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/oopStorageSet.hpp"
  35 #include "gc/shared/plab.hpp"
  36 
  37 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
  38 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
  39 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
  40 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
  41 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
  42 #include "gc/shenandoah/shenandoahConcurrentRoots.hpp"
  43 #include "gc/shenandoah/shenandoahControlThread.hpp"
  44 #include "gc/shenandoah/shenandoahFreeSet.hpp"
  45 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
  46 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
  47 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
  48 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
  49 #include "gc/shenandoah/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 ShenandoahHeap* ShenandoahHeap::_heap = NULL;
  86 
  87 #ifdef ASSERT
  88 template <class T>
  89 void ShenandoahAssertToSpaceClosure::do_oop_work(T* p) {
  90   T o = RawAccess<>::oop_load(p);
  91   if (! CompressedOops::is_null(o)) {
  92     oop obj = CompressedOops::decode_not_null(o);
  93     shenandoah_assert_not_forwarded(p, obj);
  94   }
  95 }
  96 
  97 void ShenandoahAssertToSpaceClosure::do_oop(narrowOop* p) { do_oop_work(p); }
  98 void ShenandoahAssertToSpaceClosure::do_oop(oop* p)       { do_oop_work(p); }
  99 #endif
 100 
 101 class ShenandoahPretouchHeapTask : public AbstractGangTask {
 102 private:
 103   ShenandoahRegionIterator _regions;
 104   const size_t _page_size;
 105 public:
 106   ShenandoahPretouchHeapTask(size_t page_size) :
 107     AbstractGangTask("Shenandoah Pretouch Heap"),
 108     _page_size(page_size) {}
 109 
 110   virtual void work(uint worker_id) {
 111     ShenandoahHeapRegion* r = _regions.next();
 112     while (r != NULL) {
 113       if (r->is_committed()) {
 114         os::pretouch_memory(r->bottom(), r->end(), _page_size);
 115       }
 116       r = _regions.next();
 117     }
 118   }
 119 };
 120 
 121 class ShenandoahPretouchBitmapTask : public AbstractGangTask {
 122 private:
 123   ShenandoahRegionIterator _regions;
 124   char* _bitmap_base;
 125   const size_t _bitmap_size;
 126   const size_t _page_size;
 127 public:
 128   ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
 129     AbstractGangTask("Shenandoah Pretouch Bitmap"),
 130     _bitmap_base(bitmap_base),
 131     _bitmap_size(bitmap_size),
 132     _page_size(page_size) {}
 133 
 134   virtual void work(uint worker_id) {
 135     ShenandoahHeapRegion* r = _regions.next();
 136     while (r != NULL) {
 137       size_t start = r->index()       * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 138       size_t end   = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 139       assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
 140 
 141       if (r->is_committed()) {
 142         os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
 143       }
 144 
 145       r = _regions.next();
 146     }
 147   }
 148 };
 149 
 150 jint ShenandoahHeap::initialize() {
 151   //
 152   // Figure out heap sizing
 153   //
 154 
 155   size_t init_byte_size = InitialHeapSize;
 156   size_t min_byte_size  = MinHeapSize;
 157   size_t max_byte_size  = MaxHeapSize;
 158   size_t heap_alignment = HeapAlignment;
 159 
 160   size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
 161 
 162   Universe::check_alignment(max_byte_size,  reg_size_bytes, "Shenandoah heap");
 163   Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
 164 
 165   _num_regions = ShenandoahHeapRegion::region_count();
 166 
 167   // Now we know the number of regions, initialize the heuristics.
 168   initialize_heuristics();
 169 
 170   size_t num_committed_regions = init_byte_size / reg_size_bytes;
 171   num_committed_regions = MIN2(num_committed_regions, _num_regions);
 172   assert(num_committed_regions <= _num_regions, "sanity");
 173   _initial_size = num_committed_regions * reg_size_bytes;
 174 
 175   size_t num_min_regions = min_byte_size / reg_size_bytes;
 176   num_min_regions = MIN2(num_min_regions, _num_regions);
 177   assert(num_min_regions <= _num_regions, "sanity");
 178   _minimum_size = num_min_regions * reg_size_bytes;
 179 
 180   _committed = _initial_size;
 181 
 182   size_t heap_page_size   = UseLargePages ? (size_t)os::large_page_size() : (size_t)os::vm_page_size();
 183   size_t bitmap_page_size = UseLargePages ? (size_t)os::large_page_size() : (size_t)os::vm_page_size();
 184   size_t region_page_size = UseLargePages ? (size_t)os::large_page_size() : (size_t)os::vm_page_size();
 185 
 186   //
 187   // Reserve and commit memory for heap
 188   //
 189 
 190   ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
 191   initialize_reserved_region(heap_rs);
 192   _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
 193   _heap_region_special = heap_rs.special();
 194 
 195   assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
 196          "Misaligned heap: " PTR_FORMAT, p2i(base()));
 197 
 198 #if SHENANDOAH_OPTIMIZED_OBJTASK
 199   // The optimized ObjArrayChunkedTask takes some bits away from the full object bits.
 200   // Fail if we ever attempt to address more than we can.
 201   if ((uintptr_t)heap_rs.end() >= ObjArrayChunkedTask::max_addressable()) {
 202     FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
 203                           "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
 204                           "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
 205                 p2i(heap_rs.base()), p2i(heap_rs.end()), ObjArrayChunkedTask::max_addressable());
 206     vm_exit_during_initialization("Fatal Error", buf);
 207   }
 208 #endif
 209 
 210   ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
 211   if (!_heap_region_special) {
 212     os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
 213                               "Cannot commit heap memory");
 214   }
 215 
 216   //
 217   // Reserve and commit memory for bitmap(s)
 218   //
 219 
 220   _bitmap_size = MarkBitMap::compute_size(heap_rs.size());
 221   _bitmap_size = align_up(_bitmap_size, bitmap_page_size);
 222 
 223   size_t bitmap_bytes_per_region = reg_size_bytes / MarkBitMap::heap_map_factor();
 224 
 225   guarantee(bitmap_bytes_per_region != 0,
 226             "Bitmap bytes per region should not be zero");
 227   guarantee(is_power_of_2(bitmap_bytes_per_region),
 228             "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
 229 
 230   if (bitmap_page_size > bitmap_bytes_per_region) {
 231     _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
 232     _bitmap_bytes_per_slice = bitmap_page_size;
 233   } else {
 234     _bitmap_regions_per_slice = 1;
 235     _bitmap_bytes_per_slice = bitmap_bytes_per_region;
 236   }
 237 
 238   guarantee(_bitmap_regions_per_slice >= 1,
 239             "Should have at least one region per slice: " SIZE_FORMAT,
 240             _bitmap_regions_per_slice);
 241 
 242   guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
 243             "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
 244             _bitmap_bytes_per_slice, bitmap_page_size);
 245 
 246   ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
 247   MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
 248   _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
 249   _bitmap_region_special = bitmap.special();
 250 
 251   size_t bitmap_init_commit = _bitmap_bytes_per_slice *
 252                               align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
 253   bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
 254   if (!_bitmap_region_special) {
 255     os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
 256                               "Cannot commit bitmap memory");
 257   }
 258 
 259   _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
 260 
 261   if (ShenandoahVerify) {
 262     ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
 263     if (!verify_bitmap.special()) {
 264       os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
 265                                 "Cannot commit verification bitmap memory");
 266     }
 267     MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
 268     MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
 269     _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
 270     _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
 271   }
 272 
 273   // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
 274   ReservedSpace aux_bitmap(_bitmap_size, bitmap_page_size);
 275   MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
 276   _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
 277   _aux_bitmap_region_special = aux_bitmap.special();
 278   _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
 279 
 280   //
 281   // Create regions and region sets
 282   //
 283   size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
 284   size_t region_storage_size = align_up(region_align * _num_regions, region_page_size);
 285   region_storage_size = align_up(region_storage_size, os::vm_allocation_granularity());
 286 
 287   ReservedSpace region_storage(region_storage_size, region_page_size);
 288   MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
 289   if (!region_storage.special()) {
 290     os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
 291                               "Cannot commit region memory");
 292   }
 293 
 294   // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
 295   // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
 296   // If not successful, bite a bullet and allocate at whatever address.
 297   {
 298     size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
 299     size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
 300 
 301     uintptr_t min = round_up_power_of_2(cset_align);
 302     uintptr_t max = (1u << 30u);
 303 
 304     for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
 305       char* req_addr = (char*)addr;
 306       assert(is_aligned(req_addr, cset_align), "Should be aligned");
 307       ReservedSpace cset_rs(cset_size, os::vm_page_size(), false, req_addr);
 308       if (cset_rs.is_reserved()) {
 309         assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
 310         _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
 311         break;
 312       }
 313     }
 314 
 315     if (_collection_set == NULL) {
 316       ReservedSpace cset_rs(cset_size, os::vm_page_size(), false);
 317       _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
 318     }
 319   }
 320 
 321   _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
 322   _free_set = new ShenandoahFreeSet(this, _num_regions);
 323 
 324   {
 325     ShenandoahHeapLocker locker(lock());
 326 
 327     for (size_t i = 0; i < _num_regions; i++) {
 328       HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
 329       bool is_committed = i < num_committed_regions;
 330       void* loc = region_storage.base() + i * region_align;
 331 
 332       ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
 333       assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
 334 
 335       _marking_context->initialize_top_at_mark_start(r);
 336       _regions[i] = r;
 337       assert(!collection_set()->is_in(i), "New region should not be in collection set");
 338     }
 339 
 340     // Initialize to complete
 341     _marking_context->mark_complete();
 342 
 343     _free_set->rebuild();
 344   }
 345 
 346   if (AlwaysPreTouch) {
 347     // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
 348     // before initialize() below zeroes it with initializing thread. For any given region,
 349     // we touch the region and the corresponding bitmaps from the same thread.
 350     ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
 351 
 352     _pretouch_heap_page_size = heap_page_size;
 353     _pretouch_bitmap_page_size = bitmap_page_size;
 354 
 355 #ifdef LINUX
 356     // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
 357     // pages. But, the kernel needs to know that every small page is used, in order to coalesce
 358     // them into huge one. Therefore, we need to pretouch with smaller pages.
 359     if (UseTransparentHugePages) {
 360       _pretouch_heap_page_size = (size_t)os::vm_page_size();
 361       _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
 362     }
 363 #endif
 364 
 365     // OS memory managers may want to coalesce back-to-back pages. Make their jobs
 366     // simpler by pre-touching continuous spaces (heap and bitmap) separately.
 367 
 368     ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
 369     _workers->run_task(&bcl);
 370 
 371     ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
 372     _workers->run_task(&hcl);
 373   }
 374 
 375   //
 376   // Initialize the rest of GC subsystems
 377   //
 378 
 379   _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
 380   for (uint worker = 0; worker < _max_workers; worker++) {
 381     _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
 382     Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
 383   }
 384 
 385   // There should probably be Shenandoah-specific options for these,
 386   // just as there are G1-specific options.
