1 /*
  2  * Copyright (c) 2001, 2021, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
  8  *
  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 12  * version 2 for more details (a copy is included in the LICENSE file that
 13  * accompanied this code).
 14  *
 15  * You should have received a copy of the GNU General Public License version
 16  * 2 along with this work; if not, write to the Free Software Foundation,
 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 18  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 24 
 25 #include "precompiled.hpp"
 26 #include "code/codeCache.hpp"
 27 #include "gc/parallel/parallelArguments.hpp"
 28 #include "gc/parallel/objectStartArray.inline.hpp"
 29 #include "gc/parallel/parallelInitLogger.hpp"
 30 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
 31 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
 32 #include "gc/parallel/psMemoryPool.hpp"
 33 #include "gc/parallel/psParallelCompact.inline.hpp"
 34 #include "gc/parallel/psPromotionManager.hpp"
 35 #include "gc/parallel/psScavenge.hpp"
 36 #include "gc/parallel/psVMOperations.hpp"
 37 #include "gc/shared/gcHeapSummary.hpp"
 38 #include "gc/shared/gcLocker.hpp"
 39 #include "gc/shared/gcWhen.hpp"
 40 #include "gc/shared/genArguments.hpp"
 41 #include "gc/shared/gcInitLogger.hpp"
 42 #include "gc/shared/locationPrinter.inline.hpp"
 43 #include "gc/shared/scavengableNMethods.hpp"
 44 #include "gc/shared/suspendibleThreadSet.hpp"
 45 #include "logging/log.hpp"
 46 #include "memory/iterator.hpp"
 47 #include "memory/metaspaceCounters.hpp"
 48 #include "memory/metaspaceUtils.hpp"
 49 #include "memory/universe.hpp"
 50 #include "oops/oop.inline.hpp"
 51 #include "runtime/handles.inline.hpp"
 52 #include "runtime/java.hpp"
 53 #include "runtime/vmThread.hpp"
 54 #include "services/memoryManager.hpp"
 55 #include "services/memTracker.hpp"
 56 #include "utilities/macros.hpp"
 57 #include "utilities/vmError.hpp"
 58 
 59 PSYoungGen*  ParallelScavengeHeap::_young_gen = NULL;
 60 PSOldGen*    ParallelScavengeHeap::_old_gen = NULL;
 61 PSAdaptiveSizePolicy* ParallelScavengeHeap::_size_policy = NULL;
 62 PSGCAdaptivePolicyCounters* ParallelScavengeHeap::_gc_policy_counters = NULL;
 63 
 64 jint ParallelScavengeHeap::initialize() {
 65   const size_t reserved_heap_size = ParallelArguments::heap_reserved_size_bytes();
 66 
 67   ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_heap_size, HeapAlignment);
 68 
 69   trace_actual_reserved_page_size(reserved_heap_size, heap_rs);
 70 
 71   initialize_reserved_region(heap_rs);
 72 
 73   PSCardTable* card_table = new PSCardTable(heap_rs.region());
 74   card_table->initialize();
 75   CardTableBarrierSet* const barrier_set = new CardTableBarrierSet(card_table);
 76   barrier_set->initialize();
 77   BarrierSet::set_barrier_set(barrier_set);
 78 
 79   // Make up the generations
 80   assert(MinOldSize <= OldSize && OldSize <= MaxOldSize, "Parameter check");
 81   assert(MinNewSize <= NewSize && NewSize <= MaxNewSize, "Parameter check");
 82 
 83   // Layout the reserved space for the generations.
 84   ReservedSpace old_rs   = heap_rs.first_part(MaxOldSize);
 85   ReservedSpace young_rs = heap_rs.last_part(MaxOldSize);
 86   assert(young_rs.size() == MaxNewSize, "Didn't reserve all of the heap");
 87 
 88   // Set up WorkGang
 89   _workers.initialize_workers();
 90 
 91   // Create and initialize the generations.
