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