1 /*
   2  * Copyright (c) 2013, 2019, Red Hat, Inc. All rights reserved.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  *
  22  */
  23 
  24 #include "precompiled.hpp"
  25 #include "memory/allocation.hpp"
  26 #include "memory/universe.hpp"
  27 
  28 #include "gc/shared/gcArguments.hpp"
  29 #include "gc/shared/gcTimer.hpp"
  30 #include "gc/shared/gcTraceTime.inline.hpp"
  31 #include "gc/shared/memAllocator.hpp"
  32 #include "gc/shared/parallelCleaning.hpp"
  33 #include "gc/shared/plab.hpp"
  34 
  35 #include "gc/shenandoah/shenandoahAllocTracker.hpp"
  36 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
  37 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
  38 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
  39 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
  40 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
  41 #include "gc/shenandoah/shenandoahControlThread.hpp"
  42 #include "gc/shenandoah/shenandoahFreeSet.hpp"
  43 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
  44 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
  45 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
  46 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
  47 #include "gc/shenandoah/shenandoahMarkCompact.hpp"
  48 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
  49 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
  50 #include "gc/shenandoah/shenandoahMetrics.hpp"
  51 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
  52 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
  53 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
  54 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
  55 #include "gc/shenandoah/shenandoahStringDedup.hpp"
  56 #include "gc/shenandoah/shenandoahTaskqueue.hpp"
  57 #include "gc/shenandoah/shenandoahUtils.hpp"
  58 #include "gc/shenandoah/shenandoahVerifier.hpp"
  59 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
  60 #include "gc/shenandoah/shenandoahVMOperations.hpp"
  61 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
  62 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
  63 #include "gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.hpp"
  64 #include "gc/shenandoah/heuristics/shenandoahAggressiveHeuristics.hpp"
  65 #include "gc/shenandoah/heuristics/shenandoahCompactHeuristics.hpp"
  66 #include "gc/shenandoah/heuristics/shenandoahPassiveHeuristics.hpp"
  67 #include "gc/shenandoah/heuristics/shenandoahStaticHeuristics.hpp"
  68 #include "gc/shenandoah/heuristics/shenandoahTraversalHeuristics.hpp"
  69 #if INCLUDE_JFR
  70 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
  71 #endif
  72 
  73 #include "memory/metaspace.hpp"
  74 #include "oops/compressedOops.inline.hpp"
  75 #include "runtime/globals.hpp"
  76 #include "runtime/interfaceSupport.inline.hpp"
  77 #include "runtime/safepointMechanism.hpp"
  78 #include "runtime/vmThread.hpp"
  79 #include "services/mallocTracker.hpp"
  80 
  81 #ifdef ASSERT
  82 template <class T>
  83 void ShenandoahAssertToSpaceClosure::do_oop_work(T* p) {
  84   T o = RawAccess<>::oop_load(p);
  85   if (! CompressedOops::is_null(o)) {
  86     oop obj = CompressedOops::decode_not_null(o);
  87     shenandoah_assert_not_forwarded(p, obj);
  88   }
  89 }
  90 
  91 void ShenandoahAssertToSpaceClosure::do_oop(narrowOop* p) { do_oop_work(p); }
  92 void ShenandoahAssertToSpaceClosure::do_oop(oop* p)       { do_oop_work(p); }
  93 #endif
  94 
  95 class ShenandoahPretouchHeapTask : public AbstractGangTask {
  96 private:
  97   ShenandoahRegionIterator _regions;
  98   const size_t _page_size;
  99 public:
 100   ShenandoahPretouchHeapTask(size_t page_size) :
 101     AbstractGangTask("Shenandoah Pretouch Heap"),
 102     _page_size(page_size) {}
 103 
 104   virtual void work(uint worker_id) {
 105     ShenandoahHeapRegion* r = _regions.next();
 106     while (r != NULL) {
 107       os::pretouch_memory(r->bottom(), r->end(), _page_size);
 108       r = _regions.next();
 109     }
 110   }
 111 };
 112 
 113 class ShenandoahPretouchBitmapTask : public AbstractGangTask {
 114 private:
 115   ShenandoahRegionIterator _regions;
 116   char* _bitmap_base;
 117   const size_t _bitmap_size;
 118   const size_t _page_size;
 119 public:
 120   ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
 121     AbstractGangTask("Shenandoah Pretouch Bitmap"),
 122     _bitmap_base(bitmap_base),
 123     _bitmap_size(bitmap_size),
 124     _page_size(page_size) {}
 125 
 126   virtual void work(uint worker_id) {
 127     ShenandoahHeapRegion* r = _regions.next();
 128     while (r != NULL) {
 129       size_t start = r->region_number()       * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 130       size_t end   = (r->region_number() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 131       assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
 132 
 133       os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
 134 
 135       r = _regions.next();
 136     }
 137   }
 138 };
 139 
 140 jint ShenandoahHeap::initialize() {
 141   initialize_heuristics();
 142 
 143   //
 144   // Figure out heap sizing
 145   //
 146 
 147   size_t init_byte_size = InitialHeapSize;
 148   size_t min_byte_size  = MinHeapSize;
 149   size_t max_byte_size  = MaxHeapSize;
 150   size_t heap_alignment = HeapAlignment;
 151 
 152   size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
 153 
 154   if (ShenandoahAlwaysPreTouch) {
 155     // Enabled pre-touch means the entire heap is committed right away.
 156     init_byte_size = max_byte_size;
 157   }
 158 
 159   Universe::check_alignment(max_byte_size,  reg_size_bytes, "Shenandoah heap");
 160   Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
 161 
 162   _num_regions = ShenandoahHeapRegion::region_count();
 163 
 164   size_t num_committed_regions = init_byte_size / reg_size_bytes;
 165   num_committed_regions = MIN2(num_committed_regions, _num_regions);
 166   assert(num_committed_regions <= _num_regions, "sanity");
 167   _initial_size = num_committed_regions * reg_size_bytes;
 168 
 169   size_t num_min_regions = min_byte_size / reg_size_bytes;
 170   num_min_regions = MIN2(num_min_regions, _num_regions);
 171   assert(num_min_regions <= _num_regions, "sanity");
 172   _minimum_size = num_min_regions * reg_size_bytes;
 173 
 174   _committed = _initial_size;
 175 
 176   size_t heap_page_size   = UseLargePages ? (size_t)os::large_page_size() : (size_t)os::vm_page_size();
 177   size_t bitmap_page_size = UseLargePages ? (size_t)os::large_page_size() : (size_t)os::vm_page_size();
 178 
 179   //
 180   // Reserve and commit memory for heap
 181   //
 182 
 183   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
 184   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*) (heap_rs.base() + heap_rs.size()));
 185   _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
 186   _heap_region_special = heap_rs.special();
 187 
 188   assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
 189          "Misaligned heap: " PTR_FORMAT, p2i(base()));
 190 
 191 #if SHENANDOAH_OPTIMIZED_OBJTASK
 192   // The optimized ObjArrayChunkedTask takes some bits away from the full object bits.
 193   // Fail if we ever attempt to address more than we can.
 194   if ((uintptr_t)heap_rs.end() >= ObjArrayChunkedTask::max_addressable()) {
 195     FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
 196                           "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
 197                           "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
 198                 p2i(heap_rs.base()), p2i(heap_rs.end()), ObjArrayChunkedTask::max_addressable());
 199     vm_exit_during_initialization("Fatal Error", buf);
 200   }
 201 #endif
 202 
 203   ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
 204   if (!_heap_region_special) {
 205     os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
 206                               "Cannot commit heap memory");
 207   }
 208 
 209   //
 210   // Reserve and commit memory for bitmap(s)
 211   //
 212 
 213   _bitmap_size = MarkBitMap::compute_size(heap_rs.size());
 214   _bitmap_size = align_up(_bitmap_size, bitmap_page_size);
 215 
 216   size_t bitmap_bytes_per_region = reg_size_bytes / MarkBitMap::heap_map_factor();
 217 
 218   guarantee(bitmap_bytes_per_region != 0,
 219             "Bitmap bytes per region should not be zero");
 220   guarantee(is_power_of_2(bitmap_bytes_per_region),
 221             "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
 222 
 223   if (bitmap_page_size > bitmap_bytes_per_region) {
 224     _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
 225     _bitmap_bytes_per_slice = bitmap_page_size;
 226   } else {
 227     _bitmap_regions_per_slice = 1;
 228     _bitmap_bytes_per_slice = bitmap_bytes_per_region;
 229   }
 230 
 231   guarantee(_bitmap_regions_per_slice >= 1,
 232             "Should have at least one region per slice: " SIZE_FORMAT,
 233             _bitmap_regions_per_slice);
 234 
 235   guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
 236             "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
 237             _bitmap_bytes_per_slice, bitmap_page_size);
 238 
 239   ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
 240   MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
 241   _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
 242   _bitmap_region_special = bitmap.special();
 243 
 244   size_t bitmap_init_commit = _bitmap_bytes_per_slice *
 245                               align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
 246   bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
 247   if (!_bitmap_region_special) {
 248     os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
 249                               "Cannot commit bitmap memory");
 250   }
 251 
 252   _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
 253 
 254   if (ShenandoahVerify) {
 255     ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
 256     if (!verify_bitmap.special()) {
 257       os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
 258                                 "Cannot commit verification bitmap memory");
 259     }
 260     MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
 261     MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
 262     _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
 263     _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
 264   }
 265 
 266   // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
 267   ReservedSpace aux_bitmap(_bitmap_size, bitmap_page_size);
 268   MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
 269   _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
 270   _aux_bitmap_region_special = aux_bitmap.special();
 271   _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
 272 
 273   //
 274   // Create regions and region sets
 275   //
 276 
 277   _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
 278   _free_set = new ShenandoahFreeSet(this, _num_regions);
 279   _collection_set = new ShenandoahCollectionSet(this, sh_rs.base(), sh_rs.size());
 280 
 281   {
 282     ShenandoahHeapLocker locker(lock());
 283 
 284     size_t size_words = ShenandoahHeapRegion::region_size_words();
 285 
 286     for (size_t i = 0; i < _num_regions; i++) {
 287       HeapWord* start = (HeapWord*)sh_rs.base() + size_words * i;
 288       bool is_committed = i < num_committed_regions;
 289       ShenandoahHeapRegion* r = new ShenandoahHeapRegion(this, start, size_words, i, is_committed);
 290 
 291       _marking_context->initialize_top_at_mark_start(r);
 292       _regions[i] = r;
 293       assert(!collection_set()->is_in(i), "New region should not be in collection set");
 294     }
 295 
 296     // Initialize to complete
 297     _marking_context->mark_complete();
 298 
 299     _free_set->rebuild();
 300   }
 301 
 302   if (ShenandoahAlwaysPreTouch) {
 303     assert(!AlwaysPreTouch, "Should have been overridden");
 304 
 305     // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
 306     // before initialize() below zeroes it with initializing thread. For any given region,
 307     // we touch the region and the corresponding bitmaps from the same thread.
 308     ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
 309 
 310     size_t pretouch_heap_page_size = heap_page_size;
 311     size_t pretouch_bitmap_page_size = bitmap_page_size;
 312 
 313 #ifdef LINUX
 314     // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
 315     // pages. But, the kernel needs to know that every small page is used, in order to coalesce
 316     // them into huge one. Therefore, we need to pretouch with smaller pages.
 317     if (UseTransparentHugePages) {
 318       pretouch_heap_page_size = (size_t)os::vm_page_size();
 319       pretouch_bitmap_page_size = (size_t)os::vm_page_size();
 320     }
 321 #endif
 322 
 323     // OS memory managers may want to coalesce back-to-back pages. Make their jobs
 324     // simpler by pre-touching continuous spaces (heap and bitmap) separately.
 325 
 326     log_info(gc, init)("Pretouch bitmap: " SIZE_FORMAT " regions, " SIZE_FORMAT " bytes page",
 327                        _num_regions, pretouch_bitmap_page_size);
 328     ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, pretouch_bitmap_page_size);
 329     _workers->run_task(&bcl);
 330 
 331     log_info(gc, init)("Pretouch heap: " SIZE_FORMAT " regions, " SIZE_FORMAT " bytes page",
 332                        _num_regions, pretouch_heap_page_size);
 333     ShenandoahPretouchHeapTask hcl(pretouch_heap_page_size);
 334     _workers->run_task(&hcl);
 335   }
 336 
 337   //
 338   // Initialize the rest of GC subsystems
 339   //
 340 
 341   _liveness_cache = NEW_C_HEAP_ARRAY(jushort*, _max_workers, mtGC);
 342   for (uint worker = 0; worker < _max_workers; worker++) {
 343     _liveness_cache[worker] = NEW_C_HEAP_ARRAY(jushort, _num_regions, mtGC);
 344     Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(jushort));
 345   }
 346 
 347   // The call below uses stuff (the SATB* things) that are in G1, but probably
 348   // belong into a shared location.
