1 /*
   2  * Copyright (c) 2005, 2012, 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/generationSizer.hpp"
  31 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.inline.hpp"
  32 #include "gc_implementation/parallelScavenge/pcTasks.hpp"
  33 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
  34 #include "gc_implementation/parallelScavenge/psCompactionManager.inline.hpp"
  35 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
  36 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp"
  37 #include "gc_implementation/parallelScavenge/psOldGen.hpp"
  38 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
  39 #include "gc_implementation/parallelScavenge/psPromotionManager.inline.hpp"
  40 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
  41 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"
  42 #include "gc_implementation/shared/isGCActiveMark.hpp"
  43 #include "gc_interface/gcCause.hpp"
  44 #include "memory/gcLocker.inline.hpp"
  45 #include "memory/referencePolicy.hpp"
  46 #include "memory/referenceProcessor.hpp"
  47 #include "oops/methodData.hpp"
  48 #include "oops/oop.inline.hpp"
  49 #include "oops/oop.pcgc.inline.hpp"
  50 #include "runtime/fprofiler.hpp"
  51 #include "runtime/safepoint.hpp"
  52 #include "runtime/vmThread.hpp"
  53 #include "services/management.hpp"
  54 #include "services/memoryService.hpp"
  55 #include "services/memTracker.hpp"
  56 #include "utilities/events.hpp"
  57 #include "utilities/stack.inline.hpp"
  58 
  59 #include <math.h>
  60 
  61 // All sizes are in HeapWords.
  62 const size_t ParallelCompactData::Log2RegionSize  = 9; // 512 words
  63 const size_t ParallelCompactData::RegionSize      = (size_t)1 << Log2RegionSize;
  64 const size_t ParallelCompactData::RegionSizeBytes =
  65   RegionSize << LogHeapWordSize;
  66 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
  67 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
  68 const size_t ParallelCompactData::RegionAddrMask  = ~RegionAddrOffsetMask;
  69 
  70 const ParallelCompactData::RegionData::region_sz_t
  71 ParallelCompactData::RegionData::dc_shift = 27;
  72 
  73 const ParallelCompactData::RegionData::region_sz_t
  74 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
  75 
  76 const ParallelCompactData::RegionData::region_sz_t
  77 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
  78 
  79 const ParallelCompactData::RegionData::region_sz_t
  80 ParallelCompactData::RegionData::los_mask = ~dc_mask;
  81 
  82 const ParallelCompactData::RegionData::region_sz_t
  83 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
  84 
  85 const ParallelCompactData::RegionData::region_sz_t
  86 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
  87 
  88 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
  89 bool      PSParallelCompact::_print_phases = false;
  90 
  91 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
  92 Klass*              PSParallelCompact::_updated_int_array_klass_obj = NULL;
  93 
  94 double PSParallelCompact::_dwl_mean;
  95 double PSParallelCompact::_dwl_std_dev;
  96 double PSParallelCompact::_dwl_first_term;
  97 double PSParallelCompact::_dwl_adjustment;
  98 #ifdef  ASSERT
  99 bool   PSParallelCompact::_dwl_initialized = false;
 100 #endif  // #ifdef ASSERT
 101 
 102 void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
 103                        HeapWord* destination)
 104 {
 105   assert(src_region_idx != 0, "invalid src_region_idx");
 106   assert(partial_obj_size != 0, "invalid partial_obj_size argument");
 107   assert(destination != NULL, "invalid destination argument");
 108 
 109   _src_region_idx = src_region_idx;
 110   _partial_obj_size = partial_obj_size;
 111   _destination = destination;
 112 
 113   // These fields may not be updated below, so make sure they're clear.
 114   assert(_dest_region_addr == NULL, "should have been cleared");
 115   assert(_first_src_addr == NULL, "should have been cleared");
 116 
 117   // Determine the number of destination regions for the partial object.
 118   HeapWord* const last_word = destination + partial_obj_size - 1;
 119   const ParallelCompactData& sd = PSParallelCompact::summary_data();
 120   HeapWord* const beg_region_addr = sd.region_align_down(destination);
 121   HeapWord* const end_region_addr = sd.region_align_down(last_word);
 122 
 123   if (beg_region_addr == end_region_addr) {
 124     // One destination region.
 125     _destination_count = 1;
 126     if (end_region_addr == destination) {
 127       // The destination falls on a region boundary, thus the first word of the
 128       // partial object will be the first word copied to the destination region.
 129       _dest_region_addr = end_region_addr;
 130       _first_src_addr = sd.region_to_addr(src_region_idx);
 131     }
 132   } else {
 133     // Two destination regions.  When copied, the partial object will cross a
 134     // destination region boundary, so a word somewhere within the partial
 135     // object will be the first word copied to the second destination region.
 136     _destination_count = 2;
 137     _dest_region_addr = end_region_addr;
 138     const size_t ofs = pointer_delta(end_region_addr, destination);
 139     assert(ofs < _partial_obj_size, "sanity");
 140     _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
 141   }
 142 }
 143 
 144 void SplitInfo::clear()
 145 {
 146   _src_region_idx = 0;
 147   _partial_obj_size = 0;
 148   _destination = NULL;
 149   _destination_count = 0;
 150   _dest_region_addr = NULL;
 151   _first_src_addr = NULL;
 152   assert(!is_valid(), "sanity");
 153 }
 154 
 155 #ifdef  ASSERT
 156 void SplitInfo::verify_clear()
 157 {
 158   assert(_src_region_idx == 0, "not clear");
 159   assert(_partial_obj_size == 0, "not clear");
 160   assert(_destination == NULL, "not clear");
 161   assert(_destination_count == 0, "not clear");
 162   assert(_dest_region_addr == NULL, "not clear");
 163   assert(_first_src_addr == NULL, "not clear");
 164 }
 165 #endif  // #ifdef ASSERT
 166 
 167 
 168 #ifndef PRODUCT
 169 const char* PSParallelCompact::space_names[] = {
 170   "old ", "eden", "from", "to  "
 171 };
 172 
 173 void PSParallelCompact::print_region_ranges()
 174 {
 175   tty->print_cr("space  bottom     top        end        new_top");
 176   tty->print_cr("------ ---------- ---------- ---------- ----------");
 177 
 178   for (unsigned int id = 0; id < last_space_id; ++id) {
 179     const MutableSpace* space = _space_info[id].space();
 180     tty->print_cr("%u %s "
 181                   SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
 182                   SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
 183                   id, space_names[id],
 184                   summary_data().addr_to_region_idx(space->bottom()),
 185                   summary_data().addr_to_region_idx(space->top()),
 186                   summary_data().addr_to_region_idx(space->end()),
 187                   summary_data().addr_to_region_idx(_space_info[id].new_top()));
 188   }
 189 }
 190 
 191 void
 192 print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
 193 {
 194 #define REGION_IDX_FORMAT        SIZE_FORMAT_W(7)
 195 #define REGION_DATA_FORMAT       SIZE_FORMAT_W(5)
 196 
 197   ParallelCompactData& sd = PSParallelCompact::summary_data();
 198   size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
 199   tty->print_cr(REGION_IDX_FORMAT " " PTR_FORMAT " "
 200                 REGION_IDX_FORMAT " " PTR_FORMAT " "
 201                 REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
 202                 REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
 203                 i, c->data_location(), dci, c->destination(),
 204                 c->partial_obj_size(), c->live_obj_size(),
 205                 c->data_size(), c->source_region(), c->destination_count());
 206 
 207 #undef  REGION_IDX_FORMAT
 208 #undef  REGION_DATA_FORMAT
 209 }
 210 
 211 void
 212 print_generic_summary_data(ParallelCompactData& summary_data,
 213                            HeapWord* const beg_addr,
 214                            HeapWord* const end_addr)
 215 {
 216   size_t total_words = 0;
 217   size_t i = summary_data.addr_to_region_idx(beg_addr);
 218   const size_t last = summary_data.addr_to_region_idx(end_addr);
 219   HeapWord* pdest = 0;
 220 
 221   while (i <= last) {
 222     ParallelCompactData::RegionData* c = summary_data.region(i);
 223     if (c->data_size() != 0 || c->destination() != pdest) {
 224       print_generic_summary_region(i, c);
 225       total_words += c->data_size();
 226       pdest = c->destination();
 227     }
 228     ++i;
 229   }
 230 
 231   tty->print_cr("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
 232 }
 233 
 234 void
 235 print_generic_summary_data(ParallelCompactData& summary_data,
 236                            SpaceInfo* space_info)
 237 {
 238   for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
 239     const MutableSpace* space = space_info[id].space();
 240     print_generic_summary_data(summary_data, space->bottom(),
 241                                MAX2(space->top(), space_info[id].new_top()));
 242   }
 243 }
 244 
 245 void
 246 print_initial_summary_region(size_t i,
 247                              const ParallelCompactData::RegionData* c,
 248                              bool newline = true)
 249 {
 250   tty->print(SIZE_FORMAT_W(5) " " PTR_FORMAT " "
 251              SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " "
 252              SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 253              i, c->destination(),
 254              c->partial_obj_size(), c->live_obj_size(),
 255              c->data_size(), c->source_region(), c->destination_count());
 256   if (newline) tty->cr();
 257 }
 258 
 259 void
 260 print_initial_summary_data(ParallelCompactData& summary_data,
 261                            const MutableSpace* space) {
 262   if (space->top() == space->bottom()) {
 263     return;
 264   }
 265 
 266   const size_t region_size = ParallelCompactData::RegionSize;
 267   typedef ParallelCompactData::RegionData RegionData;
 268   HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
 269   const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
 270   const RegionData* c = summary_data.region(end_region - 1);
 271   HeapWord* end_addr = c->destination() + c->data_size();
 272   const size_t live_in_space = pointer_delta(end_addr, space->bottom());
 273 
 274   // Print (and count) the full regions at the beginning of the space.
 275   size_t full_region_count = 0;
 276   size_t i = summary_data.addr_to_region_idx(space->bottom());
 277   while (i < end_region && summary_data.region(i)->data_size() == region_size) {
 278     print_initial_summary_region(i, summary_data.region(i));
 279     ++full_region_count;
 280     ++i;
 281   }
 282 
 283   size_t live_to_right = live_in_space - full_region_count * region_size;
 284 
 285   double max_reclaimed_ratio = 0.0;
 286   size_t max_reclaimed_ratio_region = 0;
 287   size_t max_dead_to_right = 0;
 288   size_t max_live_to_right = 0;
 289 
 290   // Print the 'reclaimed ratio' for regions while there is something live in
 291   // the region or to the right of it.  The remaining regions are empty (and
 292   // uninteresting), and computing the ratio will result in division by 0.
 293   while (i < end_region && live_to_right > 0) {
 294     c = summary_data.region(i);
 295     HeapWord* const region_addr = summary_data.region_to_addr(i);
 296     const size_t used_to_right = pointer_delta(space->top(), region_addr);
 297     const size_t dead_to_right = used_to_right - live_to_right;
 298     const double reclaimed_ratio = double(dead_to_right) / live_to_right;
 299 
 300     if (reclaimed_ratio > max_reclaimed_ratio) {
 301             max_reclaimed_ratio = reclaimed_ratio;
 302             max_reclaimed_ratio_region = i;
 303             max_dead_to_right = dead_to_right;
 304             max_live_to_right = live_to_right;
 305     }
 306 
 307     print_initial_summary_region(i, c, false);
 308     tty->print_cr(" %12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
 309                   reclaimed_ratio, dead_to_right, live_to_right);
 310 
 311     live_to_right -= c->data_size();
 312     ++i;
 313   }
 314 
 315   // Any remaining regions are empty.  Print one more if there is one.
 316   if (i < end_region) {
 317     print_initial_summary_region(i, summary_data.region(i));
 318   }
 319 
 320   tty->print_cr("max:  " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " "
 321                 "l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
 322                 max_reclaimed_ratio_region, max_dead_to_right,
 323                 max_live_to_right, max_reclaimed_ratio);
 324 }
 325 
 326 void
 327 print_initial_summary_data(ParallelCompactData& summary_data,
 328                            SpaceInfo* space_info) {
 329   unsigned int id = PSParallelCompact::old_space_id;
 330   const MutableSpace* space;
 331   do {
 332     space = space_info[id].space();
 333     print_initial_summary_data(summary_data, space);
 334   } while (++id < PSParallelCompact::eden_space_id);
 335 
 336   do {
 337     space = space_info[id].space();
 338     print_generic_summary_data(summary_data, space->bottom(), space->top());
 339   } while (++id < PSParallelCompact::last_space_id);
 340 }
 341 #endif  // #ifndef PRODUCT
 342 
 343 #ifdef  ASSERT
 344 size_t add_obj_count;
 345 size_t add_obj_size;
 346 size_t mark_bitmap_count;
 347 size_t mark_bitmap_size;
 348 #endif  // #ifdef ASSERT
 349 
 350 ParallelCompactData::ParallelCompactData()
 351 {
 352   _region_start = 0;
 353 
 354   _region_vspace = 0;
 355   _region_data = 0;
 356   _region_count = 0;
 357 }
 358 
 359 bool ParallelCompactData::initialize(MemRegion covered_region)
 360 {
 361   _region_start = covered_region.start();
 362   const size_t region_size = covered_region.word_size();
 363   DEBUG_ONLY(_region_end = _region_start + region_size;)
 364 
 365   assert(region_align_down(_region_start) == _region_start,
 366          "region start not aligned");
 367   assert((region_size & RegionSizeOffsetMask) == 0,
 368          "region size not a multiple of RegionSize");
 369 
 370   bool result = initialize_region_data(region_size);
 371 
 372   return result;
 373 }
 374 
 375 PSVirtualSpace*
 376 ParallelCompactData::create_vspace(size_t count, size_t element_size)
 377 {
 378   const size_t raw_bytes = count * element_size;
 379   const size_t page_sz = os::page_size_for_region(raw_bytes, raw_bytes, 10);
 380   const size_t granularity = os::vm_allocation_granularity();
 381   const size_t bytes = align_size_up(raw_bytes, MAX2(page_sz, granularity));
 382 
 383   const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
 384     MAX2(page_sz, granularity);
 385   ReservedSpace rs(bytes, rs_align, rs_align > 0);
 386   os::trace_page_sizes("par compact", raw_bytes, raw_bytes, page_sz, rs.base(),
 387                        rs.size());
 388 
 389   MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
 390 
 391   PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
 392   if (vspace != 0) {
 393     if (vspace->expand_by(bytes)) {
 394       return vspace;
 395     }
 396     delete vspace;
 397     // Release memory reserved in the space.
 398     rs.release();
 399   }
 400 
 401   return 0;
 402 }
 403 
 404 bool ParallelCompactData::initialize_region_data(size_t region_size)
 405 {
 406   const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
 407   _region_vspace = create_vspace(count, sizeof(RegionData));
 408   if (_region_vspace != 0) {
 409     _region_data = (RegionData*)_region_vspace->reserved_low_addr();
 410     _region_count = count;
 411     return true;
 412   }
 413   return false;
 414 }
 415 
 416 void ParallelCompactData::clear()
 417 {
 418   memset(_region_data, 0, _region_vspace->committed_size());
 419 }
 420 
 421 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
 422   assert(beg_region <= _region_count, "beg_region out of range");
 423   assert(end_region <= _region_count, "end_region out of range");
 424 
 425   const size_t region_cnt = end_region - beg_region;
 426   memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
 427 }
 428 
 429 HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
 430 {
 431   const RegionData* cur_cp = region(region_idx);
 432   const RegionData* const end_cp = region(region_count() - 1);
 433 
 434   HeapWord* result = region_to_addr(region_idx);
 435   if (cur_cp < end_cp) {
 436     do {
 437       result += cur_cp->partial_obj_size();
 438     } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
 439   }
 440   return result;
 441 }
 442 
 443 void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
 444 {
 445   const size_t obj_ofs = pointer_delta(addr, _region_start);
 446   const size_t beg_region = obj_ofs >> Log2RegionSize;
 447   const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
 448 
 449   DEBUG_ONLY(Atomic::inc_ptr(&add_obj_count);)
 450   DEBUG_ONLY(Atomic::add_ptr(len, &add_obj_size);)
 451 
 452   if (beg_region == end_region) {
 453     // All in one region.
