1 /*
   2  * Copyright (c) 2005, 2019, 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 "aot/aotLoader.hpp"
  27 #include "classfile/classLoaderDataGraph.hpp"
  28 #include "classfile/javaClasses.inline.hpp"
  29 #include "classfile/stringTable.hpp"
  30 #include "classfile/symbolTable.hpp"
  31 #include "classfile/systemDictionary.hpp"
  32 #include "code/codeCache.hpp"
  33 #include "gc/parallel/gcTaskManager.hpp"
  34 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
  35 #include "gc/parallel/parMarkBitMap.inline.hpp"
  36 #include "gc/parallel/pcTasks.hpp"
  37 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
  38 #include "gc/parallel/psCompactionManager.inline.hpp"
  39 #include "gc/parallel/psOldGen.hpp"
  40 #include "gc/parallel/psParallelCompact.inline.hpp"
  41 #include "gc/parallel/psPromotionManager.inline.hpp"
  42 #include "gc/parallel/psScavenge.hpp"
  43 #include "gc/parallel/psYoungGen.hpp"
  44 #include "gc/shared/gcCause.hpp"
  45 #include "gc/shared/gcHeapSummary.hpp"
  46 #include "gc/shared/gcId.hpp"
  47 #include "gc/shared/gcLocker.hpp"
  48 #include "gc/shared/gcTimer.hpp"
  49 #include "gc/shared/gcTrace.hpp"
  50 #include "gc/shared/gcTraceTime.inline.hpp"
  51 #include "gc/shared/isGCActiveMark.hpp"
  52 #include "gc/shared/referencePolicy.hpp"
  53 #include "gc/shared/referenceProcessor.hpp"
  54 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
  55 #include "gc/shared/spaceDecorator.hpp"
  56 #include "gc/shared/weakProcessor.hpp"
  57 #include "logging/log.hpp"
  58 #include "memory/iterator.inline.hpp"
  59 #include "memory/resourceArea.hpp"
  60 #include "oops/access.inline.hpp"
  61 #include "oops/instanceClassLoaderKlass.inline.hpp"
  62 #include "oops/instanceKlass.inline.hpp"
  63 #include "oops/instanceMirrorKlass.inline.hpp"
  64 #include "oops/methodData.hpp"
  65 #include "oops/objArrayKlass.inline.hpp"
  66 #include "oops/oop.inline.hpp"
  67 #include "runtime/atomic.hpp"
  68 #include "runtime/handles.inline.hpp"
  69 #include "runtime/safepoint.hpp"
  70 #include "runtime/vmThread.hpp"
  71 #include "services/management.hpp"
  72 #include "services/memTracker.hpp"
  73 #include "services/memoryService.hpp"
  74 #include "utilities/align.hpp"
  75 #include "utilities/debug.hpp"
  76 #include "utilities/events.hpp"
  77 #include "utilities/formatBuffer.hpp"
  78 #include "utilities/macros.hpp"
  79 #include "utilities/stack.inline.hpp"
  80 #if INCLUDE_JVMCI
  81 #include "jvmci/jvmci.hpp"
  82 #endif
  83 
  84 #include <math.h>
  85 
  86 // All sizes are in HeapWords.
  87 const size_t ParallelCompactData::Log2RegionSize  = 16; // 64K words
  88 const size_t ParallelCompactData::RegionSize      = (size_t)1 << Log2RegionSize;
  89 const size_t ParallelCompactData::RegionSizeBytes =
  90   RegionSize << LogHeapWordSize;
  91 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
  92 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
  93 const size_t ParallelCompactData::RegionAddrMask       = ~RegionAddrOffsetMask;
  94 
  95 const size_t ParallelCompactData::Log2BlockSize   = 7; // 128 words
  96 const size_t ParallelCompactData::BlockSize       = (size_t)1 << Log2BlockSize;
  97 const size_t ParallelCompactData::BlockSizeBytes  =
  98   BlockSize << LogHeapWordSize;
  99 const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
 100 const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
 101 const size_t ParallelCompactData::BlockAddrMask       = ~BlockAddrOffsetMask;
 102 
 103 const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
 104 const size_t ParallelCompactData::Log2BlocksPerRegion =
 105   Log2RegionSize - Log2BlockSize;
 106 
 107 const ParallelCompactData::RegionData::region_sz_t
 108 ParallelCompactData::RegionData::dc_shift = 27;
 109 
 110 const ParallelCompactData::RegionData::region_sz_t
 111 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
 112 
 113 const ParallelCompactData::RegionData::region_sz_t
 114 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
 115 
 116 const ParallelCompactData::RegionData::region_sz_t
 117 ParallelCompactData::RegionData::los_mask = ~dc_mask;
 118 
 119 const ParallelCompactData::RegionData::region_sz_t
 120 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
 121 
 122 const ParallelCompactData::RegionData::region_sz_t
 123 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
 124 
 125 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
 126 
 127 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
 128 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
 129 
 130 double PSParallelCompact::_dwl_mean;
 131 double PSParallelCompact::_dwl_std_dev;
 132 double PSParallelCompact::_dwl_first_term;
 133 double PSParallelCompact::_dwl_adjustment;
 134 #ifdef  ASSERT
 135 bool   PSParallelCompact::_dwl_initialized = false;
 136 #endif  // #ifdef ASSERT
 137 
 138 void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
 139                        HeapWord* destination)
 140 {
 141   assert(src_region_idx != 0, "invalid src_region_idx");
 142   assert(partial_obj_size != 0, "invalid partial_obj_size argument");
 143   assert(destination != NULL, "invalid destination argument");
 144 
 145   _src_region_idx = src_region_idx;
 146   _partial_obj_size = partial_obj_size;
 147   _destination = destination;
 148 
 149   // These fields may not be updated below, so make sure they're clear.
 150   assert(_dest_region_addr == NULL, "should have been cleared");
 151   assert(_first_src_addr == NULL, "should have been cleared");
 152 
 153   // Determine the number of destination regions for the partial object.
 154   HeapWord* const last_word = destination + partial_obj_size - 1;
 155   const ParallelCompactData& sd = PSParallelCompact::summary_data();
 156   HeapWord* const beg_region_addr = sd.region_align_down(destination);
 157   HeapWord* const end_region_addr = sd.region_align_down(last_word);
 158 
 159   if (beg_region_addr == end_region_addr) {
 160     // One destination region.
 161     _destination_count = 1;
 162     if (end_region_addr == destination) {
 163       // The destination falls on a region boundary, thus the first word of the
 164       // partial object will be the first word copied to the destination region.
 165       _dest_region_addr = end_region_addr;
 166       _first_src_addr = sd.region_to_addr(src_region_idx);
 167     }
 168   } else {
 169     // Two destination regions.  When copied, the partial object will cross a
 170     // destination region boundary, so a word somewhere within the partial
 171     // object will be the first word copied to the second destination region.
 172     _destination_count = 2;
 173     _dest_region_addr = end_region_addr;
 174     const size_t ofs = pointer_delta(end_region_addr, destination);
 175     assert(ofs < _partial_obj_size, "sanity");
 176     _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
 177   }
 178 }
 179 
 180 void SplitInfo::clear()
 181 {
 182   _src_region_idx = 0;
 183   _partial_obj_size = 0;
 184   _destination = NULL;
 185   _destination_count = 0;
 186   _dest_region_addr = NULL;
 187   _first_src_addr = NULL;
 188   assert(!is_valid(), "sanity");
 189 }
 190 
 191 #ifdef  ASSERT
 192 void SplitInfo::verify_clear()
 193 {
 194   assert(_src_region_idx == 0, "not clear");
 195   assert(_partial_obj_size == 0, "not clear");
 196   assert(_destination == NULL, "not clear");
 197   assert(_destination_count == 0, "not clear");
 198   assert(_dest_region_addr == NULL, "not clear");
 199   assert(_first_src_addr == NULL, "not clear");
 200 }
 201 #endif  // #ifdef ASSERT
 202 
 203 
 204 void PSParallelCompact::print_on_error(outputStream* st) {
 205   _mark_bitmap.print_on_error(st);
 206 }
 207 
 208 #ifndef PRODUCT
 209 const char* PSParallelCompact::space_names[] = {
 210   "old ", "eden", "from", "to  "
 211 };
 212 
 213 void PSParallelCompact::print_region_ranges() {
 214   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 215     return;
 216   }
 217   Log(gc, compaction) log;
 218   ResourceMark rm;
 219   LogStream ls(log.trace());
 220   Universe::print_on(&ls);
 221   log.trace("space  bottom     top        end        new_top");
 222   log.trace("------ ---------- ---------- ---------- ----------");
 223 
 224   for (unsigned int id = 0; id < last_space_id; ++id) {
 225     const MutableSpace* space = _space_info[id].space();
 226     log.trace("%u %s "
 227               SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
 228               SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
 229               id, space_names[id],
 230               summary_data().addr_to_region_idx(space->bottom()),
 231               summary_data().addr_to_region_idx(space->top()),
 232               summary_data().addr_to_region_idx(space->end()),
 233               summary_data().addr_to_region_idx(_space_info[id].new_top()));
 234   }
 235 }
 236 
 237 void
 238 print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
 239 {
 240 #define REGION_IDX_FORMAT        SIZE_FORMAT_W(7)
 241 #define REGION_DATA_FORMAT       SIZE_FORMAT_W(5)
 242 
 243   ParallelCompactData& sd = PSParallelCompact::summary_data();
 244   size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
 245   log_develop_trace(gc, compaction)(
 246       REGION_IDX_FORMAT " " PTR_FORMAT " "
 247       REGION_IDX_FORMAT " " PTR_FORMAT " "
 248       REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
 249       REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
 250       i, p2i(c->data_location()), dci, p2i(c->destination()),
 251       c->partial_obj_size(), c->live_obj_size(),
 252       c->data_size(), c->source_region(), c->destination_count());
 253 
 254 #undef  REGION_IDX_FORMAT
 255 #undef  REGION_DATA_FORMAT
 256 }
 257 
 258 void
 259 print_generic_summary_data(ParallelCompactData& summary_data,
 260                            HeapWord* const beg_addr,
 261                            HeapWord* const end_addr)
 262 {
 263   size_t total_words = 0;
 264   size_t i = summary_data.addr_to_region_idx(beg_addr);
 265   const size_t last = summary_data.addr_to_region_idx(end_addr);
 266   HeapWord* pdest = 0;
 267 
 268   while (i < last) {
 269     ParallelCompactData::RegionData* c = summary_data.region(i);
 270     if (c->data_size() != 0 || c->destination() != pdest) {
 271       print_generic_summary_region(i, c);
 272       total_words += c->data_size();
 273       pdest = c->destination();
 274     }
 275     ++i;
 276   }
 277 
 278   log_develop_trace(gc, compaction)("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
 279 }
 280 
 281 void
 282 PSParallelCompact::print_generic_summary_data(ParallelCompactData& summary_data,
 283                                               HeapWord* const beg_addr,
 284                                               HeapWord* const end_addr) {
 285   ::print_generic_summary_data(summary_data,beg_addr, end_addr);
 286 }
 287 
 288 void
 289 print_generic_summary_data(ParallelCompactData& summary_data,
 290                            SpaceInfo* space_info)
 291 {
 292   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 293     return;
 294   }
 295 
 296   for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
 297     const MutableSpace* space = space_info[id].space();
 298     print_generic_summary_data(summary_data, space->bottom(),
 299                                MAX2(space->top(), space_info[id].new_top()));
 300   }
 301 }
 302 
 303 void
 304 print_initial_summary_data(ParallelCompactData& summary_data,
 305                            const MutableSpace* space) {
 306   if (space->top() == space->bottom()) {
 307     return;
 308   }
 309 
 310   const size_t region_size = ParallelCompactData::RegionSize;
 311   typedef ParallelCompactData::RegionData RegionData;
 312   HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
 313   const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
 314   const RegionData* c = summary_data.region(end_region - 1);
 315   HeapWord* end_addr = c->destination() + c->data_size();
 316   const size_t live_in_space = pointer_delta(end_addr, space->bottom());
 317 
 318   // Print (and count) the full regions at the beginning of the space.
 319   size_t full_region_count = 0;
 320   size_t i = summary_data.addr_to_region_idx(space->bottom());
 321   while (i < end_region && summary_data.region(i)->data_size() == region_size) {
 322     ParallelCompactData::RegionData* c = summary_data.region(i);
 323     log_develop_trace(gc, compaction)(
 324         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 325         i, p2i(c->destination()),
 326         c->partial_obj_size(), c->live_obj_size(),
 327         c->data_size(), c->source_region(), c->destination_count());
 328     ++full_region_count;
 329     ++i;
 330   }
 331 
 332   size_t live_to_right = live_in_space - full_region_count * region_size;
 333 
 334   double max_reclaimed_ratio = 0.0;
 335   size_t max_reclaimed_ratio_region = 0;
 336   size_t max_dead_to_right = 0;
 337   size_t max_live_to_right = 0;
 338 
 339   // Print the 'reclaimed ratio' for regions while there is something live in
 340   // the region or to the right of it.  The remaining regions are empty (and
 341   // uninteresting), and computing the ratio will result in division by 0.
 342   while (i < end_region && live_to_right > 0) {
 343     c = summary_data.region(i);
 344     HeapWord* const region_addr = summary_data.region_to_addr(i);
 345     const size_t used_to_right = pointer_delta(space->top(), region_addr);
 346     const size_t dead_to_right = used_to_right - live_to_right;
 347     const double reclaimed_ratio = double(dead_to_right) / live_to_right;
 348 
 349     if (reclaimed_ratio > max_reclaimed_ratio) {
 350             max_reclaimed_ratio = reclaimed_ratio;
 351             max_reclaimed_ratio_region = i;
 352             max_dead_to_right = dead_to_right;
 353             max_live_to_right = live_to_right;
 354     }
 355 
 356     ParallelCompactData::RegionData* c = summary_data.region(i);
 357     log_develop_trace(gc, compaction)(
 358         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d"
 359         "%12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
 360         i, p2i(c->destination()),
 361         c->partial_obj_size(), c->live_obj_size(),
 362         c->data_size(), c->source_region(), c->destination_count(),
 363         reclaimed_ratio, dead_to_right, live_to_right);
 364 
 365 
 366     live_to_right -= c->data_size();
 367     ++i;
 368   }
 369 
 370   // Any remaining regions are empty.  Print one more if there is one.
