1 /*
  2  * Copyright (c) 2017, 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 "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.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/handles.inline.hpp"
 48 #include "utilities/debug.hpp"
 49 
 50 static void clear_and_activate_derived_pointers() {
 51 #if COMPILER2_OR_JVMCI
 52   DerivedPointerTable::clear();
 53 #endif
 54 }
 55 
 56 static void deactivate_derived_pointers() {
 57 #if COMPILER2_OR_JVMCI
 58   DerivedPointerTable::set_active(false);
 59 #endif
 60 }
 61 
 62 static void update_derived_pointers() {
 63 #if COMPILER2_OR_JVMCI
 64   DerivedPointerTable::update_pointers();
 65 #endif
 66 }
 67 
 68 G1CMBitMap* G1FullCollector::mark_bitmap() {
 69   return _heap->concurrent_mark()->next_mark_bitmap();
 70 }
 71 
 72 ReferenceProcessor* G1FullCollector::reference_processor() {
 73   return _heap->ref_processor_stw();
 74 }
 75 
 76 uint G1FullCollector::calc_active_workers() {
 77   G1CollectedHeap* heap = G1CollectedHeap::heap();
 78   uint max_worker_count = heap->workers()->max_workers();
 79   // Only calculate number of workers if UseDynamicNumberOfGCThreads
 80   // is enabled, otherwise use max.
 81   if (!UseDynamicNumberOfGCThreads) {
 82     return max_worker_count;
 83   }
 84 
 85   // Consider G1HeapWastePercent to decide max number of workers. Each worker
 86   // will in average cause half a region waste.
 87   uint max_wasted_regions_allowed = ((heap->num_regions() * G1HeapWastePercent) / 100);
 88   uint waste_worker_count = MAX2((max_wasted_regions_allowed * 2) , 1u);
 89   uint heap_waste_worker_limit = MIN2(waste_worker_count, max_worker_count);
 90 
 91   // Also consider HeapSizePerGCThread by calling WorkerPolicy to calculate
 92   // the number of workers.
 93   uint current_active_workers = heap->workers()->active_workers();
 94   uint active_worker_limit = WorkerPolicy::calc_active_workers(max_worker_count, current_active_workers, 0);
 95 
 96   // Finally consider the amount of used regions.
 97   uint used_worker_limit = heap->num_used_regions();
 98   assert(used_worker_limit > 0, "Should never have zero used regions.");
 99 
100   // Update active workers to the lower of the limits.
101   uint worker_count = MIN3(heap_waste_worker_limit, active_worker_limit, used_worker_limit);
102   log_debug(gc, task)("Requesting %u active workers for full compaction (waste limited workers: %u, "
103                       "adaptive workers: %u, used limited workers: %u)",
104                       worker_count, heap_waste_worker_limit, active_worker_limit, used_worker_limit);
105   worker_count = heap->workers()->set_active_workers(worker_count);
106   log_info(gc, task)("Using %u workers of %u for full compaction", worker_count, max_worker_count);
107 
108   return worker_count;
109 }
110 
111 G1FullCollector::G1FullCollector(G1CollectedHeap* heap,
112                                  bool explicit_gc,
113                                  bool clear_soft_refs,
114                                  bool do_maximum_compaction) :
115     _heap(heap),
116     _scope(heap->monitoring_support(), explicit_gc, clear_soft_refs, do_maximum_compaction),
117     _num_workers(calc_active_workers()),
118     _oop_queue_set(_num_workers),
119     _array_queue_set(_num_workers),
120     _preserved_marks_set(true),
121     _serial_compaction_point(),
122     _is_alive(this, heap->concurrent_mark()->next_mark_bitmap()),
123     _is_alive_mutator(heap->ref_processor_stw(), &_is_alive),
124     _always_subject_to_discovery(),
125     _is_subject_mutator(heap->ref_processor_stw(), &_always_subject_to_discovery),
126     _region_attr_table() {
127   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
128 
129   _preserved_marks_set.init(_num_workers);
130   _markers = NEW_C_HEAP_ARRAY(G1FullGCMarker*, _num_workers, mtGC);
131   _compaction_points = NEW_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _num_workers, mtGC);
132 
133   _live_stats = NEW_C_HEAP_ARRAY(G1RegionMarkStats, _heap->max_regions(), mtGC);
134   for (uint j = 0; j < heap->max_regions(); j++) {
135     _live_stats[j].clear();
136   }
137 
138   for (uint i = 0; i < _num_workers; i++) {