 349   ShenandoahBarrierSet::satb_mark_queue_set().initialize(this,
 350                                                          SATB_Q_CBL_mon,
 351                                                          20 /* G1SATBProcessCompletedThreshold */,
 352                                                          60 /* G1SATBBufferEnqueueingThresholdPercent */);
 353 
 354   _monitoring_support = new ShenandoahMonitoringSupport(this);
 355   _phase_timings = new ShenandoahPhaseTimings();
 356   ShenandoahStringDedup::initialize();
 357   ShenandoahCodeRoots::initialize();
 358 
 359   if (ShenandoahAllocationTrace) {
 360     _alloc_tracker = new ShenandoahAllocTracker();
 361   }
 362 
 363   if (ShenandoahPacing) {
 364     _pacer = new ShenandoahPacer(this);
 365     _pacer->setup_for_idle();
 366   } else {
 367     _pacer = NULL;
 368   }
 369 
 370   _traversal_gc = heuristics()->can_do_traversal_gc() ?
 371                   new ShenandoahTraversalGC(this, _num_regions) :
 372                   NULL;
 373 
 374   _control_thread = new ShenandoahControlThread();
 375 
 376   log_info(gc, init)("Initialize Shenandoah heap: " SIZE_FORMAT "%s initial, " SIZE_FORMAT "%s min, " SIZE_FORMAT "%s max",
 377                      byte_size_in_proper_unit(_initial_size),  proper_unit_for_byte_size(_initial_size),
 378                      byte_size_in_proper_unit(_minimum_size),  proper_unit_for_byte_size(_minimum_size),
 379                      byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity())
 380   );
 381 
 382   log_info(gc, init)("Safepointing mechanism: %s",
 383                      SafepointMechanism::uses_thread_local_poll() ? "thread-local poll" :
 384                      (SafepointMechanism::uses_global_page_poll() ? "global-page poll" : "unknown"));
 385 
 386   return JNI_OK;
 387 }
 388 
 389 void ShenandoahHeap::initialize_heuristics() {
 390   if (ShenandoahGCHeuristics != NULL) {
 391     if (strcmp(ShenandoahGCHeuristics, "aggressive") == 0) {
 392       _heuristics = new ShenandoahAggressiveHeuristics();
 393     } else if (strcmp(ShenandoahGCHeuristics, "static") == 0) {
 394       _heuristics = new ShenandoahStaticHeuristics();
 395     } else if (strcmp(ShenandoahGCHeuristics, "adaptive") == 0) {
 396       _heuristics = new ShenandoahAdaptiveHeuristics();
 397     } else if (strcmp(ShenandoahGCHeuristics, "passive") == 0) {
 398       _heuristics = new ShenandoahPassiveHeuristics();
 399     } else if (strcmp(ShenandoahGCHeuristics, "compact") == 0) {
 400       _heuristics = new ShenandoahCompactHeuristics();
 401     } else if (strcmp(ShenandoahGCHeuristics, "traversal") == 0) {
 402       _heuristics = new ShenandoahTraversalHeuristics();
 403     } else {
 404       vm_exit_during_initialization("Unknown -XX:ShenandoahGCHeuristics option");
 405     }
 406 
 407     if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
 408       vm_exit_during_initialization(
 409               err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
 410                       _heuristics->name()));
 411     }
 412     if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
 413       vm_exit_during_initialization(
 414               err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
 415                       _heuristics->name()));
 416     }
 417     log_info(gc, init)("Shenandoah heuristics: %s",
 418                        _heuristics->name());
 419   } else {
 420       ShouldNotReachHere();
 421   }
 422 
 423 }
 424 
 425 #ifdef _MSC_VER
 426 #pragma warning( push )
 427 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 428 #endif
 429 
 430 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
 431   CollectedHeap(),
 432   _initial_size(0),
 433   _used(0),
 434   _committed(0),
 435   _bytes_allocated_since_gc_start(0),
 436   _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
 437   _workers(NULL),
 438   _safepoint_workers(NULL),
 439   _heap_region_special(false),
 440   _num_regions(0),
 441   _regions(NULL),
 442   _update_refs_iterator(this),
 443   _control_thread(NULL),
 444   _shenandoah_policy(policy),
 445   _heuristics(NULL),
 446   _free_set(NULL),
 447   _scm(new ShenandoahConcurrentMark()),
 448   _traversal_gc(NULL),
 449   _full_gc(new ShenandoahMarkCompact()),
 450   _pacer(NULL),
 451   _verifier(NULL),
 452   _alloc_tracker(NULL),
 453   _phase_timings(NULL),
 454   _monitoring_support(NULL),
 455   _memory_pool(NULL),
 456   _stw_memory_manager("Shenandoah Pauses", "end of GC pause"),
 457   _cycle_memory_manager("Shenandoah Cycles", "end of GC cycle"),
 458   _gc_timer(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
 459   _soft_ref_policy(),
 460   _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
 461   _ref_processor(NULL),
 462   _marking_context(NULL),
 463   _bitmap_size(0),
 464   _bitmap_regions_per_slice(0),
 465   _bitmap_bytes_per_slice(0),
 466   _bitmap_region_special(false),
 467   _aux_bitmap_region_special(false),
 468   _liveness_cache(NULL),
 469   _collection_set(NULL)
 470 {
 471   log_info(gc, init)("GC threads: " UINT32_FORMAT " parallel, " UINT32_FORMAT " concurrent", ParallelGCThreads, ConcGCThreads);
 472   log_info(gc, init)("Reference processing: %s", ParallelRefProcEnabled ? "parallel" : "serial");
 473 
 474   BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
 475 
 476   _max_workers = MAX2(_max_workers, 1U);
 477   _workers = new ShenandoahWorkGang("Shenandoah GC Threads", _max_workers,
 478                             /* are_GC_task_threads */ true,
 479                             /* are_ConcurrentGC_threads */ true);
 480   if (_workers == NULL) {
 481     vm_exit_during_initialization("Failed necessary allocation.");
 482   } else {
 483     _workers->initialize_workers();
 484   }
 485 
 486   if (ShenandoahParallelSafepointThreads > 1) {
 487     _safepoint_workers = new ShenandoahWorkGang("Safepoint Cleanup Thread",
 488                                                 ShenandoahParallelSafepointThreads,
 489                       /* are_GC_task_threads */ false,
 490                  /* are_ConcurrentGC_threads */ false);
 491     _safepoint_workers->initialize_workers();
 492   }
 493 }
 494 
 495 #ifdef _MSC_VER
 496 #pragma warning( pop )
 497 #endif
 498 
 499 class ShenandoahResetBitmapTask : public AbstractGangTask {
 500 private:
 501   ShenandoahRegionIterator _regions;
 502 
 503 public:
 504   ShenandoahResetBitmapTask() :
 505     AbstractGangTask("Parallel Reset Bitmap Task") {}
 506 
 507   void work(uint worker_id) {
 508     ShenandoahHeapRegion* region = _regions.next();
 509     ShenandoahHeap* heap = ShenandoahHeap::heap();
 510     ShenandoahMarkingContext* const ctx = heap->marking_context();
 511     while (region != NULL) {
 512       if (heap->is_bitmap_slice_committed(region)) {
 513         ctx->clear_bitmap(region);
 514       }
 515       region = _regions.next();
 516     }
 517   }
 518 };
 519 
 520 void ShenandoahHeap::reset_mark_bitmap() {
 521   assert_gc_workers(_workers->active_workers());
 522   mark_incomplete_marking_context();
 523 
 524   ShenandoahResetBitmapTask task;
 525   _workers->run_task(&task);
 526 }
 527 
 528 void ShenandoahHeap::print_on(outputStream* st) const {
 529   st->print_cr("Shenandoah Heap");
 530   st->print_cr(" " SIZE_FORMAT "K total, " SIZE_FORMAT "K committed, " SIZE_FORMAT "K used",
 531                max_capacity() / K, committed() / K, used() / K);
 532   st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"K regions",
 533                num_regions(), ShenandoahHeapRegion::region_size_bytes() / K);
 534 
 535   st->print("Status: ");
 536   if (has_forwarded_objects())               st->print("has forwarded objects, ");
 537   if (is_concurrent_mark_in_progress())      st->print("marking, ");
 538   if (is_evacuation_in_progress())           st->print("evacuating, ");
 539   if (is_update_refs_in_progress())          st->print("updating refs, ");
 540   if (is_concurrent_traversal_in_progress()) st->print("traversal, ");
 541   if (is_degenerated_gc_in_progress())       st->print("degenerated gc, ");
 542   if (is_full_gc_in_progress())              st->print("full gc, ");
 543   if (is_full_gc_move_in_progress())         st->print("full gc move, ");
 544 
 545   if (cancelled_gc()) {
 546     st->print("cancelled");
 547   } else {
 548     st->print("not cancelled");
 549   }
 550   st->cr();
 551 
 552   st->print_cr("Reserved region:");
 553   st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
 554                p2i(reserved_region().start()),
 555                p2i(reserved_region().end()));
 556 
 557   ShenandoahCollectionSet* cset = collection_set();
 558   st->print_cr("Collection set:");
 559   if (cset != NULL) {
 560     st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
 561     st->print_cr(" - map (biased):  " PTR_FORMAT, p2i(cset->biased_map_address()));
 562   } else {
 563     st->print_cr(" (NULL)");
 564   }
 565 
 566   st->cr();
 567   MetaspaceUtils::print_on(st);
 568 
 569   if (Verbose) {
 570     print_heap_regions_on(st);
 571   }
 572 }
 573 
 574 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
 575 public:
 576   void do_thread(Thread* thread) {
 577     assert(thread != NULL, "Sanity");
 578     assert(thread->is_Worker_thread(), "Only worker thread expected");
 579     ShenandoahThreadLocalData::initialize_gclab(thread);
 580   }
 581 };
 582 
 583 void ShenandoahHeap::post_initialize() {
 584   CollectedHeap::post_initialize();
 585   MutexLocker ml(Threads_lock);
 586 
 587   ShenandoahInitWorkerGCLABClosure init_gclabs;
 588   _workers->threads_do(&init_gclabs);
 589 
 590   // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
 591   // Now, we will let WorkGang to initialize gclab when new worker is created.
 592   _workers->set_initialize_gclab();
 593 
 594   _scm->initialize(_max_workers);
 595   _full_gc->initialize(_gc_timer);
 596 
 597   ref_processing_init();
 598 
 599   _heuristics->initialize();
 600 
 601   JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
 602 }
 603 
 604 size_t ShenandoahHeap::used() const {
 605   return OrderAccess::load_acquire(&_used);
 606 }
 607 
 608 size_t ShenandoahHeap::committed() const {
 609   OrderAccess::acquire();
 610   return _committed;
 611 }
 612 
 613 void ShenandoahHeap::increase_committed(size_t bytes) {
 614   assert_heaplock_or_safepoint();
 615   _committed += bytes;
 616 }
 617 
 618 void ShenandoahHeap::decrease_committed(size_t bytes) {
 619   assert_heaplock_or_safepoint();
 620   _committed -= bytes;
 621 }
 622 
 623 void ShenandoahHeap::increase_used(size_t bytes) {
 624   Atomic::add(bytes, &_used);
 625 }
 626 
 627 void ShenandoahHeap::set_used(size_t bytes) {
 628   OrderAccess::release_store_fence(&_used, bytes);
 629 }
 630 
 631 void ShenandoahHeap::decrease_used(size_t bytes) {
 632   assert(used() >= bytes, "never decrease heap size by more than we've left");
 633   Atomic::sub(bytes, &_used);
 634 }
 635 
 636 void ShenandoahHeap::increase_allocated(size_t bytes) {
 637   Atomic::add(bytes, &_bytes_allocated_since_gc_start);
 638 }
 639 
 640 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
 641   size_t bytes = words * HeapWordSize;
 642   if (!waste) {
 643     increase_used(bytes);
 644   }
 645   increase_allocated(bytes);
 646   if (ShenandoahPacing) {
 647     control_thread()->pacing_notify_alloc(words);
 648     if (waste) {
 649       pacer()->claim_for_alloc(words, true);
 650     }
 651   }
 652 }
 653 
 654 size_t ShenandoahHeap::capacity() const {
 655   return committed();
 656 }
 657 
 658 size_t ShenandoahHeap::max_capacity() const {
 659   return _num_regions * ShenandoahHeapRegion::region_size_bytes();
 660 }
 661 
 662 size_t ShenandoahHeap::min_capacity() const {
 663   return _minimum_size;
 664 }
 665 
 666 size_t ShenandoahHeap::initial_capacity() const {
 667   return _initial_size;
 668 }
 669 
 670 bool ShenandoahHeap::is_in(const void* p) const {
 671   HeapWord* heap_base = (HeapWord*) base();
 672   HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
 673   return p >= heap_base && p < last_region_end;
 674 }
 675 
 676 void ShenandoahHeap::op_uncommit(double shrink_before) {
 677   assert (ShenandoahUncommit, "should be enabled");
 678 
 679   // Application allocates from the beginning of the heap, and GC allocates at
 680   // the end of it. It is more efficient to uncommit from the end, so that applications
 681   // could enjoy the near committed regions. GC allocations are much less frequent,
 682   // and therefore can accept the committing costs.
