next_index; i++) {
2214       line.append(" " SIZE_FORMAT_W(7), _regions[i]);
2215     }
2216     log.trace("%s", line.buffer());
2217     _next_index = 0;
2218   }
2219 
2220   void handle(size_t region) {
2221     if (!_enabled) {
2222       return;
2223     }
2224     _regions[_next_index++] = region;
2225     if (_next_index == LineLength) {
2226       print_line();
2227     }
2228     _total_regions++;
2229   }
2230 };
2231 
2232 void PSParallelCompact::prepare_region_draining_tasks(GCTaskQueue* q,
2233                                                       uint parallel_gc_threads)
2234 {
2235   GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
2236 
2237   // Find the threads that are active
2238   unsigned int which = 0;
2239 
2240   // Find all regions that are available (can be filled immediately) and
2241   // distribute them to the thread stacks.  The iteration is done in reverse
2242   // order (high to low) so the regions will be removed in ascending order.
2243 
2244   const ParallelCompactData& sd = PSParallelCompact::summary_data();
2245 
2246   which = 0;
2247   // id + 1 is used to test termination so unsigned  can
2248   // be used with an old_space_id == 0.
2249   FillableRegionLogger region_logger;
2250   for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2251     SpaceInfo* const space_info = _space_info + id;
2252     MutableSpace* const space = space_info->space();
2253     HeapWord* const new_top = space_info->new_top();
2254 
2255     const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2256     const size_t end_region =
2257       sd.addr_to_region_idx(sd.region_align_up(new_top));
2258 
2259     for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2260       if (sd.region(cur)->claim_unsafe()) {
2261         ParCompactionManager* cm = ParCompactionManager::manager_array(which);
2262         cm->region_stack()->push(cur);
2263         region_logger.handle(cur);
2264         // Assign regions to tasks in round-robin fashion.
2265         if (++which == parallel_gc_threads) {
2266           which = 0;
2267         }
2268       }
2269     }
2270     region_logger.print_line();
2271   }
2272 }
2273 
2274 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2275 
2276 void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q,
2277                                                     uint parallel_gc_threads) {
2278   GCTraceTime(Trace, gc, phases) tm("Dense Prefix Task Setup", &_gc_timer);
2279 
2280   ParallelCompactData& sd = PSParallelCompact::summary_data();
2281 
2282   // Iterate over all the spaces adding tasks for updating
2283   // regions in the dense prefix.  Assume that 1 gc thread
2284   // will work on opening the gaps and the remaining gc threads
2285   // will work on the dense prefix.
2286   unsigned int space_id;
2287   for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2288     HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2289     const MutableSpace* const space = _space_info[space_id].space();
2290 
2291     if (dense_prefix_end == space->bottom()) {
2292       // There is no dense prefix for this space.
2293       continue;
2294     }
2295 
2296     // The dense prefix is before this region.
2297     size_t region_index_end_dense_prefix =
2298         sd.addr_to_region_idx(dense_prefix_end);
2299     RegionData* const dense_prefix_cp =
2300       sd.region(region_index_end_dense_prefix);
2301     assert(dense_prefix_end == space->end() ||
2302            dense_prefix_cp->available() ||
2303            dense_prefix_cp->claimed(),
2304            "The region after the dense prefix should always be ready to fill");
2305 
2306     size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2307 
2308     // Is there dense prefix work?
2309     size_t total_dense_prefix_regions =
2310       region_index_end_dense_prefix - region_index_start;
2311     // How many regions of the dense prefix should be given to
2312     // each thread?
2313     if (total_dense_prefix_regions > 0) {
2314       uint tasks_for_dense_prefix = 1;
2315       if (total_dense_prefix_regions <=
2316           (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2317         // Don't over partition.  This assumes that
2318         // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2319         // so there are not many regions to process.
2320         tasks_for_dense_prefix = parallel_gc_threads;
2321       } else {
2322         // Over partition
2323         tasks_for_dense_prefix = parallel_gc_threads *
2324           PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2325       }
2326       size_t regions_per_thread = total_dense_prefix_regions /
2327         tasks_for_dense_prefix;
2328       // Give each thread at least 1 region.
2329       if (regions_per_thread == 0) {
2330         regions_per_thread = 1;
2331       }
2332 
2333       for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2334         if (region_index_start >= region_index_end_dense_prefix) {
2335           break;
2336         }
2337         // region_index_end is not processed
2338         size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2339                                        region_index_end_dense_prefix);
2340         q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2341                                              region_index_start,
2342                                              region_index_end));
2343         region_index_start = region_index_end;
2344       }
2345     }
2346     // This gets any part of the dense prefix that did not
2347     // fit evenly.
