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/parallelArguments.hpp"
  34 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
  35 #include "gc/parallel/parMarkBitMap.inline.hpp"
  36 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
  37 #include "gc/parallel/psCompactionManager.inline.hpp"
  38 #include "gc/parallel/psOldGen.hpp"
  39 #include "gc/parallel/psParallelCompact.inline.hpp"
  40 #include "gc/parallel/psPromotionManager.inline.hpp"
  41 #include "gc/parallel/psRootType.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 "gc/shared/workerPolicy.hpp"
  58 #include "gc/shared/workgroup.hpp"
  59 #include "logging/log.hpp"
  60 #include "memory/iterator.inline.hpp"
  61 #include "memory/resourceArea.hpp"
  62 #include "memory/universe.hpp"
  63 #include "oops/access.inline.hpp"
  64 #include "oops/instanceClassLoaderKlass.inline.hpp"
  65 #include "oops/instanceKlass.inline.hpp"
  66 #include "oops/instanceMirrorKlass.inline.hpp"
  67 #include "oops/methodData.hpp"
  68 #include "oops/objArrayKlass.inline.hpp"
  69 #include "oops/oop.inline.hpp"
  70 #include "runtime/atomic.hpp"
  71 #include "runtime/handles.inline.hpp"
  72 #include "runtime/safepoint.hpp"
  73 #include "runtime/vmThread.hpp"
  74 #include "services/management.hpp"
  75 #include "services/memTracker.hpp"
  76 #include "services/memoryService.hpp"
  77 #include "utilities/align.hpp"
  78 #include "utilities/debug.hpp"
  79 #include "utilities/events.hpp"
  80 #include "utilities/formatBuffer.hpp"
  81 #include "utilities/macros.hpp"
  82 #include "utilities/stack.inline.hpp"
  83 #if INCLUDE_JVMCI
  84 #include "jvmci/jvmci.hpp"
  85 #endif
  86 
  87 #include <math.h>
  88 
  89 // All sizes are in HeapWords.
  90 const size_t ParallelCompactData::Log2RegionSize  = 16; // 64K words
  91 const size_t ParallelCompactData::RegionSize      = (size_t)1 << Log2RegionSize;
  92 const size_t ParallelCompactData::RegionSizeBytes =
  93   RegionSize << LogHeapWordSize;
  94 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
  95 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
  96 const size_t ParallelCompactData::RegionAddrMask       = ~RegionAddrOffsetMask;
  97 
  98 const size_t ParallelCompactData::Log2BlockSize   = 7; // 128 words
  99 const size_t ParallelCompactData::BlockSize       = (size_t)1 << Log2BlockSize;
 100 const size_t ParallelCompactData::BlockSizeBytes  =
 101   BlockSize << LogHeapWordSize;
 102 const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
 103 const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
 104 const size_t ParallelCompactData::BlockAddrMask       = ~BlockAddrOffsetMask;
 105 
 106 const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
 107 const size_t ParallelCompactData::Log2BlocksPerRegion =
 108   Log2RegionSize - Log2BlockSize;
 109 
 110 const ParallelCompactData::RegionData::region_sz_t
 111 ParallelCompactData::RegionData::dc_shift = 27;
 112 
 113 const ParallelCompactData::RegionData::region_sz_t
 114 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
 115 
 116 const ParallelCompactData::RegionData::region_sz_t
 117 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
 118 
 119 const ParallelCompactData::RegionData::region_sz_t
 120 ParallelCompactData::RegionData::los_mask = ~dc_mask;
 121 
 122 const ParallelCompactData::RegionData::region_sz_t
 123 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
 124 
 125 const ParallelCompactData::RegionData::region_sz_t
 126 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
 127 
 128 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
 129 
 130 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
 131 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
 132 
 133 double PSParallelCompact::_dwl_mean;
 134 double PSParallelCompact::_dwl_std_dev;
 135 double PSParallelCompact::_dwl_first_term;
 136 double PSParallelCompact::_dwl_adjustment;
 137 #ifdef  ASSERT
 138 bool   PSParallelCompact::_dwl_initialized = false;
 139 #endif  // #ifdef ASSERT
 140 
 141 void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
 142                        HeapWord* destination)
 143 {
 144   assert(src_region_idx != 0, "invalid src_region_idx");
 145   assert(partial_obj_size != 0, "invalid partial_obj_size argument");
 146   assert(destination != NULL, "invalid destination argument");
 147 
 148   _src_region_idx = src_region_idx;
 149   _partial_obj_size = partial_obj_size;
 150   _destination = destination;
 151 
 152   // These fields may not be updated below, so make sure they're clear.
 153   assert(_dest_region_addr == NULL, "should have been cleared");
 154   assert(_first_src_addr == NULL, "should have been cleared");
 155 
 156   // Determine the number of destination regions for the partial object.
 157   HeapWord* const last_word = destination + partial_obj_size - 1;
 158   const ParallelCompactData& sd = PSParallelCompact::summary_data();
 159   HeapWord* const beg_region_addr = sd.region_align_down(destination);
 160   HeapWord* const end_region_addr = sd.region_align_down(last_word);
 161 
 162   if (beg_region_addr == end_region_addr) {
 163     // One destination region.
 164     _destination_count = 1;
 165     if (end_region_addr == destination) {
 166       // The destination falls on a region boundary, thus the first word of the
 167       // partial object will be the first word copied to the destination region.
 168       _dest_region_addr = end_region_addr;
 169       _first_src_addr = sd.region_to_addr(src_region_idx);
 170     }
 171   } else {
 172     // Two destination regions.  When copied, the partial object will cross a
 173     // destination region boundary, so a word somewhere within the partial
 174     // object will be the first word copied to the second destination region.
 175     _destination_count = 2;
 176     _dest_region_addr = end_region_addr;
 177     const size_t ofs = pointer_delta(end_region_addr, destination);
 178     assert(ofs < _partial_obj_size, "sanity");
 179     _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
 180   }
 181 }
 182 
 183 void SplitInfo::clear()
 184 {
 185   _src_region_idx = 0;
 186   _partial_obj_size = 0;
 187   _destination = NULL;
 188   _destination_count = 0;
 189   _dest_region_addr = NULL;
 190   _first_src_addr = NULL;
 191   assert(!is_valid(), "sanity");
 192 }
 193 
 194 #ifdef  ASSERT
 195 void SplitInfo::verify_clear()
 196 {
 197   assert(_src_region_idx == 0, "not clear");
 198   assert(_partial_obj_size == 0, "not clear");
 199   assert(_destination == NULL, "not clear");
 200   assert(_destination_count == 0, "not clear");
 201   assert(_dest_region_addr == NULL, "not clear");
 202   assert(_first_src_addr == NULL, "not clear");
 203 }
 204 #endif  // #ifdef ASSERT
 205 
 206 
 207 void PSParallelCompact::print_on_error(outputStream* st) {
 208   _mark_bitmap.print_on_error(st);
 209 }
 210 
 211 #ifndef PRODUCT
 212 const char* PSParallelCompact::space_names[] = {
 213   "old ", "eden", "from", "to  "
 214 };
 215 
 216 void PSParallelCompact::print_region_ranges() {
 217   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 218     return;
 219   }
 220   Log(gc, compaction) log;
 221   ResourceMark rm;
 222   LogStream ls(log.trace());
 223   Universe::print_on(&ls);
 224   log.trace("space  bottom     top        end        new_top");
 225   log.trace("------ ---------- ---------- ---------- ----------");
 226 
 227   for (unsigned int id = 0; id < last_space_id; ++id) {
 228     const MutableSpace* space = _space_info[id].space();
 229     log.trace("%u %s "
 230               SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
 231               SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
 232               id, space_names[id],
 233               summary_data().addr_to_region_idx(space->bottom()),
 234               summary_data().addr_to_region_idx(space->top()),
 235               summary_data().addr_to_region_idx(space->end()),
 236               summary_data().addr_to_region_idx(_space_info[id].new_top()));
 237   }
 238 }
 239 
 240 void
 241 print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
 242 {
 243 #define REGION_IDX_FORMAT        SIZE_FORMAT_W(7)
 244 #define REGION_DATA_FORMAT       SIZE_FORMAT_W(5)
 245 
 246   ParallelCompactData& sd = PSParallelCompact::summary_data();
 247   size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
 248   log_develop_trace(gc, compaction)(
 249       REGION_IDX_FORMAT " " PTR_FORMAT " "
 250       REGION_IDX_FORMAT " " PTR_FORMAT " "
 251       REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
 252       REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
 253       i, p2i(c->data_location()), dci, p2i(c->destination()),
 254       c->partial_obj_size(), c->live_obj_size(),
 255       c->data_size(), c->source_region(), c->destination_count());
 256 
 257 #undef  REGION_IDX_FORMAT
 258 #undef  REGION_DATA_FORMAT
 259 }
 260 
 261 void
 262 print_generic_summary_data(ParallelCompactData& summary_data,
 263                            HeapWord* const beg_addr,
 264                            HeapWord* const end_addr)
 265 {
 266   size_t total_words = 0;
 267   size_t i = summary_data.addr_to_region_idx(beg_addr);
 268   const size_t last = summary_data.addr_to_region_idx(end_addr);
 269   HeapWord* pdest = 0;
 270 
 271   while (i < last) {
 272     ParallelCompactData::RegionData* c = summary_data.region(i);
 273     if (c->data_size() != 0 || c->destination() != pdest) {
 274       print_generic_summary_region(i, c);
 275       total_words += c->data_size();
 276       pdest = c->destination();
 277     }
 278     ++i;
 279   }
 280 
 281   log_develop_trace(gc, compaction)("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
 282 }
 283 
 284 void
 285 PSParallelCompact::print_generic_summary_data(ParallelCompactData& summary_data,
 286                                               HeapWord* const beg_addr,
 287                                               HeapWord* const end_addr) {
 288   ::print_generic_summary_data(summary_data,beg_addr, end_addr);
 289 }
 290 
 291 void
 292 print_generic_summary_data(ParallelCompactData& summary_data,
 293                            SpaceInfo* space_info)
 294 {
 295   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 296     return;
 297   }
 298 
 299   for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
 300     const MutableSpace* space = space_info[id].space();
 301     print_generic_summary_data(summary_data, space->bottom(),
 302                                MAX2(space->top(), space_info[id].new_top()));
 303   }
 304 }
 305 
 306 void
 307 print_initial_summary_data(ParallelCompactData& summary_data,
 308                            const MutableSpace* space) {
 309   if (space->top() == space->bottom()) {
 310     return;
 311   }
 312 
 313   const size_t region_size = ParallelCompactData::RegionSize;
 314   typedef ParallelCompactData::RegionData RegionData;
 315   HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
 316   const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
 317   const RegionData* c = summary_data.region(end_region - 1);
 318   HeapWord* end_addr = c->destination() + c->data_size();
 319   const size_t live_in_space = pointer_delta(end_addr, space->bottom());
 320 
 321   // Print (and count) the full regions at the beginning of the space.
 322   size_t full_region_count = 0;
 323   size_t i = summary_data.addr_to_region_idx(space->bottom());
 324   while (i < end_region && summary_data.region(i)->data_size() == region_size) {
 325     ParallelCompactData::RegionData* c = summary_data.region(i);
 326     log_develop_trace(gc, compaction)(
 327         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 328         i, p2i(c->destination()),
 329         c->partial_obj_size(), c->live_obj_size(),
 330         c->data_size(), c->source_region(), c->destination_count());
 331     ++full_region_count;
 332     ++i;
 333   }
 334 
 335   size_t live_to_right = live_in_space - full_region_count * region_size;
 336 
 337   double max_reclaimed_ratio = 0.0;
 338   size_t max_reclaimed_ratio_region = 0;
 339   size_t max_dead_to_right = 0;
 340   size_t max_live_to_right = 0;
 341 
 342   // Print the 'reclaimed ratio' for regions while there is something live in
 343   // the region or to the right of it.  The remaining regions are empty (and
 344   // uninteresting), and computing the ratio will result in division by 0.
 345   while (i < end_region && live_to_right > 0) {
 346     c = summary_data.region(i);
 347     HeapWord* const region_addr = summary_data.region_to_addr(i);
 348     const size_t used_to_right = pointer_delta(space->top(), region_addr);
 349     const size_t dead_to_right = used_to_right - live_to_right;
 350     const double reclaimed_ratio = double(dead_to_right) / live_to_right;
 351 
 352     if (reclaimed_ratio > max_reclaimed_ratio) {
 353             max_reclaimed_ratio = reclaimed_ratio;
 354             max_reclaimed_ratio_region = i;
 355             max_dead_to_right = dead_to_right;
 356             max_live_to_right = live_to_right;
 357     }
 358 
 359     ParallelCompactData::RegionData* c = summary_data.region(i);
 360     log_develop_trace(gc, compaction)(
 361         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d"
 362         "%12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
 363         i, p2i(c->destination()),
 364         c->partial_obj_size(), c->live_obj_size(),
 365         c->data_size(), c->source_region(), c->destination_count(),
 366         reclaimed_ratio, dead_to_right, live_to_right);
 367 
 368 
 369     live_to_right -= c->data_size();
 370     ++i;
 371   }
 372 
 373   // Any remaining regions are empty.  Print one more if there is one.
 374   if (i < end_region) {
 375     ParallelCompactData::RegionData* c = summary_data.region(i);
 376     log_develop_trace(gc, compaction)(
 377         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 378          i, p2i(c->destination()),
 379          c->partial_obj_size(), c->live_obj_size(),
 380          c->data_size(), c->source_region(), c->destination_count());
 381   }
 382 
 383   log_develop_trace(gc, compaction)("max:  " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
 384                                     max_reclaimed_ratio_region, max_dead_to_right, max_live_to_right, max_reclaimed_ratio);
 385 }
 386 
 387 void
 388 print_initial_summary_data(ParallelCompactData& summary_data,
 389                            SpaceInfo* space_info) {
 390   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 391     return;
 392   }
 393 
 394   unsigned int id = PSParallelCompact::old_space_id;
 395   const MutableSpace* space;
 396   do {
 397     space = space_info[id].space();
 398     print_initial_summary_data(summary_data, space);
 399   } while (++id < PSParallelCompact::eden_space_id);
 400 
 401   do {
 402     space = space_info[id].space();
 403     print_generic_summary_data(summary_data, space->bottom(), space->top());
 404   } while (++id < PSParallelCompact::last_space_id);
 405 }
 406 #endif  // #ifndef PRODUCT
 407 
 408 #ifdef  ASSERT
 409 size_t add_obj_count;
 410 size_t add_obj_size;
 411 size_t mark_bitmap_count;
 412 size_t mark_bitmap_size;
 413 #endif  // #ifdef ASSERT
 414 
 415 ParallelCompactData::ParallelCompactData() :
 416   _region_start(NULL),
 417   DEBUG_ONLY(_region_end(NULL) COMMA)
 418   _region_vspace(NULL),
 419   _reserved_byte_size(0),
 420   _region_data(NULL),
 421   _region_count(0),
 422   _block_vspace(NULL),
 423   _block_data(NULL),
 424   _block_count(0) {}
 425 
 426 bool ParallelCompactData::initialize(MemRegion covered_region)
 427 {
 428   _region_start = covered_region.start();
 429   const size_t region_size = covered_region.word_size();
 430   DEBUG_ONLY(_region_end = _region_start + region_size;)
 431 
 432   assert(region_align_down(_region_start) == _region_start,
 433          "region start not aligned");
 434   assert((region_size & RegionSizeOffsetMask) == 0,
 435          "region size not a multiple of RegionSize");
 436 
 437   bool result = initialize_region_data(region_size) && initialize_block_data();
 438   return result;
 439 }
 440 
 441 PSVirtualSpace*
 442 ParallelCompactData::create_vspace(size_t count, size_t element_size)
 443 {
 444   const size_t raw_bytes = count * element_size;
 445   const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
 446   const size_t granularity = os::vm_allocation_granularity();
 447   _reserved_byte_size = align_up(raw_bytes, MAX2(page_sz, granularity));
 448 
 449   const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
 450     MAX2(page_sz, granularity);
 451   ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0);
 452   os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, page_sz, rs.base(),
 453                        rs.size());
 454 
 455   MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
 456 
 457   PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
 458   if (vspace != 0) {
 459     if (vspace->expand_by(_reserved_byte_size)) {
 460       return vspace;
 461     }
 462     delete vspace;
 463     // Release memory reserved in the space.
