1 /*
   2  * Copyright (c) 2013, 2018, 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 
  27 #include "gc/shared/gcTimer.hpp"
  28 #include "gc/shared/gcTraceTime.inline.hpp"
  29 #include "gc/shared/memAllocator.hpp"
  30 #include "gc/shared/parallelCleaning.hpp"
  31 #include "gc/shared/plab.hpp"
  32 
  33 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
  34 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
  35 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
  36 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
  37 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
  38 #include "gc/shenandoah/shenandoahControlThread.hpp"
  39 #include "gc/shenandoah/shenandoahFreeSet.hpp"
  40 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
  41 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
  42 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
  43 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
  44 #include "gc/shenandoah/shenandoahMarkCompact.hpp"
  45 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
  46 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
  47 #include "gc/shenandoah/shenandoahMetrics.hpp"
  48 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
  49 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
  50 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
  51 #include "gc/shenandoah/shenandoahPadding.hpp"
  52 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
  53 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
  54 #include "gc/shenandoah/shenandoahStringDedup.hpp"
  55 #include "gc/shenandoah/shenandoahTaskqueue.hpp"
  56 #include "gc/shenandoah/shenandoahUtils.hpp"
  57 #include "gc/shenandoah/shenandoahVerifier.hpp"
  58 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
  59 #include "gc/shenandoah/shenandoahVMOperations.hpp"
  60 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
  61 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
  62 #include "gc/shenandoah/mode/shenandoahIUMode.hpp"
  63 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
  64 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
  65 #if INCLUDE_JFR
  66 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
  67 #endif
  68 
  69 #include "memory/metaspace.hpp"
  70 #include "runtime/vmThread.hpp"
  71 #include "services/mallocTracker.hpp"
  72 
  73 ShenandoahHeap* ShenandoahHeap::_heap = NULL;
  74 
  75 #ifdef ASSERT
  76 template <class T>
  77 void ShenandoahAssertToSpaceClosure::do_oop_work(T* p) {
  78   T o = RawAccess<>::oop_load(p);
  79   if (! CompressedOops::is_null(o)) {
  80     oop obj = CompressedOops::decode_not_null(o);
  81     shenandoah_assert_not_forwarded(p, obj);
  82   }
  83 }
  84 
  85 void ShenandoahAssertToSpaceClosure::do_oop(narrowOop* p) { do_oop_work(p); }
  86 void ShenandoahAssertToSpaceClosure::do_oop(oop* p)       { do_oop_work(p); }
  87 #endif
  88 
  89 class ShenandoahPretouchHeapTask : public AbstractGangTask {
  90 private:
  91   ShenandoahRegionIterator _regions;
  92   const size_t _page_size;
  93 public:
  94   ShenandoahPretouchHeapTask(size_t page_size) :
  95     AbstractGangTask("Shenandoah Pretouch Heap"),
  96     _page_size(page_size) {}
  97 
  98   virtual void work(uint worker_id) {
  99     ShenandoahHeapRegion* r = _regions.next();
 100     while (r != NULL) {
 101       if (r->is_committed()) {
 102         os::pretouch_memory(r->bottom(), r->end(), _page_size);
 103       }
 104       r = _regions.next();
 105     }
 106   }
 107 };
 108 
 109 class ShenandoahPretouchBitmapTask : public AbstractGangTask {
 110 private:
 111   ShenandoahRegionIterator _regions;
 112   char* _bitmap_base;
 113   const size_t _bitmap_size;
 114   const size_t _page_size;
 115 public:
 116   ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
 117     AbstractGangTask("Shenandoah Pretouch Bitmap"),
 118     _bitmap_base(bitmap_base),
 119     _bitmap_size(bitmap_size),
 120     _page_size(page_size) {}
 121 
 122   virtual void work(uint worker_id) {
 123     ShenandoahHeapRegion* r = _regions.next();
 124     while (r != NULL) {
 125       size_t start = r->index()       * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 126       size_t end   = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
 127       assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
 128 
 129       if (r->is_committed()) {
 130         os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
 131       }
 132 
 133       r = _regions.next();
 134     }
 135   }
 136 };
 137 
 138 jint ShenandoahHeap::initialize() {
 139   //
 140   // Figure out heap sizing
 141   //
 142 
 143   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
 144   size_t min_byte_size  = collector_policy()->min_heap_byte_size();
 145   size_t max_byte_size  = collector_policy()->max_heap_byte_size();
 146   size_t heap_alignment = collector_policy()->heap_alignment();
 147 
 148   size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
 149 
 150   Universe::check_alignment(max_byte_size,  reg_size_bytes, "Shenandoah heap");
 151   Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
 152 
 153   _num_regions = ShenandoahHeapRegion::region_count();
 154 
 155   // Now we know the number of regions, initialize the heuristics.
 156   initialize_heuristics();
 157 
 158   size_t num_committed_regions = init_byte_size / reg_size_bytes;
 159   num_committed_regions = MIN2(num_committed_regions, _num_regions);
 160   assert(num_committed_regions <= _num_regions, "sanity");
 161   _initial_size = num_committed_regions * reg_size_bytes;
 162 
 163   size_t num_min_regions = min_byte_size / reg_size_bytes;
 164   num_min_regions = MIN2(num_min_regions, _num_regions);
 165   assert(num_min_regions <= _num_regions, "sanity");
 166   _minimum_size = num_min_regions * reg_size_bytes;
 167 
 168   _committed = _initial_size;
 169 
 170   size_t heap_page_size   = UseLargePages ? (size_t)os::large_page_size() : (size_t)os::vm_page_size();
 171   size_t bitmap_page_size = UseLargePages ? (size_t)os::large_page_size() : (size_t)os::vm_page_size();
 172   size_t region_page_size = UseLargePages ? (size_t)os::large_page_size() : (size_t)os::vm_page_size();
 173 
 174   //
 175   // Reserve and commit memory for heap
 176   //
 177 
 178   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
 179   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*) (heap_rs.base() + heap_rs.size()));
 180   _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
 181   _heap_region_special = heap_rs.special();
 182 
 183   assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
 184          "Misaligned heap: " PTR_FORMAT, p2i(base()));
 185 
 186 #if SHENANDOAH_OPTIMIZED_OBJTASK
 187   // The optimized ObjArrayChunkedTask takes some bits away from the full object bits.
 188   // Fail if we ever attempt to address more than we can.
 189   if ((uintptr_t)heap_rs.end() >= ObjArrayChunkedTask::max_addressable()) {
 190     FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
 191                           "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
 192                           "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
 193                 p2i(heap_rs.base()), p2i(heap_rs.end()), ObjArrayChunkedTask::max_addressable());
 194     vm_exit_during_initialization("Fatal Error", buf);
 195   }
 196 #endif
 197 
 198   ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
 199   if (!_heap_region_special) {
 200     os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
 201                               "Cannot commit heap memory");
 202   }
 203 
 204   //
 205   // Reserve and commit memory for bitmap(s)
 206   //
 207 
 208   _bitmap_size = MarkBitMap::compute_size(heap_rs.size());
 209   _bitmap_size = align_up(_bitmap_size, bitmap_page_size);
 210 
 211   size_t bitmap_bytes_per_region = reg_size_bytes / MarkBitMap::heap_map_factor();
 212 
 213   guarantee(bitmap_bytes_per_region != 0,
 214             "Bitmap bytes per region should not be zero");
 215   guarantee(is_power_of_2(bitmap_bytes_per_region),
 216             "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
 217 
 218   if (bitmap_page_size > bitmap_bytes_per_region) {
 219     _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
 220     _bitmap_bytes_per_slice = bitmap_page_size;
 221   } else {
 222     _bitmap_regions_per_slice = 1;
 223     _bitmap_bytes_per_slice = bitmap_bytes_per_region;
 224   }
 225 
 226   guarantee(_bitmap_regions_per_slice >= 1,
 227             "Should have at least one region per slice: " SIZE_FORMAT,
 228             _bitmap_regions_per_slice);
 229 
 230   guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
 231             "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
 232             _bitmap_bytes_per_slice, bitmap_page_size);
 233 
 234   ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
 235   MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
 236   _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
 237   _bitmap_region_special = bitmap.special();
 238 
 239   size_t bitmap_init_commit = _bitmap_bytes_per_slice *
 240                               align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
 241   bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
 242   if (!_bitmap_region_special) {
 243     os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
 244                               "Cannot commit bitmap memory");
 245   }
 246 
 247   _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
 248 
 249   if (ShenandoahVerify) {
 250     ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
 251     if (!verify_bitmap.special()) {
 252       os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
 253                                 "Cannot commit verification bitmap memory");
 254     }
 255     MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
 256     MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
 257     _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
 258     _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
 259   }
 260 
 261   // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
 262   ReservedSpace aux_bitmap(_bitmap_size, bitmap_page_size);
 263   MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
 264   _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
 265   _aux_bitmap_region_special = aux_bitmap.special();
 266   _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
 267 
 268   //
 269   // Create regions and region sets
 270   //
 271   size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
 272   size_t region_storage_size = align_up(region_align * _num_regions, region_page_size);
 273   region_storage_size = align_up(region_storage_size, os::vm_allocation_granularity());
 274 
 275   ReservedSpace region_storage(region_storage_size, region_page_size);
 276   MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
 277   if (!region_storage.special()) {
 278     os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
 279                               "Cannot commit region memory");
 280   }
 281 
 282   // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
 283   // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
 284   // If not successful, bite a bullet and allocate at whatever address.
 285   {
 286     size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
 287     size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
 288 
 289     uintptr_t min = ShenandoahUtils::round_up_power_of_2(cset_align);
 290     uintptr_t max = (1u << 30u);
 291 
 292     for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
 293       char* req_addr = (char*)addr;
 294       assert(is_aligned(req_addr, cset_align), "Should be aligned");
 295       ReservedSpace cset_rs(cset_size, cset_align, false, req_addr);
 296       if (cset_rs.is_reserved()) {
 297         assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
 298         _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
 299         break;
 300       }
 301     }
 302 
 303     if (_collection_set == NULL) {
 304       ReservedSpace cset_rs(cset_size, cset_align, false);
 305       _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
 306     }
 307   }
 308 
 309   _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
 310   _free_set = new ShenandoahFreeSet(this, _num_regions);
 311 
 312   {
 313     ShenandoahHeapLocker locker(lock());
 314 
 315     for (size_t i = 0; i < _num_regions; i++) {
 316       HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
 317       bool is_committed = i < num_committed_regions;
 318       void* loc = region_storage.base() + i * region_align;
 319 
 320       ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
 321       assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
 322 
 323       _marking_context->initialize_top_at_mark_start(r);
 324       _regions[i] = r;
 325       assert(!collection_set()->is_in(i), "New region should not be in collection set");
 326     }
 327 
 328     // Initialize to complete
 329     _marking_context->mark_complete();
 330 
 331     _free_set->rebuild();
 332   }
 333 
 334   if (AlwaysPreTouch) {
 335     // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
 336     // before initialize() below zeroes it with initializing thread. For any given region,
 337     // we touch the region and the corresponding bitmaps from the same thread.
 338     ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
 339 
 340     _pretouch_heap_page_size = heap_page_size;
 341     _pretouch_bitmap_page_size = bitmap_page_size;
 342 
 343 #ifdef LINUX
 344     // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
 345     // pages. But, the kernel needs to know that every small page is used, in order to coalesce
 346     // them into huge one. Therefore, we need to pretouch with smaller pages.
 347     if (UseTransparentHugePages) {
 348       _pretouch_heap_page_size = (size_t)os::vm_page_size();
 349       _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
 350     }
 351 #endif
 352 
 353     // OS memory managers may want to coalesce back-to-back pages. Make their jobs
 354     // simpler by pre-touching continuous spaces (heap and bitmap) separately.