2348     if (region_index_start < region_index_end_dense_prefix) {
2349       q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2350                                            region_index_start,
2351                                            region_index_end_dense_prefix));
2352     }
2353   }
2354 }
2355 
2356 void PSParallelCompact::enqueue_region_stealing_tasks(
2357                                      GCTaskQueue* q,
2358                                      ParallelTaskTerminator* terminator_ptr,
2359                                      uint parallel_gc_threads) {
2360   GCTraceTime(Trace, gc, phases) tm("Steal Task Setup", &_gc_timer);
2361 
2362   // Once a thread has drained it's stack, it should try to steal regions from
2363   // other threads.
2364   for (uint j = 0; j < parallel_gc_threads; j++) {
2365     q->enqueue(new CompactionWithStealingTask(terminator_ptr));
2366   }
2367 }
2368 
2369 #ifdef ASSERT
2370 // Write a histogram of the number of times the block table was filled for a
2371 // region.
2372 void PSParallelCompact::write_block_fill_histogram()
2373 {
2374   if (!log_develop_is_enabled(Trace, gc, compaction)) {
2375     return;
2376   }
2377 
2378   Log(gc, compaction) log;
2379   ResourceMark rm;
2380   LogStream ls(log.trace());
2381   outputStream* out = &ls;
2382 
2383   typedef ParallelCompactData::RegionData rd_t;
2384   ParallelCompactData& sd = summary_data();
2385 
2386   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2387     MutableSpace* const spc = _space_info[id].space();
2388     if (spc->bottom() != spc->top()) {
2389       const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
2390       HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
2391       const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
2392 
2393       size_t histo[5] = { 0, 0, 0, 0, 0 };
2394       const size_t histo_len = sizeof(histo) / sizeof(size_t);
2395       const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
2396 
2397       for (const rd_t* cur = beg; cur < end; ++cur) {
2398         ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
2399       }
2400       out->print("Block fill histogram: %u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
2401       for (size_t i = 0; i < histo_len; ++i) {
2402         out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
2403                    histo[i], 100.0 * histo[i] / region_cnt);
2404       }
2405       out->cr();
2406     }
2407   }
2408 }
2409 #endif // #ifdef ASSERT
2410 
2411 void PSParallelCompact::compact() {
2412   GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
2413 
2414   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2415   PSOldGen* old_gen = heap->old_gen();
2416   old_gen->start_array()->reset();
2417   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2418   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2419   TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2420   ParallelTaskTerminator terminator(active_gc_threads, qset);
2421 
2422   GCTaskQueue* q = GCTaskQueue::create();
2423   prepare_region_draining_tasks(q, active_gc_threads);
2424   enqueue_dense_prefix_tasks(q, active_gc_threads);
2425   enqueue_region_stealing_tasks(q, &terminator, active_gc_threads);
2426 
2427   {
2428     GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
2429 
2430     gc_task_manager()->execute_and_wait(q);
2431 
2432 #ifdef  ASSERT
2433     // Verify that all regions have been processed before the deferred updates.
2434     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2435       verify_complete(SpaceId(id));
2436     }
2437 #endif
2438   }
2439 
2440   {
2441     // Update the deferred objects, if any.  Any compaction manager can be used.
2442     GCTraceTime(Trace, gc, phases) tm("Deferred Updates", &_gc_timer);
2443     ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2444     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2445       update_deferred_objects(cm, SpaceId(id));
2446     }
2447   }
2448 
2449   DEBUG_ONLY(write_block_fill_histogram());
2450 }
2451 
2452 #ifdef  ASSERT
2453 void PSParallelCompact::verify_complete(SpaceId space_id) {
2454   // All Regions between space bottom() to new_top() should be marked as filled
2455   // and all Regions between new_top() and top() should be available (i.e.,
2456   // should have been emptied).
2457   ParallelCompactData& sd = summary_data();
2458   SpaceInfo si = _space_info[space_id];
2459   HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2460   HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2461   const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2462   const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2463   const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2464 
2465   bool issued_a_warning = false;
2466 
2467   size_t cur_region;
2468   for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2469     const RegionData* const c = sd.region(cur_region);
2470     if (!c->completed()) {
2471       log_warning(gc)("region " SIZE_FORMAT " not filled: destination_count=%u",
2472                       cur_region, c->destination_count());
2473       issued_a_warning = true;
2474     }
2475   }
2476 
2477   for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2478     const RegionData* const c = sd.region(cur_region);
2479     if (!c->available()) {
2480       log_warning(gc)("region " SIZE_FORMAT " not empty: destination_count=%u",
2481                       cur_region, c->destination_count());
2482       issued_a_warning = true;
2483     }
2484   }
2485 
2486   if (issued_a_warning) {
2487     print_region_ranges();
2488   }
2489 }
2490 #endif  // #ifdef ASSERT
2491 
2492 inline void UpdateOnlyClosure::do_addr(HeapWord* addr) {
2493   _start_array->allocate_block(addr);
2494   compaction_manager()->update_contents(oop(addr));
2495 }
2496 
2497 // Update interior oops in the ranges of regions [beg_region, end_region).