 683 
 684   size_t count = 0;
 685   for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
 686     ShenandoahHeapRegion* r = get_region(i - 1);
 687     if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
 688       ShenandoahHeapLocker locker(lock());
 689       if (r->is_empty_committed()) {
 690         // Do not uncommit below minimal capacity
 691         if (committed() < min_capacity() + ShenandoahHeapRegion::region_size_bytes()) {
 692           break;
 693         }
 694 
 695         r->make_uncommitted();
 696         count++;
 697       }
 698     }
 699     SpinPause(); // allow allocators to take the lock
 700   }
 701 
 702   if (count > 0) {
 703     control_thread()->notify_heap_changed();
 704   }
 705 }
 706 
 707 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
 708   // New object should fit the GCLAB size
 709   size_t min_size = MAX2(size, PLAB::min_size());
 710 
 711   // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
 712   size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
 713   new_size = MIN2(new_size, PLAB::max_size());
 714   new_size = MAX2(new_size, PLAB::min_size());
 715 
 716   // Record new heuristic value even if we take any shortcut. This captures
 717   // the case when moderately-sized objects always take a shortcut. At some point,
 718   // heuristics should catch up with them.
 719   ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
 720 
 721   if (new_size < size) {
 722     // New size still does not fit the object. Fall back to shared allocation.
 723     // This avoids retiring perfectly good GCLABs, when we encounter a large object.
 724     return NULL;
 725   }
 726 
 727   // Retire current GCLAB, and allocate a new one.
 728   PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
 729   gclab->retire();
 730 
 731   size_t actual_size = 0;
 732   HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
 733   if (gclab_buf == NULL) {
 734     return NULL;
 735   }
 736 
 737   assert (size <= actual_size, "allocation should fit");
 738 
 739   if (ZeroTLAB) {
 740     // ..and clear it.
 741     Copy::zero_to_words(gclab_buf, actual_size);
 742   } else {
 743     // ...and zap just allocated object.
 744 #ifdef ASSERT
 745     // Skip mangling the space corresponding to the object header to
 746     // ensure that the returned space is not considered parsable by
 747     // any concurrent GC thread.
 748     size_t hdr_size = oopDesc::header_size();
 749     Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
 750 #endif // ASSERT
 751   }
 752   gclab->set_buf(gclab_buf, actual_size);
 753   return gclab->allocate(size);
 754 }
 755 
 756 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
 757                                             size_t requested_size,
 758                                             size_t* actual_size) {
 759   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
 760   HeapWord* res = allocate_memory(req);
 761   if (res != NULL) {
 762     *actual_size = req.actual_size();
 763   } else {
 764     *actual_size = 0;
 765   }
 766   return res;
 767 }
 768 
 769 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
 770                                              size_t word_size,
 771                                              size_t* actual_size) {
 772   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
 773   HeapWord* res = allocate_memory(req);
 774   if (res != NULL) {
 775     *actual_size = req.actual_size();
 776   } else {
 777     *actual_size = 0;
 778   }
 779   return res;
 780 }
 781 
 782 ShenandoahHeap* ShenandoahHeap::heap() {
 783   CollectedHeap* heap = Universe::heap();
 784   assert(heap != NULL, "Unitialized access to ShenandoahHeap::heap()");
 785   assert(heap->kind() == CollectedHeap::Shenandoah, "not a shenandoah heap");
 786   return (ShenandoahHeap*) heap;
 787 }
 788 
 789 ShenandoahHeap* ShenandoahHeap::heap_no_check() {
 790   CollectedHeap* heap = Universe::heap();
 791   return (ShenandoahHeap*) heap;
 792 }
 793 
 794 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
 795   ShenandoahAllocTrace trace_alloc(req.size(), req.type());
 796 
 797   intptr_t pacer_epoch = 0;
 798   bool in_new_region = false;
 799   HeapWord* result = NULL;
 800 
 801   if (req.is_mutator_alloc()) {
 802     if (ShenandoahPacing) {
 803       pacer()->pace_for_alloc(req.size());
 804       pacer_epoch = pacer()->epoch();
 805     }
 806 
 807     if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
 808       result = allocate_memory_under_lock(req, in_new_region);
 809     }
 810 
 811     // Allocation failed, block until control thread reacted, then retry allocation.
 812     //
 813     // It might happen that one of the threads requesting allocation would unblock
 814     // way later after GC happened, only to fail the second allocation, because
 815     // other threads have already depleted the free storage. In this case, a better
 816     // strategy is to try again, as long as GC makes progress.
 817     //
 818     // Then, we need to make sure the allocation was retried after at least one
 819     // Full GC, which means we want to try more than ShenandoahFullGCThreshold times.
 820 
 821     size_t tries = 0;
 822 
 823     while (result == NULL && _progress_last_gc.is_set()) {
 824       tries++;
 825       control_thread()->handle_alloc_failure(req.size());
 826       result = allocate_memory_under_lock(req, in_new_region);
 827     }
 828 
 829     while (result == NULL && tries <= ShenandoahFullGCThreshold) {
 830       tries++;
 831       control_thread()->handle_alloc_failure(req.size());
 832       result = allocate_memory_under_lock(req, in_new_region);
 833     }
 834 
 835   } else {
 836     assert(req.is_gc_alloc(), "Can only accept GC allocs here");
 837     result = allocate_memory_under_lock(req, in_new_region);
 838     // Do not call handle_alloc_failure() here, because we cannot block.
 839     // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
 840   }
 841 
 842   if (in_new_region) {
 843     control_thread()->notify_heap_changed();
 844   }
 845 
 846   if (result != NULL) {
 847     size_t requested = req.size();
 848     size_t actual = req.actual_size();
 849 
 850     assert (req.is_lab_alloc() || (requested == actual),
 851             "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
 852             ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
 853 
 854     if (req.is_mutator_alloc()) {
 855       notify_mutator_alloc_words(actual, false);
 856 
 857       // If we requested more than we were granted, give the rest back to pacer.
 858       // This only matters if we are in the same pacing epoch: do not try to unpace
 859       // over the budget for the other phase.
 860       if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
 861         pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
 862       }
 863     } else {
 864       increase_used(actual*HeapWordSize);
 865     }
 866   }
 867 
 868   return result;
 869 }
 870 
 871 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
 872   ShenandoahHeapLocker locker(lock());
 873   return _free_set->allocate(req, in_new_region);
 874 }
 875 
 876 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
 877                                         bool*  gc_overhead_limit_was_exceeded) {
 878   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
 879   return allocate_memory(req);
 880 }
 881 
 882 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
 883                                                              size_t size,
 884                                                              Metaspace::MetadataType mdtype) {
 885   MetaWord* result;
 886 
 887   // Inform metaspace OOM to GC heuristics if class unloading is possible.
 888   if (heuristics()->can_unload_classes()) {
 889     ShenandoahHeuristics* h = heuristics();
 890     h->record_metaspace_oom();
 891   }
 892 
 893   // Expand and retry allocation
 894   result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
 895   if (result != NULL) {
 896     return result;
 897   }
 898 
 899   // Start full GC
 900   collect(GCCause::_metadata_GC_clear_soft_refs);
 901 
 902   // Retry allocation
 903   result = loader_data->metaspace_non_null()->allocate(size, mdtype);
 904   if (result != NULL) {
 905     return result;
 906   }
 907 
 908   // Expand and retry allocation
 909   result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
 910   if (result != NULL) {
 911     return result;
 912   }
 913 
 914   // Out of memory
 915   return NULL;
 916 }
 917 
 918 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
 919 private:
 920   ShenandoahHeap* const _heap;
 921   Thread* const _thread;
 922 public:
 923   ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
 924     _heap(heap), _thread(Thread::current()) {}
 925 
 926   void do_object(oop p) {
 927     shenandoah_assert_marked(NULL, p);
 928     if (!p->is_forwarded()) {
 929       _heap->evacuate_object(p, _thread);
 930     }
 931   }
 932 };
 933 
 934 class ShenandoahEvacuationTask : public AbstractGangTask {
 935 private:
 936   ShenandoahHeap* const _sh;
 937   ShenandoahCollectionSet* const _cs;
 938   bool _concurrent;
 939 public:
 940   ShenandoahEvacuationTask(ShenandoahHeap* sh,
 941                            ShenandoahCollectionSet* cs,
 942                            bool concurrent) :
 943     AbstractGangTask("Parallel Evacuation Task"),
 944     _sh(sh),
 945     _cs(cs),
 946     _concurrent(concurrent)
 947   {}
 948 
 949   void work(uint worker_id) {
 950     if (_concurrent) {
 951       ShenandoahConcurrentWorkerSession worker_session(worker_id);
 952       ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
 953       ShenandoahEvacOOMScope oom_evac_scope;
 954       do_work();
 955     } else {
 956       ShenandoahParallelWorkerSession worker_session(worker_id);
 957       ShenandoahEvacOOMScope oom_evac_scope;
 958       do_work();
 959     }
 960   }
 961 
 962 private:
 963   void do_work() {
 964     ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
 965     ShenandoahHeapRegion* r;
 966     while ((r =_cs->claim_next()) != NULL) {
 967       assert(r->has_live(), "all-garbage regions are reclaimed early");
 968       _sh->marked_object_iterate(r, &cl);
 969 
 970       if (ShenandoahPacing) {
 971         _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
 972       }
 973 
 974       if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
 975         break;
 976       }
 977     }
 978   }
 979 };
 980 
 981 void ShenandoahHeap::trash_cset_regions() {
 982   ShenandoahHeapLocker locker(lock());
 983 
 984   ShenandoahCollectionSet* set = collection_set();
 985   ShenandoahHeapRegion* r;
 986   set->clear_current_index();
 987   while ((r = set->next()) != NULL) {
 988     r->make_trash();
 989   }
 990   collection_set()->clear();
 991 }
 992 
 993 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
 994   st->print_cr("Heap Regions:");
 995   st->print_cr("EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HC=humongous continuation, CS=collection set, T=trash, P=pinned");
 996   st->print_cr("BTE=bottom/top/end, U=used, T=TLAB allocs, G=GCLAB allocs, S=shared allocs, L=live data");
 997   st->print_cr("R=root, CP=critical pins, TAMS=top-at-mark-start (previous, next)");
 998   st->print_cr("SN=alloc sequence numbers (first mutator, last mutator, first gc, last gc)");
 999 
1000   for (size_t i = 0; i < num_regions(); i++) {
1001     get_region(i)->print_on(st);
1002   }
1003 }
1004 
1005 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1006   assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1007 
1008   oop humongous_obj = oop(start->bottom());
1009   size_t size = humongous_obj->size();
1010   size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1011   size_t index = start->region_number() + required_regions - 1;
1012 
1013   assert(!start->has_live(), "liveness must be zero");
1014 
1015   for(size_t i = 0; i < required_regions; i++) {
1016     // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1017     // as it expects that every region belongs to a humongous region starting with a humongous start region.
