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/classUnloadingContext.hpp"
39 #include "gc/shared/collectedHeap.inline.hpp"
40 #include "gc/shared/gcHeapSummary.hpp"
41 #include "gc/shared/gcTimer.hpp"
42 #include "gc/shared/gcTrace.hpp"
43 #include "gc/shared/gcTraceTime.inline.hpp"
44 #include "gc/shared/genCollectedHeap.hpp"
45 #include "gc/shared/generation.hpp"
46 #include "gc/shared/modRefBarrierSet.hpp"
47 #include "gc/shared/referencePolicy.hpp"
48 #include "gc/shared/referenceProcessorPhaseTimes.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 mark_sweep_phase2();
92
93 // Don't add any more derived pointers during phase3
94 #if COMPILER2_OR_JVMCI
95 assert(DerivedPointerTable::is_active(), "Sanity");
96 DerivedPointerTable::set_active(false);
97 #endif
98
99 mark_sweep_phase3();
100
101 mark_sweep_phase4();
102
103 restore_marks();
104
105 // Set saved marks for allocation profiler (and other things? -- dld)
106 // (Should this be in general part?)
107 gch->save_marks();
108
109 deallocate_stacks();
110
111 MarkSweep::_string_dedup_requests->flush();
112
113 bool is_young_gen_empty = (gch->young_gen()->used() == 0);
114 gch->rem_set()->maintain_old_to_young_invariant(gch->old_gen(), is_young_gen_empty);
115
116 gch->prune_scavengable_nmethods();
117
118 // Update heap occupancy information which is used as
119 // input to soft ref clearing policy at the next gc.
120 Universe::heap()->update_capacity_and_used_at_gc();
121
122 // Signal that we have completed a visit to all live objects.
123 Universe::heap()->record_whole_heap_examined_timestamp();
124
125 gch->trace_heap_after_gc(_gc_tracer);
126 }
127
128 void GenMarkSweep::allocate_stacks() {
129 GenCollectedHeap* gch = GenCollectedHeap::heap();
130 // Scratch request on behalf of old generation; will do no allocation.
131 ScratchBlock* scratch = gch->gather_scratch(gch->old_gen(), 0);
132
133 // $$$ To cut a corner, we'll only use the first scratch block, and then
134 // revert to malloc.
135 if (scratch != nullptr) {
136 _preserved_count_max =
137 scratch->num_words * HeapWordSize / sizeof(PreservedMark);
138 } else {
139 _preserved_count_max = 0;
140 }
141
142 _preserved_marks = (PreservedMark*)scratch;
143 _preserved_count = 0;
144 }
145
146
147 void GenMarkSweep::deallocate_stacks() {
148 GenCollectedHeap* gch = GenCollectedHeap::heap();
149 gch->release_scratch();
150
151 _preserved_overflow_stack.clear(true);
152 _marking_stack.clear();
153 _objarray_stack.clear(true);
154 }
155
156 void GenMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
157 // Recursively traverse all live objects and mark them
158 GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", _gc_timer);
159
160 GenCollectedHeap* gch = GenCollectedHeap::heap();
161
162 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
163
164 ref_processor()->start_discovery(clear_all_softrefs);
165
166 {
167 StrongRootsScope srs(0);
168
169 CLDClosure* weak_cld_closure = ClassUnloading ? nullptr : &follow_cld_closure;
170 MarkingCodeBlobClosure mark_code_closure(&follow_root_closure, !CodeBlobToOopClosure::FixRelocations, true);
171 gch->process_roots(GenCollectedHeap::SO_None,
172 &follow_root_closure,
173 &follow_cld_closure,
174 weak_cld_closure,
175 &mark_code_closure);
176 }
177
178 // Process reference objects found during marking
179 {
180 GCTraceTime(Debug, gc, phases) tm_m("Reference Processing", gc_timer());
181
182 ReferenceProcessorPhaseTimes pt(_gc_timer, ref_processor()->max_num_queues());
183 SerialGCRefProcProxyTask task(is_alive, keep_alive, follow_stack_closure);
184 const ReferenceProcessorStats& stats = ref_processor()->process_discovered_references(task, pt);
185 pt.print_all_references();
186 gc_tracer()->report_gc_reference_stats(stats);
187 }
188
189 // This is the point where the entire marking should have completed.
190 assert(_marking_stack.is_empty(), "Marking should have completed");
191
192 {
193 GCTraceTime(Debug, gc, phases) tm_m("Weak Processing", gc_timer());
194 WeakProcessor::weak_oops_do(&is_alive, &do_nothing_cl);
195 }
196
197 {
198 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", gc_timer());
199
200 ClassUnloadingContext* ctx = ClassUnloadingContext::context();
201
202 bool unloading_occurred;
203 {
204 CodeCache::UnlinkingScope scope(&is_alive);
205
206 // Unload classes and purge the SystemDictionary.
207 unloading_occurred = SystemDictionary::do_unloading(gc_timer());
208
209 // Unload nmethods.
210 CodeCache::do_unloading(unloading_occurred);
211 }
212
213 {
214 GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
215 // Release unloaded nmethod's memory.
216 ctx->purge_nmethods();
217 }
218 {
219 GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", gc_timer());
220 gch->prune_unlinked_nmethods();
221 }
222 {
223 GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
224 ctx->free_code_blobs();
225 }
226
227 // Prune dead klasses from subklass/sibling/implementor lists.
228 Klass::clean_weak_klass_links(unloading_occurred);
229
230 // Clean JVMCI metadata handles.
231 JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
232 }
233
234 {
235 GCTraceTime(Debug, gc, phases) tm_m("Report Object Count", gc_timer());
236 gc_tracer()->report_object_count_after_gc(&is_alive, nullptr);
237 }
238 }
239
240
241 void GenMarkSweep::mark_sweep_phase2() {
242 // Now all live objects are marked, compute the new object addresses.
243 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", _gc_timer);
244
245 GenCollectedHeap::heap()->prepare_for_compaction();
246 }
247
248 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
249 public:
250 void do_generation(Generation* gen) {
251 gen->adjust_pointers();
252 }
253 };
254
255 void GenMarkSweep::mark_sweep_phase3() {
256 GenCollectedHeap* gch = GenCollectedHeap::heap();
257
258 // Adjust the pointers to reflect the new locations
259 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
260
261 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
262
263 CodeBlobToOopClosure code_closure(&adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
264 gch->process_roots(GenCollectedHeap::SO_AllCodeCache,
265 &adjust_pointer_closure,
266 &adjust_cld_closure,
267 &adjust_cld_closure,
268 &code_closure);
269
270 gch->gen_process_weak_roots(&adjust_pointer_closure);
271
272 adjust_marks();
273 GenAdjustPointersClosure blk;
274 gch->generation_iterate(&blk, true);
275 }
276
277 class GenCompactClosure: public GenCollectedHeap::GenClosure {
278 public:
279 void do_generation(Generation* gen) {
280 gen->compact();
281 }
282 };
283
284 void GenMarkSweep::mark_sweep_phase4() {
285 // All pointers are now adjusted, move objects accordingly
286 GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", _gc_timer);
287
288 GenCompactClosure blk;
289 GenCollectedHeap::heap()->generation_iterate(&blk, true);
290 }