1 /*
   2  * Copyright (c) 2005, 2018, 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/psOldGen.hpp"
  38 #include "gc/parallel/psParallelCompact.inline.hpp"
  39 #include "gc/parallel/psPromotionManager.inline.hpp"
  40 #include "gc/parallel/psScavenge.hpp"
  41 #include "gc/parallel/psYoungGen.hpp"
  42 #include "gc/shared/gcCause.hpp"
  43 #include "gc/shared/gcHeapSummary.hpp"
  44 #include "gc/shared/gcId.hpp"
  45 #include "gc/shared/gcLocker.hpp"
  46 #include "gc/shared/gcTimer.hpp"
  47 #include "gc/shared/gcTrace.hpp"
  48 #include "gc/shared/gcTraceTime.inline.hpp"
  49 #include "gc/shared/isGCActiveMark.hpp"
  50 #include "gc/shared/referencePolicy.hpp"
  51 #include "gc/shared/referenceProcessor.hpp"
  52 #include "gc/shared/spaceDecorator.hpp"
  53 #include "gc/shared/weakProcessor.hpp"
  54 #include "logging/log.hpp"
  55 #include "memory/resourceArea.hpp"
  56 #include "oops/access.inline.hpp"
  57 #include "oops/instanceKlass.inline.hpp"
  58 #include "oops/instanceMirrorKlass.inline.hpp"
  59 #include "oops/methodData.hpp"
  60 #include "oops/objArrayKlass.inline.hpp"
  61 #include "oops/oop.inline.hpp"
  62 #include "runtime/atomic.hpp"
  63 #include "runtime/handles.inline.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/macros.hpp"
  74 #include "utilities/stack.inline.hpp"
  75 
  76 #include <math.h>
  77 
  78 // All sizes are in HeapWords.
  79 const size_t ParallelCompactData::Log2RegionSize  = 16; // 64K words
  80 const size_t ParallelCompactData::RegionSize      = (size_t)1 << Log2RegionSize;
  81 const size_t ParallelCompactData::RegionSizeBytes =
  82   RegionSize << LogHeapWordSize;
  83 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
  84 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
  85 const size_t ParallelCompactData::RegionAddrMask       = ~RegionAddrOffsetMask;
  86 
  87 const size_t ParallelCompactData::Log2BlockSize   = 7; // 128 words
  88 const size_t ParallelCompactData::BlockSize       = (size_t)1 << Log2BlockSize;
  89 const size_t ParallelCompactData::BlockSizeBytes  =
  90   BlockSize << LogHeapWordSize;
  91 const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
  92 const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
  93 const size_t ParallelCompactData::BlockAddrMask       = ~BlockAddrOffsetMask;
  94 
  95 const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
  96 const size_t ParallelCompactData::Log2BlocksPerRegion =
  97   Log2RegionSize - Log2BlockSize;
  98 
  99 const ParallelCompactData::RegionData::region_sz_t
 100 ParallelCompactData::RegionData::dc_shift = 27;
 101 
 102 const ParallelCompactData::RegionData::region_sz_t
 103 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
 104 
 105 const ParallelCompactData::RegionData::region_sz_t
 106 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
 107 
 108 const ParallelCompactData::RegionData::region_sz_t
 109 ParallelCompactData::RegionData::los_mask = ~dc_mask;
 110 
 111 const ParallelCompactData::RegionData::region_sz_t
 112 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
 113 
 114 const ParallelCompactData::RegionData::region_sz_t
 115 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
 116 
 117 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
 118 
 119 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
 120 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
 121 
 122 double PSParallelCompact::_dwl_mean;
 123 double PSParallelCompact::_dwl_std_dev;
 124 double PSParallelCompact::_dwl_first_term;
 125 double PSParallelCompact::_dwl_adjustment;
 126 #ifdef  ASSERT
 127 bool   PSParallelCompact::_dwl_initialized = false;
 128 #endif  // #ifdef ASSERT
 129 
 130 void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
 131                        HeapWord* destination)
 132 {
 133   assert(src_region_idx != 0, "invalid src_region_idx");
 134   assert(partial_obj_size != 0, "invalid partial_obj_size argument");
 135   assert(destination != NULL, "invalid destination argument");
 136 
 137   _src_region_idx = src_region_idx;
 138   _partial_obj_size = partial_obj_size;
 139   _destination = destination;
 140 
 141   // These fields may not be updated below, so make sure they're clear.
 142   assert(_dest_region_addr == NULL, "should have been cleared");
 143   assert(_first_src_addr == NULL, "should have been cleared");
 144 
 145   // Determine the number of destination regions for the partial object.
 146   HeapWord* const last_word = destination + partial_obj_size - 1;
 147   const ParallelCompactData& sd = PSParallelCompact::summary_data();
 148   HeapWord* const beg_region_addr = sd.region_align_down(destination);
 149   HeapWord* const end_region_addr = sd.region_align_down(last_word);
 150 
 151   if (beg_region_addr == end_region_addr) {
 152     // One destination region.
 153     _destination_count = 1;
 154     if (end_region_addr == destination) {
 155       // The destination falls on a region boundary, thus the first word of the
 156       // partial object will be the first word copied to the destination region.
 157       _dest_region_addr = end_region_addr;
 158       _first_src_addr = sd.region_to_addr(src_region_idx);
 159     }
 160   } else {
 161     // Two destination regions.  When copied, the partial object will cross a
 162     // destination region boundary, so a word somewhere within the partial
 163     // object will be the first word copied to the second destination region.
 164     _destination_count = 2;
 165     _dest_region_addr = end_region_addr;
 166     const size_t ofs = pointer_delta(end_region_addr, destination);
 167     assert(ofs < _partial_obj_size, "sanity");
 168     _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
 169   }
 170 }
 171 
 172 void SplitInfo::clear()
 173 {
 174   _src_region_idx = 0;
 175   _partial_obj_size = 0;
 176   _destination = NULL;
 177   _destination_count = 0;
 178   _dest_region_addr = NULL;
 179   _first_src_addr = NULL;
 180   assert(!is_valid(), "sanity");
 181 }
 182 
 183 #ifdef  ASSERT
 184 void SplitInfo::verify_clear()
 185 {
 186   assert(_src_region_idx == 0, "not clear");
 187   assert(_partial_obj_size == 0, "not clear");
 188   assert(_destination == NULL, "not clear");
 189   assert(_destination_count == 0, "not clear");
 190   assert(_dest_region_addr == NULL, "not clear");
 191   assert(_first_src_addr == NULL, "not clear");
 192 }
 193 #endif  // #ifdef ASSERT
 194 
 195 
 196 void PSParallelCompact::print_on_error(outputStream* st) {
 197   _mark_bitmap.print_on_error(st);
 198 }
 199 
 200 #ifndef PRODUCT
 201 const char* PSParallelCompact::space_names[] = {
 202   "old ", "eden", "from", "to  "
 203 };
 204 
 205 void PSParallelCompact::print_region_ranges() {
 206   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 207     return;
 208   }
 209   Log(gc, compaction) log;
 210   ResourceMark rm;
 211   LogStream ls(log.trace());
 212   Universe::print_on(&ls);
 213   log.trace("space  bottom     top        end        new_top");
 214   log.trace("------ ---------- ---------- ---------- ----------");
 215 
 216   for (unsigned int id = 0; id < last_space_id; ++id) {
 217     const MutableSpace* space = _space_info[id].space();
 218     log.trace("%u %s "
 219               SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
 220               SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
 221               id, space_names[id],
 222               summary_data().addr_to_region_idx(space->bottom()),
 223               summary_data().addr_to_region_idx(space->top()),
 224               summary_data().addr_to_region_idx(space->end()),
 225               summary_data().addr_to_region_idx(_space_info[id].new_top()));
 226   }
 227 }
 228 
 229 void
 230 print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
 231 {
 232 #define REGION_IDX_FORMAT        SIZE_FORMAT_W(7)
 233 #define REGION_DATA_FORMAT       SIZE_FORMAT_W(5)
 234 
 235   ParallelCompactData& sd = PSParallelCompact::summary_data();
 236   size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
 237   log_develop_trace(gc, compaction)(
 238       REGION_IDX_FORMAT " " PTR_FORMAT " "
 239       REGION_IDX_FORMAT " " PTR_FORMAT " "
 240       REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
 241       REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
 242       i, p2i(c->data_location()), dci, p2i(c->destination()),
 243       c->partial_obj_size(), c->live_obj_size(),
 244       c->data_size(), c->source_region(), c->destination_count());
 245 
 246 #undef  REGION_IDX_FORMAT
 247 #undef  REGION_DATA_FORMAT
 248 }
 249 
 250 void
 251 print_generic_summary_data(ParallelCompactData& summary_data,
 252                            HeapWord* const beg_addr,
 253                            HeapWord* const end_addr)
 254 {
 255   size_t total_words = 0;
 256   size_t i = summary_data.addr_to_region_idx(beg_addr);
 257   const size_t last = summary_data.addr_to_region_idx(end_addr);
 258   HeapWord* pdest = 0;
 259 
 260   while (i < last) {
 261     ParallelCompactData::RegionData* c = summary_data.region(i);
 262     if (c->data_size() != 0 || c->destination() != pdest) {
 263       print_generic_summary_region(i, c);
 264       total_words += c->data_size();
 265       pdest = c->destination();
 266     }
 267     ++i;
 268   }
 269 
 270   log_develop_trace(gc, compaction)("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
 271 }
 272 
 273 void
 274 PSParallelCompact::print_generic_summary_data(ParallelCompactData& summary_data,
 275                                               HeapWord* const beg_addr,
 276                                               HeapWord* const end_addr) {
 277   ::print_generic_summary_data(summary_data,beg_addr, end_addr);
 278 }
 279 
 280 void
 281 print_generic_summary_data(ParallelCompactData& summary_data,
 282                            SpaceInfo* space_info)
 283 {
 284   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 285     return;
 286   }
 287 
 288   for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
 289     const MutableSpace* space = space_info[id].space();
 290     print_generic_summary_data(summary_data, space->bottom(),
 291                                MAX2(space->top(), space_info[id].new_top()));
 292   }
 293 }
 294 
 295 void
 296 print_initial_summary_data(ParallelCompactData& summary_data,
 297                            const MutableSpace* space) {
 298   if (space->top() == space->bottom()) {
 299     return;
 300   }
 301 
 302   const size_t region_size = ParallelCompactData::RegionSize;
 303   typedef ParallelCompactData::RegionData RegionData;
 304   HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
 305   const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
 306   const RegionData* c = summary_data.region(end_region - 1);
 307   HeapWord* end_addr = c->destination() + c->data_size();
 308   const size_t live_in_space = pointer_delta(end_addr, space->bottom());
 309 
 310   // Print (and count) the full regions at the beginning of the space.
 311   size_t full_region_count = 0;
 312   size_t i = summary_data.addr_to_region_idx(space->bottom());
 313   while (i < end_region && summary_data.region(i)->data_size() == region_size) {
 314     ParallelCompactData::RegionData* c = summary_data.region(i);
 315     log_develop_trace(gc, compaction)(
 316         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 317         i, p2i(c->destination()),
 318         c->partial_obj_size(), c->live_obj_size(),
 319         c->data_size(), c->source_region(), c->destination_count());
 320     ++full_region_count;
 321     ++i;
 322   }
 323 
 324   size_t live_to_right = live_in_space - full_region_count * region_size;
 325 
 326   double max_reclaimed_ratio = 0.0;
 327   size_t max_reclaimed_ratio_region = 0;
 328   size_t max_dead_to_right = 0;
 329   size_t max_live_to_right = 0;
 330 
 331   // Print the 'reclaimed ratio' for regions while there is something live in
 332   // the region or to the right of it.  The remaining regions are empty (and
 333   // uninteresting), and computing the ratio will result in division by 0.
 334   while (i < end_region && live_to_right > 0) {
 335     c = summary_data.region(i);
 336     HeapWord* const region_addr = summary_data.region_to_addr(i);
 337     const size_t used_to_right = pointer_delta(space->top(), region_addr);
 338     const size_t dead_to_right = used_to_right - live_to_right;
 339     const double reclaimed_ratio = double(dead_to_right) / live_to_right;
 340 
 341     if (reclaimed_ratio > max_reclaimed_ratio) {
 342             max_reclaimed_ratio = reclaimed_ratio;
 343             max_reclaimed_ratio_region = i;
 344             max_dead_to_right = dead_to_right;
 345             max_live_to_right = live_to_right;
 346     }
 347 
 348     ParallelCompactData::RegionData* c = summary_data.region(i);
 349     log_develop_trace(gc, compaction)(
 350         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d"
 351         "%12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
 352         i, p2i(c->destination()),
 353         c->partial_obj_size(), c->live_obj_size(),
 354         c->data_size(), c->source_region(), c->destination_count(),
 355         reclaimed_ratio, dead_to_right, live_to_right);
 356 
 357 
 358     live_to_right -= c->data_size();
 359     ++i;
 360   }
 361 
 362   // Any remaining regions are empty.  Print one more if there is one.
 363   if (i < end_region) {
 364     ParallelCompactData::RegionData* c = summary_data.region(i);
 365     log_develop_trace(gc, compaction)(
 366         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 367          i, p2i(c->destination()),
 368          c->partial_obj_size(), c->live_obj_size(),
 369          c->data_size(), c->source_region(), c->destination_count());
 370   }
 371 
 372   log_develop_trace(gc, compaction)("max:  " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
 373                                     max_reclaimed_ratio_region, max_dead_to_right, max_live_to_right, max_reclaimed_ratio);
 374 }
 375 
 376 void
 377 print_initial_summary_data(ParallelCompactData& summary_data,
 378                            SpaceInfo* space_info) {
 379   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 380     return;
 381   }
 382 
 383   unsigned int id = PSParallelCompact::old_space_id;
 384   const MutableSpace* space;
 385   do {
 386     space = space_info[id].space();
 387     print_initial_summary_data(summary_data, space);
 388   } while (++id < PSParallelCompact::eden_space_id);
 389 
 390   do {
 391     space = space_info[id].space();
 392     print_generic_summary_data(summary_data, space->bottom(), space->top());
 393   } while (++id < PSParallelCompact::last_space_id);
 394 }
 395 #endif  // #ifndef PRODUCT
 396 
 397 #ifdef  ASSERT
 398 size_t add_obj_count;
 399 size_t add_obj_size;
 400 size_t mark_bitmap_count;
 401 size_t mark_bitmap_size;
 402 #endif  // #ifdef ASSERT
 403 
 404 ParallelCompactData::ParallelCompactData()
 405 {
 406   _region_start = 0;
 407 
 408   _region_vspace = 0;
 409   _reserved_byte_size = 0;
 410   _region_data = 0;
 411   _region_count = 0;
 412 
 413   _block_vspace = 0;
 414   _block_data = 0;
 415   _block_count = 0;
 416 }
 417 
 418 bool ParallelCompactData::initialize(MemRegion covered_region)
 419 {
 420   _region_start = covered_region.start();
 421   const size_t region_size = covered_region.word_size();
 422   DEBUG_ONLY(_region_end = _region_start + region_size;)
 423 
 424   assert(region_align_down(_region_start) == _region_start,
 425          "region start not aligned");
 426   assert((region_size & RegionSizeOffsetMask) == 0,
 427          "region size not a multiple of RegionSize");
 428 
 429   bool result = initialize_region_data(region_size) && initialize_block_data();
 430   return result;
 431 }
 432 
 433 PSVirtualSpace*
 434 ParallelCompactData::create_vspace(size_t count, size_t element_size)
 435 {
 436   const size_t raw_bytes = count * element_size;
 437   const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
 438   const size_t granularity = os::vm_allocation_granularity();
 439   _reserved_byte_size = align_up(raw_bytes, MAX2(page_sz, granularity));
 440 
 441   const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
 442     MAX2(page_sz, granularity);
 443   ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0);
 444   os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, page_sz, rs.base(),
 445                        rs.size());
 446 
 447   MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
 448 
 449   PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
 450   if (vspace != 0) {
 451     if (vspace->expand_by(_reserved_byte_size)) {
 452       return vspace;
 453     }
 454     delete vspace;
 455     // Release memory reserved in the space.