1018     ShenandoahHeapRegion* region = get_region(index --);
1019 
1020     assert(region->is_humongous(), "expect correct humongous start or continuation");
1021     assert(!region->is_cset(), "Humongous region should not be in collection set");
1022 
1023     region->make_trash_immediate();
1024   }
1025 }
1026 
1027 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1028 public:
1029   void do_thread(Thread* thread) {
1030     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1031     assert(gclab != NULL, "GCLAB should be initialized for %s", thread->name());
1032     gclab->retire();
1033   }
1034 };
1035 
1036 void ShenandoahHeap::make_parsable(bool retire_tlabs) {
1037   if (UseTLAB) {
1038     CollectedHeap::ensure_parsability(retire_tlabs);
1039   }
1040   ShenandoahRetireGCLABClosure cl;
1041   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1042     cl.do_thread(t);
1043   }
1044   workers()->threads_do(&cl);
1045 }
1046 
1047 void ShenandoahHeap::resize_tlabs() {
1048   CollectedHeap::resize_all_tlabs();
1049 }
1050 
1051 class ShenandoahEvacuateUpdateRootsTask : public AbstractGangTask {
1052 private:
1053   ShenandoahRootEvacuator* _rp;
1054 
1055 public:
1056   ShenandoahEvacuateUpdateRootsTask(ShenandoahRootEvacuator* rp) :
1057     AbstractGangTask("Shenandoah evacuate and update roots"),
1058     _rp(rp) {}
1059 
1060   void work(uint worker_id) {
1061     ShenandoahParallelWorkerSession worker_session(worker_id);
1062     ShenandoahEvacOOMScope oom_evac_scope;
1063     ShenandoahEvacuateUpdateRootsClosure cl;
1064     MarkingCodeBlobClosure blobsCl(&cl, CodeBlobToOopClosure::FixRelocations);
1065     _rp->roots_do(worker_id, &cl);
1066   }
1067 };
1068 
1069 void ShenandoahHeap::evacuate_and_update_roots() {
1070 #if defined(COMPILER2) || INCLUDE_JVMCI
1071   DerivedPointerTable::clear();
1072 #endif
1073   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only iterate roots while world is stopped");
1074 
1075   {
1076     ShenandoahRootEvacuator rp(workers()->active_workers(), ShenandoahPhaseTimings::init_evac);
1077     ShenandoahEvacuateUpdateRootsTask roots_task(&rp);
1078     workers()->run_task(&roots_task);
1079   }
1080 
1081 #if defined(COMPILER2) || INCLUDE_JVMCI
1082   DerivedPointerTable::update_pointers();
1083 #endif
1084 }
1085 
1086 // Returns size in bytes
1087 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1088   if (ShenandoahElasticTLAB) {
1089     // With Elastic TLABs, return the max allowed size, and let the allocation path
1090     // figure out the safe size for current allocation.
1091     return ShenandoahHeapRegion::max_tlab_size_bytes();
1092   } else {
1093     return MIN2(_free_set->unsafe_peek_free(), ShenandoahHeapRegion::max_tlab_size_bytes());
1094   }
1095 }
1096 
1097 size_t ShenandoahHeap::max_tlab_size() const {
1098   // Returns size in words
1099   return ShenandoahHeapRegion::max_tlab_size_words();
1100 }
1101 
1102 class ShenandoahRetireAndResetGCLABClosure : public ThreadClosure {
1103 public:
1104   void do_thread(Thread* thread) {
1105     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1106     gclab->retire();
1107     if (ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1108       ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1109     }
1110   }
1111 };
1112 
1113 void ShenandoahHeap::retire_and_reset_gclabs() {
1114   ShenandoahRetireAndResetGCLABClosure cl;
1115   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1116     cl.do_thread(t);
1117   }
1118   workers()->threads_do(&cl);
1119 }
1120 
1121 void ShenandoahHeap::collect(GCCause::Cause cause) {
1122   control_thread()->request_gc(cause);
1123 }
1124 
1125 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1126   //assert(false, "Shouldn't need to do full collections");
1127 }
1128 
1129 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1130   Space* sp = heap_region_containing(addr);
1131   if (sp != NULL) {
1132     return sp->block_start(addr);
1133   }
1134   return NULL;
1135 }
1136 
1137 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1138   Space* sp = heap_region_containing(addr);
1139   return sp->block_is_obj(addr);
1140 }
1141 
1142 jlong ShenandoahHeap::millis_since_last_gc() {
1143   double v = heuristics()->time_since_last_gc() * 1000;
1144   assert(0 <= v && v <= max_jlong, "value should fit: %f", v);
1145   return (jlong)v;
1146 }
1147 
1148 void ShenandoahHeap::prepare_for_verify() {
1149   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
1150     make_parsable(false);
1151   }
1152 }
1153 
1154 void ShenandoahHeap::print_gc_threads_on(outputStream* st) const {
1155   workers()->print_worker_threads_on(st);
1156   if (ShenandoahStringDedup::is_enabled()) {
1157     ShenandoahStringDedup::print_worker_threads_on(st);
1158   }
1159 }
1160 
1161 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1162   workers()->threads_do(tcl);
1163   if (_safepoint_workers != NULL) {
1164     _safepoint_workers->threads_do(tcl);
1165   }
1166   if (ShenandoahStringDedup::is_enabled()) {
1167     ShenandoahStringDedup::threads_do(tcl);
1168   }
1169 }
1170 
1171 void ShenandoahHeap::print_tracing_info() const {
1172   LogTarget(Info, gc, stats) lt;
1173   if (lt.is_enabled()) {
1174     ResourceMark rm;
1175     LogStream ls(lt);
1176 
1177     phase_timings()->print_on(&ls);
1178 
1179     ls.cr();
1180     ls.cr();
1181 
1182     shenandoah_policy()->print_gc_stats(&ls);
1183 
1184     ls.cr();
1185     ls.cr();
1186 
1187     if (ShenandoahPacing) {
1188       pacer()->print_on(&ls);
1189     }
1190 
1191     ls.cr();
1192     ls.cr();
1193 
1194     if (ShenandoahAllocationTrace) {
1195       assert(alloc_tracker() != NULL, "Must be");
1196       alloc_tracker()->print_on(&ls);
1197     } else {
1198       ls.print_cr("  Allocation tracing is disabled, use -XX:+ShenandoahAllocationTrace to enable.");
1199     }
1200   }
1201 }
1202 
1203 void ShenandoahHeap::verify(VerifyOption vo) {
1204   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1205     if (ShenandoahVerify) {
1206       verifier()->verify_generic(vo);
1207     } else {
1208       // TODO: Consider allocating verification bitmaps on demand,
1209       // and turn this on unconditionally.
1210     }
1211   }
1212 }
1213 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1214   return _free_set->capacity();
1215 }
1216 
1217 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1218 private:
1219   MarkBitMap* _bitmap;
1220   Stack<oop,mtGC>* _oop_stack;
1221 
1222   template <class T>
1223   void do_oop_work(T* p) {
1224     T o = RawAccess<>::oop_load(p);
1225     if (!CompressedOops::is_null(o)) {
1226       oop obj = CompressedOops::decode_not_null(o);
1227       obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
1228       assert(oopDesc::is_oop(obj), "must be a valid oop");
1229       if (!_bitmap->is_marked((HeapWord*) obj)) {
1230         _bitmap->mark((HeapWord*) obj);
1231         _oop_stack->push(obj);
1232       }
1233     }
1234   }
1235 public:
1236   ObjectIterateScanRootClosure(MarkBitMap* bitmap, Stack<oop,mtGC>* oop_stack) :
1237     _bitmap(bitmap), _oop_stack(oop_stack) {}
1238   void do_oop(oop* p)       { do_oop_work(p); }
1239   void do_oop(narrowOop* p) { do_oop_work(p); }
1240 };
1241 
1242 /*
1243  * This is public API, used in preparation of object_iterate().
1244  * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1245  * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1246  * control, we call SH::make_tlabs_parsable().
1247  */
1248 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1249   // No-op.
1250 }
1251 
1252 /*
1253  * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1254  *
1255  * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1256  * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1257  * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1258  * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1259  * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1260  * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1261  * wiped the bitmap in preparation for next marking).
1262  *
1263  * For all those reasons, we implement object iteration as a single marking traversal, reporting
1264  * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1265  * is allowed to report dead objects, but is not required to do so.
1266  */
1267 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1268   assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1269   if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1270     log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1271     return;
1272   }
1273 
1274   // Reset bitmap
1275   _aux_bit_map.clear();
1276 
1277   Stack<oop,mtGC> oop_stack;
1278 
1279   // First, we process all GC roots. This populates the work stack with initial objects.
1280   ShenandoahAllRootScanner rp(1, ShenandoahPhaseTimings::_num_phases);
1281   ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1282   rp.roots_do(0, &oops);
1283 
1284   // Work through the oop stack to traverse heap.
1285   while (! oop_stack.is_empty()) {
1286     oop obj = oop_stack.pop();
1287     assert(oopDesc::is_oop(obj), "must be a valid oop");
1288     cl->do_object(obj);
1289     obj->oop_iterate(&oops);
1290   }
1291 
1292   assert(oop_stack.is_empty(), "should be empty");
1293 
1294   if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1295     log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1296   }
1297 }
1298 
1299 void ShenandoahHeap::safe_object_iterate(ObjectClosure* cl) {
1300   assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1301   object_iterate(cl);
1302 }
1303 
1304 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1305   for (size_t i = 0; i < num_regions(); i++) {
1306     ShenandoahHeapRegion* current = get_region(i);
1307     blk->heap_region_do(current);
1308   }
1309 }
1310 
1311 class ShenandoahParallelHeapRegionTask : public AbstractGangTask {
1312 private:
1313   ShenandoahHeap* const _heap;
1314   ShenandoahHeapRegionClosure* const _blk;
1315 
1316   DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile size_t));
1317   volatile size_t _index;
1318   DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, 0);
1319 
1320 public:
1321   ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1322           AbstractGangTask("Parallel Region Task"),
1323           _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1324 
1325   void work(uint worker_id) {
1326     size_t stride = ShenandoahParallelRegionStride;
1327 
1328     size_t max = _heap->num_regions();
1329     while (_index < max) {
1330       size_t cur = Atomic::add(stride, &_index) - stride;
1331       size_t start = cur;
1332       size_t end = MIN2(cur + stride, max);
1333       if (start >= max) break;
1334 
1335       for (size_t i = cur; i < end; i++) {
1336         ShenandoahHeapRegion* current = _heap->get_region(i);
1337         _blk->heap_region_do(current);
1338       }
1339     }
1340   }
1341 };
1342 
1343 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1344   assert(blk->is_thread_safe(), "Only thread-safe closures here");
1345   if (num_regions() > ShenandoahParallelRegionStride) {
1346     ShenandoahParallelHeapRegionTask task(blk);
1347     workers()->run_task(&task);
1348   } else {
1349     heap_region_iterate(blk);
1350   }
1351 }
1352 
1353 class ShenandoahClearLivenessClosure : public ShenandoahHeapRegionClosure {
1354 private:
1355   ShenandoahMarkingContext* const _ctx;
1356 public:
1357   ShenandoahClearLivenessClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1358 
1359   void heap_region_do(ShenandoahHeapRegion* r) {
1360     if (r->is_active()) {
1361       r->clear_live_data();
1362       _ctx->capture_top_at_mark_start(r);
1363     } else {
1364       assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->region_number());
1365       assert(_ctx->top_at_mark_start(r) == r->top(),
1366              "Region " SIZE_FORMAT " should already have correct TAMS", r->region_number());
1367     }
1368   }
1369 
1370   bool is_thread_safe() { return true; }
1371 };
1372 
1373 void ShenandoahHeap::op_init_mark() {
1374   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
1375   assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
1376 
1377   assert(marking_context()->is_bitmap_clear(), "need clear marking bitmap");
1378   assert(!marking_context()->is_complete(), "should not be complete");
1379 
1380   if (ShenandoahVerify) {
1381     verifier()->verify_before_concmark();
1382   }
1383 
1384   if (VerifyBeforeGC) {
1385     Universe::verify();
1386   }
1387 
1388   set_concurrent_mark_in_progress(true);
1389   // We need to reset all TLABs because we'd lose marks on all objects allocated in them.
1390   {
1391     ShenandoahGCPhase phase(ShenandoahPhaseTimings::make_parsable);
1392     make_parsable(true);
1393   }
1394 
1395   {
1396     ShenandoahGCPhase phase(ShenandoahPhaseTimings::clear_liveness);
1397     ShenandoahClearLivenessClosure clc;
1398     parallel_heap_region_iterate(&clc);
1399   }
1400 
1401   // Make above changes visible to worker threads
1402   OrderAccess::fence();
1403 
1404   concurrent_mark()->mark_roots(ShenandoahPhaseTimings::scan_roots);
1405 
1406   if (UseTLAB) {
1407     ShenandoahGCPhase phase(ShenandoahPhaseTimings::resize_tlabs);
1408     resize_tlabs();
1409   }
1410 
1411   if (ShenandoahPacing) {
1412     pacer()->setup_for_mark();
1413   }
1414 }
1415 
1416 void ShenandoahHeap::op_mark() {
1417   concurrent_mark()->mark_from_roots();
1418 }
1419 
1420 class ShenandoahCompleteLivenessClosure : public ShenandoahHeapRegionClosure {
1421 private:
1422   ShenandoahMarkingContext* const _ctx;
1423 public:
1424   ShenandoahCompleteLivenessClosure() : _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
1425 
1426   void heap_region_do(ShenandoahHeapRegion* r) {
1427     if (r->is_active()) {
1428       HeapWord *tams = _ctx->top_at_mark_start(r);
1429       HeapWord *top = r->top();
1430       if (top > tams) {
1431         r->increase_live_data_alloc_words(pointer_delta(top, tams));
1432       }
1433     } else {
1434       assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->region_number());
1435       assert(_ctx->top_at_mark_start(r) == r->top(),
1436              "Region " SIZE_FORMAT " should have correct TAMS", r->region_number());
1437     }
1438   }
1439 
1440   bool is_thread_safe() { return true; }
1441 };
1442 
1443 void ShenandoahHeap::op_final_mark() {
1444   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
1445 
1446   // It is critical that we
1447   // evacuate roots right after finishing marking, so that we don't
1448   // get unmarked objects in the roots.