 371   if (i < end_region) {
 372     ParallelCompactData::RegionData* c = summary_data.region(i);
 373     log_develop_trace(gc, compaction)(
 374         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 375          i, p2i(c->destination()),
 376          c->partial_obj_size(), c->live_obj_size(),
 377          c->data_size(), c->source_region(), c->destination_count());
 378   }
 379 
 380   log_develop_trace(gc, compaction)("max:  " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
 381                                     max_reclaimed_ratio_region, max_dead_to_right, max_live_to_right, max_reclaimed_ratio);
 382 }
 383 
 384 void
 385 print_initial_summary_data(ParallelCompactData& summary_data,
 386                            SpaceInfo* space_info) {
 387   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 388     return;
 389   }
 390 
 391   unsigned int id = PSParallelCompact::old_space_id;
 392   const MutableSpace* space;
 393   do {
 394     space = space_info[id].space();
 395     print_initial_summary_data(summary_data, space);
 396   } while (++id < PSParallelCompact::eden_space_id);
 397 
 398   do {
 399     space = space_info[id].space();
 400     print_generic_summary_data(summary_data, space->bottom(), space->top());
 401   } while (++id < PSParallelCompact::last_space_id);
 402 }
 403 #endif  // #ifndef PRODUCT
 404 
 405 #ifdef  ASSERT
 406 size_t add_obj_count;
 407 size_t add_obj_size;
 408 size_t mark_bitmap_count;
 409 size_t mark_bitmap_size;
 410 #endif  // #ifdef ASSERT
 411 
 412 ParallelCompactData::ParallelCompactData() :
 413   _region_start(NULL),
 414   DEBUG_ONLY(_region_end(NULL) COMMA)
 415   _region_vspace(NULL),
 416   _reserved_byte_size(0),
 417   _region_data(NULL),
 418   _region_count(0),
 419   _block_vspace(NULL),
 420   _block_data(NULL),
 421   _block_count(0) {}
 422 
 423 bool ParallelCompactData::initialize(MemRegion covered_region)
 424 {
 425   _region_start = covered_region.start();
 426   const size_t region_size = covered_region.word_size();
 427   DEBUG_ONLY(_region_end = _region_start + region_size;)
 428 
 429   assert(region_align_down(_region_start) == _region_start,
 430          "region start not aligned");
 431   assert((region_size & RegionSizeOffsetMask) == 0,
 432          "region size not a multiple of RegionSize");
 433 
 434   bool result = initialize_region_data(region_size) && initialize_block_data();
 435   return result;
 436 }
 437 
 438 PSVirtualSpace*
 439 ParallelCompactData::create_vspace(size_t count, size_t element_size)
 440 {
 441   const size_t raw_bytes = count * element_size;
 442   const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
 443   const size_t granularity = os::vm_allocation_granularity();
 444   _reserved_byte_size = align_up(raw_bytes, MAX2(page_sz, granularity));
 445 
 446   const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
 447     MAX2(page_sz, granularity);
 448   ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0);
 449   os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, page_sz, rs.base(),
 450                        rs.size());
 451 
 452   MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
 453 
 454   PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
 455   if (vspace != 0) {
 456     if (vspace->expand_by(_reserved_byte_size)) {
 457       return vspace;
 458     }
 459     delete vspace;
 460     // Release memory reserved in the space.
 461     rs.release();
 462   }
 463 
 464   return 0;
 465 }
 466 
 467 bool ParallelCompactData::initialize_region_data(size_t region_size)
 468 {
 469   const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
 470   _region_vspace = create_vspace(count, sizeof(RegionData));
 471   if (_region_vspace != 0) {
 472     _region_data = (RegionData*)_region_vspace->reserved_low_addr();
 473     _region_count = count;
 474     return true;
 475   }
 476   return false;
 477 }
 478 
 479 bool ParallelCompactData::initialize_block_data()
 480 {
 481   assert(_region_count != 0, "region data must be initialized first");
 482   const size_t count = _region_count << Log2BlocksPerRegion;
 483   _block_vspace = create_vspace(count, sizeof(BlockData));
 484   if (_block_vspace != 0) {
 485     _block_data = (BlockData*)_block_vspace->reserved_low_addr();
 486     _block_count = count;
 487     return true;
 488   }
 489   return false;
 490 }
 491 
 492 void ParallelCompactData::clear()
 493 {
 494   memset(_region_data, 0, _region_vspace->committed_size());
 495   memset(_block_data, 0, _block_vspace->committed_size());
 496 }
 497 
 498 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
 499   assert(beg_region <= _region_count, "beg_region out of range");
 500   assert(end_region <= _region_count, "end_region out of range");
 501   assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize");
 502 
 503   const size_t region_cnt = end_region - beg_region;
 504   memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
 505 
 506   const size_t beg_block = beg_region * BlocksPerRegion;
 507   const size_t block_cnt = region_cnt * BlocksPerRegion;
 508   memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData));
 509 }
 510 
 511 HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
 512 {
 513   const RegionData* cur_cp = region(region_idx);
 514   const RegionData* const end_cp = region(region_count() - 1);
 515 
 516   HeapWord* result = region_to_addr(region_idx);
 517   if (cur_cp < end_cp) {
 518     do {
 519       result += cur_cp->partial_obj_size();
 520     } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
 521   }
 522   return result;
 523 }
 524 
 525 void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
 526 {
 527   const size_t obj_ofs = pointer_delta(addr, _region_start);
 528   const size_t beg_region = obj_ofs >> Log2RegionSize;
 529   const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
 530 
 531   DEBUG_ONLY(Atomic::inc(&add_obj_count);)
 532   DEBUG_ONLY(Atomic::add(len, &add_obj_size);)
 533 
 534   if (beg_region == end_region) {
 535     // All in one region.
 536     _region_data[beg_region].add_live_obj(len);
 537     return;
 538   }
 539 
 540   // First region.
 541   const size_t beg_ofs = region_offset(addr);
 542   _region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
 543 
 544   Klass* klass = ((oop)addr)->klass();
 545   // Middle regions--completely spanned by this object.
 546   for (size_t region = beg_region + 1; region < end_region; ++region) {
 547     _region_data[region].set_partial_obj_size(RegionSize);
 548     _region_data[region].set_partial_obj_addr(addr);
 549   }
 550 
 551   // Last region.
 552   const size_t end_ofs = region_offset(addr + len - 1);
 553   _region_data[end_region].set_partial_obj_size(end_ofs + 1);
 554   _region_data[end_region].set_partial_obj_addr(addr);
 555 }
 556 
 557 void
 558 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
 559 {
 560   assert(region_offset(beg) == 0, "not RegionSize aligned");
 561   assert(region_offset(end) == 0, "not RegionSize aligned");
 562 
 563   size_t cur_region = addr_to_region_idx(beg);
 564   const size_t end_region = addr_to_region_idx(end);
 565   HeapWord* addr = beg;
 566   while (cur_region < end_region) {
 567     _region_data[cur_region].set_destination(addr);
 568     _region_data[cur_region].set_destination_count(0);
 569     _region_data[cur_region].set_source_region(cur_region);
 570     _region_data[cur_region].set_data_location(addr);
 571 
 572     // Update live_obj_size so the region appears completely full.
 573     size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
 574     _region_data[cur_region].set_live_obj_size(live_size);
 575 
 576     ++cur_region;
 577     addr += RegionSize;
 578   }
 579 }
 580 
 581 // Find the point at which a space can be split and, if necessary, record the
 582 // split point.
 583 //
 584 // If the current src region (which overflowed the destination space) doesn't
 585 // have a partial object, the split point is at the beginning of the current src
 586 // region (an "easy" split, no extra bookkeeping required).
 587 //
 588 // If the current src region has a partial object, the split point is in the
 589 // region where that partial object starts (call it the split_region).  If
 590 // split_region has a partial object, then the split point is just after that
 591 // partial object (a "hard" split where we have to record the split data and
 592 // zero the partial_obj_size field).  With a "hard" split, we know that the
 593 // partial_obj ends within split_region because the partial object that caused
 594 // the overflow starts in split_region.  If split_region doesn't have a partial
 595 // obj, then the split is at the beginning of split_region (another "easy"
 596 // split).
 597 HeapWord*
 598 ParallelCompactData::summarize_split_space(size_t src_region,
 599                                            SplitInfo& split_info,
 600                                            HeapWord* destination,
 601                                            HeapWord* target_end,
 602                                            HeapWord** target_next)
 603 {
 604   assert(destination <= target_end, "sanity");
 605   assert(destination + _region_data[src_region].data_size() > target_end,
 606     "region should not fit into target space");
 607   assert(is_region_aligned(target_end), "sanity");
 608 
 609   size_t split_region = src_region;
 610   HeapWord* split_destination = destination;
 611   size_t partial_obj_size = _region_data[src_region].partial_obj_size();
 612 
 613   if (destination + partial_obj_size > target_end) {
 614     // The split point is just after the partial object (if any) in the
 615     // src_region that contains the start of the object that overflowed the
 616     // destination space.
 617     //
 618     // Find the start of the "overflow" object and set split_region to the
 619     // region containing it.
 620     HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
 621     split_region = addr_to_region_idx(overflow_obj);
 622 
 623     // Clear the source_region field of all destination regions whose first word
 624     // came from data after the split point (a non-null source_region field
 625     // implies a region must be filled).
 626     //
 627     // An alternative to the simple loop below:  clear during post_compact(),
 628     // which uses memcpy instead of individual stores, and is easy to
 629     // parallelize.  (The downside is that it clears the entire RegionData
 630     // object as opposed to just one field.)
 631     //
 632     // post_compact() would have to clear the summary data up to the highest
 633     // address that was written during the summary phase, which would be
 634     //
 635     //         max(top, max(new_top, clear_top))
 636     //
 637     // where clear_top is a new field in SpaceInfo.  Would have to set clear_top
 638     // to target_end.
 639     const RegionData* const sr = region(split_region);
 640     const size_t beg_idx =
 641       addr_to_region_idx(region_align_up(sr->destination() +
 642                                          sr->partial_obj_size()));
 643     const size_t end_idx = addr_to_region_idx(target_end);
 644 
 645     log_develop_trace(gc, compaction)("split:  clearing source_region field in [" SIZE_FORMAT ", " SIZE_FORMAT ")", beg_idx, end_idx);
 646     for (size_t idx = beg_idx; idx < end_idx; ++idx) {
 647       _region_data[idx].set_source_region(0);
 648     }
 649 
 650     // Set split_destination and partial_obj_size to reflect the split region.
 651     split_destination = sr->destination();
 652     partial_obj_size = sr->partial_obj_size();
 653   }
 654 
 655   // The split is recorded only if a partial object extends onto the region.
 656   if (partial_obj_size != 0) {
 657     _region_data[split_region].set_partial_obj_size(0);
 658     split_info.record(split_region, partial_obj_size, split_destination);
 659   }
 660 
 661   // Setup the continuation addresses.
 662   *target_next = split_destination + partial_obj_size;
 663   HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
 664 
 665   if (log_develop_is_enabled(Trace, gc, compaction)) {
 666     const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
 667     log_develop_trace(gc, compaction)("%s split:  src=" PTR_FORMAT " src_c=" SIZE_FORMAT " pos=" SIZE_FORMAT,
 668                                       split_type, p2i(source_next), split_region, partial_obj_size);
 669     log_develop_trace(gc, compaction)("%s split:  dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT " tn=" PTR_FORMAT,
 670                                       split_type, p2i(split_destination),
 671                                       addr_to_region_idx(split_destination),
 672                                       p2i(*target_next));
 673 
 674     if (partial_obj_size != 0) {
 675       HeapWord* const po_beg = split_info.destination();
 676       HeapWord* const po_end = po_beg + split_info.partial_obj_size();
 677       log_develop_trace(gc, compaction)("%s split:  po_beg=" PTR_FORMAT " " SIZE_FORMAT " po_end=" PTR_FORMAT " " SIZE_FORMAT,
 678                                         split_type,
 679                                         p2i(po_beg), addr_to_region_idx(po_beg),
 680                                         p2i(po_end), addr_to_region_idx(po_end));
 681     }
 682   }
 683 
 684   return source_next;
 685 }
 686 
 687 bool ParallelCompactData::summarize(SplitInfo& split_info,
 688                                     HeapWord* source_beg, HeapWord* source_end,
 689                                     HeapWord** source_next,
 690                                     HeapWord* target_beg, HeapWord* target_end,
 691                                     HeapWord** target_next)
 692 {
 693   HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
 694   log_develop_trace(gc, compaction)(
 695       "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
 696       "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
 697       p2i(source_beg), p2i(source_end), p2i(source_next_val),
 698       p2i(target_beg), p2i(target_end), p2i(*target_next));
 699 
 700   size_t cur_region = addr_to_region_idx(source_beg);
 701   const size_t end_region = addr_to_region_idx(region_align_up(source_end));
 702 
 703   HeapWord *dest_addr = target_beg;
 704   while (cur_region < end_region) {
 705     // The destination must be set even if the region has no data.
 706     _region_data[cur_region].set_destination(dest_addr);
 707 
 708     size_t words = _region_data[cur_region].data_size();
 709     if (words > 0) {
 710       // If cur_region does not fit entirely into the target space, find a point
 711       // at which the source space can be 'split' so that part is copied to the
 712       // target space and the rest is copied elsewhere.
 713       if (dest_addr + words > target_end) {
 714         assert(source_next != NULL, "source_next is NULL when splitting");
 715         *source_next = summarize_split_space(cur_region, split_info, dest_addr,
 716                                              target_end, target_next);
 717         return false;
 718       }
 719 
 720       // Compute the destination_count for cur_region, and if necessary, update
 721       // source_region for a destination region.  The source_region field is
 722       // updated if cur_region is the first (left-most) region to be copied to a
 723       // destination region.
 724       //
 725       // The destination_count calculation is a bit subtle.  A region that has
 726       // data that compacts into itself does not count itself as a destination.
 727       // This maintains the invariant that a zero count means the region is
 728       // available and can be claimed and then filled.
 729       uint destination_count = 0;
 730       if (split_info.is_split(cur_region)) {
 731         // The current region has been split:  the partial object will be copied
 732         // to one destination space and the remaining data will be copied to
 733         // another destination space.  Adjust the initial destination_count and,
 734         // if necessary, set the source_region field if the partial object will
 735         // cross a destination region boundary.
 736         destination_count = split_info.destination_count();
 737         if (destination_count == 2) {
 738           size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
 739           _region_data[dest_idx].set_source_region(cur_region);
 740         }
 741       }
 742 
 743       HeapWord* const last_addr = dest_addr + words - 1;
 744       const size_t dest_region_1 = addr_to_region_idx(dest_addr);
 745       const size_t dest_region_2 = addr_to_region_idx(last_addr);
 746 
 747       // Initially assume that the destination regions will be the same and
 748       // adjust the value below if necessary.  Under this assumption, if
 749       // cur_region == dest_region_2, then cur_region will be compacted
 750       // completely into itself.