 454     _region_data[beg_region].add_live_obj(len);
 455     return;
 456   }
 457 
 458   // First region.
 459   const size_t beg_ofs = region_offset(addr);
 460   _region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
 461 
 462   Klass* klass = ((oop)addr)->klass();
 463   // Middle regions--completely spanned by this object.
 464   for (size_t region = beg_region + 1; region < end_region; ++region) {
 465     _region_data[region].set_partial_obj_size(RegionSize);
 466     _region_data[region].set_partial_obj_addr(addr);
 467   }
 468 
 469   // Last region.
 470   const size_t end_ofs = region_offset(addr + len - 1);
 471   _region_data[end_region].set_partial_obj_size(end_ofs + 1);
 472   _region_data[end_region].set_partial_obj_addr(addr);
 473 }
 474 
 475 void
 476 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
 477 {
 478   assert(region_offset(beg) == 0, "not RegionSize aligned");
 479   assert(region_offset(end) == 0, "not RegionSize aligned");
 480 
 481   size_t cur_region = addr_to_region_idx(beg);
 482   const size_t end_region = addr_to_region_idx(end);
 483   HeapWord* addr = beg;
 484   while (cur_region < end_region) {
 485     _region_data[cur_region].set_destination(addr);
 486     _region_data[cur_region].set_destination_count(0);
 487     _region_data[cur_region].set_source_region(cur_region);
 488     _region_data[cur_region].set_data_location(addr);
 489 
 490     // Update live_obj_size so the region appears completely full.
 491     size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
 492     _region_data[cur_region].set_live_obj_size(live_size);
 493 
 494     ++cur_region;
 495     addr += RegionSize;
 496   }
 497 }
 498 
 499 // Find the point at which a space can be split and, if necessary, record the
 500 // split point.
 501 //
 502 // If the current src region (which overflowed the destination space) doesn't
 503 // have a partial object, the split point is at the beginning of the current src
 504 // region (an "easy" split, no extra bookkeeping required).
 505 //
 506 // If the current src region has a partial object, the split point is in the
 507 // region where that partial object starts (call it the split_region).  If
 508 // split_region has a partial object, then the split point is just after that
 509 // partial object (a "hard" split where we have to record the split data and
 510 // zero the partial_obj_size field).  With a "hard" split, we know that the
 511 // partial_obj ends within split_region because the partial object that caused
 512 // the overflow starts in split_region.  If split_region doesn't have a partial
 513 // obj, then the split is at the beginning of split_region (another "easy"
 514 // split).
 515 HeapWord*
 516 ParallelCompactData::summarize_split_space(size_t src_region,
 517                                            SplitInfo& split_info,
 518                                            HeapWord* destination,
 519                                            HeapWord* target_end,
 520                                            HeapWord** target_next)
 521 {
 522   assert(destination <= target_end, "sanity");
 523   assert(destination + _region_data[src_region].data_size() > target_end,
 524     "region should not fit into target space");
 525   assert(is_region_aligned(target_end), "sanity");
 526 
 527   size_t split_region = src_region;
 528   HeapWord* split_destination = destination;
 529   size_t partial_obj_size = _region_data[src_region].partial_obj_size();
 530 
 531   if (destination + partial_obj_size > target_end) {
 532     // The split point is just after the partial object (if any) in the
 533     // src_region that contains the start of the object that overflowed the
 534     // destination space.
 535     //
 536     // Find the start of the "overflow" object and set split_region to the
 537     // region containing it.
 538     HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
 539     split_region = addr_to_region_idx(overflow_obj);
 540 
 541     // Clear the source_region field of all destination regions whose first word
 542     // came from data after the split point (a non-null source_region field
 543     // implies a region must be filled).
 544     //
 545     // An alternative to the simple loop below:  clear during post_compact(),
 546     // which uses memcpy instead of individual stores, and is easy to
 547     // parallelize.  (The downside is that it clears the entire RegionData
 548     // object as opposed to just one field.)
 549     //
 550     // post_compact() would have to clear the summary data up to the highest
 551     // address that was written during the summary phase, which would be
 552     //
 553     //         max(top, max(new_top, clear_top))
 554     //
 555     // where clear_top is a new field in SpaceInfo.  Would have to set clear_top
 556     // to target_end.
 557     const RegionData* const sr = region(split_region);
 558     const size_t beg_idx =
 559       addr_to_region_idx(region_align_up(sr->destination() +
 560                                          sr->partial_obj_size()));
 561     const size_t end_idx = addr_to_region_idx(target_end);
 562 
 563     if (TraceParallelOldGCSummaryPhase) {
 564         gclog_or_tty->print_cr("split:  clearing source_region field in ["
 565                                SIZE_FORMAT ", " SIZE_FORMAT ")",
 566                                beg_idx, end_idx);
 567     }
 568     for (size_t idx = beg_idx; idx < end_idx; ++idx) {
 569       _region_data[idx].set_source_region(0);
 570     }
 571 
 572     // Set split_destination and partial_obj_size to reflect the split region.
 573     split_destination = sr->destination();
 574     partial_obj_size = sr->partial_obj_size();
 575   }
 576 
 577   // The split is recorded only if a partial object extends onto the region.
 578   if (partial_obj_size != 0) {
 579     _region_data[split_region].set_partial_obj_size(0);
 580     split_info.record(split_region, partial_obj_size, split_destination);
 581   }
 582 
 583   // Setup the continuation addresses.
 584   *target_next = split_destination + partial_obj_size;
 585   HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
 586 
 587   if (TraceParallelOldGCSummaryPhase) {
 588     const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
 589     gclog_or_tty->print_cr("%s split:  src=" PTR_FORMAT " src_c=" SIZE_FORMAT
 590                            " pos=" SIZE_FORMAT,
 591                            split_type, source_next, split_region,
 592                            partial_obj_size);
 593     gclog_or_tty->print_cr("%s split:  dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT
 594                            " tn=" PTR_FORMAT,
 595                            split_type, split_destination,
 596                            addr_to_region_idx(split_destination),
 597                            *target_next);
 598 
 599     if (partial_obj_size != 0) {
 600       HeapWord* const po_beg = split_info.destination();
 601       HeapWord* const po_end = po_beg + split_info.partial_obj_size();
 602       gclog_or_tty->print_cr("%s split:  "
 603                              "po_beg=" PTR_FORMAT " " SIZE_FORMAT " "
 604                              "po_end=" PTR_FORMAT " " SIZE_FORMAT,
 605                              split_type,
 606                              po_beg, addr_to_region_idx(po_beg),
 607                              po_end, addr_to_region_idx(po_end));
 608     }
 609   }
 610 
 611   return source_next;
 612 }
 613 
 614 bool ParallelCompactData::summarize(SplitInfo& split_info,
 615                                     HeapWord* source_beg, HeapWord* source_end,
 616                                     HeapWord** source_next,
 617                                     HeapWord* target_beg, HeapWord* target_end,
 618                                     HeapWord** target_next)
 619 {
 620   if (TraceParallelOldGCSummaryPhase) {
 621     HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
 622     tty->print_cr("sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
 623                   "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
 624                   source_beg, source_end, source_next_val,
 625                   target_beg, target_end, *target_next);
 626   }
 627 
 628   size_t cur_region = addr_to_region_idx(source_beg);
 629   const size_t end_region = addr_to_region_idx(region_align_up(source_end));
 630 
 631   HeapWord *dest_addr = target_beg;
 632   while (cur_region < end_region) {
 633     // The destination must be set even if the region has no data.
 634     _region_data[cur_region].set_destination(dest_addr);
 635 
 636     size_t words = _region_data[cur_region].data_size();
 637     if (words > 0) {
 638       // If cur_region does not fit entirely into the target space, find a point
 639       // at which the source space can be 'split' so that part is copied to the
 640       // target space and the rest is copied elsewhere.
 641       if (dest_addr + words > target_end) {
 642         assert(source_next != NULL, "source_next is NULL when splitting");
 643         *source_next = summarize_split_space(cur_region, split_info, dest_addr,
 644                                              target_end, target_next);
 645         return false;
 646       }
 647 
 648       // Compute the destination_count for cur_region, and if necessary, update
 649       // source_region for a destination region.  The source_region field is
 650       // updated if cur_region is the first (left-most) region to be copied to a
 651       // destination region.
 652       //
 653       // The destination_count calculation is a bit subtle.  A region that has
 654       // data that compacts into itself does not count itself as a destination.
 655       // This maintains the invariant that a zero count means the region is
 656       // available and can be claimed and then filled.
 657       uint destination_count = 0;
 658       if (split_info.is_split(cur_region)) {
 659         // The current region has been split:  the partial object will be copied
 660         // to one destination space and the remaining data will be copied to
 661         // another destination space.  Adjust the initial destination_count and,
 662         // if necessary, set the source_region field if the partial object will
 663         // cross a destination region boundary.
 664         destination_count = split_info.destination_count();
 665         if (destination_count == 2) {
 666           size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
 667           _region_data[dest_idx].set_source_region(cur_region);
 668         }
 669       }
 670 
 671       HeapWord* const last_addr = dest_addr + words - 1;
 672       const size_t dest_region_1 = addr_to_region_idx(dest_addr);
 673       const size_t dest_region_2 = addr_to_region_idx(last_addr);
 674 
 675       // Initially assume that the destination regions will be the same and
 676       // adjust the value below if necessary.  Under this assumption, if
 677       // cur_region == dest_region_2, then cur_region will be compacted
 678       // completely into itself.
 679       destination_count += cur_region == dest_region_2 ? 0 : 1;
 680       if (dest_region_1 != dest_region_2) {
 681         // Destination regions differ; adjust destination_count.
 682         destination_count += 1;
 683         // Data from cur_region will be copied to the start of dest_region_2.
 684         _region_data[dest_region_2].set_source_region(cur_region);
 685       } else if (region_offset(dest_addr) == 0) {
 686         // Data from cur_region will be copied to the start of the destination
 687         // region.
 688         _region_data[dest_region_1].set_source_region(cur_region);
 689       }
 690 
 691       _region_data[cur_region].set_destination_count(destination_count);
 692       _region_data[cur_region].set_data_location(region_to_addr(cur_region));
 693       dest_addr += words;
 694     }
 695 
 696     ++cur_region;
 697   }
 698 
 699   *target_next = dest_addr;
 700   return true;
 701 }
 702 
 703 HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr) {
 704   assert(addr != NULL, "Should detect NULL oop earlier");
 705   assert(PSParallelCompact::gc_heap()->is_in(addr), "addr not in heap");
 706 #ifdef ASSERT
 707   if (PSParallelCompact::mark_bitmap()->is_unmarked(addr)) {
 708     gclog_or_tty->print_cr("calc_new_pointer:: addr " PTR_FORMAT, addr);
 709   }
 710 #endif
 711   assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "obj not marked");
 712 
 713   // Region covering the object.
 714   size_t region_index = addr_to_region_idx(addr);
 715   const RegionData* const region_ptr = region(region_index);
 716   HeapWord* const region_addr = region_align_down(addr);
 717 
 718   assert(addr < region_addr + RegionSize, "Region does not cover object");
 719   assert(addr_to_region_ptr(region_addr) == region_ptr, "sanity check");
 720 
 721   HeapWord* result = region_ptr->destination();
 722 
 723   // If all the data in the region is live, then the new location of the object
 724   // can be calculated from the destination of the region plus the offset of the
 725   // object in the region.
 726   if (region_ptr->data_size() == RegionSize) {
 727     result += pointer_delta(addr, region_addr);
 728     DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result);)
 729     return result;
 730   }
 731 
 732   // The new location of the object is
 733   //    region destination +
 734   //    size of the partial object extending onto the region +
 735   //    sizes of the live objects in the Region that are to the left of addr
 736   const size_t partial_obj_size = region_ptr->partial_obj_size();
 737   HeapWord* const search_start = region_addr + partial_obj_size;
 738 
 739   const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
 740   size_t live_to_left = bitmap->live_words_in_range(search_start, oop(addr));
 741 
 742   result += partial_obj_size + live_to_left;
 743   DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result);)
 744   return result;
 745 }
 746 
 747 #ifdef  ASSERT
 748 void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
 749 {
 750   const size_t* const beg = (const size_t*)vspace->committed_low_addr();
 751   const size_t* const end = (const size_t*)vspace->committed_high_addr();
 752   for (const size_t* p = beg; p < end; ++p) {
 753     assert(*p == 0, "not zero");
 754   }
 755 }
 756 
 757 void ParallelCompactData::verify_clear()
 758 {
 759   verify_clear(_region_vspace);
 760 }
 761 #endif  // #ifdef ASSERT
 762 
 763 #ifdef NOT_PRODUCT
 764 ParallelCompactData::RegionData* debug_region(size_t region_index) {
 765   ParallelCompactData& sd = PSParallelCompact::summary_data();
 766   return sd.region(region_index);
 767 }
 768 #endif
 769 
 770 elapsedTimer        PSParallelCompact::_accumulated_time;
 771 unsigned int        PSParallelCompact::_total_invocations = 0;
 772 unsigned int        PSParallelCompact::_maximum_compaction_gc_num = 0;
 773 jlong               PSParallelCompact::_time_of_last_gc = 0;
 774 CollectorCounters*  PSParallelCompact::_counters = NULL;
 775 ParMarkBitMap       PSParallelCompact::_mark_bitmap;
 776 ParallelCompactData PSParallelCompact::_summary_data;
 777 
 778 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
 779 
 780 void PSParallelCompact::IsAliveClosure::do_object(oop p)   { ShouldNotReachHere(); }
 781 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
 782 
 783 void PSParallelCompact::KeepAliveClosure::do_oop(oop* p)       { PSParallelCompact::KeepAliveClosure::do_oop_work(p); }
 784 void PSParallelCompact::KeepAliveClosure::do_oop(narrowOop* p) { PSParallelCompact::KeepAliveClosure::do_oop_work(p); }
 785 
 786 PSParallelCompact::AdjustPointerClosure PSParallelCompact::_adjust_root_pointer_closure(true);
 787 PSParallelCompact::AdjustPointerClosure PSParallelCompact::_adjust_pointer_closure(false);
 788 PSParallelCompact::AdjustKlassClosure PSParallelCompact::_adjust_klass_closure;
 789 
 790 void PSParallelCompact::AdjustPointerClosure::do_oop(oop* p)       { adjust_pointer(p, _is_root); }
 791 void PSParallelCompact::AdjustPointerClosure::do_oop(narrowOop* p) { adjust_pointer(p, _is_root); }
 792 
 793 void PSParallelCompact::FollowStackClosure::do_void() { _compaction_manager->follow_marking_stacks(); }
 794 
 795 void PSParallelCompact::MarkAndPushClosure::do_oop(oop* p)       {
 796   mark_and_push(_compaction_manager, p);
 797 }
 798 void PSParallelCompact::MarkAndPushClosure::do_oop(narrowOop* p) { mark_and_push(_compaction_manager, p); }
 799 
 800 void PSParallelCompact::FollowKlassClosure::do_klass(Klass* klass) {
 801   klass->oops_do(_mark_and_push_closure);
 802 }
 803 void PSParallelCompact::AdjustKlassClosure::do_klass(Klass* klass) {
 804   klass->oops_do(&PSParallelCompact::_adjust_root_pointer_closure);
 805 }
 806 
 807 void PSParallelCompact::post_initialize() {
 808   ParallelScavengeHeap* heap = gc_heap();
 809   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 810 
 811   MemRegion mr = heap->reserved_region();
 812   _ref_processor =
 813     new ReferenceProcessor(mr,            // span
 814                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 815                            (int) ParallelGCThreads, // mt processing degree
 816                            true,          // mt discovery
 817                            (int) ParallelGCThreads, // mt discovery degree
 818                            true,          // atomic_discovery
 819                            &_is_alive_closure, // non-header is alive closure
 820                            false);        // write barrier for next field updates
 821   _counters = new CollectorCounters("PSParallelCompact", 1);
 822 
 823   // Initialize static fields in ParCompactionManager.