 464     rs.release();
 465   }
 466 
 467   return 0;
 468 }
 469 
 470 bool ParallelCompactData::initialize_region_data(size_t region_size)
 471 {
 472   const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
 473   _region_vspace = create_vspace(count, sizeof(RegionData));
 474   if (_region_vspace != 0) {
 475     _region_data = (RegionData*)_region_vspace->reserved_low_addr();
 476     _region_count = count;
 477     return true;
 478   }
 479   return false;
 480 }
 481 
 482 bool ParallelCompactData::initialize_block_data()
 483 {
 484   assert(_region_count != 0, "region data must be initialized first");
 485   const size_t count = _region_count << Log2BlocksPerRegion;
 486   _block_vspace = create_vspace(count, sizeof(BlockData));
 487   if (_block_vspace != 0) {
 488     _block_data = (BlockData*)_block_vspace->reserved_low_addr();
 489     _block_count = count;
 490     return true;
 491   }
 492   return false;
 493 }
 494 
 495 void ParallelCompactData::clear()
 496 {
 497   memset(_region_data, 0, _region_vspace->committed_size());
 498   memset(_block_data, 0, _block_vspace->committed_size());
 499 }
 500 
 501 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
 502   assert(beg_region <= _region_count, "beg_region out of range");
 503   assert(end_region <= _region_count, "end_region out of range");
 504   assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize");
 505 
 506   const size_t region_cnt = end_region - beg_region;
 507   memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
 508 
 509   const size_t beg_block = beg_region * BlocksPerRegion;
 510   const size_t block_cnt = region_cnt * BlocksPerRegion;
 511   memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData));
 512 }
 513 
 514 HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
 515 {
 516   const RegionData* cur_cp = region(region_idx);
 517   const RegionData* const end_cp = region(region_count() - 1);
 518 
 519   HeapWord* result = region_to_addr(region_idx);
 520   if (cur_cp < end_cp) {
 521     do {
 522       result += cur_cp->partial_obj_size();
 523     } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
 524   }
 525   return result;
 526 }
 527 
 528 void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
 529 {
 530   const size_t obj_ofs = pointer_delta(addr, _region_start);
 531   const size_t beg_region = obj_ofs >> Log2RegionSize;
 532   const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
 533 
 534   DEBUG_ONLY(Atomic::inc(&add_obj_count);)
 535   DEBUG_ONLY(Atomic::add(len, &add_obj_size);)
 536 
 537   if (beg_region == end_region) {
 538     // All in one region.
 539     _region_data[beg_region].add_live_obj(len);
 540     return;
 541   }
 542 
 543   // First region.
 544   const size_t beg_ofs = region_offset(addr);
 545   _region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
 546 
 547   Klass* klass = ((oop)addr)->klass();
 548   // Middle regions--completely spanned by this object.
 549   for (size_t region = beg_region + 1; region < end_region; ++region) {
 550     _region_data[region].set_partial_obj_size(RegionSize);
 551     _region_data[region].set_partial_obj_addr(addr);
 552   }
 553 
 554   // Last region.
 555   const size_t end_ofs = region_offset(addr + len - 1);
 556   _region_data[end_region].set_partial_obj_size(end_ofs + 1);
 557   _region_data[end_region].set_partial_obj_addr(addr);
 558 }
 559 
 560 void
 561 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
 562 {
 563   assert(region_offset(beg) == 0, "not RegionSize aligned");
 564   assert(region_offset(end) == 0, "not RegionSize aligned");
 565 
 566   size_t cur_region = addr_to_region_idx(beg);
 567   const size_t end_region = addr_to_region_idx(end);
 568   HeapWord* addr = beg;
 569   while (cur_region < end_region) {
 570     _region_data[cur_region].set_destination(addr);
 571     _region_data[cur_region].set_destination_count(0);
 572     _region_data[cur_region].set_source_region(cur_region);
 573     _region_data[cur_region].set_data_location(addr);
 574 
 575     // Update live_obj_size so the region appears completely full.
 576     size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
 577     _region_data[cur_region].set_live_obj_size(live_size);
 578 
 579     ++cur_region;
 580     addr += RegionSize;
 581   }
 582 }
 583 
 584 // Find the point at which a space can be split and, if necessary, record the
 585 // split point.
 586 //
 587 // If the current src region (which overflowed the destination space) doesn't
 588 // have a partial object, the split point is at the beginning of the current src
 589 // region (an "easy" split, no extra bookkeeping required).
 590 //
 591 // If the current src region has a partial object, the split point is in the
 592 // region where that partial object starts (call it the split_region).  If
 593 // split_region has a partial object, then the split point is just after that
 594 // partial object (a "hard" split where we have to record the split data and
 595 // zero the partial_obj_size field).  With a "hard" split, we know that the
 596 // partial_obj ends within split_region because the partial object that caused
 597 // the overflow starts in split_region.  If split_region doesn't have a partial
 598 // obj, then the split is at the beginning of split_region (another "easy"
 599 // split).
 600 HeapWord*
 601 ParallelCompactData::summarize_split_space(size_t src_region,
 602                                            SplitInfo& split_info,
 603                                            HeapWord* destination,
 604                                            HeapWord* target_end,
 605                                            HeapWord** target_next)
 606 {
 607   assert(destination <= target_end, "sanity");
 608   assert(destination + _region_data[src_region].data_size() > target_end,
 609     "region should not fit into target space");
 610   assert(is_region_aligned(target_end), "sanity");
 611 
 612   size_t split_region = src_region;
 613   HeapWord* split_destination = destination;
 614   size_t partial_obj_size = _region_data[src_region].partial_obj_size();
 615 
 616   if (destination + partial_obj_size > target_end) {
 617     // The split point is just after the partial object (if any) in the
 618     // src_region that contains the start of the object that overflowed the
 619     // destination space.
 620     //
 621     // Find the start of the "overflow" object and set split_region to the
 622     // region containing it.
 623     HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
 624     split_region = addr_to_region_idx(overflow_obj);
 625 
 626     // Clear the source_region field of all destination regions whose first word
 627     // came from data after the split point (a non-null source_region field
 628     // implies a region must be filled).
 629     //
 630     // An alternative to the simple loop below:  clear during post_compact(),
 631     // which uses memcpy instead of individual stores, and is easy to
 632     // parallelize.  (The downside is that it clears the entire RegionData
 633     // object as opposed to just one field.)
 634     //
 635     // post_compact() would have to clear the summary data up to the highest
 636     // address that was written during the summary phase, which would be
 637     //
 638     //         max(top, max(new_top, clear_top))
 639     //
 640     // where clear_top is a new field in SpaceInfo.  Would have to set clear_top
 641     // to target_end.
 642     const RegionData* const sr = region(split_region);
 643     const size_t beg_idx =
 644       addr_to_region_idx(region_align_up(sr->destination() +
 645                                          sr->partial_obj_size()));
 646     const size_t end_idx = addr_to_region_idx(target_end);
 647 
 648     log_develop_trace(gc, compaction)("split:  clearing source_region field in [" SIZE_FORMAT ", " SIZE_FORMAT ")", beg_idx, end_idx);
 649     for (size_t idx = beg_idx; idx < end_idx; ++idx) {
 650       _region_data[idx].set_source_region(0);
 651     }
 652 
 653     // Set split_destination and partial_obj_size to reflect the split region.
 654     split_destination = sr->destination();
 655     partial_obj_size = sr->partial_obj_size();
 656   }
 657 
 658   // The split is recorded only if a partial object extends onto the region.
 659   if (partial_obj_size != 0) {
 660     _region_data[split_region].set_partial_obj_size(0);
 661     split_info.record(split_region, partial_obj_size, split_destination);
 662   }
 663 
 664   // Setup the continuation addresses.
 665   *target_next = split_destination + partial_obj_size;
 666   HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
 667 
 668   if (log_develop_is_enabled(Trace, gc, compaction)) {
 669     const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
 670     log_develop_trace(gc, compaction)("%s split:  src=" PTR_FORMAT " src_c=" SIZE_FORMAT " pos=" SIZE_FORMAT,
 671                                       split_type, p2i(source_next), split_region, partial_obj_size);
 672     log_develop_trace(gc, compaction)("%s split:  dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT " tn=" PTR_FORMAT,
 673                                       split_type, p2i(split_destination),
 674                                       addr_to_region_idx(split_destination),
 675                                       p2i(*target_next));
 676 
 677     if (partial_obj_size != 0) {
 678       HeapWord* const po_beg = split_info.destination();
 679       HeapWord* const po_end = po_beg + split_info.partial_obj_size();
 680       log_develop_trace(gc, compaction)("%s split:  po_beg=" PTR_FORMAT " " SIZE_FORMAT " po_end=" PTR_FORMAT " " SIZE_FORMAT,
 681                                         split_type,
 682                                         p2i(po_beg), addr_to_region_idx(po_beg),
 683                                         p2i(po_end), addr_to_region_idx(po_end));
 684     }
 685   }
 686 
 687   return source_next;
 688 }
 689 
 690 bool ParallelCompactData::summarize(SplitInfo& split_info,
 691                                     HeapWord* source_beg, HeapWord* source_end,
 692                                     HeapWord** source_next,
 693                                     HeapWord* target_beg, HeapWord* target_end,
 694                                     HeapWord** target_next)
 695 {
 696   HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
 697   log_develop_trace(gc, compaction)(
 698       "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
 699       "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
 700       p2i(source_beg), p2i(source_end), p2i(source_next_val),
 701       p2i(target_beg), p2i(target_end), p2i(*target_next));
 702 
 703   size_t cur_region = addr_to_region_idx(source_beg);
 704   const size_t end_region = addr_to_region_idx(region_align_up(source_end));
 705 
 706   HeapWord *dest_addr = target_beg;
 707   while (cur_region < end_region) {
 708     // The destination must be set even if the region has no data.
 709     _region_data[cur_region].set_destination(dest_addr);
 710 
 711     size_t words = _region_data[cur_region].data_size();
 712     if (words > 0) {
 713       // If cur_region does not fit entirely into the target space, find a point
 714       // at which the source space can be 'split' so that part is copied to the
 715       // target space and the rest is copied elsewhere.
 716       if (dest_addr + words > target_end) {
 717         assert(source_next != NULL, "source_next is NULL when splitting");
 718         *source_next = summarize_split_space(cur_region, split_info, dest_addr,
 719                                              target_end, target_next);
 720         return false;
 721       }
 722 
 723       // Compute the destination_count for cur_region, and if necessary, update
 724       // source_region for a destination region.  The source_region field is
 725       // updated if cur_region is the first (left-most) region to be copied to a
 726       // destination region.
 727       //
 728       // The destination_count calculation is a bit subtle.  A region that has
 729       // data that compacts into itself does not count itself as a destination.
 730       // This maintains the invariant that a zero count means the region is
 731       // available and can be claimed and then filled.
 732       uint destination_count = 0;
 733       if (split_info.is_split(cur_region)) {
 734         // The current region has been split:  the partial object will be copied
 735         // to one destination space and the remaining data will be copied to
 736         // another destination space.  Adjust the initial destination_count and,
 737         // if necessary, set the source_region field if the partial object will
 738         // cross a destination region boundary.
 739         destination_count = split_info.destination_count();
 740         if (destination_count == 2) {
 741           size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
 742           _region_data[dest_idx].set_source_region(cur_region);
 743         }
 744       }
 745 
 746       HeapWord* const last_addr = dest_addr + words - 1;
 747       const size_t dest_region_1 = addr_to_region_idx(dest_addr);
 748       const size_t dest_region_2 = addr_to_region_idx(last_addr);
 749 
 750       // Initially assume that the destination regions will be the same and
 751       // adjust the value below if necessary.  Under this assumption, if
 752       // cur_region == dest_region_2, then cur_region will be compacted
 753       // completely into itself.
 754       destination_count += cur_region == dest_region_2 ? 0 : 1;
 755       if (dest_region_1 != dest_region_2) {
 756         // Destination regions differ; adjust destination_count.
 757         destination_count += 1;
 758         // Data from cur_region will be copied to the start of dest_region_2.
 759         _region_data[dest_region_2].set_source_region(cur_region);
 760       } else if (region_offset(dest_addr) == 0) {
 761         // Data from cur_region will be copied to the start of the destination
 762         // region.
 763         _region_data[dest_region_1].set_source_region(cur_region);
 764       }
 765 
 766       _region_data[cur_region].set_destination_count(destination_count);
 767       _region_data[cur_region].set_data_location(region_to_addr(cur_region));
 768       dest_addr += words;
 769     }
 770 
 771     ++cur_region;
 772   }
 773 
 774   *target_next = dest_addr;
 775   return true;
 776 }
 777 
 778 HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr, ParCompactionManager* cm) {
 779   assert(addr != NULL, "Should detect NULL oop earlier");
 780   assert(ParallelScavengeHeap::heap()->is_in(addr), "not in heap");
 781   assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked");
 782 
 783   // Region covering the object.
 784   RegionData* const region_ptr = addr_to_region_ptr(addr);
 785   HeapWord* result = region_ptr->destination();
 786 
 787   // If the entire Region is live, the new location is region->destination + the
 788   // offset of the object within in the Region.
 789 
 790   // Run some performance tests to determine if this special case pays off.  It
 791   // is worth it for pointers into the dense prefix.  If the optimization to
 792   // avoid pointer updates in regions that only point to the dense prefix is
 793   // ever implemented, this should be revisited.
