1 /*
   2  * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
   3  * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This code is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 only, as
   8  * published by the Free Software Foundation.
   9  *
  10  * This code is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * version 2 for more details (a copy is included in the LICENSE file that
  14  * accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License version
  17  * 2 along with this work; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19  *
  20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  21  * or visit www.oracle.com if you need additional information or have any
  22  * questions.
  23  *
  24  */
  25 
  26 #include "precompiled.hpp"
  27 #include "memory/allocation.hpp"
  28 #include "memory/universe.hpp"
  29 
  30 #include "gc/shared/gcArguments.hpp"
  31 #include "gc/shared/gcTimer.hpp"
  32 #include "gc/shared/gcTraceTime.inline.hpp"
  33 #include "gc/shared/locationPrinter.inline.hpp"
  34 #include "gc/shared/memAllocator.hpp"
  35 #include "gc/shared/plab.hpp"
  36 #include "gc/shared/slidingForwarding.hpp"
  37 #include "gc/shared/tlab_globals.hpp"
  38 
  39 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
  40 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
  41 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
  42 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
  43 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
  44 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
  45 #include "gc/shenandoah/shenandoahControlThread.hpp"
  46 #include "gc/shenandoah/shenandoahFreeSet.hpp"
  47 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
  48 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
  49 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
  50 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
  51 #include "gc/shenandoah/shenandoahInitLogger.hpp"
  52 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
  53 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
  54 #include "gc/shenandoah/shenandoahMetrics.hpp"
  55 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
  56 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
  57 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
  58 #include "gc/shenandoah/shenandoahPadding.hpp"
  59 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
  60 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
  61 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
  62 #include "gc/shenandoah/shenandoahSTWMark.hpp"
  63 #include "gc/shenandoah/shenandoahUtils.hpp"
  64 #include "gc/shenandoah/shenandoahVerifier.hpp"
  65 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
  66 #include "gc/shenandoah/shenandoahVMOperations.hpp"
  67 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
  68 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
  69 #include "gc/shenandoah/mode/shenandoahIUMode.hpp"
  70 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
  71 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
  72 #if INCLUDE_JFR
  73 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
  74 #endif
  75 
  76 #include "classfile/systemDictionary.hpp"
  77 #include "code/codeCache.hpp"
  78 #include "memory/classLoaderMetaspace.hpp"
  79 #include "memory/metaspaceUtils.hpp"
  80 #include "oops/compressedOops.inline.hpp"
  81 #include "prims/jvmtiTagMap.hpp"
  82 #include "runtime/atomic.hpp"
  83 #include "runtime/globals.hpp"
  84 #include "runtime/interfaceSupport.inline.hpp"
  85 #include "runtime/java.hpp"
  86 #include "runtime/orderAccess.hpp"
  87 #include "runtime/safepointMechanism.hpp"
  88 #include "runtime/vmThread.hpp"
  89 #include "services/mallocTracker.hpp"
  90 #include "services/memTracker.hpp"
  91 #include "utilities/events.hpp"
  92 #include "utilities/powerOfTwo.hpp"
  93 
  94 class ShenandoahPretouchHeapTask : public WorkerTask {
  95 private:
  96   ShenandoahRegionIterator _regions;
  97   const size_t _page_size;
  98 public:
  99   ShenandoahPretouchHeapTask(size_t page_size) :
 100     WorkerTask("Shenandoah Pretouch Heap"),
 101     _page_size(page_size) {}
 102 
 103   virtual void work(uint worker_id) {
 104     ShenandoahHeapRegion* r = _regions.next();
 105     while (r != nullptr) {
 106       if (r->is_committed()) {
 107         os::pretouch_memory(r->bottom(), r->end(), _page_size);
 108       }
 109       r = _regions.next();
 110     }
 111   }
 112 };
 113 
 114 class ShenandoahPretouchBitmapTask : public WorkerTask {
 115 private:
 116   ShenandoahRegionIterator _regions;
 117   char* _bitmap_base;
 118   const size_t _bitmap_size;
 119   const size_t _page_size;
 120 public:
 121   ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
 122     WorkerTask("Shenandoah Pretouch Bitmap"),
 123     _bitmap_base(bitmap_base),
 124     _bitmap_size(bitmap_size),
 125     _page_size(page_size) {}
 126 
 127   virtual void work(uint worker_id) {
 128     ShenandoahHeapRegion* r = _regions.next();
 129     while (r != nullptr) {
 130       size_t start = r->index()       * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 131       size_t end   = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 132       assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
 133 
 134       if (r->is_committed()) {
 135         os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
 136       }
 137 
 138       r = _regions.next();
 139     }
 140   }
 141 };
 142 
 143 jint ShenandoahHeap::initialize() {
 144   //
 145   // Figure out heap sizing
 146   //
 147 
 148   size_t init_byte_size = InitialHeapSize;
 149   size_t min_byte_size  = MinHeapSize;
 150   size_t max_byte_size  = MaxHeapSize;
 151   size_t heap_alignment = HeapAlignment;
 152 
 153   size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
 154 
 155   Universe::check_alignment(max_byte_size,  reg_size_bytes, "Shenandoah heap");
 156   Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
 157 
 158   _num_regions = ShenandoahHeapRegion::region_count();
 159   assert(_num_regions == (max_byte_size / reg_size_bytes),
 160          "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
 161          _num_regions, max_byte_size, reg_size_bytes);
 162 
 163   // Now we know the number of regions, initialize the heuristics.
 164   initialize_heuristics();
 165 
 166   size_t num_committed_regions = init_byte_size / reg_size_bytes;
 167   num_committed_regions = MIN2(num_committed_regions, _num_regions);
 168   assert(num_committed_regions <= _num_regions, "sanity");
 169   _initial_size = num_committed_regions * reg_size_bytes;
 170 
 171   size_t num_min_regions = min_byte_size / reg_size_bytes;
 172   num_min_regions = MIN2(num_min_regions, _num_regions);
 173   assert(num_min_regions <= _num_regions, "sanity");
 174   _minimum_size = num_min_regions * reg_size_bytes;
 175 
 176   // Default to max heap size.
 177   _soft_max_size = _num_regions * reg_size_bytes;
 178 
 179   _committed = _initial_size;
 180 
 181   size_t heap_page_size   = UseLargePages ? os::large_page_size() : os::vm_page_size();
 182   size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
 183   size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
 184 
 185   //
 186   // Reserve and commit memory for heap
 187   //
 188 
 189   ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
 190   initialize_reserved_region(heap_rs);
 191   _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
 192   _heap_region_special = heap_rs.special();
 193 
 194   assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
 195          "Misaligned heap: " PTR_FORMAT, p2i(base()));
 196 
 197 #if SHENANDOAH_OPTIMIZED_MARKTASK
 198   // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
 199   // Fail if we ever attempt to address more than we can.
 200   if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
 201     FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
 202                           "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
 203                           "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
 204                 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
 205     vm_exit_during_initialization("Fatal Error", buf);
 206   }
 207 #endif
 208 
 209   ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
 210   if (!_heap_region_special) {
 211     os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
 212                               "Cannot commit heap memory");
 213   }
 214 
 215   //
 216   // Reserve and commit memory for bitmap(s)
 217   //
 218 
 219   _bitmap_size = ShenandoahMarkBitMap::compute_size(heap_rs.size());
 220   _bitmap_size = align_up(_bitmap_size, bitmap_page_size);
 221 
 222   size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
 223 
 224   guarantee(bitmap_bytes_per_region != 0,
 225             "Bitmap bytes per region should not be zero");
 226   guarantee(is_power_of_2(bitmap_bytes_per_region),
 227             "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
 228 
 229   if (bitmap_page_size > bitmap_bytes_per_region) {
 230     _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
 231     _bitmap_bytes_per_slice = bitmap_page_size;
 232   } else {
 233     _bitmap_regions_per_slice = 1;
 234     _bitmap_bytes_per_slice = bitmap_bytes_per_region;
 235   }
 236 
 237   guarantee(_bitmap_regions_per_slice >= 1,
 238             "Should have at least one region per slice: " SIZE_FORMAT,
 239             _bitmap_regions_per_slice);
 240 
 241   guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
 242             "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
 243             _bitmap_bytes_per_slice, bitmap_page_size);
 244 
 245   ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
 246   MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
 247   _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
 248   _bitmap_region_special = bitmap.special();
 249 
 250   size_t bitmap_init_commit = _bitmap_bytes_per_slice *
 251                               align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
 252   bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
 253   if (!_bitmap_region_special) {
 254     os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
 255                               "Cannot commit bitmap memory");
 256   }
 257 
 258   _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions, _max_workers);
 259 
 260   if (ShenandoahVerify) {
 261     ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
 262     if (!verify_bitmap.special()) {
 263       os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
 264                                 "Cannot commit verification bitmap memory");
 265     }
 266     MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
 267     MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
 268     _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
 269     _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
 270   }
 271 
 272   // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
 273   ReservedSpace aux_bitmap(_bitmap_size, bitmap_page_size);
 274   MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
 275   _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
 276   _aux_bitmap_region_special = aux_bitmap.special();
 277   _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
 278 
 279   //
 280   // Create regions and region sets
 281   //
 282   size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
 283   size_t region_storage_size = align_up(region_align * _num_regions, region_page_size);
 284   region_storage_size = align_up(region_storage_size, os::vm_allocation_granularity());
 285 
 286   ReservedSpace region_storage(region_storage_size, region_page_size);
 287   MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
 288   if (!region_storage.special()) {
 289     os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
 290                               "Cannot commit region memory");
 291   }
 292 
 293   // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
 294   // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
 295   // If not successful, bite a bullet and allocate at whatever address.
