1 /*
   2  * Copyright (c) 2005, 2015, 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.inline.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/instanceKlass.inline.hpp"
  52 #include "oops/instanceMirrorKlass.inline.hpp"
  53 #include "oops/methodData.hpp"
  54 #include "oops/objArrayKlass.inline.hpp"
  55 #include "oops/oop.inline.hpp"
  56 #include "runtime/atomic.inline.hpp"
  57 #include "runtime/fprofiler.hpp"
  58 #include "runtime/safepoint.hpp"
  59 #include "runtime/vmThread.hpp"
  60 #include "services/management.hpp"
  61 #include "services/memoryService.hpp"
  62 #include "services/memTracker.hpp"
  63 #include "utilities/events.hpp"
  64 #include "utilities/stack.inline.hpp"
  65 
  66 #include <math.h>
  67 
  68 // All sizes are in HeapWords.
  69 const size_t ParallelCompactData::Log2RegionSize  = 16; // 64K words
  70 const size_t ParallelCompactData::RegionSize      = (size_t)1 << Log2RegionSize;
  71 const size_t ParallelCompactData::RegionSizeBytes =
  72   RegionSize << LogHeapWordSize;
  73 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
  74 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
  75 const size_t ParallelCompactData::RegionAddrMask       = ~RegionAddrOffsetMask;
  76 
  77 const size_t ParallelCompactData::Log2BlockSize   = 7; // 128 words
  78 const size_t ParallelCompactData::BlockSize       = (size_t)1 << Log2BlockSize;
  79 const size_t ParallelCompactData::BlockSizeBytes  =
  80   BlockSize << LogHeapWordSize;
  81 const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
  82 const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
  83 const size_t ParallelCompactData::BlockAddrMask       = ~BlockAddrOffsetMask;
  84 
  85 const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
  86 const size_t ParallelCompactData::Log2BlocksPerRegion =
  87   Log2RegionSize - Log2BlockSize;
  88 
  89 const ParallelCompactData::RegionData::region_sz_t
  90 ParallelCompactData::RegionData::dc_shift = 27;
  91 
  92 const ParallelCompactData::RegionData::region_sz_t
  93 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
  94 
  95 const ParallelCompactData::RegionData::region_sz_t
  96 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
  97 
  98 const ParallelCompactData::RegionData::region_sz_t
  99 ParallelCompactData::RegionData::los_mask = ~dc_mask;
 100 
 101 const ParallelCompactData::RegionData::region_sz_t
 102 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
 103 
 104 const ParallelCompactData::RegionData::region_sz_t
 105 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
 106 
 107 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
 108 bool      PSParallelCompact::_print_phases = false;
 109 
 110 ReferenceProcessor* PSParallelCompact::_ref_processor = 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, p2i(c->data_location()), dci, p2i(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, p2i(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_aligned(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, p2i(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, p2i(split_destination),
 641                            addr_to_region_idx(split_destination),
 642                            p2i(*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                              p2i(po_beg), addr_to_region_idx(po_beg),
 652                              p2i(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                   p2i(source_beg), p2i(source_end), p2i(source_next_val),
 670                   p2i(target_beg), p2i(target_end), p2i(*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(ParallelScavengeHeap::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 PSParallelCompact::AdjustPointerClosure PSParallelCompact::_adjust_pointer_closure;
 823 PSParallelCompact::AdjustKlassClosure PSParallelCompact::_adjust_klass_closure;
 824 
 825 void PSParallelCompact::AdjustKlassClosure::do_klass(Klass* klass) {
 826   klass->oops_do(&PSParallelCompact::_adjust_pointer_closure);
 827 }
 828 
 829 void PSParallelCompact::post_initialize() {
 830   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 831   MemRegion mr = heap->reserved_region();
 832   _ref_processor =
 833     new ReferenceProcessor(mr,            // span
 834                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 835                            (int) ParallelGCThreads, // mt processing degree
 836                            true,          // mt discovery
 837                            (int) ParallelGCThreads, // mt discovery degree
 838                            true,          // atomic_discovery
 839                            &_is_alive_closure); // non-header is alive closure
 840   _counters = new CollectorCounters("PSParallelCompact", 1);
 841 
 842   // Initialize static fields in ParCompactionManager.
 843   ParCompactionManager::initialize(mark_bitmap());
 844 }
 845 
 846 bool PSParallelCompact::initialize() {
 847   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 848   MemRegion mr = heap->reserved_region();
 849 
 850   // Was the old gen get allocated successfully?
 851   if (!heap->old_gen()->is_allocated()) {
 852     return false;
 853   }
 854 
 855   initialize_space_info();
 856   initialize_dead_wood_limiter();
 857 
 858   if (!_mark_bitmap.initialize(mr)) {
 859     vm_shutdown_during_initialization(
 860       err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
 861       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 862       _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
 863     return false;
 864   }
 865 
 866   if (!_summary_data.initialize(mr)) {
 867     vm_shutdown_during_initialization(
 868       err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
 869       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 870       _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
 871     return false;
 872   }
 873 
 874   return true;
 875 }
 876 
 877 void PSParallelCompact::initialize_space_info()
 878 {
 879   memset(&_space_info, 0, sizeof(_space_info));
 880 
 881   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 882   PSYoungGen* young_gen = heap->young_gen();
 883 
 884   _space_info[old_space_id].set_space(heap->old_gen()->object_space());
 885   _space_info[eden_space_id].set_space(young_gen->eden_space());
 886   _space_info[from_space_id].set_space(young_gen->from_space());
 887   _space_info[to_space_id].set_space(young_gen->to_space());
 888 
 889   _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
 890 }
 891 
 892 void PSParallelCompact::initialize_dead_wood_limiter()
 893 {
 894   const size_t max = 100;
 895   _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
 896   _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
 897   _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
 898   DEBUG_ONLY(_dwl_initialized = true;)
 899   _dwl_adjustment = normal_distribution(1.0);
 900 }
 901 
 902 // Simple class for storing info about the heap at the start of GC, to be used
 903 // after GC for comparison/printing.
 904 class PreGCValues {
 905 public:
 906   PreGCValues() { }
 907   PreGCValues(ParallelScavengeHeap* heap) { fill(heap); }
 908 
 909   void fill(ParallelScavengeHeap* heap) {
 910     _heap_used      = heap->used();
 911     _young_gen_used = heap->young_gen()->used_in_bytes();
 912     _old_gen_used   = heap->old_gen()->used_in_bytes();
 913     _metadata_used  = MetaspaceAux::used_bytes();
 914   };
 915 
 916   size_t heap_used() const      { return _heap_used; }
 917   size_t young_gen_used() const { return _young_gen_used; }
 918   size_t old_gen_used() const   { return _old_gen_used; }
 919   size_t metadata_used() const  { return _metadata_used; }
 920 
 921 private:
 922   size_t _heap_used;
 923   size_t _young_gen_used;
 924   size_t _old_gen_used;
 925   size_t _metadata_used;
 926 };
 927 
 928 void
 929 PSParallelCompact::clear_data_covering_space(SpaceId id)
 930 {
 931   // At this point, top is the value before GC, new_top() is the value that will
 932   // be set at the end of GC.  The marking bitmap is cleared to top; nothing
 933   // should be marked above top.  The summary data is cleared to the larger of
 934   // top & new_top.
 935   MutableSpace* const space = _space_info[id].space();
 936   HeapWord* const bot = space->bottom();
 937   HeapWord* const top = space->top();
 938   HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
 939 
 940   const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
 941   const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top));
 942   _mark_bitmap.clear_range(beg_bit, end_bit);
 943 
 944   const size_t beg_region = _summary_data.addr_to_region_idx(bot);
 945   const size_t end_region =
 946     _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
 947   _summary_data.clear_range(beg_region, end_region);
 948 
 949   // Clear the data used to 'split' regions.
 950   SplitInfo& split_info = _space_info[id].split_info();
 951   if (split_info.is_valid()) {
 952     split_info.clear();
 953   }
 954   DEBUG_ONLY(split_info.verify_clear();)
 955 }
 956 
 957 void PSParallelCompact::pre_compact(PreGCValues* pre_gc_values)
 958 {
 959   // Update the from & to space pointers in space_info, since they are swapped
 960   // at each young gen gc.  Do the update unconditionally (even though a
 961   // promotion failure does not swap spaces) because an unknown number of minor
 962   // collections will have swapped the spaces an unknown number of times.
 963   GCTraceTime tm("pre compact", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
 964   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 965   _space_info[from_space_id].set_space(heap->young_gen()->from_space());
 966   _space_info[to_space_id].set_space(heap->young_gen()->to_space());
 967 
 968   pre_gc_values->fill(heap);
 969 
 970   DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
 971   DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
 972 
 973   // Increment the invocation count
 974   heap->increment_total_collections(true);
 975 
 976   // We need to track unique mark sweep invocations as well.
 977   _total_invocations++;
 978 
 979   heap->print_heap_before_gc();
 980   heap->trace_heap_before_gc(&_gc_tracer);
 981 
 982   // Fill in TLABs
 983   heap->accumulate_statistics_all_tlabs();
 984   heap->ensure_parsability(true);  // retire TLABs
 985 
 986   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 987     HandleMark hm;  // Discard invalid handles created during verification
 988     Universe::verify(" VerifyBeforeGC:");
 989   }
 990 
 991   // Verify object start arrays
 992   if (VerifyObjectStartArray &&
 993       VerifyBeforeGC) {
 994     heap->old_gen()->verify_object_start_array();
 995   }
 996 
 997   DEBUG_ONLY(mark_bitmap()->verify_clear();)
 998   DEBUG_ONLY(summary_data().verify_clear();)
 999 
1000   // Have worker threads release resources the next time they run a task.
1001   gc_task_manager()->release_all_resources();
1002 }
1003 
1004 void PSParallelCompact::post_compact()
1005 {
1006   GCTraceTime tm("post compact", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
1007 
1008   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1009     // Clear the marking bitmap, summary data and split info.
1010     clear_data_covering_space(SpaceId(id));
1011     // Update top().  Must be done after clearing the bitmap and summary data.
1012     _space_info[id].publish_new_top();
1013   }
1014 
1015   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1016   MutableSpace* const from_space = _space_info[from_space_id].space();
1017   MutableSpace* const to_space   = _space_info[to_space_id].space();
1018 
1019   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1020   bool eden_empty = eden_space->is_empty();
1021   if (!eden_empty) {
1022     eden_empty = absorb_live_data_from_eden(heap->size_policy(),
1023                                             heap->young_gen(), heap->old_gen());
1024   }
1025 
1026   // Update heap occupancy information which is used as input to the soft ref
1027   // clearing policy at the next gc.
1028   Universe::update_heap_info_at_gc();
1029 
1030   bool young_gen_empty = eden_empty && from_space->is_empty() &&
1031     to_space->is_empty();
1032 
1033   ModRefBarrierSet* modBS = barrier_set_cast<ModRefBarrierSet>(heap->barrier_set());
1034   MemRegion old_mr = heap->old_gen()->reserved();
1035   if (young_gen_empty) {
1036     modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
1037   } else {
1038     modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1039   }
1040 
1041   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1042   ClassLoaderDataGraph::purge();
1043   MetaspaceAux::verify_metrics();
1044 
1045   CodeCache::gc_epilogue();
1046   JvmtiExport::gc_epilogue();
1047 
1048   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1049 
1050   ref_processor()->enqueue_discovered_references(NULL);
1051 
1052   if (ZapUnusedHeapArea) {
1053     heap->gen_mangle_unused_area();
1054   }
1055 
1056   // Update time of last GC
1057   reset_millis_since_last_gc();
1058 }
1059 
1060 HeapWord*
1061 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1062                                                     bool maximum_compaction)
1063 {
1064   const size_t region_size = ParallelCompactData::RegionSize;
1065   const ParallelCompactData& sd = summary_data();
1066 
1067   const MutableSpace* const space = _space_info[id].space();
1068   HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1069   const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1070   const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1071 
1072   // Skip full regions at the beginning of the space--they are necessarily part
1073   // of the dense prefix.
1074   size_t full_count = 0;
1075   const RegionData* cp;
1076   for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1077     ++full_count;
1078   }
1079 
1080   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1081   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1082   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1083   if (maximum_compaction || cp == end_cp || interval_ended) {
1084     _maximum_compaction_gc_num = total_invocations();
1085     return sd.region_to_addr(cp);
1086   }
1087 
1088   HeapWord* const new_top = _space_info[id].new_top();
1089   const size_t space_live = pointer_delta(new_top, space->bottom());
1090   const size_t space_used = space->used_in_words();
1091   const size_t space_capacity = space->capacity_in_words();
1092 
1093   const double cur_density = double(space_live) / space_capacity;
1094   const double deadwood_density =
1095     (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1096   const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1097 
1098   if (TraceParallelOldGCDensePrefix) {
1099     tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1100                   cur_density, deadwood_density, deadwood_goal);
1101     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1102                   "space_cap=" SIZE_FORMAT,
1103                   space_live, space_used,
1104                   space_capacity);
1105   }
1106 
1107   // XXX - Use binary search?
