52 #include "runtime/thread.hpp"
53 #include "runtime/vmThread.hpp"
54 #include "utilities/copy.hpp"
55 #include "utilities/events.hpp"
56
57 class HeapRegion;
58
59 bool G1MarkSweep::_archive_check_enabled = false;
60 G1ArchiveRegionMap G1MarkSweep::_archive_region_map;
61
62 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
63 bool clear_all_softrefs) {
64 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
65
66 #ifdef ASSERT
67 if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) {
68 assert(clear_all_softrefs, "Policy should have been checked earler");
69 }
70 #endif
71 // hook up weak ref data so it can be used during Mark-Sweep
72 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
73 assert(rp != NULL, "should be non-NULL");
74 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
75
76 GenMarkSweep::set_ref_processor(rp);
77 rp->setup_policy(clear_all_softrefs);
78
79 // When collecting the permanent generation Method*s may be moving,
80 // so we either have to flush all bcp data or convert it into bci.
81 CodeCache::gc_prologue();
82
83 bool marked_for_unloading = false;
84
85 allocate_stacks();
86
87 // We should save the marks of the currently locked biased monitors.
88 // The marking doesn't preserve the marks of biased objects.
89 BiasedLocking::preserve_marks();
90
91 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
92
93 mark_sweep_phase2();
94
95 #if defined(COMPILER2) || INCLUDE_JVMCI
96 // Don't add any more derived pointers during phase3
97 DerivedPointerTable::set_active(false);
98 #endif
99
100 mark_sweep_phase3();
101
102 mark_sweep_phase4();
103
104 GenMarkSweep::restore_marks();
105 BiasedLocking::restore_marks();
106 GenMarkSweep::deallocate_stacks();
107
108 CodeCache::gc_epilogue();
109 JvmtiExport::gc_epilogue();
110
111 // refs processing: clean slate
112 GenMarkSweep::set_ref_processor(NULL);
113 }
114
115
116 void G1MarkSweep::allocate_stacks() {
117 GenMarkSweep::_preserved_count_max = 0;
118 GenMarkSweep::_preserved_marks = NULL;
119 GenMarkSweep::_preserved_count = 0;
120 }
121
122 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
123 bool clear_all_softrefs) {
124 // Recursively traverse all live objects and mark them
125 GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", gc_timer());
126
127 G1CollectedHeap* g1h = G1CollectedHeap::heap();
128
129 // Need cleared claim bits for the roots processing
130 ClassLoaderDataGraph::clear_claimed_marks();
131
132 MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
133 {
134 G1RootProcessor root_processor(g1h, 1);
135 if (ClassUnloading) {
136 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
137 &GenMarkSweep::follow_cld_closure,
138 &follow_code_closure);
139 } else {
140 root_processor.process_all_roots_no_string_table(
141 &GenMarkSweep::follow_root_closure,
142 &GenMarkSweep::follow_cld_closure,
143 &follow_code_closure);
144 }
145 }
146
147 {
148 GCTraceTime(Debug, gc, phases) trace("Reference Processing", gc_timer());
149
150 // Process reference objects found during marking
151 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
152 assert(rp == g1h->ref_processor_stw(), "Sanity");
153
154 rp->setup_policy(clear_all_softrefs);
155 const ReferenceProcessorStats& stats =
156 rp->process_discovered_references(&GenMarkSweep::is_alive,
157 &GenMarkSweep::keep_alive,
158 &GenMarkSweep::follow_stack_closure,
159 NULL,
160 gc_timer());
161 gc_tracer()->report_gc_reference_stats(stats);
162 }
163
164 // This is the point where the entire marking should have completed.
165 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
166
167 if (ClassUnloading) {
168 GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer());
169
170 // Unload classes and purge the SystemDictionary.
171 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
172
173 // Unload nmethods.
174 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
175
176 // Prune dead klasses from subklass/sibling/implementor lists.
177 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
178 }
179
180 {
181 GCTraceTime(Debug, gc, phases) trace("Scrub String and Symbol Tables", gc_timer());
182 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
183 g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
184 }
185
186 if (G1StringDedup::is_enabled()) {
187 GCTraceTime(Debug, gc, phases) trace("String Deduplication Unlink", gc_timer());
188 G1StringDedup::unlink(&GenMarkSweep::is_alive);
189 }
190
191 if (VerifyDuringGC) {
192 HandleMark hm; // handle scope
193 #if defined(COMPILER2) || INCLUDE_JVMCI
194 DerivedPointerTableDeactivate dpt_deact;
195 #endif
196 g1h->prepare_for_verify();
197 // Note: we can verify only the heap here. When an object is
198 // marked, the previous value of the mark word (including
199 // identity hash values, ages, etc) is preserved, and the mark
200 // word is set to markOop::marked_value - effectively removing
201 // any hash values from the mark word. These hash values are
202 // used when verifying the dictionaries and so removing them
203 // from the mark word can make verification of the dictionaries
204 // fail. At the end of the GC, the original mark word values
205 // (including hash values) are restored to the appropriate
206 // objects.
