1 /*
   2  * Copyright (c) 2005, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/stringTable.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "code/codeCache.hpp"
  29 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
  30 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.inline.hpp"
  31 #include "gc_implementation/parallelScavenge/pcTasks.hpp"
  32 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
  33 #include "gc_implementation/parallelScavenge/psCompactionManager.inline.hpp"
  34 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
  35 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp"
  36 #include "gc_implementation/parallelScavenge/psOldGen.hpp"
  37 #include "gc_implementation/parallelScavenge/psParallelCompact.inline.hpp"
  38 #include "gc_implementation/parallelScavenge/psPromotionManager.inline.hpp"
  39 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
  40 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"
  41 #include "gc_implementation/shared/gcHeapSummary.hpp"
  42 #include "gc_implementation/shared/gcTimer.hpp"
  43 #include "gc_implementation/shared/gcTrace.hpp"
  44 #include "gc_implementation/shared/gcTraceTime.hpp"
  45 #include "gc_implementation/shared/isGCActiveMark.hpp"
  46 #include "gc_implementation/shared/spaceDecorator.hpp"
  47 #include "gc_interface/gcCause.hpp"
  48 #include "memory/gcLocker.inline.hpp"
  49 #include "memory/referencePolicy.hpp"
  50 #include "memory/referenceProcessor.hpp"
  51 #include "oops/instanceKlass.inline.hpp"
  52 #include "oops/instanceMirrorKlass.inline.hpp"
  53 #include "oops/methodData.hpp"
  54 #include "oops/objArrayKlass.inline.hpp"
  55 #include "oops/oop.inline.hpp"
  56 #include "runtime/atomic.inline.hpp"
  57 #include "runtime/fprofiler.hpp"
  58 #include "runtime/safepoint.hpp"
  59 #include "runtime/vmThread.hpp"
  60 #include "services/management.hpp"
  61 #include "services/memoryService.hpp"
  62 #include "services/memTracker.hpp"
  63 #include "utilities/events.hpp"
  64 #include "utilities/stack.inline.hpp"
  65 
  66 #include <math.h>
  67 
  68 // All sizes are in HeapWords.
  69 const size_t ParallelCompactData::Log2RegionSize  = 16; // 64K words
  70 const size_t ParallelCompactData::RegionSize      = (size_t)1 << Log2RegionSize;
  71 const size_t ParallelCompactData::RegionSizeBytes =
  72   RegionSize << LogHeapWordSize;
  73 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
  74 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
  75 const size_t ParallelCompactData::RegionAddrMask       = ~RegionAddrOffsetMask;
  76 
  77 const size_t ParallelCompactData::Log2BlockSize   = 7; // 128 words
  78 const size_t ParallelCompactData::BlockSize       = (size_t)1 << Log2BlockSize;
  79 const size_t ParallelCompactData::BlockSizeBytes  =
  80   BlockSize << LogHeapWordSize;
  81 const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
  82 const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
  83 const size_t ParallelCompactData::BlockAddrMask       = ~BlockAddrOffsetMask;
  84 
  85 const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
  86 const size_t ParallelCompactData::Log2BlocksPerRegion =
  87   Log2RegionSize - Log2BlockSize;
  88 
  89 const ParallelCompactData::RegionData::region_sz_t
  90 ParallelCompactData::RegionData::dc_shift = 27;
  91 
  92 const ParallelCompactData::RegionData::region_sz_t
  93 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
  94 
  95 const ParallelCompactData::RegionData::region_sz_t
  96 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
  97 
  98 const ParallelCompactData::RegionData::region_sz_t
  99 ParallelCompactData::RegionData::los_mask = ~dc_mask;
 100 
 101 const ParallelCompactData::RegionData::region_sz_t
 102 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
 103 
 104 const ParallelCompactData::RegionData::region_sz_t
 105 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
 106 
 107 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
 108 bool      PSParallelCompact::_print_phases = false;
 109 
 110 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
 111 Klass*              PSParallelCompact::_updated_int_array_klass_obj = NULL;
 112 
 113 double PSParallelCompact::_dwl_mean;
 114 double PSParallelCompact::_dwl_std_dev;
 115 double PSParallelCompact::_dwl_first_term;
 116 double PSParallelCompact::_dwl_adjustment;
 117 #ifdef  ASSERT
 118 bool   PSParallelCompact::_dwl_initialized = false;
 119 #endif  // #ifdef ASSERT
 120 
 121 void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
 122                        HeapWord* destination)
 123 {
 124   assert(src_region_idx != 0, "invalid src_region_idx");
 125   assert(partial_obj_size != 0, "invalid partial_obj_size argument");
 126   assert(destination != NULL, "invalid destination argument");
 127 
 128   _src_region_idx = src_region_idx;
 129   _partial_obj_size = partial_obj_size;
 130   _destination = destination;
 131 
 132   // These fields may not be updated below, so make sure they're clear.
 133   assert(_dest_region_addr == NULL, "should have been cleared");
 134   assert(_first_src_addr == NULL, "should have been cleared");
 135 
 136   // Determine the number of destination regions for the partial object.
 137   HeapWord* const last_word = destination + partial_obj_size - 1;
 138   const ParallelCompactData& sd = PSParallelCompact::summary_data();
 139   HeapWord* const beg_region_addr = sd.region_align_down(destination);
 140   HeapWord* const end_region_addr = sd.region_align_down(last_word);
 141 
 142   if (beg_region_addr == end_region_addr) {
 143     // One destination region.
 144     _destination_count = 1;
 145     if (end_region_addr == destination) {
 146       // The destination falls on a region boundary, thus the first word of the
 147       // partial object will be the first word copied to the destination region.
 148       _dest_region_addr = end_region_addr;
 149       _first_src_addr = sd.region_to_addr(src_region_idx);
 150     }
 151   } else {
 152     // Two destination regions.  When copied, the partial object will cross a
 153     // destination region boundary, so a word somewhere within the partial
 154     // object will be the first word copied to the second destination region.
 155     _destination_count = 2;
 156     _dest_region_addr = end_region_addr;
 157     const size_t ofs = pointer_delta(end_region_addr, destination);
 158     assert(ofs < _partial_obj_size, "sanity");
 159     _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
 160   }
 161 }
 162 
 163 void SplitInfo::clear()
 164 {
 165   _src_region_idx = 0;
 166   _partial_obj_size = 0;
 167   _destination = NULL;
 168   _destination_count = 0;
 169   _dest_region_addr = NULL;
 170   _first_src_addr = NULL;
 171   assert(!is_valid(), "sanity");
 172 }
 173 
 174 #ifdef  ASSERT
 175 void SplitInfo::verify_clear()
 176 {
 177   assert(_src_region_idx == 0, "not clear");
 178   assert(_partial_obj_size == 0, "not clear");
 179   assert(_destination == NULL, "not clear");
 180   assert(_destination_count == 0, "not clear");
 181   assert(_dest_region_addr == NULL, "not clear");
 182   assert(_first_src_addr == NULL, "not clear");
 183 }
 184 #endif  // #ifdef ASSERT
 185 
 186 
 187 void PSParallelCompact::print_on_error(outputStream* st) {
 188   _mark_bitmap.print_on_error(st);
 189 }
 190 
 191 #ifndef PRODUCT
 192 const char* PSParallelCompact::space_names[] = {
 193   "old ", "eden", "from", "to  "
 194 };
 195 
 196 void PSParallelCompact::print_region_ranges()
 197 {
 198   tty->print_cr("space  bottom     top        end        new_top");
 199   tty->print_cr("------ ---------- ---------- ---------- ----------");
 200 
 201   for (unsigned int id = 0; id < last_space_id; ++id) {
 202     const MutableSpace* space = _space_info[id].space();
 203     tty->print_cr("%u %s "
 204                   SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
 205                   SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
 206                   id, space_names[id],
 207                   summary_data().addr_to_region_idx(space->bottom()),
 208                   summary_data().addr_to_region_idx(space->top()),
 209                   summary_data().addr_to_region_idx(space->end()),
 210                   summary_data().addr_to_region_idx(_space_info[id].new_top()));
 211   }
 212 }
 213 
 214 void
 215 print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
 216 {
 217 #define REGION_IDX_FORMAT        SIZE_FORMAT_W(7)
 218 #define REGION_DATA_FORMAT       SIZE_FORMAT_W(5)
 219 
 220   ParallelCompactData& sd = PSParallelCompact::summary_data();
 221   size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
 222   tty->print_cr(REGION_IDX_FORMAT " " PTR_FORMAT " "
 223                 REGION_IDX_FORMAT " " PTR_FORMAT " "
 224                 REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
 225                 REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
 226                 i, p2i(c->data_location()), dci, p2i(c->destination()),
 227                 c->partial_obj_size(), c->live_obj_size(),
 228                 c->data_size(), c->source_region(), c->destination_count());
 229 
 230 #undef  REGION_IDX_FORMAT
 231 #undef  REGION_DATA_FORMAT
 232 }
 233 
 234 void
 235 print_generic_summary_data(ParallelCompactData& summary_data,
 236                            HeapWord* const beg_addr,
 237                            HeapWord* const end_addr)
 238 {
 239   size_t total_words = 0;
 240   size_t i = summary_data.addr_to_region_idx(beg_addr);
 241   const size_t last = summary_data.addr_to_region_idx(end_addr);
 242   HeapWord* pdest = 0;
 243 
 244   while (i <= last) {
 245     ParallelCompactData::RegionData* c = summary_data.region(i);
 246     if (c->data_size() != 0 || c->destination() != pdest) {
 247       print_generic_summary_region(i, c);
 248       total_words += c->data_size();
 249       pdest = c->destination();
 250     }
 251     ++i;
 252   }
 253 
 254   tty->print_cr("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
 255 }
 256 
 257 void
 258 print_generic_summary_data(ParallelCompactData& summary_data,
 259                            SpaceInfo* space_info)
 260 {
 261   for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
 262     const MutableSpace* space = space_info[id].space();
 263     print_generic_summary_data(summary_data, space->bottom(),
 264                                MAX2(space->top(), space_info[id].new_top()));
 265   }
 266 }
 267 
 268 void
 269 print_initial_summary_region(size_t i,
 270                              const ParallelCompactData::RegionData* c,
 271                              bool newline = true)
 272 {
 273   tty->print(SIZE_FORMAT_W(5) " " PTR_FORMAT " "
 274              SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " "
 275              SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 276              i, p2i(c->destination()),
 277              c->partial_obj_size(), c->live_obj_size(),
 278              c->data_size(), c->source_region(), c->destination_count());
 279   if (newline) tty->cr();
 280 }
 281 
 282 void
 283 print_initial_summary_data(ParallelCompactData& summary_data,
 284                            const MutableSpace* space) {
 285   if (space->top() == space->bottom()) {
 286     return;
 287   }
 288 
 289   const size_t region_size = ParallelCompactData::RegionSize;
 290   typedef ParallelCompactData::RegionData RegionData;
 291   HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
 292   const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
 293   const RegionData* c = summary_data.region(end_region - 1);
 294   HeapWord* end_addr = c->destination() + c->data_size();
 295   const size_t live_in_space = pointer_delta(end_addr, space->bottom());
 296 
 297   // Print (and count) the full regions at the beginning of the space.
 298   size_t full_region_count = 0;
 299   size_t i = summary_data.addr_to_region_idx(space->bottom());
 300   while (i < end_region && summary_data.region(i)->data_size() == region_size) {
 301     print_initial_summary_region(i, summary_data.region(i));
 302     ++full_region_count;
 303     ++i;
 304   }
 305 
 306   size_t live_to_right = live_in_space - full_region_count * region_size;
 307 
 308   double max_reclaimed_ratio = 0.0;
 309   size_t max_reclaimed_ratio_region = 0;
 310   size_t max_dead_to_right = 0;
 311   size_t max_live_to_right = 0;
 312 
 313   // Print the 'reclaimed ratio' for regions while there is something live in
 314   // the region or to the right of it.  The remaining regions are empty (and
 315   // uninteresting), and computing the ratio will result in division by 0.
 316   while (i < end_region && live_to_right > 0) {
 317     c = summary_data.region(i);
 318     HeapWord* const region_addr = summary_data.region_to_addr(i);
 319     const size_t used_to_right = pointer_delta(space->top(), region_addr);
 320     const size_t dead_to_right = used_to_right - live_to_right;
 321     const double reclaimed_ratio = double(dead_to_right) / live_to_right;
 322 
 323     if (reclaimed_ratio > max_reclaimed_ratio) {
 324             max_reclaimed_ratio = reclaimed_ratio;
 325             max_reclaimed_ratio_region = i;
 326             max_dead_to_right = dead_to_right;
 327             max_live_to_right = live_to_right;
 328     }
 329 
 330     print_initial_summary_region(i, c, false);
 331     tty->print_cr(" %12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
 332                   reclaimed_ratio, dead_to_right, live_to_right);
 333 
 334     live_to_right -= c->data_size();
 335     ++i;
 336   }
 337 
 338   // Any remaining regions are empty.  Print one more if there is one.
 339   if (i < end_region) {
 340     print_initial_summary_region(i, summary_data.region(i));
 341   }
 342 
 343   tty->print_cr("max:  " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " "
 344                 "l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
 345                 max_reclaimed_ratio_region, max_dead_to_right,
 346                 max_live_to_right, max_reclaimed_ratio);
 347 }
 348 
 349 void
 350 print_initial_summary_data(ParallelCompactData& summary_data,
 351                            SpaceInfo* space_info) {
 352   unsigned int id = PSParallelCompact::old_space_id;
 353   const MutableSpace* space;
 354   do {
 355     space = space_info[id].space();
 356     print_initial_summary_data(summary_data, space);
 357   } while (++id < PSParallelCompact::eden_space_id);
 358 
 359   do {
 360     space = space_info[id].space();
 361     print_generic_summary_data(summary_data, space->bottom(), space->top());
 362   } while (++id < PSParallelCompact::last_space_id);
 363 }
 364 #endif  // #ifndef PRODUCT
 365 
 366 #ifdef  ASSERT
 367 size_t add_obj_count;
 368 size_t add_obj_size;
 369 size_t mark_bitmap_count;
 370 size_t mark_bitmap_size;
 371 #endif  // #ifdef ASSERT
 372 
 373 ParallelCompactData::ParallelCompactData()
 374 {
 375   _region_start = 0;
 376 
 377   _region_vspace = 0;
 378   _reserved_byte_size = 0;
 379   _region_data = 0;
 380   _region_count = 0;
 381 
 382   _block_vspace = 0;
 383   _block_data = 0;
 384   _block_count = 0;
 385 }
 386 
 387 bool ParallelCompactData::initialize(MemRegion covered_region)
 388 {
 389   _region_start = covered_region.start();
 390   const size_t region_size = covered_region.word_size();
 391   DEBUG_ONLY(_region_end = _region_start + region_size;)
 392 
 393   assert(region_align_down(_region_start) == _region_start,
 394          "region start not aligned");
 395   assert((region_size & RegionSizeOffsetMask) == 0,
 396          "region size not a multiple of RegionSize");
 397 
 398   bool result = initialize_region_data(region_size) && initialize_block_data();
 399   return result;
 400 }
 401 
 402 PSVirtualSpace*
 403 ParallelCompactData::create_vspace(size_t count, size_t element_size)
 404 {
 405   const size_t raw_bytes = count * element_size;
 406   const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
 407   const size_t granularity = os::vm_allocation_granularity();
 408   _reserved_byte_size = align_size_up(raw_bytes, MAX2(page_sz, granularity));
 409 
 410   const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
 411     MAX2(page_sz, granularity);
 412   ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0);
 413   os::trace_page_sizes("par compact", raw_bytes, raw_bytes, page_sz, rs.base(),
 414                        rs.size());
 415 
 416   MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
 417 
 418   PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
 419   if (vspace != 0) {
 420     if (vspace->expand_by(_reserved_byte_size)) {
 421       return vspace;
 422     }
 423     delete vspace;
 424     // Release memory reserved in the space.