 296   {
 297     size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
 298     size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
 299 
 300     uintptr_t min = round_up_power_of_2(cset_align);
 301     uintptr_t max = (1u << 30u);
 302 
 303     for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
 304       char* req_addr = (char*)addr;
 305       assert(is_aligned(req_addr, cset_align), "Should be aligned");
 306       ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size(), req_addr);
 307       if (cset_rs.is_reserved()) {
 308         assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
 309         _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
 310         break;
 311       }
 312     }
 313 
 314     if (_collection_set == nullptr) {
 315       ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size());
 316       _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
 317     }
 318   }
 319 
 320   _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
 321   _free_set = new ShenandoahFreeSet(this, _num_regions);
 322 
 323   {
 324     ShenandoahHeapLocker locker(lock());
 325 
 326     for (size_t i = 0; i < _num_regions; i++) {
 327       HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
 328       bool is_committed = i < num_committed_regions;
 329       void* loc = region_storage.base() + i * region_align;
 330 
 331       ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
 332       assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
 333 
 334       _marking_context->initialize_top_at_mark_start(r);
 335       _regions[i] = r;
 336       assert(!collection_set()->is_in(i), "New region should not be in collection set");
 337     }
 338 
 339     // Initialize to complete
 340     _marking_context->mark_complete();
 341 
 342     _free_set->rebuild();
 343   }
 344 
 345   if (AlwaysPreTouch) {
 346     // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
 347     // before initialize() below zeroes it with initializing thread. For any given region,
 348     // we touch the region and the corresponding bitmaps from the same thread.
 349     ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
 350 
 351     _pretouch_heap_page_size = heap_page_size;
 352     _pretouch_bitmap_page_size = bitmap_page_size;
 353 
 354 #ifdef LINUX
 355     // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
 356     // pages. But, the kernel needs to know that every small page is used, in order to coalesce
 357     // them into huge one. Therefore, we need to pretouch with smaller pages.
 358     if (UseTransparentHugePages) {
 359       _pretouch_heap_page_size = (size_t)os::vm_page_size();
 360       _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
 361     }
 362 #endif
 363 
 364     // OS memory managers may want to coalesce back-to-back pages. Make their jobs
 365     // simpler by pre-touching continuous spaces (heap and bitmap) separately.
 366 
 367     ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
 368     _workers->run_task(&bcl);
 369 
 370     ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
 371     _workers->run_task(&hcl);
 372   }
 373 
 374   //
 375   // Initialize the rest of GC subsystems
 376   //
 377 
 378   _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
 379   for (uint worker = 0; worker < _max_workers; worker++) {
 380     _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
 381     Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
 382   }
 383 
 384   // There should probably be Shenandoah-specific options for these,
 385   // just as there are G1-specific options.
 386   {
 387     ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
 388     satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
 389     satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
 390   }
 391 
 392   _monitoring_support = new ShenandoahMonitoringSupport(this);
 393   _phase_timings = new ShenandoahPhaseTimings(max_workers());
 394   ShenandoahCodeRoots::initialize();
 395 
 396   if (ShenandoahPacing) {
 397     _pacer = new ShenandoahPacer(this);
 398     _pacer->setup_for_idle();
 399   } else {
 400     _pacer = nullptr;
 401   }
 402 
 403   _control_thread = new ShenandoahControlThread();
 404 
 405   ShenandoahInitLogger::print();
 406 
 407   SlidingForwarding::initialize(_heap_region, ShenandoahHeapRegion::region_size_words());
 408 
 409   return JNI_OK;
 410 }
 411 
 412 void ShenandoahHeap::initialize_mode() {
 413   if (ShenandoahGCMode != nullptr) {
 414     if (strcmp(ShenandoahGCMode, "satb") == 0) {
 415       _gc_mode = new ShenandoahSATBMode();
 416     } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
 417       _gc_mode = new ShenandoahIUMode();
 418     } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
 419       _gc_mode = new ShenandoahPassiveMode();
 420     } else {
 421       vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
 422     }
 423   } else {
 424     vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
 425   }
 426   _gc_mode->initialize_flags();
 427   if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
 428     vm_exit_during_initialization(
 429             err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
 430                     _gc_mode->name()));
 431   }
 432   if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
 433     vm_exit_during_initialization(
 434             err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
 435                     _gc_mode->name()));
 436   }
 437 }
 438 
 439 void ShenandoahHeap::initialize_heuristics() {
 440   assert(_gc_mode != nullptr, "Must be initialized");
 441   _heuristics = _gc_mode->initialize_heuristics();
 442 
 443   if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
 444     vm_exit_during_initialization(
 445             err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
 446                     _heuristics->name()));
 447   }
 448   if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
 449     vm_exit_during_initialization(
 450             err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
 451                     _heuristics->name()));
 452   }
 453 }
 454 
 455 #ifdef _MSC_VER
 456 #pragma warning( push )
 457 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 458 #endif
 459 
 460 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
 461   CollectedHeap(),
 462   _initial_size(0),
 463   _used(0),
 464   _committed(0),
 465   _bytes_allocated_since_gc_start(0),
 466   _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
 467   _workers(nullptr),
 468   _safepoint_workers(nullptr),
 469   _heap_region_special(false),
 470   _num_regions(0),
 471   _regions(nullptr),
 472   _update_refs_iterator(this),
 473   _control_thread(nullptr),
 474   _shenandoah_policy(policy),
 475   _gc_mode(nullptr),
 476   _heuristics(nullptr),
 477   _free_set(nullptr),
 478   _pacer(nullptr),
 479   _verifier(nullptr),
 480   _phase_timings(nullptr),
 481   _monitoring_support(nullptr),
 482   _memory_pool(nullptr),
 483   _stw_memory_manager("Shenandoah Pauses"),
 484   _cycle_memory_manager("Shenandoah Cycles"),
 485   _gc_timer(new ConcurrentGCTimer()),
 486   _soft_ref_policy(),
 487   _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
 488   _ref_processor(new ShenandoahReferenceProcessor(MAX2(_max_workers, 1U))),
 489   _marking_context(nullptr),
 490   _bitmap_size(0),
 491   _bitmap_regions_per_slice(0),
 492   _bitmap_bytes_per_slice(0),
 493   _bitmap_region_special(false),
 494   _aux_bitmap_region_special(false),
 495   _liveness_cache(nullptr),
 496   _collection_set(nullptr)
 497 {
 498   // Initialize GC mode early, so we can adjust barrier support
 499   initialize_mode();
 500   BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
 501 
 502   _max_workers = MAX2(_max_workers, 1U);
 503   _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
 504   if (_workers == nullptr) {
 505     vm_exit_during_initialization("Failed necessary allocation.");
 506   } else {
 507     _workers->initialize_workers();
 508   }
 509 
 510   if (ParallelGCThreads > 1) {
 511     _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread",
 512                                                 ParallelGCThreads);
 513     _safepoint_workers->initialize_workers();
 514   }
 515 }
 516 
 517 #ifdef _MSC_VER
 518 #pragma warning( pop )
 519 #endif
 520 
 521 class ShenandoahResetBitmapTask : public WorkerTask {
 522 private:
 523   ShenandoahRegionIterator _regions;
 524 
 525 public:
 526   ShenandoahResetBitmapTask() :
 527     WorkerTask("Shenandoah Reset Bitmap") {}
 528 
 529   void work(uint worker_id) {
 530     ShenandoahHeapRegion* region = _regions.next();
 531     ShenandoahHeap* heap = ShenandoahHeap::heap();
 532     ShenandoahMarkingContext* const ctx = heap->marking_context();
 533     while (region != nullptr) {
 534       if (heap->is_bitmap_slice_committed(region)) {
 535         ctx->clear_bitmap(region);
 536       }
 537       region = _regions.next();
 538     }
 539   }
 540 };
 541 
 542 void ShenandoahHeap::reset_mark_bitmap() {
 543   assert_gc_workers(_workers->active_workers());
 544   mark_incomplete_marking_context();
 545 
 546   ShenandoahResetBitmapTask task;
 547   _workers->run_task(&task);
 548 }
 549 
 550 void ShenandoahHeap::print_on(outputStream* st) const {
 551   st->print_cr("Shenandoah Heap");
 552   st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
 553                byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
 554                byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
 555                byte_size_in_proper_unit(committed()),    proper_unit_for_byte_size(committed()),
 556                byte_size_in_proper_unit(used()),         proper_unit_for_byte_size(used()));
 557   st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
 558                num_regions(),
 559                byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
 560                proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
 561 
 562   st->print("Status: ");
 563   if (has_forwarded_objects())                 st->print("has forwarded objects, ");
 564   if (is_concurrent_mark_in_progress())        st->print("marking, ");
 565   if (is_evacuation_in_progress())             st->print("evacuating, ");
 566   if (is_update_refs_in_progress())            st->print("updating refs, ");
 567   if (is_degenerated_gc_in_progress())         st->print("degenerated gc, ");
 568   if (is_full_gc_in_progress())                st->print("full gc, ");
 569   if (is_full_gc_move_in_progress())           st->print("full gc move, ");
 570   if (is_concurrent_weak_root_in_progress())   st->print("concurrent weak roots, ");
 571   if (is_concurrent_strong_root_in_progress() &&
 572       !is_concurrent_weak_root_in_progress())  st->print("concurrent strong roots, ");
 573 
 574   if (cancelled_gc()) {
 575     st->print("cancelled");
 576   } else {
 577     st->print("not cancelled");
 578   }
 579   st->cr();
 580 
 581   st->print_cr("Reserved region:");
 582   st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
 583                p2i(reserved_region().start()),
 584                p2i(reserved_region().end()));
 585 
 586   ShenandoahCollectionSet* cset = collection_set();
 587   st->print_cr("Collection set:");
 588   if (cset != nullptr) {
 589     st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
 590     st->print_cr(" - map (biased):  " PTR_FORMAT, p2i(cset->biased_map_address()));
 591   } else {
 592     st->print_cr(" (null)");
 593   }
 594 
 595   st->cr();
 596   MetaspaceUtils::print_on(st);
 597 
 598   if (Verbose) {
 599     st->cr();
 600     print_heap_regions_on(st);
 601   }
 602 }
 603 
 604 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
 605 public:
 606   void do_thread(Thread* thread) {
 607     assert(thread != nullptr, "Sanity");
 608     assert(thread->is_Worker_thread(), "Only worker thread expected");
 609     ShenandoahThreadLocalData::initialize_gclab(thread);
 610   }
 611 };
 612 
 613 void ShenandoahHeap::post_initialize() {
 614   CollectedHeap::post_initialize();
 615   MutexLocker ml(Threads_lock);
 616 
 617   ShenandoahInitWorkerGCLABClosure init_gclabs;
 618   _workers->threads_do(&init_gclabs);
 619 
 620   // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
 621   // Now, we will let WorkerThreads to initialize gclab when new worker is created.
