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.
 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.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/slidingForwarding.hpp"
 44 #include "gc/shared/verifyOption.hpp"
 45 #include "gc/shared/weakProcessor.inline.hpp"
 46 #include "gc/shared/workerPolicy.hpp"
 47 #include "logging/log.hpp"
 48 #include "runtime/continuation.hpp"
 49 #include "runtime/handles.inline.hpp"
 50 #include "utilities/debug.hpp"
 51 
 52 static void clear_and_activate_derived_pointers() {
 53 #if COMPILER2_OR_JVMCI
 54   DerivedPointerTable::clear();
 55 #endif
 56 }
 57 
 58 static void deactivate_derived_pointers() {
 59 #if COMPILER2_OR_JVMCI
 60   DerivedPointerTable::set_active(false);
 61 #endif
 62 }
 63 
 64 static void update_derived_pointers() {
 65 #if COMPILER2_OR_JVMCI
 66   DerivedPointerTable::update_pointers();
 67 #endif
 68 }
 69 
 70 G1CMBitMap* G1FullCollector::mark_bitmap() {
 71   return _heap->concurrent_mark()->mark_bitmap();
 72 }
 73 
 74 ReferenceProcessor* G1FullCollector::reference_processor() {
 75   return _heap->ref_processor_stw();
 76 }
 77 
 78 uint G1FullCollector::calc_active_workers() {
 79   G1CollectedHeap* heap = G1CollectedHeap::heap();
 80   uint max_worker_count = heap->workers()->max_workers();
 81   // Only calculate number of workers if UseDynamicNumberOfGCThreads
 82   // is enabled, otherwise use max.
 83   if (!UseDynamicNumberOfGCThreads) {
 84     return max_worker_count;
 85   }
 86 
 87   // Consider G1HeapWastePercent to decide max number of workers. Each worker
 88   // will in average cause half a region waste.
 89   uint max_wasted_regions_allowed = ((heap->num_regions() * G1HeapWastePercent) / 100);
 90   uint waste_worker_count = MAX2((max_wasted_regions_allowed * 2) , 1u);
 91   uint heap_waste_worker_limit = MIN2(waste_worker_count, max_worker_count);
 92 
 93   // Also consider HeapSizePerGCThread by calling WorkerPolicy to calculate
 94   // the number of workers.
 95   uint current_active_workers = heap->workers()->active_workers();
 96   uint active_worker_limit = WorkerPolicy::calc_active_workers(max_worker_count, current_active_workers, 0);
 97 
 98   // Finally consider the amount of used regions.
 99   uint used_worker_limit = heap->num_used_regions();
100   assert(used_worker_limit > 0, "Should never have zero used regions.");
101 
102   // Update active workers to the lower of the limits.
103   uint worker_count = MIN3(heap_waste_worker_limit, active_worker_limit, used_worker_limit);
104   log_debug(gc, task)("Requesting %u active workers for full compaction (waste limited workers: %u, "
105                       "adaptive workers: %u, used limited workers: %u)",
106                       worker_count, heap_waste_worker_limit, active_worker_limit, used_worker_limit);
107   worker_count = heap->workers()->set_active_workers(worker_count);
108   log_info(gc, task)("Using %u workers of %u for full compaction", worker_count, max_worker_count);
109 
110   return worker_count;
111 }
112 
113 G1FullCollector::G1FullCollector(G1CollectedHeap* heap,
114                                  bool explicit_gc,
115                                  bool clear_soft_refs,
116                                  bool do_maximal_compaction) :
117     _heap(heap),
118     _scope(heap->monitoring_support(), explicit_gc, clear_soft_refs, do_maximal_compaction),
119     _num_workers(calc_active_workers()),
120     _oop_queue_set(_num_workers),
121     _array_queue_set(_num_workers),
122     _preserved_marks_set(true),
123     _serial_compaction_point(),
124     _is_alive(this, heap->concurrent_mark()->mark_bitmap()),
125     _is_alive_mutator(heap->ref_processor_stw(), &_is_alive),
126     _always_subject_to_discovery(),
127     _is_subject_mutator(heap->ref_processor_stw(), &_always_subject_to_discovery),
128     _region_attr_table() {
129   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
130 
131   _preserved_marks_set.init(_num_workers);
