1 /*
   2  * Copyright (c) 2005, 2014, 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 "classfile/symbolTable.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "code/codeCache.hpp"
  29 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
  30 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.inline.hpp"
  31 #include "gc_implementation/parallelScavenge/pcTasks.hpp"
  32 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
  33 #include "gc_implementation/parallelScavenge/psCompactionManager.inline.hpp"
  34 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
  35 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp"
  36 #include "gc_implementation/parallelScavenge/psOldGen.hpp"
  37 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
  38 #include "gc_implementation/parallelScavenge/psPromotionManager.inline.hpp"
  39 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
  40 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"
  41 #include "gc_implementation/shared/gcHeapSummary.hpp"
  42 #include "gc_implementation/shared/gcTimer.hpp"
  43 #include "gc_implementation/shared/gcTrace.hpp"
  44 #include "gc_implementation/shared/gcTraceTime.hpp"
  45 #include "gc_implementation/shared/isGCActiveMark.hpp"
  46 #include "gc_interface/gcCause.hpp"
  47 #include "memory/gcLocker.inline.hpp"
  48 #include "memory/referencePolicy.hpp"
  49 #include "memory/referenceProcessor.hpp"
  50 #include "oops/methodData.hpp"
  51 #include "oops/oop.inline.hpp"
  52 #include "oops/oop.pcgc.inline.hpp"
  53 #include "runtime/fprofiler.hpp"
  54 #include "runtime/safepoint.hpp"
  55 #include "runtime/vmThread.hpp"
  56 #include "services/management.hpp"
  57 #include "services/memoryService.hpp"
  58 #include "services/memTracker.hpp"
  59 #include "utilities/events.hpp"
  60 #include "utilities/stack.inline.hpp"
  61 #if INCLUDE_JFR
  62 #include "jfr/jfr.hpp"
  63 #endif // INCLUDE_JFR
  64 
  65 #include <math.h>
  66 
  67 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  68 
  69 // All sizes are in HeapWords.
  70 const size_t ParallelCompactData::Log2RegionSize  = 16; // 64K words
  71 const size_t ParallelCompactData::RegionSize      = (size_t)1 << Log2RegionSize;
  72 const size_t ParallelCompactData::RegionSizeBytes =
  73   RegionSize << LogHeapWordSize;
  74 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
  75 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
  76 const size_t ParallelCompactData::RegionAddrMask       = ~RegionAddrOffsetMask;
  77 
  78 const size_t ParallelCompactData::Log2BlockSize   = 7; // 128 words
  79 const size_t ParallelCompactData::BlockSize       = (size_t)1 << Log2BlockSize;
  80 const size_t ParallelCompactData::BlockSizeBytes  =
  81   BlockSize << LogHeapWordSize;
  82 const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
  83 const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
  84 const size_t ParallelCompactData::BlockAddrMask       = ~BlockAddrOffsetMask;
  85 
  86 const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
  87 const size_t ParallelCompactData::Log2BlocksPerRegion =
  88   Log2RegionSize - Log2BlockSize;
  89 
  90 const ParallelCompactData::RegionData::region_sz_t
  91 ParallelCompactData::RegionData::dc_shift = 27;
  92 
  93 const ParallelCompactData::RegionData::region_sz_t
  94 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
  95 
  96 const ParallelCompactData::RegionData::region_sz_t
  97 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
  98 
  99 const ParallelCompactData::RegionData::region_sz_t
 100 ParallelCompactData::RegionData::los_mask = ~dc_mask;
 101 
 102 const ParallelCompactData::RegionData::region_sz_t
 103 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
 104 
 105 const ParallelCompactData::RegionData::region_sz_t
 106 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
 107 
 108 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
 109 bool      PSParallelCompact::_print_phases = false;
 110 
 111 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
 112 Klass*              PSParallelCompact::_updated_int_array_klass_obj = NULL;
 113 
 114 double PSParallelCompact::_dwl_mean;
 115 double PSParallelCompact::_dwl_std_dev;
 116 double PSParallelCompact::_dwl_first_term;
 117 double PSParallelCompact::_dwl_adjustment;
 118 #ifdef  ASSERT
 119 bool   PSParallelCompact::_dwl_initialized = false;
 120 #endif  // #ifdef ASSERT
 121 
 122 void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
 123                        HeapWord* destination)
 124 {
 125   assert(src_region_idx != 0, "invalid src_region_idx");
 126   assert(partial_obj_size != 0, "invalid partial_obj_size argument");
 127   assert(destination != NULL, "invalid destination argument");
 128 
 129   _src_region_idx = src_region_idx;
 130   _partial_obj_size = partial_obj_size;
 131   _destination = destination;
 132 
 133   // These fields may not be updated below, so make sure they're clear.
 134   assert(_dest_region_addr == NULL, "should have been cleared");
 135   assert(_first_src_addr == NULL, "should have been cleared");
 136 
 137   // Determine the number of destination regions for the partial object.
 138   HeapWord* const last_word = destination + partial_obj_size - 1;
 139   const ParallelCompactData& sd = PSParallelCompact::summary_data();
 140   HeapWord* const beg_region_addr = sd.region_align_down(destination);
 141   HeapWord* const end_region_addr = sd.region_align_down(last_word);
 142 
 143   if (beg_region_addr == end_region_addr) {
 144     // One destination region.
 145     _destination_count = 1;
 146     if (end_region_addr == destination) {
 147       // The destination falls on a region boundary, thus the first word of the
 148       // partial object will be the first word copied to the destination region.
 149       _dest_region_addr = end_region_addr;
 150       _first_src_addr = sd.region_to_addr(src_region_idx);
 151     }
 152   } else {
 153     // Two destination regions.  When copied, the partial object will cross a
 154     // destination region boundary, so a word somewhere within the partial
 155     // object will be the first word copied to the second destination region.
 156     _destination_count = 2;
 157     _dest_region_addr = end_region_addr;
 158     const size_t ofs = pointer_delta(end_region_addr, destination);
 159     assert(ofs < _partial_obj_size, "sanity");
 160     _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
 161   }
 162 }
 163 
 164 void SplitInfo::clear()
 165 {
 166   _src_region_idx = 0;
 167   _partial_obj_size = 0;
 168   _destination = NULL;
 169   _destination_count = 0;
 170   _dest_region_addr = NULL;
 171   _first_src_addr = NULL;
 172   assert(!is_valid(), "sanity");
 173 }
 174 
 175 #ifdef  ASSERT
 176 void SplitInfo::verify_clear()
 177 {
 178   assert(_src_region_idx == 0, "not clear");
 179   assert(_partial_obj_size == 0, "not clear");
 180   assert(_destination == NULL, "not clear");
 181   assert(_destination_count == 0, "not clear");
 182   assert(_dest_region_addr == NULL, "not clear");
 183   assert(_first_src_addr == NULL, "not clear");
 184 }
 185 #endif  // #ifdef ASSERT
 186 
 187 
 188 void PSParallelCompact::print_on_error(outputStream* st) {
 189   _mark_bitmap.print_on_error(st);
 190 }
 191 
 192 #ifndef PRODUCT
 193 const char* PSParallelCompact::space_names[] = {
 194   "old ", "eden", "from", "to  "
 195 };
 196 
 197 void PSParallelCompact::print_region_ranges()
 198 {
 199   tty->print_cr("space  bottom     top        end        new_top");
 200   tty->print_cr("------ ---------- ---------- ---------- ----------");
 201 
 202   for (unsigned int id = 0; id < last_space_id; ++id) {
 203     const MutableSpace* space = _space_info[id].space();
 204     tty->print_cr("%u %s "
 205                   SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
 206                   SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
 207                   id, space_names[id],
 208                   summary_data().addr_to_region_idx(space->bottom()),
 209                   summary_data().addr_to_region_idx(space->top()),
 210                   summary_data().addr_to_region_idx(space->end()),
 211                   summary_data().addr_to_region_idx(_space_info[id].new_top()));
 212   }
 213 }
 214 
 215 void
 216 print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
 217 {
 218 #define REGION_IDX_FORMAT        SIZE_FORMAT_W(7)
 219 #define REGION_DATA_FORMAT       SIZE_FORMAT_W(5)
 220 
 221   ParallelCompactData& sd = PSParallelCompact::summary_data();
 222   size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
 223   tty->print_cr(REGION_IDX_FORMAT " " PTR_FORMAT " "
 224                 REGION_IDX_FORMAT " " PTR_FORMAT " "
 225                 REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
 226                 REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
 227                 i, c->data_location(), dci, c->destination(),
 228                 c->partial_obj_size(), c->live_obj_size(),
 229                 c->data_size(), c->source_region(), c->destination_count());
 230 
 231 #undef  REGION_IDX_FORMAT
 232 #undef  REGION_DATA_FORMAT
 233 }
 234 
 235 void
 236 print_generic_summary_data(ParallelCompactData& summary_data,
 237                            HeapWord* const beg_addr,
 238                            HeapWord* const end_addr)
 239 {
 240   size_t total_words = 0;
 241   size_t i = summary_data.addr_to_region_idx(beg_addr);
 242   const size_t last = summary_data.addr_to_region_idx(end_addr);
 243   HeapWord* pdest = 0;
 244 
 245   while (i <= last) {
 246     ParallelCompactData::RegionData* c = summary_data.region(i);
 247     if (c->data_size() != 0 || c->destination() != pdest) {
 248       print_generic_summary_region(i, c);
 249       total_words += c->data_size();
 250       pdest = c->destination();
 251     }
 252     ++i;
 253   }
 254 
 255   tty->print_cr("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
 256 }
 257 
 258 void
 259 print_generic_summary_data(ParallelCompactData& summary_data,
 260                            SpaceInfo* space_info)
 261 {
 262   for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
 263     const MutableSpace* space = space_info[id].space();
 264     print_generic_summary_data(summary_data, space->bottom(),
 265                                MAX2(space->top(), space_info[id].new_top()));
 266   }
 267 }
 268 
 269 void
 270 print_initial_summary_region(size_t i,
 271                              const ParallelCompactData::RegionData* c,
 272                              bool newline = true)
 273 {
 274   tty->print(SIZE_FORMAT_W(5) " " PTR_FORMAT " "
 275              SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " "
 276              SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 277              i, c->destination(),
 278              c->partial_obj_size(), c->live_obj_size(),
 279              c->data_size(), c->source_region(), c->destination_count());
 280   if (newline) tty->cr();
 281 }
 282 
 283 void
 284 print_initial_summary_data(ParallelCompactData& summary_data,
 285                            const MutableSpace* space) {
 286   if (space->top() == space->bottom()) {
 287     return;
 288   }
 289 
 290   const size_t region_size = ParallelCompactData::RegionSize;
 291   typedef ParallelCompactData::RegionData RegionData;
 292   HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
 293   const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
 294   const RegionData* c = summary_data.region(end_region - 1);
 295   HeapWord* end_addr = c->destination() + c->data_size();
 296   const size_t live_in_space = pointer_delta(end_addr, space->bottom());
 297 
 298   // Print (and count) the full regions at the beginning of the space.
 299   size_t full_region_count = 0;
 300   size_t i = summary_data.addr_to_region_idx(space->bottom());
 301   while (i < end_region && summary_data.region(i)->data_size() == region_size) {
 302     print_initial_summary_region(i, summary_data.region(i));
 303     ++full_region_count;
 304     ++i;
 305   }
 306 
 307   size_t live_to_right = live_in_space - full_region_count * region_size;
 308 
 309   double max_reclaimed_ratio = 0.0;
 310   size_t max_reclaimed_ratio_region = 0;
 311   size_t max_dead_to_right = 0;
 312   size_t max_live_to_right = 0;
 313 
 314   // Print the 'reclaimed ratio' for regions while there is something live in
 315   // the region or to the right of it.  The remaining regions are empty (and
 316   // uninteresting), and computing the ratio will result in division by 0.
 317   while (i < end_region && live_to_right > 0) {
 318     c = summary_data.region(i);
 319     HeapWord* const region_addr = summary_data.region_to_addr(i);
 320     const size_t used_to_right = pointer_delta(space->top(), region_addr);
 321     const size_t dead_to_right = used_to_right - live_to_right;
 322     const double reclaimed_ratio = double(dead_to_right) / live_to_right;
 323 
 324     if (reclaimed_ratio > max_reclaimed_ratio) {
 325             max_reclaimed_ratio = reclaimed_ratio;
 326             max_reclaimed_ratio_region = i;
 327             max_dead_to_right = dead_to_right;
 328             max_live_to_right = live_to_right;
 329     }
 330 
 331     print_initial_summary_region(i, c, false);
 332     tty->print_cr(" %12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
 333                   reclaimed_ratio, dead_to_right, live_to_right);
 334 
 335     live_to_right -= c->data_size();
 336     ++i;
 337   }
 338 
 339   // Any remaining regions are empty.  Print one more if there is one.
 340   if (i < end_region) {
 341     print_initial_summary_region(i, summary_data.region(i));
 342   }
 343 
 344   tty->print_cr("max:  " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " "
 345                 "l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
 346                 max_reclaimed_ratio_region, max_dead_to_right,
 347                 max_live_to_right, max_reclaimed_ratio);
 348 }
 349 
 350 void
 351 print_initial_summary_data(ParallelCompactData& summary_data,
 352                            SpaceInfo* space_info) {
 353   unsigned int id = PSParallelCompact::old_space_id;
 354   const MutableSpace* space;
 355   do {
 356     space = space_info[id].space();
 357     print_initial_summary_data(summary_data, space);
 358   } while (++id < PSParallelCompact::eden_space_id);
 359 
 360   do {
 361     space = space_info[id].space();
 362     print_generic_summary_data(summary_data, space->bottom(), space->top());
 363   } while (++id < PSParallelCompact::last_space_id);
 364 }
 365 #endif  // #ifndef PRODUCT
 366 
 367 #ifdef  ASSERT
 368 size_t add_obj_count;
 369 size_t add_obj_size;
 370 size_t mark_bitmap_count;
 371 size_t mark_bitmap_size;
 372 #endif  // #ifdef ASSERT
 373 
 374 ParallelCompactData::ParallelCompactData()
 375 {
 376   _region_start = 0;
 377 
 378   _region_vspace = 0;
 379   _reserved_byte_size = 0;
 380   _region_data = 0;
 381   _region_count = 0;
 382 
 383   _block_vspace = 0;
 384   _block_data = 0;
 385   _block_count = 0;
 386 }
 387 
 388 bool ParallelCompactData::initialize(MemRegion covered_region)
 389 {
 390   _region_start = covered_region.start();
 391   const size_t region_size = covered_region.word_size();
 392   DEBUG_ONLY(_region_end = _region_start + region_size;)
 393 
 394   assert(region_align_down(_region_start) == _region_start,
 395          "region start not aligned");
 396   assert((region_size & RegionSizeOffsetMask) == 0,
 397          "region size not a multiple of RegionSize");
 398 
 399   bool result = initialize_region_data(region_size) && initialize_block_data();
 400   return result;
 401 }
 402 
 403 PSVirtualSpace*
 404 ParallelCompactData::create_vspace(size_t count, size_t element_size)
 405 {
 406   const size_t raw_bytes = count * element_size;
 407   const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
 408   const size_t granularity = os::vm_allocation_granularity();
 409   _reserved_byte_size = align_size_up(raw_bytes, MAX2(page_sz, granularity));
 410 
 411   const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
 412     MAX2(page_sz, granularity);
 413   ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0);
 414   os::trace_page_sizes("par compact", raw_bytes, raw_bytes, page_sz, rs.base(),
 415                        rs.size());
 416 
 417   MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
 418 
 419   PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
 420   if (vspace != 0) {
 421     if (vspace->expand_by(_reserved_byte_size)) {
 422       return vspace;
 423     }
 424     delete vspace;
 425     // Release memory reserved in the space.