2498 void
2499 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2500                                                        SpaceId space_id,
2501                                                        size_t beg_region,
2502                                                        size_t end_region) {
2503   ParallelCompactData& sd = summary_data();
2504   ParMarkBitMap* const mbm = mark_bitmap();
2505 
2506   HeapWord* beg_addr = sd.region_to_addr(beg_region);
2507   HeapWord* const end_addr = sd.region_to_addr(end_region);
2508   assert(beg_region <= end_region, "bad region range");
2509   assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2510 
2511 #ifdef  ASSERT
2512   // Claim the regions to avoid triggering an assert when they are marked as
2513   // filled.
2514   for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2515     assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2516   }
2517 #endif  // #ifdef ASSERT
2518 
2519   if (beg_addr != space(space_id)->bottom()) {
2520     // Find the first live object or block of dead space that *starts* in this
2521     // range of regions.  If a partial object crosses onto the region, skip it;
2522     // it will be marked for 'deferred update' when the object head is
2523     // processed.  If dead space crosses onto the region, it is also skipped; it
2524     // will be filled when the prior region is processed.  If neither of those
2525     // apply, the first word in the region is the start of a live object or dead
2526     // space.
2527     assert(beg_addr > space(space_id)->bottom(), "sanity");
2528     const RegionData* const cp = sd.region(beg_region);
2529     if (cp->partial_obj_size() != 0) {
2530       beg_addr = sd.partial_obj_end(beg_region);
2531     } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2532       beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2533     }
2534   }
2535 
2536   if (beg_addr < end_addr) {
2537     // A live object or block of dead space starts in this range of Regions.
2538      HeapWord* const dense_prefix_end = dense_prefix(space_id);
2539 
2540     // Create closures and iterate.
2541     UpdateOnlyClosure update_closure(mbm, cm, space_id);
2542     FillClosure fill_closure(cm, space_id);
2543     ParMarkBitMap::IterationStatus status;
2544     status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2545                           dense_prefix_end);
2546     if (status == ParMarkBitMap::incomplete) {
2547       update_closure.do_addr(update_closure.source());
2548     }
2549   }
2550 
2551   // Mark the regions as filled.
2552   RegionData* const beg_cp = sd.region(beg_region);
2553   RegionData* const end_cp = sd.region(end_region);
2554   for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2555     cp->set_completed();
2556   }
2557 }
2558 
2559 // Return the SpaceId for the space containing addr.  If addr is not in the
2560 // heap, last_space_id is returned.  In debug mode it expects the address to be
2561 // in the heap and asserts such.
2562 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2563   assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
2564 
2565   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2566     if (_space_info[id].space()->contains(addr)) {
2567       return SpaceId(id);
2568     }
2569   }
2570 
2571   assert(false, "no space contains the addr");
2572   return last_space_id;
2573 }
2574 
2575 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2576                                                 SpaceId id) {
2577   assert(id < last_space_id, "bad space id");
2578 
2579   ParallelCompactData& sd = summary_data();
2580   const SpaceInfo* const space_info = _space_info + id;
2581   ObjectStartArray* const start_array = space_info->start_array();
2582 
2583   const MutableSpace* const space = space_info->space();
2584   assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2585   HeapWord* const beg_addr = space_info->dense_prefix();
2586   HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2587 
2588   const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2589   const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2590   const RegionData* cur_region;
2591   for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2592     HeapWord* const addr = cur_region->deferred_obj_addr();
2593     if (addr != NULL) {
2594       if (start_array != NULL) {
2595         start_array->allocate_block(addr);
2596       }
2597       cm->update_contents(oop(addr));
2598       assert(oopDesc::is_oop_or_null(oop(addr)), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(addr)));
2599     }
2600   }
2601 }
2602 
2603 // Skip over count live words starting from beg, and return the address of the
2604 // next live word.  Unless marked, the word corresponding to beg is assumed to
2605 // be dead.  Callers must either ensure beg does not correspond to the middle of
2606 // an object, or account for those live words in some other way.  Callers must
2607 // also ensure that there are enough live words in the range [beg, end) to skip.
