1 /*
   2  * Copyright (c) 2005, 2020, 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/taskTerminator.hpp"
  57 #include "gc/shared/weakProcessor.hpp"
  58 #include "gc/shared/workerPolicy.hpp"
  59 #include "gc/shared/workgroup.hpp"
  60 #include "logging/log.hpp"
  61 #include "memory/iterator.inline.hpp"
  62 #include "memory/resourceArea.hpp"
  63 #include "memory/universe.hpp"
  64 #include "oops/access.inline.hpp"
  65 #include "oops/instanceClassLoaderKlass.inline.hpp"
  66 #include "oops/instanceKlass.inline.hpp"
  67 #include "oops/instanceMirrorKlass.inline.hpp"
  68 #include "oops/methodData.hpp"
  69 #include "oops/objArrayKlass.inline.hpp"
  70 #include "oops/oop.inline.hpp"
  71 #include "runtime/atomic.hpp"
  72 #include "runtime/handles.inline.hpp"
  73 #include "runtime/safepoint.hpp"
  74 #include "runtime/vmThread.hpp"
  75 #include "services/management.hpp"
  76 #include "services/memTracker.hpp"
  77 #include "services/memoryService.hpp"
  78 #include "utilities/align.hpp"
  79 #include "utilities/debug.hpp"
  80 #include "utilities/events.hpp"
  81 #include "utilities/formatBuffer.hpp"
  82 #include "utilities/macros.hpp"
  83 #include "utilities/stack.inline.hpp"
  84 #if INCLUDE_JVMCI
  85 #include "jvmci/jvmci.hpp"
  86 #endif
  87 
  88 #include <math.h>
  89 
  90 // All sizes are in HeapWords.
  91 const size_t ParallelCompactData::Log2RegionSize  = 16; // 64K words
  92 const size_t ParallelCompactData::RegionSize      = (size_t)1 << Log2RegionSize;
  93 const size_t ParallelCompactData::RegionSizeBytes =
  94   RegionSize << LogHeapWordSize;
  95 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
  96 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
  97 const size_t ParallelCompactData::RegionAddrMask       = ~RegionAddrOffsetMask;
  98 
  99 const size_t ParallelCompactData::Log2BlockSize   = 7; // 128 words
 100 const size_t ParallelCompactData::BlockSize       = (size_t)1 << Log2BlockSize;
 101 const size_t ParallelCompactData::BlockSizeBytes  =
 102   BlockSize << LogHeapWordSize;
 103 const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
 104 const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
 105 const size_t ParallelCompactData::BlockAddrMask       = ~BlockAddrOffsetMask;
 106 
 107 const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
 108 const size_t ParallelCompactData::Log2BlocksPerRegion =
 109   Log2RegionSize - Log2BlockSize;
 110 
 111 const ParallelCompactData::RegionData::region_sz_t
 112 ParallelCompactData::RegionData::dc_shift = 27;
 113 
 114 const ParallelCompactData::RegionData::region_sz_t
 115 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
 116 
 117 const ParallelCompactData::RegionData::region_sz_t
 118 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
 119 
 120 const ParallelCompactData::RegionData::region_sz_t
 121 ParallelCompactData::RegionData::los_mask = ~dc_mask;
 122 
 123 const ParallelCompactData::RegionData::region_sz_t
 124 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
 125 
 126 const ParallelCompactData::RegionData::region_sz_t
 127 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
 128 
 129 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
 130 
 131 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
 132 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
 133 
 134 double PSParallelCompact::_dwl_mean;
 135 double PSParallelCompact::_dwl_std_dev;
 136 double PSParallelCompact::_dwl_first_term;
 137 double PSParallelCompact::_dwl_adjustment;
 138 #ifdef  ASSERT
 139 bool   PSParallelCompact::_dwl_initialized = false;
 140 #endif  // #ifdef ASSERT
 141 
 142 void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
 143                        HeapWord* destination)
 144 {
 145   assert(src_region_idx != 0, "invalid src_region_idx");
 146   assert(partial_obj_size != 0, "invalid partial_obj_size argument");
 147   assert(destination != NULL, "invalid destination argument");
 148 
 149   _src_region_idx = src_region_idx;
 150   _partial_obj_size = partial_obj_size;
 151   _destination = destination;
 152 
 153   // These fields may not be updated below, so make sure they're clear.
 154   assert(_dest_region_addr == NULL, "should have been cleared");
 155   assert(_first_src_addr == NULL, "should have been cleared");
 156 
 157   // Determine the number of destination regions for the partial object.
 158   HeapWord* const last_word = destination + partial_obj_size - 1;
 159   const ParallelCompactData& sd = PSParallelCompact::summary_data();
 160   HeapWord* const beg_region_addr = sd.region_align_down(destination);
 161   HeapWord* const end_region_addr = sd.region_align_down(last_word);
 162 
 163   if (beg_region_addr == end_region_addr) {
 164     // One destination region.
 165     _destination_count = 1;
 166     if (end_region_addr == destination) {
 167       // The destination falls on a region boundary, thus the first word of the
 168       // partial object will be the first word copied to the destination region.
 169       _dest_region_addr = end_region_addr;
 170       _first_src_addr = sd.region_to_addr(src_region_idx);
 171     }
 172   } else {
 173     // Two destination regions.  When copied, the partial object will cross a
 174     // destination region boundary, so a word somewhere within the partial
 175     // object will be the first word copied to the second destination region.
 176     _destination_count = 2;
 177     _dest_region_addr = end_region_addr;
 178     const size_t ofs = pointer_delta(end_region_addr, destination);
 179     assert(ofs < _partial_obj_size, "sanity");
 180     _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
 181   }
 182 }
 183 
 184 void SplitInfo::clear()
 185 {
 186   _src_region_idx = 0;
 187   _partial_obj_size = 0;
 188   _destination = NULL;
 189   _destination_count = 0;
 190   _dest_region_addr = NULL;
 191   _first_src_addr = NULL;
 192   assert(!is_valid(), "sanity");
 193 }
 194 
 195 #ifdef  ASSERT
 196 void SplitInfo::verify_clear()
 197 {
 198   assert(_src_region_idx == 0, "not clear");
 199   assert(_partial_obj_size == 0, "not clear");
 200   assert(_destination == NULL, "not clear");
 201   assert(_destination_count == 0, "not clear");
 202   assert(_dest_region_addr == NULL, "not clear");
 203   assert(_first_src_addr == NULL, "not clear");
 204 }
 205 #endif  // #ifdef ASSERT
 206 
 207 
 208 void PSParallelCompact::print_on_error(outputStream* st) {
 209   _mark_bitmap.print_on_error(st);
 210 }
 211 
 212 #ifndef PRODUCT
 213 const char* PSParallelCompact::space_names[] = {
 214   "old ", "eden", "from", "to  "
 215 };
 216 
 217 void PSParallelCompact::print_region_ranges() {
 218   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 219     return;
 220   }
 221   Log(gc, compaction) log;
 222   ResourceMark rm;
 223   LogStream ls(log.trace());
 224   Universe::print_on(&ls);
 225   log.trace("space  bottom     top        end        new_top");
 226   log.trace("------ ---------- ---------- ---------- ----------");
 227 
 228   for (unsigned int id = 0; id < last_space_id; ++id) {
 229     const MutableSpace* space = _space_info[id].space();
 230     log.trace("%u %s "
 231               SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
 232               SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
 233               id, space_names[id],
 234               summary_data().addr_to_region_idx(space->bottom()),
 235               summary_data().addr_to_region_idx(space->top()),
 236               summary_data().addr_to_region_idx(space->end()),
 237               summary_data().addr_to_region_idx(_space_info[id].new_top()));
 238   }
 239 }
 240 
 241 void
 242 print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
 243 {
 244 #define REGION_IDX_FORMAT        SIZE_FORMAT_W(7)
 245 #define REGION_DATA_FORMAT       SIZE_FORMAT_W(5)
 246 
 247   ParallelCompactData& sd = PSParallelCompact::summary_data();
 248   size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
 249   log_develop_trace(gc, compaction)(
 250       REGION_IDX_FORMAT " " PTR_FORMAT " "
 251       REGION_IDX_FORMAT " " PTR_FORMAT " "
 252       REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
 253       REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
 254       i, p2i(c->data_location()), dci, p2i(c->destination()),
 255       c->partial_obj_size(), c->live_obj_size(),
 256       c->data_size(), c->source_region(), c->destination_count());
 257 
 258 #undef  REGION_IDX_FORMAT
 259 #undef  REGION_DATA_FORMAT
 260 }
 261 
 262 void
 263 print_generic_summary_data(ParallelCompactData& summary_data,
 264                            HeapWord* const beg_addr,
 265                            HeapWord* const end_addr)
 266 {
 267   size_t total_words = 0;
 268   size_t i = summary_data.addr_to_region_idx(beg_addr);
 269   const size_t last = summary_data.addr_to_region_idx(end_addr);
 270   HeapWord* pdest = 0;
 271 
 272   while (i < last) {
 273     ParallelCompactData::RegionData* c = summary_data.region(i);
 274     if (c->data_size() != 0 || c->destination() != pdest) {
 275       print_generic_summary_region(i, c);
 276       total_words += c->data_size();
 277       pdest = c->destination();
 278     }
 279     ++i;
 280   }
 281 
 282   log_develop_trace(gc, compaction)("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
 283 }
 284 
 285 void
 286 PSParallelCompact::print_generic_summary_data(ParallelCompactData& summary_data,
 287                                               HeapWord* const beg_addr,
 288                                               HeapWord* const end_addr) {
 289   ::print_generic_summary_data(summary_data,beg_addr, end_addr);
 290 }
 291 
 292 void
 293 print_generic_summary_data(ParallelCompactData& summary_data,
 294                            SpaceInfo* space_info)
 295 {
 296   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 297     return;
 298   }
 299 
 300   for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
 301     const MutableSpace* space = space_info[id].space();
 302     print_generic_summary_data(summary_data, space->bottom(),
 303                                MAX2(space->top(), space_info[id].new_top()));
 304   }
 305 }
 306 
 307 void
 308 print_initial_summary_data(ParallelCompactData& summary_data,
 309                            const MutableSpace* space) {
 310   if (space->top() == space->bottom()) {
 311     return;
 312   }
 313 
 314   const size_t region_size = ParallelCompactData::RegionSize;
 315   typedef ParallelCompactData::RegionData RegionData;
 316   HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
 317   const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
 318   const RegionData* c = summary_data.region(end_region - 1);
 319   HeapWord* end_addr = c->destination() + c->data_size();
 320   const size_t live_in_space = pointer_delta(end_addr, space->bottom());
 321 
 322   // Print (and count) the full regions at the beginning of the space.