 622   _workers->set_initialize_gclab();
 623   if (_safepoint_workers != nullptr) {
 624     _safepoint_workers->threads_do(&init_gclabs);
 625     _safepoint_workers->set_initialize_gclab();
 626   }
 627 
 628   _heuristics->initialize();
 629 
 630   JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
 631 }
 632 
 633 size_t ShenandoahHeap::used() const {
 634   return Atomic::load(&_used);
 635 }
 636 
 637 size_t ShenandoahHeap::committed() const {
 638   return Atomic::load(&_committed);
 639 }
 640 
 641 void ShenandoahHeap::increase_committed(size_t bytes) {
 642   shenandoah_assert_heaplocked_or_safepoint();
 643   _committed += bytes;
 644 }
 645 
 646 void ShenandoahHeap::decrease_committed(size_t bytes) {
 647   shenandoah_assert_heaplocked_or_safepoint();
 648   _committed -= bytes;
 649 }
 650 
 651 void ShenandoahHeap::increase_used(size_t bytes) {
 652   Atomic::add(&_used, bytes, memory_order_relaxed);
 653 }
 654 
 655 void ShenandoahHeap::set_used(size_t bytes) {
 656   Atomic::store(&_used, bytes);
 657 }
 658 
 659 void ShenandoahHeap::decrease_used(size_t bytes) {
 660   assert(used() >= bytes, "never decrease heap size by more than we've left");
 661   Atomic::sub(&_used, bytes, memory_order_relaxed);
 662 }
 663 
 664 void ShenandoahHeap::increase_allocated(size_t bytes) {
 665   Atomic::add(&_bytes_allocated_since_gc_start, bytes, memory_order_relaxed);
 666 }
 667 
 668 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
 669   size_t bytes = words * HeapWordSize;
 670   if (!waste) {
 671     increase_used(bytes);
 672   }
 673   increase_allocated(bytes);
 674   if (ShenandoahPacing) {
 675     control_thread()->pacing_notify_alloc(words);
 676     if (waste) {
 677       pacer()->claim_for_alloc(words, true);
 678     }
 679   }
 680 }
 681 
 682 size_t ShenandoahHeap::capacity() const {
 683   return committed();
 684 }
 685 
 686 size_t ShenandoahHeap::max_capacity() const {
 687   return _num_regions * ShenandoahHeapRegion::region_size_bytes();
 688 }
 689 
 690 size_t ShenandoahHeap::soft_max_capacity() const {
 691   size_t v = Atomic::load(&_soft_max_size);
 692   assert(min_capacity() <= v && v <= max_capacity(),
 693          "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
 694          min_capacity(), v, max_capacity());
 695   return v;
 696 }
 697 
 698 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
 699   assert(min_capacity() <= v && v <= max_capacity(),
 700          "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
 701          min_capacity(), v, max_capacity());
 702   Atomic::store(&_soft_max_size, v);
 703 }
 704 
 705 size_t ShenandoahHeap::min_capacity() const {
 706   return _minimum_size;
 707 }
 708 
 709 size_t ShenandoahHeap::initial_capacity() const {
 710   return _initial_size;
 711 }
 712 
 713 bool ShenandoahHeap::is_in(const void* p) const {
 714   HeapWord* heap_base = (HeapWord*) base();
 715   HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
 716   return p >= heap_base && p < last_region_end;
 717 }
 718 
 719 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
 720   assert (ShenandoahUncommit, "should be enabled");
 721 
 722   // Application allocates from the beginning of the heap, and GC allocates at
 723   // the end of it. It is more efficient to uncommit from the end, so that applications
 724   // could enjoy the near committed regions. GC allocations are much less frequent,
 725   // and therefore can accept the committing costs.
 726 
 727   size_t count = 0;
 728   for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
 729     ShenandoahHeapRegion* r = get_region(i - 1);
 730     if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
 731       ShenandoahHeapLocker locker(lock());
 732       if (r->is_empty_committed()) {
 733         if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
 734           break;
 735         }
 736 
 737         r->make_uncommitted();
 738         count++;
 739       }
 740     }
 741     SpinPause(); // allow allocators to take the lock
 742   }
 743 
 744   if (count > 0) {
 745     control_thread()->notify_heap_changed();
 746   }
 747 }
 748 
 749 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
 750   // New object should fit the GCLAB size
 751   size_t min_size = MAX2(size, PLAB::min_size());
 752 
 753   // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
 754   size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
 755   new_size = MIN2(new_size, PLAB::max_size());
 756   new_size = MAX2(new_size, PLAB::min_size());
 757 
 758   // Record new heuristic value even if we take any shortcut. This captures
 759   // the case when moderately-sized objects always take a shortcut. At some point,
 760   // heuristics should catch up with them.
 761   ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
 762 
 763   if (new_size < size) {
 764     // New size still does not fit the object. Fall back to shared allocation.
 765     // This avoids retiring perfectly good GCLABs, when we encounter a large object.
 766     return nullptr;
 767   }
 768 
 769   // Retire current GCLAB, and allocate a new one.
 770   PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
 771   gclab->retire();
 772 
 773   size_t actual_size = 0;
 774   HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
 775   if (gclab_buf == nullptr) {
 776     return nullptr;
 777   }
 778 
 779   assert (size <= actual_size, "allocation should fit");
 780 
 781   if (ZeroTLAB) {
 782     // ..and clear it.
 783     Copy::zero_to_words(gclab_buf, actual_size);
 784   } else {
 785     // ...and zap just allocated object.
 786 #ifdef ASSERT
 787     // Skip mangling the space corresponding to the object header to
 788     // ensure that the returned space is not considered parsable by
 789     // any concurrent GC thread.
 790     size_t hdr_size = oopDesc::header_size();
 791     Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
 792 #endif // ASSERT
 793   }
 794   gclab->set_buf(gclab_buf, actual_size);
 795   return gclab->allocate(size);
 796 }
 797 
 798 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
 799                                             size_t requested_size,
 800                                             size_t* actual_size) {
 801   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
 802   HeapWord* res = allocate_memory(req);
 803   if (res != nullptr) {
 804     *actual_size = req.actual_size();
 805   } else {
 806     *actual_size = 0;
 807   }
 808   return res;
 809 }
 810 
 811 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
 812                                              size_t word_size,
 813                                              size_t* actual_size) {
 814   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
 815   HeapWord* res = allocate_memory(req);
 816   if (res != nullptr) {
 817     *actual_size = req.actual_size();
 818   } else {
 819     *actual_size = 0;
 820   }
 821   return res;
 822 }
 823 
 824 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
 825   intptr_t pacer_epoch = 0;
 826   bool in_new_region = false;
 827   HeapWord* result = nullptr;
 828 
 829   if (req.is_mutator_alloc()) {
 830     if (ShenandoahPacing) {
 831       pacer()->pace_for_alloc(req.size());
 832       pacer_epoch = pacer()->epoch();
 833     }
 834 
 835     if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
 836       result = allocate_memory_under_lock(req, in_new_region);
 837     }
 838 
 839     // Allocation failed, block until control thread reacted, then retry allocation.
