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/classLoaderDataGraph.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "compiler/oopMap.hpp"
30 #include "gc/g1/g1CollectedHeap.hpp"
31 #include "gc/g1/g1FullCollector.inline.hpp"
32 #include "gc/g1/g1FullGCAdjustTask.hpp"
33 #include "gc/g1/g1FullGCCompactTask.hpp"
34 #include "gc/g1/g1FullGCMarker.inline.hpp"
35 #include "gc/g1/g1FullGCMarkTask.hpp"
36 #include "gc/g1/g1FullGCPrepareTask.inline.hpp"
37 #include "gc/g1/g1FullGCScope.hpp"
38 #include "gc/g1/g1OopClosures.hpp"
39 #include "gc/g1/g1Policy.hpp"
40 #include "gc/g1/g1RegionMarkStatsCache.inline.hpp"
41 #include "gc/shared/gcTraceTime.inline.hpp"
42 #include "gc/shared/preservedMarks.hpp"
43 #include "gc/shared/referenceProcessor.hpp"
44 #include "gc/shared/slidingForwarding.hpp"
45 #include "gc/shared/verifyOption.hpp"
46 #include "gc/shared/weakProcessor.inline.hpp"
47 #include "gc/shared/workerPolicy.hpp"
48 #include "logging/log.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 G1FullGCTracer* tracer) :
118 _heap(heap),
119 _scope(heap->monitoring_support(), explicit_gc, clear_soft_refs, do_maximal_compaction, tracer),
120 _num_workers(calc_active_workers()),
121 _oop_queue_set(_num_workers),
122 _array_queue_set(_num_workers),
123 _preserved_marks_set(true),
124 _serial_compaction_point(this),
125 _is_alive(this, heap->concurrent_mark()->mark_bitmap()),
126 _is_alive_mutator(heap->ref_processor_stw(), &_is_alive),
127 _always_subject_to_discovery(),
128 _is_subject_mutator(heap->ref_processor_stw(), &_always_subject_to_discovery),
129 _region_attr_table() {
130 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
131
132 _preserved_marks_set.init(_num_workers);
133 _markers = NEW_C_HEAP_ARRAY(G1FullGCMarker*, _num_workers, mtGC);
134 _compaction_points = NEW_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _num_workers, mtGC);
135
136 _live_stats = NEW_C_HEAP_ARRAY(G1RegionMarkStats, _heap->max_regions(), mtGC);
137 _compaction_tops = NEW_C_HEAP_ARRAY(HeapWord*, _heap->max_regions(), mtGC);
138 for (uint j = 0; j < heap->max_regions(); j++) {
139 _live_stats[j].clear();
140 _compaction_tops[j] = nullptr;
141 }
142
143 for (uint i = 0; i < _num_workers; i++) {
144 _markers[i] = new G1FullGCMarker(this, i, _preserved_marks_set.get(i), _live_stats);
145 _compaction_points[i] = new G1FullGCCompactionPoint(this);
146 _oop_queue_set.register_queue(i, marker(i)->oop_stack());
147 _array_queue_set.register_queue(i, marker(i)->objarray_stack());
148 }
149 _region_attr_table.initialize(heap->reserved(), HeapRegion::GrainBytes);
150 }
151
152 G1FullCollector::~G1FullCollector() {
153 for (uint i = 0; i < _num_workers; i++) {
154 delete _markers[i];
155 delete _compaction_points[i];
156 }
157 FREE_C_HEAP_ARRAY(G1FullGCMarker*, _markers);
158 FREE_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _compaction_points);
159 FREE_C_HEAP_ARRAY(HeapWord*, _compaction_tops);
160 FREE_C_HEAP_ARRAY(G1RegionMarkStats, _live_stats);
161 }
162
163 class PrepareRegionsClosure : public HeapRegionClosure {
164 G1FullCollector* _collector;
165
166 public:
167 PrepareRegionsClosure(G1FullCollector* collector) : _collector(collector) { }
168
169 bool do_heap_region(HeapRegion* hr) {
170 G1CollectedHeap::heap()->prepare_region_for_full_compaction(hr);
171 _collector->before_marking_update_attribute_table(hr);
172 return false;
173 }
174 };
175
176 void G1FullCollector::prepare_collection() {
177 _heap->policy()->record_full_collection_start();
178
179 // Verification needs the bitmap, so we should clear the bitmap only later.
180 bool in_concurrent_cycle = _heap->abort_concurrent_cycle();
181 _heap->verify_before_full_collection(scope()->is_explicit_gc());
182 if (in_concurrent_cycle) {
183 GCTraceTime(Debug, gc) debug("Clear Bitmap");
184 _heap->concurrent_mark()->clear_bitmap(_heap->workers());
185 }
186
187 _heap->gc_prologue(true);
188 _heap->retire_tlabs();
189 _heap->prepare_heap_for_full_collection();
190
191 PrepareRegionsClosure cl(this);
192 _heap->heap_region_iterate(&cl);
193
194 reference_processor()->start_discovery(scope()->should_clear_soft_refs());
195
196 // Clear and activate derived pointer collection.