 794   if (region_ptr->data_size() == RegionSize) {
 795     result += region_offset(addr);
 796     return result;
 797   }
 798 
 799   // Otherwise, the new location is region->destination + block offset + the
 800   // number of live words in the Block that are (a) to the left of addr and (b)
 801   // due to objects that start in the Block.
 802 
 803   // Fill in the block table if necessary.  This is unsynchronized, so multiple
 804   // threads may fill the block table for a region (harmless, since it is
 805   // idempotent).
 806   if (!region_ptr->blocks_filled()) {
 807     PSParallelCompact::fill_blocks(addr_to_region_idx(addr));
 808     region_ptr->set_blocks_filled();
 809   }
 810 
 811   HeapWord* const search_start = block_align_down(addr);
 812   const size_t block_offset = addr_to_block_ptr(addr)->offset();
 813 
 814   const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
 815   const size_t live = bitmap->live_words_in_range(cm, search_start, oop(addr));
 816   result += block_offset + live;
 817   DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result));
 818   return result;
 819 }
 820 
 821 #ifdef ASSERT
 822 void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
 823 {
 824   const size_t* const beg = (const size_t*)vspace->committed_low_addr();
 825   const size_t* const end = (const size_t*)vspace->committed_high_addr();
 826   for (const size_t* p = beg; p < end; ++p) {
 827     assert(*p == 0, "not zero");
 828   }
 829 }
 830 
 831 void ParallelCompactData::verify_clear()
 832 {
 833   verify_clear(_region_vspace);
 834   verify_clear(_block_vspace);
 835 }
 836 #endif  // #ifdef ASSERT
 837 
 838 STWGCTimer          PSParallelCompact::_gc_timer;
 839 ParallelOldTracer   PSParallelCompact::_gc_tracer;
 840 elapsedTimer        PSParallelCompact::_accumulated_time;
 841 unsigned int        PSParallelCompact::_total_invocations = 0;
 842 unsigned int        PSParallelCompact::_maximum_compaction_gc_num = 0;
 843 jlong               PSParallelCompact::_time_of_last_gc = 0;
 844 CollectorCounters*  PSParallelCompact::_counters = NULL;
 845 ParMarkBitMap       PSParallelCompact::_mark_bitmap;
 846 ParallelCompactData PSParallelCompact::_summary_data;
 847 
 848 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
 849 
 850 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
 851 
 852 class PCReferenceProcessor: public ReferenceProcessor {
 853 public:
 854   PCReferenceProcessor(
 855     BoolObjectClosure* is_subject_to_discovery,
 856     BoolObjectClosure* is_alive_non_header) :
 857       ReferenceProcessor(is_subject_to_discovery,
 858       ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 859       ParallelGCThreads,   // mt processing degree
 860       true,                // mt discovery
 861       ParallelGCThreads,   // mt discovery degree
 862       true,                // atomic_discovery
 863       is_alive_non_header) {
 864   }
 865 
 866   template<typename T> bool discover(oop obj, ReferenceType type) {
 867     T* referent_addr = (T*) java_lang_ref_Reference::referent_addr_raw(obj);
 868     T heap_oop = RawAccess<>::oop_load(referent_addr);
 869     oop referent = CompressedOops::decode_not_null(heap_oop);
 870     return PSParallelCompact::mark_bitmap()->is_unmarked(referent)
 871         && ReferenceProcessor::discover_reference(obj, type);
 872   }
 873   virtual bool discover_reference(oop obj, ReferenceType type) {
 874     if (UseCompressedOops) {
 875       return discover<narrowOop>(obj, type);
 876     } else {
 877       return discover<oop>(obj, type);
 878     }
 879   }
 880 };
 881 
 882 void PSParallelCompact::post_initialize() {
 883   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 884   _span_based_discoverer.set_span(heap->reserved_region());
 885   _ref_processor =
 886     new PCReferenceProcessor(&_span_based_discoverer,
 887                              &_is_alive_closure); // non-header is alive closure
 888 
 889   _counters = new CollectorCounters("Parallel full collection pauses", 1);
 890 
 891   // Initialize static fields in ParCompactionManager.
 892   ParCompactionManager::initialize(mark_bitmap());
 893 }
 894 
 895 bool PSParallelCompact::initialize() {
 896   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 897   MemRegion mr = heap->reserved_region();
 898 
 899   // Was the old gen get allocated successfully?
 900   if (!heap->old_gen()->is_allocated()) {
 901     return false;
 902   }
 903 
 904   initialize_space_info();
 905   initialize_dead_wood_limiter();
 906 
 907   if (!_mark_bitmap.initialize(mr)) {
 908     vm_shutdown_during_initialization(
 909       err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
 910       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 911       _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
 912     return false;
 913   }
 914 
 915   if (!_summary_data.initialize(mr)) {
 916     vm_shutdown_during_initialization(
 917       err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
 918       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 919       _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
 920     return false;
 921   }
 922 
 923   return true;
 924 }
 925 
 926 void PSParallelCompact::initialize_space_info()
 927 {
 928   memset(&_space_info, 0, sizeof(_space_info));
 929 
 930   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 931   PSYoungGen* young_gen = heap->young_gen();
 932 
 933   _space_info[old_space_id].set_space(heap->old_gen()->object_space());
 934   _space_info[eden_space_id].set_space(young_gen->eden_space());
 935   _space_info[from_space_id].set_space(young_gen->from_space());
 936   _space_info[to_space_id].set_space(young_gen->to_space());
 937 
 938   _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
 939 }
 940 
 941 void PSParallelCompact::initialize_dead_wood_limiter()
 942 {
 943   const size_t max = 100;
 944   _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
 945   _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
 946   _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
 947   DEBUG_ONLY(_dwl_initialized = true;)
 948   _dwl_adjustment = normal_distribution(1.0);
 949 }
 950 
 951 void
 952 PSParallelCompact::clear_data_covering_space(SpaceId id)
 953 {
 954   // At this point, top is the value before GC, new_top() is the value that will
 955   // be set at the end of GC.  The marking bitmap is cleared to top; nothing
 956   // should be marked above top.  The summary data is cleared to the larger of
 957   // top & new_top.
 958   MutableSpace* const space = _space_info[id].space();
 959   HeapWord* const bot = space->bottom();
 960   HeapWord* const top = space->top();
 961   HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
 962 
 963   const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
 964   const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top));
 965   _mark_bitmap.clear_range(beg_bit, end_bit);
 966 
 967   const size_t beg_region = _summary_data.addr_to_region_idx(bot);
 968   const size_t end_region =
 969     _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
 970   _summary_data.clear_range(beg_region, end_region);
 971 
 972   // Clear the data used to 'split' regions.
 973   SplitInfo& split_info = _space_info[id].split_info();
 974   if (split_info.is_valid()) {
 975     split_info.clear();
 976   }
 977   DEBUG_ONLY(split_info.verify_clear();)
 978 }
 979 
 980 void PSParallelCompact::pre_compact()
 981 {
 982   // Update the from & to space pointers in space_info, since they are swapped
 983   // at each young gen gc.  Do the update unconditionally (even though a
 984   // promotion failure does not swap spaces) because an unknown number of young
 985   // collections will have swapped the spaces an unknown number of times.
 986   GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
 987   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 988   _space_info[from_space_id].set_space(heap->young_gen()->from_space());
 989   _space_info[to_space_id].set_space(heap->young_gen()->to_space());
 990 
 991   DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
 992   DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
 993 
 994   // Increment the invocation count
 995   heap->increment_total_collections(true);
 996 
 997   // We need to track unique mark sweep invocations as well.
 998   _total_invocations++;
 999 
1000   heap->print_heap_before_gc();
1001   heap->trace_heap_before_gc(&_gc_tracer);
1002 
1003   // Fill in TLABs
1004   heap->ensure_parsability(true);  // retire TLABs
1005 
1006   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
1007     HandleMark hm;  // Discard invalid handles created during verification
1008     Universe::verify("Before GC");
1009   }
1010 
1011   // Verify object start arrays
1012   if (VerifyObjectStartArray &&
1013       VerifyBeforeGC) {
1014     heap->old_gen()->verify_object_start_array();
1015   }
1016 
1017   DEBUG_ONLY(mark_bitmap()->verify_clear();)
1018   DEBUG_ONLY(summary_data().verify_clear();)
1019 
1020   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 
1066 #if COMPILER2_OR_JVMCI
1067   DerivedPointerTable::update_pointers();
1068 #endif
1069 
1070   if (ZapUnusedHeapArea) {
1071     heap->gen_mangle_unused_area();
1072   }
1073 
1074   // Update time of last GC
1075   reset_millis_since_last_gc();
1076 }
1077 
1078 HeapWord*
1079 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1080                                                     bool maximum_compaction)
1081 {
1082   const size_t region_size = ParallelCompactData::RegionSize;
1083   const ParallelCompactData& sd = summary_data();
1084 
1085   const MutableSpace* const space = _space_info[id].space();
1086   HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1087   const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1088   const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1089 
1090   // Skip full regions at the beginning of the space--they are necessarily part
1091   // of the dense prefix.
1092   size_t full_count = 0;
1093   const RegionData* cp;
1094   for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1095     ++full_count;
1096   }
1097 
1098   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1099   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1100   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1101   if (maximum_compaction || cp == end_cp || interval_ended) {
1102     _maximum_compaction_gc_num = total_invocations();
1103     return sd.region_to_addr(cp);
1104   }
1105 
1106   HeapWord* const new_top = _space_info[id].new_top();
1107   const size_t space_live = pointer_delta(new_top, space->bottom());
1108   const size_t space_used = space->used_in_words();
1109   const size_t space_capacity = space->capacity_in_words();
1110 
1111   const double cur_density = double(space_live) / space_capacity;
1112   const double deadwood_density =
1113     (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1114   const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1115 
1116   if (TraceParallelOldGCDensePrefix) {
1117     tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1118                   cur_density, deadwood_density, deadwood_goal);
1119     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1120                   "space_cap=" SIZE_FORMAT,
1121                   space_live, space_used,
1122                   space_capacity);
1123   }
1124 
1125   // XXX - Use binary search?
1126   HeapWord* dense_prefix = sd.region_to_addr(cp);
1127   const RegionData* full_cp = cp;
1128   const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1129   while (cp < end_cp) {
1130     HeapWord* region_destination = cp->destination();
1131     const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1132     if (TraceParallelOldGCDensePrefix && Verbose) {
1133       tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1134                     "dp=" PTR_FORMAT " " "cdw=" SIZE_FORMAT_W(8),
1135                     sd.region(cp), p2i(region_destination),
1136                     p2i(dense_prefix), cur_deadwood);
1137     }
1138 
1139     if (cur_deadwood >= deadwood_goal) {
1140       // Found the region that has the correct amount of deadwood to the left.
1141       // This typically occurs after crossing a fairly sparse set of regions, so
1142       // iterate backwards over those sparse regions, looking for the region
1143       // that has the lowest density of live objects 'to the right.'
1144       size_t space_to_left = sd.region(cp) * region_size;
1145       size_t live_to_left = space_to_left - cur_deadwood;
1146       size_t space_to_right = space_capacity - space_to_left;
1147       size_t live_to_right = space_live - live_to_left;
1148       double density_to_right = double(live_to_right) / space_to_right;
1149       while (cp > full_cp) {
1150         --cp;
1151         const size_t prev_region_live_to_right = live_to_right -
1152           cp->data_size();
1153         const size_t prev_region_space_to_right = space_to_right + region_size;
1154         double prev_region_density_to_right =
1155           double(prev_region_live_to_right) / prev_region_space_to_right;
1156         if (density_to_right <= prev_region_density_to_right) {
1157           return dense_prefix;
1158         }
1159         if (TraceParallelOldGCDensePrefix && Verbose) {
1160           tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1161                         "pc_d2r=%10.8f", sd.region(cp), density_to_right,
1162                         prev_region_density_to_right);
1163         }
1164         dense_prefix -= region_size;
1165         live_to_right = prev_region_live_to_right;
1166         space_to_right = prev_region_space_to_right;
1167         density_to_right = prev_region_density_to_right;
1168       }
1169       return dense_prefix;
1170     }
1171 
1172     dense_prefix += region_size;
1173     ++cp;
1174   }
1175 
1176   return dense_prefix;
1177 }
1178 
1179 #ifndef PRODUCT
1180 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1181                                                  const SpaceId id,
1182                                                  const bool maximum_compaction,
1183                                                  HeapWord* const addr)
1184 {
1185   const size_t region_idx = summary_data().addr_to_region_idx(addr);
1186   RegionData* const cp = summary_data().region(region_idx);
1187   const MutableSpace* const space = _space_info[id].space();
1188   HeapWord* const new_top = _space_info[id].new_top();
1189 
1190   const size_t space_live = pointer_delta(new_top, space->bottom());
1191   const size_t dead_to_left = pointer_delta(addr, cp->destination());
1192   const size_t space_cap = space->capacity_in_words();
1193   const double dead_to_left_pct = double(dead_to_left) / space_cap;
1194   const size_t live_to_right = new_top - cp->destination();
1195   const size_t dead_to_right = space->top() - addr - live_to_right;
1196 
1197   tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1198                 "spl=" SIZE_FORMAT " "
1199                 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1200                 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
1201                 " ratio=%10.8f",
1202                 algorithm, p2i(addr), region_idx,
1203                 space_live,
1204                 dead_to_left, dead_to_left_pct,
1205                 dead_to_right, live_to_right,
1206                 double(dead_to_right) / live_to_right);
1207 }
1208 #endif  // #ifndef PRODUCT
1209 
1210 // Return a fraction indicating how much of the generation can be treated as
1211 // "dead wood" (i.e., not reclaimed).  The function uses a normal distribution
1212 // based on the density of live objects in the generation to determine a limit,
1213 // which is then adjusted so the return value is min_percent when the density is
1214 // 1.
1215 //
1216 // The following table shows some return values for a different values of the
1217 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1218 // min_percent is 1.
1219 //
1220 //                          fraction allowed as dead wood
1221 //         -----------------------------------------------------------------
1222 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1223 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1224 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1225 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1226 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1227 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1228 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1229 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1230 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1231 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1232 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1233 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1234 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1235 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1236 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1237 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1238 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1239 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1240 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1241 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1242 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1243 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1244 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1245 
1246 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1247 {
1248   assert(_dwl_initialized, "uninitialized");
1249 
1250   // The raw limit is the value of the normal distribution at x = density.
1251   const double raw_limit = normal_distribution(density);
1252 
1253   // Adjust the raw limit so it becomes the minimum when the density is 1.
1254   //
1255   // First subtract the adjustment value (which is simply the precomputed value
1256   // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1257   // Then add the minimum value, so the minimum is returned when the density is
1258   // 1.  Finally, prevent negative values, which occur when the mean is not 0.5.
1259   const double min = double(min_percent) / 100.0;
1260   const double limit = raw_limit - _dwl_adjustment + min;
1261   return MAX2(limit, 0.0);
1262 }
1263 
1264 ParallelCompactData::RegionData*
1265 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1266                                            const RegionData* end)
1267 {
1268   const size_t region_size = ParallelCompactData::RegionSize;
1269   ParallelCompactData& sd = summary_data();
1270   size_t left = sd.region(beg);
1271   size_t right = end > beg ? sd.region(end) - 1 : left;
1272 
1273   // Binary search.