 425     rs.release();
 426   }
 427 
 428   return 0;
 429 }
 430 
 431 bool ParallelCompactData::initialize_region_data(size_t region_size)
 432 {
 433   const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
 434   _region_vspace = create_vspace(count, sizeof(RegionData));
 435   if (_region_vspace != 0) {
 436     _region_data = (RegionData*)_region_vspace->reserved_low_addr();
 437     _region_count = count;
 438     return true;
 439   }
 440   return false;
 441 }
 442 
 443 bool ParallelCompactData::initialize_block_data()
 444 {
 445   assert(_region_count != 0, "region data must be initialized first");
 446   const size_t count = _region_count << Log2BlocksPerRegion;
 447   _block_vspace = create_vspace(count, sizeof(BlockData));
 448   if (_block_vspace != 0) {
 449     _block_data = (BlockData*)_block_vspace->reserved_low_addr();
 450     _block_count = count;
 451     return true;
 452   }
 453   return false;
 454 }
 455 
 456 void ParallelCompactData::clear()
 457 {
 458   memset(_region_data, 0, _region_vspace->committed_size());
 459   memset(_block_data, 0, _block_vspace->committed_size());
 460 }
 461 
 462 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
 463   assert(beg_region <= _region_count, "beg_region out of range");
 464   assert(end_region <= _region_count, "end_region out of range");
 465   assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize");
 466 
 467   const size_t region_cnt = end_region - beg_region;
 468   memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
 469 
 470   const size_t beg_block = beg_region * BlocksPerRegion;
 471   const size_t block_cnt = region_cnt * BlocksPerRegion;
 472   memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData));
 473 }
 474 
 475 HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
 476 {
 477   const RegionData* cur_cp = region(region_idx);
 478   const RegionData* const end_cp = region(region_count() - 1);
 479 
 480   HeapWord* result = region_to_addr(region_idx);
 481   if (cur_cp < end_cp) {
 482     do {
 483       result += cur_cp->partial_obj_size();
 484     } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
 485   }
 486   return result;
 487 }
 488 
 489 void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
 490 {
 491   const size_t obj_ofs = pointer_delta(addr, _region_start);
 492   const size_t beg_region = obj_ofs >> Log2RegionSize;
 493   const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
 494 
 495   DEBUG_ONLY(Atomic::inc_ptr(&add_obj_count);)
 496   DEBUG_ONLY(Atomic::add_ptr(len, &add_obj_size);)
 497 
 498   if (beg_region == end_region) {
 499     // All in one region.
 500     _region_data[beg_region].add_live_obj(len);
 501     return;
 502   }
 503 
 504   // First region.
 505   const size_t beg_ofs = region_offset(addr);
 506   _region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
 507 
 508   Klass* klass = ((oop)addr)->klass();
 509   // Middle regions--completely spanned by this object.
 510   for (size_t region = beg_region + 1; region < end_region; ++region) {
 511     _region_data[region].set_partial_obj_size(RegionSize);
 512     _region_data[region].set_partial_obj_addr(addr);
 513   }
 514 
 515   // Last region.
 516   const size_t end_ofs = region_offset(addr + len - 1);
 517   _region_data[end_region].set_partial_obj_size(end_ofs + 1);
 518   _region_data[end_region].set_partial_obj_addr(addr);
 519 }
 520 
 521 void
 522 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
 523 {
 524   assert(region_offset(beg) == 0, "not RegionSize aligned");
 525   assert(region_offset(end) == 0, "not RegionSize aligned");
 526 
 527   size_t cur_region = addr_to_region_idx(beg);
 528   const size_t end_region = addr_to_region_idx(end);
 529   HeapWord* addr = beg;
 530   while (cur_region < end_region) {
 531     _region_data[cur_region].set_destination(addr);
 532     _region_data[cur_region].set_destination_count(0);
 533     _region_data[cur_region].set_source_region(cur_region);
 534     _region_data[cur_region].set_data_location(addr);
 535 
 536     // Update live_obj_size so the region appears completely full.
 537     size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
 538     _region_data[cur_region].set_live_obj_size(live_size);
 539 
 540     ++cur_region;
 541     addr += RegionSize;
 542   }
 543 }
 544 
 545 // Find the point at which a space can be split and, if necessary, record the
 546 // split point.
 547 //
 548 // If the current src region (which overflowed the destination space) doesn't
 549 // have a partial object, the split point is at the beginning of the current src
 550 // region (an "easy" split, no extra bookkeeping required).
 551 //
 552 // If the current src region has a partial object, the split point is in the
 553 // region where that partial object starts (call it the split_region).  If
 554 // split_region has a partial object, then the split point is just after that
 555 // partial object (a "hard" split where we have to record the split data and
 556 // zero the partial_obj_size field).  With a "hard" split, we know that the
 557 // partial_obj ends within split_region because the partial object that caused
 558 // the overflow starts in split_region.  If split_region doesn't have a partial
 559 // obj, then the split is at the beginning of split_region (another "easy"
 560 // split).
 561 HeapWord*
 562 ParallelCompactData::summarize_split_space(size_t src_region,
 563                                            SplitInfo& split_info,
 564                                            HeapWord* destination,
 565                                            HeapWord* target_end,
 566                                            HeapWord** target_next)
 567 {
 568   assert(destination <= target_end, "sanity");
 569   assert(destination + _region_data[src_region].data_size() > target_end,
 570     "region should not fit into target space");
 571   assert(is_region_aligned(target_end), "sanity");
 572 
 573   size_t split_region = src_region;
 574   HeapWord* split_destination = destination;
 575   size_t partial_obj_size = _region_data[src_region].partial_obj_size();
 576 
 577   if (destination + partial_obj_size > target_end) {
 578     // The split point is just after the partial object (if any) in the
 579     // src_region that contains the start of the object that overflowed the
 580     // destination space.
 581     //
 582     // Find the start of the "overflow" object and set split_region to the
 583     // region containing it.
 584     HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
 585     split_region = addr_to_region_idx(overflow_obj);
 586 
 587     // Clear the source_region field of all destination regions whose first word
 588     // came from data after the split point (a non-null source_region field
 589     // implies a region must be filled).
 590     //
 591     // An alternative to the simple loop below:  clear during post_compact(),
 592     // which uses memcpy instead of individual stores, and is easy to
 593     // parallelize.  (The downside is that it clears the entire RegionData
 594     // object as opposed to just one field.)
 595     //
 596     // post_compact() would have to clear the summary data up to the highest
 597     // address that was written during the summary phase, which would be
 598     //
 599     //         max(top, max(new_top, clear_top))
 600     //
 601     // where clear_top is a new field in SpaceInfo.  Would have to set clear_top
 602     // to target_end.
 603     const RegionData* const sr = region(split_region);
 604     const size_t beg_idx =
 605       addr_to_region_idx(region_align_up(sr->destination() +
 606                                          sr->partial_obj_size()));
 607     const size_t end_idx = addr_to_region_idx(target_end);
 608 
 609     if (TraceParallelOldGCSummaryPhase) {
 610         gclog_or_tty->print_cr("split:  clearing source_region field in ["
 611                                SIZE_FORMAT ", " SIZE_FORMAT ")",
 612                                beg_idx, end_idx);
 613     }
 614     for (size_t idx = beg_idx; idx < end_idx; ++idx) {
 615       _region_data[idx].set_source_region(0);
 616     }
 617 
 618     // Set split_destination and partial_obj_size to reflect the split region.
 619     split_destination = sr->destination();
 620     partial_obj_size = sr->partial_obj_size();
 621   }
 622 
 623   // The split is recorded only if a partial object extends onto the region.
 624   if (partial_obj_size != 0) {
 625     _region_data[split_region].set_partial_obj_size(0);
 626     split_info.record(split_region, partial_obj_size, split_destination);
 627   }
 628 
 629   // Setup the continuation addresses.
 630   *target_next = split_destination + partial_obj_size;
 631   HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
 632 
 633   if (TraceParallelOldGCSummaryPhase) {
 634     const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
 635     gclog_or_tty->print_cr("%s split:  src=" PTR_FORMAT " src_c=" SIZE_FORMAT
 636                            " pos=" SIZE_FORMAT,
 637                            split_type, p2i(source_next), split_region,
 638                            partial_obj_size);
 639     gclog_or_tty->print_cr("%s split:  dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT
 640                            " tn=" PTR_FORMAT,
 641                            split_type, p2i(split_destination),
 642                            addr_to_region_idx(split_destination),
 643                            p2i(*target_next));
 644 
 645     if (partial_obj_size != 0) {
 646       HeapWord* const po_beg = split_info.destination();
 647       HeapWord* const po_end = po_beg + split_info.partial_obj_size();
 648       gclog_or_tty->print_cr("%s split:  "
 649                              "po_beg=" PTR_FORMAT " " SIZE_FORMAT " "
 650                              "po_end=" PTR_FORMAT " " SIZE_FORMAT,
 651                              split_type,
 652                              p2i(po_beg), addr_to_region_idx(po_beg),
 653                              p2i(po_end), addr_to_region_idx(po_end));
 654     }
 655   }
 656 
 657   return source_next;
 658 }
 659 
 660 bool ParallelCompactData::summarize(SplitInfo& split_info,
 661                                     HeapWord* source_beg, HeapWord* source_end,
 662                                     HeapWord** source_next,
 663                                     HeapWord* target_beg, HeapWord* target_end,
 664                                     HeapWord** target_next)
 665 {
 666   if (TraceParallelOldGCSummaryPhase) {
 667     HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
 668     tty->print_cr("sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
 669                   "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
 670                   p2i(source_beg), p2i(source_end), p2i(source_next_val),
 671                   p2i(target_beg), p2i(target_end), p2i(*target_next));
 672   }
 673 
 674   size_t cur_region = addr_to_region_idx(source_beg);
 675   const size_t end_region = addr_to_region_idx(region_align_up(source_end));
 676 
 677   HeapWord *dest_addr = target_beg;
 678   while (cur_region < end_region) {
 679     // The destination must be set even if the region has no data.
 680     _region_data[cur_region].set_destination(dest_addr);
 681 
 682     size_t words = _region_data[cur_region].data_size();
 683     if (words > 0) {
 684       // If cur_region does not fit entirely into the target space, find a point
 685       // at which the source space can be 'split' so that part is copied to the
 686       // target space and the rest is copied elsewhere.
 687       if (dest_addr + words > target_end) {
 688         assert(source_next != NULL, "source_next is NULL when splitting");
 689         *source_next = summarize_split_space(cur_region, split_info, dest_addr,
 690                                              target_end, target_next);
 691         return false;
 692       }
 693 
 694       // Compute the destination_count for cur_region, and if necessary, update
 695       // source_region for a destination region.  The source_region field is
 696       // updated if cur_region is the first (left-most) region to be copied to a
 697       // destination region.
 698       //
 699       // The destination_count calculation is a bit subtle.  A region that has
 700       // data that compacts into itself does not count itself as a destination.
 701       // This maintains the invariant that a zero count means the region is
 702       // available and can be claimed and then filled.
 703       uint destination_count = 0;
 704       if (split_info.is_split(cur_region)) {
 705         // The current region has been split:  the partial object will be copied
 706         // to one destination space and the remaining data will be copied to
 707         // another destination space.  Adjust the initial destination_count and,
 708         // if necessary, set the source_region field if the partial object will
 709         // cross a destination region boundary.
 710         destination_count = split_info.destination_count();
 711         if (destination_count == 2) {
 712           size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
 713           _region_data[dest_idx].set_source_region(cur_region);
 714         }
 715       }
 716 
 717       HeapWord* const last_addr = dest_addr + words - 1;
 718       const size_t dest_region_1 = addr_to_region_idx(dest_addr);
 719       const size_t dest_region_2 = addr_to_region_idx(last_addr);
 720 
 721       // Initially assume that the destination regions will be the same and
 722       // adjust the value below if necessary.  Under this assumption, if
 723       // cur_region == dest_region_2, then cur_region will be compacted
 724       // completely into itself.
 725       destination_count += cur_region == dest_region_2 ? 0 : 1;
 726       if (dest_region_1 != dest_region_2) {
 727         // Destination regions differ; adjust destination_count.
 728         destination_count += 1;
 729         // Data from cur_region will be copied to the start of dest_region_2.
 730         _region_data[dest_region_2].set_source_region(cur_region);
 731       } else if (region_offset(dest_addr) == 0) {
 732         // Data from cur_region will be copied to the start of the destination
 733         // region.
 734         _region_data[dest_region_1].set_source_region(cur_region);
 735       }
 736 
 737       _region_data[cur_region].set_destination_count(destination_count);
 738       _region_data[cur_region].set_data_location(region_to_addr(cur_region));
 739       dest_addr += words;
 740     }
 741 
 742     ++cur_region;
 743   }
 744 
 745   *target_next = dest_addr;
 746   return true;
 747 }
 748 
 749 HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr) {
 750   assert(addr != NULL, "Should detect NULL oop earlier");
 751   assert(ParallelScavengeHeap::heap()->is_in(addr), "not in heap");
 752   assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked");
 753 
 754   // Region covering the object.
 755   RegionData* const region_ptr = addr_to_region_ptr(addr);
 756   HeapWord* result = region_ptr->destination();
 757 
 758   // If the entire Region is live, the new location is region->destination + the
 759   // offset of the object within in the Region.
 760 
 761   // Run some performance tests to determine if this special case pays off.  It
 762   // is worth it for pointers into the dense prefix.  If the optimization to
 763   // avoid pointer updates in regions that only point to the dense prefix is
 764   // ever implemented, this should be revisited.
 765   if (region_ptr->data_size() == RegionSize) {
 766     result += region_offset(addr);
 767     return result;
 768   }
 769 
 770   // Otherwise, the new location is region->destination + block offset + the
 771   // number of live words in the Block that are (a) to the left of addr and (b)
 772   // due to objects that start in the Block.
 773 
 774   // Fill in the block table if necessary.  This is unsynchronized, so multiple
 775   // threads may fill the block table for a region (harmless, since it is
 776   // idempotent).
 777   if (!region_ptr->blocks_filled()) {
 778     PSParallelCompact::fill_blocks(addr_to_region_idx(addr));
 779     region_ptr->set_blocks_filled();
 780   }
 781 
 782   HeapWord* const search_start = block_align_down(addr);
 783   const size_t block_offset = addr_to_block_ptr(addr)->offset();
 784 
 785   const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
 786   const size_t live = bitmap->live_words_in_range(search_start, oop(addr));
 787   result += block_offset + live;
 788   DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result));
 789   return result;
 790 }
 791 
 792 #ifdef ASSERT
 793 void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
 794 {
 795   const size_t* const beg = (const size_t*)vspace->committed_low_addr();
 796   const size_t* const end = (const size_t*)vspace->committed_high_addr();
 797   for (const size_t* p = beg; p < end; ++p) {
 798     assert(*p == 0, "not zero");
 799   }
 800 }
 801 
 802 void ParallelCompactData::verify_clear()
 803 {
 804   verify_clear(_region_vspace);
 805   verify_clear(_block_vspace);
 806 }
 807 #endif  // #ifdef ASSERT
 808 
 809 STWGCTimer          PSParallelCompact::_gc_timer;
 810 ParallelOldTracer   PSParallelCompact::_gc_tracer;
 811 elapsedTimer        PSParallelCompact::_accumulated_time;
 812 unsigned int        PSParallelCompact::_total_invocations = 0;
 813 unsigned int        PSParallelCompact::_maximum_compaction_gc_num = 0;
 814 jlong               PSParallelCompact::_time_of_last_gc = 0;
 815 CollectorCounters*  PSParallelCompact::_counters = NULL;
 816 ParMarkBitMap       PSParallelCompact::_mark_bitmap;
 817 ParallelCompactData PSParallelCompact::_summary_data;
 818 
 819 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
 820 
 821 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
 822 
 823 void PSParallelCompact::KeepAliveClosure::do_oop(oop* p)       { PSParallelCompact::KeepAliveClosure::do_oop_work(p); }
 824 void PSParallelCompact::KeepAliveClosure::do_oop(narrowOop* p) { PSParallelCompact::KeepAliveClosure::do_oop_work(p); }
 825 
 826 PSParallelCompact::AdjustPointerClosure PSParallelCompact::_adjust_pointer_closure;
 827 PSParallelCompact::AdjustKlassClosure PSParallelCompact::_adjust_klass_closure;
 828 
 829 void PSParallelCompact::FollowStackClosure::do_void() { _compaction_manager->follow_marking_stacks(); }
 830 
 831 void PSParallelCompact::FollowKlassClosure::do_klass(Klass* klass) {
 832   klass->oops_do(_mark_and_push_closure);
 833 }
 834 void PSParallelCompact::AdjustKlassClosure::do_klass(Klass* klass) {
 835   klass->oops_do(&PSParallelCompact::_adjust_pointer_closure);
 836 }
 837 
 838 void PSParallelCompact::post_initialize() {
 839   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 840   MemRegion mr = heap->reserved_region();
 841   _ref_processor =
 842     new ReferenceProcessor(mr,            // span
 843                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 844                            (int) ParallelGCThreads, // mt processing degree
 845                            true,          // mt discovery
 846                            (int) ParallelGCThreads, // mt discovery degree
 847                            true,          // atomic_discovery
 848                            &_is_alive_closure); // non-header is alive closure
 849   _counters = new CollectorCounters("PSParallelCompact", 1);
 850 
 851   // Initialize static fields in ParCompactionManager.
