1 /*
  2  * Copyright (c) 2017, 2022, 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.
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 23  */
 24 
 25 #include "precompiled.hpp"
 26 #include "classfile/systemDictionary.hpp"
 27 #include "code/codeCache.hpp"
 28 #include "compiler/oopMap.hpp"
 29 #include "gc/g1/g1CollectedHeap.hpp"
 30 #include "gc/g1/g1FullCollector.inline.hpp"
 31 #include "gc/g1/g1FullGCAdjustTask.hpp"
 32 #include "gc/g1/g1FullGCCompactTask.hpp"
 33 #include "gc/g1/g1FullGCMarker.inline.hpp"
 34 #include "gc/g1/g1FullGCMarkTask.hpp"
 35 #include "gc/g1/g1FullGCPrepareTask.inline.hpp"
 36 #include "gc/g1/g1FullGCScope.hpp"
 37 #include "gc/g1/g1OopClosures.hpp"
 38 #include "gc/g1/g1Policy.hpp"
 39 #include "gc/g1/g1RegionMarkStatsCache.inline.hpp"
 40 #include "gc/shared/gcTraceTime.inline.hpp"
 41 #include "gc/shared/preservedMarks.hpp"
 42 #include "gc/shared/referenceProcessor.hpp"
 43 #include "gc/shared/verifyOption.hpp"
 44 #include "gc/shared/weakProcessor.inline.hpp"
 45 #include "gc/shared/workerPolicy.hpp"
 46 #include "logging/log.hpp"
 47 #include "runtime/continuation.hpp"
 48 #include "runtime/handles.inline.hpp"
 49 #include "utilities/debug.hpp"
 50 
 51 static void clear_and_activate_derived_pointers() {
 52 #if COMPILER2_OR_JVMCI
 53   DerivedPointerTable::clear();
 54 #endif
 55 }
 56 
 57 static void deactivate_derived_pointers() {
 58 #if COMPILER2_OR_JVMCI
 59   DerivedPointerTable::set_active(false);
 60 #endif
 61 }
 62 
 63 static void update_derived_pointers() {
 64 #if COMPILER2_OR_JVMCI
 65   DerivedPointerTable::update_pointers();
 66 #endif
 67 }
 68 
 69 G1CMBitMap* G1FullCollector::mark_bitmap() {
 70   return _heap->concurrent_mark()->mark_bitmap();
 71 }
 72 
 73 ReferenceProcessor* G1FullCollector::reference_processor() {
 74   return _heap->ref_processor_stw();
 75 }
 76 
 77 uint G1FullCollector::calc_active_workers() {
 78   G1CollectedHeap* heap = G1CollectedHeap::heap();
 79   uint max_worker_count = heap->workers()->max_workers();
 80   // Only calculate number of workers if UseDynamicNumberOfGCThreads
 81   // is enabled, otherwise use max.
 82   if (!UseDynamicNumberOfGCThreads) {
 83     return max_worker_count;
 84   }
 85 
 86   // Consider G1HeapWastePercent to decide max number of workers. Each worker
 87   // will in average cause half a region waste.
 88   uint max_wasted_regions_allowed = ((heap->num_regions() * G1HeapWastePercent) / 100);
 89   uint waste_worker_count = MAX2((max_wasted_regions_allowed * 2) , 1u);
 90   uint heap_waste_worker_limit = MIN2(waste_worker_count, max_worker_count);
 91 
 92   // Also consider HeapSizePerGCThread by calling WorkerPolicy to calculate
 93   // the number of workers.
 94   uint current_active_workers = heap->workers()->active_workers();
 95   uint active_worker_limit = WorkerPolicy::calc_active_workers(max_worker_count, current_active_workers, 0);
 96 
 97   // Finally consider the amount of used regions.
 98   uint used_worker_limit = heap->num_used_regions();
 99   assert(used_worker_limit > 0, "Should never have zero used regions.");
100 
101   // Update active workers to the lower of the limits.