1449 
1450   if (!cancelled_gc()) {
1451     concurrent_mark()->finish_mark_from_roots(/* full_gc = */ false);
1452 
1453     if (has_forwarded_objects()) {
1454       // Degen may be caused by failed evacuation of roots
1455       if (is_degenerated_gc_in_progress()) {
1456         concurrent_mark()->update_roots(ShenandoahPhaseTimings::degen_gc_update_roots);
1457       } else {
1458         concurrent_mark()->update_thread_roots(ShenandoahPhaseTimings::update_roots);
1459       }
1460    }
1461 
1462     if (ShenandoahVerify) {
1463       verifier()->verify_roots_no_forwarded();
1464     }
1465 
1466     stop_concurrent_marking();
1467 
1468     {
1469       ShenandoahGCPhase phase(ShenandoahPhaseTimings::complete_liveness);
1470 
1471       // All allocations past TAMS are implicitly live, adjust the region data.
1472       // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1473       ShenandoahCompleteLivenessClosure cl;
1474       parallel_heap_region_iterate(&cl);
1475     }
1476 
1477     {
1478       ShenandoahGCPhase prepare_evac(ShenandoahPhaseTimings::prepare_evac);
1479 
1480       make_parsable(true);
1481 
1482       trash_cset_regions();
1483 
1484       {
1485         ShenandoahHeapLocker locker(lock());
1486         _collection_set->clear();
1487         _free_set->clear();
1488 
1489         heuristics()->choose_collection_set(_collection_set);
1490 
1491         _free_set->rebuild();
1492       }
1493     }
1494 
1495     // If collection set has candidates, start evacuation.
1496     // Otherwise, bypass the rest of the cycle.
1497     if (!collection_set()->is_empty()) {
1498       ShenandoahGCPhase init_evac(ShenandoahPhaseTimings::init_evac);
1499 
1500       if (ShenandoahVerify) {
1501         verifier()->verify_before_evacuation();
1502       }
1503 
1504       set_evacuation_in_progress(true);
1505       // From here on, we need to update references.
1506       set_has_forwarded_objects(true);
1507 
1508       evacuate_and_update_roots();
1509 
1510       if (ShenandoahPacing) {
1511         pacer()->setup_for_evac();
1512       }
1513 
1514       if (ShenandoahVerify) {
1515         verifier()->verify_roots_no_forwarded();
1516         verifier()->verify_during_evacuation();
1517       }
1518     } else {
1519       if (ShenandoahVerify) {
1520         verifier()->verify_after_concmark();
1521       }
1522 
1523       if (VerifyAfterGC) {
1524         Universe::verify();
1525       }
1526     }
1527 
1528   } else {
1529     concurrent_mark()->cancel();
1530     stop_concurrent_marking();
1531 
1532     if (process_references()) {
1533       // Abandon reference processing right away: pre-cleaning must have failed.
1534       ReferenceProcessor *rp = ref_processor();
1535       rp->disable_discovery();
1536       rp->abandon_partial_discovery();
1537       rp->verify_no_references_recorded();
1538     }
1539   }
1540 }
1541 
1542 void ShenandoahHeap::op_final_evac() {
1543   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
1544 
1545   set_evacuation_in_progress(false);
1546 
1547   retire_and_reset_gclabs();
1548 
1549   if (ShenandoahVerify) {
1550     verifier()->verify_after_evacuation();
1551   }
1552 
1553   if (VerifyAfterGC) {
1554     Universe::verify();
1555   }
1556 }
1557 
1558 void ShenandoahHeap::op_conc_evac() {
1559   ShenandoahEvacuationTask task(this, _collection_set, true);
1560   workers()->run_task(&task);
1561 }
1562 
1563 void ShenandoahHeap::op_stw_evac() {
1564   ShenandoahEvacuationTask task(this, _collection_set, false);
1565   workers()->run_task(&task);
1566 }
1567 
1568 void ShenandoahHeap::op_updaterefs() {
1569   update_heap_references(true);
1570 }
1571 
1572 void ShenandoahHeap::op_cleanup() {
1573   free_set()->recycle_trash();
1574 }
1575 
1576 void ShenandoahHeap::op_reset() {
1577   reset_mark_bitmap();
1578 }
1579 
1580 void ShenandoahHeap::op_preclean() {
1581   concurrent_mark()->preclean_weak_refs();
1582 }
1583 
1584 void ShenandoahHeap::op_init_traversal() {
1585   traversal_gc()->init_traversal_collection();
1586 }
1587 
1588 void ShenandoahHeap::op_traversal() {
1589   traversal_gc()->concurrent_traversal_collection();
1590 }
1591 
1592 void ShenandoahHeap::op_final_traversal() {
1593   traversal_gc()->final_traversal_collection();
1594 }
1595 
1596 void ShenandoahHeap::op_full(GCCause::Cause cause) {
1597   ShenandoahMetricsSnapshot metrics;
1598   metrics.snap_before();
1599 
1600   full_gc()->do_it(cause);
1601   if (UseTLAB) {
1602     ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_resize_tlabs);
1603     resize_all_tlabs();
1604   }
1605 
1606   metrics.snap_after();
1607   metrics.print();
1608 
1609   if (metrics.is_good_progress("Full GC")) {
1610     _progress_last_gc.set();
1611   } else {
1612     // Nothing to do. Tell the allocation path that we have failed to make
1613     // progress, and it can finally fail.
1614     _progress_last_gc.unset();
1615   }
1616 }
1617 
1618 void ShenandoahHeap::op_degenerated(ShenandoahDegenPoint point) {
1619   // Degenerated GC is STW, but it can also fail. Current mechanics communicates
1620   // GC failure via cancelled_concgc() flag. So, if we detect the failure after
1621   // some phase, we have to upgrade the Degenerate GC to Full GC.
1622 
1623   clear_cancelled_gc();
1624 
1625   ShenandoahMetricsSnapshot metrics;
1626   metrics.snap_before();
1627 
1628   switch (point) {
1629     case _degenerated_traversal:
1630       {
1631         // Drop the collection set. Note: this leaves some already forwarded objects
1632         // behind, which may be problematic, see comments for ShenandoahEvacAssist
1633         // workarounds in ShenandoahTraversalHeuristics.
1634 
1635         ShenandoahHeapLocker locker(lock());
1636         collection_set()->clear_current_index();
1637         for (size_t i = 0; i < collection_set()->count(); i++) {
1638           ShenandoahHeapRegion* r = collection_set()->next();
1639           r->make_regular_bypass();
1640         }
1641         collection_set()->clear();
1642       }
1643       op_final_traversal();
1644       op_cleanup();
1645       return;
1646 
1647     // The cases below form the Duff's-like device: it describes the actual GC cycle,
1648     // but enters it at different points, depending on which concurrent phase had
1649     // degenerated.
1650 
1651     case _degenerated_outside_cycle:
1652       // We have degenerated from outside the cycle, which means something is bad with
1653       // the heap, most probably heavy humongous fragmentation, or we are very low on free
1654       // space. It makes little sense to wait for Full GC to reclaim as much as it can, when
1655       // we can do the most aggressive degen cycle, which includes processing references and
1656       // class unloading, unless those features are explicitly disabled.
1657       //
1658       // Note that we can only do this for "outside-cycle" degens, otherwise we would risk
1659       // changing the cycle parameters mid-cycle during concurrent -> degenerated handover.
1660       set_process_references(heuristics()->can_process_references());
1661       set_unload_classes(heuristics()->can_unload_classes());
1662 
1663       if (heuristics()->can_do_traversal_gc()) {
1664         // Not possible to degenerate from here, upgrade to Full GC right away.
1665         cancel_gc(GCCause::_shenandoah_upgrade_to_full_gc);
1666         op_degenerated_fail();
1667         return;
1668       }
1669 
1670       op_reset();
1671 
1672       op_init_mark();
1673       if (cancelled_gc()) {
1674         op_degenerated_fail();
1675         return;
1676       }
1677 
1678     case _degenerated_mark:
1679       op_final_mark();
1680       if (cancelled_gc()) {
1681         op_degenerated_fail();
1682         return;
1683       }
1684 
1685       op_cleanup();
1686 
1687     case _degenerated_evac:
1688       // If heuristics thinks we should do the cycle, this flag would be set,
1689       // and we can do evacuation. Otherwise, it would be the shortcut cycle.
1690       if (is_evacuation_in_progress()) {
1691 
1692         // Degeneration under oom-evac protocol might have left some objects in
1693         // collection set un-evacuated. Restart evacuation from the beginning to
1694         // capture all objects. For all the objects that are already evacuated,
1695         // it would be a simple check, which is supposed to be fast. This is also
1696         // safe to do even without degeneration, as CSet iterator is at beginning
1697         // in preparation for evacuation anyway.
1698         collection_set()->clear_current_index();
1699 
1700         op_stw_evac();
1701         if (cancelled_gc()) {
1702           op_degenerated_fail();
1703           return;
1704         }
1705       }
1706 
1707       // If heuristics thinks we should do the cycle, this flag would be set,
1708       // and we need to do update-refs. Otherwise, it would be the shortcut cycle.
1709       if (has_forwarded_objects()) {
1710         op_init_updaterefs();
1711         if (cancelled_gc()) {
1712           op_degenerated_fail();
1713           return;
1714         }
1715       }
1716 
1717     case _degenerated_updaterefs:
1718       if (has_forwarded_objects()) {
1719         op_final_updaterefs();
1720         if (cancelled_gc()) {
1721           op_degenerated_fail();
1722           return;
1723         }
1724       }
1725 
1726       op_cleanup();
1727       break;
1728 
1729     default:
1730       ShouldNotReachHere();
1731   }
1732 
1733   if (ShenandoahVerify) {
1734     verifier()->verify_after_degenerated();
1735   }
1736 
1737   if (VerifyAfterGC) {
1738     Universe::verify();
1739   }
1740 
1741   metrics.snap_after();
1742   metrics.print();
1743 
1744   // Check for futility and fail. There is no reason to do several back-to-back Degenerated cycles,
1745   // because that probably means the heap is overloaded and/or fragmented.
1746   if (!metrics.is_good_progress("Degenerated GC")) {
1747     _progress_last_gc.unset();
1748     cancel_gc(GCCause::_shenandoah_upgrade_to_full_gc);
1749     op_degenerated_futile();
1750   } else {
1751     _progress_last_gc.set();
1752   }
1753 }
1754 
1755 void ShenandoahHeap::op_degenerated_fail() {
1756   log_info(gc)("Cannot finish degeneration, upgrading to Full GC");
1757   shenandoah_policy()->record_degenerated_upgrade_to_full();
1758   op_full(GCCause::_shenandoah_upgrade_to_full_gc);
1759 }
1760 
1761 void ShenandoahHeap::op_degenerated_futile() {
1762   shenandoah_policy()->record_degenerated_upgrade_to_full();
1763   op_full(GCCause::_shenandoah_upgrade_to_full_gc);
1764 }
1765 
1766 void ShenandoahHeap::stop_concurrent_marking() {
1767   assert(is_concurrent_mark_in_progress(), "How else could we get here?");
1768   set_concurrent_mark_in_progress(false);
1769   if (!cancelled_gc()) {
1770     // If we needed to update refs, and concurrent marking has been cancelled,
1771     // we need to finish updating references.
1772     set_has_forwarded_objects(false);
1773     mark_complete_marking_context();
1774   }
1775 }
1776 
1777 void ShenandoahHeap::force_satb_flush_all_threads() {
1778   if (!is_concurrent_mark_in_progress() && !is_concurrent_traversal_in_progress()) {
1779     // No need to flush SATBs
1780     return;
1781   }
1782 
1783   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1784     ShenandoahThreadLocalData::set_force_satb_flush(t, true);
1785   }
1786   // The threads are not "acquiring" their thread-local data, but it does not
1787   // hurt to "release" the updates here anyway.