 840     //
 841     // It might happen that one of the threads requesting allocation would unblock
 842     // way later after GC happened, only to fail the second allocation, because
 843     // other threads have already depleted the free storage. In this case, a better
 844     // strategy is to try again, as long as GC makes progress.
 845     //
 846     // Then, we need to make sure the allocation was retried after at least one
 847     // Full GC, which means we want to try more than ShenandoahFullGCThreshold times.
 848 
 849     size_t tries = 0;
 850 
 851     while (result == nullptr && _progress_last_gc.is_set()) {
 852       tries++;
 853       control_thread()->handle_alloc_failure(req);
 854       result = allocate_memory_under_lock(req, in_new_region);
 855     }
 856 
 857     while (result == nullptr && tries <= ShenandoahFullGCThreshold) {
 858       tries++;
 859       control_thread()->handle_alloc_failure(req);
 860       result = allocate_memory_under_lock(req, in_new_region);
 861     }
 862 
 863   } else {
 864     assert(req.is_gc_alloc(), "Can only accept GC allocs here");
 865     result = allocate_memory_under_lock(req, in_new_region);
 866     // Do not call handle_alloc_failure() here, because we cannot block.
 867     // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
 868   }
 869 
 870   if (in_new_region) {
 871     control_thread()->notify_heap_changed();
 872   }
 873 
 874   if (result != nullptr) {
 875     size_t requested = req.size();
 876     size_t actual = req.actual_size();
 877 
 878     assert (req.is_lab_alloc() || (requested == actual),
 879             "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
 880             ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
 881 
 882     if (req.is_mutator_alloc()) {
 883       notify_mutator_alloc_words(actual, false);
 884 
 885       // If we requested more than we were granted, give the rest back to pacer.
 886       // This only matters if we are in the same pacing epoch: do not try to unpace
 887       // over the budget for the other phase.
 888       if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
 889         pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
 890       }
 891     } else {
 892       increase_used(actual*HeapWordSize);
 893     }
 894   }
 895 
 896   return result;
 897 }
 898 
 899 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
 900   ShenandoahHeapLocker locker(lock());
 901   return _free_set->allocate(req, in_new_region);
 902 }
 903 
 904 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
 905                                         bool*  gc_overhead_limit_was_exceeded) {
 906   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
 907   return allocate_memory(req);
 908 }
 909 
 910 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
 911                                                              size_t size,
 912                                                              Metaspace::MetadataType mdtype) {
 913   MetaWord* result;
 914 
 915   // Inform metaspace OOM to GC heuristics if class unloading is possible.
 916   if (heuristics()->can_unload_classes()) {
 917     ShenandoahHeuristics* h = heuristics();
 918     h->record_metaspace_oom();
 919   }
 920 
 921   // Expand and retry allocation
 922   result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
 923   if (result != nullptr) {
 924     return result;
 925   }
 926 
 927   // Start full GC
 928   collect(GCCause::_metadata_GC_clear_soft_refs);
 929 
 930   // Retry allocation
 931   result = loader_data->metaspace_non_null()->allocate(size, mdtype);
 932   if (result != nullptr) {
 933     return result;
 934   }
 935 
 936   // Expand and retry allocation
 937   result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
 938   if (result != nullptr) {
 939     return result;
 940   }
 941 
 942   // Out of memory
 943   return nullptr;
 944 }
 945 
 946 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
 947 private:
 948   ShenandoahHeap* const _heap;
 949   Thread* const _thread;
 950 public:
 951   ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
 952     _heap(heap), _thread(Thread::current()) {}
 953 
 954   void do_object(oop p) {
 955     shenandoah_assert_marked(nullptr, p);
 956     if (!p->is_forwarded()) {
 957       _heap->evacuate_object(p, _thread);
 958     }
 959   }
 960 };
 961 
 962 class ShenandoahEvacuationTask : public WorkerTask {
 963 private:
 964   ShenandoahHeap* const _sh;
 965   ShenandoahCollectionSet* const _cs;
 966   bool _concurrent;
 967 public:
 968   ShenandoahEvacuationTask(ShenandoahHeap* sh,
 969                            ShenandoahCollectionSet* cs,
 970                            bool concurrent) :
 971     WorkerTask("Shenandoah Evacuation"),
 972     _sh(sh),
 973     _cs(cs),
 974     _concurrent(concurrent)
 975   {}
 976 
 977   void work(uint worker_id) {
 978     if (_concurrent) {
 979       ShenandoahConcurrentWorkerSession worker_session(worker_id);
 980       ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
 981       ShenandoahEvacOOMScope oom_evac_scope;
 982       do_work();
 983     } else {
 984       ShenandoahParallelWorkerSession worker_session(worker_id);
 985       ShenandoahEvacOOMScope oom_evac_scope;
 986       do_work();
 987     }
 988   }
 989 
 990 private:
 991   void do_work() {
 992     ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
 993     ShenandoahHeapRegion* r;
 994     while ((r =_cs->claim_next()) != nullptr) {
 995       assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
 996       _sh->marked_object_iterate(r, &cl);
 997 
 998       if (ShenandoahPacing) {
 999         _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1000       }
1001 
1002       if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1003         break;
1004       }
1005     }
1006   }
1007 };
1008 
1009 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1010   ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1011   workers()->run_task(&task);
1012 }
1013 
1014 void ShenandoahHeap::trash_cset_regions() {
1015   ShenandoahHeapLocker locker(lock());
1016 
1017   ShenandoahCollectionSet* set = collection_set();
1018   ShenandoahHeapRegion* r;
1019   set->clear_current_index();
1020   while ((r = set->next()) != nullptr) {
1021     r->make_trash();
1022   }
1023   collection_set()->clear();
1024 }
1025 
1026 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1027   st->print_cr("Heap Regions:");
1028   st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1029   st->print_cr("              HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1030   st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1031   st->print_cr("UWM=update watermark, U=used");
1032   st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1033   st->print_cr("S=shared allocs, L=live data");
1034   st->print_cr("CP=critical pins");
1035 
1036   for (size_t i = 0; i < num_regions(); i++) {
1037     get_region(i)->print_on(st);
1038   }
1039 }
1040 
1041 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1042   assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1043 
1044   oop humongous_obj = cast_to_oop(start->bottom());
1045   size_t size = humongous_obj->size();
1046   size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1047   size_t index = start->index() + required_regions - 1;
1048 
1049   assert(!start->has_live(), "liveness must be zero");
1050 
1051   for(size_t i = 0; i < required_regions; i++) {
1052     // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1053     // as it expects that every region belongs to a humongous region starting with a humongous start region.
1054     ShenandoahHeapRegion* region = get_region(index --);
1055 
1056     assert(region->is_humongous(), "expect correct humongous start or continuation");
1057     assert(!region->is_cset(), "Humongous region should not be in collection set");
1058 
1059     region->make_trash_immediate();
1060   }
1061 }
1062 
1063 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1064 public:
1065   ShenandoahCheckCleanGCLABClosure() {}
1066   void do_thread(Thread* thread) {
1067     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1068     assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1069     assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1070   }
1071 };
1072 
1073 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1074 private:
1075   bool const _resize;
1076 public:
1077   ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1078   void do_thread(Thread* thread) {
1079     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1080     assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1081     gclab->retire();
1082     if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1083       ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1084     }
1085   }
1086 };
1087 
1088 void ShenandoahHeap::labs_make_parsable() {
1089   assert(UseTLAB, "Only call with UseTLAB");
1090 
1091   ShenandoahRetireGCLABClosure cl(false);
1092 
1093   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1094     ThreadLocalAllocBuffer& tlab = t->tlab();
1095     tlab.make_parsable();
1096     cl.do_thread(t);
1097   }
1098 
1099   workers()->threads_do(&cl);
1100 }
1101 
1102 void ShenandoahHeap::tlabs_retire(bool resize) {
1103   assert(UseTLAB, "Only call with UseTLAB");
1104   assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1105 
1106   ThreadLocalAllocStats stats;
1107 
1108   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1109     ThreadLocalAllocBuffer& tlab = t->tlab();
1110     tlab.retire(&stats);
1111     if (resize) {
1112       tlab.resize();
1113     }
1114   }
1115 
1116   stats.publish();
1117 
1118 #ifdef ASSERT
1119   ShenandoahCheckCleanGCLABClosure cl;
1120   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1121     cl.do_thread(t);
1122   }
1123   workers()->threads_do(&cl);
1124 #endif
1125 }
1126 
1127 void ShenandoahHeap::gclabs_retire(bool resize) {
1128   assert(UseTLAB, "Only call with UseTLAB");
1129   assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1130 
1131   ShenandoahRetireGCLABClosure cl(resize);
1132   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1133     cl.do_thread(t);
1134   }
1135   workers()->threads_do(&cl);
1136 
1137   if (safepoint_workers() != nullptr) {
1138     safepoint_workers()->threads_do(&cl);
1139   }
1140 }
1141 
1142 // Returns size in bytes
1143 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1144   if (ShenandoahElasticTLAB) {
1145     // With Elastic TLABs, return the max allowed size, and let the allocation path
1146     // figure out the safe size for current allocation.