 426     rs.release();
 427   }
 428 
 429   return 0;
 430 }
 431 
 432 bool ParallelCompactData::initialize_region_data(size_t region_size)
 433 {
 434   const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
 435   _region_vspace = create_vspace(count, sizeof(RegionData));
 436   if (_region_vspace != 0) {
 437     _region_data = (RegionData*)_region_vspace->reserved_low_addr();
 438     _region_count = count;
 439     return true;
 440   }
 441   return false;
 442 }
 443 
 444 bool ParallelCompactData::initialize_block_data()
 445 {
 446   assert(_region_count != 0, "region data must be initialized first");
 447   const size_t count = _region_count << Log2BlocksPerRegion;
 448   _block_vspace = create_vspace(count, sizeof(BlockData));
 449   if (_block_vspace != 0) {
 450     _block_data = (BlockData*)_block_vspace->reserved_low_addr();
 451     _block_count = count;
 452     return true;
 453   }
 454   return false;
 455 }
 456 
 457 void ParallelCompactData::clear()
 458 {
 459   memset(_region_data, 0, _region_vspace->committed_size());
 460   memset(_block_data, 0, _block_vspace->committed_size());
 461 }
 462 
 463 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
 464   assert(beg_region <= _region_count, "beg_region out of range");
 465   assert(end_region <= _region_count, "end_region out of range");
 466   assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize");
 467 
 468   const size_t region_cnt = end_region - beg_region;
 469   memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
 470 
 471   const size_t beg_block = beg_region * BlocksPerRegion;
 472   const size_t block_cnt = region_cnt * BlocksPerRegion;
 473   memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData));
 474 }
 475 
 476 HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
 477 {
 478   const RegionData* cur_cp = region(region_idx);
 479   const RegionData* const end_cp = region(region_count() - 1);
 480 
 481   HeapWord* result = region_to_addr(region_idx);
 482   if (cur_cp < end_cp) {
 483     do {
 484       result += cur_cp->partial_obj_size();
 485     } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
 486   }
 487   return result;
 488 }
 489 
 490 void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
 491 {
 492   const size_t obj_ofs = pointer_delta(addr, _region_start);
 493   const size_t beg_region = obj_ofs >> Log2RegionSize;
 494   const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
 495 
 496   DEBUG_ONLY(Atomic::inc_ptr(&add_obj_count);)
 497   DEBUG_ONLY(Atomic::add_ptr(len, &add_obj_size);)
 498 
 499   if (beg_region == end_region) {
 500     // All in one region.
 501     _region_data[beg_region].add_live_obj(len);
 502     return;
 503   }
 504 
 505   // First region.
 506   const size_t beg_ofs = region_offset(addr);
 507   _region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
 508 
 509   Klass* klass = ((oop)addr)->klass();
 510   // Middle regions--completely spanned by this object.
 511   for (size_t region = beg_region + 1; region < end_region; ++region) {
 512     _region_data[region].set_partial_obj_size(RegionSize);
 513     _region_data[region].set_partial_obj_addr(addr);
 514   }
 515 
 516   // Last region.
 517   const size_t end_ofs = region_offset(addr + len - 1);
 518   _region_data[end_region].set_partial_obj_size(end_ofs + 1);
 519   _region_data[end_region].set_partial_obj_addr(addr);
 520 }
 521 
 522 void
 523 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
 524 {
 525   assert(region_offset(beg) == 0, "not RegionSize aligned");
 526   assert(region_offset(end) == 0, "not RegionSize aligned");
 527 
 528   size_t cur_region = addr_to_region_idx(beg);
 529   const size_t end_region = addr_to_region_idx(end);
 530   HeapWord* addr = beg;
 531   while (cur_region < end_region) {
 532     _region_data[cur_region].set_destination(addr);
 533     _region_data[cur_region].set_destination_count(0);
 534     _region_data[cur_region].set_source_region(cur_region);
 535     _region_data[cur_region].set_data_location(addr);
 536 
 537     // Update live_obj_size so the region appears completely full.
 538     size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
 539     _region_data[cur_region].set_live_obj_size(live_size);
 540 
 541     ++cur_region;
 542     addr += RegionSize;
 543   }
 544 }
 545 
 546 // Find the point at which a space can be split and, if necessary, record the
 547 // split point.
 548 //
 549 // If the current src region (which overflowed the destination space) doesn't
 550 // have a partial object, the split point is at the beginning of the current src
 551 // region (an "easy" split, no extra bookkeeping required).
 552 //
 553 // If the current src region has a partial object, the split point is in the
 554 // region where that partial object starts (call it the split_region).  If
 555 // split_region has a partial object, then the split point is just after that
 556 // partial object (a "hard" split where we have to record the split data and
 557 // zero the partial_obj_size field).  With a "hard" split, we know that the
 558 // partial_obj ends within split_region because the partial object that caused
 559 // the overflow starts in split_region.  If split_region doesn't have a partial
 560 // obj, then the split is at the beginning of split_region (another "easy"
 561 // split).
 562 HeapWord*
 563 ParallelCompactData::summarize_split_space(size_t src_region,
 564                                            SplitInfo& split_info,
 565                                            HeapWord* destination,
 566                                            HeapWord* target_end,
 567                                            HeapWord** target_next)
 568 {
 569   assert(destination <= target_end, "sanity");
 570   assert(destination + _region_data[src_region].data_size() > target_end,
 571     "region should not fit into target space");
 572   assert(is_region_aligned(target_end), "sanity");
 573 
 574   size_t split_region = src_region;
 575   HeapWord* split_destination = destination;
 576   size_t partial_obj_size = _region_data[src_region].partial_obj_size();
 577 
 578   if (destination + partial_obj_size > target_end) {
 579     // The split point is just after the partial object (if any) in the
 580     // src_region that contains the start of the object that overflowed the
 581     // destination space.
 582     //
 583     // Find the start of the "overflow" object and set split_region to the
 584     // region containing it.
 585     HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
 586     split_region = addr_to_region_idx(overflow_obj);
 587 
 588     // Clear the source_region field of all destination regions whose first word
 589     // came from data after the split point (a non-null source_region field
 590     // implies a region must be filled).
 591     //
 592     // An alternative to the simple loop below:  clear during post_compact(),
 593     // which uses memcpy instead of individual stores, and is easy to
 594     // parallelize.  (The downside is that it clears the entire RegionData
 595     // object as opposed to just one field.)
 596     //
 597     // post_compact() would have to clear the summary data up to the highest
 598     // address that was written during the summary phase, which would be
 599     //
 600     //         max(top, max(new_top, clear_top))
 601     //
 602     // where clear_top is a new field in SpaceInfo.  Would have to set clear_top
 603     // to target_end.
 604     const RegionData* const sr = region(split_region);
 605     const size_t beg_idx =
 606       addr_to_region_idx(region_align_up(sr->destination() +
 607                                          sr->partial_obj_size()));
 608     const size_t end_idx = addr_to_region_idx(target_end);
 609 
 610     if (TraceParallelOldGCSummaryPhase) {
 611         gclog_or_tty->print_cr("split:  clearing source_region field in ["
 612                                SIZE_FORMAT ", " SIZE_FORMAT ")",
 613                                beg_idx, end_idx);
 614     }
 615     for (size_t idx = beg_idx; idx < end_idx; ++idx) {
 616       _region_data[idx].set_source_region(0);
 617     }
 618 
 619     // Set split_destination and partial_obj_size to reflect the split region.
 620     split_destination = sr->destination();
 621     partial_obj_size = sr->partial_obj_size();
 622   }
 623 
 624   // The split is recorded only if a partial object extends onto the region.
 625   if (partial_obj_size != 0) {
 626     _region_data[split_region].set_partial_obj_size(0);
 627     split_info.record(split_region, partial_obj_size, split_destination);
 628   }
 629 
 630   // Setup the continuation addresses.
 631   *target_next = split_destination + partial_obj_size;
 632   HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
 633 
 634   if (TraceParallelOldGCSummaryPhase) {
 635     const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
 636     gclog_or_tty->print_cr("%s split:  src=" PTR_FORMAT " src_c=" SIZE_FORMAT
 637                            " pos=" SIZE_FORMAT,
 638                            split_type, source_next, split_region,
 639                            partial_obj_size);
 640     gclog_or_tty->print_cr("%s split:  dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT
 641                            " tn=" PTR_FORMAT,
 642                            split_type, split_destination,
 643                            addr_to_region_idx(split_destination),
 644                            *target_next);
 645 
 646     if (partial_obj_size != 0) {
 647       HeapWord* const po_beg = split_info.destination();
 648       HeapWord* const po_end = po_beg + split_info.partial_obj_size();
 649       gclog_or_tty->print_cr("%s split:  "
 650                              "po_beg=" PTR_FORMAT " " SIZE_FORMAT " "
 651                              "po_end=" PTR_FORMAT " " SIZE_FORMAT,
 652                              split_type,
 653                              po_beg, addr_to_region_idx(po_beg),
 654                              po_end, addr_to_region_idx(po_end));
 655     }
 656   }
 657 
 658   return source_next;
 659 }
 660 
 661 bool ParallelCompactData::summarize(SplitInfo& split_info,
 662                                     HeapWord* source_beg, HeapWord* source_end,
 663                                     HeapWord** source_next,
 664                                     HeapWord* target_beg, HeapWord* target_end,
 665                                     HeapWord** target_next)
 666 {
 667   if (TraceParallelOldGCSummaryPhase) {
 668     HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
 669     tty->print_cr("sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
 670                   "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
 671                   source_beg, source_end, source_next_val,
 672                   target_beg, target_end, *target_next);
 673   }
 674 
 675   size_t cur_region = addr_to_region_idx(source_beg);
 676   const size_t end_region = addr_to_region_idx(region_align_up(source_end));
 677 
 678   HeapWord *dest_addr = target_beg;
 679   while (cur_region < end_region) {
 680     // The destination must be set even if the region has no data.
 681     _region_data[cur_region].set_destination(dest_addr);
 682 
 683     size_t words = _region_data[cur_region].data_size();
 684     if (words > 0) {
 685       // If cur_region does not fit entirely into the target space, find a point
 686       // at which the source space can be 'split' so that part is copied to the
 687       // target space and the rest is copied elsewhere.
 688       if (dest_addr + words > target_end) {
 689         assert(source_next != NULL, "source_next is NULL when splitting");
 690         *source_next = summarize_split_space(cur_region, split_info, dest_addr,
 691                                              target_end, target_next);
 692         return false;
 693       }
 694 
 695       // Compute the destination_count for cur_region, and if necessary, update
 696       // source_region for a destination region.  The source_region field is
 697       // updated if cur_region is the first (left-most) region to be copied to a
 698       // destination region.
 699       //
 700       // The destination_count calculation is a bit subtle.  A region that has
 701       // data that compacts into itself does not count itself as a destination.
 702       // This maintains the invariant that a zero count means the region is
 703       // available and can be claimed and then filled.
 704       uint destination_count = 0;
 705       if (split_info.is_split(cur_region)) {
 706         // The current region has been split:  the partial object will be copied
 707         // to one destination space and the remaining data will be copied to
 708         // another destination space.  Adjust the initial destination_count and,
 709         // if necessary, set the source_region field if the partial object will
 710         // cross a destination region boundary.
 711         destination_count = split_info.destination_count();
 712         if (destination_count == 2) {
 713           size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
 714           _region_data[dest_idx].set_source_region(cur_region);
 715         }
 716       }
 717 
 718       HeapWord* const last_addr = dest_addr + words - 1;
 719       const size_t dest_region_1 = addr_to_region_idx(dest_addr);
 720       const size_t dest_region_2 = addr_to_region_idx(last_addr);
 721 
 722       // Initially assume that the destination regions will be the same and
 723       // adjust the value below if necessary.  Under this assumption, if
 724       // cur_region == dest_region_2, then cur_region will be compacted
 725       // completely into itself.
 726       destination_count += cur_region == dest_region_2 ? 0 : 1;
 727       if (dest_region_1 != dest_region_2) {
 728         // Destination regions differ; adjust destination_count.
 729         destination_count += 1;
 730         // Data from cur_region will be copied to the start of dest_region_2.
 731         _region_data[dest_region_2].set_source_region(cur_region);
 732       } else if (region_offset(dest_addr) == 0) {
 733         // Data from cur_region will be copied to the start of the destination
 734         // region.
 735         _region_data[dest_region_1].set_source_region(cur_region);
 736       }
 737 
 738       _region_data[cur_region].set_destination_count(destination_count);
 739       _region_data[cur_region].set_data_location(region_to_addr(cur_region));
 740       dest_addr += words;
 741     }
 742 
 743     ++cur_region;
 744   }
 745 
 746   *target_next = dest_addr;
 747   return true;
 748 }
 749 
 750 HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr) {
 751   assert(addr != NULL, "Should detect NULL oop earlier");
 752   assert(PSParallelCompact::gc_heap()->is_in(addr), "not in heap");
 753   assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked");
 754 
 755   // Region covering the object.
 756   RegionData* const region_ptr = addr_to_region_ptr(addr);
 757   HeapWord* result = region_ptr->destination();
 758 
 759   // If the entire Region is live, the new location is region->destination + the
 760   // offset of the object within in the Region.
 761 
 762   // Run some performance tests to determine if this special case pays off.  It
 763   // is worth it for pointers into the dense prefix.  If the optimization to
 764   // avoid pointer updates in regions that only point to the dense prefix is
 765   // ever implemented, this should be revisited.
 766   if (region_ptr->data_size() == RegionSize) {
 767     result += region_offset(addr);
 768     return result;
 769   }
 770 
 771   // Otherwise, the new location is region->destination + block offset + the
 772   // number of live words in the Block that are (a) to the left of addr and (b)
 773   // due to objects that start in the Block.
 774 
 775   // Fill in the block table if necessary.  This is unsynchronized, so multiple
 776   // threads may fill the block table for a region (harmless, since it is
 777   // idempotent).
 778   if (!region_ptr->blocks_filled()) {
 779     PSParallelCompact::fill_blocks(addr_to_region_idx(addr));
 780     region_ptr->set_blocks_filled();
 781   }
 782 
 783   HeapWord* const search_start = block_align_down(addr);
 784   const size_t block_offset = addr_to_block_ptr(addr)->offset();
 785 
 786   const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
 787   const size_t live = bitmap->live_words_in_range(search_start, oop(addr));
 788   result += block_offset + live;
 789   DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result));
 790   return result;
 791 }
 792 
 793 #ifdef ASSERT
 794 void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
 795 {
 796   const size_t* const beg = (const size_t*)vspace->committed_low_addr();
 797   const size_t* const end = (const size_t*)vspace->committed_high_addr();
 798   for (const size_t* p = beg; p < end; ++p) {
 799     assert(*p == 0, "not zero");
 800   }
 801 }
 802 
 803 void ParallelCompactData::verify_clear()
 804 {
 805   verify_clear(_region_vspace);
 806   verify_clear(_block_vspace);
 807 }
 808 #endif  // #ifdef ASSERT
 809 
 810 STWGCTimer          PSParallelCompact::_gc_timer;
 811 ParallelOldTracer   PSParallelCompact::_gc_tracer;
 812 elapsedTimer        PSParallelCompact::_accumulated_time;
 813 unsigned int        PSParallelCompact::_total_invocations = 0;
 814 unsigned int        PSParallelCompact::_maximum_compaction_gc_num = 0;
 815 jlong               PSParallelCompact::_time_of_last_gc = 0;
 816 CollectorCounters*  PSParallelCompact::_counters = NULL;
 817 ParMarkBitMap       PSParallelCompact::_mark_bitmap;
 818 ParallelCompactData PSParallelCompact::_summary_data;
 819 
 820 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
 821 
 822 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
 823 
 824 void PSParallelCompact::KeepAliveClosure::do_oop(oop* p)       { PSParallelCompact::KeepAliveClosure::do_oop_work(p); }
 825 void PSParallelCompact::KeepAliveClosure::do_oop(narrowOop* p) { PSParallelCompact::KeepAliveClosure::do_oop_work(p); }
 826 
 827 PSParallelCompact::AdjustPointerClosure PSParallelCompact::_adjust_pointer_closure;
 828 PSParallelCompact::AdjustKlassClosure PSParallelCompact::_adjust_klass_closure;
 829 
 830 void PSParallelCompact::AdjustPointerClosure::do_oop(oop* p)       { adjust_pointer(p); }
 831 void PSParallelCompact::AdjustPointerClosure::do_oop(narrowOop* p) { adjust_pointer(p); }
 832 
 833 void PSParallelCompact::FollowStackClosure::do_void() { _compaction_manager->follow_marking_stacks(); }
 834 
 835 void PSParallelCompact::MarkAndPushClosure::do_oop(oop* p)       {
 836   mark_and_push(_compaction_manager, p);
 837 }
 838 void PSParallelCompact::MarkAndPushClosure::do_oop(narrowOop* p) { mark_and_push(_compaction_manager, p); }
 839 
 840 void PSParallelCompact::FollowKlassClosure::do_klass(Klass* klass) {
 841   klass->oops_do(_mark_and_push_closure);
 842 }
 843 void PSParallelCompact::AdjustKlassClosure::do_klass(Klass* klass) {
 844   klass->oops_do(&PSParallelCompact::_adjust_pointer_closure);
 845 }
 846 
 847 void PSParallelCompact::post_initialize() {
 848   ParallelScavengeHeap* heap = gc_heap();
 849   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 850 
 851   MemRegion mr = heap->reserved_region();
 852   _ref_processor =
 853     new ReferenceProcessor(mr,            // span
 854                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 855                            (int) ParallelGCThreads, // mt processing degree
 856                            true,          // mt discovery
 857                            (int) ParallelGCThreads, // mt discovery degree
 858                            true,          // atomic_discovery
 859                            &_is_alive_closure); // non-header is alive closure
 860   _counters = new CollectorCounters("PSParallelCompact", 1);
 861 
 862   // Initialize static fields in ParCompactionManager.