 852   ParCompactionManager::initialize(mark_bitmap());
 853 }
 854 
 855 bool PSParallelCompact::initialize() {
 856   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 857   MemRegion mr = heap->reserved_region();
 858 
 859   // Was the old gen get allocated successfully?
 860   if (!heap->old_gen()->is_allocated()) {
 861     return false;
 862   }
 863 
 864   initialize_space_info();
 865   initialize_dead_wood_limiter();
 866 
 867   if (!_mark_bitmap.initialize(mr)) {
 868     vm_shutdown_during_initialization(
 869       err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
 870       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 871       _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
 872     return false;
 873   }
 874 
 875   if (!_summary_data.initialize(mr)) {
 876     vm_shutdown_during_initialization(
 877       err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
 878       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 879       _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
 880     return false;
 881   }
 882 
 883   return true;
 884 }
 885 
 886 void PSParallelCompact::initialize_space_info()
 887 {
 888   memset(&_space_info, 0, sizeof(_space_info));
 889 
 890   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 891   PSYoungGen* young_gen = heap->young_gen();
 892 
 893   _space_info[old_space_id].set_space(heap->old_gen()->object_space());
 894   _space_info[eden_space_id].set_space(young_gen->eden_space());
 895   _space_info[from_space_id].set_space(young_gen->from_space());
 896   _space_info[to_space_id].set_space(young_gen->to_space());
 897 
 898   _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
 899 }
 900 
 901 void PSParallelCompact::initialize_dead_wood_limiter()
 902 {
 903   const size_t max = 100;
 904   _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
 905   _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
 906   _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
 907   DEBUG_ONLY(_dwl_initialized = true;)
 908   _dwl_adjustment = normal_distribution(1.0);
 909 }
 910 
 911 // Simple class for storing info about the heap at the start of GC, to be used
 912 // after GC for comparison/printing.
 913 class PreGCValues {
 914 public:
 915   PreGCValues() { }
 916   PreGCValues(ParallelScavengeHeap* heap) { fill(heap); }
 917 
 918   void fill(ParallelScavengeHeap* heap) {
 919     _heap_used      = heap->used();
 920     _young_gen_used = heap->young_gen()->used_in_bytes();
 921     _old_gen_used   = heap->old_gen()->used_in_bytes();
 922     _metadata_used  = MetaspaceAux::used_bytes();
 923   };
 924 
 925   size_t heap_used() const      { return _heap_used; }
 926   size_t young_gen_used() const { return _young_gen_used; }
 927   size_t old_gen_used() const   { return _old_gen_used; }
 928   size_t metadata_used() const  { return _metadata_used; }
 929 
 930 private:
 931   size_t _heap_used;
 932   size_t _young_gen_used;
 933   size_t _old_gen_used;
 934   size_t _metadata_used;
 935 };
 936 
 937 void
 938 PSParallelCompact::clear_data_covering_space(SpaceId id)
 939 {
 940   // At this point, top is the value before GC, new_top() is the value that will
 941   // be set at the end of GC.  The marking bitmap is cleared to top; nothing
 942   // should be marked above top.  The summary data is cleared to the larger of
 943   // top & new_top.
 944   MutableSpace* const space = _space_info[id].space();
 945   HeapWord* const bot = space->bottom();
 946   HeapWord* const top = space->top();
 947   HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
 948 
 949   const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
 950   const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top));
 951   _mark_bitmap.clear_range(beg_bit, end_bit);
 952 
 953   const size_t beg_region = _summary_data.addr_to_region_idx(bot);
 954   const size_t end_region =
 955     _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
 956   _summary_data.clear_range(beg_region, end_region);
 957 
 958   // Clear the data used to 'split' regions.
 959   SplitInfo& split_info = _space_info[id].split_info();
 960   if (split_info.is_valid()) {
 961     split_info.clear();
 962   }
 963   DEBUG_ONLY(split_info.verify_clear();)
 964 }
 965 
 966 void PSParallelCompact::pre_compact(PreGCValues* pre_gc_values)
 967 {
 968   // Update the from & to space pointers in space_info, since they are swapped
 969   // at each young gen gc.  Do the update unconditionally (even though a
 970   // promotion failure does not swap spaces) because an unknown number of minor
 971   // collections will have swapped the spaces an unknown number of times.
 972   GCTraceTime tm("pre compact", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
 973   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 974   _space_info[from_space_id].set_space(heap->young_gen()->from_space());
 975   _space_info[to_space_id].set_space(heap->young_gen()->to_space());
 976 
 977   pre_gc_values->fill(heap);
 978 
 979   DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
 980   DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
 981 
 982   // Increment the invocation count
 983   heap->increment_total_collections(true);
 984 
 985   // We need to track unique mark sweep invocations as well.
 986   _total_invocations++;
 987 
 988   heap->print_heap_before_gc();
 989   heap->trace_heap_before_gc(&_gc_tracer);
 990 
 991   // Fill in TLABs
 992   heap->accumulate_statistics_all_tlabs();
 993   heap->ensure_parsability(true);  // retire TLABs
 994 
 995   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 996     HandleMark hm;  // Discard invalid handles created during verification
 997     Universe::verify(" VerifyBeforeGC:");
 998   }
 999 
1000   // Verify object start arrays
1001   if (VerifyObjectStartArray &&
1002       VerifyBeforeGC) {
1003     heap->old_gen()->verify_object_start_array();
1004   }
1005 
1006   DEBUG_ONLY(mark_bitmap()->verify_clear();)
1007   DEBUG_ONLY(summary_data().verify_clear();)
1008 
1009   // Have worker threads release resources the next time they run a task.
1010   gc_task_manager()->release_all_resources();
1011 }
1012 
1013 void PSParallelCompact::post_compact()
1014 {
1015   GCTraceTime tm("post compact", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
1016 
1017   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1018     // Clear the marking bitmap, summary data and split info.
1019     clear_data_covering_space(SpaceId(id));
1020     // Update top().  Must be done after clearing the bitmap and summary data.
1021     _space_info[id].publish_new_top();
1022   }
1023 
1024   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1025   MutableSpace* const from_space = _space_info[from_space_id].space();
1026   MutableSpace* const to_space   = _space_info[to_space_id].space();
1027 
1028   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1029   bool eden_empty = eden_space->is_empty();
1030   if (!eden_empty) {
1031     eden_empty = absorb_live_data_from_eden(heap->size_policy(),
1032                                             heap->young_gen(), heap->old_gen());
1033   }
1034 
1035   // Update heap occupancy information which is used as input to the soft ref
1036   // clearing policy at the next gc.
1037   Universe::update_heap_info_at_gc();
1038 
1039   bool young_gen_empty = eden_empty && from_space->is_empty() &&
1040     to_space->is_empty();
1041 
1042   ModRefBarrierSet* modBS = barrier_set_cast<ModRefBarrierSet>(heap->barrier_set());
1043   MemRegion old_mr = heap->old_gen()->reserved();
1044   if (young_gen_empty) {
1045     modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
1046   } else {
1047     modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1048   }
1049 
1050   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1051   ClassLoaderDataGraph::purge();
1052   MetaspaceAux::verify_metrics();
1053 
1054   CodeCache::gc_epilogue();
1055   JvmtiExport::gc_epilogue();
1056 
1057   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1058 
1059   ref_processor()->enqueue_discovered_references(NULL);
1060 
1061   if (ZapUnusedHeapArea) {
1062     heap->gen_mangle_unused_area();
1063   }
1064 
1065   // Update time of last GC
1066   reset_millis_since_last_gc();
1067 }
1068 
1069 HeapWord*
1070 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1071                                                     bool maximum_compaction)
1072 {
1073   const size_t region_size = ParallelCompactData::RegionSize;
1074   const ParallelCompactData& sd = summary_data();
1075 
1076   const MutableSpace* const space = _space_info[id].space();
1077   HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1078   const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1079   const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1080 
1081   // Skip full regions at the beginning of the space--they are necessarily part
1082   // of the dense prefix.
1083   size_t full_count = 0;
1084   const RegionData* cp;
1085   for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1086     ++full_count;
1087   }
1088 
1089   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1090   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1091   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1092   if (maximum_compaction || cp == end_cp || interval_ended) {
1093     _maximum_compaction_gc_num = total_invocations();
1094     return sd.region_to_addr(cp);
1095   }
1096 
1097   HeapWord* const new_top = _space_info[id].new_top();
1098   const size_t space_live = pointer_delta(new_top, space->bottom());
1099   const size_t space_used = space->used_in_words();
1100   const size_t space_capacity = space->capacity_in_words();
1101 
1102   const double cur_density = double(space_live) / space_capacity;
1103   const double deadwood_density =
1104     (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1105   const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1106 
1107   if (TraceParallelOldGCDensePrefix) {
1108     tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1109                   cur_density, deadwood_density, deadwood_goal);
1110     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1111                   "space_cap=" SIZE_FORMAT,
1112                   space_live, space_used,
1113                   space_capacity);
1114   }
1115 
1116   // XXX - Use binary search?
1117   HeapWord* dense_prefix = sd.region_to_addr(cp);
1118   const RegionData* full_cp = cp;
1119   const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1120   while (cp < end_cp) {
1121     HeapWord* region_destination = cp->destination();
1122     const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1123     if (TraceParallelOldGCDensePrefix && Verbose) {
1124       tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1125                     "dp=" PTR_FORMAT " " "cdw=" SIZE_FORMAT_W(8),
1126                     sd.region(cp), p2i(region_destination),
1127                     p2i(dense_prefix), cur_deadwood);
1128     }
1129 
1130     if (cur_deadwood >= deadwood_goal) {
1131       // Found the region that has the correct amount of deadwood to the left.
1132       // This typically occurs after crossing a fairly sparse set of regions, so
1133       // iterate backwards over those sparse regions, looking for the region
1134       // that has the lowest density of live objects 'to the right.'
1135       size_t space_to_left = sd.region(cp) * region_size;
1136       size_t live_to_left = space_to_left - cur_deadwood;
1137       size_t space_to_right = space_capacity - space_to_left;
1138       size_t live_to_right = space_live - live_to_left;
1139       double density_to_right = double(live_to_right) / space_to_right;
1140       while (cp > full_cp) {
1141         --cp;
1142         const size_t prev_region_live_to_right = live_to_right -
1143           cp->data_size();
1144         const size_t prev_region_space_to_right = space_to_right + region_size;
1145         double prev_region_density_to_right =
1146           double(prev_region_live_to_right) / prev_region_space_to_right;
1147         if (density_to_right <= prev_region_density_to_right) {
1148           return dense_prefix;
1149         }
1150         if (TraceParallelOldGCDensePrefix && Verbose) {
1151           tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1152                         "pc_d2r=%10.8f", sd.region(cp), density_to_right,
1153                         prev_region_density_to_right);
1154         }
1155         dense_prefix -= region_size;
1156         live_to_right = prev_region_live_to_right;
1157         space_to_right = prev_region_space_to_right;
1158         density_to_right = prev_region_density_to_right;
1159       }
1160       return dense_prefix;
1161     }
1162 
1163     dense_prefix += region_size;
1164     ++cp;
1165   }
1166 
1167   return dense_prefix;
1168 }
1169 
1170 #ifndef PRODUCT
1171 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1172                                                  const SpaceId id,
1173                                                  const bool maximum_compaction,
1174                                                  HeapWord* const addr)
1175 {
1176   const size_t region_idx = summary_data().addr_to_region_idx(addr);
1177   RegionData* const cp = summary_data().region(region_idx);
1178   const MutableSpace* const space = _space_info[id].space();
1179   HeapWord* const new_top = _space_info[id].new_top();
1180 
1181   const size_t space_live = pointer_delta(new_top, space->bottom());
1182   const size_t dead_to_left = pointer_delta(addr, cp->destination());
1183   const size_t space_cap = space->capacity_in_words();
1184   const double dead_to_left_pct = double(dead_to_left) / space_cap;
1185   const size_t live_to_right = new_top - cp->destination();
1186   const size_t dead_to_right = space->top() - addr - live_to_right;
1187 
1188   tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1189                 "spl=" SIZE_FORMAT " "
1190                 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1191                 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
1192                 " ratio=%10.8f",
1193                 algorithm, p2i(addr), region_idx,
1194                 space_live,
1195                 dead_to_left, dead_to_left_pct,
1196                 dead_to_right, live_to_right,
1197                 double(dead_to_right) / live_to_right);
1198 }
1199 #endif  // #ifndef PRODUCT
1200 
1201 // Return a fraction indicating how much of the generation can be treated as
1202 // "dead wood" (i.e., not reclaimed).  The function uses a normal distribution
1203 // based on the density of live objects in the generation to determine a limit,
1204 // which is then adjusted so the return value is min_percent when the density is
1205 // 1.
1206 //
1207 // The following table shows some return values for a different values of the
1208 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1209 // min_percent is 1.
1210 //
1211 //                          fraction allowed as dead wood
1212 //         -----------------------------------------------------------------
1213 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1214 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1215 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1216 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1217 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1218 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1219 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1220 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1221 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1222 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1223 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1224 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1225 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1226 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1227 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1228 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1229 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1230 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1231 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1232 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1233 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1234 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1235 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1236 
1237 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1238 {
1239   assert(_dwl_initialized, "uninitialized");
1240 
1241   // The raw limit is the value of the normal distribution at x = density.
1242   const double raw_limit = normal_distribution(density);
1243 
1244   // Adjust the raw limit so it becomes the minimum when the density is 1.
1245   //
1246   // First subtract the adjustment value (which is simply the precomputed value
1247   // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1248   // Then add the minimum value, so the minimum is returned when the density is
1249   // 1.  Finally, prevent negative values, which occur when the mean is not 0.5.
1250   const double min = double(min_percent) / 100.0;
1251   const double limit = raw_limit - _dwl_adjustment + min;
1252   return MAX2(limit, 0.0);
1253 }
1254 
1255 ParallelCompactData::RegionData*
1256 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1257                                            const RegionData* end)
1258 {
1259   const size_t region_size = ParallelCompactData::RegionSize;
1260   ParallelCompactData& sd = summary_data();
1261   size_t left = sd.region(beg);
1262   size_t right = end > beg ? sd.region(end) - 1 : left;
1263 
1264   // Binary search.
1265   while (left < right) {
1266     // Equivalent to (left + right) / 2, but does not overflow.
1267     const size_t middle = left + (right - left) / 2;
1268     RegionData* const middle_ptr = sd.region(middle);
1269     HeapWord* const dest = middle_ptr->destination();
1270     HeapWord* const addr = sd.region_to_addr(middle);
1271     assert(dest != NULL, "sanity");
1272     assert(dest <= addr, "must move left");
1273 
1274     if (middle > left && dest < addr) {
1275       right = middle - 1;
1276     } else if (middle < right && middle_ptr->data_size() == region_size) {
1277       left = middle + 1;
1278     } else {
1279       return middle_ptr;
1280     }
1281   }
1282   return sd.region(left);
1283 }
1284 
1285 ParallelCompactData::RegionData*
1286 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1287                                           const RegionData* end,
1288                                           size_t dead_words)
1289 {
1290   ParallelCompactData& sd = summary_data();
1291   size_t left = sd.region(beg);
1292   size_t right = end > beg ? sd.region(end) - 1 : left;
1293 
1294   // Binary search.
1295   while (left < right) {
1296     // Equivalent to (left + right) / 2, but does not overflow.
1297     const size_t middle = left + (right - left) / 2;
1298     RegionData* const middle_ptr = sd.region(middle);
1299     HeapWord* const dest = middle_ptr->destination();
1300     HeapWord* const addr = sd.region_to_addr(middle);
1301     assert(dest != NULL, "sanity");
1302     assert(dest <= addr, "must move left");
1303 
1304     const size_t dead_to_left = pointer_delta(addr, dest);
1305     if (middle > left && dead_to_left > dead_words) {
1306       right = middle - 1;
1307     } else if (middle < right && dead_to_left < dead_words) {
1308       left = middle + 1;
1309     } else {
1310       return middle_ptr;
1311     }
1312   }
1313   return sd.region(left);
1314 }
1315 
1316 // The result is valid during the summary phase, after the initial summarization
1317 // of each space into itself, and before final summarization.
