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src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp

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   1 /*
   2  * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
   3  * Copyright (c) 2013, 2019, Red Hat, Inc. All rights reserved.
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This code is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 only, as
   8  * published by the Free Software Foundation.
   9  *
  10  * This code is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * version 2 for more details (a copy is included in the LICENSE file that
  14  * accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License version
  17  * 2 along with this work; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19  *
  20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  21  * or visit www.oracle.com if you need additional information or have any
  22  * questions.
  23  *
  24  */
  25 
  26 #include "precompiled.hpp"

  27 #include "gc/shared/space.inline.hpp"
  28 #include "gc/shared/tlab_globals.hpp"

  29 #include "gc/shenandoah/shenandoahHeapRegionSet.inline.hpp"
  30 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
  31 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
  32 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"




  33 #include "jfr/jfrEvents.hpp"
  34 #include "memory/allocation.hpp"
  35 #include "memory/iterator.inline.hpp"
  36 #include "memory/resourceArea.hpp"
  37 #include "memory/universe.hpp"
  38 #include "oops/oop.inline.hpp"
  39 #include "runtime/atomic.hpp"
  40 #include "runtime/globals_extension.hpp"
  41 #include "runtime/java.hpp"
  42 #include "runtime/mutexLocker.hpp"
  43 #include "runtime/os.hpp"
  44 #include "runtime/safepoint.hpp"
  45 #include "utilities/powerOfTwo.hpp"
  46 

  47 size_t ShenandoahHeapRegion::RegionCount = 0;
  48 size_t ShenandoahHeapRegion::RegionSizeBytes = 0;
  49 size_t ShenandoahHeapRegion::RegionSizeWords = 0;
  50 size_t ShenandoahHeapRegion::RegionSizeBytesShift = 0;
  51 size_t ShenandoahHeapRegion::RegionSizeWordsShift = 0;
  52 size_t ShenandoahHeapRegion::RegionSizeBytesMask = 0;
  53 size_t ShenandoahHeapRegion::RegionSizeWordsMask = 0;
  54 size_t ShenandoahHeapRegion::HumongousThresholdBytes = 0;
  55 size_t ShenandoahHeapRegion::HumongousThresholdWords = 0;
  56 size_t ShenandoahHeapRegion::MaxTLABSizeBytes = 0;
  57 size_t ShenandoahHeapRegion::MaxTLABSizeWords = 0;
  58 
  59 ShenandoahHeapRegion::ShenandoahHeapRegion(HeapWord* start, size_t index, bool committed) :
  60   _index(index),
  61   _bottom(start),
  62   _end(start + RegionSizeWords),
  63   _new_top(nullptr),
  64   _empty_time(os::elapsedTime()),
  65   _state(committed ? _empty_committed : _empty_uncommitted),
  66   _top(start),
  67   _tlab_allocs(0),
  68   _gclab_allocs(0),


  69   _live_data(0),
  70   _critical_pins(0),
  71   _update_watermark(start) {

  72 
  73   assert(Universe::on_page_boundary(_bottom) && Universe::on_page_boundary(_end),
  74          "invalid space boundaries");
  75   if (ZapUnusedHeapArea && committed) {
  76     SpaceMangler::mangle_region(MemRegion(_bottom, _end));
  77   }
  78 }
  79 
  80 void ShenandoahHeapRegion::report_illegal_transition(const char *method) {
  81   stringStream ss;
  82   ss.print("Illegal region state transition from \"%s\", at %s\n  ", region_state_to_string(_state), method);
  83   print_on(&ss);
  84   fatal("%s", ss.freeze());
  85 }
  86 
  87 void ShenandoahHeapRegion::make_regular_allocation() {
  88   shenandoah_assert_heaplocked();
  89 
  90   switch (_state) {
  91     case _empty_uncommitted:
  92       do_commit();
  93     case _empty_committed:

  94       set_state(_regular);
  95     case _regular:
  96     case _pinned:
  97       return;
  98     default:
  99       report_illegal_transition("regular allocation");
 100   }
 101 }
 102 





















 103 void ShenandoahHeapRegion::make_regular_bypass() {
 104   shenandoah_assert_heaplocked();
 105   assert (ShenandoahHeap::heap()->is_full_gc_in_progress() || ShenandoahHeap::heap()->is_degenerated_gc_in_progress(),
 106           "only for full or degen GC");
 107 
 108   switch (_state) {
 109     case _empty_uncommitted:
 110       do_commit();
 111     case _empty_committed:
 112     case _cset:
 113     case _humongous_start:
 114     case _humongous_cont:
 115       set_state(_regular);
 116       return;
 117     case _pinned_cset:
 118       set_state(_pinned);
 119       return;
 120     case _regular:
 121     case _pinned:
 122       return;
 123     default:
 124       report_illegal_transition("regular bypass");
 125   }
 126 }
 127 
 128 void ShenandoahHeapRegion::make_humongous_start() {
 129   shenandoah_assert_heaplocked();

 130   switch (_state) {
 131     case _empty_uncommitted:
 132       do_commit();
 133     case _empty_committed:
 134       set_state(_humongous_start);
 135       return;
 136     default:
 137       report_illegal_transition("humongous start allocation");
 138   }
 139 }
 140 
 141 void ShenandoahHeapRegion::make_humongous_start_bypass() {
 142   shenandoah_assert_heaplocked();
 143   assert (ShenandoahHeap::heap()->is_full_gc_in_progress(), "only for full GC");
 144 

 145   switch (_state) {
 146     case _empty_committed:
 147     case _regular:
 148     case _humongous_start:
 149     case _humongous_cont:
 150       set_state(_humongous_start);
 151       return;
 152     default:
 153       report_illegal_transition("humongous start bypass");
 154   }
 155 }
 156 
 157 void ShenandoahHeapRegion::make_humongous_cont() {
 158   shenandoah_assert_heaplocked();

 159   switch (_state) {
 160     case _empty_uncommitted:
 161       do_commit();
 162     case _empty_committed:
 163      set_state(_humongous_cont);
 164       return;
 165     default:
 166       report_illegal_transition("humongous continuation allocation");
 167   }
 168 }
 169 
 170 void ShenandoahHeapRegion::make_humongous_cont_bypass() {
 171   shenandoah_assert_heaplocked();
 172   assert (ShenandoahHeap::heap()->is_full_gc_in_progress(), "only for full GC");
 173 

 174   switch (_state) {
 175     case _empty_committed:
 176     case _regular:
 177     case _humongous_start:
 178     case _humongous_cont:
 179       set_state(_humongous_cont);
 180       return;
 181     default:
 182       report_illegal_transition("humongous continuation bypass");
 183   }
 184 }
 185 
 186 void ShenandoahHeapRegion::make_pinned() {
 187   shenandoah_assert_heaplocked();
 188   assert(pin_count() > 0, "Should have pins: " SIZE_FORMAT, pin_count());
 189 
 190   switch (_state) {
 191     case _regular:
 192       set_state(_pinned);
 193     case _pinned_cset:
 194     case _pinned:
 195       return;
 196     case _humongous_start:
 197       set_state(_pinned_humongous_start);
 198     case _pinned_humongous_start:
 199       return;
 200     case _cset:
 201       _state = _pinned_cset;
 202       return;
 203     default:
 204       report_illegal_transition("pinning");
 205   }
 206 }
 207 
 208 void ShenandoahHeapRegion::make_unpinned() {
 209   shenandoah_assert_heaplocked();
 210   assert(pin_count() == 0, "Should not have pins: " SIZE_FORMAT, pin_count());
 211 
 212   switch (_state) {
 213     case _pinned:

 214       set_state(_regular);
 215       return;
 216     case _regular:
 217     case _humongous_start:
 218       return;
 219     case _pinned_cset:
 220       set_state(_cset);
 221       return;
 222     case _pinned_humongous_start:
 223       set_state(_humongous_start);
 224       return;
 225     default:
 226       report_illegal_transition("unpinning");
 227   }
 228 }
 229 
 230 void ShenandoahHeapRegion::make_cset() {
 231   shenandoah_assert_heaplocked();

 232   switch (_state) {
 233     case _regular:
 234       set_state(_cset);
 235     case _cset:
 236       return;
 237     default:
 238       report_illegal_transition("cset");
 239   }
 240 }
 241 
 242 void ShenandoahHeapRegion::make_trash() {
 243   shenandoah_assert_heaplocked();

 244   switch (_state) {
 245     case _cset:
 246       // Reclaiming cset regions
 247     case _humongous_start:
 248     case _humongous_cont:
 249       // Reclaiming humongous regions
 250     case _regular:
 251       // Immediate region reclaim
 252       set_state(_trash);
 253       return;
 254     default:
 255       report_illegal_transition("trashing");
 256   }
 257 }
 258 
 259 void ShenandoahHeapRegion::make_trash_immediate() {
 260   make_trash();
 261 
 262   // On this path, we know there are no marked objects in the region,
 263   // tell marking context about it to bypass bitmap resets.
 264   ShenandoahHeap::heap()->complete_marking_context()->reset_top_bitmap(this);

 265 }
 266 
 267 void ShenandoahHeapRegion::make_empty() {
 268   shenandoah_assert_heaplocked();

 269   switch (_state) {
 270     case _trash:
 271       set_state(_empty_committed);
 272       _empty_time = os::elapsedTime();
 273       return;
 274     default:
 275       report_illegal_transition("emptying");
 276   }
 277 }
 278 
 279 void ShenandoahHeapRegion::make_uncommitted() {
 280   shenandoah_assert_heaplocked();
 281   switch (_state) {
 282     case _empty_committed:
 283       do_uncommit();
 284       set_state(_empty_uncommitted);
 285       return;
 286     default:
 287       report_illegal_transition("uncommiting");
 288   }
 289 }
 290 
 291 void ShenandoahHeapRegion::make_committed_bypass() {
 292   shenandoah_assert_heaplocked();
 293   assert (ShenandoahHeap::heap()->is_full_gc_in_progress(), "only for full GC");
 294 
 295   switch (_state) {
 296     case _empty_uncommitted:
 297       do_commit();
 298       set_state(_empty_committed);
 299       return;
 300     default:
 301       report_illegal_transition("commit bypass");
 302   }
 303 }
 304 
 305 void ShenandoahHeapRegion::reset_alloc_metadata() {
 306   _tlab_allocs = 0;
 307   _gclab_allocs = 0;

 308 }
 309 
 310 size_t ShenandoahHeapRegion::get_shared_allocs() const {
 311   return used() - (_tlab_allocs + _gclab_allocs) * HeapWordSize;
 312 }
 313 
 314 size_t ShenandoahHeapRegion::get_tlab_allocs() const {
 315   return _tlab_allocs * HeapWordSize;
 316 }
 317 
 318 size_t ShenandoahHeapRegion::get_gclab_allocs() const {
 319   return _gclab_allocs * HeapWordSize;
 320 }
 321 




 322 void ShenandoahHeapRegion::set_live_data(size_t s) {
 323   assert(Thread::current()->is_VM_thread(), "by VM thread");
 324   _live_data = (s >> LogHeapWordSize);
 325 }
 326 
 327 void ShenandoahHeapRegion::print_on(outputStream* st) const {
 328   st->print("|");
 329   st->print(SIZE_FORMAT_W(5), this->_index);
 330 
 331   switch (_state) {
 332     case _empty_uncommitted:
 333       st->print("|EU ");
 334       break;
 335     case _empty_committed:
 336       st->print("|EC ");
 337       break;
 338     case _regular:
 339       st->print("|R  ");
 340       break;
 341     case _humongous_start:

 346       break;
 347     case _humongous_cont:
 348       st->print("|HC ");
 349       break;
 350     case _cset:
 351       st->print("|CS ");
 352       break;
 353     case _trash:
 354       st->print("|T  ");
 355       break;
 356     case _pinned:
 357       st->print("|P  ");
 358       break;
 359     case _pinned_cset:
 360       st->print("|CSP");
 361       break;
 362     default:
 363       ShouldNotReachHere();
 364   }
 365 














 366 #define SHR_PTR_FORMAT "%12" PRIxPTR
 367 
 368   st->print("|BTE " SHR_PTR_FORMAT  ", " SHR_PTR_FORMAT ", " SHR_PTR_FORMAT,
 369             p2i(bottom()), p2i(top()), p2i(end()));
 370   st->print("|TAMS " SHR_PTR_FORMAT,
 371             p2i(ShenandoahHeap::heap()->marking_context()->top_at_mark_start(const_cast<ShenandoahHeapRegion*>(this))));
 372   st->print("|UWM " SHR_PTR_FORMAT,
 373             p2i(_update_watermark));
 374   st->print("|U " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(used()),                proper_unit_for_byte_size(used()));
 375   st->print("|T " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_tlab_allocs()),     proper_unit_for_byte_size(get_tlab_allocs()));
 376   st->print("|G " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_gclab_allocs()),    proper_unit_for_byte_size(get_gclab_allocs()));



 377   st->print("|S " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_shared_allocs()),   proper_unit_for_byte_size(get_shared_allocs()));
 378   st->print("|L " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_live_data_bytes()), proper_unit_for_byte_size(get_live_data_bytes()));
 379   st->print("|CP " SIZE_FORMAT_W(3), pin_count());
 380   st->cr();
 381 
 382 #undef SHR_PTR_FORMAT
 383 }
 384 
 385 void ShenandoahHeapRegion::oop_iterate(OopIterateClosure* blk) {





























































































 386   if (!is_active()) return;
 387   if (is_humongous()) {


 388     oop_iterate_humongous(blk);
 389   } else {
 390     oop_iterate_objects(blk);
 391   }
 392 }
 393 
 394 void ShenandoahHeapRegion::oop_iterate_objects(OopIterateClosure* blk) {
 395   assert(! is_humongous(), "no humongous region here");
 396   HeapWord* obj_addr = bottom();
 397   HeapWord* t = top();
 398   // Could call objects iterate, but this is easier.




