 863   ParCompactionManager::initialize(mark_bitmap());
 864 }
 865 
 866 bool PSParallelCompact::initialize() {
 867   ParallelScavengeHeap* heap = gc_heap();
 868   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 869   MemRegion mr = heap->reserved_region();
 870 
 871   // Was the old gen get allocated successfully?
 872   if (!heap->old_gen()->is_allocated()) {
 873     return false;
 874   }
 875 
 876   initialize_space_info();
 877   initialize_dead_wood_limiter();
 878 
 879   if (!_mark_bitmap.initialize(mr)) {
 880     vm_shutdown_during_initialization(
 881       err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
 882       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 883       _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
 884     return false;
 885   }
 886 
 887   if (!_summary_data.initialize(mr)) {
 888     vm_shutdown_during_initialization(
 889       err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
 890       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 891       _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
 892     return false;
 893   }
 894 
 895   return true;
 896 }
 897 
 898 void PSParallelCompact::initialize_space_info()
 899 {
 900   memset(&_space_info, 0, sizeof(_space_info));
 901 
 902   ParallelScavengeHeap* heap = gc_heap();
 903   PSYoungGen* young_gen = heap->young_gen();
 904 
 905   _space_info[old_space_id].set_space(heap->old_gen()->object_space());
 906   _space_info[eden_space_id].set_space(young_gen->eden_space());
 907   _space_info[from_space_id].set_space(young_gen->from_space());
 908   _space_info[to_space_id].set_space(young_gen->to_space());
 909 
 910   _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
 911 }
 912 
 913 void PSParallelCompact::initialize_dead_wood_limiter()
 914 {
 915   const size_t max = 100;
 916   _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
 917   _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
 918   _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
 919   DEBUG_ONLY(_dwl_initialized = true;)
 920   _dwl_adjustment = normal_distribution(1.0);
 921 }
 922 
 923 // Simple class for storing info about the heap at the start of GC, to be used
 924 // after GC for comparison/printing.
 925 class PreGCValues {
 926 public:
 927   PreGCValues() { }
 928   PreGCValues(ParallelScavengeHeap* heap) { fill(heap); }
 929 
 930   void fill(ParallelScavengeHeap* heap) {
 931     _heap_used      = heap->used();
 932     _young_gen_used = heap->young_gen()->used_in_bytes();
 933     _old_gen_used   = heap->old_gen()->used_in_bytes();
 934     _metadata_used  = MetaspaceAux::used_bytes();
 935   };
 936 
 937   size_t heap_used() const      { return _heap_used; }
 938   size_t young_gen_used() const { return _young_gen_used; }
 939   size_t old_gen_used() const   { return _old_gen_used; }
 940   size_t metadata_used() const  { return _metadata_used; }
 941 
 942 private:
 943   size_t _heap_used;
 944   size_t _young_gen_used;
 945   size_t _old_gen_used;
 946   size_t _metadata_used;
 947 };
 948 
 949 void
 950 PSParallelCompact::clear_data_covering_space(SpaceId id)
 951 {
 952   // At this point, top is the value before GC, new_top() is the value that will
 953   // be set at the end of GC.  The marking bitmap is cleared to top; nothing
 954   // should be marked above top.  The summary data is cleared to the larger of
 955   // top & new_top.
 956   MutableSpace* const space = _space_info[id].space();
 957   HeapWord* const bot = space->bottom();
 958   HeapWord* const top = space->top();
 959   HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
 960 
 961   const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
 962   const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top));
 963   _mark_bitmap.clear_range(beg_bit, end_bit);
 964 
 965   const size_t beg_region = _summary_data.addr_to_region_idx(bot);
 966   const size_t end_region =
 967     _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
 968   _summary_data.clear_range(beg_region, end_region);
 969 
 970   // Clear the data used to 'split' regions.
 971   SplitInfo& split_info = _space_info[id].split_info();
 972   if (split_info.is_valid()) {
 973     split_info.clear();
 974   }
 975   DEBUG_ONLY(split_info.verify_clear();)
 976 }
 977 
 978 void PSParallelCompact::pre_compact(PreGCValues* pre_gc_values)
 979 {
 980   // Update the from & to space pointers in space_info, since they are swapped
 981   // at each young gen gc.  Do the update unconditionally (even though a
 982   // promotion failure does not swap spaces) because an unknown number of minor
 983   // collections will have swapped the spaces an unknown number of times.
 984   GCTraceTime tm("pre compact", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
 985   ParallelScavengeHeap* heap = gc_heap();
 986   _space_info[from_space_id].set_space(heap->young_gen()->from_space());
 987   _space_info[to_space_id].set_space(heap->young_gen()->to_space());
 988 
 989   pre_gc_values->fill(heap);
 990 
 991   DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
 992   DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
 993 
 994   // Increment the invocation count
 995   heap->increment_total_collections(true);
 996 
 997   // We need to track unique mark sweep invocations as well.
 998   _total_invocations++;
 999 
1000   heap->print_heap_before_gc();
1001   heap->trace_heap_before_gc(&_gc_tracer);
1002 
1003   // Fill in TLABs
1004   heap->accumulate_statistics_all_tlabs();
1005   heap->ensure_parsability(true);  // retire TLABs
1006 
1007   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
1008     HandleMark hm;  // Discard invalid handles created during verification
1009     Universe::verify(" VerifyBeforeGC:");
1010   }
1011 
1012   // Verify object start arrays
1013   if (VerifyObjectStartArray &&
1014       VerifyBeforeGC) {
1015     heap->old_gen()->verify_object_start_array();
1016   }
1017 
1018   DEBUG_ONLY(mark_bitmap()->verify_clear();)
1019   DEBUG_ONLY(summary_data().verify_clear();)
1020 
1021   // Have worker threads release resources the next time they run a task.
1022   gc_task_manager()->release_all_resources();
1023 }
1024 
1025 void PSParallelCompact::post_compact()
1026 {
1027   GCTraceTime tm("post compact", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
1028 
1029   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1030     // Clear the marking bitmap, summary data and split info.
1031     clear_data_covering_space(SpaceId(id));
1032     // Update top().  Must be done after clearing the bitmap and summary data.
1033     _space_info[id].publish_new_top();
1034   }
1035 
1036   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1037   MutableSpace* const from_space = _space_info[from_space_id].space();
1038   MutableSpace* const to_space   = _space_info[to_space_id].space();
1039 
1040   ParallelScavengeHeap* heap = gc_heap();
1041   bool eden_empty = eden_space->is_empty();
1042   if (!eden_empty) {
1043     eden_empty = absorb_live_data_from_eden(heap->size_policy(),
1044                                             heap->young_gen(), heap->old_gen());
1045   }
1046 
1047   // Update heap occupancy information which is used as input to the soft ref
1048   // clearing policy at the next gc.
1049   Universe::update_heap_info_at_gc();
1050 
1051   bool young_gen_empty = eden_empty && from_space->is_empty() &&
1052     to_space->is_empty();
1053 
1054   BarrierSet* bs = heap->barrier_set();
1055   if (bs->is_a(BarrierSet::ModRef)) {
1056     ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
1057     MemRegion old_mr = heap->old_gen()->reserved();
1058 
1059     if (young_gen_empty) {
1060       modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
1061     } else {
1062       modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1063     }
1064   }
1065 
1066   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1067   ClassLoaderDataGraph::purge();
1068   MetaspaceAux::verify_metrics();
1069 
1070   Threads::gc_epilogue();
1071   CodeCache::gc_epilogue();
1072   JvmtiExport::gc_epilogue();
1073 
1074   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1075 
1076   ref_processor()->enqueue_discovered_references(NULL);
1077 
1078   if (ZapUnusedHeapArea) {
1079     heap->gen_mangle_unused_area();
1080   }
1081 
1082   // Update time of last GC
1083   reset_millis_since_last_gc();
1084 }
1085 
1086 HeapWord*
1087 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1088                                                     bool maximum_compaction)
1089 {
1090   const size_t region_size = ParallelCompactData::RegionSize;
1091   const ParallelCompactData& sd = summary_data();
1092 
1093   const MutableSpace* const space = _space_info[id].space();
1094   HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1095   const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1096   const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1097 
1098   // Skip full regions at the beginning of the space--they are necessarily part
1099   // of the dense prefix.
1100   size_t full_count = 0;
1101   const RegionData* cp;
1102   for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1103     ++full_count;
1104   }
1105 
1106   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1107   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1108   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1109   if (maximum_compaction || cp == end_cp || interval_ended) {
1110     _maximum_compaction_gc_num = total_invocations();
1111     return sd.region_to_addr(cp);
1112   }
1113 
1114   HeapWord* const new_top = _space_info[id].new_top();
1115   const size_t space_live = pointer_delta(new_top, space->bottom());
1116   const size_t space_used = space->used_in_words();
1117   const size_t space_capacity = space->capacity_in_words();
1118 
1119   const double cur_density = double(space_live) / space_capacity;
1120   const double deadwood_density =
1121     (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1122   const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1123 
1124   if (TraceParallelOldGCDensePrefix) {
1125     tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1126                   cur_density, deadwood_density, deadwood_goal);
1127     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1128                   "space_cap=" SIZE_FORMAT,
1129                   space_live, space_used,
1130                   space_capacity);
1131   }
1132 
1133   // XXX - Use binary search?
1134   HeapWord* dense_prefix = sd.region_to_addr(cp);
1135   const RegionData* full_cp = cp;
1136   const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1137   while (cp < end_cp) {
1138     HeapWord* region_destination = cp->destination();
1139     const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1140     if (TraceParallelOldGCDensePrefix && Verbose) {
1141       tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1142                     "dp=" SIZE_FORMAT_W(8) " " "cdw=" SIZE_FORMAT_W(8),
1143                     sd.region(cp), region_destination,
1144                     dense_prefix, cur_deadwood);
1145     }
1146 
1147     if (cur_deadwood >= deadwood_goal) {
1148       // Found the region that has the correct amount of deadwood to the left.
1149       // This typically occurs after crossing a fairly sparse set of regions, so
1150       // iterate backwards over those sparse regions, looking for the region
1151       // that has the lowest density of live objects 'to the right.'
1152       size_t space_to_left = sd.region(cp) * region_size;
1153       size_t live_to_left = space_to_left - cur_deadwood;
1154       size_t space_to_right = space_capacity - space_to_left;
1155       size_t live_to_right = space_live - live_to_left;
1156       double density_to_right = double(live_to_right) / space_to_right;
1157       while (cp > full_cp) {
1158         --cp;
1159         const size_t prev_region_live_to_right = live_to_right -
1160           cp->data_size();
1161         const size_t prev_region_space_to_right = space_to_right + region_size;
1162         double prev_region_density_to_right =
1163           double(prev_region_live_to_right) / prev_region_space_to_right;
1164         if (density_to_right <= prev_region_density_to_right) {
1165           return dense_prefix;
1166         }
1167         if (TraceParallelOldGCDensePrefix && Verbose) {
1168           tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1169                         "pc_d2r=%10.8f", sd.region(cp), density_to_right,
1170                         prev_region_density_to_right);
1171         }
1172         dense_prefix -= region_size;
1173         live_to_right = prev_region_live_to_right;
1174         space_to_right = prev_region_space_to_right;
1175         density_to_right = prev_region_density_to_right;
1176       }
1177       return dense_prefix;
1178     }
1179 
1180     dense_prefix += region_size;
1181     ++cp;
1182   }
1183 
1184   return dense_prefix;
1185 }
1186 
1187 #ifndef PRODUCT
1188 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1189                                                  const SpaceId id,
1190                                                  const bool maximum_compaction,
1191                                                  HeapWord* const addr)
1192 {
1193   const size_t region_idx = summary_data().addr_to_region_idx(addr);
1194   RegionData* const cp = summary_data().region(region_idx);
1195   const MutableSpace* const space = _space_info[id].space();
1196   HeapWord* const new_top = _space_info[id].new_top();
1197 
1198   const size_t space_live = pointer_delta(new_top, space->bottom());
1199   const size_t dead_to_left = pointer_delta(addr, cp->destination());
1200   const size_t space_cap = space->capacity_in_words();
1201   const double dead_to_left_pct = double(dead_to_left) / space_cap;
1202   const size_t live_to_right = new_top - cp->destination();
1203   const size_t dead_to_right = space->top() - addr - live_to_right;
1204 
1205   tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1206                 "spl=" SIZE_FORMAT " "
1207                 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1208                 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
1209                 " ratio=%10.8f",
1210                 algorithm, addr, region_idx,
1211                 space_live,
1212                 dead_to_left, dead_to_left_pct,
1213                 dead_to_right, live_to_right,
1214                 double(dead_to_right) / live_to_right);
1215 }
1216 #endif  // #ifndef PRODUCT
1217 
1218 // Return a fraction indicating how much of the generation can be treated as
1219 // "dead wood" (i.e., not reclaimed).  The function uses a normal distribution
1220 // based on the density of live objects in the generation to determine a limit,
1221 // which is then adjusted so the return value is min_percent when the density is
1222 // 1.
1223 //
1224 // The following table shows some return values for a different values of the
1225 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1226 // min_percent is 1.
1227 //
1228 //                          fraction allowed as dead wood
1229 //         -----------------------------------------------------------------
1230 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1231 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1232 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1233 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1234 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1235 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1236 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1237 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1238 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1239 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1240 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1241 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1242 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1243 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1244 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1245 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1246 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1247 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1248 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1249 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1250 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1251 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1252 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1253 
1254 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1255 {
1256   assert(_dwl_initialized, "uninitialized");
1257 
1258   // The raw limit is the value of the normal distribution at x = density.
1259   const double raw_limit = normal_distribution(density);
1260 
1261   // Adjust the raw limit so it becomes the minimum when the density is 1.
1262   //
1263   // First subtract the adjustment value (which is simply the precomputed value
1264   // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1265   // Then add the minimum value, so the minimum is returned when the density is
1266   // 1.  Finally, prevent negative values, which occur when the mean is not 0.5.