 323   size_t full_region_count = 0;
 324   size_t i = summary_data.addr_to_region_idx(space->bottom());
 325   while (i < end_region && summary_data.region(i)->data_size() == region_size) {
 326     ParallelCompactData::RegionData* c = summary_data.region(i);
 327     log_develop_trace(gc, compaction)(
 328         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 329         i, p2i(c->destination()),
 330         c->partial_obj_size(), c->live_obj_size(),
 331         c->data_size(), c->source_region(), c->destination_count());
 332     ++full_region_count;
 333     ++i;
 334   }
 335 
 336   size_t live_to_right = live_in_space - full_region_count * region_size;
 337 
 338   double max_reclaimed_ratio = 0.0;
 339   size_t max_reclaimed_ratio_region = 0;
 340   size_t max_dead_to_right = 0;
 341   size_t max_live_to_right = 0;
 342 
 343   // Print the 'reclaimed ratio' for regions while there is something live in
 344   // the region or to the right of it.  The remaining regions are empty (and
 345   // uninteresting), and computing the ratio will result in division by 0.
 346   while (i < end_region && live_to_right > 0) {
 347     c = summary_data.region(i);
 348     HeapWord* const region_addr = summary_data.region_to_addr(i);
 349     const size_t used_to_right = pointer_delta(space->top(), region_addr);
 350     const size_t dead_to_right = used_to_right - live_to_right;
 351     const double reclaimed_ratio = double(dead_to_right) / live_to_right;
 352 
 353     if (reclaimed_ratio > max_reclaimed_ratio) {
 354             max_reclaimed_ratio = reclaimed_ratio;
 355             max_reclaimed_ratio_region = i;
 356             max_dead_to_right = dead_to_right;
 357             max_live_to_right = live_to_right;
 358     }
 359 
 360     ParallelCompactData::RegionData* c = summary_data.region(i);
 361     log_develop_trace(gc, compaction)(
 362         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d"
 363         "%12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
 364         i, p2i(c->destination()),
 365         c->partial_obj_size(), c->live_obj_size(),
 366         c->data_size(), c->source_region(), c->destination_count(),
 367         reclaimed_ratio, dead_to_right, live_to_right);
 368 
 369 
 370     live_to_right -= c->data_size();
 371     ++i;
 372   }
 373 
 374   // Any remaining regions are empty.  Print one more if there is one.
 375   if (i < end_region) {
 376     ParallelCompactData::RegionData* c = summary_data.region(i);
 377     log_develop_trace(gc, compaction)(
 378         SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
 379          i, p2i(c->destination()),
 380          c->partial_obj_size(), c->live_obj_size(),
 381          c->data_size(), c->source_region(), c->destination_count());
 382   }
 383 
 384   log_develop_trace(gc, compaction)("max:  " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
 385                                     max_reclaimed_ratio_region, max_dead_to_right, max_live_to_right, max_reclaimed_ratio);
 386 }
 387 
 388 void
 389 print_initial_summary_data(ParallelCompactData& summary_data,
 390                            SpaceInfo* space_info) {
 391   if (!log_develop_is_enabled(Trace, gc, compaction)) {
 392     return;
 393   }
 394 
 395   unsigned int id = PSParallelCompact::old_space_id;
 396   const MutableSpace* space;
 397   do {
 398     space = space_info[id].space();
 399     print_initial_summary_data(summary_data, space);
 400   } while (++id < PSParallelCompact::eden_space_id);
 401 
 402   do {
 403     space = space_info[id].space();
 404     print_generic_summary_data(summary_data, space->bottom(), space->top());
 405   } while (++id < PSParallelCompact::last_space_id);
 406 }
 407 #endif  // #ifndef PRODUCT
 408 
 409 #ifdef  ASSERT
 410 size_t add_obj_count;
 411 size_t add_obj_size;
 412 size_t mark_bitmap_count;
 413 size_t mark_bitmap_size;
 414 #endif  // #ifdef ASSERT
 415 
 416 ParallelCompactData::ParallelCompactData() :
 417   _region_start(NULL),
 418   DEBUG_ONLY(_region_end(NULL) COMMA)
 419   _region_vspace(NULL),
 420   _reserved_byte_size(0),
 421   _region_data(NULL),
 422   _region_count(0),
 423   _block_vspace(NULL),
 424   _block_data(NULL),
 425   _block_count(0) {}
 426 
 427 bool ParallelCompactData::initialize(MemRegion covered_region)
 428 {
 429   _region_start = covered_region.start();
 430   const size_t region_size = covered_region.word_size();
 431   DEBUG_ONLY(_region_end = _region_start + region_size;)
 432 
 433   assert(region_align_down(_region_start) == _region_start,
 434          "region start not aligned");
 435   assert((region_size & RegionSizeOffsetMask) == 0,
 436          "region size not a multiple of RegionSize");
 437 
 438   bool result = initialize_region_data(region_size) && initialize_block_data();
 439   return result;
 440 }
 441 
 442 PSVirtualSpace*
 443 ParallelCompactData::create_vspace(size_t count, size_t element_size)
 444 {
 445   const size_t raw_bytes = count * element_size;
 446   const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
 447   const size_t granularity = os::vm_allocation_granularity();
 448   _reserved_byte_size = align_up(raw_bytes, MAX2(page_sz, granularity));
 449 
 450   const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
 451     MAX2(page_sz, granularity);
 452   ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0);
 453   os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, page_sz, rs.base(),
 454                        rs.size());
 455 
 456   MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
 457 
 458   PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
 459   if (vspace != 0) {
 460     if (vspace->expand_by(_reserved_byte_size)) {
 461       return vspace;
 462     }
 463     delete vspace;
 464     // Release memory reserved in the space.
 465     rs.release();
 466   }
 467 
 468   return 0;
 469 }
 470 
 471 bool ParallelCompactData::initialize_region_data(size_t region_size)
 472 {
 473   const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
 474   _region_vspace = create_vspace(count, sizeof(RegionData));
 475   if (_region_vspace != 0) {
 476     _region_data = (RegionData*)_region_vspace->reserved_low_addr();
 477     _region_count = count;
 478     return true;
 479   }
 480   return false;
 481 }
 482 
 483 bool ParallelCompactData::initialize_block_data()
 484 {
 485   assert(_region_count != 0, "region data must be initialized first");
 486   const size_t count = _region_count << Log2BlocksPerRegion;
 487   _block_vspace = create_vspace(count, sizeof(BlockData));
 488   if (_block_vspace != 0) {
 489     _block_data = (BlockData*)_block_vspace->reserved_low_addr();
 490     _block_count = count;
 491     return true;
 492   }
 493   return false;
 494 }
 495 
 496 void ParallelCompactData::clear()
 497 {
 498   memset(_region_data, 0, _region_vspace->committed_size());
 499   memset(_block_data, 0, _block_vspace->committed_size());
 500 }
 501 
 502 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
 503   assert(beg_region <= _region_count, "beg_region out of range");
 504   assert(end_region <= _region_count, "end_region out of range");
 505   assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize");
 506 
 507   const size_t region_cnt = end_region - beg_region;
 508   memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
 509 
 510   const size_t beg_block = beg_region * BlocksPerRegion;
 511   const size_t block_cnt = region_cnt * BlocksPerRegion;
 512   memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData));
 513 }
 514 
 515 HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
 516 {
 517   const RegionData* cur_cp = region(region_idx);
 518   const RegionData* const end_cp = region(region_count() - 1);
 519 
 520   HeapWord* result = region_to_addr(region_idx);
 521   if (cur_cp < end_cp) {
 522     do {
 523       result += cur_cp->partial_obj_size();
 524     } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
 525   }
 526   return result;
 527 }
 528 
 529 void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
 530 {
 531   const size_t obj_ofs = pointer_delta(addr, _region_start);
 532   const size_t beg_region = obj_ofs >> Log2RegionSize;
 533   const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
 534 
 535   DEBUG_ONLY(Atomic::inc(&add_obj_count);)
 536   DEBUG_ONLY(Atomic::add(&add_obj_size, len);)
 537 
 538   if (beg_region == end_region) {
 539     // All in one region.
