1 /*
   2  * Copyright (c) 2023, 2026, Oracle and/or its affiliates. All rights reserved.
   3  * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
   4  * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
   5  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   6  *
   7  * This code is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License version 2 only, as
   9  * published by the Free Software Foundation.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  *
  25  */
  26 
  27 
  28 #include "cds/aotMappedHeapWriter.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "gc/shared/classUnloadingContext.hpp"
  31 #include "gc/shared/fullGCForwarding.hpp"
  32 #include "gc/shared/gc_globals.hpp"
  33 #include "gc/shared/gcArguments.hpp"
  34 #include "gc/shared/gcTimer.hpp"
  35 #include "gc/shared/gcTraceTime.inline.hpp"
  36 #include "gc/shared/locationPrinter.inline.hpp"
  37 #include "gc/shared/memAllocator.hpp"
  38 #include "gc/shared/plab.hpp"
  39 #include "gc/shared/tlab_globals.hpp"
  40 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp"
  41 #include "gc/shenandoah/heuristics/shenandoahYoungHeuristics.hpp"
  42 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp"
  43 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
  44 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
  45 #include "gc/shenandoah/shenandoahAllocRate.inline.hpp"
  46 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
  47 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
  48 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
  49 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
  50 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
  51 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
  52 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
  53 #include "gc/shenandoah/shenandoahControlThread.hpp"
  54 #include "gc/shenandoah/shenandoahFreeSet.hpp"
  55 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp"
  56 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
  57 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
  58 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
  59 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
  60 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp"
  61 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
  62 #include "gc/shenandoah/shenandoahInitLogger.hpp"
  63 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
  64 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
  65 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
  66 #include "gc/shenandoah/shenandoahObjArrayAllocator.hpp"
  67 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
  68 #include "gc/shenandoah/shenandoahPadding.hpp"
  69 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
  70 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
  71 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
  72 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
  73 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
  74 #include "gc/shenandoah/shenandoahSTWMark.hpp"
  75 #include "gc/shenandoah/shenandoahUncommitThread.hpp"
  76 #include "gc/shenandoah/shenandoahUtils.hpp"
  77 #include "gc/shenandoah/shenandoahVerifier.hpp"
  78 #include "gc/shenandoah/shenandoahVMOperations.hpp"
  79 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
  80 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
  81 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
  82 #include "memory/allocation.hpp"
  83 #include "memory/classLoaderMetaspace.hpp"
  84 #include "memory/memoryReserver.hpp"
  85 #include "memory/metaspaceUtils.hpp"
  86 #include "memory/universe.hpp"
  87 #include "nmt/mallocTracker.hpp"
  88 #include "nmt/memTracker.hpp"
  89 #include "oops/compressedOops.inline.hpp"
  90 #include "prims/jvmtiTagMap.hpp"
  91 #include "runtime/atomic.hpp"
  92 #include "runtime/atomicAccess.hpp"
  93 #include "runtime/globals.hpp"
  94 #include "runtime/interfaceSupport.inline.hpp"
  95 #include "runtime/java.hpp"
  96 #include "runtime/orderAccess.hpp"
  97 #include "runtime/safepointMechanism.hpp"
  98 #include "runtime/stackWatermarkSet.hpp"
  99 #include "runtime/threads.hpp"
 100 #include "runtime/vmThread.hpp"
 101 #include "utilities/events.hpp"
 102 #include "utilities/globalDefinitions.hpp"
 103 #include "utilities/powerOfTwo.hpp"
 104 #if INCLUDE_JFR
 105 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
 106 #endif
 107 
 108 class ShenandoahPretouchHeapTask : public WorkerTask {
 109 private:
 110   ShenandoahRegionIterator _regions;
 111   const size_t _page_size;
 112 public:
 113   ShenandoahPretouchHeapTask(size_t page_size) :
 114     WorkerTask("Shenandoah Pretouch Heap"),
 115     _page_size(page_size) {}
 116 
 117   virtual void work(uint worker_id) {
 118     ShenandoahHeapRegion* r = _regions.next();
 119     while (r != nullptr) {
 120       if (r->is_committed()) {
 121         os::pretouch_memory(r->bottom(), r->end(), _page_size);
 122       }
 123       r = _regions.next();
 124     }
 125   }
 126 };
 127 
 128 class ShenandoahPretouchBitmapTask : public WorkerTask {
 129 private:
 130   ShenandoahRegionIterator _regions;
 131   char* _bitmap_base;
 132   const size_t _bitmap_size;
 133   const size_t _page_size;
 134 public:
 135   ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
 136     WorkerTask("Shenandoah Pretouch Bitmap"),
 137     _bitmap_base(bitmap_base),
 138     _bitmap_size(bitmap_size),
 139     _page_size(page_size) {}
 140 
 141   virtual void work(uint worker_id) {
 142     ShenandoahHeapRegion* r = _regions.next();
 143     while (r != nullptr) {
 144       size_t start = r->index()       * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 145       size_t end   = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 146       assert (end <= _bitmap_size, "end is sane: %zu < %zu", end, _bitmap_size);
 147 
 148       if (r->is_committed()) {
 149         os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
 150       }
 151 
 152       r = _regions.next();
 153     }
 154   }
 155 };
 156 
 157 static ReservedSpace reserve(size_t size, size_t preferred_page_size) {
 158   // When a page size is given we don't want to mix large
 159   // and normal pages. If the size is not a multiple of the
 160   // page size it will be aligned up to achieve this.
 161   size_t alignment = os::vm_allocation_granularity();
 162   if (preferred_page_size != os::vm_page_size()) {
 163     alignment = MAX2(preferred_page_size, alignment);
 164     size = align_up(size, alignment);
 165   }
 166 
 167   const ReservedSpace reserved = MemoryReserver::reserve(size, alignment, preferred_page_size, mtGC);
 168   if (!reserved.is_reserved()) {
 169     vm_exit_during_initialization("Could not reserve space");
 170   }
 171   return reserved;
 172 }
 173 
 174 jint ShenandoahHeap::initialize() {
 175   //
 176   // Figure out heap sizing
 177   //
 178 
 179   size_t init_byte_size = InitialHeapSize;
 180   size_t min_byte_size  = MinHeapSize;
 181   size_t max_byte_size  = MaxHeapSize;
 182   size_t heap_alignment = HeapAlignment;
 183 
 184   size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
 185 
 186   Universe::check_alignment(max_byte_size,  reg_size_bytes, "Shenandoah heap");
 187   Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
 188 
 189   _num_regions = ShenandoahHeapRegion::region_count();
 190   assert(_num_regions == (max_byte_size / reg_size_bytes),
 191          "Regions should cover entire heap exactly: %zu != %zu/%zu",
 192          _num_regions, max_byte_size, reg_size_bytes);
 193 
 194   size_t num_committed_regions = init_byte_size / reg_size_bytes;
 195   num_committed_regions = MIN2(num_committed_regions, _num_regions);
 196   assert(num_committed_regions <= _num_regions, "sanity");
 197   _initial_size = num_committed_regions * reg_size_bytes;
 198 
 199   size_t num_min_regions = min_byte_size / reg_size_bytes;
 200   num_min_regions = MIN2(num_min_regions, _num_regions);
 201   assert(num_min_regions <= _num_regions, "sanity");
 202   _minimum_size = num_min_regions * reg_size_bytes;
 203 
 204   _soft_max_size.store_relaxed(clamp(SoftMaxHeapSize, min_capacity(), max_capacity()));
 205 
 206   _committed.store_relaxed(_initial_size);
 207 
 208   size_t heap_page_size   = UseLargePages ? os::large_page_size() : os::vm_page_size();
 209   size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
 210   size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
 211 
 212   //
 213   // Reserve and commit memory for heap
 214   //
 215 
 216   ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
 217   initialize_reserved_region(heap_rs);
 218   _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
 219   _heap_region_special = heap_rs.special();
 220 
 221   assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
 222          "Misaligned heap: " PTR_FORMAT, p2i(base()));
 223   os::trace_page_sizes_for_requested_size("Heap",
 224                                           max_byte_size, heap_alignment,
 225                                           heap_rs.base(),
 226                                           heap_rs.size(), heap_rs.page_size());
 227 
 228 #if SHENANDOAH_OPTIMIZED_MARKTASK
 229   // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
 230   // Fail if we ever attempt to address more than we can.
 231   if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
 232     FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
 233                           "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
 234                           "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
 235                 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
 236     vm_exit_during_initialization("Fatal Error", buf);
 237   }
 238 #endif
 239 
 240   ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
 241   if (!_heap_region_special) {
 242     os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
 243                               "Cannot commit heap memory");
 244   }
 245 
 246   BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
 247 
 248   // Now we know the number of regions and heap sizes, initialize the heuristics.
 249   initialize_heuristics();
 250 
 251   // If ShenandoahCardBarrier is enabled but it's not generational mode
 252   // it means we're under passive mode and we have to initialize old gen
 253   // for the purpose of having card table.
 254   if (ShenandoahCardBarrier && !(mode()->is_generational())) {
 255     _old_generation = new ShenandoahOldGeneration(max_workers());
 256   }
 257 
 258   assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table");
 259 
 260   //
 261   // Worker threads must be initialized after the barrier is configured
 262   //
 263   _workers = new ShenandoahWorkerThreads("ShenWorker", _max_workers);
 264   if (_workers == nullptr) {
 265     vm_exit_during_initialization("Failed necessary allocation.");
 266   } else {
 267     _workers->initialize_workers();
 268   }
 269 
 270   if (ParallelGCThreads > 1) {
 271     _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
 272     _safepoint_workers->initialize_workers();
 273   }
 274 
 275   //
 276   // Reserve and commit memory for bitmap(s)
 277   //
 278 
 279   size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
 280   _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
 281 
 282   size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
 283 
 284   guarantee(bitmap_bytes_per_region != 0,
 285             "Bitmap bytes per region should not be zero");
 286   guarantee(is_power_of_2(bitmap_bytes_per_region),
 287             "Bitmap bytes per region should be power of two: %zu", bitmap_bytes_per_region);
 288 
 289   if (bitmap_page_size > bitmap_bytes_per_region) {
 290     _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
 291     _bitmap_bytes_per_slice = bitmap_page_size;
 292   } else {
 293     _bitmap_regions_per_slice = 1;
 294     _bitmap_bytes_per_slice = bitmap_bytes_per_region;
 295   }
 296 
 297   guarantee(_bitmap_regions_per_slice >= 1,
 298             "Should have at least one region per slice: %zu",
 299             _bitmap_regions_per_slice);
 300 
 301   guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
 302             "Bitmap slices should be page-granular: bps = %zu, page size = %zu",
 303             _bitmap_bytes_per_slice, bitmap_page_size);
 304 
 305   ReservedSpace bitmap = reserve(_bitmap_size, bitmap_page_size);
 306   os::trace_page_sizes_for_requested_size("Mark Bitmap",
 307                                           bitmap_size_orig, bitmap_page_size,
 308                                           bitmap.base(),
 309                                           bitmap.size(), bitmap.page_size());
 310   MemTracker::record_virtual_memory_tag(bitmap, mtGC);
 311   _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
 312   _bitmap_region_special = bitmap.special();
 313 
 314   size_t bitmap_init_commit = _bitmap_bytes_per_slice *
 315     align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
 316   bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
 317   if (!_bitmap_region_special) {
 318     os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
 319                               "Cannot commit bitmap memory");
 320   }
 321 
 322   _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
 323 
 324   if (ShenandoahVerify) {
 325     ReservedSpace verify_bitmap = reserve(_bitmap_size, bitmap_page_size);
 326     os::trace_page_sizes_for_requested_size("Verify Bitmap",
 327                                             bitmap_size_orig, bitmap_page_size,
 328                                             verify_bitmap.base(),
 329                                             verify_bitmap.size(), verify_bitmap.page_size());
 330     if (!verify_bitmap.special()) {
 331       os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
 332                                 "Cannot commit verification bitmap memory");
 333     }
 334     MemTracker::record_virtual_memory_tag(verify_bitmap, mtGC);
 335     MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
 336     _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
 337     _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
 338   }
 339 
 340   // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
 341   size_t aux_bitmap_page_size = bitmap_page_size;
 342 
 343   ReservedSpace aux_bitmap = reserve(_bitmap_size, aux_bitmap_page_size);
 344   os::trace_page_sizes_for_requested_size("Aux Bitmap",
 345                                           bitmap_size_orig, aux_bitmap_page_size,
 346                                           aux_bitmap.base(),
 347                                           aux_bitmap.size(), aux_bitmap.page_size());
 348   MemTracker::record_virtual_memory_tag(aux_bitmap, mtGC);
 349   _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
 350   _aux_bitmap_region_special = aux_bitmap.special();
 351   _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
 352 
 353   //
 354   // Create regions and region sets
 355   //
 356   size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
 357   size_t region_storage_size_orig = region_align * _num_regions;
 358   size_t region_storage_size = align_up(region_storage_size_orig,
 359                                         MAX2(region_page_size, os::vm_allocation_granularity()));
 360 
 361   ReservedSpace region_storage = reserve(region_storage_size, region_page_size);
 362   os::trace_page_sizes_for_requested_size("Region Storage",
 363                                           region_storage_size_orig, region_page_size,
 364                                           region_storage.base(),
 365                                           region_storage.size(), region_storage.page_size());
 366   MemTracker::record_virtual_memory_tag(region_storage, mtGC);
 367   if (!region_storage.special()) {
 368     os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
 369                               "Cannot commit region memory");
 370   }
 371 
 372   // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
 373   // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
 374   // If not successful, bite a bullet and allocate at whatever address.