 355 
 356     ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
 357     _workers->run_task(&bcl);
 358 
 359     ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
 360     _workers->run_task(&hcl);
 361   }
 362 
 363   //
 364   // Initialize the rest of GC subsystems
 365   //
 366 
 367   BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
 368 
 369   _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
 370   for (uint worker = 0; worker < _max_workers; worker++) {
 371     _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
 372     Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
 373   }
 374 
 375   // The call below uses stuff (the SATB* things) that are in G1, but probably
 376   // belong into a shared location.
 377   ShenandoahBarrierSet::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
 378                                                SATB_Q_FL_lock,
 379                                                20 /*G1SATBProcessCompletedThreshold */,
 380                                                Shared_SATB_Q_lock);
 381 
 382   _monitoring_support = new ShenandoahMonitoringSupport(this);
 383   _phase_timings = new ShenandoahPhaseTimings(max_workers());
 384   ShenandoahStringDedup::initialize();
 385   ShenandoahCodeRoots::initialize();
 386 
 387   if (ShenandoahPacing) {
 388     _pacer = new ShenandoahPacer(this);
 389     _pacer->setup_for_idle();
 390   } else {
 391     _pacer = NULL;
 392   }
 393 
 394   _control_thread = new ShenandoahControlThread();
 395 
 396   log_info(gc, init)("Initialize Shenandoah heap: " SIZE_FORMAT "%s initial, " SIZE_FORMAT "%s min, " SIZE_FORMAT "%s max",
 397                      byte_size_in_proper_unit(_initial_size),  proper_unit_for_byte_size(_initial_size),
 398                      byte_size_in_proper_unit(_minimum_size),  proper_unit_for_byte_size(_minimum_size),
 399                      byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity())
 400   );
 401 
 402   log_info(gc, init)("Safepointing mechanism: %s",
 403                      SafepointMechanism::uses_thread_local_poll() ? "thread-local poll" :
 404                      (SafepointMechanism::uses_global_page_poll() ? "global-page poll" : "unknown"));
 405 
 406   return JNI_OK;
 407 }
 408 
 409 void ShenandoahHeap::initialize_heuristics() {
 410   if (ShenandoahGCMode != NULL) {
 411     if (strcmp(ShenandoahGCMode, "satb") == 0) {
 412       _gc_mode = new ShenandoahSATBMode();
 413     } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
 414       _gc_mode = new ShenandoahIUMode();
 415     } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
 416       _gc_mode = new ShenandoahPassiveMode();
 417     } else {
 418       vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
 419     }
 420   } else {
 421     ShouldNotReachHere();
 422   }
 423   _gc_mode->initialize_flags();
 424   if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
 425     vm_exit_during_initialization(
 426             err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
 427                     _gc_mode->name()));
 428   }
 429   if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
 430     vm_exit_during_initialization(
 431             err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
 432                     _gc_mode->name()));
 433   }
 434   log_info(gc, init)("Shenandoah GC mode: %s",
 435                      _gc_mode->name());
 436 
 437   _heuristics = _gc_mode->initialize_heuristics();
 438 
 439   if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
 440     vm_exit_during_initialization(
 441             err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
 442                     _heuristics->name()));
 443   }
 444   if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
 445     vm_exit_during_initialization(
 446             err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
 447                     _heuristics->name()));
 448   }
 449   log_info(gc, init)("Shenandoah heuristics: %s",
 450                      _heuristics->name());
 451 }
 452 
 453 #ifdef _MSC_VER
 454 #pragma warning( push )
 455 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 456 #endif
 457 
 458 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
 459   CollectedHeap(),
 460   _initial_size(0),
 461   _used(0),
 462   _committed(0),
 463   _bytes_allocated_since_gc_start(0),
 464   _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
 465   _workers(NULL),
 466   _safepoint_workers(NULL),
 467   _heap_region_special(false),
 468   _num_regions(0),
 469   _regions(NULL),
 470   _update_refs_iterator(this),
 471   _control_thread(NULL),
 472   _shenandoah_policy(policy),
 473   _heuristics(NULL),
 474   _free_set(NULL),
 475   _scm(new ShenandoahConcurrentMark()),
 476   _full_gc(new ShenandoahMarkCompact()),
 477   _pacer(NULL),
 478   _verifier(NULL),
 479   _phase_timings(NULL),
 480   _monitoring_support(NULL),
 481   _memory_pool(NULL),
 482   _stw_memory_manager("Shenandoah Pauses", "end of GC pause"),
 483   _cycle_memory_manager("Shenandoah Cycles", "end of GC cycle"),
 484   _gc_timer(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
 485   _soft_ref_policy(),
 486   _ref_processor(NULL),
 487   _marking_context(NULL),
 488   _bitmap_size(0),
 489   _bitmap_regions_per_slice(0),
 490   _bitmap_bytes_per_slice(0),
 491   _bitmap_region_special(false),
 492   _aux_bitmap_region_special(false),
 493   _liveness_cache(NULL),
 494   _collection_set(NULL)
 495 {
 496   _heap = this;
 497 
 498   log_info(gc, init)("GC threads: " UINT32_FORMAT " parallel, " UINT32_FORMAT " concurrent", ParallelGCThreads, ConcGCThreads);
 499 
 500   _max_workers = MAX2(_max_workers, 1U);
 501   _workers = new ShenandoahWorkGang("Shenandoah GC Threads", _max_workers,
 502                             /* are_GC_task_threads */ true,
 503                             /* are_ConcurrentGC_threads */ true);
 504   if (_workers == NULL) {
 505     vm_exit_during_initialization("Failed necessary allocation.");
 506   } else {
 507     _workers->initialize_workers();
 508   }
 509 
 510   if (ParallelGCThreads > 1) {
 511     _safepoint_workers = new ShenandoahWorkGang("Safepoint Cleanup Thread",
 512                                                 ParallelGCThreads,
 513                       /* are_GC_task_threads */ false,
 514                  /* are_ConcurrentGC_threads */ false);
 515     _safepoint_workers->initialize_workers();
 516   }
 517 }
 518 
 519 #ifdef _MSC_VER
 520 #pragma warning( pop )
 521 #endif
 522 
 523 class ShenandoahResetBitmapTask : public AbstractGangTask {
 524 private:
 525   ShenandoahRegionIterator _regions;
 526 
 527 public:
 528   ShenandoahResetBitmapTask() :
 529     AbstractGangTask("Parallel Reset Bitmap Task") {}
 530 
 531   void work(uint worker_id) {
 532     ShenandoahHeapRegion* region = _regions.next();
 533     ShenandoahHeap* heap = ShenandoahHeap::heap();
 534     ShenandoahMarkingContext* const ctx = heap->marking_context();
 535     while (region != NULL) {
 536       if (heap->is_bitmap_slice_committed(region)) {
 537         ctx->clear_bitmap(region);
 538       }
 539       region = _regions.next();
 540     }
 541   }
 542 };
 543 
 544 void ShenandoahHeap::reset_mark_bitmap() {
 545   assert_gc_workers(_workers->active_workers());
 546   mark_incomplete_marking_context();
 547 
 548   ShenandoahResetBitmapTask task;
 549   _workers->run_task(&task);
 550 }
 551 
 552 void ShenandoahHeap::print_on(outputStream* st) const {
 553   st->print_cr("Shenandoah Heap");
 554   st->print_cr(" " SIZE_FORMAT "%s total, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
 555                byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
 556                byte_size_in_proper_unit(committed()),    proper_unit_for_byte_size(committed()),
 557                byte_size_in_proper_unit(used()),         proper_unit_for_byte_size(used()));
 558   st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
 559                num_regions(),
 560                byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
 561                proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
 562 
 563   st->print("Status: ");
 564   if (has_forwarded_objects())               st->print("has forwarded objects, ");
 565   if (is_concurrent_mark_in_progress())      st->print("marking, ");
 566   if (is_evacuation_in_progress())           st->print("evacuating, ");
 567   if (is_update_refs_in_progress())          st->print("updating refs, ");
 568   if (is_degenerated_gc_in_progress())       st->print("degenerated gc, ");
 569   if (is_full_gc_in_progress())              st->print("full gc, ");
 570   if (is_full_gc_move_in_progress())         st->print("full gc move, ");
 571 
 572   if (cancelled_gc()) {
 573     st->print("cancelled");
 574   } else {
 575     st->print("not cancelled");
 576   }
 577   st->cr();
 578 
 579   st->print_cr("Reserved region:");
 580   st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
 581                p2i(reserved_region().start()),
 582                p2i(reserved_region().end()));
 583 
 584   ShenandoahCollectionSet* cset = collection_set();
 585   st->print_cr("Collection set:");
 586   if (cset != NULL) {
 587     st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
 588     st->print_cr(" - map (biased):  " PTR_FORMAT, p2i(cset->biased_map_address()));
 589   } else {
 590     st->print_cr(" (NULL)");
 591   }
 592 
 593   st->cr();
 594   MetaspaceUtils::print_on(st);
 595 
 596   if (Verbose) {
 597     print_heap_regions_on(st);
 598   }
 599 }
 600 
 601 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
 602 public:
 603   void do_thread(Thread* thread) {
 604     assert(thread != NULL, "Sanity");
 605     assert(thread->is_Worker_thread(), "Only worker thread expected");
 606     ShenandoahThreadLocalData::initialize_gclab(thread);
 607   }
 608 };
 609 
 610 void ShenandoahHeap::post_initialize() {
 611   CollectedHeap::post_initialize();
 612   MutexLocker ml(Threads_lock);
 613 
 614   ShenandoahInitWorkerGCLABClosure init_gclabs;
 615   _workers->threads_do(&init_gclabs);
 616 
 617   // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
 618   // Now, we will let WorkGang to initialize gclab when new worker is created.
 619   _workers->set_initialize_gclab();
 620 
 621   _scm->initialize(_max_workers);
 622   _full_gc->initialize(_gc_timer);
 623 
 624   ref_processing_init();
 625 
 626   _heuristics->initialize();
 627 
 628   JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
 629 }
 630 
 631 size_t ShenandoahHeap::used() const {
 632   return OrderAccess::load_acquire(&_used);
 633 }
 634 
 635 size_t ShenandoahHeap::committed() const {
 636   OrderAccess::acquire();
 637   return _committed;
 638 }
 639 
 640 void ShenandoahHeap::increase_committed(size_t bytes) {
 641   shenandoah_assert_heaplocked_or_safepoint();
 642   _committed += bytes;
 643 }
 644 
 645 void ShenandoahHeap::decrease_committed(size_t bytes) {
 646   shenandoah_assert_heaplocked_or_safepoint();
 647   _committed -= bytes;
 648 }
 649 
 650 void ShenandoahHeap::increase_used(size_t bytes) {
 651   Atomic::add(bytes, &_used);
 652 }
 653 
 654 void ShenandoahHeap::set_used(size_t bytes) {
 655   OrderAccess::release_store_fence(&_used, bytes);
 656 }
 657 
 658 void ShenandoahHeap::decrease_used(size_t bytes) {
 659   assert(used() >= bytes, "never decrease heap size by more than we've left");
 660   Atomic::sub(bytes, &_used);
 661 }
 662 
 663 void ShenandoahHeap::increase_allocated(size_t bytes) {
 664   Atomic::add(bytes, &_bytes_allocated_since_gc_start);
 665 }
 666 
 667 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
 668   size_t bytes = words * HeapWordSize;
 669   if (!waste) {
 670     increase_used(bytes);
 671   }
 672   increase_allocated(bytes);
 673   if (ShenandoahPacing) {
 674     control_thread()->pacing_notify_alloc(words);
 675     if (waste) {
 676       pacer()->claim_for_alloc(words, true);
 677     }
 678   }
 679 }
 680 
 681 size_t ShenandoahHeap::capacity() const {
 682   return committed();
 683 }
 684 
 685 size_t ShenandoahHeap::max_capacity() const {
 686   return _num_regions * ShenandoahHeapRegion::region_size_bytes();
 687 }
 688 
 689 size_t ShenandoahHeap::min_capacity() const {
 690   return _minimum_size;
 691 }
 692 
 693 size_t ShenandoahHeap::initial_capacity() const {
 694   return _initial_size;
 695 }
 696 
 697 bool ShenandoahHeap::is_in(const void* p) const {
 698   HeapWord* heap_base = (HeapWord*) base();
 699   HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
 700   return p >= heap_base && p < last_region_end;
 701 }
 702 
 703 void ShenandoahHeap::op_uncommit(double shrink_before) {
 704   assert (ShenandoahUncommit, "should be enabled");
 705 
 706   // Application allocates from the beginning of the heap, and GC allocates at
 707   // the end of it. It is more efficient to uncommit from the end, so that applications
 708   // could enjoy the near committed regions. GC allocations are much less frequent,
 709   // and therefore can accept the committing costs.