1267   const double min = double(min_percent) / 100.0;
1268   const double limit = raw_limit - _dwl_adjustment + min;
1269   return MAX2(limit, 0.0);
1270 }
1271 
1272 ParallelCompactData::RegionData*
1273 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1274                                            const RegionData* end)
1275 {
1276   const size_t region_size = ParallelCompactData::RegionSize;
1277   ParallelCompactData& sd = summary_data();
1278   size_t left = sd.region(beg);
1279   size_t right = end > beg ? sd.region(end) - 1 : left;
1280 
1281   // Binary search.
1282   while (left < right) {
1283     // Equivalent to (left + right) / 2, but does not overflow.
1284     const size_t middle = left + (right - left) / 2;
1285     RegionData* const middle_ptr = sd.region(middle);
1286     HeapWord* const dest = middle_ptr->destination();
1287     HeapWord* const addr = sd.region_to_addr(middle);
1288     assert(dest != NULL, "sanity");
1289     assert(dest <= addr, "must move left");
1290 
1291     if (middle > left && dest < addr) {
1292       right = middle - 1;
1293     } else if (middle < right && middle_ptr->data_size() == region_size) {
1294       left = middle + 1;
1295     } else {
1296       return middle_ptr;
1297     }
1298   }
1299   return sd.region(left);
1300 }
1301 
1302 ParallelCompactData::RegionData*
1303 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1304                                           const RegionData* end,
1305                                           size_t dead_words)
1306 {
1307   ParallelCompactData& sd = summary_data();
1308   size_t left = sd.region(beg);
1309   size_t right = end > beg ? sd.region(end) - 1 : left;
1310 
1311   // Binary search.
1312   while (left < right) {
1313     // Equivalent to (left + right) / 2, but does not overflow.
1314     const size_t middle = left + (right - left) / 2;
1315     RegionData* const middle_ptr = sd.region(middle);
1316     HeapWord* const dest = middle_ptr->destination();
1317     HeapWord* const addr = sd.region_to_addr(middle);
1318     assert(dest != NULL, "sanity");
1319     assert(dest <= addr, "must move left");
1320 
1321     const size_t dead_to_left = pointer_delta(addr, dest);
1322     if (middle > left && dead_to_left > dead_words) {
1323       right = middle - 1;
1324     } else if (middle < right && dead_to_left < dead_words) {
1325       left = middle + 1;
1326     } else {
1327       return middle_ptr;
1328     }
1329   }
1330   return sd.region(left);
1331 }
1332 
1333 // The result is valid during the summary phase, after the initial summarization
1334 // of each space into itself, and before final summarization.
1335 inline double
1336 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1337                                    HeapWord* const bottom,
1338                                    HeapWord* const top,
1339                                    HeapWord* const new_top)
1340 {
1341   ParallelCompactData& sd = summary_data();
1342 
1343   assert(cp != NULL, "sanity");
1344   assert(bottom != NULL, "sanity");
1345   assert(top != NULL, "sanity");
1346   assert(new_top != NULL, "sanity");
1347   assert(top >= new_top, "summary data problem?");
1348   assert(new_top > bottom, "space is empty; should not be here");
1349   assert(new_top >= cp->destination(), "sanity");
1350   assert(top >= sd.region_to_addr(cp), "sanity");
1351 
1352   HeapWord* const destination = cp->destination();
1353   const size_t dense_prefix_live  = pointer_delta(destination, bottom);
1354   const size_t compacted_region_live = pointer_delta(new_top, destination);
1355   const size_t compacted_region_used = pointer_delta(top,
1356                                                      sd.region_to_addr(cp));
1357   const size_t reclaimable = compacted_region_used - compacted_region_live;
1358 
1359   const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1360   return double(reclaimable) / divisor;
1361 }
1362 
1363 // Return the address of the end of the dense prefix, a.k.a. the start of the
1364 // compacted region.  The address is always on a region boundary.
1365 //
1366 // Completely full regions at the left are skipped, since no compaction can
1367 // occur in those regions.  Then the maximum amount of dead wood to allow is
1368 // computed, based on the density (amount live / capacity) of the generation;
1369 // the region with approximately that amount of dead space to the left is
1370 // identified as the limit region.  Regions between the last completely full
1371 // region and the limit region are scanned and the one that has the best
1372 // (maximum) reclaimed_ratio() is selected.
1373 HeapWord*
1374 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1375                                         bool maximum_compaction)
1376 {
1377   if (ParallelOldGCSplitALot) {
1378     if (_space_info[id].dense_prefix() != _space_info[id].space()->bottom()) {
1379       // The value was chosen to provoke splitting a young gen space; use it.
1380       return _space_info[id].dense_prefix();
1381     }
1382   }
1383 
1384   const size_t region_size = ParallelCompactData::RegionSize;
1385   const ParallelCompactData& sd = summary_data();
1386 
1387   const MutableSpace* const space = _space_info[id].space();
1388   HeapWord* const top = space->top();
1389   HeapWord* const top_aligned_up = sd.region_align_up(top);
1390   HeapWord* const new_top = _space_info[id].new_top();
1391   HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1392   HeapWord* const bottom = space->bottom();
1393   const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1394   const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1395   const RegionData* const new_top_cp =
1396     sd.addr_to_region_ptr(new_top_aligned_up);
1397 
1398   // Skip full regions at the beginning of the space--they are necessarily part
1399   // of the dense prefix.
1400   const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1401   assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1402          space->is_empty(), "no dead space allowed to the left");
1403   assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1404          "region must have dead space");
1405 
1406   // The gc number is saved whenever a maximum compaction is done, and used to
1407   // determine when the maximum compaction interval has expired.  This avoids
1408   // successive max compactions for different reasons.
1409   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1410   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1411   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1412     total_invocations() == HeapFirstMaximumCompactionCount;
1413   if (maximum_compaction || full_cp == top_cp || interval_ended) {
1414     _maximum_compaction_gc_num = total_invocations();
1415     return sd.region_to_addr(full_cp);
1416   }
1417 
1418   const size_t space_live = pointer_delta(new_top, bottom);
1419   const size_t space_used = space->used_in_words();
1420   const size_t space_capacity = space->capacity_in_words();
1421 
1422   const double density = double(space_live) / double(space_capacity);
1423   const size_t min_percent_free = MarkSweepDeadRatio;
1424   const double limiter = dead_wood_limiter(density, min_percent_free);
1425   const size_t dead_wood_max = space_used - space_live;
1426   const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1427                                       dead_wood_max);
1428 
1429   if (TraceParallelOldGCDensePrefix) {
1430     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1431                   "space_cap=" SIZE_FORMAT,
1432                   space_live, space_used,
1433                   space_capacity);
1434     tty->print_cr("dead_wood_limiter(%6.4f, %d)=%6.4f "
1435                   "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1436                   density, min_percent_free, limiter,
1437                   dead_wood_max, dead_wood_limit);
1438   }
1439 
1440   // Locate the region with the desired amount of dead space to the left.
1441   const RegionData* const limit_cp =
1442     dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1443 
1444   // Scan from the first region with dead space to the limit region and find the
1445   // one with the best (largest) reclaimed ratio.
1446   double best_ratio = 0.0;
1447   const RegionData* best_cp = full_cp;
1448   for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1449     double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1450     if (tmp_ratio > best_ratio) {
1451       best_cp = cp;
1452       best_ratio = tmp_ratio;
1453     }
1454   }
1455 
1456 #if     0
1457   // Something to consider:  if the region with the best ratio is 'close to' the
1458   // first region w/free space, choose the first region with free space
1459   // ("first-free").  The first-free region is usually near the start of the
1460   // heap, which means we are copying most of the heap already, so copy a bit
1461   // more to get complete compaction.
1462   if (pointer_delta(best_cp, full_cp, sizeof(RegionData)) < 4) {
1463     _maximum_compaction_gc_num = total_invocations();
1464     best_cp = full_cp;
1465   }
1466 #endif  // #if 0
1467 
1468   return sd.region_to_addr(best_cp);
1469 }
1470 
1471 #ifndef PRODUCT
1472 void
1473 PSParallelCompact::fill_with_live_objects(SpaceId id, HeapWord* const start,
1474                                           size_t words)
1475 {
1476   if (TraceParallelOldGCSummaryPhase) {
1477     tty->print_cr("fill_with_live_objects [" PTR_FORMAT " " PTR_FORMAT ") "
1478                   SIZE_FORMAT, start, start + words, words);
1479   }
1480 
1481   ObjectStartArray* const start_array = _space_info[id].start_array();
1482   CollectedHeap::fill_with_objects(start, words);
1483   for (HeapWord* p = start; p < start + words; p += oop(p)->size()) {
1484     _mark_bitmap.mark_obj(p, words);
1485     _summary_data.add_obj(p, words);
1486     start_array->allocate_block(p);
1487   }
1488 }
1489 
1490 void
1491 PSParallelCompact::summarize_new_objects(SpaceId id, HeapWord* start)
1492 {
1493   ParallelCompactData& sd = summary_data();
1494   MutableSpace* space = _space_info[id].space();
1495 
1496   // Find the source and destination start addresses.
1497   HeapWord* const src_addr = sd.region_align_down(start);
1498   HeapWord* dst_addr;
1499   if (src_addr < start) {
1500     dst_addr = sd.addr_to_region_ptr(src_addr)->destination();
1501   } else if (src_addr > space->bottom()) {
1502     // The start (the original top() value) is aligned to a region boundary so
1503     // the associated region does not have a destination.  Compute the
1504     // destination from the previous region.
1505     RegionData* const cp = sd.addr_to_region_ptr(src_addr) - 1;
1506     dst_addr = cp->destination() + cp->data_size();
1507   } else {
1508     // Filling the entire space.
1509     dst_addr = space->bottom();
1510   }
1511   assert(dst_addr != NULL, "sanity");
1512 
1513   // Update the summary data.
1514   bool result = _summary_data.summarize(_space_info[id].split_info(),
1515                                         src_addr, space->top(), NULL,
1516                                         dst_addr, space->end(),
1517                                         _space_info[id].new_top_addr());
1518   assert(result, "should not fail:  bad filler object size");
1519 }
1520 
1521 void
1522 PSParallelCompact::provoke_split_fill_survivor(SpaceId id)
1523 {
1524   if (total_invocations() % (ParallelOldGCSplitInterval * 3) != 0) {
1525     return;
1526   }
1527 
1528   MutableSpace* const space = _space_info[id].space();
1529   if (space->is_empty()) {
1530     HeapWord* b = space->bottom();
1531     HeapWord* t = b + space->capacity_in_words() / 2;
1532     space->set_top(t);
1533     if (ZapUnusedHeapArea) {
1534       space->set_top_for_allocations();
1535     }
1536 
1537     size_t min_size = CollectedHeap::min_fill_size();
1538     size_t obj_len = min_size;
1539     while (b + obj_len <= t) {
1540       CollectedHeap::fill_with_object(b, obj_len);
1541       mark_bitmap()->mark_obj(b, obj_len);
1542       summary_data().add_obj(b, obj_len);
1543       b += obj_len;
1544       obj_len = (obj_len & (min_size*3)) + min_size; // 8 16 24 32 8 16 24 32 ...
1545     }
1546     if (b < t) {
1547       // The loop didn't completely fill to t (top); adjust top downward.
1548       space->set_top(b);
1549       if (ZapUnusedHeapArea) {
1550         space->set_top_for_allocations();
1551       }
1552     }
1553 
1554     HeapWord** nta = _space_info[id].new_top_addr();
1555     bool result = summary_data().summarize(_space_info[id].split_info(),
1556                                            space->bottom(), space->top(), NULL,
1557                                            space->bottom(), space->end(), nta);
1558     assert(result, "space must fit into itself");
1559   }
1560 }
1561 
1562 void
1563 PSParallelCompact::provoke_split(bool & max_compaction)
1564 {
1565   if (total_invocations() % ParallelOldGCSplitInterval != 0) {
1566     return;
1567   }
1568 
1569   const size_t region_size = ParallelCompactData::RegionSize;
1570   ParallelCompactData& sd = summary_data();
1571 
1572   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1573   MutableSpace* const from_space = _space_info[from_space_id].space();
1574   const size_t eden_live = pointer_delta(eden_space->top(),
1575                                          _space_info[eden_space_id].new_top());
1576   const size_t from_live = pointer_delta(from_space->top(),
1577                                          _space_info[from_space_id].new_top());
1578 
1579   const size_t min_fill_size = CollectedHeap::min_fill_size();
1580   const size_t eden_free = pointer_delta(eden_space->end(), eden_space->top());
1581   const size_t eden_fillable = eden_free >= min_fill_size ? eden_free : 0;
1582   const size_t from_free = pointer_delta(from_space->end(), from_space->top());
1583   const size_t from_fillable = from_free >= min_fill_size ? from_free : 0;
1584 
1585   // Choose the space to split; need at least 2 regions live (or fillable).
1586   SpaceId id;
1587   MutableSpace* space;
1588   size_t live_words;
1589   size_t fill_words;
1590   if (eden_live + eden_fillable >= region_size * 2) {
1591     id = eden_space_id;
1592     space = eden_space;
1593     live_words = eden_live;
1594     fill_words = eden_fillable;
1595   } else if (from_live + from_fillable >= region_size * 2) {
1596     id = from_space_id;
1597     space = from_space;
1598     live_words = from_live;
1599     fill_words = from_fillable;
1600   } else {
1601     return; // Give up.
1602   }
1603   assert(fill_words == 0 || fill_words >= min_fill_size, "sanity");
1604 
1605   if (live_words < region_size * 2) {
1606     // Fill from top() to end() w/live objects of mixed sizes.
1607     HeapWord* const fill_start = space->top();
1608     live_words += fill_words;
1609 
1610     space->set_top(fill_start + fill_words);
1611     if (ZapUnusedHeapArea) {
1612       space->set_top_for_allocations();
1613     }
1614 
1615     HeapWord* cur_addr = fill_start;
1616     while (fill_words > 0) {
1617       const size_t r = (size_t)os::random() % (region_size / 2) + min_fill_size;
1618       size_t cur_size = MIN2(align_object_size_(r), fill_words);
1619       if (fill_words - cur_size < min_fill_size) {
1620         cur_size = fill_words; // Avoid leaving a fragment too small to fill.
1621       }
1622 
1623       CollectedHeap::fill_with_object(cur_addr, cur_size);
1624       mark_bitmap()->mark_obj(cur_addr, cur_size);
1625       sd.add_obj(cur_addr, cur_size);
1626 
1627       cur_addr += cur_size;
1628       fill_words -= cur_size;
1629     }
1630 
1631     summarize_new_objects(id, fill_start);
1632   }
1633 
1634   max_compaction = false;
1635 
1636   // Manipulate the old gen so that it has room for about half of the live data
1637   // in the target young gen space (live_words / 2).
1638   id = old_space_id;
1639   space = _space_info[id].space();
1640   const size_t free_at_end = space->free_in_words();
1641   const size_t free_target = align_object_size(live_words / 2);
1642   const size_t dead = pointer_delta(space->top(), _space_info[id].new_top());
1643 
1644   if (free_at_end >= free_target + min_fill_size) {
1645     // Fill space above top() and set the dense prefix so everything survives.
1646     HeapWord* const fill_start = space->top();
1647     const size_t fill_size = free_at_end - free_target;
1648     space->set_top(space->top() + fill_size);
1649     if (ZapUnusedHeapArea) {
1650       space->set_top_for_allocations();
1651     }
1652     fill_with_live_objects(id, fill_start, fill_size);
1653     summarize_new_objects(id, fill_start);
1654     _space_info[id].set_dense_prefix(sd.region_align_down(space->top()));
1655   } else if (dead + free_at_end > free_target) {
1656     // Find a dense prefix that makes the right amount of space available.