 375   {
 376     const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
 377     const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
 378     const size_t cset_page_size = os::vm_page_size();
 379 
 380     uintptr_t min = round_up_power_of_2(cset_align);
 381     uintptr_t max = (1u << 30u);
 382     ReservedSpace cset_rs;
 383 
 384     for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
 385       char* req_addr = (char*)addr;
 386       assert(is_aligned(req_addr, cset_align), "Should be aligned");
 387       cset_rs = MemoryReserver::reserve(req_addr, cset_size, cset_align, cset_page_size, mtGC);
 388       if (cset_rs.is_reserved()) {
 389         assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
 390         _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
 391         break;
 392       }
 393     }
 394 
 395     if (_collection_set == nullptr) {
 396       cset_rs = MemoryReserver::reserve(cset_size, cset_align, os::vm_page_size(), mtGC);
 397       if (!cset_rs.is_reserved()) {
 398         vm_exit_during_initialization("Cannot reserve memory for collection set");
 399       }
 400 
 401       _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
 402     }
 403     os::trace_page_sizes_for_requested_size("Collection Set",
 404                                             cset_size, cset_page_size,
 405                                             cset_rs.base(),
 406                                             cset_rs.size(), cset_rs.page_size());
 407   }
 408 
 409   _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
 410   _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
 411 
 412   {
 413     ShenandoahHeapLocker locker(lock());
 414     for (size_t i = 0; i < _num_regions; i++) {
 415       HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
 416       bool is_committed = i < num_committed_regions;
 417       void* loc = region_storage.base() + i * region_align;
 418 
 419       ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
 420       assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
 421 
 422       _marking_context->initialize_top_at_mark_start(r);
 423       _regions[i] = r;
 424       assert(!collection_set()->is_in(i), "New region should not be in collection set");
 425 
 426       _affiliations[i] = ShenandoahAffiliation::FREE;
 427     }
 428 
 429     if (mode()->is_generational()) {
 430       size_t young_reserve = (soft_max_capacity() * ShenandoahEvacReserve) / 100;
 431       young_generation()->set_evacuation_reserve(young_reserve);
 432       old_generation()->set_evacuation_reserve((size_t) 0);
 433       old_generation()->set_promoted_reserve((size_t) 0);
 434     }
 435 
 436     _free_set = new ShenandoahFreeSet(this, _num_regions);
 437     initialize_generations();
 438 
 439     // We are initializing free set.  We ignore cset region tallies.
 440     size_t young_trashed_regions, old_trashed_regions, first_old, last_old, num_old;
 441     _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old, last_old, num_old);
 442     if (mode()->is_generational()) {
 443       ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
 444       // We cannot call
 445       //  gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions)
 446       // until after the heap is fully initialized.  So we make up a safe value here.
 447       size_t allocation_runway = InitialHeapSize / 2;
 448       gen_heap->compute_old_generation_balance(allocation_runway, old_trashed_regions, young_trashed_regions);
 449     }
 450     _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, num_old);
 451   }
 452 
 453   if (AlwaysPreTouch) {
 454     // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
 455     // before initialize() below zeroes it with initializing thread. For any given region,
 456     // we touch the region and the corresponding bitmaps from the same thread.
 457     ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
 458 
 459     _pretouch_heap_page_size = heap_page_size;
 460     _pretouch_bitmap_page_size = bitmap_page_size;
 461 
 462     // OS memory managers may want to coalesce back-to-back pages. Make their jobs
 463     // simpler by pre-touching continuous spaces (heap and bitmap) separately.
 464 
 465     ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
 466     _workers->run_task(&bcl);
 467 
 468     ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
 469     _workers->run_task(&hcl);
 470   }
 471 
 472   //
 473   // Initialize the rest of GC subsystems
 474   //
 475 
 476   _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
 477   for (uint worker = 0; worker < _max_workers; worker++) {
 478     _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
 479     Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
 480   }
 481 
 482   // There should probably be Shenandoah-specific options for these,
 483   // just as there are G1-specific options.
 484   {
 485     ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
 486     satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
 487     satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
 488   }
 489 
 490   _monitoring_support = new ShenandoahMonitoringSupport(this);
 491   _phase_timings = new ShenandoahPhaseTimings(max_workers());
 492   ShenandoahCodeRoots::initialize();
 493 
 494   // Initialization of controller makes use of variables established by initialize_heuristics.
 495   initialize_controller();
 496 
 497   // Certain initialization of heuristics must be deferred until after controller is initialized.
 498   post_initialize_heuristics();
 499   start_idle_span();
 500   if (ShenandoahUncommit) {
 501     _uncommit_thread = new ShenandoahUncommitThread(this);
 502   }
 503   print_init_logger();
 504   FullGCForwarding::initialize(_heap_region);
 505   return JNI_OK;
 506 }
 507 
 508 void ShenandoahHeap::initialize_controller() {
 509   _control_thread = new ShenandoahControlThread();
 510 }
 511 
 512 void ShenandoahHeap::print_init_logger() const {
 513   ShenandoahInitLogger::print();
 514 }
 515 
 516 void ShenandoahHeap::initialize_mode() {
 517   if (ShenandoahGCMode != nullptr) {
 518     if (strcmp(ShenandoahGCMode, "satb") == 0) {
 519       _gc_mode = new ShenandoahSATBMode();
 520     } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
 521       _gc_mode = new ShenandoahPassiveMode();
 522     } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
 523       _gc_mode = new ShenandoahGenerationalMode();
 524     } else {
 525       vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
 526     }
 527   } else {
 528     vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
 529   }
 530   _gc_mode->initialize_flags();
 531   if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
 532     vm_exit_during_initialization(
 533             err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
 534                     _gc_mode->name()));
 535   }
 536   if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
 537     vm_exit_during_initialization(
 538             err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
 539                     _gc_mode->name()));
 540   }
 541 }
 542 
 543 void ShenandoahHeap::initialize_heuristics() {
 544   _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers());
 545   _global_generation->initialize_heuristics(mode());
 546 }
 547 
 548 #ifdef _MSC_VER
 549 #pragma warning( push )
 550 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 551 #endif
 552 
 553 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
 554   CollectedHeap(),
 555   _active_generation(nullptr),
 556   _initial_size(0),
 557   _committed(0),
 558   _alloc_rate_decay(&_alloc_rate),
 559   _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
 560   _workers(nullptr),
 561   _safepoint_workers(nullptr),
 562   _heap_region_special(false),
 563   _num_regions(0),
 564   _regions(nullptr),
 565   _affiliations(nullptr),
 566   _gc_state_changed(false),
 567   _gc_no_progress_count(0),
 568   _cancel_requested_time(0),
 569   _update_refs_iterator(this),
 570   _global_generation(nullptr),
 571   _control_thread(nullptr),
 572   _uncommit_thread(nullptr),
 573   _young_generation(nullptr),
 574   _old_generation(nullptr),
 575   _shenandoah_policy(policy),
 576   _gc_mode(nullptr),
 577   _free_set(nullptr),
 578   _verifier(nullptr),
 579   _phase_timings(nullptr),
 580   _monitoring_support(nullptr),
 581   _memory_pool(nullptr),
 582   _stw_memory_manager("Shenandoah Pauses"),
 583   _cycle_memory_manager("Shenandoah Cycles"),
 584   _gc_timer(new ConcurrentGCTimer()),
 585   _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
 586   _marking_context(nullptr),
 587   _bitmap_size(0),
 588   _bitmap_regions_per_slice(0),
 589   _bitmap_bytes_per_slice(0),
 590   _bitmap_region_special(false),
 591   _aux_bitmap_region_special(false),
 592   _liveness_cache(nullptr),
 593   _collection_set(nullptr),
 594   _evac_tracker(new ShenandoahEvacuationTracker())
 595 {
 596   // Initialize GC mode early, many subsequent initialization procedures depend on it
 597   initialize_mode();
 598   _cancelled_gc.set(GCCause::_no_gc);
 599 }
 600 
 601 #ifdef _MSC_VER
 602 #pragma warning( pop )
 603 #endif
 604 
 605 void ShenandoahHeap::print_heap_on(outputStream* st) const {
 606   const bool is_generational = mode()->is_generational();
 607   const char* front_spacing = "";
 608   if (is_generational) {
 609     st->print_cr("Generational Shenandoah Heap");
 610     st->print_cr(" Young:");
 611     st->print_cr("  " PROPERFMT " max, " PROPERFMT " used", PROPERFMTARGS(young_generation()->max_capacity()), PROPERFMTARGS(young_generation()->used()));
 612     st->print_cr(" Old:");
 613     st->print_cr("  " PROPERFMT " max, " PROPERFMT " used", PROPERFMTARGS(old_generation()->max_capacity()), PROPERFMTARGS(old_generation()->used()));
 614     st->print_cr(" Entire heap:");
 615     st->print_cr("  " PROPERFMT " soft max, " PROPERFMT " committed",
 616                 PROPERFMTARGS(soft_max_capacity()), PROPERFMTARGS(committed()));
 617     front_spacing = " ";
 618   } else {
 619     st->print_cr("Shenandoah Heap");
 620     st->print_cr("  " PROPERFMT " max, " PROPERFMT " soft max, " PROPERFMT " committed, " PROPERFMT " used",
 621       PROPERFMTARGS(max_capacity()),
 622       PROPERFMTARGS(soft_max_capacity()),
 623       PROPERFMTARGS(committed()),
 624       PROPERFMTARGS(used())
 625     );
 626   }
 627   st->print_cr("%s %zu x " PROPERFMT " regions",
 628           front_spacing,
 629           num_regions(),
 630           PROPERFMTARGS(ShenandoahHeapRegion::region_size_bytes()));
 631 
 632   st->print("Status: ");
 633   if (has_forwarded_objects())                 st->print("has forwarded objects, ");
 634   if (!is_generational) {
 635     if (is_concurrent_mark_in_progress())      st->print("marking,");
 636   } else {
 637     if (is_concurrent_old_mark_in_progress())    st->print("old marking, ");
 638     if (is_concurrent_young_mark_in_progress())  st->print("young marking, ");
 639   }
 640   if (is_evacuation_in_progress())             st->print("evacuating, ");
 641   if (is_update_refs_in_progress())            st->print("updating refs, ");
 642   if (is_degenerated_gc_in_progress())         st->print("degenerated gc, ");
 643   if (is_full_gc_in_progress())                st->print("full gc, ");
 644   if (is_full_gc_move_in_progress())           st->print("full gc move, ");
 645   if (is_concurrent_weak_root_in_progress())   st->print("concurrent weak roots, ");
 646   if (is_concurrent_strong_root_in_progress() &&
 647       !is_concurrent_weak_root_in_progress())  st->print("concurrent strong roots, ");
 648 
 649   if (cancelled_gc()) {
 650     st->print("cancelled");
 651   } else {
 652     st->print("not cancelled");
 653   }
 654   st->cr();
 655 
 656   st->print_cr("Reserved region:");
 657   st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
 658                p2i(reserved_region().start()),
 659                p2i(reserved_region().end()));
 660 
 661   ShenandoahCollectionSet* cset = collection_set();
 662   st->print_cr("Collection set:");
 663   if (cset != nullptr) {
 664     st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
 665     st->print_cr(" - map (biased):  " PTR_FORMAT, p2i(cset->biased_map_address()));
 666   } else {
 667     st->print_cr(" (null)");
 668   }
 669 
 670   st->cr();
 671 
 672   if (Verbose) {
 673     st->cr();
 674     print_heap_regions_on(st);
 675   }
 676 }
 677 
 678 void ShenandoahHeap::print_gc_on(outputStream* st) const {
 679   print_heap_regions_on(st);
 680 }
 681 
 682 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
 683 public:
 684   void do_thread(Thread* thread) {
 685     assert(thread != nullptr, "Sanity");
 686     ShenandoahThreadLocalData::initialize_gclab(thread);
 687   }
 688 };
 689 
 690 void ShenandoahHeap::initialize_generations() {
 691   _global_generation->post_initialize(this);
 692 }
 693 
 694 // We do not call this explicitly  It is called by Hotspot infrastructure.
 695 void ShenandoahHeap::post_initialize() {
 696   CollectedHeap::post_initialize();
 697 
 698   check_soft_max_changed();
 699 
 700   // Schedule periodic task to report on gc thread CPU utilization
 701   _mmu_tracker.initialize();
 702 
 703   // Periodically decay allocation rate to compensate for not being updated when allocation rate
 704   // is low. Heuristics are evaluated unconditionally from a dedicated thread so it will continue
 705   // to see the last (possibly stale) allocation rate if the allocation rate is low.