 399   while (obj_addr < t) {
 400     oop obj = cast_to_oop(obj_addr);
 401     obj_addr += obj->oop_iterate_size(blk);
 402   }
 403 }
 404 


















































 405 void ShenandoahHeapRegion::oop_iterate_humongous(OopIterateClosure* blk) {
 406   assert(is_humongous(), "only humongous region here");
 407   // Find head.
 408   ShenandoahHeapRegion* r = humongous_start_region();
 409   assert(r->is_humongous_start(), "need humongous head here");
 410   oop obj = cast_to_oop(r->bottom());
 411   obj->oop_iterate(blk, MemRegion(bottom(), top()));
 412 }
 413 
 414 ShenandoahHeapRegion* ShenandoahHeapRegion::humongous_start_region() const {
 415   ShenandoahHeap* heap = ShenandoahHeap::heap();
 416   assert(is_humongous(), "Must be a part of the humongous region");
 417   size_t i = index();
 418   ShenandoahHeapRegion* r = const_cast<ShenandoahHeapRegion*>(this);
 419   while (!r->is_humongous_start()) {
 420     assert(i > 0, "Sanity");
 421     i--;
 422     r = heap->get_region(i);
 423     assert(r->is_humongous(), "Must be a part of the humongous region");
 424   }
 425   assert(r->is_humongous_start(), "Must be");
 426   return r;
 427 }
 428 
 429 void ShenandoahHeapRegion::recycle() {





 430   set_top(bottom());
 431   clear_live_data();
 432 
 433   reset_alloc_metadata();
 434 
 435   ShenandoahHeap::heap()->marking_context()->reset_top_at_mark_start(this);
 436   set_update_watermark(bottom());
 437 
 438   make_empty();

 439 
 440   if (ZapUnusedHeapArea) {
 441     SpaceMangler::mangle_region(MemRegion(bottom(), end()));
 442   }
 443 }
 444 
 445 HeapWord* ShenandoahHeapRegion::block_start(const void* p) const {
 446   assert(MemRegion(bottom(), end()).contains(p),
 447          "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
 448          p2i(p), p2i(bottom()), p2i(end()));
 449   if (p >= top()) {
 450     return top();
 451   } else {
 452     HeapWord* last = bottom();
 453     HeapWord* cur = last;
 454     while (cur <= p) {
 455       last = cur;
 456       cur += cast_to_oop(cur)->size();
 457     }
 458     shenandoah_assert_correct(nullptr, cast_to_oop(last));

 463 size_t ShenandoahHeapRegion::block_size(const HeapWord* p) const {
 464   assert(MemRegion(bottom(), end()).contains(p),
 465          "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
 466          p2i(p), p2i(bottom()), p2i(end()));
 467   if (p < top()) {
 468     return cast_to_oop(p)->size();
 469   } else {
 470     assert(p == top(), "just checking");
 471     return pointer_delta(end(), (HeapWord*) p);
 472   }
 473 }
 474 
 475 size_t ShenandoahHeapRegion::setup_sizes(size_t max_heap_size) {
 476   // Absolute minimums we should not ever break.
 477   static const size_t MIN_REGION_SIZE = 256*K;
 478 
 479   if (FLAG_IS_DEFAULT(ShenandoahMinRegionSize)) {
 480     FLAG_SET_DEFAULT(ShenandoahMinRegionSize, MIN_REGION_SIZE);
 481   }
 482 





 483   size_t region_size;
 484   if (FLAG_IS_DEFAULT(ShenandoahRegionSize)) {
 485     if (ShenandoahMinRegionSize > max_heap_size / MIN_NUM_REGIONS) {
 486       err_msg message("Max heap size (" SIZE_FORMAT "%s) is too low to afford the minimum number "
 487                       "of regions (" SIZE_FORMAT ") of minimum region size (" SIZE_FORMAT "%s).",
 488                       byte_size_in_proper_unit(max_heap_size), proper_unit_for_byte_size(max_heap_size),
 489                       MIN_NUM_REGIONS,
 490                       byte_size_in_proper_unit(ShenandoahMinRegionSize), proper_unit_for_byte_size(ShenandoahMinRegionSize));
 491       vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
 492     }
 493     if (ShenandoahMinRegionSize < MIN_REGION_SIZE) {
 494       err_msg message("" SIZE_FORMAT "%s should not be lower than minimum region size (" SIZE_FORMAT "%s).",
 495                       byte_size_in_proper_unit(ShenandoahMinRegionSize), proper_unit_for_byte_size(ShenandoahMinRegionSize),
 496                       byte_size_in_proper_unit(MIN_REGION_SIZE),         proper_unit_for_byte_size(MIN_REGION_SIZE));
 497       vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
 498     }
 499     if (ShenandoahMinRegionSize < MinTLABSize) {
 500       err_msg message("" SIZE_FORMAT "%s should not be lower than TLAB size size (" SIZE_FORMAT "%s).",
 501                       byte_size_in_proper_unit(ShenandoahMinRegionSize), proper_unit_for_byte_size(ShenandoahMinRegionSize),
 502                       byte_size_in_proper_unit(MinTLABSize),             proper_unit_for_byte_size(MinTLABSize));

 669     evt.set_used(used());
 670     evt.set_from(_state);
 671     evt.set_to(to);
 672     evt.commit();
 673   }
 674   _state = to;
 675 }
 676 
 677 void ShenandoahHeapRegion::record_pin() {
 678   Atomic::add(&_critical_pins, (size_t)1);
 679 }
 680 
 681 void ShenandoahHeapRegion::record_unpin() {
 682   assert(pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", index());
 683   Atomic::sub(&_critical_pins, (size_t)1);
 684 }
 685 
 686 size_t ShenandoahHeapRegion::pin_count() const {
 687   return Atomic::load(&_critical_pins);
 688 }
























































































































