2608 HeapWord*
2609 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2610 {
2611   assert(count > 0, "sanity");
2612 
2613   ParMarkBitMap* m = mark_bitmap();
2614   idx_t bits_to_skip = m->words_to_bits(count);
2615   idx_t cur_beg = m->addr_to_bit(beg);
2616   const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end));
2617 
2618   do {
2619     cur_beg = m->find_obj_beg(cur_beg, search_end);
2620     idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2621     const size_t obj_bits = cur_end - cur_beg + 1;
2622     if (obj_bits > bits_to_skip) {
2623       return m->bit_to_addr(cur_beg + bits_to_skip);
2624     }
2625     bits_to_skip -= obj_bits;
2626     cur_beg = cur_end + 1;
2627   } while (bits_to_skip > 0);
2628 
2629   // Skipping the desired number of words landed just past the end of an object.
2630   // Find the start of the next object.
2631   cur_beg = m->find_obj_beg(cur_beg, search_end);
2632   assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2633   return m->bit_to_addr(cur_beg);
2634 }
2635 
2636 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2637                                             SpaceId src_space_id,
2638                                             size_t src_region_idx)
2639 {
2640   assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2641 
2642   const SplitInfo& split_info = _space_info[src_space_id].split_info();
2643   if (split_info.dest_region_addr() == dest_addr) {
2644     // The partial object ending at the split point contains the first word to
2645     // be copied to dest_addr.
2646     return split_info.first_src_addr();
2647   }
2648 
2649   const ParallelCompactData& sd = summary_data();
2650   ParMarkBitMap* const bitmap = mark_bitmap();
2651   const size_t RegionSize = ParallelCompactData::RegionSize;
2652 
2653   assert(sd.is_region_aligned(dest_addr), "not aligned");
2654   const RegionData* const src_region_ptr = sd.region(src_region_idx);
2655   const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2656   HeapWord* const src_region_destination = src_region_ptr->destination();
2657 
2658   assert(dest_addr >= src_region_destination, "wrong src region");
2659   assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2660 
2661   HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2662   HeapWord* const src_region_end = src_region_beg + RegionSize;
2663 
2664   HeapWord* addr = src_region_beg;
2665   if (dest_addr == src_region_destination) {
2666     // Return the first live word in the source region.
2667     if (partial_obj_size == 0) {
2668       addr = bitmap->find_obj_beg(addr, src_region_end);
2669       assert(addr < src_region_end, "no objects start in src region");
2670     }
2671     return addr;
2672   }
2673 
2674   // Must skip some live data.
2675   size_t words_to_skip = dest_addr - src_region_destination;
2676   assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2677 
2678   if (partial_obj_size >= words_to_skip) {
2679     // All the live words to skip are part of the partial object.
2680     addr += words_to_skip;
2681     if (partial_obj_size == words_to_skip) {
2682       // Find the first live word past the partial object.
2683       addr = bitmap->find_obj_beg(addr, src_region_end);
2684       assert(addr < src_region_end, "wrong src region");
2685     }
2686     return addr;
2687   }
2688 
2689   // Skip over the partial object (if any).
2690   if (partial_obj_size != 0) {
2691     words_to_skip -= partial_obj_size;
2692     addr += partial_obj_size;
2693   }
2694 
2695   // Skip over live words due to objects that start in the region.
2696   addr = skip_live_words(addr, src_region_end, words_to_skip);
2697   assert(addr < src_region_end, "wrong src region");
2698   return addr;
2699 }
2700 
2701 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2702                                                      SpaceId src_space_id,
2703                                                      size_t beg_region,
2704                                                      HeapWord* end_addr)
2705 {
2706   ParallelCompactData& sd = summary_data();
2707 
2708 #ifdef ASSERT
2709   MutableSpace* const src_space = _space_info[src_space_id].space();
2710   HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2711   assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2712          "src_space_id does not match beg_addr");
2713   assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2714          "src_space_id does not match end_addr");
2715 #endif // #ifdef ASSERT
2716 
2717   RegionData* const beg = sd.region(beg_region);
2718   RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2719 
2720   // Regions up to new_top() are enqueued if they become available.
