1 /*
  2  * Copyright (c) 2017, 2024, 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 "classfile/classLoaderDataGraph.hpp"
 27 #include "classfile/stringTable.hpp"
 28 #include "classfile/symbolTable.hpp"
 29 #include "classfile/vmSymbols.hpp"
 30 #include "code/codeCache.hpp"
 31 #include "compiler/oopMap.hpp"
 32 #include "gc/serial/cardTableRS.hpp"
 33 #include "gc/serial/serialFullGC.hpp"
 34 #include "gc/serial/serialHeap.inline.hpp"
 35 #include "gc/serial/serialMemoryPools.hpp"
 36 #include "gc/serial/serialVMOperations.hpp"
 37 #include "gc/serial/tenuredGeneration.inline.hpp"
 38 #include "gc/shared/cardTableBarrierSet.hpp"
 39 #include "gc/shared/classUnloadingContext.hpp"
 40 #include "gc/shared/collectedHeap.inline.hpp"
 41 #include "gc/shared/collectorCounters.hpp"
 42 #include "gc/shared/continuationGCSupport.inline.hpp"
 43 #include "gc/shared/gcId.hpp"
 44 #include "gc/shared/gcInitLogger.hpp"
 45 #include "gc/shared/gcLocker.inline.hpp"
 46 #include "gc/shared/gcPolicyCounters.hpp"
 47 #include "gc/shared/gcTrace.hpp"
 48 #include "gc/shared/gcTraceTime.inline.hpp"
 49 #include "gc/shared/gcVMOperations.hpp"
 50 #include "gc/shared/genArguments.hpp"
 51 #include "gc/shared/isGCActiveMark.hpp"
 52 #include "gc/shared/locationPrinter.inline.hpp"
 53 #include "gc/shared/oopStorage.inline.hpp"
 54 #include "gc/shared/oopStorageParState.inline.hpp"
 55 #include "gc/shared/oopStorageSet.inline.hpp"
 56 #include "gc/shared/scavengableNMethods.hpp"
 57 #include "gc/shared/slidingForwarding.hpp"
 58 #include "gc/shared/space.hpp"
 59 #include "gc/shared/strongRootsScope.hpp"
 60 #include "gc/shared/suspendibleThreadSet.hpp"
 61 #include "gc/shared/weakProcessor.hpp"
 62 #include "gc/shared/workerThread.hpp"
 63 #include "memory/iterator.hpp"
 64 #include "memory/metaspaceCounters.hpp"
 65 #include "memory/metaspaceUtils.hpp"
 66 #include "memory/resourceArea.hpp"
 67 #include "memory/universe.hpp"
 68 #include "oops/oop.inline.hpp"
 69 #include "runtime/handles.hpp"
 70 #include "runtime/handles.inline.hpp"
 71 #include "runtime/java.hpp"
 72 #include "runtime/mutexLocker.hpp"
 73 #include "runtime/threads.hpp"
 74 #include "runtime/vmThread.hpp"
 75 #include "services/memoryManager.hpp"
 76 #include "services/memoryService.hpp"
 77 #include "utilities/debug.hpp"
 78 #include "utilities/formatBuffer.hpp"
 79 #include "utilities/macros.hpp"
 80 #include "utilities/stack.inline.hpp"
 81 #include "utilities/vmError.hpp"
 82 #if INCLUDE_JVMCI
 83 #include "jvmci/jvmci.hpp"
 84 #endif
 85 
 86 SerialHeap* SerialHeap::heap() {
 87   return named_heap<SerialHeap>(CollectedHeap::Serial);
 88 }
 89 
 90 SerialHeap::SerialHeap() :
 91     CollectedHeap(),
 92     _young_gen(nullptr),
 93     _old_gen(nullptr),
 94     _rem_set(nullptr),
 95     _gc_policy_counters(new GCPolicyCounters("Copy:MSC", 2, 2)),
 96     _incremental_collection_failed(false),
 97     _young_manager(nullptr),
 98     _old_manager(nullptr),
 99     _eden_pool(nullptr),
100     _survivor_pool(nullptr),
101     _old_pool(nullptr) {
102   _young_manager = new GCMemoryManager("Copy");
103   _old_manager = new GCMemoryManager("MarkSweepCompact");
104 }
105 
106 void SerialHeap::initialize_serviceability() {
107   DefNewGeneration* young = young_gen();
108 
109   // Add a memory pool for each space and young gen doesn't
110   // support low memory detection as it is expected to get filled up.