   1 /*
   2  * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
   3  * Copyright (c) 2013, 2020, Red Hat, Inc. All rights reserved.
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This code is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 only, as
   8  * published by the Free Software Foundation.
   9  *
  10  * This code is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * version 2 for more details (a copy is included in the LICENSE file that
  14  * accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License version
  17  * 2 along with this work; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19  *
  20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  21  * or visit www.oracle.com if you need additional information or have any
  22  * questions.
  23  *
  24  */
  25 
  26 #include "precompiled.hpp"
  27 #include "gc/shared/cardTable.hpp"
  28 #include "gc/shared/space.inline.hpp"
  29 #include "gc/shared/tlab_globals.hpp"
  30 #include "gc/shenandoah/shenandoahCardTable.hpp"
  31 #include "gc/shenandoah/shenandoahHeapRegionSet.inline.hpp"
  32 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
  33 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
  34 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
  35 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
  36 #include "gc/shenandoah/shenandoahGeneration.hpp"
  37 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
  38 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
  39 #include "jfr/jfrEvents.hpp"
  40 #include "memory/allocation.hpp"
  41 #include "memory/iterator.inline.hpp"
  42 #include "memory/resourceArea.hpp"
  43 #include "memory/universe.hpp"
  44 #include "oops/oop.inline.hpp"
  45 #include "runtime/atomic.hpp"
  46 #include "runtime/globals_extension.hpp"
  47 #include "runtime/java.hpp"
  48 #include "runtime/mutexLocker.hpp"
  49 #include "runtime/os.hpp"
  50 #include "runtime/safepoint.hpp"
  51 #include "utilities/powerOfTwo.hpp"
  52 
  53 
  54 size_t ShenandoahHeapRegion::RegionCount = 0;
  55 size_t ShenandoahHeapRegion::RegionSizeBytes = 0;
  56 size_t ShenandoahHeapRegion::RegionSizeWords = 0;
  57 size_t ShenandoahHeapRegion::RegionSizeBytesShift = 0;
  58 size_t ShenandoahHeapRegion::RegionSizeWordsShift = 0;
  59 size_t ShenandoahHeapRegion::RegionSizeBytesMask = 0;
  60 size_t ShenandoahHeapRegion::RegionSizeWordsMask = 0;
  61 size_t ShenandoahHeapRegion::HumongousThresholdBytes = 0;
  62 size_t ShenandoahHeapRegion::HumongousThresholdWords = 0;
  63 size_t ShenandoahHeapRegion::MaxTLABSizeBytes = 0;
  64 size_t ShenandoahHeapRegion::MaxTLABSizeWords = 0;
  65 
  66 ShenandoahHeapRegion::ShenandoahHeapRegion(HeapWord* start, size_t index, bool committed) :
  67   _index(index),
  68   _bottom(start),
  69   _end(start + RegionSizeWords),
  70   _new_top(nullptr),
  71   _empty_time(os::elapsedTime()),
  72   _state(committed ? _empty_committed : _empty_uncommitted),
  73   _top(start),
  74   _tlab_allocs(0),
  75   _gclab_allocs(0),
  76   _plab_allocs(0),
  77   _has_young_lab(false),
  78   _live_data(0),
  79   _critical_pins(0),
  80   _update_watermark(start),
  81   _age(0) {
  82 
  83   assert(Universe::on_page_boundary(_bottom) && Universe::on_page_boundary(_end),
  84          "invalid space boundaries");
  85   if (ZapUnusedHeapArea && committed) {
  86     SpaceMangler::mangle_region(MemRegion(_bottom, _end));
  87   }
  88 }
  89 
  90 void ShenandoahHeapRegion::report_illegal_transition(const char *method) {
  91   stringStream ss;
  92   ss.print("Illegal region state transition from \"%s\", at %s\n  ", region_state_to_string(_state), method);
  93   print_on(&ss);
  94   fatal("%s", ss.freeze());
  95 }
  96 
  97 void ShenandoahHeapRegion::make_regular_allocation(ShenandoahRegionAffiliation affiliation) {
  98   shenandoah_assert_heaplocked();
  99   reset_age();
 100   switch (_state) {
 101     case _empty_uncommitted:
 102       do_commit();
 103     case _empty_committed:
 104       set_affiliation(affiliation);
 105       set_state(_regular);
 106     case _regular:
 107     case _pinned:
 108       return;
 109     default:
 110       report_illegal_transition("regular allocation");
 111   }
 112 }
 113 
 114 // Change affiliation to YOUNG_GENERATION if _state is not _pinned_cset, _regular, or _pinned.  This implements
 115 // behavior previously performed as a side effect of make_regular_bypass().
 116 void ShenandoahHeapRegion::make_young_maybe() {
 117   shenandoah_assert_heaplocked();
 118   switch (_state) {
 119    case _empty_uncommitted:
 120    case _empty_committed:
 121    case _cset:
 122    case _humongous_start:
 123    case _humongous_cont:
 124      set_affiliation(YOUNG_GENERATION);
 125      return;
 126    case _pinned_cset:
 127    case _regular:
 128    case _pinned:
 129      return;
 130    default:
 131      assert(false, "Unexpected _state in make_young_maybe");
 132   }
 133 }
 134 
 135 void ShenandoahHeapRegion::make_regular_bypass() {
 136   shenandoah_assert_heaplocked();
 137   assert (ShenandoahHeap::heap()->is_full_gc_in_progress() || ShenandoahHeap::heap()->is_degenerated_gc_in_progress(),
 138           "only for full or degen GC");
 139   reset_age();
 140   switch (_state) {
 141     case _empty_uncommitted:
 142       do_commit();
 143     case _empty_committed:
 144     case _cset:
 145     case _humongous_start:
 146     case _humongous_cont:
 147       set_state(_regular);
 148       return;
 149     case _pinned_cset:
 150       set_state(_pinned);
 151       return;
 152     case _regular:
 153     case _pinned:
 154       return;
 155     default:
 156       report_illegal_transition("regular bypass");
 157   }
 158 }
 159 
 160 void ShenandoahHeapRegion::make_humongous_start() {
 161   shenandoah_assert_heaplocked();
 162   reset_age();
 163   switch (_state) {
 164     case _empty_uncommitted:
 165       do_commit();
 166     case _empty_committed:
 167       set_state(_humongous_start);
 168       return;
 169     default:
 170       report_illegal_transition("humongous start allocation");
 171   }
 172 }
 173 
 174 void ShenandoahHeapRegion::make_humongous_start_bypass(ShenandoahRegionAffiliation affiliation) {
 175   shenandoah_assert_heaplocked();
 176   assert (ShenandoahHeap::heap()->is_full_gc_in_progress(), "only for full GC");
 177   set_affiliation(affiliation);
 178   reset_age();
 179   switch (_state) {
 180     case _empty_committed:
 181     case _regular:
 182     case _humongous_start:
 183     case _humongous_cont:
 184       set_state(_humongous_start);
 185       return;
 186     default:
 187       report_illegal_transition("humongous start bypass");
 188   }
 189 }
 190 
 191 void ShenandoahHeapRegion::make_humongous_cont() {
 192   shenandoah_assert_heaplocked();
 193   reset_age();
 194   switch (_state) {
 195     case _empty_uncommitted:
 196       do_commit();
 197     case _empty_committed:
 198      set_state(_humongous_cont);
 199       return;
 200     default:
 201       report_illegal_transition("humongous continuation allocation");
 202   }
 203 }
 204 
 205 void ShenandoahHeapRegion::make_humongous_cont_bypass(ShenandoahRegionAffiliation affiliation) {
 206   shenandoah_assert_heaplocked();
 207   assert (ShenandoahHeap::heap()->is_full_gc_in_progress(), "only for full GC");
 208   set_affiliation(affiliation);
 209   reset_age();
 210   switch (_state) {
 211     case _empty_committed:
 212     case _regular:
 213     case _humongous_start:
 214     case _humongous_cont:
 215       set_state(_humongous_cont);
 216       return;
 217     default:
 218       report_illegal_transition("humongous continuation bypass");
 219   }
 220 }
 221 
 222 void ShenandoahHeapRegion::make_pinned() {
 223   shenandoah_assert_heaplocked();
 224   assert(pin_count() > 0, "Should have pins: " SIZE_FORMAT, pin_count());
 225 
 226   switch (_state) {
 227     case _regular:
 228       set_state(_pinned);
 229     case _pinned_cset:
 230     case _pinned:
 231       return;
 232     case _humongous_start:
 233       set_state(_pinned_humongous_start);
 234     case _pinned_humongous_start:
 235       return;
 236     case _cset:
 237       _state = _pinned_cset;
 238       return;
 239     default:
 240       report_illegal_transition("pinning");
 241   }
 242 }
 243 
 244 void ShenandoahHeapRegion::make_unpinned() {
 245   shenandoah_assert_heaplocked();
 246   assert(pin_count() == 0, "Should not have pins: " SIZE_FORMAT, pin_count());
 247 
 248   switch (_state) {
 249     case _pinned:
 250       assert(affiliation() != FREE, "Pinned region should not be FREE");
 251       set_state(_regular);
 252       return;
 253     case _regular:
 254     case _humongous_start:
 255       return;
 256     case _pinned_cset:
 257       set_state(_cset);
 258       return;
 259     case _pinned_humongous_start:
 260       set_state(_humongous_start);
 261       return;
 262     default:
 263       report_illegal_transition("unpinning");
 264   }
 265 }
 266 
 267 void ShenandoahHeapRegion::make_cset() {
 268   shenandoah_assert_heaplocked();
 269   // Leave age untouched.  We need to consult the age when we are deciding whether to promote evacuated objects.
 270   switch (_state) {
 271     case _regular:
 272       set_state(_cset);
 273     case _cset:
 274       return;
 275     default:
 276       report_illegal_transition("cset");
 277   }
 278 }
 279 
 280 void ShenandoahHeapRegion::make_trash() {
 281   shenandoah_assert_heaplocked();
 282   reset_age();
 283   switch (_state) {
 284     case _cset:
 285       // Reclaiming cset regions
 286     case _humongous_start:
 287     case _humongous_cont:
 288       // Reclaiming humongous regions
 289     case _regular:
 290       // Immediate region reclaim
 291       set_state(_trash);
 292       return;
 293     default:
 294       report_illegal_transition("trashing");
 295   }
 296 }
 297 
 298 void ShenandoahHeapRegion::make_trash_immediate() {
 299   make_trash();
 300 
 301   // On this path, we know there are no marked objects in the region,
 302   // tell marking context about it to bypass bitmap resets.
 303   assert(ShenandoahHeap::heap()->active_generation()->is_mark_complete(), "Marking should be complete here.");
 304   ShenandoahHeap::heap()->marking_context()->reset_top_bitmap(this);
 305 }
 306 
 307 void ShenandoahHeapRegion::make_empty() {
 308   shenandoah_assert_heaplocked();
 309   reset_age();
 310   switch (_state) {
 311     case _trash:
 312       set_state(_empty_committed);
 313       _empty_time = os::elapsedTime();
 314       return;
 315     default:
 316       report_illegal_transition("emptying");
 317   }
 318 }
 319 
 320 void ShenandoahHeapRegion::make_uncommitted() {
 321   shenandoah_assert_heaplocked();
 322   switch (_state) {
 323     case _empty_committed:
 324       do_uncommit();
 325       set_state(_empty_uncommitted);
 326       return;
 327     default:
 328       report_illegal_transition("uncommiting");
 329   }
 330 }
 331 
 332 void ShenandoahHeapRegion::make_committed_bypass() {
 333   shenandoah_assert_heaplocked();
 334   assert (ShenandoahHeap::heap()->is_full_gc_in_progress(), "only for full GC");
 335 
 336   switch (_state) {
 337     case _empty_uncommitted:
 338       do_commit();
 339       set_state(_empty_committed);
 340       return;
 341     default:
 342       report_illegal_transition("commit bypass");
 343   }
 344 }
 345 
 346 void ShenandoahHeapRegion::reset_alloc_metadata() {
 347   _tlab_allocs = 0;
 348   _gclab_allocs = 0;
 349   _plab_allocs = 0;
 350 }
 351 
 352 size_t ShenandoahHeapRegion::get_shared_allocs() const {
 353   return used() - (_tlab_allocs + _gclab_allocs + _plab_allocs) * HeapWordSize;
 354 }
 355 
 356 size_t ShenandoahHeapRegion::get_tlab_allocs() const {
 357   return _tlab_allocs * HeapWordSize;
 358 }
 359 
 360 size_t ShenandoahHeapRegion::get_gclab_allocs() const {
 361   return _gclab_allocs * HeapWordSize;
 362 }
 363 
 364 size_t ShenandoahHeapRegion::get_plab_allocs() const {
 365   return _plab_allocs * HeapWordSize;
 366 }
 367 
 368 void ShenandoahHeapRegion::set_live_data(size_t s) {
 369   assert(Thread::current()->is_VM_thread(), "by VM thread");
 370   _live_data = (s >> LogHeapWordSize);
 371 }
 372 
 373 void ShenandoahHeapRegion::print_on(outputStream* st) const {
 374   st->print("|");
 375   st->print(SIZE_FORMAT_W(5), this->_index);
 376 
 377   switch (_state) {
 378     case _empty_uncommitted:
 379       st->print("|EU ");
 380       break;
 381     case _empty_committed:
 382       st->print("|EC ");
 383       break;
 384     case _regular:
 385       st->print("|R  ");
 386       break;
 387     case _humongous_start:

 392       break;
 393     case _humongous_cont:
 394       st->print("|HC ");
 395       break;
 396     case _cset:
 397       st->print("|CS ");
 398       break;
 399     case _trash:
 400       st->print("|T  ");
 401       break;
 402     case _pinned:
 403       st->print("|P  ");
 404       break;
 405     case _pinned_cset:
 406       st->print("|CSP");
 407       break;
 408     default:
 409       ShouldNotReachHere();
 410   }
 411 
 412   switch (ShenandoahHeap::heap()->region_affiliation(this)) {
 413     case ShenandoahRegionAffiliation::FREE:
 414       st->print("|F");
 415       break;
 416     case ShenandoahRegionAffiliation::YOUNG_GENERATION:
 417       st->print("|Y");
 418       break;
 419     case ShenandoahRegionAffiliation::OLD_GENERATION:
 420       st->print("|O");
 421       break;
 422     default:
 423       ShouldNotReachHere();
 424   }
 425 
 426 #define SHR_PTR_FORMAT "%12" PRIxPTR
 427 
 428   st->print("|BTE " SHR_PTR_FORMAT  ", " SHR_PTR_FORMAT ", " SHR_PTR_FORMAT,
 429             p2i(bottom()), p2i(top()), p2i(end()));
 430   st->print("|TAMS " SHR_PTR_FORMAT,
 431             p2i(ShenandoahHeap::heap()->marking_context()->top_at_mark_start(const_cast<ShenandoahHeapRegion*>(this))));
 432   st->print("|UWM " SHR_PTR_FORMAT,
 433             p2i(_update_watermark));
 434   st->print("|U " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(used()),                proper_unit_for_byte_size(used()));
 435   st->print("|T " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_tlab_allocs()),     proper_unit_for_byte_size(get_tlab_allocs()));
 436   st->print("|G " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_gclab_allocs()),    proper_unit_for_byte_size(get_gclab_allocs()));
 437   if (ShenandoahHeap::heap()->mode()->is_generational()) {
 438     st->print("|P " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_plab_allocs()),   proper_unit_for_byte_size(get_plab_allocs()));
 439   }
 440   st->print("|S " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_shared_allocs()),   proper_unit_for_byte_size(get_shared_allocs()));
 441   st->print("|L " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_live_data_bytes()), proper_unit_for_byte_size(get_live_data_bytes()));
 442   st->print("|CP " SIZE_FORMAT_W(3), pin_count());
 443   st->cr();
 444 
 445 #undef SHR_PTR_FORMAT
 446 }
 447 
 448 // oop_iterate without closure and without cancellation.  always return true.
 449 bool ShenandoahHeapRegion::oop_fill_and_coalesce_wo_cancel() {
 450   HeapWord* obj_addr = resume_coalesce_and_fill();
 451 
 452   assert(!is_humongous(), "No need to fill or coalesce humongous regions");
 453   if (!is_active()) {
 454     end_preemptible_coalesce_and_fill();
 455     return true;
 456   }
 457 
 458   ShenandoahHeap* heap = ShenandoahHeap::heap();
 459   ShenandoahMarkingContext* marking_context = heap->marking_context();
 460   // All objects above TAMS are considered live even though their mark bits will not be set.  Note that young-
 461   // gen evacuations that interrupt a long-running old-gen concurrent mark may promote objects into old-gen
 462   // while the old-gen concurrent marking is ongoing.  These newly promoted objects will reside above TAMS
 463   // and will be treated as live during the current old-gen marking pass, even though they will not be
 464   // explicitly marked.
 465   HeapWord* t = marking_context->top_at_mark_start(this);
 466 
 467   // Expect marking to be completed before these threads invoke this service.
 468   assert(heap->active_generation()->is_mark_complete(), "sanity");
 469   while (obj_addr < t) {
 470     oop obj = cast_to_oop(obj_addr);
 471     if (marking_context->is_marked(obj)) {
 472       assert(obj->klass() != nullptr, "klass should not be nullptr");
 473       obj_addr += obj->size();
 474     } else {
 475       // Object is not marked.  Coalesce and fill dead object with dead neighbors.
 476       HeapWord* next_marked_obj = marking_context->get_next_marked_addr(obj_addr, t);
 477       assert(next_marked_obj <= t, "next marked object cannot exceed top");
 478       size_t fill_size = next_marked_obj - obj_addr;
 479       ShenandoahHeap::fill_with_object(obj_addr, fill_size);
 480       heap->card_scan()->coalesce_objects(obj_addr, fill_size);
 481       obj_addr = next_marked_obj;
 482     }
 483   }
 484   // Mark that this region has been coalesced and filled
 485   end_preemptible_coalesce_and_fill();
 486   return true;
 487 }
 488 
 489 // oop_iterate without closure, return true if completed without cancellation
 490 bool ShenandoahHeapRegion::oop_fill_and_coalesce() {
 491   HeapWord* obj_addr = resume_coalesce_and_fill();
 492   // Consider yielding to cancel/preemption request after this many coalesce operations (skip marked, or coalesce free).
 493   const size_t preemption_stride = 128;
 494 
 495   assert(!is_humongous(), "No need to fill or coalesce humongous regions");
 496   if (!is_active()) {
 497     end_preemptible_coalesce_and_fill();
 498     return true;
 499   }
 500 
 501   ShenandoahHeap* heap = ShenandoahHeap::heap();
 502   ShenandoahMarkingContext* marking_context = heap->marking_context();
 503   // All objects above TAMS are considered live even though their mark bits will not be set.  Note that young-
 504   // gen evacuations that interrupt a long-running old-gen concurrent mark may promote objects into old-gen
 505   // while the old-gen concurrent marking is ongoing.  These newly promoted objects will reside above TAMS
 506   // and will be treated as live during the current old-gen marking pass, even though they will not be
 507   // explicitly marked.
 508   HeapWord* t = marking_context->top_at_mark_start(this);
 509 
 510   // Expect marking to be completed before these threads invoke this service.
 511   assert(heap->active_generation()->is_mark_complete(), "sanity");
 512 
 513   size_t ops_before_preempt_check = preemption_stride;
 514   while (obj_addr < t) {
 515     oop obj = cast_to_oop(obj_addr);
 516     if (marking_context->is_marked(obj)) {
 517       assert(obj->klass() != nullptr, "klass should not be nullptr");
 518       obj_addr += obj->size();
 519     } else {
 520       // Object is not marked.  Coalesce and fill dead object with dead neighbors.
 521       HeapWord* next_marked_obj = marking_context->get_next_marked_addr(obj_addr, t);
 522       assert(next_marked_obj <= t, "next marked object cannot exceed top");
 523       size_t fill_size = next_marked_obj - obj_addr;
 524       ShenandoahHeap::fill_with_object(obj_addr, fill_size);
 525       heap->card_scan()->coalesce_objects(obj_addr, fill_size);
 526       obj_addr = next_marked_obj;
 527     }
 528     if (ops_before_preempt_check-- == 0) {
 529       if (heap->cancelled_gc()) {
 530         suspend_coalesce_and_fill(obj_addr);
 531         return false;
 532       }
 533       ops_before_preempt_check = preemption_stride;
 534     }
 535   }
 536   // Mark that this region has been coalesced and filled