 456     rs.release();
 457   }
 458 
 459   return 0;
 460 }
 461 
 462 bool ParallelCompactData::initialize_region_data(size_t region_size)
 463 {
 464   const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
 465   _region_vspace = create_vspace(count, sizeof(RegionData));
 466   if (_region_vspace != 0) {
 467     _region_data = (RegionData*)_region_vspace->reserved_low_addr();
 468     _region_count = count;
 469     return true;
 470   }
 471   return false;
 472 }
 473 
 474 bool ParallelCompactData::initialize_block_data()
 475 {
 476   assert(_region_count != 0, "region data must be initialized first");
 477   const size_t count = _region_count << Log2BlocksPerRegion;
 478   _block_vspace = create_vspace(count, sizeof(BlockData));
 479   if (_block_vspace != 0) {
 480     _block_data = (BlockData*)_block_vspace->reserved_low_addr();
 481     _block_count = count;
 482     return true;
 483   }
 484   return false;
 485 }
 486 
 487 void ParallelCompactData::clear()
 488 {
 489   memset(_region_data, 0, _region_vspace->committed_size());
 490   memset(_block_data, 0, _block_vspace->committed_size());
 491 }
 492 
 493 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
 494   assert(beg_region <= _region_count, "beg_region out of range");
 495   assert(end_region <= _region_count, "end_region out of range");
 496   assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize");
 497 
 498   const size_t region_cnt = end_region - beg_region;
 499   memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
 500 
 501   const size_t beg_block = beg_region * BlocksPerRegion;
 502   const size_t block_cnt = region_cnt * BlocksPerRegion;
 503   memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData));
 504 }
 505 
 506 HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
 507 {
 508   const RegionData* cur_cp = region(region_idx);
 509   const RegionData* const end_cp = region(region_count() - 1);
 510 
 511   HeapWord* result = region_to_addr(region_idx);
 512   if (cur_cp < end_cp) {
 513     do {
 514       result += cur_cp->partial_obj_size();
 515     } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
 516   }
 517   return result;
 518 }
 519 
 520 void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
 521 {
 522   const size_t obj_ofs = pointer_delta(addr, _region_start);
 523   const size_t beg_region = obj_ofs >> Log2RegionSize;
 524   const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
 525 
 526   DEBUG_ONLY(Atomic::inc(&add_obj_count);)
 527   DEBUG_ONLY(Atomic::add(len, &add_obj_size);)
 528 
 529   if (beg_region == end_region) {
 530     // All in one region.
 531     _region_data[beg_region].add_live_obj(len);
 532     return;
 533   }
 534 
 535   // First region.
 536   const size_t beg_ofs = region_offset(addr);
 537   _region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
 538 
 539   Klass* klass = ((oop)addr)->klass();
 540   // Middle regions--completely spanned by this object.
 541   for (size_t region = beg_region + 1; region < end_region; ++region) {
 542     _region_data[region].set_partial_obj_size(RegionSize);
 543     _region_data[region].set_partial_obj_addr(addr);
 544   }
 545 
 546   // Last region.
 547   const size_t end_ofs = region_offset(addr + len - 1);
 548   _region_data[end_region].set_partial_obj_size(end_ofs + 1);
 549   _region_data[end_region].set_partial_obj_addr(addr);
 550 }
 551 
 552 void
 553 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
 554 {
 555   assert(region_offset(beg) == 0, "not RegionSize aligned");
 556   assert(region_offset(end) == 0, "not RegionSize aligned");
 557 
 558   size_t cur_region = addr_to_region_idx(beg);
 559   const size_t end_region = addr_to_region_idx(end);
 560   HeapWord* addr = beg;
 561   while (cur_region < end_region) {
 562     _region_data[cur_region].set_destination(addr);
 563     _region_data[cur_region].set_destination_count(0);
 564     _region_data[cur_region].set_source_region(cur_region);
 565     _region_data[cur_region].set_data_location(addr);
 566 
 567     // Update live_obj_size so the region appears completely full.
 568     size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
 569     _region_data[cur_region].set_live_obj_size(live_size);
 570 
 571     ++cur_region;
 572     addr += RegionSize;
 573   }
 574 }
 575 
 576 // Find the point at which a space can be split and, if necessary, record the
 577 // split point.
 578 //
 579 // If the current src region (which overflowed the destination space) doesn't
 580 // have a partial object, the split point is at the beginning of the current src
 581 // region (an "easy" split, no extra bookkeeping required).
 582 //
 583 // If the current src region has a partial object, the split point is in the
 584 // region where that partial object starts (call it the split_region).  If
 585 // split_region has a partial object, then the split point is just after that
 586 // partial object (a "hard" split where we have to record the split data and
 587 // zero the partial_obj_size field).  With a "hard" split, we know that the
 588 // partial_obj ends within split_region because the partial object that caused
 589 // the overflow starts in split_region.  If split_region doesn't have a partial
 590 // obj, then the split is at the beginning of split_region (another "easy"
 591 // split).
 592 HeapWord*
 593 ParallelCompactData::summarize_split_space(size_t src_region,
 594                                            SplitInfo& split_info,
 595                                            HeapWord* destination,
 596                                            HeapWord* target_end,
 597                                            HeapWord** target_next)
 598 {
 599   assert(destination <= target_end, "sanity");
 600   assert(destination + _region_data[src_region].data_size() > target_end,
 601     "region should not fit into target space");
 602   assert(is_region_aligned(target_end), "sanity");
 603 
 604   size_t split_region = src_region;
 605   HeapWord* split_destination = destination;
 606   size_t partial_obj_size = _region_data[src_region].partial_obj_size();
 607 
 608   if (destination + partial_obj_size > target_end) {
 609     // The split point is just after the partial object (if any) in the
 610     // src_region that contains the start of the object that overflowed the
 611     // destination space.
 612     //
 613     // Find the start of the "overflow" object and set split_region to the
 614     // region containing it.
 615     HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
 616     split_region = addr_to_region_idx(overflow_obj);
 617 
 618     // Clear the source_region field of all destination regions whose first word
 619     // came from data after the split point (a non-null source_region field
 620     // implies a region must be filled).
 621     //
 622     // An alternative to the simple loop below:  clear during post_compact(),
 623     // which uses memcpy instead of individual stores, and is easy to
 624     // parallelize.  (The downside is that it clears the entire RegionData
 625     // object as opposed to just one field.)
 626     //
 627     // post_compact() would have to clear the summary data up to the highest
 628     // address that was written during the summary phase, which would be
 629     //
 630     //         max(top, max(new_top, clear_top))
 631     //
 632     // where clear_top is a new field in SpaceInfo.  Would have to set clear_top
 633     // to target_end.
 634     const RegionData* const sr = region(split_region);
 635     const size_t beg_idx =
 636       addr_to_region_idx(region_align_up(sr->destination() +
 637                                          sr->partial_obj_size()));
 638     const size_t end_idx = addr_to_region_idx(target_end);
 639 
 640     log_develop_trace(gc, compaction)("split:  clearing source_region field in [" SIZE_FORMAT ", " SIZE_FORMAT ")", beg_idx, end_idx);
 641     for (size_t idx = beg_idx; idx < end_idx; ++idx) {
 642       _region_data[idx].set_source_region(0);
 643     }
 644 
 645     // Set split_destination and partial_obj_size to reflect the split region.
 646     split_destination = sr->destination();
 647     partial_obj_size = sr->partial_obj_size();
 648   }
 649 
 650   // The split is recorded only if a partial object extends onto the region.
 651   if (partial_obj_size != 0) {
 652     _region_data[split_region].set_partial_obj_size(0);
 653     split_info.record(split_region, partial_obj_size, split_destination);
 654   }
 655 
 656   // Setup the continuation addresses.
 657   *target_next = split_destination + partial_obj_size;
 658   HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
 659 
 660   if (log_develop_is_enabled(Trace, gc, compaction)) {
 661     const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
 662     log_develop_trace(gc, compaction)("%s split:  src=" PTR_FORMAT " src_c=" SIZE_FORMAT " pos=" SIZE_FORMAT,
 663                                       split_type, p2i(source_next), split_region, partial_obj_size);
 664     log_develop_trace(gc, compaction)("%s split:  dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT " tn=" PTR_FORMAT,
 665                                       split_type, p2i(split_destination),
 666                                       addr_to_region_idx(split_destination),
 667                                       p2i(*target_next));
 668 
 669     if (partial_obj_size != 0) {
 670       HeapWord* const po_beg = split_info.destination();
 671       HeapWord* const po_end = po_beg + split_info.partial_obj_size();
 672       log_develop_trace(gc, compaction)("%s split:  po_beg=" PTR_FORMAT " " SIZE_FORMAT " po_end=" PTR_FORMAT " " SIZE_FORMAT,
 673                                         split_type,
 674                                         p2i(po_beg), addr_to_region_idx(po_beg),
 675                                         p2i(po_end), addr_to_region_idx(po_end));
 676     }
 677   }
 678 
 679   return source_next;
 680 }
 681 
 682 bool ParallelCompactData::summarize(SplitInfo& split_info,
 683                                     HeapWord* source_beg, HeapWord* source_end,
 684                                     HeapWord** source_next,
 685                                     HeapWord* target_beg, HeapWord* target_end,
 686                                     HeapWord** target_next)
 687 {
 688   HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
 689   log_develop_trace(gc, compaction)(
 690       "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
 691       "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
 692       p2i(source_beg), p2i(source_end), p2i(source_next_val),
 693       p2i(target_beg), p2i(target_end), p2i(*target_next));
 694 
 695   size_t cur_region = addr_to_region_idx(source_beg);
 696   const size_t end_region = addr_to_region_idx(region_align_up(source_end));
 697 
 698   HeapWord *dest_addr = target_beg;
 699   while (cur_region < end_region) {
 700     // The destination must be set even if the region has no data.
 701     _region_data[cur_region].set_destination(dest_addr);
 702 
 703     size_t words = _region_data[cur_region].data_size();
 704     if (words > 0) {
 705       // If cur_region does not fit entirely into the target space, find a point
 706       // at which the source space can be 'split' so that part is copied to the
 707       // target space and the rest is copied elsewhere.
 708       if (dest_addr + words > target_end) {
 709         assert(source_next != NULL, "source_next is NULL when splitting");
 710         *source_next = summarize_split_space(cur_region, split_info, dest_addr,
 711                                              target_end, target_next);
 712         return false;
 713       }
 714 
 715       // Compute the destination_count for cur_region, and if necessary, update
 716       // source_region for a destination region.  The source_region field is
 717       // updated if cur_region is the first (left-most) region to be copied to a
 718       // destination region.
 719       //
 720       // The destination_count calculation is a bit subtle.  A region that has
 721       // data that compacts into itself does not count itself as a destination.
 722       // This maintains the invariant that a zero count means the region is
 723       // available and can be claimed and then filled.
 724       uint destination_count = 0;
 725       if (split_info.is_split(cur_region)) {
 726         // The current region has been split:  the partial object will be copied
 727         // to one destination space and the remaining data will be copied to
 728         // another destination space.  Adjust the initial destination_count and,
 729         // if necessary, set the source_region field if the partial object will
 730         // cross a destination region boundary.
 731         destination_count = split_info.destination_count();
 732         if (destination_count == 2) {
 733           size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
 734           _region_data[dest_idx].set_source_region(cur_region);
 735         }
 736       }
 737 
 738       HeapWord* const last_addr = dest_addr + words - 1;
 739       const size_t dest_region_1 = addr_to_region_idx(dest_addr);
 740       const size_t dest_region_2 = addr_to_region_idx(last_addr);
 741 
 742       // Initially assume that the destination regions will be the same and
 743       // adjust the value below if necessary.  Under this assumption, if
 744       // cur_region == dest_region_2, then cur_region will be compacted
 745       // completely into itself.
 746       destination_count += cur_region == dest_region_2 ? 0 : 1;
 747       if (dest_region_1 != dest_region_2) {
 748         // Destination regions differ; adjust destination_count.
 749         destination_count += 1;
 750         // Data from cur_region will be copied to the start of dest_region_2.
 751         _region_data[dest_region_2].set_source_region(cur_region);
 752       } else if (region_offset(dest_addr) == 0) {
 753         // Data from cur_region will be copied to the start of the destination
 754         // region.
 755         _region_data[dest_region_1].set_source_region(cur_region);
 756       }
 757 
 758       _region_data[cur_region].set_destination_count(destination_count);
 759       _region_data[cur_region].set_data_location(region_to_addr(cur_region));
 760       dest_addr += words;
 761     }
 762 
 763     ++cur_region;
 764   }
 765 
 766   *target_next = dest_addr;
 767   return true;
 768 }
 769 
 770 HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr, ParCompactionManager* cm) {
 771   assert(addr != NULL, "Should detect NULL oop earlier");
 772   assert(ParallelScavengeHeap::heap()->is_in(addr), "not in heap");
 773   assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked");
 774 
 775   // Region covering the object.
 776   RegionData* const region_ptr = addr_to_region_ptr(addr);
 777   HeapWord* result = region_ptr->destination();
 778 
 779   // If the entire Region is live, the new location is region->destination + the
 780   // offset of the object within in the Region.
