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/shenandoahStringDedup.hpp"
  63 #include "gc/shenandoah/shenandoahSTWMark.hpp"
  64 #include "gc/shenandoah/shenandoahUtils.hpp"
  65 #include "gc/shenandoah/shenandoahVerifier.hpp"
  66 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
  67 #include "gc/shenandoah/shenandoahVMOperations.hpp"
  68 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
  69 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
  70 #include "gc/shenandoah/mode/shenandoahIUMode.hpp"
  71 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
  72 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
  73 #if INCLUDE_JFR
  74 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
  75 #endif
  76 
  77 #include "classfile/systemDictionary.hpp"
  78 #include "code/codeCache.hpp"
  79 #include "memory/classLoaderMetaspace.hpp"
  80 #include "memory/metaspaceUtils.hpp"
  81 #include "oops/compressedOops.inline.hpp"
  82 #include "prims/jvmtiTagMap.hpp"
  83 #include "runtime/atomic.hpp"
  84 #include "runtime/globals.hpp"
  85 #include "runtime/interfaceSupport.inline.hpp"
  86 #include "runtime/java.hpp"
  87 #include "runtime/orderAccess.hpp"
  88 #include "runtime/safepointMechanism.hpp"
  89 #include "runtime/vmThread.hpp"
  90 #include "services/mallocTracker.hpp"
  91 #include "services/memTracker.hpp"
  92 #include "utilities/events.hpp"
  93 #include "utilities/powerOfTwo.hpp"
  94 
  95 class ShenandoahPretouchHeapTask : public WorkerTask {
  96 private:
  97   ShenandoahRegionIterator _regions;
  98   const size_t _page_size;
  99 public:
 100   ShenandoahPretouchHeapTask(size_t page_size) :
 101     WorkerTask("Shenandoah Pretouch Heap"),
 102     _page_size(page_size) {}
 103 
 104   virtual void work(uint worker_id) {
 105     ShenandoahHeapRegion* r = _regions.next();
 106     while (r != nullptr) {
 107       if (r->is_committed()) {
 108         os::pretouch_memory(r->bottom(), r->end(), _page_size);
 109       }
 110       r = _regions.next();
 111     }
 112   }
 113 };
 114 
 115 class ShenandoahPretouchBitmapTask : public WorkerTask {
 116 private:
 117   ShenandoahRegionIterator _regions;
 118   char* _bitmap_base;
 119   const size_t _bitmap_size;
 120   const size_t _page_size;
 121 public:
 122   ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
 123     WorkerTask("Shenandoah Pretouch Bitmap"),
 124     _bitmap_base(bitmap_base),
 125     _bitmap_size(bitmap_size),
 126     _page_size(page_size) {}
 127 
 128   virtual void work(uint worker_id) {
 129     ShenandoahHeapRegion* r = _regions.next();
 130     while (r != nullptr) {
 131       size_t start = r->index()       * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 132       size_t end   = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 133       assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
 134 
 135       if (r->is_committed()) {
 136         os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
 137       }
 138 
 139       r = _regions.next();
 140     }
 141   }
 142 };
 143 
 144 jint ShenandoahHeap::initialize() {
 145   //
 146   // Figure out heap sizing
 147   //
 148 
 149   size_t init_byte_size = InitialHeapSize;
 150   size_t min_byte_size  = MinHeapSize;
 151   size_t max_byte_size  = MaxHeapSize;
 152   size_t heap_alignment = HeapAlignment;
 153 
 154   size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
 155 
 156   Universe::check_alignment(max_byte_size,  reg_size_bytes, "Shenandoah heap");
 157   Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
 158 
 159   _num_regions = ShenandoahHeapRegion::region_count();
 160   assert(_num_regions == (max_byte_size / reg_size_bytes),
 161          "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
 162          _num_regions, max_byte_size, reg_size_bytes);
 163 
 164   // Now we know the number of regions, initialize the heuristics.
 165   initialize_heuristics();
 166 
 167   size_t num_committed_regions = init_byte_size / reg_size_bytes;
 168   num_committed_regions = MIN2(num_committed_regions, _num_regions);
 169   assert(num_committed_regions <= _num_regions, "sanity");
 170   _initial_size = num_committed_regions * reg_size_bytes;
 171 
 172   size_t num_min_regions = min_byte_size / reg_size_bytes;
 173   num_min_regions = MIN2(num_min_regions, _num_regions);
 174   assert(num_min_regions <= _num_regions, "sanity");
 175   _minimum_size = num_min_regions * reg_size_bytes;
 176 
 177   // Default to max heap size.
 178   _soft_max_size = _num_regions * reg_size_bytes;
 179 
 180   _committed = _initial_size;
 181 
 182   size_t heap_page_size   = UseLargePages ? os::large_page_size() : os::vm_page_size();
 183   size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
 184   size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
 185 
 186   //
 187   // Reserve and commit memory for heap
 188   //
 189 
 190   ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
 191   initialize_reserved_region(heap_rs);
 192   _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
 193   _heap_region_special = heap_rs.special();
 194 
 195   assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
 196          "Misaligned heap: " PTR_FORMAT, p2i(base()));
 197 
 198   _forwarding = new SlidingForwarding(_heap_region, ShenandoahHeapRegion::region_size_words_shift());
 199 
 200 #if SHENANDOAH_OPTIMIZED_MARKTASK
 201   // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
 202   // Fail if we ever attempt to address more than we can.
 203   if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
 204     FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
 205                           "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
 206                           "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
 207                 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
 208     vm_exit_during_initialization("Fatal Error", buf);
 209   }
 210 #endif
 211 
 212   ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
 213   if (!_heap_region_special) {
 214     os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
 215                               "Cannot commit heap memory");
 216   }
 217 
 218   //
 219   // Reserve and commit memory for bitmap(s)
 220   //
 221 
 222   _bitmap_size = ShenandoahMarkBitMap::compute_size(heap_rs.size());
 223   _bitmap_size = align_up(_bitmap_size, bitmap_page_size);
 224 
 225   size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
 226 
 227   guarantee(bitmap_bytes_per_region != 0,
 228             "Bitmap bytes per region should not be zero");
 229   guarantee(is_power_of_2(bitmap_bytes_per_region),
 230             "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
 231 
 232   if (bitmap_page_size > bitmap_bytes_per_region) {
 233     _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
 234     _bitmap_bytes_per_slice = bitmap_page_size;
 235   } else {
 236     _bitmap_regions_per_slice = 1;
 237     _bitmap_bytes_per_slice = bitmap_bytes_per_region;
 238   }
 239 
 240   guarantee(_bitmap_regions_per_slice >= 1,
 241             "Should have at least one region per slice: " SIZE_FORMAT,
 242             _bitmap_regions_per_slice);
 243 
 244   guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
 245             "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
 246             _bitmap_bytes_per_slice, bitmap_page_size);
 247 
 248   ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
 249   MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
 250   _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
 251   _bitmap_region_special = bitmap.special();
 252 
 253   size_t bitmap_init_commit = _bitmap_bytes_per_slice *
 254                               align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
 255   bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
 256   if (!_bitmap_region_special) {
 257     os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
 258                               "Cannot commit bitmap memory");
 259   }
 260 
 261   _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions, _max_workers);
 262 
 263   if (ShenandoahVerify) {
 264     ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
 265     if (!verify_bitmap.special()) {
 266       os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
 267                                 "Cannot commit verification bitmap memory");
 268     }
 269     MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
 270     MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
 271     _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
 272     _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
 273   }
 274 
 275   // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
 276   ReservedSpace aux_bitmap(_bitmap_size, bitmap_page_size);
 277   MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
 278   _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
 279   _aux_bitmap_region_special = aux_bitmap.special();
 280   _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
 281 
 282   //
 283   // Create regions and region sets
 284   //
 285   size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
 286   size_t region_storage_size = align_up(region_align * _num_regions, region_page_size);
 287   region_storage_size = align_up(region_storage_size, os::vm_allocation_granularity());
 288 
 289   ReservedSpace region_storage(region_storage_size, region_page_size);
 290   MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
 291   if (!region_storage.special()) {
 292     os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
 293                               "Cannot commit region memory");
 294   }
 295 
 296   // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
 297   // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
 298   // If not successful, bite a bullet and allocate at whatever address.