 387   {
 388     ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
 389     satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
 390     satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
 391   }
 392 
 393   _monitoring_support = new ShenandoahMonitoringSupport(this);
 394   _phase_timings = new ShenandoahPhaseTimings(max_workers());
 395   ShenandoahStringDedup::initialize();
 396   ShenandoahCodeRoots::initialize();
 397 
 398   if (ShenandoahPacing) {
 399     _pacer = new ShenandoahPacer(this);
 400     _pacer->setup_for_idle();
 401   } else {
 402     _pacer = NULL;
 403   }
 404 
 405   _control_thread = new ShenandoahControlThread();
 406 
 407   log_info(gc, init)("Initialize Shenandoah heap: " SIZE_FORMAT "%s initial, " SIZE_FORMAT "%s min, " SIZE_FORMAT "%s max",
 408                      byte_size_in_proper_unit(_initial_size),  proper_unit_for_byte_size(_initial_size),
 409                      byte_size_in_proper_unit(_minimum_size),  proper_unit_for_byte_size(_minimum_size),
 410                      byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity())
 411   );
 412 
 413   log_info(gc, init)("Safepointing mechanism: thread-local poll");
 414 
 415   return JNI_OK;
 416 }
 417 
 418 void ShenandoahHeap::initialize_heuristics() {
 419   if (ShenandoahGCMode != NULL) {
 420     if (strcmp(ShenandoahGCMode, "satb") == 0) {
 421       _gc_mode = new ShenandoahSATBMode();
 422     } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
 423       _gc_mode = new ShenandoahIUMode();
 424     } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
 425       _gc_mode = new ShenandoahPassiveMode();
 426     } else {
 427       vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
 428     }
 429   } else {
 430     ShouldNotReachHere();
 431   }
 432   _gc_mode->initialize_flags();
 433   if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
 434     vm_exit_during_initialization(
 435             err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
 436                     _gc_mode->name()));
 437   }
 438   if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
 439     vm_exit_during_initialization(
 440             err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
 441                     _gc_mode->name()));
 442   }
 443   log_info(gc, init)("Shenandoah GC mode: %s",
 444                      _gc_mode->name());
 445 
 446   _heuristics = _gc_mode->initialize_heuristics();
 447 
 448   if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
 449     vm_exit_during_initialization(
 450             err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
 451                     _heuristics->name()));
 452   }
 453   if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
 454     vm_exit_during_initialization(
 455             err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
 456                     _heuristics->name()));
 457   }
 458   log_info(gc, init)("Shenandoah heuristics: %s",
 459                      _heuristics->name());
 460 }
 461 
 462 #ifdef _MSC_VER
 463 #pragma warning( push )
 464 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 465 #endif
 466 
 467 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
 468   CollectedHeap(),
 469   _initial_size(0),
 470   _used(0),
 471   _committed(0),
 472   _bytes_allocated_since_gc_start(0),
 473   _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
 474   _workers(NULL),
 475   _safepoint_workers(NULL),
 476   _heap_region_special(false),
 477   _num_regions(0),
 478   _regions(NULL),
 479   _update_refs_iterator(this),
 480   _control_thread(NULL),
 481   _shenandoah_policy(policy),
 482   _heuristics(NULL),
 483   _free_set(NULL),
 484   _scm(new ShenandoahConcurrentMark()),
 485   _full_gc(new ShenandoahMarkCompact()),
 486   _pacer(NULL),
 487   _verifier(NULL),
 488   _phase_timings(NULL),
 489   _monitoring_support(NULL),
 490   _memory_pool(NULL),
 491   _stw_memory_manager("Shenandoah Pauses", "end of GC pause"),
 492   _cycle_memory_manager("Shenandoah Cycles", "end of GC cycle"),
 493   _gc_timer(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
 494   _soft_ref_policy(),
 495   _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
 496   _ref_processor(NULL),
 497   _marking_context(NULL),
 498   _bitmap_size(0),
 499   _bitmap_regions_per_slice(0),
 500   _bitmap_bytes_per_slice(0),
 501   _bitmap_region_special(false),
 502   _aux_bitmap_region_special(false),
 503   _liveness_cache(NULL),
 504   _collection_set(NULL)
 505 {
 506   _heap = this;
 507 
 508   log_info(gc, init)("GC threads: " UINT32_FORMAT " parallel, " UINT32_FORMAT " concurrent", ParallelGCThreads, ConcGCThreads);
 509 
 510   BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
 511 
 512   _max_workers = MAX2(_max_workers, 1U);
 513   _workers = new ShenandoahWorkGang("Shenandoah GC Threads", _max_workers,
 514                             /* are_GC_task_threads */ true,
 515                             /* are_ConcurrentGC_threads */ true);
 516   if (_workers == NULL) {
 517     vm_exit_during_initialization("Failed necessary allocation.");
 518   } else {
 519     _workers->initialize_workers();
 520   }
 521 
 522   if (ParallelGCThreads > 1) {
 523     _safepoint_workers = new ShenandoahWorkGang("Safepoint Cleanup Thread",
 524                                                 ParallelGCThreads,
 525                       /* are_GC_task_threads */ false,
 526                  /* are_ConcurrentGC_threads */ false);
 527     _safepoint_workers->initialize_workers();
 528   }
 529 }
 530 
 531 #ifdef _MSC_VER
 532 #pragma warning( pop )
 533 #endif
 534 
 535 class ShenandoahResetBitmapTask : public AbstractGangTask {
 536 private:
 537   ShenandoahRegionIterator _regions;
 538 
 539 public:
 540   ShenandoahResetBitmapTask() :
 541     AbstractGangTask("Parallel Reset Bitmap Task") {}
 542 
 543   void work(uint worker_id) {
 544     ShenandoahHeapRegion* region = _regions.next();
 545     ShenandoahHeap* heap = ShenandoahHeap::heap();
 546     ShenandoahMarkingContext* const ctx = heap->marking_context();
 547     while (region != NULL) {
 548       if (heap->is_bitmap_slice_committed(region)) {
 549         ctx->clear_bitmap(region);
 550       }
 551       region = _regions.next();
 552     }
 553   }
 554 };
 555 
 556 void ShenandoahHeap::reset_mark_bitmap() {
 557   assert_gc_workers(_workers->active_workers());
 558   mark_incomplete_marking_context();
 559 
 560   ShenandoahResetBitmapTask task;
 561   _workers->run_task(&task);
 562 }
 563 
 564 void ShenandoahHeap::print_on(outputStream* st) const {
 565   st->print_cr("Shenandoah Heap");
 566   st->print_cr(" " SIZE_FORMAT "%s total, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
 567                byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
 568                byte_size_in_proper_unit(committed()),    proper_unit_for_byte_size(committed()),
 569                byte_size_in_proper_unit(used()),         proper_unit_for_byte_size(used()));
 570   st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
 571                num_regions(),
 572                byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
 573                proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
 574 
 575   st->print("Status: ");
 576   if (has_forwarded_objects())                 st->print("has forwarded objects, ");
 577   if (is_concurrent_mark_in_progress())        st->print("marking, ");
 578   if (is_evacuation_in_progress())             st->print("evacuating, ");
 579   if (is_update_refs_in_progress())            st->print("updating refs, ");
 580   if (is_degenerated_gc_in_progress())         st->print("degenerated gc, ");
 581   if (is_full_gc_in_progress())                st->print("full gc, ");
 582   if (is_full_gc_move_in_progress())           st->print("full gc move, ");
 583   if (is_concurrent_weak_root_in_progress())   st->print("concurrent weak roots, ");
 584   if (is_concurrent_strong_root_in_progress() &&
 585       !is_concurrent_weak_root_in_progress())  st->print("concurrent strong roots, ");
 586 
 587   if (cancelled_gc()) {
 588     st->print("cancelled");
 589   } else {
 590     st->print("not cancelled");
 591   }
 592   st->cr();
 593 
 594   st->print_cr("Reserved region:");
 595   st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
 596                p2i(reserved_region().start()),
 597                p2i(reserved_region().end()));
 598 
 599   ShenandoahCollectionSet* cset = collection_set();
 600   st->print_cr("Collection set:");
 601   if (cset != NULL) {
 602     st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
 603     st->print_cr(" - map (biased):  " PTR_FORMAT, p2i(cset->biased_map_address()));
 604   } else {
 605     st->print_cr(" (NULL)");
 606   }
 607 
 608   st->cr();
 609   MetaspaceUtils::print_on(st);
 610 
 611   if (Verbose) {
 612     print_heap_regions_on(st);
 613   }
 614 }
 615 
 616 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
 617 public:
 618   void do_thread(Thread* thread) {
 619     assert(thread != NULL, "Sanity");
 620     assert(thread->is_Worker_thread(), "Only worker thread expected");
 621     ShenandoahThreadLocalData::initialize_gclab(thread);
 622   }
 623 };
 624 
 625 void ShenandoahHeap::post_initialize() {
 626   CollectedHeap::post_initialize();
 627   MutexLocker ml(Threads_lock);
 628 
 629   ShenandoahInitWorkerGCLABClosure init_gclabs;
 630   _workers->threads_do(&init_gclabs);
 631 
 632   // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
 633   // Now, we will let WorkGang to initialize gclab when new worker is created.
 634   _workers->set_initialize_gclab();
 635 
 636   _scm->initialize(_max_workers);
 637   _full_gc->initialize(_gc_timer);
 638 
 639   ref_processing_init();
 640 
 641   _heuristics->initialize();
 642 
 643   JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
 644 }
 645 
 646 size_t ShenandoahHeap::used() const {
 647   return Atomic::load_acquire(&_used);
 648 }
 649 
 650 size_t ShenandoahHeap::committed() const {
 651   OrderAccess::acquire();
 652   return _committed;
 653 }
 654 
 655 void ShenandoahHeap::increase_committed(size_t bytes) {
 656   shenandoah_assert_heaplocked_or_safepoint();
 657   _committed += bytes;
 658 }
 659 
 660 void ShenandoahHeap::decrease_committed(size_t bytes) {
 661   shenandoah_assert_heaplocked_or_safepoint();
 662   _committed -= bytes;
 663 }
 664 
 665 void ShenandoahHeap::increase_used(size_t bytes) {
 666   Atomic::add(&_used, bytes);
 667 }
 668 
 669 void ShenandoahHeap::set_used(size_t bytes) {
 670   Atomic::release_store_fence(&_used, bytes);
 671 }
 672 
 673 void ShenandoahHeap::decrease_used(size_t bytes) {
 674   assert(used() >= bytes, "never decrease heap size by more than we've left");
 675   Atomic::sub(&_used, bytes);
 676 }
 677 
 678 void ShenandoahHeap::increase_allocated(size_t bytes) {
 679   Atomic::add(&_bytes_allocated_since_gc_start, bytes);
 680 }
 681 
 682 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
 683   size_t bytes = words * HeapWordSize;
 684   if (!waste) {
 685     increase_used(bytes);
 686   }
 687   increase_allocated(bytes);
 688   if (ShenandoahPacing) {
 689     control_thread()->pacing_notify_alloc(words);
 690     if (waste) {
 691       pacer()->claim_for_alloc(words, true);
 692     }
 693   }
 694 }
 695 
 696 size_t ShenandoahHeap::capacity() const {
 697   return committed();
 698 }
 699 
 700 size_t ShenandoahHeap::max_capacity() const {
 701   return _num_regions * ShenandoahHeapRegion::region_size_bytes();
 702 }
 703 
 704 size_t ShenandoahHeap::min_capacity() const {
 705   return _minimum_size;
 706 }
 707 
 708 size_t ShenandoahHeap::initial_capacity() const {
 709   return _initial_size;
 710 }
 711 
 712 bool ShenandoahHeap::is_in(const void* p) const {
 713   HeapWord* heap_base = (HeapWord*) base();
 714   HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
 715   return p >= heap_base && p < last_region_end;
 716 }
 717 
 718 void ShenandoahHeap::op_uncommit(double shrink_before) {
 719   assert (ShenandoahUncommit, "should be enabled");
 720 
 721   // Application allocates from the beginning of the heap, and GC allocates at
 722   // the end of it. It is more efficient to uncommit from the end, so that applications
 723   // could enjoy the near committed regions. GC allocations are much less frequent,
 724   // and therefore can accept the committing costs.
 725 
 726   size_t count = 0;
 727   for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
 728     ShenandoahHeapRegion* r = get_region(i - 1);
 729     if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
 730       ShenandoahHeapLocker locker(lock());
 731       if (r->is_empty_committed()) {
 732         // Do not uncommit below minimal capacity
 733         if (committed() < min_capacity() + ShenandoahHeapRegion::region_size_bytes()) {
 734           break;
 735         }
 736 
 737         r->make_uncommitted();
 738         count++;
 739       }
 740     }
 741     SpinPause(); // allow allocators to take the lock
 742   }
 743 
 744   if (count > 0) {
 745     control_thread()->notify_heap_changed();
 746   }
 747 }
 748 
 749 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
 750   // New object should fit the GCLAB size
 751   size_t min_size = MAX2(size, PLAB::min_size());
 752 
 753   // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
 754   size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
 755   new_size = MIN2(new_size, PLAB::max_size());
 756   new_size = MAX2(new_size, PLAB::min_size());
 757 
 758   // Record new heuristic value even if we take any shortcut. This captures
 759   // the case when moderately-sized objects always take a shortcut. At some point,
 760   // heuristics should catch up with them.
 761   ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
 762 
 763   if (new_size < size) {
 764     // New size still does not fit the object. Fall back to shared allocation.
 765     // This avoids retiring perfectly good GCLABs, when we encounter a large object.
 766     return NULL;
 767   }
 768 
 769   // Retire current GCLAB, and allocate a new one.
 770   PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
 771   gclab->retire();
 772 
 773   size_t actual_size = 0;
 774   HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
 775   if (gclab_buf == NULL) {
 776     return NULL;
 777   }
 778 
 779   assert (size <= actual_size, "allocation should fit");
 780 
 781   if (ZeroTLAB) {
 782     // ..and clear it.
 783     Copy::zero_to_words(gclab_buf, actual_size);
 784   } else {
 785     // ...and zap just allocated object.
 786 #ifdef ASSERT
 787     // Skip mangling the space corresponding to the object header to
 788     // ensure that the returned space is not considered parsable by
 789     // any concurrent GC thread.
 790     size_t hdr_size = oopDesc::header_size();
 791     Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
 792 #endif // ASSERT
 793   }
 794   gclab->set_buf(gclab_buf, actual_size);
 795   return gclab->allocate(size);
 796 }
 797 
 798 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
 799                                             size_t requested_size,
 800                                             size_t* actual_size) {
 801   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
 802   HeapWord* res = allocate_memory(req);
 803   if (res != NULL) {
 804     *actual_size = req.actual_size();
 805   } else {
 806     *actual_size = 0;
 807   }
 808   return res;
 809 }
 810 
 811 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
 812                                              size_t word_size,
 813                                              size_t* actual_size) {
 814   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
 815   HeapWord* res = allocate_memory(req);
 816   if (res != NULL) {
 817     *actual_size = req.actual_size();
 818   } else {
 819     *actual_size = 0;
 820   }
 821   return res;
 822 }
 823 
 824 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
 825   intptr_t pacer_epoch = 0;
 826   bool in_new_region = false;
 827   HeapWord* result = NULL;
 828 
 829   if (req.is_mutator_alloc()) {
 830     if (ShenandoahPacing) {
 831       pacer()->pace_for_alloc(req.size());
 832       pacer_epoch = pacer()->epoch();
 833     }
 834 
 835     if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
 836       result = allocate_memory_under_lock(req, in_new_region);
 837     }
 838 
 839     // Allocation failed, block until control thread reacted, then retry allocation.
 840     //
 841     // It might happen that one of the threads requesting allocation would unblock
 842     // way later after GC happened, only to fail the second allocation, because
 843     // other threads have already depleted the free storage. In this case, a better
 844     // strategy is to try again, as long as GC makes progress.
 845     //
 846     // Then, we need to make sure the allocation was retried after at least one
 847     // Full GC, which means we want to try more than ShenandoahFullGCThreshold times.
