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/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()->next_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()->next_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 _heap->abort_concurrent_cycle();
175 _heap->verify_before_full_collection(scope()->is_explicit_gc());
176
177 _heap->gc_prologue(true);
178 _heap->retire_tlabs();
179 _heap->prepare_heap_for_full_collection();
180
181 PrepareRegionsClosure cl(this);
182 _heap->heap_region_iterate(&cl);
183
184 reference_processor()->start_discovery(scope()->should_clear_soft_refs());
185
186 // Clear and activate derived pointer collection.
187 clear_and_activate_derived_pointers();
188 }
189
190 void G1FullCollector::collect() {
191 phase1_mark_live_objects();
192 verify_after_marking();
193
194 // Don't add any more derived pointers during later phases
195 deactivate_derived_pointers();
196
197 phase2_prepare_compaction();
198
199 phase3_adjust_pointers();
200
201 phase4_do_compaction();
202 }
203
204 void G1FullCollector::complete_collection() {
205 // Restore all marks.
206 restore_marks();
207
208 // When the pointers have been adjusted and moved, we can
209 // update the derived pointer table.
210 update_derived_pointers();
211
212 _heap->concurrent_mark()->swap_mark_bitmaps();
213 // Prepare the bitmap for the next (potentially concurrent) marking.
214 _heap->concurrent_mark()->clear_next_bitmap(_heap->workers());
215
216 _heap->prepare_heap_for_mutators();
217
218 _heap->resize_all_tlabs();
219
220 _heap->policy()->record_full_collection_end();
221 _heap->gc_epilogue(true);
222
223 _heap->verify_after_full_collection();
224 }
225
226 void G1FullCollector::before_marking_update_attribute_table(HeapRegion* hr) {
227 if (hr->is_free()) {
228 _region_attr_table.set_free(hr->hrm_index());
229 } else if (hr->is_closed_archive()) {
230 _region_attr_table.set_skip_marking(hr->hrm_index());
231 } else if (hr->is_pinned()) {
232 _region_attr_table.set_skip_compacting(hr->hrm_index());
233 } else {
234 // Everything else should be compacted.
235 _region_attr_table.set_compacting(hr->hrm_index());
236 }
237 }
238
239 class G1FullGCRefProcProxyTask : public RefProcProxyTask {
240 G1FullCollector& _collector;
241
242 public:
243 G1FullGCRefProcProxyTask(G1FullCollector &collector, uint max_workers)
244 : RefProcProxyTask("G1FullGCRefProcProxyTask", max_workers),
245 _collector(collector) {}
246
247 void work(uint worker_id) override {
248 assert(worker_id < _max_workers, "sanity");
249 G1IsAliveClosure is_alive(&_collector);
250 uint index = (_tm == RefProcThreadModel::Single) ? 0 : worker_id;
251 G1FullKeepAliveClosure keep_alive(_collector.marker(index));
252 BarrierEnqueueDiscoveredFieldClosure enqueue;
253 G1FollowStackClosure* complete_gc = _collector.marker(index)->stack_closure();
254 _rp_task->rp_work(worker_id, &is_alive, &keep_alive, &enqueue, complete_gc);
255 }
256 };
257
258 void G1FullCollector::phase1_mark_live_objects() {
259 // Recursively traverse all live objects and mark them.
260 GCTraceTime(Info, gc, phases) info("Phase 1: Mark live objects", scope()->timer());
261
262 {
263 // Do the actual marking.
264 G1FullGCMarkTask marking_task(this);
265 run_task(&marking_task);
266 }
267
268 {
269 uint old_active_mt_degree = reference_processor()->num_queues();
270 reference_processor()->set_active_mt_degree(workers());
271 GCTraceTime(Debug, gc, phases) debug("Phase 1: Reference Processing", scope()->timer());
272 // Process reference objects found during marking.
273 ReferenceProcessorPhaseTimes pt(scope()->timer(), reference_processor()->max_num_queues());
274 G1FullGCRefProcProxyTask task(*this, reference_processor()->max_num_queues());
275 const ReferenceProcessorStats& stats = reference_processor()->process_discovered_references(task, pt);
276 scope()->tracer()->report_gc_reference_stats(stats);
277 pt.print_all_references();
278 assert(marker(0)->oop_stack()->is_empty(), "Should be no oops on the stack");
279
280 reference_processor()->set_active_mt_degree(old_active_mt_degree);
281 }
282
283 // Weak oops cleanup.
284 {
285 GCTraceTime(Debug, gc, phases) debug("Phase 1: Weak Processing", scope()->timer());
286 WeakProcessor::weak_oops_do(_heap->workers(), &_is_alive, &do_nothing_cl, 1);
287 }
288
289 // Class unloading and cleanup.
290 if (ClassUnloading) {
291 GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer());
292 // Unload classes and purge the SystemDictionary.