 299   {
 300     size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
 301     size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
 302 
 303     uintptr_t min = round_up_power_of_2(cset_align);
 304     uintptr_t max = (1u << 30u);
 305 
 306     for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
 307       char* req_addr = (char*)addr;
 308       assert(is_aligned(req_addr, cset_align), "Should be aligned");
 309       ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size(), req_addr);
 310       if (cset_rs.is_reserved()) {
 311         assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
 312         _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
 313         break;
 314       }
 315     }
 316 
 317     if (_collection_set == nullptr) {
 318       ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size());
 319       _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
 320     }
 321   }
 322 
 323   _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
 324   _free_set = new ShenandoahFreeSet(this, _num_regions);
 325 
 326   {
 327     ShenandoahHeapLocker locker(lock());
 328 
 329     for (size_t i = 0; i < _num_regions; i++) {
 330       HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
 331       bool is_committed = i < num_committed_regions;
 332       void* loc = region_storage.base() + i * region_align;
 333 
 334       ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
 335       assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
 336 
 337       _marking_context->initialize_top_at_mark_start(r);
 338       _regions[i] = r;
 339       assert(!collection_set()->is_in(i), "New region should not be in collection set");
 340     }
 341 
 342     // Initialize to complete
 343     _marking_context->mark_complete();
 344 
 345     _free_set->rebuild();
 346   }
 347 
 348   if (AlwaysPreTouch) {
 349     // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
 350     // before initialize() below zeroes it with initializing thread. For any given region,
 351     // we touch the region and the corresponding bitmaps from the same thread.
 352     ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
 353 
 354     _pretouch_heap_page_size = heap_page_size;
 355     _pretouch_bitmap_page_size = bitmap_page_size;
 356 
 357 #ifdef LINUX
 358     // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
 359     // pages. But, the kernel needs to know that every small page is used, in order to coalesce
 360     // them into huge one. Therefore, we need to pretouch with smaller pages.
 361     if (UseTransparentHugePages) {
 362       _pretouch_heap_page_size = (size_t)os::vm_page_size();
 363       _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
 364     }
 365 #endif
 366 
 367     // OS memory managers may want to coalesce back-to-back pages. Make their jobs
 368     // simpler by pre-touching continuous spaces (heap and bitmap) separately.
 369 
 370     ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
 371     _workers->run_task(&bcl);
 372 
 373     ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
 374     _workers->run_task(&hcl);
 375   }
 376 
 377   //
 378   // Initialize the rest of GC subsystems
 379   //
 380 
 381   _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
 382   for (uint worker = 0; worker < _max_workers; worker++) {
 383     _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
 384     Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
 385   }
 386 
 387   // There should probably be Shenandoah-specific options for these,
 388   // just as there are G1-specific options.
 389   {
 390     ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
 391     satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
 392     satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
 393   }
 394 
 395   _monitoring_support = new ShenandoahMonitoringSupport(this);
 396   _phase_timings = new ShenandoahPhaseTimings(max_workers());
 397   ShenandoahCodeRoots::initialize();
 398 
 399   if (ShenandoahPacing) {
 400     _pacer = new ShenandoahPacer(this);
 401     _pacer->setup_for_idle();
 402   } else {
 403     _pacer = nullptr;
 404   }
 405 
 406   _control_thread = new ShenandoahControlThread();
 407 
 408   ShenandoahInitLogger::print();
 409 
 410   return JNI_OK;
 411 }
 412 
 413 void ShenandoahHeap::initialize_mode() {
 414   if (ShenandoahGCMode != nullptr) {
 415     if (strcmp(ShenandoahGCMode, "satb") == 0) {
 416       _gc_mode = new ShenandoahSATBMode();
 417     } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
 418       _gc_mode = new ShenandoahIUMode();
 419     } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
 420       _gc_mode = new ShenandoahPassiveMode();
 421     } else {
 422       vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
 423     }
 424   } else {
 425     vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
 426   }
 427   _gc_mode->initialize_flags();
 428   if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
 429     vm_exit_during_initialization(
 430             err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
 431                     _gc_mode->name()));
 432   }
 433   if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
 434     vm_exit_during_initialization(
 435             err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
 436                     _gc_mode->name()));
 437   }
 438 }
 439 
 440 void ShenandoahHeap::initialize_heuristics() {
 441   assert(_gc_mode != nullptr, "Must be initialized");
 442   _heuristics = _gc_mode->initialize_heuristics();
 443 
 444   if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
 445     vm_exit_during_initialization(
 446             err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
 447                     _heuristics->name()));
 448   }
 449   if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
 450     vm_exit_during_initialization(
 451             err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
 452                     _heuristics->name()));
 453   }
 454 }
 455 
 456 #ifdef _MSC_VER
 457 #pragma warning( push )
 458 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 459 #endif
 460 
 461 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
 462   CollectedHeap(),
 463   _initial_size(0),
 464   _used(0),
 465   _committed(0),
 466   _bytes_allocated_since_gc_start(0),
 467   _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
 468   _workers(nullptr),
 469   _safepoint_workers(nullptr),
 470   _heap_region_special(false),
 471   _num_regions(0),
 472   _regions(nullptr),
 473   _update_refs_iterator(this),
 474   _control_thread(nullptr),
 475   _shenandoah_policy(policy),
 476   _gc_mode(nullptr),
 477   _heuristics(nullptr),
 478   _free_set(nullptr),
 479   _pacer(nullptr),
 480   _verifier(nullptr),
 481   _phase_timings(nullptr),
 482   _monitoring_support(nullptr),
 483   _memory_pool(nullptr),
 484   _stw_memory_manager("Shenandoah Pauses", "end of GC pause"),
 485   _cycle_memory_manager("Shenandoah Cycles", "end of GC cycle"),
 486   _gc_timer(new ConcurrentGCTimer()),
 487   _soft_ref_policy(),
 488   _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
 489   _ref_processor(new ShenandoahReferenceProcessor(MAX2(_max_workers, 1U))),
 490   _marking_context(nullptr),
 491   _bitmap_size(0),
 492   _bitmap_regions_per_slice(0),
 493   _bitmap_bytes_per_slice(0),
 494   _bitmap_region_special(false),
 495   _aux_bitmap_region_special(false),
 496   _liveness_cache(nullptr),
 497   _collection_set(nullptr)
 498 {
 499   // Initialize GC mode early, so we can adjust barrier support
 500   initialize_mode();
 501   BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
 502 
 503   _max_workers = MAX2(_max_workers, 1U);
 504   _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
 505   if (_workers == nullptr) {
 506     vm_exit_during_initialization("Failed necessary allocation.");
 507   } else {