 706   _alloc_rate_decay.enroll();
 707 
 708   MutexLocker ml(Threads_lock);
 709 
 710   ShenandoahInitWorkerGCLABClosure init_gclabs;
 711   _workers->threads_do(&init_gclabs);
 712 
 713   // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
 714   // Now, we will let WorkerThreads to initialize gclab when new worker is created.
 715   _workers->set_initialize_gclab();
 716 
 717   // Note that the safepoint workers may require gclabs if the threads are used to create a heap dump
 718   // during a concurrent evacuation phase.
 719   if (_safepoint_workers != nullptr) {
 720     _safepoint_workers->threads_do(&init_gclabs);
 721     _safepoint_workers->set_initialize_gclab();
 722   }
 723 
 724   JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
 725 }
 726 
 727 void ShenandoahHeap::post_initialize_heuristics() {
 728   _global_generation->post_initialize_heuristics();
 729 }
 730 
 731 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
 732   return _global_generation->heuristics();
 733 }
 734 
 735 size_t ShenandoahHeap::used() const {
 736   return global_generation()->used();
 737 }
 738 
 739 size_t ShenandoahHeap::committed() const {
 740   return _committed.load_relaxed();
 741 }
 742 
 743 void ShenandoahHeap::increase_committed(size_t bytes) {
 744   shenandoah_assert_heaplocked_or_safepoint();
 745   _committed.fetch_then_add(bytes, memory_order_relaxed);
 746 }
 747 
 748 void ShenandoahHeap::decrease_committed(size_t bytes) {
 749   shenandoah_assert_heaplocked_or_safepoint();
 750   _committed.fetch_then_sub(bytes, memory_order_relaxed);
 751 }
 752 
 753 size_t ShenandoahHeap::capacity() const {
 754   return committed();
 755 }
 756 
 757 size_t ShenandoahHeap::max_capacity() const {
 758   return _num_regions * ShenandoahHeapRegion::region_size_bytes();
 759 }
 760 
 761 size_t ShenandoahHeap::soft_max_capacity() const {
 762   size_t v = _soft_max_size.load_relaxed();
 763   assert(min_capacity() <= v && v <= max_capacity(),
 764          "Should be in bounds: %zu <= %zu <= %zu",
 765          min_capacity(), v, max_capacity());
 766   return v;
 767 }
 768 
 769 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
 770   assert(min_capacity() <= v && v <= max_capacity(),
 771          "Should be in bounds: %zu <= %zu <= %zu",
 772          min_capacity(), v, max_capacity());
 773   _soft_max_size.store_relaxed(v);
 774   heuristics()->compute_headroom_adjustment();
 775 }
 776 
 777 size_t ShenandoahHeap::min_capacity() const {
 778   return _minimum_size;
 779 }
 780 
 781 size_t ShenandoahHeap::initial_capacity() const {
 782   return _initial_size;
 783 }
 784 
 785 bool ShenandoahHeap::is_in(const void* p) const {
 786   if (!is_in_reserved(p)) {
 787     return false;
 788   }
 789 
 790   if (is_full_gc_move_in_progress()) {
 791     // Full GC move is running, we do not have a consistent region
 792     // information yet. But we know the pointer is in heap.
 793     return true;
 794   }
 795 
 796   // Now check if we point to a live section in active region.
 797   const ShenandoahHeapRegion* r = heap_region_containing(p);
 798   if (p >= r->top()) {
 799     return false;
 800   }
 801 
 802   if (r->is_active()) {
 803     return true;
 804   }
 805 
 806   // The region is trash, but won't be recycled until after concurrent weak
 807   // roots. We also don't allow mutators to allocate from trash regions
 808   // during weak roots. Concurrent class unloading may access unmarked oops
 809   // in trash regions.
 810   return r->is_trash() && is_concurrent_weak_root_in_progress();
 811 }
 812 
 813 void ShenandoahHeap::notify_soft_max_changed() {
 814   if (_uncommit_thread != nullptr) {
 815     _uncommit_thread->notify_soft_max_changed();
 816   }
 817 }
 818 
 819 void ShenandoahHeap::notify_explicit_gc_requested() {
 820   if (_uncommit_thread != nullptr) {
 821     _uncommit_thread->notify_explicit_gc_requested();
 822   }
 823 }
 824 
 825 bool ShenandoahHeap::check_soft_max_changed() {
 826   size_t new_soft_max = AtomicAccess::load(&SoftMaxHeapSize);
 827   size_t old_soft_max = soft_max_capacity();
 828   if (new_soft_max != old_soft_max) {
 829     new_soft_max = clamp(new_soft_max, min_capacity(), max_capacity());
 830     if (new_soft_max != old_soft_max) {
 831       log_info(gc)("Soft Max Heap Size: %zu%s -> %zu%s",
 832                    byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
 833                    byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
 834       );
 835       set_soft_max_capacity(new_soft_max);
 836       return true;
 837     }
 838   }
 839   return false;
 840 }
 841 
 842 void ShenandoahHeap::notify_heap_changed() {
 843   // Update monitoring counters when we took a new region. This amortizes the
 844   // update costs on slow path.
 845   monitoring_support()->notify_heap_changed();
 846   _heap_changed.try_set();
 847 }
 848 
 849 void ShenandoahHeap::start_idle_span() {
 850   heuristics()->start_idle_span();
 851 }
 852 
 853 void ShenandoahHeap::set_forced_counters_update(bool value) {
 854   monitoring_support()->set_forced_counters_update(value);
 855 }
 856 
 857 void ShenandoahHeap::handle_force_counters_update() {
 858   monitoring_support()->handle_force_counters_update();
 859 }
 860 
 861 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
 862   // New object should fit the GCLAB size
 863   size_t min_size = MAX2(size, PLAB::min_size());
 864 
 865   // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
 866   size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
 867 
 868   new_size = MIN2(new_size, PLAB::max_size());
 869   new_size = MAX2(new_size, PLAB::min_size());
 870 
 871   // Record new heuristic value even if we take any shortcut. This captures
 872   // the case when moderately-sized objects always take a shortcut. At some point,
 873   // heuristics should catch up with them.
 874   log_debug(gc, free)("Set new GCLAB size: %zu", new_size);
 875   ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
 876 
 877   if (new_size < size) {
 878     // New size still does not fit the object. Fall back to shared allocation.
 879     // This avoids retiring perfectly good GCLABs, when we encounter a large object.
 880     log_debug(gc, free)("New gclab size (%zu) is too small for %zu", new_size, size);
 881     return nullptr;
 882   }
 883 
 884   // Retire current GCLAB, and allocate a new one.
 885   PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
 886   gclab->retire();
 887 
 888   size_t actual_size = 0;
 889   HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
 890   if (gclab_buf == nullptr) {
 891     return nullptr;
 892   }
 893 
 894   assert (size <= actual_size, "allocation should fit");
 895 
 896   // ...and clear or zap just allocated TLAB, if needed.
 897   if (ZeroTLAB) {
 898     Copy::zero_to_words(gclab_buf, actual_size);
 899   } else if (ZapTLAB) {
 900     // Skip mangling the space corresponding to the object header to
 901     // ensure that the returned space is not considered parsable by
 902     // any concurrent GC thread.
 903     size_t hdr_size = oopDesc::header_size();
 904     Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
 905   }
 906   gclab->set_buf(gclab_buf, actual_size);
 907   return gclab->allocate(size);
 908 }
 909 
 910 // Called from stubs in JIT code or interpreter
 911 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
 912                                             size_t requested_size,
 913                                             size_t* actual_size) {
 914   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
 915   HeapWord* res = allocate_memory(req);
 916   if (res != nullptr) {
 917     *actual_size = req.actual_size();
 918   } else {
 919     *actual_size = 0;
 920   }
 921   return res;
 922 }
 923 
 924 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
 925                                              size_t word_size,
 926                                              size_t* actual_size) {
 927   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
 928   HeapWord* res = allocate_memory(req);
 929   if (res != nullptr) {
 930     *actual_size = req.actual_size();
 931   } else {
 932     *actual_size = 0;
 933   }
 934   return res;
 935 }
 936 
 937 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
 938   bool in_new_region = false;
 939   HeapWord* result = nullptr;
 940 
 941   if (req.is_mutator_alloc()) {
 942 
 943     if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
 944       result = allocate_memory_under_lock(req, in_new_region);
 945     }
 946 
 947     // Check that gc overhead is not exceeded.
 948     //
 949     // Shenandoah will grind along for quite a while allocating one
 950     // object at a time using shared (non-tlab) allocations. This check
 951     // is testing that the GC overhead limit has not been exceeded.
 952     // This will notify the collector to start a cycle, but will raise
 953     // an OOME to the mutator if the last Full GCs have not made progress.
 954     // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress().
 955     if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
 956       control_thread()->handle_alloc_failure(req, false);
 957       req.set_actual_size(0);
 958       return nullptr;
 959     }
 960 
 961     if (result == nullptr) {
 962       // Block until control thread reacted, then retry allocation.
 963       //
 964       // It might happen that one of the threads requesting allocation would unblock
 965       // way later after GC happened, only to fail the second allocation, because
 966       // other threads have already depleted the free storage. In this case, a better
 967       // strategy is to try again, until at least one full GC has completed.
 968       //
 969       // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
 970       //   a) We experienced a GC that had good progress, or
 971       //   b) We experienced at least one Full GC (whether or not it had good progress)
 972 
 973       const size_t original_count = shenandoah_policy()->full_gc_count();
 974       while (result == nullptr && should_retry_allocation(original_count)) {
 975         control_thread()->handle_alloc_failure(req, true);
 976         result = allocate_memory_under_lock(req, in_new_region);
 977       }
 978       if (result != nullptr) {
 979         // If our allocation request has been satisfied after it initially failed, we count this as good gc progress
 980         notify_gc_progress();
 981       }
 982       if (log_develop_is_enabled(Debug, gc, alloc)) {
 983         ResourceMark rm;
 984         log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: %zu"
 985                              ", Original: %zu, Latest: %zu",
 986                              Thread::current()->name(), p2i(result), req.type_string(), req.size(),
 987                              original_count, get_gc_no_progress_count());
 988       }
 989     }
 990   } else {
 991     assert(req.is_gc_alloc(), "Can only accept GC allocs here");
 992     result = allocate_memory_under_lock(req, in_new_region);
 993     // Do not call handle_alloc_failure() here, because we cannot block.
 994     // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
 995   }
 996 
 997   if (in_new_region) {
 998     notify_heap_changed();
 999   }
1000 
1001   if (result == nullptr) {
1002     req.set_actual_size(0);
1003   }
1004 
1005   if (result != nullptr) {
1006     size_t requested = req.size();
1007     size_t actual = req.actual_size();
1008 
1009     assert (req.is_lab_alloc() || (requested == actual),
1010             "Only LAB allocations are elastic: %s, requested = %zu, actual = %zu",
1011             req.type_string(), requested, actual);
1012   }
1013 
1014   return result;
1015 }
1016 
1017 inline bool ShenandoahHeap::should_retry_allocation(size_t original_full_gc_count) const {
1018   return shenandoah_policy()->full_gc_count() == original_full_gc_count
1019       && !shenandoah_policy()->is_at_shutdown();
1020 }
1021 
1022 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
1023   // If we are dealing with mutator allocation, then we may need to block for safepoint.
1024   // We cannot block for safepoint for GC allocations, because there is a high chance
1025   // we are already running at safepoint or from stack watermark machinery, and we cannot
1026   // block again.
1027   ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
1028 
1029   // Make sure the old generation has room for either evacuations or promotions before trying to allocate.
1030   if (req.is_old() && !old_generation()->can_allocate(req)) {
1031     return nullptr;
1032   }
1033 
1034   // If TLAB request size is greater than available, allocate() will attempt to downsize request to fit within available
1035   // memory.
1036   HeapWord* result = _free_set->allocate(req, in_new_region);
1037 
1038   if (result != nullptr) {
1039     if (req.is_mutator_alloc()) {
1040       _alloc_rate.allocated((req.actual_size() + req.waste()) * HeapWordSize);
1041     }
1042 
1043     if (req.is_old()) {
1044       if (req.is_lab_alloc()) {
1045         old_generation()->configure_plab_for_current_thread(req);
1046       } else if (req.is_promotion()) {
1047         const size_t actual_size = req.actual_size() * HeapWordSize;
1048         log_debug(gc, plab)("Expend shared promotion of %zu bytes", actual_size);
1049         old_generation()->expend_promoted(actual_size);
1050       }
1051     }
1052   }
1053 
1054   return result;
1055 }
1056 
1057 HeapWord* ShenandoahHeap::mem_allocate(size_t size) {
1058   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1059   return allocate_memory(req);
1060 }
1061 
1062 oop ShenandoahHeap::array_allocate(Klass* klass, size_t size, int length, bool do_zero, TRAPS) {
1063   ShenandoahObjArrayAllocator allocator(klass, size, length, do_zero, THREAD);
1064   return allocator.allocate();
1065 }
1066 
1067 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1068                                                              size_t size,
1069                                                              Metaspace::MetadataType mdtype) {
1070   MetaWord* result;
1071 
1072   // Inform metaspace OOM to GC heuristics if class unloading is possible.