111   _eden_pool = new ContiguousSpacePool(young->eden(),
112                                        "Eden Space",
113                                        young->max_eden_size(),
114                                        false /* support_usage_threshold */);
115   _survivor_pool = new SurvivorContiguousSpacePool(young,
116                                                    "Survivor Space",
117                                                    young->max_survivor_size(),
118                                                    false /* support_usage_threshold */);
119   TenuredGeneration* old = old_gen();
120   _old_pool = new TenuredGenerationPool(old, "Tenured Gen", true);
121 
122   _young_manager->add_pool(_eden_pool);
123   _young_manager->add_pool(_survivor_pool);
124   young->set_gc_manager(_young_manager);
125 
126   _old_manager->add_pool(_eden_pool);
127   _old_manager->add_pool(_survivor_pool);
128   _old_manager->add_pool(_old_pool);
129   old->set_gc_manager(_old_manager);
130 }
131 
132 GrowableArray<GCMemoryManager*> SerialHeap::memory_managers() {
133   GrowableArray<GCMemoryManager*> memory_managers(2);
134   memory_managers.append(_young_manager);
135   memory_managers.append(_old_manager);
136   return memory_managers;
137 }
138 
139 GrowableArray<MemoryPool*> SerialHeap::memory_pools() {
140   GrowableArray<MemoryPool*> memory_pools(3);
141   memory_pools.append(_eden_pool);
142   memory_pools.append(_survivor_pool);
143   memory_pools.append(_old_pool);
144   return memory_pools;
145 }
146 
147 void SerialHeap::safepoint_synchronize_begin() {
148   if (UseStringDeduplication) {
149     SuspendibleThreadSet::synchronize();
150   }
151 }
152 
153 void SerialHeap::safepoint_synchronize_end() {
154   if (UseStringDeduplication) {
155     SuspendibleThreadSet::desynchronize();
156   }
157 }
158 
159 HeapWord* SerialHeap::allocate_loaded_archive_space(size_t word_size) {
160   MutexLocker ml(Heap_lock);
161   return old_gen()->allocate(word_size, false /* is_tlab */);
162 }
163 
164 void SerialHeap::complete_loaded_archive_space(MemRegion archive_space) {
165   assert(old_gen()->used_region().contains(archive_space), "Archive space not contained in old gen");
166   old_gen()->complete_loaded_archive_space(archive_space);
167 }
168 
169 void SerialHeap::pin_object(JavaThread* thread, oop obj) {
170   GCLocker::lock_critical(thread);
171 }
172 
173 void SerialHeap::unpin_object(JavaThread* thread, oop obj) {
174   GCLocker::unlock_critical(thread);
175 }
176 
177 jint SerialHeap::initialize() {
178   // Allocate space for the heap.
179 
180   ReservedHeapSpace heap_rs = allocate(HeapAlignment);
181 
182   if (!heap_rs.is_reserved()) {
183     vm_shutdown_during_initialization(
184       "Could not reserve enough space for object heap");
185     return JNI_ENOMEM;
186   }
187 
188   initialize_reserved_region(heap_rs);
189 
190   ReservedSpace young_rs = heap_rs.first_part(MaxNewSize);
191   ReservedSpace old_rs = heap_rs.last_part(MaxNewSize);
192 
193   _rem_set = new CardTableRS(heap_rs.region());
194   _rem_set->initialize(young_rs.base(), old_rs.base());
195 
196   CardTableBarrierSet *bs = new CardTableBarrierSet(_rem_set);
197   bs->initialize();
198   BarrierSet::set_barrier_set(bs);
199 
200   _young_gen = new DefNewGeneration(young_rs, NewSize, MinNewSize, MaxNewSize);
201   _old_gen = new TenuredGeneration(old_rs, OldSize, MinOldSize, MaxOldSize, rem_set());
202 
203   GCInitLogger::print();
204 
205   SlidingForwarding::initialize(_reserved, SpaceAlignment / HeapWordSize);
206 
207   return JNI_OK;
208 }
209 
210 ReservedHeapSpace SerialHeap::allocate(size_t alignment) {
211   // Now figure out the total size.
212   const size_t pageSize = UseLargePages ? os::large_page_size() : os::vm_page_size();
213   assert(alignment % pageSize == 0, "Must be");
214 
215   // Check for overflow.