 508     _workers->initialize_workers();
 509   }
 510 
 511   if (ParallelGCThreads > 1) {
 512     _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread",
 513                                                 ParallelGCThreads);
 514     _safepoint_workers->initialize_workers();
 515   }
 516 }
 517 
 518 #ifdef _MSC_VER
 519 #pragma warning( pop )
 520 #endif
 521 
 522 class ShenandoahResetBitmapTask : public WorkerTask {
 523 private:
 524   ShenandoahRegionIterator _regions;
 525 
 526 public:
 527   ShenandoahResetBitmapTask() :
 528     WorkerTask("Shenandoah Reset Bitmap") {}
 529 
 530   void work(uint worker_id) {
 531     ShenandoahHeapRegion* region = _regions.next();
 532     ShenandoahHeap* heap = ShenandoahHeap::heap();
 533     ShenandoahMarkingContext* const ctx = heap->marking_context();
 534     while (region != nullptr) {
 535       if (heap->is_bitmap_slice_committed(region)) {
 536         ctx->clear_bitmap(region);
 537       }
 538       region = _regions.next();
 539     }
 540   }
 541 };
 542 
 543 void ShenandoahHeap::reset_mark_bitmap() {
 544   assert_gc_workers(_workers->active_workers());
 545   mark_incomplete_marking_context();
 546 
 547   ShenandoahResetBitmapTask task;
 548   _workers->run_task(&task);
 549 }
 550 
 551 void ShenandoahHeap::print_on(outputStream* st) const {
 552   st->print_cr("Shenandoah Heap");
 553   st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
 554                byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
 555                byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
 556                byte_size_in_proper_unit(committed()),    proper_unit_for_byte_size(committed()),
 557                byte_size_in_proper_unit(used()),         proper_unit_for_byte_size(used()));
 558   st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
 559                num_regions(),
 560                byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
 561                proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
 562 
 563   st->print("Status: ");
 564   if (has_forwarded_objects())                 st->print("has forwarded objects, ");
 565   if (is_concurrent_mark_in_progress())        st->print("marking, ");
 566   if (is_evacuation_in_progress())             st->print("evacuating, ");
 567   if (is_update_refs_in_progress())            st->print("updating refs, ");
 568   if (is_degenerated_gc_in_progress())         st->print("degenerated gc, ");
 569   if (is_full_gc_in_progress())                st->print("full gc, ");
 570   if (is_full_gc_move_in_progress())           st->print("full gc move, ");
 571   if (is_concurrent_weak_root_in_progress())   st->print("concurrent weak roots, ");
 572   if (is_concurrent_strong_root_in_progress() &&
 573       !is_concurrent_weak_root_in_progress())  st->print("concurrent strong roots, ");
 574 
 575   if (cancelled_gc()) {
 576     st->print("cancelled");
 577   } else {
 578     st->print("not cancelled");
 579   }
 580   st->cr();
 581 
 582   st->print_cr("Reserved region:");
 583   st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
 584                p2i(reserved_region().start()),
 585                p2i(reserved_region().end()));
 586 
 587   ShenandoahCollectionSet* cset = collection_set();
 588   st->print_cr("Collection set:");
 589   if (cset != nullptr) {
 590     st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
 591     st->print_cr(" - map (biased):  " PTR_FORMAT, p2i(cset->biased_map_address()));
 592   } else {
 593     st->print_cr(" (null)");
 594   }
 595 
 596   st->cr();
 597   MetaspaceUtils::print_on(st);
 598 
 599   if (Verbose) {
 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 (!ShenandoahForwarding::is_forwarded(p)) {
 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("EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HC=humongous continuation, CS=collection set, T=trash, P=pinned");
1029   st->print_cr("BTE=bottom/top/end, U=used, T=TLAB allocs, G=GCLAB allocs, S=shared allocs, L=live data");
1030   st->print_cr("R=root, CP=critical pins, TAMS=top-at-mark-start, UWM=update watermark");
1031   st->print_cr("SN=alloc sequence number");
1032 
1033   for (size_t i = 0; i < num_regions(); i++) {
1034     get_region(i)->print_on(st);
1035   }
1036 }
1037 
1038 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1039   assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1040 
1041   oop humongous_obj = cast_to_oop(start->bottom());
1042   size_t size = humongous_obj->size();
1043   size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1044   size_t index = start->index() + required_regions - 1;
1045 
1046   assert(!start->has_live(), "liveness must be zero");
1047 
1048   for(size_t i = 0; i < required_regions; i++) {
1049     // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1050     // as it expects that every region belongs to a humongous region starting with a humongous start region.
1051     ShenandoahHeapRegion* region = get_region(index --);
1052 
1053     assert(region->is_humongous(), "expect correct humongous start or continuation");
1054     assert(!region->is_cset(), "Humongous region should not be in collection set");
1055 
1056     region->make_trash_immediate();
1057   }
1058 }
1059 
1060 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1061 public:
1062   ShenandoahCheckCleanGCLABClosure() {}
1063   void do_thread(Thread* thread) {
1064     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1065     assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1066     assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1067   }
1068 };
1069 
1070 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1071 private:
1072   bool const _resize;
1073 public:
1074   ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1075   void do_thread(Thread* thread) {
1076     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1077     assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1078     gclab->retire();
1079     if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1080       ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1081     }
1082   }
1083 };
1084 
1085 void ShenandoahHeap::labs_make_parsable() {
1086   assert(UseTLAB, "Only call with UseTLAB");
1087 
1088   ShenandoahRetireGCLABClosure cl(false);
1089 
1090   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1091     ThreadLocalAllocBuffer& tlab = t->tlab();
1092     tlab.make_parsable();
1093     cl.do_thread(t);
1094   }
1095 
1096   workers()->threads_do(&cl);
1097 }
1098 
1099 void ShenandoahHeap::tlabs_retire(bool resize) {
1100   assert(UseTLAB, "Only call with UseTLAB");
1101   assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1102 
1103   ThreadLocalAllocStats stats;
1104 
1105   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1106     ThreadLocalAllocBuffer& tlab = t->tlab();
1107     tlab.retire(&stats);
1108     if (resize) {
1109       tlab.resize();
1110     }
1111   }
1112 
1113   stats.publish();
1114 
1115 #ifdef ASSERT
1116   ShenandoahCheckCleanGCLABClosure cl;
1117   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1118     cl.do_thread(t);
1119   }
1120   workers()->threads_do(&cl);
1121 #endif
1122 }
1123 
1124 void ShenandoahHeap::gclabs_retire(bool resize) {
1125   assert(UseTLAB, "Only call with UseTLAB");
1126   assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1127 
1128   ShenandoahRetireGCLABClosure cl(resize);
1129   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1130     cl.do_thread(t);
1131   }
1132   workers()->threads_do(&cl);
1133 
1134   if (safepoint_workers() != nullptr) {
1135     safepoint_workers()->threads_do(&cl);
1136   }
1137 }
1138 
1139 // Returns size in bytes
1140 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1141   if (ShenandoahElasticTLAB) {
1142     // With Elastic TLABs, return the max allowed size, and let the allocation path
1143     // figure out the safe size for current allocation.