207 GCTraceTime(Info, gc, verify)("During GC (full)");
208 g1h->verify(VerifyOption_G1UseMarkWord);
209 }
210
211 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
212 }
213
214
215 void G1MarkSweep::mark_sweep_phase2() {
216 // Now all live objects are marked, compute the new object addresses.
217
218 // It is not required that we traverse spaces in the same order in
219 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
220 // tracking expects us to do so. See comment under phase4.
221
222 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer());
223
224 prepare_compaction();
225 }
226
227 class G1AdjustPointersClosure: public HeapRegionClosure {
228 public:
229 bool doHeapRegion(HeapRegion* r) {
230 if (r->is_humongous()) {
231 if (r->is_starts_humongous()) {
232 // We must adjust the pointers on the single H object.
233 oop obj = oop(r->bottom());
234 // point all the oops to the new location
235 MarkSweep::adjust_pointers(obj);
236 }
237 } else if (!r->is_pinned()) {
238 // This really ought to be "as_CompactibleSpace"...
239 r->adjust_pointers();
240 }
241 return false;
242 }
243 };
244
245 void G1MarkSweep::mark_sweep_phase3() {
246 G1CollectedHeap* g1h = G1CollectedHeap::heap();
247
248 // Adjust the pointers to reflect the new locations
249 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
250
251 // Need cleared claim bits for the roots processing
252 ClassLoaderDataGraph::clear_claimed_marks();
253
254 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
255 {
256 G1RootProcessor root_processor(g1h, 1);
257 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
258 &GenMarkSweep::adjust_cld_closure,
259 &adjust_code_closure);
260 }
261
262 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
263 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
264
265 // Now adjust pointers in remaining weak roots. (All of which should
266 // have been cleared if they pointed to non-surviving objects.)
267 JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
268
269 if (G1StringDedup::is_enabled()) {
270 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
271 }
272
273 GenMarkSweep::adjust_marks();
274
275 G1AdjustPointersClosure blk;
276 g1h->heap_region_iterate(&blk);
277 }
278
279 class G1SpaceCompactClosure: public HeapRegionClosure {
280 public:
281 G1SpaceCompactClosure() {}
282
283 bool doHeapRegion(HeapRegion* hr) {
284 if (hr->is_humongous()) {
285 if (hr->is_starts_humongous()) {
286 oop obj = oop(hr->bottom());
287 if (obj->is_gc_marked()) {
288 obj->init_mark();
289 } else {
290 assert(hr->is_empty(), "Should have been cleared in phase 2.");
291 }
292 }
293 hr->reset_during_compaction();
294 } else if (!hr->is_pinned()) {
295 hr->compact();
296 }
297 return false;
298 }
299 };
300
301 void G1MarkSweep::mark_sweep_phase4() {
302 // All pointers are now adjusted, move objects accordingly
303
304 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
305 // in the same order in phase2, phase3 and phase4. We don't quite do that
306 // here (code and comment not fixed for perm removal), so we tell the validate code
307 // to use a higher index (saved from phase2) when verifying perm_gen.
308 G1CollectedHeap* g1h = G1CollectedHeap::heap();
309
310 GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", gc_timer());
311
312 G1SpaceCompactClosure blk;
313 g1h->heap_region_iterate(&blk);
314
315 }
316
317 void G1MarkSweep::enable_archive_object_check() {
318 assert(!_archive_check_enabled, "archive range check already enabled");
319 _archive_check_enabled = true;
320 size_t length = Universe::heap()->max_capacity();
321 _archive_region_map.initialize((HeapWord*)Universe::heap()->base(),
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52 #include "runtime/thread.hpp"
53 #include "runtime/vmThread.hpp"
54 #include "utilities/copy.hpp"
55 #include "utilities/events.hpp"
56
57 class HeapRegion;
58
59 bool G1MarkSweep::_archive_check_enabled = false;
60 G1ArchiveRegionMap G1MarkSweep::_archive_region_map;
61
62 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
63 bool clear_all_softrefs) {
64 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
65
66 #ifdef ASSERT
67 if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) {
68 assert(clear_all_softrefs, "Policy should have been checked earler");
69 }
70 #endif
71 // hook up weak ref data so it can be used during Mark-Sweep
72 assert(rp != NULL, "should be non-NULL");
73 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
74
75 GenMarkSweep gms;
76 gms.set_ref_processor(rp);
77 rp->setup_policy(clear_all_softrefs);
78
79 // When collecting the permanent generation Method*s may be moving,
80 // so we either have to flush all bcp data or convert it into bci.