 92   _young_gen = new PSYoungGen(
 93       young_rs,
 94       NewSize,
 95       MinNewSize,
 96       MaxNewSize);
 97   _old_gen = new PSOldGen(
 98       old_rs,
 99       OldSize,
100       MinOldSize,
101       MaxOldSize,
102       "old", 1);
103 
104   assert(young_gen()->max_gen_size() == young_rs.size(),"Consistency check");
105   assert(old_gen()->max_gen_size() == old_rs.size(), "Consistency check");
106 
107   double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
108   double max_gc_minor_pause_sec = ((double) MaxGCMinorPauseMillis)/1000.0;
109 
110   const size_t eden_capacity = _young_gen->eden_space()->capacity_in_bytes();
111   const size_t old_capacity = _old_gen->capacity_in_bytes();
112   const size_t initial_promo_size = MIN2(eden_capacity, old_capacity);
113   _size_policy =
114     new PSAdaptiveSizePolicy(eden_capacity,
115                              initial_promo_size,
116                              young_gen()->to_space()->capacity_in_bytes(),
117                              GenAlignment,
118                              max_gc_pause_sec,
119                              max_gc_minor_pause_sec,
120                              GCTimeRatio
121                              );
122 
123   assert((old_gen()->virtual_space()->high_boundary() ==
124           young_gen()->virtual_space()->low_boundary()),
125          "Boundaries must meet");
126   // initialize the policy counters - 2 collectors, 2 generations
127   _gc_policy_counters =
128     new PSGCAdaptivePolicyCounters("ParScav:MSC", 2, 2, _size_policy);
129 
130   if (!PSParallelCompact::initialize()) {
131     return JNI_ENOMEM;
132   }
133 
134   ParallelInitLogger::print();
135 
136   return JNI_OK;
137 }
138 
139 void ParallelScavengeHeap::initialize_serviceability() {
140 
141   _eden_pool = new EdenMutableSpacePool(_young_gen,
142                                         _young_gen->eden_space(),
143                                         "PS Eden Space",
144                                         false /* support_usage_threshold */);
145 
146   _survivor_pool = new SurvivorMutableSpacePool(_young_gen,
147                                                 "PS Survivor Space",
148                                                 false /* support_usage_threshold */);
149 
150   _old_pool = new PSGenerationPool(_old_gen,
151                                    "PS Old Gen",
152                                    true /* support_usage_threshold */);
153 
154   _young_manager = new GCMemoryManager("PS Scavenge", "end of minor GC");
155   _old_manager = new GCMemoryManager("PS MarkSweep", "end of major GC");
156 
157   _old_manager->add_pool(_eden_pool);
158   _old_manager->add_pool(_survivor_pool);
159   _old_manager->add_pool(_old_pool);
160 
161   _young_manager->add_pool(_eden_pool);
162   _young_manager->add_pool(_survivor_pool);
163 
164 }
165 
166 void ParallelScavengeHeap::safepoint_synchronize_begin() {
167   if (UseStringDeduplication) {
168     SuspendibleThreadSet::synchronize();
169   }
170 }
171 
172 void ParallelScavengeHeap::safepoint_synchronize_end() {
173   if (UseStringDeduplication) {
174     SuspendibleThreadSet::desynchronize();
175   }
176 }
177 class PSIsScavengable : public BoolObjectClosure {
178   bool do_object_b(oop obj) {
179     return ParallelScavengeHeap::heap()->is_in_young(obj);
180   }
181 };
182 
183 static PSIsScavengable _is_scavengable;
184 
185 void ParallelScavengeHeap::post_initialize() {
186   CollectedHeap::post_initialize();
187   // Need to init the tenuring threshold
188   PSScavenge::initialize();
189   PSParallelCompact::post_initialize();
190   PSPromotionManager::initialize();
191 
192   ScavengableNMethods::initialize(&_is_scavengable);
193 }
194 
195 void ParallelScavengeHeap::update_counters() {
196   young_gen()->update_counters();
197   old_gen()->update_counters();
198   MetaspaceCounters::update_performance_counters();
199 }
200 
201 size_t ParallelScavengeHeap::capacity() const {
202   size_t value = young_gen()->capacity_in_bytes() + old_gen()->capacity_in_bytes();
203   return value;
204 }
205 
206 size_t ParallelScavengeHeap::used() const {
207   size_t value = young_gen()->used_in_bytes() + old_gen()->used_in_bytes();
208   return value;
209 }
210 
211 bool ParallelScavengeHeap::is_maximal_no_gc() const {
212   return old_gen()->is_maximal_no_gc() && young_gen()->is_maximal_no_gc();
213 }
214 
215 
216 size_t ParallelScavengeHeap::max_capacity() const {
217   size_t estimated = reserved_region().byte_size();
218   if (UseAdaptiveSizePolicy) {
219     estimated -= _size_policy->max_survivor_size(young_gen()->max_gen_size());
220   } else {
221     estimated -= young_gen()->to_space()->capacity_in_bytes();
222   }
223   return MAX2(estimated, capacity());
224 }
225 
226 bool ParallelScavengeHeap::is_in(const void* p) const {
227   return young_gen()->is_in(p) || old_gen()->is_in(p);
228 }
229 
230 bool ParallelScavengeHeap::is_in_reserved(const void* p) const {
231   return young_gen()->is_in_reserved(p) || old_gen()->is_in_reserved(p);
232 }
233 
234 // There are two levels of allocation policy here.
