1 /*
   2  * Copyright (c) 2005, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/stringTable.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "code/codeCache.hpp"
  29 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
  30 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.inline.hpp"
  31 #include "gc_implementation/parallelScavenge/pcTasks.hpp"
  32 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
  33 #include "gc_implementation/parallelScavenge/psCompactionManager.inline.hpp"
  34 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
  35 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp"
  36 #include "gc_implementation/parallelScavenge/psOldGen.hpp"
  37 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
  38 #include "gc_implementation/parallelScavenge/psPromotionManager.inline.hpp"
  39 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
  40 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"
  41 #include "gc_implementation/shared/gcHeapSummary.hpp"
  42 #include "gc_implementation/shared/gcTimer.hpp"
  43 #include "gc_implementation/shared/gcTrace.hpp"
  44 #include "gc_implementation/shared/gcTraceTime.hpp"
  45 #include "gc_implementation/shared/isGCActiveMark.hpp"
  46 #include "gc_implementation/shared/spaceDecorator.hpp"
  47 #include "gc_interface/gcCause.hpp"
  48 #include "memory/gcLocker.inline.hpp"
  49 #include "memory/referencePolicy.hpp"
  50 #include "memory/referenceProcessor.hpp"
  51 #include "oops/methodData.hpp"
  52 #include "oops/oop.inline.hpp"
  53 #include "oops/oop.pcgc.inline.hpp"
  54 #include "runtime/fprofiler.hpp"
  55 #include "runtime/safepoint.hpp"
  56 #include "runtime/vmThread.hpp"
  57 #include "services/management.hpp"
  58 #include "services/memoryService.hpp"
  59 #include "services/memTracker.hpp"
  60 #include "utilities/events.hpp"
  61 #include "utilities/stack.inline.hpp"
  62 
  63 #include <math.h>
  64 
  65 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  66 
  67 // All sizes are in HeapWords.
  68 const size_t ParallelCompactData::Log2RegionSize  = 16; // 64K words
  69 const size_t ParallelCompactData::RegionSize      = (size_t)1 << Log2RegionSize;
  70 const size_t ParallelCompactData::RegionSizeBytes =
  71   RegionSize << LogHeapWordSize;
  72 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
  73 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
  74 const size_t ParallelCompactData::RegionAddrMask       = ~RegionAddrOffsetMask;
  75 
  76 const size_t ParallelCompactData::Log2BlockSize   = 7; // 128 words
  77 const size_t ParallelCompactData::BlockSize       = (size_t)1 << Log2BlockSize;
  78 const size_t ParallelCompactData::BlockSizeBytes  =
  79   BlockSize << LogHeapWordSize;
  80 const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
  81 const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
  82 const size_t ParallelCompactData::BlockAddrMask       = ~BlockAddrOffsetMask;
  83 
  84 const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
  85 const size_t ParallelCompactData::Log2BlocksPerRegion =
  86   Log2RegionSize - Log2BlockSize;
  87 
  88 const ParallelCompactData::RegionData::region_sz_t
  89 ParallelCompactData::RegionData::dc_shift = 27;
  90 
  91 const ParallelCompactData::RegionData::region_sz_t
  92 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
  93 
  94 const ParallelCompactData::RegionData::region_sz_t
  95 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
  96 
  97 const ParallelCompactData::RegionData::region_sz_t
  98 ParallelCompactData::RegionData::los_mask = ~dc_mask;
  99 
 100 const ParallelCompactData::RegionData::region_sz_t
 101 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
 102 
 103 const ParallelCompactData::RegionData::region_sz_t
 104 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
 105 
 106 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
 107 bool      PSParallelCompact::_print_phases = false;
 108 
 109 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
 110 Klass*              PSParallelCompact::_updated_int_array_klass_obj = NULL;
 111 
 112 double PSParallelCompact::_dwl_mean;
 113 double PSParallelCompact::_dwl_std_dev;
 114 double PSParallelCompact::_dwl_first_term;
 115 double PSParallelCompact::_dwl_adjustment;
 116 #ifdef  ASSERT
 117 bool   PSParallelCompact::_dwl_initialized = false;
 118 #endif  // #ifdef ASSERT
 119 
 120 void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
 121                        HeapWord* destination)
 122 {
 123   assert(src_region_idx != 0, "invalid src_region_idx");
 124   assert(partial_obj_size != 0, "invalid partial_obj_size argument");
 125   assert(destination != NULL, "invalid destination argument");
 126 
 127   _src_region_idx = src_region_idx;
 128   _partial_obj_size = partial_obj_size;
 129   _destination = destination;
 130 
 131   // These fields may not be updated below, so make sure they're clear.
 132   assert(_dest_region_addr == NULL, "should have been cleared");
 133   assert(_first_src_addr == NULL, "should have been cleared");
 134 
 135   // Determine the number of destination regions for the partial object.
 136   HeapWord* const last_word = destination + partial_obj_size - 1;
 137   const ParallelCompactData& sd = PSParallelCompact::summary_data();
 138   HeapWord* const beg_region_addr = sd.region_align_down(destination);
 139   HeapWord* const end_region_addr = sd.region_align_down(last_word);
 140 
 141   if (beg_region_addr == end_region_addr) {
 142     // One destination region.
 143     _destination_count = 1;
 144     if (end_region_addr == destination) {
 145       // The destination falls on a region boundary, thus the first word of the
 146       // partial object will be the first word copied to the destination region.
 147       _dest_region_addr = end_region_addr;
 148       _first_src_addr = sd.region_to_addr(src_region_idx);
 149     }
 150   } else {
 151     // Two destination regions.  When copied, the partial object will cross a
 152     // destination region boundary, so a word somewhere within the partial
 153     // object will be the first word copied to the second destination region.
 154     _destination_count = 2;
 155     _dest_region_addr = end_region_addr;
 156     const size_t ofs = pointer_delta(end_region_addr, destination);
 157     assert(ofs < _partial_obj_size, "sanity");
 158     _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
 159   }
 160 }
 161 
 162 void SplitInfo::clear()
 163 {
 164   _src_region_idx = 0;
 165   _partial_obj_size = 0;
 166   _destination = NULL;
 167   _destination_count = 0;
 168   _dest_region_addr = NULL;
 169   _first_src_addr = NULL;
 170   assert(!is_valid(), "sanity");
 171 }
 172 
 173 #ifdef  ASSERT
 174 void SplitInfo::verify_clear()
 175 {
 176   assert(_src_region_idx == 0, "not clear");
 177   assert(_partial_obj_size == 0, "not clear");
 178   assert(_destination == NULL, "not clear");
 179   assert(_destination_count == 0, "not clear");
 180   assert(_dest_region_addr == NULL, "not clear");
 181   assert(_first_src_addr == NULL, "not clear");
 182 }
 183 #endif  // #ifdef ASSERT
 184 
 185 
 186 void PSParallelCompact::print_on_error(outputStream* st) {
 187   _mark_bitmap.print_on_error(st);
 188 }
 189 
 190 #ifndef PRODUCT
 191 const char* PSParallelCompact::space_names[] = {
 192   "old ", "eden", "from", "to  "
 193 };
 194 
 195 void PSParallelCompact::print_region_ranges()
 196 {
 197   tty->print_cr("space  bottom     top        end        new_top");
 198   tty->print_cr("------ ---------- ---------- ---------- ----------");
 199 
 200   for (unsigned int id = 0; id < last_space_id; ++id) {
 201     const MutableSpace* space = _space_info[id].space();
 202     tty->print_cr("%u %s "
 203                   SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
 204                   SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
 205                   id, space_names[id],
 206                   summary_data().addr_to_region_idx(space->bottom()),
 207                   summary_data().addr_to_region_idx(space->top()),
 208                   summary_data().addr_to_region_idx(space->end()),
 209                   summary_data().addr_to_region_idx(_space_info[id].new_top()));
 210   }
 211 }
 212 
 213 void
 214 print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
 215 {
 216 #define REGION_IDX_FORMAT        SIZE_FORMAT_W(7)
 217 #define REGION_DATA_FORMAT       SIZE_FORMAT_W(5)
 218 
 219   ParallelCompactData& sd = PSParallelCompact::summary_data();
 220   size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
 221   tty->print_cr(REGION_IDX_FORMAT " " PTR_FORMAT " "
 222                 REGION_IDX_FORMAT " " PTR_FORMAT " "
 223                 REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
 224                 REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
 225                 i, c->data_location(), dci, c->destination(),
 226                 c->partial_obj_size(), c->live_obj_size(),
 227                 c->data_size(), c->source_region(), c->destination_count());
 228 
 229 #undef  REGION_IDX_FORMAT
 230 #undef  REGION_DATA_FORMAT
 231 }
 232 
 233 void
 234 print_generic_summary_data(ParallelCompactData& summary_data,
 235                            HeapWord* const beg_addr,
 236                            HeapWord* const end_addr)
 237 {
 238   size_t total_words = 0;
 239   size_t i = summary_data.addr_to_region_idx(beg_addr);
 240   const size_t last = summary_data.addr_to_region_idx(end_addr);
 241   HeapWord* pdest = 0;
 242 
 243   while (i <= last) {
 244     ParallelCompactData::RegionData* c = summary_data.region(i);
 245     if (c->data_size() != 0 || c->destination() != pdest) {
 246       print_generic_summary_region(i, c);
 247       total_words += c->data_size();
 248       pdest = c->destination();
 249     }
 250     ++i;
 251   }
 252 
 253   tty->print_cr("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
 254 }
 255 
 256 void
 257 print_generic_summary_data(ParallelCompactData& summary_data,
 258                            SpaceInfo* space_info)
 259 {
 260   for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
 261     const MutableSpace* space = space_info[id].space();
 262     print_generic_summary_data(summary_data, space->bottom(),
 263                                MAX2(space->top(), space_info[id].new_top()));
 264   }
 265 }
 266 
 267 void
 268 print_initial_summary_region(size_t i,
 269                              const ParallelCompactData::RegionData* c,
 270                              bool newline = true)
 271 {
 272   tty->print(SIZE_FORMAT_W(5) " " PTR_FORMAT " "
 273              SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " "
 274              SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 275              i, c->destination(),
 276              c->partial_obj_size(), c->live_obj_size(),
 277              c->data_size(), c->source_region(), c->destination_count());
 278   if (newline) tty->cr();
 279 }
 280 
 281 void
 282 print_initial_summary_data(ParallelCompactData& summary_data,
 283                            const MutableSpace* space) {
 284   if (space->top() == space->bottom()) {
 285     return;
 286   }
 287 
 288   const size_t region_size = ParallelCompactData::RegionSize;
 289   typedef ParallelCompactData::RegionData RegionData;
 290   HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
 291   const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
 292   const RegionData* c = summary_data.region(end_region - 1);
 293   HeapWord* end_addr = c->destination() + c->data_size();
 294   const size_t live_in_space = pointer_delta(end_addr, space->bottom());
 295 
 296   // Print (and count) the full regions at the beginning of the space.
 297   size_t full_region_count = 0;
 298   size_t i = summary_data.addr_to_region_idx(space->bottom());
 299   while (i < end_region && summary_data.region(i)->data_size() == region_size) {
 300     print_initial_summary_region(i, summary_data.region(i));
 301     ++full_region_count;
 302     ++i;
 303   }
 304 
 305   size_t live_to_right = live_in_space - full_region_count * region_size;
 306 
 307   double max_reclaimed_ratio = 0.0;
 308   size_t max_reclaimed_ratio_region = 0;
 309   size_t max_dead_to_right = 0;
 310   size_t max_live_to_right = 0;
 311 
 312   // Print the 'reclaimed ratio' for regions while there is something live in
 313   // the region or to the right of it.  The remaining regions are empty (and
 314   // uninteresting), and computing the ratio will result in division by 0.
 315   while (i < end_region && live_to_right > 0) {
 316     c = summary_data.region(i);
 317     HeapWord* const region_addr = summary_data.region_to_addr(i);
 318     const size_t used_to_right = pointer_delta(space->top(), region_addr);
 319     const size_t dead_to_right = used_to_right - live_to_right;
 320     const double reclaimed_ratio = double(dead_to_right) / live_to_right;
 321 
 322     if (reclaimed_ratio > max_reclaimed_ratio) {
 323             max_reclaimed_ratio = reclaimed_ratio;
 324             max_reclaimed_ratio_region = i;
 325             max_dead_to_right = dead_to_right;
 326             max_live_to_right = live_to_right;
 327     }
 328 
 329     print_initial_summary_region(i, c, false);
 330     tty->print_cr(" %12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
 331                   reclaimed_ratio, dead_to_right, live_to_right);
 332 
 333     live_to_right -= c->data_size();
 334     ++i;
 335   }
 336 
 337   // Any remaining regions are empty.  Print one more if there is one.
 338   if (i < end_region) {
 339     print_initial_summary_region(i, summary_data.region(i));
 340   }
 341 
 342   tty->print_cr("max:  " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " "
 343                 "l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
 344                 max_reclaimed_ratio_region, max_dead_to_right,
 345                 max_live_to_right, max_reclaimed_ratio);
 346 }
 347 
 348 void
 349 print_initial_summary_data(ParallelCompactData& summary_data,
 350                            SpaceInfo* space_info) {
 351   unsigned int id = PSParallelCompact::old_space_id;
 352   const MutableSpace* space;
 353   do {
 354     space = space_info[id].space();
 355     print_initial_summary_data(summary_data, space);
 356   } while (++id < PSParallelCompact::eden_space_id);
 357 
 358   do {
 359     space = space_info[id].space();
 360     print_generic_summary_data(summary_data, space->bottom(), space->top());
 361   } while (++id < PSParallelCompact::last_space_id);
 362 }
 363 #endif  // #ifndef PRODUCT
 364 
 365 #ifdef  ASSERT
 366 size_t add_obj_count;
 367 size_t add_obj_size;
 368 size_t mark_bitmap_count;
 369 size_t mark_bitmap_size;
 370 #endif  // #ifdef ASSERT
 371 
 372 ParallelCompactData::ParallelCompactData()
 373 {
 374   _region_start = 0;
 375 
 376   _region_vspace = 0;
 377   _reserved_byte_size = 0;
 378   _region_data = 0;
 379   _region_count = 0;
 380 
 381   _block_vspace = 0;
 382   _block_data = 0;
 383   _block_count = 0;
 384 }
 385 
 386 bool ParallelCompactData::initialize(MemRegion covered_region)
 387 {
 388   _region_start = covered_region.start();
 389   const size_t region_size = covered_region.word_size();
 390   DEBUG_ONLY(_region_end = _region_start + region_size;)
 391 
 392   assert(region_align_down(_region_start) == _region_start,
 393          "region start not aligned");
 394   assert((region_size & RegionSizeOffsetMask) == 0,
 395          "region size not a multiple of RegionSize");
 396 
 397   bool result = initialize_region_data(region_size) && initialize_block_data();
 398   return result;
 399 }
 400 
 401 PSVirtualSpace*
 402 ParallelCompactData::create_vspace(size_t count, size_t element_size)
 403 {
 404   const size_t raw_bytes = count * element_size;
 405   const size_t page_sz = os::page_size_for_region(raw_bytes, raw_bytes, 10);
 406   const size_t granularity = os::vm_allocation_granularity();
 407   _reserved_byte_size = align_size_up(raw_bytes, MAX2(page_sz, granularity));
 408 
 409   const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
 410     MAX2(page_sz, granularity);
 411   ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0);
 412   os::trace_page_sizes("par compact", raw_bytes, raw_bytes, page_sz, rs.base(),
 413                        rs.size());
 414 
 415   MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
 416 
 417   PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
 418   if (vspace != 0) {
 419     if (vspace->expand_by(_reserved_byte_size)) {
 420       return vspace;
 421     }
 422     delete vspace;
 423     // Release memory reserved in the space.
