rev 57223 : [mq]: shadow-region-final2-fixes

   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.inline.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(&add_obj_size, len);)
 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 = _mark_bitmap.align_range_end(_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   ParCompactionManager::remove_all_shadow_regions();
1027 
1028   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1029     // Clear the marking bitmap, summary data and split info.
1030     clear_data_covering_space(SpaceId(id));
1031     // Update top().  Must be done after clearing the bitmap and summary data.
1032     _space_info[id].publish_new_top();
1033   }
1034 
1035   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1036   MutableSpace* const from_space = _space_info[from_space_id].space();
1037   MutableSpace* const to_space   = _space_info[to_space_id].space();
1038 
1039   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1040   bool eden_empty = eden_space->is_empty();
1041   if (!eden_empty) {
1042     eden_empty = absorb_live_data_from_eden(heap->size_policy(),
1043                                             heap->young_gen(), heap->old_gen());
1044   }
1045 
1046   // Update heap occupancy information which is used as input to the soft ref
1047   // clearing policy at the next gc.
1048   Universe::update_heap_info_at_gc();
1049 
1050   bool young_gen_empty = eden_empty && from_space->is_empty() &&
1051     to_space->is_empty();
1052 
1053   PSCardTable* ct = heap->card_table();
1054   MemRegion old_mr = heap->old_gen()->reserved();
1055   if (young_gen_empty) {
1056     ct->clear(MemRegion(old_mr.start(), old_mr.end()));
1057   } else {
1058     ct->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1059   }
1060 
1061   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1062   ClassLoaderDataGraph::purge();
1063   MetaspaceUtils::verify_metrics();
1064 
1065   heap->prune_scavengable_nmethods();
1066 
1067 #if COMPILER2_OR_JVMCI
1068   DerivedPointerTable::update_pointers();
1069 #endif
1070 
1071   if (ZapUnusedHeapArea) {
1072     heap->gen_mangle_unused_area();
1073   }
1074 
1075   // Update time of last GC
1076   reset_millis_since_last_gc();
1077 }
1078 
1079 HeapWord*
1080 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1081                                                     bool maximum_compaction)
1082 {
1083   const size_t region_size = ParallelCompactData::RegionSize;
1084   const ParallelCompactData& sd = summary_data();
1085 
1086   const MutableSpace* const space = _space_info[id].space();
1087   HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1088   const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1089   const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1090 
1091   // Skip full regions at the beginning of the space--they are necessarily part
1092   // of the dense prefix.
1093   size_t full_count = 0;
1094   const RegionData* cp;
1095   for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1096     ++full_count;
1097   }
1098 
1099   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1100   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1101   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1102   if (maximum_compaction || cp == end_cp || interval_ended) {
1103     _maximum_compaction_gc_num = total_invocations();
1104     return sd.region_to_addr(cp);
1105   }
1106 
1107   HeapWord* const new_top = _space_info[id].new_top();
1108   const size_t space_live = pointer_delta(new_top, space->bottom());
1109   const size_t space_used = space->used_in_words();
1110   const size_t space_capacity = space->capacity_in_words();
1111 
1112   const double cur_density = double(space_live) / space_capacity;
1113   const double deadwood_density =
1114     (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1115   const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1116 
1117   if (TraceParallelOldGCDensePrefix) {
1118     tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1119                   cur_density, deadwood_density, deadwood_goal);
1120     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1121                   "space_cap=" SIZE_FORMAT,
1122                   space_live, space_used,
1123                   space_capacity);
1124   }
1125 
1126   // XXX - Use binary search?
1127   HeapWord* dense_prefix = sd.region_to_addr(cp);
1128   const RegionData* full_cp = cp;
1129   const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1130   while (cp < end_cp) {
1131     HeapWord* region_destination = cp->destination();
1132     const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1133     if (TraceParallelOldGCDensePrefix && Verbose) {
1134       tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1135                     "dp=" PTR_FORMAT " " "cdw=" SIZE_FORMAT_W(8),
1136                     sd.region(cp), p2i(region_destination),
1137                     p2i(dense_prefix), cur_deadwood);
1138     }
1139 
1140     if (cur_deadwood >= deadwood_goal) {
1141       // Found the region that has the correct amount of deadwood to the left.
1142       // This typically occurs after crossing a fairly sparse set of regions, so
1143       // iterate backwards over those sparse regions, looking for the region
1144       // that has the lowest density of live objects 'to the right.'
1145       size_t space_to_left = sd.region(cp) * region_size;
1146       size_t live_to_left = space_to_left - cur_deadwood;
1147       size_t space_to_right = space_capacity - space_to_left;
1148       size_t live_to_right = space_live - live_to_left;
1149       double density_to_right = double(live_to_right) / space_to_right;
1150       while (cp > full_cp) {
1151         --cp;
1152         const size_t prev_region_live_to_right = live_to_right -
1153           cp->data_size();
1154         const size_t prev_region_space_to_right = space_to_right + region_size;
1155         double prev_region_density_to_right =
1156           double(prev_region_live_to_right) / prev_region_space_to_right;
1157         if (density_to_right <= prev_region_density_to_right) {
1158           return dense_prefix;
1159         }
1160         if (TraceParallelOldGCDensePrefix && Verbose) {
1161           tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1162                         "pc_d2r=%10.8f", sd.region(cp), density_to_right,
1163                         prev_region_density_to_right);
1164         }
1165         dense_prefix -= region_size;
1166         live_to_right = prev_region_live_to_right;
1167         space_to_right = prev_region_space_to_right;
1168         density_to_right = prev_region_density_to_right;
1169       }
1170       return dense_prefix;
1171     }
1172 
1173     dense_prefix += region_size;
1174     ++cp;
1175   }
1176 
1177   return dense_prefix;
1178 }
1179 
1180 #ifndef PRODUCT
1181 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1182                                                  const SpaceId id,
1183                                                  const bool maximum_compaction,
1184                                                  HeapWord* const addr)
1185 {
1186   const size_t region_idx = summary_data().addr_to_region_idx(addr);
1187   RegionData* const cp = summary_data().region(region_idx);
1188   const MutableSpace* const space = _space_info[id].space();
1189   HeapWord* const new_top = _space_info[id].new_top();
1190 
1191   const size_t space_live = pointer_delta(new_top, space->bottom());
1192   const size_t dead_to_left = pointer_delta(addr, cp->destination());
1193   const size_t space_cap = space->capacity_in_words();
1194   const double dead_to_left_pct = double(dead_to_left) / space_cap;
1195   const size_t live_to_right = new_top - cp->destination();
1196   const size_t dead_to_right = space->top() - addr - live_to_right;
1197 
1198   tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1199                 "spl=" SIZE_FORMAT " "
1200                 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1201                 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
1202                 " ratio=%10.8f",
1203                 algorithm, p2i(addr), region_idx,
1204                 space_live,
1205                 dead_to_left, dead_to_left_pct,
1206                 dead_to_right, live_to_right,
1207                 double(dead_to_right) / live_to_right);
1208 }
1209 #endif  // #ifndef PRODUCT
1210 
1211 // Return a fraction indicating how much of the generation can be treated as
1212 // "dead wood" (i.e., not reclaimed).  The function uses a normal distribution
1213 // based on the density of live objects in the generation to determine a limit,
1214 // which is then adjusted so the return value is min_percent when the density is
1215 // 1.
1216 //
1217 // The following table shows some return values for a different values of the
1218 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1219 // min_percent is 1.
1220 //
1221 //                          fraction allowed as dead wood
1222 //         -----------------------------------------------------------------
1223 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1224 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1225 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1226 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1227 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1228 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1229 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1230 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1231 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1232 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1233 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1234 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1235 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1236 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1237 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1238 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1239 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1240 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1241 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1242 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1243 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1244 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1245 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1246 
1247 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1248 {
1249   assert(_dwl_initialized, "uninitialized");
1250 
1251   // The raw limit is the value of the normal distribution at x = density.
1252   const double raw_limit = normal_distribution(density);
1253 
1254   // Adjust the raw limit so it becomes the minimum when the density is 1.
1255   //
1256   // First subtract the adjustment value (which is simply the precomputed value
1257   // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1258   // Then add the minimum value, so the minimum is returned when the density is
1259   // 1.  Finally, prevent negative values, which occur when the mean is not 0.5.
1260   const double min = double(min_percent) / 100.0;
1261   const double limit = raw_limit - _dwl_adjustment + min;
1262   return MAX2(limit, 0.0);
1263 }
1264 
1265 ParallelCompactData::RegionData*
1266 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1267                                            const RegionData* end)
1268 {
1269   const size_t region_size = ParallelCompactData::RegionSize;
1270   ParallelCompactData& sd = summary_data();
1271   size_t left = sd.region(beg);
1272   size_t right = end > beg ? sd.region(end) - 1 : left;
1273 
1274   // Binary search.
1275   while (left < right) {
1276     // Equivalent to (left + right) / 2, but does not overflow.
1277     const size_t middle = left + (right - left) / 2;
1278     RegionData* const middle_ptr = sd.region(middle);
1279     HeapWord* const dest = middle_ptr->destination();
1280     HeapWord* const addr = sd.region_to_addr(middle);
1281     assert(dest != NULL, "sanity");
1282     assert(dest <= addr, "must move left");
1283 
1284     if (middle > left && dest < addr) {
1285       right = middle - 1;
1286     } else if (middle < right && middle_ptr->data_size() == region_size) {
1287       left = middle + 1;
1288     } else {
1289       return middle_ptr;
1290     }
1291   }
1292   return sd.region(left);
1293 }
1294 
1295 ParallelCompactData::RegionData*
1296 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1297                                           const RegionData* end,
1298                                           size_t dead_words)
1299 {
1300   ParallelCompactData& sd = summary_data();
1301   size_t left = sd.region(beg);
1302   size_t right = end > beg ? sd.region(end) - 1 : left;
1303 
1304   // Binary search.
1305   while (left < right) {
1306     // Equivalent to (left + right) / 2, but does not overflow.
1307     const size_t middle = left + (right - left) / 2;
1308     RegionData* const middle_ptr = sd.region(middle);
1309     HeapWord* const dest = middle_ptr->destination();
1310     HeapWord* const addr = sd.region_to_addr(middle);
1311     assert(dest != NULL, "sanity");
1312     assert(dest <= addr, "must move left");
1313 
1314     const size_t dead_to_left = pointer_delta(addr, dest);
1315     if (middle > left && dead_to_left > dead_words) {
1316       right = middle - 1;
1317     } else if (middle < right && dead_to_left < dead_words) {
1318       left = middle + 1;
1319     } else {
1320       return middle_ptr;
1321     }
1322   }
1323   return sd.region(left);
1324 }
1325 
1326 // The result is valid during the summary phase, after the initial summarization
1327 // of each space into itself, and before final summarization.