1144     return ShenandoahHeapRegion::max_tlab_size_bytes();
1145   } else {
1146     return MIN2(_free_set->unsafe_peek_free(), ShenandoahHeapRegion::max_tlab_size_bytes());
1147   }
1148 }
1149 
1150 size_t ShenandoahHeap::max_tlab_size() const {
1151   // Returns size in words
1152   return ShenandoahHeapRegion::max_tlab_size_words();
1153 }
1154 
1155 void ShenandoahHeap::collect(GCCause::Cause cause) {
1156   control_thread()->request_gc(cause);
1157 }
1158 
1159 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1160   //assert(false, "Shouldn't need to do full collections");
1161 }
1162 
1163 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1164   ShenandoahHeapRegion* r = heap_region_containing(addr);
1165   if (r != nullptr) {
1166     return r->block_start(addr);
1167   }
1168   return nullptr;
1169 }
1170 
1171 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1172   ShenandoahHeapRegion* r = heap_region_containing(addr);
1173   return r->block_is_obj(addr);
1174 }
1175 
1176 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1177   return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1178 }
1179 
1180 void ShenandoahHeap::prepare_for_verify() {
1181   if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1182     labs_make_parsable();
1183   }
1184 }
1185 
1186 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1187   tcl->do_thread(_control_thread);
1188   workers()->threads_do(tcl);
1189   if (_safepoint_workers != nullptr) {
1190     _safepoint_workers->threads_do(tcl);
1191   }
1192   if (ShenandoahStringDedup::is_enabled()) {
1193     ShenandoahStringDedup::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     shenandoah_assert_not_in_cset_except(NULL, obj, cancelled_gc());
1302     cl->do_object(obj);
1303     obj->oop_iterate(&oops);
1304   }
1305 
1306   assert(oop_stack.is_empty(), "should be empty");
1307   // Reclaim bitmap
1308   reclaim_aux_bitmap_for_iteration();
1309 }
1310 
1311 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1312   assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1313 
1314   if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1315     log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1316     return false;
1317   }
1318   // Reset bitmap
1319   _aux_bit_map.clear();
1320   return true;
1321 }
1322 
1323 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1324   // Process GC roots according to current GC cycle
1325   // This populates the work stack with initial objects
1326   // It is important to relinquish the associated locks before diving
1327   // into heap dumper
1328   uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1329   ShenandoahHeapIterationRootScanner rp(n_workers);
1330   rp.roots_do(oops);
1331 }
1332 
1333 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1334   if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1335     log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1336   }
1337 }
1338 
1339 // Closure for parallelly iterate objects
1340 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1341 private:
1342   MarkBitMap* _bitmap;
1343   ShenandoahObjToScanQueue* _queue;
1344   ShenandoahHeap* const _heap;
1345   ShenandoahMarkingContext* const _marking_context;
1346 
1347   template <class T>
1348   void do_oop_work(T* p) {
1349     T o = RawAccess<>::oop_load(p);
1350     if (!CompressedOops::is_null(o)) {
1351       oop obj = CompressedOops::decode_not_null(o);
1352       if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1353         // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1354         return;
1355       }
1356       obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1357 
1358       assert(oopDesc::is_oop(obj), "Must be a valid oop");
1359       if (_bitmap->par_mark(obj)) {
1360         _queue->push(ShenandoahMarkTask(obj));
1361       }
1362     }
1363   }
1364 public:
1365   ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1366     _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1367     _marking_context(_heap->marking_context()) {}
1368   void do_oop(oop* p)       { do_oop_work(p); }
1369   void do_oop(narrowOop* p) { do_oop_work(p); }
1370 };
1371 
1372 // Object iterator for parallel heap iteraion.
1373 // The root scanning phase happenes in construction as a preparation of
1374 // parallel marking queues.
1375 // Every worker processes it's own marking queue. work-stealing is used
1376 // to balance workload.
1377 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1378 private:
1379   uint                         _num_workers;
1380   bool                         _init_ready;
1381   MarkBitMap*                  _aux_bit_map;
1382   ShenandoahHeap*              _heap;
1383   ShenandoahScanObjectStack    _roots_stack; // global roots stack
1384   ShenandoahObjToScanQueueSet* _task_queues;
1385 public:
1386   ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1387         _num_workers(num_workers),
1388         _init_ready(false),
1389         _aux_bit_map(bitmap),
1390         _heap(ShenandoahHeap::heap()) {
1391     // Initialize bitmap
1392     _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1393     if (!_init_ready) {
1394       return;
1395     }
1396 
1397     ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1398     _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1399 
1400     _init_ready = prepare_worker_queues();
1401   }
1402 
1403   ~ShenandoahParallelObjectIterator() {
1404     // Reclaim bitmap
1405     _heap->reclaim_aux_bitmap_for_iteration();
1406     // Reclaim queue for workers
1407     if (_task_queues!= nullptr) {
1408       for (uint i = 0; i < _num_workers; ++i) {
1409         ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1410         if (q != nullptr) {
1411           delete q;
1412           _task_queues->register_queue(i, nullptr);
1413         }
1414       }
1415       delete _task_queues;
1416       _task_queues = nullptr;
1417     }
1418   }
1419 
1420   virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1421     if (_init_ready) {
1422       object_iterate_parallel(cl, worker_id, _task_queues);
1423     }
1424   }
1425 
1426 private:
1427   // Divide global root_stack into worker queues
1428   bool prepare_worker_queues() {
1429     _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1430     // Initialize queues for every workers
1431     for (uint i = 0; i < _num_workers; ++i) {
1432       ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1433       _task_queues->register_queue(i, task_queue);
1434     }
1435     // Divide roots among the workers. Assume that object referencing distribution
1436     // is related with root kind, use round-robin to make every worker have same chance
1437     // to process every kind of roots
1438     size_t roots_num = _roots_stack.size();
1439     if (roots_num == 0) {
1440       // No work to do
1441       return false;
1442     }
1443 
1444     for (uint j = 0; j < roots_num; j++) {
1445       uint stack_id = j % _num_workers;
1446       oop obj = _roots_stack.pop();
1447       _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1448     }
1449     return true;
1450   }
1451 
1452   void object_iterate_parallel(ObjectClosure* cl,
1453                                uint worker_id,
1454                                ShenandoahObjToScanQueueSet* queue_set) {
1455     assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1456     assert(queue_set != nullptr, "task queue must not be null");
1457 
1458     ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1459     assert(q != nullptr, "object iterate queue must not be null");
1460 
1461     ShenandoahMarkTask t;
1462     ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1463 
1464     // Work through the queue to traverse heap.