1147     return ShenandoahHeapRegion::max_tlab_size_bytes();
1148   } else {
1149     return MIN2(_free_set->unsafe_peek_free(), ShenandoahHeapRegion::max_tlab_size_bytes());
1150   }
1151 }
1152 
1153 size_t ShenandoahHeap::max_tlab_size() const {
1154   // Returns size in words
1155   return ShenandoahHeapRegion::max_tlab_size_words();
1156 }
1157 
1158 void ShenandoahHeap::collect(GCCause::Cause cause) {
1159   control_thread()->request_gc(cause);
1160 }
1161 
1162 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1163   //assert(false, "Shouldn't need to do full collections");
1164 }
1165 
1166 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1167   ShenandoahHeapRegion* r = heap_region_containing(addr);
1168   if (r != nullptr) {
1169     return r->block_start(addr);
1170   }
1171   return nullptr;
1172 }
1173 
1174 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1175   ShenandoahHeapRegion* r = heap_region_containing(addr);
1176   return r->block_is_obj(addr);
1177 }
1178 
1179 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1180   return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1181 }
1182 
1183 void ShenandoahHeap::prepare_for_verify() {
1184   if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1185     labs_make_parsable();
1186   }
1187 }
1188 
1189 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1190   tcl->do_thread(_control_thread);
1191   workers()->threads_do(tcl);
1192   if (_safepoint_workers != nullptr) {
1193     _safepoint_workers->threads_do(tcl);
1194   }
1195 }
1196 
1197 void ShenandoahHeap::print_tracing_info() const {
1198   LogTarget(Info, gc, stats) lt;
1199   if (lt.is_enabled()) {
1200     ResourceMark rm;
1201     LogStream ls(lt);
1202 
1203     phase_timings()->print_global_on(&ls);
1204 
1205     ls.cr();
1206     ls.cr();
1207 
1208     shenandoah_policy()->print_gc_stats(&ls);
1209 
1210     ls.cr();
1211     ls.cr();
1212   }
1213 }
1214 
1215 void ShenandoahHeap::verify(VerifyOption vo) {
1216   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1217     if (ShenandoahVerify) {
1218       verifier()->verify_generic(vo);
1219     } else {
1220       // TODO: Consider allocating verification bitmaps on demand,
1221       // and turn this on unconditionally.
1222     }
1223   }
1224 }
1225 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1226   return _free_set->capacity();
1227 }
1228 
1229 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1230 private:
1231   MarkBitMap* _bitmap;
1232   ShenandoahScanObjectStack* _oop_stack;
1233   ShenandoahHeap* const _heap;
1234   ShenandoahMarkingContext* const _marking_context;
1235 
1236   template <class T>
1237   void do_oop_work(T* p) {
1238     T o = RawAccess<>::oop_load(p);
1239     if (!CompressedOops::is_null(o)) {
1240       oop obj = CompressedOops::decode_not_null(o);
1241       if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1242         // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1243         return;
1244       }
1245       obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1246 
1247       assert(oopDesc::is_oop(obj), "must be a valid oop");
1248       if (!_bitmap->is_marked(obj)) {
1249         _bitmap->mark(obj);
1250         _oop_stack->push(obj);
1251       }
1252     }
1253   }
1254 public:
1255   ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1256     _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1257     _marking_context(_heap->marking_context()) {}
1258   void do_oop(oop* p)       { do_oop_work(p); }
1259   void do_oop(narrowOop* p) { do_oop_work(p); }
1260 };
1261 
1262 /*
1263  * This is public API, used in preparation of object_iterate().
1264  * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1265  * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1266  * control, we call SH::tlabs_retire, SH::gclabs_retire.
1267  */
1268 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1269   // No-op.
1270 }
1271 
1272 /*
1273  * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1274  *
1275  * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1276  * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1277  * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1278  * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1279  * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1280  * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1281  * wiped the bitmap in preparation for next marking).
1282  *
1283  * For all those reasons, we implement object iteration as a single marking traversal, reporting
1284  * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1285  * is allowed to report dead objects, but is not required to do so.
1286  */
1287 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1288   // Reset bitmap
1289   if (!prepare_aux_bitmap_for_iteration())
1290     return;
1291 
1292   ShenandoahScanObjectStack oop_stack;
1293   ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1294   // Seed the stack with root scan
1295   scan_roots_for_iteration(&oop_stack, &oops);
1296 
1297   // Work through the oop stack to traverse heap
1298   while (! oop_stack.is_empty()) {
1299     oop obj = oop_stack.pop();
1300     assert(oopDesc::is_oop(obj), "must be a valid oop");
1301     cl->do_object(obj);
1302     obj->oop_iterate(&oops);
1303   }
1304 
1305   assert(oop_stack.is_empty(), "should be empty");
1306   // Reclaim bitmap
1307   reclaim_aux_bitmap_for_iteration();
1308 }
1309 
1310 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1311   assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1312 
1313   if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1314     log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1315     return false;
1316   }
1317   // Reset bitmap
1318   _aux_bit_map.clear();
1319   return true;
1320 }
1321 
1322 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1323   // Process GC roots according to current GC cycle
1324   // This populates the work stack with initial objects
1325   // It is important to relinquish the associated locks before diving
1326   // into heap dumper
1327   uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1328   ShenandoahHeapIterationRootScanner rp(n_workers);
1329   rp.roots_do(oops);
1330 }
1331 
1332 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1333   if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1334     log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1335   }
1336 }
1337 
1338 // Closure for parallelly iterate objects
1339 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1340 private:
1341   MarkBitMap* _bitmap;
1342   ShenandoahObjToScanQueue* _queue;
1343   ShenandoahHeap* const _heap;
1344   ShenandoahMarkingContext* const _marking_context;
1345 
1346   template <class T>
1347   void do_oop_work(T* p) {
1348     T o = RawAccess<>::oop_load(p);
1349     if (!CompressedOops::is_null(o)) {
1350       oop obj = CompressedOops::decode_not_null(o);
1351       if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1352         // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1353         return;
1354       }
1355       obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1356 
1357       assert(oopDesc::is_oop(obj), "Must be a valid oop");
1358       if (_bitmap->par_mark(obj)) {
1359         _queue->push(ShenandoahMarkTask(obj));
1360       }
1361     }
1362   }
1363 public:
1364   ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1365     _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1366     _marking_context(_heap->marking_context()) {}
1367   void do_oop(oop* p)       { do_oop_work(p); }
1368   void do_oop(narrowOop* p) { do_oop_work(p); }
1369 };
1370 
1371 // Object iterator for parallel heap iteraion.
1372 // The root scanning phase happenes in construction as a preparation of
1373 // parallel marking queues.
1374 // Every worker processes it's own marking queue. work-stealing is used
1375 // to balance workload.
1376 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1377 private:
1378   uint                         _num_workers;
1379   bool                         _init_ready;
1380   MarkBitMap*                  _aux_bit_map;
1381   ShenandoahHeap*              _heap;
1382   ShenandoahScanObjectStack    _roots_stack; // global roots stack
1383   ShenandoahObjToScanQueueSet* _task_queues;
1384 public:
1385   ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1386         _num_workers(num_workers),
1387         _init_ready(false),
1388         _aux_bit_map(bitmap),
1389         _heap(ShenandoahHeap::heap()) {
1390     // Initialize bitmap
1391     _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1392     if (!_init_ready) {
1393       return;
1394     }
1395 
1396     ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1397     _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1398 
1399     _init_ready = prepare_worker_queues();
1400   }
1401 
1402   ~ShenandoahParallelObjectIterator() {
1403     // Reclaim bitmap
1404     _heap->reclaim_aux_bitmap_for_iteration();
1405     // Reclaim queue for workers
1406     if (_task_queues!= nullptr) {
1407       for (uint i = 0; i < _num_workers; ++i) {
1408         ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1409         if (q != nullptr) {
1410           delete q;
1411           _task_queues->register_queue(i, nullptr);
1412         }
1413       }
1414       delete _task_queues;
1415       _task_queues = nullptr;
1416     }
1417   }
1418 
1419   virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1420     if (_init_ready) {
1421       object_iterate_parallel(cl, worker_id, _task_queues);
1422     }
1423   }
1424 
1425 private:
1426   // Divide global root_stack into worker queues
1427   bool prepare_worker_queues() {
1428     _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1429     // Initialize queues for every workers
1430     for (uint i = 0; i < _num_workers; ++i) {
1431       ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1432       _task_queues->register_queue(i, task_queue);
1433     }
1434     // Divide roots among the workers. Assume that object referencing distribution
1435     // is related with root kind, use round-robin to make every worker have same chance
1436     // to process every kind of roots
1437     size_t roots_num = _roots_stack.size();
1438     if (roots_num == 0) {
1439       // No work to do
1440       return false;
1441     }
1442 
1443     for (uint j = 0; j < roots_num; j++) {
1444       uint stack_id = j % _num_workers;
1445       oop obj = _roots_stack.pop();
1446       _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1447     }
1448     return true;
1449   }
1450 
1451   void object_iterate_parallel(ObjectClosure* cl,
1452                                uint worker_id,
1453                                ShenandoahObjToScanQueueSet* queue_set) {
1454     assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1455     assert(queue_set != nullptr, "task queue must not be null");
1456 
1457     ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1458     assert(q != nullptr, "object iterate queue must not be null");
1459 
1460     ShenandoahMarkTask t;
1461     ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1462 
1463     // Work through the queue to traverse heap.