 751       destination_count += cur_region == dest_region_2 ? 0 : 1;
 752       if (dest_region_1 != dest_region_2) {
 753         // Destination regions differ; adjust destination_count.
 754         destination_count += 1;
 755         // Data from cur_region will be copied to the start of dest_region_2.
 756         _region_data[dest_region_2].set_source_region(cur_region);
 757       } else if (region_offset(dest_addr) == 0) {
 758         // Data from cur_region will be copied to the start of the destination
 759         // region.
 760         _region_data[dest_region_1].set_source_region(cur_region);
 761       }
 762 
 763       _region_data[cur_region].set_destination_count(destination_count);
 764       _region_data[cur_region].set_data_location(region_to_addr(cur_region));
 765       dest_addr += words;
 766     }
 767 
 768     ++cur_region;
 769   }
 770 
 771   *target_next = dest_addr;
 772   return true;
 773 }
 774 
 775 HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr, ParCompactionManager* cm) {
 776   assert(addr != NULL, "Should detect NULL oop earlier");
 777   assert(ParallelScavengeHeap::heap()->is_in(addr), "not in heap");
 778   assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked");
 779 
 780   // Region covering the object.
 781   RegionData* const region_ptr = addr_to_region_ptr(addr);
 782   HeapWord* result = region_ptr->destination();
 783 
 784   // If the entire Region is live, the new location is region->destination + the
 785   // offset of the object within in the Region.
 786 
 787   // Run some performance tests to determine if this special case pays off.  It
 788   // is worth it for pointers into the dense prefix.  If the optimization to
 789   // avoid pointer updates in regions that only point to the dense prefix is
 790   // ever implemented, this should be revisited.
 791   if (region_ptr->data_size() == RegionSize) {
 792     result += region_offset(addr);
 793     return result;
 794   }
 795 
 796   // Otherwise, the new location is region->destination + block offset + the
 797   // number of live words in the Block that are (a) to the left of addr and (b)
 798   // due to objects that start in the Block.
 799 
 800   // Fill in the block table if necessary.  This is unsynchronized, so multiple
 801   // threads may fill the block table for a region (harmless, since it is
 802   // idempotent).
 803   if (!region_ptr->blocks_filled()) {
 804     PSParallelCompact::fill_blocks(addr_to_region_idx(addr));
 805     region_ptr->set_blocks_filled();
 806   }
 807 
 808   HeapWord* const search_start = block_align_down(addr);
 809   const size_t block_offset = addr_to_block_ptr(addr)->offset();
 810 
 811   const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
 812   const size_t live = bitmap->live_words_in_range(cm, search_start, oop(addr));
 813   result += block_offset + live;
 814   DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result));
 815   return result;
 816 }
 817 
 818 #ifdef ASSERT
 819 void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
 820 {
 821   const size_t* const beg = (const size_t*)vspace->committed_low_addr();
 822   const size_t* const end = (const size_t*)vspace->committed_high_addr();
 823   for (const size_t* p = beg; p < end; ++p) {
 824     assert(*p == 0, "not zero");
 825   }
 826 }
 827 
 828 void ParallelCompactData::verify_clear()
 829 {
 830   verify_clear(_region_vspace);
 831   verify_clear(_block_vspace);
 832 }
 833 #endif  // #ifdef ASSERT
 834 
 835 STWGCTimer          PSParallelCompact::_gc_timer;
 836 ParallelOldTracer   PSParallelCompact::_gc_tracer;
 837 elapsedTimer        PSParallelCompact::_accumulated_time;
 838 unsigned int        PSParallelCompact::_total_invocations = 0;
 839 unsigned int        PSParallelCompact::_maximum_compaction_gc_num = 0;
 840 jlong               PSParallelCompact::_time_of_last_gc = 0;
 841 CollectorCounters*  PSParallelCompact::_counters = NULL;
 842 ParMarkBitMap       PSParallelCompact::_mark_bitmap;
 843 ParallelCompactData PSParallelCompact::_summary_data;
 844 
 845 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
 846 
 847 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
 848 
 849 class PCReferenceProcessor: public ReferenceProcessor {
 850 public:
 851   PCReferenceProcessor(
 852     BoolObjectClosure* is_subject_to_discovery,
 853     BoolObjectClosure* is_alive_non_header) :
 854       ReferenceProcessor(is_subject_to_discovery,
 855       ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 856       ParallelGCThreads,   // mt processing degree
 857       true,                // mt discovery
 858       ParallelGCThreads,   // mt discovery degree
 859       true,                // atomic_discovery
 860       is_alive_non_header) {
 861   }
 862 
 863   template<typename T> bool discover(oop obj, ReferenceType type) {
 864     T* referent_addr = (T*) java_lang_ref_Reference::referent_addr_raw(obj);
 865     T heap_oop = RawAccess<>::oop_load(referent_addr);
 866     oop referent = CompressedOops::decode_not_null(heap_oop);
 867     return PSParallelCompact::mark_bitmap()->is_unmarked(referent)
 868         && ReferenceProcessor::discover_reference(obj, type);
 869   }
 870   virtual bool discover_reference(oop obj, ReferenceType type) {
 871     if (UseCompressedOops) {
 872       return discover<narrowOop>(obj, type);
 873     } else {
 874       return discover<oop>(obj, type);
 875     }
 876   }
 877 };
 878 
 879 void PSParallelCompact::post_initialize() {
 880   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 881   _span_based_discoverer.set_span(heap->reserved_region());
 882   _ref_processor =
 883     new PCReferenceProcessor(&_span_based_discoverer,
 884                              &_is_alive_closure); // non-header is alive closure
 885 
 886   _counters = new CollectorCounters("Parallel full collection pauses", 1);
 887 
 888   // Initialize static fields in ParCompactionManager.
 889   ParCompactionManager::initialize(mark_bitmap());
 890 }
 891 
 892 bool PSParallelCompact::initialize() {
 893   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 894   MemRegion mr = heap->reserved_region();
 895 
 896   // Was the old gen get allocated successfully?
 897   if (!heap->old_gen()->is_allocated()) {
 898     return false;
 899   }
 900 
 901   initialize_space_info();
 902   initialize_dead_wood_limiter();
 903 
 904   if (!_mark_bitmap.initialize(mr)) {
 905     vm_shutdown_during_initialization(
 906       err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
 907       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 908       _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
 909     return false;
 910   }
 911 
 912   if (!_summary_data.initialize(mr)) {
 913     vm_shutdown_during_initialization(
 914       err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
 915       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 916       _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
 917     return false;
 918   }
 919 
 920   return true;
 921 }
 922 
 923 void PSParallelCompact::initialize_space_info()
 924 {
 925   memset(&_space_info, 0, sizeof(_space_info));
 926 
 927   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 928   PSYoungGen* young_gen = heap->young_gen();
 929 
 930   _space_info[old_space_id].set_space(heap->old_gen()->object_space());
 931   _space_info[eden_space_id].set_space(young_gen->eden_space());
 932   _space_info[from_space_id].set_space(young_gen->from_space());
 933   _space_info[to_space_id].set_space(young_gen->to_space());
 934 
 935   _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
 936 }
 937 
 938 void PSParallelCompact::initialize_dead_wood_limiter()
 939 {
 940   const size_t max = 100;
 941   _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
 942   _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
 943   _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
 944   DEBUG_ONLY(_dwl_initialized = true;)
 945   _dwl_adjustment = normal_distribution(1.0);
 946 }
 947 
 948 void
 949 PSParallelCompact::clear_data_covering_space(SpaceId id)
 950 {
 951   // At this point, top is the value before GC, new_top() is the value that will
 952   // be set at the end of GC.  The marking bitmap is cleared to top; nothing
 953   // should be marked above top.  The summary data is cleared to the larger of
 954   // top & new_top.
 955   MutableSpace* const space = _space_info[id].space();
 956   HeapWord* const bot = space->bottom();
 957   HeapWord* const top = space->top();
 958   HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
 959 
 960   const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
 961   const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top));
 962   _mark_bitmap.clear_range(beg_bit, end_bit);
 963 
 964   const size_t beg_region = _summary_data.addr_to_region_idx(bot);
 965   const size_t end_region =
 966     _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
 967   _summary_data.clear_range(beg_region, end_region);
 968 
 969   // Clear the data used to 'split' regions.
 970   SplitInfo& split_info = _space_info[id].split_info();
 971   if (split_info.is_valid()) {
 972     split_info.clear();
 973   }
 974   DEBUG_ONLY(split_info.verify_clear();)
 975 }
 976 
 977 void PSParallelCompact::pre_compact()
 978 {
 979   // Update the from & to space pointers in space_info, since they are swapped
 980   // at each young gen gc.  Do the update unconditionally (even though a
 981   // promotion failure does not swap spaces) because an unknown number of young
 982   // collections will have swapped the spaces an unknown number of times.
 983   GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
 984   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 985   _space_info[from_space_id].set_space(heap->young_gen()->from_space());
 986   _space_info[to_space_id].set_space(heap->young_gen()->to_space());
 987 
 988   DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
 989   DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
 990 
 991   // Increment the invocation count
 992   heap->increment_total_collections(true);
 993 
 994   // We need to track unique mark sweep invocations as well.
 995   _total_invocations++;
 996 
 997   heap->print_heap_before_gc();
 998   heap->trace_heap_before_gc(&_gc_tracer);
 999 
1000   // Fill in TLABs
1001   heap->ensure_parsability(true);  // retire TLABs
1002 
1003   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
1004     HandleMark hm;  // Discard invalid handles created during verification
1005     Universe::verify("Before GC");
1006   }
1007 
1008   // Verify object start arrays
1009   if (VerifyObjectStartArray &&
1010       VerifyBeforeGC) {
1011     heap->old_gen()->verify_object_start_array();
1012   }
1013 
1014   DEBUG_ONLY(mark_bitmap()->verify_clear();)
1015   DEBUG_ONLY(summary_data().verify_clear();)
1016 
1017   // Have worker threads release resources the next time they run a task.
1018   gc_task_manager()->release_all_resources();
1019 
1020   ParCompactionManager::reset_all_bitmap_query_caches();
1021 }
1022 
1023 void PSParallelCompact::post_compact()
1024 {
1025   GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
1026 
1027   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1028     // Clear the marking bitmap, summary data and split info.
1029     clear_data_covering_space(SpaceId(id));
1030     // Update top().  Must be done after clearing the bitmap and summary data.
1031     _space_info[id].publish_new_top();
1032   }
1033 
1034   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1035   MutableSpace* const from_space = _space_info[from_space_id].space();
1036   MutableSpace* const to_space   = _space_info[to_space_id].space();
1037 
1038   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1039   bool eden_empty = eden_space->is_empty();
1040   if (!eden_empty) {
1041     eden_empty = absorb_live_data_from_eden(heap->size_policy(),
1042                                             heap->young_gen(), heap->old_gen());
1043   }
1044 
1045   // Update heap occupancy information which is used as input to the soft ref
1046   // clearing policy at the next gc.
1047   Universe::update_heap_info_at_gc();
1048 
1049   bool young_gen_empty = eden_empty && from_space->is_empty() &&
1050     to_space->is_empty();
1051 
1052   PSCardTable* ct = heap->card_table();
1053   MemRegion old_mr = heap->old_gen()->reserved();
1054   if (young_gen_empty) {
1055     ct->clear(MemRegion(old_mr.start(), old_mr.end()));
1056   } else {
1057     ct->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1058   }
1059 
1060   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1061   ClassLoaderDataGraph::purge();
1062   MetaspaceUtils::verify_metrics();
1063 
1064   heap->prune_scavengable_nmethods();
1065   JvmtiExport::gc_epilogue();
1066 
1067 #if COMPILER2_OR_JVMCI
1068   DerivedPointerTable::update_pointers();
1069 #endif
1070 
1071   if (ZapUnusedHeapArea) {
1072     heap->gen_mangle_unused_area();
1073   }
1074 
1075   // Update time of last GC
1076   reset_millis_since_last_gc();
1077 }
1078 
1079 HeapWord*
1080 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1081                                                     bool maximum_compaction)
1082 {
1083   const size_t region_size = ParallelCompactData::RegionSize;
1084   const ParallelCompactData& sd = summary_data();
1085 
1086   const MutableSpace* const space = _space_info[id].space();
1087   HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1088   const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1089   const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1090 
1091   // Skip full regions at the beginning of the space--they are necessarily part
1092   // of the dense prefix.
1093   size_t full_count = 0;
1094   const RegionData* cp;
1095   for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1096     ++full_count;
1097   }
1098 
1099   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1100   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1101   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1102   if (maximum_compaction || cp == end_cp || interval_ended) {
1103     _maximum_compaction_gc_num = total_invocations();
1104     return sd.region_to_addr(cp);
1105   }
1106 
1107   HeapWord* const new_top = _space_info[id].new_top();
1108   const size_t space_live = pointer_delta(new_top, space->bottom());
1109   const size_t space_used = space->used_in_words();
1110   const size_t space_capacity = space->capacity_in_words();
1111 
1112   const double cur_density = double(space_live) / space_capacity;
1113   const double deadwood_density =
1114     (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1115   const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1116 
1117   if (TraceParallelOldGCDensePrefix) {
1118     tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1119                   cur_density, deadwood_density, deadwood_goal);
1120     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1121                   "space_cap=" SIZE_FORMAT,
1122                   space_live, space_used,
1123                   space_capacity);
1124   }
1125 
1126   // XXX - Use binary search?
1127   HeapWord* dense_prefix = sd.region_to_addr(cp);
1128   const RegionData* full_cp = cp;
1129   const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1130   while (cp < end_cp) {
1131     HeapWord* region_destination = cp->destination();
1132     const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1133     if (TraceParallelOldGCDensePrefix && Verbose) {
1134       tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1135                     "dp=" PTR_FORMAT " " "cdw=" SIZE_FORMAT_W(8),
1136                     sd.region(cp), p2i(region_destination),
1137                     p2i(dense_prefix), cur_deadwood);
1138     }
1139 
1140     if (cur_deadwood >= deadwood_goal) {
1141       // Found the region that has the correct amount of deadwood to the left.
1142       // This typically occurs after crossing a fairly sparse set of regions, so
1143       // iterate backwards over those sparse regions, looking for the region
1144       // that has the lowest density of live objects 'to the right.'