1465     // Steal when there is no task in queue.
1466     while (q->pop(t) || queue_set->steal(worker_id, t)) {
1467       oop obj = t.obj();
1468       assert(oopDesc::is_oop(obj), "must be a valid oop");
1469       cl->do_object(obj);
1470       obj->oop_iterate(&oops);
1471     }
1472     assert(q->is_empty(), "should be empty");
1473   }
1474 };
1475 
1476 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1477   return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1478 }
1479 
1480 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1481 void ShenandoahHeap::keep_alive(oop obj) {
1482   if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1483     ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1484   }
1485 }
1486 
1487 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1488   for (size_t i = 0; i < num_regions(); i++) {
1489     ShenandoahHeapRegion* current = get_region(i);
1490     blk->heap_region_do(current);
1491   }
1492 }
1493 
1494 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1495 private:
1496   ShenandoahHeap* const _heap;
1497   ShenandoahHeapRegionClosure* const _blk;
1498 
1499   shenandoah_padding(0);
1500   volatile size_t _index;
1501   shenandoah_padding(1);
1502 
1503 public:
1504   ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1505           WorkerTask("Shenandoah Parallel Region Operation"),
1506           _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1507 
1508   void work(uint worker_id) {
1509     ShenandoahParallelWorkerSession worker_session(worker_id);
1510     size_t stride = ShenandoahParallelRegionStride;
1511 
1512     size_t max = _heap->num_regions();
1513     while (Atomic::load(&_index) < max) {
1514       size_t cur = Atomic::fetch_and_add(&_index, stride, memory_order_relaxed);
1515       size_t start = cur;
1516       size_t end = MIN2(cur + stride, max);
1517       if (start >= max) break;
1518 
1519       for (size_t i = cur; i < end; i++) {
1520         ShenandoahHeapRegion* current = _heap->get_region(i);
1521         _blk->heap_region_do(current);
1522       }
1523     }
1524   }
1525 };
1526 
1527 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1528   assert(blk->is_thread_safe(), "Only thread-safe closures here");
1529   if (num_regions() > ShenandoahParallelRegionStride) {
1530     ShenandoahParallelHeapRegionTask task(blk);
1531     workers()->run_task(&task);
1532   } else {
1533     heap_region_iterate(blk);
1534   }
1535 }
1536 
1537 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1538 private:
1539   ShenandoahMarkingContext* const _ctx;
1540 public:
1541   ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1542 
1543   void heap_region_do(ShenandoahHeapRegion* r) {
1544     assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1545     if (r->is_active()) {
1546       // Check if region needs updating its TAMS. We have updated it already during concurrent
1547       // reset, so it is very likely we don't need to do another write here.
1548       if (_ctx->top_at_mark_start(r) != r->top()) {
1549         _ctx->capture_top_at_mark_start(r);
1550       }
1551     } else {
1552       assert(_ctx->top_at_mark_start(r) == r->top(),
1553              "Region " SIZE_FORMAT " should already have correct TAMS", r->index());
1554     }
1555   }
1556 
1557   bool is_thread_safe() { return true; }
1558 };
1559 
1560 class ShenandoahRendezvousClosure : public HandshakeClosure {
1561 public:
1562   inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
1563   inline void do_thread(Thread* thread) {}
1564 };
1565 
1566 void ShenandoahHeap::rendezvous_threads() {
1567   ShenandoahRendezvousClosure cl;
1568   Handshake::execute(&cl);
1569 }
1570 
1571 void ShenandoahHeap::recycle_trash() {
1572   free_set()->recycle_trash();
1573 }
1574 
1575 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1576 private:
1577   ShenandoahMarkingContext* const _ctx;
1578 public:
1579   ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1580 
1581   void heap_region_do(ShenandoahHeapRegion* r) {
1582     if (r->is_active()) {
1583       // Reset live data and set TAMS optimistically. We would recheck these under the pause
1584       // anyway to capture any updates that happened since now.
1585       r->clear_live_data();
1586       _ctx->capture_top_at_mark_start(r);
1587     }
1588   }
1589 
1590   bool is_thread_safe() { return true; }
1591 };
1592 
1593 void ShenandoahHeap::prepare_gc() {
1594   reset_mark_bitmap();
1595 
1596   ShenandoahResetUpdateRegionStateClosure cl;
1597   parallel_heap_region_iterate(&cl);
1598 }
1599 
1600 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1601 private:
1602   ShenandoahMarkingContext* const _ctx;
1603   ShenandoahHeapLock* const _lock;
1604 
1605 public:
1606   ShenandoahFinalMarkUpdateRegionStateClosure() :
1607     _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1608 
1609   void heap_region_do(ShenandoahHeapRegion* r) {
1610     if (r->is_active()) {
1611       // All allocations past TAMS are implicitly live, adjust the region data.
1612       // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1613       HeapWord *tams = _ctx->top_at_mark_start(r);
1614       HeapWord *top = r->top();
1615       if (top > tams) {
1616         r->increase_live_data_alloc_words(pointer_delta(top, tams));
1617       }
1618 
1619       // We are about to select the collection set, make sure it knows about
1620       // current pinning status. Also, this allows trashing more regions that
1621       // now have their pinning status dropped.
1622       if (r->is_pinned()) {
1623         if (r->pin_count() == 0) {
1624           ShenandoahHeapLocker locker(_lock);
1625           r->make_unpinned();
1626         }
1627       } else {
1628         if (r->pin_count() > 0) {
1629           ShenandoahHeapLocker locker(_lock);
1630           r->make_pinned();
1631         }
1632       }
1633 
1634       // Remember limit for updating refs. It's guaranteed that we get no
1635       // from-space-refs written from here on.
1636       r->set_update_watermark_at_safepoint(r->top());
1637     } else {
1638       assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1639       assert(_ctx->top_at_mark_start(r) == r->top(),
1640              "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1641     }
1642   }
1643 
1644   bool is_thread_safe() { return true; }
1645 };
1646 
1647 void ShenandoahHeap::prepare_regions_and_collection_set(bool concurrent) {
1648   assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
1649   {
1650     ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_update_region_states :
1651                                          ShenandoahPhaseTimings::degen_gc_final_update_region_states);
1652     ShenandoahFinalMarkUpdateRegionStateClosure cl;
1653     parallel_heap_region_iterate(&cl);
1654 
1655     assert_pinned_region_status();
1656   }
1657 
1658   {
1659     ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::choose_cset :
1660                                          ShenandoahPhaseTimings::degen_gc_choose_cset);
1661     ShenandoahHeapLocker locker(lock());
1662     _collection_set->clear();
1663     heuristics()->choose_collection_set(_collection_set);
1664   }
1665 
1666   {
1667     ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_rebuild_freeset :
1668                                          ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset);
1669     ShenandoahHeapLocker locker(lock());
1670     _free_set->rebuild();
1671   }
1672 }
1673 
1674 void ShenandoahHeap::do_class_unloading() {
1675   _unloader.unload();
1676 }
1677 
1678 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1679   // Weak refs processing
1680   ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1681                                                 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1682   ShenandoahTimingsTracker t(phase);
1683   ShenandoahGCWorkerPhase worker_phase(phase);
1684   ref_processor()->process_references(phase, workers(), false /* concurrent */);
1685 }
1686 
1687 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1688   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1689 
1690   // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1691   // make them parsable for update code to work correctly. Plus, we can compute new sizes
1692   // for future GCLABs here.