1788   OrderAccess::fence();
1789 }
1790 
1791 void ShenandoahHeap::set_gc_state_all_threads(char state) {
1792   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1793     ShenandoahThreadLocalData::set_gc_state(t, state);
1794   }
1795 }
1796 
1797 void ShenandoahHeap::set_gc_state_mask(uint mask, bool value) {
1798   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should really be Shenandoah safepoint");
1799   _gc_state.set_cond(mask, value);
1800   set_gc_state_all_threads(_gc_state.raw_value());
1801 }
1802 
1803 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
1804   if (has_forwarded_objects()) {
1805     set_gc_state_mask(MARKING | UPDATEREFS, in_progress);
1806   } else {
1807     set_gc_state_mask(MARKING, in_progress);
1808   }
1809   ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1810 }
1811 
1812 void ShenandoahHeap::set_concurrent_traversal_in_progress(bool in_progress) {
1813    set_gc_state_mask(TRAVERSAL | HAS_FORWARDED | UPDATEREFS, in_progress);
1814    ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1815 }
1816 
1817 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
1818   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
1819   set_gc_state_mask(EVACUATION, in_progress);
1820 }
1821 
1822 void ShenandoahHeap::ref_processing_init() {
1823   assert(_max_workers > 0, "Sanity");
1824 
1825   _ref_processor =
1826     new ReferenceProcessor(&_subject_to_discovery,  // is_subject_to_discovery
1827                            ParallelRefProcEnabled,  // MT processing
1828                            _max_workers,            // Degree of MT processing
1829                            true,                    // MT discovery
1830                            _max_workers,            // Degree of MT discovery
1831                            false,                   // Reference discovery is not atomic
1832                            NULL,                    // No closure, should be installed before use
1833                            true);                   // Scale worker threads
1834 
1835   shenandoah_assert_rp_isalive_not_installed();
1836 }
1837 
1838 GCTracer* ShenandoahHeap::tracer() {
1839   return shenandoah_policy()->tracer();
1840 }
1841 
1842 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
1843   return _free_set->used();
1844 }
1845 
1846 bool ShenandoahHeap::try_cancel_gc() {
1847   while (true) {
1848     jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
1849     if (prev == CANCELLABLE) return true;
1850     else if (prev == CANCELLED) return false;
1851     assert(ShenandoahSuspendibleWorkers, "should not get here when not using suspendible workers");
1852     assert(prev == NOT_CANCELLED, "must be NOT_CANCELLED");
1853     {
1854       // We need to provide a safepoint here, otherwise we might
1855       // spin forever if a SP is pending.
1856       ThreadBlockInVM sp(JavaThread::current());
1857       SpinPause();
1858     }
1859   }
1860 }
1861 
1862 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
1863   if (try_cancel_gc()) {
1864     FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
1865     log_info(gc)("%s", msg.buffer());
1866     Events::log(Thread::current(), "%s", msg.buffer());
1867   }
1868 }
1869 
1870 uint ShenandoahHeap::max_workers() {
1871   return _max_workers;
1872 }
1873 
1874 void ShenandoahHeap::stop() {
1875   // The shutdown sequence should be able to terminate when GC is running.
1876 
1877   // Step 0. Notify policy to disable event recording.
1878   _shenandoah_policy->record_shutdown();
1879 
1880   // Step 1. Notify control thread that we are in shutdown.
1881   // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
1882   // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
1883   control_thread()->prepare_for_graceful_shutdown();
1884 
1885   // Step 2. Notify GC workers that we are cancelling GC.
1886   cancel_gc(GCCause::_shenandoah_stop_vm);
1887 
1888   // Step 3. Wait until GC worker exits normally.
1889   control_thread()->stop();
1890 
1891   // Step 4. Stop String Dedup thread if it is active
1892   if (ShenandoahStringDedup::is_enabled()) {
1893     ShenandoahStringDedup::stop();
1894   }
1895 }
1896 
1897 void ShenandoahHeap::unload_classes_and_cleanup_tables(bool full_gc) {
1898   assert(heuristics()->can_unload_classes(), "Class unloading should be enabled");
1899 
1900   ShenandoahGCPhase root_phase(full_gc ?
1901                                ShenandoahPhaseTimings::full_gc_purge :
1902                                ShenandoahPhaseTimings::purge);
1903 
1904   ShenandoahIsAliveSelector alive;
1905   BoolObjectClosure* is_alive = alive.is_alive_closure();
1906 
1907   bool purged_class;
1908 
1909   // Unload classes and purge SystemDictionary.
1910   {
1911     ShenandoahGCPhase phase(full_gc ?
1912                             ShenandoahPhaseTimings::full_gc_purge_class_unload :
1913                             ShenandoahPhaseTimings::purge_class_unload);
1914     purged_class = SystemDictionary::do_unloading(gc_timer());
1915   }
1916 
1917   {
1918     ShenandoahGCPhase phase(full_gc ?
1919                             ShenandoahPhaseTimings::full_gc_purge_par :
1920                             ShenandoahPhaseTimings::purge_par);
1921     uint active = _workers->active_workers();
1922     ParallelCleaningTask unlink_task(is_alive, active, purged_class, true);
1923     _workers->run_task(&unlink_task);
1924   }
1925 
1926   {
1927     ShenandoahGCPhase phase(full_gc ?
1928                       ShenandoahPhaseTimings::full_gc_purge_cldg :
1929                       ShenandoahPhaseTimings::purge_cldg);
1930     ClassLoaderDataGraph::purge();
1931   }
1932 }
1933 
1934 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
1935   set_gc_state_mask(HAS_FORWARDED, cond);
1936 }
1937 
1938 void ShenandoahHeap::set_process_references(bool pr) {
1939   _process_references.set_cond(pr);
1940 }
1941 
1942 void ShenandoahHeap::set_unload_classes(bool uc) {
1943   _unload_classes.set_cond(uc);
1944 }
1945 
1946 bool ShenandoahHeap::process_references() const {
1947   return _process_references.is_set();
1948 }
1949 
1950 bool ShenandoahHeap::unload_classes() const {
1951   return _unload_classes.is_set();
1952 }
1953 
1954 address ShenandoahHeap::in_cset_fast_test_addr() {
1955   ShenandoahHeap* heap = ShenandoahHeap::heap();
1956   assert(heap->collection_set() != NULL, "Sanity");
1957   return (address) heap->collection_set()->biased_map_address();
1958 }
1959 
1960 address ShenandoahHeap::cancelled_gc_addr() {
1961   return (address) ShenandoahHeap::heap()->_cancelled_gc.addr_of();
1962 }
1963 
1964 address ShenandoahHeap::gc_state_addr() {
1965   return (address) ShenandoahHeap::heap()->_gc_state.addr_of();
1966 }
1967 
1968 size_t ShenandoahHeap::bytes_allocated_since_gc_start() {
1969   return OrderAccess::load_acquire(&_bytes_allocated_since_gc_start);
1970 }
1971 
1972 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
1973   OrderAccess::release_store_fence(&_bytes_allocated_since_gc_start, (size_t)0);
1974 }
1975 
1976 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
1977   _degenerated_gc_in_progress.set_cond(in_progress);
1978 }
1979 
1980 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
1981   _full_gc_in_progress.set_cond(in_progress);
1982 }
1983 
1984 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
1985   assert (is_full_gc_in_progress(), "should be");
1986   _full_gc_move_in_progress.set_cond(in_progress);
1987 }
1988 
1989 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
1990   set_gc_state_mask(UPDATEREFS, in_progress);
1991 }
1992 
1993 void ShenandoahHeap::register_nmethod(nmethod* nm) {
1994   ShenandoahCodeRoots::add_nmethod(nm);
1995 }
1996 
1997 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
1998   ShenandoahCodeRoots::remove_nmethod(nm);
1999 }
2000 
2001 oop ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2002   ShenandoahHeapLocker locker(lock());
2003   heap_region_containing(o)->make_pinned();
2004   return o;
2005 }
2006 
2007 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2008   ShenandoahHeapLocker locker(lock());
2009   heap_region_containing(o)->make_unpinned();
2010 }
2011 
2012 GCTimer* ShenandoahHeap::gc_timer() const {
2013   return _gc_timer;
2014 }
2015 
2016 #ifdef ASSERT
2017 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2018   assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2019 
2020   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2021     if (UseDynamicNumberOfGCThreads ||
2022         (FLAG_IS_DEFAULT(ParallelGCThreads) && ForceDynamicNumberOfGCThreads)) {
2023       assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
2024     } else {
2025       // Use ParallelGCThreads inside safepoints
2026       assert(nworkers == ParallelGCThreads, "Use ParalleGCThreads within safepoints");
2027     }
2028   } else {
2029     if (UseDynamicNumberOfGCThreads ||
2030         (FLAG_IS_DEFAULT(ConcGCThreads) && ForceDynamicNumberOfGCThreads)) {
2031       assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
2032     } else {
2033       // Use ConcGCThreads outside safepoints
2034       assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
2035     }
2036   }
2037 }
2038 #endif
2039 
2040 ShenandoahVerifier* ShenandoahHeap::verifier() {
2041   guarantee(ShenandoahVerify, "Should be enabled");
2042   assert (_verifier != NULL, "sanity");
2043   return _verifier;
2044 }
2045 
2046 template<class T>
2047 class ShenandoahUpdateHeapRefsTask : public AbstractGangTask {
2048 private:
2049   T cl;
2050   ShenandoahHeap* _heap;
2051   ShenandoahRegionIterator* _regions;
2052   bool _concurrent;
2053 public:
2054   ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions, bool concurrent) :
2055     AbstractGangTask("Concurrent Update References Task"),
2056     cl(T()),
2057     _heap(ShenandoahHeap::heap()),
2058     _regions(regions),
2059     _concurrent(concurrent) {
2060   }
2061 
2062   void work(uint worker_id) {
2063     if (_concurrent) {
2064       ShenandoahConcurrentWorkerSession worker_session(worker_id);
2065       ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
2066       do_work();
2067     } else {
2068       ShenandoahParallelWorkerSession worker_session(worker_id);
2069       do_work();
2070     }
2071   }
2072 
2073 private:
2074   void do_work() {
2075     ShenandoahHeapRegion* r = _regions->next();
2076     ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2077     while (r != NULL) {
2078       HeapWord* top_at_start_ur = r->concurrent_iteration_safe_limit();
2079       assert (top_at_start_ur >= r->bottom(), "sanity");
2080       if (r->is_active() && !r->is_cset()) {
2081         _heap->marked_object_oop_iterate(r, &cl, top_at_start_ur);
2082       }
2083       if (ShenandoahPacing) {
2084         _heap->pacer()->report_updaterefs(pointer_delta(top_at_start_ur, r->bottom()));
2085       }
2086       if (_heap->check_cancelled_gc_and_yield(_concurrent)) {
2087         return;
2088       }
2089       r = _regions->next();
2090     }
2091   }
2092 };
2093 
2094 void ShenandoahHeap::update_heap_references(bool concurrent) {
2095   ShenandoahUpdateHeapRefsTask<ShenandoahUpdateHeapRefsClosure> task(&_update_refs_iterator, concurrent);
2096   workers()->run_task(&task);
2097 }
2098 
2099 void ShenandoahHeap::op_init_updaterefs() {
2100   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2101 
2102   set_evacuation_in_progress(false);
2103 
2104   retire_and_reset_gclabs();
2105 
2106   if (ShenandoahVerify) {
2107     if (!is_degenerated_gc_in_progress()) {
2108       verifier()->verify_roots_no_forwarded_except(ShenandoahRootVerifier::ThreadRoots);
2109     }
2110     verifier()->verify_before_updaterefs();
2111   }
2112 
2113   set_update_refs_in_progress(true);
2114   make_parsable(true);
2115   for (uint i = 0; i < num_regions(); i++) {
2116     ShenandoahHeapRegion* r = get_region(i);
2117     r->set_concurrent_iteration_safe_limit(r->top());
2118   }
2119 
2120   // Reset iterator.
2121   _update_refs_iterator.reset();
2122 
2123   if (ShenandoahPacing) {
2124     pacer()->setup_for_updaterefs();
2125   }
2126 }
2127 
2128 void ShenandoahHeap::op_final_updaterefs() {
2129   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2130 
2131   // Check if there is left-over work, and finish it
2132   if (_update_refs_iterator.has_next()) {
2133     ShenandoahGCPhase final_work(ShenandoahPhaseTimings::final_update_refs_finish_work);
2134 
2135     // Finish updating references where we left off.
2136     clear_cancelled_gc();
2137     update_heap_references(false);
2138   }
2139 
2140   // Clear cancelled GC, if set. On cancellation path, the block before would handle
2141   // everything. On degenerated paths, cancelled gc would not be set anyway.