1108   HeapWord* dense_prefix = sd.region_to_addr(cp);
1109   const RegionData* full_cp = cp;
1110   const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1111   while (cp < end_cp) {
1112     HeapWord* region_destination = cp->destination();
1113     const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1114     if (TraceParallelOldGCDensePrefix && Verbose) {
1115       tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1116                     "dp=" PTR_FORMAT " " "cdw=" SIZE_FORMAT_W(8),
1117                     sd.region(cp), p2i(region_destination),
1118                     p2i(dense_prefix), cur_deadwood);
1119     }
1120 
1121     if (cur_deadwood >= deadwood_goal) {
1122       // Found the region that has the correct amount of deadwood to the left.
1123       // This typically occurs after crossing a fairly sparse set of regions, so
1124       // iterate backwards over those sparse regions, looking for the region
1125       // that has the lowest density of live objects 'to the right.'
1126       size_t space_to_left = sd.region(cp) * region_size;
1127       size_t live_to_left = space_to_left - cur_deadwood;
1128       size_t space_to_right = space_capacity - space_to_left;
1129       size_t live_to_right = space_live - live_to_left;
1130       double density_to_right = double(live_to_right) / space_to_right;
1131       while (cp > full_cp) {
1132         --cp;
1133         const size_t prev_region_live_to_right = live_to_right -
1134           cp->data_size();
1135         const size_t prev_region_space_to_right = space_to_right + region_size;
1136         double prev_region_density_to_right =
1137           double(prev_region_live_to_right) / prev_region_space_to_right;
1138         if (density_to_right <= prev_region_density_to_right) {
1139           return dense_prefix;
1140         }
1141         if (TraceParallelOldGCDensePrefix && Verbose) {
1142           tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1143                         "pc_d2r=%10.8f", sd.region(cp), density_to_right,
1144                         prev_region_density_to_right);
1145         }
1146         dense_prefix -= region_size;
1147         live_to_right = prev_region_live_to_right;
1148         space_to_right = prev_region_space_to_right;
1149         density_to_right = prev_region_density_to_right;
1150       }
1151       return dense_prefix;
1152     }
1153 
1154     dense_prefix += region_size;
1155     ++cp;
1156   }
1157 
1158   return dense_prefix;
1159 }
1160 
1161 #ifndef PRODUCT
1162 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1163                                                  const SpaceId id,
1164                                                  const bool maximum_compaction,
1165                                                  HeapWord* const addr)
1166 {
1167   const size_t region_idx = summary_data().addr_to_region_idx(addr);
1168   RegionData* const cp = summary_data().region(region_idx);
1169   const MutableSpace* const space = _space_info[id].space();
1170   HeapWord* const new_top = _space_info[id].new_top();
1171 
1172   const size_t space_live = pointer_delta(new_top, space->bottom());
1173   const size_t dead_to_left = pointer_delta(addr, cp->destination());
1174   const size_t space_cap = space->capacity_in_words();
1175   const double dead_to_left_pct = double(dead_to_left) / space_cap;
1176   const size_t live_to_right = new_top - cp->destination();
1177   const size_t dead_to_right = space->top() - addr - live_to_right;
1178 
1179   tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1180                 "spl=" SIZE_FORMAT " "
1181                 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1182                 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
1183                 " ratio=%10.8f",
1184                 algorithm, p2i(addr), region_idx,
1185                 space_live,
1186                 dead_to_left, dead_to_left_pct,
1187                 dead_to_right, live_to_right,
1188                 double(dead_to_right) / live_to_right);
1189 }
1190 #endif  // #ifndef PRODUCT
1191 
1192 // Return a fraction indicating how much of the generation can be treated as
1193 // "dead wood" (i.e., not reclaimed).  The function uses a normal distribution
1194 // based on the density of live objects in the generation to determine a limit,
1195 // which is then adjusted so the return value is min_percent when the density is
1196 // 1.
1197 //
1198 // The following table shows some return values for a different values of the
1199 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1200 // min_percent is 1.
1201 //
1202 //                          fraction allowed as dead wood
1203 //         -----------------------------------------------------------------
1204 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1205 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1206 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1207 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1208 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1209 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1210 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1211 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1212 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1213 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1214 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1215 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1216 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1217 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1218 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1219 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1220 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1221 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1222 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1223 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1224 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1225 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1226 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1227 
1228 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1229 {
1230   assert(_dwl_initialized, "uninitialized");
1231 
1232   // The raw limit is the value of the normal distribution at x = density.
1233   const double raw_limit = normal_distribution(density);
1234 
1235   // Adjust the raw limit so it becomes the minimum when the density is 1.
1236   //
1237   // First subtract the adjustment value (which is simply the precomputed value
1238   // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1239   // Then add the minimum value, so the minimum is returned when the density is
1240   // 1.  Finally, prevent negative values, which occur when the mean is not 0.5.
1241   const double min = double(min_percent) / 100.0;
1242   const double limit = raw_limit - _dwl_adjustment + min;
1243   return MAX2(limit, 0.0);
1244 }
1245 
1246 ParallelCompactData::RegionData*
1247 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1248                                            const RegionData* end)
1249 {
1250   const size_t region_size = ParallelCompactData::RegionSize;
1251   ParallelCompactData& sd = summary_data();
1252   size_t left = sd.region(beg);
1253   size_t right = end > beg ? sd.region(end) - 1 : left;
1254 
1255   // Binary search.
1256   while (left < right) {
1257     // Equivalent to (left + right) / 2, but does not overflow.
1258     const size_t middle = left + (right - left) / 2;
1259     RegionData* const middle_ptr = sd.region(middle);
1260     HeapWord* const dest = middle_ptr->destination();
1261     HeapWord* const addr = sd.region_to_addr(middle);
1262     assert(dest != NULL, "sanity");
1263     assert(dest <= addr, "must move left");
1264 
1265     if (middle > left && dest < addr) {
1266       right = middle - 1;
1267     } else if (middle < right && middle_ptr->data_size() == region_size) {
1268       left = middle + 1;
1269     } else {
1270       return middle_ptr;
1271     }
1272   }
1273   return sd.region(left);
1274 }
1275 
1276 ParallelCompactData::RegionData*
1277 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1278                                           const RegionData* end,
1279                                           size_t dead_words)
1280 {
1281   ParallelCompactData& sd = summary_data();
1282   size_t left = sd.region(beg);
1283   size_t right = end > beg ? sd.region(end) - 1 : left;
1284 
1285   // Binary search.
1286   while (left < right) {
1287     // Equivalent to (left + right) / 2, but does not overflow.
1288     const size_t middle = left + (right - left) / 2;
1289     RegionData* const middle_ptr = sd.region(middle);
1290     HeapWord* const dest = middle_ptr->destination();
1291     HeapWord* const addr = sd.region_to_addr(middle);
1292     assert(dest != NULL, "sanity");
1293     assert(dest <= addr, "must move left");
1294 
1295     const size_t dead_to_left = pointer_delta(addr, dest);
1296     if (middle > left && dead_to_left > dead_words) {
1297       right = middle - 1;
1298     } else if (middle < right && dead_to_left < dead_words) {
1299       left = middle + 1;
1300     } else {
1301       return middle_ptr;
1302     }
1303   }
1304   return sd.region(left);
1305 }
1306 
1307 // The result is valid during the summary phase, after the initial summarization
1308 // of each space into itself, and before final summarization.
1309 inline double
1310 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1311                                    HeapWord* const bottom,
1312                                    HeapWord* const top,
1313                                    HeapWord* const new_top)
1314 {
1315   ParallelCompactData& sd = summary_data();
1316 
1317   assert(cp != NULL, "sanity");
1318   assert(bottom != NULL, "sanity");
1319   assert(top != NULL, "sanity");
1320   assert(new_top != NULL, "sanity");
1321   assert(top >= new_top, "summary data problem?");
1322   assert(new_top > bottom, "space is empty; should not be here");
1323   assert(new_top >= cp->destination(), "sanity");
1324   assert(top >= sd.region_to_addr(cp), "sanity");
1325 
1326   HeapWord* const destination = cp->destination();
1327   const size_t dense_prefix_live  = pointer_delta(destination, bottom);
1328   const size_t compacted_region_live = pointer_delta(new_top, destination);
1329   const size_t compacted_region_used = pointer_delta(top,
1330                                                      sd.region_to_addr(cp));
1331   const size_t reclaimable = compacted_region_used - compacted_region_live;
1332 
1333   const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1334   return double(reclaimable) / divisor;
1335 }
1336 
1337 // Return the address of the end of the dense prefix, a.k.a. the start of the
1338 // compacted region.  The address is always on a region boundary.
1339 //
1340 // Completely full regions at the left are skipped, since no compaction can
1341 // occur in those regions.  Then the maximum amount of dead wood to allow is
1342 // computed, based on the density (amount live / capacity) of the generation;
1343 // the region with approximately that amount of dead space to the left is
1344 // identified as the limit region.  Regions between the last completely full
1345 // region and the limit region are scanned and the one that has the best
1346 // (maximum) reclaimed_ratio() is selected.
1347 HeapWord*
1348 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1349                                         bool maximum_compaction)
1350 {
1351   if (ParallelOldGCSplitALot) {
1352     if (_space_info[id].dense_prefix() != _space_info[id].space()->bottom()) {
1353       // The value was chosen to provoke splitting a young gen space; use it.
1354       return _space_info[id].dense_prefix();
1355     }
1356   }
1357 
1358   const size_t region_size = ParallelCompactData::RegionSize;
1359   const ParallelCompactData& sd = summary_data();
1360 
1361   const MutableSpace* const space = _space_info[id].space();
1362   HeapWord* const top = space->top();
1363   HeapWord* const top_aligned_up = sd.region_align_up(top);
1364   HeapWord* const new_top = _space_info[id].new_top();
1365   HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1366   HeapWord* const bottom = space->bottom();
1367   const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1368   const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1369   const RegionData* const new_top_cp =
1370     sd.addr_to_region_ptr(new_top_aligned_up);
1371 
1372   // Skip full regions at the beginning of the space--they are necessarily part
1373   // of the dense prefix.
1374   const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1375   assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1376          space->is_empty(), "no dead space allowed to the left");
1377   assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1378          "region must have dead space");
1379 
1380   // The gc number is saved whenever a maximum compaction is done, and used to
1381   // determine when the maximum compaction interval has expired.  This avoids
1382   // successive max compactions for different reasons.
1383   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1384   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1385   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1386     total_invocations() == HeapFirstMaximumCompactionCount;
1387   if (maximum_compaction || full_cp == top_cp || interval_ended) {
1388     _maximum_compaction_gc_num = total_invocations();
1389     return sd.region_to_addr(full_cp);
1390   }
1391 
1392   const size_t space_live = pointer_delta(new_top, bottom);
1393   const size_t space_used = space->used_in_words();
1394   const size_t space_capacity = space->capacity_in_words();
1395 
1396   const double density = double(space_live) / double(space_capacity);
1397   const size_t min_percent_free = MarkSweepDeadRatio;
1398   const double limiter = dead_wood_limiter(density, min_percent_free);
1399   const size_t dead_wood_max = space_used - space_live;
1400   const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1401                                       dead_wood_max);
1402 
1403   if (TraceParallelOldGCDensePrefix) {
1404     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1405                   "space_cap=" SIZE_FORMAT,
1406                   space_live, space_used,
1407                   space_capacity);
1408     tty->print_cr("dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
1409                   "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1410                   density, min_percent_free, limiter,
1411                   dead_wood_max, dead_wood_limit);
1412   }
1413 
1414   // Locate the region with the desired amount of dead space to the left.
1415   const RegionData* const limit_cp =
1416     dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1417 
1418   // Scan from the first region with dead space to the limit region and find the
1419   // one with the best (largest) reclaimed ratio.
1420   double best_ratio = 0.0;
1421   const RegionData* best_cp = full_cp;
1422   for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1423     double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1424     if (tmp_ratio > best_ratio) {
1425       best_cp = cp;
1426       best_ratio = tmp_ratio;
1427     }
1428   }
1429 
1430 #if     0
1431   // Something to consider:  if the region with the best ratio is 'close to' the
1432   // first region w/free space, choose the first region with free space
1433   // ("first-free").  The first-free region is usually near the start of the
1434   // heap, which means we are copying most of the heap already, so copy a bit
1435   // more to get complete compaction.