 540     _region_data[beg_region].add_live_obj(len);
 541     return;
 542   }
 543 
 544   // First region.
 545   const size_t beg_ofs = region_offset(addr);
 546   _region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
 547 
 548   Klass* klass = ((oop)addr)->klass();
 549   // Middle regions--completely spanned by this object.
 550   for (size_t region = beg_region + 1; region < end_region; ++region) {
 551     _region_data[region].set_partial_obj_size(RegionSize);
 552     _region_data[region].set_partial_obj_addr(addr);
 553   }
 554 
 555   // Last region.
 556   const size_t end_ofs = region_offset(addr + len - 1);
 557   _region_data[end_region].set_partial_obj_size(end_ofs + 1);
 558   _region_data[end_region].set_partial_obj_addr(addr);
 559 }
 560 
 561 void
 562 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
 563 {
 564   assert(region_offset(beg) == 0, "not RegionSize aligned");
 565   assert(region_offset(end) == 0, "not RegionSize aligned");
 566 
 567   size_t cur_region = addr_to_region_idx(beg);
 568   const size_t end_region = addr_to_region_idx(end);
 569   HeapWord* addr = beg;
 570   while (cur_region < end_region) {
 571     _region_data[cur_region].set_destination(addr);
 572     _region_data[cur_region].set_destination_count(0);
 573     _region_data[cur_region].set_source_region(cur_region);
 574     _region_data[cur_region].set_data_location(addr);
 575 
 576     // Update live_obj_size so the region appears completely full.
 577     size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
 578     _region_data[cur_region].set_live_obj_size(live_size);
 579 
 580     ++cur_region;
 581     addr += RegionSize;
 582   }
 583 }
 584 
 585 // Find the point at which a space can be split and, if necessary, record the
 586 // split point.
 587 //
 588 // If the current src region (which overflowed the destination space) doesn't
 589 // have a partial object, the split point is at the beginning of the current src
 590 // region (an "easy" split, no extra bookkeeping required).
 591 //
 592 // If the current src region has a partial object, the split point is in the
 593 // region where that partial object starts (call it the split_region).  If
 594 // split_region has a partial object, then the split point is just after that
 595 // partial object (a "hard" split where we have to record the split data and
 596 // zero the partial_obj_size field).  With a "hard" split, we know that the
 597 // partial_obj ends within split_region because the partial object that caused
 598 // the overflow starts in split_region.  If split_region doesn't have a partial
 599 // obj, then the split is at the beginning of split_region (another "easy"
 600 // split).
 601 HeapWord*
 602 ParallelCompactData::summarize_split_space(size_t src_region,
 603                                            SplitInfo& split_info,
 604                                            HeapWord* destination,
 605                                            HeapWord* target_end,
 606                                            HeapWord** target_next)
 607 {
 608   assert(destination <= target_end, "sanity");
 609   assert(destination + _region_data[src_region].data_size() > target_end,
 610     "region should not fit into target space");
 611   assert(is_region_aligned(target_end), "sanity");
 612 
 613   size_t split_region = src_region;
 614   HeapWord* split_destination = destination;
 615   size_t partial_obj_size = _region_data[src_region].partial_obj_size();
 616 
 617   if (destination + partial_obj_size > target_end) {
 618     // The split point is just after the partial object (if any) in the
 619     // src_region that contains the start of the object that overflowed the
 620     // destination space.
 621     //
 622     // Find the start of the "overflow" object and set split_region to the
 623     // region containing it.
 624     HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
 625     split_region = addr_to_region_idx(overflow_obj);
 626 
 627     // Clear the source_region field of all destination regions whose first word
 628     // came from data after the split point (a non-null source_region field
 629     // implies a region must be filled).
 630     //
 631     // An alternative to the simple loop below:  clear during post_compact(),
 632     // which uses memcpy instead of individual stores, and is easy to
 633     // parallelize.  (The downside is that it clears the entire RegionData
 634     // object as opposed to just one field.)
 635     //
 636     // post_compact() would have to clear the summary data up to the highest
 637     // address that was written during the summary phase, which would be
 638     //
 639     //         max(top, max(new_top, clear_top))
 640     //
 641     // where clear_top is a new field in SpaceInfo.  Would have to set clear_top
 642     // to target_end.
 643     const RegionData* const sr = region(split_region);
 644     const size_t beg_idx =
 645       addr_to_region_idx(region_align_up(sr->destination() +
 646                                          sr->partial_obj_size()));
 647     const size_t end_idx = addr_to_region_idx(target_end);
 648 
 649     log_develop_trace(gc, compaction)("split:  clearing source_region field in [" SIZE_FORMAT ", " SIZE_FORMAT ")", beg_idx, end_idx);
 650     for (size_t idx = beg_idx; idx < end_idx; ++idx) {
 651       _region_data[idx].set_source_region(0);
 652     }
 653 
 654     // Set split_destination and partial_obj_size to reflect the split region.
 655     split_destination = sr->destination();
 656     partial_obj_size = sr->partial_obj_size();
 657   }
 658 
 659   // The split is recorded only if a partial object extends onto the region.
 660   if (partial_obj_size != 0) {
 661     _region_data[split_region].set_partial_obj_size(0);
 662     split_info.record(split_region, partial_obj_size, split_destination);
 663   }
 664 
 665   // Setup the continuation addresses.
 666   *target_next = split_destination + partial_obj_size;
 667   HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
 668 
 669   if (log_develop_is_enabled(Trace, gc, compaction)) {
 670     const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
 671     log_develop_trace(gc, compaction)("%s split:  src=" PTR_FORMAT " src_c=" SIZE_FORMAT " pos=" SIZE_FORMAT,
 672                                       split_type, p2i(source_next), split_region, partial_obj_size);
 673     log_develop_trace(gc, compaction)("%s split:  dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT " tn=" PTR_FORMAT,
 674                                       split_type, p2i(split_destination),
 675                                       addr_to_region_idx(split_destination),
 676                                       p2i(*target_next));
 677 
 678     if (partial_obj_size != 0) {
 679       HeapWord* const po_beg = split_info.destination();
 680       HeapWord* const po_end = po_beg + split_info.partial_obj_size();
 681       log_develop_trace(gc, compaction)("%s split:  po_beg=" PTR_FORMAT " " SIZE_FORMAT " po_end=" PTR_FORMAT " " SIZE_FORMAT,
 682                                         split_type,
 683                                         p2i(po_beg), addr_to_region_idx(po_beg),
 684                                         p2i(po_end), addr_to_region_idx(po_end));
 685     }
 686   }
 687 
 688   return source_next;
 689 }
 690 
 691 bool ParallelCompactData::summarize(SplitInfo& split_info,
 692                                     HeapWord* source_beg, HeapWord* source_end,
 693                                     HeapWord** source_next,
 694                                     HeapWord* target_beg, HeapWord* target_end,
 695                                     HeapWord** target_next)
 696 {
 697   HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
 698   log_develop_trace(gc, compaction)(
 699       "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
 700       "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
 701       p2i(source_beg), p2i(source_end), p2i(source_next_val),
 702       p2i(target_beg), p2i(target_end), p2i(*target_next));
 703 
 704   size_t cur_region = addr_to_region_idx(source_beg);
 705   const size_t end_region = addr_to_region_idx(region_align_up(source_end));
 706 
 707   HeapWord *dest_addr = target_beg;
 708   while (cur_region < end_region) {
 709     // The destination must be set even if the region has no data.
 710     _region_data[cur_region].set_destination(dest_addr);
 711 
 712     size_t words = _region_data[cur_region].data_size();
 713     if (words > 0) {
 714       // If cur_region does not fit entirely into the target space, find a point
 715       // at which the source space can be 'split' so that part is copied to the
 716       // target space and the rest is copied elsewhere.
 717       if (dest_addr + words > target_end) {
 718         assert(source_next != NULL, "source_next is NULL when splitting");
 719         *source_next = summarize_split_space(cur_region, split_info, dest_addr,
 720                                              target_end, target_next);
 721         return false;
 722       }
 723 
 724       // Compute the destination_count for cur_region, and if necessary, update
 725       // source_region for a destination region.  The source_region field is
 726       // updated if cur_region is the first (left-most) region to be copied to a
 727       // destination region.
 728       //
 729       // The destination_count calculation is a bit subtle.  A region that has
 730       // data that compacts into itself does not count itself as a destination.
 731       // This maintains the invariant that a zero count means the region is
 732       // available and can be claimed and then filled.
 733       uint destination_count = 0;
 734       if (split_info.is_split(cur_region)) {
 735         // The current region has been split:  the partial object will be copied
 736         // to one destination space and the remaining data will be copied to
 737         // another destination space.  Adjust the initial destination_count and,
 738         // if necessary, set the source_region field if the partial object will
 739         // cross a destination region boundary.