2721   HeapWord* const new_top = _space_info[src_space_id].new_top();
2722   RegionData* const enqueue_end =
2723     sd.addr_to_region_ptr(sd.region_align_up(new_top));
2724 
2725   for (RegionData* cur = beg; cur < end; ++cur) {
2726     assert(cur->data_size() > 0, "region must have live data");
2727     cur->decrement_destination_count();
2728     if (cur < enqueue_end && cur->available() && cur->claim()) {
2729       cm->push_region(sd.region(cur));
2730     }
2731   }
2732 }
2733 
2734 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2735                                           SpaceId& src_space_id,
2736                                           HeapWord*& src_space_top,
2737                                           HeapWord* end_addr)
2738 {
2739   typedef ParallelCompactData::RegionData RegionData;
2740 
2741   ParallelCompactData& sd = PSParallelCompact::summary_data();
2742   const size_t region_size = ParallelCompactData::RegionSize;
2743 
2744   size_t src_region_idx = 0;
2745 
2746   // Skip empty regions (if any) up to the top of the space.
2747   HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2748   RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2749   HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2750   const RegionData* const top_region_ptr =
2751     sd.addr_to_region_ptr(top_aligned_up);
2752   while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2753     ++src_region_ptr;
2754   }
2755 
2756   if (src_region_ptr < top_region_ptr) {
2757     // The next source region is in the current space.  Update src_region_idx
2758     // and the source address to match src_region_ptr.
2759     src_region_idx = sd.region(src_region_ptr);
2760     HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
2761     if (src_region_addr > closure.source()) {
2762       closure.set_source(src_region_addr);
2763     }
2764     return src_region_idx;
2765   }
2766 
2767   // Switch to a new source space and find the first non-empty region.
2768   unsigned int space_id = src_space_id + 1;
2769   assert(space_id < last_space_id, "not enough spaces");
2770 
2771   HeapWord* const destination = closure.destination();
2772 
2773   do {
2774     MutableSpace* space = _space_info[space_id].space();
2775     HeapWord* const bottom = space->bottom();
2776     const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
2777 
2778     // Iterate over the spaces that do not compact into themselves.
2779     if (bottom_cp->destination() != bottom) {
2780       HeapWord* const top_aligned_up = sd.region_align_up(space->top());
2781       const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
2782 
2783       for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
2784         if (src_cp->live_obj_size() > 0) {
2785           // Found it.
2786           assert(src_cp->destination() == destination,
2787                  "first live obj in the space must match the destination");
2788           assert(src_cp->partial_obj_size() == 0,
2789                  "a space cannot begin with a partial obj");
2790 
2791           src_space_id = SpaceId(space_id);
2792           src_space_top = space->top();
2793           const size_t src_region_idx = sd.region(src_cp);
2794           closure.set_source(sd.region_to_addr(src_region_idx));
2795           return src_region_idx;
2796         } else {
2797           assert(src_cp->data_size() == 0, "sanity");
2798         }
2799       }
2800     }
2801   } while (++space_id < last_space_id);
2802 
2803   assert(false, "no source region was found");
2804   return 0;
2805 }
2806 
2807 void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx)
2808 {
2809   typedef ParMarkBitMap::IterationStatus IterationStatus;
2810   const size_t RegionSize = ParallelCompactData::RegionSize;
2811   ParMarkBitMap* const bitmap = mark_bitmap();
2812   ParallelCompactData& sd = summary_data();
2813   RegionData* const region_ptr = sd.region(region_idx);
2814 
2815   // Get the items needed to construct the closure.
2816   HeapWord* dest_addr = sd.region_to_addr(region_idx);
2817   SpaceId dest_space_id = space_id(dest_addr);
2818   ObjectStartArray* start_array = _space_info[dest_space_id].start_array();
2819   HeapWord* new_top = _space_info[dest_space_id].new_top();
2820   assert(dest_addr < new_top, "sanity");
2821   const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize);
2822 
2823   // Get the source region and related info.
2824   size_t src_region_idx = region_ptr->source_region();
2825   SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2826   HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2827 
2828   MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
2829   closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2830 
2831   // Adjust src_region_idx to prepare for decrementing destination counts (the
2832   // destination count is not decremented when a region is copied to itself).
2833   if (src_region_idx == region_idx) {
2834     src_region_idx += 1;
2835   }
2836 
2837   if (bitmap->is_unmarked(closure.source())) {
2838     // The first source word is in the middle of an object; copy the remainder
2839     // of the object or as much as will fit.  The fact that pointer updates were
2840     // deferred will be noted when the object header is processed.