1436   if (pointer_delta(best_cp, full_cp, sizeof(RegionData)) < 4) {
1437     _maximum_compaction_gc_num = total_invocations();
1438     best_cp = full_cp;
1439   }
1440 #endif  // #if 0
1441 
1442   return sd.region_to_addr(best_cp);
1443 }
1444 
1445 #ifndef PRODUCT
1446 void
1447 PSParallelCompact::fill_with_live_objects(SpaceId id, HeapWord* const start,
1448                                           size_t words)
1449 {
1450   if (TraceParallelOldGCSummaryPhase) {
1451     tty->print_cr("fill_with_live_objects [" PTR_FORMAT " " PTR_FORMAT ") "
1452                   SIZE_FORMAT, p2i(start), p2i(start + words), words);
1453   }
1454 
1455   ObjectStartArray* const start_array = _space_info[id].start_array();
1456   CollectedHeap::fill_with_objects(start, words);
1457   for (HeapWord* p = start; p < start + words; p += oop(p)->size()) {
1458     _mark_bitmap.mark_obj(p, words);
1459     _summary_data.add_obj(p, words);
1460     start_array->allocate_block(p);
1461   }
1462 }
1463 
1464 void
1465 PSParallelCompact::summarize_new_objects(SpaceId id, HeapWord* start)
1466 {
1467   ParallelCompactData& sd = summary_data();
1468   MutableSpace* space = _space_info[id].space();
1469 
1470   // Find the source and destination start addresses.
1471   HeapWord* const src_addr = sd.region_align_down(start);
1472   HeapWord* dst_addr;
1473   if (src_addr < start) {
1474     dst_addr = sd.addr_to_region_ptr(src_addr)->destination();
1475   } else if (src_addr > space->bottom()) {
1476     // The start (the original top() value) is aligned to a region boundary so
1477     // the associated region does not have a destination.  Compute the
1478     // destination from the previous region.
1479     RegionData* const cp = sd.addr_to_region_ptr(src_addr) - 1;
1480     dst_addr = cp->destination() + cp->data_size();
1481   } else {
1482     // Filling the entire space.
1483     dst_addr = space->bottom();
1484   }
1485   assert(dst_addr != NULL, "sanity");
1486 
1487   // Update the summary data.
1488   bool result = _summary_data.summarize(_space_info[id].split_info(),
1489                                         src_addr, space->top(), NULL,
1490                                         dst_addr, space->end(),
1491                                         _space_info[id].new_top_addr());
1492   assert(result, "should not fail:  bad filler object size");
1493 }
1494 
1495 void
1496 PSParallelCompact::provoke_split_fill_survivor(SpaceId id)
1497 {
1498   if (total_invocations() % (ParallelOldGCSplitInterval * 3) != 0) {
1499     return;
1500   }
1501 
1502   MutableSpace* const space = _space_info[id].space();
1503   if (space->is_empty()) {
1504     HeapWord* b = space->bottom();
1505     HeapWord* t = b + space->capacity_in_words() / 2;
1506     space->set_top(t);
1507     if (ZapUnusedHeapArea) {
1508       space->set_top_for_allocations();
1509     }
1510 
1511     size_t min_size = CollectedHeap::min_fill_size();
1512     size_t obj_len = min_size;
1513     while (b + obj_len <= t) {
1514       CollectedHeap::fill_with_object(b, obj_len);
1515       mark_bitmap()->mark_obj(b, obj_len);
1516       summary_data().add_obj(b, obj_len);
1517       b += obj_len;
1518       obj_len = (obj_len & (min_size*3)) + min_size; // 8 16 24 32 8 16 24 32 ...
1519     }
1520     if (b < t) {
1521       // The loop didn't completely fill to t (top); adjust top downward.
1522       space->set_top(b);
1523       if (ZapUnusedHeapArea) {
1524         space->set_top_for_allocations();
1525       }
1526     }
1527 
1528     HeapWord** nta = _space_info[id].new_top_addr();
1529     bool result = summary_data().summarize(_space_info[id].split_info(),
1530                                            space->bottom(), space->top(), NULL,
1531                                            space->bottom(), space->end(), nta);
1532     assert(result, "space must fit into itself");
1533   }
1534 }
1535 
1536 void
1537 PSParallelCompact::provoke_split(bool & max_compaction)
1538 {
1539   if (total_invocations() % ParallelOldGCSplitInterval != 0) {
1540     return;
1541   }
1542 
1543   const size_t region_size = ParallelCompactData::RegionSize;
1544   ParallelCompactData& sd = summary_data();
1545 
1546   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1547   MutableSpace* const from_space = _space_info[from_space_id].space();
1548   const size_t eden_live = pointer_delta(eden_space->top(),
1549                                          _space_info[eden_space_id].new_top());
1550   const size_t from_live = pointer_delta(from_space->top(),
1551                                          _space_info[from_space_id].new_top());
1552 
1553   const size_t min_fill_size = CollectedHeap::min_fill_size();
1554   const size_t eden_free = pointer_delta(eden_space->end(), eden_space->top());
1555   const size_t eden_fillable = eden_free >= min_fill_size ? eden_free : 0;
1556   const size_t from_free = pointer_delta(from_space->end(), from_space->top());
1557   const size_t from_fillable = from_free >= min_fill_size ? from_free : 0;
1558 
1559   // Choose the space to split; need at least 2 regions live (or fillable).
1560   SpaceId id;
1561   MutableSpace* space;
1562   size_t live_words;
1563   size_t fill_words;
1564   if (eden_live + eden_fillable >= region_size * 2) {
1565     id = eden_space_id;
1566     space = eden_space;
1567     live_words = eden_live;
1568     fill_words = eden_fillable;
1569   } else if (from_live + from_fillable >= region_size * 2) {
1570     id = from_space_id;
1571     space = from_space;
1572     live_words = from_live;
1573     fill_words = from_fillable;
1574   } else {
1575     return; // Give up.
1576   }
1577   assert(fill_words == 0 || fill_words >= min_fill_size, "sanity");
1578 
1579   if (live_words < region_size * 2) {
1580     // Fill from top() to end() w/live objects of mixed sizes.
1581     HeapWord* const fill_start = space->top();
1582     live_words += fill_words;
1583 
1584     space->set_top(fill_start + fill_words);
1585     if (ZapUnusedHeapArea) {
1586       space->set_top_for_allocations();
1587     }
1588 
1589     HeapWord* cur_addr = fill_start;
1590     while (fill_words > 0) {
1591       const size_t r = (size_t)os::random() % (region_size / 2) + min_fill_size;
1592       size_t cur_size = MIN2(align_object_size_(r), fill_words);
1593       if (fill_words - cur_size < min_fill_size) {
1594         cur_size = fill_words; // Avoid leaving a fragment too small to fill.
1595       }
1596 
1597       CollectedHeap::fill_with_object(cur_addr, cur_size);
1598       mark_bitmap()->mark_obj(cur_addr, cur_size);
1599       sd.add_obj(cur_addr, cur_size);
1600 
1601       cur_addr += cur_size;
1602       fill_words -= cur_size;
1603     }
1604 
1605     summarize_new_objects(id, fill_start);
1606   }
1607 
1608   max_compaction = false;
1609 
1610   // Manipulate the old gen so that it has room for about half of the live data
1611   // in the target young gen space (live_words / 2).
1612   id = old_space_id;
1613   space = _space_info[id].space();
1614   const size_t free_at_end = space->free_in_words();
1615   const size_t free_target = align_object_size(live_words / 2);
1616   const size_t dead = pointer_delta(space->top(), _space_info[id].new_top());
1617 
1618   if (free_at_end >= free_target + min_fill_size) {
1619     // Fill space above top() and set the dense prefix so everything survives.
1620     HeapWord* const fill_start = space->top();
1621     const size_t fill_size = free_at_end - free_target;
1622     space->set_top(space->top() + fill_size);
1623     if (ZapUnusedHeapArea) {
1624       space->set_top_for_allocations();
1625     }
1626     fill_with_live_objects(id, fill_start, fill_size);
1627     summarize_new_objects(id, fill_start);
1628     _space_info[id].set_dense_prefix(sd.region_align_down(space->top()));
1629   } else if (dead + free_at_end > free_target) {
1630     // Find a dense prefix that makes the right amount of space available.
1631     HeapWord* cur = sd.region_align_down(space->top());
1632     HeapWord* cur_destination = sd.addr_to_region_ptr(cur)->destination();
1633     size_t dead_to_right = pointer_delta(space->end(), cur_destination);
1634     while (dead_to_right < free_target) {
1635       cur -= region_size;
1636       cur_destination = sd.addr_to_region_ptr(cur)->destination();
1637       dead_to_right = pointer_delta(space->end(), cur_destination);
1638     }
1639     _space_info[id].set_dense_prefix(cur);
1640   }
1641 }
1642 #endif // #ifndef PRODUCT
1643 
1644 void PSParallelCompact::summarize_spaces_quick()
1645 {
1646   for (unsigned int i = 0; i < last_space_id; ++i) {
1647     const MutableSpace* space = _space_info[i].space();
1648     HeapWord** nta = _space_info[i].new_top_addr();
1649     bool result = _summary_data.summarize(_space_info[i].split_info(),
1650                                           space->bottom(), space->top(), NULL,
1651                                           space->bottom(), space->end(), nta);
1652     assert(result, "space must fit into itself");
1653     _space_info[i].set_dense_prefix(space->bottom());
1654   }
1655 
1656 #ifndef PRODUCT
1657   if (ParallelOldGCSplitALot) {
1658     provoke_split_fill_survivor(to_space_id);
1659   }
1660 #endif // #ifndef PRODUCT
1661 }
1662 
1663 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1664 {
1665   HeapWord* const dense_prefix_end = dense_prefix(id);
1666   const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1667   const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1668   if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1669     // Only enough dead space is filled so that any remaining dead space to the
1670     // left is larger than the minimum filler object.  (The remainder is filled
1671     // during the copy/update phase.)
1672     //
1673     // The size of the dead space to the right of the boundary is not a
1674     // concern, since compaction will be able to use whatever space is
1675     // available.
1676     //
1677     // Here '||' is the boundary, 'x' represents a don't care bit and a box
1678     // surrounds the space to be filled with an object.
1679     //
1680     // In the 32-bit VM, each bit represents two 32-bit words:
1681     //                              +---+
1682     // a) beg_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1683     //    end_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1684     //                              +---+
1685     //
1686     // In the 64-bit VM, each bit represents one 64-bit word:
1687     //                              +------------+
1688     // b) beg_bits:  ...  x   x   x | 0   ||   0 | x  x  ...
1689     //    end_bits:  ...  x   x   1 | 0   ||   0 | x  x  ...
1690     //                              +------------+
1691     //                          +-------+
1692     // c) beg_bits:  ...  x   x | 0   0 | ||   0   x  x  ...
1693     //    end_bits:  ...  x   1 | 0   0 | ||   0   x  x  ...
1694     //                          +-------+
1695     //                      +-----------+
1696     // d) beg_bits:  ...  x | 0   0   0 | ||   0   x  x  ...
1697     //    end_bits:  ...  1 | 0   0   0 | ||   0   x  x  ...
1698     //                      +-----------+
1699     //                          +-------+
1700     // e) beg_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1701     //    end_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1702     //                          +-------+
1703 
1704     // Initially assume case a, c or e will apply.
1705     size_t obj_len = CollectedHeap::min_fill_size();
1706     HeapWord* obj_beg = dense_prefix_end - obj_len;
1707 
1708 #ifdef  _LP64
1709     if (MinObjAlignment > 1) { // object alignment > heap word size
1710       // Cases a, c or e.
1711     } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1712       // Case b above.
1713       obj_beg = dense_prefix_end - 1;
1714     } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1715                _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1716       // Case d above.