235 //
236 // When an allocation request fails, the requesting thread must invoke a VM
237 // operation, transfer control to the VM thread, and await the results of a
238 // garbage collection. That is quite expensive, and we should avoid doing it
239 // multiple times if possible.
240 //
241 // To accomplish this, we have a basic allocation policy, and also a
242 // failed allocation policy.
243 //
244 // The basic allocation policy controls how you allocate memory without
245 // attempting garbage collection. It is okay to grab locks and
246 // expand the heap, if that can be done without coming to a safepoint.
247 // It is likely that the basic allocation policy will not be very
248 // aggressive.
249 //
250 // The failed allocation policy is invoked from the VM thread after
251 // the basic allocation policy is unable to satisfy a mem_allocate
252 // request. This policy needs to cover the entire range of collection,
253 // heap expansion, and out-of-memory conditions. It should make every
254 // attempt to allocate the requested memory.
255 
256 // Basic allocation policy. Should never be called at a safepoint, or
257 // from the VM thread.
258 //
259 // This method must handle cases where many mem_allocate requests fail
260 // simultaneously. When that happens, only one VM operation will succeed,
261 // and the rest will not be executed. For that reason, this method loops
262 // during failed allocation attempts. If the java heap becomes exhausted,
263 // we rely on the size_policy object to force a bail out.
264 HeapWord* ParallelScavengeHeap::mem_allocate(
265                                      size_t size,
266                                      bool* gc_overhead_limit_was_exceeded) {
267   assert(!SafepointSynchronize::is_at_safepoint(), "should not be at safepoint");
268   assert(Thread::current() != (Thread*)VMThread::vm_thread(), "should not be in vm thread");
269   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
270 
271   // In general gc_overhead_limit_was_exceeded should be false so
272   // set it so here and reset it to true only if the gc time
273   // limit is being exceeded as checked below.
274   *gc_overhead_limit_was_exceeded = false;
275 
276   HeapWord* result = young_gen()->allocate(size);
277 
278   uint loop_count = 0;
279   uint gc_count = 0;
280   uint gclocker_stalled_count = 0;
281 
282   while (result == NULL) {
283     // We don't want to have multiple collections for a single filled generation.
284     // To prevent this, each thread tracks the total_collections() value, and if
285     // the count has changed, does not do a new collection.
286     //
287     // The collection count must be read only while holding the heap lock. VM
288     // operations also hold the heap lock during collections. There is a lock
289     // contention case where thread A blocks waiting on the Heap_lock, while
290     // thread B is holding it doing a collection. When thread A gets the lock,
291     // the collection count has already changed. To prevent duplicate collections,
292     // The policy MUST attempt allocations during the same period it reads the
293     // total_collections() value!
294     {
295       MutexLocker ml(Heap_lock);
296       gc_count = total_collections();
297 
298       result = young_gen()->allocate(size);
299       if (result != NULL) {
300         return result;
301       }
302 
303       // If certain conditions hold, try allocating from the old gen.
304       result = mem_allocate_old_gen(size);
305       if (result != NULL) {
306         return result;
307       }
308 
309       if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
310         return NULL;
311       }
312 
313       // Failed to allocate without a gc.
314       if (GCLocker::is_active_and_needs_gc()) {
315         // If this thread is not in a jni critical section, we stall
316         // the requestor until the critical section has cleared and
317         // GC allowed. When the critical section clears, a GC is
318         // initiated by the last thread exiting the critical section; so
319         // we retry the allocation sequence from the beginning of the loop,
320         // rather than causing more, now probably unnecessary, GC attempts.
