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annotate src/share/vm/memory/genMarkSweep.cpp @ 1689:f4f596978298
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date | Mon, 09 Aug 2010 17:51:56 -0700 |
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0 | 1 /* |
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2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
25 #include "incls/_precompiled.incl" | |
26 #include "incls/_genMarkSweep.cpp.incl" | |
27 | |
28 void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp, | |
29 bool clear_all_softrefs) { | |
30 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); | |
31 | |
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32 GenCollectedHeap* gch = GenCollectedHeap::heap(); |
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33 #ifdef ASSERT |
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34 if (gch->collector_policy()->should_clear_all_soft_refs()) { |
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35 assert(clear_all_softrefs, "Policy should have been checked earlier"); |
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36 } |
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37 #endif |
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38 |
0 | 39 // hook up weak ref data so it can be used during Mark-Sweep |
40 assert(ref_processor() == NULL, "no stomping"); | |
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41 assert(rp != NULL, "should be non-NULL"); |
0 | 42 _ref_processor = rp; |
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43 rp->setup_policy(clear_all_softrefs); |
0 | 44 |
45 TraceTime t1("Full GC", PrintGC && !PrintGCDetails, true, gclog_or_tty); | |
46 | |
47 // When collecting the permanent generation methodOops may be moving, | |
48 // so we either have to flush all bcp data or convert it into bci. | |
49 CodeCache::gc_prologue(); | |
50 Threads::gc_prologue(); | |
51 | |
52 // Increment the invocation count for the permanent generation, since it is | |
53 // implicitly collected whenever we do a full mark sweep collection. | |
54 gch->perm_gen()->stat_record()->invocations++; | |
55 | |
56 // Capture heap size before collection for printing. | |
57 size_t gch_prev_used = gch->used(); | |
58 | |
59 // Some of the card table updates below assume that the perm gen is | |
60 // also being collected. | |
61 assert(level == gch->n_gens() - 1, | |
62 "All generations are being collected, ergo perm gen too."); | |
63 | |
64 // Capture used regions for each generation that will be | |
65 // subject to collection, so that card table adjustments can | |
66 // be made intelligently (see clear / invalidate further below). | |
67 gch->save_used_regions(level, true /* perm */); | |
68 | |
69 allocate_stacks(); | |
70 | |
71 mark_sweep_phase1(level, clear_all_softrefs); | |
72 | |
73 mark_sweep_phase2(); | |
74 | |
75 // Don't add any more derived pointers during phase3 | |
76 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity")); | |
77 COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); | |
78 | |
79 mark_sweep_phase3(level); | |
80 | |
81 VALIDATE_MARK_SWEEP_ONLY( | |
82 if (ValidateMarkSweep) { | |
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83 guarantee(_root_refs_stack->length() == 0, "should be empty by now"); |
0 | 84 } |
85 ) | |
86 | |
87 mark_sweep_phase4(); | |
88 | |
89 VALIDATE_MARK_SWEEP_ONLY( | |
90 if (ValidateMarkSweep) { | |
91 guarantee(_live_oops->length() == _live_oops_moved_to->length(), | |
92 "should be the same size"); | |
93 } | |
94 ) | |
95 | |
96 restore_marks(); | |
97 | |
98 // Set saved marks for allocation profiler (and other things? -- dld) | |
99 // (Should this be in general part?) | |
100 gch->save_marks(); | |
101 | |
102 deallocate_stacks(); | |
103 | |
104 // If compaction completely evacuated all generations younger than this | |
105 // one, then we can clear the card table. Otherwise, we must invalidate | |
106 // it (consider all cards dirty). In the future, we might consider doing | |
107 // compaction within generations only, and doing card-table sliding. | |
108 bool all_empty = true; | |
109 for (int i = 0; all_empty && i < level; i++) { | |
110 Generation* g = gch->get_gen(i); | |
111 all_empty = all_empty && gch->get_gen(i)->used() == 0; | |
112 } | |