 710 
 711   size_t count = 0;
 712   for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
 713     ShenandoahHeapRegion* r = get_region(i - 1);
 714     if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
 715       ShenandoahHeapLocker locker(lock());
 716       if (r->is_empty_committed()) {
 717         // Do not uncommit below minimal capacity
 718         if (committed() < min_capacity() + ShenandoahHeapRegion::region_size_bytes()) {
 719           break;
 720         }
 721 
 722         r->make_uncommitted();
 723         count++;
 724       }
 725     }
 726     SpinPause(); // allow allocators to take the lock
 727   }
 728 
 729   if (count > 0) {
 730     control_thread()->notify_heap_changed();
 731   }
 732 }
 733 
 734 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
 735   // New object should fit the GCLAB size
 736   size_t min_size = MAX2(size, PLAB::min_size());
 737 
 738   // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
 739   size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
 740   new_size = MIN2(new_size, PLAB::max_size());
 741   new_size = MAX2(new_size, PLAB::min_size());
 742 
 743   // Record new heuristic value even if we take any shortcut. This captures
 744   // the case when moderately-sized objects always take a shortcut. At some point,
 745   // heuristics should catch up with them.
 746   ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
 747 
 748   if (new_size < size) {
 749     // New size still does not fit the object. Fall back to shared allocation.
 750     // This avoids retiring perfectly good GCLABs, when we encounter a large object.
 751     return NULL;
 752   }
 753 
 754   // Retire current GCLAB, and allocate a new one.
 755   PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
 756   gclab->retire();
 757 
 758   size_t actual_size = 0;
 759   HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
 760   if (gclab_buf == NULL) {
 761     return NULL;
 762   }
 763 
 764   assert (size <= actual_size, "allocation should fit");
 765 
 766   if (ZeroTLAB) {
 767     // ..and clear it.
 768     Copy::zero_to_words(gclab_buf, actual_size);
 769   } else {
 770     // ...and zap just allocated object.
 771 #ifdef ASSERT
 772     // Skip mangling the space corresponding to the object header to
 773     // ensure that the returned space is not considered parsable by
 774     // any concurrent GC thread.
 775     size_t hdr_size = oopDesc::header_size();
 776     Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
 777 #endif // ASSERT
 778   }
 779   gclab->set_buf(gclab_buf, actual_size);
 780   return gclab->allocate(size);
 781 }
 782 
 783 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
 784                                             size_t requested_size,
 785                                             size_t* actual_size) {
 786   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
 787   HeapWord* res = allocate_memory(req);
 788   if (res != NULL) {
 789     *actual_size = req.actual_size();
 790   } else {
 791     *actual_size = 0;
 792   }
 793   return res;
 794 }
 795 
 796 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
 797                                              size_t word_size,
 798                                              size_t* actual_size) {
 799   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
 800   HeapWord* res = allocate_memory(req);
 801   if (res != NULL) {
 802     *actual_size = req.actual_size();
 803   } else {
 804     *actual_size = 0;
 805   }
 806   return res;
 807 }
 808 
 809 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
 810   intptr_t pacer_epoch = 0;
 811   bool in_new_region = false;
 812   HeapWord* result = NULL;
 813 
 814   if (req.is_mutator_alloc()) {
 815     if (ShenandoahPacing) {
 816       pacer()->pace_for_alloc(req.size());
 817       pacer_epoch = pacer()->epoch();
 818     }
 819 
 820     if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
 821       result = allocate_memory_under_lock(req, in_new_region);
 822     }
 823 
 824     // Allocation failed, block until control thread reacted, then retry allocation.
 825     //
 826     // It might happen that one of the threads requesting allocation would unblock
 827     // way later after GC happened, only to fail the second allocation, because
 828     // other threads have already depleted the free storage. In this case, a better
 829     // strategy is to try again, as long as GC makes progress.
 830     //
 831     // Then, we need to make sure the allocation was retried after at least one
 832     // Full GC, which means we want to try more than ShenandoahFullGCThreshold times.
 833 
 834     size_t tries = 0;
 835 
 836     while (result == NULL && _progress_last_gc.is_set()) {
 837       tries++;
 838       control_thread()->handle_alloc_failure(req);
 839       result = allocate_memory_under_lock(req, in_new_region);
 840     }
 841 
 842     while (result == NULL && tries <= ShenandoahFullGCThreshold) {
 843       tries++;
 844       control_thread()->handle_alloc_failure(req);
 845       result = allocate_memory_under_lock(req, in_new_region);
 846     }
 847 
 848   } else {
 849     assert(req.is_gc_alloc(), "Can only accept GC allocs here");
 850     result = allocate_memory_under_lock(req, in_new_region);
 851     // Do not call handle_alloc_failure() here, because we cannot block.
 852     // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
 853   }
 854 
 855   if (in_new_region) {
 856     control_thread()->notify_heap_changed();
 857   }
 858 
 859   if (result != NULL) {
 860     size_t requested = req.size();
 861     size_t actual = req.actual_size();
 862 
 863     assert (req.is_lab_alloc() || (requested == actual),
 864             "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
 865             ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
 866 
 867     if (req.is_mutator_alloc()) {
 868       notify_mutator_alloc_words(actual, false);
 869 
 870       // If we requested more than we were granted, give the rest back to pacer.
 871       // This only matters if we are in the same pacing epoch: do not try to unpace
 872       // over the budget for the other phase.
 873       if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
 874         pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
 875       }
 876     } else {
 877       increase_used(actual*HeapWordSize);
 878     }
 879   }
 880 
 881   return result;
 882 }
 883 
 884 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
 885   ShenandoahHeapLocker locker(lock());
 886   return _free_set->allocate(req, in_new_region);
 887 }
 888 
 889 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
 890                                         bool*  gc_overhead_limit_was_exceeded) {
 891   ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
 892   return allocate_memory(req);
 893 }
 894 
 895 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
 896                                                              size_t size,
 897                                                              Metaspace::MetadataType mdtype) {
 898   MetaWord* result;
 899 
 900   // Inform metaspace OOM to GC heuristics if class unloading is possible.
 901   if (heuristics()->can_unload_classes()) {
 902     ShenandoahHeuristics* h = heuristics();
 903     h->record_metaspace_oom();
 904   }
 905 
 906   // Expand and retry allocation
 907   result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
 908   if (result != NULL) {
 909     return result;
 910   }
 911 
 912   // Start full GC
 913   collect(GCCause::_metadata_GC_clear_soft_refs);
 914 
 915   // Retry allocation
 916   result = loader_data->metaspace_non_null()->allocate(size, mdtype);
 917   if (result != NULL) {
 918     return result;
 919   }
 920 
 921   // Expand and retry allocation
 922   result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
 923   if (result != NULL) {
 924     return result;
 925   }
 926 
 927   // Out of memory
 928   return NULL;
 929 }
 930 
 931 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
 932 private:
 933   ShenandoahHeap* const _heap;
 934   Thread* const _thread;
 935 public:
 936   ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
 937     _heap(heap), _thread(Thread::current()) {}
 938 
 939   void do_object(oop p) {
 940     shenandoah_assert_marked(NULL, p);
 941     if (!p->is_forwarded()) {
 942       _heap->evacuate_object(p, _thread);
 943     }
 944   }
 945 };
 946 
 947 class ShenandoahEvacuationTask : public AbstractGangTask {
 948 private:
 949   ShenandoahHeap* const _sh;
 950   ShenandoahCollectionSet* const _cs;
 951   bool _concurrent;
 952 public:
 953   ShenandoahEvacuationTask(ShenandoahHeap* sh,
 954                            ShenandoahCollectionSet* cs,
 955                            bool concurrent) :
 956     AbstractGangTask("Parallel Evacuation Task"),
 957     _sh(sh),
 958     _cs(cs),
 959     _concurrent(concurrent)
 960   {}
 961 
 962   void work(uint worker_id) {
 963     if (_concurrent) {
 964       ShenandoahConcurrentWorkerSession worker_session(worker_id);
 965       ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
 966       ShenandoahEvacOOMScope oom_evac_scope;
 967       do_work();
 968     } else {
 969       ShenandoahParallelWorkerSession worker_session(worker_id);
 970       ShenandoahEvacOOMScope oom_evac_scope;
 971       do_work();
 972     }
 973   }
 974 
 975 private:
 976   void do_work() {
 977     ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
 978     ShenandoahHeapRegion* r;
 979     while ((r =_cs->claim_next()) != NULL) {
 980       assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
 981       _sh->marked_object_iterate(r, &cl);
 982 
 983       if (ShenandoahPacing) {
 984         _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
 985       }
 986 
 987       if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
 988         break;
 989       }
 990     }
 991   }
 992 };
 993 
 994 void ShenandoahHeap::trash_cset_regions() {
 995   ShenandoahHeapLocker locker(lock());
 996 
 997   ShenandoahCollectionSet* set = collection_set();
 998   ShenandoahHeapRegion* r;
 999   set->clear_current_index();
1000   while ((r = set->next()) != NULL) {
1001     r->make_trash();
1002   }
1003   collection_set()->clear();
1004 }
1005 
1006 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1007   st->print_cr("Heap Regions:");
1008   st->print_cr("EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HC=humongous continuation, CS=collection set, T=trash, P=pinned");
1009   st->print_cr("BTE=bottom/top/end, U=used, T=TLAB allocs, G=GCLAB allocs, S=shared allocs, L=live data");
1010   st->print_cr("R=root, CP=critical pins, TAMS=top-at-mark-start, UWM=update watermark");
1011   st->print_cr("SN=alloc sequence number");
1012 
1013   for (size_t i = 0; i < num_regions(); i++) {
1014     get_region(i)->print_on(st);
1015   }
1016 }
1017 
1018 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1019   assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1020 
1021   oop humongous_obj = oop(start->bottom());
1022   size_t size = humongous_obj->size();
1023   size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1024   size_t index = start->index() + required_regions - 1;
1025 
1026   assert(!start->has_live(), "liveness must be zero");
1027 
1028   for(size_t i = 0; i < required_regions; i++) {
1029     // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1030     // as it expects that every region belongs to a humongous region starting with a humongous start region.
