1 /*
   2  * Copyright (c) 2013, 2020, 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 
  36 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
  37 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
  38 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
  39 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
  40 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
  41 #include "gc/shenandoah/shenandoahConcurrentRoots.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/shenandoahMarkCompact.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/shenandoahRootProcessor.inline.hpp"
  59 #include "gc/shenandoah/shenandoahStringDedup.hpp"
  60 #include "gc/shenandoah/shenandoahTaskqueue.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 "memory/metaspace.hpp"
  75 #include "oops/compressedOops.inline.hpp"
  76 #include "runtime/atomic.hpp"
  77 #include "runtime/globals.hpp"
  78 #include "runtime/interfaceSupport.inline.hpp"
  79 #include "runtime/orderAccess.hpp"
  80 #include "runtime/safepointMechanism.hpp"
  81 #include "runtime/vmThread.hpp"
  82 #include "services/mallocTracker.hpp"
  83 #include "utilities/powerOfTwo.hpp"
  84 
  85 class ShenandoahPretouchHeapTask : public AbstractGangTask {
  86 private:
  87   ShenandoahRegionIterator _regions;
  88   const size_t _page_size;
  89 public:
  90   ShenandoahPretouchHeapTask(size_t page_size) :
  91     AbstractGangTask("Shenandoah Pretouch Heap"),
  92     _page_size(page_size) {}
  93 
  94   virtual void work(uint worker_id) {
  95     ShenandoahHeapRegion* r = _regions.next();
  96     while (r != NULL) {
  97       if (r->is_committed()) {
  98         os::pretouch_memory(r->bottom(), r->end(), _page_size);
  99       }
 100       r = _regions.next();
 101     }
 102   }
 103 };
 104 
 105 class ShenandoahPretouchBitmapTask : public AbstractGangTask {
 106 private:
 107   ShenandoahRegionIterator _regions;
 108   char* _bitmap_base;
 109   const size_t _bitmap_size;
 110   const size_t _page_size;
 111 public:
 112   ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
 113     AbstractGangTask("Shenandoah Pretouch Bitmap"),
 114     _bitmap_base(bitmap_base),
 115     _bitmap_size(bitmap_size),
 116     _page_size(page_size) {}
 117 
 118   virtual void work(uint worker_id) {
 119     ShenandoahHeapRegion* r = _regions.next();
 120     while (r != NULL) {
 121       size_t start = r->index()       * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 122       size_t end   = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 123       assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
 124 
 125       if (r->is_committed()) {
 126         os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
 127       }
 128 
 129       r = _regions.next();
 130     }
 131   }
 132 };
 133 
 134 jint ShenandoahHeap::initialize() {
 135   //
 136   // Figure out heap sizing
 137   //
 138 
 139   size_t init_byte_size = InitialHeapSize;
 140   size_t min_byte_size  = MinHeapSize;
 141   size_t max_byte_size  = MaxHeapSize;
 142   size_t heap_alignment = HeapAlignment;
 143 
 144   size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
 145 
 146   Universe::check_alignment(max_byte_size,  reg_size_bytes, "Shenandoah heap");
 147   Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
 148 
 149   _num_regions = ShenandoahHeapRegion::region_count();
 150 
 151   // Now we know the number of regions, initialize the heuristics.
 152   initialize_heuristics();
 153 
 154   size_t num_committed_regions = init_byte_size / reg_size_bytes;
 155   num_committed_regions = MIN2(num_committed_regions, _num_regions);
 156   assert(num_committed_regions <= _num_regions, "sanity");
 157   _initial_size = num_committed_regions * reg_size_bytes;
 158 
 159   size_t num_min_regions = min_byte_size / reg_size_bytes;
 160   num_min_regions = MIN2(num_min_regions, _num_regions);
 161   assert(num_min_regions <= _num_regions, "sanity");
 162   _minimum_size = num_min_regions * reg_size_bytes;
 163 
 164   _committed = _initial_size;
 165 
 166   size_t heap_page_size   = UseLargePages ? (size_t)os::large_page_size() : (size_t)os::vm_page_size();
 167   size_t bitmap_page_size = UseLargePages ? (size_t)os::large_page_size() : (size_t)os::vm_page_size();
 168   size_t region_page_size = UseLargePages ? (size_t)os::large_page_size() : (size_t)os::vm_page_size();
 169 
 170   //
 171   // Reserve and commit memory for heap
 172   //
 173 
 174   ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
 175   initialize_reserved_region(heap_rs);
 176   _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
 177   _heap_region_special = heap_rs.special();
 178 
 179   assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
 180          "Misaligned heap: " PTR_FORMAT, p2i(base()));
 181 
 182 #if SHENANDOAH_OPTIMIZED_OBJTASK
 183   // The optimized ObjArrayChunkedTask takes some bits away from the full object bits.
 184   // Fail if we ever attempt to address more than we can.
 185   if ((uintptr_t)heap_rs.end() >= ObjArrayChunkedTask::max_addressable()) {
 186     FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
 187                           "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
 188                           "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
 189                 p2i(heap_rs.base()), p2i(heap_rs.end()), ObjArrayChunkedTask::max_addressable());
 190     vm_exit_during_initialization("Fatal Error", buf);
 191   }
 192 #endif
 193 
 194   ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
 195   if (!_heap_region_special) {
 196     os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
 197                               "Cannot commit heap memory");
 198   }
 199 
 200   //
 201   // Reserve and commit memory for bitmap(s)
 202   //
 203 
 204   _bitmap_size = MarkBitMap::compute_size(heap_rs.size());
 205   _bitmap_size = align_up(_bitmap_size, bitmap_page_size);
 206 
 207   size_t bitmap_bytes_per_region = reg_size_bytes / MarkBitMap::heap_map_factor();
 208 
 209   guarantee(bitmap_bytes_per_region != 0,
 210             "Bitmap bytes per region should not be zero");
 211   guarantee(is_power_of_2(bitmap_bytes_per_region),
 212             "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
 213 
 214   if (bitmap_page_size > bitmap_bytes_per_region) {
 215     _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
 216     _bitmap_bytes_per_slice = bitmap_page_size;
 217   } else {
 218     _bitmap_regions_per_slice = 1;
 219     _bitmap_bytes_per_slice = bitmap_bytes_per_region;
 220   }
 221 
 222   guarantee(_bitmap_regions_per_slice >= 1,
 223             "Should have at least one region per slice: " SIZE_FORMAT,
 224             _bitmap_regions_per_slice);
 225 
 226   guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
 227             "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
 228             _bitmap_bytes_per_slice, bitmap_page_size);
 229 
 230   ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
 231   MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
 232   _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
 233   _bitmap_region_special = bitmap.special();
 234 
 235   size_t bitmap_init_commit = _bitmap_bytes_per_slice *
 236                               align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
 237   bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
 238   if (!_bitmap_region_special) {
 239     os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
 240                               "Cannot commit bitmap memory");
 241   }
 242 
 243   _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
 244 
 245   if (ShenandoahVerify) {
 246     ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
 247     if (!verify_bitmap.special()) {
 248       os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
 249                                 "Cannot commit verification bitmap memory");
 250     }
 251     MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
 252     MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
 253     _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
 254     _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
 255   }
 256 
 257   // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
 258   ReservedSpace aux_bitmap(_bitmap_size, bitmap_page_size);
 259   MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
 260   _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
 261   _aux_bitmap_region_special = aux_bitmap.special();
 262   _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
 263 
 264   //
 265   // Create regions and region sets
 266   //
 267   size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
 268   size_t region_storage_size = align_up(region_align * _num_regions, region_page_size);
 269   region_storage_size = align_up(region_storage_size, os::vm_allocation_granularity());
 270 
 271   ReservedSpace region_storage(region_storage_size, region_page_size);
 272   MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
 273   if (!region_storage.special()) {
 274     os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
 275                               "Cannot commit region memory");
 276   }
 277 
 278   // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
 279   // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
 280   // If not successful, bite a bullet and allocate at whatever address.
 281   {
 282     size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
 283     size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
 284 
 285     uintptr_t min = round_up_power_of_2(cset_align);
 286     uintptr_t max = (1u << 30u);
 287 
 288     for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
 289       char* req_addr = (char*)addr;
 290       assert(is_aligned(req_addr, cset_align), "Should be aligned");
 291       ReservedSpace cset_rs(cset_size, cset_align, false, req_addr);
 292       if (cset_rs.is_reserved()) {
 293         assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
 294         _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
 295         break;
 296       }
 297     }
 298 
 299     if (_collection_set == NULL) {
 300       ReservedSpace cset_rs(cset_size, cset_align, false);
 301       _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
 302     }
 303   }
 304 
 305   _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
 306   _free_set = new ShenandoahFreeSet(this, _num_regions);
 307 
 308   {
 309     ShenandoahHeapLocker locker(lock());
 310 
 311     for (size_t i = 0; i < _num_regions; i++) {
 312       HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
 313       bool is_committed = i < num_committed_regions;
 314       void* loc = region_storage.base() + i * region_align;
 315 
 316       ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
 317       assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
 318 
 319       _marking_context->initialize_top_at_mark_start(r);
 320       _regions[i] = r;
 321       assert(!collection_set()->is_in(i), "New region should not be in collection set");
 322     }
 323 
 324     // Initialize to complete
 325     _marking_context->mark_complete();
 326 
 327     _free_set->rebuild();
 328   }
 329 
 330   if (AlwaysPreTouch) {
 331     // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
 332     // before initialize() below zeroes it with initializing thread. For any given region,
 333     // we touch the region and the corresponding bitmaps from the same thread.
 334     ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
 335 
 336     _pretouch_heap_page_size = heap_page_size;
 337     _pretouch_bitmap_page_size = bitmap_page_size;
 338 
 339 #ifdef LINUX
 340     // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
 341     // pages. But, the kernel needs to know that every small page is used, in order to coalesce
 342     // them into huge one. Therefore, we need to pretouch with smaller pages.
 343     if (UseTransparentHugePages) {
 344       _pretouch_heap_page_size = (size_t)os::vm_page_size();
 345       _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
 346     }
 347 #endif
 348 
 349     // OS memory managers may want to coalesce back-to-back pages. Make their jobs
 350     // simpler by pre-touching continuous spaces (heap and bitmap) separately.
 351 
 352     ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
 353     _workers->run_task(&bcl);
 354 
 355     ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
 356     _workers->run_task(&hcl);
 357   }
 358 
 359   //
 360   // Initialize the rest of GC subsystems
 361   //
 362 
 363   _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
 364   for (uint worker = 0; worker < _max_workers; worker++) {
 365     _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
 366     Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
 367   }
 368 
 369   // There should probably be Shenandoah-specific options for these,
 370   // just as there are G1-specific options.
