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