 824   ParCompactionManager::initialize(mark_bitmap());
 825 }
 826 
 827 bool PSParallelCompact::initialize() {
 828   ParallelScavengeHeap* heap = gc_heap();
 829   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 830   MemRegion mr = heap->reserved_region();
 831 
 832   // Was the old gen get allocated successfully?
 833   if (!heap->old_gen()->is_allocated()) {
 834     return false;
 835   }
 836 
 837   initialize_space_info();
 838   initialize_dead_wood_limiter();
 839 
 840   if (!_mark_bitmap.initialize(mr)) {
 841     vm_shutdown_during_initialization("Unable to allocate bit map for "
 842       "parallel garbage collection for the requested heap size.");
 843     return false;
 844   }
 845 
 846   if (!_summary_data.initialize(mr)) {
 847     vm_shutdown_during_initialization("Unable to allocate tables for "
 848       "parallel garbage collection for the requested heap size.");
 849     return false;
 850   }
 851 
 852   return true;
 853 }
 854 
 855 void PSParallelCompact::initialize_space_info()
 856 {
 857   memset(&_space_info, 0, sizeof(_space_info));
 858 
 859   ParallelScavengeHeap* heap = gc_heap();
 860   PSYoungGen* young_gen = heap->young_gen();
 861 
 862   _space_info[old_space_id].set_space(heap->old_gen()->object_space());
 863   _space_info[eden_space_id].set_space(young_gen->eden_space());
 864   _space_info[from_space_id].set_space(young_gen->from_space());
 865   _space_info[to_space_id].set_space(young_gen->to_space());
 866 
 867   _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
 868 }
 869 
 870 void PSParallelCompact::initialize_dead_wood_limiter()
 871 {
 872   const size_t max = 100;
 873   _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
 874   _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
 875   _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
 876   DEBUG_ONLY(_dwl_initialized = true;)
 877   _dwl_adjustment = normal_distribution(1.0);
 878 }
 879 
 880 // Simple class for storing info about the heap at the start of GC, to be used
 881 // after GC for comparison/printing.
 882 class PreGCValues {
 883 public:
 884   PreGCValues() { }
 885   PreGCValues(ParallelScavengeHeap* heap) { fill(heap); }
 886 
 887   void fill(ParallelScavengeHeap* heap) {
 888     _heap_used      = heap->used();
 889     _young_gen_used = heap->young_gen()->used_in_bytes();
 890     _old_gen_used   = heap->old_gen()->used_in_bytes();
 891     _metadata_used  = MetaspaceAux::used_in_bytes();
 892   };
 893 
 894   size_t heap_used() const      { return _heap_used; }
 895   size_t young_gen_used() const { return _young_gen_used; }
 896   size_t old_gen_used() const   { return _old_gen_used; }
 897   size_t metadata_used() const  { return _metadata_used; }
 898 
 899 private:
 900   size_t _heap_used;
 901   size_t _young_gen_used;
 902   size_t _old_gen_used;
 903   size_t _metadata_used;
 904 };
 905 
 906 void
 907 PSParallelCompact::clear_data_covering_space(SpaceId id)
 908 {
 909   // At this point, top is the value before GC, new_top() is the value that will
 910   // be set at the end of GC.  The marking bitmap is cleared to top; nothing
 911   // should be marked above top.  The summary data is cleared to the larger of
 912   // top & new_top.
 913   MutableSpace* const space = _space_info[id].space();
 914   HeapWord* const bot = space->bottom();
 915   HeapWord* const top = space->top();
 916   HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
 917 
 918   const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
 919   const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top));
 920   _mark_bitmap.clear_range(beg_bit, end_bit);
 921 
 922   const size_t beg_region = _summary_data.addr_to_region_idx(bot);
 923   const size_t end_region =
 924     _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
 925   _summary_data.clear_range(beg_region, end_region);
 926 
 927   // Clear the data used to 'split' regions.
 928   SplitInfo& split_info = _space_info[id].split_info();
 929   if (split_info.is_valid()) {
 930     split_info.clear();
 931   }
 932   DEBUG_ONLY(split_info.verify_clear();)
 933 }
 934 
 935 void PSParallelCompact::pre_compact(PreGCValues* pre_gc_values)
 936 {
 937   // Update the from & to space pointers in space_info, since they are swapped
 938   // at each young gen gc.  Do the update unconditionally (even though a
 939   // promotion failure does not swap spaces) because an unknown number of minor
 940   // collections will have swapped the spaces an unknown number of times.
 941   TraceTime tm("pre compact", print_phases(), true, gclog_or_tty);
 942   ParallelScavengeHeap* heap = gc_heap();
 943   _space_info[from_space_id].set_space(heap->young_gen()->from_space());
 944   _space_info[to_space_id].set_space(heap->young_gen()->to_space());
 945 
 946   pre_gc_values->fill(heap);
 947 
 948   NOT_PRODUCT(_mark_bitmap.reset_counters());
 949   DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
 950   DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
 951 
 952   // Increment the invocation count
 953   heap->increment_total_collections(true);
 954 
 955   // We need to track unique mark sweep invocations as well.
 956   _total_invocations++;
 957 
 958   heap->print_heap_before_gc();
 959 
 960   // Fill in TLABs
 961   heap->accumulate_statistics_all_tlabs();
 962   heap->ensure_parsability(true);  // retire TLABs
 963 
 964   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 965     HandleMark hm;  // Discard invalid handles created during verification
 966     gclog_or_tty->print(" VerifyBeforeGC:");
 967     Universe::verify();
 968   }
 969 
 970   // Verify object start arrays
 971   if (VerifyObjectStartArray &&
 972       VerifyBeforeGC) {
 973     heap->old_gen()->verify_object_start_array();
 974   }
 975 
 976   DEBUG_ONLY(mark_bitmap()->verify_clear();)
 977   DEBUG_ONLY(summary_data().verify_clear();)
 978 
 979   // Have worker threads release resources the next time they run a task.
 980   gc_task_manager()->release_all_resources();
 981 }
 982 
 983 void PSParallelCompact::post_compact()
 984 {
 985   TraceTime tm("post compact", print_phases(), true, gclog_or_tty);
 986 
 987   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
 988     // Clear the marking bitmap, summary data and split info.
 989     clear_data_covering_space(SpaceId(id));
 990     // Update top().  Must be done after clearing the bitmap and summary data.
 991     _space_info[id].publish_new_top();
 992   }
 993 
 994   MutableSpace* const eden_space = _space_info[eden_space_id].space();
 995   MutableSpace* const from_space = _space_info[from_space_id].space();
 996   MutableSpace* const to_space   = _space_info[to_space_id].space();
 997 
 998   ParallelScavengeHeap* heap = gc_heap();
 999   bool eden_empty = eden_space->is_empty();
1000   if (!eden_empty) {
1001     eden_empty = absorb_live_data_from_eden(heap->size_policy(),
1002                                             heap->young_gen(), heap->old_gen());
1003   }
1004 
1005   // Update heap occupancy information which is used as input to the soft ref
1006   // clearing policy at the next gc.
1007   Universe::update_heap_info_at_gc();
1008 
1009   bool young_gen_empty = eden_empty && from_space->is_empty() &&
1010     to_space->is_empty();
1011 
1012   BarrierSet* bs = heap->barrier_set();
1013   if (bs->is_a(BarrierSet::ModRef)) {
1014     ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
1015     MemRegion old_mr = heap->old_gen()->reserved();
1016 
1017     if (young_gen_empty) {
1018       modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
1019     } else {
1020       modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1021     }
1022   }
1023 
1024   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1025   ClassLoaderDataGraph::purge();
1026 
1027   Threads::gc_epilogue();
1028   CodeCache::gc_epilogue();
1029   JvmtiExport::gc_epilogue();
1030 
1031   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1032 
1033   ref_processor()->enqueue_discovered_references(NULL);
1034 
1035   if (ZapUnusedHeapArea) {
1036     heap->gen_mangle_unused_area();
1037   }
1038 
1039   // Update time of last GC
1040   reset_millis_since_last_gc();
1041 }
1042 
1043 HeapWord*
1044 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1045                                                     bool maximum_compaction)
1046 {
1047   const size_t region_size = ParallelCompactData::RegionSize;
1048   const ParallelCompactData& sd = summary_data();
1049 
1050   const MutableSpace* const space = _space_info[id].space();
1051   HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1052   const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1053   const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1054 
1055   // Skip full regions at the beginning of the space--they are necessarily part
1056   // of the dense prefix.
1057   size_t full_count = 0;
1058   const RegionData* cp;
1059   for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1060     ++full_count;
1061   }
1062 
1063   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1064   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1065   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1066   if (maximum_compaction || cp == end_cp || interval_ended) {
1067     _maximum_compaction_gc_num = total_invocations();
1068     return sd.region_to_addr(cp);
1069   }
1070 
1071   HeapWord* const new_top = _space_info[id].new_top();
1072   const size_t space_live = pointer_delta(new_top, space->bottom());
1073   const size_t space_used = space->used_in_words();
1074   const size_t space_capacity = space->capacity_in_words();
1075 
1076   const double cur_density = double(space_live) / space_capacity;
1077   const double deadwood_density =
1078     (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1079   const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1080 
1081   if (TraceParallelOldGCDensePrefix) {
1082     tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1083                   cur_density, deadwood_density, deadwood_goal);
1084     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1085                   "space_cap=" SIZE_FORMAT,
1086                   space_live, space_used,
1087                   space_capacity);
1088   }
1089 
1090   // XXX - Use binary search?
1091   HeapWord* dense_prefix = sd.region_to_addr(cp);
1092   const RegionData* full_cp = cp;
1093   const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1094   while (cp < end_cp) {
1095     HeapWord* region_destination = cp->destination();
1096     const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1097     if (TraceParallelOldGCDensePrefix && Verbose) {
1098       tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1099                     "dp=" SIZE_FORMAT_W(8) " " "cdw=" SIZE_FORMAT_W(8),
1100                     sd.region(cp), region_destination,
1101                     dense_prefix, cur_deadwood);
1102     }
1103 
1104     if (cur_deadwood >= deadwood_goal) {
1105       // Found the region that has the correct amount of deadwood to the left.
1106       // This typically occurs after crossing a fairly sparse set of regions, so
1107       // iterate backwards over those sparse regions, looking for the region
1108       // that has the lowest density of live objects 'to the right.'
1109       size_t space_to_left = sd.region(cp) * region_size;
1110       size_t live_to_left = space_to_left - cur_deadwood;
1111       size_t space_to_right = space_capacity - space_to_left;
1112       size_t live_to_right = space_live - live_to_left;
1113       double density_to_right = double(live_to_right) / space_to_right;
1114       while (cp > full_cp) {
1115         --cp;
1116         const size_t prev_region_live_to_right = live_to_right -
1117           cp->data_size();
1118         const size_t prev_region_space_to_right = space_to_right + region_size;
1119         double prev_region_density_to_right =
1120           double(prev_region_live_to_right) / prev_region_space_to_right;
1121         if (density_to_right <= prev_region_density_to_right) {
1122           return dense_prefix;
1123         }
1124         if (TraceParallelOldGCDensePrefix && Verbose) {
1125           tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1126                         "pc_d2r=%10.8f", sd.region(cp), density_to_right,
1127                         prev_region_density_to_right);
1128         }
1129         dense_prefix -= region_size;
1130         live_to_right = prev_region_live_to_right;
1131         space_to_right = prev_region_space_to_right;
1132         density_to_right = prev_region_density_to_right;
1133       }
1134       return dense_prefix;
1135     }
1136 
1137     dense_prefix += region_size;
1138     ++cp;
1139   }
1140 
1141   return dense_prefix;
1142 }
1143 
1144 #ifndef PRODUCT
1145 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1146                                                  const SpaceId id,
1147                                                  const bool maximum_compaction,
1148                                                  HeapWord* const addr)
1149 {
1150   const size_t region_idx = summary_data().addr_to_region_idx(addr);
1151   RegionData* const cp = summary_data().region(region_idx);
1152   const MutableSpace* const space = _space_info[id].space();
1153   HeapWord* const new_top = _space_info[id].new_top();
1154 
1155   const size_t space_live = pointer_delta(new_top, space->bottom());
1156   const size_t dead_to_left = pointer_delta(addr, cp->destination());
1157   const size_t space_cap = space->capacity_in_words();
1158   const double dead_to_left_pct = double(dead_to_left) / space_cap;
1159   const size_t live_to_right = new_top - cp->destination();
1160   const size_t dead_to_right = space->top() - addr - live_to_right;
1161 
1162   tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1163                 "spl=" SIZE_FORMAT " "
1164                 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1165                 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
1166                 " ratio=%10.8f",
1167                 algorithm, addr, region_idx,
1168                 space_live,
1169                 dead_to_left, dead_to_left_pct,
1170                 dead_to_right, live_to_right,
1171                 double(dead_to_right) / live_to_right);
1172 }
1173 #endif  // #ifndef PRODUCT
1174 
1175 // Return a fraction indicating how much of the generation can be treated as
1176 // "dead wood" (i.e., not reclaimed).  The function uses a normal distribution
1177 // based on the density of live objects in the generation to determine a limit,
1178 // which is then adjusted so the return value is min_percent when the density is
1179 // 1.
1180 //
1181 // The following table shows some return values for a different values of the
1182 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1183 // min_percent is 1.
1184 //
1185 //                          fraction allowed as dead wood
1186 //         -----------------------------------------------------------------
1187 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1188 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1189 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1190 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1191 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1192 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1193 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1194 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1195 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1196 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1197 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1198 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1199 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1200 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1201 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1202 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1203 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1204 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1205 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1206 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1207 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1208 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1209 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1210 
1211 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1212 {
1213   assert(_dwl_initialized, "uninitialized");
1214 
1215   // The raw limit is the value of the normal distribution at x = density.
1216   const double raw_limit = normal_distribution(density);
1217 
1218   // Adjust the raw limit so it becomes the minimum when the density is 1.
1219   //
1220   // First subtract the adjustment value (which is simply the precomputed value
1221   // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1222   // Then add the minimum value, so the minimum is returned when the density is
1223   // 1.  Finally, prevent negative values, which occur when the mean is not 0.5.
1224   const double min = double(min_percent) / 100.0;
1225   const double limit = raw_limit - _dwl_adjustment + min;
1226   return MAX2(limit, 0.0);
1227 }
1228 
1229 ParallelCompactData::RegionData*
1230 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1231                                            const RegionData* end)
1232 {
1233   const size_t region_size = ParallelCompactData::RegionSize;
1234   ParallelCompactData& sd = summary_data();
1235   size_t left = sd.region(beg);
1236   size_t right = end > beg ? sd.region(end) - 1 : left;
1237 
1238   // Binary search.