113 GenRemSet* rs = gch->rem_set(); | |
114 // Clear/invalidate below make use of the "prev_used_regions" saved earlier. | |
115 if (all_empty) { | |
116 // We've evacuated all generations below us. | |
117 Generation* g = gch->get_gen(level); | |
118 rs->clear_into_younger(g, true /* perm */); | |
119 } else { | |
120 // Invalidate the cards corresponding to the currently used | |
121 // region and clear those corresponding to the evacuated region | |
122 // of all generations just collected (i.e. level and younger). | |
123 rs->invalidate_or_clear(gch->get_gen(level), | |
124 true /* younger */, | |
125 true /* perm */); | |
126 } | |
127 | |
128 Threads::gc_epilogue(); | |
129 CodeCache::gc_epilogue(); | |
130 | |
131 if (PrintGC && !PrintGCDetails) { | |
132 gch->print_heap_change(gch_prev_used); | |
133 } | |
134 | |
135 // refs processing: clean slate | |
136 _ref_processor = NULL; | |
137 | |
138 // Update heap occupancy information which is used as | |
139 // input to soft ref clearing policy at the next gc. | |
140 Universe::update_heap_info_at_gc(); | |
141 | |
142 // Update time of last gc for all generations we collected | |
143 // (which curently is all the generations in the heap). | |
144 gch->update_time_of_last_gc(os::javaTimeMillis()); | |
145 } | |
146 | |
147 void GenMarkSweep::allocate_stacks() { | |
148 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
149 // Scratch request on behalf of oldest generation; will do no | |
150 // allocation. | |
151 ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0); | |
152 | |
153 // $$$ To cut a corner, we'll only use the first scratch block, and then | |
154 // revert to malloc. | |
155 if (scratch != NULL) { | |
156 _preserved_count_max = | |
157 scratch->num_words * HeapWordSize / sizeof(PreservedMark); | |
158 } else { | |
159 _preserved_count_max = 0; | |
160 } | |
161 | |
162 _preserved_marks = (PreservedMark*)scratch; | |
163 _preserved_count = 0; | |
164 _preserved_mark_stack = NULL; | |
165 _preserved_oop_stack = NULL; | |
166 | |
167 _marking_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true); | |
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168 _objarray_stack = new (ResourceObj::C_HEAP) GrowableArray<ObjArrayTask>(50, true); |
0 | 169 |
170 int size = SystemDictionary::number_of_classes() * 2; | |
171 _revisit_klass_stack = new (ResourceObj::C_HEAP) GrowableArray<Klass*>(size, true); | |
941 | 172 // (#klass/k)^2 for k ~ 10 appears to be a better fit, but this will have to do for |
173 // now until we have had a chance to investigate a more optimal setting. | |
174 _revisit_mdo_stack = new (ResourceObj::C_HEAP) GrowableArray<DataLayout*>(2*size, true); | |
0 | 175 |
176 #ifdef VALIDATE_MARK_SWEEP | |
177 if (ValidateMarkSweep) { | |
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178 _root_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true); |
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179 _other_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true); |
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180 _adjusted_pointers = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true); |
0 | 181 _live_oops = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true); |
182 _live_oops_moved_to = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true); | |
183 _live_oops_size = new (ResourceObj::C_HEAP) GrowableArray<size_t>(100, true); | |
184 } | |
185 if (RecordMarkSweepCompaction) { | |
186 if (_cur_gc_live_oops == NULL) { | |
187 _cur_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true); | |
188 _cur_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true); | |
189 _cur_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true); | |
190 _last_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true); | |
191 _last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true); | |
192 _last_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true); | |
193 } else { | |
194 _cur_gc_live_oops->clear(); | |
195 _cur_gc_live_oops_moved_to->clear(); | |
196 _cur_gc_live_oops_size->clear(); | |
197 } | |
198 } | |
199 #endif | |
200 } | |
201 | |
202 | |
203 void GenMarkSweep::deallocate_stacks() { | |
356 | 204 if (!UseG1GC) { |
205 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
206 gch->release_scratch(); | |
207 } | |