 848 
 849     size_t tries = 0;
 850 
 851     while (result == NULL && _progress_last_gc.is_set()) {
 852       tries++;
 853       control_thread()->handle_alloc_failure(req);
 854       result = allocate_memory_under_lock(req, in_new_region);
 855     }
 856 
 857     while (result == NULL && tries <= ShenandoahFullGCThreshold) {
 858       tries++;
 859       control_thread()->handle_alloc_failure(req);
 860       result = allocate_memory_under_lock(req, in_new_region);
 861     }
 862 
 863   } else {
 864     assert(req.is_gc_alloc(), "Can only accept GC allocs here");
 865     result = allocate_memory_under_lock(req, in_new_region);
 866     // Do not call handle_alloc_failure() here, because we cannot block.
 867     // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
 868   }
 869 
 870   if (in_new_region) {
 871     control_thread()->notify_heap_changed();
 872   }
 873 
 874   if (result != NULL) {
 875     size_t requested = req.size();
 876     size_t actual = req.actual_size();
 877 
 878     assert (req.is_lab_alloc() || (requested == actual),
 879             "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
 880             ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
 881 
 882     if (req.is_mutator_alloc()) {
 883       notify_mutator_alloc_words(actual, false);
 884 
 885       // If we requested more than we were granted, give the rest back to pacer.
 886       // This only matters if we are in the same pacing epoch: do not try to unpace
 887       // over the budget for the other phase.
 888       if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
 889         pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
 890       }
 891     } else {
 892       increase_used(actual*HeapWordSize);
 893     }
 894   }
 895 
 896   return result;
 897 }
 898 
 899 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
 900   ShenandoahHeapLocker locker(lock());
 901   return _free_set->allocate(req, in_new_region);
 902 }
 903 
 904 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
 905                                         bool*  gc_overhead_limit_was_exceeded) {
 906   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
 907   return allocate_memory(req);
 908 }
 909 
 910 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
 911                                                              size_t size,
 912                                                              Metaspace::MetadataType mdtype) {
 913   MetaWord* result;
 914 
 915   // Inform metaspace OOM to GC heuristics if class unloading is possible.
 916   if (heuristics()->can_unload_classes()) {
 917     ShenandoahHeuristics* h = heuristics();
 918     h->record_metaspace_oom();
 919   }
 920 
 921   // Expand and retry allocation
 922   result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
 923   if (result != NULL) {
 924     return result;
 925   }
 926 
 927   // Start full GC
 928   collect(GCCause::_metadata_GC_clear_soft_refs);
 929 
 930   // Retry allocation
 931   result = loader_data->metaspace_non_null()->allocate(size, mdtype);
 932   if (result != NULL) {
 933     return result;
 934   }
 935 
 936   // Expand and retry allocation
 937   result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
 938   if (result != NULL) {
 939     return result;
 940   }
 941 
 942   // Out of memory
 943   return NULL;
 944 }
 945 
 946 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
 947 private:
 948   ShenandoahHeap* const _heap;
 949   Thread* const _thread;
 950 public:
 951   ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
 952     _heap(heap), _thread(Thread::current()) {}
 953 
 954   void do_object(oop p) {
 955     shenandoah_assert_marked(NULL, p);
 956     if (!p->is_forwarded()) {
 957       _heap->evacuate_object(p, _thread);
 958     }
 959   }
 960 };
 961 
 962 class ShenandoahEvacuationTask : public AbstractGangTask {
 963 private:
 964   ShenandoahHeap* const _sh;
 965   ShenandoahCollectionSet* const _cs;
 966   bool _concurrent;
 967 public:
 968   ShenandoahEvacuationTask(ShenandoahHeap* sh,
 969                            ShenandoahCollectionSet* cs,
 970                            bool concurrent) :
 971     AbstractGangTask("Parallel Evacuation Task"),
 972     _sh(sh),
 973     _cs(cs),
 974     _concurrent(concurrent)
 975   {}
 976 
 977   void work(uint worker_id) {
 978     if (_concurrent) {
 979       ShenandoahConcurrentWorkerSession worker_session(worker_id);
 980       ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
 981       ShenandoahEvacOOMScope oom_evac_scope;
 982       do_work();
 983     } else {
 984       ShenandoahParallelWorkerSession worker_session(worker_id);
 985       ShenandoahEvacOOMScope oom_evac_scope;
 986       do_work();
 987     }
 988   }
 989 
 990 private:
 991   void do_work() {
 992     ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
 993     ShenandoahHeapRegion* r;
 994     while ((r =_cs->claim_next()) != NULL) {
 995       assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
 996       _sh->marked_object_iterate(r, &cl);
 997 
 998       if (ShenandoahPacing) {
 999         _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1000       }
1001 
1002       if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1003         break;
1004       }
1005     }
1006   }
1007 };
1008 
1009 void ShenandoahHeap::trash_cset_regions() {
1010   ShenandoahHeapLocker locker(lock());
1011 
1012   ShenandoahCollectionSet* set = collection_set();
1013   ShenandoahHeapRegion* r;
1014   set->clear_current_index();
1015   while ((r = set->next()) != NULL) {
1016     r->make_trash();
1017   }
1018   collection_set()->clear();
1019 }
1020 
1021 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1022   st->print_cr("Heap Regions:");
1023   st->print_cr("EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HC=humongous continuation, CS=collection set, T=trash, P=pinned");
1024   st->print_cr("BTE=bottom/top/end, U=used, T=TLAB allocs, G=GCLAB allocs, S=shared allocs, L=live data");
1025   st->print_cr("R=root, CP=critical pins, TAMS=top-at-mark-start, UWM=update watermark");
1026   st->print_cr("SN=alloc sequence number");
1027 
1028   for (size_t i = 0; i < num_regions(); i++) {
1029     get_region(i)->print_on(st);
1030   }
1031 }
1032 
1033 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1034   assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1035 
1036   oop humongous_obj = oop(start->bottom());
1037   size_t size = humongous_obj->size();
1038   size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1039   size_t index = start->index() + required_regions - 1;
1040 
1041   assert(!start->has_live(), "liveness must be zero");
1042 
1043   for(size_t i = 0; i < required_regions; i++) {
1044     // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1045     // as it expects that every region belongs to a humongous region starting with a humongous start region.
1046     ShenandoahHeapRegion* region = get_region(index --);
1047 
1048     assert(region->is_humongous(), "expect correct humongous start or continuation");
1049     assert(!region->is_cset(), "Humongous region should not be in collection set");
1050 
1051     region->make_trash_immediate();
1052   }
1053 }
1054 
1055 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1056 public:
1057   void do_thread(Thread* thread) {
1058     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1059     assert(gclab != NULL, "GCLAB should be initialized for %s", thread->name());
1060     gclab->retire();
1061   }
1062 };
1063 
1064 void ShenandoahHeap::make_parsable(bool retire_tlabs) {
1065   if (UseTLAB) {
1066     CollectedHeap::ensure_parsability(retire_tlabs);
1067   }
1068   ShenandoahRetireGCLABClosure cl;
1069   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1070     cl.do_thread(t);
1071   }
1072   workers()->threads_do(&cl);
1073 }
1074 
1075 void ShenandoahHeap::resize_tlabs() {
1076   CollectedHeap::resize_all_tlabs();
1077 }
1078 
1079 class ShenandoahEvacuateUpdateRootsTask : public AbstractGangTask {
1080 private:
1081   ShenandoahRootEvacuator* _rp;
1082 
1083 public:
1084   ShenandoahEvacuateUpdateRootsTask(ShenandoahRootEvacuator* rp) :
1085     AbstractGangTask("Shenandoah evacuate and update roots"),
1086     _rp(rp) {}
1087 
1088   void work(uint worker_id) {
1089     ShenandoahParallelWorkerSession worker_session(worker_id);
1090     ShenandoahEvacOOMScope oom_evac_scope;
1091     ShenandoahEvacuateUpdateRootsClosure<> cl;
1092     MarkingCodeBlobClosure blobsCl(&cl, CodeBlobToOopClosure::FixRelocations);
1093     _rp->roots_do(worker_id, &cl);
1094   }
1095 };
1096 
1097 void ShenandoahHeap::evacuate_and_update_roots() {
1098 #if COMPILER2_OR_JVMCI
1099   DerivedPointerTable::clear();
1100 #endif
1101   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only iterate roots while world is stopped");
1102   {
1103     // Include concurrent roots if current cycle can not process those roots concurrently
1104     ShenandoahRootEvacuator rp(workers()->active_workers(),
1105                                ShenandoahPhaseTimings::init_evac,
1106                                !ShenandoahConcurrentRoots::should_do_concurrent_roots(),
1107                                !ShenandoahConcurrentRoots::should_do_concurrent_class_unloading());
1108     ShenandoahEvacuateUpdateRootsTask roots_task(&rp);
1109     workers()->run_task(&roots_task);
1110   }
1111 
1112 #if COMPILER2_OR_JVMCI
1113   DerivedPointerTable::update_pointers();
1114 #endif
1115 }
1116 
1117 // Returns size in bytes
1118 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1119   if (ShenandoahElasticTLAB) {
1120     // With Elastic TLABs, return the max allowed size, and let the allocation path
1121     // figure out the safe size for current allocation.
1122     return ShenandoahHeapRegion::max_tlab_size_bytes();
1123   } else {
1124     return MIN2(_free_set->unsafe_peek_free(), ShenandoahHeapRegion::max_tlab_size_bytes());
1125   }
1126 }
1127 
1128 size_t ShenandoahHeap::max_tlab_size() const {
1129   // Returns size in words
1130   return ShenandoahHeapRegion::max_tlab_size_words();
1131 }
1132 
1133 class ShenandoahRetireAndResetGCLABClosure : public ThreadClosure {
1134 public:
1135   void do_thread(Thread* thread) {
1136     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1137     gclab->retire();
1138     if (ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1139       ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1140     }
1141   }
1142 };
1143 
1144 void ShenandoahHeap::retire_and_reset_gclabs() {
1145   ShenandoahRetireAndResetGCLABClosure cl;
1146   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1147     cl.do_thread(t);
1148   }
1149   workers()->threads_do(&cl);
1150 }
1151 
1152 void ShenandoahHeap::collect(GCCause::Cause cause) {
1153   control_thread()->request_gc(cause);
1154 }
1155 
1156 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1157   //assert(false, "Shouldn't need to do full collections");
1158 }
1159 
1160 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1161   ShenandoahHeapRegion* r = heap_region_containing(addr);
1162   if (r != NULL) {
1163     return r->block_start(addr);
1164   }
1165   return NULL;
1166 }
1167 
1168 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1169   ShenandoahHeapRegion* r = heap_region_containing(addr);
1170   return r->block_is_obj(addr);
1171 }
1172 
1173 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1174   return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1175 }
1176 
1177 jlong ShenandoahHeap::millis_since_last_gc() {
1178   double v = heuristics()->time_since_last_gc() * 1000;
1179   assert(0 <= v && v <= max_jlong, "value should fit: %f", v);
1180   return (jlong)v;
1181 }
1182 
1183 void ShenandoahHeap::prepare_for_verify() {
1184   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
1185     make_parsable(false);
1186   }
1187 }
1188 
1189 void ShenandoahHeap::print_gc_threads_on(outputStream* st) const {
1190   workers()->print_worker_threads_on(st);
1191   if (ShenandoahStringDedup::is_enabled()) {
1192     ShenandoahStringDedup::print_worker_threads_on(st);
1193   }
1194 }
1195 
1196 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1197   workers()->threads_do(tcl);
1198   if (_safepoint_workers != NULL) {
1199     _safepoint_workers->threads_do(tcl);
1200   }
1201   if (ShenandoahStringDedup::is_enabled()) {
1202     ShenandoahStringDedup::threads_do(tcl);
1203   }
1204 }
1205 
1206 void ShenandoahHeap::print_tracing_info() const {
1207   LogTarget(Info, gc, stats) lt;
1208   if (lt.is_enabled()) {
1209     ResourceMark rm;
1210     LogStream ls(lt);
1211 
1212     phase_timings()->print_global_on(&ls);
1213 
1214     ls.cr();
1215     ls.cr();
1216 
1217     shenandoah_policy()->print_gc_stats(&ls);
1218 
1219     ls.cr();
1220     ls.cr();
1221 
1222     if (ShenandoahPacing) {
1223       pacer()->print_on(&ls);
1224     }
1225 
1226     ls.cr();
1227     ls.cr();
1228   }
1229 }
1230 
1231 void ShenandoahHeap::verify(VerifyOption vo) {
1232   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1233     if (ShenandoahVerify) {
1234       verifier()->verify_generic(vo);
1235     } else {
1236       // TODO: Consider allocating verification bitmaps on demand,
1237       // and turn this on unconditionally.
1238     }
1239   }
1240 }
1241 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1242   return _free_set->capacity();
1243 }
1244 
1245 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1246 private:
1247   MarkBitMap* _bitmap;
1248   Stack<oop,mtGC>* _oop_stack;
1249   ShenandoahHeap* const _heap;
1250   ShenandoahMarkingContext* const _marking_context;
1251 
1252   template <class T>
1253   void do_oop_work(T* p) {
1254     T o = RawAccess<>::oop_load(p);
1255     if (!CompressedOops::is_null(o)) {
1256       oop obj = CompressedOops::decode_not_null(o);
1257       if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1258         // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1259         return;
1260       }
1261       obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
1262 
1263       assert(oopDesc::is_oop(obj), "must be a valid oop");
1264       if (!_bitmap->is_marked(obj)) {
1265         _bitmap->mark(obj);
1266         _oop_stack->push(obj);
1267       }
1268     }
1269   }
1270 public:
1271   ObjectIterateScanRootClosure(MarkBitMap* bitmap, Stack<oop,mtGC>* oop_stack) :
1272     _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1273     _marking_context(_heap->marking_context()) {}
1274   void do_oop(oop* p)       { do_oop_work(p); }
1275   void do_oop(narrowOop* p) { do_oop_work(p); }
1276 };
1277 
1278 /*
1279  * This is public API, used in preparation of object_iterate().