 371   {
 372     ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
 373     satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
 374     satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
 375   }
 376 
 377   _monitoring_support = new ShenandoahMonitoringSupport(this);
 378   _phase_timings = new ShenandoahPhaseTimings(max_workers());
 379   ShenandoahStringDedup::initialize();
 380   ShenandoahCodeRoots::initialize();
 381 
 382   if (ShenandoahPacing) {
 383     _pacer = new ShenandoahPacer(this);
 384     _pacer->setup_for_idle();
 385   } else {
 386     _pacer = NULL;
 387   }
 388 
 389   _control_thread = new ShenandoahControlThread();
 390 
 391   _ref_proc_mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
 392   _ref_proc_mt_discovery = _max_workers > 1;
 393 
 394   ShenandoahInitLogger::print();
 395 
 396   return JNI_OK;
 397 }
 398 
 399 void ShenandoahHeap::initialize_heuristics() {
 400   if (ShenandoahGCMode != NULL) {
 401     if (strcmp(ShenandoahGCMode, "satb") == 0) {
 402       _gc_mode = new ShenandoahSATBMode();
 403     } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
 404       _gc_mode = new ShenandoahIUMode();
 405     } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
 406       _gc_mode = new ShenandoahPassiveMode();
 407     } else {
 408       vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
 409     }
 410   } else {
 411     ShouldNotReachHere();
 412   }
 413   _gc_mode->initialize_flags();
 414   if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
 415     vm_exit_during_initialization(
 416             err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
 417                     _gc_mode->name()));
 418   }
 419   if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
 420     vm_exit_during_initialization(
 421             err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
 422                     _gc_mode->name()));
 423   }
 424 
 425   _heuristics = _gc_mode->initialize_heuristics();
 426 
 427   if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
 428     vm_exit_during_initialization(
 429             err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
 430                     _heuristics->name()));
 431   }
 432   if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
 433     vm_exit_during_initialization(
 434             err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
 435                     _heuristics->name()));
 436   }
 437 }
 438 
 439 #ifdef _MSC_VER
 440 #pragma warning( push )
 441 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 442 #endif
 443 
 444 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
 445   CollectedHeap(),
 446   _initial_size(0),
 447   _used(0),
 448   _committed(0),
 449   _bytes_allocated_since_gc_start(0),
 450   _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
 451   _workers(NULL),
 452   _safepoint_workers(NULL),
 453   _heap_region_special(false),
 454   _num_regions(0),
 455   _regions(NULL),
 456   _update_refs_iterator(this),
 457   _control_thread(NULL),
 458   _shenandoah_policy(policy),
 459   _heuristics(NULL),
 460   _free_set(NULL),
 461   _scm(new ShenandoahConcurrentMark()),
 462   _full_gc(new ShenandoahMarkCompact()),
 463   _pacer(NULL),
 464   _verifier(NULL),
 465   _phase_timings(NULL),
 466   _monitoring_support(NULL),
 467   _memory_pool(NULL),
 468   _stw_memory_manager("Shenandoah Pauses", "end of GC pause"),
 469   _cycle_memory_manager("Shenandoah Cycles", "end of GC cycle"),
 470   _gc_timer(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
 471   _soft_ref_policy(),
 472   _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
 473   _ref_processor(NULL),
 474   _marking_context(NULL),
 475   _bitmap_size(0),
 476   _bitmap_regions_per_slice(0),
 477   _bitmap_bytes_per_slice(0),
 478   _bitmap_region_special(false),
 479   _aux_bitmap_region_special(false),
 480   _liveness_cache(NULL),
 481   _collection_set(NULL)
 482 {
 483   BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
 484 
 485   _max_workers = MAX2(_max_workers, 1U);
 486   _workers = new ShenandoahWorkGang("Shenandoah GC Threads", _max_workers,
 487                             /* are_GC_task_threads */ true,
 488                             /* are_ConcurrentGC_threads */ true);
 489   if (_workers == NULL) {
 490     vm_exit_during_initialization("Failed necessary allocation.");
 491   } else {
 492     _workers->initialize_workers();
 493   }
 494 
 495   if (ParallelGCThreads > 1) {
 496     _safepoint_workers = new ShenandoahWorkGang("Safepoint Cleanup Thread",
 497                                                 ParallelGCThreads,
 498                       /* are_GC_task_threads */ false,
 499                  /* are_ConcurrentGC_threads */ false);
 500     _safepoint_workers->initialize_workers();
 501   }
 502 }
 503 
 504 #ifdef _MSC_VER
 505 #pragma warning( pop )
 506 #endif
 507 
 508 class ShenandoahResetBitmapTask : public AbstractGangTask {
 509 private:
 510   ShenandoahRegionIterator _regions;
 511 
 512 public:
 513   ShenandoahResetBitmapTask() :
 514     AbstractGangTask("Parallel Reset Bitmap Task") {}
 515 
 516   void work(uint worker_id) {
 517     ShenandoahHeapRegion* region = _regions.next();
 518     ShenandoahHeap* heap = ShenandoahHeap::heap();
 519     ShenandoahMarkingContext* const ctx = heap->marking_context();
 520     while (region != NULL) {
 521       if (heap->is_bitmap_slice_committed(region)) {
 522         ctx->clear_bitmap(region);
 523       }
 524       region = _regions.next();
 525     }
 526   }
 527 };
 528 
 529 void ShenandoahHeap::reset_mark_bitmap() {
 530   assert_gc_workers(_workers->active_workers());
 531   mark_incomplete_marking_context();
 532 
 533   ShenandoahResetBitmapTask task;
 534   _workers->run_task(&task);
 535 }
 536 
 537 void ShenandoahHeap::print_on(outputStream* st) const {
 538   st->print_cr("Shenandoah Heap");
 539   st->print_cr(" " SIZE_FORMAT "%s total, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
 540                byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
 541                byte_size_in_proper_unit(committed()),    proper_unit_for_byte_size(committed()),
 542                byte_size_in_proper_unit(used()),         proper_unit_for_byte_size(used()));
 543   st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
 544                num_regions(),
 545                byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
 546                proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
 547 
 548   st->print("Status: ");
 549   if (has_forwarded_objects())                 st->print("has forwarded objects, ");
 550   if (is_concurrent_mark_in_progress())        st->print("marking, ");
 551   if (is_evacuation_in_progress())             st->print("evacuating, ");
 552   if (is_update_refs_in_progress())            st->print("updating refs, ");
 553   if (is_degenerated_gc_in_progress())         st->print("degenerated gc, ");
 554   if (is_full_gc_in_progress())                st->print("full gc, ");
 555   if (is_full_gc_move_in_progress())           st->print("full gc move, ");
 556   if (is_concurrent_weak_root_in_progress())   st->print("concurrent weak roots, ");
 557   if (is_concurrent_strong_root_in_progress() &&
 558       !is_concurrent_weak_root_in_progress())  st->print("concurrent strong roots, ");
 559 
 560   if (cancelled_gc()) {
 561     st->print("cancelled");
 562   } else {
 563     st->print("not cancelled");
 564   }
 565   st->cr();
 566 
 567   st->print_cr("Reserved region:");
 568   st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
 569                p2i(reserved_region().start()),
 570                p2i(reserved_region().end()));
 571 
 572   ShenandoahCollectionSet* cset = collection_set();
 573   st->print_cr("Collection set:");
 574   if (cset != NULL) {
 575     st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
 576     st->print_cr(" - map (biased):  " PTR_FORMAT, p2i(cset->biased_map_address()));
 577   } else {
 578     st->print_cr(" (NULL)");
 579   }
 580 
 581   st->cr();
 582   MetaspaceUtils::print_on(st);
 583 
 584   if (Verbose) {
 585     print_heap_regions_on(st);
 586   }
 587 }
 588 
 589 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
 590 public:
 591   void do_thread(Thread* thread) {
 592     assert(thread != NULL, "Sanity");
 593     assert(thread->is_Worker_thread(), "Only worker thread expected");
 594     ShenandoahThreadLocalData::initialize_gclab(thread);
 595   }
 596 };
 597 
 598 void ShenandoahHeap::post_initialize() {
 599   CollectedHeap::post_initialize();
 600   MutexLocker ml(Threads_lock);
 601 
 602   ShenandoahInitWorkerGCLABClosure init_gclabs;
 603   _workers->threads_do(&init_gclabs);
 604 
 605   // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
 606   // Now, we will let WorkGang to initialize gclab when new worker is created.
 607   _workers->set_initialize_gclab();
 608 
 609   _scm->initialize(_max_workers);
 610   _full_gc->initialize(_gc_timer);
 611 
 612   ref_processing_init();
 613 
 614   _heuristics->initialize();
 615 
 616   JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
 617 }
 618 
 619 size_t ShenandoahHeap::used() const {
 620   return Atomic::load_acquire(&_used);
 621 }
 622 
 623 size_t ShenandoahHeap::committed() const {
 624   OrderAccess::acquire();
 625   return _committed;
 626 }
 627 
 628 void ShenandoahHeap::increase_committed(size_t bytes) {
 629   shenandoah_assert_heaplocked_or_safepoint();
 630   _committed += bytes;
 631 }
 632 
 633 void ShenandoahHeap::decrease_committed(size_t bytes) {
 634   shenandoah_assert_heaplocked_or_safepoint();
 635   _committed -= bytes;
 636 }
 637 
 638 void ShenandoahHeap::increase_used(size_t bytes) {
 639   Atomic::add(&_used, bytes);
 640 }
 641 
 642 void ShenandoahHeap::set_used(size_t bytes) {
 643   Atomic::release_store_fence(&_used, bytes);
 644 }
 645 
 646 void ShenandoahHeap::decrease_used(size_t bytes) {
 647   assert(used() >= bytes, "never decrease heap size by more than we've left");
 648   Atomic::sub(&_used, bytes);
 649 }
 650 
 651 void ShenandoahHeap::increase_allocated(size_t bytes) {
 652   Atomic::add(&_bytes_allocated_since_gc_start, bytes);
 653 }
 654 
 655 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
 656   size_t bytes = words * HeapWordSize;
 657   if (!waste) {
 658     increase_used(bytes);
 659   }
 660   increase_allocated(bytes);
 661   if (ShenandoahPacing) {
 662     control_thread()->pacing_notify_alloc(words);
 663     if (waste) {
 664       pacer()->claim_for_alloc(words, true);
 665     }
 666   }
 667 }
 668 
 669 size_t ShenandoahHeap::capacity() const {
 670   return committed();
 671 }
 672 
 673 size_t ShenandoahHeap::max_capacity() const {
 674   return _num_regions * ShenandoahHeapRegion::region_size_bytes();
 675 }
 676 
 677 size_t ShenandoahHeap::min_capacity() const {
 678   return _minimum_size;
 679 }
 680 
 681 size_t ShenandoahHeap::initial_capacity() const {
 682   return _initial_size;
 683 }
 684 
 685 bool ShenandoahHeap::is_in(const void* p) const {
 686   HeapWord* heap_base = (HeapWord*) base();
 687   HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
 688   return p >= heap_base && p < last_region_end;
 689 }
 690 
 691 void ShenandoahHeap::op_uncommit(double shrink_before) {
 692   assert (ShenandoahUncommit, "should be enabled");
 693 
 694   // Application allocates from the beginning of the heap, and GC allocates at
 695   // the end of it. It is more efficient to uncommit from the end, so that applications
 696   // could enjoy the near committed regions. GC allocations are much less frequent,
 697   // and therefore can accept the committing costs.
 698 
 699   size_t count = 0;
 700   for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
 701     ShenandoahHeapRegion* r = get_region(i - 1);
 702     if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
 703       ShenandoahHeapLocker locker(lock());
 704       if (r->is_empty_committed()) {
 705         // Do not uncommit below minimal capacity
 706         if (committed() < min_capacity() + ShenandoahHeapRegion::region_size_bytes()) {
 707           break;
 708         }
 709 
 710         r->make_uncommitted();
 711         count++;
 712       }
 713     }
 714     SpinPause(); // allow allocators to take the lock
 715   }
 716 
 717   if (count > 0) {
 718     control_thread()->notify_heap_changed();
 719   }
 720 }
 721 
 722 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
 723   // New object should fit the GCLAB size
 724   size_t min_size = MAX2(size, PLAB::min_size());
 725 
 726   // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
 727   size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
 728   new_size = MIN2(new_size, PLAB::max_size());
 729   new_size = MAX2(new_size, PLAB::min_size());
 730 
 731   // Record new heuristic value even if we take any shortcut. This captures
 732   // the case when moderately-sized objects always take a shortcut. At some point,
 733   // heuristics should catch up with them.
 734   ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
 735 
 736   if (new_size < size) {
 737     // New size still does not fit the object. Fall back to shared allocation.
 738     // This avoids retiring perfectly good GCLABs, when we encounter a large object.
 739     return NULL;
 740   }
 741 
 742   // Retire current GCLAB, and allocate a new one.
 743   PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
 744   gclab->retire();
 745 
 746   size_t actual_size = 0;
 747   HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
 748   if (gclab_buf == NULL) {
 749     return NULL;
 750   }
 751 
 752   assert (size <= actual_size, "allocation should fit");
 753 
 754   if (ZeroTLAB) {
 755     // ..and clear it.
 756     Copy::zero_to_words(gclab_buf, actual_size);
 757   } else {
 758     // ...and zap just allocated object.
 759 #ifdef ASSERT
 760     // Skip mangling the space corresponding to the object header to
 761     // ensure that the returned space is not considered parsable by
 762     // any concurrent GC thread.
 763     size_t hdr_size = oopDesc::header_size();
 764     Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
 765 #endif // ASSERT
 766   }
 767   gclab->set_buf(gclab_buf, actual_size);
 768   return gclab->allocate(size);
 769 }
 770 
 771 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
 772                                             size_t requested_size,
 773                                             size_t* actual_size) {
 774   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
 775   HeapWord* res = allocate_memory(req);
 776   if (res != NULL) {
 777     *actual_size = req.actual_size();
 778   } else {
 779     *actual_size = 0;
 780   }
 781   return res;
 782 }
 783 
 784 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
 785                                              size_t word_size,
 786                                              size_t* actual_size) {
 787   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
 788   HeapWord* res = allocate_memory(req);
 789   if (res != NULL) {
 790     *actual_size = req.actual_size();
 791   } else {
 792     *actual_size = 0;
 793   }
 794   return res;
 795 }
 796 
 797 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
 798   intptr_t pacer_epoch = 0;
 799   bool in_new_region = false;
 800   HeapWord* result = NULL;
 801 
 802   if (req.is_mutator_alloc()) {
 803     if (ShenandoahPacing) {
 804       pacer()->pace_for_alloc(req.size());
 805       pacer_epoch = pacer()->epoch();
 806     }
 807 
 808     if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
 809       result = allocate_memory_under_lock(req, in_new_region);
 810     }
 811 
 812     // Allocation failed, block until control thread reacted, then retry allocation.
 813     //
 814     // It might happen that one of the threads requesting allocation would unblock
 815     // way later after GC happened, only to fail the second allocation, because
 816     // other threads have already depleted the free storage. In this case, a better
 817     // strategy is to try again, as long as GC makes progress.
 818     //
 819     // Then, we need to make sure the allocation was retried after at least one
 820     // Full GC, which means we want to try more than ShenandoahFullGCThreshold times.