197 clear_and_activate_derived_pointers();
198 }
199
200 void G1FullCollector::collect() {
201 G1CollectedHeap::start_codecache_marking_cycle_if_inactive();
202
203 phase1_mark_live_objects();
204 verify_after_marking();
205
206 // Don't add any more derived pointers during later phases
207 deactivate_derived_pointers();
208
209 phase2_prepare_compaction();
210
211 phase3_adjust_pointers();
212
213 phase4_do_compaction();
214
215 CodeCache::on_gc_marking_cycle_finish();
216 CodeCache::arm_all_nmethods();
217 }
218
219 void G1FullCollector::complete_collection() {
220 // Restore all marks.
221 restore_marks();
222
223 // When the pointers have been adjusted and moved, we can
224 // update the derived pointer table.
225 update_derived_pointers();
226
227 // Need completely cleared claim bits for the next concurrent marking or full gc.
228 ClassLoaderDataGraph::clear_claimed_marks();
229
230 // Prepare the bitmap for the next (potentially concurrent) marking.
231 _heap->concurrent_mark()->clear_bitmap(_heap->workers());
232
233 _heap->prepare_heap_for_mutators();
234
235 _heap->resize_all_tlabs();
236
237 _heap->policy()->record_full_collection_end();
238 _heap->gc_epilogue(true);
239
240 _heap->verify_after_full_collection();
241 }
242
243 void G1FullCollector::before_marking_update_attribute_table(HeapRegion* hr) {
244 if (hr->is_free()) {
245 _region_attr_table.set_free(hr->hrm_index());
246 } else if (hr->is_closed_archive()) {
247 _region_attr_table.set_skip_marking(hr->hrm_index());
248 } else if (hr->is_pinned()) {
249 _region_attr_table.set_skip_compacting(hr->hrm_index());
250 } else {
251 // Everything else should be compacted.
252 _region_attr_table.set_compacting(hr->hrm_index());
253 }
254 }
255
256 class G1FullGCRefProcProxyTask : public RefProcProxyTask {
257 G1FullCollector& _collector;
258
259 public:
260 G1FullGCRefProcProxyTask(G1FullCollector &collector, uint max_workers)
261 : RefProcProxyTask("G1FullGCRefProcProxyTask", max_workers),
262 _collector(collector) {}
263
264 void work(uint worker_id) override {
265 assert(worker_id < _max_workers, "sanity");
266 G1IsAliveClosure is_alive(&_collector);
267 uint index = (_tm == RefProcThreadModel::Single) ? 0 : worker_id;
268 G1FullKeepAliveClosure keep_alive(_collector.marker(index));
269 BarrierEnqueueDiscoveredFieldClosure enqueue;
270 G1FollowStackClosure* complete_gc = _collector.marker(index)->stack_closure();
271 _rp_task->rp_work(worker_id, &is_alive, &keep_alive, &enqueue, complete_gc);
272 }
273 };
274
275 void G1FullCollector::phase1_mark_live_objects() {
276 // Recursively traverse all live objects and mark them.
277 GCTraceTime(Info, gc, phases) info("Phase 1: Mark live objects", scope()->timer());
278
279 {
280 // Do the actual marking.
281 G1FullGCMarkTask marking_task(this);
282 run_task(&marking_task);
283 }
284
285 {
286 uint old_active_mt_degree = reference_processor()->num_queues();
287 reference_processor()->set_active_mt_degree(workers());
288 GCTraceTime(Debug, gc, phases) debug("Phase 1: Reference Processing", scope()->timer());
289 // Process reference objects found during marking.
290 ReferenceProcessorPhaseTimes pt(scope()->timer(), reference_processor()->max_num_queues());
291 G1FullGCRefProcProxyTask task(*this, reference_processor()->max_num_queues());
292 const ReferenceProcessorStats& stats = reference_processor()->process_discovered_references(task, pt);
293 scope()->tracer()->report_gc_reference_stats(stats);
294 pt.print_all_references();
295 assert(marker(0)->oop_stack()->is_empty(), "Should be no oops on the stack");
296
297 reference_processor()->set_active_mt_degree(old_active_mt_degree);
298 }
299
300 // Weak oops cleanup.
301 {
302 GCTraceTime(Debug, gc, phases) debug("Phase 1: Weak Processing", scope()->timer());
303 WeakProcessor::weak_oops_do(_heap->workers(), &_is_alive, &do_nothing_cl, 1);
304 }
305
306 // Class unloading and cleanup.
307 if (ClassUnloading) {
308 GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer());
309 CodeCache::UnloadingScope unloading_scope(&_is_alive);
310 // Unload classes and purge the SystemDictionary.
