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/slidingForwarding.hpp"
50 #include "gc/shared/space.hpp"
51 #include "gc/shared/strongRootsScope.hpp"
52 #include "gc/shared/weakProcessor.hpp"
53 #include "memory/universe.hpp"
54 #include "oops/instanceRefKlass.hpp"
55 #include "oops/oop.inline.hpp"
56 #include "prims/jvmtiExport.hpp"
57 #include "runtime/handles.inline.hpp"
58 #include "runtime/javaThread.hpp"
59 #include "runtime/synchronizer.hpp"
60 #include "runtime/vmThread.hpp"
61 #include "utilities/copy.hpp"
62 #include "utilities/events.hpp"
63 #include "utilities/stack.inline.hpp"
64 #if INCLUDE_JVMCI
65 #include "jvmci/jvmci.hpp"
66 #endif
67
68 void GenMarkSweep::invoke_at_safepoint(bool clear_all_softrefs) {
69 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
70
71 GenCollectedHeap* gch = GenCollectedHeap::heap();
72 #ifdef ASSERT
73 if (gch->soft_ref_policy()->should_clear_all_soft_refs()) {
74 assert(clear_all_softrefs, "Policy should have been checked earlier");
75 }
76 #endif
77
78 gch->trace_heap_before_gc(_gc_tracer);
79
80 // Increment the invocation count
81 _total_invocations++;
82
83 // Capture used regions for each generation that will be
84 // subject to collection, so that card table adjustments can
85 // be made intelligently (see clear / invalidate further below).
86 gch->save_used_regions();
87
88 allocate_stacks();
89
90 mark_sweep_phase1(clear_all_softrefs);
91
92 SlidingForwarding::begin();
93
94 mark_sweep_phase2();
95
96 // Don't add any more derived pointers during phase3
97 #if COMPILER2_OR_JVMCI
98 assert(DerivedPointerTable::is_active(), "Sanity");
99 DerivedPointerTable::set_active(false);
100 #endif
101
102 mark_sweep_phase3();
103
104 mark_sweep_phase4();
105
106 restore_marks();
107
108 // Set saved marks for allocation profiler (and other things? -- dld)
109 // (Should this be in general part?)
110 gch->save_marks();
111
112 SlidingForwarding::end();
113
114 deallocate_stacks();
115
116 MarkSweep::_string_dedup_requests->flush();
117
118 bool is_young_gen_empty = (gch->young_gen()->used() == 0);
119 gch->rem_set()->maintain_old_to_young_invariant(gch->old_gen(), is_young_gen_empty);
120
121 gch->prune_scavengable_nmethods();
122
123 // Update heap occupancy information which is used as
124 // input to soft ref clearing policy at the next gc.
125 Universe::heap()->update_capacity_and_used_at_gc();
126
127 // Signal that we have completed a visit to all live objects.
128 Universe::heap()->record_whole_heap_examined_timestamp();
129
130 gch->trace_heap_after_gc(_gc_tracer);
131 }
132
133 void GenMarkSweep::allocate_stacks() {
134 GenCollectedHeap* gch = GenCollectedHeap::heap();
135 // Scratch request on behalf of old generation; will do no allocation.
136 ScratchBlock* scratch = gch->gather_scratch(gch->old_gen(), 0);
137
138 // $$$ To cut a corner, we'll only use the first scratch block, and then
139 // revert to malloc.
140 if (scratch != nullptr) {
141 _preserved_count_max =
142 scratch->num_words * HeapWordSize / sizeof(PreservedMark);
143 } else {
144 _preserved_count_max = 0;
145 }
146
147 _preserved_marks = (PreservedMark*)scratch;
148 _preserved_count = 0;
149 }
150
151
152 void GenMarkSweep::deallocate_stacks() {
153 GenCollectedHeap* gch = GenCollectedHeap::heap();
154 gch->release_scratch();
155
156 _preserved_overflow_stack.clear(true);
157 _marking_stack.clear();
158 _objarray_stack.clear(true);
159 }
160
161 void GenMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
162 // Recursively traverse all live objects and mark them
163 GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", _gc_timer);
164
165 GenCollectedHeap* gch = GenCollectedHeap::heap();
166
167 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
168
169 ref_processor()->start_discovery(clear_all_softrefs);
170
171 {
172 StrongRootsScope srs(0);
173
174 CLDClosure* weak_cld_closure = ClassUnloading ? nullptr : &follow_cld_closure;
175 MarkingCodeBlobClosure mark_code_closure(&follow_root_closure, !CodeBlobToOopClosure::FixRelocations, true);
176 gch->process_roots(GenCollectedHeap::SO_None,
177 &follow_root_closure,
178 &follow_cld_closure,
179 weak_cld_closure,
180 &mark_code_closure);
181 }
182
183 // Process reference objects found during marking
184 {
185 GCTraceTime(Debug, gc, phases) tm_m("Reference Processing", gc_timer());
186
187 ReferenceProcessorPhaseTimes pt(_gc_timer, ref_processor()->max_num_queues());
188 SerialGCRefProcProxyTask task(is_alive, keep_alive, follow_stack_closure);
189 const ReferenceProcessorStats& stats = ref_processor()->process_discovered_references(task, pt);
190 pt.print_all_references();
191 gc_tracer()->report_gc_reference_stats(stats);
192 }
193
194 // This is the point where the entire marking should have completed.