 821 
 822     size_t tries = 0;
 823 
 824     while (result == NULL && _progress_last_gc.is_set()) {
 825       tries++;
 826       control_thread()->handle_alloc_failure(req);
 827       result = allocate_memory_under_lock(req, in_new_region);
 828     }
 829 
 830     while (result == NULL && tries <= ShenandoahFullGCThreshold) {
 831       tries++;
 832       control_thread()->handle_alloc_failure(req);
 833       result = allocate_memory_under_lock(req, in_new_region);
 834     }
 835 
 836   } else {
 837     assert(req.is_gc_alloc(), "Can only accept GC allocs here");
 838     result = allocate_memory_under_lock(req, in_new_region);
 839     // Do not call handle_alloc_failure() here, because we cannot block.
 840     // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
 841   }
 842 
 843   if (in_new_region) {
 844     control_thread()->notify_heap_changed();
 845   }
 846 
 847   if (result != NULL) {
 848     size_t requested = req.size();
 849     size_t actual = req.actual_size();
 850 
 851     assert (req.is_lab_alloc() || (requested == actual),
 852             "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
 853             ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
 854 
 855     if (req.is_mutator_alloc()) {
 856       notify_mutator_alloc_words(actual, false);
 857 
 858       // If we requested more than we were granted, give the rest back to pacer.
 859       // This only matters if we are in the same pacing epoch: do not try to unpace
 860       // over the budget for the other phase.
 861       if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
 862         pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
 863       }
 864     } else {
 865       increase_used(actual*HeapWordSize);
 866     }
 867   }
 868 
 869   return result;
 870 }
 871 
 872 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
 873   ShenandoahHeapLocker locker(lock());
 874   return _free_set->allocate(req, in_new_region);
 875 }
 876 
 877 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
 878                                         bool*  gc_overhead_limit_was_exceeded) {
 879   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
 880   return allocate_memory(req);
 881 }
 882 
 883 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
 884                                                              size_t size,
 885                                                              Metaspace::MetadataType mdtype) {
 886   MetaWord* result;
 887 
 888   // Inform metaspace OOM to GC heuristics if class unloading is possible.
 889   if (heuristics()->can_unload_classes()) {
 890     ShenandoahHeuristics* h = heuristics();
 891     h->record_metaspace_oom();
 892   }
 893 
 894   // Expand and retry allocation
 895   result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
 896   if (result != NULL) {
 897     return result;
 898   }
 899 
 900   // Start full GC
 901   collect(GCCause::_metadata_GC_clear_soft_refs);
 902 
 903   // Retry allocation
 904   result = loader_data->metaspace_non_null()->allocate(size, mdtype);
 905   if (result != NULL) {
 906     return result;
 907   }
 908 
 909   // Expand and retry allocation
 910   result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
 911   if (result != NULL) {
 912     return result;
 913   }
 914 
 915   // Out of memory
 916   return NULL;
 917 }
 918 
 919 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
 920 private:
 921   ShenandoahHeap* const _heap;
 922   Thread* const _thread;
 923 public:
 924   ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
 925     _heap(heap), _thread(Thread::current()) {}
 926 
 927   void do_object(oop p) {
 928     shenandoah_assert_marked(NULL, p);
 929     if (!p->is_forwarded()) {
 930       _heap->evacuate_object(p, _thread);
 931     }
 932   }
 933 };
 934 
 935 class ShenandoahEvacuationTask : public AbstractGangTask {
 936 private:
 937   ShenandoahHeap* const _sh;
 938   ShenandoahCollectionSet* const _cs;
 939   bool _concurrent;
 940 public:
 941   ShenandoahEvacuationTask(ShenandoahHeap* sh,
 942                            ShenandoahCollectionSet* cs,
 943                            bool concurrent) :
 944     AbstractGangTask("Parallel Evacuation Task"),
 945     _sh(sh),
 946     _cs(cs),
 947     _concurrent(concurrent)
 948   {}
 949 
 950   void work(uint worker_id) {
 951     if (_concurrent) {
 952       ShenandoahConcurrentWorkerSession worker_session(worker_id);
 953       ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
 954       ShenandoahEvacOOMScope oom_evac_scope;
 955       do_work();
 956     } else {
 957       ShenandoahParallelWorkerSession worker_session(worker_id);
 958       ShenandoahEvacOOMScope oom_evac_scope;
 959       do_work();
 960     }
 961   }
 962 
 963 private:
 964   void do_work() {
 965     ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
 966     ShenandoahHeapRegion* r;
 967     while ((r =_cs->claim_next()) != NULL) {
 968       assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
 969       _sh->marked_object_iterate(r, &cl);
 970 
 971       if (ShenandoahPacing) {
 972         _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
 973       }
 974 
 975       if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
 976         break;
 977       }
 978     }
 979   }
 980 };
 981 
 982 void ShenandoahHeap::trash_cset_regions() {
 983   ShenandoahHeapLocker locker(lock());
 984 
 985   ShenandoahCollectionSet* set = collection_set();
 986   ShenandoahHeapRegion* r;
 987   set->clear_current_index();
 988   while ((r = set->next()) != NULL) {
 989     r->make_trash();
 990   }
 991   collection_set()->clear();
 992 }
 993 
 994 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
 995   st->print_cr("Heap Regions:");
 996   st->print_cr("EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HC=humongous continuation, CS=collection set, T=trash, P=pinned");
 997   st->print_cr("BTE=bottom/top/end, U=used, T=TLAB allocs, G=GCLAB allocs, S=shared allocs, L=live data");
 998   st->print_cr("R=root, CP=critical pins, TAMS=top-at-mark-start, UWM=update watermark");
 999   st->print_cr("SN=alloc sequence number");
1000 
1001   for (size_t i = 0; i < num_regions(); i++) {
1002     get_region(i)->print_on(st);
1003   }
1004 }
1005 
1006 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1007   assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1008 
1009   oop humongous_obj = oop(start->bottom());
1010   size_t size = humongous_obj->size();
1011   size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1012   size_t index = start->index() + required_regions - 1;
1013 
1014   assert(!start->has_live(), "liveness must be zero");
1015 
1016   for(size_t i = 0; i < required_regions; i++) {
1017     // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1018     // as it expects that every region belongs to a humongous region starting with a humongous start region.
1019     ShenandoahHeapRegion* region = get_region(index --);
1020 
1021     assert(region->is_humongous(), "expect correct humongous start or continuation");
1022     assert(!region->is_cset(), "Humongous region should not be in collection set");
1023 
1024     region->make_trash_immediate();
1025   }
1026 }
1027 
1028 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1029 public:
1030   ShenandoahCheckCleanGCLABClosure() {}
1031   void do_thread(Thread* thread) {
1032     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1033     assert(gclab != NULL, "GCLAB should be initialized for %s", thread->name());
1034     assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1035   }
1036 };
1037 
1038 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1039 private:
1040   bool const _resize;
1041 public:
1042   ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1043   void do_thread(Thread* thread) {
1044     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1045     assert(gclab != NULL, "GCLAB should be initialized for %s", thread->name());
1046     gclab->retire();
1047     if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1048       ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1049     }
1050   }
1051 };
1052 
1053 void ShenandoahHeap::labs_make_parsable() {
1054   assert(UseTLAB, "Only call with UseTLAB");
1055 
1056   ShenandoahRetireGCLABClosure cl(false);
1057 
1058   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1059     ThreadLocalAllocBuffer& tlab = t->tlab();
1060     tlab.make_parsable();
1061     cl.do_thread(t);
1062   }
1063 
1064   workers()->threads_do(&cl);
1065 }
1066 
1067 void ShenandoahHeap::tlabs_retire(bool resize) {
1068   assert(UseTLAB, "Only call with UseTLAB");
1069   assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1070 
1071   ThreadLocalAllocStats stats;
1072 
1073   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1074     ThreadLocalAllocBuffer& tlab = t->tlab();
1075     tlab.retire(&stats);
1076     if (resize) {
1077       tlab.resize();
1078     }
1079   }
1080 
1081   stats.publish();
1082 
1083 #ifdef ASSERT
1084   ShenandoahCheckCleanGCLABClosure cl;
1085   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1086     cl.do_thread(t);
1087   }
1088   workers()->threads_do(&cl);
1089 #endif
1090 }
1091 
1092 void ShenandoahHeap::gclabs_retire(bool resize) {
1093   assert(UseTLAB, "Only call with UseTLAB");
1094   assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1095 
1096   ShenandoahRetireGCLABClosure cl(resize);
1097   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1098     cl.do_thread(t);
1099   }
1100   workers()->threads_do(&cl);
1101 }
1102 
1103 class ShenandoahEvacuateUpdateRootsTask : public AbstractGangTask {
1104 private:
1105   ShenandoahRootEvacuator* _rp;
1106 
1107 public:
1108   ShenandoahEvacuateUpdateRootsTask(ShenandoahRootEvacuator* rp) :
1109     AbstractGangTask("Shenandoah evacuate and update roots"),
1110     _rp(rp) {}
1111 
1112   void work(uint worker_id) {
1113     ShenandoahParallelWorkerSession worker_session(worker_id);
1114     ShenandoahEvacOOMScope oom_evac_scope;
1115     ShenandoahEvacuateUpdateRootsClosure<> cl;
1116     MarkingCodeBlobClosure blobsCl(&cl, CodeBlobToOopClosure::FixRelocations);
1117     _rp->roots_do(worker_id, &cl);
1118   }
1119 };
1120 
1121 void ShenandoahHeap::evacuate_and_update_roots() {
1122 #if COMPILER2_OR_JVMCI
1123   DerivedPointerTable::clear();
1124 #endif
1125   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only iterate roots while world is stopped");
1126   {
1127     // Include concurrent roots if current cycle can not process those roots concurrently
1128     ShenandoahRootEvacuator rp(workers()->active_workers(),
1129                                ShenandoahPhaseTimings::init_evac,
1130                                !ShenandoahConcurrentRoots::should_do_concurrent_roots(),
1131                                !ShenandoahConcurrentRoots::should_do_concurrent_class_unloading());
1132     ShenandoahEvacuateUpdateRootsTask roots_task(&rp);
1133     workers()->run_task(&roots_task);
1134   }
1135 
1136 #if COMPILER2_OR_JVMCI
1137   DerivedPointerTable::update_pointers();
1138 #endif
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   workers()->threads_do(tcl);
1190   if (_safepoint_workers != NULL) {
1191     _safepoint_workers->threads_do(tcl);
1192   }
1193   if (ShenandoahStringDedup::is_enabled()) {
1194     ShenandoahStringDedup::threads_do(tcl);
1195   }
1196 }
1197 
1198 void ShenandoahHeap::print_tracing_info() const {
1199   LogTarget(Info, gc, stats) lt;
1200   if (lt.is_enabled()) {
1201     ResourceMark rm;
1202     LogStream ls(lt);
1203 
1204     phase_timings()->print_global_on(&ls);
1205 
1206     ls.cr();
1207     ls.cr();
1208 
1209     shenandoah_policy()->print_gc_stats(&ls);
1210 
1211     ls.cr();
1212     ls.cr();
1213   }
1214 }
1215 
1216 void ShenandoahHeap::verify(VerifyOption vo) {
1217   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1218     if (ShenandoahVerify) {
1219       verifier()->verify_generic(vo);
1220     } else {
1221       // TODO: Consider allocating verification bitmaps on demand,
1222       // and turn this on unconditionally.
1223     }
1224   }
1225 }
1226 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1227   return _free_set->capacity();
1228 }
1229 
1230 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1231 private:
1232   MarkBitMap* _bitmap;
1233   Stack<oop,mtGC>* _oop_stack;
1234   ShenandoahHeap* const _heap;
1235   ShenandoahMarkingContext* const _marking_context;
1236 
1237   template <class T>
1238   void do_oop_work(T* p) {
1239     T o = RawAccess<>::oop_load(p);
1240     if (!CompressedOops::is_null(o)) {
1241       oop obj = CompressedOops::decode_not_null(o);
1242       if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1243         // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1244         return;
1245       }
1246       obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
1247 
1248       assert(oopDesc::is_oop(obj), "must be a valid oop");
1249       if (!_bitmap->is_marked(obj)) {
1250         _bitmap->mark(obj);
1251         _oop_stack->push(obj);
1252       }
1253     }
1254   }
1255 public:
1256   ObjectIterateScanRootClosure(MarkBitMap* bitmap, Stack<oop,mtGC>* oop_stack) :
1257     _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1258     _marking_context(_heap->marking_context()) {}
1259   void do_oop(oop* p)       { do_oop_work(p); }
1260   void do_oop(narrowOop* p) { do_oop_work(p); }
1261 };
1262 
1263 /*
1264  * This is public API, used in preparation of object_iterate().
1265  * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1266  * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1267  * control, we call SH::tlabs_retire, SH::gclabs_retire.
1268  */
1269 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1270   // No-op.
1271 }
1272 
1273 /*
1274  * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1275  *
1276  * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1277  * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1278  * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1279  * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1280  * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1281  * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1282  * wiped the bitmap in preparation for next marking).