1274   while (left < right) {
1275     // Equivalent to (left + right) / 2, but does not overflow.
1276     const size_t middle = left + (right - left) / 2;
1277     RegionData* const middle_ptr = sd.region(middle);
1278     HeapWord* const dest = middle_ptr->destination();
1279     HeapWord* const addr = sd.region_to_addr(middle);
1280     assert(dest != NULL, "sanity");
1281     assert(dest <= addr, "must move left");
1282 
1283     if (middle > left && dest < addr) {
1284       right = middle - 1;
1285     } else if (middle < right && middle_ptr->data_size() == region_size) {
1286       left = middle + 1;
1287     } else {
1288       return middle_ptr;
1289     }
1290   }
1291   return sd.region(left);
1292 }
1293 
1294 ParallelCompactData::RegionData*
1295 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1296                                           const RegionData* end,
1297                                           size_t dead_words)
1298 {
1299   ParallelCompactData& sd = summary_data();
1300   size_t left = sd.region(beg);
1301   size_t right = end > beg ? sd.region(end) - 1 : left;
1302 
1303   // Binary search.
1304   while (left < right) {
1305     // Equivalent to (left + right) / 2, but does not overflow.
1306     const size_t middle = left + (right - left) / 2;
1307     RegionData* const middle_ptr = sd.region(middle);
1308     HeapWord* const dest = middle_ptr->destination();
1309     HeapWord* const addr = sd.region_to_addr(middle);
1310     assert(dest != NULL, "sanity");
1311     assert(dest <= addr, "must move left");
1312 
1313     const size_t dead_to_left = pointer_delta(addr, dest);
1314     if (middle > left && dead_to_left > dead_words) {
1315       right = middle - 1;
1316     } else if (middle < right && dead_to_left < dead_words) {
1317       left = middle + 1;
1318     } else {
1319       return middle_ptr;
1320     }
1321   }
1322   return sd.region(left);
1323 }
1324 
1325 // The result is valid during the summary phase, after the initial summarization
1326 // of each space into itself, and before final summarization.
1327 inline double
1328 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1329                                    HeapWord* const bottom,
1330                                    HeapWord* const top,
1331                                    HeapWord* const new_top)
1332 {
1333   ParallelCompactData& sd = summary_data();
1334 
1335   assert(cp != NULL, "sanity");
1336   assert(bottom != NULL, "sanity");
1337   assert(top != NULL, "sanity");
1338   assert(new_top != NULL, "sanity");
1339   assert(top >= new_top, "summary data problem?");
1340   assert(new_top > bottom, "space is empty; should not be here");
1341   assert(new_top >= cp->destination(), "sanity");
1342   assert(top >= sd.region_to_addr(cp), "sanity");
1343 
1344   HeapWord* const destination = cp->destination();
1345   const size_t dense_prefix_live  = pointer_delta(destination, bottom);
1346   const size_t compacted_region_live = pointer_delta(new_top, destination);
1347   const size_t compacted_region_used = pointer_delta(top,
1348                                                      sd.region_to_addr(cp));
1349   const size_t reclaimable = compacted_region_used - compacted_region_live;
1350 
1351   const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1352   return double(reclaimable) / divisor;
1353 }
1354 
1355 // Return the address of the end of the dense prefix, a.k.a. the start of the
1356 // compacted region.  The address is always on a region boundary.
1357 //
1358 // Completely full regions at the left are skipped, since no compaction can
1359 // occur in those regions.  Then the maximum amount of dead wood to allow is
1360 // computed, based on the density (amount live / capacity) of the generation;
1361 // the region with approximately that amount of dead space to the left is
1362 // identified as the limit region.  Regions between the last completely full
1363 // region and the limit region are scanned and the one that has the best
1364 // (maximum) reclaimed_ratio() is selected.
1365 HeapWord*
1366 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1367                                         bool maximum_compaction)
1368 {
1369   const size_t region_size = ParallelCompactData::RegionSize;
1370   const ParallelCompactData& sd = summary_data();
1371 
1372   const MutableSpace* const space = _space_info[id].space();
1373   HeapWord* const top = space->top();
1374   HeapWord* const top_aligned_up = sd.region_align_up(top);
1375   HeapWord* const new_top = _space_info[id].new_top();
1376   HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1377   HeapWord* const bottom = space->bottom();
1378   const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1379   const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1380   const RegionData* const new_top_cp =
1381     sd.addr_to_region_ptr(new_top_aligned_up);
1382 
1383   // Skip full regions at the beginning of the space--they are necessarily part
1384   // of the dense prefix.
1385   const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1386   assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1387          space->is_empty(), "no dead space allowed to the left");
1388   assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1389          "region must have dead space");
1390 
1391   // The gc number is saved whenever a maximum compaction is done, and used to
1392   // determine when the maximum compaction interval has expired.  This avoids
1393   // successive max compactions for different reasons.
1394   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1395   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1396   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1397     total_invocations() == HeapFirstMaximumCompactionCount;
1398   if (maximum_compaction || full_cp == top_cp || interval_ended) {
1399     _maximum_compaction_gc_num = total_invocations();
1400     return sd.region_to_addr(full_cp);
1401   }
1402 
1403   const size_t space_live = pointer_delta(new_top, bottom);
1404   const size_t space_used = space->used_in_words();
1405   const size_t space_capacity = space->capacity_in_words();
1406 
1407   const double density = double(space_live) / double(space_capacity);
1408   const size_t min_percent_free = MarkSweepDeadRatio;
1409   const double limiter = dead_wood_limiter(density, min_percent_free);
1410   const size_t dead_wood_max = space_used - space_live;
1411   const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1412                                       dead_wood_max);
1413 
1414   if (TraceParallelOldGCDensePrefix) {
1415     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1416                   "space_cap=" SIZE_FORMAT,
1417                   space_live, space_used,
1418                   space_capacity);
1419     tty->print_cr("dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
1420                   "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1421                   density, min_percent_free, limiter,
1422                   dead_wood_max, dead_wood_limit);
1423   }
1424 
1425   // Locate the region with the desired amount of dead space to the left.
1426   const RegionData* const limit_cp =
1427     dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1428 
1429   // Scan from the first region with dead space to the limit region and find the
1430   // one with the best (largest) reclaimed ratio.
1431   double best_ratio = 0.0;
1432   const RegionData* best_cp = full_cp;
1433   for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1434     double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1435     if (tmp_ratio > best_ratio) {
1436       best_cp = cp;
1437       best_ratio = tmp_ratio;
1438     }
1439   }
1440 
1441   return sd.region_to_addr(best_cp);
1442 }
1443 
1444 void PSParallelCompact::summarize_spaces_quick()
1445 {
1446   for (unsigned int i = 0; i < last_space_id; ++i) {
1447     const MutableSpace* space = _space_info[i].space();
1448     HeapWord** nta = _space_info[i].new_top_addr();
1449     bool result = _summary_data.summarize(_space_info[i].split_info(),
1450                                           space->bottom(), space->top(), NULL,
1451                                           space->bottom(), space->end(), nta);
1452     assert(result, "space must fit into itself");
1453     _space_info[i].set_dense_prefix(space->bottom());
1454   }
1455 }
1456 
1457 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1458 {
1459   HeapWord* const dense_prefix_end = dense_prefix(id);
1460   const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1461   const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1462   if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1463     // Only enough dead space is filled so that any remaining dead space to the
1464     // left is larger than the minimum filler object.  (The remainder is filled
1465     // during the copy/update phase.)
1466     //
1467     // The size of the dead space to the right of the boundary is not a
1468     // concern, since compaction will be able to use whatever space is
1469     // available.
1470     //
1471     // Here '||' is the boundary, 'x' represents a don't care bit and a box
1472     // surrounds the space to be filled with an object.
1473     //
1474     // In the 32-bit VM, each bit represents two 32-bit words:
1475     //                              +---+
1476     // a) beg_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1477     //    end_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1478     //                              +---+
1479     //
1480     // In the 64-bit VM, each bit represents one 64-bit word:
1481     //                              +------------+
1482     // b) beg_bits:  ...  x   x   x | 0   ||   0 | x  x  ...
1483     //    end_bits:  ...  x   x   1 | 0   ||   0 | x  x  ...
1484     //                              +------------+
1485     //                          +-------+
1486     // c) beg_bits:  ...  x   x | 0   0 | ||   0   x  x  ...
1487     //    end_bits:  ...  x   1 | 0   0 | ||   0   x  x  ...
1488     //                          +-------+
1489     //                      +-----------+
1490     // d) beg_bits:  ...  x | 0   0   0 | ||   0   x  x  ...
1491     //    end_bits:  ...  1 | 0   0   0 | ||   0   x  x  ...
1492     //                      +-----------+
1493     //                          +-------+
1494     // e) beg_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1495     //    end_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1496     //                          +-------+
1497 
1498     // Initially assume case a, c or e will apply.
1499     size_t obj_len = CollectedHeap::min_fill_size();
1500     HeapWord* obj_beg = dense_prefix_end - obj_len;
1501 
1502 #ifdef  _LP64
1503     if (MinObjAlignment > 1) { // object alignment > heap word size
1504       // Cases a, c or e.
1505     } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1506       // Case b above.
1507       obj_beg = dense_prefix_end - 1;
1508     } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1509                _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1510       // Case d above.
1511       obj_beg = dense_prefix_end - 3;
1512       obj_len = 3;
1513     }
1514 #endif  // #ifdef _LP64
1515 
1516     CollectedHeap::fill_with_object(obj_beg, obj_len);
1517     _mark_bitmap.mark_obj(obj_beg, obj_len);
1518     _summary_data.add_obj(obj_beg, obj_len);
1519     assert(start_array(id) != NULL, "sanity");
1520     start_array(id)->allocate_block(obj_beg);
1521   }
1522 }
1523 
1524 void
1525 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1526 {
1527   assert(id < last_space_id, "id out of range");
1528   assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom(),
1529          "should have been reset in summarize_spaces_quick()");
1530 
1531   const MutableSpace* space = _space_info[id].space();
1532   if (_space_info[id].new_top() != space->bottom()) {
1533     HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1534     _space_info[id].set_dense_prefix(dense_prefix_end);
1535 
1536 #ifndef PRODUCT
1537     if (TraceParallelOldGCDensePrefix) {
1538       print_dense_prefix_stats("ratio", id, maximum_compaction,
1539                                dense_prefix_end);
1540       HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1541       print_dense_prefix_stats("density", id, maximum_compaction, addr);
1542     }
1543 #endif  // #ifndef PRODUCT
1544 
1545     // Recompute the summary data, taking into account the dense prefix.  If
1546     // every last byte will be reclaimed, then the existing summary data which
1547     // compacts everything can be left in place.
1548     if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1549       // If dead space crosses the dense prefix boundary, it is (at least
1550       // partially) filled with a dummy object, marked live and added to the
1551       // summary data.  This simplifies the copy/update phase and must be done
1552       // before the final locations of objects are determined, to prevent
1553       // leaving a fragment of dead space that is too small to fill.
1554       fill_dense_prefix_end(id);
1555 
1556       // Compute the destination of each Region, and thus each object.
1557       _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1558       _summary_data.summarize(_space_info[id].split_info(),
1559                               dense_prefix_end, space->top(), NULL,
1560                               dense_prefix_end, space->end(),
1561                               _space_info[id].new_top_addr());
1562     }
1563   }
1564 
1565   if (log_develop_is_enabled(Trace, gc, compaction)) {
1566     const size_t region_size = ParallelCompactData::RegionSize;
1567     HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1568     const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1569     const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1570     HeapWord* const new_top = _space_info[id].new_top();
1571     const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1572     const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1573     log_develop_trace(gc, compaction)(
1574         "id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1575         "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1576         "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1577         id, space->capacity_in_words(), p2i(dense_prefix_end),
1578         dp_region, dp_words / region_size,
1579         cr_words / region_size, p2i(new_top));
1580   }
1581 }
1582 
1583 #ifndef PRODUCT
1584 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1585                                           HeapWord* dst_beg, HeapWord* dst_end,
1586                                           SpaceId src_space_id,
1587                                           HeapWord* src_beg, HeapWord* src_end)
1588 {
1589   log_develop_trace(gc, compaction)(
1590       "Summarizing %d [%s] into %d [%s]:  "
1591       "src=" PTR_FORMAT "-" PTR_FORMAT " "
1592       SIZE_FORMAT "-" SIZE_FORMAT " "
1593       "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1594       SIZE_FORMAT "-" SIZE_FORMAT,
1595       src_space_id, space_names[src_space_id],
1596       dst_space_id, space_names[dst_space_id],
1597       p2i(src_beg), p2i(src_end),
1598       _summary_data.addr_to_region_idx(src_beg),
1599       _summary_data.addr_to_region_idx(src_end),
1600       p2i(dst_beg), p2i(dst_end),
1601       _summary_data.addr_to_region_idx(dst_beg),
1602       _summary_data.addr_to_region_idx(dst_end));
1603 }
1604 #endif  // #ifndef PRODUCT
1605 
1606 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1607                                       bool maximum_compaction)
1608 {
1609   GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
1610 
1611 #ifdef  ASSERT
1612   if (TraceParallelOldGCMarkingPhase) {
1613     tty->print_cr("add_obj_count=" SIZE_FORMAT " "
1614                   "add_obj_bytes=" SIZE_FORMAT,
1615                   add_obj_count, add_obj_size * HeapWordSize);
1616     tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
1617                   "mark_bitmap_bytes=" SIZE_FORMAT,
1618                   mark_bitmap_count, mark_bitmap_size * HeapWordSize);
1619   }
1620 #endif  // #ifdef ASSERT
1621 
1622   // Quick summarization of each space into itself, to see how much is live.
1623   summarize_spaces_quick();
1624 
1625   log_develop_trace(gc, compaction)("summary phase:  after summarizing each space to self");
1626   NOT_PRODUCT(print_region_ranges());
1627   NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1628 
1629   // The amount of live data that will end up in old space (assuming it fits).
1630   size_t old_space_total_live = 0;
1631   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1632     old_space_total_live += pointer_delta(_space_info[id].new_top(),
1633                                           _space_info[id].space()->bottom());
1634   }
1635 
1636   MutableSpace* const old_space = _space_info[old_space_id].space();
1637   const size_t old_capacity = old_space->capacity_in_words();
1638   if (old_space_total_live > old_capacity) {
1639     // XXX - should also try to expand
1640     maximum_compaction = true;
1641   }
1642 
1643   // Old generations.
1644   summarize_space(old_space_id, maximum_compaction);
1645 
1646   // Summarize the remaining spaces in the young gen.  The initial target space
1647   // is the old gen.  If a space does not fit entirely into the target, then the
1648   // remainder is compacted into the space itself and that space becomes the new
1649   // target.