216   size_t total_reserved = MaxNewSize + MaxOldSize;
217   if (total_reserved < MaxNewSize) {
218     vm_exit_during_initialization("The size of the object heap + VM data exceeds "
219                                   "the maximum representable size");
220   }
221   assert(total_reserved % alignment == 0,
222          "Gen size; total_reserved=" SIZE_FORMAT ", alignment="
223          SIZE_FORMAT, total_reserved, alignment);
224 
225   ReservedHeapSpace heap_rs = Universe::reserve_heap(total_reserved, alignment);
226   size_t used_page_size = heap_rs.page_size();
227 
228   os::trace_page_sizes("Heap",
229                        MinHeapSize,
230                        total_reserved,
231                        heap_rs.base(),
232                        heap_rs.size(),
233                        used_page_size);
234 
235   return heap_rs;
236 }
237 
238 class GenIsScavengable : public BoolObjectClosure {
239 public:
240   bool do_object_b(oop obj) {
241     return SerialHeap::heap()->is_in_young(obj);
242   }
243 };
244 
245 static GenIsScavengable _is_scavengable;
246 
247 void SerialHeap::post_initialize() {
248   CollectedHeap::post_initialize();
249 
250   DefNewGeneration* def_new_gen = (DefNewGeneration*)_young_gen;
251 
252   def_new_gen->ref_processor_init();
253 
254   SerialFullGC::initialize();
255 
256   ScavengableNMethods::initialize(&_is_scavengable);
257 }
258 
259 PreGenGCValues SerialHeap::get_pre_gc_values() const {
260   const DefNewGeneration* const def_new_gen = (DefNewGeneration*) young_gen();
261 
262   return PreGenGCValues(def_new_gen->used(),
263                         def_new_gen->capacity(),
264                         def_new_gen->eden()->used(),
265                         def_new_gen->eden()->capacity(),
266                         def_new_gen->from()->used(),
267                         def_new_gen->from()->capacity(),
268                         old_gen()->used(),
269                         old_gen()->capacity());
270 }
271 
272 size_t SerialHeap::capacity() const {
273   return _young_gen->capacity() + _old_gen->capacity();
274 }
275 
276 size_t SerialHeap::used() const {
277   return _young_gen->used() + _old_gen->used();
278 }
279 
280 size_t SerialHeap::max_capacity() const {
281   return _young_gen->max_capacity() + _old_gen->max_capacity();
282 }
283 
284 // Return true if any of the following is true:
285 // . the allocation won't fit into the current young gen heap
286 // . gc locker is occupied (jni critical section)
287 // . heap memory is tight -- the most recent previous collection
288 //   was a full collection because a partial collection (would
289 //   have) failed and is likely to fail again
290 bool SerialHeap::should_try_older_generation_allocation(size_t word_size) const {
291   size_t young_capacity = _young_gen->capacity_before_gc();
292   return    (word_size > heap_word_size(young_capacity))
293          || GCLocker::is_active_and_needs_gc()
294          || incremental_collection_failed();
295 }
296 
297 HeapWord* SerialHeap::expand_heap_and_allocate(size_t size, bool is_tlab) {
298   HeapWord* result = nullptr;
299   if (_old_gen->should_allocate(size, is_tlab)) {
300     result = _old_gen->expand_and_allocate(size, is_tlab);
301   }
302   if (result == nullptr) {
303     if (_young_gen->should_allocate(size, is_tlab)) {
304       result = _young_gen->expand_and_allocate(size, is_tlab);
305     }
306   }
307   assert(result == nullptr || is_in_reserved(result), "result not in heap");
308   return result;
309 }
310 
311 HeapWord* SerialHeap::mem_allocate_work(size_t size,
312                                         bool is_tlab) {
313 
314   HeapWord* result = nullptr;
315 
316   // Loop until the allocation is satisfied, or unsatisfied after GC.
317   for (uint try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
318 
319     // First allocation attempt is lock-free.
320     DefNewGeneration *young = _young_gen;
321     if (young->should_allocate(size, is_tlab)) {
322       result = young->par_allocate(size, is_tlab);
323       if (result != nullptr) {
324         assert(is_in_reserved(result), "result not in heap");
325         return result;
326       }
327     }
328     uint gc_count_before;  // Read inside the Heap_lock locked region.
329     {
330       MutexLocker ml(Heap_lock);
331       log_trace(gc, alloc)("SerialHeap::mem_allocate_work: attempting locked slow path allocation");
332       // Note that only large objects get a shot at being
333       // allocated in later generations.
334       bool first_only = !should_try_older_generation_allocation(size);
335 
336       result = attempt_allocation(size, is_tlab, first_only);
337       if (result != nullptr) {
338         assert(is_in_reserved(result), "result not in heap");
339         return result;
340       }
341 
342       if (GCLocker::is_active_and_needs_gc()) {
343         if (is_tlab) {
344           return nullptr;  // Caller will retry allocating individual object.
345         }
346         if (!is_maximal_no_gc()) {
347           // Try and expand heap to satisfy request.