1239   while (left < right) {
1240     // Equivalent to (left + right) / 2, but does not overflow.
1241     const size_t middle = left + (right - left) / 2;
1242     RegionData* const middle_ptr = sd.region(middle);
1243     HeapWord* const dest = middle_ptr->destination();
1244     HeapWord* const addr = sd.region_to_addr(middle);
1245     assert(dest != NULL, "sanity");
1246     assert(dest <= addr, "must move left");
1247 
1248     if (middle > left && dest < addr) {
1249       right = middle - 1;
1250     } else if (middle < right && middle_ptr->data_size() == region_size) {
1251       left = middle + 1;
1252     } else {
1253       return middle_ptr;
1254     }
1255   }
1256   return sd.region(left);
1257 }
1258 
1259 ParallelCompactData::RegionData*
1260 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1261                                           const RegionData* end,
1262                                           size_t dead_words)
1263 {
1264   ParallelCompactData& sd = summary_data();
1265   size_t left = sd.region(beg);
1266   size_t right = end > beg ? sd.region(end) - 1 : left;
1267 
1268   // Binary search.
1269   while (left < right) {
1270     // Equivalent to (left + right) / 2, but does not overflow.
1271     const size_t middle = left + (right - left) / 2;
1272     RegionData* const middle_ptr = sd.region(middle);
1273     HeapWord* const dest = middle_ptr->destination();
1274     HeapWord* const addr = sd.region_to_addr(middle);
1275     assert(dest != NULL, "sanity");
1276     assert(dest <= addr, "must move left");
1277 
1278     const size_t dead_to_left = pointer_delta(addr, dest);
1279     if (middle > left && dead_to_left > dead_words) {
1280       right = middle - 1;
1281     } else if (middle < right && dead_to_left < dead_words) {
1282       left = middle + 1;
1283     } else {
1284       return middle_ptr;
1285     }
1286   }
1287   return sd.region(left);
1288 }
1289 
1290 // The result is valid during the summary phase, after the initial summarization
1291 // of each space into itself, and before final summarization.
1292 inline double
1293 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1294                                    HeapWord* const bottom,
1295                                    HeapWord* const top,
1296                                    HeapWord* const new_top)
1297 {
1298   ParallelCompactData& sd = summary_data();
1299 
1300   assert(cp != NULL, "sanity");
1301   assert(bottom != NULL, "sanity");
1302   assert(top != NULL, "sanity");
1303   assert(new_top != NULL, "sanity");
1304   assert(top >= new_top, "summary data problem?");
1305   assert(new_top > bottom, "space is empty; should not be here");
1306   assert(new_top >= cp->destination(), "sanity");
1307   assert(top >= sd.region_to_addr(cp), "sanity");
1308 
1309   HeapWord* const destination = cp->destination();
1310   const size_t dense_prefix_live  = pointer_delta(destination, bottom);
1311   const size_t compacted_region_live = pointer_delta(new_top, destination);
1312   const size_t compacted_region_used = pointer_delta(top,
1313                                                      sd.region_to_addr(cp));
1314   const size_t reclaimable = compacted_region_used - compacted_region_live;
1315 
1316   const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1317   return double(reclaimable) / divisor;
1318 }
1319 
1320 // Return the address of the end of the dense prefix, a.k.a. the start of the
1321 // compacted region.  The address is always on a region boundary.
1322 //
1323 // Completely full regions at the left are skipped, since no compaction can
1324 // occur in those regions.  Then the maximum amount of dead wood to allow is
1325 // computed, based on the density (amount live / capacity) of the generation;
1326 // the region with approximately that amount of dead space to the left is
1327 // identified as the limit region.  Regions between the last completely full
1328 // region and the limit region are scanned and the one that has the best
1329 // (maximum) reclaimed_ratio() is selected.
1330 HeapWord*
1331 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1332                                         bool maximum_compaction)
1333 {
1334   if (ParallelOldGCSplitALot) {
1335     if (_space_info[id].dense_prefix() != _space_info[id].space()->bottom()) {
1336       // The value was chosen to provoke splitting a young gen space; use it.
1337       return _space_info[id].dense_prefix();
1338     }
1339   }
1340 
1341   const size_t region_size = ParallelCompactData::RegionSize;
1342   const ParallelCompactData& sd = summary_data();
1343 
1344   const MutableSpace* const space = _space_info[id].space();
1345   HeapWord* const top = space->top();
1346   HeapWord* const top_aligned_up = sd.region_align_up(top);
1347   HeapWord* const new_top = _space_info[id].new_top();
1348   HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1349   HeapWord* const bottom = space->bottom();
1350   const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1351   const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1352   const RegionData* const new_top_cp =
1353     sd.addr_to_region_ptr(new_top_aligned_up);
1354 
1355   // Skip full regions at the beginning of the space--they are necessarily part
1356   // of the dense prefix.
1357   const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1358   assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1359          space->is_empty(), "no dead space allowed to the left");
1360   assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1361          "region must have dead space");
1362 
1363   // The gc number is saved whenever a maximum compaction is done, and used to
1364   // determine when the maximum compaction interval has expired.  This avoids
1365   // successive max compactions for different reasons.
1366   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1367   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1368   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1369     total_invocations() == HeapFirstMaximumCompactionCount;
1370   if (maximum_compaction || full_cp == top_cp || interval_ended) {
1371     _maximum_compaction_gc_num = total_invocations();
1372     return sd.region_to_addr(full_cp);
1373   }
1374 
1375   const size_t space_live = pointer_delta(new_top, bottom);
1376   const size_t space_used = space->used_in_words();
1377   const size_t space_capacity = space->capacity_in_words();
1378 
1379   const double density = double(space_live) / double(space_capacity);
1380   const size_t min_percent_free = MarkSweepDeadRatio;
1381   const double limiter = dead_wood_limiter(density, min_percent_free);
1382   const size_t dead_wood_max = space_used - space_live;
1383   const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1384                                       dead_wood_max);
1385 
1386   if (TraceParallelOldGCDensePrefix) {
1387     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1388                   "space_cap=" SIZE_FORMAT,
1389                   space_live, space_used,
1390                   space_capacity);
1391     tty->print_cr("dead_wood_limiter(%6.4f, %d)=%6.4f "
1392                   "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1393                   density, min_percent_free, limiter,
1394                   dead_wood_max, dead_wood_limit);
1395   }
1396 
1397   // Locate the region with the desired amount of dead space to the left.
1398   const RegionData* const limit_cp =
1399     dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1400 
1401   // Scan from the first region with dead space to the limit region and find the
1402   // one with the best (largest) reclaimed ratio.
1403   double best_ratio = 0.0;
1404   const RegionData* best_cp = full_cp;
1405   for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1406     double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1407     if (tmp_ratio > best_ratio) {
1408       best_cp = cp;
1409       best_ratio = tmp_ratio;
1410     }
1411   }
1412 
1413 #if     0
1414   // Something to consider:  if the region with the best ratio is 'close to' the
1415   // first region w/free space, choose the first region with free space
1416   // ("first-free").  The first-free region is usually near the start of the
1417   // heap, which means we are copying most of the heap already, so copy a bit
1418   // more to get complete compaction.
1419   if (pointer_delta(best_cp, full_cp, sizeof(RegionData)) < 4) {
1420     _maximum_compaction_gc_num = total_invocations();
1421     best_cp = full_cp;
1422   }
1423 #endif  // #if 0
1424 
1425   return sd.region_to_addr(best_cp);
1426 }
1427 
1428 #ifndef PRODUCT
1429 void
1430 PSParallelCompact::fill_with_live_objects(SpaceId id, HeapWord* const start,
1431                                           size_t words)
1432 {
1433   if (TraceParallelOldGCSummaryPhase) {
1434     tty->print_cr("fill_with_live_objects [" PTR_FORMAT " " PTR_FORMAT ") "
1435                   SIZE_FORMAT, start, start + words, words);
1436   }
1437 
1438   ObjectStartArray* const start_array = _space_info[id].start_array();
1439   CollectedHeap::fill_with_objects(start, words);
1440   for (HeapWord* p = start; p < start + words; p += oop(p)->size()) {
1441     _mark_bitmap.mark_obj(p, words);
1442     _summary_data.add_obj(p, words);
1443     start_array->allocate_block(p);
1444   }
1445 }
1446 
1447 void
1448 PSParallelCompact::summarize_new_objects(SpaceId id, HeapWord* start)
1449 {
1450   ParallelCompactData& sd = summary_data();
1451   MutableSpace* space = _space_info[id].space();
1452 
1453   // Find the source and destination start addresses.
1454   HeapWord* const src_addr = sd.region_align_down(start);
1455   HeapWord* dst_addr;
1456   if (src_addr < start) {
1457     dst_addr = sd.addr_to_region_ptr(src_addr)->destination();
1458   } else if (src_addr > space->bottom()) {
1459     // The start (the original top() value) is aligned to a region boundary so
1460     // the associated region does not have a destination.  Compute the
1461     // destination from the previous region.
1462     RegionData* const cp = sd.addr_to_region_ptr(src_addr) - 1;
1463     dst_addr = cp->destination() + cp->data_size();
1464   } else {
1465     // Filling the entire space.
1466     dst_addr = space->bottom();
1467   }
1468   assert(dst_addr != NULL, "sanity");
1469 
1470   // Update the summary data.
1471   bool result = _summary_data.summarize(_space_info[id].split_info(),
1472                                         src_addr, space->top(), NULL,
1473                                         dst_addr, space->end(),
1474                                         _space_info[id].new_top_addr());
1475   assert(result, "should not fail:  bad filler object size");
1476 }
1477 
1478 void
1479 PSParallelCompact::provoke_split_fill_survivor(SpaceId id)
1480 {
1481   if (total_invocations() % (ParallelOldGCSplitInterval * 3) != 0) {
1482     return;
1483   }
1484 
1485   MutableSpace* const space = _space_info[id].space();
1486   if (space->is_empty()) {
1487     HeapWord* b = space->bottom();
1488     HeapWord* t = b + space->capacity_in_words() / 2;
1489     space->set_top(t);
1490     if (ZapUnusedHeapArea) {
1491       space->set_top_for_allocations();
1492     }
1493 
1494     size_t min_size = CollectedHeap::min_fill_size();
1495     size_t obj_len = min_size;
1496     while (b + obj_len <= t) {
1497       CollectedHeap::fill_with_object(b, obj_len);
1498       mark_bitmap()->mark_obj(b, obj_len);
1499       summary_data().add_obj(b, obj_len);
1500       b += obj_len;
1501       obj_len = (obj_len & (min_size*3)) + min_size; // 8 16 24 32 8 16 24 32 ...
1502     }
1503     if (b < t) {
1504       // The loop didn't completely fill to t (top); adjust top downward.
1505       space->set_top(b);
1506       if (ZapUnusedHeapArea) {
1507         space->set_top_for_allocations();
1508       }
1509     }
1510 
1511     HeapWord** nta = _space_info[id].new_top_addr();
1512     bool result = summary_data().summarize(_space_info[id].split_info(),
1513                                            space->bottom(), space->top(), NULL,
1514                                            space->bottom(), space->end(), nta);
1515     assert(result, "space must fit into itself");
1516   }
1517 }
1518 
1519 void
1520 PSParallelCompact::provoke_split(bool & max_compaction)
1521 {
1522   if (total_invocations() % ParallelOldGCSplitInterval != 0) {
1523     return;
1524   }
1525 
1526   const size_t region_size = ParallelCompactData::RegionSize;
1527   ParallelCompactData& sd = summary_data();
1528 
1529   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1530   MutableSpace* const from_space = _space_info[from_space_id].space();
1531   const size_t eden_live = pointer_delta(eden_space->top(),
1532                                          _space_info[eden_space_id].new_top());
1533   const size_t from_live = pointer_delta(from_space->top(),
1534                                          _space_info[from_space_id].new_top());
1535 
1536   const size_t min_fill_size = CollectedHeap::min_fill_size();
1537   const size_t eden_free = pointer_delta(eden_space->end(), eden_space->top());
1538   const size_t eden_fillable = eden_free >= min_fill_size ? eden_free : 0;
1539   const size_t from_free = pointer_delta(from_space->end(), from_space->top());
1540   const size_t from_fillable = from_free >= min_fill_size ? from_free : 0;
1541 
1542   // Choose the space to split; need at least 2 regions live (or fillable).
1543   SpaceId id;
1544   MutableSpace* space;
1545   size_t live_words;
1546   size_t fill_words;
1547   if (eden_live + eden_fillable >= region_size * 2) {
1548     id = eden_space_id;
1549     space = eden_space;
1550     live_words = eden_live;
1551     fill_words = eden_fillable;
1552   } else if (from_live + from_fillable >= region_size * 2) {
1553     id = from_space_id;
1554     space = from_space;
1555     live_words = from_live;
1556     fill_words = from_fillable;
1557   } else {
1558     return; // Give up.
1559   }
1560   assert(fill_words == 0 || fill_words >= min_fill_size, "sanity");
1561 
1562   if (live_words < region_size * 2) {
1563     // Fill from top() to end() w/live objects of mixed sizes.
1564     HeapWord* const fill_start = space->top();
1565     live_words += fill_words;
1566 
1567     space->set_top(fill_start + fill_words);
1568     if (ZapUnusedHeapArea) {
1569       space->set_top_for_allocations();
1570     }
1571 
1572     HeapWord* cur_addr = fill_start;
1573     while (fill_words > 0) {
1574       const size_t r = (size_t)os::random() % (region_size / 2) + min_fill_size;
1575       size_t cur_size = MIN2(align_object_size_(r), fill_words);
1576       if (fill_words - cur_size < min_fill_size) {
1577         cur_size = fill_words; // Avoid leaving a fragment too small to fill.
1578       }
1579 
1580       CollectedHeap::fill_with_object(cur_addr, cur_size);
1581       mark_bitmap()->mark_obj(cur_addr, cur_size);
1582       sd.add_obj(cur_addr, cur_size);
1583 
1584       cur_addr += cur_size;
1585       fill_words -= cur_size;
1586     }
1587 
1588     summarize_new_objects(id, fill_start);
1589   }
1590 
1591   max_compaction = false;
1592 
1593   // Manipulate the old gen so that it has room for about half of the live data
1594   // in the target young gen space (live_words / 2).
1595   id = old_space_id;
1596   space = _space_info[id].space();
1597   const size_t free_at_end = space->free_in_words();
1598   const size_t free_target = align_object_size(live_words / 2);
1599   const size_t dead = pointer_delta(space->top(), _space_info[id].new_top());
1600 
1601   if (free_at_end >= free_target + min_fill_size) {
1602     // Fill space above top() and set the dense prefix so everything survives.
1603     HeapWord* const fill_start = space->top();
1604     const size_t fill_size = free_at_end - free_target;
1605     space->set_top(space->top() + fill_size);
1606     if (ZapUnusedHeapArea) {
1607       space->set_top_for_allocations();
1608     }
1609     fill_with_live_objects(id, fill_start, fill_size);
1610     summarize_new_objects(id, fill_start);
1611     _space_info[id].set_dense_prefix(sd.region_align_down(space->top()));
1612   } else if (dead + free_at_end > free_target) {
1613     // Find a dense prefix that makes the right amount of space available.