 424     rs.release();
 425   }
 426 
 427   return 0;
 428 }
 429 
 430 bool ParallelCompactData::initialize_region_data(size_t region_size)
 431 {
 432   const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
 433   _region_vspace = create_vspace(count, sizeof(RegionData));
 434   if (_region_vspace != 0) {
 435     _region_data = (RegionData*)_region_vspace->reserved_low_addr();
 436     _region_count = count;
 437     return true;
 438   }
 439   return false;
 440 }
 441 
 442 bool ParallelCompactData::initialize_block_data()
 443 {
 444   assert(_region_count != 0, "region data must be initialized first");
 445   const size_t count = _region_count << Log2BlocksPerRegion;
 446   _block_vspace = create_vspace(count, sizeof(BlockData));
 447   if (_block_vspace != 0) {
 448     _block_data = (BlockData*)_block_vspace->reserved_low_addr();
 449     _block_count = count;
 450     return true;
 451   }
 452   return false;
 453 }
 454 
 455 void ParallelCompactData::clear()
 456 {
 457   memset(_region_data, 0, _region_vspace->committed_size());
 458   memset(_block_data, 0, _block_vspace->committed_size());
 459 }
 460 
 461 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
 462   assert(beg_region <= _region_count, "beg_region out of range");
 463   assert(end_region <= _region_count, "end_region out of range");
 464   assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize");
 465 
 466   const size_t region_cnt = end_region - beg_region;
 467   memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
 468 
 469   const size_t beg_block = beg_region * BlocksPerRegion;
 470   const size_t block_cnt = region_cnt * BlocksPerRegion;
 471   memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData));
 472 }
 473 
 474 HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
 475 {
 476   const RegionData* cur_cp = region(region_idx);
 477   const RegionData* const end_cp = region(region_count() - 1);
 478 
 479   HeapWord* result = region_to_addr(region_idx);
 480   if (cur_cp < end_cp) {
 481     do {
 482       result += cur_cp->partial_obj_size();
 483     } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
 484   }
 485   return result;
 486 }
 487 
 488 void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
 489 {
 490   const size_t obj_ofs = pointer_delta(addr, _region_start);
 491   const size_t beg_region = obj_ofs >> Log2RegionSize;
 492   const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
 493 
 494   DEBUG_ONLY(Atomic::inc_ptr(&add_obj_count);)
 495   DEBUG_ONLY(Atomic::add_ptr(len, &add_obj_size);)
 496 
 497   if (beg_region == end_region) {
 498     // All in one region.
 499     _region_data[beg_region].add_live_obj(len);
 500     return;
 501   }
 502 
 503   // First region.
 504   const size_t beg_ofs = region_offset(addr);
 505   _region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
 506 
 507   Klass* klass = ((oop)addr)->klass();
 508   // Middle regions--completely spanned by this object.
 509   for (size_t region = beg_region + 1; region < end_region; ++region) {
 510     _region_data[region].set_partial_obj_size(RegionSize);
 511     _region_data[region].set_partial_obj_addr(addr);
 512   }
 513 
 514   // Last region.
 515   const size_t end_ofs = region_offset(addr + len - 1);
 516   _region_data[end_region].set_partial_obj_size(end_ofs + 1);
 517   _region_data[end_region].set_partial_obj_addr(addr);
 518 }
 519 
 520 void
 521 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
 522 {
 523   assert(region_offset(beg) == 0, "not RegionSize aligned");
 524   assert(region_offset(end) == 0, "not RegionSize aligned");
 525 
 526   size_t cur_region = addr_to_region_idx(beg);
 527   const size_t end_region = addr_to_region_idx(end);
 528   HeapWord* addr = beg;
 529   while (cur_region < end_region) {
 530     _region_data[cur_region].set_destination(addr);
 531     _region_data[cur_region].set_destination_count(0);
 532     _region_data[cur_region].set_source_region(cur_region);
 533     _region_data[cur_region].set_data_location(addr);
 534 
 535     // Update live_obj_size so the region appears completely full.
 536     size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
 537     _region_data[cur_region].set_live_obj_size(live_size);
 538 
 539     ++cur_region;
 540     addr += RegionSize;
 541   }
 542 }
 543 
 544 // Find the point at which a space can be split and, if necessary, record the
 545 // split point.
 546 //
 547 // If the current src region (which overflowed the destination space) doesn't
 548 // have a partial object, the split point is at the beginning of the current src
 549 // region (an "easy" split, no extra bookkeeping required).
 550 //
 551 // If the current src region has a partial object, the split point is in the
 552 // region where that partial object starts (call it the split_region).  If
 553 // split_region has a partial object, then the split point is just after that
 554 // partial object (a "hard" split where we have to record the split data and
 555 // zero the partial_obj_size field).  With a "hard" split, we know that the
 556 // partial_obj ends within split_region because the partial object that caused
 557 // the overflow starts in split_region.  If split_region doesn't have a partial
 558 // obj, then the split is at the beginning of split_region (another "easy"
 559 // split).
 560 HeapWord*
 561 ParallelCompactData::summarize_split_space(size_t src_region,
 562                                            SplitInfo& split_info,
 563                                            HeapWord* destination,
 564                                            HeapWord* target_end,
 565                                            HeapWord** target_next)
 566 {
 567   assert(destination <= target_end, "sanity");
 568   assert(destination + _region_data[src_region].data_size() > target_end,
 569     "region should not fit into target space");
 570   assert(is_region_aligned(target_end), "sanity");
 571 
 572   size_t split_region = src_region;
 573   HeapWord* split_destination = destination;
 574   size_t partial_obj_size = _region_data[src_region].partial_obj_size();
 575 
 576   if (destination + partial_obj_size > target_end) {
 577     // The split point is just after the partial object (if any) in the
 578     // src_region that contains the start of the object that overflowed the
 579     // destination space.
 580     //
 581     // Find the start of the "overflow" object and set split_region to the
 582     // region containing it.
 583     HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
 584     split_region = addr_to_region_idx(overflow_obj);
 585 
 586     // Clear the source_region field of all destination regions whose first word
 587     // came from data after the split point (a non-null source_region field
 588     // implies a region must be filled).
 589     //
 590     // An alternative to the simple loop below:  clear during post_compact(),
 591     // which uses memcpy instead of individual stores, and is easy to
 592     // parallelize.  (The downside is that it clears the entire RegionData
 593     // object as opposed to just one field.)
 594     //
 595     // post_compact() would have to clear the summary data up to the highest
 596     // address that was written during the summary phase, which would be
 597     //
 598     //         max(top, max(new_top, clear_top))
 599     //
 600     // where clear_top is a new field in SpaceInfo.  Would have to set clear_top
 601     // to target_end.
 602     const RegionData* const sr = region(split_region);
 603     const size_t beg_idx =
 604       addr_to_region_idx(region_align_up(sr->destination() +
 605                                          sr->partial_obj_size()));
 606     const size_t end_idx = addr_to_region_idx(target_end);
 607 
 608     if (TraceParallelOldGCSummaryPhase) {
 609         gclog_or_tty->print_cr("split:  clearing source_region field in ["
 610                                SIZE_FORMAT ", " SIZE_FORMAT ")",
 611                                beg_idx, end_idx);
 612     }
 613     for (size_t idx = beg_idx; idx < end_idx; ++idx) {
 614       _region_data[idx].set_source_region(0);
 615     }
 616 
 617     // Set split_destination and partial_obj_size to reflect the split region.
 618     split_destination = sr->destination();
 619     partial_obj_size = sr->partial_obj_size();
 620   }
 621 
 622   // The split is recorded only if a partial object extends onto the region.
 623   if (partial_obj_size != 0) {
 624     _region_data[split_region].set_partial_obj_size(0);
 625     split_info.record(split_region, partial_obj_size, split_destination);
 626   }
 627 
 628   // Setup the continuation addresses.
 629   *target_next = split_destination + partial_obj_size;
 630   HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
 631 
 632   if (TraceParallelOldGCSummaryPhase) {
 633     const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
 634     gclog_or_tty->print_cr("%s split:  src=" PTR_FORMAT " src_c=" SIZE_FORMAT
 635                            " pos=" SIZE_FORMAT,
 636                            split_type, source_next, split_region,
 637                            partial_obj_size);
 638     gclog_or_tty->print_cr("%s split:  dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT
 639                            " tn=" PTR_FORMAT,
 640                            split_type, split_destination,
 641                            addr_to_region_idx(split_destination),
 642                            *target_next);
 643 
 644     if (partial_obj_size != 0) {
 645       HeapWord* const po_beg = split_info.destination();
 646       HeapWord* const po_end = po_beg + split_info.partial_obj_size();
 647       gclog_or_tty->print_cr("%s split:  "
 648                              "po_beg=" PTR_FORMAT " " SIZE_FORMAT " "
 649                              "po_end=" PTR_FORMAT " " SIZE_FORMAT,
 650                              split_type,
 651                              po_beg, addr_to_region_idx(po_beg),
 652                              po_end, addr_to_region_idx(po_end));
 653     }
 654   }
 655 
 656   return source_next;
 657 }
 658 
 659 bool ParallelCompactData::summarize(SplitInfo& split_info,
 660                                     HeapWord* source_beg, HeapWord* source_end,
 661                                     HeapWord** source_next,
 662                                     HeapWord* target_beg, HeapWord* target_end,
 663                                     HeapWord** target_next)
 664 {
 665   if (TraceParallelOldGCSummaryPhase) {
 666     HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
 667     tty->print_cr("sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
 668                   "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
 669                   source_beg, source_end, source_next_val,
 670                   target_beg, target_end, *target_next);
 671   }
 672 
 673   size_t cur_region = addr_to_region_idx(source_beg);
 674   const size_t end_region = addr_to_region_idx(region_align_up(source_end));
 675 
 676   HeapWord *dest_addr = target_beg;
 677   while (cur_region < end_region) {
 678     // The destination must be set even if the region has no data.
 679     _region_data[cur_region].set_destination(dest_addr);
 680 
 681     size_t words = _region_data[cur_region].data_size();
 682     if (words > 0) {
 683       // If cur_region does not fit entirely into the target space, find a point
 684       // at which the source space can be 'split' so that part is copied to the
 685       // target space and the rest is copied elsewhere.
 686       if (dest_addr + words > target_end) {
 687         assert(source_next != NULL, "source_next is NULL when splitting");
 688         *source_next = summarize_split_space(cur_region, split_info, dest_addr,
 689                                              target_end, target_next);
 690         return false;
 691       }
 692 
 693       // Compute the destination_count for cur_region, and if necessary, update
 694       // source_region for a destination region.  The source_region field is
 695       // updated if cur_region is the first (left-most) region to be copied to a
 696       // destination region.
 697       //
 698       // The destination_count calculation is a bit subtle.  A region that has
 699       // data that compacts into itself does not count itself as a destination.
 700       // This maintains the invariant that a zero count means the region is
 701       // available and can be claimed and then filled.
 702       uint destination_count = 0;
 703       if (split_info.is_split(cur_region)) {
 704         // The current region has been split:  the partial object will be copied
 705         // to one destination space and the remaining data will be copied to
 706         // another destination space.  Adjust the initial destination_count and,
 707         // if necessary, set the source_region field if the partial object will
 708         // cross a destination region boundary.
 709         destination_count = split_info.destination_count();
 710         if (destination_count == 2) {
 711           size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
 712           _region_data[dest_idx].set_source_region(cur_region);
 713         }
 714       }
 715 
 716       HeapWord* const last_addr = dest_addr + words - 1;
 717       const size_t dest_region_1 = addr_to_region_idx(dest_addr);
 718       const size_t dest_region_2 = addr_to_region_idx(last_addr);
 719 
 720       // Initially assume that the destination regions will be the same and
 721       // adjust the value below if necessary.  Under this assumption, if
 722       // cur_region == dest_region_2, then cur_region will be compacted
 723       // completely into itself.
 724       destination_count += cur_region == dest_region_2 ? 0 : 1;
 725       if (dest_region_1 != dest_region_2) {
 726         // Destination regions differ; adjust destination_count.
 727         destination_count += 1;
 728         // Data from cur_region will be copied to the start of dest_region_2.
 729         _region_data[dest_region_2].set_source_region(cur_region);
 730       } else if (region_offset(dest_addr) == 0) {
 731         // Data from cur_region will be copied to the start of the destination
 732         // region.
 733         _region_data[dest_region_1].set_source_region(cur_region);
 734       }
 735 
 736       _region_data[cur_region].set_destination_count(destination_count);
 737       _region_data[cur_region].set_data_location(region_to_addr(cur_region));
 738       dest_addr += words;
 739     }
 740 
 741     ++cur_region;
 742   }
 743 
 744   *target_next = dest_addr;
 745   return true;
 746 }
 747 
 748 HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr) {
 749   assert(addr != NULL, "Should detect NULL oop earlier");
 750   assert(PSParallelCompact::gc_heap()->is_in(addr), "not in heap");
 751   assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked");
 752 
 753   // Region covering the object.
 754   RegionData* const region_ptr = addr_to_region_ptr(addr);
 755   HeapWord* result = region_ptr->destination();
 756 
 757   // If the entire Region is live, the new location is region->destination + the
 758   // offset of the object within in the Region.
 759 
 760   // Run some performance tests to determine if this special case pays off.  It
 761   // is worth it for pointers into the dense prefix.  If the optimization to
 762   // avoid pointer updates in regions that only point to the dense prefix is
 763   // ever implemented, this should be revisited.
 764   if (region_ptr->data_size() == RegionSize) {
 765     result += region_offset(addr);
 766     return result;
 767   }
 768 
 769   // Otherwise, the new location is region->destination + block offset + the
 770   // number of live words in the Block that are (a) to the left of addr and (b)
 771   // due to objects that start in the Block.
 772 
 773   // Fill in the block table if necessary.  This is unsynchronized, so multiple
 774   // threads may fill the block table for a region (harmless, since it is
 775   // idempotent).
 776   if (!region_ptr->blocks_filled()) {
 777     PSParallelCompact::fill_blocks(addr_to_region_idx(addr));
 778     region_ptr->set_blocks_filled();
 779   }
 780 
 781   HeapWord* const search_start = block_align_down(addr);
 782   const size_t block_offset = addr_to_block_ptr(addr)->offset();
 783 
 784   const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
 785   const size_t live = bitmap->live_words_in_range(search_start, oop(addr));
 786   result += block_offset + live;
 787   DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result));
 788   return result;
 789 }
 790 
 791 #ifdef ASSERT
 792 void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
 793 {
 794   const size_t* const beg = (const size_t*)vspace->committed_low_addr();
 795   const size_t* const end = (const size_t*)vspace->committed_high_addr();
 796   for (const size_t* p = beg; p < end; ++p) {
 797     assert(*p == 0, "not zero");
 798   }
 799 }
 800 
 801 void ParallelCompactData::verify_clear()
 802 {
 803   verify_clear(_region_vspace);
 804   verify_clear(_block_vspace);
 805 }
 806 #endif  // #ifdef ASSERT
 807 
 808 STWGCTimer          PSParallelCompact::_gc_timer;
 809 ParallelOldTracer   PSParallelCompact::_gc_tracer;
 810 elapsedTimer        PSParallelCompact::_accumulated_time;
 811 unsigned int        PSParallelCompact::_total_invocations = 0;
 812 unsigned int        PSParallelCompact::_maximum_compaction_gc_num = 0;
 813 jlong               PSParallelCompact::_time_of_last_gc = 0;
 814 CollectorCounters*  PSParallelCompact::_counters = NULL;
 815 ParMarkBitMap       PSParallelCompact::_mark_bitmap;
 816 ParallelCompactData PSParallelCompact::_summary_data;
 817 
 818 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
 819 
 820 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
 821 
 822 void PSParallelCompact::KeepAliveClosure::do_oop(oop* p)       { PSParallelCompact::KeepAliveClosure::do_oop_work(p); }
 823 void PSParallelCompact::KeepAliveClosure::do_oop(narrowOop* p) { PSParallelCompact::KeepAliveClosure::do_oop_work(p); }
 824 
 825 PSParallelCompact::AdjustPointerClosure PSParallelCompact::_adjust_pointer_closure;
 826 PSParallelCompact::AdjustKlassClosure PSParallelCompact::_adjust_klass_closure;
 827 
 828 void PSParallelCompact::AdjustPointerClosure::do_oop(oop* p)       { adjust_pointer(p); }
 829 void PSParallelCompact::AdjustPointerClosure::do_oop(narrowOop* p) { adjust_pointer(p); }
 830 
 831 void PSParallelCompact::FollowStackClosure::do_void() { _compaction_manager->follow_marking_stacks(); }
 832 
 833 void PSParallelCompact::MarkAndPushClosure::do_oop(oop* p)       {
 834   mark_and_push(_compaction_manager, p);
 835 }
 836 void PSParallelCompact::MarkAndPushClosure::do_oop(narrowOop* p) { mark_and_push(_compaction_manager, p); }
 837 
 838 void PSParallelCompact::FollowKlassClosure::do_klass(Klass* klass) {
 839   klass->oops_do(_mark_and_push_closure);
 840 }
 841 void PSParallelCompact::AdjustKlassClosure::do_klass(Klass* klass) {
 842   klass->oops_do(&PSParallelCompact::_adjust_pointer_closure);
 843 }
 844 
 845 void PSParallelCompact::post_initialize() {
 846   ParallelScavengeHeap* heap = gc_heap();
 847   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 848 
 849   MemRegion mr = heap->reserved_region();
 850   _ref_processor =
 851     new ReferenceProcessor(mr,            // span
 852                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 853                            (int) ParallelGCThreads, // mt processing degree
 854                            true,          // mt discovery
 855                            (int) ParallelGCThreads, // mt discovery degree
 856                            true,          // atomic_discovery
 857                            &_is_alive_closure, // non-header is alive closure
 858                            false);        // write barrier for next field updates
 859   _counters = new CollectorCounters("PSParallelCompact", 1);
 860 
 861   // Initialize static fields in ParCompactionManager.