1657     HeapWord* cur = sd.region_align_down(space->top());
1658     HeapWord* cur_destination = sd.addr_to_region_ptr(cur)->destination();
1659     size_t dead_to_right = pointer_delta(space->end(), cur_destination);
1660     while (dead_to_right < free_target) {
1661       cur -= region_size;
1662       cur_destination = sd.addr_to_region_ptr(cur)->destination();
1663       dead_to_right = pointer_delta(space->end(), cur_destination);
1664     }
1665     _space_info[id].set_dense_prefix(cur);
1666   }
1667 }
1668 #endif // #ifndef PRODUCT
1669 
1670 void PSParallelCompact::summarize_spaces_quick()
1671 {
1672   for (unsigned int i = 0; i < last_space_id; ++i) {
1673     const MutableSpace* space = _space_info[i].space();
1674     HeapWord** nta = _space_info[i].new_top_addr();
1675     bool result = _summary_data.summarize(_space_info[i].split_info(),
1676                                           space->bottom(), space->top(), NULL,
1677                                           space->bottom(), space->end(), nta);
1678     assert(result, "space must fit into itself");
1679     _space_info[i].set_dense_prefix(space->bottom());
1680   }
1681 
1682 #ifndef PRODUCT
1683   if (ParallelOldGCSplitALot) {
1684     provoke_split_fill_survivor(to_space_id);
1685   }
1686 #endif // #ifndef PRODUCT
1687 }
1688 
1689 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1690 {
1691   HeapWord* const dense_prefix_end = dense_prefix(id);
1692   const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1693   const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1694   if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1695     // Only enough dead space is filled so that any remaining dead space to the
1696     // left is larger than the minimum filler object.  (The remainder is filled
1697     // during the copy/update phase.)
1698     //
1699     // The size of the dead space to the right of the boundary is not a
1700     // concern, since compaction will be able to use whatever space is
1701     // available.
1702     //
1703     // Here '||' is the boundary, 'x' represents a don't care bit and a box
1704     // surrounds the space to be filled with an object.
1705     //
1706     // In the 32-bit VM, each bit represents two 32-bit words:
1707     //                              +---+
1708     // a) beg_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1709     //    end_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1710     //                              +---+
1711     //
1712     // In the 64-bit VM, each bit represents one 64-bit word:
1713     //                              +------------+
1714     // b) beg_bits:  ...  x   x   x | 0   ||   0 | x  x  ...
1715     //    end_bits:  ...  x   x   1 | 0   ||   0 | x  x  ...
1716     //                              +------------+
1717     //                          +-------+
1718     // c) beg_bits:  ...  x   x | 0   0 | ||   0   x  x  ...
1719     //    end_bits:  ...  x   1 | 0   0 | ||   0   x  x  ...
1720     //                          +-------+
1721     //                      +-----------+
1722     // d) beg_bits:  ...  x | 0   0   0 | ||   0   x  x  ...
1723     //    end_bits:  ...  1 | 0   0   0 | ||   0   x  x  ...
1724     //                      +-----------+
1725     //                          +-------+
1726     // e) beg_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1727     //    end_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1728     //                          +-------+
1729 
1730     // Initially assume case a, c or e will apply.
1731     size_t obj_len = CollectedHeap::min_fill_size();
1732     HeapWord* obj_beg = dense_prefix_end - obj_len;
1733 
1734 #ifdef  _LP64
1735     if (MinObjAlignment > 1) { // object alignment > heap word size
1736       // Cases a, c or e.
1737     } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1738       // Case b above.
1739       obj_beg = dense_prefix_end - 1;
1740     } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1741                _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1742       // Case d above.
1743       obj_beg = dense_prefix_end - 3;
1744       obj_len = 3;
1745     }
1746 #endif  // #ifdef _LP64
1747 
1748     CollectedHeap::fill_with_object(obj_beg, obj_len);
1749     _mark_bitmap.mark_obj(obj_beg, obj_len);
1750     _summary_data.add_obj(obj_beg, obj_len);
1751     assert(start_array(id) != NULL, "sanity");
1752     start_array(id)->allocate_block(obj_beg);
1753   }
1754 }
1755 
1756 void
1757 PSParallelCompact::clear_source_region(HeapWord* beg_addr, HeapWord* end_addr)
1758 {
1759   RegionData* const beg_ptr = _summary_data.addr_to_region_ptr(beg_addr);
1760   HeapWord* const end_aligned_up = _summary_data.region_align_up(end_addr);
1761   RegionData* const end_ptr = _summary_data.addr_to_region_ptr(end_aligned_up);
1762   for (RegionData* cur = beg_ptr; cur < end_ptr; ++cur) {
1763     cur->set_source_region(0);
1764   }
1765 }
1766 
1767 void
1768 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1769 {
1770   assert(id < last_space_id, "id out of range");
1771   assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom() ||
1772          ParallelOldGCSplitALot && id == old_space_id,
1773          "should have been reset in summarize_spaces_quick()");
1774 
1775   const MutableSpace* space = _space_info[id].space();
1776   if (_space_info[id].new_top() != space->bottom()) {
1777     HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1778     _space_info[id].set_dense_prefix(dense_prefix_end);
1779 
1780 #ifndef PRODUCT
1781     if (TraceParallelOldGCDensePrefix) {
1782       print_dense_prefix_stats("ratio", id, maximum_compaction,
1783                                dense_prefix_end);
1784       HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1785       print_dense_prefix_stats("density", id, maximum_compaction, addr);
1786     }
1787 #endif  // #ifndef PRODUCT
1788 
1789     // Recompute the summary data, taking into account the dense prefix.  If
1790     // every last byte will be reclaimed, then the existing summary data which
1791     // compacts everything can be left in place.
1792     if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1793       // If dead space crosses the dense prefix boundary, it is (at least
1794       // partially) filled with a dummy object, marked live and added to the
1795       // summary data.  This simplifies the copy/update phase and must be done
1796       // before the final locations of objects are determined, to prevent
1797       // leaving a fragment of dead space that is too small to fill.
1798       fill_dense_prefix_end(id);
1799 
1800       // Compute the destination of each Region, and thus each object.
1801       _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1802       _summary_data.summarize(_space_info[id].split_info(),
1803                               dense_prefix_end, space->top(), NULL,
1804                               dense_prefix_end, space->end(),
1805                               _space_info[id].new_top_addr());
1806     }
1807   }
1808 
1809   if (TraceParallelOldGCSummaryPhase) {
1810     const size_t region_size = ParallelCompactData::RegionSize;
1811     HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1812     const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1813     const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1814     HeapWord* const new_top = _space_info[id].new_top();
1815     const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1816     const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1817     tty->print_cr("id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1818                   "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1819                   "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1820                   id, space->capacity_in_words(), dense_prefix_end,
1821                   dp_region, dp_words / region_size,
1822                   cr_words / region_size, new_top);
1823   }
1824 }
1825 
1826 #ifndef PRODUCT
1827 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1828                                           HeapWord* dst_beg, HeapWord* dst_end,
1829                                           SpaceId src_space_id,
1830                                           HeapWord* src_beg, HeapWord* src_end)
1831 {
1832   if (TraceParallelOldGCSummaryPhase) {
1833     tty->print_cr("summarizing %d [%s] into %d [%s]:  "
1834                   "src=" PTR_FORMAT "-" PTR_FORMAT " "
1835                   SIZE_FORMAT "-" SIZE_FORMAT " "
1836                   "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1837                   SIZE_FORMAT "-" SIZE_FORMAT,
1838                   src_space_id, space_names[src_space_id],
1839                   dst_space_id, space_names[dst_space_id],
1840                   src_beg, src_end,
1841                   _summary_data.addr_to_region_idx(src_beg),
1842                   _summary_data.addr_to_region_idx(src_end),
1843                   dst_beg, dst_end,
1844                   _summary_data.addr_to_region_idx(dst_beg),
1845                   _summary_data.addr_to_region_idx(dst_end));
1846   }
1847 }
1848 #endif  // #ifndef PRODUCT
1849 
1850 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1851                                       bool maximum_compaction)
1852 {
1853   GCTraceTime tm("summary phase", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
1854   // trace("2");
1855 
1856 #ifdef  ASSERT
1857   if (TraceParallelOldGCMarkingPhase) {
1858     tty->print_cr("add_obj_count=" SIZE_FORMAT " "
1859                   "add_obj_bytes=" SIZE_FORMAT,
1860                   add_obj_count, add_obj_size * HeapWordSize);
1861     tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
1862                   "mark_bitmap_bytes=" SIZE_FORMAT,
1863                   mark_bitmap_count, mark_bitmap_size * HeapWordSize);
1864   }
1865 #endif  // #ifdef ASSERT
1866 
1867   // Quick summarization of each space into itself, to see how much is live.
1868   summarize_spaces_quick();
1869 
1870   if (TraceParallelOldGCSummaryPhase) {
1871     tty->print_cr("summary_phase:  after summarizing each space to self");
1872     Universe::print();
1873     NOT_PRODUCT(print_region_ranges());
1874     if (Verbose) {
1875       NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1876     }
1877   }
1878 
1879   // The amount of live data that will end up in old space (assuming it fits).
1880   size_t old_space_total_live = 0;
1881   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1882     old_space_total_live += pointer_delta(_space_info[id].new_top(),
1883                                           _space_info[id].space()->bottom());
1884   }
1885 
1886   MutableSpace* const old_space = _space_info[old_space_id].space();
1887   const size_t old_capacity = old_space->capacity_in_words();
1888   if (old_space_total_live > old_capacity) {
1889     // XXX - should also try to expand
1890     maximum_compaction = true;
1891   }
1892 #ifndef PRODUCT
1893   if (ParallelOldGCSplitALot && old_space_total_live < old_capacity) {
1894     provoke_split(maximum_compaction);
1895   }
1896 #endif // #ifndef PRODUCT
1897 
1898   // Old generations.
1899   summarize_space(old_space_id, maximum_compaction);
1900 
1901   // Summarize the remaining spaces in the young gen.  The initial target space
1902   // is the old gen.  If a space does not fit entirely into the target, then the
1903   // remainder is compacted into the space itself and that space becomes the new
1904   // target.
1905   SpaceId dst_space_id = old_space_id;
1906   HeapWord* dst_space_end = old_space->end();
1907   HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1908   for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1909     const MutableSpace* space = _space_info[id].space();
1910     const size_t live = pointer_delta(_space_info[id].new_top(),
1911                                       space->bottom());
1912     const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1913 
1914     NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1915                                   SpaceId(id), space->bottom(), space->top());)
1916     if (live > 0 && live <= available) {
1917       // All the live data will fit.
1918       bool done = _summary_data.summarize(_space_info[id].split_info(),
1919                                           space->bottom(), space->top(),
1920                                           NULL,
1921                                           *new_top_addr, dst_space_end,
1922                                           new_top_addr);
1923       assert(done, "space must fit into old gen");
1924 
1925       // Reset the new_top value for the space.
1926       _space_info[id].set_new_top(space->bottom());
1927     } else if (live > 0) {
1928       // Attempt to fit part of the source space into the target space.
1929       HeapWord* next_src_addr = NULL;
1930       bool done = _summary_data.summarize(_space_info[id].split_info(),
1931                                           space->bottom(), space->top(),
1932                                           &next_src_addr,
1933                                           *new_top_addr, dst_space_end,
1934                                           new_top_addr);
1935       assert(!done, "space should not fit into old gen");
1936       assert(next_src_addr != NULL, "sanity");
1937 
1938       // The source space becomes the new target, so the remainder is compacted
1939       // within the space itself.
1940       dst_space_id = SpaceId(id);
1941       dst_space_end = space->end();
1942       new_top_addr = _space_info[id].new_top_addr();
1943       NOT_PRODUCT(summary_phase_msg(dst_space_id,
1944                                     space->bottom(), dst_space_end,
1945                                     SpaceId(id), next_src_addr, space->top());)
1946       done = _summary_data.summarize(_space_info[id].split_info(),
1947                                      next_src_addr, space->top(),
1948                                      NULL,
1949                                      space->bottom(), dst_space_end,
1950                                      new_top_addr);
1951       assert(done, "space must fit when compacted into itself");
1952       assert(*new_top_addr <= space->top(), "usage should not grow");
1953     }
1954   }
1955 
1956   if (TraceParallelOldGCSummaryPhase) {
1957     tty->print_cr("summary_phase:  after final summarization");
1958     Universe::print();
1959     NOT_PRODUCT(print_region_ranges());
1960     if (Verbose) {
1961       NOT_PRODUCT(print_generic_summary_data(_summary_data, _space_info));
1962     }
1963   }
1964 }
1965 
1966 // This method should contain all heap-specific policy for invoking a full
1967 // collection.  invoke_no_policy() will only attempt to compact the heap; it
1968 // will do nothing further.  If we need to bail out for policy reasons, scavenge
1969 // before full gc, or any other specialized behavior, it needs to be added here.
1970 //
1971 // Note that this method should only be called from the vm_thread while at a
1972 // safepoint.
1973 //
1974 // Note that the all_soft_refs_clear flag in the collector policy
1975 // may be true because this method can be called without intervening
1976 // activity.  For example when the heap space is tight and full measure
1977 // are being taken to free space.
1978 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1979   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1980   assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1981          "should be in vm thread");
1982 
1983   ParallelScavengeHeap* heap = gc_heap();
1984   GCCause::Cause gc_cause = heap->gc_cause();
1985   assert(!heap->is_gc_active(), "not reentrant");
1986 
1987   PSAdaptiveSizePolicy* policy = heap->size_policy();
1988   IsGCActiveMark mark;
1989 
1990   if (ScavengeBeforeFullGC) {
1991     PSScavenge::invoke_no_policy();
1992   }
1993 
1994   const bool clear_all_soft_refs =
1995     heap->collector_policy()->should_clear_all_soft_refs();
1996 
1997   PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1998                                       maximum_heap_compaction);
1999 }
2000 
2001 // This method contains no policy. You should probably
2002 // be calling invoke() instead.
2003 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
2004   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
2005   assert(ref_processor() != NULL, "Sanity");
2006 
2007   if (GC_locker::check_active_before_gc()) {
2008     return false;
2009   }
2010 
2011   ParallelScavengeHeap* heap = gc_heap();
2012 
2013   _gc_timer.register_gc_start();
2014   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
2015 
2016   TimeStamp marking_start;
2017   TimeStamp compaction_start;
2018   TimeStamp collection_exit;
2019 
2020   GCCause::Cause gc_cause = heap->gc_cause();
2021   PSYoungGen* young_gen = heap->young_gen();
2022   PSOldGen* old_gen = heap->old_gen();
2023   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
2024 
2025   // The scope of casr should end after code that can change
2026   // CollectorPolicy::_should_clear_all_soft_refs.
2027   ClearedAllSoftRefs casr(maximum_heap_compaction,
2028                           heap->collector_policy());
2029 
2030   if (ZapUnusedHeapArea) {
2031     // Save information needed to minimize mangling
2032     heap->record_gen_tops_before_GC();
2033   }
2034 
2035   heap->pre_full_gc_dump(&_gc_timer);
2036 
2037   _print_phases = PrintGCDetails && PrintParallelOldGCPhaseTimes;
2038 
2039   // Make sure data structures are sane, make the heap parsable, and do other
2040   // miscellaneous bookkeeping.
2041   PreGCValues pre_gc_values;
2042   pre_compact(&pre_gc_values);
2043 
2044   // Get the compaction manager reserved for the VM thread.
2045   ParCompactionManager* const vmthread_cm =
2046     ParCompactionManager::manager_array(gc_task_manager()->workers());
2047 
2048   // Place after pre_compact() where the number of invocations is incremented.
2049   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
2050 
2051   {
2052     ResourceMark rm;
2053     HandleMark hm;
2054 
2055     // Set the number of GC threads to be used in this collection
2056     gc_task_manager()->set_active_gang();
2057     gc_task_manager()->task_idle_workers();
2058     heap->set_par_threads(gc_task_manager()->active_workers());
2059 
2060     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
2061     GCTraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, NULL, _gc_tracer.gc_id());
2062     TraceCollectorStats tcs(counters());
2063     TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);
2064 
2065     if (TraceGen1Time) accumulated_time()->start();
2066 
2067     // Let the size policy know we're starting
2068     size_policy->major_collection_begin();
2069 
2070     CodeCache::gc_prologue();
2071     Threads::gc_prologue();
2072 
2073     COMPILER2_PRESENT(DerivedPointerTable::clear());
2074 
2075     ref_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
2076     ref_processor()->setup_policy(maximum_heap_compaction);
2077 
2078     bool marked_for_unloading = false;
2079 
2080     marking_start.update();
2081     marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
2082 
2083     bool max_on_system_gc = UseMaximumCompactionOnSystemGC
2084       && gc_cause == GCCause::_java_lang_system_gc;
2085     summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
2086 
2087     COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
2088     COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
2089 
2090     // adjust_roots() updates Universe::_intArrayKlassObj which is
2091     // needed by the compaction for filling holes in the dense prefix.