1328 inline double
1329 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1330                                    HeapWord* const bottom,
1331                                    HeapWord* const top,
1332                                    HeapWord* const new_top)
1333 {
1334   ParallelCompactData& sd = summary_data();
1335 
1336   assert(cp != NULL, "sanity");
1337   assert(bottom != NULL, "sanity");
1338   assert(top != NULL, "sanity");
1339   assert(new_top != NULL, "sanity");
1340   assert(top >= new_top, "summary data problem?");
1341   assert(new_top > bottom, "space is empty; should not be here");
1342   assert(new_top >= cp->destination(), "sanity");
1343   assert(top >= sd.region_to_addr(cp), "sanity");
1344 
1345   HeapWord* const destination = cp->destination();
1346   const size_t dense_prefix_live  = pointer_delta(destination, bottom);
1347   const size_t compacted_region_live = pointer_delta(new_top, destination);
1348   const size_t compacted_region_used = pointer_delta(top,
1349                                                      sd.region_to_addr(cp));
1350   const size_t reclaimable = compacted_region_used - compacted_region_live;
1351 
1352   const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1353   return double(reclaimable) / divisor;
1354 }
1355 
1356 // Return the address of the end of the dense prefix, a.k.a. the start of the
1357 // compacted region.  The address is always on a region boundary.
1358 //
1359 // Completely full regions at the left are skipped, since no compaction can
1360 // occur in those regions.  Then the maximum amount of dead wood to allow is
1361 // computed, based on the density (amount live / capacity) of the generation;
1362 // the region with approximately that amount of dead space to the left is
1363 // identified as the limit region.  Regions between the last completely full
1364 // region and the limit region are scanned and the one that has the best
1365 // (maximum) reclaimed_ratio() is selected.
1366 HeapWord*
1367 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1368                                         bool maximum_compaction)
1369 {
1370   const size_t region_size = ParallelCompactData::RegionSize;
1371   const ParallelCompactData& sd = summary_data();
1372 
1373   const MutableSpace* const space = _space_info[id].space();
1374   HeapWord* const top = space->top();
1375   HeapWord* const top_aligned_up = sd.region_align_up(top);
1376   HeapWord* const new_top = _space_info[id].new_top();
1377   HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1378   HeapWord* const bottom = space->bottom();
1379   const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1380   const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1381   const RegionData* const new_top_cp =
1382     sd.addr_to_region_ptr(new_top_aligned_up);
1383 
1384   // Skip full regions at the beginning of the space--they are necessarily part
1385   // of the dense prefix.
1386   const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1387   assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1388          space->is_empty(), "no dead space allowed to the left");
1389   assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1390          "region must have dead space");
1391 
1392   // The gc number is saved whenever a maximum compaction is done, and used to
1393   // determine when the maximum compaction interval has expired.  This avoids
1394   // successive max compactions for different reasons.
1395   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1396   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1397   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1398     total_invocations() == HeapFirstMaximumCompactionCount;
1399   if (maximum_compaction || full_cp == top_cp || interval_ended) {
1400     _maximum_compaction_gc_num = total_invocations();
1401     return sd.region_to_addr(full_cp);
1402   }
1403 
1404   const size_t space_live = pointer_delta(new_top, bottom);
1405   const size_t space_used = space->used_in_words();
1406   const size_t space_capacity = space->capacity_in_words();
1407 
1408   const double density = double(space_live) / double(space_capacity);
1409   const size_t min_percent_free = MarkSweepDeadRatio;
1410   const double limiter = dead_wood_limiter(density, min_percent_free);
1411   const size_t dead_wood_max = space_used - space_live;
1412   const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1413                                       dead_wood_max);
1414 
1415   if (TraceParallelOldGCDensePrefix) {
1416     tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1417                   "space_cap=" SIZE_FORMAT,
1418                   space_live, space_used,
1419                   space_capacity);
1420     tty->print_cr("dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
1421                   "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1422                   density, min_percent_free, limiter,
1423                   dead_wood_max, dead_wood_limit);
1424   }
1425 
1426   // Locate the region with the desired amount of dead space to the left.
1427   const RegionData* const limit_cp =
1428     dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1429 
1430   // Scan from the first region with dead space to the limit region and find the
1431   // one with the best (largest) reclaimed ratio.
1432   double best_ratio = 0.0;
1433   const RegionData* best_cp = full_cp;
1434   for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1435     double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1436     if (tmp_ratio > best_ratio) {
1437       best_cp = cp;
1438       best_ratio = tmp_ratio;
1439     }
1440   }
1441 
1442   return sd.region_to_addr(best_cp);
1443 }
1444 
1445 void PSParallelCompact::summarize_spaces_quick()
1446 {
1447   for (unsigned int i = 0; i < last_space_id; ++i) {
1448     const MutableSpace* space = _space_info[i].space();
1449     HeapWord** nta = _space_info[i].new_top_addr();
1450     bool result = _summary_data.summarize(_space_info[i].split_info(),
1451                                           space->bottom(), space->top(), NULL,
1452                                           space->bottom(), space->end(), nta);
1453     assert(result, "space must fit into itself");
1454     _space_info[i].set_dense_prefix(space->bottom());
1455   }
1456 }
1457 
1458 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1459 {
1460   HeapWord* const dense_prefix_end = dense_prefix(id);
1461   const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1462   const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1463   if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1464     // Only enough dead space is filled so that any remaining dead space to the
1465     // left is larger than the minimum filler object.  (The remainder is filled
1466     // during the copy/update phase.)
1467     //
1468     // The size of the dead space to the right of the boundary is not a
1469     // concern, since compaction will be able to use whatever space is
1470     // available.
1471     //
1472     // Here '||' is the boundary, 'x' represents a don't care bit and a box
1473     // surrounds the space to be filled with an object.
1474     //
1475     // In the 32-bit VM, each bit represents two 32-bit words:
1476     //                              +---+
1477     // a) beg_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1478     //    end_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1479     //                              +---+
1480     //
1481     // In the 64-bit VM, each bit represents one 64-bit word:
1482     //                              +------------+
1483     // b) beg_bits:  ...  x   x   x | 0   ||   0 | x  x  ...
1484     //    end_bits:  ...  x   x   1 | 0   ||   0 | x  x  ...
1485     //                              +------------+
1486     //                          +-------+
1487     // c) beg_bits:  ...  x   x | 0   0 | ||   0   x  x  ...
1488     //    end_bits:  ...  x   1 | 0   0 | ||   0   x  x  ...
1489     //                          +-------+
1490     //                      +-----------+
1491     // d) beg_bits:  ...  x | 0   0   0 | ||   0   x  x  ...
1492     //    end_bits:  ...  1 | 0   0   0 | ||   0   x  x  ...
1493     //                      +-----------+
1494     //                          +-------+
1495     // e) beg_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1496     //    end_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1497     //                          +-------+
1498 
1499     // Initially assume case a, c or e will apply.
1500     size_t obj_len = CollectedHeap::min_fill_size();
1501     HeapWord* obj_beg = dense_prefix_end - obj_len;
1502 
1503 #ifdef  _LP64
1504     if (MinObjAlignment > 1) { // object alignment > heap word size
1505       // Cases a, c or e.
1506     } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1507       // Case b above.
1508       obj_beg = dense_prefix_end - 1;
1509     } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1510                _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1511       // Case d above.
1512       obj_beg = dense_prefix_end - 3;
1513       obj_len = 3;
1514     }
1515 #endif  // #ifdef _LP64
1516 
1517     CollectedHeap::fill_with_object(obj_beg, obj_len);
1518     _mark_bitmap.mark_obj(obj_beg, obj_len);
1519     _summary_data.add_obj(obj_beg, obj_len);
1520     assert(start_array(id) != NULL, "sanity");
1521     start_array(id)->allocate_block(obj_beg);
1522   }
1523 }
1524 
1525 void
1526 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1527 {
1528   assert(id < last_space_id, "id out of range");
1529   assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom(),
1530          "should have been reset in summarize_spaces_quick()");
1531 
1532   const MutableSpace* space = _space_info[id].space();
1533   if (_space_info[id].new_top() != space->bottom()) {
1534     HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1535     _space_info[id].set_dense_prefix(dense_prefix_end);
1536 
1537 #ifndef PRODUCT
1538     if (TraceParallelOldGCDensePrefix) {
1539       print_dense_prefix_stats("ratio", id, maximum_compaction,
1540                                dense_prefix_end);
1541       HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1542       print_dense_prefix_stats("density", id, maximum_compaction, addr);
1543     }
1544 #endif  // #ifndef PRODUCT
1545 
1546     // Recompute the summary data, taking into account the dense prefix.  If
1547     // every last byte will be reclaimed, then the existing summary data which
1548     // compacts everything can be left in place.
1549     if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1550       // If dead space crosses the dense prefix boundary, it is (at least
1551       // partially) filled with a dummy object, marked live and added to the
1552       // summary data.  This simplifies the copy/update phase and must be done
1553       // before the final locations of objects are determined, to prevent
1554       // leaving a fragment of dead space that is too small to fill.
1555       fill_dense_prefix_end(id);
1556 
1557       // Compute the destination of each Region, and thus each object.
1558       _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1559       _summary_data.summarize(_space_info[id].split_info(),
1560                               dense_prefix_end, space->top(), NULL,
1561                               dense_prefix_end, space->end(),
1562                               _space_info[id].new_top_addr());
1563     }
1564   }
1565 
1566   if (log_develop_is_enabled(Trace, gc, compaction)) {
1567     const size_t region_size = ParallelCompactData::RegionSize;
1568     HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1569     const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1570     const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1571     HeapWord* const new_top = _space_info[id].new_top();
1572     const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1573     const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1574     log_develop_trace(gc, compaction)(
1575         "id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1576         "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1577         "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1578         id, space->capacity_in_words(), p2i(dense_prefix_end),
1579         dp_region, dp_words / region_size,
1580         cr_words / region_size, p2i(new_top));
1581   }
1582 }
1583 
1584 #ifndef PRODUCT
1585 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1586                                           HeapWord* dst_beg, HeapWord* dst_end,
1587                                           SpaceId src_space_id,
1588                                           HeapWord* src_beg, HeapWord* src_end)
1589 {
1590   log_develop_trace(gc, compaction)(
1591       "Summarizing %d [%s] into %d [%s]:  "
1592       "src=" PTR_FORMAT "-" PTR_FORMAT " "
1593       SIZE_FORMAT "-" SIZE_FORMAT " "
1594       "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1595       SIZE_FORMAT "-" SIZE_FORMAT,
1596       src_space_id, space_names[src_space_id],
1597       dst_space_id, space_names[dst_space_id],
1598       p2i(src_beg), p2i(src_end),
1599       _summary_data.addr_to_region_idx(src_beg),
1600       _summary_data.addr_to_region_idx(src_end),
1601       p2i(dst_beg), p2i(dst_end),
1602       _summary_data.addr_to_region_idx(dst_beg),
1603       _summary_data.addr_to_region_idx(dst_end));
1604 }
1605 #endif  // #ifndef PRODUCT
1606 
1607 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1608                                       bool maximum_compaction)
1609 {
1610   GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
1611 
1612 #ifdef  ASSERT
1613   if (TraceParallelOldGCMarkingPhase) {
1614     tty->print_cr("add_obj_count=" SIZE_FORMAT " "
1615                   "add_obj_bytes=" SIZE_FORMAT,
1616                   add_obj_count, add_obj_size * HeapWordSize);
1617     tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
1618                   "mark_bitmap_bytes=" SIZE_FORMAT,
1619                   mark_bitmap_count, mark_bitmap_size * HeapWordSize);
1620   }
1621 #endif  // #ifdef ASSERT
1622 
1623   // Quick summarization of each space into itself, to see how much is live.