 781 
 782   // Run some performance tests to determine if this special case pays off.  It
 783   // is worth it for pointers into the dense prefix.  If the optimization to
 784   // avoid pointer updates in regions that only point to the dense prefix is
 785   // ever implemented, this should be revisited.
 786   if (region_ptr->data_size() == RegionSize) {
 787     result += region_offset(addr);
 788     return result;
 789   }
 790 
 791   // Otherwise, the new location is region->destination + block offset + the
 792   // number of live words in the Block that are (a) to the left of addr and (b)
 793   // due to objects that start in the Block.
 794 
 795   // Fill in the block table if necessary.  This is unsynchronized, so multiple
 796   // threads may fill the block table for a region (harmless, since it is
 797   // idempotent).
 798   if (!region_ptr->blocks_filled()) {
 799     PSParallelCompact::fill_blocks(addr_to_region_idx(addr));
 800     region_ptr->set_blocks_filled();
 801   }
 802 
 803   HeapWord* const search_start = block_align_down(addr);
 804   const size_t block_offset = addr_to_block_ptr(addr)->offset();
 805 
 806   const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
 807   const size_t live = bitmap->live_words_in_range(cm, search_start, oop(addr));
 808   result += block_offset + live;
 809   DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result));
 810   return result;
 811 }
 812 
 813 #ifdef ASSERT
 814 void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
 815 {
 816   const size_t* const beg = (const size_t*)vspace->committed_low_addr();
 817   const size_t* const end = (const size_t*)vspace->committed_high_addr();
 818   for (const size_t* p = beg; p < end; ++p) {
 819     assert(*p == 0, "not zero");
 820   }
 821 }
 822 
 823 void ParallelCompactData::verify_clear()
 824 {
 825   verify_clear(_region_vspace);
 826   verify_clear(_block_vspace);
 827 }
 828 #endif  // #ifdef ASSERT
 829 
 830 STWGCTimer          PSParallelCompact::_gc_timer;
 831 ParallelOldTracer   PSParallelCompact::_gc_tracer;
 832 elapsedTimer        PSParallelCompact::_accumulated_time;
 833 unsigned int        PSParallelCompact::_total_invocations = 0;
 834 unsigned int        PSParallelCompact::_maximum_compaction_gc_num = 0;
 835 jlong               PSParallelCompact::_time_of_last_gc = 0;
 836 CollectorCounters*  PSParallelCompact::_counters = NULL;
 837 ParMarkBitMap       PSParallelCompact::_mark_bitmap;
 838 ParallelCompactData PSParallelCompact::_summary_data;
 839 
 840 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
 841 
 842 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
 843 
 844 void PSParallelCompact::post_initialize() {
 845   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 846   _span_based_discoverer.set_span(heap->reserved_region());
 847   _ref_processor =
 848     new ReferenceProcessor(&_span_based_discoverer,
 849                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 850                            ParallelGCThreads,   // mt processing degree
 851                            true,                // mt discovery
 852                            ParallelGCThreads,   // mt discovery degree
 853                            true,                // atomic_discovery
 854                            &_is_alive_closure); // non-header is alive closure
 855   _counters = new CollectorCounters("PSParallelCompact", 1);
 856 
 857   // Initialize static fields in ParCompactionManager.
 858   ParCompactionManager::initialize(mark_bitmap());
 859 }
 860 
 861 bool PSParallelCompact::initialize() {
 862   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 863   MemRegion mr = heap->reserved_region();
 864 
 865   // Was the old gen get allocated successfully?
 866   if (!heap->old_gen()->is_allocated()) {
 867     return false;
 868   }
 869 
 870   initialize_space_info();
 871   initialize_dead_wood_limiter();
 872 
 873   if (!_mark_bitmap.initialize(mr)) {
 874     vm_shutdown_during_initialization(
 875       err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
 876       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 877       _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
 878     return false;
 879   }
 880 
 881   if (!_summary_data.initialize(mr)) {
 882     vm_shutdown_during_initialization(
 883       err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
 884       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 885       _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
 886     return false;
 887   }
 888 
 889   return true;
 890 }
 891 
 892 void PSParallelCompact::initialize_space_info()
 893 {
 894   memset(&_space_info, 0, sizeof(_space_info));
 895 
 896   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 897   PSYoungGen* young_gen = heap->young_gen();
 898 
 899   _space_info[old_space_id].set_space(heap->old_gen()->object_space());
 900   _space_info[eden_space_id].set_space(young_gen->eden_space());
 901   _space_info[from_space_id].set_space(young_gen->from_space());
 902   _space_info[to_space_id].set_space(young_gen->to_space());
 903 
 904   _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
 905 }
 906 
 907 void PSParallelCompact::initialize_dead_wood_limiter()
 908 {
 909   const size_t max = 100;
 910   _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
 911   _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
 912   _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
 913   DEBUG_ONLY(_dwl_initialized = true;)
 914   _dwl_adjustment = normal_distribution(1.0);
 915 }
 916 
 917 void
 918 PSParallelCompact::clear_data_covering_space(SpaceId id)
 919 {
 920   // At this point, top is the value before GC, new_top() is the value that will
 921   // be set at the end of GC.  The marking bitmap is cleared to top; nothing
 922   // should be marked above top.  The summary data is cleared to the larger of
 923   // top & new_top.
 924   MutableSpace* const space = _space_info[id].space();
 925   HeapWord* const bot = space->bottom();
 926   HeapWord* const top = space->top();
 927   HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
 928 
 929   const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
 930   const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top));
 931   _mark_bitmap.clear_range(beg_bit, end_bit);
 932 
 933   const size_t beg_region = _summary_data.addr_to_region_idx(bot);
 934   const size_t end_region =
 935     _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
 936   _summary_data.clear_range(beg_region, end_region);
 937 
 938   // Clear the data used to 'split' regions.
 939   SplitInfo& split_info = _space_info[id].split_info();
 940   if (split_info.is_valid()) {
 941     split_info.clear();
 942   }
 943   DEBUG_ONLY(split_info.verify_clear();)
 944 }
 945 
 946 void PSParallelCompact::pre_compact()
 947 {
 948   // Update the from & to space pointers in space_info, since they are swapped
 949   // at each young gen gc.  Do the update unconditionally (even though a
 950   // promotion failure does not swap spaces) because an unknown number of young
 951   // collections will have swapped the spaces an unknown number of times.
 952   GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
 953   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 954   _space_info[from_space_id].set_space(heap->young_gen()->from_space());
 955   _space_info[to_space_id].set_space(heap->young_gen()->to_space());
 956 
 957   DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
 958   DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
 959 
 960   // Increment the invocation count
 961   heap->increment_total_collections(true);
 962 
 963   // We need to track unique mark sweep invocations as well.
 964   _total_invocations++;
 965 
 966   heap->print_heap_before_gc();
 967   heap->trace_heap_before_gc(&_gc_tracer);
 968 
 969   // Fill in TLABs
 970   heap->accumulate_statistics_all_tlabs();
 971   heap->ensure_parsability(true);  // retire TLABs
 972 
 973   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 974     HandleMark hm;  // Discard invalid handles created during verification
 975     Universe::verify("Before GC");
 976   }
 977 
 978   // Verify object start arrays
 979   if (VerifyObjectStartArray &&
 980       VerifyBeforeGC) {
 981     heap->old_gen()->verify_object_start_array();
 982   }
 983 
 984   DEBUG_ONLY(mark_bitmap()->verify_clear();)
 985   DEBUG_ONLY(summary_data().verify_clear();)
 986 
 987   // Have worker threads release resources the next time they run a task.
 988   gc_task_manager()->release_all_resources();
 989 
 990   ParCompactionManager::reset_all_bitmap_query_caches();
 991 }
 992 
 993 void PSParallelCompact::post_compact()
 994 {
 995   GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
 996 
 997   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
 998     // Clear the marking bitmap, summary data and split info.
 999     clear_data_covering_space(SpaceId(id));
1000     // Update top().  Must be done after clearing the bitmap and summary data.
1001     _space_info[id].publish_new_top();
1002   }
1003 
1004   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1005   MutableSpace* const from_space = _space_info[from_space_id].space();
1006   MutableSpace* const to_space   = _space_info[to_space_id].space();
1007 
1008   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1009   bool eden_empty = eden_space->is_empty();
1010   if (!eden_empty) {
1011     eden_empty = absorb_live_data_from_eden(heap->size_policy(),
1012                                             heap->young_gen(), heap->old_gen());
1013   }
1014 
1015   // Update heap occupancy information which is used as input to the soft ref
1016   // clearing policy at the next gc.
1017   Universe::update_heap_info_at_gc();
1018 
1019   bool young_gen_empty = eden_empty && from_space->is_empty() &&
1020     to_space->is_empty();
1021 
1022   PSCardTable* ct = heap->card_table();
1023   MemRegion old_mr = heap->old_gen()->reserved();
1024   if (young_gen_empty) {
1025     ct->clear(MemRegion(old_mr.start(), old_mr.end()));
1026   } else {
1027     ct->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1028   }
1029 
1030   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1031   ClassLoaderDataGraph::purge();
1032   MetaspaceUtils::verify_metrics();
1033 
1034   CodeCache::gc_epilogue();
1035   JvmtiExport::gc_epilogue();
1036 
1037 #if COMPILER2_OR_JVMCI
1038   DerivedPointerTable::update_pointers();
1039 #endif
1040 
1041   if (ZapUnusedHeapArea) {
1042     heap->gen_mangle_unused_area();
1043   }
1044 
1045   // Update time of last GC
1046   reset_millis_since_last_gc();
1047 }
1048 
1049 HeapWord*
1050 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1051                                                     bool maximum_compaction)
1052 {
1053   const size_t region_size = ParallelCompactData::RegionSize;
1054   const ParallelCompactData& sd = summary_data();
1055 
1056   const MutableSpace* const space = _space_info[id].space();
1057   HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1058   const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1059   const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1060 
1061   // Skip full regions at the beginning of the space--they are necessarily part
1062   // of the dense prefix.
1063   size_t full_count = 0;
1064   const RegionData* cp;
1065   for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1066     ++full_count;
1067   }
1068 
1069   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1070   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1071   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1072   if (maximum_compaction || cp == end_cp || interval_ended) {
1073     _maximum_compaction_gc_num = total_invocations();
1074     return sd.region_to_addr(cp);
1075   }
1076 
1077   HeapWord* const new_top = _space_info[id].new_top();
1078   const size_t space_live = pointer_delta(new_top, space->bottom());
1079   const size_t space_used = space->used_in_words();
1080   const size_t space_capacity = space->capacity_in_words();
1081 
1082   const double cur_density = double(space_live) / space_capacity;
1083   const double deadwood_density =
1084     (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1085   const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1086 
1087   if (TraceParallelOldGCDensePrefix) {
1088     tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1089                   cur_density, deadwood_density, deadwood_goal);
1090     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1091                   "space_cap=" SIZE_FORMAT,
1092                   space_live, space_used,
1093                   space_capacity);
1094   }
1095 
1096   // XXX - Use binary search?
1097   HeapWord* dense_prefix = sd.region_to_addr(cp);
1098   const RegionData* full_cp = cp;
1099   const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1100   while (cp < end_cp) {
1101     HeapWord* region_destination = cp->destination();
1102     const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1103     if (TraceParallelOldGCDensePrefix && Verbose) {
1104       tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1105                     "dp=" PTR_FORMAT " " "cdw=" SIZE_FORMAT_W(8),
1106                     sd.region(cp), p2i(region_destination),
1107                     p2i(dense_prefix), cur_deadwood);
1108     }
1109 
1110     if (cur_deadwood >= deadwood_goal) {
1111       // Found the region that has the correct amount of deadwood to the left.
1112       // This typically occurs after crossing a fairly sparse set of regions, so
1113       // iterate backwards over those sparse regions, looking for the region
1114       // that has the lowest density of live objects 'to the right.'
1115       size_t space_to_left = sd.region(cp) * region_size;
1116       size_t live_to_left = space_to_left - cur_deadwood;
1117       size_t space_to_right = space_capacity - space_to_left;
1118       size_t live_to_right = space_live - live_to_left;
1119       double density_to_right = double(live_to_right) / space_to_right;
1120       while (cp > full_cp) {
1121         --cp;
1122         const size_t prev_region_live_to_right = live_to_right -
1123           cp->data_size();
1124         const size_t prev_region_space_to_right = space_to_right + region_size;
1125         double prev_region_density_to_right =
1126           double(prev_region_live_to_right) / prev_region_space_to_right;
1127         if (density_to_right <= prev_region_density_to_right) {
1128           return dense_prefix;
1129         }
1130         if (TraceParallelOldGCDensePrefix && Verbose) {
1131           tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1132                         "pc_d2r=%10.8f", sd.region(cp), density_to_right,
1133                         prev_region_density_to_right);
1134         }
1135         dense_prefix -= region_size;
1136         live_to_right = prev_region_live_to_right;
1137         space_to_right = prev_region_space_to_right;
1138         density_to_right = prev_region_density_to_right;
1139       }
1140       return dense_prefix;
1141     }
1142 
1143     dense_prefix += region_size;
1144     ++cp;
1145   }
1146 
1147   return dense_prefix;
1148 }
1149 
1150 #ifndef PRODUCT
1151 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1152                                                  const SpaceId id,
1153                                                  const bool maximum_compaction,
1154                                                  HeapWord* const addr)
1155 {
1156   const size_t region_idx = summary_data().addr_to_region_idx(addr);
1157   RegionData* const cp = summary_data().region(region_idx);
1158   const MutableSpace* const space = _space_info[id].space();
1159   HeapWord* const new_top = _space_info[id].new_top();
1160 
1161   const size_t space_live = pointer_delta(new_top, space->bottom());
1162   const size_t dead_to_left = pointer_delta(addr, cp->destination());
1163   const size_t space_cap = space->capacity_in_words();
1164   const double dead_to_left_pct = double(dead_to_left) / space_cap;
1165   const size_t live_to_right = new_top - cp->destination();
1166   const size_t dead_to_right = space->top() - addr - live_to_right;
1167 
1168   tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1169                 "spl=" SIZE_FORMAT " "
1170                 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1171                 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
1172                 " ratio=%10.8f",
1173                 algorithm, p2i(addr), region_idx,
1174                 space_live,
1175                 dead_to_left, dead_to_left_pct,
1176                 dead_to_right, live_to_right,
1177                 double(dead_to_right) / live_to_right);
1178 }
1179 #endif  // #ifndef PRODUCT
1180 
1181 // Return a fraction indicating how much of the generation can be treated as
1182 // "dead wood" (i.e., not reclaimed).  The function uses a normal distribution
1183 // based on the density of live objects in the generation to determine a limit,
1184 // which is then adjusted so the return value is min_percent when the density is
1185 // 1.