1280  * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1281  * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1282  * control, we call SH::make_tlabs_parsable().
1283  */
1284 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1285   // No-op.
1286 }
1287 
1288 /*
1289  * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1290  *
1291  * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1292  * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1293  * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1294  * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1295  * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1296  * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1297  * wiped the bitmap in preparation for next marking).
1298  *
1299  * For all those reasons, we implement object iteration as a single marking traversal, reporting
1300  * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1301  * is allowed to report dead objects, but is not required to do so.
1302  */
1303 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1304   assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1305   if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1306     log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1307     return;
1308   }
1309 
1310   // Reset bitmap
1311   _aux_bit_map.clear();
1312 
1313   Stack<oop,mtGC> oop_stack;
1314 
1315   // First, we process GC roots according to current GC cycle. This populates the work stack with initial objects.
1316   ShenandoahHeapIterationRootScanner rp;
1317   ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1318 
1319   rp.roots_do(&oops);
1320 
1321   // Work through the oop stack to traverse heap.
1322   while (! oop_stack.is_empty()) {
1323     oop obj = oop_stack.pop();
1324     assert(oopDesc::is_oop(obj), "must be a valid oop");
1325     cl->do_object(obj);
1326     obj->oop_iterate(&oops);
1327   }
1328 
1329   assert(oop_stack.is_empty(), "should be empty");
1330 
1331   if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1332     log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1333   }
1334 }
1335 
1336 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1337 void ShenandoahHeap::keep_alive(oop obj) {
1338   if (is_concurrent_mark_in_progress()) {
1339     ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1340   }
1341 }
1342 
1343 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1344   for (size_t i = 0; i < num_regions(); i++) {
1345     ShenandoahHeapRegion* current = get_region(i);
1346     blk->heap_region_do(current);
1347   }
1348 }
1349 
1350 class ShenandoahParallelHeapRegionTask : public AbstractGangTask {
1351 private:
1352   ShenandoahHeap* const _heap;
1353   ShenandoahHeapRegionClosure* const _blk;
1354 
1355   shenandoah_padding(0);
1356   volatile size_t _index;
1357   shenandoah_padding(1);
1358 
1359 public:
1360   ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1361           AbstractGangTask("Parallel Region Task"),
1362           _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1363 
1364   void work(uint worker_id) {
1365     ShenandoahParallelWorkerSession worker_session(worker_id);
1366     size_t stride = ShenandoahParallelRegionStride;
1367 
1368     size_t max = _heap->num_regions();
1369     while (_index < max) {
1370       size_t cur = Atomic::fetch_and_add(&_index, stride);
1371       size_t start = cur;
1372       size_t end = MIN2(cur + stride, max);
1373       if (start >= max) break;
1374 
1375       for (size_t i = cur; i < end; i++) {
1376         ShenandoahHeapRegion* current = _heap->get_region(i);
1377         _blk->heap_region_do(current);
1378       }
1379     }
1380   }
1381 };
1382 
1383 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1384   assert(blk->is_thread_safe(), "Only thread-safe closures here");
1385   if (num_regions() > ShenandoahParallelRegionStride) {
1386     ShenandoahParallelHeapRegionTask task(blk);
1387     workers()->run_task(&task);
1388   } else {
1389     heap_region_iterate(blk);
1390   }
1391 }
1392 
1393 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1394 private:
1395   ShenandoahMarkingContext* const _ctx;
1396 public:
1397   ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1398 
1399   void heap_region_do(ShenandoahHeapRegion* r) {
1400     assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1401     if (r->is_active()) {
1402       // Check if region needs updating its TAMS. We have updated it already during concurrent
1403       // reset, so it is very likely we don't need to do another write here.
1404       if (_ctx->top_at_mark_start(r) != r->top()) {
1405         _ctx->capture_top_at_mark_start(r);
1406       }
1407     } else {
1408       assert(_ctx->top_at_mark_start(r) == r->top(),
1409              "Region " SIZE_FORMAT " should already have correct TAMS", r->index());
1410     }
1411   }
1412 
1413   bool is_thread_safe() { return true; }
1414 };
1415 
1416 void ShenandoahHeap::op_init_mark() {
1417   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
1418   assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
1419 
1420   assert(marking_context()->is_bitmap_clear(), "need clear marking bitmap");
1421   assert(!marking_context()->is_complete(), "should not be complete");
1422   assert(!has_forwarded_objects(), "No forwarded objects on this path");
1423 
1424   if (ShenandoahVerify) {
1425     verifier()->verify_before_concmark();
1426   }
1427 
1428   if (VerifyBeforeGC) {
1429     Universe::verify();
1430   }
1431 
1432   set_concurrent_mark_in_progress(true);
1433   // We need to reset all TLABs because we'd lose marks on all objects allocated in them.
1434   {
1435     ShenandoahGCPhase phase(ShenandoahPhaseTimings::make_parsable);
1436     make_parsable(true);
1437   }
1438 
1439   {
1440     ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_region_states);
1441     ShenandoahInitMarkUpdateRegionStateClosure cl;
1442     parallel_heap_region_iterate(&cl);
1443   }
1444 
1445   // Make above changes visible to worker threads
1446   OrderAccess::fence();
1447 
1448   concurrent_mark()->mark_roots(ShenandoahPhaseTimings::scan_roots);
1449 
1450   if (UseTLAB) {
1451     ShenandoahGCPhase phase(ShenandoahPhaseTimings::resize_tlabs);
1452     resize_tlabs();
1453   }
1454 
1455   if (ShenandoahPacing) {
1456     pacer()->setup_for_mark();
1457   }
1458 
1459   // Arm nmethods for concurrent marking. When a nmethod is about to be executed,
1460   // we need to make sure that all its metadata are marked. alternative is to remark
1461   // thread roots at final mark pause, but it can be potential latency killer.
1462   if (ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
1463     ShenandoahCodeRoots::arm_nmethods();
1464   }
1465 }
1466 
1467 void ShenandoahHeap::op_mark() {
1468   concurrent_mark()->mark_from_roots();
1469 }
1470 
1471 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1472 private:
1473   ShenandoahMarkingContext* const _ctx;
1474   ShenandoahHeapLock* const _lock;
1475 
1476 public:
1477   ShenandoahFinalMarkUpdateRegionStateClosure() :
1478     _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1479 
1480   void heap_region_do(ShenandoahHeapRegion* r) {
1481     if (r->is_active()) {
1482       // All allocations past TAMS are implicitly live, adjust the region data.
1483       // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1484       HeapWord *tams = _ctx->top_at_mark_start(r);
1485       HeapWord *top = r->top();
1486       if (top > tams) {
1487         r->increase_live_data_alloc_words(pointer_delta(top, tams));
1488       }
1489 
1490       // We are about to select the collection set, make sure it knows about
1491       // current pinning status. Also, this allows trashing more regions that
1492       // now have their pinning status dropped.
1493       if (r->is_pinned()) {
1494         if (r->pin_count() == 0) {
1495           ShenandoahHeapLocker locker(_lock);
1496           r->make_unpinned();
1497         }
1498       } else {
1499         if (r->pin_count() > 0) {
1500           ShenandoahHeapLocker locker(_lock);
1501           r->make_pinned();
1502         }
1503       }
1504 
1505       // Remember limit for updating refs. It's guaranteed that we get no
1506       // from-space-refs written from here on.
1507       r->set_update_watermark_at_safepoint(r->top());
1508     } else {
1509       assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1510       assert(_ctx->top_at_mark_start(r) == r->top(),
1511              "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1512     }
1513   }
1514 
1515   bool is_thread_safe() { return true; }
1516 };
1517 
1518 void ShenandoahHeap::op_final_mark() {
1519   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
1520   assert(!has_forwarded_objects(), "No forwarded objects on this path");
1521 
1522   // It is critical that we
1523   // evacuate roots right after finishing marking, so that we don't
1524   // get unmarked objects in the roots.
1525 
1526   if (!cancelled_gc()) {
1527     concurrent_mark()->finish_mark_from_roots(/* full_gc = */ false);
1528 
1529     // Marking is completed, deactivate SATB barrier
1530     set_concurrent_mark_in_progress(false);
1531     mark_complete_marking_context();
1532 
1533     parallel_cleaning(false /* full gc*/);
1534 
1535     if (ShenandoahVerify) {
1536       verifier()->verify_roots_no_forwarded();
1537     }
1538 
1539     {
1540       ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_region_states);
1541       ShenandoahFinalMarkUpdateRegionStateClosure cl;
1542       parallel_heap_region_iterate(&cl);
1543 
1544       assert_pinned_region_status();
1545     }
1546 
1547     // Retire the TLABs, which will force threads to reacquire their TLABs after the pause.
1548     // This is needed for two reasons. Strong one: new allocations would be with new freeset,
1549     // which would be outside the collection set, so no cset writes would happen there.
1550     // Weaker one: new allocations would happen past update watermark, and so less work would
1551     // be needed for reference updates (would update the large filler instead).
1552     {
1553       ShenandoahGCPhase phase(ShenandoahPhaseTimings::retire_tlabs);
1554       make_parsable(true);
1555     }
1556 
1557     {
1558       ShenandoahGCPhase phase(ShenandoahPhaseTimings::choose_cset);
1559       ShenandoahHeapLocker locker(lock());
1560       _collection_set->clear();
1561       heuristics()->choose_collection_set(_collection_set);
1562     }
1563 
1564     {
1565       ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_rebuild_freeset);
1566       ShenandoahHeapLocker locker(lock());
1567       _free_set->rebuild();
1568     }
1569 
1570     if (!is_degenerated_gc_in_progress()) {
1571       prepare_concurrent_roots();
1572       prepare_concurrent_unloading();
1573     }
1574 
1575     // If collection set has candidates, start evacuation.
1576     // Otherwise, bypass the rest of the cycle.
1577     if (!collection_set()->is_empty()) {
1578       ShenandoahGCPhase init_evac(ShenandoahPhaseTimings::init_evac);
1579 
1580       if (ShenandoahVerify) {
1581         verifier()->verify_before_evacuation();
1582       }
1583 
1584       set_evacuation_in_progress(true);
1585       // From here on, we need to update references.
1586       set_has_forwarded_objects(true);
1587 
1588       if (!is_degenerated_gc_in_progress()) {
1589         if (ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
1590           ShenandoahCodeRoots::arm_nmethods();
1591         }
1592         evacuate_and_update_roots();
1593       }
1594 
1595       if (ShenandoahPacing) {
1596         pacer()->setup_for_evac();
1597       }
1598 
1599       if (ShenandoahVerify) {
1600         ShenandoahRootVerifier::RootTypes types = ShenandoahRootVerifier::None;
1601         if (ShenandoahConcurrentRoots::should_do_concurrent_roots()) {
1602           types = ShenandoahRootVerifier::combine(ShenandoahRootVerifier::JNIHandleRoots, ShenandoahRootVerifier::WeakRoots);
1603           types = ShenandoahRootVerifier::combine(types, ShenandoahRootVerifier::CLDGRoots);
1604           types = ShenandoahRootVerifier::combine(types, ShenandoahRootVerifier::StringDedupRoots);
1605         }
1606 
1607         if (ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
1608           types = ShenandoahRootVerifier::combine(types, ShenandoahRootVerifier::CodeRoots);
1609         }
1610         verifier()->verify_roots_no_forwarded_except(types);
1611         verifier()->verify_during_evacuation();
1612       }
1613     } else {
1614       if (ShenandoahVerify) {
1615         verifier()->verify_after_concmark();
1616       }
1617 
1618       if (VerifyAfterGC) {
1619         Universe::verify();
1620       }
1621     }
1622 
1623   } else {
1624     // If this cycle was updating references, we need to keep the has_forwarded_objects
1625     // flag on, for subsequent phases to deal with it.
1626     concurrent_mark()->cancel();
1627     set_concurrent_mark_in_progress(false);
1628 
1629     if (process_references()) {
1630       // Abandon reference processing right away: pre-cleaning must have failed.
1631       ReferenceProcessor *rp = ref_processor();
1632       rp->disable_discovery();
1633       rp->abandon_partial_discovery();
1634       rp->verify_no_references_recorded();
1635     }
1636   }
1637 }
1638 
1639 void ShenandoahHeap::op_conc_evac() {
1640   ShenandoahEvacuationTask task(this, _collection_set, true);
1641   workers()->run_task(&task);
1642 }
1643 
1644 void ShenandoahHeap::op_stw_evac() {
1645   ShenandoahEvacuationTask task(this, _collection_set, false);
1646   workers()->run_task(&task);
1647 }
1648 
1649 void ShenandoahHeap::op_updaterefs() {
1650   update_heap_references(true);
1651 }
1652 
1653 void ShenandoahHeap::op_cleanup_early() {
1654   free_set()->recycle_trash();
1655 }
1656 
1657 void ShenandoahHeap::op_cleanup_complete() {
1658   free_set()->recycle_trash();
1659 }
1660 
1661 class ShenandoahConcurrentRootsEvacUpdateTask : public AbstractGangTask {
1662 private:
1663   ShenandoahVMRoots<true /*concurrent*/>        _vm_roots;
1664   ShenandoahClassLoaderDataRoots<true /*concurrent*/, false /*single threaded*/> _cld_roots;
1665   ShenandoahConcurrentStringDedupRoots          _dedup_roots;
1666 
1667 public:
1668   ShenandoahConcurrentRootsEvacUpdateTask(ShenandoahPhaseTimings::Phase phase) :
1669     AbstractGangTask("Shenandoah Evacuate/Update Concurrent Strong Roots Task"),
1670     _vm_roots(phase),
1671     _cld_roots(phase) {}
1672 
1673   void work(uint worker_id) {
1674     ShenandoahConcurrentWorkerSession worker_session(worker_id);
1675     ShenandoahEvacOOMScope oom;
1676     {
1677       // vm_roots and weak_roots are OopStorage backed roots, concurrent iteration
1678       // may race against OopStorage::release() calls.