1464     // Steal when there is no task in queue.
1465     while (q->pop(t) || queue_set->steal(worker_id, t)) {
1466       oop obj = t.obj();
1467       assert(oopDesc::is_oop(obj), "must be a valid oop");
1468       cl->do_object(obj);
1469       obj->oop_iterate(&oops);
1470     }
1471     assert(q->is_empty(), "should be empty");
1472   }
1473 };
1474 
1475 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1476   return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1477 }
1478 
1479 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1480 void ShenandoahHeap::keep_alive(oop obj) {
1481   if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1482     ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1483   }
1484 }
1485 
1486 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1487   for (size_t i = 0; i < num_regions(); i++) {
1488     ShenandoahHeapRegion* current = get_region(i);
1489     blk->heap_region_do(current);
1490   }
1491 }
1492 
1493 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1494 private:
1495   ShenandoahHeap* const _heap;
1496   ShenandoahHeapRegionClosure* const _blk;
1497 
1498   shenandoah_padding(0);
1499   volatile size_t _index;
1500   shenandoah_padding(1);
1501 
1502 public:
1503   ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1504           WorkerTask("Shenandoah Parallel Region Operation"),
1505           _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1506 
1507   void work(uint worker_id) {
1508     ShenandoahParallelWorkerSession worker_session(worker_id);
1509     size_t stride = ShenandoahParallelRegionStride;
1510 
1511     size_t max = _heap->num_regions();
1512     while (Atomic::load(&_index) < max) {
1513       size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1514       size_t start = cur;
1515       size_t end = MIN2(cur + stride, max);
1516       if (start >= max) break;
1517 
1518       for (size_t i = cur; i < end; i++) {
1519         ShenandoahHeapRegion* current = _heap->get_region(i);
1520         _blk->heap_region_do(current);
1521       }
1522     }
1523   }
1524 };
1525 
1526 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1527   assert(blk->is_thread_safe(), "Only thread-safe closures here");
1528   if (num_regions() > ShenandoahParallelRegionStride) {
1529     ShenandoahParallelHeapRegionTask task(blk);
1530     workers()->run_task(&task);
1531   } else {
1532     heap_region_iterate(blk);
1533   }
1534 }
1535 
1536 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1537 private:
1538   ShenandoahMarkingContext* const _ctx;
1539 public:
1540   ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1541 
1542   void heap_region_do(ShenandoahHeapRegion* r) {
1543     assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1544     if (r->is_active()) {
1545       // Check if region needs updating its TAMS. We have updated it already during concurrent
1546       // reset, so it is very likely we don't need to do another write here.
1547       if (_ctx->top_at_mark_start(r) != r->top()) {
1548         _ctx->capture_top_at_mark_start(r);
1549       }
1550     } else {
1551       assert(_ctx->top_at_mark_start(r) == r->top(),
1552              "Region " SIZE_FORMAT " should already have correct TAMS", r->index());
1553     }
1554   }
1555 
1556   bool is_thread_safe() { return true; }
1557 };
1558 
1559 class ShenandoahRendezvousClosure : public HandshakeClosure {
1560 public:
1561   inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
1562   inline void do_thread(Thread* thread) {}
1563 };
1564 
1565 void ShenandoahHeap::rendezvous_threads() {
1566   ShenandoahRendezvousClosure cl;
1567   Handshake::execute(&cl);
1568 }
1569 
1570 void ShenandoahHeap::recycle_trash() {
1571   free_set()->recycle_trash();
1572 }
1573 
1574 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1575 private:
1576   ShenandoahMarkingContext* const _ctx;
1577 public:
1578   ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1579 
1580   void heap_region_do(ShenandoahHeapRegion* r) {
1581     if (r->is_active()) {
1582       // Reset live data and set TAMS optimistically. We would recheck these under the pause
1583       // anyway to capture any updates that happened since now.
1584       r->clear_live_data();
1585       _ctx->capture_top_at_mark_start(r);
1586     }
1587   }
1588 
1589   bool is_thread_safe() { return true; }
1590 };
1591 
1592 void ShenandoahHeap::prepare_gc() {
1593   reset_mark_bitmap();
1594 
1595   ShenandoahResetUpdateRegionStateClosure cl;
1596   parallel_heap_region_iterate(&cl);
1597 }
1598 
1599 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1600 private:
1601   ShenandoahMarkingContext* const _ctx;
1602   ShenandoahHeapLock* const _lock;
1603 
1604 public:
1605   ShenandoahFinalMarkUpdateRegionStateClosure() :
1606     _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1607 
1608   void heap_region_do(ShenandoahHeapRegion* r) {
1609     if (r->is_active()) {
1610       // All allocations past TAMS are implicitly live, adjust the region data.
1611       // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1612       HeapWord *tams = _ctx->top_at_mark_start(r);
1613       HeapWord *top = r->top();
1614       if (top > tams) {
1615         r->increase_live_data_alloc_words(pointer_delta(top, tams));
1616       }
1617 
1618       // We are about to select the collection set, make sure it knows about
1619       // current pinning status. Also, this allows trashing more regions that
1620       // now have their pinning status dropped.
1621       if (r->is_pinned()) {
1622         if (r->pin_count() == 0) {
1623           ShenandoahHeapLocker locker(_lock);
1624           r->make_unpinned();
1625         }
1626       } else {
1627         if (r->pin_count() > 0) {
1628           ShenandoahHeapLocker locker(_lock);
1629           r->make_pinned();
1630         }
1631       }
1632 
1633       // Remember limit for updating refs. It's guaranteed that we get no
1634       // from-space-refs written from here on.
1635       r->set_update_watermark_at_safepoint(r->top());
1636     } else {
1637       assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1638       assert(_ctx->top_at_mark_start(r) == r->top(),
1639              "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1640     }
1641   }
1642 
1643   bool is_thread_safe() { return true; }
1644 };
1645 
1646 void ShenandoahHeap::prepare_regions_and_collection_set(bool concurrent) {
1647   assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
1648   {
1649     ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_update_region_states :
1650                                          ShenandoahPhaseTimings::degen_gc_final_update_region_states);
1651     ShenandoahFinalMarkUpdateRegionStateClosure cl;
1652     parallel_heap_region_iterate(&cl);
1653 
1654     assert_pinned_region_status();
1655   }
1656 
1657   {
1658     ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::choose_cset :
1659                                          ShenandoahPhaseTimings::degen_gc_choose_cset);
1660     ShenandoahHeapLocker locker(lock());
1661     _collection_set->clear();
1662     heuristics()->choose_collection_set(_collection_set);
1663   }
1664 
1665   {
1666     ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_rebuild_freeset :
1667                                          ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset);
1668     ShenandoahHeapLocker locker(lock());
1669     _free_set->rebuild();
1670   }
1671 }
1672 
1673 void ShenandoahHeap::do_class_unloading() {
1674   _unloader.unload();
1675 }
1676 
1677 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1678   // Weak refs processing
1679   ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1680                                                 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1681   ShenandoahTimingsTracker t(phase);
1682   ShenandoahGCWorkerPhase worker_phase(phase);
1683   ref_processor()->process_references(phase, workers(), false /* concurrent */);
1684 }
1685 
1686 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1687   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1688 
1689   // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1690   // make them parsable for update code to work correctly. Plus, we can compute new sizes
1691   // for future GCLABs here.
1692   if (UseTLAB) {
1693     ShenandoahGCPhase phase(concurrent ?
1694                             ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1695                             ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1696     gclabs_retire(ResizeTLAB);
1697   }
1698 
1699   _update_refs_iterator.reset();
1700 }
1701 
1702 void ShenandoahHeap::set_gc_state_all_threads(char state) {
1703   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1704     ShenandoahThreadLocalData::set_gc_state(t, state);
1705   }
1706 }
1707 
1708 void ShenandoahHeap::set_gc_state_mask(uint mask, bool value) {
1709   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should really be Shenandoah safepoint");
1710   _gc_state.set_cond(mask, value);
1711   set_gc_state_all_threads(_gc_state.raw_value());
1712 }
1713 
1714 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
1715   assert(!has_forwarded_objects(), "Not expected before/after mark phase");
1716   set_gc_state_mask(MARKING, in_progress);
1717   ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1718 }
1719 
1720 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
1721   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
1722   set_gc_state_mask(EVACUATION, in_progress);
1723 }
1724 
1725 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
1726   if (in_progress) {
1727     _concurrent_strong_root_in_progress.set();
1728   } else {
1729     _concurrent_strong_root_in_progress.unset();
1730   }
1731 }
1732 
1733 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
1734   set_gc_state_mask(WEAK_ROOTS, cond);
1735 }
1736 
1737 GCTracer* ShenandoahHeap::tracer() {
1738   return shenandoah_policy()->tracer();
1739 }
1740 
1741 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
1742   return _free_set->used();
1743 }
1744 
1745 bool ShenandoahHeap::try_cancel_gc() {
1746   jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
1747   return prev == CANCELLABLE;
1748 }
1749 
1750 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
1751   if (try_cancel_gc()) {
1752     FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
1753     log_info(gc)("%s", msg.buffer());
1754     Events::log(Thread::current(), "%s", msg.buffer());
1755   }
1756 }
1757 
1758 uint ShenandoahHeap::max_workers() {
1759   return _max_workers;
1760 }
1761 
1762 void ShenandoahHeap::stop() {
1763   // The shutdown sequence should be able to terminate when GC is running.