 740         destination_count = split_info.destination_count();
 741         if (destination_count == 2) {
 742           size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
 743           _region_data[dest_idx].set_source_region(cur_region);
 744         }
 745       }
 746 
 747       HeapWord* const last_addr = dest_addr + words - 1;
 748       const size_t dest_region_1 = addr_to_region_idx(dest_addr);
 749       const size_t dest_region_2 = addr_to_region_idx(last_addr);
 750 
 751       // Initially assume that the destination regions will be the same and
 752       // adjust the value below if necessary.  Under this assumption, if
 753       // cur_region == dest_region_2, then cur_region will be compacted
 754       // completely into itself.
 755       destination_count += cur_region == dest_region_2 ? 0 : 1;
 756       if (dest_region_1 != dest_region_2) {
 757         // Destination regions differ; adjust destination_count.
 758         destination_count += 1;
 759         // Data from cur_region will be copied to the start of dest_region_2.
 760         _region_data[dest_region_2].set_source_region(cur_region);
 761       } else if (region_offset(dest_addr) == 0) {
 762         // Data from cur_region will be copied to the start of the destination
 763         // region.
 764         _region_data[dest_region_1].set_source_region(cur_region);
 765       }
 766 
 767       _region_data[cur_region].set_destination_count(destination_count);
 768       _region_data[cur_region].set_data_location(region_to_addr(cur_region));
 769       dest_addr += words;
 770     }
 771 
 772     ++cur_region;
 773   }
 774 
 775   *target_next = dest_addr;
 776   return true;
 777 }
 778 
 779 HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr, ParCompactionManager* cm) {
 780   assert(addr != NULL, "Should detect NULL oop earlier");
 781   assert(ParallelScavengeHeap::heap()->is_in(addr), "not in heap");
 782   assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked");
 783 
 784   // Region covering the object.
 785   RegionData* const region_ptr = addr_to_region_ptr(addr);
 786   HeapWord* result = region_ptr->destination();
 787 
 788   // If the entire Region is live, the new location is region->destination + the
 789   // offset of the object within in the Region.
 790 
 791   // Run some performance tests to determine if this special case pays off.  It
 792   // is worth it for pointers into the dense prefix.  If the optimization to
 793   // avoid pointer updates in regions that only point to the dense prefix is
 794   // ever implemented, this should be revisited.
 795   if (region_ptr->data_size() == RegionSize) {
 796     result += region_offset(addr);
 797     return result;
 798   }
 799 
 800   // Otherwise, the new location is region->destination + block offset + the
 801   // number of live words in the Block that are (a) to the left of addr and (b)
 802   // due to objects that start in the Block.
 803 
 804   // Fill in the block table if necessary.  This is unsynchronized, so multiple
 805   // threads may fill the block table for a region (harmless, since it is
 806   // idempotent).
 807   if (!region_ptr->blocks_filled()) {
 808     PSParallelCompact::fill_blocks(addr_to_region_idx(addr));
 809     region_ptr->set_blocks_filled();
 810   }
 811 
 812   HeapWord* const search_start = block_align_down(addr);
 813   const size_t block_offset = addr_to_block_ptr(addr)->offset();
 814 
 815   const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
 816   const size_t live = bitmap->live_words_in_range(cm, search_start, oop(addr));
 817   result += block_offset + live;
 818   DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result));
 819   return result;
 820 }
 821 
 822 #ifdef ASSERT
 823 void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
 824 {
 825   const size_t* const beg = (const size_t*)vspace->committed_low_addr();
 826   const size_t* const end = (const size_t*)vspace->committed_high_addr();
 827   for (const size_t* p = beg; p < end; ++p) {
 828     assert(*p == 0, "not zero");
 829   }
 830 }
 831 
 832 void ParallelCompactData::verify_clear()
 833 {
 834   verify_clear(_region_vspace);
 835   verify_clear(_block_vspace);
 836 }
 837 #endif  // #ifdef ASSERT
 838 
 839 STWGCTimer          PSParallelCompact::_gc_timer;
 840 ParallelOldTracer   PSParallelCompact::_gc_tracer;
 841 elapsedTimer        PSParallelCompact::_accumulated_time;
 842 unsigned int        PSParallelCompact::_total_invocations = 0;
 843 unsigned int        PSParallelCompact::_maximum_compaction_gc_num = 0;
 844 jlong               PSParallelCompact::_time_of_last_gc = 0;
 845 CollectorCounters*  PSParallelCompact::_counters = NULL;
 846 ParMarkBitMap       PSParallelCompact::_mark_bitmap;
 847 ParallelCompactData PSParallelCompact::_summary_data;
 848 
 849 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
 850 
 851 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
 852 
 853 class PCReferenceProcessor: public ReferenceProcessor {
 854 public:
 855   PCReferenceProcessor(
 856     BoolObjectClosure* is_subject_to_discovery,
 857     BoolObjectClosure* is_alive_non_header) :
 858       ReferenceProcessor(is_subject_to_discovery,
 859       ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 860       ParallelGCThreads,   // mt processing degree
 861       true,                // mt discovery
 862       ParallelGCThreads,   // mt discovery degree
 863       true,                // atomic_discovery
 864       is_alive_non_header) {
 865   }
 866 
 867   template<typename T> bool discover(oop obj, ReferenceType type) {
 868     T* referent_addr = (T*) java_lang_ref_Reference::referent_addr_raw(obj);
 869     T heap_oop = RawAccess<>::oop_load(referent_addr);
 870     oop referent = CompressedOops::decode_not_null(heap_oop);
 871     return PSParallelCompact::mark_bitmap()->is_unmarked(referent)
 872         && ReferenceProcessor::discover_reference(obj, type);
 873   }
 874   virtual bool discover_reference(oop obj, ReferenceType type) {
 875     if (UseCompressedOops) {
 876       return discover<narrowOop>(obj, type);
 877     } else {
 878       return discover<oop>(obj, type);
 879     }
 880   }
 881 };
 882 
 883 void PSParallelCompact::post_initialize() {
 884   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 885   _span_based_discoverer.set_span(heap->reserved_region());
 886   _ref_processor =
 887     new PCReferenceProcessor(&_span_based_discoverer,
 888                              &_is_alive_closure); // non-header is alive closure
 889 
 890   _counters = new CollectorCounters("Parallel full collection pauses", 1);
 891 
 892   // Initialize static fields in ParCompactionManager.
 893   ParCompactionManager::initialize(mark_bitmap());
 894 }
 895 
 896 bool PSParallelCompact::initialize() {
 897   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 898   MemRegion mr = heap->reserved_region();
 899 
 900   // Was the old gen get allocated successfully?
 901   if (!heap->old_gen()->is_allocated()) {
 902     return false;
 903   }
 904 
 905   initialize_space_info();
 906   initialize_dead_wood_limiter();
 907 
 908   if (!_mark_bitmap.initialize(mr)) {
 909     vm_shutdown_during_initialization(
 910       err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
 911       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 912       _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
 913     return false;
 914   }
 915 
 916   if (!_summary_data.initialize(mr)) {
 917     vm_shutdown_during_initialization(
 918       err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
 919       "garbage collection for the requested " SIZE_FORMAT "KB heap.",
 920       _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
 921     return false;
 922   }
 923 
 924   return true;
 925 }
 926 
 927 void PSParallelCompact::initialize_space_info()
 928 {
 929   memset(&_space_info, 0, sizeof(_space_info));
 930 
 931   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 932   PSYoungGen* young_gen = heap->young_gen();
 933 
 934   _space_info[old_space_id].set_space(heap->old_gen()->object_space());
 935   _space_info[eden_space_id].set_space(young_gen->eden_space());
 936   _space_info[from_space_id].set_space(young_gen->from_space());
 937   _space_info[to_space_id].set_space(young_gen->to_space());
 938 
 939   _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
 940 }
 941 
 942 void PSParallelCompact::initialize_dead_wood_limiter()
 943 {
 944   const size_t max = 100;
 945   _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
 946   _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
 947   _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
 948   DEBUG_ONLY(_dwl_initialized = true;)
 949   _dwl_adjustment = normal_distribution(1.0);
 950 }
 951 
 952 void
 953 PSParallelCompact::clear_data_covering_space(SpaceId id)
 954 {
 955   // At this point, top is the value before GC, new_top() is the value that will
 956   // be set at the end of GC.  The marking bitmap is cleared to top; nothing
 957   // should be marked above top.  The summary data is cleared to the larger of
 958   // top & new_top.
 959   MutableSpace* const space = _space_info[id].space();
 960   HeapWord* const bot = space->bottom();
 961   HeapWord* const top = space->top();
 962   HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
 963 
 964   const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
 965   const idx_t end_bit = _mark_bitmap.align_range_end(_mark_bitmap.addr_to_bit(top));
 966   _mark_bitmap.clear_range(beg_bit, end_bit);
 967 
 968   const size_t beg_region = _summary_data.addr_to_region_idx(bot);
 969   const size_t end_region =
 970     _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
 971   _summary_data.clear_range(beg_region, end_region);
 972 
 973   // Clear the data used to 'split' regions.
 974   SplitInfo& split_info = _space_info[id].split_info();
 975   if (split_info.is_valid()) {
 976     split_info.clear();
 977   }
 978   DEBUG_ONLY(split_info.verify_clear();)
 979 }
 980 
 981 void PSParallelCompact::pre_compact()
 982 {
 983   // Update the from & to space pointers in space_info, since they are swapped
 984   // at each young gen gc.  Do the update unconditionally (even though a
 985   // promotion failure does not swap spaces) because an unknown number of young
 986   // collections will have swapped the spaces an unknown number of times.