2841     HeapWord* const old_src_addr = closure.source();
2842     closure.copy_partial_obj();
2843     if (closure.is_full()) {
2844       decrement_destination_counts(cm, src_space_id, src_region_idx,
2845                                    closure.source());
2846       region_ptr->set_deferred_obj_addr(NULL);
2847       region_ptr->set_completed();
2848       return;
2849     }
2850 
2851     HeapWord* const end_addr = sd.region_align_down(closure.source());
2852     if (sd.region_align_down(old_src_addr) != end_addr) {
2853       // The partial object was copied from more than one source region.
2854       decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2855 
2856       // Move to the next source region, possibly switching spaces as well.  All
2857       // args except end_addr may be modified.
2858       src_region_idx = next_src_region(closure, src_space_id, src_space_top,
2859                                        end_addr);
2860     }
2861   }
2862 
2863   do {
2864     HeapWord* const cur_addr = closure.source();
2865     HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
2866                                     src_space_top);
2867     IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
2868 
2869     if (status == ParMarkBitMap::incomplete) {
2870       // The last obj that starts in the source region does not end in the
2871       // region.
2872       assert(closure.source() < end_addr, "sanity");
2873       HeapWord* const obj_beg = closure.source();
2874       HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
2875                                        src_space_top);
2876       HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
2877       if (obj_end < range_end) {
2878         // The end was found; the entire object will fit.
2879         status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
2880         assert(status != ParMarkBitMap::would_overflow, "sanity");
2881       } else {
2882         // The end was not found; the object will not fit.
2883         assert(range_end < src_space_top, "obj cannot cross space boundary");
2884         status = ParMarkBitMap::would_overflow;
2885       }
2886     }
2887 
2888     if (status == ParMarkBitMap::would_overflow) {
2889       // The last object did not fit.  Note that interior oop updates were
2890       // deferred, then copy enough of the object to fill the region.
2891       region_ptr->set_deferred_obj_addr(closure.destination());
2892       status = closure.copy_until_full(); // copies from closure.source()
2893 
2894       decrement_destination_counts(cm, src_space_id, src_region_idx,
2895                                    closure.source());
2896       region_ptr->set_completed();
2897       return;
2898     }
2899 
2900     if (status == ParMarkBitMap::full) {
2901       decrement_destination_counts(cm, src_space_id, src_region_idx,
2902                                    closure.source());
2903       region_ptr->set_deferred_obj_addr(NULL);
2904       region_ptr->set_completed();
2905       return;
2906     }
2907 
2908     decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2909 
2910     // Move to the next source region, possibly switching spaces as well.  All
2911     // args except end_addr may be modified.
2912     src_region_idx = next_src_region(closure, src_space_id, src_space_top,
2913                                      end_addr);
2914   } while (true);
2915 }
2916 
2917 void PSParallelCompact::fill_blocks(size_t region_idx)
2918 {
2919   // Fill in the block table elements for the specified region.  Each block
2920   // table element holds the number of live words in the region that are to the
2921   // left of the first object that starts in the block.  Thus only blocks in
2922   // which an object starts need to be filled.
2923   //
2924   // The algorithm scans the section of the bitmap that corresponds to the
2925   // region, keeping a running total of the live words.  When an object start is
2926   // found, if it's the first to start in the block that contains it, the
2927   // current total is written to the block table element.
2928   const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
2929   const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
2930   const size_t RegionSize = ParallelCompactData::RegionSize;
2931 
2932   ParallelCompactData& sd = summary_data();
2933   const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
2934   if (partial_obj_size >= RegionSize) {
2935     return; // No objects start in this region.
2936   }
2937 
2938   // Ensure the first loop iteration decides that the block has changed.
2939   size_t cur_block = sd.block_count();
2940 
2941   const ParMarkBitMap* const bitmap = mark_bitmap();
2942 
2943   const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
2944   assert((size_t)1 << Log2BitsPerBlock ==
2945          bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
2946 
2947   size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
2948   const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
2949   size_t live_bits = bitmap->words_to_bits(partial_obj_size);
2950   beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
2951   while (beg_bit < range_end) {
2952     const size_t new_block = beg_bit >> Log2BitsPerBlock;
2953     if (new_block != cur_block) {
2954       cur_block = new_block;
2955       sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
2956     }
2957 
2958     const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
2959     if (end_bit < range_end - 1) {
2960       live_bits += end_bit - beg_bit + 1;
2961       beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
2962     } else {
2963       return;
2964     }
2965   }
2966 }
2967 
2968 void
2969 PSParallelCompact::move_and_update(ParCompactionManager* cm, SpaceId space_id) {
2970   const MutableSpace* sp = space(space_id);
2971   if (sp->is_empty()) {
2972     return;
2973   }
2974 
2975   ParallelCompactData& sd = PSParallelCompact::summary_data();
2976   ParMarkBitMap* const bitmap = mark_bitmap();
2977   HeapWord* const dp_addr = dense_prefix(space_id);
2978   HeapWord* beg_addr = sp->bottom();
2979   HeapWord* end_addr = sp->top();
2980 
2981   assert(beg_addr <= dp_addr && dp_addr <= end_addr, "bad dense prefix");
2982 
2983   const size_t beg_region = sd.addr_to_region_idx(beg_addr);
2984   const size_t dp_region = sd.addr_to_region_idx(dp_addr);
2985   if (beg_region < dp_region) {
2986     update_and_deadwood_in_dense_prefix(cm, space_id, beg_region, dp_region);
2987   }
2988 
2989   // The destination of the first live object that starts in the region is one
2990   // past the end of the partial object entering the region (if any).