1073   ShenandoahHeuristics* h = global_generation()->heuristics();
1074   if (h->can_unload_classes()) {
1075     h->record_metaspace_oom();
1076   }
1077 
1078   // Expand and retry allocation
1079   result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1080   if (result != nullptr) {
1081     return result;
1082   }
1083 
1084   // Start full GC
1085   collect(GCCause::_metadata_GC_clear_soft_refs);
1086 
1087   // Retry allocation
1088   result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1089   if (result != nullptr) {
1090     return result;
1091   }
1092 
1093   // Expand and retry allocation
1094   result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1095   if (result != nullptr) {
1096     return result;
1097   }
1098 
1099   // Out of memory
1100   return nullptr;
1101 }
1102 
1103 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1104 private:
1105   ShenandoahHeap* const _heap;
1106   Thread* const _thread;
1107 public:
1108   ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1109     _heap(heap), _thread(Thread::current()) {}
1110 
1111   void do_object(oop p) {
1112     shenandoah_assert_marked(nullptr, p);
1113     if (!p->is_forwarded()) {
1114       _heap->evacuate_object(p, _thread);
1115     }
1116   }
1117 };
1118 
1119 class ShenandoahEvacuationTask : public WorkerTask {
1120 private:
1121   ShenandoahHeap* const _sh;
1122   ShenandoahCollectionSet* const _cs;
1123   bool _concurrent;
1124 public:
1125   ShenandoahEvacuationTask(ShenandoahHeap* sh,
1126                            ShenandoahCollectionSet* cs,
1127                            bool concurrent) :
1128     WorkerTask("Shenandoah Evacuation"),
1129     _sh(sh),
1130     _cs(cs),
1131     _concurrent(concurrent)
1132   {}
1133 
1134   void work(uint worker_id) {
1135     if (_concurrent) {
1136       ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_evac, ShenandoahPhaseTimings::Work, worker_id, true);
1137       ShenandoahConcurrentWorkerSession worker_session(worker_id);
1138       SuspendibleThreadSetJoiner stsj;
1139       do_work();
1140     } else {
1141       ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::degen_gc_evac, ShenandoahPhaseTimings::Work, worker_id, true);
1142       ShenandoahParallelWorkerSession worker_session(worker_id);
1143       do_work();
1144     }
1145   }
1146 
1147 private:
1148   void do_work() {
1149     ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1150     ShenandoahHeapRegion* r;
1151     while ((r =_cs->claim_next()) != nullptr) {
1152       assert(r->has_live(), "Region %zu should have been reclaimed early", r->index());
1153       _sh->marked_object_iterate(r, &cl);
1154 
1155       if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1156         break;
1157       }
1158     }
1159   }
1160 };
1161 
1162 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1163 private:
1164   bool const _resize;
1165 public:
1166   explicit ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1167   void do_thread(Thread* thread) override {
1168     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1169     assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1170     gclab->retire();
1171     if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1172       ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1173     }
1174 
1175     if (ShenandoahHeap::heap()->mode()->is_generational()) {
1176       ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
1177       assert(shenandoah_plab != nullptr, "PLAB should be initialized for %s", thread->name());
1178 
1179       // There are two reasons to retire all plabs between old-gen evacuation passes.
1180       //  1. We need to make the plab memory parsable by remembered-set scanning.
1181       //  2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1182       shenandoah_plab->retire();
1183 
1184       // Re-enable promotions for the next evacuation phase.
1185       shenandoah_plab->enable_promotions();
1186 
1187       // Reset the fill size for next evacuation phase.
1188       if (_resize && shenandoah_plab->desired_size() > 0) {
1189         shenandoah_plab->set_desired_size(0);
1190       }
1191     }
1192   }
1193 };
1194 
1195 class ShenandoahGCStatePropagatorHandshakeClosure : public HandshakeClosure {
1196 public:
1197   explicit ShenandoahGCStatePropagatorHandshakeClosure(char gc_state) :
1198     HandshakeClosure("Shenandoah GC State Change"),
1199     _gc_state(gc_state) {}
1200 
1201   void do_thread(Thread* thread) override {
1202     ShenandoahThreadLocalData::set_gc_state(thread, _gc_state);
1203   }
1204 private:
1205   char _gc_state;
1206 };
1207 
1208 class ShenandoahPrepareForUpdateRefsHandshakeClosure : public HandshakeClosure {
1209 public:
1210   explicit ShenandoahPrepareForUpdateRefsHandshakeClosure(char gc_state) :
1211     HandshakeClosure("Shenandoah Prepare for Update Refs"),
1212     _retire(ResizeTLAB), _propagator(gc_state) {}
1213 
1214   void do_thread(Thread* thread) override {
1215     _propagator.do_thread(thread);
1216     if (ShenandoahThreadLocalData::gclab(thread) != nullptr) {
1217       _retire.do_thread(thread);
1218     }
1219   }
1220 private:
1221   ShenandoahRetireGCLABClosure _retire;
1222   ShenandoahGCStatePropagatorHandshakeClosure _propagator;
1223 };
1224 
1225 void ShenandoahHeap::evacuate_collection_set(ShenandoahGeneration* generation, bool concurrent) {
1226   assert(generation->is_global(), "Only global generation expected here");
1227   ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1228   workers()->run_task(&task);
1229 }
1230 
1231 void ShenandoahHeap::concurrent_prepare_for_update_refs() {
1232   {
1233     // Java threads take this lock while they are being attached and added to the list of threads.
1234     // If another thread holds this lock before we update the gc state, it will receive a stale
1235     // gc state, but they will have been added to the list of java threads and so will be corrected
1236     // by the following handshake.
1237     MutexLocker lock(Threads_lock);
1238 
1239     // A cancellation at this point means the degenerated cycle must resume from update-refs.
1240     set_gc_state_concurrent(EVACUATION, false);
1241     set_gc_state_concurrent(WEAK_ROOTS, false);
1242     set_gc_state_concurrent(UPDATE_REFS, true);
1243   }
1244 
1245   // This will propagate the gc state and retire gclabs and plabs for threads that require it.
1246   ShenandoahPrepareForUpdateRefsHandshakeClosure prepare_for_update_refs(_gc_state.raw_value());
1247 
1248   // The handshake won't touch worker threads (or control thread, or VM thread), so do those separately.
1249   Threads::non_java_threads_do(&prepare_for_update_refs);
1250 
1251   // Now retire gclabs and plabs and propagate gc_state for mutator threads
1252   Handshake::execute(&prepare_for_update_refs);
1253 
1254   _update_refs_iterator.reset();
1255 }
1256 
1257 class ShenandoahCompositeHandshakeClosure : public HandshakeClosure {
1258   HandshakeClosure* _handshake_1;
1259   HandshakeClosure* _handshake_2;
1260   public:
1261     ShenandoahCompositeHandshakeClosure(HandshakeClosure* handshake_1, HandshakeClosure* handshake_2) :
1262       HandshakeClosure(handshake_2->name()),
1263       _handshake_1(handshake_1), _handshake_2(handshake_2) {}
1264 
1265   void do_thread(Thread* thread) override {
1266       _handshake_1->do_thread(thread);
1267       _handshake_2->do_thread(thread);
1268     }
1269 };
1270 
1271 void ShenandoahHeap::concurrent_final_roots(HandshakeClosure* handshake_closure) {
1272   {
1273     assert(!is_evacuation_in_progress(), "Should not evacuate for abbreviated or old cycles");
1274     MutexLocker lock(Threads_lock);
1275     set_gc_state_concurrent(WEAK_ROOTS, false);
1276   }
1277 
1278   ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value());
1279   Threads::non_java_threads_do(&propagator);
1280   if (handshake_closure == nullptr) {
1281     Handshake::execute(&propagator);
1282   } else {
1283     ShenandoahCompositeHandshakeClosure composite(&propagator, handshake_closure);
1284     Handshake::execute(&composite);
1285   }
1286 }
1287 
1288 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1289   assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1290 
1291   ShenandoahHeapRegion* r = heap_region_containing(p);
1292   assert(!r->is_humongous(), "never evacuate humongous objects");
1293 
1294   ShenandoahAffiliation target_gen = r->affiliation();
1295   return try_evacuate_object(p, thread, r, target_gen);
1296 }
1297 
1298 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1299                                                ShenandoahAffiliation target_gen) {
1300   assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1301   assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1302   bool alloc_from_lab = true;
1303   HeapWord* copy = nullptr;
1304   size_t size = ShenandoahForwarding::size(p);






1305 
1306 #ifdef ASSERT
1307   if (ShenandoahOOMDuringEvacALot &&
1308       (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1309     copy = nullptr;
1310   } else {
1311 #endif
1312     if (UseTLAB) {
1313       copy = allocate_from_gclab(thread, size);
1314     }
1315     if (copy == nullptr) {
1316       // If we failed to allocate in LAB, we'll try a shared allocation.
1317       ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1318       copy = allocate_memory(req);
1319       alloc_from_lab = false;
1320     }
1321 #ifdef ASSERT
1322   }
1323 #endif
1324 
1325   if (copy == nullptr) {
1326     control_thread()->handle_alloc_failure_evac(size);
1327 
1328     // Install the self-forwarded bit on p so other evacuators/LRBs see
1329     // the object as "already handled, do not try to evacuate". The CAS
1330     // may fail if another thread concurrently installed a real forwardee
1331     // (they succeeded where we failed) or self-forwarded first.
1332     markWord old_mark = p->mark();
1333     if (old_mark.is_forwarded()) {
1334       return ShenandoahForwarding::get_forwardee(p);
1335     }
1336     oop winner = ShenandoahForwarding::try_forward_to_self(p, old_mark);
1337     if (winner == nullptr) {
1338       // We own the self-forwarding. Flag the region so the degen/full GC
1339       // entry drain knows to scan it for self_fwd bits to clear.
1340       from_region->set_has_self_forwards();
1341       return p;
1342     }
1343     return winner;
1344   }
1345 
1346   if (ShenandoahEvacTracking) {
1347     evac_tracker()->begin_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1348   }
1349 
1350   // Copy the object:
1351   Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1352 
1353   oop copy_val = cast_to_oop(copy);
1354 










1355   // Relativize stack chunks before publishing the copy. After the forwarding CAS,
1356   // mutators can see the copy and thaw it via the fast path if flags == 0. We must
1357   // relativize derived pointers and set gc_mode before that happens. Skip if the
1358   // copy's mark word is already a forwarding pointer (another thread won the race
1359   // and overwrote the original's header before we copied it).
1360   if (!ShenandoahForwarding::is_forwarded(copy_val)) {
1361     ContinuationGCSupport::relativize_stack_chunk(copy_val);
1362   }
1363 
1364   // Try to install the new forwarding pointer.
1365   oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1366   if (result == copy_val) {
1367     // Successfully evacuated. Our copy is now the public one!
1368     shenandoah_assert_correct(nullptr, copy_val);
1369     if (ShenandoahEvacTracking) {
1370       evac_tracker()->end_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1371     }
1372     return copy_val;
1373   }  else {
1374     // Failed to evacuate. We need to deal with the object that is left behind. Since this
1375     // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1376     // But if it happens to contain references to evacuated regions, those references would
1377     // not get updated for this stale copy during this cycle, and we will crash while scanning
1378     // it the next cycle.
1379     if (alloc_from_lab) {
1380       // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1381       // object will overwrite this stale copy, or the filler object on LAB retirement will
1382       // do this.
1383       ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1384     } else {
1385       // For non-LAB allocations, we have no way to retract the allocation, and
1386       // have to explicitly overwrite the copy with the filler object. With that overwrite,
1387       // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1388       assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1389       fill_with_object(copy, size);
1390       shenandoah_assert_correct(nullptr, copy_val);
1391       // For non-LAB allocations, the object has already been registered
1392     }
1393     shenandoah_assert_correct(nullptr, result);
1394     return result;
1395   }
1396 }
1397 
1398 // Clear the self_fwd bit on a live cset object, if set. Runs at a safepoint,
1399 // so a plain store is sufficient — no concurrent writers to the mark word.
1400 class ShenandoahUnSelfForwardObjectClosure : public ObjectClosure {
1401 public:
1402   void do_object(oop obj) override {
1403     markWord m = obj->mark();
1404     if (m.is_self_forwarded()) {
1405       obj->set_mark(m.unset_self_forwarded());
1406     }
1407   }
1408 };
1409 
1410 // Parallel task over flagged cset regions. Iterates the live objects via the
1411 // mark bitmap (skipping evacuated and never-marked memory), clears self_fwd
1412 // bits, and resets the region flag once done.