1650   SpaceId dst_space_id = old_space_id;
1651   HeapWord* dst_space_end = old_space->end();
1652   HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1653   for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1654     const MutableSpace* space = _space_info[id].space();
1655     const size_t live = pointer_delta(_space_info[id].new_top(),
1656                                       space->bottom());
1657     const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1658 
1659     NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1660                                   SpaceId(id), space->bottom(), space->top());)
1661     if (live > 0 && live <= available) {
1662       // All the live data will fit.
1663       bool done = _summary_data.summarize(_space_info[id].split_info(),
1664                                           space->bottom(), space->top(),
1665                                           NULL,
1666                                           *new_top_addr, dst_space_end,
1667                                           new_top_addr);
1668       assert(done, "space must fit into old gen");
1669 
1670       // Reset the new_top value for the space.
1671       _space_info[id].set_new_top(space->bottom());
1672     } else if (live > 0) {
1673       // Attempt to fit part of the source space into the target space.
1674       HeapWord* next_src_addr = NULL;
1675       bool done = _summary_data.summarize(_space_info[id].split_info(),
1676                                           space->bottom(), space->top(),
1677                                           &next_src_addr,
1678                                           *new_top_addr, dst_space_end,
1679                                           new_top_addr);
1680       assert(!done, "space should not fit into old gen");
1681       assert(next_src_addr != NULL, "sanity");
1682 
1683       // The source space becomes the new target, so the remainder is compacted
1684       // within the space itself.
1685       dst_space_id = SpaceId(id);
1686       dst_space_end = space->end();
1687       new_top_addr = _space_info[id].new_top_addr();
1688       NOT_PRODUCT(summary_phase_msg(dst_space_id,
1689                                     space->bottom(), dst_space_end,
1690                                     SpaceId(id), next_src_addr, space->top());)
1691       done = _summary_data.summarize(_space_info[id].split_info(),
1692                                      next_src_addr, space->top(),
1693                                      NULL,
1694                                      space->bottom(), dst_space_end,
1695                                      new_top_addr);
1696       assert(done, "space must fit when compacted into itself");
1697       assert(*new_top_addr <= space->top(), "usage should not grow");
1698     }
1699   }
1700 
1701   log_develop_trace(gc, compaction)("Summary_phase:  after final summarization");
1702   NOT_PRODUCT(print_region_ranges());
1703   NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1704 }
1705 
1706 // This method should contain all heap-specific policy for invoking a full
1707 // collection.  invoke_no_policy() will only attempt to compact the heap; it
1708 // will do nothing further.  If we need to bail out for policy reasons, scavenge
1709 // before full gc, or any other specialized behavior, it needs to be added here.
1710 //
1711 // Note that this method should only be called from the vm_thread while at a
1712 // safepoint.
1713 //
1714 // Note that the all_soft_refs_clear flag in the soft ref policy
1715 // may be true because this method can be called without intervening
1716 // activity.  For example when the heap space is tight and full measure
1717 // are being taken to free space.
1718 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1719   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1720   assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1721          "should be in vm thread");
1722 
1723   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1724   GCCause::Cause gc_cause = heap->gc_cause();
1725   assert(!heap->is_gc_active(), "not reentrant");
1726 
1727   PSAdaptiveSizePolicy* policy = heap->size_policy();
1728   IsGCActiveMark mark;
1729 
1730   if (ScavengeBeforeFullGC) {
1731     PSScavenge::invoke_no_policy();
1732   }
1733 
1734   const bool clear_all_soft_refs =
1735     heap->soft_ref_policy()->should_clear_all_soft_refs();
1736 
1737   PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1738                                       maximum_heap_compaction);
1739 }
1740 
1741 // This method contains no policy. You should probably
1742 // be calling invoke() instead.
1743 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
1744   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
1745   assert(ref_processor() != NULL, "Sanity");
1746 
1747   if (GCLocker::check_active_before_gc()) {
1748     return false;
1749   }
1750 
1751   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1752 
1753   GCIdMark gc_id_mark;
1754   _gc_timer.register_gc_start();
1755   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1756 
1757   TimeStamp marking_start;
1758   TimeStamp compaction_start;
1759   TimeStamp collection_exit;
1760 
1761   GCCause::Cause gc_cause = heap->gc_cause();
1762   PSYoungGen* young_gen = heap->young_gen();
1763   PSOldGen* old_gen = heap->old_gen();
1764   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1765 
1766   // The scope of casr should end after code that can change
1767   // SoftRefPolicy::_should_clear_all_soft_refs.
1768   ClearedAllSoftRefs casr(maximum_heap_compaction,
1769                           heap->soft_ref_policy());
1770 
1771   if (ZapUnusedHeapArea) {
1772     // Save information needed to minimize mangling
1773     heap->record_gen_tops_before_GC();
1774   }
1775 
1776   // Make sure data structures are sane, make the heap parsable, and do other
1777   // miscellaneous bookkeeping.
1778   pre_compact();
1779 
1780   const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
1781 
1782   // Get the compaction manager reserved for the VM thread.
1783   ParCompactionManager* const vmthread_cm =
1784     ParCompactionManager::manager_array(ParallelScavengeHeap::heap()->workers().total_workers());
1785 
1786   {
1787     ResourceMark rm;
1788     HandleMark hm;
1789 
1790     const uint active_workers =
1791       WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().total_workers(),
1792                                         ParallelScavengeHeap::heap()->workers().active_workers(),
1793                                         Threads::number_of_non_daemon_threads());
1794     ParallelScavengeHeap::heap()->workers().update_active_workers(active_workers);
1795 
1796     GCTraceCPUTime tcpu;
1797     GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause, true);
1798 
1799     heap->pre_full_gc_dump(&_gc_timer);
1800 
1801     TraceCollectorStats tcs(counters());
1802     TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause);
1803 
1804     if (log_is_enabled(Debug, gc, heap, exit)) {
1805       accumulated_time()->start();
1806     }
1807 
1808     // Let the size policy know we're starting
1809     size_policy->major_collection_begin();
1810 
1811 #if COMPILER2_OR_JVMCI
1812     DerivedPointerTable::clear();
1813 #endif
1814 
1815     ref_processor()->enable_discovery();
1816     ref_processor()->setup_policy(maximum_heap_compaction);
1817 
1818     bool marked_for_unloading = false;
1819 
1820     marking_start.update();
1821     marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
1822 
1823     bool max_on_system_gc = UseMaximumCompactionOnSystemGC
1824       && GCCause::is_user_requested_gc(gc_cause);
1825     summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
1826 
1827 #if COMPILER2_OR_JVMCI
1828     assert(DerivedPointerTable::is_active(), "Sanity");
1829     DerivedPointerTable::set_active(false);
1830 #endif
1831 
1832     // adjust_roots() updates Universe::_intArrayKlassObj which is
1833     // needed by the compaction for filling holes in the dense prefix.
1834     adjust_roots(vmthread_cm);
1835 
1836     compaction_start.update();
1837     compact();
1838 
1839     // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
1840     // done before resizing.
1841     post_compact();
1842 
1843     // Let the size policy know we're done
1844     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1845 
1846     if (UseAdaptiveSizePolicy) {
1847       log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1848       log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
1849                           old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1850 
1851       // Don't check if the size_policy is ready here.  Let
1852       // the size_policy check that internally.
1853       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1854           AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1855         // Swap the survivor spaces if from_space is empty. The
1856         // resize_young_gen() called below is normally used after
1857         // a successful young GC and swapping of survivor spaces;
1858         // otherwise, it will fail to resize the young gen with
1859         // the current implementation.
1860         if (young_gen->from_space()->is_empty()) {
1861           young_gen->from_space()->clear(SpaceDecorator::Mangle);
1862           young_gen->swap_spaces();
1863         }
1864 
1865         // Calculate optimal free space amounts
1866         assert(young_gen->max_size() >
1867           young_gen->from_space()->capacity_in_bytes() +
1868           young_gen->to_space()->capacity_in_bytes(),
1869           "Sizes of space in young gen are out-of-bounds");
1870 
1871         size_t young_live = young_gen->used_in_bytes();
1872         size_t eden_live = young_gen->eden_space()->used_in_bytes();
1873         size_t old_live = old_gen->used_in_bytes();
1874         size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1875         size_t max_old_gen_size = old_gen->max_gen_size();
1876         size_t max_eden_size = young_gen->max_size() -
1877           young_gen->from_space()->capacity_in_bytes() -
1878           young_gen->to_space()->capacity_in_bytes();
1879 
1880         // Used for diagnostics
1881         size_policy->clear_generation_free_space_flags();
1882 
1883         size_policy->compute_generations_free_space(young_live,
1884                                                     eden_live,
1885                                                     old_live,
1886                                                     cur_eden,
1887                                                     max_old_gen_size,
1888                                                     max_eden_size,
1889                                                     true /* full gc*/);
1890 
1891         size_policy->check_gc_overhead_limit(eden_live,
1892                                              max_old_gen_size,
1893                                              max_eden_size,
1894                                              true /* full gc*/,
1895                                              gc_cause,
1896                                              heap->soft_ref_policy());
1897 
1898         size_policy->decay_supplemental_growth(true /* full gc*/);
1899 
1900         heap->resize_old_gen(
1901           size_policy->calculated_old_free_size_in_bytes());
1902 
1903         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1904                                size_policy->calculated_survivor_size_in_bytes());
1905       }
1906 
1907       log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1908     }
1909 
1910     if (UsePerfData) {
1911       PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1912       counters->update_counters();
1913       counters->update_old_capacity(old_gen->capacity_in_bytes());
1914       counters->update_young_capacity(young_gen->capacity_in_bytes());
1915     }
1916 
1917     heap->resize_all_tlabs();
1918 
1919     // Resize the metaspace capacity after a collection
1920     MetaspaceGC::compute_new_size();
1921 
1922     if (log_is_enabled(Debug, gc, heap, exit)) {
1923       accumulated_time()->stop();
1924     }
1925 
1926     heap->print_heap_change(pre_gc_values);
1927 
1928     // Track memory usage and detect low memory
1929     MemoryService::track_memory_usage();
1930     heap->update_counters();
1931 
1932     heap->post_full_gc_dump(&_gc_timer);
1933   }
1934 
1935 #ifdef ASSERT
1936   for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
1937     ParCompactionManager* const cm =
1938       ParCompactionManager::manager_array(int(i));
1939     assert(cm->marking_stack()->is_empty(),       "should be empty");
1940     assert(cm->region_stack()->is_empty(), "Region stack " SIZE_FORMAT " is not empty", i);
1941   }
1942 #endif // ASSERT
1943 
1944   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1945     HandleMark hm;  // Discard invalid handles created during verification
1946     Universe::verify("After GC");
1947   }
1948 
1949   // Re-verify object start arrays
1950   if (VerifyObjectStartArray &&
1951       VerifyAfterGC) {
1952     old_gen->verify_object_start_array();
1953   }
1954 
1955   if (ZapUnusedHeapArea) {
1956     old_gen->object_space()->check_mangled_unused_area_complete();
1957   }
1958 
1959   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1960 
1961   collection_exit.update();
1962 
1963   heap->print_heap_after_gc();
1964   heap->trace_heap_after_gc(&_gc_tracer);
1965 
1966   log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
1967                          marking_start.ticks(), compaction_start.ticks(),
1968                          collection_exit.ticks());
1969 
1970 #ifdef TRACESPINNING
1971   ParallelTaskTerminator::print_termination_counts();
1972 #endif
1973 
1974   AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
1975 
1976   _gc_timer.register_gc_end();
1977 
1978   _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1979   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1980 
1981   return true;
1982 }
1983 
1984 bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
1985                                              PSYoungGen* young_gen,
1986                                              PSOldGen* old_gen) {
1987   MutableSpace* const eden_space = young_gen->eden_space();
1988   assert(!eden_space->is_empty(), "eden must be non-empty");
1989   assert(young_gen->virtual_space()->alignment() ==
1990          old_gen->virtual_space()->alignment(), "alignments do not match");
1991 
1992   // We also return false when it's a heterogeneous heap because old generation cannot absorb data from eden
1993   // when it is allocated on different memory (example, nv-dimm) than young.
1994   if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary) ||
1995       ParallelArguments::is_heterogeneous_heap()) {
1996     return false;
1997   }
1998 
1999   // Both generations must be completely committed.
2000   if (young_gen->virtual_space()->uncommitted_size() != 0) {
2001     return false;
2002   }
2003   if (old_gen->virtual_space()->uncommitted_size() != 0) {
2004     return false;
2005   }
2006 
2007   // Figure out how much to take from eden.  Include the average amount promoted
2008   // in the total; otherwise the next young gen GC will simply bail out to a
2009   // full GC.
2010   const size_t alignment = old_gen->virtual_space()->alignment();
2011   const size_t eden_used = eden_space->used_in_bytes();
2012   const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
2013   const size_t absorb_size = align_up(eden_used + promoted, alignment);
2014   const size_t eden_capacity = eden_space->capacity_in_bytes();
2015 
2016   if (absorb_size >= eden_capacity) {
2017     return false; // Must leave some space in eden.
2018   }
2019 
2020   const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
2021   if (new_young_size < young_gen->min_gen_size()) {
2022     return false; // Respect young gen minimum size.
2023   }
2024 
2025   log_trace(gc, ergo, heap)(" absorbing " SIZE_FORMAT "K:  "
2026                             "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
2027                             "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
2028                             "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
2029                             absorb_size / K,
2030                             eden_capacity / K, (eden_capacity - absorb_size) / K,
2031                             young_gen->from_space()->used_in_bytes() / K,
2032                             young_gen->to_space()->used_in_bytes() / K,
2033                             young_gen->capacity_in_bytes() / K, new_young_size / K);
2034 
2035   // Fill the unused part of the old gen.
2036   MutableSpace* const old_space = old_gen->object_space();
2037   HeapWord* const unused_start = old_space->top();
2038   size_t const unused_words = pointer_delta(old_space->end(), unused_start);
2039 
2040   if (unused_words > 0) {
2041     if (unused_words < CollectedHeap::min_fill_size()) {
2042       return false;  // If the old gen cannot be filled, must give up.
2043     }
2044     CollectedHeap::fill_with_objects(unused_start, unused_words);
2045   }
2046 
2047   // Take the live data from eden and set both top and end in the old gen to
2048   // eden top.  (Need to set end because reset_after_change() mangles the region
2049   // from end to virtual_space->high() in debug builds).
2050   HeapWord* const new_top = eden_space->top();
2051   old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
2052                                         absorb_size);
2053   young_gen->reset_after_change();
2054   old_space->set_top(new_top);
2055   old_space->set_end(new_top);
2056   old_gen->reset_after_change();
2057 
2058   // Update the object start array for the filler object and the data from eden.