1186 //
1187 // The following table shows some return values for a different values of the
1188 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1189 // min_percent is 1.
1190 //
1191 //                          fraction allowed as dead wood
1192 //         -----------------------------------------------------------------
1193 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1194 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1195 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1196 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1197 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1198 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1199 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1200 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1201 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1202 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1203 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1204 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1205 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1206 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1207 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1208 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1209 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1210 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1211 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1212 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1213 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1214 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1215 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1216 
1217 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1218 {
1219   assert(_dwl_initialized, "uninitialized");
1220 
1221   // The raw limit is the value of the normal distribution at x = density.
1222   const double raw_limit = normal_distribution(density);
1223 
1224   // Adjust the raw limit so it becomes the minimum when the density is 1.
1225   //
1226   // First subtract the adjustment value (which is simply the precomputed value
1227   // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1228   // Then add the minimum value, so the minimum is returned when the density is
1229   // 1.  Finally, prevent negative values, which occur when the mean is not 0.5.
1230   const double min = double(min_percent) / 100.0;
1231   const double limit = raw_limit - _dwl_adjustment + min;
1232   return MAX2(limit, 0.0);
1233 }
1234 
1235 ParallelCompactData::RegionData*
1236 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1237                                            const RegionData* end)
1238 {
1239   const size_t region_size = ParallelCompactData::RegionSize;
1240   ParallelCompactData& sd = summary_data();
1241   size_t left = sd.region(beg);
1242   size_t right = end > beg ? sd.region(end) - 1 : left;
1243 
1244   // Binary search.
1245   while (left < right) {
1246     // Equivalent to (left + right) / 2, but does not overflow.
1247     const size_t middle = left + (right - left) / 2;
1248     RegionData* const middle_ptr = sd.region(middle);
1249     HeapWord* const dest = middle_ptr->destination();
1250     HeapWord* const addr = sd.region_to_addr(middle);
1251     assert(dest != NULL, "sanity");
1252     assert(dest <= addr, "must move left");
1253 
1254     if (middle > left && dest < addr) {
1255       right = middle - 1;
1256     } else if (middle < right && middle_ptr->data_size() == region_size) {
1257       left = middle + 1;
1258     } else {
1259       return middle_ptr;
1260     }
1261   }
1262   return sd.region(left);
1263 }
1264 
1265 ParallelCompactData::RegionData*
1266 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1267                                           const RegionData* end,
1268                                           size_t dead_words)
1269 {
1270   ParallelCompactData& sd = summary_data();
1271   size_t left = sd.region(beg);
1272   size_t right = end > beg ? sd.region(end) - 1 : left;
1273 
1274   // Binary search.
1275   while (left < right) {
1276     // Equivalent to (left + right) / 2, but does not overflow.
1277     const size_t middle = left + (right - left) / 2;
1278     RegionData* const middle_ptr = sd.region(middle);
1279     HeapWord* const dest = middle_ptr->destination();
1280     HeapWord* const addr = sd.region_to_addr(middle);
1281     assert(dest != NULL, "sanity");
1282     assert(dest <= addr, "must move left");
1283 
1284     const size_t dead_to_left = pointer_delta(addr, dest);
1285     if (middle > left && dead_to_left > dead_words) {
1286       right = middle - 1;
1287     } else if (middle < right && dead_to_left < dead_words) {
1288       left = middle + 1;
1289     } else {
1290       return middle_ptr;
1291     }
1292   }
1293   return sd.region(left);
1294 }
1295 
1296 // The result is valid during the summary phase, after the initial summarization
1297 // of each space into itself, and before final summarization.
1298 inline double
1299 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1300                                    HeapWord* const bottom,
1301                                    HeapWord* const top,
1302                                    HeapWord* const new_top)
1303 {
1304   ParallelCompactData& sd = summary_data();
1305 
1306   assert(cp != NULL, "sanity");
1307   assert(bottom != NULL, "sanity");
1308   assert(top != NULL, "sanity");
1309   assert(new_top != NULL, "sanity");
1310   assert(top >= new_top, "summary data problem?");
1311   assert(new_top > bottom, "space is empty; should not be here");
1312   assert(new_top >= cp->destination(), "sanity");
1313   assert(top >= sd.region_to_addr(cp), "sanity");
1314 
1315   HeapWord* const destination = cp->destination();
1316   const size_t dense_prefix_live  = pointer_delta(destination, bottom);
1317   const size_t compacted_region_live = pointer_delta(new_top, destination);
1318   const size_t compacted_region_used = pointer_delta(top,
1319                                                      sd.region_to_addr(cp));
1320   const size_t reclaimable = compacted_region_used - compacted_region_live;
1321 
1322   const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1323   return double(reclaimable) / divisor;
1324 }
1325 
1326 // Return the address of the end of the dense prefix, a.k.a. the start of the
1327 // compacted region.  The address is always on a region boundary.
1328 //
1329 // Completely full regions at the left are skipped, since no compaction can
1330 // occur in those regions.  Then the maximum amount of dead wood to allow is
1331 // computed, based on the density (amount live / capacity) of the generation;
1332 // the region with approximately that amount of dead space to the left is
1333 // identified as the limit region.  Regions between the last completely full
1334 // region and the limit region are scanned and the one that has the best
1335 // (maximum) reclaimed_ratio() is selected.
1336 HeapWord*
1337 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1338                                         bool maximum_compaction)
1339 {
1340   const size_t region_size = ParallelCompactData::RegionSize;
1341   const ParallelCompactData& sd = summary_data();
1342 
1343   const MutableSpace* const space = _space_info[id].space();
1344   HeapWord* const top = space->top();
1345   HeapWord* const top_aligned_up = sd.region_align_up(top);
1346   HeapWord* const new_top = _space_info[id].new_top();
1347   HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1348   HeapWord* const bottom = space->bottom();
1349   const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1350   const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1351   const RegionData* const new_top_cp =
1352     sd.addr_to_region_ptr(new_top_aligned_up);
1353 
1354   // Skip full regions at the beginning of the space--they are necessarily part
1355   // of the dense prefix.
1356   const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1357   assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1358          space->is_empty(), "no dead space allowed to the left");
1359   assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1360          "region must have dead space");
1361 
1362   // The gc number is saved whenever a maximum compaction is done, and used to
1363   // determine when the maximum compaction interval has expired.  This avoids
1364   // successive max compactions for different reasons.
1365   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1366   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1367   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1368     total_invocations() == HeapFirstMaximumCompactionCount;
1369   if (maximum_compaction || full_cp == top_cp || interval_ended) {
1370     _maximum_compaction_gc_num = total_invocations();
1371     return sd.region_to_addr(full_cp);
1372   }
1373 
1374   const size_t space_live = pointer_delta(new_top, bottom);
1375   const size_t space_used = space->used_in_words();
1376   const size_t space_capacity = space->capacity_in_words();
1377 
1378   const double density = double(space_live) / double(space_capacity);
1379   const size_t min_percent_free = MarkSweepDeadRatio;
1380   const double limiter = dead_wood_limiter(density, min_percent_free);
1381   const size_t dead_wood_max = space_used - space_live;
1382   const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1383                                       dead_wood_max);
1384 
1385   if (TraceParallelOldGCDensePrefix) {
1386     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1387                   "space_cap=" SIZE_FORMAT,
1388                   space_live, space_used,
1389                   space_capacity);
1390     tty->print_cr("dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
1391                   "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1392                   density, min_percent_free, limiter,
1393                   dead_wood_max, dead_wood_limit);
1394   }
1395 
1396   // Locate the region with the desired amount of dead space to the left.
1397   const RegionData* const limit_cp =
1398     dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1399 
1400   // Scan from the first region with dead space to the limit region and find the
1401   // one with the best (largest) reclaimed ratio.
1402   double best_ratio = 0.0;
1403   const RegionData* best_cp = full_cp;
1404   for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1405     double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1406     if (tmp_ratio > best_ratio) {
1407       best_cp = cp;
1408       best_ratio = tmp_ratio;
1409     }
1410   }
1411 
1412   return sd.region_to_addr(best_cp);
1413 }
1414 
1415 void PSParallelCompact::summarize_spaces_quick()
1416 {
1417   for (unsigned int i = 0; i < last_space_id; ++i) {
1418     const MutableSpace* space = _space_info[i].space();
1419     HeapWord** nta = _space_info[i].new_top_addr();
1420     bool result = _summary_data.summarize(_space_info[i].split_info(),
1421                                           space->bottom(), space->top(), NULL,
1422                                           space->bottom(), space->end(), nta);
1423     assert(result, "space must fit into itself");
1424     _space_info[i].set_dense_prefix(space->bottom());
1425   }
1426 }
1427 
1428 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1429 {
1430   HeapWord* const dense_prefix_end = dense_prefix(id);
1431   const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1432   const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1433   if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1434     // Only enough dead space is filled so that any remaining dead space to the
1435     // left is larger than the minimum filler object.  (The remainder is filled
1436     // during the copy/update phase.)
1437     //
1438     // The size of the dead space to the right of the boundary is not a
1439     // concern, since compaction will be able to use whatever space is
1440     // available.
1441     //
1442     // Here '||' is the boundary, 'x' represents a don't care bit and a box
1443     // surrounds the space to be filled with an object.
1444     //
1445     // In the 32-bit VM, each bit represents two 32-bit words:
1446     //                              +---+
1447     // a) beg_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1448     //    end_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1449     //                              +---+
1450     //
1451     // In the 64-bit VM, each bit represents one 64-bit word:
1452     //                              +------------+
1453     // b) beg_bits:  ...  x   x   x | 0   ||   0 | x  x  ...
1454     //    end_bits:  ...  x   x   1 | 0   ||   0 | x  x  ...
1455     //                              +------------+
1456     //                          +-------+
1457     // c) beg_bits:  ...  x   x | 0   0 | ||   0   x  x  ...
1458     //    end_bits:  ...  x   1 | 0   0 | ||   0   x  x  ...
1459     //                          +-------+
1460     //                      +-----------+
1461     // d) beg_bits:  ...  x | 0   0   0 | ||   0   x  x  ...
1462     //    end_bits:  ...  1 | 0   0   0 | ||   0   x  x  ...
1463     //                      +-----------+
1464     //                          +-------+
1465     // e) beg_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1466     //    end_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1467     //                          +-------+
1468 
1469     // Initially assume case a, c or e will apply.
1470     size_t obj_len = CollectedHeap::min_fill_size();
1471     HeapWord* obj_beg = dense_prefix_end - obj_len;
1472 
1473 #ifdef  _LP64
1474     if (MinObjAlignment > 1) { // object alignment > heap word size
1475       // Cases a, c or e.
1476     } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1477       // Case b above.
1478       obj_beg = dense_prefix_end - 1;
1479     } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1480                _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1481       // Case d above.
1482       obj_beg = dense_prefix_end - 3;
1483       obj_len = 3;
1484     }
1485 #endif  // #ifdef _LP64
1486 
1487     CollectedHeap::fill_with_object(obj_beg, obj_len);
1488     _mark_bitmap.mark_obj(obj_beg, obj_len);
1489     _summary_data.add_obj(obj_beg, obj_len);
1490     assert(start_array(id) != NULL, "sanity");
1491     start_array(id)->allocate_block(obj_beg);
1492   }
1493 }
1494 
1495 void
1496 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1497 {
1498   assert(id < last_space_id, "id out of range");
1499   assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom(),
1500          "should have been reset in summarize_spaces_quick()");
1501 
1502   const MutableSpace* space = _space_info[id].space();
1503   if (_space_info[id].new_top() != space->bottom()) {
1504     HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1505     _space_info[id].set_dense_prefix(dense_prefix_end);
1506 
1507 #ifndef PRODUCT
1508     if (TraceParallelOldGCDensePrefix) {
1509       print_dense_prefix_stats("ratio", id, maximum_compaction,
1510                                dense_prefix_end);
1511       HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1512       print_dense_prefix_stats("density", id, maximum_compaction, addr);
1513     }
1514 #endif  // #ifndef PRODUCT
1515 
1516     // Recompute the summary data, taking into account the dense prefix.  If
1517     // every last byte will be reclaimed, then the existing summary data which
1518     // compacts everything can be left in place.
1519     if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1520       // If dead space crosses the dense prefix boundary, it is (at least
1521       // partially) filled with a dummy object, marked live and added to the
1522       // summary data.  This simplifies the copy/update phase and must be done
1523       // before the final locations of objects are determined, to prevent
1524       // leaving a fragment of dead space that is too small to fill.
1525       fill_dense_prefix_end(id);
1526 
1527       // Compute the destination of each Region, and thus each object.
1528       _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1529       _summary_data.summarize(_space_info[id].split_info(),
1530                               dense_prefix_end, space->top(), NULL,
1531                               dense_prefix_end, space->end(),
1532                               _space_info[id].new_top_addr());
1533     }
1534   }
1535 
1536   if (log_develop_is_enabled(Trace, gc, compaction)) {
1537     const size_t region_size = ParallelCompactData::RegionSize;
1538     HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1539     const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1540     const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1541     HeapWord* const new_top = _space_info[id].new_top();
1542     const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1543     const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1544     log_develop_trace(gc, compaction)(
1545         "id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1546         "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1547         "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1548         id, space->capacity_in_words(), p2i(dense_prefix_end),
1549         dp_region, dp_words / region_size,
1550         cr_words / region_size, p2i(new_top));
1551   }
1552 }
1553 
1554 #ifndef PRODUCT
1555 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1556                                           HeapWord* dst_beg, HeapWord* dst_end,
1557                                           SpaceId src_space_id,
1558                                           HeapWord* src_beg, HeapWord* src_end)
1559 {
1560   log_develop_trace(gc, compaction)(
1561       "Summarizing %d [%s] into %d [%s]:  "
1562       "src=" PTR_FORMAT "-" PTR_FORMAT " "
1563       SIZE_FORMAT "-" SIZE_FORMAT " "
1564       "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1565       SIZE_FORMAT "-" SIZE_FORMAT,
1566       src_space_id, space_names[src_space_id],
1567       dst_space_id, space_names[dst_space_id],
1568       p2i(src_beg), p2i(src_end),
1569       _summary_data.addr_to_region_idx(src_beg),
1570       _summary_data.addr_to_region_idx(src_end),
1571       p2i(dst_beg), p2i(dst_end),
1572       _summary_data.addr_to_region_idx(dst_beg),
1573       _summary_data.addr_to_region_idx(dst_end));
1574 }
1575 #endif  // #ifndef PRODUCT
1576 
1577 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1578                                       bool maximum_compaction)
1579 {
1580   GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
1581 
1582 #ifdef  ASSERT
1583   if (TraceParallelOldGCMarkingPhase) {
1584     tty->print_cr("add_obj_count=" SIZE_FORMAT " "
1585                   "add_obj_bytes=" SIZE_FORMAT,
1586                   add_obj_count, add_obj_size * HeapWordSize);
1587     tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
1588                   "mark_bitmap_bytes=" SIZE_FORMAT,
1589                   mark_bitmap_count, mark_bitmap_size * HeapWordSize);
1590   }
1591 #endif  // #ifdef ASSERT
1592 
1593   // Quick summarization of each space into itself, to see how much is live.