348           result = expand_heap_and_allocate(size, is_tlab);
349           // Result could be null if we are out of space.
350           if (result != nullptr) {
351             return result;
352           }
353         }
354 
355         if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
356           return nullptr; // We didn't get to do a GC and we didn't get any memory.
357         }
358 
359         // If this thread is not in a jni critical section, we stall
360         // the requestor until the critical section has cleared and
361         // GC allowed. When the critical section clears, a GC is
362         // initiated by the last thread exiting the critical section; so
363         // we retry the allocation sequence from the beginning of the loop,
364         // rather than causing more, now probably unnecessary, GC attempts.
365         JavaThread* jthr = JavaThread::current();
366         if (!jthr->in_critical()) {
367           MutexUnlocker mul(Heap_lock);
368           // Wait for JNI critical section to be exited
369           GCLocker::stall_until_clear();
370           gclocker_stalled_count += 1;
371           continue;
372         } else {
373           if (CheckJNICalls) {
374             fatal("Possible deadlock due to allocating while"
375                   " in jni critical section");
376           }
377           return nullptr;
378         }
379       }
380 
381       // Read the gc count while the heap lock is held.
382       gc_count_before = total_collections();
383     }
384 
385     VM_SerialCollectForAllocation op(size, is_tlab, gc_count_before);
386     VMThread::execute(&op);
387     if (op.prologue_succeeded()) {
388       result = op.result();
389       if (op.gc_locked()) {
390          assert(result == nullptr, "must be null if gc_locked() is true");
391          continue;  // Retry and/or stall as necessary.
392       }
393 
394       assert(result == nullptr || is_in_reserved(result),
395              "result not in heap");
396       return result;
397     }
398 
399     // Give a warning if we seem to be looping forever.
400     if ((QueuedAllocationWarningCount > 0) &&
401         (try_count % QueuedAllocationWarningCount == 0)) {
402           log_warning(gc, ergo)("SerialHeap::mem_allocate_work retries %d times,"
403                                 " size=" SIZE_FORMAT " %s", try_count, size, is_tlab ? "(TLAB)" : "");
404     }
405   }
406 }
407 
408 HeapWord* SerialHeap::attempt_allocation(size_t size,
409                                          bool is_tlab,
410                                          bool first_only) {
411   HeapWord* res = nullptr;
412 
413   if (_young_gen->should_allocate(size, is_tlab)) {
414     res = _young_gen->allocate(size, is_tlab);
415     if (res != nullptr || first_only) {
416       return res;
417     }
418   }
419 
420   if (_old_gen->should_allocate(size, is_tlab)) {
421     res = _old_gen->allocate(size, is_tlab);
422   }
423 
424   return res;
425 }
426 
427 HeapWord* SerialHeap::mem_allocate(size_t size,
428                                    bool* gc_overhead_limit_was_exceeded) {
429   return mem_allocate_work(size,
430                            false /* is_tlab */);
431 }
432 
433 bool SerialHeap::must_clear_all_soft_refs() {
434   return _gc_cause == GCCause::_metadata_GC_clear_soft_refs ||
435          _gc_cause == GCCause::_wb_full_gc;
436 }
437 
438 bool SerialHeap::is_young_gc_safe() const {
439   if (!_young_gen->to()->is_empty()) {
440     return false;
441   }
442   return _old_gen->promotion_attempt_is_safe(_young_gen->used());
443 }
444 
445 bool SerialHeap::do_young_collection(bool clear_soft_refs) {
446   if (!is_young_gc_safe()) {
447     return false;
448   }
449   IsSTWGCActiveMark gc_active_mark;
450   SvcGCMarker sgcm(SvcGCMarker::MINOR);
451   GCIdMark gc_id_mark;
452   GCTraceCPUTime tcpu(_young_gen->gc_tracer());
453   GCTraceTime(Info, gc) t("Pause Young", nullptr, gc_cause(), true);
454   TraceCollectorStats tcs(_young_gen->counters());
455   TraceMemoryManagerStats tmms(_young_gen->gc_manager(), gc_cause(), "end of minor GC");
456   print_heap_before_gc();
457   const PreGenGCValues pre_gc_values = get_pre_gc_values();
458 
459   increment_total_collections(false);
460   const bool should_verify = total_collections() >= VerifyGCStartAt;
461   if (should_verify && VerifyBeforeGC) {
462     prepare_for_verify();
463     Universe::verify("Before GC");
464   }
465   gc_prologue(false);
466   COMPILER2_OR_JVMCI_PRESENT(DerivedPointerTable::clear());