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208 |
0 | 209 if (_preserved_oop_stack) { |
210 delete _preserved_mark_stack; | |
211 _preserved_mark_stack = NULL; | |
212 delete _preserved_oop_stack; | |
213 _preserved_oop_stack = NULL; | |
214 } | |
215 | |
216 delete _marking_stack; | |
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217 delete _objarray_stack; |
0 | 218 delete _revisit_klass_stack; |
941 | 219 delete _revisit_mdo_stack; |
0 | 220 |
221 #ifdef VALIDATE_MARK_SWEEP | |
222 if (ValidateMarkSweep) { | |
223 delete _root_refs_stack; | |
224 delete _other_refs_stack; | |
225 delete _adjusted_pointers; | |
226 delete _live_oops; | |
227 delete _live_oops_size; | |
228 delete _live_oops_moved_to; | |
229 _live_oops_index = 0; | |
230 _live_oops_index_at_perm = 0; | |
231 } | |
232 #endif | |
233 } | |
234 | |
235 void GenMarkSweep::mark_sweep_phase1(int level, | |
236 bool clear_all_softrefs) { | |
237 // Recursively traverse all live objects and mark them | |
238 EventMark m("1 mark object"); | |
239 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty); | |
240 trace(" 1"); | |
241 | |
242 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false)); | |
243 | |
244 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
245 | |
246 // Because follow_root_closure is created statically, cannot | |
247 // use OopsInGenClosure constructor which takes a generation, | |
248 // as the Universe has not been created when the static constructors | |
249 // are run. | |
250 follow_root_closure.set_orig_generation(gch->get_gen(level)); | |
251 | |
252 gch->gen_process_strong_roots(level, | |
253 false, // Younger gens are not roots. | |
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254 true, // activate StrongRootsScope |
0 | 255 true, // Collecting permanent generation. |
256 SharedHeap::SO_SystemClasses, | |
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257 &follow_root_closure, |
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258 true, // walk code active on stacks |
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259 &follow_root_closure); |
0 | 260 |
261 // Process reference objects found during marking | |
262 { | |
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263 ref_processor()->setup_policy(clear_all_softrefs); |
0 | 264 ref_processor()->process_discovered_references( |
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265 &is_alive, &keep_alive, &follow_stack_closure, NULL); |
0 | 266 } |
267 | |
268 // Follow system dictionary roots and unload classes | |
269 bool purged_class = SystemDictionary::do_unloading(&is_alive); | |
270 | |
271 // Follow code cache roots | |
272 CodeCache::do_unloading(&is_alive, &keep_alive, purged_class); | |
273 follow_stack(); // Flush marking stack | |
274 | |
275 // Update subklass/sibling/implementor links of live klasses | |
276 follow_weak_klass_links(); | |
277 assert(_marking_stack->is_empty(), "just drained"); | |
278 | |
941 | 279 // Visit memoized MDO's and clear any unmarked weak refs |
280 follow_mdo_weak_refs(); | |
281 assert(_marking_stack->is_empty(), "just drained"); | |
282 | |
0 | 283 // Visit symbol and interned string tables and delete unmarked oops |
284 SymbolTable::unlink(&is_alive); | |
285 StringTable::unlink(&is_alive); | |
286 | |
287 assert(_marking_stack->is_empty(), "stack should be empty by now"); | |
288 } | |
289 | |
290 | |
291 void GenMarkSweep::mark_sweep_phase2() { | |
292 // Now all live objects are marked, compute the new object addresses. | |
293 | |
294 // It is imperative that we traverse perm_gen LAST. If dead space is | |
295 // allowed a range of dead object may get overwritten by a dead int | |
296 // array. If perm_gen is not traversed last a klassOop may get | |
297 // overwritten. This is fine since it is dead, but if the class has dead | |
298 // instances we have to skip them, and in order to find their size we | |
299 // need the klassOop! | |
300 // | |
301 // It is not required that we traverse spaces in the same order in | |
302 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops | |
303 // tracking expects us to do so. See comment under phase4. | |
304 | |
305 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
306 Generation* pg = gch->perm_gen(); | |
307 | |
308 EventMark m("2 compute new addresses"); | |