1031     ShenandoahHeapRegion* region = get_region(index --);
1032 
1033     assert(region->is_humongous(), "expect correct humongous start or continuation");
1034     assert(!region->is_cset(), "Humongous region should not be in collection set");
1035 
1036     region->make_trash_immediate();
1037   }
1038 }
1039 
1040 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1041 public:
1042   void do_thread(Thread* thread) {
1043     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1044     assert(gclab != NULL, "GCLAB should be initialized for %s", thread->name());
1045     gclab->retire();
1046   }
1047 };
1048 
1049 void ShenandoahHeap::make_parsable(bool retire_tlabs) {
1050   if (UseTLAB) {
1051     CollectedHeap::ensure_parsability(retire_tlabs);
1052   }
1053   ShenandoahRetireGCLABClosure cl;
1054   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1055     cl.do_thread(t);
1056   }
1057   workers()->threads_do(&cl);
1058 }
1059 
1060 void ShenandoahHeap::resize_tlabs() {
1061   CollectedHeap::resize_all_tlabs();
1062 }
1063 
1064 void ShenandoahHeap::accumulate_statistics_tlabs() {
1065   CollectedHeap::accumulate_statistics_all_tlabs();
1066 }
1067 
1068 class ShenandoahEvacuateUpdateRootsTask : public AbstractGangTask {
1069 private:
1070   ShenandoahRootEvacuator* _rp;
1071 
1072 public:
1073   ShenandoahEvacuateUpdateRootsTask(ShenandoahRootEvacuator* rp) :
1074     AbstractGangTask("Shenandoah evacuate and update roots"),
1075     _rp(rp) {}
1076 
1077   void work(uint worker_id) {
1078     ShenandoahParallelWorkerSession worker_session(worker_id);
1079     ShenandoahEvacOOMScope oom_evac_scope;
1080     ShenandoahEvacuateUpdateRootsClosure cl;
1081     MarkingCodeBlobClosure blobsCl(&cl, CodeBlobToOopClosure::FixRelocations);
1082     _rp->roots_do(worker_id, &cl);
1083   }
1084 };
1085 
1086 void ShenandoahHeap::evacuate_and_update_roots() {
1087 #if COMPILER2_OR_JVMCI
1088   DerivedPointerTable::clear();
1089 #endif
1090   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only iterate roots while world is stopped");
1091 
1092   {
1093     ShenandoahRootEvacuator rp(workers()->active_workers(), ShenandoahPhaseTimings::init_evac);
1094     ShenandoahEvacuateUpdateRootsTask roots_task(&rp);
1095     workers()->run_task(&roots_task);
1096   }
1097 
1098 #if COMPILER2_OR_JVMCI
1099   DerivedPointerTable::update_pointers();
1100 #endif
1101 }
1102 
1103 // Returns size in bytes
1104 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1105   if (ShenandoahElasticTLAB) {
1106     // With Elastic TLABs, return the max allowed size, and let the allocation path
1107     // figure out the safe size for current allocation.
1108     return ShenandoahHeapRegion::max_tlab_size_bytes();
1109   } else {
1110     return MIN2(_free_set->unsafe_peek_free(), ShenandoahHeapRegion::max_tlab_size_bytes());
1111   }
1112 }
1113 
1114 size_t ShenandoahHeap::max_tlab_size() const {
1115   // Returns size in words
1116   return ShenandoahHeapRegion::max_tlab_size_words();
1117 }
1118 
1119 class ShenandoahRetireAndResetGCLABClosure : public ThreadClosure {
1120 public:
1121   void do_thread(Thread* thread) {
1122     PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1123     gclab->retire();
1124     if (ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1125       ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1126     }
1127   }
1128 };
1129 
1130 void ShenandoahHeap::retire_and_reset_gclabs() {
1131   ShenandoahRetireAndResetGCLABClosure cl;
1132   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1133     cl.do_thread(t);
1134   }
1135   workers()->threads_do(&cl);
1136 }
1137 
1138 void ShenandoahHeap::collect(GCCause::Cause cause) {
1139   control_thread()->request_gc(cause);
1140 }
1141 
1142 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1143   //assert(false, "Shouldn't need to do full collections");
1144 }
1145 
1146 CollectorPolicy* ShenandoahHeap::collector_policy() const {
1147   return _shenandoah_policy;
1148 }
1149 
1150 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1151   ShenandoahHeapRegion* r = heap_region_containing(addr);
1152   if (r != NULL) {
1153     return r->block_start(addr);
1154   }
1155   return NULL;
1156 }
1157 
1158 size_t ShenandoahHeap::block_size(const HeapWord* addr) const {
1159   ShenandoahHeapRegion* r = heap_region_containing(addr);
1160   return r->block_size(addr);
1161 }
1162 
1163 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1164   ShenandoahHeapRegion* r = heap_region_containing(addr);
1165   return r->block_is_obj(addr);
1166 }
1167 
1168 jlong ShenandoahHeap::millis_since_last_gc() {
1169   double v = heuristics()->time_since_last_gc() * 1000;
1170   assert(0 <= v && v <= max_jlong, "value should fit: %f", v);
1171   return (jlong)v;
1172 }
1173 
1174 void ShenandoahHeap::prepare_for_verify() {
1175   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
1176     make_parsable(false);
1177   }
1178 }
1179 
1180 void ShenandoahHeap::print_gc_threads_on(outputStream* st) const {
1181   workers()->print_worker_threads_on(st);
1182   if (ShenandoahStringDedup::is_enabled()) {
1183     ShenandoahStringDedup::print_worker_threads_on(st);
1184   }
1185 }
1186 
1187 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1188   workers()->threads_do(tcl);
1189   if (_safepoint_workers != NULL) {
1190     _safepoint_workers->threads_do(tcl);
1191   }
1192   if (ShenandoahStringDedup::is_enabled()) {
1193     ShenandoahStringDedup::threads_do(tcl);
1194   }
1195 }
1196 
1197 void ShenandoahHeap::print_tracing_info() const {
1198   LogTarget(Info, gc, stats) lt;
1199   if (lt.is_enabled()) {
1200     ResourceMark rm;
1201     LogStream ls(lt);
1202 
1203     phase_timings()->print_global_on(&ls);
1204 
1205     ls.cr();
1206     ls.cr();
1207 
1208     shenandoah_policy()->print_gc_stats(&ls);
1209 
1210     ls.cr();
1211     ls.cr();
1212 
1213     if (ShenandoahPacing) {
1214       pacer()->print_on(&ls);
1215     }
1216 
1217     ls.cr();
1218     ls.cr();
1219   }
1220 }
1221 
1222 void ShenandoahHeap::verify(VerifyOption vo) {
1223   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1224     if (ShenandoahVerify) {
1225       verifier()->verify_generic(vo);
1226     } else {
1227       // TODO: Consider allocating verification bitmaps on demand,
1228       // and turn this on unconditionally.
1229     }
1230   }
1231 }
1232 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1233   return _free_set->capacity();
1234 }
1235 
1236 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1237 private:
1238   MarkBitMap* _bitmap;
1239   Stack<oop,mtGC>* _oop_stack;
1240   ShenandoahHeap* const _heap;
1241   ShenandoahMarkingContext* const _marking_context;
1242 
1243   template <class T>
1244   void do_oop_work(T* p) {
1245     T o = RawAccess<>::oop_load(p);
1246     if (!CompressedOops::is_null(o)) {
1247       oop obj = CompressedOops::decode_not_null(o);
1248       obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
1249 
1250       assert(oopDesc::is_oop(obj), "must be a valid oop");
1251       if (!_bitmap->isMarked((HeapWord*) obj)) {
1252         _bitmap->mark((HeapWord*) obj);
1253         _oop_stack->push(obj);
1254       }
1255     }
1256   }
1257 public:
1258   ObjectIterateScanRootClosure(MarkBitMap* bitmap, Stack<oop,mtGC>* oop_stack) :
1259     _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1260     _marking_context(_heap->marking_context()) {}
1261   void do_oop(oop* p)       { do_oop_work(p); }
1262   void do_oop(narrowOop* p) { do_oop_work(p); }
1263 };
1264 
1265 /*
1266  * This is public API, used in preparation of object_iterate().
1267  * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1268  * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1269  * control, we call SH::make_tlabs_parsable().
1270  */
1271 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1272   // No-op.
1273 }
1274 
1275 /*
1276  * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1277  *
1278  * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1279  * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1280  * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1281  * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1282  * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1283  * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1284  * wiped the bitmap in preparation for next marking).
1285  *
1286  * For all those reasons, we implement object iteration as a single marking traversal, reporting
1287  * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1288  * is allowed to report dead objects, but is not required to do so.
1289  */
1290 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1291   assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1292   if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1293     log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1294     return;
1295   }
1296 
1297   // Reset bitmap
1298   _aux_bit_map.clear();
1299 
1300   Stack<oop,mtGC> oop_stack;
1301 
1302   ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1303 
1304   {
1305     // First, we process GC roots according to current GC cycle.
1306     // This populates the work stack with initial objects.
1307     // It is important to relinquish the associated locks before diving
1308     // into heap dumper.
1309     ShenandoahHeapIterationRootScanner rp;
1310     rp.roots_do(&oops);
1311   }
1312 
1313   // Work through the oop stack to traverse heap.
1314   while (! oop_stack.is_empty()) {
1315     oop obj = oop_stack.pop();
1316     assert(oopDesc::is_oop(obj), "must be a valid oop");
1317     cl->do_object(obj);
1318     obj->oop_iterate(&oops);
1319   }
1320 
1321   assert(oop_stack.is_empty(), "should be empty");
1322 
1323   if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1324     log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1325   }
1326 }
1327 
1328 void ShenandoahHeap::safe_object_iterate(ObjectClosure* cl) {
1329   assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1330   object_iterate(cl);
1331 }
1332 
1333 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1334   for (size_t i = 0; i < num_regions(); i++) {
1335     ShenandoahHeapRegion* current = get_region(i);
1336     blk->heap_region_do(current);
1337   }
1338 }
1339 
1340 class ShenandoahParallelHeapRegionTask : public AbstractGangTask {
1341 private:
1342   ShenandoahHeap* const _heap;
1343   ShenandoahHeapRegionClosure* const _blk;
1344 
1345   shenandoah_padding(0);
1346   volatile size_t _index;
1347   shenandoah_padding(1);
1348 
1349 public:
1350   ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1351           AbstractGangTask("Parallel Region Task"),
1352           _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1353 
1354   void work(uint worker_id) {
1355     size_t stride = ShenandoahParallelRegionStride;
1356 
1357     size_t max = _heap->num_regions();
1358     while (_index < max) {
1359       size_t cur = Atomic::add(stride, &_index) - stride;
1360       size_t start = cur;
1361       size_t end = MIN2(cur + stride, max);
1362       if (start >= max) break;
1363 
1364       for (size_t i = cur; i < end; i++) {
1365         ShenandoahHeapRegion* current = _heap->get_region(i);
1366         _blk->heap_region_do(current);
1367       }
1368     }
1369   }
1370 };
1371 
1372 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1373   assert(blk->is_thread_safe(), "Only thread-safe closures here");
1374   if (num_regions() > ShenandoahParallelRegionStride) {
1375     ShenandoahParallelHeapRegionTask task(blk);
1376     workers()->run_task(&task);
1377   } else {
1378     heap_region_iterate(blk);
1379   }
1380 }
1381 
1382 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1383 private:
1384   ShenandoahMarkingContext* const _ctx;
1385 public:
1386   ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1387 
1388   void heap_region_do(ShenandoahHeapRegion* r) {
1389     assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1390     if (r->is_active()) {
1391       // Check if region needs updating its TAMS. We have updated it already during concurrent
1392       // reset, so it is very likely we don't need to do another write here.
1393       if (_ctx->top_at_mark_start(r) != r->top()) {
1394         _ctx->capture_top_at_mark_start(r);
1395       }
1396     } else {
1397       assert(_ctx->top_at_mark_start(r) == r->top(),
1398              "Region " SIZE_FORMAT " should already have correct TAMS", r->index());
1399     }
1400   }
1401 
1402   bool is_thread_safe() { return true; }
1403 };
1404 
1405 void ShenandoahHeap::op_init_mark() {
1406   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
1407   assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
1408 
1409   assert(marking_context()->is_bitmap_clear(), "need clear marking bitmap");
1410   assert(!marking_context()->is_complete(), "should not be complete");
1411   assert(!has_forwarded_objects(), "No forwarded objects on this path");
1412 
1413   if (ShenandoahVerify) {
1414     verifier()->verify_before_concmark();
1415   }
1416 
1417   {
1418     ShenandoahGCPhase phase(ShenandoahPhaseTimings::accumulate_stats);
1419     accumulate_statistics_tlabs();
1420   }
1421 
1422   if (VerifyBeforeGC) {
1423     Universe::verify();
1424   }
1425 
1426   set_concurrent_mark_in_progress(true);
1427   // We need to reset all TLABs because we'd lose marks on all objects allocated in them.