1318 inline double
1319 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1320                                    HeapWord* const bottom,
1321                                    HeapWord* const top,
1322                                    HeapWord* const new_top)
1323 {
1324   ParallelCompactData& sd = summary_data();
1325 
1326   assert(cp != NULL, "sanity");
1327   assert(bottom != NULL, "sanity");
1328   assert(top != NULL, "sanity");
1329   assert(new_top != NULL, "sanity");
1330   assert(top >= new_top, "summary data problem?");
1331   assert(new_top > bottom, "space is empty; should not be here");
1332   assert(new_top >= cp->destination(), "sanity");
1333   assert(top >= sd.region_to_addr(cp), "sanity");
1334 
1335   HeapWord* const destination = cp->destination();
1336   const size_t dense_prefix_live  = pointer_delta(destination, bottom);
1337   const size_t compacted_region_live = pointer_delta(new_top, destination);
1338   const size_t compacted_region_used = pointer_delta(top,
1339                                                      sd.region_to_addr(cp));
1340   const size_t reclaimable = compacted_region_used - compacted_region_live;
1341 
1342   const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1343   return double(reclaimable) / divisor;
1344 }
1345 
1346 // Return the address of the end of the dense prefix, a.k.a. the start of the
1347 // compacted region.  The address is always on a region boundary.
1348 //
1349 // Completely full regions at the left are skipped, since no compaction can
1350 // occur in those regions.  Then the maximum amount of dead wood to allow is
1351 // computed, based on the density (amount live / capacity) of the generation;
1352 // the region with approximately that amount of dead space to the left is
1353 // identified as the limit region.  Regions between the last completely full
1354 // region and the limit region are scanned and the one that has the best
1355 // (maximum) reclaimed_ratio() is selected.
1356 HeapWord*
1357 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1358                                         bool maximum_compaction)
1359 {
1360   if (ParallelOldGCSplitALot) {
1361     if (_space_info[id].dense_prefix() != _space_info[id].space()->bottom()) {
1362       // The value was chosen to provoke splitting a young gen space; use it.
1363       return _space_info[id].dense_prefix();
1364     }
1365   }
1366 
1367   const size_t region_size = ParallelCompactData::RegionSize;
1368   const ParallelCompactData& sd = summary_data();
1369 
1370   const MutableSpace* const space = _space_info[id].space();
1371   HeapWord* const top = space->top();
1372   HeapWord* const top_aligned_up = sd.region_align_up(top);
1373   HeapWord* const new_top = _space_info[id].new_top();
1374   HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1375   HeapWord* const bottom = space->bottom();
1376   const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1377   const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1378   const RegionData* const new_top_cp =
1379     sd.addr_to_region_ptr(new_top_aligned_up);
1380 
1381   // Skip full regions at the beginning of the space--they are necessarily part
1382   // of the dense prefix.
1383   const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1384   assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1385          space->is_empty(), "no dead space allowed to the left");
1386   assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1387          "region must have dead space");
1388 
1389   // The gc number is saved whenever a maximum compaction is done, and used to
1390   // determine when the maximum compaction interval has expired.  This avoids
1391   // successive max compactions for different reasons.
1392   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1393   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1394   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1395     total_invocations() == HeapFirstMaximumCompactionCount;
1396   if (maximum_compaction || full_cp == top_cp || interval_ended) {
1397     _maximum_compaction_gc_num = total_invocations();
1398     return sd.region_to_addr(full_cp);
1399   }
1400 
1401   const size_t space_live = pointer_delta(new_top, bottom);
1402   const size_t space_used = space->used_in_words();
1403   const size_t space_capacity = space->capacity_in_words();
1404 
1405   const double density = double(space_live) / double(space_capacity);
1406   const size_t min_percent_free = MarkSweepDeadRatio;
1407   const double limiter = dead_wood_limiter(density, min_percent_free);
1408   const size_t dead_wood_max = space_used - space_live;
1409   const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1410                                       dead_wood_max);
1411 
1412   if (TraceParallelOldGCDensePrefix) {
1413     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1414                   "space_cap=" SIZE_FORMAT,
1415                   space_live, space_used,
1416                   space_capacity);
1417     tty->print_cr("dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
1418                   "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1419                   density, min_percent_free, limiter,
1420                   dead_wood_max, dead_wood_limit);
1421   }
1422 
1423   // Locate the region with the desired amount of dead space to the left.
1424   const RegionData* const limit_cp =
1425     dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1426 
1427   // Scan from the first region with dead space to the limit region and find the
1428   // one with the best (largest) reclaimed ratio.
1429   double best_ratio = 0.0;
1430   const RegionData* best_cp = full_cp;
1431   for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1432     double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1433     if (tmp_ratio > best_ratio) {
1434       best_cp = cp;
1435       best_ratio = tmp_ratio;
1436     }
1437   }
1438 
1439 #if     0
1440   // Something to consider:  if the region with the best ratio is 'close to' the
1441   // first region w/free space, choose the first region with free space
1442   // ("first-free").  The first-free region is usually near the start of the
1443   // heap, which means we are copying most of the heap already, so copy a bit
1444   // more to get complete compaction.
1445   if (pointer_delta(best_cp, full_cp, sizeof(RegionData)) < 4) {
1446     _maximum_compaction_gc_num = total_invocations();
1447     best_cp = full_cp;
1448   }
1449 #endif  // #if 0
1450 
1451   return sd.region_to_addr(best_cp);
1452 }
1453 
1454 #ifndef PRODUCT
1455 void
1456 PSParallelCompact::fill_with_live_objects(SpaceId id, HeapWord* const start,
1457                                           size_t words)
1458 {
1459   if (TraceParallelOldGCSummaryPhase) {
1460     tty->print_cr("fill_with_live_objects [" PTR_FORMAT " " PTR_FORMAT ") "
1461                   SIZE_FORMAT, p2i(start), p2i(start + words), words);
1462   }
1463 
1464   ObjectStartArray* const start_array = _space_info[id].start_array();
1465   CollectedHeap::fill_with_objects(start, words);
1466   for (HeapWord* p = start; p < start + words; p += oop(p)->size()) {
1467     _mark_bitmap.mark_obj(p, words);
1468     _summary_data.add_obj(p, words);
1469     start_array->allocate_block(p);
1470   }
1471 }
1472 
1473 void
1474 PSParallelCompact::summarize_new_objects(SpaceId id, HeapWord* start)
1475 {
1476   ParallelCompactData& sd = summary_data();
1477   MutableSpace* space = _space_info[id].space();
1478 
1479   // Find the source and destination start addresses.
1480   HeapWord* const src_addr = sd.region_align_down(start);
1481   HeapWord* dst_addr;
1482   if (src_addr < start) {
1483     dst_addr = sd.addr_to_region_ptr(src_addr)->destination();
1484   } else if (src_addr > space->bottom()) {
1485     // The start (the original top() value) is aligned to a region boundary so
1486     // the associated region does not have a destination.  Compute the
1487     // destination from the previous region.
1488     RegionData* const cp = sd.addr_to_region_ptr(src_addr) - 1;
1489     dst_addr = cp->destination() + cp->data_size();
1490   } else {
1491     // Filling the entire space.
1492     dst_addr = space->bottom();
1493   }
1494   assert(dst_addr != NULL, "sanity");
1495 
1496   // Update the summary data.
1497   bool result = _summary_data.summarize(_space_info[id].split_info(),
1498                                         src_addr, space->top(), NULL,
1499                                         dst_addr, space->end(),
1500                                         _space_info[id].new_top_addr());
1501   assert(result, "should not fail:  bad filler object size");
1502 }
1503 
1504 void
1505 PSParallelCompact::provoke_split_fill_survivor(SpaceId id)
1506 {
1507   if (total_invocations() % (ParallelOldGCSplitInterval * 3) != 0) {
1508     return;
1509   }
1510 
1511   MutableSpace* const space = _space_info[id].space();
1512   if (space->is_empty()) {
1513     HeapWord* b = space->bottom();
1514     HeapWord* t = b + space->capacity_in_words() / 2;
1515     space->set_top(t);
1516     if (ZapUnusedHeapArea) {
1517       space->set_top_for_allocations();
1518     }
1519 
1520     size_t min_size = CollectedHeap::min_fill_size();
1521     size_t obj_len = min_size;
1522     while (b + obj_len <= t) {
1523       CollectedHeap::fill_with_object(b, obj_len);
1524       mark_bitmap()->mark_obj(b, obj_len);
1525       summary_data().add_obj(b, obj_len);
1526       b += obj_len;
1527       obj_len = (obj_len & (min_size*3)) + min_size; // 8 16 24 32 8 16 24 32 ...
1528     }
1529     if (b < t) {
1530       // The loop didn't completely fill to t (top); adjust top downward.
1531       space->set_top(b);
1532       if (ZapUnusedHeapArea) {
1533         space->set_top_for_allocations();
1534       }
1535     }
1536 
1537     HeapWord** nta = _space_info[id].new_top_addr();
1538     bool result = summary_data().summarize(_space_info[id].split_info(),
1539                                            space->bottom(), space->top(), NULL,
1540                                            space->bottom(), space->end(), nta);
1541     assert(result, "space must fit into itself");
1542   }
1543 }
1544 
1545 void
1546 PSParallelCompact::provoke_split(bool & max_compaction)
1547 {
1548   if (total_invocations() % ParallelOldGCSplitInterval != 0) {
1549     return;
1550   }
1551 
1552   const size_t region_size = ParallelCompactData::RegionSize;
1553   ParallelCompactData& sd = summary_data();
1554 
1555   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1556   MutableSpace* const from_space = _space_info[from_space_id].space();
1557   const size_t eden_live = pointer_delta(eden_space->top(),
1558                                          _space_info[eden_space_id].new_top());
1559   const size_t from_live = pointer_delta(from_space->top(),
1560                                          _space_info[from_space_id].new_top());
1561 
1562   const size_t min_fill_size = CollectedHeap::min_fill_size();
1563   const size_t eden_free = pointer_delta(eden_space->end(), eden_space->top());
1564   const size_t eden_fillable = eden_free >= min_fill_size ? eden_free : 0;
1565   const size_t from_free = pointer_delta(from_space->end(), from_space->top());
1566   const size_t from_fillable = from_free >= min_fill_size ? from_free : 0;
1567 
1568   // Choose the space to split; need at least 2 regions live (or fillable).
1569   SpaceId id;
1570   MutableSpace* space;
1571   size_t live_words;
1572   size_t fill_words;
1573   if (eden_live + eden_fillable >= region_size * 2) {
1574     id = eden_space_id;
1575     space = eden_space;
1576     live_words = eden_live;
1577     fill_words = eden_fillable;
1578   } else if (from_live + from_fillable >= region_size * 2) {
1579     id = from_space_id;
1580     space = from_space;
1581     live_words = from_live;
1582     fill_words = from_fillable;
1583   } else {
1584     return; // Give up.
1585   }
1586   assert(fill_words == 0 || fill_words >= min_fill_size, "sanity");
1587 
1588   if (live_words < region_size * 2) {
1589     // Fill from top() to end() w/live objects of mixed sizes.
1590     HeapWord* const fill_start = space->top();
1591     live_words += fill_words;
1592 
1593     space->set_top(fill_start + fill_words);
1594     if (ZapUnusedHeapArea) {
1595       space->set_top_for_allocations();
1596     }
1597 
1598     HeapWord* cur_addr = fill_start;
1599     while (fill_words > 0) {
1600       const size_t r = (size_t)os::random() % (region_size / 2) + min_fill_size;
1601       size_t cur_size = MIN2(align_object_size_(r), fill_words);
1602       if (fill_words - cur_size < min_fill_size) {
1603         cur_size = fill_words; // Avoid leaving a fragment too small to fill.
1604       }
1605 
1606       CollectedHeap::fill_with_object(cur_addr, cur_size);
1607       mark_bitmap()->mark_obj(cur_addr, cur_size);
1608       sd.add_obj(cur_addr, cur_size);
1609 
1610       cur_addr += cur_size;
1611       fill_words -= cur_size;
1612     }
1613 
1614     summarize_new_objects(id, fill_start);
1615   }
1616 
1617   max_compaction = false;
1618 
1619   // Manipulate the old gen so that it has room for about half of the live data
1620   // in the target young gen space (live_words / 2).
1621   id = old_space_id;
1622   space = _space_info[id].space();
1623   const size_t free_at_end = space->free_in_words();
1624   const size_t free_target = align_object_size(live_words / 2);
1625   const size_t dead = pointer_delta(space->top(), _space_info[id].new_top());
1626 
1627   if (free_at_end >= free_target + min_fill_size) {
1628     // Fill space above top() and set the dense prefix so everything survives.
1629     HeapWord* const fill_start = space->top();
1630     const size_t fill_size = free_at_end - free_target;
1631     space->set_top(space->top() + fill_size);
1632     if (ZapUnusedHeapArea) {
1633       space->set_top_for_allocations();
1634     }
1635     fill_with_live_objects(id, fill_start, fill_size);
1636     summarize_new_objects(id, fill_start);
1637     _space_info[id].set_dense_prefix(sd.region_align_down(space->top()));
1638   } else if (dead + free_at_end > free_target) {
1639     // Find a dense prefix that makes the right amount of space available.
1640     HeapWord* cur = sd.region_align_down(space->top());
1641     HeapWord* cur_destination = sd.addr_to_region_ptr(cur)->destination();
1642     size_t dead_to_right = pointer_delta(space->end(), cur_destination);
1643     while (dead_to_right < free_target) {
1644       cur -= region_size;
1645       cur_destination = sd.addr_to_region_ptr(cur)->destination();
1646       dead_to_right = pointer_delta(space->end(), cur_destination);
1647     }
1648     _space_info[id].set_dense_prefix(cur);
1649   }
1650 }
1651 #endif // #ifndef PRODUCT
1652 
1653 void PSParallelCompact::summarize_spaces_quick()
1654 {
1655   for (unsigned int i = 0; i < last_space_id; ++i) {
1656     const MutableSpace* space = _space_info[i].space();
1657     HeapWord** nta = _space_info[i].new_top_addr();
1658     bool result = _summary_data.summarize(_space_info[i].split_info(),
1659                                           space->bottom(), space->top(), NULL,
1660                                           space->bottom(), space->end(), nta);
1661     assert(result, "space must fit into itself");
1662     _space_info[i].set_dense_prefix(space->bottom());
1663   }
1664 
1665 #ifndef PRODUCT
1666   if (ParallelOldGCSplitALot) {
1667     provoke_split_fill_survivor(to_space_id);
1668   }
1669 #endif // #ifndef PRODUCT
1670 }
1671 
1672 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1673 {
1674   HeapWord* const dense_prefix_end = dense_prefix(id);
1675   const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1676   const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1677   if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1678     // Only enough dead space is filled so that any remaining dead space to the
1679     // left is larger than the minimum filler object.  (The remainder is filled
1680     // during the copy/update phase.)
1681     //
1682     // The size of the dead space to the right of the boundary is not a
1683     // concern, since compaction will be able to use whatever space is
1684     // available.
1685     //
1686     // Here '||' is the boundary, 'x' represents a don't care bit and a box
1687     // surrounds the space to be filled with an object.
1688     //
1689     // In the 32-bit VM, each bit represents two 32-bit words:
1690     //                              +---+
1691     // a) beg_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1692     //    end_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1693     //                              +---+
1694     //
1695     // In the 64-bit VM, each bit represents one 64-bit word:
1696     //                              +------------+
1697     // b) beg_bits:  ...  x   x   x | 0   ||   0 | x  x  ...
1698     //    end_bits:  ...  x   x   1 | 0   ||   0 | x  x  ...
1699     //                              +------------+
1700     //                          +-------+
1701     // c) beg_bits:  ...  x   x | 0   0 | ||   0   x  x  ...
1702     //    end_bits:  ...  x   1 | 0   0 | ||   0   x  x  ...
1703     //                          +-------+
1704     //                      +-----------+
1705     // d) beg_bits:  ...  x | 0   0   0 | ||   0   x  x  ...