1693   if (UseTLAB) {
1694     ShenandoahGCPhase phase(concurrent ?
1695                             ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1696                             ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1697     gclabs_retire(ResizeTLAB);
1698   }
1699 
1700   _update_refs_iterator.reset();
1701 }
1702 
1703 void ShenandoahHeap::set_gc_state_all_threads(char state) {
1704   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1705     ShenandoahThreadLocalData::set_gc_state(t, state);
1706   }
1707 }
1708 
1709 void ShenandoahHeap::set_gc_state_mask(uint mask, bool value) {
1710   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should really be Shenandoah safepoint");
1711   _gc_state.set_cond(mask, value);
1712   set_gc_state_all_threads(_gc_state.raw_value());
1713 }
1714 
1715 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
1716   assert(!has_forwarded_objects(), "Not expected before/after mark phase");
1717   set_gc_state_mask(MARKING, in_progress);
1718   ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1719 }
1720 
1721 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
1722   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
1723   set_gc_state_mask(EVACUATION, in_progress);
1724 }
1725 
1726 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
1727   if (in_progress) {
1728     _concurrent_strong_root_in_progress.set();
1729   } else {
1730     _concurrent_strong_root_in_progress.unset();
1731   }
1732 }
1733 
1734 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
1735   set_gc_state_mask(WEAK_ROOTS, cond);
1736 }
1737 
1738 GCTracer* ShenandoahHeap::tracer() {
1739   return shenandoah_policy()->tracer();
1740 }
1741 
1742 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
1743   return _free_set->used();
1744 }
1745 
1746 bool ShenandoahHeap::try_cancel_gc() {
1747   while (true) {
1748     jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
1749     if (prev == CANCELLABLE) return true;
1750     else if (prev == CANCELLED) return false;
1751     assert(ShenandoahSuspendibleWorkers, "should not get here when not using suspendible workers");
1752     assert(prev == NOT_CANCELLED, "must be NOT_CANCELLED");
1753     Thread* thread = Thread::current();
1754     if (thread->is_Java_thread()) {
1755       // We need to provide a safepoint here, otherwise we might
1756       // spin forever if a SP is pending.
1757       ThreadBlockInVM sp(JavaThread::cast(thread));
1758       SpinPause();
1759     }
1760   }
1761 }
1762 
1763 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
1764   if (try_cancel_gc()) {
1765     FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
1766     log_info(gc)("%s", msg.buffer());
1767     Events::log(Thread::current(), "%s", msg.buffer());
1768   }
1769 }
1770 
1771 uint ShenandoahHeap::max_workers() {
1772   return _max_workers;
1773 }
1774 
1775 void ShenandoahHeap::stop() {
1776   // The shutdown sequence should be able to terminate when GC is running.
1777 
1778   // Step 0. Notify policy to disable event recording.
1779   _shenandoah_policy->record_shutdown();
1780 
1781   // Step 1. Notify control thread that we are in shutdown.
1782   // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
1783   // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
1784   control_thread()->prepare_for_graceful_shutdown();
1785 
1786   // Step 2. Notify GC workers that we are cancelling GC.
1787   cancel_gc(GCCause::_shenandoah_stop_vm);
1788 
1789   // Step 3. Wait until GC worker exits normally.
1790   control_thread()->stop();
1791 }
1792 
1793 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
1794   if (!unload_classes()) return;
1795   // Unload classes and purge SystemDictionary.
1796   {
1797     ShenandoahPhaseTimings::Phase phase = full_gc ?
1798                                           ShenandoahPhaseTimings::full_gc_purge_class_unload :
1799                                           ShenandoahPhaseTimings::degen_gc_purge_class_unload;
1800     ShenandoahIsAliveSelector is_alive;
1801     CodeCache::UnloadingScope scope(is_alive.is_alive_closure());
1802     ShenandoahGCPhase gc_phase(phase);
1803     ShenandoahGCWorkerPhase worker_phase(phase);
1804     bool purged_class = SystemDictionary::do_unloading(gc_timer());
1805 
1806     uint num_workers = _workers->active_workers();
1807     ShenandoahClassUnloadingTask unlink_task(phase, num_workers, purged_class);
1808     _workers->run_task(&unlink_task);
1809   }
1810 
1811   {
1812     ShenandoahGCPhase phase(full_gc ?
1813                             ShenandoahPhaseTimings::full_gc_purge_cldg :
1814                             ShenandoahPhaseTimings::degen_gc_purge_cldg);
1815     ClassLoaderDataGraph::purge(/*at_safepoint*/true);
1816   }
1817   // Resize and verify metaspace
1818   MetaspaceGC::compute_new_size();
1819   DEBUG_ONLY(MetaspaceUtils::verify();)
1820 }
1821 
1822 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
1823 // so they should not have forwarded oops.
1824 // However, we do need to "null" dead oops in the roots, if can not be done
1825 // in concurrent cycles.
1826 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
1827   uint num_workers = _workers->active_workers();
1828   ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
1829                                                ShenandoahPhaseTimings::full_gc_purge_weak_par :
1830                                                ShenandoahPhaseTimings::degen_gc_purge_weak_par;
1831   ShenandoahGCPhase phase(timing_phase);
1832   ShenandoahGCWorkerPhase worker_phase(timing_phase);
1833   // Cleanup weak roots
1834   if (has_forwarded_objects()) {
1835     ShenandoahForwardedIsAliveClosure is_alive;
1836     ShenandoahUpdateRefsClosure keep_alive;
1837     ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
1838       cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
1839     _workers->run_task(&cleaning_task);
1840   } else {
1841     ShenandoahIsAliveClosure is_alive;
1842 #ifdef ASSERT
1843     ShenandoahAssertNotForwardedClosure verify_cl;
1844     ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
1845       cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
1846 #else
1847     ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
1848       cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
1849 #endif
1850     _workers->run_task(&cleaning_task);
1851   }
1852 }
1853 
1854 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
1855   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1856   assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