1283  *
1284  * For all those reasons, we implement object iteration as a single marking traversal, reporting
1285  * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1286  * is allowed to report dead objects, but is not required to do so.
1287  */
1288 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1289   assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1290   if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1291     log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1292     return;
1293   }
1294 
1295   // Reset bitmap
1296   _aux_bit_map.clear();
1297 
1298   Stack<oop,mtGC> oop_stack;
1299 
1300   ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1301 
1302   {
1303     // First, we process GC roots according to current GC cycle.
1304     // This populates the work stack with initial objects.
1305     // It is important to relinquish the associated locks before diving
1306     // into heap dumper.
1307     ShenandoahHeapIterationRootScanner rp;
1308     rp.roots_do(&oops);
1309   }
1310 
1311   // Work through the oop stack to traverse heap.
1312   while (! oop_stack.is_empty()) {
1313     oop obj = oop_stack.pop();
1314     assert(oopDesc::is_oop(obj), "must be a valid oop");
1315     cl->do_object(obj);
1316     obj->oop_iterate(&oops);
1317   }
1318 
1319   assert(oop_stack.is_empty(), "should be empty");
1320 
1321   if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1322     log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1323   }
1324 }
1325 
1326 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1327 void ShenandoahHeap::keep_alive(oop obj) {
1328   if (is_concurrent_mark_in_progress() && (obj != NULL)) {
1329     ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1330   }
1331 }
1332 
1333 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1334   for (size_t i = 0; i < num_regions(); i++) {
1335     ShenandoahHeapRegion* current = get_region(i);
1336     blk->heap_region_do(current);
1337   }
1338 }
1339 
1340 class ShenandoahParallelHeapRegionTask : public AbstractGangTask {
1341 private:
1342   ShenandoahHeap* const _heap;
1343   ShenandoahHeapRegionClosure* const _blk;
1344 
1345   shenandoah_padding(0);
1346   volatile size_t _index;
1347   shenandoah_padding(1);
1348 
1349 public:
1350   ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1351           AbstractGangTask("Parallel Region Task"),
1352           _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1353 
1354   void work(uint worker_id) {
1355     ShenandoahParallelWorkerSession worker_session(worker_id);
1356     size_t stride = ShenandoahParallelRegionStride;
1357 
1358     size_t max = _heap->num_regions();
1359     while (_index < max) {
1360       size_t cur = Atomic::fetch_and_add(&_index, stride);
1361       size_t start = cur;
1362       size_t end = MIN2(cur + stride, max);
1363       if (start >= max) break;
1364 
1365       for (size_t i = cur; i < end; i++) {
1366         ShenandoahHeapRegion* current = _heap->get_region(i);
1367         _blk->heap_region_do(current);
1368       }
1369     }
1370   }
1371 };
1372 
1373 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1374   assert(blk->is_thread_safe(), "Only thread-safe closures here");
1375   if (num_regions() > ShenandoahParallelRegionStride) {
1376     ShenandoahParallelHeapRegionTask task(blk);
1377     workers()->run_task(&task);
1378   } else {
1379     heap_region_iterate(blk);
1380   }
1381 }
1382 
1383 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1384 private:
1385   ShenandoahMarkingContext* const _ctx;
1386 public:
1387   ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1388 
1389   void heap_region_do(ShenandoahHeapRegion* r) {
1390     assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1391     if (r->is_active()) {
1392       // Check if region needs updating its TAMS. We have updated it already during concurrent
1393       // reset, so it is very likely we don't need to do another write here.
1394       if (_ctx->top_at_mark_start(r) != r->top()) {
1395         _ctx->capture_top_at_mark_start(r);
1396       }
1397     } else {
1398       assert(_ctx->top_at_mark_start(r) == r->top(),
1399              "Region " SIZE_FORMAT " should already have correct TAMS", r->index());
1400     }
1401   }
1402 
1403   bool is_thread_safe() { return true; }
1404 };
1405 
1406 void ShenandoahHeap::op_init_mark() {
1407   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
1408   assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
1409 
1410   assert(marking_context()->is_bitmap_clear(), "need clear marking bitmap");
1411   assert(!marking_context()->is_complete(), "should not be complete");
1412   assert(!has_forwarded_objects(), "No forwarded objects on this path");
1413 
1414   if (ShenandoahVerify) {
1415     verifier()->verify_before_concmark();
1416   }
1417 
1418   if (VerifyBeforeGC) {
1419     Universe::verify();
1420   }
1421 
1422   set_concurrent_mark_in_progress(true);
1423 
1424   // We need to reset all TLABs because they might be below the TAMS, and we need to mark
1425   // the objects in them. Do not let mutators allocate any new objects in their current TLABs.
1426   // It is also a good place to resize the TLAB sizes for future allocations.
1427   if (UseTLAB) {
1428     ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_manage_tlabs);
1429     tlabs_retire(ResizeTLAB);
1430   }
1431 
1432   {
1433     ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_region_states);
1434     ShenandoahInitMarkUpdateRegionStateClosure cl;
1435     parallel_heap_region_iterate(&cl);
1436   }
1437 
1438   // Make above changes visible to worker threads
1439   OrderAccess::fence();
1440 
1441   concurrent_mark()->mark_roots(ShenandoahPhaseTimings::scan_roots);
1442 
1443   if (ShenandoahPacing) {
1444     pacer()->setup_for_mark();
1445   }
1446 
1447   // Arm nmethods for concurrent marking. When a nmethod is about to be executed,
1448   // we need to make sure that all its metadata are marked. alternative is to remark
1449   // thread roots at final mark pause, but it can be potential latency killer.
1450   if (ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
1451     ShenandoahCodeRoots::arm_nmethods();
1452   }
1453 }
1454 
1455 void ShenandoahHeap::op_mark() {
1456   concurrent_mark()->mark_from_roots();
1457 }
1458 
1459 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1460 private:
1461   ShenandoahMarkingContext* const _ctx;
1462   ShenandoahHeapLock* const _lock;
1463 
1464 public:
1465   ShenandoahFinalMarkUpdateRegionStateClosure() :
1466     _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1467 
1468   void heap_region_do(ShenandoahHeapRegion* r) {
1469     if (r->is_active()) {
1470       // All allocations past TAMS are implicitly live, adjust the region data.
1471       // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1472       HeapWord *tams = _ctx->top_at_mark_start(r);
1473       HeapWord *top = r->top();
1474       if (top > tams) {
1475         r->increase_live_data_alloc_words(pointer_delta(top, tams));
1476       }
1477 
1478       // We are about to select the collection set, make sure it knows about
1479       // current pinning status. Also, this allows trashing more regions that
1480       // now have their pinning status dropped.
1481       if (r->is_pinned()) {
1482         if (r->pin_count() == 0) {
1483           ShenandoahHeapLocker locker(_lock);
1484           r->make_unpinned();
1485         }
1486       } else {
1487         if (r->pin_count() > 0) {
1488           ShenandoahHeapLocker locker(_lock);
1489           r->make_pinned();
1490         }
1491       }
1492 
1493       // Remember limit for updating refs. It's guaranteed that we get no
1494       // from-space-refs written from here on.
1495       r->set_update_watermark_at_safepoint(r->top());
1496     } else {
1497       assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1498       assert(_ctx->top_at_mark_start(r) == r->top(),
1499              "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1500     }
1501   }
1502 
1503   bool is_thread_safe() { return true; }
1504 };
1505 
1506 void ShenandoahHeap::op_final_mark() {
1507   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
1508   assert(!has_forwarded_objects(), "No forwarded objects on this path");
1509 
1510   // It is critical that we
1511   // evacuate roots right after finishing marking, so that we don't
1512   // get unmarked objects in the roots.
1513 
1514   if (!cancelled_gc()) {
1515     concurrent_mark()->finish_mark_from_roots(/* full_gc = */ false);
1516 
1517     // Marking is completed, deactivate SATB barrier
1518     set_concurrent_mark_in_progress(false);
1519     mark_complete_marking_context();
1520 
1521     parallel_cleaning(false /* full gc*/);
1522 
1523     if (ShenandoahVerify) {
1524       verifier()->verify_roots_no_forwarded();
1525     }
1526 
1527     {
1528       ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_region_states);
1529       ShenandoahFinalMarkUpdateRegionStateClosure cl;
1530       parallel_heap_region_iterate(&cl);
1531 
1532       assert_pinned_region_status();
1533     }
1534 
1535     // Retire the TLABs, which will force threads to reacquire their TLABs after the pause.
1536     // This is needed for two reasons. Strong one: new allocations would be with new freeset,
1537     // which would be outside the collection set, so no cset writes would happen there.
1538     // Weaker one: new allocations would happen past update watermark, and so less work would
1539     // be needed for reference updates (would update the large filler instead).
1540     if (UseTLAB) {
1541       ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_manage_labs);
1542       tlabs_retire(false);
1543     }
1544 
1545     {
1546       ShenandoahGCPhase phase(ShenandoahPhaseTimings::choose_cset);
1547       ShenandoahHeapLocker locker(lock());
1548       _collection_set->clear();
1549       heuristics()->choose_collection_set(_collection_set);
1550     }
1551 
1552     {
1553       ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_rebuild_freeset);
1554       ShenandoahHeapLocker locker(lock());
1555       _free_set->rebuild();
1556     }
1557 
1558     if (!is_degenerated_gc_in_progress()) {
1559       prepare_concurrent_roots();
1560       prepare_concurrent_unloading();
1561     }
1562 
1563     // If collection set has candidates, start evacuation.
1564     // Otherwise, bypass the rest of the cycle.
1565     if (!collection_set()->is_empty()) {
1566       ShenandoahGCPhase init_evac(ShenandoahPhaseTimings::init_evac);
1567 
1568       if (ShenandoahVerify) {
1569         verifier()->verify_before_evacuation();
1570       }
1571 
1572       set_evacuation_in_progress(true);
1573       // From here on, we need to update references.
1574       set_has_forwarded_objects(true);
1575 
1576       if (!is_degenerated_gc_in_progress()) {
1577         if (ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
1578           ShenandoahCodeRoots::arm_nmethods();
1579         }
1580         evacuate_and_update_roots();
1581       }
1582 
1583       if (ShenandoahPacing) {
1584         pacer()->setup_for_evac();
1585       }
1586 
1587       if (ShenandoahVerify) {
1588         // If OOM while evacuating/updating of roots, there is no guarantee of their consistencies
1589         if (!cancelled_gc()) {
1590           ShenandoahRootVerifier::RootTypes types = ShenandoahRootVerifier::None;
1591           if (ShenandoahConcurrentRoots::should_do_concurrent_roots()) {
1592             types = ShenandoahRootVerifier::combine(ShenandoahRootVerifier::JNIHandleRoots, ShenandoahRootVerifier::WeakRoots);
1593             types = ShenandoahRootVerifier::combine(types, ShenandoahRootVerifier::CLDGRoots);
1594             types = ShenandoahRootVerifier::combine(types, ShenandoahRootVerifier::StringDedupRoots);
1595           }
1596 
1597           if (ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
1598             types = ShenandoahRootVerifier::combine(types, ShenandoahRootVerifier::CodeRoots);
1599           }
1600           verifier()->verify_roots_no_forwarded_except(types);
1601         }
1602         verifier()->verify_during_evacuation();
1603       }
1604     } else {
1605       if (ShenandoahVerify) {
1606         verifier()->verify_after_concmark();
1607       }
1608 
1609       if (VerifyAfterGC) {
1610         Universe::verify();
1611       }
1612     }
1613 
1614   } else {
1615     // If this cycle was updating references, we need to keep the has_forwarded_objects
1616     // flag on, for subsequent phases to deal with it.
1617     concurrent_mark()->cancel();
1618     set_concurrent_mark_in_progress(false);
1619 
1620     if (process_references()) {
1621       // Abandon reference processing right away: pre-cleaning must have failed.
1622       ReferenceProcessor *rp = ref_processor();
1623       rp->disable_discovery();
1624       rp->abandon_partial_discovery();
1625       rp->verify_no_references_recorded();
1626     }
1627   }
1628 }
1629 
1630 void ShenandoahHeap::op_conc_evac() {
1631   ShenandoahEvacuationTask task(this, _collection_set, true);
1632   workers()->run_task(&task);
1633 }
1634 
1635 void ShenandoahHeap::op_stw_evac() {
1636   ShenandoahEvacuationTask task(this, _collection_set, false);
1637   workers()->run_task(&task);
1638 }
1639 
1640 void ShenandoahHeap::op_updaterefs() {
1641   update_heap_references(true);
1642 }
1643 
1644 void ShenandoahHeap::op_cleanup_early() {
1645   free_set()->recycle_trash();
1646 }
1647 
1648 void ShenandoahHeap::op_cleanup_complete() {
1649   free_set()->recycle_trash();
1650 }
1651 
1652 class ShenandoahConcurrentRootsEvacUpdateTask : public AbstractGangTask {
1653 private:
1654   ShenandoahVMRoots<true /*concurrent*/>        _vm_roots;
1655   ShenandoahClassLoaderDataRoots<true /*concurrent*/, false /*single threaded*/> _cld_roots;
1656 
1657 public:
1658   ShenandoahConcurrentRootsEvacUpdateTask(ShenandoahPhaseTimings::Phase phase) :
1659     AbstractGangTask("Shenandoah Evacuate/Update Concurrent Strong Roots Task"),
1660     _vm_roots(phase),
1661     _cld_roots(phase, ShenandoahHeap::heap()->workers()->active_workers()) {}
1662 
1663   void work(uint worker_id) {
1664     ShenandoahConcurrentWorkerSession worker_session(worker_id);
1665     ShenandoahEvacOOMScope oom;
1666     {
1667       // vm_roots and weak_roots are OopStorage backed roots, concurrent iteration
1668       // may race against OopStorage::release() calls.