 987   GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
 988   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 989   _space_info[from_space_id].set_space(heap->young_gen()->from_space());
 990   _space_info[to_space_id].set_space(heap->young_gen()->to_space());
 991 
 992   DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
 993   DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
 994 
 995   // Increment the invocation count
 996   heap->increment_total_collections(true);
 997 
 998   // We need to track unique mark sweep invocations as well.
 999   _total_invocations++;
1000 
1001   heap->print_heap_before_gc();
1002   heap->trace_heap_before_gc(&_gc_tracer);
1003 
1004   // Fill in TLABs
1005   heap->ensure_parsability(true);  // retire TLABs
1006 
1007   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
1008     HandleMark hm;  // Discard invalid handles created during verification
1009     Universe::verify("Before GC");
1010   }
1011 
1012   // Verify object start arrays
1013   if (VerifyObjectStartArray &&
1014       VerifyBeforeGC) {
1015     heap->old_gen()->verify_object_start_array();
1016   }
1017 
1018   DEBUG_ONLY(mark_bitmap()->verify_clear();)
1019   DEBUG_ONLY(summary_data().verify_clear();)
1020 
1021   ParCompactionManager::reset_all_bitmap_query_caches();
1022 }
1023 
1024 void PSParallelCompact::post_compact()
1025 {
1026   GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
1027   ParCompactionManager::remove_all_shadow_regions();
1028 
1029   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1030     // Clear the marking bitmap, summary data and split info.
1031     clear_data_covering_space(SpaceId(id));
1032     // Update top().  Must be done after clearing the bitmap and summary data.
1033     _space_info[id].publish_new_top();
1034   }
1035 
1036   MutableSpace* const eden_space = _space_info[eden_space_id].space();
1037   MutableSpace* const from_space = _space_info[from_space_id].space();
1038   MutableSpace* const to_space   = _space_info[to_space_id].space();
1039 
1040   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1041   bool eden_empty = eden_space->is_empty();
1042   if (!eden_empty) {
1043     eden_empty = absorb_live_data_from_eden(heap->size_policy(),
1044                                             heap->young_gen(), heap->old_gen());
1045   }
1046 
1047   // Update heap occupancy information which is used as input to the soft ref
1048   // clearing policy at the next gc.
1049   Universe::update_heap_info_at_gc();
1050 
1051   bool young_gen_empty = eden_empty && from_space->is_empty() &&
1052     to_space->is_empty();
1053 
1054   PSCardTable* ct = heap->card_table();
1055   MemRegion old_mr = heap->old_gen()->reserved();
1056   if (young_gen_empty) {
1057     ct->clear(MemRegion(old_mr.start(), old_mr.end()));
1058   } else {
1059     ct->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1060   }
1061 
1062   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1063   ClassLoaderDataGraph::purge();
1064   MetaspaceUtils::verify_metrics();
1065 
1066   heap->prune_scavengable_nmethods();
1067 
1068 #if COMPILER2_OR_JVMCI
1069   DerivedPointerTable::update_pointers();
1070 #endif
1071 
1072   if (ZapUnusedHeapArea) {
1073     heap->gen_mangle_unused_area();
1074   }
1075 
1076   // Update time of last GC
1077   reset_millis_since_last_gc();
1078 }
1079 
1080 HeapWord*
1081 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1082                                                     bool maximum_compaction)
1083 {
1084   const size_t region_size = ParallelCompactData::RegionSize;
1085   const ParallelCompactData& sd = summary_data();
1086 
1087   const MutableSpace* const space = _space_info[id].space();
1088   HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1089   const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1090   const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1091 
1092   // Skip full regions at the beginning of the space--they are necessarily part
1093   // of the dense prefix.
1094   size_t full_count = 0;
1095   const RegionData* cp;
1096   for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1097     ++full_count;
1098   }
1099 
1100   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1101   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1102   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1103   if (maximum_compaction || cp == end_cp || interval_ended) {
1104     _maximum_compaction_gc_num = total_invocations();
1105     return sd.region_to_addr(cp);
1106   }
1107 
1108   HeapWord* const new_top = _space_info[id].new_top();
1109   const size_t space_live = pointer_delta(new_top, space->bottom());
1110   const size_t space_used = space->used_in_words();
1111   const size_t space_capacity = space->capacity_in_words();
1112 
1113   const double cur_density = double(space_live) / space_capacity;
1114   const double deadwood_density =
1115     (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1116   const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1117 
1118   log_develop_debug(gc, compaction)(
1119       "cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1120       cur_density, deadwood_density, deadwood_goal);
1121   log_develop_debug(gc, compaction)(
1122       "space_live=" SIZE_FORMAT " space_used=" SIZE_FORMAT " "
1123       "space_cap=" SIZE_FORMAT,
1124       space_live, space_used,
1125       space_capacity);
1126 
1127   // XXX - Use binary search?
1128   HeapWord* dense_prefix = sd.region_to_addr(cp);
1129   const RegionData* full_cp = cp;
1130   const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1131   while (cp < end_cp) {
1132     HeapWord* region_destination = cp->destination();
1133     const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1134 
1135     log_develop_trace(gc, compaction)(
1136         "c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1137         "dp=" PTR_FORMAT " cdw=" SIZE_FORMAT_W(8),
1138         sd.region(cp), p2i(region_destination),
1139         p2i(dense_prefix), cur_deadwood);
1140 
1141     if (cur_deadwood >= deadwood_goal) {
1142       // Found the region that has the correct amount of deadwood to the left.
1143       // This typically occurs after crossing a fairly sparse set of regions, so
1144       // iterate backwards over those sparse regions, looking for the region
1145       // that has the lowest density of live objects 'to the right.'
1146       size_t space_to_left = sd.region(cp) * region_size;
1147       size_t live_to_left = space_to_left - cur_deadwood;
1148       size_t space_to_right = space_capacity - space_to_left;
1149       size_t live_to_right = space_live - live_to_left;
1150       double density_to_right = double(live_to_right) / space_to_right;
1151       while (cp > full_cp) {
1152         --cp;
1153         const size_t prev_region_live_to_right = live_to_right -
1154           cp->data_size();
1155         const size_t prev_region_space_to_right = space_to_right + region_size;
1156         double prev_region_density_to_right =
1157           double(prev_region_live_to_right) / prev_region_space_to_right;
1158         if (density_to_right <= prev_region_density_to_right) {
1159           return dense_prefix;
1160         }
1161 
1162         log_develop_trace(gc, compaction)(
1163             "backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1164             "pc_d2r=%10.8f",
1165             sd.region(cp), density_to_right,
1166             prev_region_density_to_right);
1167 
1168         dense_prefix -= region_size;
1169         live_to_right = prev_region_live_to_right;
1170         space_to_right = prev_region_space_to_right;
1171         density_to_right = prev_region_density_to_right;
1172       }
1173       return dense_prefix;
1174     }
1175 
1176     dense_prefix += region_size;
1177     ++cp;
1178   }
1179 
1180   return dense_prefix;
1181 }
1182 
1183 #ifndef PRODUCT
1184 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1185                                                  const SpaceId id,
1186                                                  const bool maximum_compaction,
1187                                                  HeapWord* const addr)
1188 {
1189   const size_t region_idx = summary_data().addr_to_region_idx(addr);
1190   RegionData* const cp = summary_data().region(region_idx);
1191   const MutableSpace* const space = _space_info[id].space();
1192   HeapWord* const new_top = _space_info[id].new_top();
1193 
1194   const size_t space_live = pointer_delta(new_top, space->bottom());
1195   const size_t dead_to_left = pointer_delta(addr, cp->destination());
1196   const size_t space_cap = space->capacity_in_words();
1197   const double dead_to_left_pct = double(dead_to_left) / space_cap;
1198   const size_t live_to_right = new_top - cp->destination();
1199   const size_t dead_to_right = space->top() - addr - live_to_right;
1200 
1201   log_develop_debug(gc, compaction)(
1202       "%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1203       "spl=" SIZE_FORMAT " "
1204       "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1205       "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT " "
1206       "ratio=%10.8f",
1207       algorithm, p2i(addr), region_idx,
1208       space_live,
1209       dead_to_left, dead_to_left_pct,
1210       dead_to_right, live_to_right,
1211       double(dead_to_right) / live_to_right);
1212 }
1213 #endif  // #ifndef PRODUCT
1214 
1215 // Return a fraction indicating how much of the generation can be treated as
1216 // "dead wood" (i.e., not reclaimed).  The function uses a normal distribution
1217 // based on the density of live objects in the generation to determine a limit,
1218 // which is then adjusted so the return value is min_percent when the density is
1219 // 1.
1220 //
1221 // The following table shows some return values for a different values of the
1222 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1223 // min_percent is 1.
1224 //
1225 //                          fraction allowed as dead wood
1226 //         -----------------------------------------------------------------
1227 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1228 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1229 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1230 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1231 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1232 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1233 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1234 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1235 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1236 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1237 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1238 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1239 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1240 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1241 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1242 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1243 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1244 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1245 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1246 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1247 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1248 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1249 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1250 
1251 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1252 {
1253   assert(_dwl_initialized, "uninitialized");
1254 
1255   // The raw limit is the value of the normal distribution at x = density.