1717       obj_beg = dense_prefix_end - 3;
1718       obj_len = 3;
1719     }
1720 #endif  // #ifdef _LP64
1721 
1722     CollectedHeap::fill_with_object(obj_beg, obj_len);
1723     _mark_bitmap.mark_obj(obj_beg, obj_len);
1724     _summary_data.add_obj(obj_beg, obj_len);
1725     assert(start_array(id) != NULL, "sanity");
1726     start_array(id)->allocate_block(obj_beg);
1727   }
1728 }
1729 
1730 void
1731 PSParallelCompact::clear_source_region(HeapWord* beg_addr, HeapWord* end_addr)
1732 {
1733   RegionData* const beg_ptr = _summary_data.addr_to_region_ptr(beg_addr);
1734   HeapWord* const end_aligned_up = _summary_data.region_align_up(end_addr);
1735   RegionData* const end_ptr = _summary_data.addr_to_region_ptr(end_aligned_up);
1736   for (RegionData* cur = beg_ptr; cur < end_ptr; ++cur) {
1737     cur->set_source_region(0);
1738   }
1739 }
1740 
1741 void
1742 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1743 {
1744   assert(id < last_space_id, "id out of range");
1745   assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom() ||
1746          ParallelOldGCSplitALot && id == old_space_id,
1747          "should have been reset in summarize_spaces_quick()");
1748 
1749   const MutableSpace* space = _space_info[id].space();
1750   if (_space_info[id].new_top() != space->bottom()) {
1751     HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1752     _space_info[id].set_dense_prefix(dense_prefix_end);
1753 
1754 #ifndef PRODUCT
1755     if (TraceParallelOldGCDensePrefix) {
1756       print_dense_prefix_stats("ratio", id, maximum_compaction,
1757                                dense_prefix_end);
1758       HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1759       print_dense_prefix_stats("density", id, maximum_compaction, addr);
1760     }
1761 #endif  // #ifndef PRODUCT
1762 
1763     // Recompute the summary data, taking into account the dense prefix.  If
1764     // every last byte will be reclaimed, then the existing summary data which
1765     // compacts everything can be left in place.
1766     if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1767       // If dead space crosses the dense prefix boundary, it is (at least
1768       // partially) filled with a dummy object, marked live and added to the
1769       // summary data.  This simplifies the copy/update phase and must be done
1770       // before the final locations of objects are determined, to prevent
1771       // leaving a fragment of dead space that is too small to fill.
1772       fill_dense_prefix_end(id);
1773 
1774       // Compute the destination of each Region, and thus each object.
1775       _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1776       _summary_data.summarize(_space_info[id].split_info(),
1777                               dense_prefix_end, space->top(), NULL,
1778                               dense_prefix_end, space->end(),
1779                               _space_info[id].new_top_addr());
1780     }
1781   }
1782 
1783   if (TraceParallelOldGCSummaryPhase) {
1784     const size_t region_size = ParallelCompactData::RegionSize;
1785     HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1786     const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1787     const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1788     HeapWord* const new_top = _space_info[id].new_top();
1789     const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1790     const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1791     tty->print_cr("id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1792                   "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1793                   "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1794                   id, space->capacity_in_words(), p2i(dense_prefix_end),
1795                   dp_region, dp_words / region_size,
1796                   cr_words / region_size, p2i(new_top));
1797   }
1798 }
1799 
1800 #ifndef PRODUCT
1801 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1802                                           HeapWord* dst_beg, HeapWord* dst_end,
1803                                           SpaceId src_space_id,
1804                                           HeapWord* src_beg, HeapWord* src_end)
1805 {
1806   if (TraceParallelOldGCSummaryPhase) {
1807     tty->print_cr("summarizing %d [%s] into %d [%s]:  "
1808                   "src=" PTR_FORMAT "-" PTR_FORMAT " "
1809                   SIZE_FORMAT "-" SIZE_FORMAT " "
1810                   "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1811                   SIZE_FORMAT "-" SIZE_FORMAT,
1812                   src_space_id, space_names[src_space_id],
1813                   dst_space_id, space_names[dst_space_id],
1814                   p2i(src_beg), p2i(src_end),
1815                   _summary_data.addr_to_region_idx(src_beg),
1816                   _summary_data.addr_to_region_idx(src_end),
1817                   p2i(dst_beg), p2i(dst_end),
1818                   _summary_data.addr_to_region_idx(dst_beg),
1819                   _summary_data.addr_to_region_idx(dst_end));
1820   }
1821 }
1822 #endif  // #ifndef PRODUCT
1823 
1824 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1825                                       bool maximum_compaction)
1826 {
1827   GCTraceTime tm("summary phase", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
1828   // trace("2");
1829 
1830 #ifdef  ASSERT
1831   if (TraceParallelOldGCMarkingPhase) {
1832     tty->print_cr("add_obj_count=" SIZE_FORMAT " "
1833                   "add_obj_bytes=" SIZE_FORMAT,
1834                   add_obj_count, add_obj_size * HeapWordSize);
1835     tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
1836                   "mark_bitmap_bytes=" SIZE_FORMAT,
1837                   mark_bitmap_count, mark_bitmap_size * HeapWordSize);
1838   }
1839 #endif  // #ifdef ASSERT
1840 
1841   // Quick summarization of each space into itself, to see how much is live.
1842   summarize_spaces_quick();
1843 
1844   if (TraceParallelOldGCSummaryPhase) {
1845     tty->print_cr("summary_phase:  after summarizing each space to self");
1846     Universe::print();
1847     NOT_PRODUCT(print_region_ranges());
1848     if (Verbose) {
1849       NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1850     }
1851   }
1852 
1853   // The amount of live data that will end up in old space (assuming it fits).
1854   size_t old_space_total_live = 0;
1855   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1856     old_space_total_live += pointer_delta(_space_info[id].new_top(),
1857                                           _space_info[id].space()->bottom());
1858   }
1859 
1860   MutableSpace* const old_space = _space_info[old_space_id].space();
1861   const size_t old_capacity = old_space->capacity_in_words();
1862   if (old_space_total_live > old_capacity) {
1863     // XXX - should also try to expand
1864     maximum_compaction = true;
1865   }
1866 #ifndef PRODUCT
1867   if (ParallelOldGCSplitALot && old_space_total_live < old_capacity) {
1868     provoke_split(maximum_compaction);
1869   }
1870 #endif // #ifndef PRODUCT
1871 
1872   // Old generations.
1873   summarize_space(old_space_id, maximum_compaction);
1874 
1875   // Summarize the remaining spaces in the young gen.  The initial target space
1876   // is the old gen.  If a space does not fit entirely into the target, then the
1877   // remainder is compacted into the space itself and that space becomes the new
1878   // target.
1879   SpaceId dst_space_id = old_space_id;
1880   HeapWord* dst_space_end = old_space->end();
1881   HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1882   for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1883     const MutableSpace* space = _space_info[id].space();
1884     const size_t live = pointer_delta(_space_info[id].new_top(),
1885                                       space->bottom());
1886     const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1887 
1888     NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1889                                   SpaceId(id), space->bottom(), space->top());)
1890     if (live > 0 && live <= available) {
1891       // All the live data will fit.
1892       bool done = _summary_data.summarize(_space_info[id].split_info(),
1893                                           space->bottom(), space->top(),
1894                                           NULL,
1895                                           *new_top_addr, dst_space_end,
1896                                           new_top_addr);
1897       assert(done, "space must fit into old gen");
1898 
1899       // Reset the new_top value for the space.
1900       _space_info[id].set_new_top(space->bottom());
1901     } else if (live > 0) {
1902       // Attempt to fit part of the source space into the target space.
1903       HeapWord* next_src_addr = NULL;
1904       bool done = _summary_data.summarize(_space_info[id].split_info(),
1905                                           space->bottom(), space->top(),
1906                                           &next_src_addr,
1907                                           *new_top_addr, dst_space_end,
1908                                           new_top_addr);
1909       assert(!done, "space should not fit into old gen");
1910       assert(next_src_addr != NULL, "sanity");
1911 
1912       // The source space becomes the new target, so the remainder is compacted
1913       // within the space itself.
1914       dst_space_id = SpaceId(id);
1915       dst_space_end = space->end();
1916       new_top_addr = _space_info[id].new_top_addr();
1917       NOT_PRODUCT(summary_phase_msg(dst_space_id,
1918                                     space->bottom(), dst_space_end,
1919                                     SpaceId(id), next_src_addr, space->top());)
1920       done = _summary_data.summarize(_space_info[id].split_info(),
1921                                      next_src_addr, space->top(),
1922                                      NULL,
1923                                      space->bottom(), dst_space_end,
1924                                      new_top_addr);
1925       assert(done, "space must fit when compacted into itself");
1926       assert(*new_top_addr <= space->top(), "usage should not grow");
1927     }
1928   }
1929 
1930   if (TraceParallelOldGCSummaryPhase) {
1931     tty->print_cr("summary_phase:  after final summarization");
1932     Universe::print();
1933     NOT_PRODUCT(print_region_ranges());
1934     if (Verbose) {
1935       NOT_PRODUCT(print_generic_summary_data(_summary_data, _space_info));
1936     }
1937   }
1938 }
1939 
1940 // This method should contain all heap-specific policy for invoking a full
1941 // collection.  invoke_no_policy() will only attempt to compact the heap; it
1942 // will do nothing further.  If we need to bail out for policy reasons, scavenge
1943 // before full gc, or any other specialized behavior, it needs to be added here.
1944 //
1945 // Note that this method should only be called from the vm_thread while at a
1946 // safepoint.
1947 //
1948 // Note that the all_soft_refs_clear flag in the collector policy
1949 // may be true because this method can be called without intervening
1950 // activity.  For example when the heap space is tight and full measure
1951 // are being taken to free space.
1952 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1953   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1954   assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1955          "should be in vm thread");
1956 
1957   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1958   GCCause::Cause gc_cause = heap->gc_cause();
1959   assert(!heap->is_gc_active(), "not reentrant");
1960 
1961   PSAdaptiveSizePolicy* policy = heap->size_policy();
1962   IsGCActiveMark mark;
1963 
1964   if (ScavengeBeforeFullGC) {
1965     PSScavenge::invoke_no_policy();
1966   }
1967 
1968   const bool clear_all_soft_refs =
1969     heap->collector_policy()->should_clear_all_soft_refs();
1970 
1971   PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1972                                       maximum_heap_compaction);
1973 }
1974 
1975 // This method contains no policy. You should probably
1976 // be calling invoke() instead.
1977 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
1978   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
1979   assert(ref_processor() != NULL, "Sanity");
1980 
1981   if (GC_locker::check_active_before_gc()) {
1982     return false;
1983   }
1984 
1985   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1986 
1987   _gc_timer.register_gc_start();
1988   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1989 
1990   TimeStamp marking_start;
1991   TimeStamp compaction_start;
1992   TimeStamp collection_exit;
1993 
1994   GCCause::Cause gc_cause = heap->gc_cause();
1995   PSYoungGen* young_gen = heap->young_gen();
1996   PSOldGen* old_gen = heap->old_gen();
1997   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1998 
1999   // The scope of casr should end after code that can change
2000   // CollectorPolicy::_should_clear_all_soft_refs.
2001   ClearedAllSoftRefs casr(maximum_heap_compaction,
2002                           heap->collector_policy());
2003 
2004   if (ZapUnusedHeapArea) {
2005     // Save information needed to minimize mangling
2006     heap->record_gen_tops_before_GC();
2007   }
2008 
2009   heap->pre_full_gc_dump(&_gc_timer);
2010 
2011   _print_phases = PrintGCDetails && PrintParallelOldGCPhaseTimes;
2012 
2013   // Make sure data structures are sane, make the heap parsable, and do other
2014   // miscellaneous bookkeeping.
2015   PreGCValues pre_gc_values;
2016   pre_compact(&pre_gc_values);
2017 
2018   // Get the compaction manager reserved for the VM thread.
2019   ParCompactionManager* const vmthread_cm =
2020     ParCompactionManager::manager_array(gc_task_manager()->workers());
2021 
2022   // Place after pre_compact() where the number of invocations is incremented.
2023   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
2024 
2025   {
2026     ResourceMark rm;
2027     HandleMark hm;
2028 
2029     // Set the number of GC threads to be used in this collection
2030     gc_task_manager()->set_active_gang();
2031     gc_task_manager()->task_idle_workers();
2032     heap->set_par_threads(gc_task_manager()->active_workers());
2033 
2034     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
2035     GCTraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, NULL, _gc_tracer.gc_id());
2036     TraceCollectorStats tcs(counters());
2037     TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);
2038 
2039     if (TraceOldGenTime) accumulated_time()->start();
2040 
2041     // Let the size policy know we're starting
2042     size_policy->major_collection_begin();
2043 
2044     CodeCache::gc_prologue();
2045 
2046     COMPILER2_PRESENT(DerivedPointerTable::clear());
2047 
2048     ref_processor()->enable_discovery();
2049     ref_processor()->setup_policy(maximum_heap_compaction);
2050 
2051     bool marked_for_unloading = false;
2052 
2053     marking_start.update();
2054     marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
2055 
2056     bool max_on_system_gc = UseMaximumCompactionOnSystemGC
2057       && gc_cause == GCCause::_java_lang_system_gc;
2058     summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
2059 
2060     COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
2061     COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
2062 
2063     // adjust_roots() updates Universe::_intArrayKlassObj which is
2064     // needed by the compaction for filling holes in the dense prefix.
2065     adjust_roots();
2066 
2067     compaction_start.update();
2068     compact();
2069 
2070     // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
2071     // done before resizing.