1669       ShenandoahEvacUpdateOopStorageRootsClosure cl;
1670       _vm_roots.oops_do<ShenandoahEvacUpdateOopStorageRootsClosure>(&cl, worker_id);
1671     }
1672 
1673     {
1674       ShenandoahEvacuateUpdateRootsClosure<> cl;
1675       CLDToOopClosure clds(&cl, ClassLoaderData::_claim_strong);
1676       _cld_roots.cld_do(&clds, worker_id);
1677     }
1678   }
1679 };
1680 
1681 class ShenandoahEvacUpdateCleanupOopStorageRootsClosure : public BasicOopIterateClosure {
1682 private:
1683   ShenandoahHeap* const _heap;
1684   ShenandoahMarkingContext* const _mark_context;
1685   bool  _evac_in_progress;
1686   Thread* const _thread;
1687 
1688 public:
1689   ShenandoahEvacUpdateCleanupOopStorageRootsClosure();
1690   void do_oop(oop* p);
1691   void do_oop(narrowOop* p);
1692 };
1693 
1694 ShenandoahEvacUpdateCleanupOopStorageRootsClosure::ShenandoahEvacUpdateCleanupOopStorageRootsClosure() :
1695   _heap(ShenandoahHeap::heap()),
1696   _mark_context(ShenandoahHeap::heap()->marking_context()),
1697   _evac_in_progress(ShenandoahHeap::heap()->is_evacuation_in_progress()),
1698   _thread(Thread::current()) {
1699 }
1700 
1701 void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::do_oop(oop* p) {
1702   const oop obj = RawAccess<>::oop_load(p);
1703   if (!CompressedOops::is_null(obj)) {
1704     if (!_mark_context->is_marked(obj)) {
1705       shenandoah_assert_correct(p, obj);
1706       Atomic::cmpxchg(p, obj, oop(NULL));
1707     } else if (_evac_in_progress && _heap->in_collection_set(obj)) {
1708       oop resolved = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
1709       if (resolved == obj) {
1710         resolved = _heap->evacuate_object(obj, _thread);
1711       }
1712       Atomic::cmpxchg(p, obj, resolved);
1713       assert(_heap->cancelled_gc() ||
1714              _mark_context->is_marked(resolved) && !_heap->in_collection_set(resolved),
1715              "Sanity");
1716     }
1717   }
1718 }
1719 
1720 void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::do_oop(narrowOop* p) {
1721   ShouldNotReachHere();
1722 }
1723 
1724 class ShenandoahIsCLDAliveClosure : public CLDClosure {
1725 public:
1726   void do_cld(ClassLoaderData* cld) {
1727     cld->is_alive();
1728   }
1729 };
1730 
1731 class ShenandoahIsNMethodAliveClosure: public NMethodClosure {
1732 public:
1733   void do_nmethod(nmethod* n) {
1734     n->is_unloading();
1735   }
1736 };
1737 
1738 // This task not only evacuates/updates marked weak roots, but also "NULL"
1739 // dead weak roots.
1740 class ShenandoahConcurrentWeakRootsEvacUpdateTask : public AbstractGangTask {
1741 private:
1742   ShenandoahVMWeakRoots<true /*concurrent*/> _vm_roots;
1743 
1744   // Roots related to concurrent class unloading
1745   ShenandoahClassLoaderDataRoots<true /* concurrent */, false /* single thread*/>
1746                                              _cld_roots;
1747   ShenandoahConcurrentNMethodIterator        _nmethod_itr;
1748   ShenandoahConcurrentStringDedupRoots       _dedup_roots;
1749   bool                                       _concurrent_class_unloading;
1750 
1751 public:
1752   ShenandoahConcurrentWeakRootsEvacUpdateTask(ShenandoahPhaseTimings::Phase phase) :
1753     AbstractGangTask("Shenandoah Concurrent Weak Root Task"),
1754     _vm_roots(phase),
1755     _cld_roots(phase, ShenandoahHeap::heap()->workers()->active_workers()),
1756     _nmethod_itr(ShenandoahCodeRoots::table()),
1757     _dedup_roots(phase),
1758     _concurrent_class_unloading(ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
1759     if (_concurrent_class_unloading) {
1760       MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
1761       _nmethod_itr.nmethods_do_begin();
1762     }
1763   }
1764 
1765   ~ShenandoahConcurrentWeakRootsEvacUpdateTask() {
1766     if (_concurrent_class_unloading) {
1767       MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
1768       _nmethod_itr.nmethods_do_end();
1769     }
1770     // Notify runtime data structures of potentially dead oops
1771     _vm_roots.report_num_dead();
1772   }
1773 
1774   void work(uint worker_id) {
1775     ShenandoahConcurrentWorkerSession worker_session(worker_id);
1776     {
1777       ShenandoahEvacOOMScope oom;
1778       // jni_roots and weak_roots are OopStorage backed roots, concurrent iteration
1779       // may race against OopStorage::release() calls.
1780       ShenandoahEvacUpdateCleanupOopStorageRootsClosure cl;
1781       _vm_roots.oops_do(&cl, worker_id);
1782 
1783       // String dedup weak roots
1784       ShenandoahForwardedIsAliveClosure is_alive;
1785       ShenandoahEvacuateUpdateRootsClosure<MO_RELEASE> keep_alive;
1786       _dedup_roots.oops_do(&is_alive, &keep_alive, worker_id);
1787     }
1788 
1789     // If we are going to perform concurrent class unloading later on, we need to
1790     // cleanup the weak oops in CLD and determinate nmethod's unloading state, so that we
1791     // can cleanup immediate garbage sooner.
1792     if (_concurrent_class_unloading) {
1793       // Applies ShenandoahIsCLDAlive closure to CLDs, native barrier will either NULL the
1794       // CLD's holder or evacuate it.
1795       ShenandoahIsCLDAliveClosure is_cld_alive;
1796       _cld_roots.cld_do(&is_cld_alive, worker_id);
1797 
1798       // Applies ShenandoahIsNMethodAliveClosure to registered nmethods.
1799       // The closure calls nmethod->is_unloading(). The is_unloading
1800       // state is cached, therefore, during concurrent class unloading phase,
1801       // we will not touch the metadata of unloading nmethods
1802       ShenandoahIsNMethodAliveClosure is_nmethod_alive;
1803       _nmethod_itr.nmethods_do(&is_nmethod_alive);
1804     }
1805   }
1806 };
1807 
1808 void ShenandoahHeap::op_weak_roots() {
1809   if (is_concurrent_weak_root_in_progress()) {
1810     // Concurrent weak root processing
1811     {
1812       ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_weak_roots_work);
1813       ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_weak_roots_work);
1814       ShenandoahConcurrentWeakRootsEvacUpdateTask task(ShenandoahPhaseTimings::conc_weak_roots_work);
1815       workers()->run_task(&task);
1816       if (!ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
1817         set_concurrent_weak_root_in_progress(false);
1818       }
1819     }
1820 
1821     // Perform handshake to flush out dead oops
1822     {
1823       ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_weak_roots_rendezvous);
1824       ShenandoahRendezvousClosure cl;
1825       Handshake::execute(&cl);
1826     }
1827   }
1828 }
1829 
1830 void ShenandoahHeap::op_class_unloading() {
1831   assert (is_concurrent_weak_root_in_progress() &&
1832           ShenandoahConcurrentRoots::should_do_concurrent_class_unloading(),
1833           "Checked by caller");
1834   _unloader.unload();
1835   set_concurrent_weak_root_in_progress(false);
1836 }
1837 
1838 void ShenandoahHeap::op_strong_roots() {
1839   assert(is_concurrent_strong_root_in_progress(), "Checked by caller");
1840   ShenandoahConcurrentRootsEvacUpdateTask task(ShenandoahPhaseTimings::conc_strong_roots);
1841   workers()->run_task(&task);
1842   set_concurrent_strong_root_in_progress(false);
1843 }
1844 
1845 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1846 private:
1847   ShenandoahMarkingContext* const _ctx;
1848 public:
1849   ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1850 
1851   void heap_region_do(ShenandoahHeapRegion* r) {
1852     if (r->is_active()) {
1853       // Reset live data and set TAMS optimistically. We would recheck these under the pause
1854       // anyway to capture any updates that happened since now.
1855       r->clear_live_data();
1856       _ctx->capture_top_at_mark_start(r);
1857     }
1858   }
1859 
1860   bool is_thread_safe() { return true; }
1861 };
1862 
1863 void ShenandoahHeap::op_reset() {
1864   if (ShenandoahPacing) {
1865     pacer()->setup_for_reset();
1866   }
1867   reset_mark_bitmap();
1868 
1869   ShenandoahResetUpdateRegionStateClosure cl;
1870   parallel_heap_region_iterate(&cl);
1871 }
1872 
1873 void ShenandoahHeap::op_preclean() {
1874   if (ShenandoahPacing) {
1875     pacer()->setup_for_preclean();
1876   }
1877   concurrent_mark()->preclean_weak_refs();
1878 }
1879 
1880 void ShenandoahHeap::op_full(GCCause::Cause cause) {
1881   ShenandoahMetricsSnapshot metrics;
1882   metrics.snap_before();
1883 
1884   full_gc()->do_it(cause);
1885 
1886   metrics.snap_after();
1887 
1888   if (metrics.is_good_progress()) {
1889     _progress_last_gc.set();
1890   } else {
1891     // Nothing to do. Tell the allocation path that we have failed to make
1892     // progress, and it can finally fail.
1893     _progress_last_gc.unset();
1894   }
1895 }
1896 
1897 void ShenandoahHeap::op_degenerated(ShenandoahDegenPoint point) {
1898   // Degenerated GC is STW, but it can also fail. Current mechanics communicates
1899   // GC failure via cancelled_concgc() flag. So, if we detect the failure after
1900   // some phase, we have to upgrade the Degenerate GC to Full GC.
1901 
1902   clear_cancelled_gc();
1903 
1904   ShenandoahMetricsSnapshot metrics;
1905   metrics.snap_before();
1906 
1907   switch (point) {
1908     // The cases below form the Duff's-like device: it describes the actual GC cycle,
1909     // but enters it at different points, depending on which concurrent phase had
1910     // degenerated.
1911 
1912     case _degenerated_outside_cycle:
1913       // We have degenerated from outside the cycle, which means something is bad with
1914       // the heap, most probably heavy humongous fragmentation, or we are very low on free
1915       // space. It makes little sense to wait for Full GC to reclaim as much as it can, when
1916       // we can do the most aggressive degen cycle, which includes processing references and
1917       // class unloading, unless those features are explicitly disabled.
1918       //
1919       // Note that we can only do this for "outside-cycle" degens, otherwise we would risk
1920       // changing the cycle parameters mid-cycle during concurrent -> degenerated handover.
1921       set_process_references(heuristics()->can_process_references());
1922       set_unload_classes(heuristics()->can_unload_classes());
1923 
1924       op_reset();
1925 
1926       op_init_mark();
1927       if (cancelled_gc()) {
1928         op_degenerated_fail();
1929         return;
1930       }
1931 
1932     case _degenerated_mark:
1933       op_final_mark();
1934       if (cancelled_gc()) {
1935         op_degenerated_fail();
1936         return;
1937       }
1938 
1939       if (!has_forwarded_objects() && ShenandoahConcurrentRoots::can_do_concurrent_class_unloading()) {
1940         // Disarm nmethods that armed for concurrent mark. On normal cycle, it would
1941         // be disarmed while conc-roots phase is running.
1942         // TODO: Call op_conc_roots() here instead
1943         ShenandoahCodeRoots::disarm_nmethods();
1944       }
1945 
1946       op_cleanup_early();
1947 
1948     case _degenerated_evac:
1949       // If heuristics thinks we should do the cycle, this flag would be set,
1950       // and we can do evacuation. Otherwise, it would be the shortcut cycle.
1951       if (is_evacuation_in_progress()) {
1952 
1953         // Degeneration under oom-evac protocol might have left some objects in
1954         // collection set un-evacuated. Restart evacuation from the beginning to
1955         // capture all objects. For all the objects that are already evacuated,
1956         // it would be a simple check, which is supposed to be fast. This is also
1957         // safe to do even without degeneration, as CSet iterator is at beginning
1958         // in preparation for evacuation anyway.
