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