1614     HeapWord* cur = sd.region_align_down(space->top());
1615     HeapWord* cur_destination = sd.addr_to_region_ptr(cur)->destination();
1616     size_t dead_to_right = pointer_delta(space->end(), cur_destination);
1617     while (dead_to_right < free_target) {
1618       cur -= region_size;
1619       cur_destination = sd.addr_to_region_ptr(cur)->destination();
1620       dead_to_right = pointer_delta(space->end(), cur_destination);
1621     }
1622     _space_info[id].set_dense_prefix(cur);
1623   }
1624 }
1625 #endif // #ifndef PRODUCT
1626 
1627 void PSParallelCompact::summarize_spaces_quick()
1628 {
1629   for (unsigned int i = 0; i < last_space_id; ++i) {
1630     const MutableSpace* space = _space_info[i].space();
1631     HeapWord** nta = _space_info[i].new_top_addr();
1632     bool result = _summary_data.summarize(_space_info[i].split_info(),
1633                                           space->bottom(), space->top(), NULL,
1634                                           space->bottom(), space->end(), nta);
1635     assert(result, "space must fit into itself");
1636     _space_info[i].set_dense_prefix(space->bottom());
1637   }
1638 
1639 #ifndef PRODUCT
1640   if (ParallelOldGCSplitALot) {
1641     provoke_split_fill_survivor(to_space_id);
1642   }
1643 #endif // #ifndef PRODUCT
1644 }
1645 
1646 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1647 {
1648   HeapWord* const dense_prefix_end = dense_prefix(id);
1649   const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1650   const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1651   if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1652     // Only enough dead space is filled so that any remaining dead space to the
1653     // left is larger than the minimum filler object.  (The remainder is filled
1654     // during the copy/update phase.)
1655     //
1656     // The size of the dead space to the right of the boundary is not a
1657     // concern, since compaction will be able to use whatever space is
1658     // available.
1659     //
1660     // Here '||' is the boundary, 'x' represents a don't care bit and a box
1661     // surrounds the space to be filled with an object.
1662     //
1663     // In the 32-bit VM, each bit represents two 32-bit words:
1664     //                              +---+
1665     // a) beg_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1666     //    end_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1667     //                              +---+
1668     //
1669     // In the 64-bit VM, each bit represents one 64-bit word:
1670     //                              +------------+
1671     // b) beg_bits:  ...  x   x   x | 0   ||   0 | x  x  ...
1672     //    end_bits:  ...  x   x   1 | 0   ||   0 | x  x  ...
1673     //                              +------------+
1674     //                          +-------+
1675     // c) beg_bits:  ...  x   x | 0   0 | ||   0   x  x  ...
1676     //    end_bits:  ...  x   1 | 0   0 | ||   0   x  x  ...
1677     //                          +-------+
1678     //                      +-----------+
1679     // d) beg_bits:  ...  x | 0   0   0 | ||   0   x  x  ...
1680     //    end_bits:  ...  1 | 0   0   0 | ||   0   x  x  ...
1681     //                      +-----------+
1682     //                          +-------+
1683     // e) beg_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1684     //    end_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1685     //                          +-------+
1686 
1687     // Initially assume case a, c or e will apply.
1688     size_t obj_len = CollectedHeap::min_fill_size();
1689     HeapWord* obj_beg = dense_prefix_end - obj_len;
1690 
1691 #ifdef  _LP64
1692     if (MinObjAlignment > 1) { // object alignment > heap word size
1693       // Cases a, c or e.
1694     } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1695       // Case b above.
1696       obj_beg = dense_prefix_end - 1;
1697     } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1698                _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1699       // Case d above.
1700       obj_beg = dense_prefix_end - 3;
1701       obj_len = 3;
1702     }
1703 #endif  // #ifdef _LP64
1704 
1705     CollectedHeap::fill_with_object(obj_beg, obj_len);
1706     _mark_bitmap.mark_obj(obj_beg, obj_len);
1707     _summary_data.add_obj(obj_beg, obj_len);
1708     assert(start_array(id) != NULL, "sanity");
1709     start_array(id)->allocate_block(obj_beg);
1710   }
1711 }
1712 
1713 void
1714 PSParallelCompact::clear_source_region(HeapWord* beg_addr, HeapWord* end_addr)
1715 {
1716   RegionData* const beg_ptr = _summary_data.addr_to_region_ptr(beg_addr);
1717   HeapWord* const end_aligned_up = _summary_data.region_align_up(end_addr);
1718   RegionData* const end_ptr = _summary_data.addr_to_region_ptr(end_aligned_up);
1719   for (RegionData* cur = beg_ptr; cur < end_ptr; ++cur) {
1720     cur->set_source_region(0);
1721   }
1722 }
1723 
1724 void
1725 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1726 {
1727   assert(id < last_space_id, "id out of range");
1728   assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom() ||
1729          ParallelOldGCSplitALot && id == old_space_id,
1730          "should have been reset in summarize_spaces_quick()");
1731 
1732   const MutableSpace* space = _space_info[id].space();
1733   if (_space_info[id].new_top() != space->bottom()) {
1734     HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1735     _space_info[id].set_dense_prefix(dense_prefix_end);
1736 
1737 #ifndef PRODUCT
1738     if (TraceParallelOldGCDensePrefix) {
1739       print_dense_prefix_stats("ratio", id, maximum_compaction,
1740                                dense_prefix_end);
1741       HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1742       print_dense_prefix_stats("density", id, maximum_compaction, addr);
1743     }
1744 #endif  // #ifndef PRODUCT
1745 
1746     // Recompute the summary data, taking into account the dense prefix.  If
1747     // every last byte will be reclaimed, then the existing summary data which
1748     // compacts everything can be left in place.
1749     if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1750       // If dead space crosses the dense prefix boundary, it is (at least
1751       // partially) filled with a dummy object, marked live and added to the
1752       // summary data.  This simplifies the copy/update phase and must be done
1753       // before the final locations of objects are determined, to prevent
1754       // leaving a fragment of dead space that is too small to fill.
1755       fill_dense_prefix_end(id);
1756 
1757       // Compute the destination of each Region, and thus each object.
1758       _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1759       _summary_data.summarize(_space_info[id].split_info(),
1760                               dense_prefix_end, space->top(), NULL,
1761                               dense_prefix_end, space->end(),
1762                               _space_info[id].new_top_addr());
1763     }
1764   }
1765 
1766   if (TraceParallelOldGCSummaryPhase) {
1767     const size_t region_size = ParallelCompactData::RegionSize;
1768     HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1769     const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1770     const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1771     HeapWord* const new_top = _space_info[id].new_top();
1772     const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1773     const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1774     tty->print_cr("id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1775                   "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1776                   "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1777                   id, space->capacity_in_words(), dense_prefix_end,
1778                   dp_region, dp_words / region_size,
1779                   cr_words / region_size, new_top);
1780   }
1781 }
1782 
1783 #ifndef PRODUCT
1784 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1785                                           HeapWord* dst_beg, HeapWord* dst_end,
1786                                           SpaceId src_space_id,
1787                                           HeapWord* src_beg, HeapWord* src_end)
1788 {
1789   if (TraceParallelOldGCSummaryPhase) {
1790     tty->print_cr("summarizing %d [%s] into %d [%s]:  "
1791                   "src=" PTR_FORMAT "-" PTR_FORMAT " "
1792                   SIZE_FORMAT "-" SIZE_FORMAT " "
1793                   "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1794                   SIZE_FORMAT "-" SIZE_FORMAT,
1795                   src_space_id, space_names[src_space_id],
1796                   dst_space_id, space_names[dst_space_id],
1797                   src_beg, src_end,
1798                   _summary_data.addr_to_region_idx(src_beg),
1799                   _summary_data.addr_to_region_idx(src_end),
1800                   dst_beg, dst_end,
1801                   _summary_data.addr_to_region_idx(dst_beg),
1802                   _summary_data.addr_to_region_idx(dst_end));
1803   }
1804 }
1805 #endif  // #ifndef PRODUCT
1806 
1807 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1808                                       bool maximum_compaction)
1809 {
1810   TraceTime tm("summary phase", print_phases(), true, gclog_or_tty);
1811   // trace("2");
1812 
1813 #ifdef  ASSERT
1814   if (TraceParallelOldGCMarkingPhase) {
1815     tty->print_cr("add_obj_count=" SIZE_FORMAT " "
1816                   "add_obj_bytes=" SIZE_FORMAT,
1817                   add_obj_count, add_obj_size * HeapWordSize);
1818     tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
1819                   "mark_bitmap_bytes=" SIZE_FORMAT,
1820                   mark_bitmap_count, mark_bitmap_size * HeapWordSize);
1821   }
1822 #endif  // #ifdef ASSERT
1823 
1824   // Quick summarization of each space into itself, to see how much is live.
1825   summarize_spaces_quick();
1826 
1827   if (TraceParallelOldGCSummaryPhase) {
1828     tty->print_cr("summary_phase:  after summarizing each space to self");
1829     Universe::print();
1830     NOT_PRODUCT(print_region_ranges());
1831     if (Verbose) {
1832       NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1833     }
1834   }
1835 
1836   // The amount of live data that will end up in old space (assuming it fits).
1837   size_t old_space_total_live = 0;
1838   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1839     old_space_total_live += pointer_delta(_space_info[id].new_top(),
1840                                           _space_info[id].space()->bottom());
1841   }
1842 
1843   MutableSpace* const old_space = _space_info[old_space_id].space();
1844   const size_t old_capacity = old_space->capacity_in_words();
1845   if (old_space_total_live > old_capacity) {
1846     // XXX - should also try to expand
1847     maximum_compaction = true;
1848   }
1849 #ifndef PRODUCT
1850   if (ParallelOldGCSplitALot && old_space_total_live < old_capacity) {
1851     provoke_split(maximum_compaction);
1852   }
1853 #endif // #ifndef PRODUCT
1854 
1855   // Old generations.
1856   summarize_space(old_space_id, maximum_compaction);
1857 
1858   // Summarize the remaining spaces in the young gen.  The initial target space
1859   // is the old gen.  If a space does not fit entirely into the target, then the
1860   // remainder is compacted into the space itself and that space becomes the new
1861   // target.
1862   SpaceId dst_space_id = old_space_id;
1863   HeapWord* dst_space_end = old_space->end();
1864   HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1865   for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1866     const MutableSpace* space = _space_info[id].space();
1867     const size_t live = pointer_delta(_space_info[id].new_top(),
1868                                       space->bottom());
1869     const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1870 
1871     NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1872                                   SpaceId(id), space->bottom(), space->top());)
1873     if (live > 0 && live <= available) {
1874       // All the live data will fit.
1875       bool done = _summary_data.summarize(_space_info[id].split_info(),
1876                                           space->bottom(), space->top(),
1877                                           NULL,
1878                                           *new_top_addr, dst_space_end,
1879                                           new_top_addr);
1880       assert(done, "space must fit into old gen");
1881 
1882       // Reset the new_top value for the space.
1883       _space_info[id].set_new_top(space->bottom());
1884     } else if (live > 0) {
1885       // Attempt to fit part of the source space into the target space.
1886       HeapWord* next_src_addr = NULL;
1887       bool done = _summary_data.summarize(_space_info[id].split_info(),
1888                                           space->bottom(), space->top(),
1889                                           &next_src_addr,
1890                                           *new_top_addr, dst_space_end,
1891                                           new_top_addr);
1892       assert(!done, "space should not fit into old gen");
1893       assert(next_src_addr != NULL, "sanity");
1894 
1895       // The source space becomes the new target, so the remainder is compacted
1896       // within the space itself.
1897       dst_space_id = SpaceId(id);
1898       dst_space_end = space->end();
1899       new_top_addr = _space_info[id].new_top_addr();
1900       NOT_PRODUCT(summary_phase_msg(dst_space_id,
1901                                     space->bottom(), dst_space_end,
1902                                     SpaceId(id), next_src_addr, space->top());)
1903       done = _summary_data.summarize(_space_info[id].split_info(),
1904                                      next_src_addr, space->top(),
1905                                      NULL,
1906                                      space->bottom(), dst_space_end,
1907                                      new_top_addr);
1908       assert(done, "space must fit when compacted into itself");
1909       assert(*new_top_addr <= space->top(), "usage should not grow");
1910     }
1911   }
1912 
1913   if (TraceParallelOldGCSummaryPhase) {
1914     tty->print_cr("summary_phase:  after final summarization");
1915     Universe::print();
1916     NOT_PRODUCT(print_region_ranges());
1917     if (Verbose) {
1918       NOT_PRODUCT(print_generic_summary_data(_summary_data, _space_info));
1919     }
1920   }
1921 }
1922 
1923 // This method should contain all heap-specific policy for invoking a full
1924 // collection.  invoke_no_policy() will only attempt to compact the heap; it
1925 // will do nothing further.  If we need to bail out for policy reasons, scavenge
1926 // before full gc, or any other specialized behavior, it needs to be added here.
1927 //
1928 // Note that this method should only be called from the vm_thread while at a
1929 // safepoint.
1930 //
1931 // Note that the all_soft_refs_clear flag in the collector policy
1932 // may be true because this method can be called without intervening
1933 // activity.  For example when the heap space is tight and full measure
1934 // are being taken to free space.
1935 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1936   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1937   assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1938          "should be in vm thread");
1939 
1940   ParallelScavengeHeap* heap = gc_heap();
1941   GCCause::Cause gc_cause = heap->gc_cause();
1942   assert(!heap->is_gc_active(), "not reentrant");
1943 
1944   PSAdaptiveSizePolicy* policy = heap->size_policy();
1945   IsGCActiveMark mark;
1946 
1947   if (ScavengeBeforeFullGC) {
1948     PSScavenge::invoke_no_policy();
1949   }
1950 
1951   const bool clear_all_soft_refs =
1952     heap->collector_policy()->should_clear_all_soft_refs();
1953 
1954   PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1955                                       maximum_heap_compaction);
1956 }
1957 
1958 bool ParallelCompactData::region_contains(size_t region_index, HeapWord* addr) {
1959   size_t addr_region_index = addr_to_region_idx(addr);
1960   return region_index == addr_region_index;
1961 }
1962 
1963 // This method contains no policy. You should probably
1964 // be calling invoke() instead.
1965 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
1966   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
1967   assert(ref_processor() != NULL, "Sanity");
1968 
1969   if (GC_locker::check_active_before_gc()) {
1970     return false;
1971   }
1972 
1973   TimeStamp marking_start;
1974   TimeStamp compaction_start;
1975   TimeStamp collection_exit;
1976 
1977   ParallelScavengeHeap* heap = gc_heap();
1978   GCCause::Cause gc_cause = heap->gc_cause();
1979   PSYoungGen* young_gen = heap->young_gen();
1980   PSOldGen* old_gen = heap->old_gen();
1981   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1982 
1983   // The scope of casr should end after code that can change
1984   // CollectorPolicy::_should_clear_all_soft_refs.
1985   ClearedAllSoftRefs casr(maximum_heap_compaction,
1986                           heap->collector_policy());
1987 
1988   if (ZapUnusedHeapArea) {
1989     // Save information needed to minimize mangling
1990     heap->record_gen_tops_before_GC();
1991   }
1992 
1993   heap->pre_full_gc_dump();
1994 
1995   _print_phases = PrintGCDetails && PrintParallelOldGCPhaseTimes;
1996 
1997   // Make sure data structures are sane, make the heap parsable, and do other
1998   // miscellaneous bookkeeping.
1999   PreGCValues pre_gc_values;
2000   pre_compact(&pre_gc_values);
2001 
2002   // Get the compaction manager reserved for the VM thread.