1256   const double raw_limit = normal_distribution(density);
1257 
1258   // Adjust the raw limit so it becomes the minimum when the density is 1.
1259   //
1260   // First subtract the adjustment value (which is simply the precomputed value
1261   // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1262   // Then add the minimum value, so the minimum is returned when the density is
1263   // 1.  Finally, prevent negative values, which occur when the mean is not 0.5.
1264   const double min = double(min_percent) / 100.0;
1265   const double limit = raw_limit - _dwl_adjustment + min;
1266   return MAX2(limit, 0.0);
1267 }
1268 
1269 ParallelCompactData::RegionData*
1270 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1271                                            const RegionData* end)
1272 {
1273   const size_t region_size = ParallelCompactData::RegionSize;
1274   ParallelCompactData& sd = summary_data();
1275   size_t left = sd.region(beg);
1276   size_t right = end > beg ? sd.region(end) - 1 : left;
1277 
1278   // Binary search.
1279   while (left < right) {
1280     // Equivalent to (left + right) / 2, but does not overflow.
1281     const size_t middle = left + (right - left) / 2;
1282     RegionData* const middle_ptr = sd.region(middle);
1283     HeapWord* const dest = middle_ptr->destination();
1284     HeapWord* const addr = sd.region_to_addr(middle);
1285     assert(dest != NULL, "sanity");
1286     assert(dest <= addr, "must move left");
1287 
1288     if (middle > left && dest < addr) {
1289       right = middle - 1;
1290     } else if (middle < right && middle_ptr->data_size() == region_size) {
1291       left = middle + 1;
1292     } else {
1293       return middle_ptr;
1294     }
1295   }
1296   return sd.region(left);
1297 }
1298 
1299 ParallelCompactData::RegionData*
1300 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1301                                           const RegionData* end,
1302                                           size_t dead_words)
1303 {
1304   ParallelCompactData& sd = summary_data();
1305   size_t left = sd.region(beg);
1306   size_t right = end > beg ? sd.region(end) - 1 : left;
1307 
1308   // Binary search.
1309   while (left < right) {
1310     // Equivalent to (left + right) / 2, but does not overflow.
1311     const size_t middle = left + (right - left) / 2;
1312     RegionData* const middle_ptr = sd.region(middle);
1313     HeapWord* const dest = middle_ptr->destination();
1314     HeapWord* const addr = sd.region_to_addr(middle);
1315     assert(dest != NULL, "sanity");
1316     assert(dest <= addr, "must move left");
1317 
1318     const size_t dead_to_left = pointer_delta(addr, dest);
1319     if (middle > left && dead_to_left > dead_words) {
1320       right = middle - 1;
1321     } else if (middle < right && dead_to_left < dead_words) {
1322       left = middle + 1;
1323     } else {
1324       return middle_ptr;
1325     }
1326   }
1327   return sd.region(left);
1328 }
1329 
1330 // The result is valid during the summary phase, after the initial summarization
1331 // of each space into itself, and before final summarization.
1332 inline double
1333 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1334                                    HeapWord* const bottom,
1335                                    HeapWord* const top,
1336                                    HeapWord* const new_top)
1337 {
1338   ParallelCompactData& sd = summary_data();
1339 
1340   assert(cp != NULL, "sanity");
1341   assert(bottom != NULL, "sanity");
1342   assert(top != NULL, "sanity");
1343   assert(new_top != NULL, "sanity");
1344   assert(top >= new_top, "summary data problem?");
1345   assert(new_top > bottom, "space is empty; should not be here");
1346   assert(new_top >= cp->destination(), "sanity");
1347   assert(top >= sd.region_to_addr(cp), "sanity");
1348 
1349   HeapWord* const destination = cp->destination();
1350   const size_t dense_prefix_live  = pointer_delta(destination, bottom);
1351   const size_t compacted_region_live = pointer_delta(new_top, destination);
1352   const size_t compacted_region_used = pointer_delta(top,
1353                                                      sd.region_to_addr(cp));
1354   const size_t reclaimable = compacted_region_used - compacted_region_live;
1355 
1356   const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1357   return double(reclaimable) / divisor;
1358 }
1359 
1360 // Return the address of the end of the dense prefix, a.k.a. the start of the
1361 // compacted region.  The address is always on a region boundary.
1362 //
1363 // Completely full regions at the left are skipped, since no compaction can
1364 // occur in those regions.  Then the maximum amount of dead wood to allow is
1365 // computed, based on the density (amount live / capacity) of the generation;
1366 // the region with approximately that amount of dead space to the left is
1367 // identified as the limit region.  Regions between the last completely full
1368 // region and the limit region are scanned and the one that has the best
1369 // (maximum) reclaimed_ratio() is selected.
1370 HeapWord*
1371 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1372                                         bool maximum_compaction)
1373 {
1374   const size_t region_size = ParallelCompactData::RegionSize;
1375   const ParallelCompactData& sd = summary_data();
1376 
1377   const MutableSpace* const space = _space_info[id].space();
1378   HeapWord* const top = space->top();
1379   HeapWord* const top_aligned_up = sd.region_align_up(top);
1380   HeapWord* const new_top = _space_info[id].new_top();
1381   HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1382   HeapWord* const bottom = space->bottom();
1383   const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1384   const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1385   const RegionData* const new_top_cp =
1386     sd.addr_to_region_ptr(new_top_aligned_up);
1387 
1388   // Skip full regions at the beginning of the space--they are necessarily part
1389   // of the dense prefix.
1390   const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1391   assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1392          space->is_empty(), "no dead space allowed to the left");
1393   assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1394          "region must have dead space");
1395 
1396   // The gc number is saved whenever a maximum compaction is done, and used to
1397   // determine when the maximum compaction interval has expired.  This avoids
1398   // successive max compactions for different reasons.
1399   assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1400   const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1401   const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1402     total_invocations() == HeapFirstMaximumCompactionCount;
1403   if (maximum_compaction || full_cp == top_cp || interval_ended) {
1404     _maximum_compaction_gc_num = total_invocations();
1405     return sd.region_to_addr(full_cp);
1406   }
1407 
1408   const size_t space_live = pointer_delta(new_top, bottom);
1409   const size_t space_used = space->used_in_words();
1410   const size_t space_capacity = space->capacity_in_words();
1411 
1412   const double density = double(space_live) / double(space_capacity);
1413   const size_t min_percent_free = MarkSweepDeadRatio;
1414   const double limiter = dead_wood_limiter(density, min_percent_free);
1415   const size_t dead_wood_max = space_used - space_live;
1416   const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1417                                       dead_wood_max);
1418 
1419   log_develop_debug(gc, compaction)(
1420       "space_live=" SIZE_FORMAT " space_used=" SIZE_FORMAT " "
1421       "space_cap=" SIZE_FORMAT,
1422       space_live, space_used,
1423       space_capacity);
1424   log_develop_debug(gc, compaction)(
1425       "dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
1426       "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1427       density, min_percent_free, limiter,
1428       dead_wood_max, dead_wood_limit);
1429 
1430   // Locate the region with the desired amount of dead space to the left.
1431   const RegionData* const limit_cp =
1432     dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1433 
1434   // Scan from the first region with dead space to the limit region and find the
1435   // one with the best (largest) reclaimed ratio.
1436   double best_ratio = 0.0;
1437   const RegionData* best_cp = full_cp;
1438   for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1439     double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1440     if (tmp_ratio > best_ratio) {
1441       best_cp = cp;
1442       best_ratio = tmp_ratio;
1443     }
1444   }
1445 
1446   return sd.region_to_addr(best_cp);
1447 }
1448 
1449 void PSParallelCompact::summarize_spaces_quick()
1450 {
1451   for (unsigned int i = 0; i < last_space_id; ++i) {
1452     const MutableSpace* space = _space_info[i].space();
1453     HeapWord** nta = _space_info[i].new_top_addr();
1454     bool result = _summary_data.summarize(_space_info[i].split_info(),
1455                                           space->bottom(), space->top(), NULL,
1456                                           space->bottom(), space->end(), nta);
1457     assert(result, "space must fit into itself");
1458     _space_info[i].set_dense_prefix(space->bottom());
1459   }
1460 }
1461 
1462 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1463 {
1464   HeapWord* const dense_prefix_end = dense_prefix(id);
1465   const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1466   const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1467   if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1468     // Only enough dead space is filled so that any remaining dead space to the
1469     // left is larger than the minimum filler object.  (The remainder is filled
1470     // during the copy/update phase.)
1471     //
1472     // The size of the dead space to the right of the boundary is not a
1473     // concern, since compaction will be able to use whatever space is
1474     // available.
1475     //
1476     // Here '||' is the boundary, 'x' represents a don't care bit and a box
1477     // surrounds the space to be filled with an object.
1478     //
1479     // In the 32-bit VM, each bit represents two 32-bit words:
1480     //                              +---+
1481     // a) beg_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1482     //    end_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
1483     //                              +---+
1484     //
1485     // In the 64-bit VM, each bit represents one 64-bit word:
1486     //                              +------------+
1487     // b) beg_bits:  ...  x   x   x | 0   ||   0 | x  x  ...