2072     post_compact();
2073 
2074     // Let the size policy know we're done
2075     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
2076 
2077     if (UseAdaptiveSizePolicy) {
2078       if (PrintAdaptiveSizePolicy) {
2079         gclog_or_tty->print("AdaptiveSizeStart: ");
2080         gclog_or_tty->stamp();
2081         gclog_or_tty->print_cr(" collection: %d ",
2082                        heap->total_collections());
2083         if (Verbose) {
2084           gclog_or_tty->print("old_gen_capacity: " SIZE_FORMAT
2085             " young_gen_capacity: " SIZE_FORMAT,
2086             old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
2087         }
2088       }
2089 
2090       // Don't check if the size_policy is ready here.  Let
2091       // the size_policy check that internally.
2092       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
2093           AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
2094         // Swap the survivor spaces if from_space is empty. The
2095         // resize_young_gen() called below is normally used after
2096         // a successful young GC and swapping of survivor spaces;
2097         // otherwise, it will fail to resize the young gen with
2098         // the current implementation.
2099         if (young_gen->from_space()->is_empty()) {
2100           young_gen->from_space()->clear(SpaceDecorator::Mangle);
2101           young_gen->swap_spaces();
2102         }
2103 
2104         // Calculate optimal free space amounts
2105         assert(young_gen->max_size() >
2106           young_gen->from_space()->capacity_in_bytes() +
2107           young_gen->to_space()->capacity_in_bytes(),
2108           "Sizes of space in young gen are out-of-bounds");
2109 
2110         size_t young_live = young_gen->used_in_bytes();
2111         size_t eden_live = young_gen->eden_space()->used_in_bytes();
2112         size_t old_live = old_gen->used_in_bytes();
2113         size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
2114         size_t max_old_gen_size = old_gen->max_gen_size();
2115         size_t max_eden_size = young_gen->max_size() -
2116           young_gen->from_space()->capacity_in_bytes() -
2117           young_gen->to_space()->capacity_in_bytes();
2118 
2119         // Used for diagnostics
2120         size_policy->clear_generation_free_space_flags();
2121 
2122         size_policy->compute_generations_free_space(young_live,
2123                                                     eden_live,
2124                                                     old_live,
2125                                                     cur_eden,
2126                                                     max_old_gen_size,
2127                                                     max_eden_size,
2128                                                     true /* full gc*/);
2129 
2130         size_policy->check_gc_overhead_limit(young_live,
2131                                              eden_live,
2132                                              max_old_gen_size,
2133                                              max_eden_size,
2134                                              true /* full gc*/,
2135                                              gc_cause,
2136                                              heap->collector_policy());
2137 
2138         size_policy->decay_supplemental_growth(true /* full gc*/);
2139 
2140         heap->resize_old_gen(
2141           size_policy->calculated_old_free_size_in_bytes());
2142 
2143         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
2144                                size_policy->calculated_survivor_size_in_bytes());
2145       }
2146       if (PrintAdaptiveSizePolicy) {
2147         gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
2148                        heap->total_collections());
2149       }
2150     }
2151 
2152     if (UsePerfData) {
2153       PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
2154       counters->update_counters();
2155       counters->update_old_capacity(old_gen->capacity_in_bytes());
2156       counters->update_young_capacity(young_gen->capacity_in_bytes());
2157     }
2158 
2159     heap->resize_all_tlabs();
2160 
2161     // Resize the metaspace capacity after a collection
2162     MetaspaceGC::compute_new_size();
2163 
2164     if (TraceOldGenTime) accumulated_time()->stop();
2165 
2166     if (PrintGC) {
2167       if (PrintGCDetails) {
2168         // No GC timestamp here.  This is after GC so it would be confusing.
2169         young_gen->print_used_change(pre_gc_values.young_gen_used());
2170         old_gen->print_used_change(pre_gc_values.old_gen_used());
2171         heap->print_heap_change(pre_gc_values.heap_used());
2172         MetaspaceAux::print_metaspace_change(pre_gc_values.metadata_used());
2173       } else {
2174         heap->print_heap_change(pre_gc_values.heap_used());
2175       }
2176     }
2177 
2178     // Track memory usage and detect low memory
2179     MemoryService::track_memory_usage();
2180     heap->update_counters();
2181     gc_task_manager()->release_idle_workers();
2182   }
2183 
2184 #ifdef ASSERT
2185   for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
2186     ParCompactionManager* const cm =
2187       ParCompactionManager::manager_array(int(i));
2188     assert(cm->marking_stack()->is_empty(),       "should be empty");
2189     assert(ParCompactionManager::region_list(int(i))->is_empty(), "should be empty");
2190   }
2191 #endif // ASSERT
2192 
2193   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
2194     HandleMark hm;  // Discard invalid handles created during verification
2195     Universe::verify(" VerifyAfterGC:");
2196   }
2197 
2198   // Re-verify object start arrays
2199   if (VerifyObjectStartArray &&
2200       VerifyAfterGC) {
2201     old_gen->verify_object_start_array();
2202   }
2203 
2204   if (ZapUnusedHeapArea) {
2205     old_gen->object_space()->check_mangled_unused_area_complete();
2206   }
2207 
2208   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
2209 
2210   collection_exit.update();
2211 
2212   heap->print_heap_after_gc();
2213   heap->trace_heap_after_gc(&_gc_tracer);
2214 
2215   if (PrintGCTaskTimeStamps) {
2216     gclog_or_tty->print_cr("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " "
2217                            JLONG_FORMAT,
2218                            marking_start.ticks(), compaction_start.ticks(),
2219                            collection_exit.ticks());
2220     gc_task_manager()->print_task_time_stamps();
2221   }
2222 
2223   heap->post_full_gc_dump(&_gc_timer);
2224 
2225 #ifdef TRACESPINNING
2226   ParallelTaskTerminator::print_termination_counts();
2227 #endif
2228 
2229   _gc_timer.register_gc_end();
2230 
2231   _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
2232   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
2233 
2234   return true;
2235 }
2236 
2237 bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
2238                                              PSYoungGen* young_gen,
2239                                              PSOldGen* old_gen) {
2240   MutableSpace* const eden_space = young_gen->eden_space();
2241   assert(!eden_space->is_empty(), "eden must be non-empty");
2242   assert(young_gen->virtual_space()->alignment() ==
2243          old_gen->virtual_space()->alignment(), "alignments do not match");
2244 
2245   if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
2246     return false;
2247   }
2248 
2249   // Both generations must be completely committed.
2250   if (young_gen->virtual_space()->uncommitted_size() != 0) {
2251     return false;
2252   }
2253   if (old_gen->virtual_space()->uncommitted_size() != 0) {
2254     return false;
2255   }
2256 
2257   // Figure out how much to take from eden.  Include the average amount promoted
2258   // in the total; otherwise the next young gen GC will simply bail out to a
2259   // full GC.
2260   const size_t alignment = old_gen->virtual_space()->alignment();
2261   const size_t eden_used = eden_space->used_in_bytes();
2262   const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
2263   const size_t absorb_size = align_size_up(eden_used + promoted, alignment);
2264   const size_t eden_capacity = eden_space->capacity_in_bytes();
2265 
2266   if (absorb_size >= eden_capacity) {
2267     return false; // Must leave some space in eden.
2268   }
2269 
2270   const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
2271   if (new_young_size < young_gen->min_gen_size()) {
2272     return false; // Respect young gen minimum size.
2273   }
2274 
2275   if (TraceAdaptiveGCBoundary && Verbose) {
2276     gclog_or_tty->print(" absorbing " SIZE_FORMAT "K:  "
2277                         "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
2278                         "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
2279                         "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
2280                         absorb_size / K,
2281                         eden_capacity / K, (eden_capacity - absorb_size) / K,
2282                         young_gen->from_space()->used_in_bytes() / K,
2283                         young_gen->to_space()->used_in_bytes() / K,
2284                         young_gen->capacity_in_bytes() / K, new_young_size / K);
2285   }
2286 
2287   // Fill the unused part of the old gen.
2288   MutableSpace* const old_space = old_gen->object_space();
2289   HeapWord* const unused_start = old_space->top();
2290   size_t const unused_words = pointer_delta(old_space->end(), unused_start);
2291 
2292   if (unused_words > 0) {
2293     if (unused_words < CollectedHeap::min_fill_size()) {
2294       return false;  // If the old gen cannot be filled, must give up.
2295     }
2296     CollectedHeap::fill_with_objects(unused_start, unused_words);
2297   }
2298 
2299   // Take the live data from eden and set both top and end in the old gen to
2300   // eden top.  (Need to set end because reset_after_change() mangles the region
2301   // from end to virtual_space->high() in debug builds).
2302   HeapWord* const new_top = eden_space->top();
2303   old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
2304                                         absorb_size);
2305   young_gen->reset_after_change();
2306   old_space->set_top(new_top);
2307   old_space->set_end(new_top);
2308   old_gen->reset_after_change();
2309 
2310   // Update the object start array for the filler object and the data from eden.
2311   ObjectStartArray* const start_array = old_gen->start_array();
2312   for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
2313     start_array->allocate_block(p);
2314   }
2315 
2316   // Could update the promoted average here, but it is not typically updated at
2317   // full GCs and the value to use is unclear.  Something like
2318   //
2319   // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
2320 
2321   size_policy->set_bytes_absorbed_from_eden(absorb_size);
2322   return true;
2323 }
2324 
2325 GCTaskManager* const PSParallelCompact::gc_task_manager() {
2326   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
2327     "shouldn't return NULL");
2328   return ParallelScavengeHeap::gc_task_manager();
2329 }
2330 
2331 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2332                                       bool maximum_heap_compaction,
2333                                       ParallelOldTracer *gc_tracer) {
2334   // Recursively traverse all live objects and mark them
2335   GCTraceTime tm("marking phase", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2336 
2337   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2338   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2339   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2340   TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2341   ParallelTaskTerminator terminator(active_gc_threads, qset);
2342 
2343   ParCompactionManager::MarkAndPushClosure mark_and_push_closure(cm);
2344   ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
2345 
2346   // Need new claim bits before marking starts.
2347   ClassLoaderDataGraph::clear_claimed_marks();
2348 
2349   {
2350     GCTraceTime tm_m("par mark", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2351 
2352     ParallelScavengeHeap::ParStrongRootsScope psrs;
2353 
2354     GCTaskQueue* q = GCTaskQueue::create();
2355 
2356     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::universe));
2357     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jni_handles));
2358     // We scan the thread roots in parallel
2359     Threads::create_thread_roots_marking_tasks(q);
2360     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::object_synchronizer));
2361     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::flat_profiler));
2362     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::management));
2363     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::system_dictionary));
2364     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::class_loader_data));
2365     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jvmti));
2366     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::code_cache));
2367 
2368     if (active_gc_threads > 1) {
2369       for (uint j = 0; j < active_gc_threads; j++) {
2370         q->enqueue(new StealMarkingTask(&terminator));
2371       }
2372     }
2373 
2374     gc_task_manager()->execute_and_wait(q);
2375   }
2376 
2377   // Process reference objects found during marking
2378   {
2379     GCTraceTime tm_r("reference processing", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2380 
2381     ReferenceProcessorStats stats;
2382     if (ref_processor()->processing_is_mt()) {
2383       RefProcTaskExecutor task_executor;
2384       stats = ref_processor()->process_discovered_references(
2385         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2386         &task_executor, &_gc_timer, _gc_tracer.gc_id());
2387     } else {
2388       stats = ref_processor()->process_discovered_references(
2389         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
2390         &_gc_timer, _gc_tracer.gc_id());
2391     }
2392 
2393     gc_tracer->report_gc_reference_stats(stats);
2394   }
2395 
2396   GCTraceTime tm_c("class unloading", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2397 
2398   // This is the point where the entire marking should have completed.
2399   assert(cm->marking_stacks_empty(), "Marking should have completed");
2400 
2401   // Follow system dictionary roots and unload classes.
2402   bool purged_class = SystemDictionary::do_unloading(is_alive_closure());
2403 
2404   // Unload nmethods.
2405   CodeCache::do_unloading(is_alive_closure(), purged_class);
2406 
2407   // Prune dead klasses from subklass/sibling/implementor lists.
2408   Klass::clean_weak_klass_links(is_alive_closure());
2409 
2410   // Delete entries for dead interned strings.
2411   StringTable::unlink(is_alive_closure());
2412 
2413   // Clean up unreferenced symbols in symbol table.
2414   SymbolTable::unlink();
2415   _gc_tracer.report_object_count_after_gc(is_alive_closure());
2416 }
2417 
2418 // This should be moved to the shared markSweep code!