1706     //    end_bits:  ...  1 | 0   0   0 | ||   0   x  x  ...
1707     //                      +-----------+
1708     //                          +-------+
1709     // e) beg_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1710     //    end_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1711     //                          +-------+
1712 
1713     // Initially assume case a, c or e will apply.
1714     size_t obj_len = CollectedHeap::min_fill_size();
1715     HeapWord* obj_beg = dense_prefix_end - obj_len;
1716 
1717 #ifdef  _LP64
1718     if (MinObjAlignment > 1) { // object alignment > heap word size
1719       // Cases a, c or e.
1720     } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1721       // Case b above.
1722       obj_beg = dense_prefix_end - 1;
1723     } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1724                _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1725       // Case d above.
1726       obj_beg = dense_prefix_end - 3;
1727       obj_len = 3;
1728     }
1729 #endif  // #ifdef _LP64
1730 
1731     CollectedHeap::fill_with_object(obj_beg, obj_len);
1732     _mark_bitmap.mark_obj(obj_beg, obj_len);
1733     _summary_data.add_obj(obj_beg, obj_len);
1734     assert(start_array(id) != NULL, "sanity");
1735     start_array(id)->allocate_block(obj_beg);
1736   }
1737 }
1738 
1739 void
1740 PSParallelCompact::clear_source_region(HeapWord* beg_addr, HeapWord* end_addr)
1741 {
1742   RegionData* const beg_ptr = _summary_data.addr_to_region_ptr(beg_addr);
1743   HeapWord* const end_aligned_up = _summary_data.region_align_up(end_addr);
1744   RegionData* const end_ptr = _summary_data.addr_to_region_ptr(end_aligned_up);
1745   for (RegionData* cur = beg_ptr; cur < end_ptr; ++cur) {
1746     cur->set_source_region(0);
1747   }
1748 }
1749 
1750 void
1751 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1752 {
1753   assert(id < last_space_id, "id out of range");
1754   assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom() ||
1755          ParallelOldGCSplitALot && id == old_space_id,
1756          "should have been reset in summarize_spaces_quick()");
1757 
1758   const MutableSpace* space = _space_info[id].space();
1759   if (_space_info[id].new_top() != space->bottom()) {
1760     HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1761     _space_info[id].set_dense_prefix(dense_prefix_end);
1762 
1763 #ifndef PRODUCT
1764     if (TraceParallelOldGCDensePrefix) {
1765       print_dense_prefix_stats("ratio", id, maximum_compaction,
1766                                dense_prefix_end);
1767       HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1768       print_dense_prefix_stats("density", id, maximum_compaction, addr);
1769     }
1770 #endif  // #ifndef PRODUCT
1771 
1772     // Recompute the summary data, taking into account the dense prefix.  If
1773     // every last byte will be reclaimed, then the existing summary data which
1774     // compacts everything can be left in place.
1775     if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1776       // If dead space crosses the dense prefix boundary, it is (at least
1777       // partially) filled with a dummy object, marked live and added to the
1778       // summary data.  This simplifies the copy/update phase and must be done
1779       // before the final locations of objects are determined, to prevent
1780       // leaving a fragment of dead space that is too small to fill.
1781       fill_dense_prefix_end(id);
1782 
1783       // Compute the destination of each Region, and thus each object.
1784       _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1785       _summary_data.summarize(_space_info[id].split_info(),
1786                               dense_prefix_end, space->top(), NULL,
1787                               dense_prefix_end, space->end(),
1788                               _space_info[id].new_top_addr());
1789     }
1790   }
1791 
1792   if (TraceParallelOldGCSummaryPhase) {
1793     const size_t region_size = ParallelCompactData::RegionSize;
1794     HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1795     const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1796     const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1797     HeapWord* const new_top = _space_info[id].new_top();
1798     const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1799     const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1800     tty->print_cr("id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1801                   "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1802                   "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1803                   id, space->capacity_in_words(), p2i(dense_prefix_end),
1804                   dp_region, dp_words / region_size,
1805                   cr_words / region_size, p2i(new_top));
1806   }
1807 }
1808 
1809 #ifndef PRODUCT
1810 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1811                                           HeapWord* dst_beg, HeapWord* dst_end,
1812                                           SpaceId src_space_id,
1813                                           HeapWord* src_beg, HeapWord* src_end)
1814 {
1815   if (TraceParallelOldGCSummaryPhase) {
1816     tty->print_cr("summarizing %d [%s] into %d [%s]:  "
1817                   "src=" PTR_FORMAT "-" PTR_FORMAT " "
1818                   SIZE_FORMAT "-" SIZE_FORMAT " "
1819                   "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1820                   SIZE_FORMAT "-" SIZE_FORMAT,
1821                   src_space_id, space_names[src_space_id],
1822                   dst_space_id, space_names[dst_space_id],
1823                   p2i(src_beg), p2i(src_end),
1824                   _summary_data.addr_to_region_idx(src_beg),
1825                   _summary_data.addr_to_region_idx(src_end),
1826                   p2i(dst_beg), p2i(dst_end),
1827                   _summary_data.addr_to_region_idx(dst_beg),
1828                   _summary_data.addr_to_region_idx(dst_end));
1829   }
1830 }
1831 #endif  // #ifndef PRODUCT
1832 
1833 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1834                                       bool maximum_compaction)
1835 {
1836   GCTraceTime tm("summary phase", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
1837   // trace("2");
1838 
1839 #ifdef  ASSERT
1840   if (TraceParallelOldGCMarkingPhase) {
1841     tty->print_cr("add_obj_count=" SIZE_FORMAT " "
1842                   "add_obj_bytes=" SIZE_FORMAT,
1843                   add_obj_count, add_obj_size * HeapWordSize);
1844     tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
1845                   "mark_bitmap_bytes=" SIZE_FORMAT,
1846                   mark_bitmap_count, mark_bitmap_size * HeapWordSize);
1847   }
1848 #endif  // #ifdef ASSERT
1849 
1850   // Quick summarization of each space into itself, to see how much is live.
1851   summarize_spaces_quick();
1852 
1853   if (TraceParallelOldGCSummaryPhase) {
1854     tty->print_cr("summary_phase:  after summarizing each space to self");
1855     Universe::print();
1856     NOT_PRODUCT(print_region_ranges());
1857     if (Verbose) {
1858       NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1859     }
1860   }
1861 
1862   // The amount of live data that will end up in old space (assuming it fits).
1863   size_t old_space_total_live = 0;
1864   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1865     old_space_total_live += pointer_delta(_space_info[id].new_top(),
1866                                           _space_info[id].space()->bottom());
1867   }
1868 
1869   MutableSpace* const old_space = _space_info[old_space_id].space();
1870   const size_t old_capacity = old_space->capacity_in_words();
1871   if (old_space_total_live > old_capacity) {
1872     // XXX - should also try to expand
1873     maximum_compaction = true;
1874   }
1875 #ifndef PRODUCT
1876   if (ParallelOldGCSplitALot && old_space_total_live < old_capacity) {
1877     provoke_split(maximum_compaction);
1878   }
1879 #endif // #ifndef PRODUCT
1880 
1881   // Old generations.
1882   summarize_space(old_space_id, maximum_compaction);
1883 
1884   // Summarize the remaining spaces in the young gen.  The initial target space
1885   // is the old gen.  If a space does not fit entirely into the target, then the
1886   // remainder is compacted into the space itself and that space becomes the new
1887   // target.
1888   SpaceId dst_space_id = old_space_id;
1889   HeapWord* dst_space_end = old_space->end();
1890   HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1891   for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1892     const MutableSpace* space = _space_info[id].space();
1893     const size_t live = pointer_delta(_space_info[id].new_top(),
1894                                       space->bottom());
1895     const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1896 
1897     NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1898                                   SpaceId(id), space->bottom(), space->top());)
1899     if (live > 0 && live <= available) {
1900       // All the live data will fit.
1901       bool done = _summary_data.summarize(_space_info[id].split_info(),
1902                                           space->bottom(), space->top(),
1903                                           NULL,
1904                                           *new_top_addr, dst_space_end,
1905                                           new_top_addr);
1906       assert(done, "space must fit into old gen");
1907 
1908       // Reset the new_top value for the space.
1909       _space_info[id].set_new_top(space->bottom());
1910     } else if (live > 0) {
1911       // Attempt to fit part of the source space into the target space.
1912       HeapWord* next_src_addr = NULL;
1913       bool done = _summary_data.summarize(_space_info[id].split_info(),
1914                                           space->bottom(), space->top(),
1915                                           &next_src_addr,
1916                                           *new_top_addr, dst_space_end,
1917                                           new_top_addr);
1918       assert(!done, "space should not fit into old gen");
1919       assert(next_src_addr != NULL, "sanity");
1920 
1921       // The source space becomes the new target, so the remainder is compacted
1922       // within the space itself.
1923       dst_space_id = SpaceId(id);
1924       dst_space_end = space->end();
1925       new_top_addr = _space_info[id].new_top_addr();
1926       NOT_PRODUCT(summary_phase_msg(dst_space_id,
1927                                     space->bottom(), dst_space_end,
1928                                     SpaceId(id), next_src_addr, space->top());)
1929       done = _summary_data.summarize(_space_info[id].split_info(),
1930                                      next_src_addr, space->top(),
1931                                      NULL,
1932                                      space->bottom(), dst_space_end,
1933                                      new_top_addr);
1934       assert(done, "space must fit when compacted into itself");
1935       assert(*new_top_addr <= space->top(), "usage should not grow");
1936     }
1937   }
1938 
1939   if (TraceParallelOldGCSummaryPhase) {
1940     tty->print_cr("summary_phase:  after final summarization");
1941     Universe::print();
1942     NOT_PRODUCT(print_region_ranges());
1943     if (Verbose) {
1944       NOT_PRODUCT(print_generic_summary_data(_summary_data, _space_info));
1945     }
1946   }
1947 }
1948 
1949 // This method should contain all heap-specific policy for invoking a full
1950 // collection.  invoke_no_policy() will only attempt to compact the heap; it
1951 // will do nothing further.  If we need to bail out for policy reasons, scavenge
1952 // before full gc, or any other specialized behavior, it needs to be added here.
1953 //
1954 // Note that this method should only be called from the vm_thread while at a
1955 // safepoint.
1956 //
1957 // Note that the all_soft_refs_clear flag in the collector policy
1958 // may be true because this method can be called without intervening
1959 // activity.  For example when the heap space is tight and full measure
1960 // are being taken to free space.
1961 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1962   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1963   assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1964          "should be in vm thread");
1965 
1966   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1967   GCCause::Cause gc_cause = heap->gc_cause();
1968   assert(!heap->is_gc_active(), "not reentrant");
1969 
1970   PSAdaptiveSizePolicy* policy = heap->size_policy();
1971   IsGCActiveMark mark;
1972 
1973   if (ScavengeBeforeFullGC) {
1974     PSScavenge::invoke_no_policy();
1975   }
1976 
1977   const bool clear_all_soft_refs =
1978     heap->collector_policy()->should_clear_all_soft_refs();
1979 
1980   PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1981                                       maximum_heap_compaction);
1982 }
1983 
1984 // This method contains no policy. You should probably
1985 // be calling invoke() instead.
1986 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
1987   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
1988   assert(ref_processor() != NULL, "Sanity");
1989 
1990   if (GC_locker::check_active_before_gc()) {
1991     return false;
1992   }
1993 
1994   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1995 
1996   _gc_timer.register_gc_start();
1997   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1998 
1999   TimeStamp marking_start;
2000   TimeStamp compaction_start;
2001   TimeStamp collection_exit;
2002 
2003   GCCause::Cause gc_cause = heap->gc_cause();
2004   PSYoungGen* young_gen = heap->young_gen();
2005   PSOldGen* old_gen = heap->old_gen();
2006   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
2007 
2008   // The scope of casr should end after code that can change
2009   // CollectorPolicy::_should_clear_all_soft_refs.
2010   ClearedAllSoftRefs casr(maximum_heap_compaction,
2011                           heap->collector_policy());
2012 
2013   if (ZapUnusedHeapArea) {
2014     // Save information needed to minimize mangling
2015     heap->record_gen_tops_before_GC();
2016   }
2017 
2018   heap->pre_full_gc_dump(&_gc_timer);
2019 
2020   _print_phases = PrintGCDetails && PrintParallelOldGCPhaseTimes;
2021 
2022   // Make sure data structures are sane, make the heap parsable, and do other
2023   // miscellaneous bookkeeping.
2024   PreGCValues pre_gc_values;
2025   pre_compact(&pre_gc_values);
2026 
2027   // Get the compaction manager reserved for the VM thread.
2028   ParCompactionManager* const vmthread_cm =
2029     ParCompactionManager::manager_array(gc_task_manager()->workers());
2030 
2031   // Place after pre_compact() where the number of invocations is incremented.
2032   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
2033 
2034   {
2035     ResourceMark rm;
2036     HandleMark hm;
2037 
2038     // Set the number of GC threads to be used in this collection
2039     gc_task_manager()->set_active_gang();
2040     gc_task_manager()->task_idle_workers();
2041     heap->set_par_threads(gc_task_manager()->active_workers());
2042 
2043     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
2044     GCTraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, NULL, _gc_tracer.gc_id());
2045     TraceCollectorStats tcs(counters());
2046     TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);
2047 
2048     if (TraceOldGenTime) accumulated_time()->start();
2049 
2050     // Let the size policy know we're starting
2051     size_policy->major_collection_begin();
2052 
2053     CodeCache::gc_prologue();
2054 
2055     COMPILER2_PRESENT(DerivedPointerTable::clear());
2056 
2057     ref_processor()->enable_discovery();
2058     ref_processor()->setup_policy(maximum_heap_compaction);
2059 
2060     bool marked_for_unloading = false;
2061 
2062     marking_start.update();
2063     marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
2064 
2065     bool max_on_system_gc = UseMaximumCompactionOnSystemGC
2066       && gc_cause == GCCause::_java_lang_system_gc;
2067     summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
2068 
2069     COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
2070     COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
2071 
2072     // adjust_roots() updates Universe::_intArrayKlassObj which is
2073     // needed by the compaction for filling holes in the dense prefix.
2074     adjust_roots();
2075 
2076     compaction_start.update();
2077     compact();
2078 
2079     // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
2080     // done before resizing.
2081     post_compact();
2082 
2083     // Let the size policy know we're done
2084     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
2085 
2086     if (UseAdaptiveSizePolicy) {
2087       if (PrintAdaptiveSizePolicy) {
2088         gclog_or_tty->print("AdaptiveSizeStart: ");
2089         gclog_or_tty->stamp();
2090         gclog_or_tty->print_cr(" collection: %d ",
2091                        heap->total_collections());
2092         if (Verbose) {
2093           gclog_or_tty->print("old_gen_capacity: " SIZE_FORMAT
2094             " young_gen_capacity: " SIZE_FORMAT,
2095             old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
2096         }
2097       }
2098 
2099       // Don't check if the size_policy is ready here.  Let
2100       // the size_policy check that internally.
2101       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
2102           ((gc_cause != GCCause::_java_lang_system_gc) ||
2103             UseAdaptiveSizePolicyWithSystemGC)) {
2104         // Swap the survivor spaces if from_space is empty. The
2105         // resize_young_gen() called below is normally used after
2106         // a successful young GC and swapping of survivor spaces;
2107         // otherwise, it will fail to resize the young gen with
2108         // the current implementation.