1488     //    end_bits:  ...  x   x   1 | 0   ||   0 | x  x  ...
1489     //                              +------------+
1490     //                          +-------+
1491     // c) beg_bits:  ...  x   x | 0   0 | ||   0   x  x  ...
1492     //    end_bits:  ...  x   1 | 0   0 | ||   0   x  x  ...
1493     //                          +-------+
1494     //                      +-----------+
1495     // d) beg_bits:  ...  x | 0   0   0 | ||   0   x  x  ...
1496     //    end_bits:  ...  1 | 0   0   0 | ||   0   x  x  ...
1497     //                      +-----------+
1498     //                          +-------+
1499     // e) beg_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1500     //    end_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
1501     //                          +-------+
1502 
1503     // Initially assume case a, c or e will apply.
1504     size_t obj_len = CollectedHeap::min_fill_size();
1505     HeapWord* obj_beg = dense_prefix_end - obj_len;
1506 
1507 #ifdef  _LP64
1508     if (MinObjAlignment > 1) { // object alignment > heap word size
1509       // Cases a, c or e.
1510     } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1511       // Case b above.
1512       obj_beg = dense_prefix_end - 1;
1513     } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1514                _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1515       // Case d above.
1516       obj_beg = dense_prefix_end - 3;
1517       obj_len = 3;
1518     }
1519 #endif  // #ifdef _LP64
1520 
1521     CollectedHeap::fill_with_object(obj_beg, obj_len);
1522     _mark_bitmap.mark_obj(obj_beg, obj_len);
1523     _summary_data.add_obj(obj_beg, obj_len);
1524     assert(start_array(id) != NULL, "sanity");
1525     start_array(id)->allocate_block(obj_beg);
1526   }
1527 }
1528 
1529 void
1530 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1531 {
1532   assert(id < last_space_id, "id out of range");
1533   assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom(),
1534          "should have been reset in summarize_spaces_quick()");
1535 
1536   const MutableSpace* space = _space_info[id].space();
1537   if (_space_info[id].new_top() != space->bottom()) {
1538     HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1539     _space_info[id].set_dense_prefix(dense_prefix_end);
1540 
1541 #ifndef PRODUCT
1542     if (log_is_enabled(Debug, gc, compaction)) {
1543       print_dense_prefix_stats("ratio", id, maximum_compaction,
1544                                dense_prefix_end);
1545       HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1546       print_dense_prefix_stats("density", id, maximum_compaction, addr);
1547     }
1548 #endif  // #ifndef PRODUCT
1549 
1550     // Recompute the summary data, taking into account the dense prefix.  If
1551     // every last byte will be reclaimed, then the existing summary data which
1552     // compacts everything can be left in place.
1553     if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1554       // If dead space crosses the dense prefix boundary, it is (at least
1555       // partially) filled with a dummy object, marked live and added to the
1556       // summary data.  This simplifies the copy/update phase and must be done
1557       // before the final locations of objects are determined, to prevent
1558       // leaving a fragment of dead space that is too small to fill.
1559       fill_dense_prefix_end(id);
1560 
1561       // Compute the destination of each Region, and thus each object.
1562       _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1563       _summary_data.summarize(_space_info[id].split_info(),
1564                               dense_prefix_end, space->top(), NULL,
1565                               dense_prefix_end, space->end(),
1566                               _space_info[id].new_top_addr());
1567     }
1568   }
1569 
1570   if (log_develop_is_enabled(Trace, gc, compaction)) {
1571     const size_t region_size = ParallelCompactData::RegionSize;
1572     HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1573     const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1574     const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1575     HeapWord* const new_top = _space_info[id].new_top();
1576     const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1577     const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1578     log_develop_trace(gc, compaction)(
1579         "id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1580         "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1581         "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1582         id, space->capacity_in_words(), p2i(dense_prefix_end),
1583         dp_region, dp_words / region_size,
1584         cr_words / region_size, p2i(new_top));
1585   }
1586 }
1587 
1588 #ifndef PRODUCT
1589 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1590                                           HeapWord* dst_beg, HeapWord* dst_end,
1591                                           SpaceId src_space_id,
1592                                           HeapWord* src_beg, HeapWord* src_end)
1593 {
1594   log_develop_trace(gc, compaction)(
1595       "Summarizing %d [%s] into %d [%s]:  "
1596       "src=" PTR_FORMAT "-" PTR_FORMAT " "
1597       SIZE_FORMAT "-" SIZE_FORMAT " "
1598       "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1599       SIZE_FORMAT "-" SIZE_FORMAT,
1600       src_space_id, space_names[src_space_id],
1601       dst_space_id, space_names[dst_space_id],
1602       p2i(src_beg), p2i(src_end),
1603       _summary_data.addr_to_region_idx(src_beg),
1604       _summary_data.addr_to_region_idx(src_end),
1605       p2i(dst_beg), p2i(dst_end),
1606       _summary_data.addr_to_region_idx(dst_beg),
1607       _summary_data.addr_to_region_idx(dst_end));
1608 }
1609 #endif  // #ifndef PRODUCT
1610 
1611 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1612                                       bool maximum_compaction)
1613 {
1614   GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
1615 
1616   log_develop_debug(gc, marking)(
1617       "add_obj_count=" SIZE_FORMAT " "
1618       "add_obj_bytes=" SIZE_FORMAT,
1619       add_obj_count,
1620       add_obj_size * HeapWordSize);
1621   log_develop_debug(gc, marking)(
1622       "mark_bitmap_count=" SIZE_FORMAT " "
1623       "mark_bitmap_bytes=" SIZE_FORMAT,
1624       mark_bitmap_count,
1625       mark_bitmap_size * HeapWordSize);
1626 
1627   // Quick summarization of each space into itself, to see how much is live.
1628   summarize_spaces_quick();
1629 
1630   log_develop_trace(gc, compaction)("summary phase:  after summarizing each space to self");
1631   NOT_PRODUCT(print_region_ranges());
1632   NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1633 
1634   // The amount of live data that will end up in old space (assuming it fits).
1635   size_t old_space_total_live = 0;
1636   for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1637     old_space_total_live += pointer_delta(_space_info[id].new_top(),
1638                                           _space_info[id].space()->bottom());
1639   }
1640 
1641   MutableSpace* const old_space = _space_info[old_space_id].space();
1642   const size_t old_capacity = old_space->capacity_in_words();
1643   if (old_space_total_live > old_capacity) {
1644     // XXX - should also try to expand
1645     maximum_compaction = true;
1646   }
1647 
1648   // Old generations.
1649   summarize_space(old_space_id, maximum_compaction);
1650 
1651   // Summarize the remaining spaces in the young gen.  The initial target space
1652   // is the old gen.  If a space does not fit entirely into the target, then the
1653   // remainder is compacted into the space itself and that space becomes the new
1654   // target.
1655   SpaceId dst_space_id = old_space_id;
1656   HeapWord* dst_space_end = old_space->end();
1657   HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1658   for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1659     const MutableSpace* space = _space_info[id].space();
1660     const size_t live = pointer_delta(_space_info[id].new_top(),
1661                                       space->bottom());
1662     const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1663 
1664     NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1665                                   SpaceId(id), space->bottom(), space->top());)
1666     if (live > 0 && live <= available) {
1667       // All the live data will fit.
1668       bool done = _summary_data.summarize(_space_info[id].split_info(),
1669                                           space->bottom(), space->top(),
1670                                           NULL,
1671                                           *new_top_addr, dst_space_end,
1672                                           new_top_addr);
1673       assert(done, "space must fit into old gen");
1674 
1675       // Reset the new_top value for the space.
1676       _space_info[id].set_new_top(space->bottom());
1677     } else if (live > 0) {
1678       // Attempt to fit part of the source space into the target space.
1679       HeapWord* next_src_addr = NULL;
1680       bool done = _summary_data.summarize(_space_info[id].split_info(),
1681                                           space->bottom(), space->top(),
1682                                           &next_src_addr,
1683                                           *new_top_addr, dst_space_end,
1684                                           new_top_addr);
1685       assert(!done, "space should not fit into old gen");
1686       assert(next_src_addr != NULL, "sanity");
1687 
1688       // The source space becomes the new target, so the remainder is compacted
1689       // within the space itself.
1690       dst_space_id = SpaceId(id);
1691       dst_space_end = space->end();
1692       new_top_addr = _space_info[id].new_top_addr();
1693       NOT_PRODUCT(summary_phase_msg(dst_space_id,
1694                                     space->bottom(), dst_space_end,
1695                                     SpaceId(id), next_src_addr, space->top());)
1696       done = _summary_data.summarize(_space_info[id].split_info(),
1697                                      next_src_addr, space->top(),
1698                                      NULL,
1699                                      space->bottom(), dst_space_end,
1700                                      new_top_addr);
1701       assert(done, "space must fit when compacted into itself");
1702       assert(*new_top_addr <= space->top(), "usage should not grow");
1703     }
1704   }
1705 
1706   log_develop_trace(gc, compaction)("Summary_phase:  after final summarization");
1707   NOT_PRODUCT(print_region_ranges());
1708   NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1709 }
1710 
1711 // This method should contain all heap-specific policy for invoking a full
1712 // collection.  invoke_no_policy() will only attempt to compact the heap; it
1713 // will do nothing further.  If we need to bail out for policy reasons, scavenge
1714 // before full gc, or any other specialized behavior, it needs to be added here.
