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