1679       ShenandoahEvacUpdateOopStorageRootsClosure cl;
1680       _vm_roots.oops_do<ShenandoahEvacUpdateOopStorageRootsClosure>(&cl, worker_id);
1681     }
1682 
1683     {
1684       ShenandoahEvacuateUpdateRootsClosure<> cl;
1685       CLDToOopClosure clds(&cl, ClassLoaderData::_claim_strong);
1686       _cld_roots.cld_do(&clds, worker_id);
1687     }
1688 
1689     {
1690       ShenandoahForwardedIsAliveClosure is_alive;
1691       ShenandoahEvacuateUpdateRootsClosure<MO_RELEASE> keep_alive;
1692       _dedup_roots.oops_do(&is_alive, &keep_alive, worker_id);
1693     }
1694   }
1695 };
1696 
1697 class ShenandoahEvacUpdateCleanupOopStorageRootsClosure : public BasicOopIterateClosure {
1698 private:
1699   ShenandoahHeap* const _heap;
1700   ShenandoahMarkingContext* const _mark_context;
1701   bool  _evac_in_progress;
1702   Thread* const _thread;
1703   size_t  _dead_counter;
1704 
1705 public:
1706   ShenandoahEvacUpdateCleanupOopStorageRootsClosure();
1707   void do_oop(oop* p);
1708   void do_oop(narrowOop* p);
1709 
1710   size_t dead_counter() const;
1711   void reset_dead_counter();
1712 };
1713 
1714 ShenandoahEvacUpdateCleanupOopStorageRootsClosure::ShenandoahEvacUpdateCleanupOopStorageRootsClosure() :
1715   _heap(ShenandoahHeap::heap()),
1716   _mark_context(ShenandoahHeap::heap()->marking_context()),
1717   _evac_in_progress(ShenandoahHeap::heap()->is_evacuation_in_progress()),
1718   _thread(Thread::current()),
1719   _dead_counter(0) {
1720 }
1721 
1722 void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::do_oop(oop* p) {
1723   const oop obj = RawAccess<>::oop_load(p);
1724   if (!CompressedOops::is_null(obj)) {
1725     if (!_mark_context->is_marked(obj)) {
1726       shenandoah_assert_correct(p, obj);
1727       oop old = Atomic::cmpxchg(p, obj, oop(NULL));
1728       if (obj == old) {
1729         _dead_counter ++;
1730       }
1731     } else if (_evac_in_progress && _heap->in_collection_set(obj)) {
1732       oop resolved = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
1733       if (resolved == obj) {
1734         resolved = _heap->evacuate_object(obj, _thread);
1735       }
1736       Atomic::cmpxchg(p, obj, resolved);
1737       assert(_heap->cancelled_gc() ||
1738              _mark_context->is_marked(resolved) && !_heap->in_collection_set(resolved),
1739              "Sanity");
1740     }
1741   }
1742 }
1743 
1744 void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::do_oop(narrowOop* p) {
1745   ShouldNotReachHere();
1746 }
1747 
1748 size_t ShenandoahEvacUpdateCleanupOopStorageRootsClosure::dead_counter() const {
1749   return _dead_counter;
1750 }
1751 
1752 void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::reset_dead_counter() {
1753   _dead_counter = 0;
1754 }
1755 
1756 class ShenandoahIsCLDAliveClosure : public CLDClosure {
1757 public:
1758   void do_cld(ClassLoaderData* cld) {
1759     cld->is_alive();
1760   }
1761 };
1762 
1763 class ShenandoahIsNMethodAliveClosure: public NMethodClosure {
1764 public:
1765   void do_nmethod(nmethod* n) {
1766     n->is_unloading();
1767   }
1768 };
1769 
1770 // This task not only evacuates/updates marked weak roots, but also "NULL"
1771 // dead weak roots.
1772 class ShenandoahConcurrentWeakRootsEvacUpdateTask : public AbstractGangTask {
1773 private:
1774   ShenandoahWeakRoot<true /*concurrent*/>  _jni_roots;
1775   ShenandoahWeakRoot<true /*concurrent*/>  _string_table_roots;
1776   ShenandoahWeakRoot<true /*concurrent*/>  _resolved_method_table_roots;
1777   ShenandoahWeakRoot<true /*concurrent*/>  _vm_roots;
1778 
1779   // Roots related to concurrent class unloading
1780   ShenandoahClassLoaderDataRoots<true /* concurrent */, false /* single thread*/>
1781                                            _cld_roots;
1782   ShenandoahConcurrentNMethodIterator      _nmethod_itr;
1783   bool                                     _concurrent_class_unloading;
1784 
1785 public:
1786   ShenandoahConcurrentWeakRootsEvacUpdateTask(ShenandoahPhaseTimings::Phase phase) :
1787     AbstractGangTask("Shenandoah Concurrent Weak Root Task"),
1788     _jni_roots(OopStorageSet::jni_weak(), phase, ShenandoahPhaseTimings::JNIWeakRoots),
1789     _string_table_roots(OopStorageSet::string_table_weak(), phase, ShenandoahPhaseTimings::StringTableRoots),
1790     _resolved_method_table_roots(OopStorageSet::resolved_method_table_weak(), phase, ShenandoahPhaseTimings::ResolvedMethodTableRoots),
1791     _vm_roots(OopStorageSet::vm_weak(), phase, ShenandoahPhaseTimings::VMWeakRoots),
1792     _cld_roots(phase),
1793     _nmethod_itr(ShenandoahCodeRoots::table()),
1794     _concurrent_class_unloading(ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
1795     StringTable::reset_dead_counter();
1796     ResolvedMethodTable::reset_dead_counter();
1797     if (_concurrent_class_unloading) {
1798       MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
1799       _nmethod_itr.nmethods_do_begin();
1800     }
1801   }
1802 
1803   ~ShenandoahConcurrentWeakRootsEvacUpdateTask() {
1804     StringTable::finish_dead_counter();
1805     ResolvedMethodTable::finish_dead_counter();
1806     if (_concurrent_class_unloading) {
1807       MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
1808       _nmethod_itr.nmethods_do_end();
1809     }
1810   }
1811 
1812   void work(uint worker_id) {
1813     ShenandoahConcurrentWorkerSession worker_session(worker_id);
1814     {
1815       ShenandoahEvacOOMScope oom;
1816       // jni_roots and weak_roots are OopStorage backed roots, concurrent iteration
1817       // may race against OopStorage::release() calls.
1818       ShenandoahEvacUpdateCleanupOopStorageRootsClosure cl;
1819       _jni_roots.oops_do(&cl, worker_id);
1820       _vm_roots.oops_do(&cl, worker_id);
1821 
1822       cl.reset_dead_counter();
1823       _string_table_roots.oops_do(&cl, worker_id);
1824       StringTable::inc_dead_counter(cl.dead_counter());
1825 
1826       cl.reset_dead_counter();
1827       _resolved_method_table_roots.oops_do(&cl, worker_id);
1828       ResolvedMethodTable::inc_dead_counter(cl.dead_counter());
1829     }
1830 
1831     // If we are going to perform concurrent class unloading later on, we need to
1832     // cleanup the weak oops in CLD and determinate nmethod's unloading state, so that we
1833     // can cleanup immediate garbage sooner.
1834     if (_concurrent_class_unloading) {
1835       // Applies ShenandoahIsCLDAlive closure to CLDs, native barrier will either NULL the
1836       // CLD's holder or evacuate it.
1837       ShenandoahIsCLDAliveClosure is_cld_alive;
1838       _cld_roots.cld_do(&is_cld_alive, worker_id);
1839 
1840       // Applies ShenandoahIsNMethodAliveClosure to registered nmethods.
1841       // The closure calls nmethod->is_unloading(). The is_unloading
1842       // state is cached, therefore, during concurrent class unloading phase,
1843       // we will not touch the metadata of unloading nmethods
1844       ShenandoahIsNMethodAliveClosure is_nmethod_alive;
1845       _nmethod_itr.nmethods_do(&is_nmethod_alive);
1846     }
1847   }
1848 };
1849 
1850 void ShenandoahHeap::op_weak_roots() {
1851   if (is_concurrent_weak_root_in_progress()) {
1852     // Concurrent weak root processing
1853     {
1854       ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_weak_roots_work);
1855       ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_weak_roots_work);
1856       ShenandoahConcurrentWeakRootsEvacUpdateTask task(ShenandoahPhaseTimings::conc_weak_roots_work);
1857       workers()->run_task(&task);
1858       if (!ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
1859         set_concurrent_weak_root_in_progress(false);
1860       }
1861     }
1862 
1863     // Perform handshake to flush out dead oops
1864     {
1865       ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_weak_roots_rendezvous);
1866       ShenandoahRendezvousClosure cl;
1867       Handshake::execute(&cl);
1868     }
1869   }
1870 }
1871 
1872 void ShenandoahHeap::op_class_unloading() {
1873   assert (is_concurrent_weak_root_in_progress() &&
1874           ShenandoahConcurrentRoots::should_do_concurrent_class_unloading(),
1875           "Checked by caller");
1876   _unloader.unload();
1877   set_concurrent_weak_root_in_progress(false);
1878 }
1879 
1880 void ShenandoahHeap::op_strong_roots() {
1881   assert(is_concurrent_strong_root_in_progress(), "Checked by caller");
1882   ShenandoahConcurrentRootsEvacUpdateTask task(ShenandoahPhaseTimings::conc_strong_roots);
1883   workers()->run_task(&task);
1884   set_concurrent_strong_root_in_progress(false);
1885 }
1886 
1887 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1888 private:
1889   ShenandoahMarkingContext* const _ctx;
1890 public:
1891   ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1892 
1893   void heap_region_do(ShenandoahHeapRegion* r) {
1894     if (r->is_active()) {
1895       // Reset live data and set TAMS optimistically. We would recheck these under the pause
1896       // anyway to capture any updates that happened since now.
1897       r->clear_live_data();
1898       _ctx->capture_top_at_mark_start(r);
1899     }
1900   }
1901 
1902   bool is_thread_safe() { return true; }
1903 };
1904 
1905 void ShenandoahHeap::op_reset() {
1906   if (ShenandoahPacing) {
1907     pacer()->setup_for_reset();
1908   }
1909   reset_mark_bitmap();
1910 
1911   ShenandoahResetUpdateRegionStateClosure cl;
1912   parallel_heap_region_iterate(&cl);
1913 }
1914 
1915 void ShenandoahHeap::op_preclean() {
1916   if (ShenandoahPacing) {
1917     pacer()->setup_for_preclean();
1918   }
1919   concurrent_mark()->preclean_weak_refs();
1920 }
1921 
1922 void ShenandoahHeap::op_full(GCCause::Cause cause) {
1923   ShenandoahMetricsSnapshot metrics;
1924   metrics.snap_before();
1925 
1926   full_gc()->do_it(cause);
1927   if (UseTLAB) {
1928     ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_resize_tlabs);
1929     resize_all_tlabs();
1930   }
1931 
1932   metrics.snap_after();
1933 
1934   if (metrics.is_good_progress()) {
1935     _progress_last_gc.set();
1936   } else {
1937     // Nothing to do. Tell the allocation path that we have failed to make
1938     // progress, and it can finally fail.
1939     _progress_last_gc.unset();
1940   }
1941 }
1942 
1943 void ShenandoahHeap::op_degenerated(ShenandoahDegenPoint point) {
1944   // Degenerated GC is STW, but it can also fail. Current mechanics communicates
1945   // GC failure via cancelled_concgc() flag. So, if we detect the failure after
1946   // some phase, we have to upgrade the Degenerate GC to Full GC.
1947 
1948   clear_cancelled_gc();
1949 
1950   ShenandoahMetricsSnapshot metrics;
1951   metrics.snap_before();
1952 
1953   switch (point) {
1954     // The cases below form the Duff's-like device: it describes the actual GC cycle,
1955     // but enters it at different points, depending on which concurrent phase had
1956     // degenerated.
1957 
1958     case _degenerated_outside_cycle:
1959       // We have degenerated from outside the cycle, which means something is bad with
1960       // the heap, most probably heavy humongous fragmentation, or we are very low on free
1961       // space. It makes little sense to wait for Full GC to reclaim as much as it can, when
1962       // we can do the most aggressive degen cycle, which includes processing references and
1963       // class unloading, unless those features are explicitly disabled.
1964       //
1965       // Note that we can only do this for "outside-cycle" degens, otherwise we would risk
1966       // changing the cycle parameters mid-cycle during concurrent -> degenerated handover.