1594   summarize_spaces_quick();
1595 
1596   log_develop_trace(gc, compaction)("summary phase:  after summarizing each space to self");
1597   NOT_PRODUCT(print_region_ranges());
1598   NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1599 
1600   // The amount of live data that will end up in old space (assuming it fits).
1601   size_t old_space_total_live = 0;
1602   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1603     old_space_total_live += pointer_delta(_space_info[id].new_top(),
1604                                           _space_info[id].space()->bottom());
1605   }
1606 
1607   MutableSpace* const old_space = _space_info[old_space_id].space();
1608   const size_t old_capacity = old_space->capacity_in_words();
1609   if (old_space_total_live > old_capacity) {
1610     // XXX - should also try to expand
1611     maximum_compaction = true;
1612   }
1613 
1614   // Old generations.
1615   summarize_space(old_space_id, maximum_compaction);
1616 
1617   // Summarize the remaining spaces in the young gen.  The initial target space
1618   // is the old gen.  If a space does not fit entirely into the target, then the
1619   // remainder is compacted into the space itself and that space becomes the new
1620   // target.
1621   SpaceId dst_space_id = old_space_id;
1622   HeapWord* dst_space_end = old_space->end();
1623   HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1624   for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1625     const MutableSpace* space = _space_info[id].space();
1626     const size_t live = pointer_delta(_space_info[id].new_top(),
1627                                       space->bottom());
1628     const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1629 
1630     NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1631                                   SpaceId(id), space->bottom(), space->top());)
1632     if (live > 0 && live <= available) {
1633       // All the live data will fit.
1634       bool done = _summary_data.summarize(_space_info[id].split_info(),
1635                                           space->bottom(), space->top(),
1636                                           NULL,
1637                                           *new_top_addr, dst_space_end,
1638                                           new_top_addr);
1639       assert(done, "space must fit into old gen");
1640 
1641       // Reset the new_top value for the space.
1642       _space_info[id].set_new_top(space->bottom());
1643     } else if (live > 0) {
1644       // Attempt to fit part of the source space into the target space.
1645       HeapWord* next_src_addr = NULL;
1646       bool done = _summary_data.summarize(_space_info[id].split_info(),
1647                                           space->bottom(), space->top(),
1648                                           &next_src_addr,
1649                                           *new_top_addr, dst_space_end,
1650                                           new_top_addr);
1651       assert(!done, "space should not fit into old gen");
1652       assert(next_src_addr != NULL, "sanity");
1653 
1654       // The source space becomes the new target, so the remainder is compacted
1655       // within the space itself.
1656       dst_space_id = SpaceId(id);
1657       dst_space_end = space->end();
1658       new_top_addr = _space_info[id].new_top_addr();
1659       NOT_PRODUCT(summary_phase_msg(dst_space_id,
1660                                     space->bottom(), dst_space_end,
1661                                     SpaceId(id), next_src_addr, space->top());)
1662       done = _summary_data.summarize(_space_info[id].split_info(),
1663                                      next_src_addr, space->top(),
1664                                      NULL,
1665                                      space->bottom(), dst_space_end,
1666                                      new_top_addr);
1667       assert(done, "space must fit when compacted into itself");
1668       assert(*new_top_addr <= space->top(), "usage should not grow");
1669     }
1670   }
1671 
1672   log_develop_trace(gc, compaction)("Summary_phase:  after final summarization");
1673   NOT_PRODUCT(print_region_ranges());
1674   NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1675 }
1676 
1677 // This method should contain all heap-specific policy for invoking a full
1678 // collection.  invoke_no_policy() will only attempt to compact the heap; it
1679 // will do nothing further.  If we need to bail out for policy reasons, scavenge
1680 // before full gc, or any other specialized behavior, it needs to be added here.
1681 //
1682 // Note that this method should only be called from the vm_thread while at a
1683 // safepoint.
1684 //
1685 // Note that the all_soft_refs_clear flag in the collector policy
1686 // may be true because this method can be called without intervening
1687 // activity.  For example when the heap space is tight and full measure
1688 // are being taken to free space.
1689 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1690   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1691   assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1692          "should be in vm thread");
1693 
1694   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1695   GCCause::Cause gc_cause = heap->gc_cause();
1696   assert(!heap->is_gc_active(), "not reentrant");
1697 
1698   PSAdaptiveSizePolicy* policy = heap->size_policy();
1699   IsGCActiveMark mark;
1700 
1701   if (ScavengeBeforeFullGC) {
1702     PSScavenge::invoke_no_policy();
1703   }
1704 
1705   const bool clear_all_soft_refs =
1706     heap->soft_ref_policy()->should_clear_all_soft_refs();
1707 
1708   PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1709                                       maximum_heap_compaction);
1710 }
1711 
1712 // This method contains no policy. You should probably
1713 // be calling invoke() instead.
1714 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
1715   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
1716   assert(ref_processor() != NULL, "Sanity");
1717 
1718   if (GCLocker::check_active_before_gc()) {
1719     return false;
1720   }
1721 
1722   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1723 
1724   GCIdMark gc_id_mark;
1725   _gc_timer.register_gc_start();
1726   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1727 
1728   TimeStamp marking_start;
1729   TimeStamp compaction_start;
1730   TimeStamp collection_exit;
1731 
1732   GCCause::Cause gc_cause = heap->gc_cause();
1733   PSYoungGen* young_gen = heap->young_gen();
1734   PSOldGen* old_gen = heap->old_gen();
1735   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1736 
1737   // The scope of casr should end after code that can change
1738   // CollectorPolicy::_should_clear_all_soft_refs.
1739   ClearedAllSoftRefs casr(maximum_heap_compaction,
1740                           heap->soft_ref_policy());
1741 
1742   if (ZapUnusedHeapArea) {
1743     // Save information needed to minimize mangling
1744     heap->record_gen_tops_before_GC();
1745   }
1746 
1747   // Make sure data structures are sane, make the heap parsable, and do other
1748   // miscellaneous bookkeeping.
1749   pre_compact();
1750 
1751   PreGCValues pre_gc_values(heap);
1752 
1753   // Get the compaction manager reserved for the VM thread.
1754   ParCompactionManager* const vmthread_cm =
1755     ParCompactionManager::manager_array(gc_task_manager()->workers());
1756 
1757   {
1758     ResourceMark rm;
1759     HandleMark hm;
1760 
1761     // Set the number of GC threads to be used in this collection
1762     gc_task_manager()->set_active_gang();
1763     gc_task_manager()->task_idle_workers();
1764 
1765     GCTraceCPUTime tcpu;
1766     GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause, true);
1767 
1768     heap->pre_full_gc_dump(&_gc_timer);
1769 
1770     TraceCollectorStats tcs(counters());
1771     TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause);
1772 
1773     if (log_is_enabled(Debug, gc, heap, exit)) {
1774       accumulated_time()->start();
1775     }
1776 
1777     // Let the size policy know we're starting
1778     size_policy->major_collection_begin();
1779 
1780     CodeCache::gc_prologue();
1781 
1782 #if COMPILER2_OR_JVMCI
1783     DerivedPointerTable::clear();
1784 #endif
1785 
1786     ref_processor()->enable_discovery();
1787     ref_processor()->setup_policy(maximum_heap_compaction);
1788 
1789     bool marked_for_unloading = false;
1790 
1791     marking_start.update();
1792     marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
1793 
1794     bool max_on_system_gc = UseMaximumCompactionOnSystemGC
1795       && GCCause::is_user_requested_gc(gc_cause);
1796     summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
1797 
1798 #if COMPILER2_OR_JVMCI
1799     assert(DerivedPointerTable::is_active(), "Sanity");
1800     DerivedPointerTable::set_active(false);
1801 #endif
1802 
1803     // adjust_roots() updates Universe::_intArrayKlassObj which is
1804     // needed by the compaction for filling holes in the dense prefix.
1805     adjust_roots(vmthread_cm);
1806 
1807     compaction_start.update();
1808     compact();
1809 
1810     // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
1811     // done before resizing.
1812     post_compact();
1813 
1814     // Let the size policy know we're done
1815     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1816 
1817     if (UseAdaptiveSizePolicy) {
1818       log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1819       log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
1820                           old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1821 
1822       // Don't check if the size_policy is ready here.  Let
1823       // the size_policy check that internally.
1824       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1825           AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1826         // Swap the survivor spaces if from_space is empty. The
1827         // resize_young_gen() called below is normally used after
1828         // a successful young GC and swapping of survivor spaces;
1829         // otherwise, it will fail to resize the young gen with
1830         // the current implementation.
1831         if (young_gen->from_space()->is_empty()) {
1832           young_gen->from_space()->clear(SpaceDecorator::Mangle);
1833           young_gen->swap_spaces();
1834         }
1835 
1836         // Calculate optimal free space amounts
1837         assert(young_gen->max_size() >
1838           young_gen->from_space()->capacity_in_bytes() +
1839           young_gen->to_space()->capacity_in_bytes(),
1840           "Sizes of space in young gen are out-of-bounds");
1841 
1842         size_t young_live = young_gen->used_in_bytes();
1843         size_t eden_live = young_gen->eden_space()->used_in_bytes();
1844         size_t old_live = old_gen->used_in_bytes();
1845         size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1846         size_t max_old_gen_size = old_gen->max_gen_size();
1847         size_t max_eden_size = young_gen->max_size() -
1848           young_gen->from_space()->capacity_in_bytes() -
1849           young_gen->to_space()->capacity_in_bytes();
1850 
1851         // Used for diagnostics
1852         size_policy->clear_generation_free_space_flags();
1853 
1854         size_policy->compute_generations_free_space(young_live,
1855                                                     eden_live,
1856                                                     old_live,
1857                                                     cur_eden,
1858                                                     max_old_gen_size,
1859                                                     max_eden_size,
1860                                                     true /* full gc*/);
1861 
1862         size_policy->check_gc_overhead_limit(young_live,
1863                                              eden_live,
1864                                              max_old_gen_size,
1865                                              max_eden_size,
1866                                              true /* full gc*/,
1867                                              gc_cause,
1868                                              heap->soft_ref_policy());
1869 
1870         size_policy->decay_supplemental_growth(true /* full gc*/);
1871 
1872         heap->resize_old_gen(
1873           size_policy->calculated_old_free_size_in_bytes());
1874 
1875         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1876                                size_policy->calculated_survivor_size_in_bytes());
1877       }
1878 
1879       log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1880     }
1881 
1882     if (UsePerfData) {
1883       PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1884       counters->update_counters();
1885       counters->update_old_capacity(old_gen->capacity_in_bytes());
1886       counters->update_young_capacity(young_gen->capacity_in_bytes());
1887     }
1888 
1889     heap->resize_all_tlabs();
1890 
1891     // Resize the metaspace capacity after a collection
1892     MetaspaceGC::compute_new_size();
1893 
1894     if (log_is_enabled(Debug, gc, heap, exit)) {
1895       accumulated_time()->stop();
1896     }
1897 
1898     young_gen->print_used_change(pre_gc_values.young_gen_used());
1899     old_gen->print_used_change(pre_gc_values.old_gen_used());
1900     MetaspaceUtils::print_metaspace_change(pre_gc_values.metadata_used());
1901 
1902     // Track memory usage and detect low memory
1903     MemoryService::track_memory_usage();
1904     heap->update_counters();
1905     gc_task_manager()->release_idle_workers();
1906 
1907     heap->post_full_gc_dump(&_gc_timer);
1908   }
1909 
1910 #ifdef ASSERT
1911   for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
1912     ParCompactionManager* const cm =
1913       ParCompactionManager::manager_array(int(i));
1914     assert(cm->marking_stack()->is_empty(),       "should be empty");
1915     assert(cm->region_stack()->is_empty(), "Region stack " SIZE_FORMAT " is not empty", i);
1916   }
1917 #endif // ASSERT
1918 
1919   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1920     HandleMark hm;  // Discard invalid handles created during verification
1921     Universe::verify("After GC");
1922   }
1923 
1924   // Re-verify object start arrays
1925   if (VerifyObjectStartArray &&
1926       VerifyAfterGC) {
1927     old_gen->verify_object_start_array();
1928   }
1929 
1930   if (ZapUnusedHeapArea) {
1931     old_gen->object_space()->check_mangled_unused_area_complete();
1932   }
1933 
1934   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1935 
1936   collection_exit.update();
1937 
1938   heap->print_heap_after_gc();
1939   heap->trace_heap_after_gc(&_gc_tracer);
1940 
1941   log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
1942                          marking_start.ticks(), compaction_start.ticks(),
1943                          collection_exit.ticks());
1944   gc_task_manager()->print_task_time_stamps();
1945 
1946 #ifdef TRACESPINNING
1947   ParallelTaskTerminator::print_termination_counts();
1948 #endif
1949 
1950   AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
1951 
1952   _gc_timer.register_gc_end();
1953 
1954   _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1955   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1956 
1957   return true;
1958 }
1959 
1960 bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
1961                                              PSYoungGen* young_gen,
1962                                              PSOldGen* old_gen) {
1963   MutableSpace* const eden_space = young_gen->eden_space();
1964   assert(!eden_space->is_empty(), "eden must be non-empty");
1965   assert(young_gen->virtual_space()->alignment() ==
1966          old_gen->virtual_space()->alignment(), "alignments do not match");
1967 
1968   if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
1969     return false;
1970   }
1971 
1972   // Both generations must be completely committed.
1973   if (young_gen->virtual_space()->uncommitted_size() != 0) {
1974     return false;
1975   }
1976   if (old_gen->virtual_space()->uncommitted_size() != 0) {
1977     return false;
1978   }
1979 
1980   // Figure out how much to take from eden.  Include the average amount promoted
1981   // in the total; otherwise the next young gen GC will simply bail out to a
1982   // full GC.
1983   const size_t alignment = old_gen->virtual_space()->alignment();
1984   const size_t eden_used = eden_space->used_in_bytes();
1985   const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
1986   const size_t absorb_size = align_up(eden_used + promoted, alignment);
1987   const size_t eden_capacity = eden_space->capacity_in_bytes();
1988 
1989   if (absorb_size >= eden_capacity) {
1990     return false; // Must leave some space in eden.