102   uint worker_count = MIN3(heap_waste_worker_limit, active_worker_limit, used_worker_limit);
103   log_debug(gc, task)("Requesting %u active workers for full compaction (waste limited workers: %u, "
104                       "adaptive workers: %u, used limited workers: %u)",
105                       worker_count, heap_waste_worker_limit, active_worker_limit, used_worker_limit);
106   worker_count = heap->workers()->set_active_workers(worker_count);
107   log_info(gc, task)("Using %u workers of %u for full compaction", worker_count, max_worker_count);
108 
109   return worker_count;
110 }
111 
112 G1FullCollector::G1FullCollector(G1CollectedHeap* heap,
113                                  bool explicit_gc,
114                                  bool clear_soft_refs,
115                                  bool do_maximal_compaction) :
116     _heap(heap),
117     _scope(heap->monitoring_support(), explicit_gc, clear_soft_refs, do_maximal_compaction),
118     _num_workers(calc_active_workers()),
119     _oop_queue_set(_num_workers),
120     _array_queue_set(_num_workers),
121     _preserved_marks_set(true),
122     _serial_compaction_point(),
123     _is_alive(this, heap->concurrent_mark()->mark_bitmap()),
124     _is_alive_mutator(heap->ref_processor_stw(), &_is_alive),
125     _always_subject_to_discovery(),
126     _is_subject_mutator(heap->ref_processor_stw(), &_always_subject_to_discovery),
127     _region_attr_table() {
128   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
129 
130   _preserved_marks_set.init(_num_workers);
131   _markers = NEW_C_HEAP_ARRAY(G1FullGCMarker*, _num_workers, mtGC);
132   _compaction_points = NEW_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _num_workers, mtGC);
133 
134   _live_stats = NEW_C_HEAP_ARRAY(G1RegionMarkStats, _heap->max_regions(), mtGC);
135   for (uint j = 0; j < heap->max_regions(); j++) {
136     _live_stats[j].clear();
137   }
138 
139   for (uint i = 0; i < _num_workers; i++) {
140     _markers[i] = new G1FullGCMarker(this, i, _preserved_marks_set.get(i), _live_stats);
141     _compaction_points[i] = new G1FullGCCompactionPoint();
142     _oop_queue_set.register_queue(i, marker(i)->oop_stack());
143     _array_queue_set.register_queue(i, marker(i)->objarray_stack());
144   }
145   _region_attr_table.initialize(heap->reserved(), HeapRegion::GrainBytes);
146 }
147 
148 G1FullCollector::~G1FullCollector() {
149   for (uint i = 0; i < _num_workers; i++) {
150     delete _markers[i];
151     delete _compaction_points[i];
152   }
153   FREE_C_HEAP_ARRAY(G1FullGCMarker*, _markers);
154   FREE_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _compaction_points);
155   FREE_C_HEAP_ARRAY(G1RegionMarkStats, _live_stats);
156 }
157 
158 class PrepareRegionsClosure : public HeapRegionClosure {
159   G1FullCollector* _collector;
160 
161 public:
162   PrepareRegionsClosure(G1FullCollector* collector) : _collector(collector) { }
163 
164   bool do_heap_region(HeapRegion* hr) {
165     G1CollectedHeap::heap()->prepare_region_for_full_compaction(hr);
166     _collector->before_marking_update_attribute_table(hr);
167     return false;
168   }
169 };
170 
171 void G1FullCollector::prepare_collection() {
172   _heap->policy()->record_full_collection_start();
173 
174   // Verification needs the bitmap, so we should clear the bitmap only later.
175   bool in_concurrent_cycle = _heap->abort_concurrent_cycle();
176   _heap->verify_before_full_collection(scope()->is_explicit_gc());
177   if (in_concurrent_cycle) {
178     GCTraceTime(Debug, gc) debug("Clear Bitmap");
179     _heap->concurrent_mark()->clear_bitmap(_heap->workers());
180   }
181 
182   _heap->gc_prologue(true);
183   _heap->retire_tlabs();
184   _heap->prepare_heap_for_full_collection();
185 
186   PrepareRegionsClosure cl(this);
187   _heap->heap_region_iterate(&cl);
188 
189   reference_processor()->start_discovery(scope()->should_clear_soft_refs());
190 
191   // Clear and activate derived pointer collection.
192   clear_and_activate_derived_pointers();
193 }
194 
195 void G1FullCollector::collect() {
196   G1CollectedHeap::start_codecache_marking_cycle_if_inactive();
197 
198   phase1_mark_live_objects();
199   verify_after_marking();
200 
201   // Don't add any more derived pointers during later phases
202   deactivate_derived_pointers();
203 
204   phase2_prepare_compaction();
205 
206   phase3_adjust_pointers();
207 
208   phase4_do_compaction();
209 
210   Continuations::on_gc_marking_cycle_finish();
211   Continuations::arm_all_nmethods();
212 }
213 
214 void G1FullCollector::complete_collection() {
215   // Restore all marks.
216   restore_marks();
217 
218   // When the pointers have been adjusted and moved, we can
219   // update the derived pointer table.