139     _markers[i] = new G1FullGCMarker(this, i, _preserved_marks_set.get(i), _live_stats);
140     _compaction_points[i] = new G1FullGCCompactionPoint();
141     _oop_queue_set.register_queue(i, marker(i)->oop_stack());
142     _array_queue_set.register_queue(i, marker(i)->objarray_stack());
143   }
144   _region_attr_table.initialize(heap->reserved(), HeapRegion::GrainBytes);
145 }
146 
147 G1FullCollector::~G1FullCollector() {
148   for (uint i = 0; i < _num_workers; i++) {
149     delete _markers[i];
150     delete _compaction_points[i];
151   }
152   FREE_C_HEAP_ARRAY(G1FullGCMarker*, _markers);
153   FREE_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _compaction_points);
154   FREE_C_HEAP_ARRAY(G1RegionMarkStats, _live_stats);
155 }
156 
157 class PrepareRegionsClosure : public HeapRegionClosure {
158   G1FullCollector* _collector;
159 
160 public:
161   PrepareRegionsClosure(G1FullCollector* collector) : _collector(collector) { }
162 
163   bool do_heap_region(HeapRegion* hr) {
164     G1CollectedHeap::heap()->prepare_region_for_full_compaction(hr);
165     _collector->before_marking_update_attribute_table(hr);
166     return false;
167   }
168 };
169 
170 void G1FullCollector::prepare_collection() {
171   _heap->policy()->record_full_collection_start();
172 
173   _heap->abort_concurrent_cycle();
174   _heap->verify_before_full_collection(scope()->is_explicit_gc());
175 
176   _heap->gc_prologue(true);
177   _heap->retire_tlabs();
178   _heap->prepare_heap_for_full_collection();
179 
180   PrepareRegionsClosure cl(this);
181   _heap->heap_region_iterate(&cl);
182 
183   reference_processor()->start_discovery(scope()->should_clear_soft_refs());
184 
185   // Clear and activate derived pointer collection.
186   clear_and_activate_derived_pointers();
187 }
188 
189 void G1FullCollector::collect() {


190   phase1_mark_live_objects();
191   verify_after_marking();
192 
193   // Don't add any more derived pointers during later phases
194   deactivate_derived_pointers();
195 
196   phase2_prepare_compaction();
197 
198   phase3_adjust_pointers();
199 
200   phase4_do_compaction();


201 }
202 
203 void G1FullCollector::complete_collection() {
204   // Restore all marks.
205   restore_marks();
206 
207   // When the pointers have been adjusted and moved, we can
208   // update the derived pointer table.
209   update_derived_pointers();
210 
211   _heap->concurrent_mark()->swap_mark_bitmaps();
212   // Prepare the bitmap for the next (potentially concurrent) marking.
213   _heap->concurrent_mark()->clear_next_bitmap(_heap->workers());
214 
215   _heap->prepare_heap_for_mutators();
216 
217   _heap->resize_all_tlabs();
218 
219   _heap->policy()->record_full_collection_end();
220   _heap->gc_epilogue(true);
221 
222   _heap->verify_after_full_collection();
223 }
224 
225 void G1FullCollector::before_marking_update_attribute_table(HeapRegion* hr) {
226   if (hr->is_free()) {
227     _region_attr_table.set_free(hr->hrm_index());
228   } else if (hr->is_closed_archive()) {
229     _region_attr_table.set_skip_marking(hr->hrm_index());
230   } else if (hr->is_pinned()) {
231     _region_attr_table.set_skip_compacting(hr->hrm_index());
232   } else {
233     // Everything else should be compacted.
234     _region_attr_table.set_compacting(hr->hrm_index());
235   }
236 }
237 
238 class G1FullGCRefProcProxyTask : public RefProcProxyTask {
239   G1FullCollector& _collector;
240 
241 public:
242   G1FullGCRefProcProxyTask(G1FullCollector &collector, uint max_workers)
243     : RefProcProxyTask("G1FullGCRefProcProxyTask", max_workers),
244       _collector(collector) {}
245 
246   void work(uint worker_id) override {
247     assert(worker_id < _max_workers, "sanity");
248     G1IsAliveClosure is_alive(&_collector);
249     uint index = (_tm == RefProcThreadModel::Single) ? 0 : worker_id;
250     G1FullKeepAliveClosure keep_alive(_collector.marker(index));
251     BarrierEnqueueDiscoveredFieldClosure enqueue;
252     G1FollowStackClosure* complete_gc = _collector.marker(index)->stack_closure();
253     _rp_task->rp_work(worker_id, &is_alive, &keep_alive, &enqueue, complete_gc);
254   }
255 };
256 
257 void G1FullCollector::phase1_mark_live_objects() {
258   // Recursively traverse all live objects and mark them.