2109         if (young_gen->from_space()->is_empty()) {
2110           young_gen->from_space()->clear(SpaceDecorator::Mangle);
2111           young_gen->swap_spaces();
2112         }
2113 
2114         // Calculate optimal free space amounts
2115         assert(young_gen->max_size() >
2116           young_gen->from_space()->capacity_in_bytes() +
2117           young_gen->to_space()->capacity_in_bytes(),
2118           "Sizes of space in young gen are out-of-bounds");
2119 
2120         size_t young_live = young_gen->used_in_bytes();
2121         size_t eden_live = young_gen->eden_space()->used_in_bytes();
2122         size_t old_live = old_gen->used_in_bytes();
2123         size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
2124         size_t max_old_gen_size = old_gen->max_gen_size();
2125         size_t max_eden_size = young_gen->max_size() -
2126           young_gen->from_space()->capacity_in_bytes() -
2127           young_gen->to_space()->capacity_in_bytes();
2128 
2129         // Used for diagnostics
2130         size_policy->clear_generation_free_space_flags();
2131 
2132         size_policy->compute_generations_free_space(young_live,
2133                                                     eden_live,
2134                                                     old_live,
2135                                                     cur_eden,
2136                                                     max_old_gen_size,
2137                                                     max_eden_size,
2138                                                     true /* full gc*/);
2139 
2140         size_policy->check_gc_overhead_limit(young_live,
2141                                              eden_live,
2142                                              max_old_gen_size,
2143                                              max_eden_size,
2144                                              true /* full gc*/,
2145                                              gc_cause,
2146                                              heap->collector_policy());
2147 
2148         size_policy->decay_supplemental_growth(true /* full gc*/);
2149 
2150         heap->resize_old_gen(
2151           size_policy->calculated_old_free_size_in_bytes());
2152 
2153         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
2154                                size_policy->calculated_survivor_size_in_bytes());
2155       }
2156       if (PrintAdaptiveSizePolicy) {
2157         gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
2158                        heap->total_collections());
2159       }
2160     }
2161 
2162     if (UsePerfData) {
2163       PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
2164       counters->update_counters();
2165       counters->update_old_capacity(old_gen->capacity_in_bytes());
2166       counters->update_young_capacity(young_gen->capacity_in_bytes());
2167     }
2168 
2169     heap->resize_all_tlabs();
2170 
2171     // Resize the metaspace capacity after a collection
2172     MetaspaceGC::compute_new_size();
2173 
2174     if (TraceOldGenTime) accumulated_time()->stop();
2175 
2176     if (PrintGC) {
2177       if (PrintGCDetails) {
2178         // No GC timestamp here.  This is after GC so it would be confusing.
2179         young_gen->print_used_change(pre_gc_values.young_gen_used());
2180         old_gen->print_used_change(pre_gc_values.old_gen_used());
2181         heap->print_heap_change(pre_gc_values.heap_used());
2182         MetaspaceAux::print_metaspace_change(pre_gc_values.metadata_used());
2183       } else {
2184         heap->print_heap_change(pre_gc_values.heap_used());
2185       }
2186     }
2187 
2188     // Track memory usage and detect low memory
2189     MemoryService::track_memory_usage();
2190     heap->update_counters();
2191     gc_task_manager()->release_idle_workers();
2192   }
2193 
2194 #ifdef ASSERT
2195   for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
2196     ParCompactionManager* const cm =
2197       ParCompactionManager::manager_array(int(i));
2198     assert(cm->marking_stack()->is_empty(),       "should be empty");
2199     assert(ParCompactionManager::region_list(int(i))->is_empty(), "should be empty");
2200   }
2201 #endif // ASSERT
2202 
2203   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
2204     HandleMark hm;  // Discard invalid handles created during verification
2205     Universe::verify(" VerifyAfterGC:");
2206   }
2207 
2208   // Re-verify object start arrays
2209   if (VerifyObjectStartArray &&
2210       VerifyAfterGC) {
2211     old_gen->verify_object_start_array();
2212   }
2213 
2214   if (ZapUnusedHeapArea) {
2215     old_gen->object_space()->check_mangled_unused_area_complete();
2216   }
2217 
2218   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
2219 
2220   collection_exit.update();
2221 
2222   heap->print_heap_after_gc();
2223   heap->trace_heap_after_gc(&_gc_tracer);
2224 
2225   if (PrintGCTaskTimeStamps) {
2226     gclog_or_tty->print_cr("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " "
2227                            JLONG_FORMAT,
2228                            marking_start.ticks(), compaction_start.ticks(),
2229                            collection_exit.ticks());
2230     gc_task_manager()->print_task_time_stamps();
2231   }
2232 
2233   heap->post_full_gc_dump(&_gc_timer);
2234 
2235 #ifdef TRACESPINNING
2236   ParallelTaskTerminator::print_termination_counts();
2237 #endif
2238 
2239   _gc_timer.register_gc_end();
2240 
2241   _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
2242   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
2243 
2244   return true;
2245 }
2246 
2247 bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
2248                                              PSYoungGen* young_gen,
2249                                              PSOldGen* old_gen) {
2250   MutableSpace* const eden_space = young_gen->eden_space();
2251   assert(!eden_space->is_empty(), "eden must be non-empty");
2252   assert(young_gen->virtual_space()->alignment() ==
2253          old_gen->virtual_space()->alignment(), "alignments do not match");
2254 
2255   if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
2256     return false;
2257   }
2258 
2259   // Both generations must be completely committed.
2260   if (young_gen->virtual_space()->uncommitted_size() != 0) {
2261     return false;
2262   }
2263   if (old_gen->virtual_space()->uncommitted_size() != 0) {
2264     return false;
2265   }
2266 
2267   // Figure out how much to take from eden.  Include the average amount promoted
2268   // in the total; otherwise the next young gen GC will simply bail out to a
2269   // full GC.
2270   const size_t alignment = old_gen->virtual_space()->alignment();
2271   const size_t eden_used = eden_space->used_in_bytes();
2272   const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
2273   const size_t absorb_size = align_size_up(eden_used + promoted, alignment);
2274   const size_t eden_capacity = eden_space->capacity_in_bytes();
2275 
2276   if (absorb_size >= eden_capacity) {
2277     return false; // Must leave some space in eden.
2278   }
2279 
2280   const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
2281   if (new_young_size < young_gen->min_gen_size()) {
2282     return false; // Respect young gen minimum size.
2283   }
2284 
2285   if (TraceAdaptiveGCBoundary && Verbose) {
2286     gclog_or_tty->print(" absorbing " SIZE_FORMAT "K:  "
2287                         "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
2288                         "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
2289                         "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
2290                         absorb_size / K,
2291                         eden_capacity / K, (eden_capacity - absorb_size) / K,
2292                         young_gen->from_space()->used_in_bytes() / K,
2293                         young_gen->to_space()->used_in_bytes() / K,
2294                         young_gen->capacity_in_bytes() / K, new_young_size / K);
2295   }
2296 
2297   // Fill the unused part of the old gen.
2298   MutableSpace* const old_space = old_gen->object_space();
2299   HeapWord* const unused_start = old_space->top();
2300   size_t const unused_words = pointer_delta(old_space->end(), unused_start);
2301 
2302   if (unused_words > 0) {
2303     if (unused_words < CollectedHeap::min_fill_size()) {
2304       return false;  // If the old gen cannot be filled, must give up.
2305     }
2306     CollectedHeap::fill_with_objects(unused_start, unused_words);
2307   }
2308 
2309   // Take the live data from eden and set both top and end in the old gen to
2310   // eden top.  (Need to set end because reset_after_change() mangles the region
2311   // from end to virtual_space->high() in debug builds).
2312   HeapWord* const new_top = eden_space->top();
2313   old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
2314                                         absorb_size);
2315   young_gen->reset_after_change();
2316   old_space->set_top(new_top);
2317   old_space->set_end(new_top);
2318   old_gen->reset_after_change();
2319 
2320   // Update the object start array for the filler object and the data from eden.
2321   ObjectStartArray* const start_array = old_gen->start_array();
2322   for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
2323     start_array->allocate_block(p);
2324   }
2325 
2326   // Could update the promoted average here, but it is not typically updated at
2327   // full GCs and the value to use is unclear.  Something like
2328   //
2329   // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
2330 
2331   size_policy->set_bytes_absorbed_from_eden(absorb_size);
2332   return true;
2333 }
2334 
2335 GCTaskManager* const PSParallelCompact::gc_task_manager() {
2336   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
2337     "shouldn't return NULL");
2338   return ParallelScavengeHeap::gc_task_manager();
2339 }
2340 
2341 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2342                                       bool maximum_heap_compaction,
2343                                       ParallelOldTracer *gc_tracer) {
2344   // Recursively traverse all live objects and mark them
2345   GCTraceTime tm("marking phase", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2346 
2347   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2348   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2349   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2350   TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2351   ParallelTaskTerminator terminator(active_gc_threads, qset);
2352 
2353   PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm);
2354   PSParallelCompact::FollowStackClosure follow_stack_closure(cm);
2355 
2356   // Need new claim bits before marking starts.
2357   ClassLoaderDataGraph::clear_claimed_marks();
2358 
2359   {
2360     GCTraceTime tm_m("par mark", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2361 
2362     ParallelScavengeHeap::ParStrongRootsScope psrs;
2363 
2364     GCTaskQueue* q = GCTaskQueue::create();
2365 
2366     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::universe));
2367     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jni_handles));
2368     // We scan the thread roots in parallel
2369     Threads::create_thread_roots_marking_tasks(q);
2370     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::object_synchronizer));
2371     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::flat_profiler));
2372     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::management));
2373     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::system_dictionary));
2374     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::class_loader_data));
2375     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jvmti));
2376     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::code_cache));
2377 
2378     if (active_gc_threads > 1) {
2379       for (uint j = 0; j < active_gc_threads; j++) {
2380         q->enqueue(new StealMarkingTask(&terminator));
2381       }
2382     }
2383 
2384     gc_task_manager()->execute_and_wait(q);
2385   }
2386 
2387   // Process reference objects found during marking
2388   {
2389     GCTraceTime tm_r("reference processing", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2390 
2391     ReferenceProcessorStats stats;
2392     if (ref_processor()->processing_is_mt()) {
2393       RefProcTaskExecutor task_executor;
2394       stats = ref_processor()->process_discovered_references(
2395         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2396         &task_executor, &_gc_timer, _gc_tracer.gc_id());
2397     } else {
2398       stats = ref_processor()->process_discovered_references(
2399         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
2400         &_gc_timer, _gc_tracer.gc_id());
2401     }
2402 
2403     gc_tracer->report_gc_reference_stats(stats);
2404   }
2405 
2406   GCTraceTime tm_c("class unloading", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2407 
2408   // This is the point where the entire marking should have completed.
2409   assert(cm->marking_stacks_empty(), "Marking should have completed");
2410 
2411   // Follow system dictionary roots and unload classes.
2412   bool purged_class = SystemDictionary::do_unloading(is_alive_closure());
2413 
2414   // Unload nmethods.
2415   CodeCache::do_unloading(is_alive_closure(), purged_class);
2416 
2417   // Prune dead klasses from subklass/sibling/implementor lists.
2418   Klass::clean_weak_klass_links(is_alive_closure());
2419 
2420   // Delete entries for dead interned strings.
2421   StringTable::unlink(is_alive_closure());
2422 
2423   // Clean up unreferenced symbols in symbol table.
2424   SymbolTable::unlink();
2425   _gc_tracer.report_object_count_after_gc(is_alive_closure());
2426 }
2427 
2428 void PSParallelCompact::follow_class_loader(ParCompactionManager* cm,
2429                                             ClassLoaderData* cld) {
2430   PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm);
2431   PSParallelCompact::FollowKlassClosure follow_klass_closure(&mark_and_push_closure);
2432 
2433   cld->oops_do(&mark_and_push_closure, &follow_klass_closure, true);
2434 }
2435 
2436 // This should be moved to the shared markSweep code!
2437 class PSAlwaysTrueClosure: public BoolObjectClosure {
2438 public:
2439   bool do_object_b(oop p) { return true; }
2440 };
2441 static PSAlwaysTrueClosure always_true;
2442 
2443 void PSParallelCompact::adjust_roots() {
2444   // Adjust the pointers to reflect the new locations
2445   GCTraceTime tm("adjust roots", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2446 
2447   // Need new claim bits when tracing through and adjusting pointers.
2448   ClassLoaderDataGraph::clear_claimed_marks();
2449 
2450   // General strong roots.
2451   Universe::oops_do(adjust_pointer_closure());
2452   JNIHandles::oops_do(adjust_pointer_closure());   // Global (strong) JNI handles
2453   CLDToOopClosure adjust_from_cld(adjust_pointer_closure());
2454   Threads::oops_do(adjust_pointer_closure(), &adjust_from_cld, NULL);
2455   ObjectSynchronizer::oops_do(adjust_pointer_closure());
2456   FlatProfiler::oops_do(adjust_pointer_closure());
2457   Management::oops_do(adjust_pointer_closure());
2458   JvmtiExport::oops_do(adjust_pointer_closure());
2459   SystemDictionary::oops_do(adjust_pointer_closure());
2460   ClassLoaderDataGraph::oops_do(adjust_pointer_closure(), adjust_klass_closure(), true);
2461 
2462   // Now adjust pointers in remaining weak roots.  (All of which should
2463   // have been cleared if they pointed to non-surviving objects.)
2464   // Global (weak) JNI handles
2465   JNIHandles::weak_oops_do(&always_true, adjust_pointer_closure());
2466 
2467   CodeBlobToOopClosure adjust_from_blobs(adjust_pointer_closure(), CodeBlobToOopClosure::FixRelocations);
2468   CodeCache::blobs_do(&adjust_from_blobs);
2469   StringTable::oops_do(adjust_pointer_closure());
2470   ref_processor()->weak_oops_do(adjust_pointer_closure());
2471   // Roots were visited so references into the young gen in roots
2472   // may have been scanned.  Process them also.
2473   // Should the reference processor have a span that excludes
2474   // young gen objects?
2475   PSScavenge::reference_processor()->weak_oops_do(adjust_pointer_closure());
2476 }
2477 
2478 void PSParallelCompact::enqueue_region_draining_tasks(GCTaskQueue* q,
2479                                                       uint parallel_gc_threads)
2480 {
2481   GCTraceTime tm("drain task setup", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2482 
2483   // Find the threads that are active
2484   unsigned int which = 0;
2485 
2486   const uint task_count = MAX2(parallel_gc_threads, 1U);
2487   for (uint j = 0; j < task_count; j++) {
2488     q->enqueue(new DrainStacksCompactionTask(j));
2489     ParCompactionManager::verify_region_list_empty(j);
2490     // Set the region stacks variables to "no" region stack values
2491     // so that they will be recognized and needing a region stack
2492     // in the stealing tasks if they do not get one by executing
2493     // a draining stack.
2494     ParCompactionManager* cm = ParCompactionManager::manager_array(j);
2495     cm->set_region_stack(NULL);
2496     cm->set_region_stack_index((uint)max_uintx);
2497   }
2498   ParCompactionManager::reset_recycled_stack_index();
2499 
2500   // Find all regions that are available (can be filled immediately) and
2501   // distribute them to the thread stacks.  The iteration is done in reverse
2502   // order (high to low) so the regions will be removed in ascending order.
2503 
2504   const ParallelCompactData& sd = PSParallelCompact::summary_data();
2505 
2506   size_t fillable_regions = 0;   // A count for diagnostic purposes.
2507   // A region index which corresponds to the tasks created above.
2508   // "which" must be 0 <= which < task_count
2509 
2510   which = 0;
2511   // id + 1 is used to test termination so unsigned  can
2512   // be used with an old_space_id == 0.
2513   for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2514     SpaceInfo* const space_info = _space_info + id;
2515     MutableSpace* const space = space_info->space();
2516     HeapWord* const new_top = space_info->new_top();
2517 
2518     const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2519     const size_t end_region =
2520       sd.addr_to_region_idx(sd.region_align_up(new_top));
2521 
2522     for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2523       if (sd.region(cur)->claim_unsafe()) {
2524         ParCompactionManager::region_list_push(which, cur);
2525 
2526         if (TraceParallelOldGCCompactionPhase && Verbose) {
2527           const size_t count_mod_8 = fillable_regions & 7;
2528           if (count_mod_8 == 0) gclog_or_tty->print("fillable: ");
2529           gclog_or_tty->print(" " SIZE_FORMAT_W(7), cur);
2530           if (count_mod_8 == 7) gclog_or_tty->cr();
2531         }
2532 
2533         NOT_PRODUCT(++fillable_regions;)
2534 
2535         // Assign regions to tasks in round-robin fashion.
2536         if (++which == task_count) {
2537           assert(which <= parallel_gc_threads,
2538             "Inconsistent number of workers");
2539           which = 0;
2540         }
2541       }
2542     }
2543   }
2544 
2545   if (TraceParallelOldGCCompactionPhase) {
2546     if (Verbose && (fillable_regions & 7) != 0) gclog_or_tty->cr();
2547     gclog_or_tty->print_cr(SIZE_FORMAT " initially fillable regions", fillable_regions);
2548   }
2549 }
2550 
2551 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2552 
2553 void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q,
2554                                                     uint parallel_gc_threads) {
2555   GCTraceTime tm("dense prefix task setup", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2556 
2557   ParallelCompactData& sd = PSParallelCompact::summary_data();
2558 
2559   // Iterate over all the spaces adding tasks for updating
2560   // regions in the dense prefix.  Assume that 1 gc thread
2561   // will work on opening the gaps and the remaining gc threads
2562   // will work on the dense prefix.