 862   ParCompactionManager::initialize(mark_bitmap());
 863 }
 864 
 865 bool PSParallelCompact::initialize() {
 866   ParallelScavengeHeap* heap = gc_heap();
 867   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 868   MemRegion mr = heap->reserved_region();
 869 
 870   // Was the old gen get allocated successfully?
 871   if (!heap->old_gen()->is_allocated()) {
 872     return false;
 873   }
 874 
 875   initialize_space_info();
 876   initialize_dead_wood_limiter();
 877 
 878   if (!_mark_bitmap.initialize(mr)) {
 879     vm_shutdown_during_initialization(
 880       err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
 881       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 882       _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
 883     return false;
 884   }
 885 
 886   if (!_summary_data.initialize(mr)) {
 887     vm_shutdown_during_initialization(
 888       err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
 889       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 890       _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
 891     return false;
 892   }
 893 
 894   return true;
 895 }
 896 
 897 void PSParallelCompact::initialize_space_info()
 898 {
 899   memset(&_space_info, 0, sizeof(_space_info));
 900 
 901   ParallelScavengeHeap* heap = gc_heap();
 902   PSYoungGen* young_gen = heap->young_gen();
 903 
 904   _space_info[old_space_id].set_space(heap->old_gen()->object_space());
 905   _space_info[eden_space_id].set_space(young_gen->eden_space());
 906   _space_info[from_space_id].set_space(young_gen->from_space());
 907   _space_info[to_space_id].set_space(young_gen->to_space());
 908 
 909   _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
 910 }
 911 
 912 void PSParallelCompact::initialize_dead_wood_limiter()
 913 {
 914   const size_t max = 100;
 915   _dwl_mean = double(MIN2((size_t)ParallelOldDeadWoodLimiterMean, max)) / 100.0;
 916   _dwl_std_dev = double(MIN2((size_t)ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
 917   _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
 918   DEBUG_ONLY(_dwl_initialized = true;)
 919   _dwl_adjustment = normal_distribution(1.0);
 920 }
 921 
 922 // Simple class for storing info about the heap at the start of GC, to be used
 923 // after GC for comparison/printing.
 924 class PreGCValues {
 925 public:
 926   PreGCValues() { }
 927   PreGCValues(ParallelScavengeHeap* heap) { fill(heap); }
 928 
 929   void fill(ParallelScavengeHeap* heap) {
 930     _heap_used      = heap->used();
 931     _young_gen_used = heap->young_gen()->used_in_bytes();
 932     _old_gen_used   = heap->old_gen()->used_in_bytes();
 933     _metadata_used  = MetaspaceAux::used_bytes();
 934   };
 935 
 936   size_t heap_used() const      { return _heap_used; }
 937   size_t young_gen_used() const { return _young_gen_used; }
 938   size_t old_gen_used() const   { return _old_gen_used; }
 939   size_t metadata_used() const  { return _metadata_used; }
 940 
 941 private:
 942   size_t _heap_used;
 943   size_t _young_gen_used;
 944   size_t _old_gen_used;
 945   size_t _metadata_used;
 946 };
 947 
 948 void
 949 PSParallelCompact::clear_data_covering_space(SpaceId id)
 950 {
 951   // At this point, top is the value before GC, new_top() is the value that will
 952   // be set at the end of GC.  The marking bitmap is cleared to top; nothing
 953   // should be marked above top.  The summary data is cleared to the larger of
 954   // top & new_top.
 955   MutableSpace* const space = _space_info[id].space();
 956   HeapWord* const bot = space->bottom();
 957   HeapWord* const top = space->top();
 958   HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
 959 
 960   const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
 961   const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top));
 962   _mark_bitmap.clear_range(beg_bit, end_bit);
 963 
 964   const size_t beg_region = _summary_data.addr_to_region_idx(bot);
 965   const size_t end_region =
 966     _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
 967   _summary_data.clear_range(beg_region, end_region);
 968 
 969   // Clear the data used to 'split' regions.
 970   SplitInfo& split_info = _space_info[id].split_info();
 971   if (split_info.is_valid()) {
 972     split_info.clear();
 973   }
 974   DEBUG_ONLY(split_info.verify_clear();)
 975 }
 976 
 977 void PSParallelCompact::pre_compact(PreGCValues* pre_gc_values)
 978 {
 979   // Update the from & to space pointers in space_info, since they are swapped
 980   // at each young gen gc.  Do the update unconditionally (even though a
 981   // promotion failure does not swap spaces) because an unknown number of minor
 982   // collections will have swapped the spaces an unknown number of times.
 983   GCTraceTime tm("pre compact", print_phases(), true, &_gc_timer);
 984   ParallelScavengeHeap* heap = gc_heap();
 985   _space_info[from_space_id].set_space(heap->young_gen()->from_space());
 986   _space_info[to_space_id].set_space(heap->young_gen()->to_space());
 987 
 988   pre_gc_values->fill(heap);
 989 
 990   DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
 991   DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
 992 
 993   // Increment the invocation count
 994   heap->increment_total_collections(true);
 995 
 996   // We need to track unique mark sweep invocations as well.
 997   _total_invocations++;
 998 
 999   heap->print_heap_before_gc();
1000   heap->trace_heap_before_gc(&_gc_tracer);
1001 
1002   // Fill in TLABs
1003   heap->accumulate_statistics_all_tlabs();
1004   heap->ensure_parsability(true);  // retire TLABs
1005 
1006   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
1007     HandleMark hm;  // Discard invalid handles created during verification
1008     Universe::verify(" VerifyBeforeGC:");
1009   }
1010 
1011   // Verify object start arrays
1012   if (VerifyObjectStartArray &&
1013       VerifyBeforeGC) {
1014     heap->old_gen()->verify_object_start_array();
1015   }
1016 
1017   DEBUG_ONLY(mark_bitmap()->verify_clear();)
1018   DEBUG_ONLY(summary_data().verify_clear();)
1019 
1020   // Have worker threads release resources the next time they run a task.
1021   gc_task_manager()->release_all_resources();
1022 }
1023 
1024 void PSParallelCompact::post_compact()
1025 {
1026   GCTraceTime tm("post compact", print_phases(), true, &_gc_timer);
1027 
1028   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1029     // Clear the marking bitmap, summary data and split info.
1030     clear_data_covering_space(SpaceId(id));
1031     // Update top().  Must be done after clearing the bitmap and summary data.
1032     _space_info[id].publish_new_top();
1033   }
1034 
1035   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1036   MutableSpace* const from_space = _space_info[from_space_id].space();
1037   MutableSpace* const to_space   = _space_info[to_space_id].space();
1038 
1039   ParallelScavengeHeap* heap = gc_heap();
1040   bool eden_empty = eden_space->is_empty();
1041   if (!eden_empty) {
1042     eden_empty = absorb_live_data_from_eden(heap->size_policy(),
1043                                             heap->young_gen(), heap->old_gen());
1044   }
1045 
1046   // Update heap occupancy information which is used as input to the soft ref
1047   // clearing policy at the next gc.
1048   Universe::update_heap_info_at_gc();
1049 
1050   bool young_gen_empty = eden_empty && from_space->is_empty() &&
1051     to_space->is_empty();
1052 
1053   BarrierSet* bs = heap->barrier_set();
1054   if (bs->is_a(BarrierSet::ModRef)) {
1055     ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
1056     MemRegion old_mr = heap->old_gen()->reserved();
1057 
1058     if (young_gen_empty) {
1059       modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
1060     } else {
1061       modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1062     }
1063   }
1064 
1065   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1066   ClassLoaderDataGraph::purge();
1067   MetaspaceAux::verify_metrics();
1068 
1069   Threads::gc_epilogue();
1070   CodeCache::gc_epilogue();
1071   JvmtiExport::gc_epilogue();
1072 
1073   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1074 
1075   ref_processor()->enqueue_discovered_references(NULL);
1076 
1077   if (ZapUnusedHeapArea) {
1078     heap->gen_mangle_unused_area();
1079   }
1080 
1081   // Update time of last GC
1082   reset_millis_since_last_gc();
1083 }
1084 
1085 HeapWord*
1086 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1087                                                     bool maximum_compaction)
1088 {
1089   const size_t region_size = ParallelCompactData::RegionSize;
1090   const ParallelCompactData& sd = summary_data();
1091 
1092   const MutableSpace* const space = _space_info[id].space();
1093   HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1094   const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1095   const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1096 
1097   // Skip full regions at the beginning of the space--they are necessarily part
1098   // of the dense prefix.
1099   size_t full_count = 0;
1100   const RegionData* cp;
1101   for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1102     ++full_count;
1103   }
1104 
1105   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1106   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1107   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1108   if (maximum_compaction || cp == end_cp || interval_ended) {
1109     _maximum_compaction_gc_num = total_invocations();
1110     return sd.region_to_addr(cp);
1111   }
1112 
1113   HeapWord* const new_top = _space_info[id].new_top();
1114   const size_t space_live = pointer_delta(new_top, space->bottom());
1115   const size_t space_used = space->used_in_words();
1116   const size_t space_capacity = space->capacity_in_words();
1117 
1118   const double cur_density = double(space_live) / space_capacity;
1119   const double deadwood_density =
1120     (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1121   const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1122 
1123   if (TraceParallelOldGCDensePrefix) {
1124     tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1125                   cur_density, deadwood_density, deadwood_goal);
1126     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1127                   "space_cap=" SIZE_FORMAT,
1128                   space_live, space_used,
1129                   space_capacity);
1130   }
1131 
1132   // XXX - Use binary search?
1133   HeapWord* dense_prefix = sd.region_to_addr(cp);
1134   const RegionData* full_cp = cp;
1135   const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1136   while (cp < end_cp) {
1137     HeapWord* region_destination = cp->destination();
1138     const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1139     if (TraceParallelOldGCDensePrefix && Verbose) {
1140       tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1141                     "dp=" SIZE_FORMAT_W(8) " " "cdw=" SIZE_FORMAT_W(8),
1142                     sd.region(cp), region_destination,
1143                     dense_prefix, cur_deadwood);
1144     }
1145 
1146     if (cur_deadwood >= deadwood_goal) {
1147       // Found the region that has the correct amount of deadwood to the left.
1148       // This typically occurs after crossing a fairly sparse set of regions, so
1149       // iterate backwards over those sparse regions, looking for the region
1150       // that has the lowest density of live objects 'to the right.'
1151       size_t space_to_left = sd.region(cp) * region_size;
1152       size_t live_to_left = space_to_left - cur_deadwood;
1153       size_t space_to_right = space_capacity - space_to_left;
1154       size_t live_to_right = space_live - live_to_left;
1155       double density_to_right = double(live_to_right) / space_to_right;
1156       while (cp > full_cp) {
1157         --cp;
1158         const size_t prev_region_live_to_right = live_to_right -
1159           cp->data_size();
1160         const size_t prev_region_space_to_right = space_to_right + region_size;
1161         double prev_region_density_to_right =
1162           double(prev_region_live_to_right) / prev_region_space_to_right;
1163         if (density_to_right <= prev_region_density_to_right) {
1164           return dense_prefix;
1165         }
1166         if (TraceParallelOldGCDensePrefix && Verbose) {
1167           tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1168                         "pc_d2r=%10.8f", sd.region(cp), density_to_right,
1169                         prev_region_density_to_right);
1170         }
1171         dense_prefix -= region_size;
1172         live_to_right = prev_region_live_to_right;
1173         space_to_right = prev_region_space_to_right;
1174         density_to_right = prev_region_density_to_right;
1175       }
1176       return dense_prefix;
1177     }
1178 
1179     dense_prefix += region_size;
1180     ++cp;
1181   }
1182 
1183   return dense_prefix;
1184 }
1185 
1186 #ifndef PRODUCT
1187 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1188                                                  const SpaceId id,
1189                                                  const bool maximum_compaction,
1190                                                  HeapWord* const addr)
1191 {
1192   const size_t region_idx = summary_data().addr_to_region_idx(addr);
1193   RegionData* const cp = summary_data().region(region_idx);
1194   const MutableSpace* const space = _space_info[id].space();
1195   HeapWord* const new_top = _space_info[id].new_top();
1196 
1197   const size_t space_live = pointer_delta(new_top, space->bottom());
1198   const size_t dead_to_left = pointer_delta(addr, cp->destination());
1199   const size_t space_cap = space->capacity_in_words();
1200   const double dead_to_left_pct = double(dead_to_left) / space_cap;
1201   const size_t live_to_right = new_top - cp->destination();
1202   const size_t dead_to_right = space->top() - addr - live_to_right;
1203 
1204   tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1205                 "spl=" SIZE_FORMAT " "
1206                 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1207                 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
1208                 " ratio=%10.8f",
1209                 algorithm, addr, region_idx,
1210                 space_live,
1211                 dead_to_left, dead_to_left_pct,
1212                 dead_to_right, live_to_right,
1213                 double(dead_to_right) / live_to_right);
1214 }
1215 #endif  // #ifndef PRODUCT
1216 
1217 // Return a fraction indicating how much of the generation can be treated as
1218 // "dead wood" (i.e., not reclaimed).  The function uses a normal distribution
1219 // based on the density of live objects in the generation to determine a limit,
1220 // which is then adjusted so the return value is min_percent when the density is
1221 // 1.
1222 //
1223 // The following table shows some return values for a different values of the
1224 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1225 // min_percent is 1.
1226 //
1227 //                          fraction allowed as dead wood
1228 //         -----------------------------------------------------------------
1229 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1230 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1231 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1232 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1233 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1234 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1235 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1236 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1237 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1238 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1239 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1240 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1241 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1242 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1243 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1244 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1245 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1246 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1247 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1248 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1249 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1250 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1251 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1252 
1253 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1254 {
1255   assert(_dwl_initialized, "uninitialized");
1256 
1257   // The raw limit is the value of the normal distribution at x = density.
1258   const double raw_limit = normal_distribution(density);
1259 
1260   // Adjust the raw limit so it becomes the minimum when the density is 1.
1261   //
1262   // First subtract the adjustment value (which is simply the precomputed value
1263   // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1264   // Then add the minimum value, so the minimum is returned when the density is
1265   // 1.  Finally, prevent negative values, which occur when the mean is not 0.5.
1266   const double min = double(min_percent) / 100.0;
1267   const double limit = raw_limit - _dwl_adjustment + min;
1268   return MAX2(limit, 0.0);
1269 }
1270 
1271 ParallelCompactData::RegionData*
1272 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1273                                            const RegionData* end)
1274 {
1275   const size_t region_size = ParallelCompactData::RegionSize;
1276   ParallelCompactData& sd = summary_data();
1277   size_t left = sd.region(beg);
1278   size_t right = end > beg ? sd.region(end) - 1 : left;
1279 
1280   // Binary search.