132   _markers = NEW_C_HEAP_ARRAY(G1FullGCMarker*, _num_workers, mtGC);
133   _compaction_points = NEW_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _num_workers, mtGC);
134 
135   _live_stats = NEW_C_HEAP_ARRAY(G1RegionMarkStats, _heap->max_regions(), mtGC);
136   for (uint j = 0; j < heap->max_regions(); j++) {
137     _live_stats[j].clear();
138   }
139 
140   for (uint i = 0; i < _num_workers; i++) {
141     _markers[i] = new G1FullGCMarker(this, i, _preserved_marks_set.get(i), _live_stats);
142     _compaction_points[i] = new G1FullGCCompactionPoint();
143     _oop_queue_set.register_queue(i, marker(i)->oop_stack());
144     _array_queue_set.register_queue(i, marker(i)->objarray_stack());
145   }
146   _region_attr_table.initialize(heap->reserved(), HeapRegion::GrainBytes);
147 }
148 
149 G1FullCollector::~G1FullCollector() {
150   for (uint i = 0; i < _num_workers; i++) {
151     delete _markers[i];
152     delete _compaction_points[i];
153   }
154   FREE_C_HEAP_ARRAY(G1FullGCMarker*, _markers);
155   FREE_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _compaction_points);
156   FREE_C_HEAP_ARRAY(G1RegionMarkStats, _live_stats);
157 }
158 
159 class PrepareRegionsClosure : public HeapRegionClosure {
160   G1FullCollector* _collector;
161 
162 public:
163   PrepareRegionsClosure(G1FullCollector* collector) : _collector(collector) { }
164 
165   bool do_heap_region(HeapRegion* hr) {
166     G1CollectedHeap::heap()->prepare_region_for_full_compaction(hr);
167     _collector->before_marking_update_attribute_table(hr);
168     return false;
169   }
170 };
171 
172 void G1FullCollector::prepare_collection() {
173   _heap->policy()->record_full_collection_start();
174 
175   // Verification needs the bitmap, so we should clear the bitmap only later.
176   bool in_concurrent_cycle = _heap->abort_concurrent_cycle();
177   _heap->verify_before_full_collection(scope()->is_explicit_gc());
178   if (in_concurrent_cycle) {
179     GCTraceTime(Debug, gc) debug("Clear Bitmap");
180     _heap->concurrent_mark()->clear_bitmap(_heap->workers());
181   }
182 
183   _heap->gc_prologue(true);
184   _heap->retire_tlabs();
185   _heap->prepare_heap_for_full_collection();
186 
187   PrepareRegionsClosure cl(this);
188   _heap->heap_region_iterate(&cl);
189 
190   reference_processor()->start_discovery(scope()->should_clear_soft_refs());
191 
192   // Clear and activate derived pointer collection.
193   clear_and_activate_derived_pointers();
194 }
195 
196 void G1FullCollector::collect() {
197   G1CollectedHeap::start_codecache_marking_cycle_if_inactive();
198 
199   phase1_mark_live_objects();
200   verify_after_marking();
201 
202   // Don't add any more derived pointers during later phases
203   deactivate_derived_pointers();
204 
205   phase2_prepare_compaction();
206 
207   phase3_adjust_pointers();
208 
209   phase4_do_compaction();
210 
211   Continuations::on_gc_marking_cycle_finish();
212   Continuations::arm_all_nmethods();
213 }
214 
215 void G1FullCollector::complete_collection() {
216   // Restore all marks.
217   restore_marks();
218 
219   // When the pointers have been adjusted and moved, we can
220   // update the derived pointer table.
221   update_derived_pointers();
222 
223   // Prepare the bitmap for the next (potentially concurrent) marking.
224   _heap->concurrent_mark()->clear_bitmap(_heap->workers());
225 
226   _heap->prepare_heap_for_mutators();
227 
228   _heap->resize_all_tlabs();
229 
230   _heap->policy()->record_full_collection_end();
231   _heap->gc_epilogue(true);
232 
233   _heap->verify_after_full_collection();
234 }
235 
236 void G1FullCollector::before_marking_update_attribute_table(HeapRegion* hr) {
237   if (hr->is_free()) {
238     _region_attr_table.set_free(hr->hrm_index());
239   } else if (hr->is_closed_archive()) {
240     _region_attr_table.set_skip_marking(hr->hrm_index());
241   } else if (hr->is_pinned()) {
242     _region_attr_table.set_skip_compacting(hr->hrm_index());
243   } else {
244     // Everything else should be compacted.