2419 class PSAlwaysTrueClosure: public BoolObjectClosure {
2420 public:
2421   bool do_object_b(oop p) { return true; }
2422 };
2423 static PSAlwaysTrueClosure always_true;
2424 
2425 void PSParallelCompact::adjust_roots() {
2426   // Adjust the pointers to reflect the new locations
2427   GCTraceTime tm("adjust roots", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2428 
2429   // Need new claim bits when tracing through and adjusting pointers.
2430   ClassLoaderDataGraph::clear_claimed_marks();
2431 
2432   // General strong roots.
2433   Universe::oops_do(adjust_pointer_closure());
2434   JNIHandles::oops_do(adjust_pointer_closure());   // Global (strong) JNI handles
2435   CLDToOopClosure adjust_from_cld(adjust_pointer_closure());
2436   Threads::oops_do(adjust_pointer_closure(), &adjust_from_cld, NULL);
2437   ObjectSynchronizer::oops_do(adjust_pointer_closure());
2438   FlatProfiler::oops_do(adjust_pointer_closure());
2439   Management::oops_do(adjust_pointer_closure());
2440   JvmtiExport::oops_do(adjust_pointer_closure());
2441   SystemDictionary::oops_do(adjust_pointer_closure());
2442   ClassLoaderDataGraph::oops_do(adjust_pointer_closure(), adjust_klass_closure(), true);
2443 
2444   // Now adjust pointers in remaining weak roots.  (All of which should
2445   // have been cleared if they pointed to non-surviving objects.)
2446   // Global (weak) JNI handles
2447   JNIHandles::weak_oops_do(&always_true, adjust_pointer_closure());
2448 
2449   CodeBlobToOopClosure adjust_from_blobs(adjust_pointer_closure(), CodeBlobToOopClosure::FixRelocations);
2450   CodeCache::blobs_do(&adjust_from_blobs);
2451   StringTable::oops_do(adjust_pointer_closure());
2452   ref_processor()->weak_oops_do(adjust_pointer_closure());
2453   // Roots were visited so references into the young gen in roots
2454   // may have been scanned.  Process them also.
2455   // Should the reference processor have a span that excludes
2456   // young gen objects?
2457   PSScavenge::reference_processor()->weak_oops_do(adjust_pointer_closure());
2458 }
2459 
2460 void PSParallelCompact::enqueue_region_draining_tasks(GCTaskQueue* q,
2461                                                       uint parallel_gc_threads)
2462 {
2463   GCTraceTime tm("drain task setup", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2464 
2465   // Find the threads that are active
2466   unsigned int which = 0;
2467 
2468   const uint task_count = MAX2(parallel_gc_threads, 1U);
2469   for (uint j = 0; j < task_count; j++) {
2470     q->enqueue(new DrainStacksCompactionTask(j));
2471     ParCompactionManager::verify_region_list_empty(j);
2472     // Set the region stacks variables to "no" region stack values
2473     // so that they will be recognized and needing a region stack
2474     // in the stealing tasks if they do not get one by executing
2475     // a draining stack.
2476     ParCompactionManager* cm = ParCompactionManager::manager_array(j);
2477     cm->set_region_stack(NULL);
2478     cm->set_region_stack_index((uint)max_uintx);
2479   }
2480   ParCompactionManager::reset_recycled_stack_index();
2481 
2482   // Find all regions that are available (can be filled immediately) and
2483   // distribute them to the thread stacks.  The iteration is done in reverse
2484   // order (high to low) so the regions will be removed in ascending order.
2485 
2486   const ParallelCompactData& sd = PSParallelCompact::summary_data();
2487 
2488   size_t fillable_regions = 0;   // A count for diagnostic purposes.
2489   // A region index which corresponds to the tasks created above.
2490   // "which" must be 0 <= which < task_count
2491 
2492   which = 0;
2493   // id + 1 is used to test termination so unsigned  can
2494   // be used with an old_space_id == 0.
2495   for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2496     SpaceInfo* const space_info = _space_info + id;
2497     MutableSpace* const space = space_info->space();
2498     HeapWord* const new_top = space_info->new_top();
2499 
2500     const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2501     const size_t end_region =
2502       sd.addr_to_region_idx(sd.region_align_up(new_top));
2503 
2504     for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2505       if (sd.region(cur)->claim_unsafe()) {
2506         ParCompactionManager::region_list_push(which, cur);
2507 
2508         if (TraceParallelOldGCCompactionPhase && Verbose) {
2509           const size_t count_mod_8 = fillable_regions & 7;
2510           if (count_mod_8 == 0) gclog_or_tty->print("fillable: ");
2511           gclog_or_tty->print(" " SIZE_FORMAT_W(7), cur);
2512           if (count_mod_8 == 7) gclog_or_tty->cr();
2513         }
2514 
2515         NOT_PRODUCT(++fillable_regions;)
2516 
2517         // Assign regions to tasks in round-robin fashion.
2518         if (++which == task_count) {
2519           assert(which <= parallel_gc_threads,
2520             "Inconsistent number of workers");
2521           which = 0;
2522         }
2523       }
2524     }
2525   }
2526 
2527   if (TraceParallelOldGCCompactionPhase) {
2528     if (Verbose && (fillable_regions & 7) != 0) gclog_or_tty->cr();
2529     gclog_or_tty->print_cr(SIZE_FORMAT " initially fillable regions", fillable_regions);
2530   }
2531 }
2532 
2533 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2534 
2535 void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q,
2536                                                     uint parallel_gc_threads) {
2537   GCTraceTime tm("dense prefix task setup", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2538 
2539   ParallelCompactData& sd = PSParallelCompact::summary_data();
2540 
2541   // Iterate over all the spaces adding tasks for updating
2542   // regions in the dense prefix.  Assume that 1 gc thread
2543   // will work on opening the gaps and the remaining gc threads
2544   // will work on the dense prefix.
2545   unsigned int space_id;
2546   for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2547     HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2548     const MutableSpace* const space = _space_info[space_id].space();
2549 
2550     if (dense_prefix_end == space->bottom()) {
2551       // There is no dense prefix for this space.
2552       continue;
2553     }
2554 
2555     // The dense prefix is before this region.
2556     size_t region_index_end_dense_prefix =
2557         sd.addr_to_region_idx(dense_prefix_end);
2558     RegionData* const dense_prefix_cp =
2559       sd.region(region_index_end_dense_prefix);
2560     assert(dense_prefix_end == space->end() ||
2561            dense_prefix_cp->available() ||
2562            dense_prefix_cp->claimed(),
2563            "The region after the dense prefix should always be ready to fill");
2564 
2565     size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2566 
2567     // Is there dense prefix work?
2568     size_t total_dense_prefix_regions =
2569       region_index_end_dense_prefix - region_index_start;
2570     // How many regions of the dense prefix should be given to
2571     // each thread?
2572     if (total_dense_prefix_regions > 0) {
2573       uint tasks_for_dense_prefix = 1;
2574       if (total_dense_prefix_regions <=
2575           (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2576         // Don't over partition.  This assumes that
2577         // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2578         // so there are not many regions to process.
2579         tasks_for_dense_prefix = parallel_gc_threads;
2580       } else {
2581         // Over partition
2582         tasks_for_dense_prefix = parallel_gc_threads *
2583           PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2584       }
2585       size_t regions_per_thread = total_dense_prefix_regions /
2586         tasks_for_dense_prefix;
2587       // Give each thread at least 1 region.
2588       if (regions_per_thread == 0) {
2589         regions_per_thread = 1;
2590       }
2591 
2592       for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2593         if (region_index_start >= region_index_end_dense_prefix) {
2594           break;
2595         }
2596         // region_index_end is not processed
2597         size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2598                                        region_index_end_dense_prefix);
2599         q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2600                                              region_index_start,
2601                                              region_index_end));
2602         region_index_start = region_index_end;
2603       }
2604     }
2605     // This gets any part of the dense prefix that did not
2606     // fit evenly.
2607     if (region_index_start < region_index_end_dense_prefix) {
2608       q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2609                                            region_index_start,
2610                                            region_index_end_dense_prefix));
2611     }
2612   }
2613 }
2614 
2615 void PSParallelCompact::enqueue_region_stealing_tasks(
2616                                      GCTaskQueue* q,
2617                                      ParallelTaskTerminator* terminator_ptr,
2618                                      uint parallel_gc_threads) {
2619   GCTraceTime tm("steal task setup", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2620 
2621   // Once a thread has drained it's stack, it should try to steal regions from
2622   // other threads.
2623   if (parallel_gc_threads > 1) {
2624     for (uint j = 0; j < parallel_gc_threads; j++) {
2625       q->enqueue(new StealRegionCompactionTask(terminator_ptr));
2626     }
2627   }
2628 }
2629 
2630 #ifdef ASSERT
2631 // Write a histogram of the number of times the block table was filled for a
2632 // region.
2633 void PSParallelCompact::write_block_fill_histogram(outputStream* const out)
2634 {
2635   if (!TraceParallelOldGCCompactionPhase) return;
2636 
2637   typedef ParallelCompactData::RegionData rd_t;
2638   ParallelCompactData& sd = summary_data();
2639 
2640   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2641     MutableSpace* const spc = _space_info[id].space();
2642     if (spc->bottom() != spc->top()) {
2643       const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
2644       HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
2645       const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
2646 
2647       size_t histo[5] = { 0, 0, 0, 0, 0 };
2648       const size_t histo_len = sizeof(histo) / sizeof(size_t);
2649       const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
2650 
2651       for (const rd_t* cur = beg; cur < end; ++cur) {
2652         ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
2653       }
2654       out->print("%u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
2655       for (size_t i = 0; i < histo_len; ++i) {
2656         out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
2657                    histo[i], 100.0 * histo[i] / region_cnt);
2658       }
2659       out->cr();
2660     }
2661   }
2662 }
2663 #endif // #ifdef ASSERT
2664 
2665 void PSParallelCompact::compact() {
2666   // trace("5");
2667   GCTraceTime tm("compaction phase", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2668 
2669   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2670   PSOldGen* old_gen = heap->old_gen();
2671   old_gen->start_array()->reset();
2672   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2673   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2674   TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2675   ParallelTaskTerminator terminator(active_gc_threads, qset);
2676 
2677   GCTaskQueue* q = GCTaskQueue::create();
2678   enqueue_region_draining_tasks(q, active_gc_threads);
2679   enqueue_dense_prefix_tasks(q, active_gc_threads);
2680   enqueue_region_stealing_tasks(q, &terminator, active_gc_threads);
2681 
2682   {
2683     GCTraceTime tm_pc("par compact", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2684 
2685     gc_task_manager()->execute_and_wait(q);
2686 
2687 #ifdef  ASSERT
2688     // Verify that all regions have been processed before the deferred updates.
2689     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2690       verify_complete(SpaceId(id));
2691     }
2692 #endif
2693   }
2694 
2695   {
2696     // Update the deferred objects, if any.  Any compaction manager can be used.
2697     GCTraceTime tm_du("deferred updates", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2698     ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2699     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2700       update_deferred_objects(cm, SpaceId(id));
2701     }
2702   }
2703 
2704   DEBUG_ONLY(write_block_fill_histogram(gclog_or_tty));
2705 }
2706 
2707 #ifdef  ASSERT
2708 void PSParallelCompact::verify_complete(SpaceId space_id) {
2709   // All Regions between space bottom() to new_top() should be marked as filled
2710   // and all Regions between new_top() and top() should be available (i.e.,
2711   // should have been emptied).
2712   ParallelCompactData& sd = summary_data();
2713   SpaceInfo si = _space_info[space_id];
2714   HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2715   HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2716   const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2717   const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2718   const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2719 
2720   bool issued_a_warning = false;
2721 
2722   size_t cur_region;
2723   for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2724     const RegionData* const c = sd.region(cur_region);
2725     if (!c->completed()) {
2726       warning("region " SIZE_FORMAT " not filled:  "
2727               "destination_count=%u",
2728               cur_region, c->destination_count());
2729       issued_a_warning = true;
2730     }
2731   }
2732 
2733   for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2734     const RegionData* const c = sd.region(cur_region);
2735     if (!c->available()) {
2736       warning("region " SIZE_FORMAT " not empty:   "
2737               "destination_count=%u",
2738               cur_region, c->destination_count());
2739       issued_a_warning = true;
2740     }
2741   }
2742 
2743   if (issued_a_warning) {
2744     print_region_ranges();
2745   }
2746 }
2747 #endif  // #ifdef ASSERT
2748 
2749 inline void UpdateOnlyClosure::do_addr(HeapWord* addr) {
2750   _start_array->allocate_block(addr);
2751   compaction_manager()->update_contents(oop(addr));
2752 }
2753 
2754 // Update interior oops in the ranges of regions [beg_region, end_region).