311 bool purged_class = SystemDictionary::do_unloading(scope()->timer());
312 _heap->complete_cleaning(purged_class);
313 }
314
315 scope()->tracer()->report_object_count_after_gc(&_is_alive);
316 #if TASKQUEUE_STATS
317 oop_queue_set()->print_and_reset_taskqueue_stats("Oop Queue");
318 array_queue_set()->print_and_reset_taskqueue_stats("ObjArrayOop Queue");
319 #endif
320 }
321
322 void G1FullCollector::phase2_prepare_compaction() {
323 GCTraceTime(Info, gc, phases) info("Phase 2: Prepare compaction", scope()->timer());
324
325 _heap->forwarding()->clear();
326
327 phase2a_determine_worklists();
328
329 bool has_free_compaction_targets = phase2b_forward_oops();
330
331 // Try to avoid OOM immediately after Full GC in case there are no free regions
332 // left after determining the result locations (i.e. this phase). Prepare to
333 // maximally compact the tail regions of the compaction queues serially.
334 // TODO: Disabled for now because it violates sliding-forwarding assumption.
335 // if (!has_free_compaction_targets) {
336 // phase2c_prepare_serial_compaction();
337 // }
338 }
339
340 void G1FullCollector::phase2a_determine_worklists() {
341 GCTraceTime(Debug, gc, phases) debug("Phase 2: Determine work lists", scope()->timer());
342
343 G1DetermineCompactionQueueClosure cl(this);
344 _heap->heap_region_iterate(&cl);
345 }
346
347 bool G1FullCollector::phase2b_forward_oops() {
348 GCTraceTime(Debug, gc, phases) debug("Phase 2: Prepare parallel compaction", scope()->timer());
349
350 G1FullGCPrepareTask task(this);
351 run_task(&task);
352
353 return task.has_free_compaction_targets();
354 }
355
356 void G1FullCollector::phase2c_prepare_serial_compaction() {
357 ShouldNotReachHere(); // Disabled in Lilliput.
358 //GCTraceTime(Debug, gc, phases) debug("Phase 2: Prepare serial compaction", scope()->timer());
359 // At this point we know that after parallel compaction there will be no
360 // completely free regions. That means that the last region of
361 // all compaction queues still have data in them. We try to compact
362 // these regions in serial to avoid a premature OOM when the mutator wants
363 // to allocate the first eden region after gc.
364 /*
365 for (uint i = 0; i < workers(); i++) {
366 G1FullGCCompactionPoint* cp = compaction_point(i);
367 if (cp->has_regions()) {
368 serial_compaction_point()->add(cp->remove_last());
369 }
370 }
371 */
372
373 // Update the forwarding information for the regions in the serial
374 // compaction point.
375 /*
376 G1FullGCCompactionPoint* cp = serial_compaction_point();
377 for (GrowableArrayIterator<HeapRegion*> it = cp->regions()->begin(); it != cp->regions()->end(); ++it) {
378 HeapRegion* current = *it;
379 if (!cp->is_initialized()) {
380 // Initialize the compaction point. Nothing more is needed for the first heap region
381 // since it is already prepared for compaction.
382 cp->initialize(current);
383 } else {
384 assert(!current->is_humongous(), "Should be no humongous regions in compaction queue");
385 G1SerialRePrepareClosure re_prepare(cp, current);
386 set_compaction_top(current, current->bottom());
387 current->apply_to_marked_objects(mark_bitmap(), &re_prepare);
388 }
389 }
390 cp->update();
391 */
392 }
393
394 void G1FullCollector::phase3_adjust_pointers() {
395 // Adjust the pointers to reflect the new locations
396 GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers", scope()->timer());
397
398 G1FullGCAdjustTask task(this);
399 run_task(&task);
400 }
401
402 void G1FullCollector::phase4_do_compaction() {
403 // Compact the heap using the compaction queues created in phase 2.
404 GCTraceTime(Info, gc, phases) info("Phase 4: Compact heap", scope()->timer());
405 G1FullGCCompactTask task(this);
406 run_task(&task);
407
408 // Serial compact to avoid OOM when very few free regions.
409 if (serial_compaction_point()->has_regions()) {
410 task.serial_compaction();
411 }
412 }
413
414 void G1FullCollector::restore_marks() {
415 _preserved_marks_set.restore(_heap->workers());
416 _preserved_marks_set.reclaim();
417 }
418
419 void G1FullCollector::run_task(WorkerTask* task) {
420 _heap->workers()->run_task(task, _num_workers);
421 }
422
423 void G1FullCollector::verify_after_marking() {
424 if (!VerifyDuringGC || !_heap->verifier()->should_verify(G1HeapVerifier::G1VerifyFull)) {
425 // Only do verification if VerifyDuringGC and G1VerifyFull is set.
426 return;
427 }
428
429 #if COMPILER2_OR_JVMCI
430 DerivedPointerTableDeactivate dpt_deact;
431 #endif
432 _heap->prepare_for_verify();
433 // Note: we can verify only the heap here. When an object is
434 // marked, the previous value of the mark word (including
435 // identity hash values, ages, etc) is preserved, and the mark
436 // word is set to markWord::marked_value - effectively removing
437 // any hash values from the mark word. These hash values are
438 // used when verifying the dictionaries and so removing them
439 // from the mark word can make verification of the dictionaries
440 // fail. At the end of the GC, the original mark word values
441 // (including hash values) are restored to the appropriate
442 // objects.
443 GCTraceTime(Info, gc, verify) tm("Verifying During GC (full)");
444 _heap->verify(VerifyOption::G1UseFullMarking);
445 }