1764 
1765   // Step 0. Notify policy to disable event recording.
1766   _shenandoah_policy->record_shutdown();
1767 
1768   // Step 1. Notify control thread that we are in shutdown.
1769   // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
1770   // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
1771   control_thread()->prepare_for_graceful_shutdown();
1772 
1773   // Step 2. Notify GC workers that we are cancelling GC.
1774   cancel_gc(GCCause::_shenandoah_stop_vm);
1775 
1776   // Step 3. Wait until GC worker exits normally.
1777   control_thread()->stop();
1778 }
1779 
1780 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
1781   if (!unload_classes()) return;
1782   // Unload classes and purge SystemDictionary.
1783   {
1784     ShenandoahPhaseTimings::Phase phase = full_gc ?
1785                                           ShenandoahPhaseTimings::full_gc_purge_class_unload :
1786                                           ShenandoahPhaseTimings::degen_gc_purge_class_unload;
1787     ShenandoahIsAliveSelector is_alive;
1788     CodeCache::UnloadingScope scope(is_alive.is_alive_closure());
1789     ShenandoahGCPhase gc_phase(phase);
1790     ShenandoahGCWorkerPhase worker_phase(phase);
1791     bool purged_class = SystemDictionary::do_unloading(gc_timer());
1792 
1793     uint num_workers = _workers->active_workers();
1794     ShenandoahClassUnloadingTask unlink_task(phase, num_workers, purged_class);
1795     _workers->run_task(&unlink_task);
1796   }
1797 
1798   {
1799     ShenandoahGCPhase phase(full_gc ?
1800                             ShenandoahPhaseTimings::full_gc_purge_cldg :
1801                             ShenandoahPhaseTimings::degen_gc_purge_cldg);
1802     ClassLoaderDataGraph::purge(/*at_safepoint*/true);
1803   }
1804   // Resize and verify metaspace
1805   MetaspaceGC::compute_new_size();
1806   DEBUG_ONLY(MetaspaceUtils::verify();)
1807 }
1808 
1809 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
1810 // so they should not have forwarded oops.
1811 // However, we do need to "null" dead oops in the roots, if can not be done
1812 // in concurrent cycles.
1813 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
1814   uint num_workers = _workers->active_workers();
1815   ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
1816                                                ShenandoahPhaseTimings::full_gc_purge_weak_par :
1817                                                ShenandoahPhaseTimings::degen_gc_purge_weak_par;
1818   ShenandoahGCPhase phase(timing_phase);
1819   ShenandoahGCWorkerPhase worker_phase(timing_phase);
1820   // Cleanup weak roots
1821   if (has_forwarded_objects()) {
1822     ShenandoahForwardedIsAliveClosure is_alive;
1823     ShenandoahUpdateRefsClosure keep_alive;
1824     ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
1825       cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
1826     _workers->run_task(&cleaning_task);
1827   } else {
1828     ShenandoahIsAliveClosure is_alive;
1829 #ifdef ASSERT
1830     ShenandoahAssertNotForwardedClosure verify_cl;
1831     ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
1832       cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
1833 #else
1834     ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
1835       cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
1836 #endif
1837     _workers->run_task(&cleaning_task);
1838   }
1839 }
1840 
1841 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
1842   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1843   assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
1844   ShenandoahGCPhase phase(full_gc ?
1845                           ShenandoahPhaseTimings::full_gc_purge :
1846                           ShenandoahPhaseTimings::degen_gc_purge);
1847   stw_weak_refs(full_gc);
1848   stw_process_weak_roots(full_gc);
1849   stw_unload_classes(full_gc);
1850 }
1851 
1852 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
1853   set_gc_state_mask(HAS_FORWARDED, cond);
1854 }
1855 
1856 void ShenandoahHeap::set_unload_classes(bool uc) {
1857   _unload_classes.set_cond(uc);
1858 }
1859 
1860 bool ShenandoahHeap::unload_classes() const {
1861   return _unload_classes.is_set();
1862 }
1863 
1864 address ShenandoahHeap::in_cset_fast_test_addr() {
1865   ShenandoahHeap* heap = ShenandoahHeap::heap();
1866   assert(heap->collection_set() != nullptr, "Sanity");
1867   return (address) heap->collection_set()->biased_map_address();
1868 }
1869 
1870 address ShenandoahHeap::cancelled_gc_addr() {
1871   return (address) ShenandoahHeap::heap()->_cancelled_gc.addr_of();
1872 }
1873 
1874 address ShenandoahHeap::gc_state_addr() {
1875   return (address) ShenandoahHeap::heap()->_gc_state.addr_of();
1876 }
1877 
1878 size_t ShenandoahHeap::bytes_allocated_since_gc_start() {
1879   return Atomic::load(&_bytes_allocated_since_gc_start);
1880 }
1881 
1882 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
1883   Atomic::store(&_bytes_allocated_since_gc_start, (size_t)0);
1884 }
1885 
1886 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
1887   _degenerated_gc_in_progress.set_cond(in_progress);
1888 }
1889 
1890 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
1891   _full_gc_in_progress.set_cond(in_progress);
1892 }
1893 
1894 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
1895   assert (is_full_gc_in_progress(), "should be");
1896   _full_gc_move_in_progress.set_cond(in_progress);
1897 }
1898 
1899 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
1900   set_gc_state_mask(UPDATEREFS, in_progress);
1901 }
1902 
1903 void ShenandoahHeap::register_nmethod(nmethod* nm) {
1904   ShenandoahCodeRoots::register_nmethod(nm);
1905 }
1906 
1907 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
1908   ShenandoahCodeRoots::unregister_nmethod(nm);
1909 }
1910 
1911 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
1912   heap_region_containing(o)->record_pin();
1913 }
1914 
1915 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
1916   ShenandoahHeapRegion* r = heap_region_containing(o);
1917   assert(r != nullptr, "Sanity");
1918   assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
1919   r->record_unpin();
1920 }
1921 
1922 void ShenandoahHeap::sync_pinned_region_status() {
1923   ShenandoahHeapLocker locker(lock());
1924 
1925   for (size_t i = 0; i < num_regions(); i++) {
1926     ShenandoahHeapRegion *r = get_region(i);
1927     if (r->is_active()) {
1928       if (r->is_pinned()) {
1929         if (r->pin_count() == 0) {
1930           r->make_unpinned();
1931         }
1932       } else {
1933         if (r->pin_count() > 0) {
1934           r->make_pinned();
1935         }
1936       }
1937     }
1938   }
1939 
1940   assert_pinned_region_status();
1941 }
1942 
1943 #ifdef ASSERT
1944 void ShenandoahHeap::assert_pinned_region_status() {
1945   for (size_t i = 0; i < num_regions(); i++) {
1946     ShenandoahHeapRegion* r = get_region(i);
1947     assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
1948            "Region " SIZE_FORMAT " pinning status is inconsistent", i);
1949   }
1950 }
1951 #endif
1952 
1953 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
1954   return _gc_timer;
1955 }
1956 
1957 void ShenandoahHeap::prepare_concurrent_roots() {
1958   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1959   assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1960   set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
1961   set_concurrent_weak_root_in_progress(true);
1962   if (unload_classes()) {
1963     _unloader.prepare();
1964   }
1965 }
1966 
1967 void ShenandoahHeap::finish_concurrent_roots() {
1968   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1969   assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1970   if (unload_classes()) {
1971     _unloader.finish();
1972   }
1973 }
1974 
1975 #ifdef ASSERT
1976 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
1977   assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
1978 
1979   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1980     if (UseDynamicNumberOfGCThreads) {
1981       assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
1982     } else {
1983       // Use ParallelGCThreads inside safepoints
1984       assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads within safepoints");
1985     }
1986   } else {
1987     if (UseDynamicNumberOfGCThreads) {
1988       assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
1989     } else {
1990       // Use ConcGCThreads outside safepoints
1991       assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
1992     }
1993   }
1994 }
1995 #endif
1996 
1997 ShenandoahVerifier* ShenandoahHeap::verifier() {
1998   guarantee(ShenandoahVerify, "Should be enabled");
1999   assert (_verifier != nullptr, "sanity");
2000   return _verifier;
2001 }
2002 
2003 template<bool CONCURRENT>
2004 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2005 private:
2006   ShenandoahHeap* _heap;
2007   ShenandoahRegionIterator* _regions;
2008 public:
2009   ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2010     WorkerTask("Shenandoah Update References"),
2011     _heap(ShenandoahHeap::heap()),
2012     _regions(regions) {
2013   }
2014 
2015   void work(uint worker_id) {
2016     if (CONCURRENT) {
2017       ShenandoahConcurrentWorkerSession worker_session(worker_id);
2018       ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
2019       do_work<ShenandoahConcUpdateRefsClosure>();
2020     } else {
2021       ShenandoahParallelWorkerSession worker_session(worker_id);
2022       do_work<ShenandoahSTWUpdateRefsClosure>();
2023     }
2024   }
2025 
2026 private:
2027   template<class T>
2028   void do_work() {
2029     T cl;
2030     ShenandoahHeapRegion* r = _regions->next();
2031     ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2032     while (r != nullptr) {
2033       HeapWord* update_watermark = r->get_update_watermark();
2034       assert (update_watermark >= r->bottom(), "sanity");
2035       if (r->is_active() && !r->is_cset()) {
2036         _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2037       }
2038       if (ShenandoahPacing) {
2039         _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2040       }
2041       if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2042         return;
2043       }
2044       r = _regions->next();
2045     }
2046   }
2047 };
2048 
2049 void ShenandoahHeap::update_heap_references(bool concurrent) {
2050   assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2051 
2052   if (concurrent) {
2053     ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2054     workers()->run_task(&task);
2055   } else {
2056     ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2057     workers()->run_task(&task);
2058   }
2059 }
2060 
2061 
2062 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2063 private:
2064   ShenandoahHeapLock* const _lock;
2065 
2066 public:
2067   ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2068 
2069   void heap_region_do(ShenandoahHeapRegion* r) {
2070     // Drop unnecessary "pinned" state from regions that does not have CP marks
2071     // anymore, as this would allow trashing them.