321         JavaThread* jthr = JavaThread::current();
322         if (!jthr->in_critical()) {
323           MutexUnlocker mul(Heap_lock);
324           GCLocker::stall_until_clear();
325           gclocker_stalled_count += 1;
326           continue;
327         } else {
328           if (CheckJNICalls) {
329             fatal("Possible deadlock due to allocating while"
330                   " in jni critical section");
331           }
332           return NULL;
333         }
334       }
335     }
336 
337     if (result == NULL) {
338       // Generate a VM operation
339       VM_ParallelGCFailedAllocation op(size, gc_count);
340       VMThread::execute(&op);
341 
342       // Did the VM operation execute? If so, return the result directly.
343       // This prevents us from looping until time out on requests that can
344       // not be satisfied.
345       if (op.prologue_succeeded()) {
346         assert(is_in_or_null(op.result()), "result not in heap");
347 
348         // If GC was locked out during VM operation then retry allocation
349         // and/or stall as necessary.
350         if (op.gc_locked()) {
351           assert(op.result() == NULL, "must be NULL if gc_locked() is true");
352           continue;  // retry and/or stall as necessary
353         }
354 
355         // Exit the loop if the gc time limit has been exceeded.
356         // The allocation must have failed above ("result" guarding
357         // this path is NULL) and the most recent collection has exceeded the
358         // gc overhead limit (although enough may have been collected to
359         // satisfy the allocation).  Exit the loop so that an out-of-memory
360         // will be thrown (return a NULL ignoring the contents of
361         // op.result()),
362         // but clear gc_overhead_limit_exceeded so that the next collection
363         // starts with a clean slate (i.e., forgets about previous overhead
364         // excesses).  Fill op.result() with a filler object so that the
365         // heap remains parsable.
366         const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
367         const bool softrefs_clear = soft_ref_policy()->all_soft_refs_clear();
368 
369         if (limit_exceeded && softrefs_clear) {
370           *gc_overhead_limit_was_exceeded = true;
371           size_policy()->set_gc_overhead_limit_exceeded(false);
372           log_trace(gc)("ParallelScavengeHeap::mem_allocate: return NULL because gc_overhead_limit_exceeded is set");
373           if (op.result() != NULL) {
374             CollectedHeap::fill_with_object(op.result(), size);
375           }
376           return NULL;
377         }
378 
379         return op.result();
380       }
381     }
382 
383     // The policy object will prevent us from looping forever. If the
384     // time spent in gc crosses a threshold, we will bail out.
385     loop_count++;
386     if ((result == NULL) && (QueuedAllocationWarningCount > 0) &&
387         (loop_count % QueuedAllocationWarningCount == 0)) {
388       log_warning(gc)("ParallelScavengeHeap::mem_allocate retries %d times", loop_count);
389       log_warning(gc)("\tsize=" SIZE_FORMAT, size);
390     }
391   }
392 
393   return result;
394 }
395 
396 // A "death march" is a series of ultra-slow allocations in which a full gc is
397 // done before each allocation, and after the full gc the allocation still
398 // cannot be satisfied from the young gen.  This routine detects that condition;
399 // it should be called after a full gc has been done and the allocation
400 // attempted from the young gen. The parameter 'addr' should be the result of
401 // that young gen allocation attempt.
402 void
403 ParallelScavengeHeap::death_march_check(HeapWord* const addr, size_t size) {
404   if (addr != NULL) {
405     _death_march_count = 0;  // death march has ended
406   } else if (_death_march_count == 0) {
407     if (should_alloc_in_eden(size)) {
408       _death_march_count = 1;    // death march has started
409     }
410   }
411 }
412 
413 HeapWord* ParallelScavengeHeap::allocate_old_gen_and_record(size_t size) {
414   assert_locked_or_safepoint(Heap_lock);
415   HeapWord* res = old_gen()->allocate(size);
416   if (res != NULL) {
417     _size_policy->tenured_allocation(size * HeapWordSize);
418   }
419   return res;
420 }
421 
422 HeapWord* ParallelScavengeHeap::mem_allocate_old_gen(size_t size) {
423   if (!should_alloc_in_eden(size) || GCLocker::is_active_and_needs_gc()) {
424     // Size is too big for eden, or gc is locked out.
425     return allocate_old_gen_and_record(size);
426   }
427 
428   // If a "death march" is in progress, allocate from the old gen a limited
429   // number of times before doing a GC.