1145       size_t space_to_left = sd.region(cp) * region_size;
1146       size_t live_to_left = space_to_left - cur_deadwood;
1147       size_t space_to_right = space_capacity - space_to_left;
1148       size_t live_to_right = space_live - live_to_left;
1149       double density_to_right = double(live_to_right) / space_to_right;
1150       while (cp > full_cp) {
1151         --cp;
1152         const size_t prev_region_live_to_right = live_to_right -
1153           cp->data_size();
1154         const size_t prev_region_space_to_right = space_to_right + region_size;
1155         double prev_region_density_to_right =
1156           double(prev_region_live_to_right) / prev_region_space_to_right;
1157         if (density_to_right <= prev_region_density_to_right) {
1158           return dense_prefix;
1159         }
1160         if (TraceParallelOldGCDensePrefix && Verbose) {
1161           tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1162                         "pc_d2r=%10.8f", sd.region(cp), density_to_right,
1163                         prev_region_density_to_right);
1164         }
1165         dense_prefix -= region_size;
1166         live_to_right = prev_region_live_to_right;
1167         space_to_right = prev_region_space_to_right;
1168         density_to_right = prev_region_density_to_right;
1169       }
1170       return dense_prefix;
1171     }
1172 
1173     dense_prefix += region_size;
1174     ++cp;
1175   }
1176 
1177   return dense_prefix;
1178 }
1179 
1180 #ifndef PRODUCT
1181 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1182                                                  const SpaceId id,
1183                                                  const bool maximum_compaction,
1184                                                  HeapWord* const addr)
1185 {
1186   const size_t region_idx = summary_data().addr_to_region_idx(addr);
1187   RegionData* const cp = summary_data().region(region_idx);
1188   const MutableSpace* const space = _space_info[id].space();
1189   HeapWord* const new_top = _space_info[id].new_top();
1190 
1191   const size_t space_live = pointer_delta(new_top, space->bottom());
1192   const size_t dead_to_left = pointer_delta(addr, cp->destination());
1193   const size_t space_cap = space->capacity_in_words();
1194   const double dead_to_left_pct = double(dead_to_left) / space_cap;
1195   const size_t live_to_right = new_top - cp->destination();
1196   const size_t dead_to_right = space->top() - addr - live_to_right;
1197 
1198   tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1199                 "spl=" SIZE_FORMAT " "
1200                 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1201                 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
1202                 " ratio=%10.8f",
1203                 algorithm, p2i(addr), region_idx,
1204                 space_live,
1205                 dead_to_left, dead_to_left_pct,
1206                 dead_to_right, live_to_right,
1207                 double(dead_to_right) / live_to_right);
1208 }
1209 #endif  // #ifndef PRODUCT
1210 
1211 // Return a fraction indicating how much of the generation can be treated as
1212 // "dead wood" (i.e., not reclaimed).  The function uses a normal distribution
1213 // based on the density of live objects in the generation to determine a limit,
1214 // which is then adjusted so the return value is min_percent when the density is
1215 // 1.
1216 //
1217 // The following table shows some return values for a different values of the
1218 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1219 // min_percent is 1.
1220 //
1221 //                          fraction allowed as dead wood
1222 //         -----------------------------------------------------------------
1223 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1224 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1225 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1226 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1227 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1228 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1229 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1230 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1231 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1232 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1233 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1234 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1235 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1236 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1237 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1238 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1239 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1240 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1241 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1242 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1243 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1244 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1245 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1246 
1247 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1248 {
1249   assert(_dwl_initialized, "uninitialized");
1250 
1251   // The raw limit is the value of the normal distribution at x = density.
1252   const double raw_limit = normal_distribution(density);
1253 
1254   // Adjust the raw limit so it becomes the minimum when the density is 1.
1255   //
1256   // First subtract the adjustment value (which is simply the precomputed value
1257   // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1258   // Then add the minimum value, so the minimum is returned when the density is
1259   // 1.  Finally, prevent negative values, which occur when the mean is not 0.5.
1260   const double min = double(min_percent) / 100.0;
1261   const double limit = raw_limit - _dwl_adjustment + min;
1262   return MAX2(limit, 0.0);
1263 }
1264 
1265 ParallelCompactData::RegionData*
1266 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1267                                            const RegionData* end)
1268 {
1269   const size_t region_size = ParallelCompactData::RegionSize;
1270   ParallelCompactData& sd = summary_data();
1271   size_t left = sd.region(beg);
1272   size_t right = end > beg ? sd.region(end) - 1 : left;
1273 
1274   // Binary search.
1275   while (left < right) {
1276     // Equivalent to (left + right) / 2, but does not overflow.
1277     const size_t middle = left + (right - left) / 2;
1278     RegionData* const middle_ptr = sd.region(middle);
1279     HeapWord* const dest = middle_ptr->destination();
1280     HeapWord* const addr = sd.region_to_addr(middle);
1281     assert(dest != NULL, "sanity");
1282     assert(dest <= addr, "must move left");
1283 
1284     if (middle > left && dest < addr) {
1285       right = middle - 1;
1286     } else if (middle < right && middle_ptr->data_size() == region_size) {
1287       left = middle + 1;
1288     } else {
1289       return middle_ptr;
1290     }
1291   }
1292   return sd.region(left);
1293 }
1294 
1295 ParallelCompactData::RegionData*
1296 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1297                                           const RegionData* end,
1298                                           size_t dead_words)
1299 {
1300   ParallelCompactData& sd = summary_data();
1301   size_t left = sd.region(beg);
1302   size_t right = end > beg ? sd.region(end) - 1 : left;
1303 
1304   // Binary search.
1305   while (left < right) {
1306     // Equivalent to (left + right) / 2, but does not overflow.
1307     const size_t middle = left + (right - left) / 2;
1308     RegionData* const middle_ptr = sd.region(middle);
1309     HeapWord* const dest = middle_ptr->destination();
1310     HeapWord* const addr = sd.region_to_addr(middle);
1311     assert(dest != NULL, "sanity");
1312     assert(dest <= addr, "must move left");
1313 
1314     const size_t dead_to_left = pointer_delta(addr, dest);
1315     if (middle > left && dead_to_left > dead_words) {
1316       right = middle - 1;
1317     } else if (middle < right && dead_to_left < dead_words) {
1318       left = middle + 1;
1319     } else {
1320       return middle_ptr;
1321     }
1322   }
1323   return sd.region(left);
1324 }
1325 
1326 // The result is valid during the summary phase, after the initial summarization
1327 // of each space into itself, and before final summarization.
1328 inline double
1329 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1330                                    HeapWord* const bottom,
1331                                    HeapWord* const top,
1332                                    HeapWord* const new_top)
1333 {
1334   ParallelCompactData& sd = summary_data();
1335 
1336   assert(cp != NULL, "sanity");
1337   assert(bottom != NULL, "sanity");
1338   assert(top != NULL, "sanity");
1339   assert(new_top != NULL, "sanity");
1340   assert(top >= new_top, "summary data problem?");
1341   assert(new_top > bottom, "space is empty; should not be here");
1342   assert(new_top >= cp->destination(), "sanity");
1343   assert(top >= sd.region_to_addr(cp), "sanity");
1344 
1345   HeapWord* const destination = cp->destination();
1346   const size_t dense_prefix_live  = pointer_delta(destination, bottom);
1347   const size_t compacted_region_live = pointer_delta(new_top, destination);
1348   const size_t compacted_region_used = pointer_delta(top,
1349                                                      sd.region_to_addr(cp));
1350   const size_t reclaimable = compacted_region_used - compacted_region_live;
1351 
1352   const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1353   return double(reclaimable) / divisor;
1354 }
1355 
1356 // Return the address of the end of the dense prefix, a.k.a. the start of the
1357 // compacted region.  The address is always on a region boundary.
1358 //
1359 // Completely full regions at the left are skipped, since no compaction can
1360 // occur in those regions.  Then the maximum amount of dead wood to allow is
1361 // computed, based on the density (amount live / capacity) of the generation;
1362 // the region with approximately that amount of dead space to the left is
1363 // identified as the limit region.  Regions between the last completely full
1364 // region and the limit region are scanned and the one that has the best
1365 // (maximum) reclaimed_ratio() is selected.
1366 HeapWord*
1367 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1368                                         bool maximum_compaction)
1369 {
1370   const size_t region_size = ParallelCompactData::RegionSize;
1371   const ParallelCompactData& sd = summary_data();
1372 
1373   const MutableSpace* const space = _space_info[id].space();
1374   HeapWord* const top = space->top();
1375   HeapWord* const top_aligned_up = sd.region_align_up(top);
1376   HeapWord* const new_top = _space_info[id].new_top();
1377   HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1378   HeapWord* const bottom = space->bottom();
1379   const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1380   const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1381   const RegionData* const new_top_cp =
1382     sd.addr_to_region_ptr(new_top_aligned_up);
1383 
1384   // Skip full regions at the beginning of the space--they are necessarily part
1385   // of the dense prefix.
1386   const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1387   assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1388          space->is_empty(), "no dead space allowed to the left");
1389   assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1390          "region must have dead space");
1391 
1392   // The gc number is saved whenever a maximum compaction is done, and used to
1393   // determine when the maximum compaction interval has expired.  This avoids
1394   // successive max compactions for different reasons.
1395   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1396   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1397   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1398     total_invocations() == HeapFirstMaximumCompactionCount;
1399   if (maximum_compaction || full_cp == top_cp || interval_ended) {
1400     _maximum_compaction_gc_num = total_invocations();
1401     return sd.region_to_addr(full_cp);
1402   }
1403 
1404   const size_t space_live = pointer_delta(new_top, bottom);
1405   const size_t space_used = space->used_in_words();
1406   const size_t space_capacity = space->capacity_in_words();
1407 
1408   const double density = double(space_live) / double(space_capacity);
1409   const size_t min_percent_free = MarkSweepDeadRatio;
1410   const double limiter = dead_wood_limiter(density, min_percent_free);
1411   const size_t dead_wood_max = space_used - space_live;
1412   const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1413                                       dead_wood_max);
1414 
1415   if (TraceParallelOldGCDensePrefix) {
1416     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1417                   "space_cap=" SIZE_FORMAT,
1418                   space_live, space_used,
1419                   space_capacity);
1420     tty->print_cr("dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
1421                   "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1422                   density, min_percent_free, limiter,
1423                   dead_wood_max, dead_wood_limit);
1424   }
1425 
1426   // Locate the region with the desired amount of dead space to the left.
1427   const RegionData* const limit_cp =
1428     dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1429 
1430   // Scan from the first region with dead space to the limit region and find the
1431   // one with the best (largest) reclaimed ratio.
1432   double best_ratio = 0.0;
1433   const RegionData* best_cp = full_cp;
1434   for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1435     double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1436     if (tmp_ratio > best_ratio) {
1437       best_cp = cp;
1438       best_ratio = tmp_ratio;
1439     }
1440   }
1441 
1442   return sd.region_to_addr(best_cp);
1443 }
1444 
1445 void PSParallelCompact::summarize_spaces_quick()
1446 {
1447   for (unsigned int i = 0; i < last_space_id; ++i) {
1448     const MutableSpace* space = _space_info[i].space();
1449     HeapWord** nta = _space_info[i].new_top_addr();
1450     bool result = _summary_data.summarize(_space_info[i].split_info(),
1451                                           space->bottom(), space->top(), NULL,
1452                                           space->bottom(), space->end(), nta);
1453     assert(result, "space must fit into itself");
1454     _space_info[i].set_dense_prefix(space->bottom());
1455   }
1456 }
1457 
1458 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1459 {
1460   HeapWord* const dense_prefix_end = dense_prefix(id);
1461   const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1462   const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1463   if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1464     // Only enough dead space is filled so that any remaining dead space to the
1465     // left is larger than the minimum filler object.  (The remainder is filled
1466     // during the copy/update phase.)
1467     //
1468     // The size of the dead space to the right of the boundary is not a
1469     // concern, since compaction will be able to use whatever space is
1470     // available.
1471     //
1472     // Here '||' is the boundary, 'x' represents a don't care bit and a box
1473     // surrounds the space to be filled with an object.
1474     //
1475     // In the 32-bit VM, each bit represents two 32-bit words:
1476     //                              +---+
1477     // a) beg_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1478     //    end_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1479     //                              +---+
1480     //
1481     // In the 64-bit VM, each bit represents one 64-bit word:
1482     //                              +------------+
1483     // b) beg_bits:  ...  x   x   x | 0   ||   0 | x  x  ...
1484     //    end_bits:  ...  x   x   1 | 0   ||   0 | x  x  ...
1485     //                              +------------+
1486     //                          +-------+
1487     // c) beg_bits:  ...  x   x | 0   0 | ||   0   x  x  ...
1488     //    end_bits:  ...  x   1 | 0   0 | ||   0   x  x  ...
1489     //                          +-------+
1490     //                      +-----------+
1491     // d) beg_bits:  ...  x | 0   0   0 | ||   0   x  x  ...
1492     //    end_bits:  ...  1 | 0   0   0 | ||   0   x  x  ...
1493     //                      +-----------+
1494     //                          +-------+
1495     // e) beg_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1496     //    end_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1497     //                          +-------+
1498 
1499     // Initially assume case a, c or e will apply.
1500     size_t obj_len = CollectedHeap::min_fill_size();
1501     HeapWord* obj_beg = dense_prefix_end - obj_len;
1502 
1503 #ifdef  _LP64
1504     if (MinObjAlignment > 1) { // object alignment > heap word size
1505       // Cases a, c or e.
1506     } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1507       // Case b above.
1508       obj_beg = dense_prefix_end - 1;
1509     } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1510                _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1511       // Case d above.
1512       obj_beg = dense_prefix_end - 3;
1513       obj_len = 3;
1514     }
1515 #endif  // #ifdef _LP64
1516 
1517     CollectedHeap::fill_with_object(obj_beg, obj_len);
1518     _mark_bitmap.mark_obj(obj_beg, obj_len);
1519     _summary_data.add_obj(obj_beg, obj_len);
1520     assert(start_array(id) != NULL, "sanity");
1521     start_array(id)->allocate_block(obj_beg);
1522   }
1523 }
1524 
1525 void
1526 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1527 {
1528   assert(id < last_space_id, "id out of range");
1529   assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom(),
1530          "should have been reset in summarize_spaces_quick()");
1531 
1532   const MutableSpace* space = _space_info[id].space();
1533   if (_space_info[id].new_top() != space->bottom()) {
1534     HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1535     _space_info[id].set_dense_prefix(dense_prefix_end);
1536 
1537 #ifndef PRODUCT
1538     if (TraceParallelOldGCDensePrefix) {
1539       print_dense_prefix_stats("ratio", id, maximum_compaction,
1540                                dense_prefix_end);
1541       HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1542       print_dense_prefix_stats("density", id, maximum_compaction, addr);
1543     }
1544 #endif  // #ifndef PRODUCT
1545 
1546     // Recompute the summary data, taking into account the dense prefix.  If
1547     // every last byte will be reclaimed, then the existing summary data which
1548     // compacts everything can be left in place.