1281   while (left < right) {
1282     // Equivalent to (left + right) / 2, but does not overflow.
1283     const size_t middle = left + (right - left) / 2;
1284     RegionData* const middle_ptr = sd.region(middle);
1285     HeapWord* const dest = middle_ptr->destination();
1286     HeapWord* const addr = sd.region_to_addr(middle);
1287     assert(dest != NULL, "sanity");
1288     assert(dest <= addr, "must move left");
1289 
1290     if (middle > left && dest < addr) {
1291       right = middle - 1;
1292     } else if (middle < right && middle_ptr->data_size() == region_size) {
1293       left = middle + 1;
1294     } else {
1295       return middle_ptr;
1296     }
1297   }
1298   return sd.region(left);
1299 }
1300 
1301 ParallelCompactData::RegionData*
1302 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1303                                           const RegionData* end,
1304                                           size_t dead_words)
1305 {
1306   ParallelCompactData& sd = summary_data();
1307   size_t left = sd.region(beg);
1308   size_t right = end > beg ? sd.region(end) - 1 : left;
1309 
1310   // Binary search.
1311   while (left < right) {
1312     // Equivalent to (left + right) / 2, but does not overflow.
1313     const size_t middle = left + (right - left) / 2;
1314     RegionData* const middle_ptr = sd.region(middle);
1315     HeapWord* const dest = middle_ptr->destination();
1316     HeapWord* const addr = sd.region_to_addr(middle);
1317     assert(dest != NULL, "sanity");
1318     assert(dest <= addr, "must move left");
1319 
1320     const size_t dead_to_left = pointer_delta(addr, dest);
1321     if (middle > left && dead_to_left > dead_words) {
1322       right = middle - 1;
1323     } else if (middle < right && dead_to_left < dead_words) {
1324       left = middle + 1;
1325     } else {
1326       return middle_ptr;
1327     }
1328   }
1329   return sd.region(left);
1330 }
1331 
1332 // The result is valid during the summary phase, after the initial summarization
1333 // of each space into itself, and before final summarization.
1334 inline double
1335 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1336                                    HeapWord* const bottom,
1337                                    HeapWord* const top,
1338                                    HeapWord* const new_top)
1339 {
1340   ParallelCompactData& sd = summary_data();
1341 
1342   assert(cp != NULL, "sanity");
1343   assert(bottom != NULL, "sanity");
1344   assert(top != NULL, "sanity");
1345   assert(new_top != NULL, "sanity");
1346   assert(top >= new_top, "summary data problem?");
1347   assert(new_top > bottom, "space is empty; should not be here");
1348   assert(new_top >= cp->destination(), "sanity");
1349   assert(top >= sd.region_to_addr(cp), "sanity");
1350 
1351   HeapWord* const destination = cp->destination();
1352   const size_t dense_prefix_live  = pointer_delta(destination, bottom);
1353   const size_t compacted_region_live = pointer_delta(new_top, destination);
1354   const size_t compacted_region_used = pointer_delta(top,
1355                                                      sd.region_to_addr(cp));
1356   const size_t reclaimable = compacted_region_used - compacted_region_live;
1357 
1358   const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1359   return double(reclaimable) / divisor;
1360 }
1361 
1362 // Return the address of the end of the dense prefix, a.k.a. the start of the
1363 // compacted region.  The address is always on a region boundary.
1364 //
1365 // Completely full regions at the left are skipped, since no compaction can
1366 // occur in those regions.  Then the maximum amount of dead wood to allow is
1367 // computed, based on the density (amount live / capacity) of the generation;
1368 // the region with approximately that amount of dead space to the left is
1369 // identified as the limit region.  Regions between the last completely full
1370 // region and the limit region are scanned and the one that has the best
1371 // (maximum) reclaimed_ratio() is selected.
1372 HeapWord*
1373 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1374                                         bool maximum_compaction)
1375 {
1376   if (ParallelOldGCSplitALot) {
1377     if (_space_info[id].dense_prefix() != _space_info[id].space()->bottom()) {
1378       // The value was chosen to provoke splitting a young gen space; use it.
1379       return _space_info[id].dense_prefix();
1380     }
1381   }
1382 
1383   const size_t region_size = ParallelCompactData::RegionSize;
1384   const ParallelCompactData& sd = summary_data();
1385 
1386   const MutableSpace* const space = _space_info[id].space();
1387   HeapWord* const top = space->top();
1388   HeapWord* const top_aligned_up = sd.region_align_up(top);
1389   HeapWord* const new_top = _space_info[id].new_top();
1390   HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1391   HeapWord* const bottom = space->bottom();
1392   const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1393   const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1394   const RegionData* const new_top_cp =
1395     sd.addr_to_region_ptr(new_top_aligned_up);
1396 
1397   // Skip full regions at the beginning of the space--they are necessarily part
1398   // of the dense prefix.
1399   const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1400   assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1401          space->is_empty(), "no dead space allowed to the left");
1402   assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1403          "region must have dead space");
1404 
1405   // The gc number is saved whenever a maximum compaction is done, and used to
1406   // determine when the maximum compaction interval has expired.  This avoids
1407   // successive max compactions for different reasons.
1408   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1409   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1410   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1411     total_invocations() == HeapFirstMaximumCompactionCount;
1412   if (maximum_compaction || full_cp == top_cp || interval_ended) {
1413     _maximum_compaction_gc_num = total_invocations();
1414     return sd.region_to_addr(full_cp);
1415   }
1416 
1417   const size_t space_live = pointer_delta(new_top, bottom);
1418   const size_t space_used = space->used_in_words();
1419   const size_t space_capacity = space->capacity_in_words();
1420 
1421   const double density = double(space_live) / double(space_capacity);
1422   const size_t min_percent_free = MarkSweepDeadRatio;
1423   const double limiter = dead_wood_limiter(density, min_percent_free);
1424   const size_t dead_wood_max = space_used - space_live;
1425   const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1426                                       dead_wood_max);
1427 
1428   if (TraceParallelOldGCDensePrefix) {
1429     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1430                   "space_cap=" SIZE_FORMAT,
1431                   space_live, space_used,
1432                   space_capacity);
1433     tty->print_cr("dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
1434                   "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1435                   density, min_percent_free, limiter,
1436                   dead_wood_max, dead_wood_limit);
1437   }
1438 
1439   // Locate the region with the desired amount of dead space to the left.
1440   const RegionData* const limit_cp =
1441     dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1442 
1443   // Scan from the first region with dead space to the limit region and find the
1444   // one with the best (largest) reclaimed ratio.
1445   double best_ratio = 0.0;
1446   const RegionData* best_cp = full_cp;
1447   for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1448     double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1449     if (tmp_ratio > best_ratio) {
1450       best_cp = cp;
1451       best_ratio = tmp_ratio;
1452     }
1453   }
1454 
1455 #if     0
1456   // Something to consider:  if the region with the best ratio is 'close to' the
1457   // first region w/free space, choose the first region with free space
1458   // ("first-free").  The first-free region is usually near the start of the
1459   // heap, which means we are copying most of the heap already, so copy a bit
1460   // more to get complete compaction.
1461   if (pointer_delta(best_cp, full_cp, sizeof(RegionData)) < 4) {
1462     _maximum_compaction_gc_num = total_invocations();
1463     best_cp = full_cp;
1464   }
1465 #endif  // #if 0
1466 
1467   return sd.region_to_addr(best_cp);
1468 }
1469 
1470 #ifndef PRODUCT
1471 void
1472 PSParallelCompact::fill_with_live_objects(SpaceId id, HeapWord* const start,
1473                                           size_t words)
1474 {
1475   if (TraceParallelOldGCSummaryPhase) {
1476     tty->print_cr("fill_with_live_objects [" PTR_FORMAT " " PTR_FORMAT ") "
1477                   SIZE_FORMAT, start, start + words, words);
1478   }
1479 
1480   ObjectStartArray* const start_array = _space_info[id].start_array();
1481   CollectedHeap::fill_with_objects(start, words);
1482   for (HeapWord* p = start; p < start + words; p += oop(p)->size()) {
1483     _mark_bitmap.mark_obj(p, words);
1484     _summary_data.add_obj(p, words);
1485     start_array->allocate_block(p);
1486   }
1487 }
1488 
1489 void
1490 PSParallelCompact::summarize_new_objects(SpaceId id, HeapWord* start)
1491 {
1492   ParallelCompactData& sd = summary_data();
1493   MutableSpace* space = _space_info[id].space();
1494 
1495   // Find the source and destination start addresses.
1496   HeapWord* const src_addr = sd.region_align_down(start);
1497   HeapWord* dst_addr;
1498   if (src_addr < start) {
1499     dst_addr = sd.addr_to_region_ptr(src_addr)->destination();
1500   } else if (src_addr > space->bottom()) {
1501     // The start (the original top() value) is aligned to a region boundary so
1502     // the associated region does not have a destination.  Compute the
1503     // destination from the previous region.
1504     RegionData* const cp = sd.addr_to_region_ptr(src_addr) - 1;
1505     dst_addr = cp->destination() + cp->data_size();
1506   } else {
1507     // Filling the entire space.
1508     dst_addr = space->bottom();
1509   }
1510   assert(dst_addr != NULL, "sanity");
1511 
1512   // Update the summary data.
1513   bool result = _summary_data.summarize(_space_info[id].split_info(),
1514                                         src_addr, space->top(), NULL,
1515                                         dst_addr, space->end(),
1516                                         _space_info[id].new_top_addr());
1517   assert(result, "should not fail:  bad filler object size");
1518 }
1519 
1520 void
1521 PSParallelCompact::provoke_split_fill_survivor(SpaceId id)
1522 {
1523   if (total_invocations() % (ParallelOldGCSplitInterval * 3) != 0) {
1524     return;
1525   }
1526 
1527   MutableSpace* const space = _space_info[id].space();
1528   if (space->is_empty()) {
1529     HeapWord* b = space->bottom();
1530     HeapWord* t = b + space->capacity_in_words() / 2;
1531     space->set_top(t);
1532     if (ZapUnusedHeapArea) {
1533       space->set_top_for_allocations();
1534     }
1535 
1536     size_t min_size = CollectedHeap::min_fill_size();
1537     size_t obj_len = min_size;
1538     while (b + obj_len <= t) {
1539       CollectedHeap::fill_with_object(b, obj_len);
1540       mark_bitmap()->mark_obj(b, obj_len);
1541       summary_data().add_obj(b, obj_len);
1542       b += obj_len;
1543       obj_len = (obj_len & (min_size*3)) + min_size; // 8 16 24 32 8 16 24 32 ...
1544     }
1545     if (b < t) {
1546       // The loop didn't completely fill to t (top); adjust top downward.
1547       space->set_top(b);
1548       if (ZapUnusedHeapArea) {
1549         space->set_top_for_allocations();
1550       }
1551     }
1552 
1553     HeapWord** nta = _space_info[id].new_top_addr();
1554     bool result = summary_data().summarize(_space_info[id].split_info(),
1555                                            space->bottom(), space->top(), NULL,
1556                                            space->bottom(), space->end(), nta);
1557     assert(result, "space must fit into itself");
1558   }
1559 }
1560 
1561 void
1562 PSParallelCompact::provoke_split(bool & max_compaction)
1563 {
1564   if (total_invocations() % ParallelOldGCSplitInterval != 0) {
1565     return;
1566   }
1567 
1568   const size_t region_size = ParallelCompactData::RegionSize;
1569   ParallelCompactData& sd = summary_data();
1570 
1571   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1572   MutableSpace* const from_space = _space_info[from_space_id].space();
1573   const size_t eden_live = pointer_delta(eden_space->top(),
1574                                          _space_info[eden_space_id].new_top());
1575   const size_t from_live = pointer_delta(from_space->top(),
1576                                          _space_info[from_space_id].new_top());
1577 
1578   const size_t min_fill_size = CollectedHeap::min_fill_size();
1579   const size_t eden_free = pointer_delta(eden_space->end(), eden_space->top());
1580   const size_t eden_fillable = eden_free >= min_fill_size ? eden_free : 0;
1581   const size_t from_free = pointer_delta(from_space->end(), from_space->top());
1582   const size_t from_fillable = from_free >= min_fill_size ? from_free : 0;
1583 
1584   // Choose the space to split; need at least 2 regions live (or fillable).
1585   SpaceId id;
1586   MutableSpace* space;
1587   size_t live_words;
1588   size_t fill_words;
1589   if (eden_live + eden_fillable >= region_size * 2) {
1590     id = eden_space_id;
1591     space = eden_space;
1592     live_words = eden_live;
1593     fill_words = eden_fillable;
1594   } else if (from_live + from_fillable >= region_size * 2) {
1595     id = from_space_id;
1596     space = from_space;
1597     live_words = from_live;
1598     fill_words = from_fillable;
1599   } else {
1600     return; // Give up.
1601   }
1602   assert(fill_words == 0 || fill_words >= min_fill_size, "sanity");
1603 
1604   if (live_words < region_size * 2) {
1605     // Fill from top() to end() w/live objects of mixed sizes.
1606     HeapWord* const fill_start = space->top();
1607     live_words += fill_words;
1608 
1609     space->set_top(fill_start + fill_words);
1610     if (ZapUnusedHeapArea) {
1611       space->set_top_for_allocations();
1612     }
1613 
1614     HeapWord* cur_addr = fill_start;
1615     while (fill_words > 0) {
1616       const size_t r = (size_t)os::random() % (region_size / 2) + min_fill_size;
1617       size_t cur_size = MIN2(align_object_size_(r), fill_words);
1618       if (fill_words - cur_size < min_fill_size) {
1619         cur_size = fill_words; // Avoid leaving a fragment too small to fill.
1620       }
1621 
1622       CollectedHeap::fill_with_object(cur_addr, cur_size);
1623       mark_bitmap()->mark_obj(cur_addr, cur_size);
1624       sd.add_obj(cur_addr, cur_size);
1625 
1626       cur_addr += cur_size;
1627       fill_words -= cur_size;
1628     }
1629 
1630     summarize_new_objects(id, fill_start);
1631   }
1632 
1633   max_compaction = false;
1634 
1635   // Manipulate the old gen so that it has room for about half of the live data
1636   // in the target young gen space (live_words / 2).
1637   id = old_space_id;
1638   space = _space_info[id].space();
1639   const size_t free_at_end = space->free_in_words();
1640   const size_t free_target = align_object_size(live_words / 2);
1641   const size_t dead = pointer_delta(space->top(), _space_info[id].new_top());
1642 
1643   if (free_at_end >= free_target + min_fill_size) {
1644     // Fill space above top() and set the dense prefix so everything survives.
1645     HeapWord* const fill_start = space->top();
1646     const size_t fill_size = free_at_end - free_target;
1647     space->set_top(space->top() + fill_size);
1648     if (ZapUnusedHeapArea) {
1649       space->set_top_for_allocations();
1650     }
1651     fill_with_live_objects(id, fill_start, fill_size);
1652     summarize_new_objects(id, fill_start);
1653     _space_info[id].set_dense_prefix(sd.region_align_down(space->top()));
1654   } else if (dead + free_at_end > free_target) {
1655     // Find a dense prefix that makes the right amount of space available.