430   if (_death_march_count > 0) {
431     if (_death_march_count < 64) {
432       ++_death_march_count;
433       return allocate_old_gen_and_record(size);
434     } else {
435       _death_march_count = 0;
436     }
437   }
438   return NULL;
439 }
440 
441 void ParallelScavengeHeap::do_full_collection(bool clear_all_soft_refs) {
442   // The do_full_collection() parameter clear_all_soft_refs
443   // is interpreted here as maximum_compaction which will
444   // cause SoftRefs to be cleared.
445   bool maximum_compaction = clear_all_soft_refs;
446   PSParallelCompact::invoke(maximum_compaction);
447 }
448 
449 // Failed allocation policy. Must be called from the VM thread, and
450 // only at a safepoint! Note that this method has policy for allocation
451 // flow, and NOT collection policy. So we do not check for gc collection
452 // time over limit here, that is the responsibility of the heap specific
453 // collection methods. This method decides where to attempt allocations,
454 // and when to attempt collections, but no collection specific policy.
455 HeapWord* ParallelScavengeHeap::failed_mem_allocate(size_t size) {
456   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
457   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
458   assert(!is_gc_active(), "not reentrant");
459   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
460 
461   // We assume that allocation in eden will fail unless we collect.
462 
463   // First level allocation failure, scavenge and allocate in young gen.
464   GCCauseSetter gccs(this, GCCause::_allocation_failure);
465   const bool invoked_full_gc = PSScavenge::invoke();
466   HeapWord* result = young_gen()->allocate(size);
467 
468   // Second level allocation failure.
469   //   Mark sweep and allocate in young generation.
470   if (result == NULL && !invoked_full_gc) {
471     do_full_collection(false);
472     result = young_gen()->allocate(size);
473   }
474 
475   death_march_check(result, size);
476 
477   // Third level allocation failure.
478   //   After mark sweep and young generation allocation failure,
479   //   allocate in old generation.
480   if (result == NULL) {
481     result = allocate_old_gen_and_record(size);
482   }
483 
484   // Fourth level allocation failure. We're running out of memory.
485   //   More complete mark sweep and allocate in young generation.
486   if (result == NULL) {
487     do_full_collection(true);
488     result = young_gen()->allocate(size);
489   }
490 
491   // Fifth level allocation failure.
492   //   After more complete mark sweep, allocate in old generation.
493   if (result == NULL) {
494     result = allocate_old_gen_and_record(size);
495   }
496 
497   return result;
498 }
499 
500 void ParallelScavengeHeap::ensure_parsability(bool retire_tlabs) {
501   CollectedHeap::ensure_parsability(retire_tlabs);
502   young_gen()->eden_space()->ensure_parsability();
503 }
504 
505 size_t ParallelScavengeHeap::tlab_capacity(Thread* thr) const {
506   return young_gen()->eden_space()->tlab_capacity(thr);
507 }
508 
509 size_t ParallelScavengeHeap::tlab_used(Thread* thr) const {
510   return young_gen()->eden_space()->tlab_used(thr);
511 }
512 
513 size_t ParallelScavengeHeap::unsafe_max_tlab_alloc(Thread* thr) const {
514   return young_gen()->eden_space()->unsafe_max_tlab_alloc(thr);
515 }
516 
517 HeapWord* ParallelScavengeHeap::allocate_new_tlab(size_t min_size, size_t requested_size, size_t* actual_size) {
518   HeapWord* result = young_gen()->allocate(requested_size);
519   if (result != NULL) {
520     *actual_size = requested_size;
521   }
522 
523   return result;
524 }
525 
526 void ParallelScavengeHeap::resize_all_tlabs() {
527   CollectedHeap::resize_all_tlabs();
528 }
529 
530 // This method is used by System.gc() and JVMTI.
531 void ParallelScavengeHeap::collect(GCCause::Cause cause) {
532   assert(!Heap_lock->owned_by_self(),
533     "this thread should not own the Heap_lock");
534 
535   uint gc_count      = 0;
536   uint full_gc_count = 0;
537   {
538     MutexLocker ml(Heap_lock);
539     // This value is guarded by the Heap_lock
540     gc_count      = total_collections();
541     full_gc_count = total_full_collections();
542   }
543 
544   if (GCLocker::should_discard(cause, gc_count)) {
545     return;
546   }
547 
548   VM_ParallelGCSystemGC op(gc_count, full_gc_count, cause);
549   VMThread::execute(&op);
550 }
551 
552 void ParallelScavengeHeap::object_iterate(ObjectClosure* cl) {
553   young_gen()->object_iterate(cl);
554   old_gen()->object_iterate(cl);
555 }
556 
557 // The HeapBlockClaimer is used during parallel iteration over the heap,
558 // allowing workers to claim heap areas ("blocks"), gaining exclusive rights to these.