1624   summarize_spaces_quick();
1625 
1626   log_develop_trace(gc, compaction)("summary phase:  after summarizing each space to self");
1627   NOT_PRODUCT(print_region_ranges());
1628   NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1629 
1630   // The amount of live data that will end up in old space (assuming it fits).
1631   size_t old_space_total_live = 0;
1632   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1633     old_space_total_live += pointer_delta(_space_info[id].new_top(),
1634                                           _space_info[id].space()->bottom());
1635   }
1636 
1637   MutableSpace* const old_space = _space_info[old_space_id].space();
1638   const size_t old_capacity = old_space->capacity_in_words();
1639   if (old_space_total_live > old_capacity) {
1640     // XXX - should also try to expand
1641     maximum_compaction = true;
1642   }
1643 
1644   // Old generations.
1645   summarize_space(old_space_id, maximum_compaction);
1646 
1647   // Summarize the remaining spaces in the young gen.  The initial target space
1648   // is the old gen.  If a space does not fit entirely into the target, then the
1649   // remainder is compacted into the space itself and that space becomes the new
1650   // target.
1651   SpaceId dst_space_id = old_space_id;
1652   HeapWord* dst_space_end = old_space->end();
1653   HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1654   for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1655     const MutableSpace* space = _space_info[id].space();
1656     const size_t live = pointer_delta(_space_info[id].new_top(),
1657                                       space->bottom());
1658     const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1659 
1660     NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1661                                   SpaceId(id), space->bottom(), space->top());)
1662     if (live > 0 && live <= available) {
1663       // All the live data will fit.
1664       bool done = _summary_data.summarize(_space_info[id].split_info(),
1665                                           space->bottom(), space->top(),
1666                                           NULL,
1667                                           *new_top_addr, dst_space_end,
1668                                           new_top_addr);
1669       assert(done, "space must fit into old gen");
1670 
1671       // Reset the new_top value for the space.
1672       _space_info[id].set_new_top(space->bottom());
1673     } else if (live > 0) {
1674       // Attempt to fit part of the source space into the target space.
1675       HeapWord* next_src_addr = NULL;
1676       bool done = _summary_data.summarize(_space_info[id].split_info(),
1677                                           space->bottom(), space->top(),
1678                                           &next_src_addr,
1679                                           *new_top_addr, dst_space_end,
1680                                           new_top_addr);
1681       assert(!done, "space should not fit into old gen");
1682       assert(next_src_addr != NULL, "sanity");
1683 
1684       // The source space becomes the new target, so the remainder is compacted
1685       // within the space itself.
1686       dst_space_id = SpaceId(id);
1687       dst_space_end = space->end();
1688       new_top_addr = _space_info[id].new_top_addr();
1689       NOT_PRODUCT(summary_phase_msg(dst_space_id,
1690                                     space->bottom(), dst_space_end,
1691                                     SpaceId(id), next_src_addr, space->top());)
1692       done = _summary_data.summarize(_space_info[id].split_info(),
1693                                      next_src_addr, space->top(),
1694                                      NULL,
1695                                      space->bottom(), dst_space_end,
1696                                      new_top_addr);
1697       assert(done, "space must fit when compacted into itself");
1698       assert(*new_top_addr <= space->top(), "usage should not grow");
1699     }
1700   }
1701 
1702   log_develop_trace(gc, compaction)("Summary_phase:  after final summarization");
1703   NOT_PRODUCT(print_region_ranges());
1704   NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1705 }
1706 
1707 // This method should contain all heap-specific policy for invoking a full
1708 // collection.  invoke_no_policy() will only attempt to compact the heap; it
1709 // will do nothing further.  If we need to bail out for policy reasons, scavenge
1710 // before full gc, or any other specialized behavior, it needs to be added here.
1711 //
1712 // Note that this method should only be called from the vm_thread while at a
1713 // safepoint.
1714 //
1715 // Note that the all_soft_refs_clear flag in the soft ref policy
1716 // may be true because this method can be called without intervening
1717 // activity.  For example when the heap space is tight and full measure
1718 // are being taken to free space.
1719 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1720   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1721   assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1722          "should be in vm thread");
1723 
1724   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1725   GCCause::Cause gc_cause = heap->gc_cause();
1726   assert(!heap->is_gc_active(), "not reentrant");
1727 
1728   PSAdaptiveSizePolicy* policy = heap->size_policy();
1729   IsGCActiveMark mark;
1730 
1731   if (ScavengeBeforeFullGC) {
1732     PSScavenge::invoke_no_policy();
1733   }
1734 
1735   const bool clear_all_soft_refs =
1736     heap->soft_ref_policy()->should_clear_all_soft_refs();
1737 
1738   PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1739                                       maximum_heap_compaction);
1740 }
1741 
1742 // This method contains no policy. You should probably
1743 // be calling invoke() instead.
1744 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
1745   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
1746   assert(ref_processor() != NULL, "Sanity");
1747 
1748   if (GCLocker::check_active_before_gc()) {
1749     return false;
1750   }
1751 
1752   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1753 
1754   GCIdMark gc_id_mark;
1755   _gc_timer.register_gc_start();
1756   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1757 
1758   TimeStamp marking_start;
1759   TimeStamp compaction_start;
1760   TimeStamp collection_exit;
1761 
1762   GCCause::Cause gc_cause = heap->gc_cause();
1763   PSYoungGen* young_gen = heap->young_gen();
1764   PSOldGen* old_gen = heap->old_gen();
1765   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1766 
1767   // The scope of casr should end after code that can change
1768   // SoftRefPolicy::_should_clear_all_soft_refs.
1769   ClearedAllSoftRefs casr(maximum_heap_compaction,
1770                           heap->soft_ref_policy());
1771 
1772   if (ZapUnusedHeapArea) {
1773     // Save information needed to minimize mangling
1774     heap->record_gen_tops_before_GC();
1775   }
1776 
1777   // Make sure data structures are sane, make the heap parsable, and do other
1778   // miscellaneous bookkeeping.
1779   pre_compact();
1780 
1781   const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
1782 
1783   // Get the compaction manager reserved for the VM thread.
1784   ParCompactionManager* const vmthread_cm =
1785     ParCompactionManager::manager_array(ParallelScavengeHeap::heap()->workers().total_workers());
1786 
1787   {
1788     ResourceMark rm;
1789     HandleMark hm;
1790 
1791     const uint active_workers =
1792       WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().total_workers(),
1793                                         ParallelScavengeHeap::heap()->workers().active_workers(),
1794                                         Threads::number_of_non_daemon_threads());
1795     ParallelScavengeHeap::heap()->workers().update_active_workers(active_workers);
1796 
1797     GCTraceCPUTime tcpu;
1798     GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause, true);
1799 
1800     heap->pre_full_gc_dump(&_gc_timer);
1801 
1802     TraceCollectorStats tcs(counters());
1803     TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause);
1804 
1805     if (log_is_enabled(Debug, gc, heap, exit)) {
1806       accumulated_time()->start();
1807     }
1808 
1809     // Let the size policy know we're starting
1810     size_policy->major_collection_begin();
1811 
1812 #if COMPILER2_OR_JVMCI
1813     DerivedPointerTable::clear();
1814 #endif
1815 
1816     ref_processor()->enable_discovery();
1817     ref_processor()->setup_policy(maximum_heap_compaction);
1818 
1819     bool marked_for_unloading = false;
1820 
1821     marking_start.update();
1822     marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
1823 
1824     bool max_on_system_gc = UseMaximumCompactionOnSystemGC
1825       && GCCause::is_user_requested_gc(gc_cause);
1826     summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
1827 
1828 #if COMPILER2_OR_JVMCI
1829     assert(DerivedPointerTable::is_active(), "Sanity");
1830     DerivedPointerTable::set_active(false);
1831 #endif
1832 
1833     // adjust_roots() updates Universe::_intArrayKlassObj which is
1834     // needed by the compaction for filling holes in the dense prefix.
1835     adjust_roots(vmthread_cm);
1836 
1837     compaction_start.update();
1838     compact();
1839 
1840     // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
1841     // done before resizing.
1842     post_compact();
1843 
1844     // Let the size policy know we're done
1845     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1846 
1847     if (UseAdaptiveSizePolicy) {
1848       log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1849       log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
1850                           old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1851 
1852       // Don't check if the size_policy is ready here.  Let
1853       // the size_policy check that internally.
1854       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1855           AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1856         // Swap the survivor spaces if from_space is empty. The
1857         // resize_young_gen() called below is normally used after
1858         // a successful young GC and swapping of survivor spaces;
1859         // otherwise, it will fail to resize the young gen with
1860         // the current implementation.