1413 class ShenandoahUnSelfForwardTask : public WorkerTask {
1414 private:
1415   ShenandoahHeap*          const _heap;
1416   ShenandoahCollectionSet* const _cs;
1417 
1418 public:
1419   ShenandoahUnSelfForwardTask(ShenandoahHeap* heap, ShenandoahCollectionSet* cs) :
1420     WorkerTask("Shenandoah Un-Self-Forward"),
1421     _heap(heap),
1422     _cs(cs) {}
1423 
1424   void work(uint worker_id) override {
1425     ShenandoahParallelWorkerSession worker_session(worker_id);
1426     ShenandoahUnSelfForwardObjectClosure cl;
1427     ShenandoahHeapRegion* r;
1428     while ((r = _cs->claim_next()) != nullptr) {
1429       if (r->has_self_forwards()) {
1430         _heap->marked_object_iterate(r, &cl);
1431         r->clear_has_self_forwards();
1432       }
1433     }
1434   }
1435 };
1436 
1437 void ShenandoahHeap::un_self_forward_cset_regions() {
1438   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1439   ShenandoahCollectionSet* cs = collection_set();
1440   if (cs == nullptr || cs->is_empty()) {
1441     return;
1442   }
1443   cs->clear_current_index();
1444   ShenandoahUnSelfForwardTask task(this, cs);
1445   workers()->run_task(&task);
1446   DEBUG_ONLY(assert_no_self_forwards());
1447 }
1448 
1449 #ifdef ASSERT
1450 void ShenandoahHeap::assert_no_self_forwards() const {
1451   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1452   ShenandoahCollectionSet* cs = collection_set();
1453   if (cs == nullptr) return;
1454   cs->clear_current_index();
1455   ShenandoahHeapRegion* r;
1456   while ((r = cs->next()) != nullptr) {
1457     assert(!r->has_self_forwards(), "region still flagged after drain");
1458   }
1459   cs->clear_current_index();
1460 }
1461 #endif
1462 
1463 void ShenandoahHeap::trash_cset_regions() {
1464   ShenandoahHeapLocker locker(lock());
1465 
1466   ShenandoahCollectionSet* set = collection_set();
1467   ShenandoahHeapRegion* r;
1468   set->clear_current_index();
1469   while ((r = set->next()) != nullptr) {
1470     r->make_trash();
1471   }
1472   collection_set()->clear();
1473 }
1474 
1475 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1476   st->print_cr("Heap Regions:");
1477   st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1478   st->print_cr("              HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1479   st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1480   st->print_cr("UWM=update watermark, U=used");
1481   st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1482   st->print_cr("S=shared allocs, L=live data");
1483   st->print_cr("CP=critical pins");
1484 
1485   for (size_t i = 0; i < num_regions(); i++) {
1486     get_region(i)->print_on(st);
1487   }
1488 }
1489 
1490 void ShenandoahHeap::process_gc_stats() const {
1491   // Commit worker statistics to cycle data
1492   phase_timings()->flush_par_workers_to_cycle();
1493 
1494   // Print GC stats for current cycle
1495   LogTarget(Info, gc, stats) lt;
1496   if (lt.is_enabled()) {
1497     ResourceMark rm;
1498     LogStream ls(lt);
1499     phase_timings()->print_cycle_on(&ls);
1500     if (ShenandoahEvacTracking) {
1501       ShenandoahCycleStats  evac_stats = evac_tracker()->flush_cycle_to_global();
1502       evac_tracker()->print_evacuations_on(&ls, &evac_stats.workers,
1503                                                &evac_stats.mutators);
1504     }
1505   }
1506 
1507   // Commit statistics to globals
1508   phase_timings()->flush_cycle_to_global();
1509 }
1510 
1511 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) const {
1512   assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1513   assert(!start->has_live(), "liveness must be zero");
1514 
1515   // Do not try to get the size of this humongous object. STW collections will
1516   // have already unloaded classes, so an unmarked object may have a bad klass pointer.
1517   ShenandoahHeapRegion* region = start;
1518   size_t index = region->index();
1519   do {
1520     assert(region->is_humongous(), "Expect correct humongous start or continuation");
1521     assert(!region->is_cset(), "Humongous region should not be in collection set");
1522     region->make_trash_immediate();
1523     region = get_region(++index);
1524   } while (region != nullptr && region->is_humongous_continuation());
1525 
1526   // Return number of regions trashed
1527   return index - start->index();
1528 }
1529 
1530 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1531 public:
1532   ShenandoahCheckCleanGCLABClosure() {}
1533   void do_thread(Thread* thread) {
1534     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1535     assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1536     assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1537 
1538     if (ShenandoahHeap::heap()->mode()->is_generational()) {
1539       ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
1540       assert(shenandoah_plab != nullptr, "PLAB should be initialized for %s", thread->name());
1541       assert(shenandoah_plab->plab()->words_remaining() == 0, "PLAB should not need retirement");
1542     }
1543   }
1544 };
1545 
1546 void ShenandoahHeap::labs_make_parsable() {
1547   assert(UseTLAB, "Only call with UseTLAB");
1548 
1549   ShenandoahRetireGCLABClosure cl(false);
1550 
1551   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1552     ThreadLocalAllocBuffer& tlab = t->tlab();
1553     tlab.make_parsable();
1554     if (ZeroTLAB) {
1555       t->retire_tlab();
1556     }
1557     cl.do_thread(t);
1558   }
1559 
1560   workers()->threads_do(&cl);
1561 
1562   if (safepoint_workers() != nullptr) {
1563     safepoint_workers()->threads_do(&cl);
1564   }
1565 }
1566 
1567 void ShenandoahHeap::tlabs_retire(bool resize) {
1568   assert(UseTLAB, "Only call with UseTLAB");
1569   assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1570 
1571   ThreadLocalAllocStats stats;
1572 
1573   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1574     t->retire_tlab(&stats);
1575     if (resize) {
1576       t->tlab().resize();
1577     }
1578   }
1579 
1580   stats.publish();
1581 
1582 #ifdef ASSERT
1583   ShenandoahCheckCleanGCLABClosure cl;
1584   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1585     cl.do_thread(t);
1586   }
1587   workers()->threads_do(&cl);
1588 #endif
1589 }
1590 
1591 void ShenandoahHeap::gclabs_retire(bool resize) {
1592   assert(UseTLAB, "Only call with UseTLAB");
1593   assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1594 
1595   ShenandoahRetireGCLABClosure cl(resize);
1596   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1597     cl.do_thread(t);
1598   }
1599 
1600   workers()->threads_do(&cl);
1601 
1602   if (safepoint_workers() != nullptr) {
1603     safepoint_workers()->threads_do(&cl);
1604   }
1605 }
1606 
1607 // Returns size in bytes
1608 size_t ShenandoahHeap::unsafe_max_tlab_alloc() const {
1609   // Return the max allowed size, and let the allocation path
1610   // figure out the safe size for current allocation.
1611   return ShenandoahHeapRegion::max_tlab_size_bytes();
1612 }
1613 
1614 size_t ShenandoahHeap::max_tlab_size() const {
1615   // Returns size in words
1616   return ShenandoahHeapRegion::max_tlab_size_words();
1617 }
1618 
1619 void ShenandoahHeap::collect_as_vm_thread(GCCause::Cause cause) {
1620   // These requests are ignored because we can't easily have Shenandoah jump into
1621   // a synchronous (degenerated or full) cycle while it is in the middle of a concurrent
1622   // cycle. We _could_ cancel the concurrent cycle and then try to run a cycle directly
1623   // on the VM thread, but this would confuse the control thread mightily and doesn't
1624   // seem worth the trouble. Instead, we will have the caller thread run (and wait for) a
1625   // concurrent cycle in the prologue of the heap inspect/dump operation (see VM_HeapDumper::doit_prologue).
1626   // This is how other concurrent collectors in the JVM handle this scenario as well.
1627   assert(Thread::current()->is_VM_thread(), "Should be the VM thread");
1628   guarantee(cause == GCCause::_heap_dump || cause == GCCause::_heap_inspection, "Invalid cause");
1629 }
1630 
1631 void ShenandoahHeap::collect(GCCause::Cause cause) {
1632   control_thread()->request_gc(cause);
1633 }
1634 
1635 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1636   // This method is only called by `CollectedHeap::collect_as_vm_thread`, which we have
1637   // overridden to do nothing. See the comment there for an explanation of how heap inspections
1638   // work for Shenandoah.
1639   ShouldNotReachHere();
1640 }
1641 
1642 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1643   ShenandoahHeapRegion* r = heap_region_containing(addr);
1644   if (r != nullptr) {
1645     return r->block_start(addr);
1646   }
1647   return nullptr;
1648 }
1649 
1650 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1651   ShenandoahHeapRegion* r = heap_region_containing(addr);
1652   return r->block_is_obj(addr);
1653 }
1654 
1655 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1656   return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1657 }
1658 
1659 void ShenandoahHeap::prepare_for_verify() {
1660   if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1661     labs_make_parsable();
1662   }
1663 }
1664 
1665 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1666   if (_shenandoah_policy->is_at_shutdown()) {
1667     return;
1668   }
1669 
1670   if (_control_thread != nullptr) {
1671     tcl->do_thread(_control_thread);
1672   }
1673 
1674   if (_uncommit_thread != nullptr) {
1675     tcl->do_thread(_uncommit_thread);
1676   }
1677 
1678   workers()->threads_do(tcl);
1679   if (_safepoint_workers != nullptr) {
1680     _safepoint_workers->threads_do(tcl);
1681   }
1682 }
1683 
1684 void ShenandoahHeap::print_tracing_info() const {
1685   LogTarget(Info, gc, stats) lt;
1686   if (lt.is_enabled()) {
1687     ResourceMark rm;
1688     LogStream ls(lt);
1689 
1690     if (ShenandoahEvacTracking) {
1691       evac_tracker()->print_global_on(&ls);
1692       ls.cr();
1693       ls.cr();
1694     }
1695 
1696     phase_timings()->print_global_on(&ls);
1697 
1698     ls.cr();
1699     ls.cr();
1700 
1701     shenandoah_policy()->print_gc_stats(&ls);
1702 
1703     ls.cr();
1704     ls.cr();
1705   }
1706 }
1707 
1708 // Active generation may only be set by the VM thread at a safepoint.
1709 void ShenandoahHeap::set_active_generation(ShenandoahGeneration* generation) {
1710   assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1711   assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1712   _active_generation = generation;
1713 }
1714 
1715 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation,
1716                                     bool is_degenerated, bool is_out_of_cycle) {
1717   shenandoah_policy()->record_collection_cause(cause);
1718 
1719   const GCCause::Cause current = gc_cause();
1720   assert(current == GCCause::_no_gc, "Over-writing cause: %s, with: %s",
1721          GCCause::to_string(current), GCCause::to_string(cause));
1722 
1723   set_gc_cause(cause);
1724 
1725   if (is_degenerated) {
1726     generation->heuristics()->record_degenerated_cycle_start(is_out_of_cycle);
1727   } else {
1728     generation->heuristics()->record_cycle_start();
1729   }
1730 }
1731 
1732 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1733   assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1734 
1735   generation->heuristics()->record_cycle_end();
1736   if (mode()->is_generational() && generation->is_global()) {
1737     // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1738     young_generation()->heuristics()->record_cycle_end();
1739     old_generation()->heuristics()->record_cycle_end();
1740   }
1741 
1742   set_gc_cause(GCCause::_no_gc);
1743 }
1744 
1745 void ShenandoahHeap::verify(VerifyOption vo) {
1746   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1747     if (ShenandoahVerify) {
1748       verifier()->verify_generic(active_generation(), vo);
1749     } else {
1750       // TODO: Consider allocating verification bitmaps on demand,
1751       // and turn this on unconditionally.
1752     }
1753   }
1754 }
1755 size_t ShenandoahHeap::tlab_capacity() const {
1756   return _free_set->capacity_not_holding_lock();
1757 }
1758 
1759 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1760 private:
1761   MarkBitMap* _bitmap;
1762   ShenandoahScanObjectStack* _oop_stack;
1763   ShenandoahHeap* const _heap;
1764   ShenandoahMarkingContext* const _marking_context;
1765 
1766   template <class T>
1767   void do_oop_work(T* p) {
1768     T o = RawAccess<>::oop_load(p);
1769     if (!CompressedOops::is_null(o)) {
1770       oop obj = CompressedOops::decode_not_null(o);
1771       if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1772         // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1773         return;
1774       }
1775       obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1776 
1777       assert(oopDesc::is_oop(obj), "must be a valid oop");
1778       if (!_bitmap->is_marked(obj)) {
1779         _bitmap->mark(obj);
1780         _oop_stack->push(obj);
1781       }
1782     }
1783   }
1784 public:
1785   ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1786     _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1787     _marking_context(_heap->marking_context()) {}
1788   void do_oop(oop* p)       { do_oop_work(p); }
1789   void do_oop(narrowOop* p) { do_oop_work(p); }
1790 };
1791 
1792 /*
1793  * This is public API, used in preparation of object_iterate().
1794  * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1795  * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1796  * control, we call SH::tlabs_retire, SH::gclabs_retire.
1797  */
1798 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1799   // No-op.