220   update_derived_pointers();
221 
222   // Prepare the bitmap for the next (potentially concurrent) marking.
223   _heap->concurrent_mark()->clear_bitmap(_heap->workers());
224 
225   _heap->prepare_heap_for_mutators();
226 
227   _heap->resize_all_tlabs();
228 
229   _heap->policy()->record_full_collection_end();
230   _heap->gc_epilogue(true);
231 
232   _heap->verify_after_full_collection();
233 }
234 
235 void G1FullCollector::before_marking_update_attribute_table(HeapRegion* hr) {
236   if (hr->is_free()) {
237     _region_attr_table.set_free(hr->hrm_index());
238   } else if (hr->is_closed_archive()) {
239     _region_attr_table.set_skip_marking(hr->hrm_index());
240   } else if (hr->is_pinned()) {
241     _region_attr_table.set_skip_compacting(hr->hrm_index());
242   } else {
243     // Everything else should be compacted.
244     _region_attr_table.set_compacting(hr->hrm_index());
245   }
246 }
247 
248 class G1FullGCRefProcProxyTask : public RefProcProxyTask {
249   G1FullCollector& _collector;
250 
251 public:
252   G1FullGCRefProcProxyTask(G1FullCollector &collector, uint max_workers)
253     : RefProcProxyTask("G1FullGCRefProcProxyTask", max_workers),
254       _collector(collector) {}
255 
256   void work(uint worker_id) override {
257     assert(worker_id < _max_workers, "sanity");
258     G1IsAliveClosure is_alive(&_collector);
259     uint index = (_tm == RefProcThreadModel::Single) ? 0 : worker_id;
260     G1FullKeepAliveClosure keep_alive(_collector.marker(index));
261     BarrierEnqueueDiscoveredFieldClosure enqueue;
262     G1FollowStackClosure* complete_gc = _collector.marker(index)->stack_closure();
263     _rp_task->rp_work(worker_id, &is_alive, &keep_alive, &enqueue, complete_gc);
264   }
265 };
266 
267 void G1FullCollector::phase1_mark_live_objects() {
268   // Recursively traverse all live objects and mark them.
269   GCTraceTime(Info, gc, phases) info("Phase 1: Mark live objects", scope()->timer());
270 
271   {
272     // Do the actual marking.
273     G1FullGCMarkTask marking_task(this);
274     run_task(&marking_task);
275   }
276 
277   {
278     uint old_active_mt_degree = reference_processor()->num_queues();
279     reference_processor()->set_active_mt_degree(workers());
280     GCTraceTime(Debug, gc, phases) debug("Phase 1: Reference Processing", scope()->timer());
281     // Process reference objects found during marking.
282     ReferenceProcessorPhaseTimes pt(scope()->timer(), reference_processor()->max_num_queues());
283     G1FullGCRefProcProxyTask task(*this, reference_processor()->max_num_queues());
284     const ReferenceProcessorStats& stats = reference_processor()->process_discovered_references(task, pt);
285     scope()->tracer()->report_gc_reference_stats(stats);
286     pt.print_all_references();
287     assert(marker(0)->oop_stack()->is_empty(), "Should be no oops on the stack");
288 
289     reference_processor()->set_active_mt_degree(old_active_mt_degree);
290   }
291 
292   // Weak oops cleanup.
293   {
294     GCTraceTime(Debug, gc, phases) debug("Phase 1: Weak Processing", scope()->timer());
295     WeakProcessor::weak_oops_do(_heap->workers(), &_is_alive, &do_nothing_cl, 1);
296   }
297 
298   // Class unloading and cleanup.
299   if (ClassUnloading) {
300     GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer());
301     // Unload classes and purge the SystemDictionary.
302     bool purged_class = SystemDictionary::do_unloading(scope()->timer());
303     _heap->complete_cleaning(&_is_alive, purged_class);
304   }
305 
306   scope()->tracer()->report_object_count_after_gc(&_is_alive);
307 #if TASKQUEUE_STATS
308   oop_queue_set()->print_and_reset_taskqueue_stats("Oop Queue");
309   array_queue_set()->print_and_reset_taskqueue_stats("ObjArrayOop Queue");
310 #endif
311 }
312 
313 void G1FullCollector::phase2_prepare_compaction() {
314   GCTraceTime(Info, gc, phases) info("Phase 2: Prepare compaction", scope()->timer());
315 
316   phase2a_determine_worklists();
317 
318   bool has_free_compaction_targets = phase2b_forward_oops();
319 
320   // Try to avoid OOM immediately after Full GC in case there are no free regions
321   // left after determining the result locations (i.e. this phase). Prepare to
322   // maximally compact the tail regions of the compaction queues serially.