467 
468   save_marks();
469 
470   bool result = _young_gen->collect(clear_soft_refs);
471 
472   COMPILER2_OR_JVMCI_PRESENT(DerivedPointerTable::update_pointers());
473 
474   // Only update stats for successful young-gc
475   if (result) {
476     _old_gen->update_promote_stats();
477   }
478 
479   if (should_verify && VerifyAfterGC) {
480     Universe::verify("After GC");
481   }
482 
483   _young_gen->compute_new_size();
484 
485   print_heap_change(pre_gc_values);
486 
487   // Track memory usage and detect low memory after GC finishes
488   MemoryService::track_memory_usage();
489 
490   gc_epilogue(false);
491 
492   print_heap_after_gc();
493 
494   return result;
495 }
496 
497 void SerialHeap::register_nmethod(nmethod* nm) {
498   ScavengableNMethods::register_nmethod(nm);
499 }
500 
501 void SerialHeap::unregister_nmethod(nmethod* nm) {
502   ScavengableNMethods::unregister_nmethod(nm);
503 }
504 
505 void SerialHeap::verify_nmethod(nmethod* nm) {
506   ScavengableNMethods::verify_nmethod(nm);
507 }
508 
509 void SerialHeap::prune_scavengable_nmethods() {
510   ScavengableNMethods::prune_nmethods_not_into_young();
511 }
512 
513 void SerialHeap::prune_unlinked_nmethods() {
514   ScavengableNMethods::prune_unlinked_nmethods();
515 }
516 
517 HeapWord* SerialHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
518   assert(size != 0, "precondition");
519 
520   HeapWord* result = nullptr;
521 
522   GCLocker::check_active_before_gc();
523   if (GCLocker::is_active_and_needs_gc()) {
524     // GC locker is active; instead of a collection we will attempt
525     // to expand the heap, if there's room for expansion.
526     if (!is_maximal_no_gc()) {
527       result = expand_heap_and_allocate(size, is_tlab);
528     }
529     return result;   // Could be null if we are out of space.
530   }
531 
532   // If young-gen can handle this allocation, attempt young-gc firstly.
533   bool should_run_young_gc = _young_gen->should_allocate(size, is_tlab);
534   collect_at_safepoint(!should_run_young_gc);
535 
536   result = attempt_allocation(size, is_tlab, false /*first_only*/);
537   if (result != nullptr) {
538     return result;
539   }
540 
541   // OK, collection failed, try expansion.
542   result = expand_heap_and_allocate(size, is_tlab);
543   if (result != nullptr) {
544     return result;
545   }
546 
547   // If we reach this point, we're really out of memory. Try every trick
548   // we can to reclaim memory. Force collection of soft references. Force
549   // a complete compaction of the heap. Any additional methods for finding
550   // free memory should be here, especially if they are expensive. If this
551   // attempt fails, an OOM exception will be thrown.
552   {
553     UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
554     const bool clear_all_soft_refs = true;
555     do_full_collection_no_gc_locker(clear_all_soft_refs);
556   }
557 
558   result = attempt_allocation(size, is_tlab, false /* first_only */);
559   if (result != nullptr) {
560     return result;
561   }
562   // The previous full-gc can shrink the heap, so re-expand it.
563   result = expand_heap_and_allocate(size, is_tlab);
564   if (result != nullptr) {
565     return result;
566   }
567 
568   // What else?  We might try synchronous finalization later.  If the total
569   // space available is large enough for the allocation, then a more
570   // complete compaction phase than we've tried so far might be
571   // appropriate.
572   return nullptr;
573 }
574 
575 void SerialHeap::process_roots(ScanningOption so,
576                                OopClosure* strong_roots,
577                                CLDClosure* strong_cld_closure,
578                                CLDClosure* weak_cld_closure,
579                                NMethodToOopClosure* code_roots) {
580   // General roots.
581   assert(code_roots != nullptr, "code root closure should always be set");
582 
583   ClassLoaderDataGraph::roots_cld_do(strong_cld_closure, weak_cld_closure);
584 
585   // Only process code roots from thread stacks if we aren't visiting the entire CodeCache anyway
586   NMethodToOopClosure* roots_from_code_p = (so & SO_AllCodeCache) ? nullptr : code_roots;
587 
588   Threads::oops_do(strong_roots, roots_from_code_p);
589 
590   OopStorageSet::strong_oops_do(strong_roots);
591 
592   if (so & SO_ScavengeCodeCache) {
593     assert(code_roots != nullptr, "must supply closure for code cache");
594 
595     // We only visit parts of the CodeCache when scavenging.