1656     HeapWord* cur = sd.region_align_down(space->top());
1657     HeapWord* cur_destination = sd.addr_to_region_ptr(cur)->destination();
1658     size_t dead_to_right = pointer_delta(space->end(), cur_destination);
1659     while (dead_to_right < free_target) {
1660       cur -= region_size;
1661       cur_destination = sd.addr_to_region_ptr(cur)->destination();
1662       dead_to_right = pointer_delta(space->end(), cur_destination);
1663     }
1664     _space_info[id].set_dense_prefix(cur);
1665   }
1666 }
1667 #endif // #ifndef PRODUCT
1668 
1669 void PSParallelCompact::summarize_spaces_quick()
1670 {
1671   for (unsigned int i = 0; i < last_space_id; ++i) {
1672     const MutableSpace* space = _space_info[i].space();
1673     HeapWord** nta = _space_info[i].new_top_addr();
1674     bool result = _summary_data.summarize(_space_info[i].split_info(),
1675                                           space->bottom(), space->top(), NULL,
1676                                           space->bottom(), space->end(), nta);
1677     assert(result, "space must fit into itself");
1678     _space_info[i].set_dense_prefix(space->bottom());
1679   }
1680 
1681 #ifndef PRODUCT
1682   if (ParallelOldGCSplitALot) {
1683     provoke_split_fill_survivor(to_space_id);
1684   }
1685 #endif // #ifndef PRODUCT
1686 }
1687 
1688 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1689 {
1690   HeapWord* const dense_prefix_end = dense_prefix(id);
1691   const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1692   const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1693   if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1694     // Only enough dead space is filled so that any remaining dead space to the
1695     // left is larger than the minimum filler object.  (The remainder is filled
1696     // during the copy/update phase.)
1697     //
1698     // The size of the dead space to the right of the boundary is not a
1699     // concern, since compaction will be able to use whatever space is
1700     // available.
1701     //
1702     // Here '||' is the boundary, 'x' represents a don't care bit and a box
1703     // surrounds the space to be filled with an object.
1704     //
1705     // In the 32-bit VM, each bit represents two 32-bit words:
1706     //                              +---+
1707     // a) beg_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1708     //    end_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1709     //                              +---+
1710     //
1711     // In the 64-bit VM, each bit represents one 64-bit word:
1712     //                              +------------+
1713     // b) beg_bits:  ...  x   x   x | 0   ||   0 | x  x  ...
1714     //    end_bits:  ...  x   x   1 | 0   ||   0 | x  x  ...
1715     //                              +------------+
1716     //                          +-------+
1717     // c) beg_bits:  ...  x   x | 0   0 | ||   0   x  x  ...
1718     //    end_bits:  ...  x   1 | 0   0 | ||   0   x  x  ...
1719     //                          +-------+
1720     //                      +-----------+
1721     // d) beg_bits:  ...  x | 0   0   0 | ||   0   x  x  ...
1722     //    end_bits:  ...  1 | 0   0   0 | ||   0   x  x  ...
1723     //                      +-----------+
1724     //                          +-------+
1725     // e) beg_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1726     //    end_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1727     //                          +-------+
1728 
1729     // Initially assume case a, c or e will apply.
1730     size_t obj_len = CollectedHeap::min_fill_size();
1731     HeapWord* obj_beg = dense_prefix_end - obj_len;
1732 
1733 #ifdef  _LP64
1734     if (MinObjAlignment > 1) { // object alignment > heap word size
1735       // Cases a, c or e.
1736     } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1737       // Case b above.
1738       obj_beg = dense_prefix_end - 1;
1739     } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1740                _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1741       // Case d above.
1742       obj_beg = dense_prefix_end - 3;
1743       obj_len = 3;
1744     }
1745 #endif  // #ifdef _LP64
1746 
1747     CollectedHeap::fill_with_object(obj_beg, obj_len);
1748     _mark_bitmap.mark_obj(obj_beg, obj_len);
1749     _summary_data.add_obj(obj_beg, obj_len);
1750     assert(start_array(id) != NULL, "sanity");
1751     start_array(id)->allocate_block(obj_beg);
1752   }
1753 }
1754 
1755 void
1756 PSParallelCompact::clear_source_region(HeapWord* beg_addr, HeapWord* end_addr)
1757 {
1758   RegionData* const beg_ptr = _summary_data.addr_to_region_ptr(beg_addr);
1759   HeapWord* const end_aligned_up = _summary_data.region_align_up(end_addr);
1760   RegionData* const end_ptr = _summary_data.addr_to_region_ptr(end_aligned_up);
1761   for (RegionData* cur = beg_ptr; cur < end_ptr; ++cur) {
1762     cur->set_source_region(0);
1763   }
1764 }
1765 
1766 void
1767 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1768 {
1769   assert(id < last_space_id, "id out of range");
1770   assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom() ||
1771          ParallelOldGCSplitALot && id == old_space_id,
1772          "should have been reset in summarize_spaces_quick()");
1773 
1774   const MutableSpace* space = _space_info[id].space();
1775   if (_space_info[id].new_top() != space->bottom()) {
1776     HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1777     _space_info[id].set_dense_prefix(dense_prefix_end);
1778 
1779 #ifndef PRODUCT
1780     if (TraceParallelOldGCDensePrefix) {
1781       print_dense_prefix_stats("ratio", id, maximum_compaction,
1782                                dense_prefix_end);
1783       HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1784       print_dense_prefix_stats("density", id, maximum_compaction, addr);
1785     }
1786 #endif  // #ifndef PRODUCT
1787 
1788     // Recompute the summary data, taking into account the dense prefix.  If
1789     // every last byte will be reclaimed, then the existing summary data which
1790     // compacts everything can be left in place.
1791     if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1792       // If dead space crosses the dense prefix boundary, it is (at least
1793       // partially) filled with a dummy object, marked live and added to the
1794       // summary data.  This simplifies the copy/update phase and must be done
1795       // before the final locations of objects are determined, to prevent
1796       // leaving a fragment of dead space that is too small to fill.
1797       fill_dense_prefix_end(id);
1798 
1799       // Compute the destination of each Region, and thus each object.
1800       _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1801       _summary_data.summarize(_space_info[id].split_info(),
1802                               dense_prefix_end, space->top(), NULL,
1803                               dense_prefix_end, space->end(),
1804                               _space_info[id].new_top_addr());
1805     }
1806   }
1807 
1808   if (TraceParallelOldGCSummaryPhase) {
1809     const size_t region_size = ParallelCompactData::RegionSize;
1810     HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1811     const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1812     const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1813     HeapWord* const new_top = _space_info[id].new_top();
1814     const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1815     const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1816     tty->print_cr("id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1817                   "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1818                   "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1819                   id, space->capacity_in_words(), dense_prefix_end,
1820                   dp_region, dp_words / region_size,
1821                   cr_words / region_size, new_top);
1822   }
1823 }
1824 
1825 #ifndef PRODUCT
1826 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1827                                           HeapWord* dst_beg, HeapWord* dst_end,
1828                                           SpaceId src_space_id,
1829                                           HeapWord* src_beg, HeapWord* src_end)
1830 {
1831   if (TraceParallelOldGCSummaryPhase) {
1832     tty->print_cr("summarizing %d [%s] into %d [%s]:  "
1833                   "src=" PTR_FORMAT "-" PTR_FORMAT " "
1834                   SIZE_FORMAT "-" SIZE_FORMAT " "
1835                   "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1836                   SIZE_FORMAT "-" SIZE_FORMAT,
1837                   src_space_id, space_names[src_space_id],
1838                   dst_space_id, space_names[dst_space_id],
1839                   src_beg, src_end,
1840                   _summary_data.addr_to_region_idx(src_beg),
1841                   _summary_data.addr_to_region_idx(src_end),
1842                   dst_beg, dst_end,
1843                   _summary_data.addr_to_region_idx(dst_beg),
1844                   _summary_data.addr_to_region_idx(dst_end));
1845   }
1846 }
1847 #endif  // #ifndef PRODUCT
1848 
1849 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1850                                       bool maximum_compaction)
1851 {
1852   GCTraceTime tm("summary phase", print_phases(), true, &_gc_timer);
1853   // trace("2");
1854 
1855 #ifdef  ASSERT
1856   if (TraceParallelOldGCMarkingPhase) {
1857     tty->print_cr("add_obj_count=" SIZE_FORMAT " "
1858                   "add_obj_bytes=" SIZE_FORMAT,
1859                   add_obj_count, add_obj_size * HeapWordSize);
1860     tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
1861                   "mark_bitmap_bytes=" SIZE_FORMAT,
1862                   mark_bitmap_count, mark_bitmap_size * HeapWordSize);
1863   }
1864 #endif  // #ifdef ASSERT
1865 
1866   // Quick summarization of each space into itself, to see how much is live.
1867   summarize_spaces_quick();
1868 
1869   if (TraceParallelOldGCSummaryPhase) {
1870     tty->print_cr("summary_phase:  after summarizing each space to self");
1871     Universe::print();
1872     NOT_PRODUCT(print_region_ranges());
1873     if (Verbose) {
1874       NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1875     }
1876   }
1877 
1878   // The amount of live data that will end up in old space (assuming it fits).
1879   size_t old_space_total_live = 0;
1880   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1881     old_space_total_live += pointer_delta(_space_info[id].new_top(),
1882                                           _space_info[id].space()->bottom());
1883   }
1884 
1885   MutableSpace* const old_space = _space_info[old_space_id].space();
1886   const size_t old_capacity = old_space->capacity_in_words();
1887   if (old_space_total_live > old_capacity) {
1888     // XXX - should also try to expand
1889     maximum_compaction = true;
1890   }
1891 #ifndef PRODUCT
1892   if (ParallelOldGCSplitALot && old_space_total_live < old_capacity) {
1893     provoke_split(maximum_compaction);
1894   }
1895 #endif // #ifndef PRODUCT
1896 
1897   // Old generations.
1898   summarize_space(old_space_id, maximum_compaction);
1899 
1900   // Summarize the remaining spaces in the young gen.  The initial target space
1901   // is the old gen.  If a space does not fit entirely into the target, then the
1902   // remainder is compacted into the space itself and that space becomes the new
1903   // target.
1904   SpaceId dst_space_id = old_space_id;
1905   HeapWord* dst_space_end = old_space->end();
1906   HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1907   for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1908     const MutableSpace* space = _space_info[id].space();
1909     const size_t live = pointer_delta(_space_info[id].new_top(),
1910                                       space->bottom());
1911     const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1912 
1913     NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1914                                   SpaceId(id), space->bottom(), space->top());)
1915     if (live > 0 && live <= available) {
1916       // All the live data will fit.
1917       bool done = _summary_data.summarize(_space_info[id].split_info(),
1918                                           space->bottom(), space->top(),
1919                                           NULL,
1920                                           *new_top_addr, dst_space_end,
1921                                           new_top_addr);
1922       assert(done, "space must fit into old gen");
1923 
1924       // Reset the new_top value for the space.
1925       _space_info[id].set_new_top(space->bottom());
1926     } else if (live > 0) {
1927       // Attempt to fit part of the source space into the target space.
1928       HeapWord* next_src_addr = NULL;
1929       bool done = _summary_data.summarize(_space_info[id].split_info(),
1930                                           space->bottom(), space->top(),
1931                                           &next_src_addr,
1932                                           *new_top_addr, dst_space_end,
1933                                           new_top_addr);
1934       assert(!done, "space should not fit into old gen");
1935       assert(next_src_addr != NULL, "sanity");
1936 
1937       // The source space becomes the new target, so the remainder is compacted
1938       // within the space itself.
1939       dst_space_id = SpaceId(id);
1940       dst_space_end = space->end();
1941       new_top_addr = _space_info[id].new_top_addr();
1942       NOT_PRODUCT(summary_phase_msg(dst_space_id,
1943                                     space->bottom(), dst_space_end,
1944                                     SpaceId(id), next_src_addr, space->top());)
1945       done = _summary_data.summarize(_space_info[id].split_info(),
1946                                      next_src_addr, space->top(),
1947                                      NULL,
1948                                      space->bottom(), dst_space_end,
1949                                      new_top_addr);
1950       assert(done, "space must fit when compacted into itself");
1951       assert(*new_top_addr <= space->top(), "usage should not grow");
1952     }
1953   }
1954 
1955   if (TraceParallelOldGCSummaryPhase) {
1956     tty->print_cr("summary_phase:  after final summarization");
1957     Universe::print();
1958     NOT_PRODUCT(print_region_ranges());
1959     if (Verbose) {
1960       NOT_PRODUCT(print_generic_summary_data(_summary_data, _space_info));
1961     }
1962   }
1963 }
1964 
1965 // This method should contain all heap-specific policy for invoking a full
1966 // collection.  invoke_no_policy() will only attempt to compact the heap; it
1967 // will do nothing further.  If we need to bail out for policy reasons, scavenge
1968 // before full gc, or any other specialized behavior, it needs to be added here.
1969 //
1970 // Note that this method should only be called from the vm_thread while at a
1971 // safepoint.
1972 //
1973 // Note that the all_soft_refs_clear flag in the collector policy
1974 // may be true because this method can be called without intervening
1975 // activity.  For example when the heap space is tight and full measure
1976 // are being taken to free space.
1977 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1978   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1979   assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1980          "should be in vm thread");
1981 
1982   ParallelScavengeHeap* heap = gc_heap();
1983   GCCause::Cause gc_cause = heap->gc_cause();
1984   assert(!heap->is_gc_active(), "not reentrant");
1985 
1986   PSAdaptiveSizePolicy* policy = heap->size_policy();
1987   IsGCActiveMark mark;
1988 
1989   if (ScavengeBeforeFullGC) {
1990     PSScavenge::invoke_no_policy();
1991   }
1992 
1993   const bool clear_all_soft_refs =
1994     heap->collector_policy()->should_clear_all_soft_refs();
1995 
1996   PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1997                                       maximum_heap_compaction);
1998 }
1999 
2000 // This method contains no policy. You should probably
2001 // be calling invoke() instead.
2002 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
2003   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
2004   assert(ref_processor() != NULL, "Sanity");
2005 
2006   if (GC_locker::check_active_before_gc()) {
2007     return false;
2008   }
2009 
2010   ParallelScavengeHeap* heap = gc_heap();
2011 
2012   _gc_timer.register_gc_start();
2013   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
2014 
2015   TimeStamp marking_start;
2016   TimeStamp compaction_start;
2017   TimeStamp collection_exit;
2018 
2019   GCCause::Cause gc_cause = heap->gc_cause();
2020   PSYoungGen* young_gen = heap->young_gen();
2021   PSOldGen* old_gen = heap->old_gen();
2022   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
2023 
2024   // The scope of casr should end after code that can change
2025   // CollectorPolicy::_should_clear_all_soft_refs.
2026   ClearedAllSoftRefs casr(maximum_heap_compaction,
2027                           heap->collector_policy());
2028 
2029   if (ZapUnusedHeapArea) {
2030     // Save information needed to minimize mangling
2031     heap->record_gen_tops_before_GC();
2032   }
2033 
2034   heap->pre_full_gc_dump(&_gc_timer);
2035 
2036   _print_phases = PrintGCDetails && PrintParallelOldGCPhaseTimes;
2037 
2038   // Make sure data structures are sane, make the heap parsable, and do other
2039   // miscellaneous bookkeeping.
2040   PreGCValues pre_gc_values;
2041   pre_compact(&pre_gc_values);
2042 
2043   // Get the compaction manager reserved for the VM thread.
2044   ParCompactionManager* const vmthread_cm =
2045     ParCompactionManager::manager_array(gc_task_manager()->workers());
2046 
2047   // Place after pre_compact() where the number of invocations is incremented.
2048   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
2049 
2050   {
2051     ResourceMark rm;
2052     HandleMark hm;
2053 
2054     // Set the number of GC threads to be used in this collection
2055     gc_task_manager()->set_active_gang();
2056     gc_task_manager()->task_idle_workers();
2057     heap->set_par_threads(gc_task_manager()->active_workers());
2058 
2059     gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
2060     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
2061     GCTraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, NULL);
2062     TraceCollectorStats tcs(counters());
2063     TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);
2064 
2065     if (TraceGen1Time) accumulated_time()->start();
2066 
2067     // Let the size policy know we're starting
2068     size_policy->major_collection_begin();
2069 
2070     CodeCache::gc_prologue();
2071     Threads::gc_prologue();
2072 
2073     COMPILER2_PRESENT(DerivedPointerTable::clear());
2074 
2075     ref_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
2076     ref_processor()->setup_policy(maximum_heap_compaction);
2077 
2078     bool marked_for_unloading = false;
2079 
2080     marking_start.update();
2081     marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
2082 
2083     bool max_on_system_gc = UseMaximumCompactionOnSystemGC
2084       && gc_cause == GCCause::_java_lang_system_gc;
2085     summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
2086 
2087     COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
2088     COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
2089 
2090     // adjust_roots() updates Universe::_intArrayKlassObj which is
2091     // needed by the compaction for filling holes in the dense prefix.