1549     if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1550       // If dead space crosses the dense prefix boundary, it is (at least
1551       // partially) filled with a dummy object, marked live and added to the
1552       // summary data.  This simplifies the copy/update phase and must be done
1553       // before the final locations of objects are determined, to prevent
1554       // leaving a fragment of dead space that is too small to fill.
1555       fill_dense_prefix_end(id);
1556 
1557       // Compute the destination of each Region, and thus each object.
1558       _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1559       _summary_data.summarize(_space_info[id].split_info(),
1560                               dense_prefix_end, space->top(), NULL,
1561                               dense_prefix_end, space->end(),
1562                               _space_info[id].new_top_addr());
1563     }
1564   }
1565 
1566   if (log_develop_is_enabled(Trace, gc, compaction)) {
1567     const size_t region_size = ParallelCompactData::RegionSize;
1568     HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1569     const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1570     const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1571     HeapWord* const new_top = _space_info[id].new_top();
1572     const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1573     const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1574     log_develop_trace(gc, compaction)(
1575         "id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1576         "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1577         "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1578         id, space->capacity_in_words(), p2i(dense_prefix_end),
1579         dp_region, dp_words / region_size,
1580         cr_words / region_size, p2i(new_top));
1581   }
1582 }
1583 
1584 #ifndef PRODUCT
1585 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1586                                           HeapWord* dst_beg, HeapWord* dst_end,
1587                                           SpaceId src_space_id,
1588                                           HeapWord* src_beg, HeapWord* src_end)
1589 {
1590   log_develop_trace(gc, compaction)(
1591       "Summarizing %d [%s] into %d [%s]:  "
1592       "src=" PTR_FORMAT "-" PTR_FORMAT " "
1593       SIZE_FORMAT "-" SIZE_FORMAT " "
1594       "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1595       SIZE_FORMAT "-" SIZE_FORMAT,
1596       src_space_id, space_names[src_space_id],
1597       dst_space_id, space_names[dst_space_id],
1598       p2i(src_beg), p2i(src_end),
1599       _summary_data.addr_to_region_idx(src_beg),
1600       _summary_data.addr_to_region_idx(src_end),
1601       p2i(dst_beg), p2i(dst_end),
1602       _summary_data.addr_to_region_idx(dst_beg),
1603       _summary_data.addr_to_region_idx(dst_end));
1604 }
1605 #endif  // #ifndef PRODUCT
1606 
1607 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1608                                       bool maximum_compaction)
1609 {
1610   GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
1611 
1612 #ifdef  ASSERT
1613   if (TraceParallelOldGCMarkingPhase) {
1614     tty->print_cr("add_obj_count=" SIZE_FORMAT " "
1615                   "add_obj_bytes=" SIZE_FORMAT,
1616                   add_obj_count, add_obj_size * HeapWordSize);
1617     tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
1618                   "mark_bitmap_bytes=" SIZE_FORMAT,
1619                   mark_bitmap_count, mark_bitmap_size * HeapWordSize);
1620   }
1621 #endif  // #ifdef ASSERT
1622 
1623   // Quick summarization of each space into itself, to see how much is live.
1624   summarize_spaces_quick();
1625 
1626   log_develop_trace(gc, compaction)("summary phase:  after summarizing each space to self");
1627   NOT_PRODUCT(print_region_ranges());
1628   NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1629 
1630   // The amount of live data that will end up in old space (assuming it fits).
1631   size_t old_space_total_live = 0;
1632   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1633     old_space_total_live += pointer_delta(_space_info[id].new_top(),
1634                                           _space_info[id].space()->bottom());
1635   }
1636 
1637   MutableSpace* const old_space = _space_info[old_space_id].space();
1638   const size_t old_capacity = old_space->capacity_in_words();
1639   if (old_space_total_live > old_capacity) {
1640     // XXX - should also try to expand
1641     maximum_compaction = true;
1642   }
1643 
1644   // Old generations.
1645   summarize_space(old_space_id, maximum_compaction);
1646 
1647   // Summarize the remaining spaces in the young gen.  The initial target space
1648   // is the old gen.  If a space does not fit entirely into the target, then the
1649   // remainder is compacted into the space itself and that space becomes the new
1650   // target.
1651   SpaceId dst_space_id = old_space_id;
1652   HeapWord* dst_space_end = old_space->end();
1653   HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1654   for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1655     const MutableSpace* space = _space_info[id].space();
1656     const size_t live = pointer_delta(_space_info[id].new_top(),
1657                                       space->bottom());
1658     const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1659 
1660     NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1661                                   SpaceId(id), space->bottom(), space->top());)
1662     if (live > 0 && live <= available) {
1663       // All the live data will fit.
1664       bool done = _summary_data.summarize(_space_info[id].split_info(),
1665                                           space->bottom(), space->top(),
1666                                           NULL,
1667                                           *new_top_addr, dst_space_end,
1668                                           new_top_addr);
1669       assert(done, "space must fit into old gen");
1670 
1671       // Reset the new_top value for the space.
1672       _space_info[id].set_new_top(space->bottom());
1673     } else if (live > 0) {
1674       // Attempt to fit part of the source space into the target space.
1675       HeapWord* next_src_addr = NULL;
1676       bool done = _summary_data.summarize(_space_info[id].split_info(),
1677                                           space->bottom(), space->top(),
1678                                           &next_src_addr,
1679                                           *new_top_addr, dst_space_end,
1680                                           new_top_addr);
1681       assert(!done, "space should not fit into old gen");
1682       assert(next_src_addr != NULL, "sanity");
1683 
1684       // The source space becomes the new target, so the remainder is compacted
1685       // within the space itself.
1686       dst_space_id = SpaceId(id);
1687       dst_space_end = space->end();
1688       new_top_addr = _space_info[id].new_top_addr();
1689       NOT_PRODUCT(summary_phase_msg(dst_space_id,
1690                                     space->bottom(), dst_space_end,
1691                                     SpaceId(id), next_src_addr, space->top());)
1692       done = _summary_data.summarize(_space_info[id].split_info(),
1693                                      next_src_addr, space->top(),
1694                                      NULL,
1695                                      space->bottom(), dst_space_end,
1696                                      new_top_addr);
1697       assert(done, "space must fit when compacted into itself");
1698       assert(*new_top_addr <= space->top(), "usage should not grow");
1699     }
1700   }
1701 
1702   log_develop_trace(gc, compaction)("Summary_phase:  after final summarization");
1703   NOT_PRODUCT(print_region_ranges());
1704   NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1705 }
1706 
1707 // This method should contain all heap-specific policy for invoking a full
1708 // collection.  invoke_no_policy() will only attempt to compact the heap; it
1709 // will do nothing further.  If we need to bail out for policy reasons, scavenge
1710 // before full gc, or any other specialized behavior, it needs to be added here.
1711 //
1712 // Note that this method should only be called from the vm_thread while at a
1713 // safepoint.
1714 //
1715 // Note that the all_soft_refs_clear flag in the collector policy
1716 // may be true because this method can be called without intervening
1717 // activity.  For example when the heap space is tight and full measure
1718 // are being taken to free space.
1719 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1720   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1721   assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1722          "should be in vm thread");
1723 
1724   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1725   GCCause::Cause gc_cause = heap->gc_cause();
1726   assert(!heap->is_gc_active(), "not reentrant");
1727 
1728   PSAdaptiveSizePolicy* policy = heap->size_policy();
1729   IsGCActiveMark mark;
1730 
1731   if (ScavengeBeforeFullGC) {
1732     PSScavenge::invoke_no_policy();
1733   }
1734 
1735   const bool clear_all_soft_refs =
1736     heap->soft_ref_policy()->should_clear_all_soft_refs();
1737 
1738   PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1739                                       maximum_heap_compaction);
1740 }
1741 
1742 // This method contains no policy. You should probably
1743 // be calling invoke() instead.
1744 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
1745   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
1746   assert(ref_processor() != NULL, "Sanity");
1747 
1748   if (GCLocker::check_active_before_gc()) {
1749     return false;
1750   }
1751 
1752   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1753 
1754   GCIdMark gc_id_mark;
1755   _gc_timer.register_gc_start();
1756   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1757 
1758   TimeStamp marking_start;
1759   TimeStamp compaction_start;
1760   TimeStamp collection_exit;
1761 
1762   GCCause::Cause gc_cause = heap->gc_cause();
1763   PSYoungGen* young_gen = heap->young_gen();
1764   PSOldGen* old_gen = heap->old_gen();
1765   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1766 
1767   // The scope of casr should end after code that can change
1768   // CollectorPolicy::_should_clear_all_soft_refs.
1769   ClearedAllSoftRefs casr(maximum_heap_compaction,
1770                           heap->soft_ref_policy());
1771 
1772   if (ZapUnusedHeapArea) {
1773     // Save information needed to minimize mangling
1774     heap->record_gen_tops_before_GC();
1775   }
1776 
1777   // Make sure data structures are sane, make the heap parsable, and do other
1778   // miscellaneous bookkeeping.
1779   pre_compact();
1780 
1781   PreGCValues pre_gc_values(heap);
1782 
1783   // Get the compaction manager reserved for the VM thread.
1784   ParCompactionManager* const vmthread_cm =
1785     ParCompactionManager::manager_array(gc_task_manager()->workers());
1786 
1787   {
1788     ResourceMark rm;
1789     HandleMark hm;
1790 
1791     // Set the number of GC threads to be used in this collection
1792     gc_task_manager()->set_active_gang();
1793     gc_task_manager()->task_idle_workers();
1794 
1795     GCTraceCPUTime tcpu;
1796     GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause, true);
1797 
1798     heap->pre_full_gc_dump(&_gc_timer);
1799 
1800     TraceCollectorStats tcs(counters());
1801     TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause);
1802 
1803     if (log_is_enabled(Debug, gc, heap, exit)) {
1804       accumulated_time()->start();
1805     }
1806 
1807     // Let the size policy know we're starting
1808     size_policy->major_collection_begin();
1809 
1810 #if COMPILER2_OR_JVMCI
1811     DerivedPointerTable::clear();
1812 #endif
1813 
1814     ref_processor()->enable_discovery();
1815     ref_processor()->setup_policy(maximum_heap_compaction);
1816 
1817     bool marked_for_unloading = false;
1818 
1819     marking_start.update();
1820     marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
1821 
1822     bool max_on_system_gc = UseMaximumCompactionOnSystemGC
1823       && GCCause::is_user_requested_gc(gc_cause);
1824     summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
1825 
1826 #if COMPILER2_OR_JVMCI
1827     assert(DerivedPointerTable::is_active(), "Sanity");
1828     DerivedPointerTable::set_active(false);
1829 #endif
1830 
1831     // adjust_roots() updates Universe::_intArrayKlassObj which is
1832     // needed by the compaction for filling holes in the dense prefix.
1833     adjust_roots(vmthread_cm);
1834 
1835     compaction_start.update();
1836     compact();
1837 
1838     // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
1839     // done before resizing.
1840     post_compact();
1841 
1842     // Let the size policy know we're done
1843     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1844 
1845     if (UseAdaptiveSizePolicy) {
1846       log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1847       log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
1848                           old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1849 
1850       // Don't check if the size_policy is ready here.  Let
1851       // the size_policy check that internally.
1852       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1853           AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1854         // Swap the survivor spaces if from_space is empty. The
1855         // resize_young_gen() called below is normally used after
1856         // a successful young GC and swapping of survivor spaces;
1857         // otherwise, it will fail to resize the young gen with
1858         // the current implementation.
1859         if (young_gen->from_space()->is_empty()) {
1860           young_gen->from_space()->clear(SpaceDecorator::Mangle);
1861           young_gen->swap_spaces();
1862         }
1863 
1864         // Calculate optimal free space amounts
1865         assert(young_gen->max_size() >
1866           young_gen->from_space()->capacity_in_bytes() +
1867           young_gen->to_space()->capacity_in_bytes(),
1868           "Sizes of space in young gen are out-of-bounds");
1869 
1870         size_t young_live = young_gen->used_in_bytes();
1871         size_t eden_live = young_gen->eden_space()->used_in_bytes();
1872         size_t old_live = old_gen->used_in_bytes();
1873         size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1874         size_t max_old_gen_size = old_gen->max_gen_size();
1875         size_t max_eden_size = young_gen->max_size() -
1876           young_gen->from_space()->capacity_in_bytes() -
1877           young_gen->to_space()->capacity_in_bytes();
1878 
1879         // Used for diagnostics
1880         size_policy->clear_generation_free_space_flags();
1881 
1882         size_policy->compute_generations_free_space(young_live,
1883                                                     eden_live,
1884                                                     old_live,
1885                                                     cur_eden,
1886                                                     max_old_gen_size,
1887                                                     max_eden_size,
1888                                                     true /* full gc*/);
1889 
1890         size_policy->check_gc_overhead_limit(eden_live,
1891                                              max_old_gen_size,
1892                                              max_eden_size,
1893                                              true /* full gc*/,
1894                                              gc_cause,
1895                                              heap->soft_ref_policy());
1896 
1897         size_policy->decay_supplemental_growth(true /* full gc*/);
1898 
1899         heap->resize_old_gen(
1900           size_policy->calculated_old_free_size_in_bytes());
1901 
1902         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1903                                size_policy->calculated_survivor_size_in_bytes());
1904       }
1905 
1906       log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1907     }
1908 
1909     if (UsePerfData) {
1910       PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1911       counters->update_counters();
1912       counters->update_old_capacity(old_gen->capacity_in_bytes());
1913       counters->update_young_capacity(young_gen->capacity_in_bytes());
1914     }
1915 
1916     heap->resize_all_tlabs();
1917 
1918     // Resize the metaspace capacity after a collection
1919     MetaspaceGC::compute_new_size();
1920 
1921     if (log_is_enabled(Debug, gc, heap, exit)) {
1922       accumulated_time()->stop();
1923     }
1924 
1925     young_gen->print_used_change(pre_gc_values.young_gen_used());
1926     old_gen->print_used_change(pre_gc_values.old_gen_used());
1927     MetaspaceUtils::print_metaspace_change(pre_gc_values.metadata_used());
1928 
1929     // Track memory usage and detect low memory
1930     MemoryService::track_memory_usage();
1931     heap->update_counters();
1932     gc_task_manager()->release_idle_workers();
1933 
1934     heap->post_full_gc_dump(&_gc_timer);
1935   }
1936 
1937 #ifdef ASSERT
1938   for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
1939     ParCompactionManager* const cm =
1940       ParCompactionManager::manager_array(int(i));
1941     assert(cm->marking_stack()->is_empty(),       "should be empty");
1942     assert(cm->region_stack()->is_empty(), "Region stack " SIZE_FORMAT " is not empty", i);
1943   }
1944 #endif // ASSERT
1945 
1946   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1947     HandleMark hm;  // Discard invalid handles created during verification
1948     Universe::verify("After GC");
1949   }
1950 
1951   // Re-verify object start arrays
1952   if (VerifyObjectStartArray &&
1953       VerifyAfterGC) {
1954     old_gen->verify_object_start_array();
1955   }
1956 
1957   if (ZapUnusedHeapArea) {
1958     old_gen->object_space()->check_mangled_unused_area_complete();
1959   }
1960 
1961   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1962 
1963   collection_exit.update();
1964 
1965   heap->print_heap_after_gc();
1966   heap->trace_heap_after_gc(&_gc_tracer);
1967 
1968   log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
1969                          marking_start.ticks(), compaction_start.ticks(),
1970                          collection_exit.ticks());
1971   gc_task_manager()->print_task_time_stamps();
1972 
1973 #ifdef TRACESPINNING
1974   ParallelTaskTerminator::print_termination_counts();
1975 #endif
1976 
1977   AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
1978 
1979   _gc_timer.register_gc_end();
1980 
1981   _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1982   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1983 
1984   return true;
1985 }
1986 
1987 bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
1988                                              PSYoungGen* young_gen,
1989                                              PSOldGen* old_gen) {
1990   MutableSpace* const eden_space = young_gen->eden_space();
1991   assert(!eden_space->is_empty(), "eden must be non-empty");
1992   assert(young_gen->virtual_space()->alignment() ==
1993          old_gen->virtual_space()->alignment(), "alignments do not match");
1994 
1995   // We also return false when it's a heterogenous heap because old generation cannot absorb data from eden
1996   // when it is allocated on different memory (example, nv-dimm) than young.