2563   unsigned int space_id;
2564   for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2565     HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2566     const MutableSpace* const space = _space_info[space_id].space();
2567 
2568     if (dense_prefix_end == space->bottom()) {
2569       // There is no dense prefix for this space.
2570       continue;
2571     }
2572 
2573     // The dense prefix is before this region.
2574     size_t region_index_end_dense_prefix =
2575         sd.addr_to_region_idx(dense_prefix_end);
2576     RegionData* const dense_prefix_cp =
2577       sd.region(region_index_end_dense_prefix);
2578     assert(dense_prefix_end == space->end() ||
2579            dense_prefix_cp->available() ||
2580            dense_prefix_cp->claimed(),
2581            "The region after the dense prefix should always be ready to fill");
2582 
2583     size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2584 
2585     // Is there dense prefix work?
2586     size_t total_dense_prefix_regions =
2587       region_index_end_dense_prefix - region_index_start;
2588     // How many regions of the dense prefix should be given to
2589     // each thread?
2590     if (total_dense_prefix_regions > 0) {
2591       uint tasks_for_dense_prefix = 1;
2592       if (total_dense_prefix_regions <=
2593           (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2594         // Don't over partition.  This assumes that
2595         // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2596         // so there are not many regions to process.
2597         tasks_for_dense_prefix = parallel_gc_threads;
2598       } else {
2599         // Over partition
2600         tasks_for_dense_prefix = parallel_gc_threads *
2601           PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2602       }
2603       size_t regions_per_thread = total_dense_prefix_regions /
2604         tasks_for_dense_prefix;
2605       // Give each thread at least 1 region.
2606       if (regions_per_thread == 0) {
2607         regions_per_thread = 1;
2608       }
2609 
2610       for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2611         if (region_index_start >= region_index_end_dense_prefix) {
2612           break;
2613         }
2614         // region_index_end is not processed
2615         size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2616                                        region_index_end_dense_prefix);
2617         q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2618                                              region_index_start,
2619                                              region_index_end));
2620         region_index_start = region_index_end;
2621       }
2622     }
2623     // This gets any part of the dense prefix that did not
2624     // fit evenly.
2625     if (region_index_start < region_index_end_dense_prefix) {
2626       q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2627                                            region_index_start,
2628                                            region_index_end_dense_prefix));
2629     }
2630   }
2631 }
2632 
2633 void PSParallelCompact::enqueue_region_stealing_tasks(
2634                                      GCTaskQueue* q,
2635                                      ParallelTaskTerminator* terminator_ptr,
2636                                      uint parallel_gc_threads) {
2637   GCTraceTime tm("steal task setup", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2638 
2639   // Once a thread has drained it's stack, it should try to steal regions from
2640   // other threads.
2641   if (parallel_gc_threads > 1) {
2642     for (uint j = 0; j < parallel_gc_threads; j++) {
2643       q->enqueue(new StealRegionCompactionTask(terminator_ptr));
2644     }
2645   }
2646 }
2647 
2648 #ifdef ASSERT
2649 // Write a histogram of the number of times the block table was filled for a
2650 // region.
2651 void PSParallelCompact::write_block_fill_histogram(outputStream* const out)
2652 {
2653   if (!TraceParallelOldGCCompactionPhase) return;
2654 
2655   typedef ParallelCompactData::RegionData rd_t;
2656   ParallelCompactData& sd = summary_data();
2657 
2658   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2659     MutableSpace* const spc = _space_info[id].space();
2660     if (spc->bottom() != spc->top()) {
2661       const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
2662       HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
2663       const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
2664 
2665       size_t histo[5] = { 0, 0, 0, 0, 0 };
2666       const size_t histo_len = sizeof(histo) / sizeof(size_t);
2667       const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
2668 
2669       for (const rd_t* cur = beg; cur < end; ++cur) {
2670         ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
2671       }
2672       out->print("%u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
2673       for (size_t i = 0; i < histo_len; ++i) {
2674         out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
2675                    histo[i], 100.0 * histo[i] / region_cnt);
2676       }
2677       out->cr();
2678     }
2679   }
2680 }
2681 #endif // #ifdef ASSERT
2682 
2683 void PSParallelCompact::compact() {
2684   // trace("5");
2685   GCTraceTime tm("compaction phase", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2686 
2687   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2688   PSOldGen* old_gen = heap->old_gen();
2689   old_gen->start_array()->reset();
2690   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2691   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2692   TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2693   ParallelTaskTerminator terminator(active_gc_threads, qset);
2694 
2695   GCTaskQueue* q = GCTaskQueue::create();
2696   enqueue_region_draining_tasks(q, active_gc_threads);
2697   enqueue_dense_prefix_tasks(q, active_gc_threads);
2698   enqueue_region_stealing_tasks(q, &terminator, active_gc_threads);
2699 
2700   {
2701     GCTraceTime tm_pc("par compact", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2702 
2703     gc_task_manager()->execute_and_wait(q);
2704 
2705 #ifdef  ASSERT
2706     // Verify that all regions have been processed before the deferred updates.
2707     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2708       verify_complete(SpaceId(id));
2709     }
2710 #endif
2711   }
2712 
2713   {
2714     // Update the deferred objects, if any.  Any compaction manager can be used.
2715     GCTraceTime tm_du("deferred updates", print_phases(), true, &_gc_timer, _gc_tracer.gc_id());
2716     ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2717     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2718       update_deferred_objects(cm, SpaceId(id));
2719     }
2720   }
2721 
2722   DEBUG_ONLY(write_block_fill_histogram(gclog_or_tty));
2723 }
2724 
2725 #ifdef  ASSERT
2726 void PSParallelCompact::verify_complete(SpaceId space_id) {
2727   // All Regions between space bottom() to new_top() should be marked as filled
2728   // and all Regions between new_top() and top() should be available (i.e.,
2729   // should have been emptied).
2730   ParallelCompactData& sd = summary_data();
2731   SpaceInfo si = _space_info[space_id];
2732   HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2733   HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2734   const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2735   const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2736   const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2737 
2738   bool issued_a_warning = false;
2739 
2740   size_t cur_region;
2741   for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2742     const RegionData* const c = sd.region(cur_region);
2743     if (!c->completed()) {
2744       warning("region " SIZE_FORMAT " not filled:  "
2745               "destination_count=%u",
2746               cur_region, c->destination_count());
2747       issued_a_warning = true;
2748     }
2749   }
2750 
2751   for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2752     const RegionData* const c = sd.region(cur_region);
2753     if (!c->available()) {
2754       warning("region " SIZE_FORMAT " not empty:   "
2755               "destination_count=%u",
2756               cur_region, c->destination_count());
2757       issued_a_warning = true;
2758     }
2759   }
2760 
2761   if (issued_a_warning) {
2762     print_region_ranges();
2763   }
2764 }
2765 #endif  // #ifdef ASSERT
2766 
2767 inline void UpdateOnlyClosure::do_addr(HeapWord* addr) {
2768   _start_array->allocate_block(addr);
2769   compaction_manager()->update_contents(oop(addr));
2770 }
2771 
2772 // Update interior oops in the ranges of regions [beg_region, end_region).
2773 void
2774 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2775                                                        SpaceId space_id,
2776                                                        size_t beg_region,
2777                                                        size_t end_region) {
2778   ParallelCompactData& sd = summary_data();
2779   ParMarkBitMap* const mbm = mark_bitmap();
2780 
2781   HeapWord* beg_addr = sd.region_to_addr(beg_region);
2782   HeapWord* const end_addr = sd.region_to_addr(end_region);
2783   assert(beg_region <= end_region, "bad region range");
2784   assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2785 
2786 #ifdef  ASSERT
2787   // Claim the regions to avoid triggering an assert when they are marked as
2788   // filled.
2789   for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2790     assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2791   }
2792 #endif  // #ifdef ASSERT
2793 
2794   if (beg_addr != space(space_id)->bottom()) {
2795     // Find the first live object or block of dead space that *starts* in this
2796     // range of regions.  If a partial object crosses onto the region, skip it;
2797     // it will be marked for 'deferred update' when the object head is
2798     // processed.  If dead space crosses onto the region, it is also skipped; it
2799     // will be filled when the prior region is processed.  If neither of those
2800     // apply, the first word in the region is the start of a live object or dead
2801     // space.
2802     assert(beg_addr > space(space_id)->bottom(), "sanity");
2803     const RegionData* const cp = sd.region(beg_region);
2804     if (cp->partial_obj_size() != 0) {
2805       beg_addr = sd.partial_obj_end(beg_region);
2806     } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2807       beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2808     }
2809   }
2810 
2811   if (beg_addr < end_addr) {
2812     // A live object or block of dead space starts in this range of Regions.
2813      HeapWord* const dense_prefix_end = dense_prefix(space_id);
2814 
2815     // Create closures and iterate.
2816     UpdateOnlyClosure update_closure(mbm, cm, space_id);
2817     FillClosure fill_closure(cm, space_id);
2818     ParMarkBitMap::IterationStatus status;
2819     status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2820                           dense_prefix_end);
2821     if (status == ParMarkBitMap::incomplete) {
2822       update_closure.do_addr(update_closure.source());
2823     }
2824   }
2825 
2826   // Mark the regions as filled.
2827   RegionData* const beg_cp = sd.region(beg_region);
2828   RegionData* const end_cp = sd.region(end_region);
2829   for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2830     cp->set_completed();
2831   }
2832 }
2833 
2834 // Return the SpaceId for the space containing addr.  If addr is not in the
2835 // heap, last_space_id is returned.  In debug mode it expects the address to be
2836 // in the heap and asserts such.
2837 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2838   assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
2839 
2840   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2841     if (_space_info[id].space()->contains(addr)) {
2842       return SpaceId(id);
2843     }
2844   }
2845 
2846   assert(false, "no space contains the addr");
2847   return last_space_id;
2848 }
2849 
2850 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2851                                                 SpaceId id) {
2852   assert(id < last_space_id, "bad space id");
2853 
2854   ParallelCompactData& sd = summary_data();
2855   const SpaceInfo* const space_info = _space_info + id;
2856   ObjectStartArray* const start_array = space_info->start_array();
2857 
2858   const MutableSpace* const space = space_info->space();
2859   assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2860   HeapWord* const beg_addr = space_info->dense_prefix();
2861   HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2862 
2863   const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2864   const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2865   const RegionData* cur_region;
2866   for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2867     HeapWord* const addr = cur_region->deferred_obj_addr();
2868     if (addr != NULL) {
2869       if (start_array != NULL) {
2870         start_array->allocate_block(addr);
2871       }
2872       cm->update_contents(oop(addr));
2873       assert(oop(addr)->is_oop_or_null(), err_msg("Expected an oop or NULL at " PTR_FORMAT, p2i(oop(addr))));
2874     }
2875   }
2876 }
2877 
2878 // Skip over count live words starting from beg, and return the address of the
2879 // next live word.  Unless marked, the word corresponding to beg is assumed to
2880 // be dead.  Callers must either ensure beg does not correspond to the middle of
2881 // an object, or account for those live words in some other way.  Callers must
2882 // also ensure that there are enough live words in the range [beg, end) to skip.
2883 HeapWord*
2884 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2885 {
2886   assert(count > 0, "sanity");
2887 
2888   ParMarkBitMap* m = mark_bitmap();
2889   idx_t bits_to_skip = m->words_to_bits(count);
2890   idx_t cur_beg = m->addr_to_bit(beg);
2891   const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end));
2892 
2893   do {
2894     cur_beg = m->find_obj_beg(cur_beg, search_end);
2895     idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2896     const size_t obj_bits = cur_end - cur_beg + 1;
2897     if (obj_bits > bits_to_skip) {
2898       return m->bit_to_addr(cur_beg + bits_to_skip);
2899     }
2900     bits_to_skip -= obj_bits;
2901     cur_beg = cur_end + 1;
2902   } while (bits_to_skip > 0);
2903 
2904   // Skipping the desired number of words landed just past the end of an object.
2905   // Find the start of the next object.
2906   cur_beg = m->find_obj_beg(cur_beg, search_end);
2907   assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2908   return m->bit_to_addr(cur_beg);
2909 }
2910 
2911 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2912                                             SpaceId src_space_id,
2913                                             size_t src_region_idx)
2914 {
2915   assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2916 
2917   const SplitInfo& split_info = _space_info[src_space_id].split_info();
2918   if (split_info.dest_region_addr() == dest_addr) {
2919     // The partial object ending at the split point contains the first word to
2920     // be copied to dest_addr.
2921     return split_info.first_src_addr();
2922   }
2923 
2924   const ParallelCompactData& sd = summary_data();
2925   ParMarkBitMap* const bitmap = mark_bitmap();
2926   const size_t RegionSize = ParallelCompactData::RegionSize;
2927 
2928   assert(sd.is_region_aligned(dest_addr), "not aligned");
2929   const RegionData* const src_region_ptr = sd.region(src_region_idx);
2930   const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2931   HeapWord* const src_region_destination = src_region_ptr->destination();
2932 
2933   assert(dest_addr >= src_region_destination, "wrong src region");
2934   assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2935 
2936   HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2937   HeapWord* const src_region_end = src_region_beg + RegionSize;
2938 
2939   HeapWord* addr = src_region_beg;
2940   if (dest_addr == src_region_destination) {
2941     // Return the first live word in the source region.
2942     if (partial_obj_size == 0) {
2943       addr = bitmap->find_obj_beg(addr, src_region_end);
2944       assert(addr < src_region_end, "no objects start in src region");
2945     }
2946     return addr;
2947   }
2948 
2949   // Must skip some live data.
2950   size_t words_to_skip = dest_addr - src_region_destination;
2951   assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2952 
2953   if (partial_obj_size >= words_to_skip) {
2954     // All the live words to skip are part of the partial object.
2955     addr += words_to_skip;
2956     if (partial_obj_size == words_to_skip) {
2957       // Find the first live word past the partial object.
2958       addr = bitmap->find_obj_beg(addr, src_region_end);
2959       assert(addr < src_region_end, "wrong src region");
2960     }
2961     return addr;
2962   }
2963 
2964   // Skip over the partial object (if any).
2965   if (partial_obj_size != 0) {
2966     words_to_skip -= partial_obj_size;
2967     addr += partial_obj_size;
2968   }
2969 
2970   // Skip over live words due to objects that start in the region.
2971   addr = skip_live_words(addr, src_region_end, words_to_skip);
2972   assert(addr < src_region_end, "wrong src region");
2973   return addr;
2974 }
2975 
2976 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2977                                                      SpaceId src_space_id,
2978                                                      size_t beg_region,
2979                                                      HeapWord* end_addr)
2980 {
2981   ParallelCompactData& sd = summary_data();
2982 
2983 #ifdef ASSERT
2984   MutableSpace* const src_space = _space_info[src_space_id].space();
2985   HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2986   assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2987          "src_space_id does not match beg_addr");
2988   assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2989          "src_space_id does not match end_addr");
2990 #endif // #ifdef ASSERT
2991 
2992   RegionData* const beg = sd.region(beg_region);
2993   RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2994 
2995   // Regions up to new_top() are enqueued if they become available.
2996   HeapWord* const new_top = _space_info[src_space_id].new_top();
2997   RegionData* const enqueue_end =
2998     sd.addr_to_region_ptr(sd.region_align_up(new_top));
2999 
3000   for (RegionData* cur = beg; cur < end; ++cur) {
3001     assert(cur->data_size() > 0, "region must have live data");
3002     cur->decrement_destination_count();
3003     if (cur < enqueue_end && cur->available() && cur->claim()) {
3004       cm->push_region(sd.region(cur));
3005     }
3006   }
3007 }
3008 
3009 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
3010                                           SpaceId& src_space_id,
3011                                           HeapWord*& src_space_top,
3012                                           HeapWord* end_addr)
3013 {
3014   typedef ParallelCompactData::RegionData RegionData;
3015 
3016   ParallelCompactData& sd = PSParallelCompact::summary_data();
3017   const size_t region_size = ParallelCompactData::RegionSize;
3018 
3019   size_t src_region_idx = 0;
3020 
3021   // Skip empty regions (if any) up to the top of the space.