2092     adjust_roots();
2093 
2094     compaction_start.update();
2095     compact();
2096 
2097     // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
2098     // done before resizing.
2099     post_compact();
2100 
2101     // Let the size policy know we're done
2102     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
2103 
2104     if (UseAdaptiveSizePolicy) {
2105       if (PrintAdaptiveSizePolicy) {
2106         gclog_or_tty->print("AdaptiveSizeStart: ");
2107         gclog_or_tty->stamp();
2108         gclog_or_tty->print_cr(" collection: %d ",
2109                        heap->total_collections());
2110         if (Verbose) {
2111           gclog_or_tty->print("old_gen_capacity: " SIZE_FORMAT
2112             " young_gen_capacity: " SIZE_FORMAT,
2113             old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
2114         }
2115       }
2116 
2117       // Don't check if the size_policy is ready here.  Let
2118       // the size_policy check that internally.
2119       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
2120           ((gc_cause != GCCause::_java_lang_system_gc) ||
2121             UseAdaptiveSizePolicyWithSystemGC)) {
2122         // Swap the survivor spaces if from_space is empty. The
2123         // resize_young_gen() called below is normally used after
2124         // a successful young GC and swapping of survivor spaces;
2125         // otherwise, it will fail to resize the young gen with
2126         // the current implementation.
2127         if (young_gen->from_space()->is_empty()) {
2128           young_gen->from_space()->clear(SpaceDecorator::Mangle);
2129           young_gen->swap_spaces();
2130         }
2131 
2132         // Calculate optimal free space amounts
2133         assert(young_gen->max_size() >
2134           young_gen->from_space()->capacity_in_bytes() +
2135           young_gen->to_space()->capacity_in_bytes(),
2136           "Sizes of space in young gen are out-of-bounds");
2137 
2138         size_t young_live = young_gen->used_in_bytes();
2139         size_t eden_live = young_gen->eden_space()->used_in_bytes();
2140         size_t old_live = old_gen->used_in_bytes();
2141         size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
2142         size_t max_old_gen_size = old_gen->max_gen_size();
2143         size_t max_eden_size = young_gen->max_size() -
2144           young_gen->from_space()->capacity_in_bytes() -
2145           young_gen->to_space()->capacity_in_bytes();
2146 
2147         // Used for diagnostics
2148         size_policy->clear_generation_free_space_flags();
2149 
2150         size_policy->compute_generations_free_space(young_live,
2151                                                     eden_live,
2152                                                     old_live,
2153                                                     cur_eden,
2154                                                     max_old_gen_size,
2155                                                     max_eden_size,
2156                                                     true /* full gc*/);
2157 
2158         size_policy->check_gc_overhead_limit(young_live,
2159                                              eden_live,
2160                                              max_old_gen_size,
2161                                              max_eden_size,
2162                                              true /* full gc*/,
2163                                              gc_cause,
2164                                              heap->collector_policy());
2165 
2166         size_policy->decay_supplemental_growth(true /* full gc*/);
2167 
2168         heap->resize_old_gen(
2169           size_policy->calculated_old_free_size_in_bytes());
2170 
2171         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
2172                                size_policy->calculated_survivor_size_in_bytes());
2173       }
2174       if (PrintAdaptiveSizePolicy) {
2175         gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
2176                        heap->total_collections());
2177       }
2178     }
2179 
2180     if (UsePerfData) {
2181       PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
2182       counters->update_counters();
2183       counters->update_old_capacity(old_gen->capacity_in_bytes());
2184       counters->update_young_capacity(young_gen->capacity_in_bytes());
2185     }
2186 
2187     heap->resize_all_tlabs();
2188 
2189     // Resize the metaspace capacity after a collection
2190     MetaspaceGC::compute_new_size();
2191 
2192     if (TraceGen1Time) accumulated_time()->stop();
2193 
2194     if (PrintGC) {
2195       if (PrintGCDetails) {
2196         // No GC timestamp here.  This is after GC so it would be confusing.
2197         young_gen->print_used_change(pre_gc_values.young_gen_used());
2198         old_gen->print_used_change(pre_gc_values.old_gen_used());
2199         heap->print_heap_change(pre_gc_values.heap_used());
2200         MetaspaceAux::print_metaspace_change(pre_gc_values.metadata_used());
2201       } else {
2202         heap->print_heap_change(pre_gc_values.heap_used());
2203       }
2204     }
2205 
2206     // Track memory usage and detect low memory
2207     MemoryService::track_memory_usage();
2208     heap->update_counters();
2209     gc_task_manager()->release_idle_workers();
2210   }
2211 
2212 #ifdef ASSERT
2213   for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
2214     ParCompactionManager* const cm =
2215       ParCompactionManager::manager_array(int(i));
2216     assert(cm->marking_stack()->is_empty(),       "should be empty");
2217     assert(ParCompactionManager::region_list(int(i))->is_empty(), "should be empty");
2218   }
2219 #endif // ASSERT
2220 
2221   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
2222     HandleMark hm;  // Discard invalid handles created during verification
2223     Universe::verify(" VerifyAfterGC:");
2224   }
2225 
2226   // Re-verify object start arrays
2227   if (VerifyObjectStartArray &&
2228       VerifyAfterGC) {
2229     old_gen->verify_object_start_array();
2230   }
2231 
2232   if (ZapUnusedHeapArea) {
2233     old_gen->object_space()->check_mangled_unused_area_complete();
2234   }
2235 
2236   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
2237 
2238   collection_exit.update();
2239 
2240   heap->print_heap_after_gc();
2241   heap->trace_heap_after_gc(&_gc_tracer);
2242 
2243   if (PrintGCTaskTimeStamps) {
2244     gclog_or_tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " "
2245                            INT64_FORMAT,
2246                            marking_start.ticks(), compaction_start.ticks(),
2247                            collection_exit.ticks());
2248     gc_task_manager()->print_task_time_stamps();
2249   }
2250 
2251   heap->post_full_gc_dump(&_gc_timer);
2252 
2253 #ifdef TRACESPINNING
2254   ParallelTaskTerminator::print_termination_counts();
2255 #endif
2256 
2257   _gc_timer.register_gc_end();
2258 
2259   _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
2260   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
2261 
2262   return true;
2263 }
2264 
2265 bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
2266                                              PSYoungGen* young_gen,
2267                                              PSOldGen* old_gen) {
2268   MutableSpace* const eden_space = young_gen->eden_space();
2269   assert(!eden_space->is_empty(), "eden must be non-empty");
2270   assert(young_gen->virtual_space()->alignment() ==
2271          old_gen->virtual_space()->alignment(), "alignments do not match");
2272 
2273   if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
2274     return false;
2275   }
2276 
2277   // Both generations must be completely committed.
2278   if (young_gen->virtual_space()->uncommitted_size() != 0) {
2279     return false;
2280   }
2281   if (old_gen->virtual_space()->uncommitted_size() != 0) {
2282     return false;
2283   }
2284 
2285   // Figure out how much to take from eden.  Include the average amount promoted
2286   // in the total; otherwise the next young gen GC will simply bail out to a
2287   // full GC.
2288   const size_t alignment = old_gen->virtual_space()->alignment();
2289   const size_t eden_used = eden_space->used_in_bytes();
2290   const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
2291   const size_t absorb_size = align_size_up(eden_used + promoted, alignment);
2292   const size_t eden_capacity = eden_space->capacity_in_bytes();
2293 
2294   if (absorb_size >= eden_capacity) {
2295     return false; // Must leave some space in eden.
2296   }
2297 
2298   const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
2299   if (new_young_size < young_gen->min_gen_size()) {
2300     return false; // Respect young gen minimum size.
2301   }
2302 
2303   if (TraceAdaptiveGCBoundary && Verbose) {
2304     gclog_or_tty->print(" absorbing " SIZE_FORMAT "K:  "
2305                         "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
2306                         "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
2307                         "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
2308                         absorb_size / K,
2309                         eden_capacity / K, (eden_capacity - absorb_size) / K,
2310                         young_gen->from_space()->used_in_bytes() / K,
2311                         young_gen->to_space()->used_in_bytes() / K,
2312                         young_gen->capacity_in_bytes() / K, new_young_size / K);
2313   }
2314 
2315   // Fill the unused part of the old gen.
2316   MutableSpace* const old_space = old_gen->object_space();
2317   HeapWord* const unused_start = old_space->top();
2318   size_t const unused_words = pointer_delta(old_space->end(), unused_start);
2319 
2320   if (unused_words > 0) {
2321     if (unused_words < CollectedHeap::min_fill_size()) {
2322       return false;  // If the old gen cannot be filled, must give up.
2323     }
2324     CollectedHeap::fill_with_objects(unused_start, unused_words);
2325   }
2326 
2327   // Take the live data from eden and set both top and end in the old gen to
2328   // eden top.  (Need to set end because reset_after_change() mangles the region
2329   // from end to virtual_space->high() in debug builds).
2330   HeapWord* const new_top = eden_space->top();
2331   old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
2332                                         absorb_size);
2333   young_gen->reset_after_change();
2334   old_space->set_top(new_top);
2335   old_space->set_end(new_top);
2336   old_gen->reset_after_change();
2337 
2338   // Update the object start array for the filler object and the data from eden.
2339   ObjectStartArray* const start_array = old_gen->start_array();
2340   for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
2341     start_array->allocate_block(p);
2342   }
2343 
2344   // Could update the promoted average here, but it is not typically updated at
2345   // full GCs and the value to use is unclear.  Something like
2346   //
2347   // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
2348 
2349   size_policy->set_bytes_absorbed_from_eden(absorb_size);
2350   return true;
2351 }
2352 
2353 GCTaskManager* const PSParallelCompact::gc_task_manager() {
2354   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
2355     "shouldn't return NULL");
2356   return ParallelScavengeHeap::gc_task_manager();
2357 }
2358 
2359 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2360                                       bool maximum_heap_compaction,
2361                                       ParallelOldTracer *gc_tracer) {
2362   // Recursively traverse all live objects and mark them
2363   GCTraceTime tm("marking phase", print_phases(), true, &_gc_timer);
2364 
2365   ParallelScavengeHeap* heap = gc_heap();
2366   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2367   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2368   TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2369   ParallelTaskTerminator terminator(active_gc_threads, qset);
2370 
2371   PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm);
2372   PSParallelCompact::FollowStackClosure follow_stack_closure(cm);
2373 
2374   // Need new claim bits before marking starts.
2375   ClassLoaderDataGraph::clear_claimed_marks();
2376 
2377   {
2378     GCTraceTime tm_m("par mark", print_phases(), true, &_gc_timer);
2379 
2380     ParallelScavengeHeap::ParStrongRootsScope psrs;
2381 
2382     GCTaskQueue* q = GCTaskQueue::create();
2383 
2384     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::universe));
2385     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jni_handles));
2386     // We scan the thread roots in parallel
2387     Threads::create_thread_roots_marking_tasks(q);
2388     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::object_synchronizer));
2389     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::flat_profiler));
2390     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::management));
2391     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::system_dictionary));
2392     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::class_loader_data));
2393     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jvmti));
2394     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::code_cache));
2395 
2396     if (active_gc_threads > 1) {
2397       for (uint j = 0; j < active_gc_threads; j++) {
2398         q->enqueue(new StealMarkingTask(&terminator));
2399       }
2400     }
2401 
2402     gc_task_manager()->execute_and_wait(q);
2403   }
2404 
2405   // Process reference objects found during marking
2406   {
2407     GCTraceTime tm_r("reference processing", print_phases(), true, &_gc_timer);
2408 
2409     ReferenceProcessorStats stats;
2410     if (ref_processor()->processing_is_mt()) {
2411       RefProcTaskExecutor task_executor;
2412       stats = ref_processor()->process_discovered_references(
2413         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2414         &task_executor, &_gc_timer);
2415     } else {
2416       stats = ref_processor()->process_discovered_references(
2417         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
2418         &_gc_timer);
2419     }
2420 
2421     gc_tracer->report_gc_reference_stats(stats);
2422   }
2423 
2424   GCTraceTime tm_c("class unloading", print_phases(), true, &_gc_timer);
2425 
2426   // This is the point where the entire marking should have completed.
2427   assert(cm->marking_stacks_empty(), "Marking should have completed");
2428 
2429   // Follow system dictionary roots and unload classes.
2430   bool purged_class = SystemDictionary::do_unloading(is_alive_closure());
2431 
2432   // Unload nmethods.
2433   CodeCache::do_unloading(is_alive_closure(), purged_class);
2434 
2435   // Prune dead klasses from subklass/sibling/implementor lists.
2436   Klass::clean_weak_klass_links(is_alive_closure());
2437 
2438   // Delete entries for dead interned strings.
2439   StringTable::unlink(is_alive_closure());
2440 
2441   // Clean up unreferenced symbols in symbol table.
2442   SymbolTable::unlink();
2443   _gc_tracer.report_object_count_after_gc(is_alive_closure());
2444 }
2445 
2446 void PSParallelCompact::follow_class_loader(ParCompactionManager* cm,
2447                                             ClassLoaderData* cld) {
2448   PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm);
2449   PSParallelCompact::FollowKlassClosure follow_klass_closure(&mark_and_push_closure);
2450 
2451   cld->oops_do(&mark_and_push_closure, &follow_klass_closure, true);
2452 }
2453 
2454 // This should be moved to the shared markSweep code!
2455 class PSAlwaysTrueClosure: public BoolObjectClosure {
2456 public:
2457   bool do_object_b(oop p) { return true; }
2458 };
2459 static PSAlwaysTrueClosure always_true;
2460 
2461 void PSParallelCompact::adjust_roots() {
2462   // Adjust the pointers to reflect the new locations
2463   GCTraceTime tm("adjust roots", print_phases(), true, &_gc_timer);
2464 
2465   // Need new claim bits when tracing through and adjusting pointers.
2466   ClassLoaderDataGraph::clear_claimed_marks();
2467 
2468   // General strong roots.
2469   Universe::oops_do(adjust_pointer_closure());
2470   JNIHandles::oops_do(adjust_pointer_closure());   // Global (strong) JNI handles
2471   CLDToOopClosure adjust_from_cld(adjust_pointer_closure());
2472   Threads::oops_do(adjust_pointer_closure(), &adjust_from_cld, NULL);
2473   ObjectSynchronizer::oops_do(adjust_pointer_closure());
2474   FlatProfiler::oops_do(adjust_pointer_closure());
2475   Management::oops_do(adjust_pointer_closure());
2476   JvmtiExport::oops_do(adjust_pointer_closure());
2477   // SO_AllClasses
2478   SystemDictionary::oops_do(adjust_pointer_closure());
2479   ClassLoaderDataGraph::oops_do(adjust_pointer_closure(), adjust_klass_closure(), true);
2480 
2481   // Now adjust pointers in remaining weak roots.  (All of which should
2482   // have been cleared if they pointed to non-surviving objects.)
2483   // Global (weak) JNI handles
2484   JNIHandles::weak_oops_do(&always_true, adjust_pointer_closure());
2485 
2486   CodeCache::oops_do(adjust_pointer_closure());
2487   StringTable::oops_do(adjust_pointer_closure());
2488   ref_processor()->weak_oops_do(adjust_pointer_closure());
2489   // Roots were visited so references into the young gen in roots
2490   // may have been scanned.  Process them also.
2491   // Should the reference processor have a span that excludes
2492   // young gen objects?
2493   PSScavenge::reference_processor()->weak_oops_do(adjust_pointer_closure());
2494 }
2495 
2496 void PSParallelCompact::enqueue_region_draining_tasks(GCTaskQueue* q,
2497                                                       uint parallel_gc_threads)
2498 {
2499   GCTraceTime tm("drain task setup", print_phases(), true, &_gc_timer);
2500 
2501   // Find the threads that are active
2502   unsigned int which = 0;
2503 
2504   const uint task_count = MAX2(parallel_gc_threads, 1U);
2505   for (uint j = 0; j < task_count; j++) {
2506     q->enqueue(new DrainStacksCompactionTask(j));
2507     ParCompactionManager::verify_region_list_empty(j);
2508     // Set the region stacks variables to "no" region stack values
2509     // so that they will be recognized and needing a region stack
2510     // in the stealing tasks if they do not get one by executing
2511     // a draining stack.