559 // The eden and survivor spaces are treated as single blocks as it is hard to divide
560 // these spaces.
561 // The old space is divided into fixed-size blocks.
562 class HeapBlockClaimer : public StackObj {
563   size_t _claimed_index;
564 
565 public:
566   static const size_t InvalidIndex = SIZE_MAX;
567   static const size_t EdenIndex = 0;
568   static const size_t SurvivorIndex = 1;
569   static const size_t NumNonOldGenClaims = 2;
570 
571   HeapBlockClaimer() : _claimed_index(EdenIndex) { }
572   // Claim the block and get the block index.
573   size_t claim_and_get_block() {
574     size_t block_index;
575     block_index = Atomic::fetch_and_add(&_claimed_index, 1u);
576 
577     PSOldGen* old_gen = ParallelScavengeHeap::heap()->old_gen();
578     size_t num_claims = old_gen->num_iterable_blocks() + NumNonOldGenClaims;
579 
580     return block_index < num_claims ? block_index : InvalidIndex;
581   }
582 };
583 
584 void ParallelScavengeHeap::object_iterate_parallel(ObjectClosure* cl,
585                                                    HeapBlockClaimer* claimer) {
586   size_t block_index = claimer->claim_and_get_block();
587   // Iterate until all blocks are claimed
588   if (block_index == HeapBlockClaimer::EdenIndex) {
589     young_gen()->eden_space()->object_iterate(cl);
590     block_index = claimer->claim_and_get_block();
591   }
592   if (block_index == HeapBlockClaimer::SurvivorIndex) {
593     young_gen()->from_space()->object_iterate(cl);
594     young_gen()->to_space()->object_iterate(cl);
595     block_index = claimer->claim_and_get_block();
596   }
597   while (block_index != HeapBlockClaimer::InvalidIndex) {
598     old_gen()->object_iterate_block(cl, block_index - HeapBlockClaimer::NumNonOldGenClaims);
599     block_index = claimer->claim_and_get_block();
600   }
601 }
602 
603 class PSScavengeParallelObjectIterator : public ParallelObjectIterator {
604 private:
605   ParallelScavengeHeap*  _heap;
606   HeapBlockClaimer      _claimer;
607 
608 public:
609   PSScavengeParallelObjectIterator() :
610       _heap(ParallelScavengeHeap::heap()),
611       _claimer() {}
612 
613   virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
614     _heap->object_iterate_parallel(cl, &_claimer);
615   }
616 };
617 
618 ParallelObjectIterator* ParallelScavengeHeap::parallel_object_iterator(uint thread_num) {
619   return new PSScavengeParallelObjectIterator();
620 }
621 
622 HeapWord* ParallelScavengeHeap::block_start(const void* addr) const {
623   if (young_gen()->is_in_reserved(addr)) {
624     assert(young_gen()->is_in(addr),
625            "addr should be in allocated part of young gen");
626     // called from os::print_location by find or VMError
627     if (Debugging || VMError::is_error_reported())  return NULL;
628     Unimplemented();
629   } else if (old_gen()->is_in_reserved(addr)) {
630     assert(old_gen()->is_in(addr),
631            "addr should be in allocated part of old gen");
632     return old_gen()->start_array()->object_start((HeapWord*)addr);
633   }
634   return 0;
635 }
636 
637 bool ParallelScavengeHeap::block_is_obj(const HeapWord* addr) const {
638   return block_start(addr) == addr;
639 }
640 
641 void ParallelScavengeHeap::prepare_for_verify() {
642   ensure_parsability(false);  // no need to retire TLABs for verification
643 }
644 
645 PSHeapSummary ParallelScavengeHeap::create_ps_heap_summary() {
646   PSOldGen* old = old_gen();
647   HeapWord* old_committed_end = (HeapWord*)old->virtual_space()->committed_high_addr();
648   VirtualSpaceSummary old_summary(old->reserved().start(), old_committed_end, old->reserved().end());
649   SpaceSummary old_space(old->reserved().start(), old_committed_end, old->used_in_bytes());
650 
651   PSYoungGen* young = young_gen();
652   VirtualSpaceSummary young_summary(young->reserved().start(),
653     (HeapWord*)young->virtual_space()->committed_high_addr(), young->reserved().end());
654 
655   MutableSpace* eden = young_gen()->eden_space();
656   SpaceSummary eden_space(eden->bottom(), eden->end(), eden->used_in_bytes());
657 
658   MutableSpace* from = young_gen()->from_space();
659   SpaceSummary from_space(from->bottom(), from->end(), from->used_in_bytes());
660 
661   MutableSpace* to = young_gen()->to_space();
662   SpaceSummary to_space(to->bottom(), to->end(), to->used_in_bytes());