1715 //
1716 // Note that this method should only be called from the vm_thread while at a
1717 // safepoint.
1718 //
1719 // Note that the all_soft_refs_clear flag in the soft ref policy
1720 // may be true because this method can be called without intervening
1721 // activity.  For example when the heap space is tight and full measure
1722 // are being taken to free space.
1723 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1724   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1725   assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1726          "should be in vm thread");
1727 
1728   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1729   GCCause::Cause gc_cause = heap->gc_cause();
1730   assert(!heap->is_gc_active(), "not reentrant");
1731 
1732   PSAdaptiveSizePolicy* policy = heap->size_policy();
1733   IsGCActiveMark mark;
1734 
1735   if (ScavengeBeforeFullGC) {
1736     PSScavenge::invoke_no_policy();
1737   }
1738 
1739   const bool clear_all_soft_refs =
1740     heap->soft_ref_policy()->should_clear_all_soft_refs();
1741 
1742   PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1743                                       maximum_heap_compaction);
1744 }
1745 
1746 // This method contains no policy. You should probably
1747 // be calling invoke() instead.
1748 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
1749   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
1750   assert(ref_processor() != NULL, "Sanity");
1751 
1752   if (GCLocker::check_active_before_gc()) {
1753     return false;
1754   }
1755 
1756   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1757 
1758   GCIdMark gc_id_mark;
1759   _gc_timer.register_gc_start();
1760   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1761 
1762   TimeStamp marking_start;
1763   TimeStamp compaction_start;
1764   TimeStamp collection_exit;
1765 
1766   GCCause::Cause gc_cause = heap->gc_cause();
1767   PSYoungGen* young_gen = heap->young_gen();
1768   PSOldGen* old_gen = heap->old_gen();
1769   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1770 
1771   // The scope of casr should end after code that can change
1772   // SoftRefPolicy::_should_clear_all_soft_refs.
1773   ClearedAllSoftRefs casr(maximum_heap_compaction,
1774                           heap->soft_ref_policy());
1775 
1776   if (ZapUnusedHeapArea) {
1777     // Save information needed to minimize mangling
1778     heap->record_gen_tops_before_GC();
1779   }
1780 
1781   // Make sure data structures are sane, make the heap parsable, and do other
1782   // miscellaneous bookkeeping.
1783   pre_compact();
1784 
1785   const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
1786 
1787   // Get the compaction manager reserved for the VM thread.
1788   ParCompactionManager* const vmthread_cm =
1789     ParCompactionManager::manager_array(ParallelScavengeHeap::heap()->workers().total_workers());
1790 
1791   {
1792     ResourceMark rm;
1793     HandleMark hm;
1794 
1795     const uint active_workers =
1796       WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().total_workers(),
1797                                         ParallelScavengeHeap::heap()->workers().active_workers(),
1798                                         Threads::number_of_non_daemon_threads());
1799     ParallelScavengeHeap::heap()->workers().update_active_workers(active_workers);
1800 
1801     GCTraceCPUTime tcpu;
1802     GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause, true);
1803 
1804     heap->pre_full_gc_dump(&_gc_timer);
1805 
1806     TraceCollectorStats tcs(counters());
1807     TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause);
1808 
1809     if (log_is_enabled(Debug, gc, heap, exit)) {
1810       accumulated_time()->start();
1811     }
1812 
1813     // Let the size policy know we're starting
1814     size_policy->major_collection_begin();
1815 
1816 #if COMPILER2_OR_JVMCI
1817     DerivedPointerTable::clear();
1818 #endif
1819 
1820     ref_processor()->enable_discovery();
1821     ref_processor()->setup_policy(maximum_heap_compaction);
1822 
1823     bool marked_for_unloading = false;
1824 
1825     marking_start.update();
1826     marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
1827 
1828     bool max_on_system_gc = UseMaximumCompactionOnSystemGC
1829       && GCCause::is_user_requested_gc(gc_cause);
1830     summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
1831 
1832 #if COMPILER2_OR_JVMCI
1833     assert(DerivedPointerTable::is_active(), "Sanity");
1834     DerivedPointerTable::set_active(false);
1835 #endif
1836 
1837     // adjust_roots() updates Universe::_intArrayKlassObj which is
1838     // needed by the compaction for filling holes in the dense prefix.
1839     adjust_roots(vmthread_cm);
1840 
1841     compaction_start.update();
1842     compact();
1843 
1844     // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
1845     // done before resizing.
1846     post_compact();
1847 
1848     // Let the size policy know we're done
1849     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1850 
1851     if (UseAdaptiveSizePolicy) {
1852       log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1853       log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
1854                           old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1855 
1856       // Don't check if the size_policy is ready here.  Let
1857       // the size_policy check that internally.
1858       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1859           AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1860         // Swap the survivor spaces if from_space is empty. The
1861         // resize_young_gen() called below is normally used after
1862         // a successful young GC and swapping of survivor spaces;
1863         // otherwise, it will fail to resize the young gen with
1864         // the current implementation.
1865         if (young_gen->from_space()->is_empty()) {
1866           young_gen->from_space()->clear(SpaceDecorator::Mangle);
1867           young_gen->swap_spaces();
1868         }
1869 
1870         // Calculate optimal free space amounts
1871         assert(young_gen->max_size() >
1872           young_gen->from_space()->capacity_in_bytes() +
1873           young_gen->to_space()->capacity_in_bytes(),
1874           "Sizes of space in young gen are out-of-bounds");
1875 
1876         size_t young_live = young_gen->used_in_bytes();
1877         size_t eden_live = young_gen->eden_space()->used_in_bytes();
1878         size_t old_live = old_gen->used_in_bytes();
1879         size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1880         size_t max_old_gen_size = old_gen->max_gen_size();
1881         size_t max_eden_size = young_gen->max_size() -
1882           young_gen->from_space()->capacity_in_bytes() -
1883           young_gen->to_space()->capacity_in_bytes();
1884 
1885         // Used for diagnostics
1886         size_policy->clear_generation_free_space_flags();
1887 
1888         size_policy->compute_generations_free_space(young_live,
1889                                                     eden_live,
1890                                                     old_live,
1891                                                     cur_eden,
1892                                                     max_old_gen_size,
1893                                                     max_eden_size,
1894                                                     true /* full gc*/);
1895 
1896         size_policy->check_gc_overhead_limit(eden_live,
1897                                              max_old_gen_size,
1898                                              max_eden_size,
1899                                              true /* full gc*/,
1900                                              gc_cause,
1901                                              heap->soft_ref_policy());
1902 
1903         size_policy->decay_supplemental_growth(true /* full gc*/);
1904 
1905         heap->resize_old_gen(
1906           size_policy->calculated_old_free_size_in_bytes());
1907 
1908         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1909                                size_policy->calculated_survivor_size_in_bytes());
1910       }
1911 
1912       log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1913     }
1914 
1915     if (UsePerfData) {
1916       PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1917       counters->update_counters();
1918       counters->update_old_capacity(old_gen->capacity_in_bytes());
1919       counters->update_young_capacity(young_gen->capacity_in_bytes());
1920     }
1921 
1922     heap->resize_all_tlabs();
1923 
1924     // Resize the metaspace capacity after a collection
1925     MetaspaceGC::compute_new_size();
1926 
1927     if (log_is_enabled(Debug, gc, heap, exit)) {
1928       accumulated_time()->stop();
1929     }
1930 
1931     heap->print_heap_change(pre_gc_values);
1932 
1933     // Track memory usage and detect low memory
1934     MemoryService::track_memory_usage();
1935     heap->update_counters();
1936 
1937     heap->post_full_gc_dump(&_gc_timer);
1938   }
1939 
1940 #ifdef ASSERT
1941   for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
1942     ParCompactionManager* const cm =
1943       ParCompactionManager::manager_array(int(i));
1944     assert(cm->marking_stack()->is_empty(),       "should be empty");
1945     assert(cm->region_stack()->is_empty(), "Region stack " SIZE_FORMAT " is not empty", i);
1946   }
1947 #endif // ASSERT
1948 
1949   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1950     HandleMark hm;  // Discard invalid handles created during verification
1951     Universe::verify("After GC");
1952   }
1953 
1954   // Re-verify object start arrays
1955   if (VerifyObjectStartArray &&
1956       VerifyAfterGC) {
1957     old_gen->verify_object_start_array();
1958   }
1959 
1960   if (ZapUnusedHeapArea) {
1961     old_gen->object_space()->check_mangled_unused_area_complete();
1962   }
1963 
1964   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1965 
1966   collection_exit.update();
1967 
1968   heap->print_heap_after_gc();
1969   heap->trace_heap_after_gc(&_gc_tracer);
1970 
1971   log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
1972                          marking_start.ticks(), compaction_start.ticks(),
1973                          collection_exit.ticks());
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(TaskTerminator& 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, 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, 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::fetch_and_add(&_counter, 1u);
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(TaskTerminator* 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, 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         ParCompactionManager::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 == ParCompactionManager::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() == cast_from_oop<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     ParCompactionManager::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 }