1997   if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary) ||
1998       ParallelScavengeHeap::heap()->ps_collector_policy()->is_hetero_heap()) {
1999     return false;
2000   }
2001 
2002   // Both generations must be completely committed.
2003   if (young_gen->virtual_space()->uncommitted_size() != 0) {
2004     return false;
2005   }
2006   if (old_gen->virtual_space()->uncommitted_size() != 0) {
2007     return false;
2008   }
2009 
2010   // Figure out how much to take from eden.  Include the average amount promoted
2011   // in the total; otherwise the next young gen GC will simply bail out to a
2012   // full GC.
2013   const size_t alignment = old_gen->virtual_space()->alignment();
2014   const size_t eden_used = eden_space->used_in_bytes();
2015   const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
2016   const size_t absorb_size = align_up(eden_used + promoted, alignment);
2017   const size_t eden_capacity = eden_space->capacity_in_bytes();
2018 
2019   if (absorb_size >= eden_capacity) {
2020     return false; // Must leave some space in eden.
2021   }
2022 
2023   const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
2024   if (new_young_size < young_gen->min_gen_size()) {
2025     return false; // Respect young gen minimum size.
2026   }
2027 
2028   log_trace(gc, ergo, heap)(" absorbing " SIZE_FORMAT "K:  "
2029                             "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
2030                             "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
2031                             "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
2032                             absorb_size / K,
2033                             eden_capacity / K, (eden_capacity - absorb_size) / K,
2034                             young_gen->from_space()->used_in_bytes() / K,
2035                             young_gen->to_space()->used_in_bytes() / K,
2036                             young_gen->capacity_in_bytes() / K, new_young_size / K);
2037 
2038   // Fill the unused part of the old gen.
2039   MutableSpace* const old_space = old_gen->object_space();
2040   HeapWord* const unused_start = old_space->top();
2041   size_t const unused_words = pointer_delta(old_space->end(), unused_start);
2042 
2043   if (unused_words > 0) {
2044     if (unused_words < CollectedHeap::min_fill_size()) {
2045       return false;  // If the old gen cannot be filled, must give up.
2046     }
2047     CollectedHeap::fill_with_objects(unused_start, unused_words);
2048   }
2049 
2050   // Take the live data from eden and set both top and end in the old gen to
2051   // eden top.  (Need to set end because reset_after_change() mangles the region
2052   // from end to virtual_space->high() in debug builds).
2053   HeapWord* const new_top = eden_space->top();
2054   old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
2055                                         absorb_size);
2056   young_gen->reset_after_change();
2057   old_space->set_top(new_top);
2058   old_space->set_end(new_top);
2059   old_gen->reset_after_change();
2060 
2061   // Update the object start array for the filler object and the data from eden.
2062   ObjectStartArray* const start_array = old_gen->start_array();
2063   for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
2064     start_array->allocate_block(p);
2065   }
2066 
2067   // Could update the promoted average here, but it is not typically updated at
2068   // full GCs and the value to use is unclear.  Something like
2069   //
2070   // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
2071 
2072   size_policy->set_bytes_absorbed_from_eden(absorb_size);
2073   return true;
2074 }
2075 
2076 GCTaskManager* const PSParallelCompact::gc_task_manager() {
2077   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
2078     "shouldn't return NULL");
2079   return ParallelScavengeHeap::gc_task_manager();
2080 }
2081 
2082 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
2083 private:
2084   GCTaskQueue* _q;
2085 
2086 public:
2087   PCAddThreadRootsMarkingTaskClosure(GCTaskQueue* q) : _q(q) { }
2088   void do_thread(Thread* t) {
2089     _q->enqueue(new ThreadRootsMarkingTask(t));
2090   }
2091 };
2092 
2093 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2094                                       bool maximum_heap_compaction,
2095                                       ParallelOldTracer *gc_tracer) {
2096   // Recursively traverse all live objects and mark them
2097   GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
2098 
2099   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2100   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2101   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2102   TaskQueueSetSuper* qset = ParCompactionManager::stack_array();
2103   TaskTerminator terminator(active_gc_threads, qset);
2104 
2105   PCMarkAndPushClosure mark_and_push_closure(cm);
2106   ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
2107 
2108   // Need new claim bits before marking starts.
2109   ClassLoaderDataGraph::clear_claimed_marks();
2110 
2111   {
2112     GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
2113 
2114     ParallelScavengeHeap::ParStrongRootsScope psrs;
2115 
2116     GCTaskQueue* q = GCTaskQueue::create();
2117 
2118     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::universe));
2119     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jni_handles));
2120     // We scan the thread roots in parallel
2121     PCAddThreadRootsMarkingTaskClosure cl(q);
2122     Threads::java_threads_and_vm_thread_do(&cl);
2123     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::object_synchronizer));
2124     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::management));
2125     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::system_dictionary));
2126     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::class_loader_data));
2127     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jvmti));
2128     q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::code_cache));
2129 
2130     if (active_gc_threads > 1) {
2131       for (uint j = 0; j < active_gc_threads; j++) {
2132         q->enqueue(new StealMarkingTask(terminator.terminator()));
2133       }
2134     }
2135 
2136     gc_task_manager()->execute_and_wait(q);
2137   }
2138 
2139   // Process reference objects found during marking
2140   {
2141     GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
2142 
2143     ReferenceProcessorStats stats;
2144     ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
2145 
2146     if (ref_processor()->processing_is_mt()) {
2147       ref_processor()->set_active_mt_degree(active_gc_threads);
2148 
2149       RefProcTaskExecutor task_executor;
2150       stats = ref_processor()->process_discovered_references(
2151         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2152         &task_executor, &pt);
2153     } else {
2154       stats = ref_processor()->process_discovered_references(
2155         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
2156         &pt);
2157     }
2158 
2159     gc_tracer->report_gc_reference_stats(stats);
2160     pt.print_all_references();
2161   }
2162 
2163   // This is the point where the entire marking should have completed.
2164   assert(cm->marking_stacks_empty(), "Marking should have completed");
2165 
2166   {
2167     GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
2168     WeakProcessor::weak_oops_do(is_alive_closure(), &do_nothing_cl);
2169   }
2170 
2171   {
2172     GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
2173 
2174     // Follow system dictionary roots and unload classes.
2175     bool purged_class = SystemDictionary::do_unloading(&_gc_timer);
2176 
2177     // Unload nmethods.
2178     CodeCache::do_unloading(is_alive_closure(), purged_class);
2179 
2180     // Prune dead klasses from subklass/sibling/implementor lists.
2181     Klass::clean_weak_klass_links(purged_class);
2182 
2183     // Clean JVMCI metadata handles.
2184     JVMCI_ONLY(JVMCI::do_unloading(is_alive_closure(), purged_class));
2185   }
2186 
2187   _gc_tracer.report_object_count_after_gc(is_alive_closure());
2188 }
2189 
2190 void PSParallelCompact::adjust_roots(ParCompactionManager* cm) {
2191   // Adjust the pointers to reflect the new locations
2192   GCTraceTime(Info, gc, phases) tm("Adjust Roots", &_gc_timer);
2193 
2194   // Need new claim bits when tracing through and adjusting pointers.
2195   ClassLoaderDataGraph::clear_claimed_marks();
2196 
2197   PCAdjustPointerClosure oop_closure(cm);
2198 
2199   // General strong roots.
2200   Universe::oops_do(&oop_closure);
2201   JNIHandles::oops_do(&oop_closure);   // Global (strong) JNI handles
2202   Threads::oops_do(&oop_closure, NULL);
2203   ObjectSynchronizer::oops_do(&oop_closure);
2204   Management::oops_do(&oop_closure);
2205   JvmtiExport::oops_do(&oop_closure);
2206   SystemDictionary::oops_do(&oop_closure);
2207   CLDToOopClosure cld_closure(&oop_closure, ClassLoaderData::_claim_strong);
2208   ClassLoaderDataGraph::cld_do(&cld_closure);
2209 
2210   // Now adjust pointers in remaining weak roots.  (All of which should
2211   // have been cleared if they pointed to non-surviving objects.)
2212   WeakProcessor::oops_do(&oop_closure);
2213 
2214   CodeBlobToOopClosure adjust_from_blobs(&oop_closure, CodeBlobToOopClosure::FixRelocations);
2215   CodeCache::blobs_do(&adjust_from_blobs);
2216   AOTLoader::oops_do(&oop_closure);
2217   ref_processor()->weak_oops_do(&oop_closure);
2218   // Roots were visited so references into the young gen in roots
2219   // may have been scanned.  Process them also.
2220   // Should the reference processor have a span that excludes
2221   // young gen objects?
2222   PSScavenge::reference_processor()->weak_oops_do(&oop_closure);
2223 }
2224 
2225 // Helper class to print 8 region numbers per line and then print the total at the end.
2226 class FillableRegionLogger : public StackObj {
2227 private:
2228   Log(gc, compaction) log;
2229   static const int LineLength = 8;
2230   size_t _regions[LineLength];
2231   int _next_index;
2232   bool _enabled;
2233   size_t _total_regions;
2234 public:
2235   FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
2236   ~FillableRegionLogger() {
2237     log.trace(SIZE_FORMAT " initially fillable regions", _total_regions);
2238   }
2239 
2240   void print_line() {
2241     if (!_enabled || _next_index == 0) {
2242       return;
2243     }
2244     FormatBuffer<> line("Fillable: ");
2245     for (int i = 0; i < _next_index; i++) {
2246       line.append(" " SIZE_FORMAT_W(7), _regions[i]);
2247     }
2248     log.trace("%s", line.buffer());
2249     _next_index = 0;
2250   }
2251 
2252   void handle(size_t region) {
2253     if (!_enabled) {
2254       return;
2255     }
2256     _regions[_next_index++] = region;
2257     if (_next_index == LineLength) {
2258       print_line();
2259     }
2260     _total_regions++;
2261   }
2262 };
2263 
2264 void PSParallelCompact::prepare_region_draining_tasks(GCTaskQueue* q,
2265                                                       uint parallel_gc_threads)
2266 {
2267   GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
2268 
2269   // Find the threads that are active
2270   unsigned int which = 0;
2271 
2272   // Find all regions that are available (can be filled immediately) and
2273   // distribute them to the thread stacks.  The iteration is done in reverse
2274   // order (high to low) so the regions will be removed in ascending order.
2275 
2276   const ParallelCompactData& sd = PSParallelCompact::summary_data();
2277 
2278   which = 0;
2279   // id + 1 is used to test termination so unsigned  can
2280   // be used with an old_space_id == 0.
2281   FillableRegionLogger region_logger;
2282   for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2283     SpaceInfo* const space_info = _space_info + id;
2284     MutableSpace* const space = space_info->space();
2285     HeapWord* const new_top = space_info->new_top();
2286 
2287     const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2288     const size_t end_region =
2289       sd.addr_to_region_idx(sd.region_align_up(new_top));
2290 
2291     for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2292       if (sd.region(cur)->claim_unsafe()) {
2293         ParCompactionManager* cm = ParCompactionManager::manager_array(which);
2294         cm->region_stack()->push(cur);
2295         region_logger.handle(cur);
2296         // Assign regions to tasks in round-robin fashion.
2297         if (++which == parallel_gc_threads) {
2298           which = 0;
2299         }
2300       }
2301     }
2302     region_logger.print_line();
2303   }
2304 }
2305 
2306 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2307 
2308 void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q,
2309                                                     uint parallel_gc_threads) {
2310   GCTraceTime(Trace, gc, phases) tm("Dense Prefix Task Setup", &_gc_timer);
2311 
2312   ParallelCompactData& sd = PSParallelCompact::summary_data();
2313 
2314   // Iterate over all the spaces adding tasks for updating
2315   // regions in the dense prefix.  Assume that 1 gc thread
2316   // will work on opening the gaps and the remaining gc threads
2317   // will work on the dense prefix.
2318   unsigned int space_id;
2319   for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2320     HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2321     const MutableSpace* const space = _space_info[space_id].space();
2322 
2323     if (dense_prefix_end == space->bottom()) {
2324       // There is no dense prefix for this space.
2325       continue;
2326     }
2327 
2328     // The dense prefix is before this region.
2329     size_t region_index_end_dense_prefix =
2330         sd.addr_to_region_idx(dense_prefix_end);
2331     RegionData* const dense_prefix_cp =
2332       sd.region(region_index_end_dense_prefix);
2333     assert(dense_prefix_end == space->end() ||
2334            dense_prefix_cp->available() ||
2335            dense_prefix_cp->claimed(),
2336            "The region after the dense prefix should always be ready to fill");
2337 
2338     size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2339 
2340     // Is there dense prefix work?