1800 }
1801 
1802 /*
1803  * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1804  *
1805  * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1806  * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1807  * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1808  * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1809  * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1810  * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1811  * wiped the bitmap in preparation for next marking).
1812  *
1813  * For all those reasons, we implement object iteration as a single marking traversal, reporting
1814  * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1815  * is allowed to report dead objects, but is not required to do so.
1816  */
1817 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1818   // Reset bitmap
1819   if (!prepare_aux_bitmap_for_iteration())
1820     return;
1821 
1822   ShenandoahScanObjectStack oop_stack;
1823   ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1824   // Seed the stack with root scan
1825   scan_roots_for_iteration(&oop_stack, &oops);
1826 
1827   // Work through the oop stack to traverse heap
1828   while (! oop_stack.is_empty()) {
1829     oop obj = oop_stack.pop();
1830     assert(oopDesc::is_oop(obj), "must be a valid oop");
1831     cl->do_object(obj);
1832     obj->oop_iterate(&oops);
1833   }
1834 
1835   assert(oop_stack.is_empty(), "should be empty");
1836   // Reclaim bitmap
1837   reclaim_aux_bitmap_for_iteration();
1838 }
1839 
1840 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1841   assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1842   if (!_aux_bitmap_region_special) {
1843     bool success = os::commit_memory((char *) _aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false);
1844     if (!success) {
1845       log_warning(gc)("Auxiliary marking bitmap commit failed: " PTR_FORMAT " (%zu bytes)",
1846                       p2i(_aux_bitmap_region.start()), _aux_bitmap_region.byte_size());
1847       return false;
1848     }
1849   }
1850   _aux_bit_map.clear();
1851   return true;
1852 }
1853 
1854 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1855   // Process GC roots according to current GC cycle
1856   // This populates the work stack with initial objects
1857   // It is important to relinquish the associated locks before diving
1858   // into heap dumper
1859   uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1860   ShenandoahHeapIterationRootScanner rp(n_workers);
1861   rp.roots_do(oops);
1862 }
1863 
1864 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1865   if (!_aux_bitmap_region_special) {
1866     os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size());
1867   }
1868 }
1869 
1870 // Closure for parallelly iterate objects
1871 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1872 private:
1873   MarkBitMap* _bitmap;
1874   ShenandoahObjToScanQueue* _queue;
1875   ShenandoahHeap* const _heap;
1876   ShenandoahMarkingContext* const _marking_context;
1877 
1878   template <class T>
1879   void do_oop_work(T* p) {
1880     T o = RawAccess<>::oop_load(p);
1881     if (!CompressedOops::is_null(o)) {
1882       oop obj = CompressedOops::decode_not_null(o);
1883       if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1884         // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1885         return;
1886       }
1887       obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1888 
1889       assert(oopDesc::is_oop(obj), "Must be a valid oop");
1890       if (_bitmap->par_mark(obj)) {
1891         _queue->push(ShenandoahMarkTask(obj));
1892       }
1893     }
1894   }
1895 public:
1896   ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1897     _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1898     _marking_context(_heap->marking_context()) {}
1899   void do_oop(oop* p)       { do_oop_work(p); }
1900   void do_oop(narrowOop* p) { do_oop_work(p); }
1901 };
1902 
1903 // Object iterator for parallel heap iteraion.
1904 // The root scanning phase happenes in construction as a preparation of
1905 // parallel marking queues.
1906 // Every worker processes it's own marking queue. work-stealing is used
1907 // to balance workload.
1908 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1909 private:
1910   uint                         _num_workers;
1911   bool                         _init_ready;
1912   MarkBitMap*                  _aux_bit_map;
1913   ShenandoahHeap*              _heap;
1914   ShenandoahScanObjectStack    _roots_stack; // global roots stack
1915   ShenandoahObjToScanQueueSet* _task_queues;
1916 public:
1917   ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1918         _num_workers(num_workers),
1919         _init_ready(false),
1920         _aux_bit_map(bitmap),
1921         _heap(ShenandoahHeap::heap()) {
1922     // Initialize bitmap
1923     _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1924     if (!_init_ready) {
1925       return;
1926     }
1927 
1928     ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1929     _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1930 
1931     _init_ready = prepare_worker_queues();
1932   }
1933 
1934   ~ShenandoahParallelObjectIterator() {
1935     // Reclaim bitmap
1936     _heap->reclaim_aux_bitmap_for_iteration();
1937     // Reclaim queue for workers
1938     if (_task_queues!= nullptr) {
1939       for (uint i = 0; i < _num_workers; ++i) {
1940         ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1941         if (q != nullptr) {
1942           delete q;
1943           _task_queues->register_queue(i, nullptr);
1944         }
1945       }
1946       delete _task_queues;
1947       _task_queues = nullptr;
1948     }
1949   }
1950 
1951   virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1952     if (_init_ready) {
1953       object_iterate_parallel(cl, worker_id, _task_queues);
1954     }
1955   }
1956 
1957 private:
1958   // Divide global root_stack into worker queues
1959   bool prepare_worker_queues() {
1960     _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1961     // Initialize queues for every workers
1962     for (uint i = 0; i < _num_workers; ++i) {
1963       ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1964       _task_queues->register_queue(i, task_queue);
1965     }
1966     // Divide roots among the workers. Assume that object referencing distribution
1967     // is related with root kind, use round-robin to make every worker have same chance
1968     // to process every kind of roots
1969     size_t roots_num = _roots_stack.size();
1970     if (roots_num == 0) {
1971       // No work to do
1972       return false;
1973     }
1974 
1975     for (uint j = 0; j < roots_num; j++) {
1976       uint stack_id = j % _num_workers;
1977       oop obj = _roots_stack.pop();
1978       _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1979     }
1980     return true;
1981   }
1982 
1983   void object_iterate_parallel(ObjectClosure* cl,
1984                                uint worker_id,
1985                                ShenandoahObjToScanQueueSet* queue_set) {
1986     assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1987     assert(queue_set != nullptr, "task queue must not be null");
1988 
1989     ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1990     assert(q != nullptr, "object iterate queue must not be null");
1991 
1992     ShenandoahMarkTask t;
1993     ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1994 
1995     // Work through the queue to traverse heap.
1996     // Steal when there is no task in queue.
1997     while (q->pop(t) || queue_set->steal(worker_id, t)) {
1998       oop obj = t.obj();
1999       assert(oopDesc::is_oop(obj), "must be a valid oop");
2000       cl->do_object(obj);
2001       obj->oop_iterate(&oops);
2002     }
2003     assert(q->is_empty(), "should be empty");
2004   }
2005 };
2006 
2007 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
2008   return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
2009 }
2010 
2011 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
2012 void ShenandoahHeap::keep_alive(oop obj) {
2013   if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
2014     ShenandoahBarrierSet::barrier_set()->enqueue(obj);
2015   }
2016 }
2017 
2018 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2019   for (size_t i = 0; i < num_regions(); i++) {
2020     ShenandoahHeapRegion* current = get_region(i);
2021     blk->heap_region_do(current);
2022   }
2023 }
2024 
2025 class ShenandoahHeapRegionIteratorTask : public WorkerTask {
2026 private:
2027   ShenandoahRegionIterator _regions;
2028   ShenandoahHeapRegionClosure* _closure;
2029 
2030 public:
2031   ShenandoahHeapRegionIteratorTask(ShenandoahHeapRegionClosure* closure)
2032     : WorkerTask("Shenandoah Heap Region Iterator")
2033     , _closure(closure) {}
2034 
2035   void work(uint worker_id) override {
2036     ShenandoahParallelWorkerSession worker_session(worker_id);
2037     ShenandoahHeapRegion* region = _regions.next();
2038     while (region != nullptr) {
2039       _closure->heap_region_do(region);
2040       region = _regions.next();
2041     }
2042   }
2043 };
2044 
2045 class ShenandoahParallelHeapRegionTask : public WorkerTask {
2046 private:
2047   ShenandoahHeap* const _heap;
2048   ShenandoahHeapRegionClosure* const _blk;
2049   size_t const _stride;
2050 
2051   shenandoah_padding(0);
2052   Atomic<size_t> _index;
2053   shenandoah_padding(1);
2054 
2055 public:
2056   ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
2057           WorkerTask("Shenandoah Parallel Region Operation"),
2058           _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
2059 
2060   void work(uint worker_id) {
2061     ShenandoahParallelWorkerSession worker_session(worker_id);
2062     size_t stride = _stride;
2063 
2064     size_t max = _heap->num_regions();
2065     while (_index.load_relaxed() < max) {
2066       size_t cur = _index.fetch_then_add(stride, memory_order_relaxed);
2067       size_t start = cur;
2068       size_t end = MIN2(cur + stride, max);
2069       if (start >= max) break;
2070 
2071       for (size_t i = cur; i < end; i++) {
2072         ShenandoahHeapRegion* current = _heap->get_region(i);
2073         _blk->heap_region_do(current);
2074       }
2075     }
2076   }
2077 };
2078 
2079 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2080   assert(blk->is_thread_safe(), "Only thread-safe closures here");
2081   const uint active_workers = workers()->active_workers();
2082   const size_t n_regions = num_regions();
2083   size_t stride = blk->parallel_region_stride();
2084   if (stride == 0 && active_workers > 1) {
2085     // Automatically derive the stride to balance the work between threads
2086     // evenly. Do not try to split work if below the reasonable threshold.
2087     constexpr size_t threshold = 4096;
2088     stride = n_regions <= threshold ?
2089             threshold :
2090             (n_regions + active_workers - 1) / active_workers;
2091   }
2092 
2093   if (n_regions > stride && active_workers > 1) {
2094     ShenandoahParallelHeapRegionTask task(blk, stride);
2095     workers()->run_task(&task);
2096   } else {
2097     heap_region_iterate(blk);
2098   }
2099 }
2100 
2101 void ShenandoahHeap::heap_region_iterator(ShenandoahHeapRegionClosure* closure) const {
2102   ShenandoahHeapRegionIteratorTask task(closure);
2103   workers()->run_task(&task);
2104 }
2105 
2106 class ShenandoahRendezvousHandshakeClosure : public HandshakeClosure {
2107 public:
2108   inline ShenandoahRendezvousHandshakeClosure(const char* name) : HandshakeClosure(name) {}
2109   inline void do_thread(Thread* thread) {}
2110 };
2111 
2112 void ShenandoahHeap::rendezvous_threads(const char* name) {
2113   ShenandoahRendezvousHandshakeClosure cl(name);
2114   Handshake::execute(&cl);
2115 }
2116 
2117 void ShenandoahHeap::recycle_trash() {
2118   free_set()->recycle_trash();
2119 }
2120 
2121 void ShenandoahHeap::do_class_unloading() {
2122   _unloader.unload();
2123   if (mode()->is_generational()) {
2124     old_generation()->set_parsable(false);
2125   }
2126 }
2127 
2128 void ShenandoahHeap::stw_weak_refs(ShenandoahGeneration* generation, bool full_gc) {
2129   // Weak refs processing
2130   ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
2131                                                 : ShenandoahPhaseTimings::degen_gc_weakrefs;
2132   ShenandoahTimingsTracker t(phase);
2133   ShenandoahGCWorkerPhase worker_phase(phase);
2134   generation->ref_processor()->process_references(phase, workers(), false /* concurrent */);
2135 }
2136 
2137 void ShenandoahHeap::prepare_update_heap_references() {
2138   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2139 
2140   // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2141   // make them parsable for update code to work correctly. Plus, we can compute new sizes
2142   // for future GCLABs here.
2143   if (UseTLAB) {
2144     ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
2145     gclabs_retire(ResizeTLAB);
2146   }
2147 
2148   _update_refs_iterator.reset();
2149 }
2150 
2151 void ShenandoahHeap::propagate_gc_state_to_all_threads() {
2152   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2153   if (_gc_state_changed) {
2154     // If we are only marking old, we do not need to process young pointers
2155     ShenandoahBarrierSet::satb_mark_queue_set().set_filter_out_young(
2156       is_concurrent_old_mark_in_progress() && !is_concurrent_young_mark_in_progress()
2157     );
2158     ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value());
2159     Threads::threads_do(&propagator);
2160     _gc_state_changed = false;
2161   }
2162 }
2163 
2164 void ShenandoahHeap::set_gc_state_at_safepoint(uint mask, bool value) {
2165   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2166   _gc_state.set_cond(mask, value);
2167   _gc_state_changed = true;
2168 }
2169 
2170 void ShenandoahHeap::set_gc_state_concurrent(uint mask, bool value) {
2171   // Holding the thread lock here assures that any thread created after we change the gc
2172   // state will have the correct state. It also prevents attaching threads from seeing
2173   // an inconsistent state. See ShenandoahBarrierSet::on_thread_attach for reference. Established
2174   // threads will use their thread local copy of the gc state (changed by a handshake, or on a
2175   // safepoint).