1428   {
1429     ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::make_parsable);
1430     make_parsable(true);
1431   }
1432 
1433   {
1434     ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::init_update_region_states);
1435     ShenandoahInitMarkUpdateRegionStateClosure cl;
1436     parallel_heap_region_iterate(&cl);
1437   }
1438 
1439   // Make above changes visible to worker threads
1440   OrderAccess::fence();
1441 
1442   concurrent_mark()->mark_roots(ShenandoahPhaseTimings::scan_roots);
1443 
1444   if (UseTLAB) {
1445     ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::resize_tlabs);
1446     resize_tlabs();
1447   }
1448 
1449   if (ShenandoahPacing) {
1450     pacer()->setup_for_mark();
1451   }
1452 }
1453 
1454 void ShenandoahHeap::op_mark() {
1455   concurrent_mark()->mark_from_roots();
1456 }
1457 
1458 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1459 private:
1460   ShenandoahMarkingContext* const _ctx;
1461   ShenandoahHeapLock* const _lock;
1462 
1463 public:
1464   ShenandoahFinalMarkUpdateRegionStateClosure() :
1465     _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1466 
1467   void heap_region_do(ShenandoahHeapRegion* r) {
1468     if (r->is_active()) {
1469       // All allocations past TAMS are implicitly live, adjust the region data.
1470       // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1471       HeapWord *tams = _ctx->top_at_mark_start(r);
1472       HeapWord *top = r->top();
1473       if (top > tams) {
1474         r->increase_live_data_alloc_words(pointer_delta(top, tams));
1475       }
1476 
1477       // We are about to select the collection set, make sure it knows about
1478       // current pinning status. Also, this allows trashing more regions that
1479       // now have their pinning status dropped.
1480       if (r->is_pinned()) {
1481         if (r->pin_count() == 0) {
1482           ShenandoahHeapLocker locker(_lock);
1483           r->make_unpinned();
1484         }
1485       } else {
1486         if (r->pin_count() > 0) {
1487           ShenandoahHeapLocker locker(_lock);
1488           r->make_pinned();
1489         }
1490       }
1491 
1492       // Remember limit for updating refs. It's guaranteed that we get no
1493       // from-space-refs written from here on.
1494       r->set_update_watermark_at_safepoint(r->top());
1495     } else {
1496       assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1497       assert(_ctx->top_at_mark_start(r) == r->top(),
1498              "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1499     }
1500   }
1501 
1502   bool is_thread_safe() { return true; }
1503 };
1504 
1505 void ShenandoahHeap::op_final_mark() {
1506   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
1507   assert(!has_forwarded_objects(), "No forwarded objects on this path");
1508 
1509   // It is critical that we
1510   // evacuate roots right after finishing marking, so that we don't
1511   // get unmarked objects in the roots.
1512 
1513   if (!cancelled_gc()) {
1514     concurrent_mark()->finish_mark_from_roots(/* full_gc = */ false);
1515 
1516     // Marking is completed, deactivate SATB barrier
1517     set_concurrent_mark_in_progress(false);
1518     mark_complete_marking_context();
1519 
1520     parallel_cleaning(false /* full gc*/);
1521 
1522     if (ShenandoahVerify) {
1523       verifier()->verify_roots_no_forwarded();
1524     }
1525 
1526     {
1527       ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::final_update_region_states);
1528       ShenandoahFinalMarkUpdateRegionStateClosure cl;
1529       parallel_heap_region_iterate(&cl);
1530 
1531       assert_pinned_region_status();
1532     }
1533 
1534     // Retire the TLABs, which will force threads to reacquire their TLABs after the pause.
1535     // This is needed for two reasons. Strong one: new allocations would be with new freeset,
1536     // which would be outside the collection set, so no cset writes would happen there.
1537     // Weaker one: new allocations would happen past update watermark, and so less work would
1538     // be needed for reference updates (would update the large filler instead).
1539     {
1540       ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::retire_tlabs);
1541       make_parsable(true);
1542     }
1543 
1544     {
1545       ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::choose_cset);
1546       ShenandoahHeapLocker locker(lock());
1547       _collection_set->clear();
1548       heuristics()->choose_collection_set(_collection_set);
1549     }
1550 
1551     {
1552       ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::final_rebuild_freeset);
1553       ShenandoahHeapLocker locker(lock());
1554       _free_set->rebuild();
1555     }
1556 
1557     // If collection set has candidates, start evacuation.
1558     // Otherwise, bypass the rest of the cycle.
1559     if (!collection_set()->is_empty()) {
1560       ShenandoahGCSubPhase init_evac(ShenandoahPhaseTimings::init_evac);
1561 
1562       if (ShenandoahVerify) {
1563         verifier()->verify_before_evacuation();
1564       }
1565 
1566       set_evacuation_in_progress(true);
1567       // From here on, we need to update references.
1568       set_has_forwarded_objects(true);
1569 
1570       if (!is_degenerated_gc_in_progress()) {
1571         evacuate_and_update_roots();
1572       }
1573 
1574       if (ShenandoahPacing) {
1575         pacer()->setup_for_evac();
1576       }
1577 
1578       if (ShenandoahVerify) {
1579         verifier()->verify_roots_no_forwarded();
1580         verifier()->verify_during_evacuation();
1581       }
1582     } else {
1583       if (ShenandoahVerify) {
1584         verifier()->verify_after_concmark();
1585       }
1586 
1587       if (VerifyAfterGC) {
1588         Universe::verify();
1589       }
1590     }
1591 
1592   } else {
1593     // If this cycle was updating references, we need to keep the has_forwarded_objects
1594     // flag on, for subsequent phases to deal with it.
1595     concurrent_mark()->cancel();
1596     set_concurrent_mark_in_progress(false);
1597 
1598     if (process_references()) {
1599       // Abandon reference processing right away: pre-cleaning must have failed.
1600       ReferenceProcessor *rp = ref_processor();
1601       rp->disable_discovery();
1602       rp->abandon_partial_discovery();
1603       rp->verify_no_references_recorded();
1604     }
1605   }
1606 }
1607 
1608 void ShenandoahHeap::op_conc_evac() {
1609   ShenandoahEvacuationTask task(this, _collection_set, true);
1610   workers()->run_task(&task);
1611 }
1612 
1613 void ShenandoahHeap::op_stw_evac() {
1614   ShenandoahEvacuationTask task(this, _collection_set, false);
1615   workers()->run_task(&task);
1616 }
1617 
1618 void ShenandoahHeap::op_updaterefs() {
1619   update_heap_references(true);
1620 }
1621 
1622 void ShenandoahHeap::op_cleanup_early() {
1623   free_set()->recycle_trash();
1624 }
1625 
1626 void ShenandoahHeap::op_cleanup_complete() {
1627   free_set()->recycle_trash();
1628 }
1629 
1630 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1631 private:
1632   ShenandoahMarkingContext* const _ctx;
1633 public:
1634   ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1635 
1636   void heap_region_do(ShenandoahHeapRegion* r) {
1637     if (r->is_active()) {
1638       // Reset live data and set TAMS optimistically. We would recheck these under the pause
1639       // anyway to capture any updates that happened since now.
1640       r->clear_live_data();
1641       _ctx->capture_top_at_mark_start(r);
1642     }
1643   }
1644 
1645   bool is_thread_safe() { return true; }
1646 };
1647 
1648 void ShenandoahHeap::op_reset() {
1649   if (ShenandoahPacing) {
1650     pacer()->setup_for_reset();
1651   }
1652   reset_mark_bitmap();
1653 
1654   ShenandoahResetUpdateRegionStateClosure cl;
1655   parallel_heap_region_iterate(&cl);
1656 }
1657 
1658 void ShenandoahHeap::op_preclean() {
1659   if (ShenandoahPacing) {
1660     pacer()->setup_for_preclean();
1661   }
1662   concurrent_mark()->preclean_weak_refs();
1663 }
1664 
1665 void ShenandoahHeap::op_full(GCCause::Cause cause) {
1666   ShenandoahMetricsSnapshot metrics;
1667   metrics.snap_before();
1668 
1669   full_gc()->do_it(cause);
1670   if (UseTLAB) {
1671     ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::full_gc_resize_tlabs);
1672     resize_all_tlabs();
1673   }
1674 
1675   metrics.snap_after();
1676 
1677   if (metrics.is_good_progress()) {
1678     _progress_last_gc.set();
1679   } else {
1680     // Nothing to do. Tell the allocation path that we have failed to make
1681     // progress, and it can finally fail.
1682     _progress_last_gc.unset();
1683   }
1684 }
1685 
1686 void ShenandoahHeap::op_degenerated(ShenandoahDegenPoint point) {
1687   // Degenerated GC is STW, but it can also fail. Current mechanics communicates
1688   // GC failure via cancelled_concgc() flag. So, if we detect the failure after
1689   // some phase, we have to upgrade the Degenerate GC to Full GC.
1690 
1691   clear_cancelled_gc();
1692 
1693   ShenandoahMetricsSnapshot metrics;
1694   metrics.snap_before();
1695 
1696   switch (point) {
1697     // The cases below form the Duff's-like device: it describes the actual GC cycle,
1698     // but enters it at different points, depending on which concurrent phase had
1699     // degenerated.
1700 
1701     case _degenerated_outside_cycle:
1702       // We have degenerated from outside the cycle, which means something is bad with
1703       // the heap, most probably heavy humongous fragmentation, or we are very low on free
1704       // space. It makes little sense to wait for Full GC to reclaim as much as it can, when
1705       // we can do the most aggressive degen cycle, which includes processing references and
1706       // class unloading, unless those features are explicitly disabled.
1707       //
1708       // Note that we can only do this for "outside-cycle" degens, otherwise we would risk
1709       // changing the cycle parameters mid-cycle during concurrent -> degenerated handover.
1710       set_process_references(heuristics()->can_process_references());
1711       set_unload_classes(heuristics()->can_unload_classes());
1712 
1713       op_reset();
1714 
1715       op_init_mark();
1716       if (cancelled_gc()) {
1717         op_degenerated_fail();
1718         return;
1719       }
1720 
1721     case _degenerated_mark:
1722       op_final_mark();
1723       if (cancelled_gc()) {
1724         op_degenerated_fail();
1725         return;
1726       }
1727 
1728       op_cleanup_early();
1729 
1730     case _degenerated_evac:
1731       // If heuristics thinks we should do the cycle, this flag would be set,
1732       // and we can do evacuation. Otherwise, it would be the shortcut cycle.
1733       if (is_evacuation_in_progress()) {
1734 
1735         // Degeneration under oom-evac protocol might have left some objects in
1736         // collection set un-evacuated. Restart evacuation from the beginning to
1737         // capture all objects. For all the objects that are already evacuated,
1738         // it would be a simple check, which is supposed to be fast. This is also
1739         // safe to do even without degeneration, as CSet iterator is at beginning
1740         // in preparation for evacuation anyway.
1741         //
1742         // Before doing that, we need to make sure we never had any cset-pinned
1743         // regions. This may happen if allocation failure happened when evacuating
1744         // the about-to-be-pinned object, oom-evac protocol left the object in
1745         // the collection set, and then the pin reached the cset region. If we continue
1746         // the cycle here, we would trash the cset and alive objects in it. To avoid
1747         // it, we fail degeneration right away and slide into Full GC to recover.
1748 
1749         {
1750           sync_pinned_region_status();
1751           collection_set()->clear_current_index();
1752 
1753           ShenandoahHeapRegion* r;
1754           while ((r = collection_set()->next()) != NULL) {
1755             if (r->is_pinned()) {
1756               cancel_gc(GCCause::_shenandoah_upgrade_to_full_gc);
1757               op_degenerated_fail();
1758               return;
1759             }
1760           }
1761 
1762           collection_set()->clear_current_index();
1763         }
1764 
1765         op_stw_evac();
1766         if (cancelled_gc()) {
1767           op_degenerated_fail();
1768           return;
1769         }
1770       }
1771 
1772       // If heuristics thinks we should do the cycle, this flag would be set,
1773       // and we need to do update-refs. Otherwise, it would be the shortcut cycle.