1991   }
1992 
1993   const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
1994   if (new_young_size < young_gen->min_gen_size()) {
1995     return false; // Respect young gen minimum size.
1996   }
1997 
1998   log_trace(heap, ergo)(" absorbing " SIZE_FORMAT "K:  "
1999                         "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
2000                         "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
2001                         "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
2002                         absorb_size / K,
2003                         eden_capacity / K, (eden_capacity - absorb_size) / K,
2004                         young_gen->from_space()->used_in_bytes() / K,
2005                         young_gen->to_space()->used_in_bytes() / K,
2006                         young_gen->capacity_in_bytes() / K, new_young_size / K);
2007 
2008   // Fill the unused part of the old gen.
2009   MutableSpace* const old_space = old_gen->object_space();
2010   HeapWord* const unused_start = old_space->top();
2011   size_t const unused_words = pointer_delta(old_space->end(), unused_start);
2012 
2013   if (unused_words > 0) {
2014     if (unused_words < CollectedHeap::min_fill_size()) {
2015       return false;  // If the old gen cannot be filled, must give up.
2016     }
2017     CollectedHeap::fill_with_objects(unused_start, unused_words);
2018   }
2019 
2020   // Take the live data from eden and set both top and end in the old gen to
2021   // eden top.  (Need to set end because reset_after_change() mangles the region
2022   // from end to virtual_space->high() in debug builds).
2023   HeapWord* const new_top = eden_space->top();
2024   old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
2025                                         absorb_size);
2026   young_gen->reset_after_change();
2027   old_space->set_top(new_top);
2028   old_space->set_end(new_top);
2029   old_gen->reset_after_change();
2030 
2031   // Update the object start array for the filler object and the data from eden.
2032   ObjectStartArray* const start_array = old_gen->start_array();
2033   for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
2034     start_array->allocate_block(p);
2035   }
2036 
2037   // Could update the promoted average here, but it is not typically updated at
2038   // full GCs and the value to use is unclear.  Something like
2039   //
2040   // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
2041 
2042   size_policy->set_bytes_absorbed_from_eden(absorb_size);
2043   return true;
2044 }
2045 
2046 GCTaskManager* const PSParallelCompact::gc_task_manager() {
2047   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
2048     "shouldn't return NULL");
2049   return ParallelScavengeHeap::gc_task_manager();
2050 }
2051 
2052 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
2053 private:
2054   GCTaskQueue* _q;
2055 
2056 public:
2057   PCAddThreadRootsMarkingTaskClosure(GCTaskQueue* q) : _q(q) { }
2058   void do_thread(Thread* t) {
2059     _q->enqueue(new ThreadRootsMarkingTask(t));
2060   }
2061 };
2062 
2063 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2064                                       bool maximum_heap_compaction,
2065                                       ParallelOldTracer *gc_tracer) {
2066   // Recursively traverse all live objects and mark them
2067   GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
2068 
2069   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2070   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2071   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2072   TaskQueueSetSuper* qset = ParCompactionManager::stack_array();
2073   ParallelTaskTerminator terminator(active_gc_threads, qset);
2074 
2075   ParCompactionManager::MarkAndPushClosure mark_and_push_closure(cm);
2076   ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
2077 
2078   // Need new claim bits before marking starts.
2079   ClassLoaderDataGraph::clear_claimed_marks();
2080 
2081   {
2082     GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
2083 
2084     ParallelScavengeHeap::ParStrongRootsScope psrs;
2085 
2086     GCTaskQueue* q = GCTaskQueue::create();
2087 
2088     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::universe));
2089     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jni_handles));
2090     // We scan the thread roots in parallel
2091     PCAddThreadRootsMarkingTaskClosure cl(q);
2092     Threads::java_threads_and_vm_thread_do(&cl);
2093     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::object_synchronizer));
2094     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::management));
2095     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::system_dictionary));
2096     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::class_loader_data));
2097     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jvmti));
2098     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::code_cache));
2099 
2100     if (active_gc_threads > 1) {
2101       for (uint j = 0; j < active_gc_threads; j++) {
2102         q->enqueue(new StealMarkingTask(&terminator));
2103       }
2104     }
2105 
2106     gc_task_manager()->execute_and_wait(q);
2107   }
2108 
2109   // Process reference objects found during marking
2110   {
2111     GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
2112 
2113     ReferenceProcessorStats stats;
2114     ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
2115 
2116     if (ref_processor()->processing_is_mt()) {
2117       ref_processor()->set_active_mt_degree(active_gc_threads);
2118 
2119       RefProcTaskExecutor task_executor;
2120       stats = ref_processor()->process_discovered_references(
2121         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2122         &task_executor, &pt);
2123     } else {
2124       stats = ref_processor()->process_discovered_references(
2125         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
2126         &pt);
2127     }
2128 
2129     gc_tracer->report_gc_reference_stats(stats);
2130     pt.print_all_references();
2131   }
2132 
2133   // This is the point where the entire marking should have completed.
2134   assert(cm->marking_stacks_empty(), "Marking should have completed");
2135 
2136   {
2137     GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
2138     WeakProcessor::weak_oops_do(is_alive_closure(), &do_nothing_cl);
2139   }
2140 
2141   {
2142     GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
2143 
2144     // Follow system dictionary roots and unload classes.
2145     bool purged_class = SystemDictionary::do_unloading(&_gc_timer);
2146 
2147     // Unload nmethods.
2148     CodeCache::do_unloading(is_alive_closure(), purged_class);
2149 
2150     // Prune dead klasses from subklass/sibling/implementor lists.
2151     Klass::clean_weak_klass_links(purged_class);
2152   }
2153 
2154   {
2155     GCTraceTime(Debug, gc, phases) t("Scrub String Table", &_gc_timer);
2156     // Delete entries for dead interned strings.
2157     StringTable::unlink(is_alive_closure());
2158   }
2159 
2160   {
2161     GCTraceTime(Debug, gc, phases) t("Scrub Symbol Table", &_gc_timer);
2162     // Clean up unreferenced symbols in symbol table.
2163     SymbolTable::unlink();
2164   }
2165 
2166   _gc_tracer.report_object_count_after_gc(is_alive_closure());
2167 }
2168 
2169 void PSParallelCompact::adjust_roots(ParCompactionManager* cm) {
2170   // Adjust the pointers to reflect the new locations
2171   GCTraceTime(Info, gc, phases) tm("Adjust Roots", &_gc_timer);
2172 
2173   // Need new claim bits when tracing through and adjusting pointers.
2174   ClassLoaderDataGraph::clear_claimed_marks();
2175 
2176   PSParallelCompact::AdjustPointerClosure oop_closure(cm);
2177 
2178   // General strong roots.
2179   Universe::oops_do(&oop_closure);
2180   JNIHandles::oops_do(&oop_closure);   // Global (strong) JNI handles
2181   Threads::oops_do(&oop_closure, NULL);
2182   ObjectSynchronizer::oops_do(&oop_closure);
2183   Management::oops_do(&oop_closure);
2184   JvmtiExport::oops_do(&oop_closure);
2185   SystemDictionary::oops_do(&oop_closure);
2186   ClassLoaderDataGraph::oops_do(&oop_closure, true);
2187 
2188   // Now adjust pointers in remaining weak roots.  (All of which should
2189   // have been cleared if they pointed to non-surviving objects.)
2190   WeakProcessor::oops_do(&oop_closure);
2191 
2192   CodeBlobToOopClosure adjust_from_blobs(&oop_closure, CodeBlobToOopClosure::FixRelocations);
2193   CodeCache::blobs_do(&adjust_from_blobs);
2194   AOTLoader::oops_do(&oop_closure);
2195   StringTable::oops_do(&oop_closure);
2196   ref_processor()->weak_oops_do(&oop_closure);
2197   // Roots were visited so references into the young gen in roots
2198   // may have been scanned.  Process them also.
2199   // Should the reference processor have a span that excludes
2200   // young gen objects?
2201   PSScavenge::reference_processor()->weak_oops_do(&oop_closure);
2202 }
2203 
2204 // Helper class to print 8 region numbers per line and then print the total at the end.
2205 class FillableRegionLogger : public StackObj {
2206 private:
2207   Log(gc, compaction) log;
2208   static const int LineLength = 8;
2209   size_t _regions[LineLength];
2210   int _next_index;
2211   bool _enabled;
2212   size_t _total_regions;
2213 public:
2214   FillableRegionLogger() : _next_index(0), _total_regions(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)) { }
2215   ~FillableRegionLogger() {
2216     log.trace(SIZE_FORMAT " initially fillable regions", _total_regions);
2217   }
2218 
2219   void print_line() {
2220     if (!_enabled || _next_index == 0) {
2221       return;
2222     }
2223     FormatBuffer<> line("Fillable: ");
2224     for (int i = 0; i < _next_index; i++) {
2225       line.append(" " SIZE_FORMAT_W(7), _regions[i]);
2226     }
2227     log.trace("%s", line.buffer());
2228     _next_index = 0;
2229   }
2230 
2231   void handle(size_t region) {
2232     if (!_enabled) {
2233       return;
2234     }
2235     _regions[_next_index++] = region;
2236     if (_next_index == LineLength) {
2237       print_line();
2238     }
2239     _total_regions++;
2240   }
2241 };
2242 
2243 void PSParallelCompact::prepare_region_draining_tasks(GCTaskQueue* q,
2244                                                       uint parallel_gc_threads)
2245 {
2246   GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
2247 
2248   // Find the threads that are active
2249   unsigned int which = 0;
2250 
2251   // Find all regions that are available (can be filled immediately) and
2252   // distribute them to the thread stacks.  The iteration is done in reverse
2253   // order (high to low) so the regions will be removed in ascending order.
2254 
2255   const ParallelCompactData& sd = PSParallelCompact::summary_data();
2256 
2257   which = 0;
2258   // id + 1 is used to test termination so unsigned  can
2259   // be used with an old_space_id == 0.
2260   FillableRegionLogger region_logger;
2261   for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2262     SpaceInfo* const space_info = _space_info + id;
2263     MutableSpace* const space = space_info->space();
2264     HeapWord* const new_top = space_info->new_top();
2265 
2266     const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2267     const size_t end_region =
2268       sd.addr_to_region_idx(sd.region_align_up(new_top));
2269 
2270     for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2271       if (sd.region(cur)->claim_unsafe()) {
2272         ParCompactionManager* cm = ParCompactionManager::manager_array(which);
2273         cm->region_stack()->push(cur);
2274         region_logger.handle(cur);
2275         // Assign regions to tasks in round-robin fashion.
2276         if (++which == parallel_gc_threads) {
2277           which = 0;
2278         }
2279       }
2280     }
2281     region_logger.print_line();
2282   }
2283 }
2284 
2285 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2286 
2287 void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q,
2288                                                     uint parallel_gc_threads) {
2289   GCTraceTime(Trace, gc, phases) tm("Dense Prefix Task Setup", &_gc_timer);
2290 
2291   ParallelCompactData& sd = PSParallelCompact::summary_data();
2292 
2293   // Iterate over all the spaces adding tasks for updating
2294   // regions in the dense prefix.  Assume that 1 gc thread
2295   // will work on opening the gaps and the remaining gc threads
2296   // will work on the dense prefix.
2297   unsigned int space_id;
2298   for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2299     HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2300     const MutableSpace* const space = _space_info[space_id].space();
2301 
2302     if (dense_prefix_end == space->bottom()) {
2303       // There is no dense prefix for this space.
2304       continue;
2305     }
2306 
2307     // The dense prefix is before this region.
2308     size_t region_index_end_dense_prefix =
2309         sd.addr_to_region_idx(dense_prefix_end);
2310     RegionData* const dense_prefix_cp =
2311       sd.region(region_index_end_dense_prefix);
2312     assert(dense_prefix_end == space->end() ||
2313            dense_prefix_cp->available() ||
2314            dense_prefix_cp->claimed(),
2315            "The region after the dense prefix should always be ready to fill");
2316 
2317     size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2318 
2319     // Is there dense prefix work?
2320     size_t total_dense_prefix_regions =
2321       region_index_end_dense_prefix - region_index_start;
2322     // How many regions of the dense prefix should be given to
2323     // each thread?
2324     if (total_dense_prefix_regions > 0) {
2325       uint tasks_for_dense_prefix = 1;
2326       if (total_dense_prefix_regions <=
2327           (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2328         // Don't over partition.  This assumes that
2329         // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2330         // so there are not many regions to process.
2331         tasks_for_dense_prefix = parallel_gc_threads;
2332       } else {
2333         // Over partition
2334         tasks_for_dense_prefix = parallel_gc_threads *
2335           PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2336       }
2337       size_t regions_per_thread = total_dense_prefix_regions /
2338         tasks_for_dense_prefix;
2339       // Give each thread at least 1 region.
2340       if (regions_per_thread == 0) {
2341         regions_per_thread = 1;
2342       }
2343 
2344       for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2345         if (region_index_start >= region_index_end_dense_prefix) {
2346           break;
2347         }
2348         // region_index_end is not processed
2349         size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2350                                        region_index_end_dense_prefix);
2351         q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2352                                              region_index_start,
2353                                              region_index_end));
2354         region_index_start = region_index_end;
2355       }
2356     }
2357     // This gets any part of the dense prefix that did not
2358     // fit evenly.
2359     if (region_index_start < region_index_end_dense_prefix) {
2360       q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2361                                            region_index_start,
2362                                            region_index_end_dense_prefix));
2363     }
2364   }
2365 }
2366 
2367 void PSParallelCompact::enqueue_region_stealing_tasks(
2368                                      GCTaskQueue* q,
2369                                      ParallelTaskTerminator* terminator_ptr,
2370                                      uint parallel_gc_threads) {
2371   GCTraceTime(Trace, gc, phases) tm("Steal Task Setup", &_gc_timer);
2372 
2373   // Once a thread has drained it's stack, it should try to steal regions from
2374   // other threads.
2375   for (uint j = 0; j < parallel_gc_threads; j++) {
2376     q->enqueue(new CompactionWithStealingTask(terminator_ptr));
2377   }
2378 }
2379 
2380 #ifdef ASSERT
2381 // Write a histogram of the number of times the block table was filled for a
2382 // region.