2059   ObjectStartArray* const start_array = old_gen->start_array();
2060   for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
2061     start_array->allocate_block(p);
2062   }
2063 
2064   // Could update the promoted average here, but it is not typically updated at
2065   // full GCs and the value to use is unclear.  Something like
2066   //
2067   // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
2068 
2069   size_policy->set_bytes_absorbed_from_eden(absorb_size);
2070   return true;
2071 }
2072 
2073 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
2074 private:
2075   uint _worker_id;
2076 
2077 public:
2078   PCAddThreadRootsMarkingTaskClosure(uint worker_id) : _worker_id(worker_id) { }
2079   void do_thread(Thread* thread) {
2080     assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2081 
2082     ResourceMark rm;
2083 
2084     ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(_worker_id);
2085 
2086     PCMarkAndPushClosure mark_and_push_closure(cm);
2087     MarkingCodeBlobClosure mark_and_push_in_blobs(&mark_and_push_closure, !CodeBlobToOopClosure::FixRelocations);
2088 
2089     thread->oops_do(&mark_and_push_closure, &mark_and_push_in_blobs);
2090 
2091     // Do the real work
2092     cm->follow_marking_stacks();
2093   }
2094 };
2095 
2096 static void mark_from_roots_work(ParallelRootType::Value root_type, uint worker_id) {
2097   assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2098 
2099   ParCompactionManager* cm =
2100     ParCompactionManager::gc_thread_compaction_manager(worker_id);
2101   PCMarkAndPushClosure mark_and_push_closure(cm);
2102 
2103   switch (root_type) {
2104     case ParallelRootType::universe:
2105       Universe::oops_do(&mark_and_push_closure);
2106       break;
2107 
2108     case ParallelRootType::jni_handles:
2109       JNIHandles::oops_do(&mark_and_push_closure);
2110       break;
2111 
2112     case ParallelRootType::object_synchronizer:
2113       ObjectSynchronizer::oops_do(&mark_and_push_closure);
2114       break;
2115 
2116     case ParallelRootType::management:
2117       Management::oops_do(&mark_and_push_closure);
2118       break;
2119 
2120     case ParallelRootType::jvmti:
2121       JvmtiExport::oops_do(&mark_and_push_closure);
2122       break;
2123 
2124     case ParallelRootType::system_dictionary:
2125       SystemDictionary::oops_do(&mark_and_push_closure);
2126       break;
2127 
2128     case ParallelRootType::class_loader_data:
2129       {
2130         CLDToOopClosure cld_closure(&mark_and_push_closure, ClassLoaderData::_claim_strong);
2131         ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
2132       }
2133       break;
2134 
2135     case ParallelRootType::code_cache:
2136       // Do not treat nmethods as strong roots for mark/sweep, since we can unload them.
2137       //ScavengableNMethods::scavengable_nmethods_do(CodeBlobToOopClosure(&mark_and_push_closure));
2138       AOTLoader::oops_do(&mark_and_push_closure);
2139       break;
2140 
2141     case ParallelRootType::sentinel:
2142     DEBUG_ONLY(default:) // DEBUG_ONLY hack will create compile error on release builds (-Wswitch) and runtime check on debug builds
2143       fatal("Bad enumeration value: %u", root_type);
2144       break;
2145   }
2146 
2147   // Do the real work
2148   cm->follow_marking_stacks();
2149 }
2150 
2151 static void steal_marking_work(ParallelTaskTerminator& terminator, uint worker_id) {
2152   assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2153 
2154   ParCompactionManager* cm =
2155     ParCompactionManager::gc_thread_compaction_manager(worker_id);
2156 
2157   oop obj = NULL;
2158   ObjArrayTask task;
2159   do {
2160     while (ParCompactionManager::steal_objarray(worker_id,  task)) {
2161       cm->follow_array((objArrayOop)task.obj(), task.index());
2162       cm->follow_marking_stacks();
2163     }
2164     while (ParCompactionManager::steal(worker_id, obj)) {
2165       cm->follow_contents(obj);
2166       cm->follow_marking_stacks();
2167     }
2168   } while (!terminator.offer_termination());
2169 }
2170 
2171 class MarkFromRootsTask : public AbstractGangTask {
2172   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2173   StrongRootsScope _strong_roots_scope; // needed for Threads::possibly_parallel_threads_do
2174   SequentialSubTasksDone _subtasks;
2175   TaskTerminator _terminator;
2176   uint _active_workers;
2177 
2178 public:
2179   MarkFromRootsTask(uint active_workers) :
2180       AbstractGangTask("MarkFromRootsTask"),
2181       _strong_roots_scope(active_workers),
2182       _subtasks(),
2183       _terminator(active_workers, ParCompactionManager::stack_array()),
2184       _active_workers(active_workers) {
2185     _subtasks.set_n_threads(active_workers);
2186     _subtasks.set_n_tasks(ParallelRootType::sentinel);
2187   }
2188 
2189   virtual void work(uint worker_id) {
2190     for (uint task = 0; _subtasks.try_claim_task(task); /*empty*/ ) {
2191       mark_from_roots_work(static_cast<ParallelRootType::Value>(task), worker_id);
2192     }
2193     _subtasks.all_tasks_completed();
2194 
2195     PCAddThreadRootsMarkingTaskClosure closure(worker_id);
2196     Threads::possibly_parallel_threads_do(true /*parallel */, &closure);
2197 
2198     if (_active_workers > 1) {
2199       steal_marking_work(*_terminator.terminator(), worker_id);
2200     }
2201   }
2202 };
2203 
2204 class PCRefProcTask : public AbstractGangTask {
2205   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2206   ProcessTask& _task;
2207   uint _ergo_workers;
2208   TaskTerminator _terminator;
2209 
2210 public:
2211   PCRefProcTask(ProcessTask& task, uint ergo_workers) :
2212       AbstractGangTask("PCRefProcTask"),
2213       _task(task),
2214       _ergo_workers(ergo_workers),
2215       _terminator(_ergo_workers, ParCompactionManager::stack_array()) {
2216   }
2217 
2218   virtual void work(uint worker_id) {
2219     ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2220     assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2221 
2222     ParCompactionManager* cm =
2223       ParCompactionManager::gc_thread_compaction_manager(worker_id);
2224     PCMarkAndPushClosure mark_and_push_closure(cm);
2225     ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
2226     _task.work(worker_id, *PSParallelCompact::is_alive_closure(),
2227                mark_and_push_closure, follow_stack_closure);
2228 
2229     steal_marking_work(*_terminator.terminator(), worker_id);
2230   }
2231 };
2232 
2233 class RefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2234   void execute(ProcessTask& process_task, uint ergo_workers) {
2235     assert(ParallelScavengeHeap::heap()->workers().active_workers() == ergo_workers,
2236            "Ergonomically chosen workers (%u) must be equal to active workers (%u)",
2237            ergo_workers, ParallelScavengeHeap::heap()->workers().active_workers());
2238 
2239     PCRefProcTask task(process_task, ergo_workers);
2240     ParallelScavengeHeap::heap()->workers().run_task(&task);
2241   }
2242 };
2243 
2244 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2245                                       bool maximum_heap_compaction,
2246                                       ParallelOldTracer *gc_tracer) {
2247   // Recursively traverse all live objects and mark them
2248   GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
2249 
2250   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2251   uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2252 
2253   PCMarkAndPushClosure mark_and_push_closure(cm);
2254   ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
2255 
2256   // Need new claim bits before marking starts.
2257   ClassLoaderDataGraph::clear_claimed_marks();
2258 
2259   {
2260     GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
2261 
2262     MarkFromRootsTask task(active_gc_threads);
2263     ParallelScavengeHeap::heap()->workers().run_task(&task);
2264   }
2265 
2266   // Process reference objects found during marking
2267   {
2268     GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
2269 
2270     ReferenceProcessorStats stats;
2271     ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
2272 
2273     if (ref_processor()->processing_is_mt()) {
2274       ref_processor()->set_active_mt_degree(active_gc_threads);
2275 
2276       RefProcTaskExecutor task_executor;
2277       stats = ref_processor()->process_discovered_references(
2278         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2279         &task_executor, &pt);
2280     } else {
2281       stats = ref_processor()->process_discovered_references(
2282         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
2283         &pt);
2284     }
2285 
2286     gc_tracer->report_gc_reference_stats(stats);
2287     pt.print_all_references();
2288   }
2289 
2290   // This is the point where the entire marking should have completed.
2291   assert(cm->marking_stacks_empty(), "Marking should have completed");
2292 
2293   {
2294     GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
2295     WeakProcessor::weak_oops_do(is_alive_closure(), &do_nothing_cl);
2296   }
2297 
2298   {
2299     GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
2300 
2301     // Follow system dictionary roots and unload classes.
2302     bool purged_class = SystemDictionary::do_unloading(&_gc_timer);
2303 
2304     // Unload nmethods.
2305     CodeCache::do_unloading(is_alive_closure(), purged_class);
2306 
2307     // Prune dead klasses from subklass/sibling/implementor lists.
2308     Klass::clean_weak_klass_links(purged_class);
2309 
2310     // Clean JVMCI metadata handles.
2311     JVMCI_ONLY(JVMCI::do_unloading(purged_class));
2312   }
2313 
2314   _gc_tracer.report_object_count_after_gc(is_alive_closure());
2315 }
2316 
2317 void PSParallelCompact::adjust_roots(ParCompactionManager* cm) {
2318   // Adjust the pointers to reflect the new locations
2319   GCTraceTime(Info, gc, phases) tm("Adjust Roots", &_gc_timer);
2320 
2321   // Need new claim bits when tracing through and adjusting pointers.
2322   ClassLoaderDataGraph::clear_claimed_marks();
2323 
2324   PCAdjustPointerClosure oop_closure(cm);
2325 
2326   // General strong roots.
2327   Universe::oops_do(&oop_closure);
2328   JNIHandles::oops_do(&oop_closure);   // Global (strong) JNI handles
2329   Threads::oops_do(&oop_closure, NULL);
2330   ObjectSynchronizer::oops_do(&oop_closure);
2331   Management::oops_do(&oop_closure);
2332   JvmtiExport::oops_do(&oop_closure);
2333   SystemDictionary::oops_do(&oop_closure);
2334   CLDToOopClosure cld_closure(&oop_closure, ClassLoaderData::_claim_strong);
2335   ClassLoaderDataGraph::cld_do(&cld_closure);
2336 
2337   // Now adjust pointers in remaining weak roots.  (All of which should
2338   // have been cleared if they pointed to non-surviving objects.)
2339   WeakProcessor::oops_do(&oop_closure);
2340 
2341   CodeBlobToOopClosure adjust_from_blobs(&oop_closure, CodeBlobToOopClosure::FixRelocations);
2342   CodeCache::blobs_do(&adjust_from_blobs);
2343   AOT_ONLY(AOTLoader::oops_do(&oop_closure);)
2344 
2345   ref_processor()->weak_oops_do(&oop_closure);
2346   // Roots were visited so references into the young gen in roots
2347   // may have been scanned.  Process them also.
2348   // Should the reference processor have a span that excludes
2349   // young gen objects?
2350   PSScavenge::reference_processor()->weak_oops_do(&oop_closure);
2351 }
2352 
2353 // Helper class to print 8 region numbers per line and then print the total at the end.
2354 class FillableRegionLogger : public StackObj {
2355 private:
2356   Log(gc, compaction) log;
2357   static const int LineLength = 8;
2358   size_t _regions[LineLength];
2359   int _next_index;
2360   bool _enabled;
2361   size_t _total_regions;
2362 public:
2363   FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
2364   ~FillableRegionLogger() {
2365     log.trace(SIZE_FORMAT " initially fillable regions", _total_regions);
2366   }
2367 
2368   void print_line() {
2369     if (!_enabled || _next_index == 0) {
2370       return;
2371     }
2372     FormatBuffer<> line("Fillable: ");
2373     for (int i = 0; i < _next_index; i++) {
2374       line.append(" " SIZE_FORMAT_W(7), _regions[i]);
2375     }
2376     log.trace("%s", line.buffer());
2377     _next_index = 0;
2378   }
2379 
2380   void handle(size_t region) {
2381     if (!_enabled) {
2382       return;
2383     }
2384     _regions[_next_index++] = region;
2385     if (_next_index == LineLength) {
2386       print_line();
2387     }
2388     _total_regions++;
2389   }
2390 };
2391 
2392 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
2393 {
2394   GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
2395 
2396   // Find the threads that are active
2397   uint worker_id = 0;
2398 
2399   // Find all regions that are available (can be filled immediately) and
2400   // distribute them to the thread stacks.  The iteration is done in reverse
2401   // order (high to low) so the regions will be removed in ascending order.
2402 
2403   const ParallelCompactData& sd = PSParallelCompact::summary_data();
2404 
2405   // id + 1 is used to test termination so unsigned  can
2406   // be used with an old_space_id == 0.
2407   FillableRegionLogger region_logger;
2408   for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2409     SpaceInfo* const space_info = _space_info + id;
2410     MutableSpace* const space = space_info->space();
2411     HeapWord* const new_top = space_info->new_top();
2412 
2413     const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2414     const size_t end_region =
2415       sd.addr_to_region_idx(sd.region_align_up(new_top));
2416 
2417     for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2418       if (sd.region(cur)->claim_unsafe()) {
2419         ParCompactionManager* cm = ParCompactionManager::manager_array(worker_id);
2420         cm->region_stack()->push(cur);
2421         region_logger.handle(cur);
2422         // Assign regions to tasks in round-robin fashion.
2423         if (++worker_id == parallel_gc_threads) {
2424           worker_id = 0;
2425         }
2426       }
2427     }
2428     region_logger.print_line();
2429   }
2430 }
2431 
2432 class TaskQueue : StackObj {
2433   volatile uint _counter;
2434   uint _size;
2435   uint _insert_index;
2436   PSParallelCompact::UpdateDensePrefixTask* _backing_array;
2437 public:
2438   explicit TaskQueue(uint size) : _counter(0), _size(size), _insert_index(0), _backing_array(NULL) {
2439     _backing_array = NEW_C_HEAP_ARRAY(PSParallelCompact::UpdateDensePrefixTask, _size, mtGC);
2440   }
2441   ~TaskQueue() {
2442     assert(_counter >= _insert_index, "not all queue elements were claimed");
2443     FREE_C_HEAP_ARRAY(T, _backing_array);
2444   }
2445 
2446   void push(const PSParallelCompact::UpdateDensePrefixTask& value) {
2447     assert(_insert_index < _size, "too small backing array");
2448     _backing_array[_insert_index++] = value;
2449   }
2450 
2451   bool try_claim(PSParallelCompact::UpdateDensePrefixTask& reference) {
2452     uint claimed = Atomic::add(1u, &_counter) - 1; // -1 is so that we start with zero
2453     if (claimed < _insert_index) {
2454       reference = _backing_array[claimed];
2455       return true;
2456     } else {
2457       return false;
2458     }
2459   }
2460 };
2461 
2462 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2463 
2464 void PSParallelCompact::enqueue_dense_prefix_tasks(TaskQueue& task_queue,
2465                                                    uint parallel_gc_threads) {
2466   GCTraceTime(Trace, gc, phases) tm("Dense Prefix Task Setup", &_gc_timer);
2467 
2468   ParallelCompactData& sd = PSParallelCompact::summary_data();
2469 
2470   // Iterate over all the spaces adding tasks for updating
2471   // regions in the dense prefix.  Assume that 1 gc thread
2472   // will work on opening the gaps and the remaining gc threads
2473   // will work on the dense prefix.