1774       if (has_forwarded_objects()) {
1775         op_init_updaterefs();
1776         if (cancelled_gc()) {
1777           op_degenerated_fail();
1778           return;
1779         }
1780       }
1781 
1782     case _degenerated_updaterefs:
1783       if (has_forwarded_objects()) {
1784         op_final_updaterefs();
1785         if (cancelled_gc()) {
1786           op_degenerated_fail();
1787           return;
1788         }
1789       }
1790 
1791       op_cleanup_complete();
1792       break;
1793 
1794     default:
1795       ShouldNotReachHere();
1796   }
1797 
1798   if (ShenandoahVerify) {
1799     verifier()->verify_after_degenerated();
1800   }
1801 
1802   if (VerifyAfterGC) {
1803     Universe::verify();
1804   }
1805 
1806   metrics.snap_after();
1807 
1808   // Check for futility and fail. There is no reason to do several back-to-back Degenerated cycles,
1809   // because that probably means the heap is overloaded and/or fragmented.
1810   if (!metrics.is_good_progress()) {
1811     _progress_last_gc.unset();
1812     cancel_gc(GCCause::_shenandoah_upgrade_to_full_gc);
1813     op_degenerated_futile();
1814   } else {
1815     _progress_last_gc.set();
1816   }
1817 }
1818 
1819 void ShenandoahHeap::op_degenerated_fail() {
1820   log_info(gc)("Cannot finish degeneration, upgrading to Full GC");
1821   shenandoah_policy()->record_degenerated_upgrade_to_full();
1822   op_full(GCCause::_shenandoah_upgrade_to_full_gc);
1823 }
1824 
1825 void ShenandoahHeap::op_degenerated_futile() {
1826   shenandoah_policy()->record_degenerated_upgrade_to_full();
1827   op_full(GCCause::_shenandoah_upgrade_to_full_gc);
1828 }
1829 
1830 void ShenandoahHeap::force_satb_flush_all_threads() {
1831   if (!is_concurrent_mark_in_progress()) {
1832     // No need to flush SATBs
1833     return;
1834   }
1835 
1836   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1837     ShenandoahThreadLocalData::set_force_satb_flush(t, true);
1838   }
1839   // The threads are not "acquiring" their thread-local data, but it does not
1840   // hurt to "release" the updates here anyway.
1841   OrderAccess::fence();
1842 }
1843 
1844 void ShenandoahHeap::set_gc_state_all_threads(char state) {
1845   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1846     ShenandoahThreadLocalData::set_gc_state(t, state);
1847   }
1848 }
1849 
1850 void ShenandoahHeap::set_gc_state_mask(uint mask, bool value) {
1851   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should really be Shenandoah safepoint");
1852   _gc_state.set_cond(mask, value);
1853   set_gc_state_all_threads(_gc_state.raw_value());
1854 }
1855 
1856 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
1857   if (has_forwarded_objects()) {
1858     set_gc_state_mask(MARKING | UPDATEREFS, in_progress);
1859   } else {
1860     set_gc_state_mask(MARKING, in_progress);
1861   }
1862   ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1863 }
1864 
1865 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
1866   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
1867   set_gc_state_mask(EVACUATION, in_progress);
1868 }
1869 
1870 void ShenandoahHeap::ref_processing_init() {
1871   assert(_max_workers > 0, "Sanity");
1872 
1873   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1874   bool mt_discovery = _max_workers > 1;
1875 
1876   _ref_processor =
1877     new ReferenceProcessor(&_subject_to_discovery,  // is_subject_to_discovery
1878                            mt_processing,           // MT processing
1879                            _max_workers,            // Degree of MT processing
1880                            mt_discovery,            // MT discovery
1881                            _max_workers,            // Degree of MT discovery
1882                            false,                   // Reference discovery is not atomic
1883                            NULL,                    // No closure, should be installed before use
1884                            true);                   // Scale worker threads
1885 
1886   log_info(gc, init)("Reference processing: %s discovery, %s processing",
1887           mt_discovery ? "parallel" : "serial",
1888           mt_processing ? "parallel" : "serial");
1889 
1890   shenandoah_assert_rp_isalive_not_installed();
1891 }
1892 
1893 GCTracer* ShenandoahHeap::tracer() {
1894   return shenandoah_policy()->tracer();
1895 }
1896 
1897 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
1898   return _free_set->used();
1899 }
1900 
1901 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
1902   if (try_cancel_gc()) {
1903     FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
1904     log_info(gc)("%s", msg.buffer());
1905     Events::log(Thread::current(), "%s", msg.buffer());
1906   }
1907 }
1908 
1909 uint ShenandoahHeap::max_workers() {
1910   return _max_workers;
1911 }
1912 
1913 void ShenandoahHeap::stop() {
1914   // The shutdown sequence should be able to terminate when GC is running.
1915 
1916   // Step 0. Notify policy to disable event recording.
1917   _shenandoah_policy->record_shutdown();
1918 
1919   // Step 1. Notify control thread that we are in shutdown.
1920   // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
1921   // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
1922   control_thread()->prepare_for_graceful_shutdown();
1923 
1924   // Step 2. Notify GC workers that we are cancelling GC.
1925   cancel_gc(GCCause::_shenandoah_stop_vm);
1926 
1927   // Step 3. Wait until GC worker exits normally.
1928   control_thread()->stop();
1929 
1930   // Step 4. Stop String Dedup thread if it is active
1931   if (ShenandoahStringDedup::is_enabled()) {
1932     ShenandoahStringDedup::stop();
1933   }
1934 }
1935 
1936 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
1937   if (!unload_classes()) return;
1938 
1939   // Unload classes and purge SystemDictionary.
1940   {
1941     ShenandoahGCSubPhase phase(full_gc ?
1942                                ShenandoahPhaseTimings::full_gc_purge_class_unload :
1943                                ShenandoahPhaseTimings::purge_class_unload);
1944     bool purged_class = SystemDictionary::do_unloading(gc_timer());
1945 
1946     ShenandoahIsAliveSelector is_alive;
1947     uint num_workers = _workers->active_workers();
1948     ParallelCleaningTask unlink_task(is_alive.is_alive_closure(), true, true, num_workers, purged_class);
1949     _workers->run_task(&unlink_task);
1950   }
1951 
1952   {
1953     ShenandoahGCSubPhase phase(full_gc ?
1954                                ShenandoahPhaseTimings::full_gc_purge_cldg :
1955                                ShenandoahPhaseTimings::purge_cldg);
1956     ClassLoaderDataGraph::purge();
1957   }
1958   // Resize and verify metaspace
1959   MetaspaceGC::compute_new_size();
1960   MetaspaceUtils::verify_metrics();
1961 }
1962 
1963 // Process leftover weak oops: update them, if needed or assert they do not
1964 // need updating otherwise.
1965 // Weak processor API requires us to visit the oops, even if we are not doing
1966 // anything to them.
1967 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
1968   ShenandoahGCSubPhase root_phase(full_gc ?
1969                                   ShenandoahPhaseTimings::full_gc_purge :
1970                                   ShenandoahPhaseTimings::purge);
1971   uint num_workers = _workers->active_workers();
1972   ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
1973                                                ShenandoahPhaseTimings::full_gc_purge_weak_par :
1974                                                ShenandoahPhaseTimings::purge_weak_par;
1975   ShenandoahGCSubPhase phase(timing_phase);
1976 
1977   // Cleanup weak roots
1978   if (has_forwarded_objects()) {
1979     ShenandoahForwardedIsAliveClosure is_alive;
1980     ShenandoahUpdateRefsClosure keep_alive;
1981     ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
1982       cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
1983     _workers->run_task(&cleaning_task);
1984   } else {
1985     ShenandoahIsAliveClosure is_alive;
1986 #ifdef ASSERT
1987   ShenandoahAssertNotForwardedClosure verify_cl;
1988   ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
1989     cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
1990 #else
1991   ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
1992     cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
1993 #endif
1994     _workers->run_task(&cleaning_task);
1995   }
1996 }
1997 
1998 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
1999   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2000   stw_process_weak_roots(full_gc);
2001   stw_unload_classes(full_gc);
2002 }
2003 
2004 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2005   set_gc_state_mask(HAS_FORWARDED, cond);
2006 }
2007 
2008 void ShenandoahHeap::set_process_references(bool pr) {
2009   _process_references.set_cond(pr);
2010 }
2011 
2012 void ShenandoahHeap::set_unload_classes(bool uc) {
2013   _unload_classes.set_cond(uc);
2014 }
2015 
2016 bool ShenandoahHeap::process_references() const {
2017   return _process_references.is_set();
2018 }
2019 
2020 bool ShenandoahHeap::unload_classes() const {
2021   return _unload_classes.is_set();
2022 }
2023 
2024 address ShenandoahHeap::in_cset_fast_test_addr() {
2025   ShenandoahHeap* heap = ShenandoahHeap::heap();
2026   assert(heap->collection_set() != NULL, "Sanity");
2027   return (address) heap->collection_set()->biased_map_address();
2028 }
2029 
2030 address ShenandoahHeap::cancelled_gc_addr() {
2031   return (address) ShenandoahHeap::heap()->_cancelled_gc.addr_of();
2032 }
2033 
2034 address ShenandoahHeap::gc_state_addr() {
2035   return (address) ShenandoahHeap::heap()->_gc_state.addr_of();
2036 }
2037 
2038 size_t ShenandoahHeap::bytes_allocated_since_gc_start() {
2039   return OrderAccess::load_acquire(&_bytes_allocated_since_gc_start);
2040 }
2041 
2042 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2043   OrderAccess::release_store_fence(&_bytes_allocated_since_gc_start, (size_t)0);
2044 }
2045 
2046 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2047   _degenerated_gc_in_progress.set_cond(in_progress);
2048 }
2049 
2050 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2051   _full_gc_in_progress.set_cond(in_progress);
2052 }
2053 
2054 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2055   assert (is_full_gc_in_progress(), "should be");
2056   _full_gc_move_in_progress.set_cond(in_progress);
2057 }
2058 
2059 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2060   set_gc_state_mask(UPDATEREFS, in_progress);
2061 }
2062 
2063 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2064   ShenandoahCodeRoots::add_nmethod(nm);
2065 }
2066 
2067 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2068   ShenandoahCodeRoots::remove_nmethod(nm);
2069 }
2070 
2071 oop ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2072   heap_region_containing(o)->record_pin();
2073   return o;
2074 }
2075 
2076 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2077   heap_region_containing(o)->record_unpin();
2078 }
2079 
2080 void ShenandoahHeap::sync_pinned_region_status() {
2081   ShenandoahHeapLocker locker(lock());
2082 
2083   for (size_t i = 0; i < num_regions(); i++) {
2084     ShenandoahHeapRegion *r = get_region(i);
2085     if (r->is_active()) {
2086       if (r->is_pinned()) {
2087         if (r->pin_count() == 0) {
2088           r->make_unpinned();
2089         }
2090       } else {
2091         if (r->pin_count() > 0) {
2092           r->make_pinned();
2093         }
2094       }
2095     }
2096   }
2097 
2098   assert_pinned_region_status();
2099 }
2100 
2101 #ifdef ASSERT
2102 void ShenandoahHeap::assert_pinned_region_status() {
2103   for (size_t i = 0; i < num_regions(); i++) {
2104     ShenandoahHeapRegion* r = get_region(i);
2105     assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2106            "Region " SIZE_FORMAT " pinning status is inconsistent", i);
2107   }
2108 }
2109 #endif
2110 
2111 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2112   return _gc_timer;
2113 }
2114 
2115 #ifdef ASSERT
2116 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2117   assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2118 
2119   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2120     if (UseDynamicNumberOfGCThreads ||
2121         (FLAG_IS_DEFAULT(ParallelGCThreads) && ForceDynamicNumberOfGCThreads)) {
2122       assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
2123     } else {
2124       // Use ParallelGCThreads inside safepoints
2125       assert(nworkers == ParallelGCThreads, "Use ParalleGCThreads within safepoints");
2126     }
2127   } else {
2128     if (UseDynamicNumberOfGCThreads ||
2129         (FLAG_IS_DEFAULT(ConcGCThreads) && ForceDynamicNumberOfGCThreads)) {
2130       assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
2131     } else {
2132       // Use ConcGCThreads outside safepoints
2133       assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
2134     }
2135   }
2136 }
2137 #endif
2138 
2139 ShenandoahVerifier* ShenandoahHeap::verifier() {
2140   guarantee(ShenandoahVerify, "Should be enabled");
2141   assert (_verifier != NULL, "sanity");
2142   return _verifier;
2143 }
2144 
2145 template<class T>
2146 class ShenandoahUpdateHeapRefsTask : public AbstractGangTask {
2147 private:
2148   T cl;
2149   ShenandoahHeap* _heap;
2150   ShenandoahRegionIterator* _regions;
2151   bool _concurrent;
2152 public:
2153   ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions, bool concurrent) :
2154     AbstractGangTask("Concurrent Update References Task"),
2155     cl(T()),
2156     _heap(ShenandoahHeap::heap()),
2157     _regions(regions),
2158     _concurrent(concurrent) {
2159   }
2160 
2161   void work(uint worker_id) {
2162     if (_concurrent) {
2163       ShenandoahConcurrentWorkerSession worker_session(worker_id);
2164       ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
2165       do_work();
2166     } else {
2167       ShenandoahParallelWorkerSession worker_session(worker_id);
2168       do_work();
2169     }
2170   }
2171 
2172 private:
2173   void do_work() {
2174     ShenandoahHeapRegion* r = _regions->next();
2175     ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2176     while (r != NULL) {
2177       HeapWord* update_watermark = r->get_update_watermark();
2178       assert (update_watermark >= r->bottom(), "sanity");
2179       if (r->is_active() && !r->is_cset()) {
2180         _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2181       }
2182       if (ShenandoahPacing) {
2183         _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2184       }
2185       if (_heap->check_cancelled_gc_and_yield(_concurrent)) {
2186         return;
2187       }
2188       r = _regions->next();
2189     }
2190   }
2191 };
2192 
2193 void ShenandoahHeap::update_heap_references(bool concurrent) {
2194   ShenandoahUpdateHeapRefsTask<ShenandoahUpdateHeapRefsClosure> task(&_update_refs_iterator, concurrent);
2195   workers()->run_task(&task);
2196 }
2197 
2198 void ShenandoahHeap::op_init_updaterefs() {
2199   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2200 
2201   set_evacuation_in_progress(false);
2202 
2203   {
2204     ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::init_update_refs_retire_gclabs);
2205     retire_and_reset_gclabs();
2206   }
2207 
2208   if (ShenandoahVerify) {
2209     if (!is_degenerated_gc_in_progress()) {
2210       verifier()->verify_roots_no_forwarded_except(ShenandoahRootVerifier::ThreadRoots);
2211     }
2212     verifier()->verify_before_updaterefs();
2213   }
2214 
2215   set_update_refs_in_progress(true);
2216 
2217   _update_refs_iterator.reset();
2218 
2219   if (ShenandoahPacing) {
2220     pacer()->setup_for_updaterefs();
2221   }
2222 }
2223 
2224 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2225 private:
2226   ShenandoahHeapLock* const _lock;
2227 
2228 public:
2229   ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2230 
2231   void heap_region_do(ShenandoahHeapRegion* r) {
2232     // Drop unnecessary "pinned" state from regions that does not have CP marks
2233     // anymore, as this would allow trashing them.