2092     adjust_roots();
2093 
2094     compaction_start.update();
2095     compact();
2096 
2097     // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
2098     // done before resizing.
2099     post_compact();
2100 
2101     // Let the size policy know we're done
2102     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
2103 
2104     if (UseAdaptiveSizePolicy) {
2105       if (PrintAdaptiveSizePolicy) {
2106         gclog_or_tty->print("AdaptiveSizeStart: ");
2107         gclog_or_tty->stamp();
2108         gclog_or_tty->print_cr(" collection: %d ",
2109                        heap->total_collections());
2110         if (Verbose) {
2111           gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d",
2112             old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
2113         }
2114       }
2115 
2116       // Don't check if the size_policy is ready here.  Let
2117       // the size_policy check that internally.
2118       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
2119           ((gc_cause != GCCause::_java_lang_system_gc) ||
2120             UseAdaptiveSizePolicyWithSystemGC)) {
2121         // Calculate optimal free space amounts
2122         assert(young_gen->max_size() >
2123           young_gen->from_space()->capacity_in_bytes() +
2124           young_gen->to_space()->capacity_in_bytes(),
2125           "Sizes of space in young gen are out-of-bounds");
2126 
2127         size_t young_live = young_gen->used_in_bytes();
2128         size_t eden_live = young_gen->eden_space()->used_in_bytes();
2129         size_t old_live = old_gen->used_in_bytes();
2130         size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
2131         size_t max_old_gen_size = old_gen->max_gen_size();
2132         size_t max_eden_size = young_gen->max_size() -
2133           young_gen->from_space()->capacity_in_bytes() -
2134           young_gen->to_space()->capacity_in_bytes();
2135 
2136         // Used for diagnostics
2137         size_policy->clear_generation_free_space_flags();
2138 
2139         size_policy->compute_generations_free_space(young_live,
2140                                                     eden_live,
2141                                                     old_live,
2142                                                     cur_eden,
2143                                                     max_old_gen_size,
2144                                                     max_eden_size,
2145                                                     true /* full gc*/);
2146 
2147         size_policy->check_gc_overhead_limit(young_live,
2148                                              eden_live,
2149                                              max_old_gen_size,
2150                                              max_eden_size,
2151                                              true /* full gc*/,
2152                                              gc_cause,
2153                                              heap->collector_policy());
2154 
2155         size_policy->decay_supplemental_growth(true /* full gc*/);
2156 
2157         heap->resize_old_gen(
2158           size_policy->calculated_old_free_size_in_bytes());
2159 
2160         // Don't resize the young generation at an major collection.  A
2161         // desired young generation size may have been calculated but
2162         // resizing the young generation complicates the code because the
2163         // resizing of the old generation may have moved the boundary
2164         // between the young generation and the old generation.  Let the
2165         // young generation resizing happen at the minor collections.
2166       }
2167       if (PrintAdaptiveSizePolicy) {
2168         gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
2169                        heap->total_collections());
2170       }
2171     }
2172 
2173     if (UsePerfData) {
2174       PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
2175       counters->update_counters();
2176       counters->update_old_capacity(old_gen->capacity_in_bytes());
2177       counters->update_young_capacity(young_gen->capacity_in_bytes());
2178     }
2179 
2180     heap->resize_all_tlabs();
2181 
2182     // Resize the metaspace capactiy after a collection
2183     MetaspaceGC::compute_new_size();
2184 
2185     if (TraceGen1Time) accumulated_time()->stop();
2186 
2187     if (PrintGC) {
2188       if (PrintGCDetails) {
2189         // No GC timestamp here.  This is after GC so it would be confusing.
2190         young_gen->print_used_change(pre_gc_values.young_gen_used());
2191         old_gen->print_used_change(pre_gc_values.old_gen_used());
2192         heap->print_heap_change(pre_gc_values.heap_used());
2193         MetaspaceAux::print_metaspace_change(pre_gc_values.metadata_used());
2194       } else {
2195         heap->print_heap_change(pre_gc_values.heap_used());
2196       }
2197     }
2198 
2199     // Track memory usage and detect low memory
2200     MemoryService::track_memory_usage();
2201     heap->update_counters();
2202     gc_task_manager()->release_idle_workers();
2203   }
2204 
2205 #ifdef ASSERT
2206   for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
2207     ParCompactionManager* const cm =
2208       ParCompactionManager::manager_array(int(i));
2209     assert(cm->marking_stack()->is_empty(),       "should be empty");
2210     assert(ParCompactionManager::region_list(int(i))->is_empty(), "should be empty");
2211   }
2212 #endif // ASSERT
2213 
2214   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
2215     HandleMark hm;  // Discard invalid handles created during verification
2216     Universe::verify(" VerifyAfterGC:");
2217   }
2218 
2219   // Re-verify object start arrays
2220   if (VerifyObjectStartArray &&
2221       VerifyAfterGC) {
2222     old_gen->verify_object_start_array();
2223   }
2224 
2225   if (ZapUnusedHeapArea) {
2226     old_gen->object_space()->check_mangled_unused_area_complete();
2227   }
2228 
2229   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
2230 
2231   collection_exit.update();
2232 
2233   heap->print_heap_after_gc();
2234   heap->trace_heap_after_gc(&_gc_tracer);
2235 
2236   if (PrintGCTaskTimeStamps) {
2237     gclog_or_tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " "
2238                            INT64_FORMAT,
2239                            marking_start.ticks(), compaction_start.ticks(),
2240                            collection_exit.ticks());
2241     gc_task_manager()->print_task_time_stamps();
2242   }
2243 
2244   heap->post_full_gc_dump(&_gc_timer);
2245 
2246 #ifdef TRACESPINNING
2247   ParallelTaskTerminator::print_termination_counts();
2248 #endif
2249 
2250   _gc_timer.register_gc_end();
2251 
2252   _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
2253   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
2254 
2255   return true;
2256 }
2257 
2258 bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
2259                                              PSYoungGen* young_gen,
2260                                              PSOldGen* old_gen) {
2261   MutableSpace* const eden_space = young_gen->eden_space();
2262   assert(!eden_space->is_empty(), "eden must be non-empty");
2263   assert(young_gen->virtual_space()->alignment() ==
2264          old_gen->virtual_space()->alignment(), "alignments do not match");
2265 
2266   if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
2267     return false;
2268   }
2269 
2270   // Both generations must be completely committed.
2271   if (young_gen->virtual_space()->uncommitted_size() != 0) {
2272     return false;
2273   }
2274   if (old_gen->virtual_space()->uncommitted_size() != 0) {
2275     return false;
2276   }
2277 
2278   // Figure out how much to take from eden.  Include the average amount promoted
2279   // in the total; otherwise the next young gen GC will simply bail out to a
2280   // full GC.
2281   const size_t alignment = old_gen->virtual_space()->alignment();
2282   const size_t eden_used = eden_space->used_in_bytes();
2283   const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
2284   const size_t absorb_size = align_size_up(eden_used + promoted, alignment);
2285   const size_t eden_capacity = eden_space->capacity_in_bytes();
2286 
2287   if (absorb_size >= eden_capacity) {
2288     return false; // Must leave some space in eden.
2289   }
2290 
2291   const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
2292   if (new_young_size < young_gen->min_gen_size()) {
2293     return false; // Respect young gen minimum size.
2294   }
2295 
2296   if (TraceAdaptiveGCBoundary && Verbose) {
2297     gclog_or_tty->print(" absorbing " SIZE_FORMAT "K:  "
2298                         "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
2299                         "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
2300                         "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
2301                         absorb_size / K,
2302                         eden_capacity / K, (eden_capacity - absorb_size) / K,
2303                         young_gen->from_space()->used_in_bytes() / K,
2304                         young_gen->to_space()->used_in_bytes() / K,
2305                         young_gen->capacity_in_bytes() / K, new_young_size / K);
2306   }
2307 
2308   // Fill the unused part of the old gen.
2309   MutableSpace* const old_space = old_gen->object_space();
2310   HeapWord* const unused_start = old_space->top();
2311   size_t const unused_words = pointer_delta(old_space->end(), unused_start);
2312 
2313   if (unused_words > 0) {
2314     if (unused_words < CollectedHeap::min_fill_size()) {
2315       return false;  // If the old gen cannot be filled, must give up.
2316     }
2317     CollectedHeap::fill_with_objects(unused_start, unused_words);
2318   }
2319 
2320   // Take the live data from eden and set both top and end in the old gen to
2321   // eden top.  (Need to set end because reset_after_change() mangles the region
2322   // from end to virtual_space->high() in debug builds).
2323   HeapWord* const new_top = eden_space->top();
2324   old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
2325                                         absorb_size);
2326   young_gen->reset_after_change();
2327   old_space->set_top(new_top);
2328   old_space->set_end(new_top);
2329   old_gen->reset_after_change();
2330 
2331   // Update the object start array for the filler object and the data from eden.
2332   ObjectStartArray* const start_array = old_gen->start_array();
2333   for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
2334     start_array->allocate_block(p);
2335   }
2336 
2337   // Could update the promoted average here, but it is not typically updated at
2338   // full GCs and the value to use is unclear.  Something like
2339   //
2340   // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
2341 
2342   size_policy->set_bytes_absorbed_from_eden(absorb_size);
2343   return true;
2344 }
2345 
2346 GCTaskManager* const PSParallelCompact::gc_task_manager() {
2347   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
2348     "shouldn't return NULL");
2349   return ParallelScavengeHeap::gc_task_manager();
2350 }
2351 
2352 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2353                                       bool maximum_heap_compaction,
2354                                       ParallelOldTracer *gc_tracer) {
2355   // Recursively traverse all live objects and mark them
2356   GCTraceTime tm("marking phase", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2357 
2358   ParallelScavengeHeap* heap = gc_heap();
2359   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2360   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2361   TaskQueueSetSuper* qset = ParCompactionManager::stack_array();
2362   ParallelTaskTerminator terminator(active_gc_threads, qset);
2363 
2364   PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm);
2365   PSParallelCompact::FollowStackClosure follow_stack_closure(cm);
2366 
2367   // Need new claim bits before marking starts.
2368   ClassLoaderDataGraph::clear_claimed_marks();
2369 
2370   {
2371     GCTraceTime tm_m("par mark", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2372 
2373     ParallelScavengeHeap::ParStrongRootsScope psrs;
2374 
2375     GCTaskQueue* q = GCTaskQueue::create();
2376 
2377     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::universe));
2378     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jni_handles));
2379     // We scan the thread roots in parallel
2380     Threads::create_thread_roots_marking_tasks(q);
2381     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::object_synchronizer));
2382     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::flat_profiler));
2383     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::management));
2384     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::system_dictionary));
2385     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::class_loader_data));
2386     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jvmti));
2387     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::code_cache));
2388 
2389     if (active_gc_threads > 1) {
2390       for (uint j = 0; j < active_gc_threads; j++) {
2391         q->enqueue(new StealMarkingTask(&terminator));
2392       }
2393     }
2394 
2395     gc_task_manager()->execute_and_wait(q);
2396   }
2397 
2398   // Process reference objects found during marking
2399   {
2400     GCTraceTime tm_r("reference processing", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2401 
2402     ReferenceProcessorStats stats;
2403     if (ref_processor()->processing_is_mt()) {
2404       RefProcTaskExecutor task_executor;
2405       stats = ref_processor()->process_discovered_references(
2406         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2407         &task_executor, &_gc_timer, _gc_tracer.gc_id());
2408     } else {
2409       stats = ref_processor()->process_discovered_references(
2410         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
2411         &_gc_timer, _gc_tracer.gc_id());
2412     }
2413 
2414     gc_tracer->report_gc_reference_stats(stats);
2415   }
2416 
2417   GCTraceTime tm_c("class unloading", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2418 
2419   // This is the point where the entire marking should have completed.
2420   assert(cm->marking_stacks_empty(), "Marking should have completed");
2421 
2422   // Follow system dictionary roots and unload classes.
2423   bool purged_class = SystemDictionary::do_unloading(is_alive_closure());
2424 
2425   // Unload nmethods.
2426   CodeCache::do_unloading(is_alive_closure(), purged_class);
2427 
2428   // Prune dead klasses from subklass/sibling/implementor lists.
2429   Klass::clean_weak_klass_links(is_alive_closure());
2430 
2431   // Delete entries for dead interned strings.
2432   StringTable::unlink(is_alive_closure());
2433 
2434   // Clean up unreferenced symbols in symbol table.
2435   SymbolTable::unlink();
2436   _gc_tracer.report_object_count_after_gc(is_alive_closure());
2437 }
2438 
2439 void PSParallelCompact::follow_class_loader(ParCompactionManager* cm,
2440                                             ClassLoaderData* cld) {
2441   PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm);
2442   PSParallelCompact::FollowKlassClosure follow_klass_closure(&mark_and_push_closure);
2443 
2444   cld->oops_do(&mark_and_push_closure, &follow_klass_closure, true);
2445 }
2446 
2447 void PSParallelCompact::adjust_roots() {
2448   // Adjust the pointers to reflect the new locations
2449   GCTraceTime tm("adjust roots", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2450 
2451   // Need new claim bits when tracing through and adjusting pointers.
2452   ClassLoaderDataGraph::clear_claimed_marks();
2453 
2454   // General strong roots.
2455   Universe::oops_do(adjust_pointer_closure());
2456   JNIHandles::oops_do(adjust_pointer_closure());   // Global (strong) JNI handles
2457   CLDToOopClosure adjust_from_cld(adjust_pointer_closure());
2458   Threads::oops_do(adjust_pointer_closure(), &adjust_from_cld, NULL);
2459   ObjectSynchronizer::oops_do(adjust_pointer_closure());
2460   FlatProfiler::oops_do(adjust_pointer_closure());
2461   Management::oops_do(adjust_pointer_closure());
2462   JvmtiExport::oops_do(adjust_pointer_closure());
2463   SystemDictionary::oops_do(adjust_pointer_closure());
2464   ClassLoaderDataGraph::oops_do(adjust_pointer_closure(), adjust_klass_closure(), true);
2465 
2466   // Now adjust pointers in remaining weak roots.  (All of which should
2467   // have been cleared if they pointed to non-surviving objects.)
2468   // Global (weak) JNI handles
2469   JNIHandles::weak_oops_do(adjust_pointer_closure());
2470   JFR_ONLY(Jfr::weak_oops_do(adjust_pointer_closure()));
2471 
2472   CodeBlobToOopClosure adjust_from_blobs(adjust_pointer_closure(), CodeBlobToOopClosure::FixRelocations);
2473   CodeCache::blobs_do(&adjust_from_blobs);
2474   StringTable::oops_do(adjust_pointer_closure());
2475   ref_processor()->weak_oops_do(adjust_pointer_closure());
2476   // Roots were visited so references into the young gen in roots
2477   // may have been scanned.  Process them also.
2478   // Should the reference processor have a span that excludes
2479   // young gen objects?