2341     size_t total_dense_prefix_regions =
2342       region_index_end_dense_prefix - region_index_start;
2343     // How many regions of the dense prefix should be given to
2344     // each thread?
2345     if (total_dense_prefix_regions > 0) {
2346       uint tasks_for_dense_prefix = 1;
2347       if (total_dense_prefix_regions <=
2348           (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2349         // Don't over partition.  This assumes that
2350         // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2351         // so there are not many regions to process.
2352         tasks_for_dense_prefix = parallel_gc_threads;
2353       } else {
2354         // Over partition
2355         tasks_for_dense_prefix = parallel_gc_threads *
2356           PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2357       }
2358       size_t regions_per_thread = total_dense_prefix_regions /
2359         tasks_for_dense_prefix;
2360       // Give each thread at least 1 region.
2361       if (regions_per_thread == 0) {
2362         regions_per_thread = 1;
2363       }
2364 
2365       for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2366         if (region_index_start >= region_index_end_dense_prefix) {
2367           break;
2368         }
2369         // region_index_end is not processed
2370         size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2371                                        region_index_end_dense_prefix);
2372         q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2373                                              region_index_start,
2374                                              region_index_end));
2375         region_index_start = region_index_end;
2376       }
2377     }
2378     // This gets any part of the dense prefix that did not
2379     // fit evenly.
2380     if (region_index_start < region_index_end_dense_prefix) {
2381       q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2382                                            region_index_start,
2383                                            region_index_end_dense_prefix));
2384     }
2385   }
2386 }
2387 
2388 void PSParallelCompact::enqueue_region_stealing_tasks(
2389                                      GCTaskQueue* q,
2390                                      ParallelTaskTerminator* terminator_ptr,
2391                                      uint parallel_gc_threads) {
2392   GCTraceTime(Trace, gc, phases) tm("Steal Task Setup", &_gc_timer);
2393 
2394   // Once a thread has drained it's stack, it should try to steal regions from
2395   // other threads.
2396   for (uint j = 0; j < parallel_gc_threads; j++) {
2397     q->enqueue(new CompactionWithStealingTask(terminator_ptr));
2398   }
2399 }
2400 
2401 #ifdef ASSERT
2402 // Write a histogram of the number of times the block table was filled for a
2403 // region.
2404 void PSParallelCompact::write_block_fill_histogram()
2405 {
2406   if (!log_develop_is_enabled(Trace, gc, compaction)) {
2407     return;
2408   }
2409 
2410   Log(gc, compaction) log;
2411   ResourceMark rm;
2412   LogStream ls(log.trace());
2413   outputStream* out = &ls;
2414 
2415   typedef ParallelCompactData::RegionData rd_t;
2416   ParallelCompactData& sd = summary_data();
2417 
2418   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2419     MutableSpace* const spc = _space_info[id].space();
2420     if (spc->bottom() != spc->top()) {
2421       const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
2422       HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
2423       const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
2424 
2425       size_t histo[5] = { 0, 0, 0, 0, 0 };
2426       const size_t histo_len = sizeof(histo) / sizeof(size_t);
2427       const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
2428 
2429       for (const rd_t* cur = beg; cur < end; ++cur) {
2430         ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
2431       }
2432       out->print("Block fill histogram: %u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
2433       for (size_t i = 0; i < histo_len; ++i) {
2434         out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
2435                    histo[i], 100.0 * histo[i] / region_cnt);
2436       }
2437       out->cr();
2438     }
2439   }
2440 }
2441 #endif // #ifdef ASSERT
2442 
2443 void PSParallelCompact::compact() {
2444   GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
2445 
2446   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2447   PSOldGen* old_gen = heap->old_gen();
2448   old_gen->start_array()->reset();
2449   uint parallel_gc_threads = heap->gc_task_manager()->workers();
2450   uint active_gc_threads = heap->gc_task_manager()->active_workers();
2451   TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2452   TaskTerminator terminator(active_gc_threads, qset);
2453 
2454   GCTaskQueue* q = GCTaskQueue::create();
2455   prepare_region_draining_tasks(q, active_gc_threads);
2456   enqueue_dense_prefix_tasks(q, active_gc_threads);
2457   enqueue_region_stealing_tasks(q, terminator.terminator(), active_gc_threads);
2458 
2459   {
2460     GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
2461 
2462     gc_task_manager()->execute_and_wait(q);
2463 
2464 #ifdef  ASSERT
2465     // Verify that all regions have been processed before the deferred updates.
2466     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2467       verify_complete(SpaceId(id));
2468     }
2469 #endif
2470   }
2471 
2472   {
2473     // Update the deferred objects, if any.  Any compaction manager can be used.
2474     GCTraceTime(Trace, gc, phases) tm("Deferred Updates", &_gc_timer);
2475     ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2476     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2477       update_deferred_objects(cm, SpaceId(id));
2478     }
2479   }
2480 
2481   DEBUG_ONLY(write_block_fill_histogram());
2482 }
2483 
2484 #ifdef  ASSERT
2485 void PSParallelCompact::verify_complete(SpaceId space_id) {
2486   // All Regions between space bottom() to new_top() should be marked as filled
2487   // and all Regions between new_top() and top() should be available (i.e.,
2488   // should have been emptied).
2489   ParallelCompactData& sd = summary_data();
2490   SpaceInfo si = _space_info[space_id];
2491   HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2492   HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2493   const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2494   const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2495   const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2496 
2497   bool issued_a_warning = false;
2498 
2499   size_t cur_region;
2500   for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2501     const RegionData* const c = sd.region(cur_region);
2502     if (!c->completed()) {
2503       log_warning(gc)("region " SIZE_FORMAT " not filled: destination_count=%u",
2504                       cur_region, c->destination_count());
2505       issued_a_warning = true;
2506     }
2507   }
2508 
2509   for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2510     const RegionData* const c = sd.region(cur_region);
2511     if (!c->available()) {
2512       log_warning(gc)("region " SIZE_FORMAT " not empty: destination_count=%u",
2513                       cur_region, c->destination_count());
2514       issued_a_warning = true;
2515     }
2516   }
2517 
2518   if (issued_a_warning) {
2519     print_region_ranges();
2520   }
2521 }
2522 #endif  // #ifdef ASSERT
2523 
2524 inline void UpdateOnlyClosure::do_addr(HeapWord* addr) {
2525   _start_array->allocate_block(addr);
2526   compaction_manager()->update_contents(oop(addr));
2527 }
2528 
2529 // Update interior oops in the ranges of regions [beg_region, end_region).
2530 void
2531 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2532                                                        SpaceId space_id,
2533                                                        size_t beg_region,
2534                                                        size_t end_region) {
2535   ParallelCompactData& sd = summary_data();
2536   ParMarkBitMap* const mbm = mark_bitmap();
2537 
2538   HeapWord* beg_addr = sd.region_to_addr(beg_region);
2539   HeapWord* const end_addr = sd.region_to_addr(end_region);
2540   assert(beg_region <= end_region, "bad region range");
2541   assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2542 
2543 #ifdef  ASSERT
2544   // Claim the regions to avoid triggering an assert when they are marked as
2545   // filled.
2546   for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2547     assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2548   }
2549 #endif  // #ifdef ASSERT
2550 
2551   if (beg_addr != space(space_id)->bottom()) {
2552     // Find the first live object or block of dead space that *starts* in this
2553     // range of regions.  If a partial object crosses onto the region, skip it;
2554     // it will be marked for 'deferred update' when the object head is
2555     // processed.  If dead space crosses onto the region, it is also skipped; it
2556     // will be filled when the prior region is processed.  If neither of those
2557     // apply, the first word in the region is the start of a live object or dead
2558     // space.
2559     assert(beg_addr > space(space_id)->bottom(), "sanity");
2560     const RegionData* const cp = sd.region(beg_region);
2561     if (cp->partial_obj_size() != 0) {
2562       beg_addr = sd.partial_obj_end(beg_region);
2563     } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2564       beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2565     }
2566   }
2567 
2568   if (beg_addr < end_addr) {
2569     // A live object or block of dead space starts in this range of Regions.
2570      HeapWord* const dense_prefix_end = dense_prefix(space_id);
2571 
2572     // Create closures and iterate.
2573     UpdateOnlyClosure update_closure(mbm, cm, space_id);
2574     FillClosure fill_closure(cm, space_id);
2575     ParMarkBitMap::IterationStatus status;
2576     status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2577                           dense_prefix_end);
2578     if (status == ParMarkBitMap::incomplete) {
2579       update_closure.do_addr(update_closure.source());
2580     }
2581   }
2582 
2583   // Mark the regions as filled.
2584   RegionData* const beg_cp = sd.region(beg_region);
2585   RegionData* const end_cp = sd.region(end_region);
2586   for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2587     cp->set_completed();
2588   }
2589 }
2590 
2591 // Return the SpaceId for the space containing addr.  If addr is not in the
2592 // heap, last_space_id is returned.  In debug mode it expects the address to be
2593 // in the heap and asserts such.
2594 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2595   assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
2596 
2597   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2598     if (_space_info[id].space()->contains(addr)) {
2599       return SpaceId(id);
2600     }
2601   }
2602 
2603   assert(false, "no space contains the addr");
2604   return last_space_id;
2605 }
2606 
2607 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2608                                                 SpaceId id) {
2609   assert(id < last_space_id, "bad space id");
2610 
2611   ParallelCompactData& sd = summary_data();
2612   const SpaceInfo* const space_info = _space_info + id;
2613   ObjectStartArray* const start_array = space_info->start_array();
2614 
2615   const MutableSpace* const space = space_info->space();
2616   assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2617   HeapWord* const beg_addr = space_info->dense_prefix();
2618   HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2619 
2620   const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2621   const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2622   const RegionData* cur_region;
2623   for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2624     HeapWord* const addr = cur_region->deferred_obj_addr();
2625     if (addr != NULL) {
2626       if (start_array != NULL) {
2627         start_array->allocate_block(addr);
2628       }
2629       cm->update_contents(oop(addr));
2630       assert(oopDesc::is_oop_or_null(oop(addr)), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(addr)));
2631     }
2632   }
2633 }
2634 
2635 // Skip over count live words starting from beg, and return the address of the
2636 // next live word.  Unless marked, the word corresponding to beg is assumed to
2637 // be dead.  Callers must either ensure beg does not correspond to the middle of
2638 // an object, or account for those live words in some other way.  Callers must
2639 // also ensure that there are enough live words in the range [beg, end) to skip.
2640 HeapWord*
2641 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2642 {
2643   assert(count > 0, "sanity");
2644 
2645   ParMarkBitMap* m = mark_bitmap();
2646   idx_t bits_to_skip = m->words_to_bits(count);
2647   idx_t cur_beg = m->addr_to_bit(beg);
2648   const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end));
2649 
2650   do {
2651     cur_beg = m->find_obj_beg(cur_beg, search_end);
2652     idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2653     const size_t obj_bits = cur_end - cur_beg + 1;
2654     if (obj_bits > bits_to_skip) {
2655       return m->bit_to_addr(cur_beg + bits_to_skip);
2656     }
2657     bits_to_skip -= obj_bits;
2658     cur_beg = cur_end + 1;
2659   } while (bits_to_skip > 0);
2660 
2661   // Skipping the desired number of words landed just past the end of an object.
2662   // Find the start of the next object.
2663   cur_beg = m->find_obj_beg(cur_beg, search_end);
2664   assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2665   return m->bit_to_addr(cur_beg);
2666 }
2667 
2668 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2669                                             SpaceId src_space_id,
2670                                             size_t src_region_idx)
2671 {
2672   assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2673 
2674   const SplitInfo& split_info = _space_info[src_space_id].split_info();
2675   if (split_info.dest_region_addr() == dest_addr) {
2676     // The partial object ending at the split point contains the first word to
2677     // be copied to dest_addr.
2678     return split_info.first_src_addr();
2679   }
2680 
2681   const ParallelCompactData& sd = summary_data();
2682   ParMarkBitMap* const bitmap = mark_bitmap();
2683   const size_t RegionSize = ParallelCompactData::RegionSize;
2684 
2685   assert(sd.is_region_aligned(dest_addr), "not aligned");
2686   const RegionData* const src_region_ptr = sd.region(src_region_idx);
2687   const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2688   HeapWord* const src_region_destination = src_region_ptr->destination();
2689 
2690   assert(dest_addr >= src_region_destination, "wrong src region");
2691   assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2692 
2693   HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2694   HeapWord* const src_region_end = src_region_beg + RegionSize;
2695 
2696   HeapWord* addr = src_region_beg;
2697   if (dest_addr == src_region_destination) {
2698     // Return the first live word in the source region.
2699     if (partial_obj_size == 0) {
2700       addr = bitmap->find_obj_beg(addr, src_region_end);
2701       assert(addr < src_region_end, "no objects start in src region");
2702     }
2703     return addr;
2704   }
2705 
2706   // Must skip some live data.
2707   size_t words_to_skip = dest_addr - src_region_destination;
2708   assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2709 
2710   if (partial_obj_size >= words_to_skip) {
2711     // All the live words to skip are part of the partial object.
2712     addr += words_to_skip;
2713     if (partial_obj_size == words_to_skip) {
2714       // Find the first live word past the partial object.
2715       addr = bitmap->find_obj_beg(addr, src_region_end);
2716       assert(addr < src_region_end, "wrong src region");
2717     }
2718     return addr;
2719   }
2720 
2721   // Skip over the partial object (if any).
2722   if (partial_obj_size != 0) {
2723     words_to_skip -= partial_obj_size;
2724     addr += partial_obj_size;
2725   }
2726 
2727   // Skip over live words due to objects that start in the region.
2728   addr = skip_live_words(addr, src_region_end, words_to_skip);
2729   assert(addr < src_region_end, "wrong src region");
2730   return addr;
2731 }
2732 
2733 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2734                                                      SpaceId src_space_id,
2735                                                      size_t beg_region,
2736                                                      HeapWord* end_addr)
2737 {
2738   ParallelCompactData& sd = summary_data();
2739 
2740 #ifdef ASSERT
2741   MutableSpace* const src_space = _space_info[src_space_id].space();
2742   HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2743   assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2744          "src_space_id does not match beg_addr");
2745   assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2746          "src_space_id does not match end_addr");
2747 #endif // #ifdef ASSERT
2748 
2749   RegionData* const beg = sd.region(beg_region);
2750   RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2751 
2752   // Regions up to new_top() are enqueued if they become available.