 537   end_preemptible_coalesce_and_fill();
 538   return true;
 539 }
 540 
 541 void ShenandoahHeapRegion::global_oop_iterate_and_fill_dead(OopIterateClosure* blk) {
 542   if (!is_active()) return;
 543   if (is_humongous()) {
 544     // No need to fill dead within humongous regions.  Either the entire region is dead, or the entire region is
 545     // unchanged.  A humongous region holds no more than one humongous object.
 546     oop_iterate_humongous(blk);
 547   } else {
 548     global_oop_iterate_objects_and_fill_dead(blk);
 549   }
 550 }
 551 
 552 void ShenandoahHeapRegion::global_oop_iterate_objects_and_fill_dead(OopIterateClosure* blk) {
 553   assert(!is_humongous(), "no humongous region here");
 554   HeapWord* obj_addr = bottom();
 555 
 556   ShenandoahHeap* heap = ShenandoahHeap::heap();
 557   ShenandoahMarkingContext* marking_context = heap->marking_context();
 558   RememberedScanner* rem_set_scanner = heap->card_scan();
 559   // Objects allocated above TAMS are not marked, but are considered live for purposes of current GC efforts.
 560   HeapWord* t = marking_context->top_at_mark_start(this);
 561 
 562   assert(heap->active_generation()->is_mark_complete(), "sanity");
 563 
 564   while (obj_addr < t) {
 565     oop obj = cast_to_oop(obj_addr);
 566     if (marking_context->is_marked(obj)) {
 567       assert(obj->klass() != nullptr, "klass should not be nullptr");
 568       // when promoting an entire region, we have to register the marked objects as well
 569       obj_addr += obj->oop_iterate_size(blk);
 570     } else {
 571       // Object is not marked.  Coalesce and fill dead object with dead neighbors.
 572       HeapWord* next_marked_obj = marking_context->get_next_marked_addr(obj_addr, t);
 573       assert(next_marked_obj <= t, "next marked object cannot exceed top");
 574       size_t fill_size = next_marked_obj - obj_addr;
 575       ShenandoahHeap::fill_with_object(obj_addr, fill_size);
 576 
 577       // coalesce_objects() unregisters all but first object subsumed within coalesced range.
 578       rem_set_scanner->coalesce_objects(obj_addr, fill_size);
 579       obj_addr = next_marked_obj;
 580     }
 581   }
 582 
 583   // Any object above TAMS and below top() is considered live.
 584   t = top();
 585   while (obj_addr < t) {
 586     oop obj = cast_to_oop(obj_addr);
 587     obj_addr += obj->oop_iterate_size(blk);
 588   }
 589 }
 590 
 591 // DO NOT CANCEL.  If this worker thread has accepted responsibility for scanning a particular range of addresses, it
 592 // must finish the work before it can be cancelled.
 593 void ShenandoahHeapRegion::oop_iterate_humongous_slice(OopIterateClosure* blk, bool dirty_only,
 594                                                        HeapWord* start, size_t words, bool write_table) {
 595   assert(words % CardTable::card_size_in_words() == 0, "Humongous iteration must span whole number of cards");
 596   assert(is_humongous(), "only humongous region here");
 597   ShenandoahHeap* heap = ShenandoahHeap::heap();
 598 
 599   // Find head.
 600   ShenandoahHeapRegion* r = humongous_start_region();
 601   assert(r->is_humongous_start(), "need humongous head here");
 602   assert(CardTable::card_size_in_words() * (words / CardTable::card_size_in_words()) == words,
 603          "slice must be integral number of cards");
 604 
 605   oop obj = cast_to_oop(r->bottom());
 606   RememberedScanner* scanner = ShenandoahHeap::heap()->card_scan();
 607   size_t card_index = scanner->card_index_for_addr(start);
 608   size_t num_cards = words / CardTable::card_size_in_words();
 609 
 610   if (dirty_only) {
 611     if (write_table) {
 612       while (num_cards-- > 0) {
 613         if (scanner->is_write_card_dirty(card_index++)) {
 614           obj->oop_iterate(blk, MemRegion(start, start + CardTable::card_size_in_words()));
 615         }
 616         start += CardTable::card_size_in_words();
 617       }
 618     } else {
 619       while (num_cards-- > 0) {
 620         if (scanner->is_card_dirty(card_index++)) {
 621           obj->oop_iterate(blk, MemRegion(start, start + CardTable::card_size_in_words()));
 622         }
 623         start += CardTable::card_size_in_words();
 624       }
 625     }
 626   } else {
 627     // Scan all data, regardless of whether cards are dirty
 628     obj->oop_iterate(blk, MemRegion(start, start + num_cards * CardTable::card_size_in_words()));
 629   }
 630 }
 631 
 632 void ShenandoahHeapRegion::oop_iterate_humongous(OopIterateClosure* blk, HeapWord* start, size_t words) {
 633   assert(is_humongous(), "only humongous region here");
 634   // Find head.
 635   ShenandoahHeapRegion* r = humongous_start_region();
 636   assert(r->is_humongous_start(), "need humongous head here");
 637   oop obj = cast_to_oop(r->bottom());
 638   obj->oop_iterate(blk, MemRegion(start, start + words));
 639 }
 640 
 641 void ShenandoahHeapRegion::oop_iterate_humongous(OopIterateClosure* blk) {
 642   assert(is_humongous(), "only humongous region here");
 643   // Find head.
 644   ShenandoahHeapRegion* r = humongous_start_region();
 645   assert(r->is_humongous_start(), "need humongous head here");
 646   oop obj = cast_to_oop(r->bottom());
 647   obj->oop_iterate(blk, MemRegion(bottom(), top()));
 648 }
 649 
 650 ShenandoahHeapRegion* ShenandoahHeapRegion::humongous_start_region() const {
 651   ShenandoahHeap* heap = ShenandoahHeap::heap();
 652   assert(is_humongous(), "Must be a part of the humongous region");
 653   size_t i = index();
 654   ShenandoahHeapRegion* r = const_cast<ShenandoahHeapRegion*>(this);
 655   while (!r->is_humongous_start()) {
 656     assert(i > 0, "Sanity");
 657     i--;
 658     r = heap->get_region(i);
 659     assert(r->is_humongous(), "Must be a part of the humongous region");
 660   }
 661   assert(r->is_humongous_start(), "Must be");
 662   return r;
 663 }
 664 
 665 void ShenandoahHeapRegion::recycle() {
 666   ShenandoahHeap* heap = ShenandoahHeap::heap();
 667   shenandoah_assert_heaplocked();
 668 
 669   heap->generation_for(affiliation())->decrease_used(used());
 670 
 671   set_top(bottom());
 672   clear_live_data();
 673 
 674   reset_alloc_metadata();
 675 
 676   heap->marking_context()->reset_top_at_mark_start(this);
 677   set_update_watermark(bottom());
 678 
 679   make_empty();
 680   set_affiliation(FREE);
 681 
 682   if (ZapUnusedHeapArea) {
 683     SpaceMangler::mangle_region(MemRegion(bottom(), end()));
 684   }
 685 }
 686 
 687 HeapWord* ShenandoahHeapRegion::block_start(const void* p) const {
 688   assert(MemRegion(bottom(), end()).contains(p),
 689          "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
 690          p2i(p), p2i(bottom()), p2i(end()));
 691   if (p >= top()) {
 692     return top();
 693   } else {
 694     HeapWord* last = bottom();
 695     HeapWord* cur = last;
 696     while (cur <= p) {
 697       last = cur;
 698       cur += cast_to_oop(cur)->size();
 699     }
 700     shenandoah_assert_correct(nullptr, cast_to_oop(last));