2480   PSScavenge::reference_processor()->weak_oops_do(adjust_pointer_closure());
2481 }
2482 
2483 void PSParallelCompact::enqueue_region_draining_tasks(GCTaskQueue* q,
2484                                                       uint parallel_gc_threads)
2485 {
2486   GCTraceTime tm("drain task setup", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2487 
2488   // Find the threads that are active
2489   unsigned int which = 0;
2490 
2491   const uint task_count = MAX2(parallel_gc_threads, 1U);
2492   for (uint j = 0; j < task_count; j++) {
2493     q->enqueue(new DrainStacksCompactionTask(j));
2494     ParCompactionManager::verify_region_list_empty(j);
2495     // Set the region stacks variables to "no" region stack values
2496     // so that they will be recognized and needing a region stack
2497     // in the stealing tasks if they do not get one by executing
2498     // a draining stack.
2499     ParCompactionManager* cm = ParCompactionManager::manager_array(j);
2500     cm->set_region_stack(NULL);
2501     cm->set_region_stack_index((uint)max_uintx);
2502   }
2503   ParCompactionManager::reset_recycled_stack_index();
2504 
2505   // Find all regions that are available (can be filled immediately) and
2506   // distribute them to the thread stacks.  The iteration is done in reverse
2507   // order (high to low) so the regions will be removed in ascending order.
2508 
2509   const ParallelCompactData& sd = PSParallelCompact::summary_data();
2510 
2511   size_t fillable_regions = 0;   // A count for diagnostic purposes.
2512   // A region index which corresponds to the tasks created above.
2513   // "which" must be 0 <= which < task_count
2514 
2515   which = 0;
2516   // id + 1 is used to test termination so unsigned  can
2517   // be used with an old_space_id == 0.
2518   for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2519     SpaceInfo* const space_info = _space_info + id;
2520     MutableSpace* const space = space_info->space();
2521     HeapWord* const new_top = space_info->new_top();
2522 
2523     const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2524     const size_t end_region =
2525       sd.addr_to_region_idx(sd.region_align_up(new_top));
2526 
2527     for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2528       if (sd.region(cur)->claim_unsafe()) {
2529         ParCompactionManager::region_list_push(which, cur);
2530 
2531         if (TraceParallelOldGCCompactionPhase && Verbose) {
2532           const size_t count_mod_8 = fillable_regions & 7;
2533           if (count_mod_8 == 0) gclog_or_tty->print("fillable: ");
2534           gclog_or_tty->print(" " SIZE_FORMAT_W(7), cur);
2535           if (count_mod_8 == 7) gclog_or_tty->cr();
2536         }
2537 
2538         NOT_PRODUCT(++fillable_regions;)
2539 
2540         // Assign regions to tasks in round-robin fashion.
2541         if (++which == task_count) {
2542           assert(which <= parallel_gc_threads,
2543             "Inconsistent number of workers");
2544           which = 0;
2545         }
2546       }
2547     }
2548   }
2549 
2550   if (TraceParallelOldGCCompactionPhase) {
2551     if (Verbose && (fillable_regions & 7) != 0) gclog_or_tty->cr();
2552     gclog_or_tty->print_cr("%u initially fillable regions", fillable_regions);
2553   }
2554 }
2555 
2556 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2557 
2558 void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q,
2559                                                     uint parallel_gc_threads) {
2560   GCTraceTime tm("dense prefix task setup", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2561 
2562   ParallelCompactData& sd = PSParallelCompact::summary_data();
2563 
2564   // Iterate over all the spaces adding tasks for updating
2565   // regions in the dense prefix.  Assume that 1 gc thread
2566   // will work on opening the gaps and the remaining gc threads
2567   // will work on the dense prefix.
2568   unsigned int space_id;
2569   for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2570     HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2571     const MutableSpace* const space = _space_info[space_id].space();
2572 
2573     if (dense_prefix_end == space->bottom()) {
2574       // There is no dense prefix for this space.
2575       continue;
2576     }
2577 
2578     // The dense prefix is before this region.
2579     size_t region_index_end_dense_prefix =
2580         sd.addr_to_region_idx(dense_prefix_end);
2581     RegionData* const dense_prefix_cp =
2582       sd.region(region_index_end_dense_prefix);
2583     assert(dense_prefix_end == space->end() ||
2584            dense_prefix_cp->available() ||
2585            dense_prefix_cp->claimed(),
2586            "The region after the dense prefix should always be ready to fill");
2587 
2588     size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2589 
2590     // Is there dense prefix work?
2591     size_t total_dense_prefix_regions =
2592       region_index_end_dense_prefix - region_index_start;
2593     // How many regions of the dense prefix should be given to
2594     // each thread?
2595     if (total_dense_prefix_regions > 0) {
2596       uint tasks_for_dense_prefix = 1;
2597       if (total_dense_prefix_regions <=
2598           (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2599         // Don't over partition.  This assumes that
2600         // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2601         // so there are not many regions to process.
2602         tasks_for_dense_prefix = parallel_gc_threads;
2603       } else {
2604         // Over partition
2605         tasks_for_dense_prefix = parallel_gc_threads *
2606           PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2607       }
2608       size_t regions_per_thread = total_dense_prefix_regions /
2609         tasks_for_dense_prefix;
2610       // Give each thread at least 1 region.
2611       if (regions_per_thread == 0) {
2612         regions_per_thread = 1;
2613       }
2614 
2615       for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2616         if (region_index_start >= region_index_end_dense_prefix) {
2617           break;
2618         }
2619         // region_index_end is not processed
2620         size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2621                                        region_index_end_dense_prefix);
2622         q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2623                                              region_index_start,
2624                                              region_index_end));
2625         region_index_start = region_index_end;
2626       }
2627     }
2628     // This gets any part of the dense prefix that did not
2629     // fit evenly.
2630     if (region_index_start < region_index_end_dense_prefix) {
2631       q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2632                                            region_index_start,
2633                                            region_index_end_dense_prefix));
2634     }
2635   }
2636 }
2637 
2638 void PSParallelCompact::enqueue_region_stealing_tasks(
2639                                      GCTaskQueue* q,
2640                                      ParallelTaskTerminator* terminator_ptr,
2641                                      uint parallel_gc_threads) {
2642   GCTraceTime tm("steal task setup", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2643 
2644   // Once a thread has drained it's stack, it should try to steal regions from
2645   // other threads.
2646   if (parallel_gc_threads > 1) {
2647     for (uint j = 0; j < parallel_gc_threads; j++) {
2648       q->enqueue(new StealRegionCompactionTask(terminator_ptr));
2649     }
2650   }
2651 }
2652 
2653 #ifdef ASSERT
2654 // Write a histogram of the number of times the block table was filled for a
2655 // region.
2656 void PSParallelCompact::write_block_fill_histogram(outputStream* const out)
2657 {
2658   if (!TraceParallelOldGCCompactionPhase) return;
2659 
2660   typedef ParallelCompactData::RegionData rd_t;
2661   ParallelCompactData& sd = summary_data();
2662 
2663   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2664     MutableSpace* const spc = _space_info[id].space();
2665     if (spc->bottom() != spc->top()) {
2666       const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
2667       HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
2668       const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
2669 
2670       size_t histo[5] = { 0, 0, 0, 0, 0 };
2671       const size_t histo_len = sizeof(histo) / sizeof(size_t);
2672       const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
2673 
2674       for (const rd_t* cur = beg; cur < end; ++cur) {
2675         ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
2676       }
2677       out->print("%u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
2678       for (size_t i = 0; i < histo_len; ++i) {
2679         out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
2680                    histo[i], 100.0 * histo[i] / region_cnt);
2681       }
2682       out->cr();
2683     }
2684   }
2685 }
2686 #endif // #ifdef ASSERT
2687 
2688 void PSParallelCompact::compact() {
2689   // trace("5");
2690   GCTraceTime tm("compaction phase", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2691 
2692   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
2693   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
2694   PSOldGen* old_gen = heap->old_gen();
2695   old_gen->start_array()->reset();
2696   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2697   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2698   TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2699   ParallelTaskTerminator terminator(active_gc_threads, qset);
2700 
2701   GCTaskQueue* q = GCTaskQueue::create();
2702   enqueue_region_draining_tasks(q, active_gc_threads);
2703   enqueue_dense_prefix_tasks(q, active_gc_threads);
2704   enqueue_region_stealing_tasks(q, &terminator, active_gc_threads);
2705 
2706   {
2707     GCTraceTime tm_pc("par compact", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2708 
2709     gc_task_manager()->execute_and_wait(q);
2710 
2711 #ifdef  ASSERT
2712     // Verify that all regions have been processed before the deferred updates.
2713     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2714       verify_complete(SpaceId(id));
2715     }
2716 #endif
2717   }
2718 
2719   {
2720     // Update the deferred objects, if any.  Any compaction manager can be used.
2721     GCTraceTime tm_du("deferred updates", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2722     ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2723     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2724       update_deferred_objects(cm, SpaceId(id));
2725     }
2726   }
2727 
2728   DEBUG_ONLY(write_block_fill_histogram(gclog_or_tty));
2729 }
2730 
2731 #ifdef  ASSERT
2732 void PSParallelCompact::verify_complete(SpaceId space_id) {
2733   // All Regions between space bottom() to new_top() should be marked as filled
2734   // and all Regions between new_top() and top() should be available (i.e.,
2735   // should have been emptied).
2736   ParallelCompactData& sd = summary_data();
2737   SpaceInfo si = _space_info[space_id];
2738   HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2739   HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2740   const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2741   const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2742   const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2743 
2744   bool issued_a_warning = false;
2745 
2746   size_t cur_region;
2747   for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2748     const RegionData* const c = sd.region(cur_region);
2749     if (!c->completed()) {
2750       warning("region " SIZE_FORMAT " not filled:  "
2751               "destination_count=" SIZE_FORMAT,
2752               cur_region, c->destination_count());
2753       issued_a_warning = true;
2754     }
2755   }
2756 
2757   for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2758     const RegionData* const c = sd.region(cur_region);
2759     if (!c->available()) {
2760       warning("region " SIZE_FORMAT " not empty:   "
2761               "destination_count=" SIZE_FORMAT,
2762               cur_region, c->destination_count());
2763       issued_a_warning = true;
2764     }
2765   }
2766 
2767   if (issued_a_warning) {
2768     print_region_ranges();
2769   }
2770 }
2771 #endif  // #ifdef ASSERT
2772 
2773 // Update interior oops in the ranges of regions [beg_region, end_region).
2774 void
2775 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2776                                                        SpaceId space_id,
2777                                                        size_t beg_region,
2778                                                        size_t end_region) {
2779   ParallelCompactData& sd = summary_data();
2780   ParMarkBitMap* const mbm = mark_bitmap();
2781 
2782   HeapWord* beg_addr = sd.region_to_addr(beg_region);
2783   HeapWord* const end_addr = sd.region_to_addr(end_region);
2784   assert(beg_region <= end_region, "bad region range");
2785   assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2786 
2787 #ifdef  ASSERT
2788   // Claim the regions to avoid triggering an assert when they are marked as
2789   // filled.
2790   for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2791     assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2792   }
2793 #endif  // #ifdef ASSERT
2794 
2795   if (beg_addr != space(space_id)->bottom()) {
2796     // Find the first live object or block of dead space that *starts* in this
2797     // range of regions.  If a partial object crosses onto the region, skip it;
2798     // it will be marked for 'deferred update' when the object head is
2799     // processed.  If dead space crosses onto the region, it is also skipped; it
2800     // will be filled when the prior region is processed.  If neither of those
2801     // apply, the first word in the region is the start of a live object or dead
2802     // space.
2803     assert(beg_addr > space(space_id)->bottom(), "sanity");
2804     const RegionData* const cp = sd.region(beg_region);
2805     if (cp->partial_obj_size() != 0) {
2806       beg_addr = sd.partial_obj_end(beg_region);
2807     } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2808       beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2809     }
2810   }
2811 
2812   if (beg_addr < end_addr) {
2813     // A live object or block of dead space starts in this range of Regions.
2814      HeapWord* const dense_prefix_end = dense_prefix(space_id);
2815 
2816     // Create closures and iterate.
2817     UpdateOnlyClosure update_closure(mbm, cm, space_id);
2818     FillClosure fill_closure(cm, space_id);
2819     ParMarkBitMap::IterationStatus status;
2820     status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2821                           dense_prefix_end);
2822     if (status == ParMarkBitMap::incomplete) {
2823       update_closure.do_addr(update_closure.source());
2824     }
2825   }
2826 
2827   // Mark the regions as filled.
2828   RegionData* const beg_cp = sd.region(beg_region);
2829   RegionData* const end_cp = sd.region(end_region);
2830   for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2831     cp->set_completed();
2832   }
2833 }
2834 
2835 // Return the SpaceId for the space containing addr.  If addr is not in the
2836 // heap, last_space_id is returned.  In debug mode it expects the address to be
2837 // in the heap and asserts such.
2838 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2839   assert(Universe::heap()->is_in_reserved(addr), "addr not in the heap");
2840 
2841   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2842     if (_space_info[id].space()->contains(addr)) {
2843       return SpaceId(id);
2844     }
2845   }
2846 
2847   assert(false, "no space contains the addr");
2848   return last_space_id;
2849 }
2850 
2851 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2852                                                 SpaceId id) {
2853   assert(id < last_space_id, "bad space id");
2854 
2855   ParallelCompactData& sd = summary_data();
2856   const SpaceInfo* const space_info = _space_info + id;
2857   ObjectStartArray* const start_array = space_info->start_array();
2858 
2859   const MutableSpace* const space = space_info->space();
2860   assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2861   HeapWord* const beg_addr = space_info->dense_prefix();
2862   HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2863 
2864   const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2865   const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2866   const RegionData* cur_region;
2867   for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2868     HeapWord* const addr = cur_region->deferred_obj_addr();
2869     if (addr != NULL) {
2870       if (start_array != NULL) {
2871         start_array->allocate_block(addr);
2872       }
2873       oop(addr)->update_contents(cm);
2874       assert(oop(addr)->is_oop_or_null(), "should be an oop now");
2875     }
2876   }
2877 }
2878 
2879 // Skip over count live words starting from beg, and return the address of the
2880 // next live word.  Unless marked, the word corresponding to beg is assumed to
2881 // be dead.  Callers must either ensure beg does not correspond to the middle of
2882 // an object, or account for those live words in some other way.  Callers must
2883 // also ensure that there are enough live words in the range [beg, end) to skip.
2884 HeapWord*
2885 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2886 {
2887   assert(count > 0, "sanity");
2888 
2889   ParMarkBitMap* m = mark_bitmap();
2890   idx_t bits_to_skip = m->words_to_bits(count);
2891   idx_t cur_beg = m->addr_to_bit(beg);
2892   const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end));
2893 
2894   do {
2895     cur_beg = m->find_obj_beg(cur_beg, search_end);
2896     idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2897     const size_t obj_bits = cur_end - cur_beg + 1;
2898     if (obj_bits > bits_to_skip) {
2899       return m->bit_to_addr(cur_beg + bits_to_skip);
2900     }
2901     bits_to_skip -= obj_bits;
2902     cur_beg = cur_end + 1;
2903   } while (bits_to_skip > 0);
2904 
2905   // Skipping the desired number of words landed just past the end of an object.
2906   // Find the start of the next object.
2907   cur_beg = m->find_obj_beg(cur_beg, search_end);
2908   assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2909   return m->bit_to_addr(cur_beg);
2910 }
2911 
2912 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2913                                             SpaceId src_space_id,
2914                                             size_t src_region_idx)
2915 {
2916   assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2917 
2918   const SplitInfo& split_info = _space_info[src_space_id].split_info();
2919   if (split_info.dest_region_addr() == dest_addr) {
2920     // The partial object ending at the split point contains the first word to
2921     // be copied to dest_addr.
2922     return split_info.first_src_addr();
2923   }
2924 
2925   const ParallelCompactData& sd = summary_data();
2926   ParMarkBitMap* const bitmap = mark_bitmap();
2927   const size_t RegionSize = ParallelCompactData::RegionSize;
2928 
2929   assert(sd.is_region_aligned(dest_addr), "not aligned");
2930   const RegionData* const src_region_ptr = sd.region(src_region_idx);
2931   const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2932   HeapWord* const src_region_destination = src_region_ptr->destination();
2933 
2934   assert(dest_addr >= src_region_destination, "wrong src region");
2935   assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2936 
2937   HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2938   HeapWord* const src_region_end = src_region_beg + RegionSize;
2939 
2940   HeapWord* addr = src_region_beg;
2941   if (dest_addr == src_region_destination) {
2942     // Return the first live word in the source region.