1861         if (young_gen->from_space()->is_empty()) {
1862           young_gen->from_space()->clear(SpaceDecorator::Mangle);
1863           young_gen->swap_spaces();
1864         }
1865 
1866         // Calculate optimal free space amounts
1867         assert(young_gen->max_size() >
1868           young_gen->from_space()->capacity_in_bytes() +
1869           young_gen->to_space()->capacity_in_bytes(),
1870           "Sizes of space in young gen are out-of-bounds");
1871 
1872         size_t young_live = young_gen->used_in_bytes();
1873         size_t eden_live = young_gen->eden_space()->used_in_bytes();
1874         size_t old_live = old_gen->used_in_bytes();
1875         size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1876         size_t max_old_gen_size = old_gen->max_gen_size();
1877         size_t max_eden_size = young_gen->max_size() -
1878           young_gen->from_space()->capacity_in_bytes() -
1879           young_gen->to_space()->capacity_in_bytes();
1880 
1881         // Used for diagnostics
1882         size_policy->clear_generation_free_space_flags();
1883 
1884         size_policy->compute_generations_free_space(young_live,
1885                                                     eden_live,
1886                                                     old_live,
1887                                                     cur_eden,
1888                                                     max_old_gen_size,
1889                                                     max_eden_size,
1890                                                     true /* full gc*/);
1891 
1892         size_policy->check_gc_overhead_limit(eden_live,
1893                                              max_old_gen_size,
1894                                              max_eden_size,
1895                                              true /* full gc*/,
1896                                              gc_cause,
1897                                              heap->soft_ref_policy());
1898 
1899         size_policy->decay_supplemental_growth(true /* full gc*/);
1900 
1901         heap->resize_old_gen(
1902           size_policy->calculated_old_free_size_in_bytes());
1903 
1904         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1905                                size_policy->calculated_survivor_size_in_bytes());
1906       }
1907 
1908       log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1909     }
1910 
1911     if (UsePerfData) {
1912       PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1913       counters->update_counters();
1914       counters->update_old_capacity(old_gen->capacity_in_bytes());
1915       counters->update_young_capacity(young_gen->capacity_in_bytes());
1916     }
1917 
1918     heap->resize_all_tlabs();
1919 
1920     // Resize the metaspace capacity after a collection
1921     MetaspaceGC::compute_new_size();
1922 
1923     if (log_is_enabled(Debug, gc, heap, exit)) {
1924       accumulated_time()->stop();
1925     }
1926 
1927     heap->print_heap_change(pre_gc_values);
1928 
1929     // Track memory usage and detect low memory
1930     MemoryService::track_memory_usage();
1931     heap->update_counters();
1932 
1933     heap->post_full_gc_dump(&_gc_timer);
1934   }
1935 
1936 #ifdef ASSERT
1937   for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
1938     ParCompactionManager* const cm =
1939       ParCompactionManager::manager_array(int(i));
1940     assert(cm->marking_stack()->is_empty(),       "should be empty");
1941     assert(cm->region_stack()->is_empty(), "Region stack " SIZE_FORMAT " is not empty", i);
1942   }
1943 #endif // ASSERT
1944 
1945   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1946     HandleMark hm;  // Discard invalid handles created during verification
1947     Universe::verify("After GC");
1948   }
1949 
1950   // Re-verify object start arrays
1951   if (VerifyObjectStartArray &&
1952       VerifyAfterGC) {
1953     old_gen->verify_object_start_array();
1954   }
1955 
1956   if (ZapUnusedHeapArea) {
1957     old_gen->object_space()->check_mangled_unused_area_complete();
1958   }
1959 
1960   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1961 
1962   collection_exit.update();
1963 
1964   heap->print_heap_after_gc();
1965   heap->trace_heap_after_gc(&_gc_tracer);
1966 
1967   log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
1968                          marking_start.ticks(), compaction_start.ticks(),
1969                          collection_exit.ticks());
1970 
1971 #ifdef TRACESPINNING
1972   ParallelTaskTerminator::print_termination_counts();
1973 #endif
1974 
1975   AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
1976 
1977   _gc_timer.register_gc_end();
1978 
1979   _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1980   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1981 
1982   return true;
1983 }
1984 
1985 bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
1986                                              PSYoungGen* young_gen,
1987                                              PSOldGen* old_gen) {
1988   MutableSpace* const eden_space = young_gen->eden_space();
1989   assert(!eden_space->is_empty(), "eden must be non-empty");
1990   assert(young_gen->virtual_space()->alignment() ==
1991          old_gen->virtual_space()->alignment(), "alignments do not match");
1992 
1993   // We also return false when it's a heterogeneous heap because old generation cannot absorb data from eden
1994   // when it is allocated on different memory (example, nv-dimm) than young.
1995   if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary) ||
1996       ParallelArguments::is_heterogeneous_heap()) {
1997     return false;
1998   }
1999 
2000   // Both generations must be completely committed.
2001   if (young_gen->virtual_space()->uncommitted_size() != 0) {
2002     return false;
2003   }
2004   if (old_gen->virtual_space()->uncommitted_size() != 0) {
2005     return false;
2006   }
2007 
2008   // Figure out how much to take from eden.  Include the average amount promoted
2009   // in the total; otherwise the next young gen GC will simply bail out to a
2010   // full GC.
2011   const size_t alignment = old_gen->virtual_space()->alignment();
2012   const size_t eden_used = eden_space->used_in_bytes();
2013   const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
2014   const size_t absorb_size = align_up(eden_used + promoted, alignment);
2015   const size_t eden_capacity = eden_space->capacity_in_bytes();
2016 
2017   if (absorb_size >= eden_capacity) {
2018     return false; // Must leave some space in eden.
2019   }
2020 
2021   const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
2022   if (new_young_size < young_gen->min_gen_size()) {
2023     return false; // Respect young gen minimum size.
2024   }
2025 
2026   log_trace(gc, ergo, heap)(" absorbing " SIZE_FORMAT "K:  "
2027                             "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
2028                             "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
2029                             "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
2030                             absorb_size / K,
2031                             eden_capacity / K, (eden_capacity - absorb_size) / K,
2032                             young_gen->from_space()->used_in_bytes() / K,
2033                             young_gen->to_space()->used_in_bytes() / K,
2034                             young_gen->capacity_in_bytes() / K, new_young_size / K);
2035 
2036   // Fill the unused part of the old gen.
2037   MutableSpace* const old_space = old_gen->object_space();
2038   HeapWord* const unused_start = old_space->top();
2039   size_t const unused_words = pointer_delta(old_space->end(), unused_start);
2040 
2041   if (unused_words > 0) {
2042     if (unused_words < CollectedHeap::min_fill_size()) {
2043       return false;  // If the old gen cannot be filled, must give up.
2044     }
2045     CollectedHeap::fill_with_objects(unused_start, unused_words);
2046   }
2047 
2048   // Take the live data from eden and set both top and end in the old gen to
2049   // eden top.  (Need to set end because reset_after_change() mangles the region
2050   // from end to virtual_space->high() in debug builds).
2051   HeapWord* const new_top = eden_space->top();
2052   old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
2053                                         absorb_size);
2054   young_gen->reset_after_change();
2055   old_space->set_top(new_top);
2056   old_space->set_end(new_top);
2057   old_gen->reset_after_change();
2058 
2059   // Update the object start array for the filler object and the data from eden.
2060   ObjectStartArray* const start_array = old_gen->start_array();
2061   for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
2062     start_array->allocate_block(p);
2063   }
2064 
2065   // Could update the promoted average here, but it is not typically updated at
2066   // full GCs and the value to use is unclear.  Something like
2067   //
2068   // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
2069 
2070   size_policy->set_bytes_absorbed_from_eden(absorb_size);
2071   return true;
2072 }
2073 
2074 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
2075 private:
2076   uint _worker_id;
2077 
2078 public:
2079   PCAddThreadRootsMarkingTaskClosure(uint worker_id) : _worker_id(worker_id) { }
2080   void do_thread(Thread* thread) {
2081     assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2082 
2083     ResourceMark rm;
2084 
2085     ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(_worker_id);
2086 
2087     PCMarkAndPushClosure mark_and_push_closure(cm);
2088     MarkingCodeBlobClosure mark_and_push_in_blobs(&mark_and_push_closure, !CodeBlobToOopClosure::FixRelocations);
2089 
2090     thread->oops_do(&mark_and_push_closure, &mark_and_push_in_blobs);
2091 
2092     // Do the real work
2093     cm->follow_marking_stacks();
2094   }
2095 };
2096 
2097 static void mark_from_roots_work(ParallelRootType::Value root_type, uint worker_id) {
2098   assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2099 
2100   ParCompactionManager* cm =
2101     ParCompactionManager::gc_thread_compaction_manager(worker_id);
2102   PCMarkAndPushClosure mark_and_push_closure(cm);
2103 
2104   switch (root_type) {
2105     case ParallelRootType::universe:
2106       Universe::oops_do(&mark_and_push_closure);
2107       break;
2108 
2109     case ParallelRootType::jni_handles:
2110       JNIHandles::oops_do(&mark_and_push_closure);
2111       break;
2112 
2113     case ParallelRootType::object_synchronizer:
2114       ObjectSynchronizer::oops_do(&mark_and_push_closure);
2115       break;
2116 
2117     case ParallelRootType::management:
2118       Management::oops_do(&mark_and_push_closure);
2119       break;
2120 
2121     case ParallelRootType::jvmti:
2122       JvmtiExport::oops_do(&mark_and_push_closure);
2123       break;
2124 
2125     case ParallelRootType::system_dictionary:
2126       SystemDictionary::oops_do(&mark_and_push_closure);
2127       break;
2128 
2129     case ParallelRootType::class_loader_data:
2130       {
2131         CLDToOopClosure cld_closure(&mark_and_push_closure, ClassLoaderData::_claim_strong);
2132         ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
2133       }
2134       break;
2135 
2136     case ParallelRootType::code_cache:
2137       // Do not treat nmethods as strong roots for mark/sweep, since we can unload them.
2138       //ScavengableNMethods::scavengable_nmethods_do(CodeBlobToOopClosure(&mark_and_push_closure));
2139       AOTLoader::oops_do(&mark_and_push_closure);
2140       break;
2141 
2142     case ParallelRootType::sentinel:
2143     DEBUG_ONLY(default:) // DEBUG_ONLY hack will create compile error on release builds (-Wswitch) and runtime check on debug builds
2144       fatal("Bad enumeration value: %u", root_type);
2145       break;
2146   }
2147 
2148   // Do the real work
2149   cm->follow_marking_stacks();
2150 }
2151 
2152 static void steal_marking_work(ParallelTaskTerminator& terminator, uint worker_id) {
2153   assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2154 
2155   ParCompactionManager* cm =
2156     ParCompactionManager::gc_thread_compaction_manager(worker_id);
2157 
2158   oop obj = NULL;
2159   ObjArrayTask task;
2160   do {
2161     while (ParCompactionManager::steal_objarray(worker_id,  task)) {
2162       cm->follow_array((objArrayOop)task.obj(), task.index());
2163       cm->follow_marking_stacks();
2164     }
2165     while (ParCompactionManager::steal(worker_id, obj)) {
2166       cm->follow_contents(obj);
2167       cm->follow_marking_stacks();
2168     }
2169   } while (!terminator.offer_termination());
2170 }
2171 
2172 class MarkFromRootsTask : public AbstractGangTask {
2173   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2174   StrongRootsScope _strong_roots_scope; // needed for Threads::possibly_parallel_threads_do
2175   SequentialSubTasksDone _subtasks;
2176   TaskTerminator _terminator;
2177   uint _active_workers;
2178 
2179 public:
2180   MarkFromRootsTask(uint active_workers) :
2181       AbstractGangTask("MarkFromRootsTask"),
2182       _strong_roots_scope(active_workers),
2183       _subtasks(),
2184       _terminator(active_workers, ParCompactionManager::stack_array()),
2185       _active_workers(active_workers) {
2186     _subtasks.set_n_threads(active_workers);
2187     _subtasks.set_n_tasks(ParallelRootType::sentinel);
2188   }
2189 
2190   virtual void work(uint worker_id) {
2191     for (uint task = 0; _subtasks.try_claim_task(task); /*empty*/ ) {
2192       mark_from_roots_work(static_cast<ParallelRootType::Value>(task), worker_id);
2193     }
2194     _subtasks.all_tasks_completed();
2195 
2196     PCAddThreadRootsMarkingTaskClosure closure(worker_id);
2197     Threads::possibly_parallel_threads_do(true /*parallel */, &closure);
2198 
2199     if (_active_workers > 1) {
2200       steal_marking_work(*_terminator.terminator(), worker_id);
2201     }
2202   }
2203 };
2204 
2205 class PCRefProcTask : public AbstractGangTask {
2206   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2207   ProcessTask& _task;
2208   uint _ergo_workers;
2209   TaskTerminator _terminator;
2210 
2211 public:
2212   PCRefProcTask(ProcessTask& task, uint ergo_workers) :
2213       AbstractGangTask("PCRefProcTask"),
2214       _task(task),
2215       _ergo_workers(ergo_workers),
2216       _terminator(_ergo_workers, ParCompactionManager::stack_array()) {
2217   }
2218 
2219   virtual void work(uint worker_id) {
2220     ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2221     assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2222 
2223     ParCompactionManager* cm =
2224       ParCompactionManager::gc_thread_compaction_manager(worker_id);
2225     PCMarkAndPushClosure mark_and_push_closure(cm);
2226     ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
2227     _task.work(worker_id, *PSParallelCompact::is_alive_closure(),
2228                mark_and_push_closure, follow_stack_closure);
2229 
2230     steal_marking_work(*_terminator.terminator(), worker_id);
2231   }
2232 };
2233 
2234 class RefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2235   void execute(ProcessTask& process_task, uint ergo_workers) {
2236     assert(ParallelScavengeHeap::heap()->workers().active_workers() == ergo_workers,
2237            "Ergonomically chosen workers (%u) must be equal to active workers (%u)",
2238            ergo_workers, ParallelScavengeHeap::heap()->workers().active_workers());
2239 
2240     PCRefProcTask task(process_task, ergo_workers);
2241     ParallelScavengeHeap::heap()->workers().run_task(&task);
2242   }
2243 };
2244 
2245 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2246                                       bool maximum_heap_compaction,
2247                                       ParallelOldTracer *gc_tracer) {
2248   // Recursively traverse all live objects and mark them
2249   GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
2250 
2251   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2252   uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2253 
2254   PCMarkAndPushClosure mark_and_push_closure(cm);
2255   ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
2256 
2257   // Need new claim bits before marking starts.