3022   HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
3023   RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
3024   HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
3025   const RegionData* const top_region_ptr =
3026     sd.addr_to_region_ptr(top_aligned_up);
3027   while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
3028     ++src_region_ptr;
3029   }
3030 
3031   if (src_region_ptr < top_region_ptr) {
3032     // The next source region is in the current space.  Update src_region_idx
3033     // and the source address to match src_region_ptr.
3034     src_region_idx = sd.region(src_region_ptr);
3035     HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
3036     if (src_region_addr > closure.source()) {
3037       closure.set_source(src_region_addr);
3038     }
3039     return src_region_idx;
3040   }
3041 
3042   // Switch to a new source space and find the first non-empty region.
3043   unsigned int space_id = src_space_id + 1;
3044   assert(space_id < last_space_id, "not enough spaces");
3045 
3046   HeapWord* const destination = closure.destination();
3047 
3048   do {
3049     MutableSpace* space = _space_info[space_id].space();
3050     HeapWord* const bottom = space->bottom();
3051     const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
3052 
3053     // Iterate over the spaces that do not compact into themselves.
3054     if (bottom_cp->destination() != bottom) {
3055       HeapWord* const top_aligned_up = sd.region_align_up(space->top());
3056       const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
3057 
3058       for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
3059         if (src_cp->live_obj_size() > 0) {
3060           // Found it.
3061           assert(src_cp->destination() == destination,
3062                  "first live obj in the space must match the destination");
3063           assert(src_cp->partial_obj_size() == 0,
3064                  "a space cannot begin with a partial obj");
3065 
3066           src_space_id = SpaceId(space_id);
3067           src_space_top = space->top();
3068           const size_t src_region_idx = sd.region(src_cp);
3069           closure.set_source(sd.region_to_addr(src_region_idx));
3070           return src_region_idx;
3071         } else {
3072           assert(src_cp->data_size() == 0, "sanity");
3073         }
3074       }
3075     }
3076   } while (++space_id < last_space_id);
3077 
3078   assert(false, "no source region was found");
3079   return 0;
3080 }
3081 
3082 void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx)
3083 {
3084   typedef ParMarkBitMap::IterationStatus IterationStatus;
3085   const size_t RegionSize = ParallelCompactData::RegionSize;
3086   ParMarkBitMap* const bitmap = mark_bitmap();
3087   ParallelCompactData& sd = summary_data();
3088   RegionData* const region_ptr = sd.region(region_idx);
3089 
3090   // Get the items needed to construct the closure.
3091   HeapWord* dest_addr = sd.region_to_addr(region_idx);
3092   SpaceId dest_space_id = space_id(dest_addr);
3093   ObjectStartArray* start_array = _space_info[dest_space_id].start_array();
3094   HeapWord* new_top = _space_info[dest_space_id].new_top();
3095   assert(dest_addr < new_top, "sanity");
3096   const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize);
3097 
3098   // Get the source region and related info.
3099   size_t src_region_idx = region_ptr->source_region();
3100   SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
3101   HeapWord* src_space_top = _space_info[src_space_id].space()->top();
3102 
3103   MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3104   closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
3105 
3106   // Adjust src_region_idx to prepare for decrementing destination counts (the
3107   // destination count is not decremented when a region is copied to itself).
3108   if (src_region_idx == region_idx) {
3109     src_region_idx += 1;
3110   }
3111 
3112   if (bitmap->is_unmarked(closure.source())) {
3113     // The first source word is in the middle of an object; copy the remainder
3114     // of the object or as much as will fit.  The fact that pointer updates were
3115     // deferred will be noted when the object header is processed.
3116     HeapWord* const old_src_addr = closure.source();
3117     closure.copy_partial_obj();
3118     if (closure.is_full()) {
3119       decrement_destination_counts(cm, src_space_id, src_region_idx,
3120                                    closure.source());
3121       region_ptr->set_deferred_obj_addr(NULL);
3122       region_ptr->set_completed();
3123       return;
3124     }
3125 
3126     HeapWord* const end_addr = sd.region_align_down(closure.source());
3127     if (sd.region_align_down(old_src_addr) != end_addr) {
3128       // The partial object was copied from more than one source region.
3129       decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3130 
3131       // Move to the next source region, possibly switching spaces as well.  All
3132       // args except end_addr may be modified.
3133       src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3134                                        end_addr);
3135     }
3136   }
3137 
3138   do {
3139     HeapWord* const cur_addr = closure.source();
3140     HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
3141                                     src_space_top);
3142     IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
3143 
3144     if (status == ParMarkBitMap::incomplete) {
3145       // The last obj that starts in the source region does not end in the
3146       // region.
3147       assert(closure.source() < end_addr, "sanity");
3148       HeapWord* const obj_beg = closure.source();
3149       HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
3150                                        src_space_top);
3151       HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
3152       if (obj_end < range_end) {
3153         // The end was found; the entire object will fit.
3154         status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
3155         assert(status != ParMarkBitMap::would_overflow, "sanity");
3156       } else {
3157         // The end was not found; the object will not fit.
3158         assert(range_end < src_space_top, "obj cannot cross space boundary");
3159         status = ParMarkBitMap::would_overflow;
3160       }
3161     }
3162 
3163     if (status == ParMarkBitMap::would_overflow) {
3164       // The last object did not fit.  Note that interior oop updates were
3165       // deferred, then copy enough of the object to fill the region.
3166       region_ptr->set_deferred_obj_addr(closure.destination());
3167       status = closure.copy_until_full(); // copies from closure.source()
3168 
3169       decrement_destination_counts(cm, src_space_id, src_region_idx,
3170                                    closure.source());
3171       region_ptr->set_completed();
3172       return;
3173     }
3174 
3175     if (status == ParMarkBitMap::full) {
3176       decrement_destination_counts(cm, src_space_id, src_region_idx,
3177                                    closure.source());
3178       region_ptr->set_deferred_obj_addr(NULL);
3179       region_ptr->set_completed();
3180       return;
3181     }
3182 
3183     decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3184 
3185     // Move to the next source region, possibly switching spaces as well.  All
3186     // args except end_addr may be modified.
3187     src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3188                                      end_addr);
3189   } while (true);
3190 }
3191 
3192 void PSParallelCompact::fill_blocks(size_t region_idx)
3193 {
3194   // Fill in the block table elements for the specified region.  Each block
3195   // table element holds the number of live words in the region that are to the
3196   // left of the first object that starts in the block.  Thus only blocks in
3197   // which an object starts need to be filled.
3198   //
3199   // The algorithm scans the section of the bitmap that corresponds to the
3200   // region, keeping a running total of the live words.  When an object start is
3201   // found, if it's the first to start in the block that contains it, the
3202   // current total is written to the block table element.
3203   const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
3204   const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
3205   const size_t RegionSize = ParallelCompactData::RegionSize;
3206 
3207   ParallelCompactData& sd = summary_data();
3208   const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
3209   if (partial_obj_size >= RegionSize) {
3210     return; // No objects start in this region.
3211   }
3212 
3213   // Ensure the first loop iteration decides that the block has changed.
3214   size_t cur_block = sd.block_count();
3215 
3216   const ParMarkBitMap* const bitmap = mark_bitmap();
3217 
3218   const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
3219   assert((size_t)1 << Log2BitsPerBlock ==
3220          bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
3221 
3222   size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
3223   const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
3224   size_t live_bits = bitmap->words_to_bits(partial_obj_size);
3225   beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
3226   while (beg_bit < range_end) {
3227     const size_t new_block = beg_bit >> Log2BitsPerBlock;
3228     if (new_block != cur_block) {
3229       cur_block = new_block;
3230       sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
3231     }
3232 
3233     const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
3234     if (end_bit < range_end - 1) {
3235       live_bits += end_bit - beg_bit + 1;
3236       beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
3237     } else {
3238       return;
3239     }
3240   }
3241 }
3242 
3243 void
3244 PSParallelCompact::move_and_update(ParCompactionManager* cm, SpaceId space_id) {
3245   const MutableSpace* sp = space(space_id);
3246   if (sp->is_empty()) {
3247     return;
3248   }
3249 
3250   ParallelCompactData& sd = PSParallelCompact::summary_data();
3251   ParMarkBitMap* const bitmap = mark_bitmap();
3252   HeapWord* const dp_addr = dense_prefix(space_id);
3253   HeapWord* beg_addr = sp->bottom();
3254   HeapWord* end_addr = sp->top();
3255 
3256   assert(beg_addr <= dp_addr && dp_addr <= end_addr, "bad dense prefix");
3257 
3258   const size_t beg_region = sd.addr_to_region_idx(beg_addr);
3259   const size_t dp_region = sd.addr_to_region_idx(dp_addr);
3260   if (beg_region < dp_region) {
3261     update_and_deadwood_in_dense_prefix(cm, space_id, beg_region, dp_region);
3262   }
3263 
3264   // The destination of the first live object that starts in the region is one
3265   // past the end of the partial object entering the region (if any).
3266   HeapWord* const dest_addr = sd.partial_obj_end(dp_region);
3267   HeapWord* const new_top = _space_info[space_id].new_top();
3268   assert(new_top >= dest_addr, "bad new_top value");
3269   const size_t words = pointer_delta(new_top, dest_addr);
3270 
3271   if (words > 0) {
3272     ObjectStartArray* start_array = _space_info[space_id].start_array();
3273     MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3274 
3275     ParMarkBitMap::IterationStatus status;
3276     status = bitmap->iterate(&closure, dest_addr, end_addr);
3277     assert(status == ParMarkBitMap::full, "iteration not complete");
3278     assert(bitmap->find_obj_beg(closure.source(), end_addr) == end_addr,
3279            "live objects skipped because closure is full");
3280   }
3281 }
3282 
3283 jlong PSParallelCompact::millis_since_last_gc() {
3284   // We need a monotonically non-decreasing time in ms but
3285   // os::javaTimeMillis() does not guarantee monotonicity.
3286   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3287   jlong ret_val = now - _time_of_last_gc;
3288   // XXX See note in genCollectedHeap::millis_since_last_gc().
3289   if (ret_val < 0) {
3290     NOT_PRODUCT(warning("time warp: " JLONG_FORMAT, ret_val);)
3291     return 0;
3292   }
3293   return ret_val;
3294 }
3295 
3296 void PSParallelCompact::reset_millis_since_last_gc() {
3297   // We need a monotonically non-decreasing time in ms but
3298   // os::javaTimeMillis() does not guarantee monotonicity.
3299   _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3300 }
3301 
3302 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3303 {
3304   if (source() != destination()) {
3305     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3306     Copy::aligned_conjoint_words(source(), destination(), words_remaining());
3307   }
3308   update_state(words_remaining());
3309   assert(is_full(), "sanity");
3310   return ParMarkBitMap::full;
3311 }
3312 
3313 void MoveAndUpdateClosure::copy_partial_obj()
3314 {
3315   size_t words = words_remaining();
3316 
3317   HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3318   HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3319   if (end_addr < range_end) {
3320     words = bitmap()->obj_size(source(), end_addr);
3321   }
3322 
3323   // This test is necessary; if omitted, the pointer updates to a partial object
3324   // that crosses the dense prefix boundary could be overwritten.
3325   if (source() != destination()) {
3326     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3327     Copy::aligned_conjoint_words(source(), destination(), words);
3328   }
3329   update_state(words);
3330 }
3331 
3332 void InstanceKlass::oop_pc_update_pointers(oop obj) {
3333   oop_oop_iterate_oop_maps<true>(obj, PSParallelCompact::adjust_pointer_closure());
3334 }
3335 
3336 void InstanceMirrorKlass::oop_pc_update_pointers(oop obj) {
3337   InstanceKlass::oop_pc_update_pointers(obj);
3338 
3339   oop_oop_iterate_statics<true>(obj, PSParallelCompact::adjust_pointer_closure());
3340 }
3341 
3342 void InstanceClassLoaderKlass::oop_pc_update_pointers(oop obj) {
3343   InstanceKlass::oop_pc_update_pointers(obj);
3344 }
3345 
3346 #ifdef ASSERT
3347 template <class T> static void trace_reference_gc(const char *s, oop obj,
3348                                                   T* referent_addr,
3349                                                   T* next_addr,
3350                                                   T* discovered_addr) {
3351   if(TraceReferenceGC && PrintGCDetails) {
3352     gclog_or_tty->print_cr("%s obj " PTR_FORMAT, s, p2i(obj));
3353     gclog_or_tty->print_cr("     referent_addr/* " PTR_FORMAT " / "
3354                            PTR_FORMAT, p2i(referent_addr),
3355                            referent_addr ? p2i(oopDesc::load_decode_heap_oop(referent_addr)) : NULL);
3356     gclog_or_tty->print_cr("     next_addr/* " PTR_FORMAT " / "
3357                            PTR_FORMAT, p2i(next_addr),
3358                            next_addr ? p2i(oopDesc::load_decode_heap_oop(next_addr)) : NULL);
3359     gclog_or_tty->print_cr("     discovered_addr/* " PTR_FORMAT " / "
3360                            PTR_FORMAT, p2i(discovered_addr),
3361                            discovered_addr ? p2i(oopDesc::load_decode_heap_oop(discovered_addr)) : NULL);
3362   }
3363 }
3364 #endif
3365 
3366 template <class T>
3367 static void oop_pc_update_pointers_specialized(oop obj) {
3368   T* referent_addr = (T*)java_lang_ref_Reference::referent_addr(obj);
3369   PSParallelCompact::adjust_pointer(referent_addr);
3370   T* next_addr = (T*)java_lang_ref_Reference::next_addr(obj);
3371   PSParallelCompact::adjust_pointer(next_addr);
3372   T* discovered_addr = (T*)java_lang_ref_Reference::discovered_addr(obj);
3373   PSParallelCompact::adjust_pointer(discovered_addr);
3374   debug_only(trace_reference_gc("InstanceRefKlass::oop_update_ptrs", obj,
3375                                 referent_addr, next_addr, discovered_addr);)
3376 }
3377 
3378 void InstanceRefKlass::oop_pc_update_pointers(oop obj) {
3379   InstanceKlass::oop_pc_update_pointers(obj);
3380 
3381   if (UseCompressedOops) {
3382     oop_pc_update_pointers_specialized<narrowOop>(obj);
3383   } else {
3384     oop_pc_update_pointers_specialized<oop>(obj);
3385   }
3386 }
3387 
3388 void ObjArrayKlass::oop_pc_update_pointers(oop obj) {
3389   assert(obj->is_objArray(), "obj must be obj array");
3390   oop_oop_iterate_elements<true>(objArrayOop(obj), PSParallelCompact::adjust_pointer_closure());
3391 }
3392 
3393 void TypeArrayKlass::oop_pc_update_pointers(oop obj) {
3394   assert(obj->is_typeArray(),"must be a type array");
3395 }
3396 
3397 ParMarkBitMapClosure::IterationStatus
3398 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3399   assert(destination() != NULL, "sanity");
3400   assert(bitmap()->obj_size(addr) == words, "bad size");
3401 
3402   _source = addr;
3403   assert(PSParallelCompact::summary_data().calc_new_pointer(source()) ==
3404          destination(), "wrong destination");
3405 
3406   if (words > words_remaining()) {
3407     return ParMarkBitMap::would_overflow;
3408   }
3409 
3410   // The start_array must be updated even if the object is not moving.
3411   if (_start_array != NULL) {
3412     _start_array->allocate_block(destination());
3413   }
3414 
3415   if (destination() != source()) {
3416     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3417     Copy::aligned_conjoint_words(source(), destination(), words);
3418   }
3419 
3420   oop moved_oop = (oop) destination();
3421   compaction_manager()->update_contents(moved_oop);
3422   assert(moved_oop->is_oop_or_null(), err_msg("Expected an oop or NULL at " PTR_FORMAT, p2i(moved_oop)));
3423 
3424   update_state(words);
3425   assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
3426   return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3427 }
3428 
3429 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3430                                      ParCompactionManager* cm,
3431                                      PSParallelCompact::SpaceId space_id) :
3432   ParMarkBitMapClosure(mbm, cm),
3433   _space_id(space_id),
3434   _start_array(PSParallelCompact::start_array(space_id))
3435 {
3436 }
3437 
3438 // Updates the references in the object to their new values.
3439 ParMarkBitMapClosure::IterationStatus
3440 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3441   do_addr(addr);
3442   return ParMarkBitMap::incomplete;
3443 }
--- EOF ---