195 assert(_marking_stack.is_empty(), "Marking should have completed");
196
197 {
198 GCTraceTime(Debug, gc, phases) tm_m("Weak Processing", gc_timer());
199 WeakProcessor::weak_oops_do(&is_alive, &do_nothing_cl);
200 }
201
202 {
203 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", gc_timer());
204
205 ClassUnloadingContext* ctx = ClassUnloadingContext::context();
206
207 bool unloading_occurred;
208 {
209 CodeCache::UnlinkingScope scope(&is_alive);
210
211 // Unload classes and purge the SystemDictionary.
212 unloading_occurred = SystemDictionary::do_unloading(gc_timer());
213
214 // Unload nmethods.
215 CodeCache::do_unloading(unloading_occurred);
216 }
217
218 {
219 GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
220 // Release unloaded nmethod's memory.
221 ctx->purge_nmethods();
222 }
223 {
224 GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", gc_timer());
225 gch->prune_unlinked_nmethods();
226 }
227 {
228 GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
229 ctx->free_code_blobs();
230 }
231
232 // Prune dead klasses from subklass/sibling/implementor lists.
233 Klass::clean_weak_klass_links(unloading_occurred);
234
235 // Clean JVMCI metadata handles.
236 JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
237 }
238
239 {
240 GCTraceTime(Debug, gc, phases) tm_m("Report Object Count", gc_timer());
241 gc_tracer()->report_object_count_after_gc(&is_alive, nullptr);
242 }
243 }
244
245
246 void GenMarkSweep::mark_sweep_phase2() {
247 // Now all live objects are marked, compute the new object addresses.
248 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", _gc_timer);
249
250 GenCollectedHeap::heap()->prepare_for_compaction();
251 }
252
253 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
254 public:
255 void do_generation(Generation* gen) {
256 gen->adjust_pointers();
257 }
258 };
259
260 void GenMarkSweep::mark_sweep_phase3() {
261 GenCollectedHeap* gch = GenCollectedHeap::heap();
262
263 // Adjust the pointers to reflect the new locations
264 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
265
266 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
267
268 if (UseAltGCForwarding) {
269 AdjustPointerClosure<true> adjust_pointer_closure;
270 CLDToOopClosure adjust_cld_closure(&adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
271 CodeBlobToOopClosure code_closure(&adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
272 gch->process_roots(GenCollectedHeap::SO_AllCodeCache,
273 &adjust_pointer_closure,
274 &adjust_cld_closure,
275 &adjust_cld_closure,
276 &code_closure);
277 gch->gen_process_weak_roots(&adjust_pointer_closure);
278 } else {
279 AdjustPointerClosure<false> adjust_pointer_closure;
280 CLDToOopClosure adjust_cld_closure(&adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
281 CodeBlobToOopClosure code_closure(&adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
282 gch->process_roots(GenCollectedHeap::SO_AllCodeCache,
283 &adjust_pointer_closure,
284 &adjust_cld_closure,
285 &adjust_cld_closure,
286 &code_closure);
287 gch->gen_process_weak_roots(&adjust_pointer_closure);
288 }
289 adjust_marks();
290 GenAdjustPointersClosure blk;
291 gch->generation_iterate(&blk, true);
292 }
293
294 class GenCompactClosure: public GenCollectedHeap::GenClosure {
295 public:
296 void do_generation(Generation* gen) {
297 gen->compact();
298 }
299 };
300
301 void GenMarkSweep::mark_sweep_phase4() {
302 // All pointers are now adjusted, move objects accordingly
303 GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", _gc_timer);
304
305 GenCompactClosure blk;
306 GenCollectedHeap::heap()->generation_iterate(&blk, true);
307 }