1 /*
2 * Copyright (c) 2001, 2023, 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/javaClasses.hpp"
28 #include "classfile/stringTable.hpp"
29 #include "classfile/symbolTable.hpp"
30 #include "classfile/systemDictionary.hpp"
31 #include "classfile/vmSymbols.hpp"
32 #include "code/codeCache.hpp"
33 #include "code/icBuffer.hpp"
34 #include "compiler/oopMap.hpp"
35 #include "gc/serial/cardTableRS.hpp"
36 #include "gc/serial/genMarkSweep.hpp"
37 #include "gc/serial/serialGcRefProcProxyTask.hpp"
38 #include "gc/shared/collectedHeap.inline.hpp"
39 #include "gc/shared/gcHeapSummary.hpp"
40 #include "gc/shared/gcTimer.hpp"
41 #include "gc/shared/gcTrace.hpp"
42 #include "gc/shared/gcTraceTime.inline.hpp"
43 #include "gc/shared/genCollectedHeap.hpp"
44 #include "gc/shared/generation.hpp"
45 #include "gc/shared/modRefBarrierSet.hpp"
46 #include "gc/shared/referencePolicy.hpp"
47 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
48 #include "gc/shared/slidingForwarding.hpp"
49 #include "gc/shared/space.hpp"
50 #include "gc/shared/strongRootsScope.hpp"
51 #include "gc/shared/weakProcessor.hpp"
52 #include "memory/universe.hpp"
53 #include "oops/instanceRefKlass.hpp"
54 #include "oops/oop.inline.hpp"
55 #include "prims/jvmtiExport.hpp"
56 #include "runtime/handles.inline.hpp"
57 #include "runtime/javaThread.hpp"
58 #include "runtime/synchronizer.hpp"
59 #include "runtime/vmThread.hpp"
60 #include "utilities/copy.hpp"
61 #include "utilities/events.hpp"
62 #include "utilities/stack.inline.hpp"
63 #if INCLUDE_JVMCI
64 #include "jvmci/jvmci.hpp"
65 #endif
66
67 void GenMarkSweep::invoke_at_safepoint(bool clear_all_softrefs) {
68 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
69
70 GenCollectedHeap* gch = GenCollectedHeap::heap();
71 #ifdef ASSERT
72 if (gch->soft_ref_policy()->should_clear_all_soft_refs()) {
73 assert(clear_all_softrefs, "Policy should have been checked earlier");
74 }
75 #endif
76
77 gch->trace_heap_before_gc(_gc_tracer);
78
79 // Increment the invocation count
80 _total_invocations++;
81
82 // Capture used regions for each generation that will be
83 // subject to collection, so that card table adjustments can
84 // be made intelligently (see clear / invalidate further below).
85 gch->save_used_regions();
86
87 allocate_stacks();
88
89 mark_sweep_phase1(clear_all_softrefs);
90
91 SlidingForwarding::begin();
92
93 mark_sweep_phase2();
94
95 // Don't add any more derived pointers during phase3
96 #if COMPILER2_OR_JVMCI
97 assert(DerivedPointerTable::is_active(), "Sanity");
98 DerivedPointerTable::set_active(false);
99 #endif
100
101 mark_sweep_phase3();
102
103 mark_sweep_phase4();
104
105 restore_marks();
106
107 // Set saved marks for allocation profiler (and other things? -- dld)
108 // (Should this be in general part?)
109 gch->save_marks();
110
111 SlidingForwarding::end();
112
113 deallocate_stacks();
114
115 MarkSweep::_string_dedup_requests->flush();
116
117 bool is_young_gen_empty = (gch->young_gen()->used() == 0);
118 gch->rem_set()->maintain_old_to_young_invariant(gch->old_gen(), is_young_gen_empty);
119
120 gch->prune_scavengable_nmethods();
121
122 // Update heap occupancy information which is used as
123 // input to soft ref clearing policy at the next gc.
124 Universe::heap()->update_capacity_and_used_at_gc();
125
126 // Signal that we have completed a visit to all live objects.
127 Universe::heap()->record_whole_heap_examined_timestamp();
128
129 gch->trace_heap_after_gc(_gc_tracer);
130 }
131
132 void GenMarkSweep::allocate_stacks() {
133 GenCollectedHeap* gch = GenCollectedHeap::heap();
134 // Scratch request on behalf of old generation; will do no allocation.
135 ScratchBlock* scratch = gch->gather_scratch(gch->old_gen(), 0);
136
137 // $$$ To cut a corner, we'll only use the first scratch block, and then
138 // revert to malloc.