1959         //
1960         // Before doing that, we need to make sure we never had any cset-pinned
1961         // regions. This may happen if allocation failure happened when evacuating
1962         // the about-to-be-pinned object, oom-evac protocol left the object in
1963         // the collection set, and then the pin reached the cset region. If we continue
1964         // the cycle here, we would trash the cset and alive objects in it. To avoid
1965         // it, we fail degeneration right away and slide into Full GC to recover.
1966 
1967         {
1968           sync_pinned_region_status();
1969           collection_set()->clear_current_index();
1970 
1971           ShenandoahHeapRegion* r;
1972           while ((r = collection_set()->next()) != NULL) {
1973             if (r->is_pinned()) {
1974               cancel_gc(GCCause::_shenandoah_upgrade_to_full_gc);
1975               op_degenerated_fail();
1976               return;
1977             }
1978           }
1979 
1980           collection_set()->clear_current_index();
1981         }
1982 
1983         op_stw_evac();
1984         if (cancelled_gc()) {
1985           op_degenerated_fail();
1986           return;
1987         }
1988       }
1989 
1990       // If heuristics thinks we should do the cycle, this flag would be set,
1991       // and we need to do update-refs. Otherwise, it would be the shortcut cycle.
1992       if (has_forwarded_objects()) {
1993         op_init_updaterefs();
1994         if (cancelled_gc()) {
1995           op_degenerated_fail();
1996           return;
1997         }
1998       }
1999 
2000     case _degenerated_updaterefs:
2001       if (has_forwarded_objects()) {
2002         op_final_updaterefs();
2003         if (cancelled_gc()) {
2004           op_degenerated_fail();
2005           return;
2006         }
2007       }
2008 
2009       op_cleanup_complete();
2010       break;
2011 
2012     default:
2013       ShouldNotReachHere();
2014   }
2015 
2016   if (ShenandoahVerify) {
2017     verifier()->verify_after_degenerated();
2018   }
2019 
2020   if (VerifyAfterGC) {
2021     Universe::verify();
2022   }
2023 
2024   metrics.snap_after();
2025 
2026   // Check for futility and fail. There is no reason to do several back-to-back Degenerated cycles,
2027   // because that probably means the heap is overloaded and/or fragmented.
2028   if (!metrics.is_good_progress()) {
2029     _progress_last_gc.unset();
2030     cancel_gc(GCCause::_shenandoah_upgrade_to_full_gc);
2031     op_degenerated_futile();
2032   } else {
2033     _progress_last_gc.set();
2034   }
2035 }
2036 
2037 void ShenandoahHeap::op_degenerated_fail() {
2038   log_info(gc)("Cannot finish degeneration, upgrading to Full GC");
2039   shenandoah_policy()->record_degenerated_upgrade_to_full();
2040   op_full(GCCause::_shenandoah_upgrade_to_full_gc);
2041 }
2042 
2043 void ShenandoahHeap::op_degenerated_futile() {
2044   shenandoah_policy()->record_degenerated_upgrade_to_full();
2045   op_full(GCCause::_shenandoah_upgrade_to_full_gc);
2046 }
2047 
2048 void ShenandoahHeap::force_satb_flush_all_threads() {
2049   if (!is_concurrent_mark_in_progress()) {
2050     // No need to flush SATBs
2051     return;
2052   }
2053 
2054   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
2055     ShenandoahThreadLocalData::set_force_satb_flush(t, true);
2056   }
2057   // The threads are not "acquiring" their thread-local data, but it does not
2058   // hurt to "release" the updates here anyway.
2059   OrderAccess::fence();
2060 }
2061 
2062 void ShenandoahHeap::set_gc_state_all_threads(char state) {
2063   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
2064     ShenandoahThreadLocalData::set_gc_state(t, state);
2065   }
2066 }
2067 
2068 void ShenandoahHeap::set_gc_state_mask(uint mask, bool value) {
2069   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should really be Shenandoah safepoint");
2070   _gc_state.set_cond(mask, value);
2071   set_gc_state_all_threads(_gc_state.raw_value());
2072 }
2073 
2074 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
2075   if (has_forwarded_objects()) {
2076     set_gc_state_mask(MARKING | UPDATEREFS, in_progress);
2077   } else {
2078     set_gc_state_mask(MARKING, in_progress);
2079   }
2080   ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
2081 }
2082 
2083 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2084   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2085   set_gc_state_mask(EVACUATION, in_progress);
2086 }
2087 
2088 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2089   assert(ShenandoahConcurrentRoots::can_do_concurrent_roots(), "Why set the flag?");
2090   if (in_progress) {
2091     _concurrent_strong_root_in_progress.set();
2092   } else {
2093     _concurrent_strong_root_in_progress.unset();
2094   }
2095 }
2096 
2097 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool in_progress) {
2098   assert(ShenandoahConcurrentRoots::can_do_concurrent_roots(), "Why set the flag?");
2099   if (in_progress) {
2100     _concurrent_weak_root_in_progress.set();
2101   } else {
2102     _concurrent_weak_root_in_progress.unset();
2103   }
2104 }
2105 
2106 void ShenandoahHeap::ref_processing_init() {
2107   assert(_max_workers > 0, "Sanity");
2108 
2109   _ref_processor =
2110     new ReferenceProcessor(&_subject_to_discovery,  // is_subject_to_discovery
2111                            _ref_proc_mt_processing, // MT processing
2112                            _max_workers,            // Degree of MT processing
2113                            _ref_proc_mt_discovery,  // MT discovery
2114                            _max_workers,            // Degree of MT discovery
2115                            false,                   // Reference discovery is not atomic
2116                            NULL,                    // No closure, should be installed before use
2117                            true);                   // Scale worker threads
2118 
2119   shenandoah_assert_rp_isalive_not_installed();
2120 }
2121 
2122 GCTracer* ShenandoahHeap::tracer() {
2123   return shenandoah_policy()->tracer();
2124 }
2125 
2126 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
2127   return _free_set->used();
2128 }
2129 
2130 bool ShenandoahHeap::try_cancel_gc() {
2131   while (true) {
2132     jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
2133     if (prev == CANCELLABLE) return true;
2134     else if (prev == CANCELLED) return false;
2135     assert(ShenandoahSuspendibleWorkers, "should not get here when not using suspendible workers");
2136     assert(prev == NOT_CANCELLED, "must be NOT_CANCELLED");
2137     if (Thread::current()->is_Java_thread()) {
2138       // We need to provide a safepoint here, otherwise we might
2139       // spin forever if a SP is pending.
2140       ThreadBlockInVM sp(JavaThread::current());
2141       SpinPause();
2142     }
2143   }
2144 }
2145 
2146 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2147   if (try_cancel_gc()) {
2148     FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2149     log_info(gc)("%s", msg.buffer());
2150     Events::log(Thread::current(), "%s", msg.buffer());
2151   }
2152 }
2153 
2154 uint ShenandoahHeap::max_workers() {
2155   return _max_workers;
2156 }
2157 
2158 void ShenandoahHeap::stop() {
2159   // The shutdown sequence should be able to terminate when GC is running.
2160 
2161   // Step 0. Notify policy to disable event recording.
2162   _shenandoah_policy->record_shutdown();
2163 
2164   // Step 1. Notify control thread that we are in shutdown.
2165   // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
2166   // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
2167   control_thread()->prepare_for_graceful_shutdown();
2168 
2169   // Step 2. Notify GC workers that we are cancelling GC.
2170   cancel_gc(GCCause::_shenandoah_stop_vm);
2171 
2172   // Step 3. Wait until GC worker exits normally.
2173   control_thread()->stop();
2174 
2175   // Step 4. Stop String Dedup thread if it is active
2176   if (ShenandoahStringDedup::is_enabled()) {
2177     ShenandoahStringDedup::stop();
2178   }
2179 }
2180 
2181 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2182   if (!unload_classes()) return;
2183 
2184   // Unload classes and purge SystemDictionary.
2185   {
2186     ShenandoahGCPhase phase(full_gc ?
2187                             ShenandoahPhaseTimings::full_gc_purge_class_unload :
2188                             ShenandoahPhaseTimings::purge_class_unload);
2189     bool purged_class = SystemDictionary::do_unloading(gc_timer());
2190 
2191     ShenandoahIsAliveSelector is_alive;
2192     uint num_workers = _workers->active_workers();
2193     ShenandoahClassUnloadingTask unlink_task(is_alive.is_alive_closure(), num_workers, purged_class);
2194     _workers->run_task(&unlink_task);
2195   }
2196 
2197   {
2198     ShenandoahGCPhase phase(full_gc ?
2199                             ShenandoahPhaseTimings::full_gc_purge_cldg :
2200                             ShenandoahPhaseTimings::purge_cldg);
2201     ClassLoaderDataGraph::purge();
2202   }
2203   // Resize and verify metaspace
2204   MetaspaceGC::compute_new_size();
2205   MetaspaceUtils::verify_metrics();
2206 }
2207 
2208 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
2209 // so they should not have forwarded oops.
2210 // However, we do need to "null" dead oops in the roots, if can not be done
2211 // in concurrent cycles.
2212 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2213   ShenandoahGCPhase root_phase(full_gc ?