2991   HeapWord* const dest_addr = sd.partial_obj_end(dp_region);
2992   HeapWord* const new_top = _space_info[space_id].new_top();
2993   assert(new_top >= dest_addr, "bad new_top value");
2994   const size_t words = pointer_delta(new_top, dest_addr);
2995 
2996   if (words > 0) {
2997     ObjectStartArray* start_array = _space_info[space_id].start_array();
2998     MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
2999 
3000     ParMarkBitMap::IterationStatus status;
3001     status = bitmap->iterate(&closure, dest_addr, end_addr);
3002     assert(status == ParMarkBitMap::full, "iteration not complete");
3003     assert(bitmap->find_obj_beg(closure.source(), end_addr) == end_addr,
3004            "live objects skipped because closure is full");
3005   }
3006 }
3007 
3008 jlong PSParallelCompact::millis_since_last_gc() {
3009   // We need a monotonically non-decreasing time in ms but
3010   // os::javaTimeMillis() does not guarantee monotonicity.
3011   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3012   jlong ret_val = now - _time_of_last_gc;
3013   // XXX See note in genCollectedHeap::millis_since_last_gc().
3014   if (ret_val < 0) {
3015     NOT_PRODUCT(log_warning(gc)("time warp: " JLONG_FORMAT, ret_val);)
3016     return 0;
3017   }
3018   return ret_val;
3019 }
3020 
3021 void PSParallelCompact::reset_millis_since_last_gc() {
3022   // We need a monotonically non-decreasing time in ms but
3023   // os::javaTimeMillis() does not guarantee monotonicity.
3024   _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3025 }
3026 
3027 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3028 {
3029   if (source() != destination()) {
3030     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3031     Copy::aligned_conjoint_words(source(), destination(), words_remaining());
3032   }
3033   update_state(words_remaining());
3034   assert(is_full(), "sanity");
3035   return ParMarkBitMap::full;
3036 }
3037 
3038 void MoveAndUpdateClosure::copy_partial_obj()
3039 {
3040   size_t words = words_remaining();
3041 
3042   HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3043   HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3044   if (end_addr < range_end) {
3045     words = bitmap()->obj_size(source(), end_addr);
3046   }
3047 
3048   // This test is necessary; if omitted, the pointer updates to a partial object
3049   // that crosses the dense prefix boundary could be overwritten.
3050   if (source() != destination()) {
3051     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3052     Copy::aligned_conjoint_words(source(), destination(), words);
3053   }
3054   update_state(words);
3055 }
3056 
3057 void InstanceKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
3058   PSParallelCompact::AdjustPointerClosure closure(cm);
3059   oop_oop_iterate_oop_maps<true>(obj, &closure);
3060 }
3061 
3062 void InstanceMirrorKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
3063   InstanceKlass::oop_pc_update_pointers(obj, cm);
3064 
3065   PSParallelCompact::AdjustPointerClosure closure(cm);
3066   oop_oop_iterate_statics<true>(obj, &closure);
3067 }
3068 
3069 void InstanceClassLoaderKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
3070   InstanceKlass::oop_pc_update_pointers(obj, cm);
3071 }
3072 
3073 #ifdef ASSERT
3074 template <class T> static void trace_reference_gc(const char *s, oop obj,
3075                                                   T* referent_addr,
3076                                                   T* next_addr,
3077                                                   T* discovered_addr) {
3078   log_develop_trace(gc, ref)("%s obj " PTR_FORMAT, s, p2i(obj));
3079   log_develop_trace(gc, ref)("     referent_addr/* " PTR_FORMAT " / " PTR_FORMAT,
3080                              p2i(referent_addr), referent_addr ? p2i(oopDesc::load_decode_heap_oop(referent_addr)) : NULL);
3081   log_develop_trace(gc, ref)("     next_addr/* " PTR_FORMAT " / " PTR_FORMAT,
3082                              p2i(next_addr), next_addr ? p2i(oopDesc::load_decode_heap_oop(next_addr)) : NULL);
3083   log_develop_trace(gc, ref)("     discovered_addr/* " PTR_FORMAT " / " PTR_FORMAT,