596     ScavengableNMethods::nmethods_do(code_roots);
597   }
598   if (so & SO_AllCodeCache) {
599     assert(code_roots != nullptr, "must supply closure for code cache");
600 
601     // CMSCollector uses this to do intermediate-strength collections.
602     // We scan the entire code cache, since CodeCache::do_unloading is not called.
603     CodeCache::nmethods_do(code_roots);
604   }
605 }
606 
607 template <typename OopClosureType>
608 static void oop_iterate_from(OopClosureType* blk, ContiguousSpace* space, HeapWord** from) {
609   assert(*from != nullptr, "precondition");
610   HeapWord* t;
611   HeapWord* p = *from;
612 
613   const intx interval = PrefetchScanIntervalInBytes;
614   do {
615     t = space->top();
616     while (p < t) {
617       Prefetch::write(p, interval);
618       p += cast_to_oop(p)->oop_iterate_size(blk);
619     }
620   } while (t < space->top());
621 
622   *from = space->top();
623 }
624 
625 void SerialHeap::scan_evacuated_objs(YoungGenScanClosure* young_cl,
626                                      OldGenScanClosure* old_cl) {
627   ContiguousSpace* to_space = young_gen()->to();
628   do {
629     oop_iterate_from(young_cl, to_space, &_young_gen_saved_top);
630     oop_iterate_from(old_cl, old_gen()->space(), &_old_gen_saved_top);
631     // Recheck to-space only, because postcondition of oop_iterate_from is no
632     // unscanned objs
633   } while (_young_gen_saved_top != to_space->top());
634   guarantee(young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
635 }
636 
637 void SerialHeap::try_collect_at_safepoint(bool full) {
638   assert(SafepointSynchronize::is_at_safepoint(), "precondition");
639   if (GCLocker::check_active_before_gc()) {
640     return;
641   }
642   collect_at_safepoint(full);
643 }
644 
645 void SerialHeap::collect_at_safepoint(bool full) {
646   assert(!GCLocker::is_active(), "precondition");
647   bool clear_soft_refs = must_clear_all_soft_refs();
648 
649   if (!full) {
650     bool success = do_young_collection(clear_soft_refs);
651     if (success) {
652       return;
653     }
654     // Upgrade to Full-GC if young-gc fails
655   }
656   do_full_collection_no_gc_locker(clear_soft_refs);
657 }
658 
659 // public collection interfaces
660 void SerialHeap::collect(GCCause::Cause cause) {
661   // The caller doesn't have the Heap_lock
662   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
663 
664   unsigned int gc_count_before;
665   unsigned int full_gc_count_before;
666 
667   {
668     MutexLocker ml(Heap_lock);
669     // Read the GC count while holding the Heap_lock
670     gc_count_before      = total_collections();
671     full_gc_count_before = total_full_collections();
672   }
673 
674   if (GCLocker::should_discard(cause, gc_count_before)) {
675     return;
676   }
677 
678   bool should_run_young_gc =  (cause == GCCause::_wb_young_gc)
679                            || (cause == GCCause::_gc_locker)
680                 DEBUG_ONLY(|| (cause == GCCause::_scavenge_alot));
681 
682   while (true) {
683     VM_SerialGCCollect op(!should_run_young_gc,
684                           gc_count_before,
685                           full_gc_count_before,
686                           cause);
687     VMThread::execute(&op);
688 
689     if (!GCCause::is_explicit_full_gc(cause)) {
690       return;
691     }
692 
693     {
694       MutexLocker ml(Heap_lock);
695       // Read the GC count while holding the Heap_lock
696       if (full_gc_count_before != total_full_collections()) {
697         return;
698       }
699     }
700 
701     if (GCLocker::is_active_and_needs_gc()) {
702       // If GCLocker is active, wait until clear before retrying.