2214                                ShenandoahPhaseTimings::full_gc_purge :
2215                                ShenandoahPhaseTimings::purge);
2216   uint num_workers = _workers->active_workers();
2217   ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2218                                                ShenandoahPhaseTimings::full_gc_purge_weak_par :
2219                                                ShenandoahPhaseTimings::purge_weak_par;
2220   ShenandoahGCPhase phase(timing_phase);
2221   ShenandoahGCWorkerPhase worker_phase(timing_phase);
2222 
2223   // Cleanup weak roots
2224   if (has_forwarded_objects()) {
2225     ShenandoahForwardedIsAliveClosure is_alive;
2226     ShenandoahUpdateRefsClosure keep_alive;
2227     ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
2228       cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers, !ShenandoahConcurrentRoots::should_do_concurrent_class_unloading());
2229     _workers->run_task(&cleaning_task);
2230   } else {
2231     ShenandoahIsAliveClosure is_alive;
2232 #ifdef ASSERT
2233     ShenandoahAssertNotForwardedClosure verify_cl;
2234     ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2235       cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers, !ShenandoahConcurrentRoots::should_do_concurrent_class_unloading());
2236 #else
2237     ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2238       cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers, !ShenandoahConcurrentRoots::should_do_concurrent_class_unloading());
2239 #endif
2240     _workers->run_task(&cleaning_task);
2241   }
2242 }
2243 
2244 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2245   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2246   stw_process_weak_roots(full_gc);
2247   if (!ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
2248     stw_unload_classes(full_gc);
2249   }
2250 }
2251 
2252 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2253   set_gc_state_mask(HAS_FORWARDED, cond);
2254 }
2255 
2256 void ShenandoahHeap::set_process_references(bool pr) {
2257   _process_references.set_cond(pr);
2258 }
2259 
2260 void ShenandoahHeap::set_unload_classes(bool uc) {
2261   _unload_classes.set_cond(uc);
2262 }
2263 
2264 bool ShenandoahHeap::process_references() const {
2265   return _process_references.is_set();
2266 }
2267 
2268 bool ShenandoahHeap::unload_classes() const {
2269   return _unload_classes.is_set();
2270 }
2271 
2272 address ShenandoahHeap::in_cset_fast_test_addr() {
2273   ShenandoahHeap* heap = ShenandoahHeap::heap();
2274   assert(heap->collection_set() != NULL, "Sanity");
2275   return (address) heap->collection_set()->biased_map_address();
2276 }
2277 
2278 address ShenandoahHeap::cancelled_gc_addr() {
2279   return (address) ShenandoahHeap::heap()->_cancelled_gc.addr_of();
2280 }
2281 
2282 address ShenandoahHeap::gc_state_addr() {
2283   return (address) ShenandoahHeap::heap()->_gc_state.addr_of();
2284 }
2285 
2286 size_t ShenandoahHeap::bytes_allocated_since_gc_start() {
2287   return Atomic::load_acquire(&_bytes_allocated_since_gc_start);
2288 }
2289 
2290 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2291   Atomic::release_store_fence(&_bytes_allocated_since_gc_start, (size_t)0);
2292 }
2293 
2294 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2295   _degenerated_gc_in_progress.set_cond(in_progress);
2296 }
2297 
2298 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2299   _full_gc_in_progress.set_cond(in_progress);
2300 }
2301 
2302 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2303   assert (is_full_gc_in_progress(), "should be");
2304   _full_gc_move_in_progress.set_cond(in_progress);
2305 }
2306 
2307 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2308   set_gc_state_mask(UPDATEREFS, in_progress);
2309 }
2310 
2311 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2312   ShenandoahCodeRoots::register_nmethod(nm);
2313 }
2314 
2315 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2316   ShenandoahCodeRoots::unregister_nmethod(nm);
2317 }
2318 
2319 void ShenandoahHeap::flush_nmethod(nmethod* nm) {
2320   ShenandoahCodeRoots::flush_nmethod(nm);
2321 }
2322 
2323 oop ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2324   heap_region_containing(o)->record_pin();
2325   return o;
2326 }
2327 
2328 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2329   heap_region_containing(o)->record_unpin();
2330 }
2331 
2332 void ShenandoahHeap::sync_pinned_region_status() {
2333   ShenandoahHeapLocker locker(lock());
2334 
2335   for (size_t i = 0; i < num_regions(); i++) {
2336     ShenandoahHeapRegion *r = get_region(i);
2337     if (r->is_active()) {
2338       if (r->is_pinned()) {
2339         if (r->pin_count() == 0) {
2340           r->make_unpinned();
2341         }
2342       } else {
2343         if (r->pin_count() > 0) {
2344           r->make_pinned();
2345         }
2346       }
2347     }
2348   }
2349 
2350   assert_pinned_region_status();
2351 }
2352 
2353 #ifdef ASSERT
2354 void ShenandoahHeap::assert_pinned_region_status() {
2355   for (size_t i = 0; i < num_regions(); i++) {
2356     ShenandoahHeapRegion* r = get_region(i);
2357     assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2358            "Region " SIZE_FORMAT " pinning status is inconsistent", i);
2359   }
2360 }
2361 #endif
2362 
2363 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2364   return _gc_timer;
2365 }
2366 
2367 void ShenandoahHeap::prepare_concurrent_roots() {
2368   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2369   if (ShenandoahConcurrentRoots::should_do_concurrent_roots()) {
2370     set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2371     set_concurrent_weak_root_in_progress(true);
2372   }
2373 }
2374 
2375 void ShenandoahHeap::prepare_concurrent_unloading() {
2376   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2377   if (ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
2378     _unloader.prepare();
2379   }
2380 }
2381 
2382 void ShenandoahHeap::finish_concurrent_unloading() {
2383   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2384   if (ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
2385     _unloader.finish();
2386   }
2387 }
2388 
2389 #ifdef ASSERT
2390 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2391   assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2392 
2393   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2394     if (UseDynamicNumberOfGCThreads) {
2395       assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
2396     } else {
2397       // Use ParallelGCThreads inside safepoints
2398       assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads within safepoints");
2399     }
2400   } else {
2401     if (UseDynamicNumberOfGCThreads) {
2402       assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
2403     } else {
2404       // Use ConcGCThreads outside safepoints
2405       assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
2406     }
2407   }
2408 }
2409 #endif
2410 
2411 ShenandoahVerifier* ShenandoahHeap::verifier() {
2412   guarantee(ShenandoahVerify, "Should be enabled");
2413   assert (_verifier != NULL, "sanity");
2414   return _verifier;
2415 }
2416 
2417 template<class T>
2418 class ShenandoahUpdateHeapRefsTask : public AbstractGangTask {
2419 private:
2420   T cl;
2421   ShenandoahHeap* _heap;
2422   ShenandoahRegionIterator* _regions;
2423   bool _concurrent;
2424 public:
2425   ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions, bool concurrent) :
2426     AbstractGangTask("Concurrent Update References Task"),
2427     cl(T()),
2428     _heap(ShenandoahHeap::heap()),
2429     _regions(regions),
2430     _concurrent(concurrent) {
2431   }
2432 
2433   void work(uint worker_id) {
2434     if (_concurrent) {
2435       ShenandoahConcurrentWorkerSession worker_session(worker_id);
2436       ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
2437       do_work();
2438     } else {
2439       ShenandoahParallelWorkerSession worker_session(worker_id);
2440       do_work();
2441     }
2442   }
2443 
2444 private:
2445   void do_work() {
2446     ShenandoahHeapRegion* r = _regions->next();
2447     ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2448     while (r != NULL) {
2449       HeapWord* update_watermark = r->get_update_watermark();
2450       assert (update_watermark >= r->bottom(), "sanity");
2451       if (r->is_active() && !r->is_cset()) {
2452         _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2453       }
2454       if (ShenandoahPacing) {
2455         _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2456       }
2457       if (_heap->check_cancelled_gc_and_yield(_concurrent)) {
2458         return;
2459       }
2460       r = _regions->next();
2461     }
2462   }
2463 };
2464 
2465 void ShenandoahHeap::update_heap_references(bool concurrent) {
2466   ShenandoahUpdateHeapRefsTask<ShenandoahUpdateHeapRefsClosure> task(&_update_refs_iterator, concurrent);
2467   workers()->run_task(&task);
2468 }
2469 
2470 void ShenandoahHeap::op_init_updaterefs() {
2471   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2472 
2473   set_evacuation_in_progress(false);
2474 
2475   // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2476   // make them parsable for update code to work correctly. Plus, we can compute new sizes
2477   // for future GCLABs here.
2478   if (UseTLAB) {
2479     ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_refs_manage_gclabs);
2480     gclabs_retire(ResizeTLAB);
2481   }
2482 
2483   if (ShenandoahVerify) {
2484     if (!is_degenerated_gc_in_progress()) {
2485       verifier()->verify_roots_in_to_space_except(ShenandoahRootVerifier::ThreadRoots);
2486     }
2487     verifier()->verify_before_updaterefs();
2488   }
2489 
2490   set_update_refs_in_progress(true);
2491 
2492   _update_refs_iterator.reset();
2493 
2494   if (ShenandoahPacing) {
2495     pacer()->setup_for_updaterefs();
2496   }
2497 }
2498 
2499 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2500 private:
2501   ShenandoahHeapLock* const _lock;
2502 
2503 public:
2504   ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2505 
2506   void heap_region_do(ShenandoahHeapRegion* r) {
2507     // Drop unnecessary "pinned" state from regions that does not have CP marks
2508     // anymore, as this would allow trashing them.
2509 
2510     if (r->is_active()) {
2511       if (r->is_pinned()) {
2512         if (r->pin_count() == 0) {
2513           ShenandoahHeapLocker locker(_lock);
2514           r->make_unpinned();
2515         }
2516       } else {
2517         if (r->pin_count() > 0) {
2518           ShenandoahHeapLocker locker(_lock);
2519           r->make_pinned();
2520         }
2521       }
2522     }
2523   }
2524 
2525   bool is_thread_safe() { return true; }
2526 };
2527 
2528 void ShenandoahHeap::op_final_updaterefs() {
2529   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2530 
2531   finish_concurrent_unloading();
2532 
2533   // Check if there is left-over work, and finish it
2534   if (_update_refs_iterator.has_next()) {
2535     ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_refs_finish_work);
2536 
2537     // Finish updating references where we left off.
2538     clear_cancelled_gc();
2539     update_heap_references(false);
2540   }
2541 
2542   // Clear cancelled GC, if set. On cancellation path, the block before would handle
2543   // everything. On degenerated paths, cancelled gc would not be set anyway.
2544   if (cancelled_gc()) {
2545     clear_cancelled_gc();
2546   }
2547   assert(!cancelled_gc(), "Should have been done right before");
2548 
2549   if (ShenandoahVerify && !is_degenerated_gc_in_progress()) {
2550     verifier()->verify_roots_in_to_space_except(ShenandoahRootVerifier::ThreadRoots);
2551   }
2552 
2553   if (is_degenerated_gc_in_progress()) {
2554     concurrent_mark()->update_roots(ShenandoahPhaseTimings::degen_gc_update_roots);
2555   } else {
2556     concurrent_mark()->update_thread_roots(ShenandoahPhaseTimings::final_update_refs_roots);
2557   }
2558 
2559   // Has to be done before cset is clear
2560   if (ShenandoahVerify) {
2561     verifier()->verify_roots_in_to_space();
2562   }
2563 
2564   {
2565     ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_refs_update_region_states);
2566     ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2567     parallel_heap_region_iterate(&cl);
2568 
2569     assert_pinned_region_status();
2570   }
2571 
2572   {
2573     ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_refs_trash_cset);
2574     trash_cset_regions();
2575   }
2576 
2577   set_has_forwarded_objects(false);
2578   set_update_refs_in_progress(false);
2579 
2580   if (ShenandoahVerify) {
2581     verifier()->verify_after_updaterefs();
2582   }
2583 
2584   if (VerifyAfterGC) {
2585     Universe::verify();
2586   }
2587 
2588   {
2589     ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_refs_rebuild_freeset);
2590     ShenandoahHeapLocker locker(lock());
2591     _free_set->rebuild();
2592   }
2593 }
2594 
2595 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2596   print_on(st);
2597   print_heap_regions_on(st);
2598 }
2599 
2600 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2601   size_t slice = r->index() / _bitmap_regions_per_slice;
2602 
2603   size_t regions_from = _bitmap_regions_per_slice * slice;
2604   size_t regions_to   = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2605   for (size_t g = regions_from; g < regions_to; g++) {
2606     assert (g / _bitmap_regions_per_slice == slice, "same slice");
2607     if (skip_self && g == r->index()) continue;
2608     if (get_region(g)->is_committed()) {
2609       return true;
2610     }
2611   }
2612   return false;
2613 }
2614 
2615 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2616   shenandoah_assert_heaplocked();
2617 
2618   // Bitmaps in special regions do not need commits
2619   if (_bitmap_region_special) {
2620     return true;
2621   }
2622 
2623   if (is_bitmap_slice_committed(r, true)) {
2624     // Some other region from the group is already committed, meaning the bitmap
2625     // slice is already committed, we exit right away.
2626     return true;
2627   }
2628 
2629   // Commit the bitmap slice:
2630   size_t slice = r->index() / _bitmap_regions_per_slice;
2631   size_t off = _bitmap_bytes_per_slice * slice;
2632   size_t len = _bitmap_bytes_per_slice;
2633   char* start = (char*) _bitmap_region.start() + off;
2634 
2635   if (!os::commit_memory(start, len, false)) {
2636     return false;
2637   }
2638 
2639   if (AlwaysPreTouch) {
2640     os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2641   }
2642 
2643   return true;
2644 }
2645 
2646 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2647   shenandoah_assert_heaplocked();
2648 
2649   // Bitmaps in special regions do not need uncommits
2650   if (_bitmap_region_special) {
2651     return true;
2652   }
2653 
2654   if (is_bitmap_slice_committed(r, true)) {
2655     // Some other region from the group is still committed, meaning the bitmap
2656     // slice is should stay committed, exit right away.