663 
664   VirtualSpaceSummary heap_summary = create_heap_space_summary();
665   return PSHeapSummary(heap_summary, used(), old_summary, old_space, young_summary, eden_space, from_space, to_space);
666 }
667 
668 bool ParallelScavengeHeap::print_location(outputStream* st, void* addr) const {
669   return BlockLocationPrinter<ParallelScavengeHeap>::print_location(st, addr);
670 }
671 
672 void ParallelScavengeHeap::print_on(outputStream* st) const {
673   if (young_gen() != NULL) {
674     young_gen()->print_on(st);
675   }
676   if (old_gen() != NULL) {
677     old_gen()->print_on(st);
678   }
679   MetaspaceUtils::print_on(st);
680 }
681 
682 void ParallelScavengeHeap::print_on_error(outputStream* st) const {
683   this->CollectedHeap::print_on_error(st);
684 
685   st->cr();
686   PSParallelCompact::print_on_error(st);
687 }
688 
689 void ParallelScavengeHeap::gc_threads_do(ThreadClosure* tc) const {
690   ParallelScavengeHeap::heap()->workers().threads_do(tc);
691 }
692 
693 void ParallelScavengeHeap::print_tracing_info() const {
694   AdaptiveSizePolicyOutput::print();
695   log_debug(gc, heap, exit)("Accumulated young generation GC time %3.7f secs", PSScavenge::accumulated_time()->seconds());
696   log_debug(gc, heap, exit)("Accumulated old generation GC time %3.7f secs", PSParallelCompact::accumulated_time()->seconds());
697 }
698 
699 PreGenGCValues ParallelScavengeHeap::get_pre_gc_values() const {
700   const PSYoungGen* const young = young_gen();
701   const MutableSpace* const eden = young->eden_space();
702   const MutableSpace* const from = young->from_space();
703   const PSOldGen* const old = old_gen();
704 
705   return PreGenGCValues(young->used_in_bytes(),
706                         young->capacity_in_bytes(),
707                         eden->used_in_bytes(),
708                         eden->capacity_in_bytes(),
709                         from->used_in_bytes(),
710                         from->capacity_in_bytes(),
711                         old->used_in_bytes(),
712                         old->capacity_in_bytes());
713 }
714 
715 void ParallelScavengeHeap::print_heap_change(const PreGenGCValues& pre_gc_values) const {
716   const PSYoungGen* const young = young_gen();
717   const MutableSpace* const eden = young->eden_space();
718   const MutableSpace* const from = young->from_space();
719   const PSOldGen* const old = old_gen();
720 
721   log_info(gc, heap)(HEAP_CHANGE_FORMAT" "
722                      HEAP_CHANGE_FORMAT" "
723                      HEAP_CHANGE_FORMAT,
724                      HEAP_CHANGE_FORMAT_ARGS(young->name(),
725                                              pre_gc_values.young_gen_used(),
726                                              pre_gc_values.young_gen_capacity(),
727                                              young->used_in_bytes(),
728                                              young->capacity_in_bytes()),
729                      HEAP_CHANGE_FORMAT_ARGS("Eden",
730                                              pre_gc_values.eden_used(),
731                                              pre_gc_values.eden_capacity(),
732                                              eden->used_in_bytes(),
733                                              eden->capacity_in_bytes()),
734                      HEAP_CHANGE_FORMAT_ARGS("From",
735                                              pre_gc_values.from_used(),
736                                              pre_gc_values.from_capacity(),
737                                              from->used_in_bytes(),
738                                              from->capacity_in_bytes()));
739   log_info(gc, heap)(HEAP_CHANGE_FORMAT,
740                      HEAP_CHANGE_FORMAT_ARGS(old->name(),
741                                              pre_gc_values.old_gen_used(),
742                                              pre_gc_values.old_gen_capacity(),
743                                              old->used_in_bytes(),
744                                              old->capacity_in_bytes()));
745   MetaspaceUtils::print_metaspace_change(pre_gc_values.metaspace_sizes());
746 }
747 
748 void ParallelScavengeHeap::verify(VerifyOption option /* ignored */) {
749   // Why do we need the total_collections()-filter below?