1967       set_process_references(heuristics()->can_process_references());
1968       set_unload_classes(heuristics()->can_unload_classes());
1969 
1970       op_reset();
1971 
1972       op_init_mark();
1973       if (cancelled_gc()) {
1974         op_degenerated_fail();
1975         return;
1976       }
1977 
1978     case _degenerated_mark:
1979       op_final_mark();
1980       if (cancelled_gc()) {
1981         op_degenerated_fail();
1982         return;
1983       }
1984 
1985       if (!has_forwarded_objects() && ShenandoahConcurrentRoots::can_do_concurrent_class_unloading()) {
1986         // Disarm nmethods that armed for concurrent mark. On normal cycle, it would
1987         // be disarmed while conc-roots phase is running.
1988         // TODO: Call op_conc_roots() here instead
1989         ShenandoahCodeRoots::disarm_nmethods();
1990       }
1991 
1992       op_cleanup_early();
1993 
1994     case _degenerated_evac:
1995       // If heuristics thinks we should do the cycle, this flag would be set,
1996       // and we can do evacuation. Otherwise, it would be the shortcut cycle.
1997       if (is_evacuation_in_progress()) {
1998 
1999         // Degeneration under oom-evac protocol might have left some objects in
2000         // collection set un-evacuated. Restart evacuation from the beginning to
2001         // capture all objects. For all the objects that are already evacuated,
2002         // it would be a simple check, which is supposed to be fast. This is also
2003         // safe to do even without degeneration, as CSet iterator is at beginning
2004         // in preparation for evacuation anyway.
2005         //
2006         // Before doing that, we need to make sure we never had any cset-pinned
2007         // regions. This may happen if allocation failure happened when evacuating
2008         // the about-to-be-pinned object, oom-evac protocol left the object in
2009         // the collection set, and then the pin reached the cset region. If we continue
2010         // the cycle here, we would trash the cset and alive objects in it. To avoid
2011         // it, we fail degeneration right away and slide into Full GC to recover.
2012 
2013         {
2014           sync_pinned_region_status();
2015           collection_set()->clear_current_index();
2016 
2017           ShenandoahHeapRegion* r;
2018           while ((r = collection_set()->next()) != NULL) {
2019             if (r->is_pinned()) {
2020               cancel_gc(GCCause::_shenandoah_upgrade_to_full_gc);
2021               op_degenerated_fail();
2022               return;
2023             }
2024           }
2025 
2026           collection_set()->clear_current_index();
2027         }
2028 
2029         op_stw_evac();
2030         if (cancelled_gc()) {
2031           op_degenerated_fail();
2032           return;
2033         }
2034       }
2035 
2036       // If heuristics thinks we should do the cycle, this flag would be set,
2037       // and we need to do update-refs. Otherwise, it would be the shortcut cycle.
2038       if (has_forwarded_objects()) {
2039         op_init_updaterefs();
2040         if (cancelled_gc()) {
2041           op_degenerated_fail();
2042           return;
2043         }
2044       }
2045 
2046     case _degenerated_updaterefs:
2047       if (has_forwarded_objects()) {
2048         op_final_updaterefs();
2049         if (cancelled_gc()) {
2050           op_degenerated_fail();
2051           return;
2052         }
2053       }
2054 
2055       op_cleanup_complete();
2056       break;
2057 
2058     default:
2059       ShouldNotReachHere();
2060   }
2061 
2062   if (ShenandoahVerify) {
2063     verifier()->verify_after_degenerated();
2064   }
2065 
2066   if (VerifyAfterGC) {
2067     Universe::verify();
2068   }
2069 
2070   metrics.snap_after();
2071 
2072   // Check for futility and fail. There is no reason to do several back-to-back Degenerated cycles,
2073   // because that probably means the heap is overloaded and/or fragmented.
2074   if (!metrics.is_good_progress()) {
2075     _progress_last_gc.unset();
2076     cancel_gc(GCCause::_shenandoah_upgrade_to_full_gc);
2077     op_degenerated_futile();
2078   } else {
2079     _progress_last_gc.set();
2080   }
2081 }
2082 
2083 void ShenandoahHeap::op_degenerated_fail() {
2084   log_info(gc)("Cannot finish degeneration, upgrading to Full GC");
2085   shenandoah_policy()->record_degenerated_upgrade_to_full();
2086   op_full(GCCause::_shenandoah_upgrade_to_full_gc);
2087 }
2088 
2089 void ShenandoahHeap::op_degenerated_futile() {
2090   shenandoah_policy()->record_degenerated_upgrade_to_full();
2091   op_full(GCCause::_shenandoah_upgrade_to_full_gc);
2092 }
2093 
2094 void ShenandoahHeap::force_satb_flush_all_threads() {
2095   if (!is_concurrent_mark_in_progress()) {
2096     // No need to flush SATBs
2097     return;
2098   }
2099 
2100   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
2101     ShenandoahThreadLocalData::set_force_satb_flush(t, true);
2102   }
2103   // The threads are not "acquiring" their thread-local data, but it does not
2104   // hurt to "release" the updates here anyway.
2105   OrderAccess::fence();
2106 }
2107 
2108 void ShenandoahHeap::set_gc_state_all_threads(char state) {
2109   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
2110     ShenandoahThreadLocalData::set_gc_state(t, state);
2111   }
2112 }
2113 
2114 void ShenandoahHeap::set_gc_state_mask(uint mask, bool value) {
2115   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should really be Shenandoah safepoint");
2116   _gc_state.set_cond(mask, value);
2117   set_gc_state_all_threads(_gc_state.raw_value());
2118 }
2119 
2120 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
2121   if (has_forwarded_objects()) {
2122     set_gc_state_mask(MARKING | UPDATEREFS, in_progress);
2123   } else {
2124     set_gc_state_mask(MARKING, in_progress);
2125   }
2126   ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
2127 }
2128 
2129 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2130   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2131   set_gc_state_mask(EVACUATION, in_progress);
2132 }
2133 
2134 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2135   assert(ShenandoahConcurrentRoots::can_do_concurrent_roots(), "Why set the flag?");
2136   if (in_progress) {
2137     _concurrent_strong_root_in_progress.set();
2138   } else {
2139     _concurrent_strong_root_in_progress.unset();
2140   }
2141 }
2142 
2143 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool in_progress) {
2144   assert(ShenandoahConcurrentRoots::can_do_concurrent_roots(), "Why set the flag?");
2145   if (in_progress) {
2146     _concurrent_weak_root_in_progress.set();
2147   } else {
2148     _concurrent_weak_root_in_progress.unset();
2149   }
2150 }
2151 
2152 void ShenandoahHeap::ref_processing_init() {
2153   assert(_max_workers > 0, "Sanity");
2154 
2155   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
2156   bool mt_discovery = _max_workers > 1;
2157 
2158   _ref_processor =
2159     new ReferenceProcessor(&_subject_to_discovery,  // is_subject_to_discovery
2160                            mt_processing,           // MT processing
2161                            _max_workers,            // Degree of MT processing
2162                            mt_discovery,            // MT discovery
2163                            _max_workers,            // Degree of MT discovery
2164                            false,                   // Reference discovery is not atomic
2165                            NULL,                    // No closure, should be installed before use
2166                            true);                   // Scale worker threads
2167 
2168   log_info(gc, init)("Reference processing: %s discovery, %s processing",
2169           mt_discovery ? "parallel" : "serial",
2170           mt_processing ? "parallel" : "serial");
2171 
2172   shenandoah_assert_rp_isalive_not_installed();
2173 }
2174 
2175 GCTracer* ShenandoahHeap::tracer() {
2176   return shenandoah_policy()->tracer();
2177 }
2178 
2179 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
2180   return _free_set->used();
2181 }
2182 
2183 bool ShenandoahHeap::try_cancel_gc() {
2184   while (true) {
2185     jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
2186     if (prev == CANCELLABLE) return true;
2187     else if (prev == CANCELLED) return false;
2188     assert(ShenandoahSuspendibleWorkers, "should not get here when not using suspendible workers");
2189     assert(prev == NOT_CANCELLED, "must be NOT_CANCELLED");
2190     if (Thread::current()->is_Java_thread()) {
2191       // We need to provide a safepoint here, otherwise we might
2192       // spin forever if a SP is pending.
2193       ThreadBlockInVM sp(JavaThread::current());
2194       SpinPause();
2195     }
2196   }
2197 }
2198 
2199 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2200   if (try_cancel_gc()) {
2201     FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2202     log_info(gc)("%s", msg.buffer());
2203     Events::log(Thread::current(), "%s", msg.buffer());
2204   }
2205 }
2206 
2207 uint ShenandoahHeap::max_workers() {
2208   return _max_workers;
2209 }
2210 
2211 void ShenandoahHeap::stop() {
2212   // The shutdown sequence should be able to terminate when GC is running.
2213 
2214   // Step 0. Notify policy to disable event recording.
2215   _shenandoah_policy->record_shutdown();
2216 
2217   // Step 1. Notify control thread that we are in shutdown.
2218   // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
2219   // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
2220   control_thread()->prepare_for_graceful_shutdown();
2221 
2222   // Step 2. Notify GC workers that we are cancelling GC.
2223   cancel_gc(GCCause::_shenandoah_stop_vm);
2224 
2225   // Step 3. Wait until GC worker exits normally.
2226   control_thread()->stop();
2227 
2228   // Step 4. Stop String Dedup thread if it is active
2229   if (ShenandoahStringDedup::is_enabled()) {
2230     ShenandoahStringDedup::stop();
2231   }
2232 }
2233 
2234 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2235   if (!unload_classes()) return;
2236 
2237   // Unload classes and purge SystemDictionary.
2238   {
2239     ShenandoahGCPhase phase(full_gc ?
2240                             ShenandoahPhaseTimings::full_gc_purge_class_unload :
2241                             ShenandoahPhaseTimings::purge_class_unload);
2242     bool purged_class = SystemDictionary::do_unloading(gc_timer());
2243 
2244     ShenandoahIsAliveSelector is_alive;
2245     uint num_workers = _workers->active_workers();
2246     ShenandoahClassUnloadingTask unlink_task(is_alive.is_alive_closure(), num_workers, purged_class);
2247     _workers->run_task(&unlink_task);
2248   }
2249 
2250   {
2251     ShenandoahGCPhase phase(full_gc ?
2252                             ShenandoahPhaseTimings::full_gc_purge_cldg :
2253                             ShenandoahPhaseTimings::purge_cldg);
2254     ClassLoaderDataGraph::purge();
2255   }
2256   // Resize and verify metaspace
2257   MetaspaceGC::compute_new_size();
2258   MetaspaceUtils::verify_metrics();
2259 }
2260 
2261 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
2262 // so they should not have forwarded oops.
2263 // However, we do need to "null" dead oops in the roots, if can not be done
2264 // in concurrent cycles.
2265 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2266   ShenandoahGCPhase root_phase(full_gc ?