703       GCLocker::stall_until_clear();
704     }
705   }
706 }
707 
708 void SerialHeap::do_full_collection(bool clear_all_soft_refs) {
709   if (GCLocker::check_active_before_gc()) {
710     return;
711   }
712   do_full_collection_no_gc_locker(clear_all_soft_refs);
713 }
714 
715 void SerialHeap::do_full_collection_no_gc_locker(bool clear_all_soft_refs) {
716   IsSTWGCActiveMark gc_active_mark;
717   SvcGCMarker sgcm(SvcGCMarker::FULL);
718   GCIdMark gc_id_mark;
719   GCTraceCPUTime tcpu(SerialFullGC::gc_tracer());
720   GCTraceTime(Info, gc) t("Pause Full", nullptr, gc_cause(), true);
721   TraceCollectorStats tcs(_old_gen->counters());
722   TraceMemoryManagerStats tmms(_old_gen->gc_manager(), gc_cause(), "end of major GC");
723   const PreGenGCValues pre_gc_values = get_pre_gc_values();
724   print_heap_before_gc();
725 
726   increment_total_collections(true);
727   const bool should_verify = total_collections() >= VerifyGCStartAt;
728   if (should_verify && VerifyBeforeGC) {
729     prepare_for_verify();
730     Universe::verify("Before GC");
731   }
732 
733   gc_prologue(true);
734   COMPILER2_OR_JVMCI_PRESENT(DerivedPointerTable::clear());
735   CodeCache::on_gc_marking_cycle_start();
736   ClassUnloadingContext ctx(1 /* num_nmethod_unlink_workers */,
737                             false /* unregister_nmethods_during_purge */,
738                             false /* lock_nmethod_free_separately */);
739 
740   STWGCTimer* gc_timer = SerialFullGC::gc_timer();
741   gc_timer->register_gc_start();
742 
743   SerialOldTracer* gc_tracer = SerialFullGC::gc_tracer();
744   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
745 
746   pre_full_gc_dump(gc_timer);
747 
748   SerialFullGC::invoke_at_safepoint(clear_all_soft_refs);
749 
750   post_full_gc_dump(gc_timer);
751 
752   gc_timer->register_gc_end();
753 
754   gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
755   CodeCache::on_gc_marking_cycle_finish();
756   CodeCache::arm_all_nmethods();
757   COMPILER2_OR_JVMCI_PRESENT(DerivedPointerTable::update_pointers());
758 
759   // Adjust generation sizes.
760   _old_gen->compute_new_size();
761   _young_gen->compute_new_size();
762 
763   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
764   ClassLoaderDataGraph::purge(/*at_safepoint*/true);
765   DEBUG_ONLY(MetaspaceUtils::verify();)
766 
767   // Need to clear claim bits for the next mark.
768   ClassLoaderDataGraph::clear_claimed_marks();
769 
770   _old_gen->update_promote_stats();
771 
772   // Resize the metaspace capacity after full collections
773   MetaspaceGC::compute_new_size();
774 
775   print_heap_change(pre_gc_values);
776 
777   // Track memory usage and detect low memory after GC finishes
778   MemoryService::track_memory_usage();
779 
780   // Need to tell the epilogue code we are done with Full GC, regardless what was
781   // the initial value for "complete" flag.
782   gc_epilogue(true);
783 
784   print_heap_after_gc();
785 
786   if (should_verify && VerifyAfterGC) {
787     Universe::verify("After GC");
788   }
789 }
790 
791 bool SerialHeap::is_in_young(const void* p) const {
792   bool result = p < _old_gen->reserved().start();
793   assert(result == _young_gen->is_in_reserved(p),
794          "incorrect test - result=%d, p=" PTR_FORMAT, result, p2i(p));
795   return result;
796 }
797 
798 bool SerialHeap::requires_barriers(stackChunkOop obj) const {
799   return !is_in_young(obj);
800 }
801 
802 // Returns "TRUE" iff "p" points into the committed areas of the heap.
803 bool SerialHeap::is_in(const void* p) const {
804   return _young_gen->is_in(p) || _old_gen->is_in(p);
805 }
806 
807 void SerialHeap::object_iterate(ObjectClosure* cl) {
808   _young_gen->object_iterate(cl);
809   _old_gen->object_iterate(cl);
810 }
811 
812 HeapWord* SerialHeap::block_start(const void* addr) const {
813   assert(is_in_reserved(addr), "block_start of address outside of heap");
814   if (_young_gen->is_in_reserved(addr)) {
815     assert(_young_gen->is_in(addr), "addr should be in allocated part of generation");
816     return _young_gen->block_start(addr);
817   }
818 
819   assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
820   assert(_old_gen->is_in(addr), "addr should be in allocated part of generation");
821   return _old_gen->block_start(addr);
822 }
823 
824 bool SerialHeap::block_is_obj(const HeapWord* addr) const {
825   assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
826   assert(block_start(addr) == addr, "addr must be a block start");
827 
828   if (_young_gen->is_in_reserved(addr)) {
829     return _young_gen->eden()->is_in(addr)
830         || _young_gen->from()->is_in(addr)
831         || _young_gen->to()  ->is_in(addr);
832   }
833 
834   assert(_old_gen->is_in_reserved(addr), "must be in old-gen");
835   return addr < _old_gen->space()->top();
836 }
837 
838 size_t SerialHeap::tlab_capacity(Thread* thr) const {
839   // Only young-gen supports tlab allocation.