2234 
2235     if (r->is_active()) {
2236       if (r->is_pinned()) {
2237         if (r->pin_count() == 0) {
2238           ShenandoahHeapLocker locker(_lock);
2239           r->make_unpinned();
2240         }
2241       } else {
2242         if (r->pin_count() > 0) {
2243           ShenandoahHeapLocker locker(_lock);
2244           r->make_pinned();
2245         }
2246       }
2247     }
2248   }
2249 
2250   bool is_thread_safe() { return true; }
2251 };
2252 
2253 void ShenandoahHeap::op_final_updaterefs() {
2254   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2255 
2256   // Check if there is left-over work, and finish it
2257   if (_update_refs_iterator.has_next()) {
2258     ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::final_update_refs_finish_work);
2259 
2260     // Finish updating references where we left off.
2261     clear_cancelled_gc();
2262     update_heap_references(false);
2263   }
2264 
2265   // Clear cancelled GC, if set. On cancellation path, the block before would handle
2266   // everything. On degenerated paths, cancelled gc would not be set anyway.
2267   if (cancelled_gc()) {
2268     clear_cancelled_gc();
2269   }
2270   assert(!cancelled_gc(), "Should have been done right before");
2271 
2272   if (ShenandoahVerify && !is_degenerated_gc_in_progress()) {
2273     verifier()->verify_roots_no_forwarded_except(ShenandoahRootVerifier::ThreadRoots);
2274   }
2275 
2276   if (is_degenerated_gc_in_progress()) {
2277     concurrent_mark()->update_roots(ShenandoahPhaseTimings::degen_gc_update_roots);
2278   } else {
2279     concurrent_mark()->update_thread_roots(ShenandoahPhaseTimings::final_update_refs_roots);
2280   }
2281 
2282   // Has to be done before cset is clear
2283   if (ShenandoahVerify) {
2284     verifier()->verify_roots_in_to_space();
2285   }
2286 
2287   {
2288     ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::final_update_refs_update_region_states);
2289     ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2290     parallel_heap_region_iterate(&cl);
2291 
2292     assert_pinned_region_status();
2293   }
2294 
2295   {
2296     ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::final_update_refs_trash_cset);
2297     trash_cset_regions();
2298   }
2299 
2300   set_has_forwarded_objects(false);
2301   set_update_refs_in_progress(false);
2302 
2303   if (ShenandoahVerify) {
2304     verifier()->verify_after_updaterefs();
2305   }
2306 
2307   if (VerifyAfterGC) {
2308     Universe::verify();
2309   }
2310 
2311   {
2312     ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::final_update_refs_rebuild_freeset);
2313     ShenandoahHeapLocker locker(lock());
2314     _free_set->rebuild();
2315   }
2316 }
2317 
2318 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2319   print_on(st);
2320   print_heap_regions_on(st);
2321 }
2322 
2323 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2324   size_t slice = r->index() / _bitmap_regions_per_slice;
2325 
2326   size_t regions_from = _bitmap_regions_per_slice * slice;
2327   size_t regions_to   = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2328   for (size_t g = regions_from; g < regions_to; g++) {
2329     assert (g / _bitmap_regions_per_slice == slice, "same slice");
2330     if (skip_self && g == r->index()) continue;
2331     if (get_region(g)->is_committed()) {
2332       return true;
2333     }
2334   }
2335   return false;
2336 }
2337 
2338 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2339   shenandoah_assert_heaplocked();
2340 
2341   // Bitmaps in special regions do not need commits
2342   if (_bitmap_region_special) {
2343     return true;
2344   }
2345 
2346   if (is_bitmap_slice_committed(r, true)) {
2347     // Some other region from the group is already committed, meaning the bitmap
2348     // slice is already committed, we exit right away.
2349     return true;
2350   }
2351 
2352   // Commit the bitmap slice:
2353   size_t slice = r->index() / _bitmap_regions_per_slice;
2354   size_t off = _bitmap_bytes_per_slice * slice;
2355   size_t len = _bitmap_bytes_per_slice;
2356   char* start = (char*) _bitmap_region.start() + off;
2357 
2358   if (!os::commit_memory(start, len, false)) {
2359     return false;
2360   }
2361 
2362   if (AlwaysPreTouch) {
2363     os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2364   }
2365 
2366   return true;
2367 }
2368 
2369 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2370   shenandoah_assert_heaplocked();
2371 
2372   // Bitmaps in special regions do not need uncommits
2373   if (_bitmap_region_special) {
2374     return true;
2375   }
2376 
2377   if (is_bitmap_slice_committed(r, true)) {
2378     // Some other region from the group is still committed, meaning the bitmap
2379     // slice is should stay committed, exit right away.
2380     return true;
2381   }
2382 
2383   // Uncommit the bitmap slice:
2384   size_t slice = r->index() / _bitmap_regions_per_slice;
2385   size_t off = _bitmap_bytes_per_slice * slice;
2386   size_t len = _bitmap_bytes_per_slice;
2387   if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2388     return false;
2389   }
2390   return true;
2391 }
2392 
2393 void ShenandoahHeap::safepoint_synchronize_begin() {
2394   if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2395     SuspendibleThreadSet::synchronize();
2396   }
2397 }
2398 
2399 void ShenandoahHeap::safepoint_synchronize_end() {
2400   if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2401     SuspendibleThreadSet::desynchronize();
2402   }
2403 }
2404 
2405 void ShenandoahHeap::vmop_entry_init_mark() {
2406   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2407   ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_mark_gross);
2408 
2409   try_inject_alloc_failure();
2410   VM_ShenandoahInitMark op;
2411   VMThread::execute(&op); // jump to entry_init_mark() under safepoint
2412 }
2413 
2414 void ShenandoahHeap::vmop_entry_final_mark() {
2415   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2416   ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_mark_gross);
2417 
2418   try_inject_alloc_failure();
2419   VM_ShenandoahFinalMarkStartEvac op;
2420   VMThread::execute(&op); // jump to entry_final_mark under safepoint
2421 }
2422 
2423 void ShenandoahHeap::vmop_entry_init_updaterefs() {
2424   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2425   ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_refs_gross);
2426 
2427   try_inject_alloc_failure();
2428   VM_ShenandoahInitUpdateRefs op;
2429   VMThread::execute(&op);
2430 }
2431 
2432 void ShenandoahHeap::vmop_entry_final_updaterefs() {
2433   TraceCollectorStats tcs(monitoring_support()->stw_collection_counters());
2434   ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_refs_gross);
2435 
2436   try_inject_alloc_failure();
2437   VM_ShenandoahFinalUpdateRefs op;
2438   VMThread::execute(&op);
2439 }
2440 
2441 void ShenandoahHeap::vmop_entry_full(GCCause::Cause cause) {
2442   TraceCollectorStats tcs(monitoring_support()->full_stw_collection_counters());
2443   ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_gross);
2444 
2445   try_inject_alloc_failure();
2446   VM_ShenandoahFullGC op(cause);
2447   VMThread::execute(&op);
2448 }
2449 
2450 void ShenandoahHeap::vmop_degenerated(ShenandoahDegenPoint point) {
2451   TraceCollectorStats tcs(monitoring_support()->full_stw_collection_counters());
2452   ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_gross);
2453 
2454   VM_ShenandoahDegeneratedGC degenerated_gc((int)point);
2455   VMThread::execute(&degenerated_gc);
2456 }
2457 
2458 void ShenandoahHeap::entry_init_mark() {
2459   const char* msg = init_mark_event_message();
2460   ShenandoahPausePhase gc_phase(msg);
2461   EventMark em("%s", msg);
2462 
2463   ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_mark);
2464 
2465   ShenandoahWorkerScope scope(workers(),
2466                               ShenandoahWorkerPolicy::calc_workers_for_init_marking(),
2467                               "init marking");
2468 
2469   op_init_mark();
2470 }
2471 
2472 void ShenandoahHeap::entry_final_mark() {
2473   const char* msg = final_mark_event_message();
2474   ShenandoahPausePhase gc_phase(msg);
2475   EventMark em("%s", msg);
2476 
2477   ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_mark);
2478 
2479   ShenandoahWorkerScope scope(workers(),
2480                               ShenandoahWorkerPolicy::calc_workers_for_final_marking(),
2481                               "final marking");
2482 
2483   op_final_mark();
2484 }
2485 
2486 void ShenandoahHeap::entry_init_updaterefs() {
2487   static const char* msg = "Pause Init Update Refs";
2488   ShenandoahPausePhase gc_phase(msg);
2489   EventMark em("%s", msg);
2490 
2491   ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_refs);
2492 
2493   // No workers used in this phase, no setup required
2494 
2495   op_init_updaterefs();
2496 }
2497 
2498 void ShenandoahHeap::entry_final_updaterefs() {
2499   static const char* msg = "Pause Final Update Refs";
2500   ShenandoahPausePhase gc_phase(msg);
2501   EventMark em("%s", msg);
2502 
2503   ShenandoahGCPhase phase(ShenandoahPhaseTimings::final_update_refs);
2504 
2505   ShenandoahWorkerScope scope(workers(),
2506                               ShenandoahWorkerPolicy::calc_workers_for_final_update_ref(),
2507                               "final reference update");
2508 
2509   op_final_updaterefs();
2510 }
2511 
2512 void ShenandoahHeap::entry_full(GCCause::Cause cause) {
2513   static const char* msg = "Pause Full";
2514   ShenandoahPausePhase gc_phase(msg, true /* log_heap_usage */);
2515   EventMark em("%s", msg);
2516 
2517   ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc);
2518 
2519   ShenandoahWorkerScope scope(workers(),
2520                               ShenandoahWorkerPolicy::calc_workers_for_fullgc(),
2521                               "full gc");
2522 
2523   op_full(cause);
2524 }
2525 
2526 void ShenandoahHeap::entry_degenerated(int point) {
2527   ShenandoahDegenPoint dpoint = (ShenandoahDegenPoint)point;
2528   const char* msg = degen_event_message(dpoint);
2529   ShenandoahPausePhase gc_phase(msg, true /* log_heap_usage */);
2530   EventMark em("%s", msg);
2531 