2258   ClassLoaderDataGraph::clear_claimed_marks();
2259 
2260   {
2261     GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
2262 
2263     MarkFromRootsTask task(active_gc_threads);
2264     ParallelScavengeHeap::heap()->workers().run_task(&task);
2265   }
2266 
2267   // Process reference objects found during marking
2268   {
2269     GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
2270 
2271     ReferenceProcessorStats stats;
2272     ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
2273 
2274     if (ref_processor()->processing_is_mt()) {
2275       ref_processor()->set_active_mt_degree(active_gc_threads);
2276 
2277       RefProcTaskExecutor task_executor;
2278       stats = ref_processor()->process_discovered_references(
2279         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2280         &task_executor, &pt);
2281     } else {
2282       stats = ref_processor()->process_discovered_references(
2283         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
2284         &pt);
2285     }
2286 
2287     gc_tracer->report_gc_reference_stats(stats);
2288     pt.print_all_references();
2289   }
2290 
2291   // This is the point where the entire marking should have completed.
2292   assert(cm->marking_stacks_empty(), "Marking should have completed");
2293 
2294   {
2295     GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
2296     WeakProcessor::weak_oops_do(is_alive_closure(), &do_nothing_cl);
2297   }
2298 
2299   {
2300     GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
2301 
2302     // Follow system dictionary roots and unload classes.
2303     bool purged_class = SystemDictionary::do_unloading(&_gc_timer);
2304 
2305     // Unload nmethods.
2306     CodeCache::do_unloading(is_alive_closure(), purged_class);
2307 
2308     // Prune dead klasses from subklass/sibling/implementor lists.
2309     Klass::clean_weak_klass_links(purged_class);
2310 
2311     // Clean JVMCI metadata handles.
2312     JVMCI_ONLY(JVMCI::do_unloading(purged_class));
2313   }
2314 
2315   _gc_tracer.report_object_count_after_gc(is_alive_closure());
2316 }
2317 
2318 void PSParallelCompact::adjust_roots(ParCompactionManager* cm) {
2319   // Adjust the pointers to reflect the new locations
2320   GCTraceTime(Info, gc, phases) tm("Adjust Roots", &_gc_timer);
2321 
2322   // Need new claim bits when tracing through and adjusting pointers.
2323   ClassLoaderDataGraph::clear_claimed_marks();
2324 
2325   PCAdjustPointerClosure oop_closure(cm);
2326 
2327   // General strong roots.
2328   Universe::oops_do(&oop_closure);
2329   JNIHandles::oops_do(&oop_closure);   // Global (strong) JNI handles
2330   Threads::oops_do(&oop_closure, NULL);
2331   ObjectSynchronizer::oops_do(&oop_closure);
2332   Management::oops_do(&oop_closure);
2333   JvmtiExport::oops_do(&oop_closure);
2334   SystemDictionary::oops_do(&oop_closure);
2335   CLDToOopClosure cld_closure(&oop_closure, ClassLoaderData::_claim_strong);
2336   ClassLoaderDataGraph::cld_do(&cld_closure);
2337 
2338   // Now adjust pointers in remaining weak roots.  (All of which should
2339   // have been cleared if they pointed to non-surviving objects.)
2340   WeakProcessor::oops_do(&oop_closure);
2341 
2342   CodeBlobToOopClosure adjust_from_blobs(&oop_closure, CodeBlobToOopClosure::FixRelocations);
2343   CodeCache::blobs_do(&adjust_from_blobs);
2344   AOT_ONLY(AOTLoader::oops_do(&oop_closure);)
2345 
2346   ref_processor()->weak_oops_do(&oop_closure);
2347   // Roots were visited so references into the young gen in roots
2348   // may have been scanned.  Process them also.
2349   // Should the reference processor have a span that excludes
2350   // young gen objects?
2351   PSScavenge::reference_processor()->weak_oops_do(&oop_closure);
2352 }
2353 
2354 // Helper class to print 8 region numbers per line and then print the total at the end.
2355 class FillableRegionLogger : public StackObj {
2356 private:
2357   Log(gc, compaction) log;
2358   static const int LineLength = 8;
2359   size_t _regions[LineLength];
2360   int _next_index;
2361   bool _enabled;
2362   size_t _total_regions;
2363 public:
2364   FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
2365   ~FillableRegionLogger() {
2366     log.trace(SIZE_FORMAT " initially fillable regions", _total_regions);
2367   }
2368 
2369   void print_line() {
2370     if (!_enabled || _next_index == 0) {
2371       return;
2372     }
2373     FormatBuffer<> line("Fillable: ");
2374     for (int i = 0; i < _next_index; i++) {
2375       line.append(" " SIZE_FORMAT_W(7), _regions[i]);
2376     }
2377     log.trace("%s", line.buffer());
2378     _next_index = 0;
2379   }
2380 
2381   void handle(size_t region) {
2382     if (!_enabled) {
2383       return;
2384     }
2385     _regions[_next_index++] = region;
2386     if (_next_index == LineLength) {
2387       print_line();
2388     }
2389     _total_regions++;
2390   }
2391 };
2392 
2393 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
2394 {
2395   GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
2396 
2397   // Find the threads that are active
2398   uint worker_id = 0;
2399 
2400   // Find all regions that are available (can be filled immediately) and
2401   // distribute them to the thread stacks.  The iteration is done in reverse
2402   // order (high to low) so the regions will be removed in ascending order.
2403 
2404   const ParallelCompactData& sd = PSParallelCompact::summary_data();
2405 
2406   // id + 1 is used to test termination so unsigned  can
2407   // be used with an old_space_id == 0.
2408   FillableRegionLogger region_logger;
2409   for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2410     SpaceInfo* const space_info = _space_info + id;
2411     MutableSpace* const space = space_info->space();
2412     HeapWord* const new_top = space_info->new_top();
2413 
2414     const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2415     const size_t end_region =
2416       sd.addr_to_region_idx(sd.region_align_up(new_top));
2417 
2418     for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2419       if (sd.region(cur)->claim_unsafe()) {
2420         ParCompactionManager* cm = ParCompactionManager::manager_array(worker_id);
2421         bool result = sd.region(cur)->mark_normal();
2422         assert(result, "Must succeed at this point.");
2423         cm->region_stack()->push(cur);
2424         region_logger.handle(cur);
2425         // Assign regions to tasks in round-robin fashion.
2426         if (++worker_id == parallel_gc_threads) {
2427           worker_id = 0;
2428         }
2429       }
2430     }
2431     region_logger.print_line();
2432   }
2433 }
2434 
2435 class TaskQueue : StackObj {
2436   volatile uint _counter;
2437   uint _size;
2438   uint _insert_index;
2439   PSParallelCompact::UpdateDensePrefixTask* _backing_array;
2440 public:
2441   explicit TaskQueue(uint size) : _counter(0), _size(size), _insert_index(0), _backing_array(NULL) {
2442     _backing_array = NEW_C_HEAP_ARRAY(PSParallelCompact::UpdateDensePrefixTask, _size, mtGC);
2443   }
2444   ~TaskQueue() {
2445     assert(_counter >= _insert_index, "not all queue elements were claimed");
2446     FREE_C_HEAP_ARRAY(T, _backing_array);
2447   }
2448 
2449   void push(const PSParallelCompact::UpdateDensePrefixTask& value) {
2450     assert(_insert_index < _size, "too small backing array");
2451     _backing_array[_insert_index++] = value;
2452   }
2453 
2454   bool try_claim(PSParallelCompact::UpdateDensePrefixTask& reference) {
2455     uint claimed = Atomic::add(&_counter, 1u) - 1; // -1 is so that we start with zero
2456     if (claimed < _insert_index) {
2457       reference = _backing_array[claimed];
2458       return true;
2459     } else {
2460       return false;
2461     }
2462   }
2463 };
2464 
2465 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2466 
2467 void PSParallelCompact::enqueue_dense_prefix_tasks(TaskQueue& task_queue,
2468                                                    uint parallel_gc_threads) {
2469   GCTraceTime(Trace, gc, phases) tm("Dense Prefix Task Setup", &_gc_timer);
2470 
2471   ParallelCompactData& sd = PSParallelCompact::summary_data();
2472 
2473   // Iterate over all the spaces adding tasks for updating
2474   // regions in the dense prefix.  Assume that 1 gc thread
2475   // will work on opening the gaps and the remaining gc threads
2476   // will work on the dense prefix.
2477   unsigned int space_id;
2478   for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2479     HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2480     const MutableSpace* const space = _space_info[space_id].space();
2481 
2482     if (dense_prefix_end == space->bottom()) {
2483       // There is no dense prefix for this space.
2484       continue;
2485     }
2486 
2487     // The dense prefix is before this region.
2488     size_t region_index_end_dense_prefix =
2489         sd.addr_to_region_idx(dense_prefix_end);
2490     RegionData* const dense_prefix_cp =
2491       sd.region(region_index_end_dense_prefix);
2492     assert(dense_prefix_end == space->end() ||
2493            dense_prefix_cp->available() ||
2494            dense_prefix_cp->claimed(),
2495            "The region after the dense prefix should always be ready to fill");
2496 
2497     size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2498 
2499     // Is there dense prefix work?
2500     size_t total_dense_prefix_regions =
2501       region_index_end_dense_prefix - region_index_start;
2502     // How many regions of the dense prefix should be given to
2503     // each thread?
2504     if (total_dense_prefix_regions > 0) {
2505       uint tasks_for_dense_prefix = 1;
2506       if (total_dense_prefix_regions <=
2507           (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2508         // Don't over partition.  This assumes that
2509         // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2510         // so there are not many regions to process.
2511         tasks_for_dense_prefix = parallel_gc_threads;
2512       } else {
2513         // Over partition
2514         tasks_for_dense_prefix = parallel_gc_threads *
2515           PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2516       }
2517       size_t regions_per_thread = total_dense_prefix_regions /
2518         tasks_for_dense_prefix;
2519       // Give each thread at least 1 region.