323   if (!has_free_compaction_targets) {
324     phase2c_prepare_serial_compaction();
325   }
326 }
327 
328 void G1FullCollector::phase2a_determine_worklists() {
329   GCTraceTime(Debug, gc, phases) debug("Phase 2: Determine work lists", scope()->timer());
330 
331   G1DetermineCompactionQueueClosure cl(this);
332   _heap->heap_region_iterate(&cl);
333 }
334 
335 bool G1FullCollector::phase2b_forward_oops() {
336   GCTraceTime(Debug, gc, phases) debug("Phase 2: Prepare parallel compaction", scope()->timer());
337 
338   G1FullGCPrepareTask task(this);
339   run_task(&task);
340 
341   return task.has_free_compaction_targets();
342 }
343 
344 void G1FullCollector::phase2c_prepare_serial_compaction() {
345   GCTraceTime(Debug, gc, phases) debug("Phase 2: Prepare serial compaction", scope()->timer());
346   // At this point we know that after parallel compaction there will be no
347   // completely free regions. That means that the last region of
348   // all compaction queues still have data in them. We try to compact
349   // these regions in serial to avoid a premature OOM when the mutator wants
350   // to allocate the first eden region after gc.
351   for (uint i = 0; i < workers(); i++) {
352     G1FullGCCompactionPoint* cp = compaction_point(i);
353     if (cp->has_regions()) {
354       serial_compaction_point()->add(cp->remove_last());
355     }
356   }
357 
358   // Update the forwarding information for the regions in the serial
359   // compaction point.
360   G1FullGCCompactionPoint* cp = serial_compaction_point();
361   for (GrowableArrayIterator<HeapRegion*> it = cp->regions()->begin(); it != cp->regions()->end(); ++it) {
362     HeapRegion* current = *it;
363     if (!cp->is_initialized()) {
364       // Initialize the compaction point. Nothing more is needed for the first heap region
365       // since it is already prepared for compaction.
366       cp->initialize(current);
367     } else {
368       assert(!current->is_humongous(), "Should be no humongous regions in compaction queue");
369       G1SerialRePrepareClosure re_prepare(cp, current);
370       current->set_compaction_top(current->bottom());
371       current->apply_to_marked_objects(mark_bitmap(), &re_prepare);
372     }
373   }
374   cp->update();
375 }
376 
377 void G1FullCollector::phase3_adjust_pointers() {
378   // Adjust the pointers to reflect the new locations
379   GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers", scope()->timer());
380 
381   G1FullGCAdjustTask task(this);
382   run_task(&task);
383 }
384 
385 void G1FullCollector::phase4_do_compaction() {
386   // Compact the heap using the compaction queues created in phase 2.
387   GCTraceTime(Info, gc, phases) info("Phase 4: Compact heap", scope()->timer());
388   G1FullGCCompactTask task(this);
389   run_task(&task);
390 
391   // Serial compact to avoid OOM when very few free regions.
392   if (serial_compaction_point()->has_regions()) {
393     task.serial_compaction();
394   }
395 }
396 
397 void G1FullCollector::restore_marks() {
398   _preserved_marks_set.restore(_heap->workers());
399   _preserved_marks_set.reclaim();
400 }
401 
402 void G1FullCollector::run_task(WorkerTask* task) {
403   _heap->workers()->run_task(task, _num_workers);
404 }
405 
406 void G1FullCollector::verify_after_marking() {
407   if (!VerifyDuringGC || !_heap->verifier()->should_verify(G1HeapVerifier::G1VerifyFull)) {
408     // Only do verification if VerifyDuringGC and G1VerifyFull is set.
409     return;
410   }
411 
412 #if COMPILER2_OR_JVMCI
413   DerivedPointerTableDeactivate dpt_deact;
414 #endif
415   _heap->prepare_for_verify();
416   // Note: we can verify only the heap here. When an object is
417   // marked, the previous value of the mark word (including
418   // identity hash values, ages, etc) is preserved, and the mark
419   // word is set to markWord::marked_value - effectively removing
420   // any hash values from the mark word. These hash values are
421   // used when verifying the dictionaries and so removing them
422   // from the mark word can make verification of the dictionaries
423   // fail. At the end of the GC, the original mark word values
424   // (including hash values) are restored to the appropriate
425   // objects.
426   GCTraceTime(Info, gc, verify) tm("Verifying During GC (full)");
427   _heap->verify(VerifyOption::G1UseFullMarking);
428 }