2176   assert(Threads_lock->is_locked(), "Must hold thread lock for concurrent gc state change");
2177   _gc_state.set_cond(mask, value);
2178 }
2179 
2180 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
2181   uint mask;
2182   assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
2183   if (!in_progress && is_concurrent_old_mark_in_progress()) {
2184     assert(mode()->is_generational(), "Only generational GC has old marking");
2185     assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
2186     // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
2187     mask = YOUNG_MARKING;
2188   } else {
2189     mask = MARKING | YOUNG_MARKING;
2190   }
2191   set_gc_state_at_safepoint(mask, in_progress);
2192   manage_satb_barrier(in_progress);
2193 }
2194 
2195 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2196 #ifdef ASSERT
2197   // has_forwarded_objects() iff UPDATE_REFS or EVACUATION
2198   bool has_forwarded = has_forwarded_objects();
2199   bool updating_or_evacuating = _gc_state.is_set(UPDATE_REFS | EVACUATION);
2200   bool evacuating = _gc_state.is_set(EVACUATION);
2201   assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
2202           "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
2203 #endif
2204   if (!in_progress && is_concurrent_young_mark_in_progress()) {
2205     // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2206     assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2207     set_gc_state_at_safepoint(OLD_MARKING, in_progress);
2208   } else {
2209     set_gc_state_at_safepoint(MARKING | OLD_MARKING, in_progress);
2210   }
2211   manage_satb_barrier(in_progress);
2212 }
2213 
2214 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2215   return old_generation()->is_preparing_for_mark();
2216 }
2217 
2218 void ShenandoahHeap::manage_satb_barrier(bool active) {
2219   if (is_concurrent_mark_in_progress()) {
2220     // Ignore request to deactivate barrier while concurrent mark is in progress.
2221     // Do not attempt to re-activate the barrier if it is already active.
2222     if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2223       ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2224     }
2225   } else {
2226     // No concurrent marking is in progress so honor request to deactivate,
2227     // but only if the barrier is already active.
2228     if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2229       ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2230     }
2231   }
2232 }
2233 
2234 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2235   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2236   set_gc_state_at_safepoint(EVACUATION, in_progress);
2237 }
2238 
2239 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2240   if (in_progress) {
2241     _concurrent_strong_root_in_progress.set();
2242   } else {
2243     _concurrent_strong_root_in_progress.unset();
2244   }
2245 }
2246 
2247 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2248   set_gc_state_at_safepoint(WEAK_ROOTS, cond);
2249 }
2250 
2251 GCTracer* ShenandoahHeap::tracer() {
2252   return shenandoah_policy()->tracer();
2253 }
2254 
2255 size_t ShenandoahHeap::tlab_used() const {
2256   return _free_set->used_not_holding_lock();
2257 }
2258 
2259 bool ShenandoahHeap::try_cancel_gc(GCCause::Cause cause) {
2260   const GCCause::Cause prev = _cancelled_gc.xchg(cause);
2261   return prev == GCCause::_no_gc || prev == GCCause::_shenandoah_concurrent_gc;
2262 }
2263 
2264 void ShenandoahHeap::cancel_concurrent_mark() {
2265   if (mode()->is_generational()) {
2266     young_generation()->cancel_marking();
2267     old_generation()->cancel_marking();
2268   }
2269 
2270   global_generation()->cancel_marking();
2271 
2272   ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2273 }
2274 
2275 bool ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2276   if (try_cancel_gc(cause)) {
2277     FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2278     log_info(gc,thread)("%s", msg.buffer());
2279     Events::log(Thread::current(), "%s", msg.buffer());
2280     _cancel_requested_time = os::elapsedTime();
2281     return true;
2282   }
2283   return false;
2284 }
2285 
2286 uint ShenandoahHeap::max_workers() {
2287   return _max_workers;
2288 }
2289 
2290 void ShenandoahHeap::stop() {
2291   // The shutdown sequence should be able to terminate when GC is running.
2292 
2293   // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2294   _shenandoah_policy->record_shutdown();
2295 
2296   // Step 1. Stop reporting on gc thread cpu utilization
2297   mmu_tracker()->stop();
2298 
2299   // Step 2. Stop decaying allocation rate.
2300   _alloc_rate_decay.disenroll();
2301 
2302   // Step 3. Wait until GC worker exits normally (this will cancel any ongoing GC).
2303   control_thread()->stop();
2304 
2305   // Step 4. Shutdown uncommit thread.
2306   if (_uncommit_thread != nullptr) {
2307     _uncommit_thread->stop();
2308   }
2309 }
2310 
2311 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2312   if (!unload_classes()) return;
2313   ClassUnloadingContext ctx(_workers->active_workers(),
2314                             true /* unregister_nmethods_during_purge */,
2315                             false /* lock_nmethod_free_separately */);
2316 
2317   // Unload classes and purge SystemDictionary.
2318   {
2319     ShenandoahPhaseTimings::Phase phase = full_gc ?
2320                                           ShenandoahPhaseTimings::full_gc_purge_class_unload :
2321                                           ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2322     ShenandoahIsAliveSelector is_alive;
2323     {
2324       CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2325       ShenandoahGCPhase gc_phase(phase);
2326       ShenandoahGCWorkerPhase worker_phase(phase);
2327       bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2328 
2329       ShenandoahClassUnloadingTask unlink_task(phase, unloading_occurred);
2330       _workers->run_task(&unlink_task);
2331     }
2332     // Release unloaded nmethods's memory.
2333     ClassUnloadingContext::context()->purge_and_free_nmethods();
2334   }
2335 
2336   {
2337     ShenandoahGCPhase phase(full_gc ?
2338                             ShenandoahPhaseTimings::full_gc_purge_cldg :
2339                             ShenandoahPhaseTimings::degen_gc_purge_cldg);
2340     ClassLoaderDataGraph::purge(true /* at_safepoint */);
2341   }
2342   // Resize and verify metaspace
2343   MetaspaceGC::compute_new_size();
2344 
2345   if (mode()->is_generational()) {
2346     old_generation()->set_parsable(false);
2347   }
2348 
2349   DEBUG_ONLY(MetaspaceUtils::verify();)
2350 }
2351 
2352 // Weak roots are either pre-evacuated (final mark) or updated (final update refs),
2353 // so they should not have forwarded oops.
2354 // However, we do need to "null" dead oops in the roots, if can not be done
2355 // in concurrent cycles.
2356 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2357   uint num_workers = _workers->active_workers();
2358   ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2359                                                ShenandoahPhaseTimings::full_gc_purge_weak_par :
2360                                                ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2361   ShenandoahGCPhase phase(timing_phase);
2362   ShenandoahGCWorkerPhase worker_phase(timing_phase);
2363   // Cleanup weak roots
2364   if (has_forwarded_objects()) {
2365     ShenandoahForwardedIsAliveClosure is_alive;
2366     ShenandoahNonConcUpdateRefsClosure keep_alive;
2367     ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure>
2368       cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2369     _workers->run_task(&cleaning_task);
2370   } else {
2371     ShenandoahIsAliveClosure is_alive;
2372 #ifdef ASSERT
2373     ShenandoahAssertNotForwardedClosure verify_cl;
2374     ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2375       cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2376 #else
2377     ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2378       cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2379 #endif
2380     _workers->run_task(&cleaning_task);
2381   }
2382 }
2383 
2384 void ShenandoahHeap::parallel_cleaning(ShenandoahGeneration* generation, bool full_gc) {
2385   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2386   assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2387   ShenandoahGCPhase phase(full_gc ?
2388                           ShenandoahPhaseTimings::full_gc_purge :
2389                           ShenandoahPhaseTimings::degen_gc_purge);
2390   stw_weak_refs(generation, full_gc);
2391   stw_process_weak_roots(full_gc);
2392   stw_unload_classes(full_gc);
2393 }
2394 
2395 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2396   set_gc_state_at_safepoint(HAS_FORWARDED, cond);
2397 }
2398 
2399 void ShenandoahHeap::set_unload_classes(bool uc) {
2400   _unload_classes.set_cond(uc);
2401 }
2402 
2403 bool ShenandoahHeap::unload_classes() const {
2404   return _unload_classes.is_set();
2405 }
2406 
2407 address ShenandoahHeap::in_cset_fast_test_addr() {
2408   ShenandoahHeap* heap = ShenandoahHeap::heap();
2409   assert(heap->collection_set() != nullptr, "Sanity");
2410   return (address) heap->collection_set()->biased_map_address();
2411 }
2412 
2413 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2414   _degenerated_gc_in_progress.set_cond(in_progress);
2415 }
2416 
2417 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2418   _full_gc_in_progress.set_cond(in_progress);
2419 }
2420 
2421 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2422   assert (is_full_gc_in_progress(), "should be");
2423   _full_gc_move_in_progress.set_cond(in_progress);
2424 }
2425 
2426 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2427   set_gc_state_at_safepoint(UPDATE_REFS, in_progress);
2428 }
2429 
2430 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2431   ShenandoahCodeRoots::register_nmethod(nm);
2432 }
2433 
2434 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2435   ShenandoahCodeRoots::unregister_nmethod(nm);
2436 }
2437 
2438 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2439   heap_region_containing(o)->record_pin();
2440 }
2441 
2442 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2443   ShenandoahHeapRegion* r = heap_region_containing(o);
2444   assert(r != nullptr, "Sanity");
2445   assert(r->pin_count() > 0, "Region %zu should have non-zero pins", r->index());
2446   r->record_unpin();
2447 }
2448 
2449 void ShenandoahHeap::sync_pinned_region_status() {
2450   ShenandoahHeapLocker locker(lock());
2451 
2452   for (size_t i = 0; i < num_regions(); i++) {
2453     ShenandoahHeapRegion *r = get_region(i);
2454     if (r->is_active()) {
2455       if (r->is_pinned()) {
2456         if (r->pin_count() == 0) {
2457           r->make_unpinned();
2458         }
2459       } else {
2460         if (r->pin_count() > 0) {
2461           r->make_pinned();
2462         }
2463       }
2464     }
2465   }
2466 
2467   assert_pinned_region_status();
2468 }
2469 
2470 #ifdef ASSERT
2471 void ShenandoahHeap::assert_pinned_region_status() const {
2472   assert_pinned_region_status(global_generation());
2473 }
2474 
2475 void ShenandoahHeap::assert_pinned_region_status(ShenandoahGeneration* generation) const {
2476   for (size_t i = 0; i < num_regions(); i++) {
2477     ShenandoahHeapRegion* r = get_region(i);
2478     if (generation->contains(r)) {
2479       assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2480              "Region %zu pinning status is inconsistent", i);
2481     }
2482   }
2483 }
2484 #endif
2485 
2486 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2487   return _gc_timer;
2488 }
2489 
2490 void ShenandoahHeap::prepare_concurrent_roots() {
2491   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2492   assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2493   set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2494   set_concurrent_weak_root_in_progress(true);
2495   if (unload_classes()) {
2496     _unloader.prepare();
2497   }
2498 }
2499 
2500 void ShenandoahHeap::finish_concurrent_roots() {
2501   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2502   assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2503   if (unload_classes()) {
2504     _unloader.finish();
2505   }
2506 }
2507 
2508 #ifdef ASSERT
2509 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2510   assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2511 
2512   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2513     // Use ParallelGCThreads inside safepoints
2514     assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2515            ParallelGCThreads, nworkers);
2516   } else {
2517     // Use ConcGCThreads outside safepoints
2518     assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2519            ConcGCThreads, nworkers);
2520   }
2521 }
2522 #endif
2523 
2524 ShenandoahVerifier* ShenandoahHeap::verifier() {
2525   guarantee(ShenandoahVerify, "Should be enabled");
2526   assert (_verifier != nullptr, "sanity");
2527   return _verifier;
2528 }
2529 
2530 template<bool CONCURRENT>
2531 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2532 private:
2533   ShenandoahHeap* _heap;
2534   ShenandoahRegionIterator* _regions;
2535 public:
2536   explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2537     WorkerTask("Shenandoah Update References"),
2538     _heap(ShenandoahHeap::heap()),
2539     _regions(regions) {
2540   }
2541 
2542   void work(uint worker_id) {
2543     if (CONCURRENT) {
2544       ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_update_refs, ShenandoahPhaseTimings::Work, worker_id, true);
2545       ShenandoahConcurrentWorkerSession worker_session(worker_id);
2546       SuspendibleThreadSetJoiner stsj;
2547       do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2548     } else {
2549       ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::degen_gc_update_refs, ShenandoahPhaseTimings::Work, worker_id, true);
2550       ShenandoahParallelWorkerSession worker_session(worker_id);
2551       do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
2552     }
2553   }
2554 
2555 private:
2556   template<class T>
2557   void do_work(uint worker_id) {
2558     if (CONCURRENT && (worker_id == 0)) {
2559       // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2560       // results of evacuation.  These reserves are no longer necessary because evacuation has completed.
2561       size_t cset_regions = _heap->collection_set()->count();
2562 
2563       // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2564       // to the mutator free set.  At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2565       // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2566       // next GC cycle.
