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