2755 void
2756 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2757                                                        SpaceId space_id,
2758                                                        size_t beg_region,
2759                                                        size_t end_region) {
2760   ParallelCompactData& sd = summary_data();
2761   ParMarkBitMap* const mbm = mark_bitmap();
2762 
2763   HeapWord* beg_addr = sd.region_to_addr(beg_region);
2764   HeapWord* const end_addr = sd.region_to_addr(end_region);
2765   assert(beg_region <= end_region, "bad region range");
2766   assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2767 
2768 #ifdef  ASSERT
2769   // Claim the regions to avoid triggering an assert when they are marked as
2770   // filled.
2771   for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2772     assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2773   }
2774 #endif  // #ifdef ASSERT
2775 
2776   if (beg_addr != space(space_id)->bottom()) {
2777     // Find the first live object or block of dead space that *starts* in this
2778     // range of regions.  If a partial object crosses onto the region, skip it;
2779     // it will be marked for 'deferred update' when the object head is
2780     // processed.  If dead space crosses onto the region, it is also skipped; it
2781     // will be filled when the prior region is processed.  If neither of those
2782     // apply, the first word in the region is the start of a live object or dead
2783     // space.
2784     assert(beg_addr > space(space_id)->bottom(), "sanity");
2785     const RegionData* const cp = sd.region(beg_region);
2786     if (cp->partial_obj_size() != 0) {
2787       beg_addr = sd.partial_obj_end(beg_region);
2788     } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2789       beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2790     }
2791   }
2792 
2793   if (beg_addr < end_addr) {
2794     // A live object or block of dead space starts in this range of Regions.
2795      HeapWord* const dense_prefix_end = dense_prefix(space_id);
2796 
2797     // Create closures and iterate.
2798     UpdateOnlyClosure update_closure(mbm, cm, space_id);
2799     FillClosure fill_closure(cm, space_id);
2800     ParMarkBitMap::IterationStatus status;
2801     status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2802                           dense_prefix_end);
2803     if (status == ParMarkBitMap::incomplete) {
2804       update_closure.do_addr(update_closure.source());
2805     }
2806   }
2807 
2808   // Mark the regions as filled.
2809   RegionData* const beg_cp = sd.region(beg_region);
2810   RegionData* const end_cp = sd.region(end_region);
2811   for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2812     cp->set_completed();
2813   }
2814 }
2815 
2816 // Return the SpaceId for the space containing addr.  If addr is not in the
2817 // heap, last_space_id is returned.  In debug mode it expects the address to be
2818 // in the heap and asserts such.
2819 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2820   assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
2821 
2822   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2823     if (_space_info[id].space()->contains(addr)) {
2824       return SpaceId(id);
2825     }
2826   }
2827 
2828   assert(false, "no space contains the addr");
2829   return last_space_id;
2830 }
2831 
2832 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2833                                                 SpaceId id) {
2834   assert(id < last_space_id, "bad space id");
2835 
2836   ParallelCompactData& sd = summary_data();
2837   const SpaceInfo* const space_info = _space_info + id;
2838   ObjectStartArray* const start_array = space_info->start_array();
2839 
2840   const MutableSpace* const space = space_info->space();
2841   assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2842   HeapWord* const beg_addr = space_info->dense_prefix();
2843   HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2844 
2845   const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2846   const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2847   const RegionData* cur_region;
2848   for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2849     HeapWord* const addr = cur_region->deferred_obj_addr();
2850     if (addr != NULL) {
2851       if (start_array != NULL) {
2852         start_array->allocate_block(addr);
2853       }
2854       cm->update_contents(oop(addr));
2855       assert(oop(addr)->is_oop_or_null(), err_msg("Expected an oop or NULL at " PTR_FORMAT, p2i(oop(addr))));
2856     }
2857   }
2858 }
2859 
2860 // Skip over count live words starting from beg, and return the address of the
2861 // next live word.  Unless marked, the word corresponding to beg is assumed to
2862 // be dead.  Callers must either ensure beg does not correspond to the middle of
2863 // an object, or account for those live words in some other way.  Callers must
2864 // also ensure that there are enough live words in the range [beg, end) to skip.
2865 HeapWord*
2866 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2867 {
2868   assert(count > 0, "sanity");
2869 
2870   ParMarkBitMap* m = mark_bitmap();
2871   idx_t bits_to_skip = m->words_to_bits(count);
2872   idx_t cur_beg = m->addr_to_bit(beg);
2873   const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end));
2874 
2875   do {
2876     cur_beg = m->find_obj_beg(cur_beg, search_end);
2877     idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2878     const size_t obj_bits = cur_end - cur_beg + 1;
2879     if (obj_bits > bits_to_skip) {
2880       return m->bit_to_addr(cur_beg + bits_to_skip);
2881     }
2882     bits_to_skip -= obj_bits;
2883     cur_beg = cur_end + 1;
2884   } while (bits_to_skip > 0);
2885 
2886   // Skipping the desired number of words landed just past the end of an object.
2887   // Find the start of the next object.
2888   cur_beg = m->find_obj_beg(cur_beg, search_end);
2889   assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2890   return m->bit_to_addr(cur_beg);
2891 }
2892 
2893 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2894                                             SpaceId src_space_id,
2895                                             size_t src_region_idx)
2896 {
2897   assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2898 
2899   const SplitInfo& split_info = _space_info[src_space_id].split_info();
2900   if (split_info.dest_region_addr() == dest_addr) {
2901     // The partial object ending at the split point contains the first word to
2902     // be copied to dest_addr.
2903     return split_info.first_src_addr();
2904   }
2905 
2906   const ParallelCompactData& sd = summary_data();
2907   ParMarkBitMap* const bitmap = mark_bitmap();
2908   const size_t RegionSize = ParallelCompactData::RegionSize;
2909 
2910   assert(sd.is_region_aligned(dest_addr), "not aligned");
2911   const RegionData* const src_region_ptr = sd.region(src_region_idx);
2912   const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2913   HeapWord* const src_region_destination = src_region_ptr->destination();
2914 
2915   assert(dest_addr >= src_region_destination, "wrong src region");
2916   assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2917 
2918   HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2919   HeapWord* const src_region_end = src_region_beg + RegionSize;
2920 
2921   HeapWord* addr = src_region_beg;
2922   if (dest_addr == src_region_destination) {
2923     // Return the first live word in the source region.
2924     if (partial_obj_size == 0) {
2925       addr = bitmap->find_obj_beg(addr, src_region_end);
2926       assert(addr < src_region_end, "no objects start in src region");
2927     }
2928     return addr;
2929   }
2930 
2931   // Must skip some live data.
2932   size_t words_to_skip = dest_addr - src_region_destination;
2933   assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2934 
2935   if (partial_obj_size >= words_to_skip) {
2936     // All the live words to skip are part of the partial object.
2937     addr += words_to_skip;
2938     if (partial_obj_size == words_to_skip) {
2939       // Find the first live word past the partial object.
2940       addr = bitmap->find_obj_beg(addr, src_region_end);
2941       assert(addr < src_region_end, "wrong src region");
2942     }
2943     return addr;
2944   }
2945 
2946   // Skip over the partial object (if any).
2947   if (partial_obj_size != 0) {
2948     words_to_skip -= partial_obj_size;
2949     addr += partial_obj_size;
2950   }
2951 
2952   // Skip over live words due to objects that start in the region.
2953   addr = skip_live_words(addr, src_region_end, words_to_skip);
2954   assert(addr < src_region_end, "wrong src region");
2955   return addr;
2956 }
2957 
2958 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2959                                                      SpaceId src_space_id,
2960                                                      size_t beg_region,
2961                                                      HeapWord* end_addr)
2962 {
2963   ParallelCompactData& sd = summary_data();
2964 
2965 #ifdef ASSERT
2966   MutableSpace* const src_space = _space_info[src_space_id].space();
2967   HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2968   assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2969          "src_space_id does not match beg_addr");
2970   assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2971          "src_space_id does not match end_addr");
2972 #endif // #ifdef ASSERT
2973 
2974   RegionData* const beg = sd.region(beg_region);
2975   RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2976 
2977   // Regions up to new_top() are enqueued if they become available.
2978   HeapWord* const new_top = _space_info[src_space_id].new_top();
2979   RegionData* const enqueue_end =
2980     sd.addr_to_region_ptr(sd.region_align_up(new_top));
2981 
2982   for (RegionData* cur = beg; cur < end; ++cur) {
2983     assert(cur->data_size() > 0, "region must have live data");
2984     cur->decrement_destination_count();
2985     if (cur < enqueue_end && cur->available() && cur->claim()) {
2986       cm->push_region(sd.region(cur));
2987     }
2988   }
2989 }
2990 
2991 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2992                                           SpaceId& src_space_id,
2993                                           HeapWord*& src_space_top,
2994                                           HeapWord* end_addr)
2995 {
2996   typedef ParallelCompactData::RegionData RegionData;
2997 
2998   ParallelCompactData& sd = PSParallelCompact::summary_data();
2999   const size_t region_size = ParallelCompactData::RegionSize;
3000 
3001   size_t src_region_idx = 0;
3002 
3003   // Skip empty regions (if any) up to the top of the space.
3004   HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
3005   RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
3006   HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
3007   const RegionData* const top_region_ptr =
3008     sd.addr_to_region_ptr(top_aligned_up);
3009   while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
3010     ++src_region_ptr;
3011   }
3012 
3013   if (src_region_ptr < top_region_ptr) {
3014     // The next source region is in the current space.  Update src_region_idx
3015     // and the source address to match src_region_ptr.
3016     src_region_idx = sd.region(src_region_ptr);
3017     HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
3018     if (src_region_addr > closure.source()) {
3019       closure.set_source(src_region_addr);
3020     }
3021     return src_region_idx;
3022   }
3023 
3024   // Switch to a new source space and find the first non-empty region.
3025   unsigned int space_id = src_space_id + 1;
3026   assert(space_id < last_space_id, "not enough spaces");
3027 
3028   HeapWord* const destination = closure.destination();
3029 
3030   do {
3031     MutableSpace* space = _space_info[space_id].space();
3032     HeapWord* const bottom = space->bottom();
3033     const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
3034 
3035     // Iterate over the spaces that do not compact into themselves.
3036     if (bottom_cp->destination() != bottom) {
3037       HeapWord* const top_aligned_up = sd.region_align_up(space->top());
3038       const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
3039 
3040       for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
3041         if (src_cp->live_obj_size() > 0) {
3042           // Found it.
3043           assert(src_cp->destination() == destination,
3044                  "first live obj in the space must match the destination");
3045           assert(src_cp->partial_obj_size() == 0,
3046                  "a space cannot begin with a partial obj");
3047 
3048           src_space_id = SpaceId(space_id);
3049           src_space_top = space->top();
3050           const size_t src_region_idx = sd.region(src_cp);
3051           closure.set_source(sd.region_to_addr(src_region_idx));
3052           return src_region_idx;
3053         } else {
3054           assert(src_cp->data_size() == 0, "sanity");
3055         }
3056       }
3057     }
3058   } while (++space_id < last_space_id);
3059 
3060   assert(false, "no source region was found");
3061   return 0;
3062 }
3063 
3064 void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx)
3065 {
3066   typedef ParMarkBitMap::IterationStatus IterationStatus;
3067   const size_t RegionSize = ParallelCompactData::RegionSize;
3068   ParMarkBitMap* const bitmap = mark_bitmap();
3069   ParallelCompactData& sd = summary_data();
3070   RegionData* const region_ptr = sd.region(region_idx);
3071 
3072   // Get the items needed to construct the closure.
3073   HeapWord* dest_addr = sd.region_to_addr(region_idx);
3074   SpaceId dest_space_id = space_id(dest_addr);
3075   ObjectStartArray* start_array = _space_info[dest_space_id].start_array();
3076   HeapWord* new_top = _space_info[dest_space_id].new_top();
3077   assert(dest_addr < new_top, "sanity");
3078   const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize);
3079 
3080   // Get the source region and related info.
3081   size_t src_region_idx = region_ptr->source_region();
3082   SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
3083   HeapWord* src_space_top = _space_info[src_space_id].space()->top();
3084 
3085   MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3086   closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
3087 
3088   // Adjust src_region_idx to prepare for decrementing destination counts (the
3089   // destination count is not decremented when a region is copied to itself).
3090   if (src_region_idx == region_idx) {
3091     src_region_idx += 1;
3092   }
3093 
3094   if (bitmap->is_unmarked(closure.source())) {
3095     // The first source word is in the middle of an object; copy the remainder
3096     // of the object or as much as will fit.  The fact that pointer updates were
3097     // deferred will be noted when the object header is processed.