2567       _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2568     }
2569     // If !CONCURRENT, there's no value in expanding Mutator free set
2570     T cl;
2571     ShenandoahHeapRegion* r = _regions->next();
2572     while (r != nullptr) {
2573       HeapWord* update_watermark = r->get_update_watermark();
2574       assert (update_watermark >= r->bottom(), "sanity");
2575       if (r->is_active() && !r->is_cset()) {
2576         _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2577       }
2578       if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2579         return;
2580       }
2581       r = _regions->next();
2582     }
2583   }
2584 };
2585 
2586 void ShenandoahHeap::update_heap_references(ShenandoahGeneration* generation, bool concurrent) {
2587   assert(generation->is_global(), "Should only get global generation here");
2588   assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2589 
2590   if (concurrent) {
2591     ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2592     workers()->run_task(&task);
2593   } else {
2594     ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2595     workers()->run_task(&task);
2596   }
2597 }
2598 
2599 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2600   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2601   assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2602 
2603   {
2604     ShenandoahGCPhase phase(concurrent ?
2605                             ShenandoahPhaseTimings::final_update_refs_update_region_states :
2606                             ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2607 
2608     final_update_refs_update_region_states();
2609 
2610     assert_pinned_region_status();
2611   }
2612 
2613   {
2614     ShenandoahGCPhase phase(concurrent ?
2615                             ShenandoahPhaseTimings::final_update_refs_trash_cset :
2616                             ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2617     trash_cset_regions();
2618   }
2619 }
2620 
2621 void ShenandoahHeap::final_update_refs_update_region_states() {
2622   ShenandoahSynchronizePinnedRegionStates cl;
2623   parallel_heap_region_iterate(&cl);
2624 }
2625 
2626 void ShenandoahHeap::rebuild_free_set_within_phase() {
2627   ShenandoahHeapLocker locker(lock());
2628   size_t young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count;
2629   _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count);
2630   // If there are no old regions, first_old_region will be greater than last_old_region
2631   assert((first_old_region > last_old_region) ||
2632          ((last_old_region + 1 - first_old_region >= old_region_count) &&
2633           get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2634          "sanity: old_region_count: %zu, first_old_region: %zu, last_old_region: %zu",
2635          old_region_count, first_old_region, last_old_region);
2636 
2637   if (mode()->is_generational()) {
2638 #ifdef ASSERT
2639     if (ShenandoahVerify) {
2640       verifier()->verify_before_rebuilding_free_set();
2641     }
2642 #endif
2643 
2644     // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2645     // available for transfer to old. Note that transfer of humongous regions does not impact available.
2646     ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2647     size_t allocation_runway =
2648       gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_trashed_regions);
2649     gen_heap->compute_old_generation_balance(allocation_runway, old_trashed_regions, young_trashed_regions);
2650   }
2651   // Rebuild free set based on adjusted generation sizes.
2652   _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, old_region_count);
2653 
2654   if (mode()->is_generational()) {
2655     ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2656     ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2657     old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions());
2658   }
2659 }
2660 
2661 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2662   ShenandoahGCPhase phase(concurrent ?
2663                           ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2664                           ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2665   rebuild_free_set_within_phase();
2666 }
2667 
2668 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2669   size_t slice = r->index() / _bitmap_regions_per_slice;
2670 
2671   size_t regions_from = _bitmap_regions_per_slice * slice;
2672   size_t regions_to   = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2673   for (size_t g = regions_from; g < regions_to; g++) {
2674     assert (g / _bitmap_regions_per_slice == slice, "same slice");
2675     if (skip_self && g == r->index()) continue;
2676     if (get_region(g)->is_committed()) {
2677       return true;
2678     }
2679   }
2680   return false;
2681 }
2682 
2683 void ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2684   shenandoah_assert_heaplocked();
2685   assert(!is_bitmap_region_special(), "Not for special memory");
2686 
2687   if (is_bitmap_slice_committed(r, true)) {
2688     // Some other region from the group is already committed, meaning the bitmap
2689     // slice is already committed, we exit right away.
2690     return;
2691   }
2692 
2693   // Commit the bitmap slice:
2694   size_t slice = r->index() / _bitmap_regions_per_slice;
2695   size_t off = _bitmap_bytes_per_slice * slice;
2696   size_t len = _bitmap_bytes_per_slice;
2697   char* start = (char*) _bitmap_region.start() + off;
2698 
2699   os::commit_memory_or_exit(start, len, false, "Unable to commit bitmap slice");
2700 
2701   if (AlwaysPreTouch) {
2702     os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2703   }
2704 }
2705 
2706 void ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2707   shenandoah_assert_heaplocked();
2708   assert(!is_bitmap_region_special(), "Not for special memory");
2709 
2710   if (is_bitmap_slice_committed(r, true)) {
2711     // Some other region from the group is still committed, meaning the bitmap
2712     // slice should stay committed, exit right away.
2713     return;
2714   }
2715 
2716   // Uncommit the bitmap slice:
2717   size_t slice = r->index() / _bitmap_regions_per_slice;
2718   size_t off = _bitmap_bytes_per_slice * slice;
2719   size_t len = _bitmap_bytes_per_slice;
2720 
2721   char* addr = (char*) _bitmap_region.start() + off;
2722   os::uncommit_memory(addr, len);
2723 }
2724 
2725 void ShenandoahHeap::forbid_uncommit() {
2726   if (_uncommit_thread != nullptr) {
2727     _uncommit_thread->forbid_uncommit();
2728   }
2729 }
2730 
2731 void ShenandoahHeap::allow_uncommit() {
2732   if (_uncommit_thread != nullptr) {
2733     _uncommit_thread->allow_uncommit();
2734   }
2735 }
2736 
2737 #ifdef ASSERT
2738 bool ShenandoahHeap::is_uncommit_in_progress() {
2739   if (_uncommit_thread != nullptr) {
2740     return _uncommit_thread->is_uncommit_in_progress();
2741   }
2742   return false;
2743 }
2744 #endif
2745 
2746 void ShenandoahHeap::safepoint_synchronize_begin() {
2747   StackWatermarkSet::safepoint_synchronize_begin();
2748   SuspendibleThreadSet::synchronize();
2749 }
2750 
2751 void ShenandoahHeap::safepoint_synchronize_end() {
2752   SuspendibleThreadSet::desynchronize();
2753 }
2754 
2755 void ShenandoahHeap::try_inject_alloc_failure() {
2756   if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2757     _inject_alloc_failure.set();
2758     os::naked_short_sleep(1);
2759     if (cancelled_gc()) {
2760       log_info(gc)("Allocation failure was successfully injected");
2761     }
2762   }
2763 }
2764 
2765 bool ShenandoahHeap::should_inject_alloc_failure() {
2766   return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2767 }
2768 
2769 void ShenandoahHeap::initialize_serviceability() {
2770   _memory_pool = new ShenandoahMemoryPool(this);
2771   _cycle_memory_manager.add_pool(_memory_pool);
2772   _stw_memory_manager.add_pool(_memory_pool);
2773 }
2774 
2775 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2776   GrowableArray<GCMemoryManager*> memory_managers(2);
2777   memory_managers.append(&_cycle_memory_manager);
2778   memory_managers.append(&_stw_memory_manager);
2779   return memory_managers;
2780 }
2781 
2782 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2783   GrowableArray<MemoryPool*> memory_pools(1);
2784   memory_pools.append(_memory_pool);
2785   return memory_pools;
2786 }
2787 
2788 MemoryUsage ShenandoahHeap::memory_usage() {
2789   return shenandoah_memory_usage(_initial_size, used(), committed(), max_capacity());
2790 }
2791 
2792 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2793   _heap(ShenandoahHeap::heap()),
2794   _index(0) {}
2795 
2796 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2797   _heap(heap),
2798   _index(0) {}
2799 
2800 void ShenandoahRegionIterator::reset() {
2801   _index.store_relaxed(0);
2802 }
2803 
2804 bool ShenandoahRegionIterator::has_next() const {
2805   return _index.load_relaxed() < _heap->num_regions();
2806 }
2807 
2808 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2809 #ifdef ASSERT
2810   assert(_liveness_cache != nullptr, "sanity");
2811   assert(worker_id < _max_workers, "sanity");
2812   for (uint i = 0; i < num_regions(); i++) {
2813     assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2814   }
2815 #endif
2816   return _liveness_cache[worker_id];
2817 }
2818 
2819 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2820   assert(worker_id < _max_workers, "sanity");
2821   assert(_liveness_cache != nullptr, "sanity");
2822   ShenandoahLiveData* ld = _liveness_cache[worker_id];
2823   for (uint i = 0; i < num_regions(); i++) {
2824     ShenandoahLiveData live = ld[i];
2825     if (live > 0) {
2826       ShenandoahHeapRegion* r = get_region(i);
2827       r->increase_live_data_gc_words(live);
2828       ld[i] = 0;
2829     }
2830   }
2831 }
2832 
2833 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2834   if (is_idle()) return false;
2835 
2836   // Objects allocated after marking start are implicitly alive, don't need any barriers during
2837   // marking phase.
2838   if (is_concurrent_mark_in_progress() &&
2839      !marking_context()->allocated_after_mark_start(obj)) {
2840     return true;
2841   }
2842 
2843   // Can not guarantee obj is deeply good.
2844   if (has_forwarded_objects()) {
2845     return true;
2846   }
2847 
2848   return false;
2849 }
2850 
2851 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2852 #if INCLUDE_CDS_JAVA_HEAP
2853   // CDS wants a raw continuous memory range to load a bunch of objects itself.
2854   // This is an unusual request, since all requested regions should be regular, not humongous.
2855   //
2856   // CDS would guarantee no objects straddle multiple regions, as long as regions are as large
2857   // as MIN_GC_REGION_ALIGNMENT.
2858   guarantee(ShenandoahHeapRegion::region_size_bytes() >= AOTMappedHeapWriter::MIN_GC_REGION_ALIGNMENT, "Must be");
2859 
2860   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_cds(size);
2861   return allocate_memory(req);
2862 #else
2863   assert(false, "Archive heap loader should not be available, should not be here");
2864   return nullptr;
2865 #endif // INCLUDE_CDS_JAVA_HEAP
2866 }
2867 
2868 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2869   // Nothing to do here, except checking that heap looks fine.
2870 #ifdef ASSERT
2871   HeapWord* start = archive_space.start();
2872   HeapWord* end = archive_space.end();
2873 
2874   // No unclaimed space between the objects.
2875   // Objects are properly allocated in correct regions.
2876   HeapWord* cur = start;
2877   while (cur < end) {
2878     oop oop = cast_to_oop(cur);
2879     shenandoah_assert_in_correct_region(nullptr, oop);
2880     cur += oop->size();
2881   }
2882 
2883   // No unclaimed tail at the end of archive space.
2884   assert(cur == end,
2885          "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2886          p2i(cur), p2i(end));
2887 
2888   // All regions in contiguous space have good state.
2889   size_t begin_reg_idx = heap_region_index_containing(start);
2890   size_t end_reg_idx   = heap_region_index_containing(end);
2891 
2892   for (size_t idx = begin_reg_idx; idx <= end_reg_idx; idx++) {
2893     ShenandoahHeapRegion* r = get_region(idx);
2894     assert(r->is_regular(), "Must be regular");
2895     assert(r->is_young(), "Must be young");
2896     assert(idx == end_reg_idx || r->top() == r->end(),
2897            "All regions except the last one should be full: " PTR_FORMAT " " PTR_FORMAT,
2898            p2i(r->top()), p2i(r->end()));
2899     assert(idx != begin_reg_idx || r->bottom() == start,
2900            "Archive space start should be at the bottom of first region: " PTR_FORMAT " " PTR_FORMAT,
2901            p2i(r->bottom()), p2i(start));
2902     assert(idx != end_reg_idx || r->top() == end,
2903            "Archive space end should be at the top of last region: " PTR_FORMAT " " PTR_FORMAT,
2904            p2i(r->top()), p2i(end));
2905   }
2906 
2907 #endif
2908 }
2909 
2910 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
2911   if (!mode()->is_generational()) {
2912     return global_generation();
2913   } else if (affiliation == YOUNG_GENERATION) {
2914     return young_generation();
2915   } else if (affiliation == OLD_GENERATION) {
2916     return old_generation();
2917   }
2918 
2919   ShouldNotReachHere();
2920   return nullptr;
2921 }
2922 
2923 void ShenandoahHeap::log_heap_status(const char* msg) const {
2924   if (mode()->is_generational()) {
2925     young_generation()->log_status(msg);
2926     old_generation()->log_status(msg);
2927   } else {
2928     global_generation()->log_status(msg);
2929   }
2930 }
2931 
2932 ShenandoahHeapLocker::ShenandoahHeapLocker(ShenandoahHeapLock* lock, bool allow_block_for_safepoint) : _lock(lock) {
2933 #ifdef ASSERT
2934   ShenandoahFreeSet* free_set = ShenandoahHeap::heap()->free_set();
2935   // free_set is nullptr only at pre-initialized state
2936   assert(free_set == nullptr || !free_set->rebuild_lock()->owned_by_self(), "Dead lock, can't acquire heap lock while holding free-set rebuild lock");
2937   assert(_lock != nullptr, "Must not");
2938 #endif
2939   _lock->lock(allow_block_for_safepoint);
2940 }
--- EOF ---