259   GCTraceTime(Info, gc, phases) info("Phase 1: Mark live objects", scope()->timer());
260 
261   {
262     // Do the actual marking.
263     G1FullGCMarkTask marking_task(this);
264     run_task(&marking_task);
265   }
266 
267   {
268     uint old_active_mt_degree = reference_processor()->num_queues();
269     reference_processor()->set_active_mt_degree(workers());
270     GCTraceTime(Debug, gc, phases) debug("Phase 1: Reference Processing", scope()->timer());
271     // Process reference objects found during marking.
272     ReferenceProcessorPhaseTimes pt(scope()->timer(), reference_processor()->max_num_queues());
273     G1FullGCRefProcProxyTask task(*this, reference_processor()->max_num_queues());
274     const ReferenceProcessorStats& stats = reference_processor()->process_discovered_references(task, pt);
275     scope()->tracer()->report_gc_reference_stats(stats);
276     pt.print_all_references();
277     assert(marker(0)->oop_stack()->is_empty(), "Should be no oops on the stack");
278 
279     reference_processor()->set_active_mt_degree(old_active_mt_degree);
280   }
281 
282   // Weak oops cleanup.
283   {
284     GCTraceTime(Debug, gc, phases) debug("Phase 1: Weak Processing", scope()->timer());
285     WeakProcessor::weak_oops_do(_heap->workers(), &_is_alive, &do_nothing_cl, 1);
286   }
287 
288   // Class unloading and cleanup.
289   if (ClassUnloading) {
290     GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer());
291     // Unload classes and purge the SystemDictionary.
292     bool purged_class = SystemDictionary::do_unloading(scope()->timer());
293     _heap->complete_cleaning(&_is_alive, purged_class);
294   }
295 
296   scope()->tracer()->report_object_count_after_gc(&_is_alive);
297 }
298 
299 void G1FullCollector::phase2_prepare_compaction() {
300   GCTraceTime(Info, gc, phases) info("Phase 2: Prepare for compaction", scope()->timer());
301   G1FullGCPrepareTask task(this);
302   run_task(&task);
303 
304   // To avoid OOM when there is memory left.
305   if (!task.has_freed_regions()) {
306     task.prepare_serial_compaction();
307   }
308 }
309 
310 void G1FullCollector::phase3_adjust_pointers() {
311   // Adjust the pointers to reflect the new locations
312   GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers", scope()->timer());
313 
314   G1FullGCAdjustTask task(this);
315   run_task(&task);
316 }
317 
318 void G1FullCollector::phase4_do_compaction() {
319   // Compact the heap using the compaction queues created in phase 2.
320   GCTraceTime(Info, gc, phases) info("Phase 4: Compact heap", scope()->timer());
321   G1FullGCCompactTask task(this);
322   run_task(&task);
323 
324   // Serial compact to avoid OOM when very few free regions.
325   if (serial_compaction_point()->has_regions()) {
326     task.serial_compaction();
327   }
328 }
329 
330 void G1FullCollector::restore_marks() {
331   _preserved_marks_set.restore(_heap->workers());
332   _preserved_marks_set.reclaim();
333 }
334 
335 void G1FullCollector::run_task(WorkerTask* task) {
336   _heap->workers()->run_task(task, _num_workers);
337 }
338 
339 void G1FullCollector::verify_after_marking() {
340   if (!VerifyDuringGC || !_heap->verifier()->should_verify(G1HeapVerifier::G1VerifyFull)) {
341     // Only do verification if VerifyDuringGC and G1VerifyFull is set.
342     return;
343   }
344 
345 #if COMPILER2_OR_JVMCI
346   DerivedPointerTableDeactivate dpt_deact;
347 #endif
348   _heap->prepare_for_verify();
349   // Note: we can verify only the heap here. When an object is
350   // marked, the previous value of the mark word (including
351   // identity hash values, ages, etc) is preserved, and the mark
352   // word is set to markWord::marked_value - effectively removing
353   // any hash values from the mark word. These hash values are
354   // used when verifying the dictionaries and so removing them
355   // from the mark word can make verification of the dictionaries
356   // fail. At the end of the GC, the original mark word values
357   // (including hash values) are restored to the appropriate
358   // objects.
359   GCTraceTime(Info, gc, verify) tm("Verifying During GC (full)");
360   _heap->verify(VerifyOption_G1UseFullMarking);
361 }
--- EOF ---