2474   unsigned int space_id;
2475   for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2476     HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2477     const MutableSpace* const space = _space_info[space_id].space();
2478 
2479     if (dense_prefix_end == space->bottom()) {
2480       // There is no dense prefix for this space.
2481       continue;
2482     }
2483 
2484     // The dense prefix is before this region.
2485     size_t region_index_end_dense_prefix =
2486         sd.addr_to_region_idx(dense_prefix_end);
2487     RegionData* const dense_prefix_cp =
2488       sd.region(region_index_end_dense_prefix);
2489     assert(dense_prefix_end == space->end() ||
2490            dense_prefix_cp->available() ||
2491            dense_prefix_cp->claimed(),
2492            "The region after the dense prefix should always be ready to fill");
2493 
2494     size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2495 
2496     // Is there dense prefix work?
2497     size_t total_dense_prefix_regions =
2498       region_index_end_dense_prefix - region_index_start;
2499     // How many regions of the dense prefix should be given to
2500     // each thread?
2501     if (total_dense_prefix_regions > 0) {
2502       uint tasks_for_dense_prefix = 1;
2503       if (total_dense_prefix_regions <=
2504           (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2505         // Don't over partition.  This assumes that
2506         // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2507         // so there are not many regions to process.
2508         tasks_for_dense_prefix = parallel_gc_threads;
2509       } else {
2510         // Over partition
2511         tasks_for_dense_prefix = parallel_gc_threads *
2512           PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2513       }
2514       size_t regions_per_thread = total_dense_prefix_regions /
2515         tasks_for_dense_prefix;
2516       // Give each thread at least 1 region.
2517       if (regions_per_thread == 0) {
2518         regions_per_thread = 1;
2519       }
2520 
2521       for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2522         if (region_index_start >= region_index_end_dense_prefix) {
2523           break;
2524         }
2525         // region_index_end is not processed
2526         size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2527                                        region_index_end_dense_prefix);
2528         task_queue.push(UpdateDensePrefixTask(SpaceId(space_id),
2529                                               region_index_start,
2530                                               region_index_end));
2531         region_index_start = region_index_end;
2532       }
2533     }
2534     // This gets any part of the dense prefix that did not
2535     // fit evenly.
2536     if (region_index_start < region_index_end_dense_prefix) {
2537       task_queue.push(UpdateDensePrefixTask(SpaceId(space_id),
2538                                             region_index_start,
2539                                             region_index_end_dense_prefix));
2540     }
2541   }
2542 }
2543 
2544 #ifdef ASSERT
2545 // Write a histogram of the number of times the block table was filled for a
2546 // region.
2547 void PSParallelCompact::write_block_fill_histogram()
2548 {
2549   if (!log_develop_is_enabled(Trace, gc, compaction)) {
2550     return;
2551   }
2552 
2553   Log(gc, compaction) log;
2554   ResourceMark rm;
2555   LogStream ls(log.trace());
2556   outputStream* out = &ls;
2557 
2558   typedef ParallelCompactData::RegionData rd_t;
2559   ParallelCompactData& sd = summary_data();
2560 
2561   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2562     MutableSpace* const spc = _space_info[id].space();
2563     if (spc->bottom() != spc->top()) {
2564       const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
2565       HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
2566       const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
2567 
2568       size_t histo[5] = { 0, 0, 0, 0, 0 };
2569       const size_t histo_len = sizeof(histo) / sizeof(size_t);
2570       const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
2571 
2572       for (const rd_t* cur = beg; cur < end; ++cur) {
2573         ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
2574       }
2575       out->print("Block fill histogram: %u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
2576       for (size_t i = 0; i < histo_len; ++i) {
2577         out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
2578                    histo[i], 100.0 * histo[i] / region_cnt);
2579       }
2580       out->cr();
2581     }
2582   }
2583 }
2584 #endif // #ifdef ASSERT
2585 
2586 static void compaction_with_stealing_work(ParallelTaskTerminator* terminator, uint worker_id) {
2587   assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2588 
2589   ParCompactionManager* cm =
2590     ParCompactionManager::gc_thread_compaction_manager(worker_id);
2591 
2592   // Drain the stacks that have been preloaded with regions
2593   // that are ready to fill.
2594 
2595   cm->drain_region_stacks();
2596 
2597   guarantee(cm->region_stack()->is_empty(), "Not empty");
2598 
2599   size_t region_index = 0;
2600 
2601   while (true) {
2602     if (ParCompactionManager::steal(worker_id, region_index)) {
2603       PSParallelCompact::fill_and_update_region(cm, region_index);
2604       cm->drain_region_stacks();
2605     } else {
2606       if (terminator->offer_termination()) {
2607         break;
2608       }
2609       // Go around again.
2610     }
2611   }
2612   return;
2613 }
2614 
2615 class UpdateDensePrefixAndCompactionTask: public AbstractGangTask {
2616   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2617   TaskQueue& _tq;
2618   TaskTerminator _terminator;
2619   uint _active_workers;
2620 
2621 public:
2622   UpdateDensePrefixAndCompactionTask(TaskQueue& tq, uint active_workers) :
2623       AbstractGangTask("UpdateDensePrefixAndCompactionTask"),
2624       _tq(tq),
2625       _terminator(active_workers, ParCompactionManager::region_array()),
2626       _active_workers(active_workers) {
2627   }
2628   virtual void work(uint worker_id) {
2629     ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
2630 
2631     for (PSParallelCompact::UpdateDensePrefixTask task; _tq.try_claim(task); /* empty */) {
2632       PSParallelCompact::update_and_deadwood_in_dense_prefix(cm,
2633                                                              task._space_id,
2634                                                              task._region_index_start,
2635                                                              task._region_index_end);
2636     }
2637 
2638     // Once a thread has drained it's stack, it should try to steal regions from
2639     // other threads.
2640     compaction_with_stealing_work(_terminator.terminator(), worker_id);
2641   }
2642 };
2643 
2644 void PSParallelCompact::compact() {
2645   GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
2646 
2647   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2648   PSOldGen* old_gen = heap->old_gen();
2649   old_gen->start_array()->reset();
2650   uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2651 
2652   // for [0..last_space_id)
2653   //     for [0..active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)
2654   //         push
2655   //     push
2656   //
2657   // max push count is thus: last_space_id * (active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING + 1)
2658   TaskQueue task_queue(last_space_id * (active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING + 1));
2659   prepare_region_draining_tasks(active_gc_threads);
2660   enqueue_dense_prefix_tasks(task_queue, active_gc_threads);
2661 
2662   {
2663     GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
2664 
2665     UpdateDensePrefixAndCompactionTask task(task_queue, active_gc_threads);
2666     ParallelScavengeHeap::heap()->workers().run_task(&task);
2667 
2668 #ifdef  ASSERT
2669     // Verify that all regions have been processed before the deferred updates.
2670     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2671       verify_complete(SpaceId(id));
2672     }
2673 #endif
2674   }
2675 
2676   {
2677     // Update the deferred objects, if any.  Any compaction manager can be used.
2678     GCTraceTime(Trace, gc, phases) tm("Deferred Updates", &_gc_timer);
2679     ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2680     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2681       update_deferred_objects(cm, SpaceId(id));
2682     }
2683   }
2684 
2685   DEBUG_ONLY(write_block_fill_histogram());
2686 }
2687 
2688 #ifdef  ASSERT
2689 void PSParallelCompact::verify_complete(SpaceId space_id) {
2690   // All Regions between space bottom() to new_top() should be marked as filled
2691   // and all Regions between new_top() and top() should be available (i.e.,
2692   // should have been emptied).
2693   ParallelCompactData& sd = summary_data();
2694   SpaceInfo si = _space_info[space_id];
2695   HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2696   HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2697   const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2698   const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2699   const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2700 
2701   bool issued_a_warning = false;
2702 
2703   size_t cur_region;
2704   for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2705     const RegionData* const c = sd.region(cur_region);
2706     if (!c->completed()) {
2707       log_warning(gc)("region " SIZE_FORMAT " not filled: destination_count=%u",
2708                       cur_region, c->destination_count());
2709       issued_a_warning = true;
2710     }
2711   }
2712 
2713   for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2714     const RegionData* const c = sd.region(cur_region);
2715     if (!c->available()) {
2716       log_warning(gc)("region " SIZE_FORMAT " not empty: destination_count=%u",
2717                       cur_region, c->destination_count());
2718       issued_a_warning = true;
2719     }
2720   }
2721 
2722   if (issued_a_warning) {
2723     print_region_ranges();
2724   }
2725 }
2726 #endif  // #ifdef ASSERT
2727 
2728 inline void UpdateOnlyClosure::do_addr(HeapWord* addr) {
2729   _start_array->allocate_block(addr);
2730   compaction_manager()->update_contents(oop(addr));
2731 }
2732 
2733 // Update interior oops in the ranges of regions [beg_region, end_region).
2734 void
2735 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2736                                                        SpaceId space_id,
2737                                                        size_t beg_region,
2738                                                        size_t end_region) {
2739   ParallelCompactData& sd = summary_data();
2740   ParMarkBitMap* const mbm = mark_bitmap();
2741 
2742   HeapWord* beg_addr = sd.region_to_addr(beg_region);
2743   HeapWord* const end_addr = sd.region_to_addr(end_region);
2744   assert(beg_region <= end_region, "bad region range");
2745   assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2746 
2747 #ifdef  ASSERT
2748   // Claim the regions to avoid triggering an assert when they are marked as
2749   // filled.
2750   for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2751     assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2752   }
2753 #endif  // #ifdef ASSERT
2754 
2755   if (beg_addr != space(space_id)->bottom()) {
2756     // Find the first live object or block of dead space that *starts* in this
2757     // range of regions.  If a partial object crosses onto the region, skip it;
2758     // it will be marked for 'deferred update' when the object head is
2759     // processed.  If dead space crosses onto the region, it is also skipped; it
2760     // will be filled when the prior region is processed.  If neither of those
2761     // apply, the first word in the region is the start of a live object or dead
2762     // space.
2763     assert(beg_addr > space(space_id)->bottom(), "sanity");
2764     const RegionData* const cp = sd.region(beg_region);
2765     if (cp->partial_obj_size() != 0) {
2766       beg_addr = sd.partial_obj_end(beg_region);
2767     } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2768       beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2769     }
2770   }
2771 
2772   if (beg_addr < end_addr) {
2773     // A live object or block of dead space starts in this range of Regions.
2774      HeapWord* const dense_prefix_end = dense_prefix(space_id);
2775 
2776     // Create closures and iterate.
2777     UpdateOnlyClosure update_closure(mbm, cm, space_id);
2778     FillClosure fill_closure(cm, space_id);
2779     ParMarkBitMap::IterationStatus status;
2780     status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2781                           dense_prefix_end);
2782     if (status == ParMarkBitMap::incomplete) {
2783       update_closure.do_addr(update_closure.source());
2784     }
2785   }
2786 
2787   // Mark the regions as filled.
2788   RegionData* const beg_cp = sd.region(beg_region);
2789   RegionData* const end_cp = sd.region(end_region);
2790   for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2791     cp->set_completed();
2792   }
2793 }
2794 
2795 // Return the SpaceId for the space containing addr.  If addr is not in the
2796 // heap, last_space_id is returned.  In debug mode it expects the address to be
2797 // in the heap and asserts such.
2798 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2799   assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
2800 
2801   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2802     if (_space_info[id].space()->contains(addr)) {
2803       return SpaceId(id);
2804     }
2805   }
2806 
2807   assert(false, "no space contains the addr");
2808   return last_space_id;
2809 }
2810 
2811 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2812                                                 SpaceId id) {
2813   assert(id < last_space_id, "bad space id");
2814 
2815   ParallelCompactData& sd = summary_data();
2816   const SpaceInfo* const space_info = _space_info + id;
2817   ObjectStartArray* const start_array = space_info->start_array();
2818 
2819   const MutableSpace* const space = space_info->space();
2820   assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2821   HeapWord* const beg_addr = space_info->dense_prefix();
2822   HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2823 
2824   const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2825   const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2826   const RegionData* cur_region;
2827   for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2828     HeapWord* const addr = cur_region->deferred_obj_addr();
2829     if (addr != NULL) {
2830       if (start_array != NULL) {
2831         start_array->allocate_block(addr);
2832       }
2833       cm->update_contents(oop(addr));
2834       assert(oopDesc::is_oop_or_null(oop(addr)), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(addr)));
2835     }
2836   }
2837 }
2838 
2839 // Skip over count live words starting from beg, and return the address of the
2840 // next live word.  Unless marked, the word corresponding to beg is assumed to
2841 // be dead.  Callers must either ensure beg does not correspond to the middle of
2842 // an object, or account for those live words in some other way.  Callers must
2843 // also ensure that there are enough live words in the range [beg, end) to skip.
2844 HeapWord*
2845 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2846 {
2847   assert(count > 0, "sanity");
2848 
2849   ParMarkBitMap* m = mark_bitmap();
2850   idx_t bits_to_skip = m->words_to_bits(count);
2851   idx_t cur_beg = m->addr_to_bit(beg);
2852   const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end));
2853 
2854   do {
2855     cur_beg = m->find_obj_beg(cur_beg, search_end);
2856     idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2857     const size_t obj_bits = cur_end - cur_beg + 1;
2858     if (obj_bits > bits_to_skip) {
2859       return m->bit_to_addr(cur_beg + bits_to_skip);
2860     }
2861     bits_to_skip -= obj_bits;
2862     cur_beg = cur_end + 1;
2863   } while (bits_to_skip > 0);
2864 
2865   // Skipping the desired number of words landed just past the end of an object.
2866   // Find the start of the next object.
2867   cur_beg = m->find_obj_beg(cur_beg, search_end);
2868   assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2869   return m->bit_to_addr(cur_beg);
2870 }
2871 
2872 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2873                                             SpaceId src_space_id,
2874                                             size_t src_region_idx)
2875 {
2876   assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2877 
2878   const SplitInfo& split_info = _space_info[src_space_id].split_info();
2879   if (split_info.dest_region_addr() == dest_addr) {
2880     // The partial object ending at the split point contains the first word to
2881     // be copied to dest_addr.
2882     return split_info.first_src_addr();
2883   }
2884 
2885   const ParallelCompactData& sd = summary_data();
2886   ParMarkBitMap* const bitmap = mark_bitmap();
2887   const size_t RegionSize = ParallelCompactData::RegionSize;
2888 
2889   assert(sd.is_region_aligned(dest_addr), "not aligned");
2890   const RegionData* const src_region_ptr = sd.region(src_region_idx);
2891   const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2892   HeapWord* const src_region_destination = src_region_ptr->destination();
2893 
2894   assert(dest_addr >= src_region_destination, "wrong src region");
2895   assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2896 
2897   HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2898   HeapWord* const src_region_end = src_region_beg + RegionSize;
2899 
2900   HeapWord* addr = src_region_beg;
2901   if (dest_addr == src_region_destination) {
2902     // Return the first live word in the source region.