2003   ParCompactionManager* const vmthread_cm =
2004     ParCompactionManager::manager_array(gc_task_manager()->workers());
2005 
2006   // Place after pre_compact() where the number of invocations is incremented.
2007   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
2008 
2009   {
2010     ResourceMark rm;
2011     HandleMark hm;
2012 
2013     // Set the number of GC threads to be used in this collection
2014     gc_task_manager()->set_active_gang();
2015     gc_task_manager()->task_idle_workers();
2016     heap->set_par_threads(gc_task_manager()->active_workers());
2017 
2018     gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
2019     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
2020     TraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty);
2021     TraceCollectorStats tcs(counters());
2022     TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);
2023 
2024     if (TraceGen1Time) accumulated_time()->start();
2025 
2026     // Let the size policy know we're starting
2027     size_policy->major_collection_begin();
2028 
2029     CodeCache::gc_prologue();
2030     Threads::gc_prologue();
2031 
2032     COMPILER2_PRESENT(DerivedPointerTable::clear());
2033 
2034     ref_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
2035     ref_processor()->setup_policy(maximum_heap_compaction);
2036 
2037     bool marked_for_unloading = false;
2038 
2039     marking_start.update();
2040     marking_phase(vmthread_cm, maximum_heap_compaction);
2041 
2042 #ifndef PRODUCT
2043     if (TraceParallelOldGCMarkingPhase) {
2044       gclog_or_tty->print_cr("marking_phase: cas_tries %d  cas_retries %d "
2045         "cas_by_another %d",
2046         mark_bitmap()->cas_tries(), mark_bitmap()->cas_retries(),
2047         mark_bitmap()->cas_by_another());
2048     }
2049 #endif  // #ifndef PRODUCT
2050 
2051     bool max_on_system_gc = UseMaximumCompactionOnSystemGC
2052       && gc_cause == GCCause::_java_lang_system_gc;
2053     summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
2054 
2055     COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
2056     COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
2057 
2058     // adjust_roots() updates Universe::_intArrayKlassObj which is
2059     // needed by the compaction for filling holes in the dense prefix.
2060     adjust_roots();
2061 
2062     compaction_start.update();
2063     compact();
2064 
2065     // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
2066     // done before resizing.
2067     post_compact();
2068 
2069     // Let the size policy know we're done
2070     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
2071 
2072     if (UseAdaptiveSizePolicy) {
2073       if (PrintAdaptiveSizePolicy) {
2074         gclog_or_tty->print("AdaptiveSizeStart: ");
2075         gclog_or_tty->stamp();
2076         gclog_or_tty->print_cr(" collection: %d ",
2077                        heap->total_collections());
2078         if (Verbose) {
2079           gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d",
2080             old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
2081         }
2082       }
2083 
2084       // Don't check if the size_policy is ready here.  Let
2085       // the size_policy check that internally.
2086       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
2087           ((gc_cause != GCCause::_java_lang_system_gc) ||
2088             UseAdaptiveSizePolicyWithSystemGC)) {
2089         // Calculate optimal free space amounts
2090         assert(young_gen->max_size() >
2091           young_gen->from_space()->capacity_in_bytes() +
2092           young_gen->to_space()->capacity_in_bytes(),
2093           "Sizes of space in young gen are out-of-bounds");
2094         size_t max_eden_size = young_gen->max_size() -
2095           young_gen->from_space()->capacity_in_bytes() -
2096           young_gen->to_space()->capacity_in_bytes();
2097         size_policy->compute_generations_free_space(
2098                               young_gen->used_in_bytes(),
2099                               young_gen->eden_space()->used_in_bytes(),
2100                               old_gen->used_in_bytes(),
2101                               young_gen->eden_space()->capacity_in_bytes(),
2102                               old_gen->max_gen_size(),
2103                               max_eden_size,
2104                               true /* full gc*/,
2105                               gc_cause,
2106                               heap->collector_policy());
2107 
2108         heap->resize_old_gen(
2109           size_policy->calculated_old_free_size_in_bytes());
2110 
2111         // Don't resize the young generation at an major collection.  A
2112         // desired young generation size may have been calculated but
2113         // resizing the young generation complicates the code because the
2114         // resizing of the old generation may have moved the boundary
2115         // between the young generation and the old generation.  Let the
2116         // young generation resizing happen at the minor collections.
2117       }
2118       if (PrintAdaptiveSizePolicy) {
2119         gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
2120                        heap->total_collections());
2121       }
2122     }
2123 
2124     if (UsePerfData) {
2125       PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
2126       counters->update_counters();
2127       counters->update_old_capacity(old_gen->capacity_in_bytes());
2128       counters->update_young_capacity(young_gen->capacity_in_bytes());
2129     }
2130 
2131     heap->resize_all_tlabs();
2132 
2133     // Resize the metaspace capactiy after a collection
2134     MetaspaceGC::compute_new_size();
2135 
2136     if (TraceGen1Time) accumulated_time()->stop();
2137 
2138     if (PrintGC) {
2139       if (PrintGCDetails) {
2140         // No GC timestamp here.  This is after GC so it would be confusing.
2141         young_gen->print_used_change(pre_gc_values.young_gen_used());
2142         old_gen->print_used_change(pre_gc_values.old_gen_used());
2143         heap->print_heap_change(pre_gc_values.heap_used());
2144         MetaspaceAux::print_metaspace_change(pre_gc_values.metadata_used());
2145       } else {
2146         heap->print_heap_change(pre_gc_values.heap_used());
2147       }
2148     }
2149 
2150     // Track memory usage and detect low memory
2151     MemoryService::track_memory_usage();
2152     heap->update_counters();
2153     gc_task_manager()->release_idle_workers();
2154   }
2155 
2156 #ifdef ASSERT
2157   for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
2158     ParCompactionManager* const cm =
2159       ParCompactionManager::manager_array(int(i));
2160     assert(cm->marking_stack()->is_empty(),       "should be empty");
2161     assert(ParCompactionManager::region_list(int(i))->is_empty(), "should be empty");
2162   }
2163 #endif // ASSERT
2164 
2165   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
2166     HandleMark hm;  // Discard invalid handles created during verification
2167     gclog_or_tty->print(" VerifyAfterGC:");
2168     Universe::verify();
2169   }
2170 
2171   // Re-verify object start arrays
2172   if (VerifyObjectStartArray &&
2173       VerifyAfterGC) {
2174     old_gen->verify_object_start_array();
2175   }
2176 
2177   if (ZapUnusedHeapArea) {
2178     old_gen->object_space()->check_mangled_unused_area_complete();
2179   }
2180 
2181   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
2182 
2183   collection_exit.update();
2184 
2185   heap->print_heap_after_gc();
2186   if (PrintGCTaskTimeStamps) {
2187     gclog_or_tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " "
2188                            INT64_FORMAT,
2189                            marking_start.ticks(), compaction_start.ticks(),
2190                            collection_exit.ticks());
2191     gc_task_manager()->print_task_time_stamps();
2192   }
2193 
2194   heap->post_full_gc_dump();
2195 
2196 #ifdef TRACESPINNING
2197   ParallelTaskTerminator::print_termination_counts();
2198 #endif
2199 
2200   return true;
2201 }
2202 
2203 bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
2204                                              PSYoungGen* young_gen,
2205                                              PSOldGen* old_gen) {
2206   MutableSpace* const eden_space = young_gen->eden_space();
2207   assert(!eden_space->is_empty(), "eden must be non-empty");
2208   assert(young_gen->virtual_space()->alignment() ==
2209          old_gen->virtual_space()->alignment(), "alignments do not match");
2210 
2211   if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
2212     return false;
2213   }
2214 
2215   // Both generations must be completely committed.
2216   if (young_gen->virtual_space()->uncommitted_size() != 0) {
2217     return false;
2218   }
2219   if (old_gen->virtual_space()->uncommitted_size() != 0) {
2220     return false;
2221   }
2222 
2223   // Figure out how much to take from eden.  Include the average amount promoted
2224   // in the total; otherwise the next young gen GC will simply bail out to a
2225   // full GC.
2226   const size_t alignment = old_gen->virtual_space()->alignment();
2227   const size_t eden_used = eden_space->used_in_bytes();
2228   const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
2229   const size_t absorb_size = align_size_up(eden_used + promoted, alignment);
2230   const size_t eden_capacity = eden_space->capacity_in_bytes();
2231 
2232   if (absorb_size >= eden_capacity) {
2233     return false; // Must leave some space in eden.
2234   }
2235 
2236   const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
2237   if (new_young_size < young_gen->min_gen_size()) {
2238     return false; // Respect young gen minimum size.
2239   }
2240 
2241   if (TraceAdaptiveGCBoundary && Verbose) {
2242     gclog_or_tty->print(" absorbing " SIZE_FORMAT "K:  "
2243                         "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
2244                         "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
2245                         "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
2246                         absorb_size / K,
2247                         eden_capacity / K, (eden_capacity - absorb_size) / K,
2248                         young_gen->from_space()->used_in_bytes() / K,
2249                         young_gen->to_space()->used_in_bytes() / K,
2250                         young_gen->capacity_in_bytes() / K, new_young_size / K);
2251   }
2252 
2253   // Fill the unused part of the old gen.
2254   MutableSpace* const old_space = old_gen->object_space();
2255   HeapWord* const unused_start = old_space->top();
2256   size_t const unused_words = pointer_delta(old_space->end(), unused_start);
2257 
2258   if (unused_words > 0) {
2259     if (unused_words < CollectedHeap::min_fill_size()) {
2260       return false;  // If the old gen cannot be filled, must give up.
2261     }
2262     CollectedHeap::fill_with_objects(unused_start, unused_words);
2263   }
2264 
2265   // Take the live data from eden and set both top and end in the old gen to
2266   // eden top.  (Need to set end because reset_after_change() mangles the region
2267   // from end to virtual_space->high() in debug builds).
2268   HeapWord* const new_top = eden_space->top();
2269   old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
2270                                         absorb_size);
2271   young_gen->reset_after_change();
2272   old_space->set_top(new_top);
2273   old_space->set_end(new_top);
2274   old_gen->reset_after_change();
2275 
2276   // Update the object start array for the filler object and the data from eden.
2277   ObjectStartArray* const start_array = old_gen->start_array();
2278   for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
2279     start_array->allocate_block(p);
2280   }
2281 
2282   // Could update the promoted average here, but it is not typically updated at
2283   // full GCs and the value to use is unclear.  Something like
2284   //
2285   // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
2286 
2287   size_policy->set_bytes_absorbed_from_eden(absorb_size);
2288   return true;
2289 }
2290 
2291 GCTaskManager* const PSParallelCompact::gc_task_manager() {
2292   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
2293     "shouldn't return NULL");
2294   return ParallelScavengeHeap::gc_task_manager();
2295 }
2296 
2297 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2298                                       bool maximum_heap_compaction) {
2299   // Recursively traverse all live objects and mark them
2300   TraceTime tm("marking phase", print_phases(), true, gclog_or_tty);
2301 
2302   ParallelScavengeHeap* heap = gc_heap();
2303   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2304   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2305   TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2306   ParallelTaskTerminator terminator(active_gc_threads, qset);
2307 
2308   PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm);
2309   PSParallelCompact::FollowStackClosure follow_stack_closure(cm);
2310 
2311   // Need new claim bits before marking starts.
2312   ClassLoaderDataGraph::clear_claimed_marks();
2313 
2314   {
2315     TraceTime tm_m("par mark", print_phases(), true, gclog_or_tty);
2316     ParallelScavengeHeap::ParStrongRootsScope psrs;
2317 
2318     GCTaskQueue* q = GCTaskQueue::create();
2319 
2320     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::universe));
2321     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jni_handles));
2322     // We scan the thread roots in parallel
2323     Threads::create_thread_roots_marking_tasks(q);
2324     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::object_synchronizer));
2325     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::flat_profiler));
2326     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::management));
2327     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::system_dictionary));
2328     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jvmti));
2329     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::code_cache));
2330 
2331     if (active_gc_threads > 1) {
2332       for (uint j = 0; j < active_gc_threads; j++) {
2333         q->enqueue(new StealMarkingTask(&terminator));
2334       }
2335     }
2336 
2337     gc_task_manager()->execute_and_wait(q);
2338   }
2339 
2340   // Process reference objects found during marking
2341   {
2342     TraceTime tm_r("reference processing", print_phases(), true, gclog_or_tty);
2343     if (ref_processor()->processing_is_mt()) {
2344       RefProcTaskExecutor task_executor;
2345       ref_processor()->process_discovered_references(
2346         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2347         &task_executor);
2348     } else {
2349       ref_processor()->process_discovered_references(
2350         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL);
2351     }
2352   }
2353 
2354   TraceTime tm_c("class unloading", print_phases(), true, gclog_or_tty);
2355   // Follow system dictionary roots and unload classes.
2356   bool purged_class = SystemDictionary::do_unloading(is_alive_closure());
2357 
2358   // Follow code cache roots.
2359   CodeCache::do_unloading(is_alive_closure(), purged_class);
2360   cm->follow_marking_stacks(); // Flush marking stack.
2361 
2362   // Update subklass/sibling/implementor links of live klasses
2363   Klass::clean_weak_klass_links(is_alive_closure());
2364 
2365   // Visit interned string tables and delete unmarked oops
2366   StringTable::unlink(is_alive_closure());
2367   // Clean up unreferenced symbols in symbol table.
2368   SymbolTable::unlink();
2369 
2370   assert(cm->marking_stacks_empty(), "marking stacks should be empty");
2371 }
2372 
2373 void PSParallelCompact::follow_klass(ParCompactionManager* cm, Klass* klass) {
2374   ClassLoaderData* cld = klass->class_loader_data();
2375   // The actual processing of the klass is done when we
2376   // traverse the list of Klasses in the class loader data.
2377   PSParallelCompact::follow_class_loader(cm, cld);
2378 }
2379 
2380 void PSParallelCompact::adjust_klass(ParCompactionManager* cm, Klass* klass) {
2381   ClassLoaderData* cld = klass->class_loader_data();
2382   // The actual processing of the klass is done when we
2383   // traverse the list of Klasses in the class loader data.
2384   PSParallelCompact::adjust_class_loader(cm, cld);
2385 }
2386 
2387 void PSParallelCompact::follow_class_loader(ParCompactionManager* cm,
2388                                             ClassLoaderData* cld) {
2389   PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm);
2390   PSParallelCompact::FollowKlassClosure follow_klass_closure(&mark_and_push_closure);
2391 
2392   cld->oops_do(&mark_and_push_closure, &follow_klass_closure, true);
2393 }
2394 
2395 void PSParallelCompact::adjust_class_loader(ParCompactionManager* cm,
2396                                             ClassLoaderData* cld) {
2397   cld->oops_do(PSParallelCompact::adjust_root_pointer_closure(),
2398                PSParallelCompact::adjust_klass_closure(),
2399                true);
2400 }
2401 
2402 // This should be moved to the shared markSweep code!
2403 class PSAlwaysTrueClosure: public BoolObjectClosure {
2404 public:
2405   void do_object(oop p) { ShouldNotReachHere(); }
2406   bool do_object_b(oop p) { return true; }
2407 };
2408 static PSAlwaysTrueClosure always_true;
2409 
2410 void PSParallelCompact::adjust_roots() {
2411   // Adjust the pointers to reflect the new locations
2412   TraceTime tm("adjust roots", print_phases(), true, gclog_or_tty);
2413 
2414   // Need new claim bits when tracing through and adjusting pointers.
2415   ClassLoaderDataGraph::clear_claimed_marks();
2416 
2417   // General strong roots.