3098     HeapWord* const old_src_addr = closure.source();
3099     closure.copy_partial_obj();
3100     if (closure.is_full()) {
3101       decrement_destination_counts(cm, src_space_id, src_region_idx,
3102                                    closure.source());
3103       region_ptr->set_deferred_obj_addr(NULL);
3104       region_ptr->set_completed();
3105       return;
3106     }
3107 
3108     HeapWord* const end_addr = sd.region_align_down(closure.source());
3109     if (sd.region_align_down(old_src_addr) != end_addr) {
3110       // The partial object was copied from more than one source region.
3111       decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3112 
3113       // Move to the next source region, possibly switching spaces as well.  All
3114       // args except end_addr may be modified.
3115       src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3116                                        end_addr);
3117     }
3118   }
3119 
3120   do {
3121     HeapWord* const cur_addr = closure.source();
3122     HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
3123                                     src_space_top);
3124     IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
3125 
3126     if (status == ParMarkBitMap::incomplete) {
3127       // The last obj that starts in the source region does not end in the
3128       // region.
3129       assert(closure.source() < end_addr, "sanity");
3130       HeapWord* const obj_beg = closure.source();
3131       HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
3132                                        src_space_top);
3133       HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
3134       if (obj_end < range_end) {
3135         // The end was found; the entire object will fit.
3136         status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
3137         assert(status != ParMarkBitMap::would_overflow, "sanity");
3138       } else {
3139         // The end was not found; the object will not fit.
3140         assert(range_end < src_space_top, "obj cannot cross space boundary");
3141         status = ParMarkBitMap::would_overflow;
3142       }
3143     }
3144 
3145     if (status == ParMarkBitMap::would_overflow) {
3146       // The last object did not fit.  Note that interior oop updates were
3147       // deferred, then copy enough of the object to fill the region.
3148       region_ptr->set_deferred_obj_addr(closure.destination());
3149       status = closure.copy_until_full(); // copies from closure.source()
3150 
3151       decrement_destination_counts(cm, src_space_id, src_region_idx,
3152                                    closure.source());
3153       region_ptr->set_completed();
3154       return;
3155     }
3156 
3157     if (status == ParMarkBitMap::full) {
3158       decrement_destination_counts(cm, src_space_id, src_region_idx,
3159                                    closure.source());
3160       region_ptr->set_deferred_obj_addr(NULL);
3161       region_ptr->set_completed();
3162       return;
3163     }
3164 
3165     decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3166 
3167     // Move to the next source region, possibly switching spaces as well.  All
3168     // args except end_addr may be modified.
3169     src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3170                                      end_addr);
3171   } while (true);
3172 }
3173 
3174 void PSParallelCompact::fill_blocks(size_t region_idx)
3175 {
3176   // Fill in the block table elements for the specified region.  Each block
3177   // table element holds the number of live words in the region that are to the
3178   // left of the first object that starts in the block.  Thus only blocks in
3179   // which an object starts need to be filled.
3180   //
3181   // The algorithm scans the section of the bitmap that corresponds to the
3182   // region, keeping a running total of the live words.  When an object start is
3183   // found, if it's the first to start in the block that contains it, the
3184   // current total is written to the block table element.
3185   const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
3186   const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
3187   const size_t RegionSize = ParallelCompactData::RegionSize;
3188 
3189   ParallelCompactData& sd = summary_data();
3190   const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
3191   if (partial_obj_size >= RegionSize) {
3192     return; // No objects start in this region.
3193   }
3194 
3195   // Ensure the first loop iteration decides that the block has changed.
3196   size_t cur_block = sd.block_count();
3197 
3198   const ParMarkBitMap* const bitmap = mark_bitmap();
3199 
3200   const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
3201   assert((size_t)1 << Log2BitsPerBlock ==
3202          bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
3203 
3204   size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
3205   const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
3206   size_t live_bits = bitmap->words_to_bits(partial_obj_size);
3207   beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
3208   while (beg_bit < range_end) {
3209     const size_t new_block = beg_bit >> Log2BitsPerBlock;
3210     if (new_block != cur_block) {
3211       cur_block = new_block;
3212       sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
3213     }
3214 
3215     const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
3216     if (end_bit < range_end - 1) {
3217       live_bits += end_bit - beg_bit + 1;
3218       beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
3219     } else {
3220       return;
3221     }
3222   }
3223 }
3224 
3225 void
3226 PSParallelCompact::move_and_update(ParCompactionManager* cm, SpaceId space_id) {
3227   const MutableSpace* sp = space(space_id);
3228   if (sp->is_empty()) {
3229     return;
3230   }
3231 
3232   ParallelCompactData& sd = PSParallelCompact::summary_data();
3233   ParMarkBitMap* const bitmap = mark_bitmap();
3234   HeapWord* const dp_addr = dense_prefix(space_id);
3235   HeapWord* beg_addr = sp->bottom();
3236   HeapWord* end_addr = sp->top();
3237 
3238   assert(beg_addr <= dp_addr && dp_addr <= end_addr, "bad dense prefix");
3239 
3240   const size_t beg_region = sd.addr_to_region_idx(beg_addr);
3241   const size_t dp_region = sd.addr_to_region_idx(dp_addr);
3242   if (beg_region < dp_region) {
3243     update_and_deadwood_in_dense_prefix(cm, space_id, beg_region, dp_region);
3244   }
3245 
3246   // The destination of the first live object that starts in the region is one
3247   // past the end of the partial object entering the region (if any).
3248   HeapWord* const dest_addr = sd.partial_obj_end(dp_region);
3249   HeapWord* const new_top = _space_info[space_id].new_top();
3250   assert(new_top >= dest_addr, "bad new_top value");
3251   const size_t words = pointer_delta(new_top, dest_addr);
3252 
3253   if (words > 0) {
3254     ObjectStartArray* start_array = _space_info[space_id].start_array();
3255     MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3256 
3257     ParMarkBitMap::IterationStatus status;
3258     status = bitmap->iterate(&closure, dest_addr, end_addr);
3259     assert(status == ParMarkBitMap::full, "iteration not complete");
3260     assert(bitmap->find_obj_beg(closure.source(), end_addr) == end_addr,
3261            "live objects skipped because closure is full");
3262   }
3263 }
3264 
3265 jlong PSParallelCompact::millis_since_last_gc() {
3266   // We need a monotonically non-decreasing time in ms but
3267   // os::javaTimeMillis() does not guarantee monotonicity.
3268   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3269   jlong ret_val = now - _time_of_last_gc;
3270   // XXX See note in genCollectedHeap::millis_since_last_gc().
3271   if (ret_val < 0) {
3272     NOT_PRODUCT(warning("time warp: " JLONG_FORMAT, ret_val);)
3273     return 0;
3274   }
3275   return ret_val;
3276 }
3277 
3278 void PSParallelCompact::reset_millis_since_last_gc() {
3279   // We need a monotonically non-decreasing time in ms but
3280   // os::javaTimeMillis() does not guarantee monotonicity.
3281   _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3282 }
3283 
3284 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3285 {
3286   if (source() != destination()) {
3287     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3288     Copy::aligned_conjoint_words(source(), destination(), words_remaining());
3289   }
3290   update_state(words_remaining());
3291   assert(is_full(), "sanity");
3292   return ParMarkBitMap::full;
3293 }
3294 
3295 void MoveAndUpdateClosure::copy_partial_obj()
3296 {
3297   size_t words = words_remaining();
3298 
3299   HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3300   HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3301   if (end_addr < range_end) {
3302     words = bitmap()->obj_size(source(), end_addr);
3303   }
3304 
3305   // This test is necessary; if omitted, the pointer updates to a partial object
3306   // that crosses the dense prefix boundary could be overwritten.
3307   if (source() != destination()) {
3308     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3309     Copy::aligned_conjoint_words(source(), destination(), words);
3310   }
3311   update_state(words);
3312 }
3313 
3314 void InstanceKlass::oop_pc_update_pointers(oop obj) {
3315   oop_oop_iterate_oop_maps<true>(obj, PSParallelCompact::adjust_pointer_closure());
3316 }
3317 
3318 void InstanceMirrorKlass::oop_pc_update_pointers(oop obj) {
3319   InstanceKlass::oop_pc_update_pointers(obj);
3320 
3321   oop_oop_iterate_statics<true>(obj, PSParallelCompact::adjust_pointer_closure());
3322 }
3323 
3324 void InstanceClassLoaderKlass::oop_pc_update_pointers(oop obj) {
3325   InstanceKlass::oop_pc_update_pointers(obj);
3326 }
3327 
3328 #ifdef ASSERT
3329 template <class T> static void trace_reference_gc(const char *s, oop obj,
3330                                                   T* referent_addr,
3331                                                   T* next_addr,
3332                                                   T* discovered_addr) {
3333   if(TraceReferenceGC && PrintGCDetails) {
3334     gclog_or_tty->print_cr("%s obj " PTR_FORMAT, s, p2i(obj));
3335     gclog_or_tty->print_cr("     referent_addr/* " PTR_FORMAT " / "
3336                            PTR_FORMAT, p2i(referent_addr),
3337                            referent_addr ? p2i(oopDesc::load_decode_heap_oop(referent_addr)) : NULL);
3338     gclog_or_tty->print_cr("     next_addr/* " PTR_FORMAT " / "
3339                            PTR_FORMAT, p2i(next_addr),
3340                            next_addr ? p2i(oopDesc::load_decode_heap_oop(next_addr)) : NULL);
3341     gclog_or_tty->print_cr("     discovered_addr/* " PTR_FORMAT " / "
3342                            PTR_FORMAT, p2i(discovered_addr),
3343                            discovered_addr ? p2i(oopDesc::load_decode_heap_oop(discovered_addr)) : NULL);
3344   }
3345 }
3346 #endif
3347 
3348 template <class T>
3349 static void oop_pc_update_pointers_specialized(oop obj) {
3350   T* referent_addr = (T*)java_lang_ref_Reference::referent_addr(obj);
3351   PSParallelCompact::adjust_pointer(referent_addr);
3352   T* next_addr = (T*)java_lang_ref_Reference::next_addr(obj);
3353   PSParallelCompact::adjust_pointer(next_addr);
3354   T* discovered_addr = (T*)java_lang_ref_Reference::discovered_addr(obj);
3355   PSParallelCompact::adjust_pointer(discovered_addr);
3356   debug_only(trace_reference_gc("InstanceRefKlass::oop_update_ptrs", obj,
3357                                 referent_addr, next_addr, discovered_addr);)
3358 }
3359 
3360 void InstanceRefKlass::oop_pc_update_pointers(oop obj) {
3361   InstanceKlass::oop_pc_update_pointers(obj);
3362 
3363   if (UseCompressedOops) {
3364     oop_pc_update_pointers_specialized<narrowOop>(obj);
3365   } else {
3366     oop_pc_update_pointers_specialized<oop>(obj);
3367   }
3368 }
3369 
3370 void ObjArrayKlass::oop_pc_update_pointers(oop obj) {
3371   assert(obj->is_objArray(), "obj must be obj array");
3372   oop_oop_iterate_elements<true>(objArrayOop(obj), PSParallelCompact::adjust_pointer_closure());
3373 }
3374 
3375 void TypeArrayKlass::oop_pc_update_pointers(oop obj) {
3376   assert(obj->is_typeArray(),"must be a type array");
3377 }
3378 
3379 ParMarkBitMapClosure::IterationStatus
3380 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3381   assert(destination() != NULL, "sanity");
3382   assert(bitmap()->obj_size(addr) == words, "bad size");
3383 
3384   _source = addr;
3385   assert(PSParallelCompact::summary_data().calc_new_pointer(source()) ==
3386          destination(), "wrong destination");
3387 
3388   if (words > words_remaining()) {
3389     return ParMarkBitMap::would_overflow;
3390   }
3391 
3392   // The start_array must be updated even if the object is not moving.
3393   if (_start_array != NULL) {
3394     _start_array->allocate_block(destination());
3395   }
3396 
3397   if (destination() != source()) {
3398     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3399     Copy::aligned_conjoint_words(source(), destination(), words);
3400   }
3401 
3402   oop moved_oop = (oop) destination();
3403   compaction_manager()->update_contents(moved_oop);
3404   assert(moved_oop->is_oop_or_null(), err_msg("Expected an oop or NULL at " PTR_FORMAT, p2i(moved_oop)));
3405 
3406   update_state(words);
3407   assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
3408   return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3409 }
3410 
3411 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3412                                      ParCompactionManager* cm,
3413                                      PSParallelCompact::SpaceId space_id) :
3414   ParMarkBitMapClosure(mbm, cm),
3415   _space_id(space_id),
3416   _start_array(PSParallelCompact::start_array(space_id))
3417 {
3418 }
3419 
3420 // Updates the references in the object to their new values.
3421 ParMarkBitMapClosure::IterationStatus
3422 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3423   do_addr(addr);
3424   return ParMarkBitMap::incomplete;
3425 }