1857   ShenandoahGCPhase phase(full_gc ?
1858                           ShenandoahPhaseTimings::full_gc_purge :
1859                           ShenandoahPhaseTimings::degen_gc_purge);
1860   stw_weak_refs(full_gc);
1861   stw_process_weak_roots(full_gc);
1862   stw_unload_classes(full_gc);
1863 }
1864 
1865 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
1866   set_gc_state_mask(HAS_FORWARDED, cond);
1867 }
1868 
1869 void ShenandoahHeap::set_unload_classes(bool uc) {
1870   _unload_classes.set_cond(uc);
1871 }
1872 
1873 bool ShenandoahHeap::unload_classes() const {
1874   return _unload_classes.is_set();
1875 }
1876 
1877 address ShenandoahHeap::in_cset_fast_test_addr() {
1878   ShenandoahHeap* heap = ShenandoahHeap::heap();
1879   assert(heap->collection_set() != nullptr, "Sanity");
1880   return (address) heap->collection_set()->biased_map_address();
1881 }
1882 
1883 address ShenandoahHeap::cancelled_gc_addr() {
1884   return (address) ShenandoahHeap::heap()->_cancelled_gc.addr_of();
1885 }
1886 
1887 address ShenandoahHeap::gc_state_addr() {
1888   return (address) ShenandoahHeap::heap()->_gc_state.addr_of();
1889 }
1890 
1891 size_t ShenandoahHeap::bytes_allocated_since_gc_start() {
1892   return Atomic::load(&_bytes_allocated_since_gc_start);
1893 }
1894 
1895 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
1896   Atomic::store(&_bytes_allocated_since_gc_start, (size_t)0);
1897 }
1898 
1899 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
1900   _degenerated_gc_in_progress.set_cond(in_progress);
1901 }
1902 
1903 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
1904   _full_gc_in_progress.set_cond(in_progress);
1905 }
1906 
1907 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
1908   assert (is_full_gc_in_progress(), "should be");
1909   _full_gc_move_in_progress.set_cond(in_progress);
1910 }
1911 
1912 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
1913   set_gc_state_mask(UPDATEREFS, in_progress);
1914 }
1915 
1916 void ShenandoahHeap::register_nmethod(nmethod* nm) {
1917   ShenandoahCodeRoots::register_nmethod(nm);
1918 }
1919 
1920 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
1921   ShenandoahCodeRoots::unregister_nmethod(nm);
1922 }
1923 
1924 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
1925   heap_region_containing(o)->record_pin();
1926 }
1927 
1928 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
1929   ShenandoahHeapRegion* r = heap_region_containing(o);
1930   assert(r != nullptr, "Sanity");
1931   assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
1932   r->record_unpin();
1933 }
1934 
1935 void ShenandoahHeap::sync_pinned_region_status() {
1936   ShenandoahHeapLocker locker(lock());
1937 
1938   for (size_t i = 0; i < num_regions(); i++) {
1939     ShenandoahHeapRegion *r = get_region(i);
1940     if (r->is_active()) {
1941       if (r->is_pinned()) {
1942         if (r->pin_count() == 0) {
1943           r->make_unpinned();
1944         }
1945       } else {
1946         if (r->pin_count() > 0) {
1947           r->make_pinned();
1948         }
1949       }
1950     }
1951   }
1952 
1953   assert_pinned_region_status();
1954 }
1955 
1956 #ifdef ASSERT
1957 void ShenandoahHeap::assert_pinned_region_status() {
1958   for (size_t i = 0; i < num_regions(); i++) {
1959     ShenandoahHeapRegion* r = get_region(i);
1960     assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
1961            "Region " SIZE_FORMAT " pinning status is inconsistent", i);
1962   }
1963 }
1964 #endif
1965 
1966 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
1967   return _gc_timer;
1968 }
1969 
1970 void ShenandoahHeap::prepare_concurrent_roots() {
1971   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1972   assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1973   set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
1974   set_concurrent_weak_root_in_progress(true);
1975   if (unload_classes()) {
1976     _unloader.prepare();
1977   }
1978 }
1979 
1980 void ShenandoahHeap::finish_concurrent_roots() {
1981   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1982   assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1983   if (unload_classes()) {
1984     _unloader.finish();
1985   }
1986 }
1987 
1988 #ifdef ASSERT
1989 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
1990   assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
1991 
1992   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1993     if (UseDynamicNumberOfGCThreads) {
1994       assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
1995     } else {
1996       // Use ParallelGCThreads inside safepoints
1997       assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads within safepoints");
1998     }
1999   } else {
2000     if (UseDynamicNumberOfGCThreads) {
2001       assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
2002     } else {
2003       // Use ConcGCThreads outside safepoints
2004       assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
2005     }
2006   }
2007 }
2008 #endif
2009 
2010 ShenandoahVerifier* ShenandoahHeap::verifier() {
2011   guarantee(ShenandoahVerify, "Should be enabled");
2012   assert (_verifier != nullptr, "sanity");
2013   return _verifier;
2014 }
2015 
2016 template<bool CONCURRENT>
2017 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2018 private:
2019   ShenandoahHeap* _heap;
2020   ShenandoahRegionIterator* _regions;
2021 public:
2022   ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2023     WorkerTask("Shenandoah Update References"),
2024     _heap(ShenandoahHeap::heap()),
2025     _regions(regions) {
2026   }
2027 
2028   void work(uint worker_id) {
2029     if (CONCURRENT) {
2030       ShenandoahConcurrentWorkerSession worker_session(worker_id);
2031       ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
2032       do_work<ShenandoahConcUpdateRefsClosure>();
2033     } else {
2034       ShenandoahParallelWorkerSession worker_session(worker_id);
2035       do_work<ShenandoahSTWUpdateRefsClosure>();
2036     }
2037   }
2038 
2039 private:
2040   template<class T>
2041   void do_work() {
2042     T cl;
2043     ShenandoahHeapRegion* r = _regions->next();
2044     ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2045     while (r != nullptr) {
2046       HeapWord* update_watermark = r->get_update_watermark();
2047       assert (update_watermark >= r->bottom(), "sanity");
2048       if (r->is_active() && !r->is_cset()) {
2049         _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2050       }
2051       if (ShenandoahPacing) {
2052         _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2053       }
2054       if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2055         return;
2056       }
2057       r = _regions->next();
2058     }
2059   }
2060 };
2061 
2062 void ShenandoahHeap::update_heap_references(bool concurrent) {
2063   assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2064 
2065   if (concurrent) {
2066     ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2067     workers()->run_task(&task);
2068   } else {
2069     ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2070     workers()->run_task(&task);
2071   }
2072 }
2073 
2074 
2075 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2076 private:
2077   ShenandoahHeapLock* const _lock;
2078 
2079 public:
2080   ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2081 
2082   void heap_region_do(ShenandoahHeapRegion* r) {
2083     // Drop unnecessary "pinned" state from regions that does not have CP marks
2084     // anymore, as this would allow trashing them.
