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