750   if (total_collections() > 0) {
751     log_debug(gc, verify)("Tenured");
752     old_gen()->verify();
753 
754     log_debug(gc, verify)("Eden");
755     young_gen()->verify();
756   }
757 }
758 
759 void ParallelScavengeHeap::trace_actual_reserved_page_size(const size_t reserved_heap_size, const ReservedSpace rs) {
760   // Check if Info level is enabled, since os::trace_page_sizes() logs on Info level.
761   if(log_is_enabled(Info, pagesize)) {
762     const size_t page_size = rs.page_size();
763     os::trace_page_sizes("Heap",
764                          MinHeapSize,
765                          reserved_heap_size,
766                          page_size,
767                          rs.base(),
768                          rs.size());
769   }
770 }
771 
772 void ParallelScavengeHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
773   const PSHeapSummary& heap_summary = create_ps_heap_summary();
774   gc_tracer->report_gc_heap_summary(when, heap_summary);
775 
776   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
777   gc_tracer->report_metaspace_summary(when, metaspace_summary);
778 }
779 
780 CardTableBarrierSet* ParallelScavengeHeap::barrier_set() {
781   return barrier_set_cast<CardTableBarrierSet>(BarrierSet::barrier_set());
782 }
783 
784 PSCardTable* ParallelScavengeHeap::card_table() {
785   return static_cast<PSCardTable*>(barrier_set()->card_table());
786 }
787 
788 void ParallelScavengeHeap::resize_young_gen(size_t eden_size,
789                                             size_t survivor_size) {
790   // Delegate the resize to the generation.
791   _young_gen->resize(eden_size, survivor_size);
792 }
793 
794 void ParallelScavengeHeap::resize_old_gen(size_t desired_free_space) {
795   // Delegate the resize to the generation.
796   _old_gen->resize(desired_free_space);
797 }
798 
799 #ifndef PRODUCT
800 void ParallelScavengeHeap::record_gen_tops_before_GC() {
801   if (ZapUnusedHeapArea) {
802     young_gen()->record_spaces_top();
803     old_gen()->record_spaces_top();
804   }
805 }
806 
807 void ParallelScavengeHeap::gen_mangle_unused_area() {
808   if (ZapUnusedHeapArea) {
809     young_gen()->eden_space()->mangle_unused_area();
810     young_gen()->to_space()->mangle_unused_area();
811     young_gen()->from_space()->mangle_unused_area();
812     old_gen()->object_space()->mangle_unused_area();
813   }
814 }
815 #endif
816 
817 void ParallelScavengeHeap::register_nmethod(nmethod* nm) {
818   ScavengableNMethods::register_nmethod(nm);
819 }
820 
821 void ParallelScavengeHeap::unregister_nmethod(nmethod* nm) {
822   ScavengableNMethods::unregister_nmethod(nm);
823 }
824 
825 void ParallelScavengeHeap::verify_nmethod(nmethod* nm) {
826   ScavengableNMethods::verify_nmethod(nm);
827 }
828 
829 void ParallelScavengeHeap::flush_nmethod(nmethod* nm) {
830   // nothing particular
831 }
832 
833 void ParallelScavengeHeap::prune_scavengable_nmethods() {
834   ScavengableNMethods::prune_nmethods();
835 }
836 
837 GrowableArray<GCMemoryManager*> ParallelScavengeHeap::memory_managers() {
838   GrowableArray<GCMemoryManager*> memory_managers(2);
839   memory_managers.append(_young_manager);
840   memory_managers.append(_old_manager);
841   return memory_managers;
842 }
843 
844 GrowableArray<MemoryPool*> ParallelScavengeHeap::memory_pools() {
845   GrowableArray<MemoryPool*> memory_pools(3);
846   memory_pools.append(_eden_pool);
847   memory_pools.append(_survivor_pool);
848   memory_pools.append(_old_pool);
849   return memory_pools;
850 }