2903     if (partial_obj_size == 0) {
2904       addr = bitmap->find_obj_beg(addr, src_region_end);
2905       assert(addr < src_region_end, "no objects start in src region");
2906     }
2907     return addr;
2908   }
2909 
2910   // Must skip some live data.
2911   size_t words_to_skip = dest_addr - src_region_destination;
2912   assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2913 
2914   if (partial_obj_size >= words_to_skip) {
2915     // All the live words to skip are part of the partial object.
2916     addr += words_to_skip;
2917     if (partial_obj_size == words_to_skip) {
2918       // Find the first live word past the partial object.
2919       addr = bitmap->find_obj_beg(addr, src_region_end);
2920       assert(addr < src_region_end, "wrong src region");
2921     }
2922     return addr;
2923   }
2924 
2925   // Skip over the partial object (if any).
2926   if (partial_obj_size != 0) {
2927     words_to_skip -= partial_obj_size;
2928     addr += partial_obj_size;
2929   }
2930 
2931   // Skip over live words due to objects that start in the region.
2932   addr = skip_live_words(addr, src_region_end, words_to_skip);
2933   assert(addr < src_region_end, "wrong src region");
2934   return addr;
2935 }
2936 
2937 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2938                                                      SpaceId src_space_id,
2939                                                      size_t beg_region,
2940                                                      HeapWord* end_addr)
2941 {
2942   ParallelCompactData& sd = summary_data();
2943 
2944 #ifdef ASSERT
2945   MutableSpace* const src_space = _space_info[src_space_id].space();
2946   HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2947   assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2948          "src_space_id does not match beg_addr");
2949   assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2950          "src_space_id does not match end_addr");
2951 #endif // #ifdef ASSERT
2952 
2953   RegionData* const beg = sd.region(beg_region);
2954   RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2955 
2956   // Regions up to new_top() are enqueued if they become available.
2957   HeapWord* const new_top = _space_info[src_space_id].new_top();
2958   RegionData* const enqueue_end =
2959     sd.addr_to_region_ptr(sd.region_align_up(new_top));
2960 
2961   for (RegionData* cur = beg; cur < end; ++cur) {
2962     assert(cur->data_size() > 0, "region must have live data");
2963     cur->decrement_destination_count();
2964     if (cur < enqueue_end && cur->available() && cur->claim()) {
2965       cm->push_region(sd.region(cur));
2966     }
2967   }
2968 }
2969 
2970 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2971                                           SpaceId& src_space_id,
2972                                           HeapWord*& src_space_top,
2973                                           HeapWord* end_addr)
2974 {
2975   typedef ParallelCompactData::RegionData RegionData;
2976 
2977   ParallelCompactData& sd = PSParallelCompact::summary_data();
2978   const size_t region_size = ParallelCompactData::RegionSize;
2979 
2980   size_t src_region_idx = 0;
2981 
2982   // Skip empty regions (if any) up to the top of the space.
2983   HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2984   RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2985   HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2986   const RegionData* const top_region_ptr =
2987     sd.addr_to_region_ptr(top_aligned_up);
2988   while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2989     ++src_region_ptr;
2990   }
2991 
2992   if (src_region_ptr < top_region_ptr) {
2993     // The next source region is in the current space.  Update src_region_idx
2994     // and the source address to match src_region_ptr.
2995     src_region_idx = sd.region(src_region_ptr);
2996     HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
2997     if (src_region_addr > closure.source()) {
2998       closure.set_source(src_region_addr);
2999     }
3000     return src_region_idx;
3001   }
3002 
3003   // Switch to a new source space and find the first non-empty region.
3004   unsigned int space_id = src_space_id + 1;
3005   assert(space_id < last_space_id, "not enough spaces");
3006 
3007   HeapWord* const destination = closure.destination();
3008 
3009   do {
3010     MutableSpace* space = _space_info[space_id].space();
3011     HeapWord* const bottom = space->bottom();
3012     const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
3013 
3014     // Iterate over the spaces that do not compact into themselves.
3015     if (bottom_cp->destination() != bottom) {
3016       HeapWord* const top_aligned_up = sd.region_align_up(space->top());
3017       const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
3018 
3019       for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
3020         if (src_cp->live_obj_size() > 0) {
3021           // Found it.
3022           assert(src_cp->destination() == destination,
3023                  "first live obj in the space must match the destination");
3024           assert(src_cp->partial_obj_size() == 0,
3025                  "a space cannot begin with a partial obj");
3026 
3027           src_space_id = SpaceId(space_id);
3028           src_space_top = space->top();
3029           const size_t src_region_idx = sd.region(src_cp);
3030           closure.set_source(sd.region_to_addr(src_region_idx));
3031           return src_region_idx;
3032         } else {
3033           assert(src_cp->data_size() == 0, "sanity");
3034         }
3035       }
3036     }
3037   } while (++space_id < last_space_id);
3038 
3039   assert(false, "no source region was found");
3040   return 0;
3041 }
3042 
3043 void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx)
3044 {
3045   typedef ParMarkBitMap::IterationStatus IterationStatus;
3046   const size_t RegionSize = ParallelCompactData::RegionSize;
3047   ParMarkBitMap* const bitmap = mark_bitmap();
3048   ParallelCompactData& sd = summary_data();
3049   RegionData* const region_ptr = sd.region(region_idx);
3050 
3051   // Get the items needed to construct the closure.
3052   HeapWord* dest_addr = sd.region_to_addr(region_idx);
3053   SpaceId dest_space_id = space_id(dest_addr);
3054   ObjectStartArray* start_array = _space_info[dest_space_id].start_array();
3055   HeapWord* new_top = _space_info[dest_space_id].new_top();
3056   assert(dest_addr < new_top, "sanity");
3057   const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize);
3058 
3059   // Get the source region and related info.
3060   size_t src_region_idx = region_ptr->source_region();
3061   SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
3062   HeapWord* src_space_top = _space_info[src_space_id].space()->top();
3063 
3064   MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3065   closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
3066 
3067   // Adjust src_region_idx to prepare for decrementing destination counts (the
3068   // destination count is not decremented when a region is copied to itself).
3069   if (src_region_idx == region_idx) {
3070     src_region_idx += 1;
3071   }
3072 
3073   if (bitmap->is_unmarked(closure.source())) {
3074     // The first source word is in the middle of an object; copy the remainder
3075     // of the object or as much as will fit.  The fact that pointer updates were
3076     // deferred will be noted when the object header is processed.
3077     HeapWord* const old_src_addr = closure.source();
3078     closure.copy_partial_obj();
3079     if (closure.is_full()) {
3080       decrement_destination_counts(cm, src_space_id, src_region_idx,
3081                                    closure.source());
3082       region_ptr->set_deferred_obj_addr(NULL);
3083       region_ptr->set_completed();
3084       return;
3085     }
3086 
3087     HeapWord* const end_addr = sd.region_align_down(closure.source());
3088     if (sd.region_align_down(old_src_addr) != end_addr) {
3089       // The partial object was copied from more than one source region.
3090       decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3091 
3092       // Move to the next source region, possibly switching spaces as well.  All
3093       // args except end_addr may be modified.
3094       src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3095                                        end_addr);
3096     }
3097   }
3098 
3099   do {
3100     HeapWord* const cur_addr = closure.source();
3101     HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
3102                                     src_space_top);
3103     IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
3104 
3105     if (status == ParMarkBitMap::incomplete) {
3106       // The last obj that starts in the source region does not end in the
3107       // region.
3108       assert(closure.source() < end_addr, "sanity");
3109       HeapWord* const obj_beg = closure.source();
3110       HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
3111                                        src_space_top);
3112       HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
3113       if (obj_end < range_end) {
3114         // The end was found; the entire object will fit.
3115         status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
3116         assert(status != ParMarkBitMap::would_overflow, "sanity");
3117       } else {
3118         // The end was not found; the object will not fit.
3119         assert(range_end < src_space_top, "obj cannot cross space boundary");
3120         status = ParMarkBitMap::would_overflow;
3121       }
3122     }
3123 
3124     if (status == ParMarkBitMap::would_overflow) {
3125       // The last object did not fit.  Note that interior oop updates were
3126       // deferred, then copy enough of the object to fill the region.
3127       region_ptr->set_deferred_obj_addr(closure.destination());
3128       status = closure.copy_until_full(); // copies from closure.source()
3129 
3130       decrement_destination_counts(cm, src_space_id, src_region_idx,
3131                                    closure.source());
3132       region_ptr->set_completed();
3133       return;
3134     }
3135 
3136     if (status == ParMarkBitMap::full) {
3137       decrement_destination_counts(cm, src_space_id, src_region_idx,
3138                                    closure.source());
3139       region_ptr->set_deferred_obj_addr(NULL);
3140       region_ptr->set_completed();
3141       return;
3142     }
3143 
3144     decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3145 
3146     // Move to the next source region, possibly switching spaces as well.  All
3147     // args except end_addr may be modified.
3148     src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3149                                      end_addr);
3150   } while (true);
3151 }
3152 
3153 void PSParallelCompact::fill_blocks(size_t region_idx)
3154 {
3155   // Fill in the block table elements for the specified region.  Each block
3156   // table element holds the number of live words in the region that are to the
3157   // left of the first object that starts in the block.  Thus only blocks in
3158   // which an object starts need to be filled.
3159   //
3160   // The algorithm scans the section of the bitmap that corresponds to the
3161   // region, keeping a running total of the live words.  When an object start is
3162   // found, if it's the first to start in the block that contains it, the
3163   // current total is written to the block table element.
3164   const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
3165   const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
3166   const size_t RegionSize = ParallelCompactData::RegionSize;
3167 
3168   ParallelCompactData& sd = summary_data();
3169   const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
3170   if (partial_obj_size >= RegionSize) {
3171     return; // No objects start in this region.
3172   }
3173 
3174   // Ensure the first loop iteration decides that the block has changed.
3175   size_t cur_block = sd.block_count();
3176 
3177   const ParMarkBitMap* const bitmap = mark_bitmap();
3178 
3179   const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
3180   assert((size_t)1 << Log2BitsPerBlock ==
3181          bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
3182 
3183   size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
3184   const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
3185   size_t live_bits = bitmap->words_to_bits(partial_obj_size);
3186   beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
3187   while (beg_bit < range_end) {
3188     const size_t new_block = beg_bit >> Log2BitsPerBlock;
3189     if (new_block != cur_block) {
3190       cur_block = new_block;
3191       sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
3192     }
3193 
3194     const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
3195     if (end_bit < range_end - 1) {
3196       live_bits += end_bit - beg_bit + 1;
3197       beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
3198     } else {
3199       return;
3200     }
3201   }
3202 }
3203 
3204 jlong PSParallelCompact::millis_since_last_gc() {
3205   // We need a monotonically non-decreasing time in ms but
3206   // os::javaTimeMillis() does not guarantee monotonicity.
3207   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3208   jlong ret_val = now - _time_of_last_gc;
3209   // XXX See note in genCollectedHeap::millis_since_last_gc().
3210   if (ret_val < 0) {
3211     NOT_PRODUCT(log_warning(gc)("time warp: " JLONG_FORMAT, ret_val);)
3212     return 0;
3213   }
3214   return ret_val;
3215 }
3216 
3217 void PSParallelCompact::reset_millis_since_last_gc() {
3218   // We need a monotonically non-decreasing time in ms but
3219   // os::javaTimeMillis() does not guarantee monotonicity.
3220   _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3221 }
3222 
3223 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3224 {
3225   if (source() != destination()) {
3226     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3227     Copy::aligned_conjoint_words(source(), destination(), words_remaining());
3228   }
3229   update_state(words_remaining());
3230   assert(is_full(), "sanity");
3231   return ParMarkBitMap::full;
3232 }
3233 
3234 void MoveAndUpdateClosure::copy_partial_obj()
3235 {
3236   size_t words = words_remaining();
3237 
3238   HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3239   HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3240   if (end_addr < range_end) {
3241     words = bitmap()->obj_size(source(), end_addr);
3242   }
3243 
3244   // This test is necessary; if omitted, the pointer updates to a partial object
3245   // that crosses the dense prefix boundary could be overwritten.
3246   if (source() != destination()) {
3247     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3248     Copy::aligned_conjoint_words(source(), destination(), words);
3249   }
3250   update_state(words);
3251 }
3252 
3253 ParMarkBitMapClosure::IterationStatus
3254 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3255   assert(destination() != NULL, "sanity");
3256   assert(bitmap()->obj_size(addr) == words, "bad size");
3257 
3258   _source = addr;
3259   assert(PSParallelCompact::summary_data().calc_new_pointer(source(), compaction_manager()) ==
3260          destination(), "wrong destination");
3261 
3262   if (words > words_remaining()) {
3263     return ParMarkBitMap::would_overflow;
3264   }
3265 
3266   // The start_array must be updated even if the object is not moving.
3267   if (_start_array != NULL) {
3268     _start_array->allocate_block(destination());
3269   }
3270 
3271   if (destination() != source()) {
3272     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3273     Copy::aligned_conjoint_words(source(), destination(), words);
3274   }
3275 
3276   oop moved_oop = (oop) destination();
3277   compaction_manager()->update_contents(moved_oop);
3278   assert(oopDesc::is_oop_or_null(moved_oop), "Expected an oop or NULL at " PTR_FORMAT, p2i(moved_oop));
3279 
3280   update_state(words);
3281   assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
3282   return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3283 }
3284 
3285 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3286                                      ParCompactionManager* cm,
3287                                      PSParallelCompact::SpaceId space_id) :
3288   ParMarkBitMapClosure(mbm, cm),
3289   _space_id(space_id),
3290   _start_array(PSParallelCompact::start_array(space_id))
3291 {
3292 }
3293 
3294 // Updates the references in the object to their new values.
3295 ParMarkBitMapClosure::IterationStatus
3296 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3297   do_addr(addr);
3298   return ParMarkBitMap::incomplete;
3299 }
3300 
3301 FillClosure::FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id) :
3302   ParMarkBitMapClosure(PSParallelCompact::mark_bitmap(), cm),
3303   _start_array(PSParallelCompact::start_array(space_id))
3304 {
3305   assert(space_id == PSParallelCompact::old_space_id,
3306          "cannot use FillClosure in the young gen");
3307 }
3308 
3309 ParMarkBitMapClosure::IterationStatus
3310 FillClosure::do_addr(HeapWord* addr, size_t size) {
3311   CollectedHeap::fill_with_objects(addr, size);
3312   HeapWord* const end = addr + size;
3313   do {
3314     _start_array->allocate_block(addr);
3315     addr += oop(addr)->size();
3316   } while (addr < end);
3317   return ParMarkBitMap::incomplete;
3318 }