2418   Universe::oops_do(adjust_root_pointer_closure());
2419   JNIHandles::oops_do(adjust_root_pointer_closure());   // Global (strong) JNI handles
2420   CLDToOopClosure adjust_from_cld(adjust_root_pointer_closure());
2421   Threads::oops_do(adjust_root_pointer_closure(), &adjust_from_cld, NULL);
2422   ObjectSynchronizer::oops_do(adjust_root_pointer_closure());
2423   FlatProfiler::oops_do(adjust_root_pointer_closure());
2424   Management::oops_do(adjust_root_pointer_closure());
2425   JvmtiExport::oops_do(adjust_root_pointer_closure());
2426   // SO_AllClasses
2427   SystemDictionary::oops_do(adjust_root_pointer_closure());
2428   ClassLoaderDataGraph::oops_do(adjust_root_pointer_closure(), adjust_klass_closure(), true);
2429 
2430   // Now adjust pointers in remaining weak roots.  (All of which should
2431   // have been cleared if they pointed to non-surviving objects.)
2432   // Global (weak) JNI handles
2433   JNIHandles::weak_oops_do(&always_true, adjust_root_pointer_closure());
2434 
2435   CodeCache::oops_do(adjust_pointer_closure());
2436   StringTable::oops_do(adjust_root_pointer_closure());
2437   ref_processor()->weak_oops_do(adjust_root_pointer_closure());
2438   // Roots were visited so references into the young gen in roots
2439   // may have been scanned.  Process them also.
2440   // Should the reference processor have a span that excludes
2441   // young gen objects?
2442   PSScavenge::reference_processor()->weak_oops_do(
2443                                               adjust_root_pointer_closure());
2444 }
2445 
2446 void PSParallelCompact::enqueue_region_draining_tasks(GCTaskQueue* q,
2447                                                       uint parallel_gc_threads)
2448 {
2449   TraceTime tm("drain task setup", print_phases(), true, gclog_or_tty);
2450 
2451   // Find the threads that are active
2452   unsigned int which = 0;
2453 
2454   const uint task_count = MAX2(parallel_gc_threads, 1U);
2455   for (uint j = 0; j < task_count; j++) {
2456     q->enqueue(new DrainStacksCompactionTask(j));
2457     ParCompactionManager::verify_region_list_empty(j);
2458     // Set the region stacks variables to "no" region stack values
2459     // so that they will be recognized and needing a region stack
2460     // in the stealing tasks if they do not get one by executing
2461     // a draining stack.
2462     ParCompactionManager* cm = ParCompactionManager::manager_array(j);
2463     cm->set_region_stack(NULL);
2464     cm->set_region_stack_index((uint)max_uintx);
2465   }
2466   ParCompactionManager::reset_recycled_stack_index();
2467 
2468   // Find all regions that are available (can be filled immediately) and
2469   // distribute them to the thread stacks.  The iteration is done in reverse
2470   // order (high to low) so the regions will be removed in ascending order.
2471 
2472   const ParallelCompactData& sd = PSParallelCompact::summary_data();
2473 
2474   size_t fillable_regions = 0;   // A count for diagnostic purposes.
2475   // A region index which corresponds to the tasks created above.
2476   // "which" must be 0 <= which < task_count
2477 
2478   which = 0;
2479   // id + 1 is used to test termination so unsigned  can
2480   // be used with an old_space_id == 0.
2481   for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2482     SpaceInfo* const space_info = _space_info + id;
2483     MutableSpace* const space = space_info->space();
2484     HeapWord* const new_top = space_info->new_top();
2485 
2486     const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2487     const size_t end_region =
2488       sd.addr_to_region_idx(sd.region_align_up(new_top));
2489 
2490     for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2491       if (sd.region(cur)->claim_unsafe()) {
2492         ParCompactionManager::region_list_push(which, cur);
2493 
2494         if (TraceParallelOldGCCompactionPhase && Verbose) {
2495           const size_t count_mod_8 = fillable_regions & 7;
2496           if (count_mod_8 == 0) gclog_or_tty->print("fillable: ");
2497           gclog_or_tty->print(" " SIZE_FORMAT_W(7), cur);
2498           if (count_mod_8 == 7) gclog_or_tty->cr();
2499         }
2500 
2501         NOT_PRODUCT(++fillable_regions;)
2502 
2503         // Assign regions to tasks in round-robin fashion.
2504         if (++which == task_count) {
2505           assert(which <= parallel_gc_threads,
2506             "Inconsistent number of workers");
2507           which = 0;
2508         }
2509       }
2510     }
2511   }
2512 
2513   if (TraceParallelOldGCCompactionPhase) {
2514     if (Verbose && (fillable_regions & 7) != 0) gclog_or_tty->cr();
2515     gclog_or_tty->print_cr("%u initially fillable regions", fillable_regions);
2516   }
2517 }
2518 
2519 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2520 
2521 void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q,
2522                                                     uint parallel_gc_threads) {
2523   TraceTime tm("dense prefix task setup", print_phases(), true, gclog_or_tty);
2524 
2525   ParallelCompactData& sd = PSParallelCompact::summary_data();
2526 
2527   // Iterate over all the spaces adding tasks for updating
2528   // regions in the dense prefix.  Assume that 1 gc thread
2529   // will work on opening the gaps and the remaining gc threads
2530   // will work on the dense prefix.
2531   unsigned int space_id;
2532   for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2533     HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2534     const MutableSpace* const space = _space_info[space_id].space();
2535 
2536     if (dense_prefix_end == space->bottom()) {
2537       // There is no dense prefix for this space.
2538       continue;
2539     }
2540 
2541     // The dense prefix is before this region.
2542     size_t region_index_end_dense_prefix =
2543         sd.addr_to_region_idx(dense_prefix_end);
2544     RegionData* const dense_prefix_cp =
2545       sd.region(region_index_end_dense_prefix);
2546     assert(dense_prefix_end == space->end() ||
2547            dense_prefix_cp->available() ||
2548            dense_prefix_cp->claimed(),
2549            "The region after the dense prefix should always be ready to fill");
2550 
2551     size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2552 
2553     // Is there dense prefix work?
2554     size_t total_dense_prefix_regions =
2555       region_index_end_dense_prefix - region_index_start;
2556     // How many regions of the dense prefix should be given to
2557     // each thread?
2558     if (total_dense_prefix_regions > 0) {
2559       uint tasks_for_dense_prefix = 1;
2560       if (total_dense_prefix_regions <=
2561           (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2562         // Don't over partition.  This assumes that
2563         // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2564         // so there are not many regions to process.
2565         tasks_for_dense_prefix = parallel_gc_threads;
2566       } else {
2567         // Over partition
2568         tasks_for_dense_prefix = parallel_gc_threads *
2569           PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2570       }
2571       size_t regions_per_thread = total_dense_prefix_regions /
2572         tasks_for_dense_prefix;
2573       // Give each thread at least 1 region.
2574       if (regions_per_thread == 0) {
2575         regions_per_thread = 1;
2576       }
2577 
2578       for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2579         if (region_index_start >= region_index_end_dense_prefix) {
2580           break;
2581         }
2582         // region_index_end is not processed
2583         size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2584                                        region_index_end_dense_prefix);
2585         q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2586                                              region_index_start,
2587                                              region_index_end));
2588         region_index_start = region_index_end;
2589       }
2590     }
2591     // This gets any part of the dense prefix that did not
2592     // fit evenly.
2593     if (region_index_start < region_index_end_dense_prefix) {
2594       q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2595                                            region_index_start,
2596                                            region_index_end_dense_prefix));
2597     }
2598   }
2599 }
2600 
2601 void PSParallelCompact::enqueue_region_stealing_tasks(
2602                                      GCTaskQueue* q,
2603                                      ParallelTaskTerminator* terminator_ptr,
2604                                      uint parallel_gc_threads) {
2605   TraceTime tm("steal task setup", print_phases(), true, gclog_or_tty);
2606 
2607   // Once a thread has drained it's stack, it should try to steal regions from
2608   // other threads.
2609   if (parallel_gc_threads > 1) {
2610     for (uint j = 0; j < parallel_gc_threads; j++) {
2611       q->enqueue(new StealRegionCompactionTask(terminator_ptr));
2612     }
2613   }
2614 }
2615 
2616 void PSParallelCompact::compact() {
2617   // trace("5");
2618   TraceTime tm("compaction phase", print_phases(), true, gclog_or_tty);
2619 
2620   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
2621   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
2622   PSOldGen* old_gen = heap->old_gen();
2623   old_gen->start_array()->reset();
2624   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2625   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2626   TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2627   ParallelTaskTerminator terminator(active_gc_threads, qset);
2628 
2629   GCTaskQueue* q = GCTaskQueue::create();
2630   enqueue_region_draining_tasks(q, active_gc_threads);
2631   enqueue_dense_prefix_tasks(q, active_gc_threads);
2632   enqueue_region_stealing_tasks(q, &terminator, active_gc_threads);
2633 
2634   {
2635     TraceTime tm_pc("par compact", print_phases(), true, gclog_or_tty);
2636 
2637     gc_task_manager()->execute_and_wait(q);
2638 
2639 #ifdef  ASSERT
2640     // Verify that all regions have been processed before the deferred updates.
2641     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2642       verify_complete(SpaceId(id));
2643     }
2644 #endif
2645   }
2646 
2647   {
2648     // Update the deferred objects, if any.  Any compaction manager can be used.
2649     TraceTime tm_du("deferred updates", print_phases(), true, gclog_or_tty);
2650     ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2651     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2652       update_deferred_objects(cm, SpaceId(id));
2653     }
2654   }
2655 }
2656 
2657 #ifdef  ASSERT
2658 void PSParallelCompact::verify_complete(SpaceId space_id) {
2659   // All Regions between space bottom() to new_top() should be marked as filled
2660   // and all Regions between new_top() and top() should be available (i.e.,
2661   // should have been emptied).
2662   ParallelCompactData& sd = summary_data();
2663   SpaceInfo si = _space_info[space_id];
2664   HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2665   HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2666   const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2667   const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2668   const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2669 
2670   bool issued_a_warning = false;
2671 
2672   size_t cur_region;
2673   for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2674     const RegionData* const c = sd.region(cur_region);
2675     if (!c->completed()) {
2676       warning("region " SIZE_FORMAT " not filled:  "
2677               "destination_count=" SIZE_FORMAT,
2678               cur_region, c->destination_count());
2679       issued_a_warning = true;
2680     }
2681   }
2682 
2683   for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2684     const RegionData* const c = sd.region(cur_region);
2685     if (!c->available()) {
2686       warning("region " SIZE_FORMAT " not empty:   "
2687               "destination_count=" SIZE_FORMAT,
2688               cur_region, c->destination_count());
2689       issued_a_warning = true;
2690     }
2691   }
2692 
2693   if (issued_a_warning) {
2694     print_region_ranges();
2695   }
2696 }
2697 #endif  // #ifdef ASSERT
2698 
2699 // Update interior oops in the ranges of regions [beg_region, end_region).
2700 void
2701 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2702                                                        SpaceId space_id,
2703                                                        size_t beg_region,
2704                                                        size_t end_region) {
2705   ParallelCompactData& sd = summary_data();
2706   ParMarkBitMap* const mbm = mark_bitmap();
2707 
2708   HeapWord* beg_addr = sd.region_to_addr(beg_region);
2709   HeapWord* const end_addr = sd.region_to_addr(end_region);
2710   assert(beg_region <= end_region, "bad region range");
2711   assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2712 
2713 #ifdef  ASSERT
2714   // Claim the regions to avoid triggering an assert when they are marked as
2715   // filled.
2716   for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2717     assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2718   }
2719 #endif  // #ifdef ASSERT
2720 
2721   if (beg_addr != space(space_id)->bottom()) {
2722     // Find the first live object or block of dead space that *starts* in this
2723     // range of regions.  If a partial object crosses onto the region, skip it;
2724     // it will be marked for 'deferred update' when the object head is
2725     // processed.  If dead space crosses onto the region, it is also skipped; it
2726     // will be filled when the prior region is processed.  If neither of those
2727     // apply, the first word in the region is the start of a live object or dead
2728     // space.
2729     assert(beg_addr > space(space_id)->bottom(), "sanity");
2730     const RegionData* const cp = sd.region(beg_region);
2731     if (cp->partial_obj_size() != 0) {
2732       beg_addr = sd.partial_obj_end(beg_region);
2733     } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2734       beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2735     }
2736   }
2737 
2738   if (beg_addr < end_addr) {
2739     // A live object or block of dead space starts in this range of Regions.
2740      HeapWord* const dense_prefix_end = dense_prefix(space_id);
2741 
2742     // Create closures and iterate.
2743     UpdateOnlyClosure update_closure(mbm, cm, space_id);
2744     FillClosure fill_closure(cm, space_id);
2745     ParMarkBitMap::IterationStatus status;
2746     status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2747                           dense_prefix_end);
2748     if (status == ParMarkBitMap::incomplete) {
2749       update_closure.do_addr(update_closure.source());
2750     }
2751   }
2752 
2753   // Mark the regions as filled.
2754   RegionData* const beg_cp = sd.region(beg_region);
2755   RegionData* const end_cp = sd.region(end_region);
2756   for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2757     cp->set_completed();
2758   }
2759 }
2760 
2761 // Return the SpaceId for the space containing addr.  If addr is not in the
2762 // heap, last_space_id is returned.  In debug mode it expects the address to be
2763 // in the heap and asserts such.
2764 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2765   assert(Universe::heap()->is_in_reserved(addr), "addr not in the heap");
2766 
2767   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2768     if (_space_info[id].space()->contains(addr)) {
2769       return SpaceId(id);
2770     }
2771   }
2772 
2773   assert(false, "no space contains the addr");
2774   return last_space_id;
2775 }
2776 
2777 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2778                                                 SpaceId id) {
2779   assert(id < last_space_id, "bad space id");
2780 
2781   ParallelCompactData& sd = summary_data();
2782   const SpaceInfo* const space_info = _space_info + id;
2783   ObjectStartArray* const start_array = space_info->start_array();
2784 
2785   const MutableSpace* const space = space_info->space();
2786   assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2787   HeapWord* const beg_addr = space_info->dense_prefix();
2788   HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2789 
2790   const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2791   const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2792   const RegionData* cur_region;
2793   for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2794     HeapWord* const addr = cur_region->deferred_obj_addr();
2795     if (addr != NULL) {
2796       if (start_array != NULL) {
2797         start_array->allocate_block(addr);
2798       }
2799       oop(addr)->update_contents(cm);
2800       assert(oop(addr)->is_oop_or_null(), "should be an oop now");
2801     }
2802   }
2803 }
2804 
2805 // Skip over count live words starting from beg, and return the address of the
2806 // next live word.  Unless marked, the word corresponding to beg is assumed to
2807 // be dead.  Callers must either ensure beg does not correspond to the middle of
2808 // an object, or account for those live words in some other way.  Callers must
2809 // also ensure that there are enough live words in the range [beg, end) to skip.
2810 HeapWord*
2811 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2812 {
2813   assert(count > 0, "sanity");
2814 
2815   ParMarkBitMap* m = mark_bitmap();
2816   idx_t bits_to_skip = m->words_to_bits(count);
2817   idx_t cur_beg = m->addr_to_bit(beg);
2818   const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end));
2819 
2820   do {
2821     cur_beg = m->find_obj_beg(cur_beg, search_end);
2822     idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2823     const size_t obj_bits = cur_end - cur_beg + 1;
2824     if (obj_bits > bits_to_skip) {
2825       return m->bit_to_addr(cur_beg + bits_to_skip);
2826     }
2827     bits_to_skip -= obj_bits;
2828     cur_beg = cur_end + 1;
2829   } while (bits_to_skip > 0);
2830 
2831   // Skipping the desired number of words landed just past the end of an object.