2142   if (cancelled_gc()) {
2143     clear_cancelled_gc();
2144   }
2145   assert(!cancelled_gc(), "Should have been done right before");
2146 
2147   if (ShenandoahVerify && !is_degenerated_gc_in_progress()) {
2148     verifier()->verify_roots_no_forwarded_except(ShenandoahRootVerifier::ThreadRoots);
2149   }
2150 
2151   if (is_degenerated_gc_in_progress()) {
2152     concurrent_mark()->update_roots(ShenandoahPhaseTimings::degen_gc_update_roots);
2153   } else {
2154     concurrent_mark()->update_thread_roots(ShenandoahPhaseTimings::final_update_refs_roots);
2155   }
2156 
2157   ShenandoahGCPhase final_update_refs(ShenandoahPhaseTimings::final_update_refs_recycle);
2158 
2159   trash_cset_regions();
2160   set_has_forwarded_objects(false);
2161   set_update_refs_in_progress(false);
2162 
2163   if (ShenandoahVerify) {
2164     verifier()->verify_roots_no_forwarded();
2165     verifier()->verify_after_updaterefs();
2166   }
2167 
2168   if (VerifyAfterGC) {
2169     Universe::verify();
2170   }
2171 
2172   {
2173     ShenandoahHeapLocker locker(lock());
2174     _free_set->rebuild();
2175   }
2176 }
2177 
2178 #ifdef ASSERT
2179 void ShenandoahHeap::assert_heaplock_owned_by_current_thread() {
2180   _lock.assert_owned_by_current_thread();
2181 }
2182 
2183 void ShenandoahHeap::assert_heaplock_not_owned_by_current_thread() {
2184   _lock.assert_not_owned_by_current_thread();
2185 }
2186 
2187 void ShenandoahHeap::assert_heaplock_or_safepoint() {
2188   _lock.assert_owned_by_current_thread_or_safepoint();
2189 }
2190 #endif
2191 
2192 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2193   print_on(st);
2194   print_heap_regions_on(st);
2195 }
2196 
2197 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2198   size_t slice = r->region_number() / _bitmap_regions_per_slice;
2199 
2200   size_t regions_from = _bitmap_regions_per_slice * slice;
2201   size_t regions_to   = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2202   for (size_t g = regions_from; g < regions_to; g++) {
2203     assert (g / _bitmap_regions_per_slice == slice, "same slice");
2204     if (skip_self && g == r->region_number()) continue;
2205     if (get_region(g)->is_committed()) {
2206       return true;
2207     }
2208   }
2209   return false;
2210 }
2211 
2212 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2213   assert_heaplock_owned_by_current_thread();
2214 
2215   // Bitmaps in special regions do not need commits
2216   if (_bitmap_region_special) {
2217     return true;
2218   }
2219 
2220   if (is_bitmap_slice_committed(r, true)) {
2221     // Some other region from the group is already committed, meaning the bitmap
2222     // slice is already committed, we exit right away.
2223     return true;
2224   }
2225 
2226   // Commit the bitmap slice:
2227   size_t slice = r->region_number() / _bitmap_regions_per_slice;
2228   size_t off = _bitmap_bytes_per_slice * slice;
2229   size_t len = _bitmap_bytes_per_slice;
2230   if (!os::commit_memory((char*)_bitmap_region.start() + off, len, false)) {
2231     return false;
2232   }
2233   return true;
2234 }
2235 
2236 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2237   assert_heaplock_owned_by_current_thread();
2238 
2239   // Bitmaps in special regions do not need uncommits
2240   if (_bitmap_region_special) {
2241     return true;
2242   }
2243 
2244   if (is_bitmap_slice_committed(r, true)) {
2245     // Some other region from the group is still committed, meaning the bitmap
2246     // slice is should stay committed, exit right away.
2247     return true;
2248   }
2249 
2250   // Uncommit the bitmap slice:
2251   size_t slice = r->region_number() / _bitmap_regions_per_slice;
2252   size_t off = _bitmap_bytes_per_slice * slice;
2253   size_t len = _bitmap_bytes_per_slice;
2254   if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2255     return false;
2256   }
2257   return true;
2258 }
2259 
2260 void ShenandoahHeap::safepoint_synchronize_begin() {
2261   if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2262     SuspendibleThreadSet::synchronize();
2263   }
2264 }
2265 
2266 void ShenandoahHeap::safepoint_synchronize_end() {
2267   if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2268     SuspendibleThreadSet::desynchronize();
2269   }
2270 }
2271 
2272 void ShenandoahHeap::vmop_entry_init_mark() {
2273   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2274   ShenandoahGCPhase total(ShenandoahPhaseTimings::total_pause_gross);
2275   ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_mark_gross);
2276 
2277   try_inject_alloc_failure();
2278   VM_ShenandoahInitMark op;
2279   VMThread::execute(&op); // jump to entry_init_mark() under safepoint
2280 }
2281 
2282 void ShenandoahHeap::vmop_entry_final_mark() {
2283   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2284   ShenandoahGCPhase total(ShenandoahPhaseTimings::total_pause_gross);
2285   ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_mark_gross);
2286 
2287   try_inject_alloc_failure();
2288   VM_ShenandoahFinalMarkStartEvac op;
2289   VMThread::execute(&op); // jump to entry_final_mark under safepoint
2290 }
2291 
2292 void ShenandoahHeap::vmop_entry_final_evac() {
2293   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2294   ShenandoahGCPhase total(ShenandoahPhaseTimings::total_pause_gross);
2295   ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_evac_gross);
2296 
2297   VM_ShenandoahFinalEvac op;
2298   VMThread::execute(&op); // jump to entry_final_evac under safepoint
2299 }
2300 
2301 void ShenandoahHeap::vmop_entry_init_updaterefs() {
2302   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2303   ShenandoahGCPhase total(ShenandoahPhaseTimings::total_pause_gross);
2304   ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_refs_gross);
2305 
2306   try_inject_alloc_failure();
2307   VM_ShenandoahInitUpdateRefs op;
2308   VMThread::execute(&op);
2309 }
2310 
2311 void ShenandoahHeap::vmop_entry_final_updaterefs() {
2312   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2313   ShenandoahGCPhase total(ShenandoahPhaseTimings::total_pause_gross);
2314   ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_refs_gross);
2315 
2316   try_inject_alloc_failure();
2317   VM_ShenandoahFinalUpdateRefs op;
2318   VMThread::execute(&op);
2319 }
2320 
2321 void ShenandoahHeap::vmop_entry_init_traversal() {
2322   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2323   ShenandoahGCPhase total(ShenandoahPhaseTimings::total_pause_gross);
2324   ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_traversal_gc_gross);
2325 
2326   try_inject_alloc_failure();
2327   VM_ShenandoahInitTraversalGC op;
2328   VMThread::execute(&op);
2329 }
2330 
2331 void ShenandoahHeap::vmop_entry_final_traversal() {
2332   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2333   ShenandoahGCPhase total(ShenandoahPhaseTimings::total_pause_gross);
2334   ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_traversal_gc_gross);
2335 
2336   try_inject_alloc_failure();
2337   VM_ShenandoahFinalTraversalGC op;
2338   VMThread::execute(&op);
2339 }
2340 
2341 void ShenandoahHeap::vmop_entry_full(GCCause::Cause cause) {
2342   TraceCollectorStats tcs(monitoring_support()->full_stw_collection_counters());
2343   ShenandoahGCPhase total(ShenandoahPhaseTimings::total_pause_gross);
2344   ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_gross);
2345 
2346   try_inject_alloc_failure();
2347   VM_ShenandoahFullGC op(cause);
2348   VMThread::execute(&op);
2349 }
2350 
2351 void ShenandoahHeap::vmop_degenerated(ShenandoahDegenPoint point) {
2352   TraceCollectorStats tcs(monitoring_support()->full_stw_collection_counters());
2353   ShenandoahGCPhase total(ShenandoahPhaseTimings::total_pause_gross);
2354   ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_gross);
2355 
2356   VM_ShenandoahDegeneratedGC degenerated_gc((int)point);
2357   VMThread::execute(&degenerated_gc);
2358 }
2359 
2360 void ShenandoahHeap::entry_init_mark() {
2361   ShenandoahGCPhase total_phase(ShenandoahPhaseTimings::total_pause);
2362   ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_mark);
2363   const char* msg = init_mark_event_message();
2364   GCTraceTime(Info, gc) time(msg, gc_timer());
2365   EventMark em("%s", msg);
2366 
2367   ShenandoahWorkerScope scope(workers(),
2368                               ShenandoahWorkerPolicy::calc_workers_for_init_marking(),
2369                               "init marking");
2370 
2371   op_init_mark();
2372 }
2373 
2374 void ShenandoahHeap::entry_final_mark() {
2375   ShenandoahGCPhase total_phase(ShenandoahPhaseTimings::total_pause);
2376   ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_mark);
2377   const char* msg = final_mark_event_message();
2378   GCTraceTime(Info, gc) time(msg, gc_timer());
2379   EventMark em("%s", msg);
2380 
2381   ShenandoahWorkerScope scope(workers(),
2382                               ShenandoahWorkerPolicy::calc_workers_for_final_marking(),
2383                               "final marking");
2384 
2385   op_final_mark();
2386 }
2387 
2388 void ShenandoahHeap::entry_final_evac() {
2389   ShenandoahGCPhase total_phase(ShenandoahPhaseTimings::total_pause);
2390   ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_evac);
2391   static const char* msg = "Pause Final Evac";
2392   GCTraceTime(Info, gc) time(msg, gc_timer());
2393   EventMark em("%s", msg);
2394 
2395   op_final_evac();
2396 }
2397 
2398 void ShenandoahHeap::entry_init_updaterefs() {
2399   ShenandoahGCPhase total_phase(ShenandoahPhaseTimings::total_pause);
2400   ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_refs);
2401 
2402   static const char* msg = "Pause Init Update Refs";
2403   GCTraceTime(Info, gc) time(msg, gc_timer());
2404   EventMark em("%s", msg);
2405 
2406   // No workers used in this phase, no setup required
2407 
2408   op_init_updaterefs();
2409 }
2410 
2411 void ShenandoahHeap::entry_final_updaterefs() {
2412   ShenandoahGCPhase total_phase(ShenandoahPhaseTimings::total_pause);
2413   ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_refs);
2414 
2415   static const char* msg = "Pause Final Update Refs";
2416   GCTraceTime(Info, gc) time(msg, gc_timer());
2417   EventMark em("%s", msg);
2418 
2419   ShenandoahWorkerScope scope(workers(),
2420                               ShenandoahWorkerPolicy::calc_workers_for_final_update_ref(),
2421                               "final reference update");
2422 
2423   op_final_updaterefs();
2424 }
2425 
2426 void ShenandoahHeap::entry_init_traversal() {
2427   ShenandoahGCPhase total_phase(ShenandoahPhaseTimings::total_pause);
2428   ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_traversal_gc);
2429 
2430   static const char* msg = "Pause Init Traversal";
2431   GCTraceTime(Info, gc) time(msg, gc_timer());
2432   EventMark em("%s", msg);
2433 
2434   ShenandoahWorkerScope scope(workers(),
2435                               ShenandoahWorkerPolicy::calc_workers_for_stw_traversal(),
2436                               "init traversal");
2437 
2438   op_init_traversal();
2439 }
2440 
2441 void ShenandoahHeap::entry_final_traversal() {
2442   ShenandoahGCPhase total_phase(ShenandoahPhaseTimings::total_pause);
2443   ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_traversal_gc);
2444 
2445   static const char* msg = "Pause Final Traversal";
2446   GCTraceTime(Info, gc) time(msg, gc_timer());
2447   EventMark em("%s", msg);
2448 
2449   ShenandoahWorkerScope scope(workers(),
2450                               ShenandoahWorkerPolicy::calc_workers_for_stw_traversal(),
2451                               "final traversal");
2452 
2453   op_final_traversal();
2454 }
2455 
2456 void ShenandoahHeap::entry_full(GCCause::Cause cause) {
2457   ShenandoahGCPhase total_phase(ShenandoahPhaseTimings::total_pause);
2458   ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc);
2459 
2460   static const char* msg = "Pause Full";
2461   GCTraceTime(Info, gc) time(msg, gc_timer(), cause, true);
2462   EventMark em("%s", msg);
2463 
2464   ShenandoahWorkerScope scope(workers(),
2465                               ShenandoahWorkerPolicy::calc_workers_for_fullgc(),