2657     return true;
2658   }
2659 
2660   // Uncommit the bitmap slice:
2661   size_t slice = r->index() / _bitmap_regions_per_slice;
2662   size_t off = _bitmap_bytes_per_slice * slice;
2663   size_t len = _bitmap_bytes_per_slice;
2664   if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2665     return false;
2666   }
2667   return true;
2668 }
2669 
2670 void ShenandoahHeap::safepoint_synchronize_begin() {
2671   if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2672     SuspendibleThreadSet::synchronize();
2673   }
2674 }
2675 
2676 void ShenandoahHeap::safepoint_synchronize_end() {
2677   if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2678     SuspendibleThreadSet::desynchronize();
2679   }
2680 }
2681 
2682 void ShenandoahHeap::vmop_entry_init_mark() {
2683   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2684   ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::init_mark_gross);
2685 
2686   try_inject_alloc_failure();
2687   VM_ShenandoahInitMark op;
2688   VMThread::execute(&op); // jump to entry_init_mark() under safepoint
2689 }
2690 
2691 void ShenandoahHeap::vmop_entry_final_mark() {
2692   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2693   ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_mark_gross);
2694 
2695   try_inject_alloc_failure();
2696   VM_ShenandoahFinalMarkStartEvac op;
2697   VMThread::execute(&op); // jump to entry_final_mark under safepoint
2698 }
2699 
2700 void ShenandoahHeap::vmop_entry_init_updaterefs() {
2701   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2702   ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::init_update_refs_gross);
2703 
2704   try_inject_alloc_failure();
2705   VM_ShenandoahInitUpdateRefs op;
2706   VMThread::execute(&op);
2707 }
2708 
2709 void ShenandoahHeap::vmop_entry_final_updaterefs() {
2710   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2711   ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_update_refs_gross);
2712 
2713   try_inject_alloc_failure();
2714   VM_ShenandoahFinalUpdateRefs op;
2715   VMThread::execute(&op);
2716 }
2717 
2718 void ShenandoahHeap::vmop_entry_full(GCCause::Cause cause) {
2719   TraceCollectorStats tcs(monitoring_support()->full_stw_collection_counters());
2720   ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::full_gc_gross);
2721 
2722   try_inject_alloc_failure();
2723   VM_ShenandoahFullGC op(cause);
2724   VMThread::execute(&op);
2725 }
2726 
2727 void ShenandoahHeap::vmop_degenerated(ShenandoahDegenPoint point) {
2728   TraceCollectorStats tcs(monitoring_support()->full_stw_collection_counters());
2729   ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::degen_gc_gross);
2730 
2731   VM_ShenandoahDegeneratedGC degenerated_gc((int)point);
2732   VMThread::execute(&degenerated_gc);
2733 }
2734 
2735 void ShenandoahHeap::entry_init_mark() {
2736   const char* msg = init_mark_event_message();
2737   ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::init_mark);
2738   EventMark em("%s", msg);
2739 
2740   ShenandoahWorkerScope scope(workers(),
2741                               ShenandoahWorkerPolicy::calc_workers_for_init_marking(),
2742                               "init marking");
2743 
2744   op_init_mark();
2745 }
2746 
2747 void ShenandoahHeap::entry_final_mark() {
2748   const char* msg = final_mark_event_message();
2749   ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::final_mark);
2750   EventMark em("%s", msg);
2751 
2752   ShenandoahWorkerScope scope(workers(),
2753                               ShenandoahWorkerPolicy::calc_workers_for_final_marking(),
2754                               "final marking");
2755 
2756   op_final_mark();
2757 }
2758 
2759 void ShenandoahHeap::entry_init_updaterefs() {
2760   static const char* msg = "Pause Init Update Refs";
2761   ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::init_update_refs);
2762   EventMark em("%s", msg);
2763 
2764   // No workers used in this phase, no setup required
2765 
2766   op_init_updaterefs();
2767 }
2768 
2769 void ShenandoahHeap::entry_final_updaterefs() {
2770   static const char* msg = "Pause Final Update Refs";
2771   ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::final_update_refs);
2772   EventMark em("%s", msg);
2773 
2774   ShenandoahWorkerScope scope(workers(),
2775                               ShenandoahWorkerPolicy::calc_workers_for_final_update_ref(),
2776                               "final reference update");
2777 
2778   op_final_updaterefs();
2779 }
2780 
2781 void ShenandoahHeap::entry_full(GCCause::Cause cause) {
2782   static const char* msg = "Pause Full";
2783   ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::full_gc, true /* log_heap_usage */);
2784   EventMark em("%s", msg);
2785 
2786   ShenandoahWorkerScope scope(workers(),
2787                               ShenandoahWorkerPolicy::calc_workers_for_fullgc(),
2788                               "full gc");
2789 
2790   op_full(cause);
2791 }
2792 
2793 void ShenandoahHeap::entry_degenerated(int point) {
2794   ShenandoahDegenPoint dpoint = (ShenandoahDegenPoint)point;
2795   const char* msg = degen_event_message(dpoint);
2796   ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::degen_gc, true /* log_heap_usage */);
2797   EventMark em("%s", msg);
2798 
2799   ShenandoahWorkerScope scope(workers(),
2800                               ShenandoahWorkerPolicy::calc_workers_for_stw_degenerated(),
2801                               "stw degenerated gc");
2802 
2803   set_degenerated_gc_in_progress(true);
2804   op_degenerated(dpoint);
2805   set_degenerated_gc_in_progress(false);
2806 }
2807 
2808 void ShenandoahHeap::entry_mark() {
2809   TraceCollectorStats tcs(monitoring_support()->concurrent_collection_counters());
2810 
2811   const char* msg = conc_mark_event_message();
2812   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_mark);
2813   EventMark em("%s", msg);
2814 
2815   ShenandoahWorkerScope scope(workers(),
2816                               ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
2817                               "concurrent marking");
2818 
2819   try_inject_alloc_failure();
2820   op_mark();
2821 }
2822 
2823 void ShenandoahHeap::entry_evac() {
2824   TraceCollectorStats tcs(monitoring_support()->concurrent_collection_counters());
2825 
2826   static const char* msg = "Concurrent evacuation";
2827   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_evac);
2828   EventMark em("%s", msg);
2829 
2830   ShenandoahWorkerScope scope(workers(),
2831                               ShenandoahWorkerPolicy::calc_workers_for_conc_evac(),
2832                               "concurrent evacuation");
2833 
2834   try_inject_alloc_failure();
2835   op_conc_evac();
2836 }
2837 
2838 void ShenandoahHeap::entry_updaterefs() {
2839   static const char* msg = "Concurrent update references";
2840   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_update_refs);
2841   EventMark em("%s", msg);
2842 
2843   ShenandoahWorkerScope scope(workers(),
2844                               ShenandoahWorkerPolicy::calc_workers_for_conc_update_ref(),
2845                               "concurrent reference update");
2846 
2847   try_inject_alloc_failure();
2848   op_updaterefs();
2849 }
2850 
2851 void ShenandoahHeap::entry_weak_roots() {
2852   static const char* msg = "Concurrent weak roots";
2853   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_weak_roots);
2854   EventMark em("%s", msg);
2855 
2856   ShenandoahWorkerScope scope(workers(),
2857                               ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
2858                               "concurrent weak root");
2859 
2860   try_inject_alloc_failure();
2861   op_weak_roots();
2862 }
2863 
2864 void ShenandoahHeap::entry_class_unloading() {
2865   static const char* msg = "Concurrent class unloading";
2866   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_class_unload);
2867   EventMark em("%s", msg);
2868 
2869   ShenandoahWorkerScope scope(workers(),
2870                               ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
2871                               "concurrent class unloading");
2872 
2873   try_inject_alloc_failure();
2874   op_class_unloading();
2875 }
2876 
2877 void ShenandoahHeap::entry_strong_roots() {
2878   static const char* msg = "Concurrent strong roots";
2879   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_strong_roots);
2880   EventMark em("%s", msg);
2881 
2882   ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_strong_roots);
2883 
2884   ShenandoahWorkerScope scope(workers(),
2885                               ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
2886                               "concurrent strong root");
2887 
2888   try_inject_alloc_failure();
2889   op_strong_roots();
2890 }
2891 
2892 void ShenandoahHeap::entry_cleanup_early() {
2893   static const char* msg = "Concurrent cleanup";
2894   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_cleanup_early, true /* log_heap_usage */);
2895   EventMark em("%s", msg);
2896 
2897   // This phase does not use workers, no need for setup
2898 
2899   try_inject_alloc_failure();
2900   op_cleanup_early();
2901 }
2902 
2903 void ShenandoahHeap::entry_cleanup_complete() {
2904   static const char* msg = "Concurrent cleanup";
2905   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_cleanup_complete, true /* log_heap_usage */);
2906   EventMark em("%s", msg);
2907 
2908   // This phase does not use workers, no need for setup
2909 
2910   try_inject_alloc_failure();
2911   op_cleanup_complete();
2912 }
2913 
2914 void ShenandoahHeap::entry_reset() {
2915   static const char* msg = "Concurrent reset";
2916   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_reset);
2917   EventMark em("%s", msg);
2918 
2919   ShenandoahWorkerScope scope(workers(),
2920                               ShenandoahWorkerPolicy::calc_workers_for_conc_reset(),
2921                               "concurrent reset");
2922 
2923   try_inject_alloc_failure();
2924   op_reset();
2925 }
2926 
2927 void ShenandoahHeap::entry_preclean() {
2928   if (ShenandoahPreclean && process_references()) {
2929     static const char* msg = "Concurrent precleaning";
2930     ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_preclean);
2931     EventMark em("%s", msg);
2932 
2933     ShenandoahWorkerScope scope(workers(),
2934                                 ShenandoahWorkerPolicy::calc_workers_for_conc_preclean(),
2935                                 "concurrent preclean",
2936                                 /* check_workers = */ false);
2937 
2938     try_inject_alloc_failure();
2939     op_preclean();
2940   }
2941 }
2942 
2943 void ShenandoahHeap::entry_uncommit(double shrink_before) {
2944   static const char *msg = "Concurrent uncommit";
2945   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
2946   EventMark em("%s", msg);
2947 
2948   op_uncommit(shrink_before);
2949 }
2950 
2951 void ShenandoahHeap::try_inject_alloc_failure() {
2952   if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2953     _inject_alloc_failure.set();
2954     os::naked_short_sleep(1);
2955     if (cancelled_gc()) {
2956       log_info(gc)("Allocation failure was successfully injected");
2957     }
2958   }
2959 }
2960 
2961 bool ShenandoahHeap::should_inject_alloc_failure() {
2962   return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2963 }
2964 
2965 void ShenandoahHeap::initialize_serviceability() {
2966   _memory_pool = new ShenandoahMemoryPool(this);
2967   _cycle_memory_manager.add_pool(_memory_pool);
2968   _stw_memory_manager.add_pool(_memory_pool);
2969 }
2970 
2971 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2972   GrowableArray<GCMemoryManager*> memory_managers(2);
2973   memory_managers.append(&_cycle_memory_manager);
2974   memory_managers.append(&_stw_memory_manager);
2975   return memory_managers;
2976 }
2977 
2978 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2979   GrowableArray<MemoryPool*> memory_pools(1);
2980   memory_pools.append(_memory_pool);
2981   return memory_pools;
2982 }
2983 
2984 MemoryUsage ShenandoahHeap::memory_usage() {
2985   return _memory_pool->get_memory_usage();
2986 }
2987 
2988 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2989   _heap(ShenandoahHeap::heap()),
2990   _index(0) {}
2991 
2992 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2993   _heap(heap),
2994   _index(0) {}
2995 
2996 void ShenandoahRegionIterator::reset() {
2997   _index = 0;
2998 }
2999 
3000 bool ShenandoahRegionIterator::has_next() const {
3001   return _index < _heap->num_regions();
3002 }
3003 
3004 char ShenandoahHeap::gc_state() const {
3005   return _gc_state.raw_value();
3006 }
3007 
3008 void ShenandoahHeap::deduplicate_string(oop str) {
3009   assert(java_lang_String::is_instance(str), "invariant");
3010 
3011   if (ShenandoahStringDedup::is_enabled()) {
3012     ShenandoahStringDedup::deduplicate(str);
3013   }
3014 }
3015 
3016 const char* ShenandoahHeap::init_mark_event_message() const {
3017   assert(!has_forwarded_objects(), "Should not have forwarded objects here");
3018 
3019   bool proc_refs = process_references();
3020   bool unload_cls = unload_classes();
3021 
3022   if (proc_refs && unload_cls) {
3023     return "Pause Init Mark (process weakrefs) (unload classes)";
3024   } else if (proc_refs) {
3025     return "Pause Init Mark (process weakrefs)";
3026   } else if (unload_cls) {
3027     return "Pause Init Mark (unload classes)";
3028   } else {
3029     return "Pause Init Mark";
3030   }
3031 }
3032 
3033 const char* ShenandoahHeap::final_mark_event_message() const {
3034   assert(!has_forwarded_objects(), "Should not have forwarded objects here");
3035 
3036   bool proc_refs = process_references();
3037   bool unload_cls = unload_classes();
3038 
3039   if (proc_refs && unload_cls) {
3040     return "Pause Final Mark (process weakrefs) (unload classes)";
3041   } else if (proc_refs) {
3042     return "Pause Final Mark (process weakrefs)";
3043   } else if (unload_cls) {
3044     return "Pause Final Mark (unload classes)";
3045   } else {
3046     return "Pause Final Mark";
3047   }
3048 }
3049 
3050 const char* ShenandoahHeap::conc_mark_event_message() const {
3051   assert(!has_forwarded_objects(), "Should not have forwarded objects here");
3052 
3053   bool proc_refs = process_references();
3054   bool unload_cls = unload_classes();
3055 
3056   if (proc_refs && unload_cls) {
3057     return "Concurrent marking (process weakrefs) (unload classes)";
3058   } else if (proc_refs) {
3059     return "Concurrent marking (process weakrefs)";
3060   } else if (unload_cls) {
3061     return "Concurrent marking (unload classes)";
3062   } else {
3063     return "Concurrent marking";
3064   }
3065 }
3066 
3067 const char* ShenandoahHeap::degen_event_message(ShenandoahDegenPoint point) const {
3068   switch (point) {
3069     case _degenerated_unset:
3070       return "Pause Degenerated GC (<UNSET>)";
3071     case _degenerated_outside_cycle:
3072       return "Pause Degenerated GC (Outside of Cycle)";
3073     case _degenerated_mark:
3074       return "Pause Degenerated GC (Mark)";
3075     case _degenerated_evac:
3076       return "Pause Degenerated GC (Evacuation)";
3077     case _degenerated_updaterefs:
3078       return "Pause Degenerated GC (Update Refs)";
3079     default:
3080       ShouldNotReachHere();
3081       return "ERROR";
3082   }
3083 }
3084 
3085 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
3086 #ifdef ASSERT
3087   assert(_liveness_cache != NULL, "sanity");
3088   assert(worker_id < _max_workers, "sanity");
3089   for (uint i = 0; i < num_regions(); i++) {
3090     assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
3091   }
3092 #endif
3093   return _liveness_cache[worker_id];
3094 }
3095 
3096 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
3097   assert(worker_id < _max_workers, "sanity");
3098   assert(_liveness_cache != NULL, "sanity");
3099   ShenandoahLiveData* ld = _liveness_cache[worker_id];
3100   for (uint i = 0; i < num_regions(); i++) {
3101     ShenandoahLiveData live = ld[i];
3102     if (live > 0) {
3103       ShenandoahHeapRegion* r = get_region(i);
3104       r->increase_live_data_gc_words(live);
3105       ld[i] = 0;
3106     }
3107   }
3108 }