139 if (scratch != nullptr) {
140 _preserved_count_max =
141 scratch->num_words * HeapWordSize / sizeof(PreservedMark);
142 } else {
143 _preserved_count_max = 0;
144 }
145
146 _preserved_marks = (PreservedMark*)scratch;
147 _preserved_count = 0;
148 }
149
150
151 void GenMarkSweep::deallocate_stacks() {
152 GenCollectedHeap* gch = GenCollectedHeap::heap();
153 gch->release_scratch();
154
155 _preserved_overflow_stack.clear(true);
156 _marking_stack.clear();
157 _objarray_stack.clear(true);
158 }
159
160 void GenMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
161 // Recursively traverse all live objects and mark them
162 GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", _gc_timer);
163
164 GenCollectedHeap* gch = GenCollectedHeap::heap();
165
166 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
167
168 ref_processor()->start_discovery(clear_all_softrefs);
169
170 {
171 StrongRootsScope srs(0);
172
173 CLDClosure* weak_cld_closure = ClassUnloading ? nullptr : &follow_cld_closure;
174 MarkingCodeBlobClosure mark_code_closure(&follow_root_closure, !CodeBlobToOopClosure::FixRelocations, true);
175 gch->process_roots(GenCollectedHeap::SO_None,
176 &follow_root_closure,
177 &follow_cld_closure,
178 weak_cld_closure,
179 &mark_code_closure);
180 }
181
182 // Process reference objects found during marking
183 {
184 GCTraceTime(Debug, gc, phases) tm_m("Reference Processing", gc_timer());
185
186 ReferenceProcessorPhaseTimes pt(_gc_timer, ref_processor()->max_num_queues());
187 SerialGCRefProcProxyTask task(is_alive, keep_alive, follow_stack_closure);
188 const ReferenceProcessorStats& stats = ref_processor()->process_discovered_references(task, pt);
189 pt.print_all_references();
190 gc_tracer()->report_gc_reference_stats(stats);
191 }
192
193 // This is the point where the entire marking should have completed.
194 assert(_marking_stack.is_empty(), "Marking should have completed");
195
196 {
197 GCTraceTime(Debug, gc, phases) tm_m("Weak Processing", gc_timer());
198 WeakProcessor::weak_oops_do(&is_alive, &do_nothing_cl);
199 }
200
201 {
202 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", gc_timer());
203 CodeCache::UnloadingScope scope(&is_alive);
204
205 // Unload classes and purge the SystemDictionary.
206 bool purged_class = SystemDictionary::do_unloading(gc_timer());
207
208 // Unload nmethods.
209 CodeCache::do_unloading(purged_class);
210
211 // Prune dead klasses from subklass/sibling/implementor lists.
212 Klass::clean_weak_klass_links(purged_class);
213
214 // Clean JVMCI metadata handles.
215 JVMCI_ONLY(JVMCI::do_unloading(purged_class));
216 }
217
218 {
219 GCTraceTime(Debug, gc, phases) tm_m("Report Object Count", gc_timer());
220 gc_tracer()->report_object_count_after_gc(&is_alive, nullptr);
221 }
222 }
223
224
225 void GenMarkSweep::mark_sweep_phase2() {
226 // Now all live objects are marked, compute the new object addresses.
227 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", _gc_timer);
228
229 GenCollectedHeap::heap()->prepare_for_compaction();
230 }
231
232 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
233 public:
234 void do_generation(Generation* gen) {
235 gen->adjust_pointers();
236 }
237 };
238
239 void GenMarkSweep::mark_sweep_phase3() {
240 GenCollectedHeap* gch = GenCollectedHeap::heap();
241
242 // Adjust the pointers to reflect the new locations
243 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
244
245 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
246
247 if (UseAltGCForwarding) {
248 AdjustPointerClosure<true> adjust_pointer_closure;
249 CLDToOopClosure adjust_cld_closure(&adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
250 CodeBlobToOopClosure code_closure(&adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
251 gch->process_roots(GenCollectedHeap::SO_AllCodeCache,
252 &adjust_pointer_closure,
253 &adjust_cld_closure,
254 &adjust_cld_closure,
255 &code_closure);
256 gch->gen_process_weak_roots(&adjust_pointer_closure);
257 } else {
258 AdjustPointerClosure<false> adjust_pointer_closure;
259 CLDToOopClosure adjust_cld_closure(&adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
260 CodeBlobToOopClosure code_closure(&adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
261 gch->process_roots(GenCollectedHeap::SO_AllCodeCache,
262 &adjust_pointer_closure,
263 &adjust_cld_closure,
264 &adjust_cld_closure,
265 &code_closure);
266 gch->gen_process_weak_roots(&adjust_pointer_closure);
267 }
268 adjust_marks();
269 GenAdjustPointersClosure blk;
270 gch->generation_iterate(&blk, true);
271 }
272
273 class GenCompactClosure: public GenCollectedHeap::GenClosure {
274 public:
275 void do_generation(Generation* gen) {
276 gen->compact();
277 }
278 };
279
280 void GenMarkSweep::mark_sweep_phase4() {
281 // All pointers are now adjusted, move objects accordingly
282 GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", _gc_timer);
283
284 GenCompactClosure blk;
285 GenCollectedHeap::heap()->generation_iterate(&blk, true);
286 }