2383 void PSParallelCompact::write_block_fill_histogram()
2384 {
2385   if (!log_develop_is_enabled(Trace, gc, compaction)) {
2386     return;
2387   }
2388 
2389   Log(gc, compaction) log;
2390   ResourceMark rm;
2391   LogStream ls(log.trace());
2392   outputStream* out = &ls;
2393 
2394   typedef ParallelCompactData::RegionData rd_t;
2395   ParallelCompactData& sd = summary_data();
2396 
2397   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2398     MutableSpace* const spc = _space_info[id].space();
2399     if (spc->bottom() != spc->top()) {
2400       const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
2401       HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
2402       const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
2403 
2404       size_t histo[5] = { 0, 0, 0, 0, 0 };
2405       const size_t histo_len = sizeof(histo) / sizeof(size_t);
2406       const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
2407 
2408       for (const rd_t* cur = beg; cur < end; ++cur) {
2409         ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
2410       }
2411       out->print("Block fill histogram: %u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
2412       for (size_t i = 0; i < histo_len; ++i) {
2413         out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
2414                    histo[i], 100.0 * histo[i] / region_cnt);
2415       }
2416       out->cr();
2417     }
2418   }
2419 }
2420 #endif // #ifdef ASSERT
2421 
2422 void PSParallelCompact::compact() {
2423   GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
2424 
2425   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2426   PSOldGen* old_gen = heap->old_gen();
2427   old_gen->start_array()->reset();
2428   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2429   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2430   TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2431   ParallelTaskTerminator terminator(active_gc_threads, qset);
2432 
2433   GCTaskQueue* q = GCTaskQueue::create();
2434   prepare_region_draining_tasks(q, active_gc_threads);
2435   enqueue_dense_prefix_tasks(q, active_gc_threads);
2436   enqueue_region_stealing_tasks(q, &terminator, active_gc_threads);
2437 
2438   {
2439     GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
2440 
2441     gc_task_manager()->execute_and_wait(q);
2442 
2443 #ifdef  ASSERT
2444     // Verify that all regions have been processed before the deferred updates.
2445     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2446       verify_complete(SpaceId(id));
2447     }
2448 #endif
2449   }
2450 
2451   {
2452     // Update the deferred objects, if any.  Any compaction manager can be used.
2453     GCTraceTime(Trace, gc, phases) tm("Deferred Updates", &_gc_timer);
2454     ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2455     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2456       update_deferred_objects(cm, SpaceId(id));
2457     }
2458   }
2459 
2460   DEBUG_ONLY(write_block_fill_histogram());
2461 }
2462 
2463 #ifdef  ASSERT
2464 void PSParallelCompact::verify_complete(SpaceId space_id) {
2465   // All Regions between space bottom() to new_top() should be marked as filled
2466   // and all Regions between new_top() and top() should be available (i.e.,
2467   // should have been emptied).
2468   ParallelCompactData& sd = summary_data();
2469   SpaceInfo si = _space_info[space_id];
2470   HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2471   HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2472   const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2473   const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2474   const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2475 
2476   bool issued_a_warning = false;
2477 
2478   size_t cur_region;
2479   for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2480     const RegionData* const c = sd.region(cur_region);
2481     if (!c->completed()) {
2482       log_warning(gc)("region " SIZE_FORMAT " not filled: destination_count=%u",
2483                       cur_region, c->destination_count());
2484       issued_a_warning = true;
2485     }
2486   }
2487 
2488   for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2489     const RegionData* const c = sd.region(cur_region);
2490     if (!c->available()) {
2491       log_warning(gc)("region " SIZE_FORMAT " not empty: destination_count=%u",
2492                       cur_region, c->destination_count());
2493       issued_a_warning = true;
2494     }
2495   }
2496 
2497   if (issued_a_warning) {
2498     print_region_ranges();
2499   }
2500 }
2501 #endif  // #ifdef ASSERT
2502 
2503 inline void UpdateOnlyClosure::do_addr(HeapWord* addr) {
2504   _start_array->allocate_block(addr);
2505   compaction_manager()->update_contents(oop(addr));
2506 }
2507 
2508 // Update interior oops in the ranges of regions [beg_region, end_region).
2509 void
2510 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2511                                                        SpaceId space_id,
2512                                                        size_t beg_region,
2513                                                        size_t end_region) {
2514   ParallelCompactData& sd = summary_data();
2515   ParMarkBitMap* const mbm = mark_bitmap();
2516 
2517   HeapWord* beg_addr = sd.region_to_addr(beg_region);
2518   HeapWord* const end_addr = sd.region_to_addr(end_region);
2519   assert(beg_region <= end_region, "bad region range");
2520   assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2521 
2522 #ifdef  ASSERT
2523   // Claim the regions to avoid triggering an assert when they are marked as
2524   // filled.
2525   for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2526     assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2527   }
2528 #endif  // #ifdef ASSERT
2529 
2530   if (beg_addr != space(space_id)->bottom()) {
2531     // Find the first live object or block of dead space that *starts* in this
2532     // range of regions.  If a partial object crosses onto the region, skip it;
2533     // it will be marked for 'deferred update' when the object head is
2534     // processed.  If dead space crosses onto the region, it is also skipped; it
2535     // will be filled when the prior region is processed.  If neither of those
2536     // apply, the first word in the region is the start of a live object or dead
2537     // space.
2538     assert(beg_addr > space(space_id)->bottom(), "sanity");
2539     const RegionData* const cp = sd.region(beg_region);
2540     if (cp->partial_obj_size() != 0) {
2541       beg_addr = sd.partial_obj_end(beg_region);
2542     } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2543       beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2544     }
2545   }
2546 
2547   if (beg_addr < end_addr) {
2548     // A live object or block of dead space starts in this range of Regions.
2549      HeapWord* const dense_prefix_end = dense_prefix(space_id);
2550 
2551     // Create closures and iterate.
2552     UpdateOnlyClosure update_closure(mbm, cm, space_id);
2553     FillClosure fill_closure(cm, space_id);
2554     ParMarkBitMap::IterationStatus status;
2555     status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2556                           dense_prefix_end);
2557     if (status == ParMarkBitMap::incomplete) {
2558       update_closure.do_addr(update_closure.source());
2559     }
2560   }
2561 
2562   // Mark the regions as filled.
2563   RegionData* const beg_cp = sd.region(beg_region);
2564   RegionData* const end_cp = sd.region(end_region);
2565   for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2566     cp->set_completed();
2567   }
2568 }
2569 
2570 // Return the SpaceId for the space containing addr.  If addr is not in the
2571 // heap, last_space_id is returned.  In debug mode it expects the address to be
2572 // in the heap and asserts such.
2573 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2574   assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
2575 
2576   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2577     if (_space_info[id].space()->contains(addr)) {
2578       return SpaceId(id);
2579     }
2580   }
2581 
2582   assert(false, "no space contains the addr");
2583   return last_space_id;
2584 }
2585 
2586 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2587                                                 SpaceId id) {
2588   assert(id < last_space_id, "bad space id");
2589 
2590   ParallelCompactData& sd = summary_data();
2591   const SpaceInfo* const space_info = _space_info + id;
2592   ObjectStartArray* const start_array = space_info->start_array();
2593 
2594   const MutableSpace* const space = space_info->space();
2595   assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2596   HeapWord* const beg_addr = space_info->dense_prefix();
2597   HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2598 
2599   const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2600   const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2601   const RegionData* cur_region;
2602   for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2603     HeapWord* const addr = cur_region->deferred_obj_addr();
2604     if (addr != NULL) {
2605       if (start_array != NULL) {
2606         start_array->allocate_block(addr);
2607       }
2608       cm->update_contents(oop(addr));
2609       assert(oopDesc::is_oop_or_null(oop(addr)), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(addr)));
2610     }
2611   }
2612 }
2613 
2614 // Skip over count live words starting from beg, and return the address of the
2615 // next live word.  Unless marked, the word corresponding to beg is assumed to
2616 // be dead.  Callers must either ensure beg does not correspond to the middle of
2617 // an object, or account for those live words in some other way.  Callers must
2618 // also ensure that there are enough live words in the range [beg, end) to skip.
2619 HeapWord*
2620 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2621 {
2622   assert(count > 0, "sanity");
2623 
2624   ParMarkBitMap* m = mark_bitmap();
2625   idx_t bits_to_skip = m->words_to_bits(count);
2626   idx_t cur_beg = m->addr_to_bit(beg);
2627   const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end));
2628 
2629   do {
2630     cur_beg = m->find_obj_beg(cur_beg, search_end);
2631     idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2632     const size_t obj_bits = cur_end - cur_beg + 1;
2633     if (obj_bits > bits_to_skip) {
2634       return m->bit_to_addr(cur_beg + bits_to_skip);
2635     }
2636     bits_to_skip -= obj_bits;
2637     cur_beg = cur_end + 1;
2638   } while (bits_to_skip > 0);
2639 
2640   // Skipping the desired number of words landed just past the end of an object.
2641   // Find the start of the next object.
2642   cur_beg = m->find_obj_beg(cur_beg, search_end);
2643   assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2644   return m->bit_to_addr(cur_beg);
2645 }
2646 
2647 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2648                                             SpaceId src_space_id,
2649                                             size_t src_region_idx)
2650 {
2651   assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2652 
2653   const SplitInfo& split_info = _space_info[src_space_id].split_info();
2654   if (split_info.dest_region_addr() == dest_addr) {
2655     // The partial object ending at the split point contains the first word to
2656     // be copied to dest_addr.
2657     return split_info.first_src_addr();
2658   }
2659 
2660   const ParallelCompactData& sd = summary_data();
2661   ParMarkBitMap* const bitmap = mark_bitmap();
2662   const size_t RegionSize = ParallelCompactData::RegionSize;
2663 
2664   assert(sd.is_region_aligned(dest_addr), "not aligned");
2665   const RegionData* const src_region_ptr = sd.region(src_region_idx);
2666   const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2667   HeapWord* const src_region_destination = src_region_ptr->destination();
2668 
2669   assert(dest_addr >= src_region_destination, "wrong src region");
2670   assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2671 
2672   HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2673   HeapWord* const src_region_end = src_region_beg + RegionSize;
2674 
2675   HeapWord* addr = src_region_beg;
2676   if (dest_addr == src_region_destination) {
2677     // Return the first live word in the source region.
2678     if (partial_obj_size == 0) {
2679       addr = bitmap->find_obj_beg(addr, src_region_end);
2680       assert(addr < src_region_end, "no objects start in src region");
2681     }
2682     return addr;
2683   }
2684 
2685   // Must skip some live data.
2686   size_t words_to_skip = dest_addr - src_region_destination;
2687   assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2688 
2689   if (partial_obj_size >= words_to_skip) {
2690     // All the live words to skip are part of the partial object.
2691     addr += words_to_skip;
2692     if (partial_obj_size == words_to_skip) {
2693       // Find the first live word past the partial object.
2694       addr = bitmap->find_obj_beg(addr, src_region_end);
2695       assert(addr < src_region_end, "wrong src region");
2696     }
2697     return addr;
2698   }
2699 
2700   // Skip over the partial object (if any).
2701   if (partial_obj_size != 0) {
2702     words_to_skip -= partial_obj_size;
2703     addr += partial_obj_size;
2704   }
2705 
2706   // Skip over live words due to objects that start in the region.
2707   addr = skip_live_words(addr, src_region_end, words_to_skip);
2708   assert(addr < src_region_end, "wrong src region");
2709   return addr;
2710 }
2711 
2712 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2713                                                      SpaceId src_space_id,
2714                                                      size_t beg_region,
2715                                                      HeapWord* end_addr)
2716 {
2717   ParallelCompactData& sd = summary_data();
2718 
2719 #ifdef ASSERT
2720   MutableSpace* const src_space = _space_info[src_space_id].space();
2721   HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2722   assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2723          "src_space_id does not match beg_addr");
2724   assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2725          "src_space_id does not match end_addr");
2726 #endif // #ifdef ASSERT
2727 
2728   RegionData* const beg = sd.region(beg_region);
2729   RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2730 
2731   // Regions up to new_top() are enqueued if they become available.
2732   HeapWord* const new_top = _space_info[src_space_id].new_top();
2733   RegionData* const enqueue_end =
2734     sd.addr_to_region_ptr(sd.region_align_up(new_top));
2735 
2736   for (RegionData* cur = beg; cur < end; ++cur) {
2737     assert(cur->data_size() > 0, "region must have live data");
2738     cur->decrement_destination_count();
2739     if (cur < enqueue_end && cur->available() && cur->claim()) {
2740       cm->push_region(sd.region(cur));
2741     }
2742   }
2743 }
2744 
2745 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2746                                           SpaceId& src_space_id,
2747                                           HeapWord*& src_space_top,
2748                                           HeapWord* end_addr)
2749 {
2750   typedef ParallelCompactData::RegionData RegionData;
2751 
2752   ParallelCompactData& sd = PSParallelCompact::summary_data();
2753   const size_t region_size = ParallelCompactData::RegionSize;
2754 
2755   size_t src_region_idx = 0;
2756 
2757   // Skip empty regions (if any) up to the top of the space.
2758   HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2759   RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2760   HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2761   const RegionData* const top_region_ptr =
2762     sd.addr_to_region_ptr(top_aligned_up);
2763   while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2764     ++src_region_ptr;
2765   }
2766 
2767   if (src_region_ptr < top_region_ptr) {
2768     // The next source region is in the current space.  Update src_region_idx
2769     // and the source address to match src_region_ptr.
2770     src_region_idx = sd.region(src_region_ptr);
2771     HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
2772     if (src_region_addr > closure.source()) {
2773       closure.set_source(src_region_addr);
2774     }
2775     return src_region_idx;
2776   }
2777 
2778   // Switch to a new source space and find the first non-empty region.
2779   unsigned int space_id = src_space_id + 1;
2780   assert(space_id < last_space_id, "not enough spaces");
2781 
2782   HeapWord* const destination = closure.destination();
2783 
2784   do {
2785     MutableSpace* space = _space_info[space_id].space();
2786     HeapWord* const bottom = space->bottom();
2787     const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
2788 
2789     // Iterate over the spaces that do not compact into themselves.
2790     if (bottom_cp->destination() != bottom) {
2791       HeapWord* const top_aligned_up = sd.region_align_up(space->top());
2792       const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
2793 
2794       for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
2795         if (src_cp->live_obj_size() > 0) {
2796           // Found it.
2797           assert(src_cp->destination() == destination,
2798                  "first live obj in the space must match the destination");
2799           assert(src_cp->partial_obj_size() == 0,
2800                  "a space cannot begin with a partial obj");
2801 
2802           src_space_id = SpaceId(space_id);
2803           src_space_top = space->top();
2804           const size_t src_region_idx = sd.region(src_cp);
2805           closure.set_source(sd.region_to_addr(src_region_idx));
2806           return src_region_idx;
2807         } else {
2808           assert(src_cp->data_size() == 0, "sanity");
2809         }
2810       }
2811     }
2812   } while (++space_id < last_space_id);
2813 
2814   assert(false, "no source region was found");
2815   return 0;
2816 }
2817 
2818 void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx)
2819 {
2820   typedef ParMarkBitMap::IterationStatus IterationStatus;
2821   const size_t RegionSize = ParallelCompactData::RegionSize;
2822   ParMarkBitMap* const bitmap = mark_bitmap();
2823   ParallelCompactData& sd = summary_data();
2824   RegionData* const region_ptr = sd.region(region_idx);
2825 
2826   // Get the items needed to construct the closure.
