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