2520       if (regions_per_thread == 0) {
2521         regions_per_thread = 1;
2522       }
2523 
2524       for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2525         if (region_index_start >= region_index_end_dense_prefix) {
2526           break;
2527         }
2528         // region_index_end is not processed
2529         size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2530                                        region_index_end_dense_prefix);
2531         task_queue.push(UpdateDensePrefixTask(SpaceId(space_id),
2532                                               region_index_start,
2533                                               region_index_end));
2534         region_index_start = region_index_end;
2535       }
2536     }
2537     // This gets any part of the dense prefix that did not
2538     // fit evenly.
2539     if (region_index_start < region_index_end_dense_prefix) {
2540       task_queue.push(UpdateDensePrefixTask(SpaceId(space_id),
2541                                             region_index_start,
2542                                             region_index_end_dense_prefix));
2543     }
2544   }
2545 }
2546 
2547 #ifdef ASSERT
2548 // Write a histogram of the number of times the block table was filled for a
2549 // region.
2550 void PSParallelCompact::write_block_fill_histogram()
2551 {
2552   if (!log_develop_is_enabled(Trace, gc, compaction)) {
2553     return;
2554   }
2555 
2556   Log(gc, compaction) log;
2557   ResourceMark rm;
2558   LogStream ls(log.trace());
2559   outputStream* out = &ls;
2560 
2561   typedef ParallelCompactData::RegionData rd_t;
2562   ParallelCompactData& sd = summary_data();
2563 
2564   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2565     MutableSpace* const spc = _space_info[id].space();
2566     if (spc->bottom() != spc->top()) {
2567       const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
2568       HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
2569       const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
2570 
2571       size_t histo[5] = { 0, 0, 0, 0, 0 };
2572       const size_t histo_len = sizeof(histo) / sizeof(size_t);
2573       const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
2574 
2575       for (const rd_t* cur = beg; cur < end; ++cur) {
2576         ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
2577       }
2578       out->print("Block fill histogram: %u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
2579       for (size_t i = 0; i < histo_len; ++i) {
2580         out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
2581                    histo[i], 100.0 * histo[i] / region_cnt);
2582       }
2583       out->cr();
2584     }
2585   }
2586 }
2587 #endif // #ifdef ASSERT
2588 
2589 static void compaction_with_stealing_work(ParallelTaskTerminator* terminator, uint worker_id) {
2590   assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2591 
2592   ParCompactionManager* cm =
2593     ParCompactionManager::gc_thread_compaction_manager(worker_id);
2594 
2595   // Drain the stacks that have been preloaded with regions
2596   // that are ready to fill.
2597 
2598   cm->drain_region_stacks();
2599 
2600   guarantee(cm->region_stack()->is_empty(), "Not empty");
2601 
2602   size_t region_index = 0;
2603 
2604   while (true) {
2605     if (ParCompactionManager::steal(worker_id, region_index)) {
2606       PSParallelCompact::fill_and_update_region(cm, region_index);
2607       cm->drain_region_stacks();
2608     } else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
2609       // Fill and update an unavailable region with the help of a shadow region
2610       PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
2611       cm->drain_region_stacks();
2612     } else {
2613       if (terminator->offer_termination()) {
2614         break;
2615       }
2616       // Go around again.
2617     }
2618   }
2619   return;
2620 }
2621 
2622 class UpdateDensePrefixAndCompactionTask: public AbstractGangTask {
2623   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2624   TaskQueue& _tq;
2625   TaskTerminator _terminator;
2626   uint _active_workers;
2627 
2628 public:
2629   UpdateDensePrefixAndCompactionTask(TaskQueue& tq, uint active_workers) :
2630       AbstractGangTask("UpdateDensePrefixAndCompactionTask"),
2631       _tq(tq),
2632       _terminator(active_workers, ParCompactionManager::region_array()),
2633       _active_workers(active_workers) {
2634   }
2635   virtual void work(uint worker_id) {
2636     ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
2637 
2638     for (PSParallelCompact::UpdateDensePrefixTask task; _tq.try_claim(task); /* empty */) {
2639       PSParallelCompact::update_and_deadwood_in_dense_prefix(cm,
2640                                                              task._space_id,
2641                                                              task._region_index_start,
2642                                                              task._region_index_end);
2643     }
2644 
2645     // Once a thread has drained it's stack, it should try to steal regions from
2646     // other threads.
2647     compaction_with_stealing_work(_terminator.terminator(), worker_id);
2648   }
2649 };
2650 
2651 void PSParallelCompact::compact() {
2652   GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
2653 
2654   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2655   PSOldGen* old_gen = heap->old_gen();
2656   old_gen->start_array()->reset();
2657   uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2658 
2659   // for [0..last_space_id)
2660   //     for [0..active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)
2661   //         push
2662   //     push
2663   //
2664   // max push count is thus: last_space_id * (active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING + 1)
2665   TaskQueue task_queue(last_space_id * (active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING + 1));
2666   initialize_shadow_regions(active_gc_threads);
2667   prepare_region_draining_tasks(active_gc_threads);
2668   enqueue_dense_prefix_tasks(task_queue, active_gc_threads);
2669 
2670   {
2671     GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
2672 
2673     UpdateDensePrefixAndCompactionTask task(task_queue, active_gc_threads);
2674     ParallelScavengeHeap::heap()->workers().run_task(&task);
2675 
2676 #ifdef  ASSERT
2677     // Verify that all regions have been processed before the deferred updates.
2678     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2679       verify_complete(SpaceId(id));
2680     }
2681 #endif
2682   }
2683 
2684   {
2685     // Update the deferred objects, if any.  Any compaction manager can be used.
2686     GCTraceTime(Trace, gc, phases) tm("Deferred Updates", &_gc_timer);
2687     ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2688     for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2689       update_deferred_objects(cm, SpaceId(id));
2690     }
2691   }
2692 
2693   DEBUG_ONLY(write_block_fill_histogram());
2694 }
2695 
2696 #ifdef  ASSERT
2697 void PSParallelCompact::verify_complete(SpaceId space_id) {
2698   // All Regions between space bottom() to new_top() should be marked as filled
2699   // and all Regions between new_top() and top() should be available (i.e.,
2700   // should have been emptied).
2701   ParallelCompactData& sd = summary_data();
2702   SpaceInfo si = _space_info[space_id];
2703   HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2704   HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2705   const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2706   const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2707   const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2708 
2709   bool issued_a_warning = false;
2710 
2711   size_t cur_region;
2712   for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2713     const RegionData* const c = sd.region(cur_region);
2714     if (!c->completed()) {
2715       log_warning(gc)("region " SIZE_FORMAT " not filled: destination_count=%u",
2716                       cur_region, c->destination_count());
2717       issued_a_warning = true;
2718     }
2719   }
2720 
2721   for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2722     const RegionData* const c = sd.region(cur_region);
2723     if (!c->available()) {
2724       log_warning(gc)("region " SIZE_FORMAT " not empty: destination_count=%u",
2725                       cur_region, c->destination_count());
2726       issued_a_warning = true;
2727     }
2728   }
2729 
2730   if (issued_a_warning) {
2731     print_region_ranges();
2732   }
2733 }
2734 #endif  // #ifdef ASSERT
2735 
2736 inline void UpdateOnlyClosure::do_addr(HeapWord* addr) {
2737   _start_array->allocate_block(addr);
2738   compaction_manager()->update_contents(oop(addr));
2739 }
2740 
2741 // Update interior oops in the ranges of regions [beg_region, end_region).
2742 void
2743 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2744                                                        SpaceId space_id,
2745                                                        size_t beg_region,
2746                                                        size_t end_region) {
2747   ParallelCompactData& sd = summary_data();
2748   ParMarkBitMap* const mbm = mark_bitmap();
2749 
2750   HeapWord* beg_addr = sd.region_to_addr(beg_region);
2751   HeapWord* const end_addr = sd.region_to_addr(end_region);
2752   assert(beg_region <= end_region, "bad region range");
2753   assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2754 
2755 #ifdef  ASSERT
2756   // Claim the regions to avoid triggering an assert when they are marked as
2757   // filled.
2758   for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2759     assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2760   }
2761 #endif  // #ifdef ASSERT
2762 
2763   if (beg_addr != space(space_id)->bottom()) {
2764     // Find the first live object or block of dead space that *starts* in this
2765     // range of regions.  If a partial object crosses onto the region, skip it;
2766     // it will be marked for 'deferred update' when the object head is
2767     // processed.  If dead space crosses onto the region, it is also skipped; it
2768     // will be filled when the prior region is processed.  If neither of those
2769     // apply, the first word in the region is the start of a live object or dead
2770     // space.
2771     assert(beg_addr > space(space_id)->bottom(), "sanity");
2772     const RegionData* const cp = sd.region(beg_region);
2773     if (cp->partial_obj_size() != 0) {
2774       beg_addr = sd.partial_obj_end(beg_region);
2775     } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2776       beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2777     }
2778   }
2779 
2780   if (beg_addr < end_addr) {
2781     // A live object or block of dead space starts in this range of Regions.
2782      HeapWord* const dense_prefix_end = dense_prefix(space_id);
2783 
2784     // Create closures and iterate.
2785     UpdateOnlyClosure update_closure(mbm, cm, space_id);
2786     FillClosure fill_closure(cm, space_id);
2787     ParMarkBitMap::IterationStatus status;
2788     status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2789                           dense_prefix_end);
2790     if (status == ParMarkBitMap::incomplete) {
2791       update_closure.do_addr(update_closure.source());
2792     }
2793   }
2794 
2795   // Mark the regions as filled.
2796   RegionData* const beg_cp = sd.region(beg_region);
2797   RegionData* const end_cp = sd.region(end_region);
2798   for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2799     cp->set_completed();
2800   }
2801 }
2802 
2803 // Return the SpaceId for the space containing addr.  If addr is not in the
2804 // heap, last_space_id is returned.  In debug mode it expects the address to be
2805 // in the heap and asserts such.
2806 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2807   assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
2808 
2809   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2810     if (_space_info[id].space()->contains(addr)) {
2811       return SpaceId(id);
2812     }
2813   }
2814 
2815   assert(false, "no space contains the addr");
2816   return last_space_id;
2817 }
2818 
2819 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2820                                                 SpaceId id) {
2821   assert(id < last_space_id, "bad space id");
2822 
2823   ParallelCompactData& sd = summary_data();
2824   const SpaceInfo* const space_info = _space_info + id;
2825   ObjectStartArray* const start_array = space_info->start_array();
2826 
2827   const MutableSpace* const space = space_info->space();
2828   assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2829   HeapWord* const beg_addr = space_info->dense_prefix();
2830   HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2831 
2832   const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2833   const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2834   const RegionData* cur_region;
2835   for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2836     HeapWord* const addr = cur_region->deferred_obj_addr();
2837     if (addr != NULL) {
2838       if (start_array != NULL) {
2839         start_array->allocate_block(addr);
2840       }
2841       cm->update_contents(oop(addr));
2842       assert(oopDesc::is_oop_or_null(oop(addr)), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(addr)));
2843     }
2844   }
2845 }
2846 
2847 // Skip over count live words starting from beg, and return the address of the
2848 // next live word.  Unless marked, the word corresponding to beg is assumed to
2849 // be dead.  Callers must either ensure beg does not correspond to the middle of
2850 // an object, or account for those live words in some other way.  Callers must
2851 // also ensure that there are enough live words in the range [beg, end) to skip.