2532   ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc);
2533 
2534   ShenandoahWorkerScope scope(workers(),
2535                               ShenandoahWorkerPolicy::calc_workers_for_stw_degenerated(),
2536                               "stw degenerated gc");
2537 
2538   set_degenerated_gc_in_progress(true);
2539   op_degenerated(dpoint);
2540   set_degenerated_gc_in_progress(false);
2541 }
2542 
2543 void ShenandoahHeap::entry_mark() {
2544   TraceCollectorStats tcs(monitoring_support()->concurrent_collection_counters());
2545 
2546   const char* msg = conc_mark_event_message();
2547   ShenandoahConcurrentPhase gc_phase(msg);
2548   EventMark em("%s", msg);
2549 
2550   ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
2551 
2552   ShenandoahWorkerScope scope(workers(),
2553                               ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
2554                               "concurrent marking");
2555 
2556   try_inject_alloc_failure();
2557   op_mark();
2558 }
2559 
2560 void ShenandoahHeap::entry_evac() {
2561   TraceCollectorStats tcs(monitoring_support()->concurrent_collection_counters());
2562 
2563   static const char* msg = "Concurrent evacuation";
2564   ShenandoahConcurrentPhase gc_phase(msg);
2565   EventMark em("%s", msg);
2566 
2567   ShenandoahGCPhase conc_evac_phase(ShenandoahPhaseTimings::conc_evac);
2568 
2569   ShenandoahWorkerScope scope(workers(),
2570                               ShenandoahWorkerPolicy::calc_workers_for_conc_evac(),
2571                               "concurrent evacuation");
2572 
2573   try_inject_alloc_failure();
2574   op_conc_evac();
2575 }
2576 
2577 void ShenandoahHeap::entry_updaterefs() {
2578   static const char* msg = "Concurrent update references";
2579   ShenandoahConcurrentPhase gc_phase(msg);
2580   EventMark em("%s", msg);
2581 
2582   ShenandoahGCPhase phase(ShenandoahPhaseTimings::conc_update_refs);
2583 
2584   ShenandoahWorkerScope scope(workers(),
2585                               ShenandoahWorkerPolicy::calc_workers_for_conc_update_ref(),
2586                               "concurrent reference update");
2587 
2588   try_inject_alloc_failure();
2589   op_updaterefs();
2590 }
2591 
2592 void ShenandoahHeap::entry_cleanup_early() {
2593   static const char* msg = "Concurrent cleanup";
2594   ShenandoahConcurrentPhase gc_phase(msg,  true /* log_heap_usage */);
2595   EventMark em("%s", msg);
2596 
2597   ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::conc_cleanup_early);
2598 
2599   // This phase does not use workers, no need for setup
2600 
2601   try_inject_alloc_failure();
2602   op_cleanup_early();
2603 }
2604 
2605 void ShenandoahHeap::entry_cleanup_complete() {
2606   static const char* msg = "Concurrent cleanup";
2607   ShenandoahConcurrentPhase gc_phase(msg,  true /* log_heap_usage */);
2608   EventMark em("%s", msg);
2609 
2610   ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::conc_cleanup_complete);
2611 
2612   // This phase does not use workers, no need for setup
2613 
2614   try_inject_alloc_failure();
2615   op_cleanup_complete();
2616 }
2617 
2618 void ShenandoahHeap::entry_reset() {
2619   static const char* msg = "Concurrent reset";
2620   ShenandoahConcurrentPhase gc_phase(msg);
2621   EventMark em("%s", msg);
2622 
2623   ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::conc_reset);
2624 
2625   ShenandoahWorkerScope scope(workers(),
2626                               ShenandoahWorkerPolicy::calc_workers_for_conc_reset(),
2627                               "concurrent reset");
2628 
2629   try_inject_alloc_failure();
2630   op_reset();
2631 }
2632 
2633 void ShenandoahHeap::entry_preclean() {
2634   if (ShenandoahPreclean && process_references()) {
2635     static const char* msg = "Concurrent precleaning";
2636     ShenandoahConcurrentPhase gc_phase(msg);
2637     EventMark em("%s", msg);
2638 
2639     ShenandoahGCSubPhase conc_preclean(ShenandoahPhaseTimings::conc_preclean);
2640 
2641     ShenandoahWorkerScope scope(workers(),
2642                                 ShenandoahWorkerPolicy::calc_workers_for_conc_preclean(),
2643                                 "concurrent preclean",
2644                                 /* check_workers = */ false);
2645 
2646     try_inject_alloc_failure();
2647     op_preclean();
2648   }
2649 }
2650 
2651 void ShenandoahHeap::entry_uncommit(double shrink_before) {
2652   static const char *msg = "Concurrent uncommit";
2653   ShenandoahConcurrentPhase gc_phase(msg, true /* log_heap_usage */);
2654   EventMark em("%s", msg);
2655 
2656   ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::conc_uncommit);
2657 
2658   op_uncommit(shrink_before);
2659 }
2660 
2661 void ShenandoahHeap::try_inject_alloc_failure() {
2662   if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2663     _inject_alloc_failure.set();
2664     os::naked_short_sleep(1);
2665     if (cancelled_gc()) {
2666       log_info(gc)("Allocation failure was successfully injected");
2667     }
2668   }
2669 }
2670 
2671 bool ShenandoahHeap::should_inject_alloc_failure() {
2672   return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2673 }
2674 
2675 void ShenandoahHeap::initialize_serviceability() {
2676   _memory_pool = new ShenandoahMemoryPool(this);
2677   _cycle_memory_manager.add_pool(_memory_pool);
2678   _stw_memory_manager.add_pool(_memory_pool);
2679 }
2680 
2681 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2682   GrowableArray<GCMemoryManager*> memory_managers(2);
2683   memory_managers.append(&_cycle_memory_manager);
2684   memory_managers.append(&_stw_memory_manager);
2685   return memory_managers;
2686 }
2687 
2688 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2689   GrowableArray<MemoryPool*> memory_pools(1);
2690   memory_pools.append(_memory_pool);
2691   return memory_pools;
2692 }
2693 
2694 MemoryUsage ShenandoahHeap::memory_usage() {
2695   return _memory_pool->get_memory_usage();
2696 }
2697 
2698 void ShenandoahHeap::enter_evacuation() {
2699   _oom_evac_handler.enter_evacuation();
2700 }
2701 
2702 void ShenandoahHeap::leave_evacuation() {
2703   _oom_evac_handler.leave_evacuation();
2704 }
2705 
2706 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2707   _heap(ShenandoahHeap::heap()),
2708   _index(0) {}
2709 
2710 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2711   _heap(heap),
2712   _index(0) {}
2713 
2714 void ShenandoahRegionIterator::reset() {
2715   _index = 0;
2716 }
2717 
2718 bool ShenandoahRegionIterator::has_next() const {
2719   return _index < _heap->num_regions();
2720 }
2721 
2722 char ShenandoahHeap::gc_state() const {
2723   return _gc_state.raw_value();
2724 }
2725 
2726 void ShenandoahHeap::deduplicate_string(oop str) {
2727   assert(java_lang_String::is_instance(str), "invariant");
2728 
2729   if (ShenandoahStringDedup::is_enabled()) {
2730     ShenandoahStringDedup::deduplicate(str);
2731   }
2732 }
2733 
2734 const char* ShenandoahHeap::init_mark_event_message() const {
2735   assert(!has_forwarded_objects(), "Should not have forwarded objects here");
2736 
2737   bool proc_refs = process_references();
2738   bool unload_cls = unload_classes();
2739 
2740   if (proc_refs && unload_cls) {
2741     return "Pause Init Mark (process weakrefs) (unload classes)";
2742   } else if (proc_refs) {
2743     return "Pause Init Mark (process weakrefs)";
2744   } else if (unload_cls) {
2745     return "Pause Init Mark (unload classes)";
2746   } else {
2747     return "Pause Init Mark";
2748   }
2749 }
2750 
2751 const char* ShenandoahHeap::final_mark_event_message() const {
2752   assert(!has_forwarded_objects(), "Should not have forwarded objects here");
2753 
2754   bool proc_refs = process_references();
2755   bool unload_cls = unload_classes();
2756 
2757   if (proc_refs && unload_cls) {
2758     return "Pause Final Mark (process weakrefs) (unload classes)";
2759   } else if (proc_refs) {
2760     return "Pause Final Mark (process weakrefs)";
2761   } else if (unload_cls) {
2762     return "Pause Final Mark (unload classes)";
2763   } else {
2764     return "Pause Final Mark";
2765   }
2766 }
2767 
2768 const char* ShenandoahHeap::conc_mark_event_message() const {
2769   assert(!has_forwarded_objects(), "Should not have forwarded objects here");
2770 
2771   bool proc_refs = process_references();
2772   bool unload_cls = unload_classes();
2773 
2774   if (proc_refs && unload_cls) {
2775     return "Concurrent marking (process weakrefs) (unload classes)";
2776   } else if (proc_refs) {
2777     return "Concurrent marking (process weakrefs)";
2778   } else if (unload_cls) {
2779     return "Concurrent marking (unload classes)";
2780   } else {
2781     return "Concurrent marking";
2782   }
2783 }
2784 
2785 const char* ShenandoahHeap::degen_event_message(ShenandoahDegenPoint point) const {
2786   switch (point) {
2787     case _degenerated_unset:
2788       return "Pause Degenerated GC (<UNSET>)";
2789     case _degenerated_outside_cycle:
2790       return "Pause Degenerated GC (Outside of Cycle)";
2791     case _degenerated_mark:
2792       return "Pause Degenerated GC (Mark)";
2793     case _degenerated_evac:
2794       return "Pause Degenerated GC (Evacuation)";
2795     case _degenerated_updaterefs:
2796       return "Pause Degenerated GC (Update Refs)";
2797     default:
2798       ShouldNotReachHere();
2799       return "ERROR";
2800   }
2801 }
2802 
2803 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2804 #ifdef ASSERT
2805   assert(_liveness_cache != NULL, "sanity");
2806   assert(worker_id < _max_workers, "sanity");
2807   for (uint i = 0; i < num_regions(); i++) {
2808     assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2809   }
2810 #endif
2811   return _liveness_cache[worker_id];
2812 }
2813 
2814 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2815   assert(worker_id < _max_workers, "sanity");
2816   assert(_liveness_cache != NULL, "sanity");
2817   ShenandoahLiveData* ld = _liveness_cache[worker_id];
2818   for (uint i = 0; i < num_regions(); i++) {
2819     ShenandoahLiveData live = ld[i];
2820     if (live > 0) {
2821       ShenandoahHeapRegion* r = get_region(i);
2822       r->increase_live_data_gc_words(live);
2823       ld[i] = 0;
2824     }
2825   }
2826 }