 705 size_t ShenandoahHeapRegion::block_size(const HeapWord* p) const {
 706   assert(MemRegion(bottom(), end()).contains(p),
 707          "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
 708          p2i(p), p2i(bottom()), p2i(end()));
 709   if (p < top()) {
 710     return cast_to_oop(p)->size();
 711   } else {
 712     assert(p == top(), "just checking");
 713     return pointer_delta(end(), (HeapWord*) p);
 714   }
 715 }
 716 
 717 size_t ShenandoahHeapRegion::setup_sizes(size_t max_heap_size) {
 718   // Absolute minimums we should not ever break.
 719   static const size_t MIN_REGION_SIZE = 256*K;
 720 
 721   if (FLAG_IS_DEFAULT(ShenandoahMinRegionSize)) {
 722     FLAG_SET_DEFAULT(ShenandoahMinRegionSize, MIN_REGION_SIZE);
 723   }
 724 
 725   // Generational Shenandoah needs this alignment for card tables.
 726   if (strcmp(ShenandoahGCMode, "generational") == 0) {
 727     max_heap_size = align_up(max_heap_size , CardTable::ct_max_alignment_constraint());
 728   }
 729 
 730   size_t region_size;
 731   if (FLAG_IS_DEFAULT(ShenandoahRegionSize)) {
 732     if (ShenandoahMinRegionSize > max_heap_size / MIN_NUM_REGIONS) {
 733       err_msg message("Max heap size (" SIZE_FORMAT "%s) is too low to afford the minimum number "
 734                       "of regions (" SIZE_FORMAT ") of minimum region size (" SIZE_FORMAT "%s).",
 735                       byte_size_in_proper_unit(max_heap_size), proper_unit_for_byte_size(max_heap_size),
 736                       MIN_NUM_REGIONS,
 737                       byte_size_in_proper_unit(ShenandoahMinRegionSize), proper_unit_for_byte_size(ShenandoahMinRegionSize));
 738       vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
 739     }
 740     if (ShenandoahMinRegionSize < MIN_REGION_SIZE) {
 741       err_msg message("" SIZE_FORMAT "%s should not be lower than minimum region size (" SIZE_FORMAT "%s).",
 742                       byte_size_in_proper_unit(ShenandoahMinRegionSize), proper_unit_for_byte_size(ShenandoahMinRegionSize),
 743                       byte_size_in_proper_unit(MIN_REGION_SIZE),         proper_unit_for_byte_size(MIN_REGION_SIZE));
 744       vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
 745     }
 746     if (ShenandoahMinRegionSize < MinTLABSize) {
 747       err_msg message("" SIZE_FORMAT "%s should not be lower than TLAB size size (" SIZE_FORMAT "%s).",
 748                       byte_size_in_proper_unit(ShenandoahMinRegionSize), proper_unit_for_byte_size(ShenandoahMinRegionSize),
 749                       byte_size_in_proper_unit(MinTLABSize),             proper_unit_for_byte_size(MinTLABSize));