2267                                ShenandoahPhaseTimings::full_gc_purge :
2268                                ShenandoahPhaseTimings::purge);
2269   uint num_workers = _workers->active_workers();
2270   ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2271                                                ShenandoahPhaseTimings::full_gc_purge_weak_par :
2272                                                ShenandoahPhaseTimings::purge_weak_par;
2273   ShenandoahGCPhase phase(timing_phase);
2274   ShenandoahGCWorkerPhase worker_phase(timing_phase);
2275 
2276   // Cleanup weak roots
2277   if (has_forwarded_objects()) {
2278     ShenandoahForwardedIsAliveClosure is_alive;
2279     ShenandoahUpdateRefsClosure keep_alive;
2280     ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
2281       cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers, !ShenandoahConcurrentRoots::should_do_concurrent_class_unloading());
2282     _workers->run_task(&cleaning_task);
2283   } else {
2284     ShenandoahIsAliveClosure is_alive;
2285 #ifdef ASSERT
2286     ShenandoahAssertNotForwardedClosure verify_cl;
2287     ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2288       cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers, !ShenandoahConcurrentRoots::should_do_concurrent_class_unloading());
2289 #else
2290     ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2291       cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers, !ShenandoahConcurrentRoots::should_do_concurrent_class_unloading());
2292 #endif
2293     _workers->run_task(&cleaning_task);
2294   }
2295 }
2296 
2297 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2298   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2299   stw_process_weak_roots(full_gc);
2300   if (!ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
2301     stw_unload_classes(full_gc);
2302   }
2303 }
2304 
2305 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2306   set_gc_state_mask(HAS_FORWARDED, cond);
2307 }
2308 
2309 void ShenandoahHeap::set_process_references(bool pr) {
2310   _process_references.set_cond(pr);
2311 }
2312 
2313 void ShenandoahHeap::set_unload_classes(bool uc) {
2314   _unload_classes.set_cond(uc);
2315 }
2316 
2317 bool ShenandoahHeap::process_references() const {
2318   return _process_references.is_set();
2319 }
2320 
2321 bool ShenandoahHeap::unload_classes() const {
2322   return _unload_classes.is_set();
2323 }
2324 
2325 address ShenandoahHeap::in_cset_fast_test_addr() {
2326   ShenandoahHeap* heap = ShenandoahHeap::heap();
2327   assert(heap->collection_set() != NULL, "Sanity");
2328   return (address) heap->collection_set()->biased_map_address();
2329 }
2330 
2331 address ShenandoahHeap::cancelled_gc_addr() {
2332   return (address) ShenandoahHeap::heap()->_cancelled_gc.addr_of();
2333 }
2334 
2335 address ShenandoahHeap::gc_state_addr() {
2336   return (address) ShenandoahHeap::heap()->_gc_state.addr_of();
2337 }
2338 
2339 size_t ShenandoahHeap::bytes_allocated_since_gc_start() {
2340   return Atomic::load_acquire(&_bytes_allocated_since_gc_start);
2341 }
2342 
2343 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2344   Atomic::release_store_fence(&_bytes_allocated_since_gc_start, (size_t)0);
2345 }
2346 
2347 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2348   _degenerated_gc_in_progress.set_cond(in_progress);
2349 }
2350 
2351 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2352   _full_gc_in_progress.set_cond(in_progress);
2353 }
2354 
2355 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2356   assert (is_full_gc_in_progress(), "should be");
2357   _full_gc_move_in_progress.set_cond(in_progress);
2358 }
2359 
2360 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2361   set_gc_state_mask(UPDATEREFS, in_progress);
2362 }
2363 
2364 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2365   ShenandoahCodeRoots::register_nmethod(nm);
2366 }
2367 
2368 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2369   ShenandoahCodeRoots::unregister_nmethod(nm);
2370 }
2371 
2372 void ShenandoahHeap::flush_nmethod(nmethod* nm) {
2373   ShenandoahCodeRoots::flush_nmethod(nm);
2374 }
2375 
2376 oop ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2377   heap_region_containing(o)->record_pin();
2378   return o;
2379 }
2380 
2381 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2382   heap_region_containing(o)->record_unpin();
2383 }
2384 
2385 void ShenandoahHeap::sync_pinned_region_status() {
2386   ShenandoahHeapLocker locker(lock());
2387 
2388   for (size_t i = 0; i < num_regions(); i++) {
2389     ShenandoahHeapRegion *r = get_region(i);
2390     if (r->is_active()) {
2391       if (r->is_pinned()) {
2392         if (r->pin_count() == 0) {
2393           r->make_unpinned();
2394         }
2395       } else {
2396         if (r->pin_count() > 0) {
2397           r->make_pinned();
2398         }
2399       }
2400     }
2401   }
2402 
2403   assert_pinned_region_status();
2404 }
2405 
2406 #ifdef ASSERT
2407 void ShenandoahHeap::assert_pinned_region_status() {
2408   for (size_t i = 0; i < num_regions(); i++) {
2409     ShenandoahHeapRegion* r = get_region(i);
2410     assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2411            "Region " SIZE_FORMAT " pinning status is inconsistent", i);
2412   }
2413 }
2414 #endif
2415 
2416 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2417   return _gc_timer;
2418 }
2419 
2420 void ShenandoahHeap::prepare_concurrent_roots() {
2421   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2422   if (ShenandoahConcurrentRoots::should_do_concurrent_roots()) {
2423     set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2424     set_concurrent_weak_root_in_progress(true);
2425   }
2426 }
2427 
2428 void ShenandoahHeap::prepare_concurrent_unloading() {
2429   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2430   if (ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
2431     _unloader.prepare();
2432   }
2433 }
2434 
2435 void ShenandoahHeap::finish_concurrent_unloading() {
2436   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2437   if (ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
2438     _unloader.finish();
2439   }
2440 }
2441 
2442 #ifdef ASSERT
2443 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2444   assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2445 
2446   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2447     if (UseDynamicNumberOfGCThreads) {
2448       assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
2449     } else {
2450       // Use ParallelGCThreads inside safepoints
2451       assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads within safepoints");
2452     }
2453   } else {
2454     if (UseDynamicNumberOfGCThreads) {
2455       assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
2456     } else {
2457       // Use ConcGCThreads outside safepoints
2458       assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
2459     }
2460   }
2461 }
2462 #endif
2463 
2464 ShenandoahVerifier* ShenandoahHeap::verifier() {
2465   guarantee(ShenandoahVerify, "Should be enabled");
2466   assert (_verifier != NULL, "sanity");
2467   return _verifier;
2468 }
2469 
2470 template<class T>
2471 class ShenandoahUpdateHeapRefsTask : public AbstractGangTask {
2472 private:
2473   T cl;
2474   ShenandoahHeap* _heap;
2475   ShenandoahRegionIterator* _regions;
2476   bool _concurrent;
2477 public:
2478   ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions, bool concurrent) :
2479     AbstractGangTask("Concurrent Update References Task"),
2480     cl(T()),
2481     _heap(ShenandoahHeap::heap()),
2482     _regions(regions),
2483     _concurrent(concurrent) {
2484   }
2485 
2486   void work(uint worker_id) {
2487     if (_concurrent) {
2488       ShenandoahConcurrentWorkerSession worker_session(worker_id);
2489       ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
2490       do_work();
2491     } else {
2492       ShenandoahParallelWorkerSession worker_session(worker_id);
2493       do_work();
2494     }
2495   }
2496 
2497 private:
2498   void do_work() {
2499     ShenandoahHeapRegion* r = _regions->next();
2500     ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2501     while (r != NULL) {
2502       HeapWord* update_watermark = r->get_update_watermark();
2503       assert (update_watermark >= r->bottom(), "sanity");
2504       if (r->is_active() && !r->is_cset()) {
2505         _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2506       }
2507       if (ShenandoahPacing) {
2508         _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2509       }
2510       if (_heap->check_cancelled_gc_and_yield(_concurrent)) {
2511         return;
2512       }
2513       r = _regions->next();
2514     }
2515   }
2516 };
2517 
2518 void ShenandoahHeap::update_heap_references(bool concurrent) {
2519   ShenandoahUpdateHeapRefsTask<ShenandoahUpdateHeapRefsClosure> task(&_update_refs_iterator, concurrent);
2520   workers()->run_task(&task);
2521 }
2522 
2523 void ShenandoahHeap::op_init_updaterefs() {
2524   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2525 
2526   set_evacuation_in_progress(false);
2527 
2528   {
2529     ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_refs_retire_gclabs);
2530     retire_and_reset_gclabs();
2531   }
2532 
2533   if (ShenandoahVerify) {
2534     if (!is_degenerated_gc_in_progress()) {
2535       verifier()->verify_roots_in_to_space_except(ShenandoahRootVerifier::ThreadRoots);
2536     }
2537     verifier()->verify_before_updaterefs();
2538   }
2539 
2540   set_update_refs_in_progress(true);
2541 
2542   _update_refs_iterator.reset();
2543 
2544   if (ShenandoahPacing) {
2545     pacer()->setup_for_updaterefs();
2546   }
2547 }
2548 
2549 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2550 private:
2551   ShenandoahHeapLock* const _lock;
2552 
2553 public:
2554   ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2555 
2556   void heap_region_do(ShenandoahHeapRegion* r) {
2557     // Drop unnecessary "pinned" state from regions that does not have CP marks
2558     // anymore, as this would allow trashing them.
2559 
2560     if (r->is_active()) {
2561       if (r->is_pinned()) {
2562         if (r->pin_count() == 0) {
2563           ShenandoahHeapLocker locker(_lock);
2564           r->make_unpinned();
2565         }
2566       } else {
2567         if (r->pin_count() > 0) {
2568           ShenandoahHeapLocker locker(_lock);
2569           r->make_pinned();
2570         }
2571       }
2572     }
2573   }
2574 
2575   bool is_thread_safe() { return true; }
2576 };
2577 
2578 void ShenandoahHeap::op_final_updaterefs() {
2579   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2580 
2581   finish_concurrent_unloading();
2582 
2583   // Check if there is left-over work, and finish it
2584   if (_update_refs_iterator.has_next()) {
2585     ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_refs_finish_work);
2586 
2587     // Finish updating references where we left off.
2588     clear_cancelled_gc();
2589     update_heap_references(false);
2590   }
2591 
2592   // Clear cancelled GC, if set. On cancellation path, the block before would handle
2593   // everything. On degenerated paths, cancelled gc would not be set anyway.
2594   if (cancelled_gc()) {
2595     clear_cancelled_gc();
2596   }
2597   assert(!cancelled_gc(), "Should have been done right before");
2598 
2599   if (ShenandoahVerify && !is_degenerated_gc_in_progress()) {
2600     verifier()->verify_roots_in_to_space_except(ShenandoahRootVerifier::ThreadRoots);
2601   }
2602 
2603   if (is_degenerated_gc_in_progress()) {
2604     concurrent_mark()->update_roots(ShenandoahPhaseTimings::degen_gc_update_roots);
2605   } else {
2606     concurrent_mark()->update_thread_roots(ShenandoahPhaseTimings::final_update_refs_roots);
2607   }
2608 
2609   // Has to be done before cset is clear
2610   if (ShenandoahVerify) {
2611     verifier()->verify_roots_in_to_space();
2612   }
2613 
2614   {
2615     ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_refs_update_region_states);
2616     ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2617     parallel_heap_region_iterate(&cl);
2618 
2619     assert_pinned_region_status();
2620   }
2621 
2622   {
2623     ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_refs_trash_cset);
2624     trash_cset_regions();
2625   }
2626 
2627   set_has_forwarded_objects(false);
2628   set_update_refs_in_progress(false);
2629 
2630   if (ShenandoahVerify) {
2631     verifier()->verify_after_updaterefs();
2632   }
2633 
2634   if (VerifyAfterGC) {
2635     Universe::verify();
2636   }
2637 
2638   {
2639     ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_refs_rebuild_freeset);
2640     ShenandoahHeapLocker locker(lock());
2641     _free_set->rebuild();
2642   }
2643 }
2644 
2645 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2646   print_on(st);
2647   print_heap_regions_on(st);
2648 }
2649 
2650 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2651   size_t slice = r->index() / _bitmap_regions_per_slice;
2652 
2653   size_t regions_from = _bitmap_regions_per_slice * slice;
2654   size_t regions_to   = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2655   for (size_t g = regions_from; g < regions_to; g++) {
2656     assert (g / _bitmap_regions_per_slice == slice, "same slice");
2657     if (skip_self && g == r->index()) continue;
2658     if (get_region(g)->is_committed()) {
2659       return true;
2660     }
2661   }
2662   return false;
2663 }
2664 
2665 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2666   shenandoah_assert_heaplocked();
2667 
2668   // Bitmaps in special regions do not need commits
2669   if (_bitmap_region_special) {
2670     return true;
2671   }
2672 
2673   if (is_bitmap_slice_committed(r, true)) {
2674     // Some other region from the group is already committed, meaning the bitmap
2675     // slice is already committed, we exit right away.
2676     return true;
2677   }
2678 
2679   // Commit the bitmap slice:
2680   size_t slice = r->index() / _bitmap_regions_per_slice;
2681   size_t off = _bitmap_bytes_per_slice * slice;
2682   size_t len = _bitmap_bytes_per_slice;
2683   char* start = (char*) _bitmap_region.start() + off;
2684 
2685   if (!os::commit_memory(start, len, false)) {
2686     return false;
2687   }
2688 
2689   if (AlwaysPreTouch) {
2690     os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2691   }
2692 
2693   return true;
2694 }
2695 
2696 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2697   shenandoah_assert_heaplocked();
2698 
2699   // Bitmaps in special regions do not need uncommits
2700   if (_bitmap_region_special) {
2701     return true;
2702   }
2703 
2704   if (is_bitmap_slice_committed(r, true)) {
2705     // Some other region from the group is still committed, meaning the bitmap
2706     // slice is should stay committed, exit right away.