3084                              p2i(discovered_addr), discovered_addr ? p2i(oopDesc::load_decode_heap_oop(discovered_addr)) : NULL);
3085 }
3086 #endif
3087 
3088 template <class T>
3089 static void oop_pc_update_pointers_specialized(oop obj, ParCompactionManager* cm) {
3090   T* referent_addr = (T*)java_lang_ref_Reference::referent_addr(obj);
3091   PSParallelCompact::adjust_pointer(referent_addr, cm);
3092   T* next_addr = (T*)java_lang_ref_Reference::next_addr(obj);
3093   PSParallelCompact::adjust_pointer(next_addr, cm);
3094   T* discovered_addr = (T*)java_lang_ref_Reference::discovered_addr(obj);
3095   PSParallelCompact::adjust_pointer(discovered_addr, cm);
3096   debug_only(trace_reference_gc("InstanceRefKlass::oop_update_ptrs", obj,
3097                                 referent_addr, next_addr, discovered_addr);)
3098 }
3099 
3100 void InstanceRefKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
3101   InstanceKlass::oop_pc_update_pointers(obj, cm);
3102 
3103   if (UseCompressedOops) {
3104     oop_pc_update_pointers_specialized<narrowOop>(obj, cm);
3105   } else {
3106     oop_pc_update_pointers_specialized<oop>(obj, cm);
3107   }
3108 }
3109 
3110 void ObjArrayKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
3111   assert(obj->is_objArray(), "obj must be obj array");
3112   PSParallelCompact::AdjustPointerClosure closure(cm);
3113   oop_oop_iterate_elements<true>(objArrayOop(obj), &closure);
3114 }
3115 
3116 void TypeArrayKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
3117   assert(obj->is_typeArray(),"must be a type array");
3118 }
3119 
3120 ParMarkBitMapClosure::IterationStatus
3121 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3122   assert(destination() != NULL, "sanity");
3123   assert(bitmap()->obj_size(addr) == words, "bad size");
3124 
3125   _source = addr;
3126   assert(PSParallelCompact::summary_data().calc_new_pointer(source(), compaction_manager()) ==
3127          destination(), "wrong destination");
3128 
3129   if (words > words_remaining()) {
3130     return ParMarkBitMap::would_overflow;
3131   }
3132 
3133   // The start_array must be updated even if the object is not moving.
3134   if (_start_array != NULL) {
3135     _start_array->allocate_block(destination());
3136   }
3137 
3138   if (destination() != source()) {
3139     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3140     Copy::aligned_conjoint_words(source(), destination(), words);
3141   }
3142 
3143   oop moved_oop = (oop) destination();
3144   compaction_manager()->update_contents(moved_oop);
3145   assert(oopDesc::is_oop_or_null(moved_oop), "Expected an oop or NULL at " PTR_FORMAT, p2i(moved_oop));
3146 
3147   update_state(words);
3148   assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
3149   return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3150 }
3151 
3152 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3153                                      ParCompactionManager* cm,
3154                                      PSParallelCompact::SpaceId space_id) :
3155   ParMarkBitMapClosure(mbm, cm),
3156   _space_id(space_id),
3157   _start_array(PSParallelCompact::start_array(space_id))
3158 {
3159 }
3160 
3161 // Updates the references in the object to their new values.
3162 ParMarkBitMapClosure::IterationStatus
3163 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3164   do_addr(addr);
3165   return ParMarkBitMap::incomplete;
3166 }
3167 
3168 FillClosure::FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id) :
3169   ParMarkBitMapClosure(PSParallelCompact::mark_bitmap(), cm),
3170   _start_array(PSParallelCompact::start_array(space_id))
3171 {
3172   assert(space_id == PSParallelCompact::old_space_id,
3173          "cannot use FillClosure in the young gen");
3174 }
3175 
3176 ParMarkBitMapClosure::IterationStatus
3177 FillClosure::do_addr(HeapWord* addr, size_t size) {
3178   CollectedHeap::fill_with_objects(addr, size);
3179   HeapWord* const end = addr + size;
3180   do {
3181     _start_array->allocate_block(addr);
3182     addr += oop(addr)->size();
3183   } while (addr < end);
3184   return ParMarkBitMap::incomplete;
3185 }