2852 HeapWord*
2853 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2854 {
2855   assert(count > 0, "sanity");
2856 
2857   ParMarkBitMap* m = mark_bitmap();
2858   idx_t bits_to_skip = m->words_to_bits(count);
2859   idx_t cur_beg = m->addr_to_bit(beg);
2860   const idx_t search_end = m->align_range_end(m->addr_to_bit(end));
2861 
2862   do {
2863     cur_beg = m->find_obj_beg(cur_beg, search_end);
2864     idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2865     const size_t obj_bits = cur_end - cur_beg + 1;
2866     if (obj_bits > bits_to_skip) {
2867       return m->bit_to_addr(cur_beg + bits_to_skip);
2868     }
2869     bits_to_skip -= obj_bits;
2870     cur_beg = cur_end + 1;
2871   } while (bits_to_skip > 0);
2872 
2873   // Skipping the desired number of words landed just past the end of an object.
2874   // Find the start of the next object.
2875   cur_beg = m->find_obj_beg(cur_beg, search_end);
2876   assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2877   return m->bit_to_addr(cur_beg);
2878 }
2879 
2880 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2881                                             SpaceId src_space_id,
2882                                             size_t src_region_idx)
2883 {
2884   assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2885 
2886   const SplitInfo& split_info = _space_info[src_space_id].split_info();
2887   if (split_info.dest_region_addr() == dest_addr) {
2888     // The partial object ending at the split point contains the first word to
2889     // be copied to dest_addr.
2890     return split_info.first_src_addr();
2891   }
2892 
2893   const ParallelCompactData& sd = summary_data();
2894   ParMarkBitMap* const bitmap = mark_bitmap();
2895   const size_t RegionSize = ParallelCompactData::RegionSize;
2896 
2897   assert(sd.is_region_aligned(dest_addr), "not aligned");
2898   const RegionData* const src_region_ptr = sd.region(src_region_idx);
2899   const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2900   HeapWord* const src_region_destination = src_region_ptr->destination();
2901 
2902   assert(dest_addr >= src_region_destination, "wrong src region");
2903   assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2904 
2905   HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2906   HeapWord* const src_region_end = src_region_beg + RegionSize;
2907 
2908   HeapWord* addr = src_region_beg;
2909   if (dest_addr == src_region_destination) {
2910     // Return the first live word in the source region.
2911     if (partial_obj_size == 0) {
2912       addr = bitmap->find_obj_beg(addr, src_region_end);
2913       assert(addr < src_region_end, "no objects start in src region");
2914     }
2915     return addr;
2916   }
2917 
2918   // Must skip some live data.
2919   size_t words_to_skip = dest_addr - src_region_destination;
2920   assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2921 
2922   if (partial_obj_size >= words_to_skip) {
2923     // All the live words to skip are part of the partial object.
2924     addr += words_to_skip;
2925     if (partial_obj_size == words_to_skip) {
2926       // Find the first live word past the partial object.
2927       addr = bitmap->find_obj_beg(addr, src_region_end);
2928       assert(addr < src_region_end, "wrong src region");
2929     }
2930     return addr;
2931   }
2932 
2933   // Skip over the partial object (if any).
2934   if (partial_obj_size != 0) {
2935     words_to_skip -= partial_obj_size;
2936     addr += partial_obj_size;
2937   }
2938 
2939   // Skip over live words due to objects that start in the region.
2940   addr = skip_live_words(addr, src_region_end, words_to_skip);
2941   assert(addr < src_region_end, "wrong src region");
2942   return addr;
2943 }
2944 
2945 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2946                                                      SpaceId src_space_id,
2947                                                      size_t beg_region,
2948                                                      HeapWord* end_addr)
2949 {
2950   ParallelCompactData& sd = summary_data();
2951 
2952 #ifdef ASSERT
2953   MutableSpace* const src_space = _space_info[src_space_id].space();
2954   HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2955   assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2956          "src_space_id does not match beg_addr");
2957   assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2958          "src_space_id does not match end_addr");
2959 #endif // #ifdef ASSERT
2960 
2961   RegionData* const beg = sd.region(beg_region);
2962   RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2963 
2964   // Regions up to new_top() are enqueued if they become available.
2965   HeapWord* const new_top = _space_info[src_space_id].new_top();
2966   RegionData* const enqueue_end =
2967     sd.addr_to_region_ptr(sd.region_align_up(new_top));
2968 
2969   for (RegionData* cur = beg; cur < end; ++cur) {
2970     assert(cur->data_size() > 0, "region must have live data");
2971     cur->decrement_destination_count();
2972     if (cur < enqueue_end && cur->available() && cur->claim()) {
2973       if (cur->mark_normal()) {
2974         cm->push_region(sd.region(cur));
2975       } else if (cur->mark_copied()) {
2976         // Try to copy the content of the shadow region back to its corresponding
2977         // heap region if the shadow region is filled. Otherwise, the GC thread
2978         // fills the shadow region will copy the data back (see
2979         // MoveAndUpdateShadowClosure::complete_region).
2980         copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
2981         cm->push_shadow_region_mt_safe(cur->shadow_region());
2982         cur->set_completed();
2983       }
2984     }
2985   }
2986 }
2987 
2988 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2989                                           SpaceId& src_space_id,
2990                                           HeapWord*& src_space_top,
2991                                           HeapWord* end_addr)
2992 {
2993   typedef ParallelCompactData::RegionData RegionData;
2994 
2995   ParallelCompactData& sd = PSParallelCompact::summary_data();
2996   const size_t region_size = ParallelCompactData::RegionSize;
2997 
2998   size_t src_region_idx = 0;
2999 
3000   // Skip empty regions (if any) up to the top of the space.
3001   HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
3002   RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
3003   HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
3004   const RegionData* const top_region_ptr =
3005     sd.addr_to_region_ptr(top_aligned_up);
3006   while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
3007     ++src_region_ptr;
3008   }
3009 
3010   if (src_region_ptr < top_region_ptr) {
3011     // The next source region is in the current space.  Update src_region_idx
3012     // and the source address to match src_region_ptr.
3013     src_region_idx = sd.region(src_region_ptr);
3014     HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
3015     if (src_region_addr > closure.source()) {
3016       closure.set_source(src_region_addr);
3017     }
3018     return src_region_idx;
3019   }
3020 
3021   // Switch to a new source space and find the first non-empty region.
3022   unsigned int space_id = src_space_id + 1;
3023   assert(space_id < last_space_id, "not enough spaces");
3024 
3025   HeapWord* const destination = closure.destination();
3026 
3027   do {
3028     MutableSpace* space = _space_info[space_id].space();
3029     HeapWord* const bottom = space->bottom();
3030     const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
3031 
3032     // Iterate over the spaces that do not compact into themselves.
3033     if (bottom_cp->destination() != bottom) {
3034       HeapWord* const top_aligned_up = sd.region_align_up(space->top());
3035       const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
3036 
3037       for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
3038         if (src_cp->live_obj_size() > 0) {
3039           // Found it.
3040           assert(src_cp->destination() == destination,
3041                  "first live obj in the space must match the destination");
3042           assert(src_cp->partial_obj_size() == 0,
3043                  "a space cannot begin with a partial obj");
3044 
3045           src_space_id = SpaceId(space_id);
3046           src_space_top = space->top();
3047           const size_t src_region_idx = sd.region(src_cp);
3048           closure.set_source(sd.region_to_addr(src_region_idx));
3049           return src_region_idx;
3050         } else {
3051           assert(src_cp->data_size() == 0, "sanity");
3052         }
3053       }
3054     }
3055   } while (++space_id < last_space_id);
3056 
3057   assert(false, "no source region was found");
3058   return 0;
3059 }
3060 
3061 void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
3062 {
3063   typedef ParMarkBitMap::IterationStatus IterationStatus;
3064   ParMarkBitMap* const bitmap = mark_bitmap();
3065   ParallelCompactData& sd = summary_data();
3066   RegionData* const region_ptr = sd.region(region_idx);
3067 
3068   // Get the source region and related info.
3069   size_t src_region_idx = region_ptr->source_region();
3070   SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
3071   HeapWord* src_space_top = _space_info[src_space_id].space()->top();
3072   HeapWord* dest_addr = sd.region_to_addr(region_idx);
3073 
3074   closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
3075 
3076   // Adjust src_region_idx to prepare for decrementing destination counts (the
3077   // destination count is not decremented when a region is copied to itself).
3078   if (src_region_idx == region_idx) {
3079     src_region_idx += 1;
3080   }
3081 
3082   if (bitmap->is_unmarked(closure.source())) {
3083     // The first source word is in the middle of an object; copy the remainder
3084     // of the object or as much as will fit.  The fact that pointer updates were
3085     // deferred will be noted when the object header is processed.
3086     HeapWord* const old_src_addr = closure.source();
3087     closure.copy_partial_obj();
3088     if (closure.is_full()) {
3089       decrement_destination_counts(cm, src_space_id, src_region_idx,
3090                                    closure.source());
3091       region_ptr->set_deferred_obj_addr(NULL);
3092       closure.complete_region(cm, dest_addr, region_ptr);
3093       return;
3094     }
3095 
3096     HeapWord* const end_addr = sd.region_align_down(closure.source());
3097     if (sd.region_align_down(old_src_addr) != end_addr) {
3098       // The partial object was copied from more than one source region.
3099       decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3100 
3101       // Move to the next source region, possibly switching spaces as well.  All
3102       // args except end_addr may be modified.
3103       src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3104                                        end_addr);
3105     }
3106   }
3107 
3108   do {
3109     HeapWord* const cur_addr = closure.source();
3110     HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
3111                                     src_space_top);
3112     IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
3113 
3114     if (status == ParMarkBitMap::incomplete) {
3115       // The last obj that starts in the source region does not end in the
3116       // region.
3117       assert(closure.source() < end_addr, "sanity");
3118       HeapWord* const obj_beg = closure.source();
3119       HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
3120                                        src_space_top);
3121       HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
3122       if (obj_end < range_end) {
3123         // The end was found; the entire object will fit.
3124         status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
3125         assert(status != ParMarkBitMap::would_overflow, "sanity");
3126       } else {
3127         // The end was not found; the object will not fit.
3128         assert(range_end < src_space_top, "obj cannot cross space boundary");
3129         status = ParMarkBitMap::would_overflow;
3130       }
3131     }
3132 
3133     if (status == ParMarkBitMap::would_overflow) {
3134       // The last object did not fit.  Note that interior oop updates were
3135       // deferred, then copy enough of the object to fill the region.