309 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty); | |
310 trace("2"); | |
311 | |
312 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false)); | |
313 | |
314 gch->prepare_for_compaction(); | |
315 | |
316 VALIDATE_MARK_SWEEP_ONLY(_live_oops_index_at_perm = _live_oops_index); | |
317 CompactPoint perm_cp(pg, NULL, NULL); | |
318 pg->prepare_for_compaction(&perm_cp); | |
319 } | |
320 | |
321 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure { | |
322 public: | |
323 void do_generation(Generation* gen) { | |
324 gen->adjust_pointers(); | |
325 } | |
326 }; | |
327 | |
328 void GenMarkSweep::mark_sweep_phase3(int level) { | |
329 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
330 Generation* pg = gch->perm_gen(); | |
331 | |
332 // Adjust the pointers to reflect the new locations | |
333 EventMark m("3 adjust pointers"); | |
334 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty); | |
335 trace("3"); | |
336 | |
337 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false)); | |
338 | |
339 // Needs to be done before the system dictionary is adjusted. | |
340 pg->pre_adjust_pointers(); | |
341 | |
342 // Because the two closures below are created statically, cannot | |
343 // use OopsInGenClosure constructor which takes a generation, | |
344 // as the Universe has not been created when the static constructors | |
345 // are run. | |
346 adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level)); | |
347 adjust_pointer_closure.set_orig_generation(gch->get_gen(level)); | |
348 | |
349 gch->gen_process_strong_roots(level, | |
350 false, // Younger gens are not roots. | |
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351 true, // activate StrongRootsScope |
0 | 352 true, // Collecting permanent generation. |
353 SharedHeap::SO_AllClasses, | |
354 &adjust_root_pointer_closure, | |
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355 false, // do not walk code |
0 | 356 &adjust_root_pointer_closure); |
357 | |
358 // Now adjust pointers in remaining weak roots. (All of which should | |
359 // have been cleared if they pointed to non-surviving objects.) | |
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360 CodeBlobToOopClosure adjust_code_pointer_closure(&adjust_pointer_closure, |
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361 /*do_marking=*/ false); |
0 | 362 gch->gen_process_weak_roots(&adjust_root_pointer_closure, |
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363 &adjust_code_pointer_closure, |
0 | 364 &adjust_pointer_closure); |
365 | |
366 adjust_marks(); | |
367 GenAdjustPointersClosure blk; | |
368 gch->generation_iterate(&blk, true); | |
369 pg->adjust_pointers(); | |
370 } | |
371 | |
372 class GenCompactClosure: public GenCollectedHeap::GenClosure { | |
373 public: | |
374 void do_generation(Generation* gen) { | |
375 gen->compact(); | |
376 } | |
377 }; | |
378 | |
379 void GenMarkSweep::mark_sweep_phase4() { | |
380 // All pointers are now adjusted, move objects accordingly | |
381 | |
382 // It is imperative that we traverse perm_gen first in phase4. All | |
383 // classes must be allocated earlier than their instances, and traversing | |
384 // perm_gen first makes sure that all klassOops have moved to their new | |
385 // location before any instance does a dispatch through it's klass! | |
386 | |
387 // The ValidateMarkSweep live oops tracking expects us to traverse spaces | |
388 // in the same order in phase2, phase3 and phase4. We don't quite do that | |
389 // here (perm_gen first rather than last), so we tell the validate code | |
390 // to use a higher index (saved from phase2) when verifying perm_gen. | |
391 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
392 Generation* pg = gch->perm_gen(); | |
393 | |
394 EventMark m("4 compact heap"); | |
395 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty); | |
396 trace("4"); | |
397 | |
398 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(true)); | |
399 | |
400 pg->compact(); | |
401 | |
402 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false)); | |
403 | |
404 GenCompactClosure blk; | |
405 gch->generation_iterate(&blk, true); | |
406 | |
407 VALIDATE_MARK_SWEEP_ONLY(compaction_complete()); | |
408 | |
409 pg->post_compact(); // Shared spaces verification. | |
410 } |