293 bool purged_class = SystemDictionary::do_unloading(scope()->timer());
294 _heap->complete_cleaning(&_is_alive, purged_class);
295 }
296
297 scope()->tracer()->report_object_count_after_gc(&_is_alive);
298 #if TASKQUEUE_STATS
299 oop_queue_set()->print_and_reset_taskqueue_stats("Oop Queue");
300 array_queue_set()->print_and_reset_taskqueue_stats("ObjArrayOop Queue");
301 #endif
302 }
303
304 void G1FullCollector::phase2_prepare_compaction() {
305 GCTraceTime(Info, gc, phases) info("Phase 2: Prepare compaction", scope()->timer());
306
307 _heap->forwarding()->clear();
308
309 phase2a_determine_worklists();
310
311 bool has_free_compaction_targets = phase2b_forward_oops();
312
313 // Try to avoid OOM immediately after Full GC in case there are no free regions
314 // left after determining the result locations (i.e. this phase). Prepare to
315 // maximally compact the tail regions of the compaction queues serially.
316 // TODO: Disabled for now because it violates sliding-forwarding assumption.
317 // if (!has_free_compaction_targets) {
318 // phase2c_prepare_serial_compaction();
319 // }
320 }
321
322 void G1FullCollector::phase2a_determine_worklists() {
323 GCTraceTime(Debug, gc, phases) debug("Phase 2: Determine work lists", scope()->timer());
324
325 G1DetermineCompactionQueueClosure cl(this);
326 _heap->heap_region_iterate(&cl);
327 }
328
329 bool G1FullCollector::phase2b_forward_oops() {
330 GCTraceTime(Debug, gc, phases) debug("Phase 2: Prepare parallel compaction", scope()->timer());
331
332 G1FullGCPrepareTask task(this);
333 run_task(&task);
334
335 return task.has_free_compaction_targets();
336 }
337
338 void G1FullCollector::phase2c_prepare_serial_compaction() {
339 ShouldNotReachHere(); // Disabled in Lilliput.
340 // GCTraceTime(Debug, gc, phases) debug("Phase 2: Prepare serial compaction", scope()->timer());
341 // // At this point we know that after parallel compaction there will be no
342 // // completely free regions. That means that the last region of
343 // // all compaction queues still have data in them. We try to compact
344 // // these regions in serial to avoid a premature OOM when the mutator wants
345 // // to allocate the first eden region after gc.
346 // for (uint i = 0; i < workers(); i++) {
347 // G1FullGCCompactionPoint* cp = compaction_point(i);
348 // if (cp->has_regions()) {
349 // serial_compaction_point()->add(cp->remove_last());
350 // }
351 // }
352 //
353 // // Update the forwarding information for the regions in the serial
354 // // compaction point.
355 // G1FullGCCompactionPoint* cp = serial_compaction_point();
356 // for (GrowableArrayIterator<HeapRegion*> it = cp->regions()->begin(); it != cp->regions()->end(); ++it) {
357 // HeapRegion* current = *it;
358 // if (!cp->is_initialized()) {
359 // // Initialize the compaction point. Nothing more is needed for the first heap region
360 // // since it is already prepared for compaction.
361 // cp->initialize(current);
362 // } else {
363 // assert(!current->is_humongous(), "Should be no humongous regions in compaction queue");
364 // G1SerialRePrepareClosure re_prepare(cp, current);
365 // current->set_compaction_top(current->bottom());
366 // current->apply_to_marked_objects(mark_bitmap(), &re_prepare);
367 // }
368 // }
369 // cp->update();
370 }
371
372 void G1FullCollector::phase3_adjust_pointers() {
373 // Adjust the pointers to reflect the new locations
374 GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers", scope()->timer());
375
376 G1FullGCAdjustTask task(this);
377 run_task(&task);
378 }
379
380 void G1FullCollector::phase4_do_compaction() {
381 // Compact the heap using the compaction queues created in phase 2.
382 GCTraceTime(Info, gc, phases) info("Phase 4: Compact heap", scope()->timer());
383 G1FullGCCompactTask task(this);
384 run_task(&task);
385
386 // Serial compact to avoid OOM when very few free regions.
387 if (serial_compaction_point()->has_regions()) {
388 task.serial_compaction();
389 }
390 }
391
392 void G1FullCollector::restore_marks() {
393 _preserved_marks_set.restore(_heap->workers());
394 _preserved_marks_set.reclaim();
395 }
396
397 void G1FullCollector::run_task(WorkerTask* task) {
398 _heap->workers()->run_task(task, _num_workers);
399 }
400
401 void G1FullCollector::verify_after_marking() {
402 if (!VerifyDuringGC || !_heap->verifier()->should_verify(G1HeapVerifier::G1VerifyFull)) {
403 // Only do verification if VerifyDuringGC and G1VerifyFull is set.
404 return;
405 }
406
407 #if COMPILER2_OR_JVMCI
408 DerivedPointerTableDeactivate dpt_deact;
409 #endif
410 _heap->prepare_for_verify();
411 // Note: we can verify only the heap here. When an object is
412 // marked, the previous value of the mark word (including
413 // identity hash values, ages, etc) is preserved, and the mark
414 // word is set to markWord::marked_value - effectively removing
415 // any hash values from the mark word. These hash values are
416 // used when verifying the dictionaries and so removing them
417 // from the mark word can make verification of the dictionaries
418 // fail. At the end of the GC, the original mark word values
419 // (including hash values) are restored to the appropriate
420 // objects.
421 GCTraceTime(Info, gc, verify) tm("Verifying During GC (full)");
422 _heap->verify(VerifyOption_G1UseFullMarking);
423 }