840   return _young_gen->tlab_capacity();
841 }
842 
843 size_t SerialHeap::tlab_used(Thread* thr) const {
844   return _young_gen->tlab_used();
845 }
846 
847 size_t SerialHeap::unsafe_max_tlab_alloc(Thread* thr) const {
848   return _young_gen->unsafe_max_tlab_alloc();
849 }
850 
851 HeapWord* SerialHeap::allocate_new_tlab(size_t min_size,
852                                         size_t requested_size,
853                                         size_t* actual_size) {
854   HeapWord* result = mem_allocate_work(requested_size /* size */,
855                                        true /* is_tlab */);
856   if (result != nullptr) {
857     *actual_size = requested_size;
858   }
859 
860   return result;
861 }
862 
863 void SerialHeap::prepare_for_verify() {
864   ensure_parsability(false);        // no need to retire TLABs
865 }
866 
867 bool SerialHeap::is_maximal_no_gc() const {
868   // We don't expand young-gen except at a GC.
869   return _old_gen->is_maximal_no_gc();
870 }
871 
872 void SerialHeap::save_marks() {
873   _young_gen_saved_top = _young_gen->to()->top();
874   _old_gen_saved_top = _old_gen->space()->top();
875 }
876 
877 void SerialHeap::verify(VerifyOption option /* ignored */) {
878   log_debug(gc, verify)("%s", _old_gen->name());
879   _old_gen->verify();
880 
881   log_debug(gc, verify)("%s", _young_gen->name());
882   _young_gen->verify();
883 
884   log_debug(gc, verify)("RemSet");
885   rem_set()->verify();
886 }
887 
888 void SerialHeap::print_on(outputStream* st) const {
889   if (_young_gen != nullptr) {
890     _young_gen->print_on(st);
891   }
892   if (_old_gen != nullptr) {
893     _old_gen->print_on(st);
894   }
895   MetaspaceUtils::print_on(st);
896 }
897 
898 void SerialHeap::gc_threads_do(ThreadClosure* tc) const {
899 }
900 
901 bool SerialHeap::print_location(outputStream* st, void* addr) const {
902   return BlockLocationPrinter<SerialHeap>::print_location(st, addr);
903 }
904 
905 void SerialHeap::print_tracing_info() const {
906  // Does nothing
907 }
908 
909 void SerialHeap::print_heap_change(const PreGenGCValues& pre_gc_values) const {
910   const DefNewGeneration* const def_new_gen = (DefNewGeneration*) young_gen();
911 
912   log_info(gc, heap)(HEAP_CHANGE_FORMAT" "
913                      HEAP_CHANGE_FORMAT" "
914                      HEAP_CHANGE_FORMAT,
915                      HEAP_CHANGE_FORMAT_ARGS(def_new_gen->short_name(),
916                                              pre_gc_values.young_gen_used(),
917                                              pre_gc_values.young_gen_capacity(),
918                                              def_new_gen->used(),
919                                              def_new_gen->capacity()),
920                      HEAP_CHANGE_FORMAT_ARGS("Eden",
921                                              pre_gc_values.eden_used(),
922                                              pre_gc_values.eden_capacity(),
923                                              def_new_gen->eden()->used(),
924                                              def_new_gen->eden()->capacity()),
925                      HEAP_CHANGE_FORMAT_ARGS("From",
926                                              pre_gc_values.from_used(),
927                                              pre_gc_values.from_capacity(),
928                                              def_new_gen->from()->used(),
929                                              def_new_gen->from()->capacity()));
930   log_info(gc, heap)(HEAP_CHANGE_FORMAT,
931                      HEAP_CHANGE_FORMAT_ARGS(old_gen()->short_name(),
932                                              pre_gc_values.old_gen_used(),
933                                              pre_gc_values.old_gen_capacity(),
934                                              old_gen()->used(),
935                                              old_gen()->capacity()));
936   MetaspaceUtils::print_metaspace_change(pre_gc_values.metaspace_sizes());
937 }
938 
939 void SerialHeap::gc_prologue(bool full) {
940   // Fill TLAB's and such
941   ensure_parsability(true);   // retire TLABs
942 
943   _old_gen->gc_prologue();
944 };
945 
946 void SerialHeap::gc_epilogue(bool full) {
947 #if COMPILER2_OR_JVMCI
948   assert(DerivedPointerTable::is_empty(), "derived pointer present");
949 #endif // COMPILER2_OR_JVMCI
950 
951   resize_all_tlabs();
952 
953   _young_gen->gc_epilogue(full);
954   _old_gen->gc_epilogue();
955 
956   MetaspaceCounters::update_performance_counters();
957 };
--- EOF ---