2512     ParCompactionManager* cm = ParCompactionManager::manager_array(j);
2513     cm->set_region_stack(NULL);
2514     cm->set_region_stack_index((uint)max_uintx);
2515   }
2516   ParCompactionManager::reset_recycled_stack_index();
2517 
2518   // Find all regions that are available (can be filled immediately) and
2519   // distribute them to the thread stacks.  The iteration is done in reverse
2520   // order (high to low) so the regions will be removed in ascending order.
2521 
2522   const ParallelCompactData& sd = PSParallelCompact::summary_data();
2523 
2524   size_t fillable_regions = 0;   // A count for diagnostic purposes.
2525   // A region index which corresponds to the tasks created above.
2526   // "which" must be 0 <= which < task_count
2527 
2528   which = 0;
2529   // id + 1 is used to test termination so unsigned  can
2530   // be used with an old_space_id == 0.
2531   for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2532     SpaceInfo* const space_info = _space_info + id;
2533     MutableSpace* const space = space_info->space();
2534     HeapWord* const new_top = space_info->new_top();
2535 
2536     const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2537     const size_t end_region =
2538       sd.addr_to_region_idx(sd.region_align_up(new_top));
2539 
2540     for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2541       if (sd.region(cur)->claim_unsafe()) {
2542         ParCompactionManager::region_list_push(which, cur);
2543 
2544         if (TraceParallelOldGCCompactionPhase && Verbose) {
2545           const size_t count_mod_8 = fillable_regions & 7;
2546           if (count_mod_8 == 0) gclog_or_tty->print("fillable: ");
2547           gclog_or_tty->print(" " SIZE_FORMAT_W(7), cur);
2548           if (count_mod_8 == 7) gclog_or_tty->cr();
2549         }
2550 
2551         NOT_PRODUCT(++fillable_regions;)
2552 
2553         // Assign regions to tasks in round-robin fashion.
2554         if (++which == task_count) {
2555           assert(which <= parallel_gc_threads,
2556             "Inconsistent number of workers");
2557           which = 0;
2558         }
2559       }
2560     }
2561   }
2562 
2563   if (TraceParallelOldGCCompactionPhase) {
2564     if (Verbose && (fillable_regions & 7) != 0) gclog_or_tty->cr();
2565     gclog_or_tty->print_cr(SIZE_FORMAT " initially fillable regions", fillable_regions);
2566   }
2567 }
2568 
2569 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2570 
2571 void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q,
2572                                                     uint parallel_gc_threads) {
2573   GCTraceTime tm("dense prefix task setup", print_phases(), true, &_gc_timer);
2574 
2575   ParallelCompactData& sd = PSParallelCompact::summary_data();
2576 
2577   // Iterate over all the spaces adding tasks for updating
2578   // regions in the dense prefix.  Assume that 1 gc thread
2579   // will work on opening the gaps and the remaining gc threads
2580   // will work on the dense prefix.
2581   unsigned int space_id;
2582   for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2583     HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2584     const MutableSpace* const space = _space_info[space_id].space();
2585 
2586     if (dense_prefix_end == space->bottom()) {
2587       // There is no dense prefix for this space.
2588       continue;
2589     }
2590 
2591     // The dense prefix is before this region.
2592     size_t region_index_end_dense_prefix =
2593         sd.addr_to_region_idx(dense_prefix_end);
2594     RegionData* const dense_prefix_cp =
2595       sd.region(region_index_end_dense_prefix);
2596     assert(dense_prefix_end == space->end() ||
2597            dense_prefix_cp->available() ||
2598            dense_prefix_cp->claimed(),
2599            "The region after the dense prefix should always be ready to fill");
2600 
2601     size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2602 
2603     // Is there dense prefix work?
2604     size_t total_dense_prefix_regions =
2605       region_index_end_dense_prefix - region_index_start;
2606     // How many regions of the dense prefix should be given to
2607     // each thread?
2608     if (total_dense_prefix_regions > 0) {
2609       uint tasks_for_dense_prefix = 1;
2610       if (total_dense_prefix_regions <=
2611           (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2612         // Don't over partition.  This assumes that
2613         // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2614         // so there are not many regions to process.
2615         tasks_for_dense_prefix = parallel_gc_threads;
2616       } else {
2617         // Over partition
2618         tasks_for_dense_prefix = parallel_gc_threads *
2619           PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2620       }
2621       size_t regions_per_thread = total_dense_prefix_regions /
2622         tasks_for_dense_prefix;
2623       // Give each thread at least 1 region.
2624       if (regions_per_thread == 0) {
2625         regions_per_thread = 1;
2626       }
2627 
2628       for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2629         if (region_index_start >= region_index_end_dense_prefix) {
2630           break;
2631         }
2632         // region_index_end is not processed
2633         size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2634                                        region_index_end_dense_prefix);
2635         q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2636                                              region_index_start,
2637                                              region_index_end));
2638         region_index_start = region_index_end;
2639       }
2640     }
2641     // This gets any part of the dense prefix that did not
2642     // fit evenly.
2643     if (region_index_start < region_index_end_dense_prefix) {
2644       q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2645                                            region_index_start,
2646                                            region_index_end_dense_prefix));
2647     }
2648   }
2649 }
2650 
2651 void PSParallelCompact::enqueue_region_stealing_tasks(
2652                                      GCTaskQueue* q,
2653                                      ParallelTaskTerminator* terminator_ptr,
2654                                      uint parallel_gc_threads) {
2655   GCTraceTime tm("steal task setup", print_phases(), true, &_gc_timer);
2656 
2657   // Once a thread has drained it's stack, it should try to steal regions from
2658   // other threads.
2659   if (parallel_gc_threads > 1) {
2660     for (uint j = 0; j < parallel_gc_threads; j++) {
2661       q->enqueue(new StealRegionCompactionTask(terminator_ptr));
2662     }
2663   }
2664 }
2665 
2666 #ifdef ASSERT
2667 // Write a histogram of the number of times the block table was filled for a
2668 // region.
2669 void PSParallelCompact::write_block_fill_histogram(outputStream* const out)
2670 {
2671   if (!TraceParallelOldGCCompactionPhase) return;
2672 
2673   typedef ParallelCompactData::RegionData rd_t;
2674   ParallelCompactData& sd = summary_data();
2675 
2676   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2677     MutableSpace* const spc = _space_info[id].space();
2678     if (spc->bottom() != spc->top()) {
2679       const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
2680       HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
2681       const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
2682 
2683       size_t histo[5] = { 0, 0, 0, 0, 0 };
2684       const size_t histo_len = sizeof(histo) / sizeof(size_t);
2685       const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
2686 
2687       for (const rd_t* cur = beg; cur < end; ++cur) {
2688         ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
2689       }
2690       out->print("%u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
2691       for (size_t i = 0; i < histo_len; ++i) {
2692         out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
2693                    histo[i], 100.0 * histo[i] / region_cnt);
2694       }
2695       out->cr();
2696     }
2697   }
2698 }
2699 #endif // #ifdef ASSERT
2700 
2701 void PSParallelCompact::compact() {
2702   // trace("5");
2703   GCTraceTime tm("compaction phase", print_phases(), true, &_gc_timer);
2704 
2705   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
2706   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
2707   PSOldGen* old_gen = heap->old_gen();
2708   old_gen->start_array()->reset();
2709   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2710   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2711   TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2712   ParallelTaskTerminator terminator(active_gc_threads, qset);
2713 
2714   GCTaskQueue* q = GCTaskQueue::create();
2715   enqueue_region_draining_tasks(q, active_gc_threads);
2716   enqueue_dense_prefix_tasks(q, active_gc_threads);
2717   enqueue_region_stealing_tasks(q, &terminator, active_gc_threads);
2718 
2719   {
2720     GCTraceTime tm_pc("par compact", print_phases(), true, &_gc_timer);
2721 
2722     gc_task_manager()->execute_and_wait(q);
2723 
2724 #ifdef  ASSERT
2725     // Verify that all regions have been processed before the deferred updates.
2726     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2727       verify_complete(SpaceId(id));
2728     }
2729 #endif
2730   }
2731 
2732   {
2733     // Update the deferred objects, if any.  Any compaction manager can be used.
2734     GCTraceTime tm_du("deferred updates", print_phases(), true, &_gc_timer);
2735     ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2736     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2737       update_deferred_objects(cm, SpaceId(id));
2738     }
2739   }
2740 
2741   DEBUG_ONLY(write_block_fill_histogram(gclog_or_tty));
2742 }
2743 
2744 #ifdef  ASSERT
2745 void PSParallelCompact::verify_complete(SpaceId space_id) {
2746   // All Regions between space bottom() to new_top() should be marked as filled
2747   // and all Regions between new_top() and top() should be available (i.e.,
2748   // should have been emptied).
2749   ParallelCompactData& sd = summary_data();
2750   SpaceInfo si = _space_info[space_id];
2751   HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2752   HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2753   const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2754   const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2755   const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2756 
2757   bool issued_a_warning = false;
2758 
2759   size_t cur_region;
2760   for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2761     const RegionData* const c = sd.region(cur_region);
2762     if (!c->completed()) {
2763       warning("region " SIZE_FORMAT " not filled:  "
2764               "destination_count=" SIZE_FORMAT,
2765               cur_region, c->destination_count());
2766       issued_a_warning = true;
2767     }
2768   }
2769 
2770   for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2771     const RegionData* const c = sd.region(cur_region);
2772     if (!c->available()) {
2773       warning("region " SIZE_FORMAT " not empty:   "
2774               "destination_count=" SIZE_FORMAT,
2775               cur_region, c->destination_count());
2776       issued_a_warning = true;
2777     }
2778   }
2779 
2780   if (issued_a_warning) {
2781     print_region_ranges();
2782   }
2783 }
2784 #endif  // #ifdef ASSERT
2785 
2786 // Update interior oops in the ranges of regions [beg_region, end_region).
2787 void
2788 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2789                                                        SpaceId space_id,
2790                                                        size_t beg_region,
2791                                                        size_t end_region) {
2792   ParallelCompactData& sd = summary_data();
2793   ParMarkBitMap* const mbm = mark_bitmap();
2794 
2795   HeapWord* beg_addr = sd.region_to_addr(beg_region);
2796   HeapWord* const end_addr = sd.region_to_addr(end_region);
2797   assert(beg_region <= end_region, "bad region range");
2798   assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2799 
2800 #ifdef  ASSERT
2801   // Claim the regions to avoid triggering an assert when they are marked as
2802   // filled.
2803   for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2804     assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2805   }
2806 #endif  // #ifdef ASSERT
2807 
2808   if (beg_addr != space(space_id)->bottom()) {
2809     // Find the first live object or block of dead space that *starts* in this
2810     // range of regions.  If a partial object crosses onto the region, skip it;
2811     // it will be marked for 'deferred update' when the object head is
2812     // processed.  If dead space crosses onto the region, it is also skipped; it
2813     // will be filled when the prior region is processed.  If neither of those
2814     // apply, the first word in the region is the start of a live object or dead
2815     // space.
2816     assert(beg_addr > space(space_id)->bottom(), "sanity");
2817     const RegionData* const cp = sd.region(beg_region);
2818     if (cp->partial_obj_size() != 0) {
2819       beg_addr = sd.partial_obj_end(beg_region);
2820     } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2821       beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2822     }
2823   }
2824 
2825   if (beg_addr < end_addr) {
2826     // A live object or block of dead space starts in this range of Regions.
2827      HeapWord* const dense_prefix_end = dense_prefix(space_id);
2828 
2829     // Create closures and iterate.
2830     UpdateOnlyClosure update_closure(mbm, cm, space_id);
2831     FillClosure fill_closure(cm, space_id);
2832     ParMarkBitMap::IterationStatus status;
2833     status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2834                           dense_prefix_end);
2835     if (status == ParMarkBitMap::incomplete) {
2836       update_closure.do_addr(update_closure.source());
2837     }
2838   }
2839 
2840   // Mark the regions as filled.
2841   RegionData* const beg_cp = sd.region(beg_region);
2842   RegionData* const end_cp = sd.region(end_region);
2843   for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2844     cp->set_completed();
2845   }
2846 }
2847 
2848 // Return the SpaceId for the space containing addr.  If addr is not in the
2849 // heap, last_space_id is returned.  In debug mode it expects the address to be
2850 // in the heap and asserts such.
2851 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2852   assert(Universe::heap()->is_in_reserved(addr), "addr not in the heap");
2853 
2854   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2855     if (_space_info[id].space()->contains(addr)) {
2856       return SpaceId(id);
2857     }
2858   }
2859 
2860   assert(false, "no space contains the addr");
2861   return last_space_id;
2862 }
2863 
2864 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2865                                                 SpaceId id) {
2866   assert(id < last_space_id, "bad space id");
2867 
2868   ParallelCompactData& sd = summary_data();
2869   const SpaceInfo* const space_info = _space_info + id;
2870   ObjectStartArray* const start_array = space_info->start_array();
2871 
2872   const MutableSpace* const space = space_info->space();
2873   assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2874   HeapWord* const beg_addr = space_info->dense_prefix();
2875   HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2876 
2877   const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2878   const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2879   const RegionData* cur_region;
2880   for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2881     HeapWord* const addr = cur_region->deferred_obj_addr();
2882     if (addr != NULL) {
2883       if (start_array != NULL) {
2884         start_array->allocate_block(addr);
2885       }
2886       oop(addr)->update_contents(cm);
2887       assert(oop(addr)->is_oop_or_null(), "should be an oop now");
2888     }
2889   }
2890 }
2891 
2892 // Skip over count live words starting from beg, and return the address of the
2893 // next live word.  Unless marked, the word corresponding to beg is assumed to
2894 // be dead.  Callers must either ensure beg does not correspond to the middle of
2895 // an object, or account for those live words in some other way.  Callers must
2896 // also ensure that there are enough live words in the range [beg, end) to skip.
2897 HeapWord*
2898 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2899 {
2900   assert(count > 0, "sanity");
2901 
2902   ParMarkBitMap* m = mark_bitmap();
2903   idx_t bits_to_skip = m->words_to_bits(count);
2904   idx_t cur_beg = m->addr_to_bit(beg);
2905   const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end));
2906 
2907   do {
2908     cur_beg = m->find_obj_beg(cur_beg, search_end);
2909     idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2910     const size_t obj_bits = cur_end - cur_beg + 1;
2911     if (obj_bits > bits_to_skip) {
2912       return m->bit_to_addr(cur_beg + bits_to_skip);
2913     }
2914     bits_to_skip -= obj_bits;
2915     cur_beg = cur_end + 1;
2916   } while (bits_to_skip > 0);
2917 
2918   // Skipping the desired number of words landed just past the end of an object.
2919   // Find the start of the next object.
2920   cur_beg = m->find_obj_beg(cur_beg, search_end);
2921   assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2922   return m->bit_to_addr(cur_beg);
2923 }
2924 
2925 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2926                                             SpaceId src_space_id,
2927                                             size_t src_region_idx)
2928 {
2929   assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2930 
2931   const SplitInfo& split_info = _space_info[src_space_id].split_info();
2932   if (split_info.dest_region_addr() == dest_addr) {
2933     // The partial object ending at the split point contains the first word to
2934     // be copied to dest_addr.
2935     return split_info.first_src_addr();
2936   }
2937 
2938   const ParallelCompactData& sd = summary_data();
2939   ParMarkBitMap* const bitmap = mark_bitmap();
2940   const size_t RegionSize = ParallelCompactData::RegionSize;
2941 
2942   assert(sd.is_region_aligned(dest_addr), "not aligned");
2943   const RegionData* const src_region_ptr = sd.region(src_region_idx);
2944   const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2945   HeapWord* const src_region_destination = src_region_ptr->destination();
2946 
2947   assert(dest_addr >= src_region_destination, "wrong src region");
2948   assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2949 
2950   HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2951   HeapWord* const src_region_end = src_region_beg + RegionSize;
2952 
2953   HeapWord* addr = src_region_beg;
2954   if (dest_addr == src_region_destination) {
2955     // Return the first live word in the source region.