2827   HeapWord* dest_addr = sd.region_to_addr(region_idx);
2828   SpaceId dest_space_id = space_id(dest_addr);
2829   ObjectStartArray* start_array = _space_info[dest_space_id].start_array();
2830   HeapWord* new_top = _space_info[dest_space_id].new_top();
2831   assert(dest_addr < new_top, "sanity");
2832   const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize);
2833 
2834   // Get the source region and related info.
2835   size_t src_region_idx = region_ptr->source_region();
2836   SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2837   HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2838 
2839   MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
2840   closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2841 
2842   // Adjust src_region_idx to prepare for decrementing destination counts (the
2843   // destination count is not decremented when a region is copied to itself).
2844   if (src_region_idx == region_idx) {
2845     src_region_idx += 1;
2846   }
2847 
2848   if (bitmap->is_unmarked(closure.source())) {
2849     // The first source word is in the middle of an object; copy the remainder
2850     // of the object or as much as will fit.  The fact that pointer updates were
2851     // deferred will be noted when the object header is processed.
2852     HeapWord* const old_src_addr = closure.source();
2853     closure.copy_partial_obj();
2854     if (closure.is_full()) {
2855       decrement_destination_counts(cm, src_space_id, src_region_idx,
2856                                    closure.source());
2857       region_ptr->set_deferred_obj_addr(NULL);
2858       region_ptr->set_completed();
2859       return;
2860     }
2861 
2862     HeapWord* const end_addr = sd.region_align_down(closure.source());
2863     if (sd.region_align_down(old_src_addr) != end_addr) {
2864       // The partial object was copied from more than one source region.
2865       decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2866 
2867       // Move to the next source region, possibly switching spaces as well.  All
2868       // args except end_addr may be modified.
2869       src_region_idx = next_src_region(closure, src_space_id, src_space_top,
2870                                        end_addr);
2871     }
2872   }
2873 
2874   do {
2875     HeapWord* const cur_addr = closure.source();
2876     HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
2877                                     src_space_top);
2878     IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
2879 
2880     if (status == ParMarkBitMap::incomplete) {
2881       // The last obj that starts in the source region does not end in the
2882       // region.
2883       assert(closure.source() < end_addr, "sanity");
2884       HeapWord* const obj_beg = closure.source();
2885       HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
2886                                        src_space_top);
2887       HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
2888       if (obj_end < range_end) {
2889         // The end was found; the entire object will fit.
2890         status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
2891         assert(status != ParMarkBitMap::would_overflow, "sanity");
2892       } else {
2893         // The end was not found; the object will not fit.
2894         assert(range_end < src_space_top, "obj cannot cross space boundary");
2895         status = ParMarkBitMap::would_overflow;
2896       }
2897     }
2898 
2899     if (status == ParMarkBitMap::would_overflow) {
2900       // The last object did not fit.  Note that interior oop updates were
2901       // deferred, then copy enough of the object to fill the region.
2902       region_ptr->set_deferred_obj_addr(closure.destination());
2903       status = closure.copy_until_full(); // copies from closure.source()
2904 
2905       decrement_destination_counts(cm, src_space_id, src_region_idx,
2906                                    closure.source());
2907       region_ptr->set_completed();
2908       return;
2909     }
2910 
2911     if (status == ParMarkBitMap::full) {
2912       decrement_destination_counts(cm, src_space_id, src_region_idx,
2913                                    closure.source());
2914       region_ptr->set_deferred_obj_addr(NULL);
2915       region_ptr->set_completed();
2916       return;
2917     }
2918 
2919     decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2920 
2921     // Move to the next source region, possibly switching spaces as well.  All
2922     // args except end_addr may be modified.
2923     src_region_idx = next_src_region(closure, src_space_id, src_space_top,
2924                                      end_addr);
2925   } while (true);
2926 }
2927 
2928 void PSParallelCompact::fill_blocks(size_t region_idx)
2929 {
2930   // Fill in the block table elements for the specified region.  Each block
2931   // table element holds the number of live words in the region that are to the
2932   // left of the first object that starts in the block.  Thus only blocks in
2933   // which an object starts need to be filled.
2934   //
2935   // The algorithm scans the section of the bitmap that corresponds to the
2936   // region, keeping a running total of the live words.  When an object start is
2937   // found, if it's the first to start in the block that contains it, the
2938   // current total is written to the block table element.
2939   const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
2940   const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
2941   const size_t RegionSize = ParallelCompactData::RegionSize;
2942 
2943   ParallelCompactData& sd = summary_data();
2944   const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
2945   if (partial_obj_size >= RegionSize) {
2946     return; // No objects start in this region.
2947   }
2948 
2949   // Ensure the first loop iteration decides that the block has changed.
2950   size_t cur_block = sd.block_count();
2951 
2952   const ParMarkBitMap* const bitmap = mark_bitmap();
2953 
2954   const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
2955   assert((size_t)1 << Log2BitsPerBlock ==
2956          bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
2957 
2958   size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
2959   const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
2960   size_t live_bits = bitmap->words_to_bits(partial_obj_size);
2961   beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
2962   while (beg_bit < range_end) {
2963     const size_t new_block = beg_bit >> Log2BitsPerBlock;
2964     if (new_block != cur_block) {
2965       cur_block = new_block;
2966       sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
2967     }
2968 
2969     const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
2970     if (end_bit < range_end - 1) {
2971       live_bits += end_bit - beg_bit + 1;
2972       beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
2973     } else {
2974       return;
2975     }
2976   }
2977 }
2978 
2979 void
2980 PSParallelCompact::move_and_update(ParCompactionManager* cm, SpaceId space_id) {
2981   const MutableSpace* sp = space(space_id);
2982   if (sp->is_empty()) {
2983     return;
2984   }
2985 
2986   ParallelCompactData& sd = PSParallelCompact::summary_data();
2987   ParMarkBitMap* const bitmap = mark_bitmap();
2988   HeapWord* const dp_addr = dense_prefix(space_id);
2989   HeapWord* beg_addr = sp->bottom();
2990   HeapWord* end_addr = sp->top();
2991 
2992   assert(beg_addr <= dp_addr && dp_addr <= end_addr, "bad dense prefix");
2993 
2994   const size_t beg_region = sd.addr_to_region_idx(beg_addr);
2995   const size_t dp_region = sd.addr_to_region_idx(dp_addr);
2996   if (beg_region < dp_region) {
2997     update_and_deadwood_in_dense_prefix(cm, space_id, beg_region, dp_region);
2998   }
2999 
3000   // The destination of the first live object that starts in the region is one
3001   // past the end of the partial object entering the region (if any).
3002   HeapWord* const dest_addr = sd.partial_obj_end(dp_region);
3003   HeapWord* const new_top = _space_info[space_id].new_top();
3004   assert(new_top >= dest_addr, "bad new_top value");
3005   const size_t words = pointer_delta(new_top, dest_addr);
3006 
3007   if (words > 0) {
3008     ObjectStartArray* start_array = _space_info[space_id].start_array();
3009     MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3010 
3011     ParMarkBitMap::IterationStatus status;
3012     status = bitmap->iterate(&closure, dest_addr, end_addr);
3013     assert(status == ParMarkBitMap::full, "iteration not complete");
3014     assert(bitmap->find_obj_beg(closure.source(), end_addr) == end_addr,
3015            "live objects skipped because closure is full");
3016   }
3017 }
3018 
3019 jlong PSParallelCompact::millis_since_last_gc() {
3020   // We need a monotonically non-decreasing time in ms but
3021   // os::javaTimeMillis() does not guarantee monotonicity.
3022   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3023   jlong ret_val = now - _time_of_last_gc;
3024   // XXX See note in genCollectedHeap::millis_since_last_gc().
3025   if (ret_val < 0) {
3026     NOT_PRODUCT(log_warning(gc)("time warp: " JLONG_FORMAT, ret_val);)
3027     return 0;
3028   }
3029   return ret_val;
3030 }
3031 
3032 void PSParallelCompact::reset_millis_since_last_gc() {
3033   // We need a monotonically non-decreasing time in ms but
3034   // os::javaTimeMillis() does not guarantee monotonicity.
3035   _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3036 }
3037 
3038 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3039 {
3040   if (source() != destination()) {
3041     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3042     Copy::aligned_conjoint_words(source(), destination(), words_remaining());
3043   }
3044   update_state(words_remaining());
3045   assert(is_full(), "sanity");
3046   return ParMarkBitMap::full;
3047 }
3048 
3049 void MoveAndUpdateClosure::copy_partial_obj()
3050 {
3051   size_t words = words_remaining();
3052 
3053   HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3054   HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3055   if (end_addr < range_end) {
3056     words = bitmap()->obj_size(source(), end_addr);
3057   }
3058 
3059   // This test is necessary; if omitted, the pointer updates to a partial object
3060   // that crosses the dense prefix boundary could be overwritten.
3061   if (source() != destination()) {
3062     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3063     Copy::aligned_conjoint_words(source(), destination(), words);
3064   }
3065   update_state(words);
3066 }
3067 
3068 void InstanceKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
3069   PSParallelCompact::AdjustPointerClosure closure(cm);
3070   oop_oop_iterate_oop_maps<true>(obj, &closure);
3071 }
3072 
3073 void InstanceMirrorKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
3074   InstanceKlass::oop_pc_update_pointers(obj, cm);
3075 
3076   PSParallelCompact::AdjustPointerClosure closure(cm);
3077   oop_oop_iterate_statics<true>(obj, &closure);
3078 }
3079 
3080 void InstanceClassLoaderKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
3081   InstanceKlass::oop_pc_update_pointers(obj, cm);
3082 }
3083 
3084 #ifdef ASSERT
3085 template <class T> static void trace_reference_gc(const char *s, oop obj,
3086                                                   T* referent_addr,
3087                                                   T* discovered_addr) {
3088   log_develop_trace(gc, ref)("%s obj " PTR_FORMAT, s, p2i(obj));
3089   log_develop_trace(gc, ref)("     referent_addr/* " PTR_FORMAT " / " PTR_FORMAT,
3090                              p2i(referent_addr), referent_addr ? p2i((oop)RawAccess<>::oop_load(referent_addr)) : NULL);
3091   log_develop_trace(gc, ref)("     discovered_addr/* " PTR_FORMAT " / " PTR_FORMAT,
3092                              p2i(discovered_addr), discovered_addr ? p2i((oop)RawAccess<>::oop_load(discovered_addr)) : NULL);
3093 }
3094 #endif
3095 
3096 template <class T>
3097 static void oop_pc_update_pointers_specialized(oop obj, ParCompactionManager* cm) {
3098   T* referent_addr = (T*)java_lang_ref_Reference::referent_addr_raw(obj);
3099   PSParallelCompact::adjust_pointer(referent_addr, cm);
3100   T* discovered_addr = (T*)java_lang_ref_Reference::discovered_addr_raw(obj);
3101   PSParallelCompact::adjust_pointer(discovered_addr, cm);
3102   debug_only(trace_reference_gc("InstanceRefKlass::oop_update_ptrs", obj,
3103                                 referent_addr, discovered_addr);)
3104 }
3105 
3106 void InstanceRefKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
3107   InstanceKlass::oop_pc_update_pointers(obj, cm);
3108 
3109   if (UseCompressedOops) {
3110     oop_pc_update_pointers_specialized<narrowOop>(obj, cm);
3111   } else {
3112     oop_pc_update_pointers_specialized<oop>(obj, cm);
3113   }
3114 }
3115 
3116 void ObjArrayKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
3117   assert(obj->is_objArray(), "obj must be obj array");
3118   PSParallelCompact::AdjustPointerClosure closure(cm);
3119   oop_oop_iterate_elements<true>(objArrayOop(obj), &closure);
3120 }
3121 
3122 void TypeArrayKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
3123   assert(obj->is_typeArray(),"must be a type array");
3124 }
3125 
3126 ParMarkBitMapClosure::IterationStatus
3127 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3128   assert(destination() != NULL, "sanity");
3129   assert(bitmap()->obj_size(addr) == words, "bad size");
3130 
3131   _source = addr;
3132   assert(PSParallelCompact::summary_data().calc_new_pointer(source(), compaction_manager()) ==
3133          destination(), "wrong destination");
3134 
3135   if (words > words_remaining()) {
3136     return ParMarkBitMap::would_overflow;
3137   }
3138 
3139   // The start_array must be updated even if the object is not moving.
3140   if (_start_array != NULL) {
3141     _start_array->allocate_block(destination());
3142   }
3143 
3144   if (destination() != source()) {
3145     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3146     Copy::aligned_conjoint_words(source(), destination(), words);
3147   }
3148 
3149   oop moved_oop = (oop) destination();
3150   compaction_manager()->update_contents(moved_oop);
3151   assert(oopDesc::is_oop_or_null(moved_oop), "Expected an oop or NULL at " PTR_FORMAT, p2i(moved_oop));
3152 
3153   update_state(words);
3154   assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
3155   return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3156 }
3157 
3158 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3159                                      ParCompactionManager* cm,
3160                                      PSParallelCompact::SpaceId space_id) :
3161   ParMarkBitMapClosure(mbm, cm),
3162   _space_id(space_id),
3163   _start_array(PSParallelCompact::start_array(space_id))
3164 {
3165 }
3166 
3167 // Updates the references in the object to their new values.
3168 ParMarkBitMapClosure::IterationStatus
3169 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3170   do_addr(addr);
3171   return ParMarkBitMap::incomplete;
3172 }
3173 
3174 FillClosure::FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id) :
3175   ParMarkBitMapClosure(PSParallelCompact::mark_bitmap(), cm),
3176   _start_array(PSParallelCompact::start_array(space_id))
3177 {
3178   assert(space_id == PSParallelCompact::old_space_id,
3179          "cannot use FillClosure in the young gen");
3180 }
3181 
3182 ParMarkBitMapClosure::IterationStatus
3183 FillClosure::do_addr(HeapWord* addr, size_t size) {
3184   CollectedHeap::fill_with_objects(addr, size);
3185   HeapWord* const end = addr + size;
3186   do {
3187     _start_array->allocate_block(addr);
3188     addr += oop(addr)->size();
3189   } while (addr < end);
3190   return ParMarkBitMap::incomplete;
3191 }