245     _region_attr_table.set_compacting(hr->hrm_index());
246   }
247 }
248 
249 class G1FullGCRefProcProxyTask : public RefProcProxyTask {
250   G1FullCollector& _collector;
251 
252 public:
253   G1FullGCRefProcProxyTask(G1FullCollector &collector, uint max_workers)
254     : RefProcProxyTask("G1FullGCRefProcProxyTask", max_workers),
255       _collector(collector) {}
256 
257   void work(uint worker_id) override {
258     assert(worker_id < _max_workers, "sanity");
259     G1IsAliveClosure is_alive(&_collector);
260     uint index = (_tm == RefProcThreadModel::Single) ? 0 : worker_id;
261     G1FullKeepAliveClosure keep_alive(_collector.marker(index));
262     BarrierEnqueueDiscoveredFieldClosure enqueue;
263     G1FollowStackClosure* complete_gc = _collector.marker(index)->stack_closure();
264     _rp_task->rp_work(worker_id, &is_alive, &keep_alive, &enqueue, complete_gc);
265   }
266 };
267 
268 void G1FullCollector::phase1_mark_live_objects() {
269   // Recursively traverse all live objects and mark them.
270   GCTraceTime(Info, gc, phases) info("Phase 1: Mark live objects", scope()->timer());
271 
272   {
273     // Do the actual marking.
274     G1FullGCMarkTask marking_task(this);
275     run_task(&marking_task);
276   }
277 
278   {
279     uint old_active_mt_degree = reference_processor()->num_queues();
280     reference_processor()->set_active_mt_degree(workers());
281     GCTraceTime(Debug, gc, phases) debug("Phase 1: Reference Processing", scope()->timer());
282     // Process reference objects found during marking.
283     ReferenceProcessorPhaseTimes pt(scope()->timer(), reference_processor()->max_num_queues());
284     G1FullGCRefProcProxyTask task(*this, reference_processor()->max_num_queues());
285     const ReferenceProcessorStats& stats = reference_processor()->process_discovered_references(task, pt);
286     scope()->tracer()->report_gc_reference_stats(stats);
287     pt.print_all_references();
288     assert(marker(0)->oop_stack()->is_empty(), "Should be no oops on the stack");
289 
290     reference_processor()->set_active_mt_degree(old_active_mt_degree);
291   }
292 
293   // Weak oops cleanup.
294   {
295     GCTraceTime(Debug, gc, phases) debug("Phase 1: Weak Processing", scope()->timer());
296     WeakProcessor::weak_oops_do(_heap->workers(), &_is_alive, &do_nothing_cl, 1);
297   }
298 
299   // Class unloading and cleanup.
300   if (ClassUnloading) {
301     GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer());
302     // Unload classes and purge the SystemDictionary.
303     bool purged_class = SystemDictionary::do_unloading(scope()->timer());
304     _heap->complete_cleaning(&_is_alive, purged_class);
305   }
306 
307   scope()->tracer()->report_object_count_after_gc(&_is_alive);
308 #if TASKQUEUE_STATS
309   oop_queue_set()->print_and_reset_taskqueue_stats("Oop Queue");
310   array_queue_set()->print_and_reset_taskqueue_stats("ObjArrayOop Queue");
311 #endif
312 }
313 
314 void G1FullCollector::phase2_prepare_compaction() {
315   GCTraceTime(Info, gc, phases) info("Phase 2: Prepare compaction", scope()->timer());
316 
317   _heap->forwarding()->clear();
318 
319   phase2a_determine_worklists();
320 
321   bool has_free_compaction_targets = phase2b_forward_oops();
322 
323   // Try to avoid OOM immediately after Full GC in case there are no free regions
324   // left after determining the result locations (i.e. this phase). Prepare to
325   // maximally compact the tail regions of the compaction queues serially.
326   // TODO: Disabled for now because it violates sliding-forwarding assumption.