81 CodeCache::gc_prologue();
82
83 bool marked_for_unloading = false;
84
85 allocate_stacks(&gms);
86
87 // We should save the marks of the currently locked biased monitors.
88 // The marking doesn't preserve the marks of biased objects.
89 BiasedLocking::preserve_marks();
90
91 mark_sweep_phase1(&gms, marked_for_unloading, clear_all_softrefs);
92
93 mark_sweep_phase2(&gms);
94
95 #if defined(COMPILER2) || INCLUDE_JVMCI
96 // Don't add any more derived pointers during phase3
97 DerivedPointerTable::set_active(false);
98 #endif
99
100 mark_sweep_phase3(&gms);
101
102 mark_sweep_phase4(&gms);
103
104 gms.restore_marks();
105 BiasedLocking::restore_marks();
106 gms.deallocate_stacks();
107
108 CodeCache::gc_epilogue();
109 JvmtiExport::gc_epilogue();
110
111 // refs processing: clean slate
112 gms.set_ref_processor(NULL);
113 }
114
115
116 void G1MarkSweep::allocate_stacks(GenMarkSweep* gms) {
117 gms->_preserved_count_max = 0;
118 gms->_preserved_marks = NULL;
119 gms->_preserved_count = 0;
120 }
121
122 void G1MarkSweep::mark_sweep_phase1(GenMarkSweep* gms, bool& marked_for_unloading,
123 bool clear_all_softrefs) {
124 // Recursively traverse all live objects and mark them
125 GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", gc_timer());
126
127 G1CollectedHeap* g1h = G1CollectedHeap::heap();
128
129 // Need cleared claim bits for the roots processing
130 ClassLoaderDataGraph::clear_claimed_marks();
131
132 MarkingCodeBlobClosure follow_code_closure(&gms->follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
133 {
134 G1RootProcessor root_processor(g1h, 1);
135 if (ClassUnloading) {
136 root_processor.process_strong_roots(&gms->follow_root_closure,
137 &gms->follow_cld_closure,
138 &follow_code_closure);
139 } else {
140 root_processor.process_all_roots_no_string_table(
141 &gms->follow_root_closure,
142 &gms->follow_cld_closure,
143 &follow_code_closure);
144 }
145 }
146
147 {
148 GCTraceTime(Debug, gc, phases) trace("Reference Processing", gc_timer());
149
150 // Process reference objects found during marking
151 ReferenceProcessor* rp = gms->ref_processor();
152 assert(rp == g1h->ref_processor_stw(), "Sanity");
153
154 rp->setup_policy(clear_all_softrefs);
155 const ReferenceProcessorStats& stats =
156 rp->process_discovered_references(&gms->is_alive,
157 &gms->keep_alive,
158 &gms->follow_stack_closure,
159 NULL,
160 gc_timer());
161 gc_tracer()->report_gc_reference_stats(stats);
162 }
163
164 // This is the point where the entire marking should have completed.
165 assert(gms->_marking_stack.is_empty(), "Marking should have completed");
166
167 if (ClassUnloading) {
168 GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer());
169
170 // Unload classes and purge the SystemDictionary.
171 bool purged_class = SystemDictionary::do_unloading(&gms->is_alive);
172
173 // Unload nmethods.
174 CodeCache::do_unloading(&gms->is_alive, purged_class);
175
176 // Prune dead klasses from subklass/sibling/implementor lists.
177 Klass::clean_weak_klass_links(&gms->is_alive);
178 }
179
180 {
181 GCTraceTime(Debug, gc, phases) trace("Scrub String and Symbol Tables", gc_timer());
182 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
183 g1h->unlink_string_and_symbol_table(&gms->is_alive);
184 }
185
186 if (G1StringDedup::is_enabled()) {
187 GCTraceTime(Debug, gc, phases) trace("String Deduplication Unlink", gc_timer());
188 G1StringDedup::unlink(&gms->is_alive);
189 }
190
191 if (VerifyDuringGC) {
192 HandleMark hm; // handle scope
193 #if defined(COMPILER2) || INCLUDE_JVMCI
194 DerivedPointerTableDeactivate dpt_deact;
195 #endif
196 g1h->prepare_for_verify();
197 // Note: we can verify only the heap here. When an object is
198 // marked, the previous value of the mark word (including
199 // identity hash values, ages, etc) is preserved, and the mark
200 // word is set to markOop::marked_value - effectively removing
201 // any hash values from the mark word. These hash values are
202 // used when verifying the dictionaries and so removing them
203 // from the mark word can make verification of the dictionaries
204 // fail. At the end of the GC, the original mark word values
205 // (including hash values) are restored to the appropriate
206 // objects.