2753   HeapWord* const new_top = _space_info[src_space_id].new_top();
2754   RegionData* const enqueue_end =
2755     sd.addr_to_region_ptr(sd.region_align_up(new_top));
2756 
2757   for (RegionData* cur = beg; cur < end; ++cur) {
2758     assert(cur->data_size() > 0, "region must have live data");
2759     cur->decrement_destination_count();
2760     if (cur < enqueue_end && cur->available() && cur->claim()) {
2761       cm->push_region(sd.region(cur));
2762     }
2763   }
2764 }
2765 
2766 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2767                                           SpaceId& src_space_id,
2768                                           HeapWord*& src_space_top,
2769                                           HeapWord* end_addr)
2770 {
2771   typedef ParallelCompactData::RegionData RegionData;
2772 
2773   ParallelCompactData& sd = PSParallelCompact::summary_data();
2774   const size_t region_size = ParallelCompactData::RegionSize;
2775 
2776   size_t src_region_idx = 0;
2777 
2778   // Skip empty regions (if any) up to the top of the space.
2779   HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2780   RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2781   HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2782   const RegionData* const top_region_ptr =
2783     sd.addr_to_region_ptr(top_aligned_up);
2784   while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2785     ++src_region_ptr;
2786   }
2787 
2788   if (src_region_ptr < top_region_ptr) {
2789     // The next source region is in the current space.  Update src_region_idx
2790     // and the source address to match src_region_ptr.
2791     src_region_idx = sd.region(src_region_ptr);
2792     HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
2793     if (src_region_addr > closure.source()) {
2794       closure.set_source(src_region_addr);
2795     }
2796     return src_region_idx;
2797   }
2798 
2799   // Switch to a new source space and find the first non-empty region.
2800   unsigned int space_id = src_space_id + 1;
2801   assert(space_id < last_space_id, "not enough spaces");
2802 
2803   HeapWord* const destination = closure.destination();
2804 
2805   do {
2806     MutableSpace* space = _space_info[space_id].space();
2807     HeapWord* const bottom = space->bottom();
2808     const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
2809 
2810     // Iterate over the spaces that do not compact into themselves.
2811     if (bottom_cp->destination() != bottom) {
2812       HeapWord* const top_aligned_up = sd.region_align_up(space->top());
2813       const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
2814 
2815       for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
2816         if (src_cp->live_obj_size() > 0) {
2817           // Found it.
2818           assert(src_cp->destination() == destination,
2819                  "first live obj in the space must match the destination");
2820           assert(src_cp->partial_obj_size() == 0,
2821                  "a space cannot begin with a partial obj");
2822 
2823           src_space_id = SpaceId(space_id);
2824           src_space_top = space->top();
2825           const size_t src_region_idx = sd.region(src_cp);
2826           closure.set_source(sd.region_to_addr(src_region_idx));
2827           return src_region_idx;
2828         } else {
2829           assert(src_cp->data_size() == 0, "sanity");
2830         }
2831       }
2832     }
2833   } while (++space_id < last_space_id);
2834 
2835   assert(false, "no source region was found");
2836   return 0;
2837 }
2838 
2839 void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx)
2840 {
2841   typedef ParMarkBitMap::IterationStatus IterationStatus;
2842   const size_t RegionSize = ParallelCompactData::RegionSize;
2843   ParMarkBitMap* const bitmap = mark_bitmap();
2844   ParallelCompactData& sd = summary_data();
2845   RegionData* const region_ptr = sd.region(region_idx);
2846 
2847   // Get the items needed to construct the closure.
2848   HeapWord* dest_addr = sd.region_to_addr(region_idx);
2849   SpaceId dest_space_id = space_id(dest_addr);
2850   ObjectStartArray* start_array = _space_info[dest_space_id].start_array();
2851   HeapWord* new_top = _space_info[dest_space_id].new_top();
2852   assert(dest_addr < new_top, "sanity");
2853   const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize);
2854 
2855   // Get the source region and related info.
2856   size_t src_region_idx = region_ptr->source_region();
2857   SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2858   HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2859 
2860   MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
2861   closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2862 
2863   // Adjust src_region_idx to prepare for decrementing destination counts (the
2864   // destination count is not decremented when a region is copied to itself).
2865   if (src_region_idx == region_idx) {
2866     src_region_idx += 1;
2867   }
2868 
2869   if (bitmap->is_unmarked(closure.source())) {
2870     // The first source word is in the middle of an object; copy the remainder
2871     // of the object or as much as will fit.  The fact that pointer updates were
2872     // deferred will be noted when the object header is processed.
2873     HeapWord* const old_src_addr = closure.source();
2874     closure.copy_partial_obj();
2875     if (closure.is_full()) {
2876       decrement_destination_counts(cm, src_space_id, src_region_idx,
2877                                    closure.source());
2878       region_ptr->set_deferred_obj_addr(NULL);
2879       region_ptr->set_completed();
2880       return;
2881     }
2882 
2883     HeapWord* const end_addr = sd.region_align_down(closure.source());
2884     if (sd.region_align_down(old_src_addr) != end_addr) {
2885       // The partial object was copied from more than one source region.
2886       decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2887 
2888       // Move to the next source region, possibly switching spaces as well.  All
2889       // args except end_addr may be modified.
2890       src_region_idx = next_src_region(closure, src_space_id, src_space_top,
2891                                        end_addr);
2892     }
2893   }
2894 
2895   do {
2896     HeapWord* const cur_addr = closure.source();
2897     HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
2898                                     src_space_top);
2899     IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
2900 
2901     if (status == ParMarkBitMap::incomplete) {
2902       // The last obj that starts in the source region does not end in the
2903       // region.
2904       assert(closure.source() < end_addr, "sanity");
2905       HeapWord* const obj_beg = closure.source();
2906       HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
2907                                        src_space_top);
2908       HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
2909       if (obj_end < range_end) {
2910         // The end was found; the entire object will fit.
2911         status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
2912         assert(status != ParMarkBitMap::would_overflow, "sanity");
2913       } else {
2914         // The end was not found; the object will not fit.
2915         assert(range_end < src_space_top, "obj cannot cross space boundary");
2916         status = ParMarkBitMap::would_overflow;
2917       }
2918     }
2919 
2920     if (status == ParMarkBitMap::would_overflow) {
2921       // The last object did not fit.  Note that interior oop updates were
2922       // deferred, then copy enough of the object to fill the region.
2923       region_ptr->set_deferred_obj_addr(closure.destination());
2924       status = closure.copy_until_full(); // copies from closure.source()
2925 
2926       decrement_destination_counts(cm, src_space_id, src_region_idx,
2927                                    closure.source());
2928       region_ptr->set_completed();
2929       return;
2930     }
2931 
2932     if (status == ParMarkBitMap::full) {
2933       decrement_destination_counts(cm, src_space_id, src_region_idx,
2934                                    closure.source());
2935       region_ptr->set_deferred_obj_addr(NULL);
2936       region_ptr->set_completed();
2937       return;
2938     }
2939 
2940     decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2941 
2942     // Move to the next source region, possibly switching spaces as well.  All
2943     // args except end_addr may be modified.
2944     src_region_idx = next_src_region(closure, src_space_id, src_space_top,
2945                                      end_addr);
2946   } while (true);
2947 }
2948 
2949 void PSParallelCompact::fill_blocks(size_t region_idx)
2950 {
2951   // Fill in the block table elements for the specified region.  Each block
2952   // table element holds the number of live words in the region that are to the
2953   // left of the first object that starts in the block.  Thus only blocks in
2954   // which an object starts need to be filled.
2955   //
2956   // The algorithm scans the section of the bitmap that corresponds to the
2957   // region, keeping a running total of the live words.  When an object start is
2958   // found, if it's the first to start in the block that contains it, the
2959   // current total is written to the block table element.
2960   const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
2961   const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
2962   const size_t RegionSize = ParallelCompactData::RegionSize;
2963 
2964   ParallelCompactData& sd = summary_data();
2965   const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
2966   if (partial_obj_size >= RegionSize) {
2967     return; // No objects start in this region.
2968   }
2969 
2970   // Ensure the first loop iteration decides that the block has changed.
2971   size_t cur_block = sd.block_count();
2972 
2973   const ParMarkBitMap* const bitmap = mark_bitmap();
2974 
2975   const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
2976   assert((size_t)1 << Log2BitsPerBlock ==
2977          bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
2978 
2979   size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
2980   const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
2981   size_t live_bits = bitmap->words_to_bits(partial_obj_size);
2982   beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
2983   while (beg_bit < range_end) {
2984     const size_t new_block = beg_bit >> Log2BitsPerBlock;
2985     if (new_block != cur_block) {
2986       cur_block = new_block;
2987       sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
2988     }
2989 
2990     const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
2991     if (end_bit < range_end - 1) {
2992       live_bits += end_bit - beg_bit + 1;
2993       beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
2994     } else {
2995       return;
2996     }
2997   }
2998 }
2999 
3000 void
3001 PSParallelCompact::move_and_update(ParCompactionManager* cm, SpaceId space_id) {
3002   const MutableSpace* sp = space(space_id);
3003   if (sp->is_empty()) {
3004     return;
3005   }
3006 
3007   ParallelCompactData& sd = PSParallelCompact::summary_data();
3008   ParMarkBitMap* const bitmap = mark_bitmap();
3009   HeapWord* const dp_addr = dense_prefix(space_id);
3010   HeapWord* beg_addr = sp->bottom();
3011   HeapWord* end_addr = sp->top();
3012 
3013   assert(beg_addr <= dp_addr && dp_addr <= end_addr, "bad dense prefix");
3014 
3015   const size_t beg_region = sd.addr_to_region_idx(beg_addr);
3016   const size_t dp_region = sd.addr_to_region_idx(dp_addr);
3017   if (beg_region < dp_region) {
3018     update_and_deadwood_in_dense_prefix(cm, space_id, beg_region, dp_region);
3019   }
3020 
3021   // The destination of the first live object that starts in the region is one
3022   // past the end of the partial object entering the region (if any).
3023   HeapWord* const dest_addr = sd.partial_obj_end(dp_region);
3024   HeapWord* const new_top = _space_info[space_id].new_top();
3025   assert(new_top >= dest_addr, "bad new_top value");
3026   const size_t words = pointer_delta(new_top, dest_addr);
3027 
3028   if (words > 0) {
3029     ObjectStartArray* start_array = _space_info[space_id].start_array();
3030     MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3031 
3032     ParMarkBitMap::IterationStatus status;
3033     status = bitmap->iterate(&closure, dest_addr, end_addr);
3034     assert(status == ParMarkBitMap::full, "iteration not complete");
3035     assert(bitmap->find_obj_beg(closure.source(), end_addr) == end_addr,
3036            "live objects skipped because closure is full");
3037   }
3038 }
3039 
3040 jlong PSParallelCompact::millis_since_last_gc() {
3041   // We need a monotonically non-decreasing time in ms but
3042   // os::javaTimeMillis() does not guarantee monotonicity.
3043   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3044   jlong ret_val = now - _time_of_last_gc;
3045   // XXX See note in genCollectedHeap::millis_since_last_gc().
3046   if (ret_val < 0) {
3047     NOT_PRODUCT(log_warning(gc)("time warp: " JLONG_FORMAT, ret_val);)
3048     return 0;
3049   }
3050   return ret_val;
3051 }
3052 
3053 void PSParallelCompact::reset_millis_since_last_gc() {
3054   // We need a monotonically non-decreasing time in ms but
3055   // os::javaTimeMillis() does not guarantee monotonicity.
3056   _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3057 }
3058 
3059 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3060 {
3061   if (source() != destination()) {
3062     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3063     Copy::aligned_conjoint_words(source(), destination(), words_remaining());
3064   }
3065   update_state(words_remaining());
3066   assert(is_full(), "sanity");
3067   return ParMarkBitMap::full;
3068 }
3069 
3070 void MoveAndUpdateClosure::copy_partial_obj()
3071 {
3072   size_t words = words_remaining();
3073 
3074   HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3075   HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3076   if (end_addr < range_end) {
3077     words = bitmap()->obj_size(source(), end_addr);
3078   }
3079 
3080   // This test is necessary; if omitted, the pointer updates to a partial object
3081   // that crosses the dense prefix boundary could be overwritten.
3082   if (source() != destination()) {
3083     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3084     Copy::aligned_conjoint_words(source(), destination(), words);
3085   }
3086   update_state(words);
3087 }
3088 
3089 ParMarkBitMapClosure::IterationStatus
3090 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3091   assert(destination() != NULL, "sanity");
3092   assert(bitmap()->obj_size(addr) == words, "bad size");
3093 
3094   _source = addr;
3095   assert(PSParallelCompact::summary_data().calc_new_pointer(source(), compaction_manager()) ==
3096          destination(), "wrong destination");
3097 
3098   if (words > words_remaining()) {
3099     return ParMarkBitMap::would_overflow;
3100   }
3101 
3102   // The start_array must be updated even if the object is not moving.
3103   if (_start_array != NULL) {
3104     _start_array->allocate_block(destination());
3105   }
3106 
3107   if (destination() != source()) {
3108     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3109     Copy::aligned_conjoint_words(source(), destination(), words);
3110   }
3111 
3112   oop moved_oop = (oop) destination();
3113   compaction_manager()->update_contents(moved_oop);
3114   assert(oopDesc::is_oop_or_null(moved_oop), "Expected an oop or NULL at " PTR_FORMAT, p2i(moved_oop));
3115 
3116   update_state(words);
3117   assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
3118   return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3119 }
3120 
3121 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3122                                      ParCompactionManager* cm,
3123                                      PSParallelCompact::SpaceId space_id) :
3124   ParMarkBitMapClosure(mbm, cm),
3125   _space_id(space_id),
3126   _start_array(PSParallelCompact::start_array(space_id))
3127 {
3128 }
3129 
3130 // Updates the references in the object to their new values.
3131 ParMarkBitMapClosure::IterationStatus
3132 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3133   do_addr(addr);
3134   return ParMarkBitMap::incomplete;
3135 }
3136 
3137 FillClosure::FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id) :
3138   ParMarkBitMapClosure(PSParallelCompact::mark_bitmap(), cm),
3139   _start_array(PSParallelCompact::start_array(space_id))
3140 {
3141   assert(space_id == PSParallelCompact::old_space_id,
3142          "cannot use FillClosure in the young gen");
3143 }
3144 
3145 ParMarkBitMapClosure::IterationStatus
3146 FillClosure::do_addr(HeapWord* addr, size_t size) {
3147   CollectedHeap::fill_with_objects(addr, size);
3148   HeapWord* const end = addr + size;
3149   do {
3150     _start_array->allocate_block(addr);
3151     addr += oop(addr)->size();
3152   } while (addr < end);
3153   return ParMarkBitMap::incomplete;
3154 }