327   // if (!has_free_compaction_targets) {
328   //   phase2c_prepare_serial_compaction();
329   // }
330 }
331 
332 void G1FullCollector::phase2a_determine_worklists() {
333   GCTraceTime(Debug, gc, phases) debug("Phase 2: Determine work lists", scope()->timer());
334 
335   G1DetermineCompactionQueueClosure cl(this);
336   _heap->heap_region_iterate(&cl);
337 }
338 
339 bool G1FullCollector::phase2b_forward_oops() {
340   GCTraceTime(Debug, gc, phases) debug("Phase 2: Prepare parallel compaction", scope()->timer());
341 
342   G1FullGCPrepareTask task(this);
343   run_task(&task);
344 
345   return task.has_free_compaction_targets();
346 }
347 
348 void G1FullCollector::phase2c_prepare_serial_compaction() {
349   ShouldNotReachHere(); // Disabled in Lilliput.
350 //  GCTraceTime(Debug, gc, phases) debug("Phase 2: Prepare serial compaction", scope()->timer());
351 //  // At this point we know that after parallel compaction there will be no
352 //  // completely free regions. That means that the last region of
353 //  // all compaction queues still have data in them. We try to compact
354 //  // these regions in serial to avoid a premature OOM when the mutator wants
355 //  // to allocate the first eden region after gc.
356 //  for (uint i = 0; i < workers(); i++) {
357 //    G1FullGCCompactionPoint* cp = compaction_point(i);
358 //    if (cp->has_regions()) {
359 //      serial_compaction_point()->add(cp->remove_last());
360 //    }
361 //  }
362 //
363 //  // Update the forwarding information for the regions in the serial
364 //  // compaction point.
365 //  G1FullGCCompactionPoint* cp = serial_compaction_point();
366 //  for (GrowableArrayIterator<HeapRegion*> it = cp->regions()->begin(); it != cp->regions()->end(); ++it) {
367 //    HeapRegion* current = *it;
368 //    if (!cp->is_initialized()) {
369 //      // Initialize the compaction point. Nothing more is needed for the first heap region
370 //      // since it is already prepared for compaction.
371 //      cp->initialize(current);
372 //    } else {
373 //      assert(!current->is_humongous(), "Should be no humongous regions in compaction queue");
374 //      G1SerialRePrepareClosure re_prepare(cp, current);
375 //      current->set_compaction_top(current->bottom());
376 //      current->apply_to_marked_objects(mark_bitmap(), &re_prepare);
377 //    }
378 //  }
379 //  cp->update();
380 }
381 
382 void G1FullCollector::phase3_adjust_pointers() {
383   // Adjust the pointers to reflect the new locations
384   GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers", scope()->timer());
385 
386   G1FullGCAdjustTask task(this);
387   run_task(&task);
388 }
389 
390 void G1FullCollector::phase4_do_compaction() {
391   // Compact the heap using the compaction queues created in phase 2.
392   GCTraceTime(Info, gc, phases) info("Phase 4: Compact heap", scope()->timer());
393   G1FullGCCompactTask task(this);
394   run_task(&task);
395 
396   // Serial compact to avoid OOM when very few free regions.
397   if (serial_compaction_point()->has_regions()) {
398     task.serial_compaction();
399   }
400 }
401 
402 void G1FullCollector::restore_marks() {
403   _preserved_marks_set.restore(_heap->workers());
404   _preserved_marks_set.reclaim();
405 }
406 
407 void G1FullCollector::run_task(WorkerTask* task) {
408   _heap->workers()->run_task(task, _num_workers);
409 }
410 
411 void G1FullCollector::verify_after_marking() {
412   if (!VerifyDuringGC || !_heap->verifier()->should_verify(G1HeapVerifier::G1VerifyFull)) {
413     // Only do verification if VerifyDuringGC and G1VerifyFull is set.
414     return;
415   }
416 
417 #if COMPILER2_OR_JVMCI
418   DerivedPointerTableDeactivate dpt_deact;
419 #endif
420   _heap->prepare_for_verify();
421   // Note: we can verify only the heap here. When an object is
422   // marked, the previous value of the mark word (including
423   // identity hash values, ages, etc) is preserved, and the mark
424   // word is set to markWord::marked_value - effectively removing
425   // any hash values from the mark word. These hash values are
426   // used when verifying the dictionaries and so removing them
427   // from the mark word can make verification of the dictionaries
428   // fail. At the end of the GC, the original mark word values
429   // (including hash values) are restored to the appropriate
430   // objects.
431   GCTraceTime(Info, gc, verify) tm("Verifying During GC (full)");
432   _heap->verify(VerifyOption::G1UseFullMarking);
433 }