2707     return true;
2708   }
2709 
2710   // Uncommit the bitmap slice:
2711   size_t slice = r->index() / _bitmap_regions_per_slice;
2712   size_t off = _bitmap_bytes_per_slice * slice;
2713   size_t len = _bitmap_bytes_per_slice;
2714   if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2715     return false;
2716   }
2717   return true;
2718 }
2719 
2720 void ShenandoahHeap::safepoint_synchronize_begin() {
2721   if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2722     SuspendibleThreadSet::synchronize();
2723   }
2724 }
2725 
2726 void ShenandoahHeap::safepoint_synchronize_end() {
2727   if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2728     SuspendibleThreadSet::desynchronize();
2729   }
2730 }
2731 
2732 void ShenandoahHeap::vmop_entry_init_mark() {
2733   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2734   ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::init_mark_gross);
2735 
2736   try_inject_alloc_failure();
2737   VM_ShenandoahInitMark op;
2738   VMThread::execute(&op); // jump to entry_init_mark() under safepoint
2739 }
2740 
2741 void ShenandoahHeap::vmop_entry_final_mark() {
2742   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2743   ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_mark_gross);
2744 
2745   try_inject_alloc_failure();
2746   VM_ShenandoahFinalMarkStartEvac op;
2747   VMThread::execute(&op); // jump to entry_final_mark under safepoint
2748 }
2749 
2750 void ShenandoahHeap::vmop_entry_init_updaterefs() {
2751   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2752   ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::init_update_refs_gross);
2753 
2754   try_inject_alloc_failure();
2755   VM_ShenandoahInitUpdateRefs op;
2756   VMThread::execute(&op);
2757 }
2758 
2759 void ShenandoahHeap::vmop_entry_final_updaterefs() {
2760   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2761   ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_update_refs_gross);
2762 
2763   try_inject_alloc_failure();
2764   VM_ShenandoahFinalUpdateRefs op;
2765   VMThread::execute(&op);
2766 }
2767 
2768 void ShenandoahHeap::vmop_entry_full(GCCause::Cause cause) {
2769   TraceCollectorStats tcs(monitoring_support()->full_stw_collection_counters());
2770   ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::full_gc_gross);
2771 
2772   try_inject_alloc_failure();
2773   VM_ShenandoahFullGC op(cause);
2774   VMThread::execute(&op);
2775 }
2776 
2777 void ShenandoahHeap::vmop_degenerated(ShenandoahDegenPoint point) {
2778   TraceCollectorStats tcs(monitoring_support()->full_stw_collection_counters());
2779   ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::degen_gc_gross);
2780 
2781   VM_ShenandoahDegeneratedGC degenerated_gc((int)point);
2782   VMThread::execute(&degenerated_gc);
2783 }
2784 
2785 void ShenandoahHeap::entry_init_mark() {
2786   const char* msg = init_mark_event_message();
2787   ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::init_mark);
2788   EventMark em("%s", msg);
2789 
2790   ShenandoahWorkerScope scope(workers(),
2791                               ShenandoahWorkerPolicy::calc_workers_for_init_marking(),
2792                               "init marking");
2793 
2794   op_init_mark();
2795 }
2796 
2797 void ShenandoahHeap::entry_final_mark() {
2798   const char* msg = final_mark_event_message();
2799   ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::final_mark);
2800   EventMark em("%s", msg);
2801 
2802   ShenandoahWorkerScope scope(workers(),
2803                               ShenandoahWorkerPolicy::calc_workers_for_final_marking(),
2804                               "final marking");
2805 
2806   op_final_mark();
2807 }
2808 
2809 void ShenandoahHeap::entry_init_updaterefs() {
2810   static const char* msg = "Pause Init Update Refs";
2811   ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::init_update_refs);
2812   EventMark em("%s", msg);
2813 
2814   // No workers used in this phase, no setup required
2815 
2816   op_init_updaterefs();
2817 }
2818 
2819 void ShenandoahHeap::entry_final_updaterefs() {
2820   static const char* msg = "Pause Final Update Refs";
2821   ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::final_update_refs);
2822   EventMark em("%s", msg);
2823 
2824   ShenandoahWorkerScope scope(workers(),
2825                               ShenandoahWorkerPolicy::calc_workers_for_final_update_ref(),
2826                               "final reference update");
2827 
2828   op_final_updaterefs();
2829 }
2830 
2831 void ShenandoahHeap::entry_full(GCCause::Cause cause) {
2832   static const char* msg = "Pause Full";
2833   ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::full_gc, true /* log_heap_usage */);
2834   EventMark em("%s", msg);
2835 
2836   ShenandoahWorkerScope scope(workers(),
2837                               ShenandoahWorkerPolicy::calc_workers_for_fullgc(),
2838                               "full gc");
2839 
2840   op_full(cause);
2841 }
2842 
2843 void ShenandoahHeap::entry_degenerated(int point) {
2844   ShenandoahDegenPoint dpoint = (ShenandoahDegenPoint)point;
2845   const char* msg = degen_event_message(dpoint);
2846   ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::degen_gc, true /* log_heap_usage */);
2847   EventMark em("%s", msg);
2848 
2849   ShenandoahWorkerScope scope(workers(),
2850                               ShenandoahWorkerPolicy::calc_workers_for_stw_degenerated(),
2851                               "stw degenerated gc");
2852 
2853   set_degenerated_gc_in_progress(true);
2854   op_degenerated(dpoint);
2855   set_degenerated_gc_in_progress(false);
2856 }
2857 
2858 void ShenandoahHeap::entry_mark() {
2859   TraceCollectorStats tcs(monitoring_support()->concurrent_collection_counters());
2860 
2861   const char* msg = conc_mark_event_message();
2862   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_mark);
2863   EventMark em("%s", msg);
2864 
2865   ShenandoahWorkerScope scope(workers(),
2866                               ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
2867                               "concurrent marking");
2868 
2869   try_inject_alloc_failure();
2870   op_mark();
2871 }
2872 
2873 void ShenandoahHeap::entry_evac() {
2874   TraceCollectorStats tcs(monitoring_support()->concurrent_collection_counters());
2875 
2876   static const char* msg = "Concurrent evacuation";
2877   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_evac);
2878   EventMark em("%s", msg);
2879 
2880   ShenandoahWorkerScope scope(workers(),
2881                               ShenandoahWorkerPolicy::calc_workers_for_conc_evac(),
2882                               "concurrent evacuation");
2883 
2884   try_inject_alloc_failure();
2885   op_conc_evac();
2886 }
2887 
2888 void ShenandoahHeap::entry_updaterefs() {
2889   static const char* msg = "Concurrent update references";
2890   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_update_refs);
2891   EventMark em("%s", msg);
2892 
2893   ShenandoahWorkerScope scope(workers(),
2894                               ShenandoahWorkerPolicy::calc_workers_for_conc_update_ref(),
2895                               "concurrent reference update");
2896 
2897   try_inject_alloc_failure();
2898   op_updaterefs();
2899 }
2900 
2901 void ShenandoahHeap::entry_weak_roots() {
2902   static const char* msg = "Concurrent weak roots";
2903   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_weak_roots);
2904   EventMark em("%s", msg);
2905 
2906   ShenandoahWorkerScope scope(workers(),
2907                               ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
2908                               "concurrent weak root");
2909 
2910   try_inject_alloc_failure();
2911   op_weak_roots();
2912 }
2913 
2914 void ShenandoahHeap::entry_class_unloading() {
2915   static const char* msg = "Concurrent class unloading";
2916   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_class_unload);
2917   EventMark em("%s", msg);
2918 
2919   ShenandoahWorkerScope scope(workers(),
2920                               ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
2921                               "concurrent class unloading");
2922 
2923   try_inject_alloc_failure();
2924   op_class_unloading();
2925 }
2926 
2927 void ShenandoahHeap::entry_strong_roots() {
2928   static const char* msg = "Concurrent strong roots";
2929   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_strong_roots);
2930   EventMark em("%s", msg);
2931 
2932   ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_strong_roots);
2933 
2934   ShenandoahWorkerScope scope(workers(),
2935                               ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
2936                               "concurrent strong root");
2937 
2938   try_inject_alloc_failure();
2939   op_strong_roots();
2940 }
2941 
2942 void ShenandoahHeap::entry_cleanup_early() {
2943   static const char* msg = "Concurrent cleanup";
2944   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_cleanup_early, true /* log_heap_usage */);
2945   EventMark em("%s", msg);
2946 
2947   // This phase does not use workers, no need for setup
2948 
2949   try_inject_alloc_failure();
2950   op_cleanup_early();
2951 }
2952 
2953 void ShenandoahHeap::entry_cleanup_complete() {
2954   static const char* msg = "Concurrent cleanup";
2955   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_cleanup_complete, true /* log_heap_usage */);
2956   EventMark em("%s", msg);
2957 
2958   // This phase does not use workers, no need for setup
2959 
2960   try_inject_alloc_failure();
2961   op_cleanup_complete();
2962 }
2963 
2964 void ShenandoahHeap::entry_reset() {
2965   static const char* msg = "Concurrent reset";
2966   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_reset);
2967   EventMark em("%s", msg);
2968 
2969   ShenandoahWorkerScope scope(workers(),
2970                               ShenandoahWorkerPolicy::calc_workers_for_conc_reset(),
2971                               "concurrent reset");
2972 
2973   try_inject_alloc_failure();
2974   op_reset();
2975 }
2976 
2977 void ShenandoahHeap::entry_preclean() {
2978   if (ShenandoahPreclean && process_references()) {
2979     static const char* msg = "Concurrent precleaning";
2980     ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_preclean);
2981     EventMark em("%s", msg);
2982 
2983     ShenandoahWorkerScope scope(workers(),
2984                                 ShenandoahWorkerPolicy::calc_workers_for_conc_preclean(),
2985                                 "concurrent preclean",
2986                                 /* check_workers = */ false);
2987 
2988     try_inject_alloc_failure();
2989     op_preclean();
2990   }
2991 }
2992 
2993 void ShenandoahHeap::entry_uncommit(double shrink_before) {
2994   static const char *msg = "Concurrent uncommit";
2995   ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
2996   EventMark em("%s", msg);
2997 
2998   op_uncommit(shrink_before);
2999 }
3000 
3001 void ShenandoahHeap::try_inject_alloc_failure() {
3002   if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
3003     _inject_alloc_failure.set();
3004     os::naked_short_sleep(1);
3005     if (cancelled_gc()) {
3006       log_info(gc)("Allocation failure was successfully injected");
3007     }
3008   }
3009 }
3010 
3011 bool ShenandoahHeap::should_inject_alloc_failure() {
3012   return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
3013 }
3014 
3015 void ShenandoahHeap::initialize_serviceability() {
3016   _memory_pool = new ShenandoahMemoryPool(this);
3017   _cycle_memory_manager.add_pool(_memory_pool);
3018   _stw_memory_manager.add_pool(_memory_pool);
3019 }
3020 
3021 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
3022   GrowableArray<GCMemoryManager*> memory_managers(2);
3023   memory_managers.append(&_cycle_memory_manager);
3024   memory_managers.append(&_stw_memory_manager);
3025   return memory_managers;
3026 }
3027 
3028 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
3029   GrowableArray<MemoryPool*> memory_pools(1);
3030   memory_pools.append(_memory_pool);
3031   return memory_pools;
3032 }
3033 
3034 MemoryUsage ShenandoahHeap::memory_usage() {
3035   return _memory_pool->get_memory_usage();
3036 }
3037 
3038 void ShenandoahHeap::enter_evacuation() {
3039   _oom_evac_handler.enter_evacuation();
3040 }
3041 
3042 void ShenandoahHeap::leave_evacuation() {
3043   _oom_evac_handler.leave_evacuation();
3044 }
3045 
3046 ShenandoahRegionIterator::ShenandoahRegionIterator() :
3047   _heap(ShenandoahHeap::heap()),
3048   _index(0) {}
3049 
3050 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
3051   _heap(heap),
3052   _index(0) {}
3053 
3054 void ShenandoahRegionIterator::reset() {
3055   _index = 0;
3056 }
3057 
3058 bool ShenandoahRegionIterator::has_next() const {
3059   return _index < _heap->num_regions();
3060 }
3061 
3062 char ShenandoahHeap::gc_state() const {
3063   return _gc_state.raw_value();
3064 }
3065 
3066 void ShenandoahHeap::deduplicate_string(oop str) {
3067   assert(java_lang_String::is_instance(str), "invariant");
3068 
3069   if (ShenandoahStringDedup::is_enabled()) {
3070     ShenandoahStringDedup::deduplicate(str);
3071   }
3072 }
3073 
3074 const char* ShenandoahHeap::init_mark_event_message() const {
3075   assert(!has_forwarded_objects(), "Should not have forwarded objects here");
3076 
3077   bool proc_refs = process_references();
3078   bool unload_cls = unload_classes();
3079 
3080   if (proc_refs && unload_cls) {
3081     return "Pause Init Mark (process weakrefs) (unload classes)";
3082   } else if (proc_refs) {
3083     return "Pause Init Mark (process weakrefs)";
3084   } else if (unload_cls) {
3085     return "Pause Init Mark (unload classes)";
3086   } else {
3087     return "Pause Init Mark";
3088   }
3089 }
3090 
3091 const char* ShenandoahHeap::final_mark_event_message() const {
3092   assert(!has_forwarded_objects(), "Should not have forwarded objects here");
3093 
3094   bool proc_refs = process_references();
3095   bool unload_cls = unload_classes();
3096 
3097   if (proc_refs && unload_cls) {
3098     return "Pause Final Mark (process weakrefs) (unload classes)";
3099   } else if (proc_refs) {
3100     return "Pause Final Mark (process weakrefs)";
3101   } else if (unload_cls) {
3102     return "Pause Final Mark (unload classes)";
3103   } else {
3104     return "Pause Final Mark";
3105   }
3106 }
3107 
3108 const char* ShenandoahHeap::conc_mark_event_message() const {
3109   assert(!has_forwarded_objects(), "Should not have forwarded objects here");
3110 
3111   bool proc_refs = process_references();
3112   bool unload_cls = unload_classes();
3113 
3114   if (proc_refs && unload_cls) {
3115     return "Concurrent marking (process weakrefs) (unload classes)";
3116   } else if (proc_refs) {
3117     return "Concurrent marking (process weakrefs)";
3118   } else if (unload_cls) {
3119     return "Concurrent marking (unload classes)";
3120   } else {
3121     return "Concurrent marking";
3122   }
3123 }
3124 
3125 const char* ShenandoahHeap::degen_event_message(ShenandoahDegenPoint point) const {
3126   switch (point) {
3127     case _degenerated_unset:
3128       return "Pause Degenerated GC (<UNSET>)";
3129     case _degenerated_outside_cycle:
3130       return "Pause Degenerated GC (Outside of Cycle)";
3131     case _degenerated_mark:
3132       return "Pause Degenerated GC (Mark)";
3133     case _degenerated_evac:
3134       return "Pause Degenerated GC (Evacuation)";
3135     case _degenerated_updaterefs:
3136       return "Pause Degenerated GC (Update Refs)";
3137     default:
3138       ShouldNotReachHere();
3139       return "ERROR";
3140   }
3141 }
3142 
3143 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
3144 #ifdef ASSERT
3145   assert(_liveness_cache != NULL, "sanity");
3146   assert(worker_id < _max_workers, "sanity");
3147   for (uint i = 0; i < num_regions(); i++) {
3148     assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
3149   }
3150 #endif
3151   return _liveness_cache[worker_id];
3152 }
3153 
3154 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
3155   assert(worker_id < _max_workers, "sanity");
3156   assert(_liveness_cache != NULL, "sanity");
3157   ShenandoahLiveData* ld = _liveness_cache[worker_id];
3158   for (uint i = 0; i < num_regions(); i++) {
3159     ShenandoahLiveData live = ld[i];
3160     if (live > 0) {
3161       ShenandoahHeapRegion* r = get_region(i);
3162       r->increase_live_data_gc_words(live);
3163       ld[i] = 0;
3164     }
3165   }
3166 }