2956     if (partial_obj_size == 0) {
2957       addr = bitmap->find_obj_beg(addr, src_region_end);
2958       assert(addr < src_region_end, "no objects start in src region");
2959     }
2960     return addr;
2961   }
2962 
2963   // Must skip some live data.
2964   size_t words_to_skip = dest_addr - src_region_destination;
2965   assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2966 
2967   if (partial_obj_size >= words_to_skip) {
2968     // All the live words to skip are part of the partial object.
2969     addr += words_to_skip;
2970     if (partial_obj_size == words_to_skip) {
2971       // Find the first live word past the partial object.
2972       addr = bitmap->find_obj_beg(addr, src_region_end);
2973       assert(addr < src_region_end, "wrong src region");
2974     }
2975     return addr;
2976   }
2977 
2978   // Skip over the partial object (if any).
2979   if (partial_obj_size != 0) {
2980     words_to_skip -= partial_obj_size;
2981     addr += partial_obj_size;
2982   }
2983 
2984   // Skip over live words due to objects that start in the region.
2985   addr = skip_live_words(addr, src_region_end, words_to_skip);
2986   assert(addr < src_region_end, "wrong src region");
2987   return addr;
2988 }
2989 
2990 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2991                                                      SpaceId src_space_id,
2992                                                      size_t beg_region,
2993                                                      HeapWord* end_addr)
2994 {
2995   ParallelCompactData& sd = summary_data();
2996 
2997 #ifdef ASSERT
2998   MutableSpace* const src_space = _space_info[src_space_id].space();
2999   HeapWord* const beg_addr = sd.region_to_addr(beg_region);
3000   assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
3001          "src_space_id does not match beg_addr");
3002   assert(src_space->contains(end_addr) || end_addr == src_space->end(),
3003          "src_space_id does not match end_addr");
3004 #endif // #ifdef ASSERT
3005 
3006   RegionData* const beg = sd.region(beg_region);
3007   RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
3008 
3009   // Regions up to new_top() are enqueued if they become available.
3010   HeapWord* const new_top = _space_info[src_space_id].new_top();
3011   RegionData* const enqueue_end =
3012     sd.addr_to_region_ptr(sd.region_align_up(new_top));
3013 
3014   for (RegionData* cur = beg; cur < end; ++cur) {
3015     assert(cur->data_size() > 0, "region must have live data");
3016     cur->decrement_destination_count();
3017     if (cur < enqueue_end && cur->available() && cur->claim()) {
3018       cm->push_region(sd.region(cur));
3019     }
3020   }
3021 }
3022 
3023 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
3024                                           SpaceId& src_space_id,
3025                                           HeapWord*& src_space_top,
3026                                           HeapWord* end_addr)
3027 {
3028   typedef ParallelCompactData::RegionData RegionData;
3029 
3030   ParallelCompactData& sd = PSParallelCompact::summary_data();
3031   const size_t region_size = ParallelCompactData::RegionSize;
3032 
3033   size_t src_region_idx = 0;
3034 
3035   // Skip empty regions (if any) up to the top of the space.
3036   HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
3037   RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
3038   HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
3039   const RegionData* const top_region_ptr =
3040     sd.addr_to_region_ptr(top_aligned_up);
3041   while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
3042     ++src_region_ptr;
3043   }
3044 
3045   if (src_region_ptr < top_region_ptr) {
3046     // The next source region is in the current space.  Update src_region_idx
3047     // and the source address to match src_region_ptr.
3048     src_region_idx = sd.region(src_region_ptr);
3049     HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
3050     if (src_region_addr > closure.source()) {
3051       closure.set_source(src_region_addr);
3052     }
3053     return src_region_idx;
3054   }
3055 
3056   // Switch to a new source space and find the first non-empty region.
3057   unsigned int space_id = src_space_id + 1;
3058   assert(space_id < last_space_id, "not enough spaces");
3059 
3060   HeapWord* const destination = closure.destination();
3061 
3062   do {
3063     MutableSpace* space = _space_info[space_id].space();
3064     HeapWord* const bottom = space->bottom();
3065     const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
3066 
3067     // Iterate over the spaces that do not compact into themselves.
3068     if (bottom_cp->destination() != bottom) {
3069       HeapWord* const top_aligned_up = sd.region_align_up(space->top());
3070       const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
3071 
3072       for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
3073         if (src_cp->live_obj_size() > 0) {
3074           // Found it.
3075           assert(src_cp->destination() == destination,
3076                  "first live obj in the space must match the destination");
3077           assert(src_cp->partial_obj_size() == 0,
3078                  "a space cannot begin with a partial obj");
3079 
3080           src_space_id = SpaceId(space_id);
3081           src_space_top = space->top();
3082           const size_t src_region_idx = sd.region(src_cp);
3083           closure.set_source(sd.region_to_addr(src_region_idx));
3084           return src_region_idx;
3085         } else {
3086           assert(src_cp->data_size() == 0, "sanity");
3087         }
3088       }
3089     }
3090   } while (++space_id < last_space_id);
3091 
3092   assert(false, "no source region was found");
3093   return 0;
3094 }
3095 
3096 void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx)
3097 {
3098   typedef ParMarkBitMap::IterationStatus IterationStatus;
3099   const size_t RegionSize = ParallelCompactData::RegionSize;
3100   ParMarkBitMap* const bitmap = mark_bitmap();
3101   ParallelCompactData& sd = summary_data();
3102   RegionData* const region_ptr = sd.region(region_idx);
3103 
3104   // Get the items needed to construct the closure.
3105   HeapWord* dest_addr = sd.region_to_addr(region_idx);
3106   SpaceId dest_space_id = space_id(dest_addr);
3107   ObjectStartArray* start_array = _space_info[dest_space_id].start_array();
3108   HeapWord* new_top = _space_info[dest_space_id].new_top();
3109   assert(dest_addr < new_top, "sanity");
3110   const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize);
3111 
3112   // Get the source region and related info.
3113   size_t src_region_idx = region_ptr->source_region();
3114   SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
3115   HeapWord* src_space_top = _space_info[src_space_id].space()->top();
3116 
3117   MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3118   closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
3119 
3120   // Adjust src_region_idx to prepare for decrementing destination counts (the
3121   // destination count is not decremented when a region is copied to itself).
3122   if (src_region_idx == region_idx) {
3123     src_region_idx += 1;
3124   }
3125 
3126   if (bitmap->is_unmarked(closure.source())) {
3127     // The first source word is in the middle of an object; copy the remainder
3128     // of the object or as much as will fit.  The fact that pointer updates were
3129     // deferred will be noted when the object header is processed.
3130     HeapWord* const old_src_addr = closure.source();
3131     closure.copy_partial_obj();
3132     if (closure.is_full()) {
3133       decrement_destination_counts(cm, src_space_id, src_region_idx,
3134                                    closure.source());
3135       region_ptr->set_deferred_obj_addr(NULL);
3136       region_ptr->set_completed();
3137       return;
3138     }
3139 
3140     HeapWord* const end_addr = sd.region_align_down(closure.source());
3141     if (sd.region_align_down(old_src_addr) != end_addr) {
3142       // The partial object was copied from more than one source region.
3143       decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3144 
3145       // Move to the next source region, possibly switching spaces as well.  All
3146       // args except end_addr may be modified.
3147       src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3148                                        end_addr);
3149     }
3150   }
3151 
3152   do {
3153     HeapWord* const cur_addr = closure.source();
3154     HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
3155                                     src_space_top);
3156     IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
3157 
3158     if (status == ParMarkBitMap::incomplete) {
3159       // The last obj that starts in the source region does not end in the
3160       // region.
3161       assert(closure.source() < end_addr, "sanity");
3162       HeapWord* const obj_beg = closure.source();
3163       HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
3164                                        src_space_top);
3165       HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
3166       if (obj_end < range_end) {
3167         // The end was found; the entire object will fit.
3168         status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
3169         assert(status != ParMarkBitMap::would_overflow, "sanity");
3170       } else {
3171         // The end was not found; the object will not fit.
3172         assert(range_end < src_space_top, "obj cannot cross space boundary");
3173         status = ParMarkBitMap::would_overflow;
3174       }
3175     }
3176 
3177     if (status == ParMarkBitMap::would_overflow) {
3178       // The last object did not fit.  Note that interior oop updates were
3179       // deferred, then copy enough of the object to fill the region.
3180       region_ptr->set_deferred_obj_addr(closure.destination());
3181       status = closure.copy_until_full(); // copies from closure.source()
3182 
3183       decrement_destination_counts(cm, src_space_id, src_region_idx,
3184                                    closure.source());
3185       region_ptr->set_completed();
3186       return;
3187     }
3188 
3189     if (status == ParMarkBitMap::full) {
3190       decrement_destination_counts(cm, src_space_id, src_region_idx,
3191                                    closure.source());
3192       region_ptr->set_deferred_obj_addr(NULL);
3193       region_ptr->set_completed();
3194       return;
3195     }
3196 
3197     decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3198 
3199     // Move to the next source region, possibly switching spaces as well.  All
3200     // args except end_addr may be modified.
3201     src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3202                                      end_addr);
3203   } while (true);
3204 }
3205 
3206 void PSParallelCompact::fill_blocks(size_t region_idx)
3207 {
3208   // Fill in the block table elements for the specified region.  Each block
3209   // table element holds the number of live words in the region that are to the
3210   // left of the first object that starts in the block.  Thus only blocks in
3211   // which an object starts need to be filled.
3212   //
3213   // The algorithm scans the section of the bitmap that corresponds to the
3214   // region, keeping a running total of the live words.  When an object start is
3215   // found, if it's the first to start in the block that contains it, the
3216   // current total is written to the block table element.
3217   const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
3218   const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
3219   const size_t RegionSize = ParallelCompactData::RegionSize;
3220 
3221   ParallelCompactData& sd = summary_data();
3222   const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
3223   if (partial_obj_size >= RegionSize) {
3224     return; // No objects start in this region.
3225   }
3226 
3227   // Ensure the first loop iteration decides that the block has changed.
3228   size_t cur_block = sd.block_count();
3229 
3230   const ParMarkBitMap* const bitmap = mark_bitmap();
3231 
3232   const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
3233   assert((size_t)1 << Log2BitsPerBlock ==
3234          bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
3235 
3236   size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
3237   const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
3238   size_t live_bits = bitmap->words_to_bits(partial_obj_size);
3239   beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
3240   while (beg_bit < range_end) {
3241     const size_t new_block = beg_bit >> Log2BitsPerBlock;
3242     if (new_block != cur_block) {
3243       cur_block = new_block;
3244       sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
3245     }
3246 
3247     const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
3248     if (end_bit < range_end - 1) {
3249       live_bits += end_bit - beg_bit + 1;
3250       beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
3251     } else {
3252       return;
3253     }
3254   }
3255 }
3256 
3257 void
3258 PSParallelCompact::move_and_update(ParCompactionManager* cm, SpaceId space_id) {
3259   const MutableSpace* sp = space(space_id);
3260   if (sp->is_empty()) {
3261     return;
3262   }
3263 
3264   ParallelCompactData& sd = PSParallelCompact::summary_data();
3265   ParMarkBitMap* const bitmap = mark_bitmap();
3266   HeapWord* const dp_addr = dense_prefix(space_id);
3267   HeapWord* beg_addr = sp->bottom();
3268   HeapWord* end_addr = sp->top();
3269 
3270   assert(beg_addr <= dp_addr && dp_addr <= end_addr, "bad dense prefix");
3271 
3272   const size_t beg_region = sd.addr_to_region_idx(beg_addr);
3273   const size_t dp_region = sd.addr_to_region_idx(dp_addr);
3274   if (beg_region < dp_region) {
3275     update_and_deadwood_in_dense_prefix(cm, space_id, beg_region, dp_region);
3276   }
3277 
3278   // The destination of the first live object that starts in the region is one
3279   // past the end of the partial object entering the region (if any).
3280   HeapWord* const dest_addr = sd.partial_obj_end(dp_region);
3281   HeapWord* const new_top = _space_info[space_id].new_top();
3282   assert(new_top >= dest_addr, "bad new_top value");
3283   const size_t words = pointer_delta(new_top, dest_addr);
3284 
3285   if (words > 0) {
3286     ObjectStartArray* start_array = _space_info[space_id].start_array();
3287     MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3288 
3289     ParMarkBitMap::IterationStatus status;
3290     status = bitmap->iterate(&closure, dest_addr, end_addr);
3291     assert(status == ParMarkBitMap::full, "iteration not complete");
3292     assert(bitmap->find_obj_beg(closure.source(), end_addr) == end_addr,
3293            "live objects skipped because closure is full");
3294   }
3295 }
3296 
3297 jlong PSParallelCompact::millis_since_last_gc() {
3298   // We need a monotonically non-decreasing time in ms but
3299   // os::javaTimeMillis() does not guarantee monotonicity.
3300   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3301   jlong ret_val = now - _time_of_last_gc;
3302   // XXX See note in genCollectedHeap::millis_since_last_gc().
3303   if (ret_val < 0) {
3304     NOT_PRODUCT(warning("time warp: "INT64_FORMAT, ret_val);)
3305     return 0;
3306   }
3307   return ret_val;
3308 }
3309 
3310 void PSParallelCompact::reset_millis_since_last_gc() {
3311   // We need a monotonically non-decreasing time in ms but
3312   // os::javaTimeMillis() does not guarantee monotonicity.
3313   _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3314 }
3315 
3316 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3317 {
3318   if (source() != destination()) {
3319     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3320     Copy::aligned_conjoint_words(source(), destination(), words_remaining());
3321   }
3322   update_state(words_remaining());
3323   assert(is_full(), "sanity");
3324   return ParMarkBitMap::full;
3325 }
3326 
3327 void MoveAndUpdateClosure::copy_partial_obj()
3328 {
3329   size_t words = words_remaining();
3330 
3331   HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3332   HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3333   if (end_addr < range_end) {
3334     words = bitmap()->obj_size(source(), end_addr);
3335   }
3336 
3337   // This test is necessary; if omitted, the pointer updates to a partial object
3338   // that crosses the dense prefix boundary could be overwritten.
3339   if (source() != destination()) {
3340     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3341     Copy::aligned_conjoint_words(source(), destination(), words);
3342   }
3343   update_state(words);
3344 }
3345 
3346 ParMarkBitMapClosure::IterationStatus
3347 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3348   assert(destination() != NULL, "sanity");
3349   assert(bitmap()->obj_size(addr) == words, "bad size");
3350 
3351   _source = addr;
3352   assert(PSParallelCompact::summary_data().calc_new_pointer(source()) ==
3353          destination(), "wrong destination");
3354 
3355   if (words > words_remaining()) {
3356     return ParMarkBitMap::would_overflow;
3357   }
3358 
3359   // The start_array must be updated even if the object is not moving.
3360   if (_start_array != NULL) {
3361     _start_array->allocate_block(destination());
3362   }
3363 
3364   if (destination() != source()) {
3365     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3366     Copy::aligned_conjoint_words(source(), destination(), words);
3367   }
3368 
3369   oop moved_oop = (oop) destination();
3370   moved_oop->update_contents(compaction_manager());
3371   assert(moved_oop->is_oop_or_null(), "Object should be whole at this point");
3372 
3373   update_state(words);
3374   assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
3375   return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3376 }
3377 
3378 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3379                                      ParCompactionManager* cm,
3380                                      PSParallelCompact::SpaceId space_id) :
3381   ParMarkBitMapClosure(mbm, cm),
3382   _space_id(space_id),
3383   _start_array(PSParallelCompact::start_array(space_id))
3384 {
3385 }
3386 
3387 // Updates the references in the object to their new values.
3388 ParMarkBitMapClosure::IterationStatus
3389 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3390   do_addr(addr);
3391   return ParMarkBitMap::incomplete;
3392 }