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 }