 916     evt.set_used(used());
 917     evt.set_from(_state);
 918     evt.set_to(to);
 919     evt.commit();
 920   }
 921   _state = to;
 922 }
 923 
 924 void ShenandoahHeapRegion::record_pin() {
 925   Atomic::add(&_critical_pins, (size_t)1);
 926 }
 927 
 928 void ShenandoahHeapRegion::record_unpin() {
 929   assert(pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", index());
 930   Atomic::sub(&_critical_pins, (size_t)1);
 931 }
 932 
 933 size_t ShenandoahHeapRegion::pin_count() const {
 934   return Atomic::load(&_critical_pins);
 935 }
 936 
 937 void ShenandoahHeapRegion::set_affiliation(ShenandoahRegionAffiliation new_affiliation) {
 938   ShenandoahHeap* heap = ShenandoahHeap::heap();
 939 
 940   ShenandoahRegionAffiliation region_affiliation = heap->region_affiliation(this);
 941   {
 942     ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
 943     log_debug(gc)("Setting affiliation of Region " SIZE_FORMAT " from %s to %s, top: " PTR_FORMAT ", TAMS: " PTR_FORMAT
 944                   ", watermark: " PTR_FORMAT ", top_bitmap: " PTR_FORMAT,
 945                   index(), affiliation_name(region_affiliation), affiliation_name(new_affiliation),
 946                   p2i(top()), p2i(ctx->top_at_mark_start(this)), p2i(_update_watermark), p2i(ctx->top_bitmap(this)));
 947   }
 948 
 949 #ifdef ASSERT
 950   {
 951     // During full gc, heap->complete_marking_context() is not valid, may equal nullptr.
 952     ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
 953     size_t idx = this->index();
 954     HeapWord* top_bitmap = ctx->top_bitmap(this);
 955 
 956     assert(ctx->is_bitmap_clear_range(top_bitmap, _end),
 957            "Region " SIZE_FORMAT ", bitmap should be clear between top_bitmap: " PTR_FORMAT " and end: " PTR_FORMAT, idx,
 958            p2i(top_bitmap), p2i(_end));
 959   }
 960 #endif
 961 
 962   if (region_affiliation == new_affiliation) {
 963     return;
 964   }
 965 
 966   if (!heap->mode()->is_generational()) {
 967     heap->set_affiliation(this, new_affiliation);
 968     return;
 969   }
 970 
 971   log_trace(gc)("Changing affiliation of region %zu from %s to %s",
 972     index(), affiliation_name(region_affiliation), affiliation_name(new_affiliation));
 973 
 974   if (region_affiliation == ShenandoahRegionAffiliation::YOUNG_GENERATION) {
 975     heap->young_generation()->decrement_affiliated_region_count();
 976   } else if (region_affiliation == ShenandoahRegionAffiliation::OLD_GENERATION) {
 977     heap->old_generation()->decrement_affiliated_region_count();
 978   }
 979 
 980   size_t regions;
 981   switch (new_affiliation) {
 982     case FREE:
 983       assert(!has_live(), "Free region should not have live data");
 984       break;
 985     case YOUNG_GENERATION:
 986       reset_age();
 987       regions = heap->young_generation()->increment_affiliated_region_count();
 988       // During Full GC, we allow temporary violation of this requirement.  We enforce that this condition is
 989       // restored upon completion of Full GC.
 990       assert(heap->is_full_gc_in_progress() ||
 991              (regions * ShenandoahHeapRegion::region_size_bytes() <= heap->young_generation()->adjusted_capacity()),
 992              "Number of young regions cannot exceed adjusted capacity");
 993       break;
 994     case OLD_GENERATION:
 995       regions = heap->old_generation()->increment_affiliated_region_count();
 996       // During Full GC, we allow temporary violation of this requirement.  We enforce that this condition is
 997       // restored upon completion of Full GC.
 998       assert(heap->is_full_gc_in_progress() ||
 999              (regions * ShenandoahHeapRegion::region_size_bytes() <= heap->old_generation()->adjusted_capacity()),
1000              "Number of old regions cannot exceed adjusted capacity");
1001       break;
1002     default:
1003       ShouldNotReachHere();
1004       return;
1005   }
1006   heap->set_affiliation(this, new_affiliation);
1007 }
1008 
1009 // Returns number of regions promoted, or zero if we choose not to promote.
1010 size_t ShenandoahHeapRegion::promote_humongous() {
1011   ShenandoahHeap* heap = ShenandoahHeap::heap();
1012   ShenandoahMarkingContext* marking_context = heap->marking_context();
1013   assert(heap->active_generation()->is_mark_complete(), "sanity");
1014   assert(is_young(), "Only young regions can be promoted");
1015   assert(is_humongous_start(), "Should not promote humongous continuation in isolation");
1016   assert(age() >= InitialTenuringThreshold, "Only promote regions that are sufficiently aged");
1017 
1018   ShenandoahGeneration* old_generation = heap->old_generation();
1019   ShenandoahGeneration* young_generation = heap->young_generation();
1020 
1021   oop obj = cast_to_oop(bottom());
1022   assert(marking_context->is_marked(obj), "promoted humongous object should be alive");
1023 
1024   // TODO: Consider not promoting humongous objects that represent primitive arrays.  Leaving a primitive array
1025   // (obj->is_typeArray()) in young-gen is harmless because these objects are never relocated and they are not
1026   // scanned.  Leaving primitive arrays in young-gen memory allows their memory to be reclaimed more quickly when
1027   // it becomes garbage.  Better to not make this change until sizes of young-gen and old-gen are completely
1028   // adaptive, as leaving primitive arrays in young-gen might be perceived as an "astonishing result" by someone
1029   // has carefully analyzed the required sizes of an application's young-gen and old-gen.
1030 
1031   size_t spanned_regions = ShenandoahHeapRegion::required_regions(obj->size() * HeapWordSize);
1032   size_t index_limit = index() + spanned_regions;
1033 
1034   {
1035     // We need to grab the heap lock in order to avoid a race when changing the affiliations of spanned_regions from
1036     // young to old.
1037     ShenandoahHeapLocker locker(heap->lock());
1038     size_t available_old_regions = old_generation->adjusted_unaffiliated_regions();
1039     if (spanned_regions <= available_old_regions) {
1040       log_debug(gc)("promoting humongous region " SIZE_FORMAT ", spanning " SIZE_FORMAT, index(), spanned_regions);
1041 
1042       // For this region and each humongous continuation region spanned by this humongous object, change
1043       // affiliation to OLD_GENERATION and adjust the generation-use tallies.  The remnant of memory
1044       // in the last humongous region that is not spanned by obj is currently not used.
1045       for (size_t i = index(); i < index_limit; i++) {
1046         ShenandoahHeapRegion* r = heap->get_region(i);
1047         log_debug(gc)("promoting humongous region " SIZE_FORMAT ", from " PTR_FORMAT " to " PTR_FORMAT,
1048                       r->index(), p2i(r->bottom()), p2i(r->top()));
1049         // We mark the entire humongous object's range as dirty after loop terminates, so no need to dirty the range here
1050         r->set_affiliation(OLD_GENERATION);
1051         old_generation->increase_used(r->used());
1052         young_generation->decrease_used(r->used());
1053       }
1054       // Then fall through to finish the promotion after releasing the heap lock.
1055     } else {
1056       // There are not enough available old regions to promote this humongous region at this time, so defer promotion.
1057       // TODO: Consider allowing the promotion now, with the expectation that we can resize and/or collect OLD
1058       // momentarily to address the transient violation of budgets.  Some problems that need to be addressed in order
1059       // to allow transient violation of capacity budgets are:
1060       //  1. Various size_t subtractions assume usage is less than capacity, and thus assume there will be no
1061       //     arithmetic underflow when we subtract usage from capacity.  The results of such size_t subtractions
1062       //     would need to be guarded and special handling provided.
1063       //  2. ShenandoahVerifier enforces that usage is less than capacity.  If we are going to relax this constraint,
1064       //     we need to think about what conditions allow the constraint to be violated and document and implement the
1065       //     changes.
1066       return 0;
1067     }
1068   }
1069 
1070   // Since this region may have served previously as OLD, it may hold obsolete object range info.
1071   heap->card_scan()->reset_object_range(bottom(), bottom() + spanned_regions * ShenandoahHeapRegion::region_size_words());
1072   // Since the humongous region holds only one object, no lock is necessary for this register_object() invocation.
1073   heap->card_scan()->register_object_wo_lock(bottom());
1074 
1075   if (obj->is_typeArray()) {
1076     // Primitive arrays don't need to be scanned.
1077     log_debug(gc)("Clean cards for promoted humongous object (Region " SIZE_FORMAT ") from " PTR_FORMAT " to " PTR_FORMAT,
1078                   index(), p2i(bottom()), p2i(bottom() + obj->size()));
1079     heap->card_scan()->mark_range_as_clean(bottom(), obj->size());
1080   } else {
1081     log_debug(gc)("Dirty cards for promoted humongous object (Region " SIZE_FORMAT ") from " PTR_FORMAT " to " PTR_FORMAT,
1082                   index(), p2i(bottom()), p2i(bottom() + obj->size()));
1083     heap->card_scan()->mark_range_as_dirty(bottom(), obj->size());
1084   }
1085   return index_limit - index();
1086 }
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