2466                               "full gc");
2467 
2468   op_full(cause);
2469 }
2470 
2471 void ShenandoahHeap::entry_degenerated(int point) {
2472   ShenandoahGCPhase total_phase(ShenandoahPhaseTimings::total_pause);
2473   ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc);
2474 
2475   ShenandoahDegenPoint dpoint = (ShenandoahDegenPoint)point;
2476   const char* msg = degen_event_message(dpoint);
2477   GCTraceTime(Info, gc) time(msg, NULL, GCCause::_no_gc, true);
2478   EventMark em("%s", msg);
2479 
2480   ShenandoahWorkerScope scope(workers(),
2481                               ShenandoahWorkerPolicy::calc_workers_for_stw_degenerated(),
2482                               "stw degenerated gc");
2483 
2484   set_degenerated_gc_in_progress(true);
2485   op_degenerated(dpoint);
2486   set_degenerated_gc_in_progress(false);
2487 }
2488 
2489 void ShenandoahHeap::entry_mark() {
2490   TraceCollectorStats tcs(monitoring_support()->concurrent_collection_counters());
2491 
2492   const char* msg = conc_mark_event_message();
2493   GCTraceTime(Info, gc) time(msg, NULL, GCCause::_no_gc, true);
2494   EventMark em("%s", msg);
2495 
2496   ShenandoahWorkerScope scope(workers(),
2497                               ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
2498                               "concurrent marking");
2499 
2500   try_inject_alloc_failure();
2501   op_mark();
2502 }
2503 
2504 void ShenandoahHeap::entry_evac() {
2505   ShenandoahGCPhase conc_evac_phase(ShenandoahPhaseTimings::conc_evac);
2506   TraceCollectorStats tcs(monitoring_support()->concurrent_collection_counters());
2507 
2508   static const char* msg = "Concurrent evacuation";
2509   GCTraceTime(Info, gc) time(msg, NULL, GCCause::_no_gc, true);
2510   EventMark em("%s", msg);
2511 
2512   ShenandoahWorkerScope scope(workers(),
2513                               ShenandoahWorkerPolicy::calc_workers_for_conc_evac(),
2514                               "concurrent evacuation");
2515 
2516   try_inject_alloc_failure();
2517   op_conc_evac();
2518 }
2519 
2520 void ShenandoahHeap::entry_updaterefs() {
2521   ShenandoahGCPhase phase(ShenandoahPhaseTimings::conc_update_refs);
2522 
2523   static const char* msg = "Concurrent update references";
2524   GCTraceTime(Info, gc) time(msg, NULL, GCCause::_no_gc, true);
2525   EventMark em("%s", msg);
2526 
2527   ShenandoahWorkerScope scope(workers(),
2528                               ShenandoahWorkerPolicy::calc_workers_for_conc_update_ref(),
2529                               "concurrent reference update");
2530 
2531   try_inject_alloc_failure();
2532   op_updaterefs();
2533 }
2534 void ShenandoahHeap::entry_cleanup() {
2535   ShenandoahGCPhase phase(ShenandoahPhaseTimings::conc_cleanup);
2536 
2537   static const char* msg = "Concurrent cleanup";
2538   GCTraceTime(Info, gc) time(msg, NULL, GCCause::_no_gc, true);
2539   EventMark em("%s", msg);
2540 
2541   // This phase does not use workers, no need for setup
2542 
2543   try_inject_alloc_failure();
2544   op_cleanup();
2545 }
2546 
2547 void ShenandoahHeap::entry_reset() {
2548   ShenandoahGCPhase phase(ShenandoahPhaseTimings::conc_reset);
2549 
2550   static const char* msg = "Concurrent reset";
2551   GCTraceTime(Info, gc) time(msg, NULL, GCCause::_no_gc, true);
2552   EventMark em("%s", msg);
2553 
2554   ShenandoahWorkerScope scope(workers(),
2555                               ShenandoahWorkerPolicy::calc_workers_for_conc_reset(),
2556                               "concurrent reset");
2557 
2558   try_inject_alloc_failure();
2559   op_reset();
2560 }
2561 
2562 void ShenandoahHeap::entry_preclean() {
2563   if (ShenandoahPreclean && process_references()) {
2564     static const char* msg = "Concurrent precleaning";
2565     GCTraceTime(Info, gc) time(msg, NULL, GCCause::_no_gc, true);
2566     EventMark em("%s", msg);
2567 
2568     ShenandoahGCPhase conc_preclean(ShenandoahPhaseTimings::conc_preclean);
2569 
2570     ShenandoahWorkerScope scope(workers(),
2571                                 ShenandoahWorkerPolicy::calc_workers_for_conc_preclean(),
2572                                 "concurrent preclean",
2573                                 /* check_workers = */ false);
2574 
2575     try_inject_alloc_failure();
2576     op_preclean();
2577   }
2578 }
2579 
2580 void ShenandoahHeap::entry_traversal() {
2581   static const char* msg = "Concurrent traversal";
2582   GCTraceTime(Info, gc) time(msg, NULL, GCCause::_no_gc, true);
2583   EventMark em("%s", msg);
2584 
2585   TraceCollectorStats tcs(monitoring_support()->concurrent_collection_counters());
2586 
2587   ShenandoahWorkerScope scope(workers(),
2588                               ShenandoahWorkerPolicy::calc_workers_for_conc_traversal(),
2589                               "concurrent traversal");
2590 
2591   try_inject_alloc_failure();
2592   op_traversal();
2593 }
2594 
2595 void ShenandoahHeap::entry_uncommit(double shrink_before) {
2596   static const char *msg = "Concurrent uncommit";
2597   GCTraceTime(Info, gc) time(msg, NULL, GCCause::_no_gc, true);
2598   EventMark em("%s", msg);
2599 
2600   ShenandoahGCPhase phase(ShenandoahPhaseTimings::conc_uncommit);
2601 
2602   op_uncommit(shrink_before);
2603 }
2604 
2605 void ShenandoahHeap::try_inject_alloc_failure() {
2606   if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2607     _inject_alloc_failure.set();
2608     os::naked_short_sleep(1);
2609     if (cancelled_gc()) {
2610       log_info(gc)("Allocation failure was successfully injected");
2611     }
2612   }
2613 }
2614 
2615 bool ShenandoahHeap::should_inject_alloc_failure() {
2616   return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2617 }
2618 
2619 void ShenandoahHeap::initialize_serviceability() {
2620   _memory_pool = new ShenandoahMemoryPool(this);
2621   _cycle_memory_manager.add_pool(_memory_pool);
2622   _stw_memory_manager.add_pool(_memory_pool);
2623 }
2624 
2625 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2626   GrowableArray<GCMemoryManager*> memory_managers(2);
2627   memory_managers.append(&_cycle_memory_manager);
2628   memory_managers.append(&_stw_memory_manager);
2629   return memory_managers;
2630 }
2631 
2632 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2633   GrowableArray<MemoryPool*> memory_pools(1);
2634   memory_pools.append(_memory_pool);
2635   return memory_pools;
2636 }
2637 
2638 MemoryUsage ShenandoahHeap::memory_usage() {
2639   return _memory_pool->get_memory_usage();
2640 }
2641 
2642 void ShenandoahHeap::enter_evacuation() {
2643   _oom_evac_handler.enter_evacuation();
2644 }
2645 
2646 void ShenandoahHeap::leave_evacuation() {
2647   _oom_evac_handler.leave_evacuation();
2648 }
2649 
2650 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2651   _heap(ShenandoahHeap::heap()),
2652   _index(0) {}
2653 
2654 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2655   _heap(heap),
2656   _index(0) {}
2657 
2658 void ShenandoahRegionIterator::reset() {
2659   _index = 0;
2660 }
2661 
2662 bool ShenandoahRegionIterator::has_next() const {
2663   return _index < _heap->num_regions();
2664 }
2665 
2666 char ShenandoahHeap::gc_state() const {
2667   return _gc_state.raw_value();
2668 }
2669 
2670 void ShenandoahHeap::deduplicate_string(oop str) {
2671   assert(java_lang_String::is_instance(str), "invariant");
2672 
2673   if (ShenandoahStringDedup::is_enabled()) {
2674     ShenandoahStringDedup::deduplicate(str);
2675   }
2676 }
2677 
2678 const char* ShenandoahHeap::init_mark_event_message() const {
2679   bool update_refs = has_forwarded_objects();
2680   bool proc_refs = process_references();
2681   bool unload_cls = unload_classes();
2682 
2683   if (update_refs && proc_refs && unload_cls) {
2684     return "Pause Init Mark (update refs) (process weakrefs) (unload classes)";
2685   } else if (update_refs && proc_refs) {
2686     return "Pause Init Mark (update refs) (process weakrefs)";
2687   } else if (update_refs && unload_cls) {
2688     return "Pause Init Mark (update refs) (unload classes)";
2689   } else if (proc_refs && unload_cls) {
2690     return "Pause Init Mark (process weakrefs) (unload classes)";
2691   } else if (update_refs) {
2692     return "Pause Init Mark (update refs)";
2693   } else if (proc_refs) {
2694     return "Pause Init Mark (process weakrefs)";
2695   } else if (unload_cls) {
2696     return "Pause Init Mark (unload classes)";
2697   } else {
2698     return "Pause Init Mark";
2699   }
2700 }
2701 
2702 const char* ShenandoahHeap::final_mark_event_message() const {
2703   bool update_refs = has_forwarded_objects();
2704   bool proc_refs = process_references();
2705   bool unload_cls = unload_classes();
2706 
2707   if (update_refs && proc_refs && unload_cls) {
2708     return "Pause Final Mark (update refs) (process weakrefs) (unload classes)";
2709   } else if (update_refs && proc_refs) {
2710     return "Pause Final Mark (update refs) (process weakrefs)";
2711   } else if (update_refs && unload_cls) {
2712     return "Pause Final Mark (update refs) (unload classes)";
2713   } else if (proc_refs && unload_cls) {
2714     return "Pause Final Mark (process weakrefs) (unload classes)";
2715   } else if (update_refs) {
2716     return "Pause Final Mark (update refs)";
2717   } else if (proc_refs) {
2718     return "Pause Final Mark (process weakrefs)";
2719   } else if (unload_cls) {
2720     return "Pause Final Mark (unload classes)";
2721   } else {
2722     return "Pause Final Mark";
2723   }
2724 }
2725 
2726 const char* ShenandoahHeap::conc_mark_event_message() const {
2727   bool update_refs = has_forwarded_objects();
2728   bool proc_refs = process_references();
2729   bool unload_cls = unload_classes();
2730 
2731   if (update_refs && proc_refs && unload_cls) {
2732     return "Concurrent marking (update refs) (process weakrefs) (unload classes)";
2733   } else if (update_refs && proc_refs) {
2734     return "Concurrent marking (update refs) (process weakrefs)";
2735   } else if (update_refs && unload_cls) {
2736     return "Concurrent marking (update refs) (unload classes)";
2737   } else if (proc_refs && unload_cls) {
2738     return "Concurrent marking (process weakrefs) (unload classes)";
2739   } else if (update_refs) {
2740     return "Concurrent marking (update refs)";
2741   } else if (proc_refs) {
2742     return "Concurrent marking (process weakrefs)";
2743   } else if (unload_cls) {
2744     return "Concurrent marking (unload classes)";
2745   } else {
2746     return "Concurrent marking";
2747   }
2748 }
2749 
2750 const char* ShenandoahHeap::degen_event_message(ShenandoahDegenPoint point) const {
2751   switch (point) {
2752     case _degenerated_unset:
2753       return "Pause Degenerated GC (<UNSET>)";
2754     case _degenerated_traversal:
2755       return "Pause Degenerated GC (Traversal)";
2756     case _degenerated_outside_cycle:
2757       return "Pause Degenerated GC (Outside of Cycle)";
2758     case _degenerated_mark:
2759       return "Pause Degenerated GC (Mark)";
2760     case _degenerated_evac:
2761       return "Pause Degenerated GC (Evacuation)";
2762     case _degenerated_updaterefs:
2763       return "Pause Degenerated GC (Update Refs)";
2764     default:
2765       ShouldNotReachHere();
2766       return "ERROR";
2767   }
2768 }
2769 
2770 jushort* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2771 #ifdef ASSERT
2772   assert(_liveness_cache != NULL, "sanity");
2773   assert(worker_id < _max_workers, "sanity");
2774   for (uint i = 0; i < num_regions(); i++) {
2775     assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2776   }
2777 #endif
2778   return _liveness_cache[worker_id];
2779 }
2780 
2781 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2782   assert(worker_id < _max_workers, "sanity");
2783   assert(_liveness_cache != NULL, "sanity");
2784   jushort* ld = _liveness_cache[worker_id];
2785   for (uint i = 0; i < num_regions(); i++) {
2786     ShenandoahHeapRegion* r = get_region(i);
2787     jushort live = ld[i];
2788     if (live > 0) {
2789       r->increase_live_data_gc_words(live);
2790       ld[i] = 0;
2791     }
2792   }
2793 }