207 GCTraceTime(Info, gc, verify)("During GC (full)");
208 g1h->verify(VerifyOption_G1UseMarkWord);
209 }
210
211 gc_tracer()->report_object_count_after_gc(&gms->is_alive);
212 }
213
214
215 void G1MarkSweep::mark_sweep_phase2(GenMarkSweep* /* gms */) {
216 // Now all live objects are marked, compute the new object addresses.
217
218 // It is not required that we traverse spaces in the same order in
219 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
220 // tracking expects us to do so. See comment under phase4.
221
222 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer());
223
224 prepare_compaction();
225 }
226
227 class G1AdjustPointersClosure: public HeapRegionClosure {
228 MarkSweep* _ms;
229 public:
230 G1AdjustPointersClosure(MarkSweep* ms) : _ms(ms) {}
231 bool doHeapRegion(HeapRegion* r) {
232 if (r->is_humongous()) {
233 if (r->is_starts_humongous()) {
234 // We must adjust the pointers on the single H object.
235 oop obj = oop(r->bottom());
236 // point all the oops to the new location
237 _ms->adjust_pointers(obj);
238 }
239 } else if (!r->is_pinned()) {
240 // This really ought to be "as_CompactibleSpace"...
241 r->adjust_pointers(_ms);
242 }
243 return false;
244 }
245 };
246
247 void G1MarkSweep::mark_sweep_phase3(GenMarkSweep* gms) {
248 G1CollectedHeap* g1h = G1CollectedHeap::heap();
249
250 // Adjust the pointers to reflect the new locations
251 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
252
253 // Need cleared claim bits for the roots processing
254 ClassLoaderDataGraph::clear_claimed_marks();
255
256 CodeBlobToOopClosure adjust_code_closure(&gms->adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
257 {
258 G1RootProcessor root_processor(g1h, 1);
259 root_processor.process_all_roots(&gms->adjust_pointer_closure,
260 &gms->adjust_cld_closure,
261 &adjust_code_closure);
262 }
263
264 assert(gms->ref_processor() == g1h->ref_processor_stw(), "Sanity");
265 g1h->ref_processor_stw()->weak_oops_do(&gms->adjust_pointer_closure);
266
267 // Now adjust pointers in remaining weak roots. (All of which should
268 // have been cleared if they pointed to non-surviving objects.)
269 JNIHandles::weak_oops_do(&gms->adjust_pointer_closure);
270
271 if (G1StringDedup::is_enabled()) {
272 G1StringDedup::oops_do(&gms->adjust_pointer_closure);
273 }
274
275 gms->adjust_marks();
276
277 G1AdjustPointersClosure blk(gms);
278 g1h->heap_region_iterate(&blk);
279 }
280
281 class G1SpaceCompactClosure: public HeapRegionClosure {
282 public:
283 G1SpaceCompactClosure() {}
284
285 bool doHeapRegion(HeapRegion* hr) {
286 if (hr->is_humongous()) {
287 if (hr->is_starts_humongous()) {
288 oop obj = oop(hr->bottom());
289 if (obj->is_gc_marked()) {
290 obj->init_mark();
291 } else {
292 assert(hr->is_empty(), "Should have been cleared in phase 2.");
293 }
294 }
295 hr->reset_during_compaction();
296 } else if (!hr->is_pinned()) {
297 hr->compact();
298 }
299 return false;
300 }
301 };
302
303 void G1MarkSweep::mark_sweep_phase4(GenMarkSweep* /* gms */) {
304 // All pointers are now adjusted, move objects accordingly
305
306 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
307 // in the same order in phase2, phase3 and phase4. We don't quite do that
308 // here (code and comment not fixed for perm removal), so we tell the validate code
309 // to use a higher index (saved from phase2) when verifying perm_gen.
310 G1CollectedHeap* g1h = G1CollectedHeap::heap();
311
312 GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", gc_timer());
313
314 G1SpaceCompactClosure blk;
315 g1h->heap_region_iterate(&blk);
316
317 }
318
319 void G1MarkSweep::enable_archive_object_check() {
320 assert(!_archive_check_enabled, "archive range check already enabled");
321 _archive_check_enabled = true;
322 size_t length = Universe::heap()->max_capacity();
323 _archive_region_map.initialize((HeapWord*)Universe::heap()->base(),
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