2072 
2073     if (r->is_active()) {
2074       if (r->is_pinned()) {
2075         if (r->pin_count() == 0) {
2076           ShenandoahHeapLocker locker(_lock);
2077           r->make_unpinned();
2078         }
2079       } else {
2080         if (r->pin_count() > 0) {
2081           ShenandoahHeapLocker locker(_lock);
2082           r->make_pinned();
2083         }
2084       }
2085     }
2086   }
2087 
2088   bool is_thread_safe() { return true; }
2089 };
2090 
2091 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2092   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2093   assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2094 
2095   {
2096     ShenandoahGCPhase phase(concurrent ?
2097                             ShenandoahPhaseTimings::final_update_refs_update_region_states :
2098                             ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2099     ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2100     parallel_heap_region_iterate(&cl);
2101 
2102     assert_pinned_region_status();
2103   }
2104 
2105   {
2106     ShenandoahGCPhase phase(concurrent ?
2107                             ShenandoahPhaseTimings::final_update_refs_trash_cset :
2108                             ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2109     trash_cset_regions();
2110   }
2111 }
2112 
2113 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2114   {
2115     ShenandoahGCPhase phase(concurrent ?
2116                             ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2117                             ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2118     ShenandoahHeapLocker locker(lock());
2119     _free_set->rebuild();
2120   }
2121 }
2122 
2123 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2124   print_on(st);
2125   st->cr();
2126   print_heap_regions_on(st);
2127 }
2128 
2129 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2130   size_t slice = r->index() / _bitmap_regions_per_slice;
2131 
2132   size_t regions_from = _bitmap_regions_per_slice * slice;
2133   size_t regions_to   = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2134   for (size_t g = regions_from; g < regions_to; g++) {
2135     assert (g / _bitmap_regions_per_slice == slice, "same slice");
2136     if (skip_self && g == r->index()) continue;
2137     if (get_region(g)->is_committed()) {
2138       return true;
2139     }
2140   }
2141   return false;
2142 }
2143 
2144 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2145   shenandoah_assert_heaplocked();
2146 
2147   // Bitmaps in special regions do not need commits
2148   if (_bitmap_region_special) {
2149     return true;
2150   }
2151 
2152   if (is_bitmap_slice_committed(r, true)) {
2153     // Some other region from the group is already committed, meaning the bitmap
2154     // slice is already committed, we exit right away.
2155     return true;
2156   }
2157 
2158   // Commit the bitmap slice:
2159   size_t slice = r->index() / _bitmap_regions_per_slice;
2160   size_t off = _bitmap_bytes_per_slice * slice;
2161   size_t len = _bitmap_bytes_per_slice;
2162   char* start = (char*) _bitmap_region.start() + off;
2163 
2164   if (!os::commit_memory(start, len, false)) {
2165     return false;
2166   }
2167 
2168   if (AlwaysPreTouch) {
2169     os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2170   }
2171 
2172   return true;
2173 }
2174 
2175 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2176   shenandoah_assert_heaplocked();
2177 
2178   // Bitmaps in special regions do not need uncommits
2179   if (_bitmap_region_special) {
2180     return true;
2181   }
2182 
2183   if (is_bitmap_slice_committed(r, true)) {
2184     // Some other region from the group is still committed, meaning the bitmap
2185     // slice is should stay committed, exit right away.
2186     return true;
2187   }
2188 
2189   // Uncommit the bitmap slice:
2190   size_t slice = r->index() / _bitmap_regions_per_slice;
2191   size_t off = _bitmap_bytes_per_slice * slice;
2192   size_t len = _bitmap_bytes_per_slice;
2193   if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2194     return false;
2195   }
2196   return true;
2197 }
2198 
2199 void ShenandoahHeap::safepoint_synchronize_begin() {
2200   if (ShenandoahSuspendibleWorkers) {
2201     SuspendibleThreadSet::synchronize();
2202   }
2203 }
2204 
2205 void ShenandoahHeap::safepoint_synchronize_end() {
2206   if (ShenandoahSuspendibleWorkers) {
2207     SuspendibleThreadSet::desynchronize();
2208   }
2209 }
2210 
2211 void ShenandoahHeap::entry_uncommit(double shrink_before, size_t shrink_until) {
2212   static const char *msg = "Concurrent uncommit";
2213   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
2214   EventMark em("%s", msg);
2215 
2216   op_uncommit(shrink_before, shrink_until);
2217 }
2218 
2219 void ShenandoahHeap::try_inject_alloc_failure() {
2220   if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2221     _inject_alloc_failure.set();
2222     os::naked_short_sleep(1);
2223     if (cancelled_gc()) {
2224       log_info(gc)("Allocation failure was successfully injected");
2225     }
2226   }
2227 }
2228 
2229 bool ShenandoahHeap::should_inject_alloc_failure() {
2230   return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2231 }
2232 
2233 void ShenandoahHeap::initialize_serviceability() {
2234   _memory_pool = new ShenandoahMemoryPool(this);
2235   _cycle_memory_manager.add_pool(_memory_pool);
2236   _stw_memory_manager.add_pool(_memory_pool);
2237 }
2238 
2239 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2240   GrowableArray<GCMemoryManager*> memory_managers(2);
2241   memory_managers.append(&_cycle_memory_manager);
2242   memory_managers.append(&_stw_memory_manager);
2243   return memory_managers;
2244 }
2245 
2246 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2247   GrowableArray<MemoryPool*> memory_pools(1);
2248   memory_pools.append(_memory_pool);
2249   return memory_pools;
2250 }
2251 
2252 MemoryUsage ShenandoahHeap::memory_usage() {
2253   return _memory_pool->get_memory_usage();
2254 }
2255 
2256 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2257   _heap(ShenandoahHeap::heap()),
2258   _index(0) {}
2259 
2260 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2261   _heap(heap),
2262   _index(0) {}
2263 
2264 void ShenandoahRegionIterator::reset() {
2265   _index = 0;
2266 }
2267 
2268 bool ShenandoahRegionIterator::has_next() const {
2269   return _index < _heap->num_regions();
2270 }
2271 
2272 char ShenandoahHeap::gc_state() const {
2273   return _gc_state.raw_value();
2274 }
2275 
2276 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2277 #ifdef ASSERT
2278   assert(_liveness_cache != nullptr, "sanity");
2279   assert(worker_id < _max_workers, "sanity");
2280   for (uint i = 0; i < num_regions(); i++) {
2281     assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2282   }
2283 #endif
2284   return _liveness_cache[worker_id];
2285 }
2286 
2287 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2288   assert(worker_id < _max_workers, "sanity");
2289   assert(_liveness_cache != nullptr, "sanity");
2290   ShenandoahLiveData* ld = _liveness_cache[worker_id];
2291   for (uint i = 0; i < num_regions(); i++) {
2292     ShenandoahLiveData live = ld[i];
2293     if (live > 0) {
2294       ShenandoahHeapRegion* r = get_region(i);
2295       r->increase_live_data_gc_words(live);
2296       ld[i] = 0;
2297     }
2298   }
2299 }
2300 
2301 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2302   if (is_idle()) return false;
2303 
2304   // Objects allocated after marking start are implicitly alive, don't need any barriers during
2305   // marking phase.
2306   if (is_concurrent_mark_in_progress() &&
2307      !marking_context()->allocated_after_mark_start(obj)) {
2308     return true;
2309   }
2310 
2311   // Can not guarantee obj is deeply good.
2312   if (has_forwarded_objects()) {
2313     return true;
2314   }
2315 
2316   return false;
2317 }