2085 
2086     if (r->is_active()) {
2087       if (r->is_pinned()) {
2088         if (r->pin_count() == 0) {
2089           ShenandoahHeapLocker locker(_lock);
2090           r->make_unpinned();
2091         }
2092       } else {
2093         if (r->pin_count() > 0) {
2094           ShenandoahHeapLocker locker(_lock);
2095           r->make_pinned();
2096         }
2097       }
2098     }
2099   }
2100 
2101   bool is_thread_safe() { return true; }
2102 };
2103 
2104 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2105   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2106   assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2107 
2108   {
2109     ShenandoahGCPhase phase(concurrent ?
2110                             ShenandoahPhaseTimings::final_update_refs_update_region_states :
2111                             ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2112     ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2113     parallel_heap_region_iterate(&cl);
2114 
2115     assert_pinned_region_status();
2116   }
2117 
2118   {
2119     ShenandoahGCPhase phase(concurrent ?
2120                             ShenandoahPhaseTimings::final_update_refs_trash_cset :
2121                             ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2122     trash_cset_regions();
2123   }
2124 }
2125 
2126 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2127   {
2128     ShenandoahGCPhase phase(concurrent ?
2129                             ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2130                             ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2131     ShenandoahHeapLocker locker(lock());
2132     _free_set->rebuild();
2133   }
2134 }
2135 
2136 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2137   print_on(st);
2138   print_heap_regions_on(st);
2139 }
2140 
2141 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2142   size_t slice = r->index() / _bitmap_regions_per_slice;
2143 
2144   size_t regions_from = _bitmap_regions_per_slice * slice;
2145   size_t regions_to   = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2146   for (size_t g = regions_from; g < regions_to; g++) {
2147     assert (g / _bitmap_regions_per_slice == slice, "same slice");
2148     if (skip_self && g == r->index()) continue;
2149     if (get_region(g)->is_committed()) {
2150       return true;
2151     }
2152   }
2153   return false;
2154 }
2155 
2156 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2157   shenandoah_assert_heaplocked();
2158 
2159   // Bitmaps in special regions do not need commits
2160   if (_bitmap_region_special) {
2161     return true;
2162   }
2163 
2164   if (is_bitmap_slice_committed(r, true)) {
2165     // Some other region from the group is already committed, meaning the bitmap
2166     // slice is already committed, we exit right away.
2167     return true;
2168   }
2169 
2170   // Commit the bitmap slice:
2171   size_t slice = r->index() / _bitmap_regions_per_slice;
2172   size_t off = _bitmap_bytes_per_slice * slice;
2173   size_t len = _bitmap_bytes_per_slice;
2174   char* start = (char*) _bitmap_region.start() + off;
2175 
2176   if (!os::commit_memory(start, len, false)) {
2177     return false;
2178   }
2179 
2180   if (AlwaysPreTouch) {
2181     os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2182   }
2183 
2184   return true;
2185 }
2186 
2187 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2188   shenandoah_assert_heaplocked();
2189 
2190   // Bitmaps in special regions do not need uncommits
2191   if (_bitmap_region_special) {
2192     return true;
2193   }
2194 
2195   if (is_bitmap_slice_committed(r, true)) {
2196     // Some other region from the group is still committed, meaning the bitmap
2197     // slice is should stay committed, exit right away.
2198     return true;
2199   }
2200 
2201   // Uncommit the bitmap slice:
2202   size_t slice = r->index() / _bitmap_regions_per_slice;
2203   size_t off = _bitmap_bytes_per_slice * slice;
2204   size_t len = _bitmap_bytes_per_slice;
2205   if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2206     return false;
2207   }
2208   return true;
2209 }
2210 
2211 void ShenandoahHeap::safepoint_synchronize_begin() {
2212   if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2213     SuspendibleThreadSet::synchronize();
2214   }
2215 }
2216 
2217 void ShenandoahHeap::safepoint_synchronize_end() {
2218   if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2219     SuspendibleThreadSet::desynchronize();
2220   }
2221 }
2222 
2223 void ShenandoahHeap::entry_uncommit(double shrink_before, size_t shrink_until) {
2224   static const char *msg = "Concurrent uncommit";
2225   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
2226   EventMark em("%s", msg);
2227 
2228   op_uncommit(shrink_before, shrink_until);
2229 }
2230 
2231 void ShenandoahHeap::try_inject_alloc_failure() {
2232   if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2233     _inject_alloc_failure.set();
2234     os::naked_short_sleep(1);
2235     if (cancelled_gc()) {
2236       log_info(gc)("Allocation failure was successfully injected");
2237     }
2238   }
2239 }
2240 
2241 bool ShenandoahHeap::should_inject_alloc_failure() {
2242   return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2243 }
2244 
2245 void ShenandoahHeap::initialize_serviceability() {
2246   _memory_pool = new ShenandoahMemoryPool(this);
2247   _cycle_memory_manager.add_pool(_memory_pool);
2248   _stw_memory_manager.add_pool(_memory_pool);
2249 }
2250 
2251 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2252   GrowableArray<GCMemoryManager*> memory_managers(2);
2253   memory_managers.append(&_cycle_memory_manager);
2254   memory_managers.append(&_stw_memory_manager);
2255   return memory_managers;
2256 }
2257 
2258 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2259   GrowableArray<MemoryPool*> memory_pools(1);
2260   memory_pools.append(_memory_pool);
2261   return memory_pools;
2262 }
2263 
2264 MemoryUsage ShenandoahHeap::memory_usage() {
2265   return _memory_pool->get_memory_usage();
2266 }
2267 
2268 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2269   _heap(ShenandoahHeap::heap()),
2270   _index(0) {}
2271 
2272 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2273   _heap(heap),
2274   _index(0) {}
2275 
2276 void ShenandoahRegionIterator::reset() {
2277   _index = 0;
2278 }
2279 
2280 bool ShenandoahRegionIterator::has_next() const {
2281   return _index < _heap->num_regions();
2282 }
2283 
2284 char ShenandoahHeap::gc_state() const {
2285   return _gc_state.raw_value();
2286 }
2287 
2288 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2289 #ifdef ASSERT
2290   assert(_liveness_cache != nullptr, "sanity");
2291   assert(worker_id < _max_workers, "sanity");
2292   for (uint i = 0; i < num_regions(); i++) {
2293     assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2294   }
2295 #endif
2296   return _liveness_cache[worker_id];
2297 }
2298 
2299 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2300   assert(worker_id < _max_workers, "sanity");
2301   assert(_liveness_cache != nullptr, "sanity");
2302   ShenandoahLiveData* ld = _liveness_cache[worker_id];
2303   for (uint i = 0; i < num_regions(); i++) {
2304     ShenandoahLiveData live = ld[i];
2305     if (live > 0) {
2306       ShenandoahHeapRegion* r = get_region(i);
2307       r->increase_live_data_gc_words(live);
2308       ld[i] = 0;
2309     }
2310   }
2311 }
2312 
2313 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2314   if (is_idle()) return false;
2315 
2316   // Objects allocated after marking start are implicitly alive, don't need any barriers during
2317   // marking phase.
2318   if (is_concurrent_mark_in_progress() &&
2319      !marking_context()->allocated_after_mark_start(obj)) {
2320     return true;
2321   }
2322 
2323   // Can not guarantee obj is deeply good.
2324   if (has_forwarded_objects()) {
2325     return true;
2326   }
2327 
2328   return false;
2329 }