2832   // Find the start of the next object.
2833   cur_beg = m->find_obj_beg(cur_beg, search_end);
2834   assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2835   return m->bit_to_addr(cur_beg);
2836 }
2837 
2838 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2839                                             SpaceId src_space_id,
2840                                             size_t src_region_idx)
2841 {
2842   assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2843 
2844   const SplitInfo& split_info = _space_info[src_space_id].split_info();
2845   if (split_info.dest_region_addr() == dest_addr) {
2846     // The partial object ending at the split point contains the first word to
2847     // be copied to dest_addr.
2848     return split_info.first_src_addr();
2849   }
2850 
2851   const ParallelCompactData& sd = summary_data();
2852   ParMarkBitMap* const bitmap = mark_bitmap();
2853   const size_t RegionSize = ParallelCompactData::RegionSize;
2854 
2855   assert(sd.is_region_aligned(dest_addr), "not aligned");
2856   const RegionData* const src_region_ptr = sd.region(src_region_idx);
2857   const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2858   HeapWord* const src_region_destination = src_region_ptr->destination();
2859 
2860   assert(dest_addr >= src_region_destination, "wrong src region");
2861   assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2862 
2863   HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2864   HeapWord* const src_region_end = src_region_beg + RegionSize;
2865 
2866   HeapWord* addr = src_region_beg;
2867   if (dest_addr == src_region_destination) {
2868     // Return the first live word in the source region.
2869     if (partial_obj_size == 0) {
2870       addr = bitmap->find_obj_beg(addr, src_region_end);
2871       assert(addr < src_region_end, "no objects start in src region");
2872     }
2873     return addr;
2874   }
2875 
2876   // Must skip some live data.
2877   size_t words_to_skip = dest_addr - src_region_destination;
2878   assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2879 
2880   if (partial_obj_size >= words_to_skip) {
2881     // All the live words to skip are part of the partial object.
2882     addr += words_to_skip;
2883     if (partial_obj_size == words_to_skip) {
2884       // Find the first live word past the partial object.
2885       addr = bitmap->find_obj_beg(addr, src_region_end);
2886       assert(addr < src_region_end, "wrong src region");
2887     }
2888     return addr;
2889   }
2890 
2891   // Skip over the partial object (if any).
2892   if (partial_obj_size != 0) {
2893     words_to_skip -= partial_obj_size;
2894     addr += partial_obj_size;
2895   }
2896 
2897   // Skip over live words due to objects that start in the region.
2898   addr = skip_live_words(addr, src_region_end, words_to_skip);
2899   assert(addr < src_region_end, "wrong src region");
2900   return addr;
2901 }
2902 
2903 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2904                                                      SpaceId src_space_id,
2905                                                      size_t beg_region,
2906                                                      HeapWord* end_addr)
2907 {
2908   ParallelCompactData& sd = summary_data();
2909 
2910 #ifdef ASSERT
2911   MutableSpace* const src_space = _space_info[src_space_id].space();
2912   HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2913   assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2914          "src_space_id does not match beg_addr");
2915   assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2916          "src_space_id does not match end_addr");
2917 #endif // #ifdef ASSERT
2918 
2919   RegionData* const beg = sd.region(beg_region);
2920   RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2921 
2922   // Regions up to new_top() are enqueued if they become available.
2923   HeapWord* const new_top = _space_info[src_space_id].new_top();
2924   RegionData* const enqueue_end =
2925     sd.addr_to_region_ptr(sd.region_align_up(new_top));
2926 
2927   for (RegionData* cur = beg; cur < end; ++cur) {
2928     assert(cur->data_size() > 0, "region must have live data");
2929     cur->decrement_destination_count();
2930     if (cur < enqueue_end && cur->available() && cur->claim()) {
2931       cm->push_region(sd.region(cur));
2932     }
2933   }
2934 }
2935 
2936 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2937                                           SpaceId& src_space_id,
2938                                           HeapWord*& src_space_top,
2939                                           HeapWord* end_addr)
2940 {
2941   typedef ParallelCompactData::RegionData RegionData;
2942 
2943   ParallelCompactData& sd = PSParallelCompact::summary_data();
2944   const size_t region_size = ParallelCompactData::RegionSize;
2945 
2946   size_t src_region_idx = 0;
2947 
2948   // Skip empty regions (if any) up to the top of the space.
2949   HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2950   RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2951   HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2952   const RegionData* const top_region_ptr =
2953     sd.addr_to_region_ptr(top_aligned_up);
2954   while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2955     ++src_region_ptr;
2956   }
2957 
2958   if (src_region_ptr < top_region_ptr) {
2959     // The next source region is in the current space.  Update src_region_idx
2960     // and the source address to match src_region_ptr.
2961     src_region_idx = sd.region(src_region_ptr);
2962     HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
2963     if (src_region_addr > closure.source()) {
2964       closure.set_source(src_region_addr);
2965     }
2966     return src_region_idx;
2967   }
2968 
2969   // Switch to a new source space and find the first non-empty region.
2970   unsigned int space_id = src_space_id + 1;
2971   assert(space_id < last_space_id, "not enough spaces");
2972 
2973   HeapWord* const destination = closure.destination();
2974 
2975   do {
2976     MutableSpace* space = _space_info[space_id].space();
2977     HeapWord* const bottom = space->bottom();
2978     const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
2979 
2980     // Iterate over the spaces that do not compact into themselves.
2981     if (bottom_cp->destination() != bottom) {
2982       HeapWord* const top_aligned_up = sd.region_align_up(space->top());
2983       const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
2984 
2985       for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
2986         if (src_cp->live_obj_size() > 0) {
2987           // Found it.
2988           assert(src_cp->destination() == destination,
2989                  "first live obj in the space must match the destination");
2990           assert(src_cp->partial_obj_size() == 0,
2991                  "a space cannot begin with a partial obj");
2992 
2993           src_space_id = SpaceId(space_id);
2994           src_space_top = space->top();
2995           const size_t src_region_idx = sd.region(src_cp);
2996           closure.set_source(sd.region_to_addr(src_region_idx));
2997           return src_region_idx;
2998         } else {
2999           assert(src_cp->data_size() == 0, "sanity");
3000         }
3001       }
3002     }
3003   } while (++space_id < last_space_id);
3004 
3005   assert(false, "no source region was found");
3006   return 0;
3007 }
3008 
3009 void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx)
3010 {
3011   typedef ParMarkBitMap::IterationStatus IterationStatus;
3012   const size_t RegionSize = ParallelCompactData::RegionSize;
3013   ParMarkBitMap* const bitmap = mark_bitmap();
3014   ParallelCompactData& sd = summary_data();
3015   RegionData* const region_ptr = sd.region(region_idx);
3016 
3017   // Get the items needed to construct the closure.
3018   HeapWord* dest_addr = sd.region_to_addr(region_idx);
3019   SpaceId dest_space_id = space_id(dest_addr);
3020   ObjectStartArray* start_array = _space_info[dest_space_id].start_array();
3021   HeapWord* new_top = _space_info[dest_space_id].new_top();
3022   assert(dest_addr < new_top, "sanity");
3023   const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize);
3024 
3025   // Get the source region and related info.
3026   size_t src_region_idx = region_ptr->source_region();
3027   SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
3028   HeapWord* src_space_top = _space_info[src_space_id].space()->top();
3029 
3030   MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3031   closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
3032 
3033   // Adjust src_region_idx to prepare for decrementing destination counts (the
3034   // destination count is not decremented when a region is copied to itself).
3035   if (src_region_idx == region_idx) {
3036     src_region_idx += 1;
3037   }
3038 
3039   if (bitmap->is_unmarked(closure.source())) {
3040     // The first source word is in the middle of an object; copy the remainder
3041     // of the object or as much as will fit.  The fact that pointer updates were
3042     // deferred will be noted when the object header is processed.
3043     HeapWord* const old_src_addr = closure.source();
3044     closure.copy_partial_obj();
3045     if (closure.is_full()) {
3046       decrement_destination_counts(cm, src_space_id, src_region_idx,
3047                                    closure.source());
3048       region_ptr->set_deferred_obj_addr(NULL);
3049       region_ptr->set_completed();
3050       return;
3051     }
3052 
3053     HeapWord* const end_addr = sd.region_align_down(closure.source());
3054     if (sd.region_align_down(old_src_addr) != end_addr) {
3055       // The partial object was copied from more than one source region.
3056       decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3057 
3058       // Move to the next source region, possibly switching spaces as well.  All
3059       // args except end_addr may be modified.
3060       src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3061                                        end_addr);
3062     }
3063   }
3064 
3065   do {
3066     HeapWord* const cur_addr = closure.source();
3067     HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
3068                                     src_space_top);
3069     IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
3070 
3071     if (status == ParMarkBitMap::incomplete) {
3072       // The last obj that starts in the source region does not end in the
3073       // region.
3074       assert(closure.source() < end_addr, "sanity");
3075       HeapWord* const obj_beg = closure.source();
3076       HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
3077                                        src_space_top);
3078       HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
3079       if (obj_end < range_end) {
3080         // The end was found; the entire object will fit.
3081         status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
3082         assert(status != ParMarkBitMap::would_overflow, "sanity");
3083       } else {
3084         // The end was not found; the object will not fit.
3085         assert(range_end < src_space_top, "obj cannot cross space boundary");
3086         status = ParMarkBitMap::would_overflow;
3087       }
3088     }
3089 
3090     if (status == ParMarkBitMap::would_overflow) {
3091       // The last object did not fit.  Note that interior oop updates were
3092       // deferred, then copy enough of the object to fill the region.
3093       region_ptr->set_deferred_obj_addr(closure.destination());
3094       status = closure.copy_until_full(); // copies from closure.source()
3095 
3096       decrement_destination_counts(cm, src_space_id, src_region_idx,
3097                                    closure.source());
3098       region_ptr->set_completed();
3099       return;
3100     }
3101 
3102     if (status == ParMarkBitMap::full) {
3103       decrement_destination_counts(cm, src_space_id, src_region_idx,
3104                                    closure.source());
3105       region_ptr->set_deferred_obj_addr(NULL);
3106       region_ptr->set_completed();
3107       return;
3108     }
3109 
3110     decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3111 
3112     // Move to the next source region, possibly switching spaces as well.  All
3113     // args except end_addr may be modified.
3114     src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3115                                      end_addr);
3116   } while (true);
3117 }
3118 
3119 void
3120 PSParallelCompact::move_and_update(ParCompactionManager* cm, SpaceId space_id) {
3121   const MutableSpace* sp = space(space_id);
3122   if (sp->is_empty()) {
3123     return;
3124   }
3125 
3126   ParallelCompactData& sd = PSParallelCompact::summary_data();
3127   ParMarkBitMap* const bitmap = mark_bitmap();
3128   HeapWord* const dp_addr = dense_prefix(space_id);
3129   HeapWord* beg_addr = sp->bottom();
3130   HeapWord* end_addr = sp->top();
3131 
3132   assert(beg_addr <= dp_addr && dp_addr <= end_addr, "bad dense prefix");
3133 
3134   const size_t beg_region = sd.addr_to_region_idx(beg_addr);
3135   const size_t dp_region = sd.addr_to_region_idx(dp_addr);
3136   if (beg_region < dp_region) {
3137     update_and_deadwood_in_dense_prefix(cm, space_id, beg_region, dp_region);
3138   }
3139 
3140   // The destination of the first live object that starts in the region is one
3141   // past the end of the partial object entering the region (if any).
3142   HeapWord* const dest_addr = sd.partial_obj_end(dp_region);
3143   HeapWord* const new_top = _space_info[space_id].new_top();
3144   assert(new_top >= dest_addr, "bad new_top value");
3145   const size_t words = pointer_delta(new_top, dest_addr);
3146 
3147   if (words > 0) {
3148     ObjectStartArray* start_array = _space_info[space_id].start_array();
3149     MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3150 
3151     ParMarkBitMap::IterationStatus status;
3152     status = bitmap->iterate(&closure, dest_addr, end_addr);
3153     assert(status == ParMarkBitMap::full, "iteration not complete");
3154     assert(bitmap->find_obj_beg(closure.source(), end_addr) == end_addr,
3155            "live objects skipped because closure is full");
3156   }
3157 }
3158 
3159 jlong PSParallelCompact::millis_since_last_gc() {
3160   // We need a monotonically non-deccreasing time in ms but
3161   // os::javaTimeMillis() does not guarantee monotonicity.
3162   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3163   jlong ret_val = now - _time_of_last_gc;
3164   // XXX See note in genCollectedHeap::millis_since_last_gc().
3165   if (ret_val < 0) {
3166     NOT_PRODUCT(warning("time warp: "INT64_FORMAT, ret_val);)
3167     return 0;
3168   }
3169   return ret_val;
3170 }
3171 
3172 void PSParallelCompact::reset_millis_since_last_gc() {
3173   // We need a monotonically non-deccreasing time in ms but
3174   // os::javaTimeMillis() does not guarantee monotonicity.
3175   _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3176 }
3177 
3178 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3179 {
3180   if (source() != destination()) {
3181     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3182     Copy::aligned_conjoint_words(source(), destination(), words_remaining());
3183   }
3184   update_state(words_remaining());
3185   assert(is_full(), "sanity");
3186   return ParMarkBitMap::full;
3187 }
3188 
3189 void MoveAndUpdateClosure::copy_partial_obj()
3190 {
3191   size_t words = words_remaining();
3192 
3193   HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3194   HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3195   if (end_addr < range_end) {
3196     words = bitmap()->obj_size(source(), end_addr);
3197   }
3198 
3199   // This test is necessary; if omitted, the pointer updates to a partial object
3200   // that crosses the dense prefix boundary could be overwritten.
3201   if (source() != destination()) {
3202     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3203     Copy::aligned_conjoint_words(source(), destination(), words);
3204   }
3205   update_state(words);
3206 }
3207 
3208 ParMarkBitMapClosure::IterationStatus
3209 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3210   assert(destination() != NULL, "sanity");
3211   assert(bitmap()->obj_size(addr) == words, "bad size");
3212 
3213   _source = addr;
3214   assert(PSParallelCompact::summary_data().calc_new_pointer(source()) ==
3215          destination(), "wrong destination");
3216 
3217   if (words > words_remaining()) {
3218     return ParMarkBitMap::would_overflow;
3219   }
3220 
3221   // The start_array must be updated even if the object is not moving.
3222   if (_start_array != NULL) {
3223     _start_array->allocate_block(destination());
3224   }
3225 
3226   if (destination() != source()) {
3227     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3228     Copy::aligned_conjoint_words(source(), destination(), words);
3229   }
3230 
3231   oop moved_oop = (oop) destination();
3232   moved_oop->update_contents(compaction_manager());
3233   assert(moved_oop->is_oop_or_null(), "Object should be whole at this point");
3234 
3235   update_state(words);
3236   assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
3237   return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3238 }
3239 
3240 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3241                                      ParCompactionManager* cm,
3242                                      PSParallelCompact::SpaceId space_id) :
3243   ParMarkBitMapClosure(mbm, cm),
3244   _space_id(space_id),
3245   _start_array(PSParallelCompact::start_array(space_id))
3246 {
3247 }
3248 
3249 // Updates the references in the object to their new values.
3250 ParMarkBitMapClosure::IterationStatus
3251 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3252   do_addr(addr);
3253   return ParMarkBitMap::incomplete;
3254 }