3136       region_ptr->set_deferred_obj_addr(closure.destination());
3137       status = closure.copy_until_full(); // copies from closure.source()
3138 
3139       decrement_destination_counts(cm, src_space_id, src_region_idx,
3140                                    closure.source());
3141       closure.complete_region(cm, dest_addr, region_ptr);
3142       return;
3143     }
3144 
3145     if (status == ParMarkBitMap::full) {
3146       decrement_destination_counts(cm, src_space_id, src_region_idx,
3147                                    closure.source());
3148       region_ptr->set_deferred_obj_addr(NULL);
3149       closure.complete_region(cm, dest_addr, region_ptr);
3150       return;
3151     }
3152 
3153     decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3154 
3155     // Move to the next source region, possibly switching spaces as well.  All
3156     // args except end_addr may be modified.
3157     src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3158                                      end_addr);
3159   } while (true);
3160 }
3161 
3162 void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
3163 {
3164   MoveAndUpdateClosure cl(mark_bitmap(), cm, region_idx);
3165   fill_region(cm, cl, region_idx);
3166 }
3167 
3168 void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
3169 {
3170   // Get a shadow region first
3171   ParallelCompactData& sd = summary_data();
3172   RegionData* const region_ptr = sd.region(region_idx);
3173   size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
3174   // The InvalidShadow return value indicates the corresponding heap region is available,
3175   // so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
3176   // MoveAndUpdateShadowClosure to fill the acquired shadow region.
3177   if (shadow_region == cm->InvalidShadow) {
3178     MoveAndUpdateClosure cl(mark_bitmap(), cm, region_idx);
3179     region_ptr->shadow_to_normal();
3180     return fill_region(cm, cl, region_idx);
3181   } else {
3182     MoveAndUpdateShadowClosure cl(mark_bitmap(), cm, region_idx, shadow_region);
3183     return fill_region(cm, cl, region_idx);
3184   }
3185 }
3186 
3187 void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
3188 {
3189   Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
3190 }
3191 
3192 bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t &region_idx)
3193 {
3194   size_t next = cm->next_shadow_region();
3195   ParallelCompactData& sd = summary_data();
3196   size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
3197   uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
3198 
3199   while (next < old_new_top) {
3200     if (sd.region(next)->mark_shadow()) {
3201       region_idx = next;
3202       return true;
3203     }
3204     next = cm->move_next_shadow_region_by(active_gc_threads);
3205   }
3206 
3207   return false;
3208 }
3209 
3210 // The shadow region is an optimization to address region dependencies in full GC. The basic
3211 // idea is making more regions available by temporally storing their live objects in empty
3212 // shadow regions to resolve dependencies between them and the destination regions. Therefore,
3213 // GC threads need not wait destination regions to be available before processing sources.
3214 //
3215 // A typical workflow would be:
3216 // After draining its own stack and failing to steal from others, a GC worker would pick an
3217 // unavailable region (destination count > 0) and get a shadow region. Then the worker fills
3218 // the shadow region by copying live objects from source regions of the unavailable one. Once
3219 // the unavailable region becomes available, the data in the shadow region will be copied back.
3220 // Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
3221 //
3222 // For more details, please refer to ยง4.2 of the VEE'19 paper:
3223 // Haoyu Li, Mingyu Wu, Binyu Zang, and Haibo Chen. 2019. ScissorGC: scalable and efficient
3224 // compaction for Java full garbage collection. In Proceedings of the 15th ACM SIGPLAN/SIGOPS
3225 // International Conference on Virtual Execution Environments (VEE 2019). ACM, New York, NY, USA,
3226 // 108-121. DOI: https://doi.org/10.1145/3313808.3313820
3227 void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
3228 {
3229   const ParallelCompactData& sd = PSParallelCompact::summary_data();
3230 
3231   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
3232     SpaceInfo* const space_info = _space_info + id;
3233     MutableSpace* const space = space_info->space();
3234 
3235     const size_t beg_region =
3236       sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
3237     const size_t end_region =
3238       sd.addr_to_region_idx(sd.region_align_down(space->end()));
3239 
3240     for (size_t cur = beg_region; cur < end_region; ++cur) {
3241       ParCompactionManager::push_shadow_region(cur);
3242     }
3243   }
3244 
3245   size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
3246   for (uint i = 0; i < parallel_gc_threads; i++) {
3247     ParCompactionManager *cm = ParCompactionManager::manager_array(i);
3248     cm->set_next_shadow_region(beg_region + i);
3249   }
3250 }
3251 
3252 void PSParallelCompact::fill_blocks(size_t region_idx)
3253 {
3254   // Fill in the block table elements for the specified region.  Each block
3255   // table element holds the number of live words in the region that are to the
3256   // left of the first object that starts in the block.  Thus only blocks in
3257   // which an object starts need to be filled.
3258   //
3259   // The algorithm scans the section of the bitmap that corresponds to the
3260   // region, keeping a running total of the live words.  When an object start is
3261   // found, if it's the first to start in the block that contains it, the
3262   // current total is written to the block table element.
3263   const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
3264   const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
3265   const size_t RegionSize = ParallelCompactData::RegionSize;
3266 
3267   ParallelCompactData& sd = summary_data();
3268   const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
3269   if (partial_obj_size >= RegionSize) {
3270     return; // No objects start in this region.
3271   }
3272 
3273   // Ensure the first loop iteration decides that the block has changed.
3274   size_t cur_block = sd.block_count();
3275 
3276   const ParMarkBitMap* const bitmap = mark_bitmap();
3277 
3278   const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
3279   assert((size_t)1 << Log2BitsPerBlock ==
3280          bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
3281 
3282   size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
3283   const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
3284   size_t live_bits = bitmap->words_to_bits(partial_obj_size);
3285   beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
3286   while (beg_bit < range_end) {
3287     const size_t new_block = beg_bit >> Log2BitsPerBlock;
3288     if (new_block != cur_block) {
3289       cur_block = new_block;
3290       sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
3291     }
3292 
3293     const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
3294     if (end_bit < range_end - 1) {
3295       live_bits += end_bit - beg_bit + 1;
3296       beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
3297     } else {
3298       return;
3299     }
3300   }
3301 }
3302 
3303 jlong PSParallelCompact::millis_since_last_gc() {
3304   // We need a monotonically non-decreasing time in ms but
3305   // os::javaTimeMillis() does not guarantee monotonicity.
3306   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3307   jlong ret_val = now - _time_of_last_gc;
3308   // XXX See note in genCollectedHeap::millis_since_last_gc().
3309   if (ret_val < 0) {
3310     NOT_PRODUCT(log_warning(gc)("time warp: " JLONG_FORMAT, ret_val);)
3311     return 0;
3312   }
3313   return ret_val;
3314 }
3315 
3316 void PSParallelCompact::reset_millis_since_last_gc() {
3317   // We need a monotonically non-decreasing time in ms but
3318   // os::javaTimeMillis() does not guarantee monotonicity.
3319   _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3320 }
3321 
3322 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3323 {
3324   if (source() != copy_destination()) {
3325     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3326     Copy::aligned_conjoint_words(source(), copy_destination(), words_remaining());
3327   }
3328   update_state(words_remaining());
3329   assert(is_full(), "sanity");
3330   return ParMarkBitMap::full;
3331 }
3332 
3333 void MoveAndUpdateClosure::copy_partial_obj()
3334 {
3335   size_t words = words_remaining();
3336 
3337   HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3338   HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3339   if (end_addr < range_end) {
3340     words = bitmap()->obj_size(source(), end_addr);
3341   }
3342 
3343   // This test is necessary; if omitted, the pointer updates to a partial object
3344   // that crosses the dense prefix boundary could be overwritten.
3345   if (source() != copy_destination()) {
3346     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3347     Copy::aligned_conjoint_words(source(), copy_destination(), words);
3348   }
3349   update_state(words);
3350 }
3351 
3352 void MoveAndUpdateClosure::complete_region(ParCompactionManager *cm, HeapWord *dest_addr,
3353                                            PSParallelCompact::RegionData *region_ptr) {
3354   assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
3355   region_ptr->set_completed();
3356 }
3357 
3358 ParMarkBitMapClosure::IterationStatus
3359 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3360   assert(destination() != NULL, "sanity");
3361   assert(bitmap()->obj_size(addr) == words, "bad size");
3362 
3363   _source = addr;
3364   assert(PSParallelCompact::summary_data().calc_new_pointer(source(), compaction_manager()) ==
3365          destination(), "wrong destination");
3366 
3367   if (words > words_remaining()) {
3368     return ParMarkBitMap::would_overflow;
3369   }
3370 
3371   // The start_array must be updated even if the object is not moving.
3372   if (_start_array != NULL) {
3373     _start_array->allocate_block(destination());
3374   }
3375 
3376   if (copy_destination() != source()) {
3377     DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3378     Copy::aligned_conjoint_words(source(), copy_destination(), words);
3379   }
3380 
3381   oop moved_oop = (oop) copy_destination();
3382   compaction_manager()->update_contents(moved_oop);
3383   assert(oopDesc::is_oop_or_null(moved_oop), "Expected an oop or NULL at " PTR_FORMAT, p2i(moved_oop));
3384 
3385   update_state(words);
3386   assert(copy_destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
3387   return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3388 }
3389 
3390 void MoveAndUpdateShadowClosure::complete_region(ParCompactionManager *cm, HeapWord *dest_addr,
3391                                                  PSParallelCompact::RegionData *region_ptr) {
3392   assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
3393   // Record the shadow region index
3394   region_ptr->set_shadow_region(_shadow);
3395   // Mark the shadow region as filled to indicate the data is ready to be
3396   // copied back
3397   region_ptr->mark_filled();
3398   // Try to copy the content of the shadow region back to its corresponding
3399   // heap region if available; the GC thread that decreases the destination
3400   // count to zero will do the copying otherwise (see
3401   // PSParallelCompact::decrement_destination_counts).
3402   if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
3403     region_ptr->set_completed();
3404     PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
3405     cm->push_shadow_region_mt_safe(_shadow);
3406   }
3407 }
3408 
3409 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3410                                      ParCompactionManager* cm,
3411                                      PSParallelCompact::SpaceId space_id) :
3412   ParMarkBitMapClosure(mbm, cm),
3413   _space_id(space_id),
3414   _start_array(PSParallelCompact::start_array(space_id))
3415 {
3416 }
3417 
3418 // Updates the references in the object to their new values.
3419 ParMarkBitMapClosure::IterationStatus
3420 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3421   do_addr(addr);
3422   return ParMarkBitMap::incomplete;
3423 }
3424 
3425 FillClosure::FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id) :
3426   ParMarkBitMapClosure(PSParallelCompact::mark_bitmap(), cm),
3427   _start_array(PSParallelCompact::start_array(space_id))
3428 {
3429   assert(space_id == PSParallelCompact::old_space_id,
3430          "cannot use FillClosure in the young gen");
3431 }
3432 
3433 ParMarkBitMapClosure::IterationStatus
3434 FillClosure::do_addr(HeapWord* addr, size_t size) {
3435   CollectedHeap::fill_with_objects(addr, size);
3436   HeapWord* const end = addr + size;
3437   do {
3438     _start_array->allocate_block(addr);
3439     addr += oop(addr)->size();
3440   } while (addr < end);
3441   return ParMarkBitMap::incomplete;
3442 }
--- EOF ---