2943     if (partial_obj_size == 0) {
2944       addr = bitmap->find_obj_beg(addr, src_region_end);
2945       assert(addr < src_region_end, "no objects start in src region");
2946     }
2947     return addr;
2948   }
2949 
2950   // Must skip some live data.
2951   size_t words_to_skip = dest_addr - src_region_destination;
2952   assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2953 
2954   if (partial_obj_size >= words_to_skip) {
2955     // All the live words to skip are part of the partial object.
2956     addr += words_to_skip;
2957     if (partial_obj_size == words_to_skip) {
2958       // Find the first live word past the partial object.
2959       addr = bitmap->find_obj_beg(addr, src_region_end);
2960       assert(addr < src_region_end, "wrong src region");
2961     }
2962     return addr;
2963   }
2964 
2965   // Skip over the partial object (if any).
2966   if (partial_obj_size != 0) {
2967     words_to_skip -= partial_obj_size;
2968     addr += partial_obj_size;
2969   }
2970 
2971   // Skip over live words due to objects that start in the region.
2972   addr = skip_live_words(addr, src_region_end, words_to_skip);
2973   assert(addr < src_region_end, "wrong src region");
2974   return addr;
2975 }
2976 
2977 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2978                                                      SpaceId src_space_id,
2979                                                      size_t beg_region,
2980                                                      HeapWord* end_addr)
2981 {
2982   ParallelCompactData& sd = summary_data();
2983 
2984 #ifdef ASSERT
2985   MutableSpace* const src_space = _space_info[src_space_id].space();
2986   HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2987   assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2988          "src_space_id does not match beg_addr");
2989   assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2990          "src_space_id does not match end_addr");
2991 #endif // #ifdef ASSERT
2992 
2993   RegionData* const beg = sd.region(beg_region);
2994   RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2995 
2996   // Regions up to new_top() are enqueued if they become available.
2997   HeapWord* const new_top = _space_info[src_space_id].new_top();
2998   RegionData* const enqueue_end =
2999     sd.addr_to_region_ptr(sd.region_align_up(new_top));
3000 
3001   for (RegionData* cur = beg; cur < end; ++cur) {
3002     assert(cur->data_size() > 0, "region must have live data");
3003     cur->decrement_destination_count();
3004     if (cur < enqueue_end && cur->available() && cur->claim()) {
3005       cm->push_region(sd.region(cur));
3006     }
3007   }
3008 }
3009 
3010 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
3011                                           SpaceId& src_space_id,
3012                                           HeapWord*& src_space_top,
3013                                           HeapWord* end_addr)
3014 {
3015   typedef ParallelCompactData::RegionData RegionData;
3016 
3017   ParallelCompactData& sd = PSParallelCompact::summary_data();
3018   const size_t region_size = ParallelCompactData::RegionSize;
3019 
3020   size_t src_region_idx = 0;
3021 
3022   // Skip empty regions (if any) up to the top of the space.
3023   HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
3024   RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
3025   HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
3026   const RegionData* const top_region_ptr =
3027     sd.addr_to_region_ptr(top_aligned_up);
3028   while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
3029     ++src_region_ptr;
3030   }
3031 
3032   if (src_region_ptr < top_region_ptr) {
3033     // The next source region is in the current space.  Update src_region_idx
3034     // and the source address to match src_region_ptr.
3035     src_region_idx = sd.region(src_region_ptr);
3036     HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
3037     if (src_region_addr > closure.source()) {
3038       closure.set_source(src_region_addr);
3039     }
3040     return src_region_idx;
3041   }
3042 
3043   // Switch to a new source space and find the first non-empty region.
3044   unsigned int space_id = src_space_id + 1;
3045   assert(space_id < last_space_id, "not enough spaces");
3046 
3047   HeapWord* const destination = closure.destination();
3048 
3049   do {
3050     MutableSpace* space = _space_info[space_id].space();
3051     HeapWord* const bottom = space->bottom();
3052     const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
3053 
3054     // Iterate over the spaces that do not compact into themselves.
3055     if (bottom_cp->destination() != bottom) {
3056       HeapWord* const top_aligned_up = sd.region_align_up(space->top());
3057       const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
3058 
3059       for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
3060         if (src_cp->live_obj_size() > 0) {
3061           // Found it.
3062           assert(src_cp->destination() == destination,
3063                  "first live obj in the space must match the destination");
3064           assert(src_cp->partial_obj_size() == 0,
3065                  "a space cannot begin with a partial obj");
3066 
3067           src_space_id = SpaceId(space_id);
3068           src_space_top = space->top();
3069           const size_t src_region_idx = sd.region(src_cp);
3070           closure.set_source(sd.region_to_addr(src_region_idx));
3071           return src_region_idx;
3072         } else {
3073           assert(src_cp->data_size() == 0, "sanity");
3074         }
3075       }
3076     }
3077   } while (++space_id < last_space_id);
3078 
3079   assert(false, "no source region was found");
3080   return 0;
3081 }
3082 
3083 void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx)
3084 {
3085   typedef ParMarkBitMap::IterationStatus IterationStatus;
3086   const size_t RegionSize = ParallelCompactData::RegionSize;
3087   ParMarkBitMap* const bitmap = mark_bitmap();
3088   ParallelCompactData& sd = summary_data();
3089   RegionData* const region_ptr = sd.region(region_idx);
3090 
3091   // Get the items needed to construct the closure.
3092   HeapWord* dest_addr = sd.region_to_addr(region_idx);
3093   SpaceId dest_space_id = space_id(dest_addr);
3094   ObjectStartArray* start_array = _space_info[dest_space_id].start_array();
3095   HeapWord* new_top = _space_info[dest_space_id].new_top();
3096   assert(dest_addr < new_top, "sanity");
3097   const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize);
3098 
3099   // Get the source region and related info.
3100   size_t src_region_idx = region_ptr->source_region();
3101   SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
3102   HeapWord* src_space_top = _space_info[src_space_id].space()->top();
3103 
3104   MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3105   closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
3106 
3107   // Adjust src_region_idx to prepare for decrementing destination counts (the
3108   // destination count is not decremented when a region is copied to itself).
3109   if (src_region_idx == region_idx) {
3110     src_region_idx += 1;
3111   }
3112 
3113   if (bitmap->is_unmarked(closure.source())) {
3114     // The first source word is in the middle of an object; copy the remainder
3115     // of the object or as much as will fit.  The fact that pointer updates were
3116     // deferred will be noted when the object header is processed.
3117     HeapWord* const old_src_addr = closure.source();
3118     closure.copy_partial_obj();
3119     if (closure.is_full()) {
3120       decrement_destination_counts(cm, src_space_id, src_region_idx,
3121                                    closure.source());
3122       region_ptr->set_deferred_obj_addr(NULL);
3123       region_ptr->set_completed();
3124       return;
3125     }
3126 
3127     HeapWord* const end_addr = sd.region_align_down(closure.source());
3128     if (sd.region_align_down(old_src_addr) != end_addr) {
3129       // The partial object was copied from more than one source region.
3130       decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3131 
3132       // Move to the next source region, possibly switching spaces as well.  All
3133       // args except end_addr may be modified.
3134       src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3135                                        end_addr);
3136     }
3137   }
3138 
3139   do {
3140     HeapWord* const cur_addr = closure.source();
3141     HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
3142                                     src_space_top);
3143     IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
3144 
3145     if (status == ParMarkBitMap::incomplete) {
3146       // The last obj that starts in the source region does not end in the
3147       // region.
3148       assert(closure.source() < end_addr, "sanity");
3149       HeapWord* const obj_beg = closure.source();
3150       HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
3151                                        src_space_top);
3152       HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
3153       if (obj_end < range_end) {
3154         // The end was found; the entire object will fit.
3155         status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
3156         assert(status != ParMarkBitMap::would_overflow, "sanity");
3157       } else {
3158         // The end was not found; the object will not fit.
3159         assert(range_end < src_space_top, "obj cannot cross space boundary");
3160         status = ParMarkBitMap::would_overflow;
3161       }
3162     }
3163 
3164     if (status == ParMarkBitMap::would_overflow) {
3165       // The last object did not fit.  Note that interior oop updates were
3166       // deferred, then copy enough of the object to fill the region.
3167       region_ptr->set_deferred_obj_addr(closure.destination());
3168       status = closure.copy_until_full(); // copies from closure.source()
3169 
3170       decrement_destination_counts(cm, src_space_id, src_region_idx,
3171                                    closure.source());
3172       region_ptr->set_completed();
3173       return;
3174     }
3175 
3176     if (status == ParMarkBitMap::full) {
3177       decrement_destination_counts(cm, src_space_id, src_region_idx,
3178                                    closure.source());
3179       region_ptr->set_deferred_obj_addr(NULL);
3180       region_ptr->set_completed();
3181       return;
3182     }
3183 
3184     decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3185 
3186     // Move to the next source region, possibly switching spaces as well.  All
3187     // args except end_addr may be modified.
3188     src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3189                                      end_addr);
3190   } while (true);
3191 }
3192 
3193 void PSParallelCompact::fill_blocks(size_t region_idx)
3194 {
3195   // Fill in the block table elements for the specified region.  Each block
3196   // table element holds the number of live words in the region that are to the
3197   // left of the first object that starts in the block.  Thus only blocks in
3198   // which an object starts need to be filled.
3199   //
3200   // The algorithm scans the section of the bitmap that corresponds to the
3201   // region, keeping a running total of the live words.  When an object start is
3202   // found, if it's the first to start in the block that contains it, the
3203   // current total is written to the block table element.
3204   const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
3205   const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
3206   const size_t RegionSize = ParallelCompactData::RegionSize;
3207 
3208   ParallelCompactData& sd = summary_data();
3209   const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
3210   if (partial_obj_size >= RegionSize) {
3211     return; // No objects start in this region.
3212   }
3213 
3214   // Ensure the first loop iteration decides that the block has changed.
3215   size_t cur_block = sd.block_count();
3216 
3217   const ParMarkBitMap* const bitmap = mark_bitmap();
3218 
3219   const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
3220   assert((size_t)1 << Log2BitsPerBlock ==
3221          bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
3222 
3223   size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
3224   const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
3225   size_t live_bits = bitmap->words_to_bits(partial_obj_size);
3226   beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
3227   while (beg_bit < range_end) {
3228     const size_t new_block = beg_bit >> Log2BitsPerBlock;
3229     if (new_block != cur_block) {
3230       cur_block = new_block;
3231       sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
3232     }
3233 
3234     const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
3235     if (end_bit < range_end - 1) {
3236       live_bits += end_bit - beg_bit + 1;
3237       beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
3238     } else {
3239       return;
3240     }
3241   }
3242 }
3243 
3244 void
3245 PSParallelCompact::move_and_update(ParCompactionManager* cm, SpaceId space_id) {
3246   const MutableSpace* sp = space(space_id);
3247   if (sp->is_empty()) {
3248     return;
3249   }
3250 
3251   ParallelCompactData& sd = PSParallelCompact::summary_data();
3252   ParMarkBitMap* const bitmap = mark_bitmap();
3253   HeapWord* const dp_addr = dense_prefix(space_id);
3254   HeapWord* beg_addr = sp->bottom();
3255   HeapWord* end_addr = sp->top();
3256 
3257   assert(beg_addr <= dp_addr && dp_addr <= end_addr, "bad dense prefix");
3258 
3259   const size_t beg_region = sd.addr_to_region_idx(beg_addr);
3260   const size_t dp_region = sd.addr_to_region_idx(dp_addr);
3261   if (beg_region < dp_region) {
3262     update_and_deadwood_in_dense_prefix(cm, space_id, beg_region, dp_region);
3263   }
3264 
3265   // The destination of the first live object that starts in the region is one
3266   // past the end of the partial object entering the region (if any).
3267   HeapWord* const dest_addr = sd.partial_obj_end(dp_region);
3268   HeapWord* const new_top = _space_info[space_id].new_top();
3269   assert(new_top >= dest_addr, "bad new_top value");
3270   const size_t words = pointer_delta(new_top, dest_addr);
3271 
3272   if (words > 0) {
3273     ObjectStartArray* start_array = _space_info[space_id].start_array();
3274     MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3275 
3276     ParMarkBitMap::IterationStatus status;
3277     status = bitmap->iterate(&closure, dest_addr, end_addr);
3278     assert(status == ParMarkBitMap::full, "iteration not complete");
3279     assert(bitmap->find_obj_beg(closure.source(), end_addr) == end_addr,
3280            "live objects skipped because closure is full");
3281   }
3282 }
3283 
3284 jlong PSParallelCompact::millis_since_last_gc() {
3285   // We need a monotonically non-deccreasing time in ms but
3286   // os::javaTimeMillis() does not guarantee monotonicity.
3287   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3288   jlong ret_val = now - _time_of_last_gc;
3289   // XXX See note in genCollectedHeap::millis_since_last_gc().
3290   if (ret_val < 0) {
3291     NOT_PRODUCT(warning("time warp: "INT64_FORMAT, ret_val);)
3292     return 0;
3293   }
3294   return ret_val;
3295 }
3296 
3297 void PSParallelCompact::reset_millis_since_last_gc() {
3298   // We need a monotonically non-deccreasing time in ms but
3299   // os::javaTimeMillis() does not guarantee monotonicity.
3300   _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3301 }
3302 
3303 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3304 {
3305   if (source() != destination()) {
3306     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3307     Copy::aligned_conjoint_words(source(), destination(), words_remaining());
3308   }
3309   update_state(words_remaining());
3310   assert(is_full(), "sanity");
3311   return ParMarkBitMap::full;
3312 }
3313 
3314 void MoveAndUpdateClosure::copy_partial_obj()
3315 {
3316   size_t words = words_remaining();
3317 
3318   HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3319   HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3320   if (end_addr < range_end) {
3321     words = bitmap()->obj_size(source(), end_addr);
3322   }
3323 
3324   // This test is necessary; if omitted, the pointer updates to a partial object
3325   // that crosses the dense prefix boundary could be overwritten.
3326   if (source() != destination()) {
3327     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3328     Copy::aligned_conjoint_words(source(), destination(), words);
3329   }
3330   update_state(words);
3331 }
3332 
3333 ParMarkBitMapClosure::IterationStatus
3334 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3335   assert(destination() != NULL, "sanity");
3336   assert(bitmap()->obj_size(addr) == words, "bad size");
3337 
3338   _source = addr;
3339   assert(PSParallelCompact::summary_data().calc_new_pointer(source()) ==
3340          destination(), "wrong destination");
3341 
3342   if (words > words_remaining()) {
3343     return ParMarkBitMap::would_overflow;
3344   }
3345 
3346   // The start_array must be updated even if the object is not moving.
3347   if (_start_array != NULL) {
3348     _start_array->allocate_block(destination());
3349   }
3350 
3351   if (destination() != source()) {
3352     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3353     Copy::aligned_conjoint_words(source(), destination(), words);
3354   }
3355 
3356   oop moved_oop = (oop) destination();
3357   moved_oop->update_contents(compaction_manager());
3358   assert(moved_oop->is_oop_or_null(), "Object should be whole at this point");
3359 
3360   update_state(words);
3361   assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
3362   return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3363 }
3364 
3365 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3366                                      ParCompactionManager* cm,
3367                                      PSParallelCompact::SpaceId space_id) :
3368   ParMarkBitMapClosure(mbm, cm),
3369   _space_id(space_id),
3370   _start_array(PSParallelCompact::start_array(space_id))
3371 {
3372 }
3373 
3374 // Updates the references in the object to their new values.
3375 ParMarkBitMapClosure::IterationStatus
3376 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3377   do_addr(addr);
3378   return ParMarkBitMap::incomplete;
3379 }