Mercurial > hg > truffle
annotate src/share/vm/gc_implementation/parNew/parNewGeneration.cpp @ 652:4aaa9f5e02a8
4766230: Hotspot vtable inconsistencies cause core dumps. 6579515. 6582242.
Reviewed-by: kamg, coleenp
author | acorn |
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date | Wed, 18 Mar 2009 17:20:57 -0400 |
parents | 0fbdb4381b99 |
children | cea947c8a988 |
rev | line source |
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0 | 1 /* |
579 | 2 * Copyright 2001-2009 Sun Microsystems, Inc. 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 * | |
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
21 * have any questions. | |
22 * | |
23 */ | |
24 | |
25 # include "incls/_precompiled.incl" | |
26 # include "incls/_parNewGeneration.cpp.incl" | |
27 | |
28 #ifdef _MSC_VER | |
29 #pragma warning( push ) | |
30 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list | |
31 #endif | |
32 ParScanThreadState::ParScanThreadState(Space* to_space_, | |
33 ParNewGeneration* gen_, | |
34 Generation* old_gen_, | |
35 int thread_num_, | |
36 ObjToScanQueueSet* work_queue_set_, | |
37 size_t desired_plab_sz_, | |
38 ParallelTaskTerminator& term_) : | |
39 _to_space(to_space_), _old_gen(old_gen_), _thread_num(thread_num_), | |
40 _work_queue(work_queue_set_->queue(thread_num_)), _to_space_full(false), | |
41 _ageTable(false), // false ==> not the global age table, no perf data. | |
42 _to_space_alloc_buffer(desired_plab_sz_), | |
43 _to_space_closure(gen_, this), _old_gen_closure(gen_, this), | |
44 _to_space_root_closure(gen_, this), _old_gen_root_closure(gen_, this), | |
45 _older_gen_closure(gen_, this), | |
46 _evacuate_followers(this, &_to_space_closure, &_old_gen_closure, | |
47 &_to_space_root_closure, gen_, &_old_gen_root_closure, | |
48 work_queue_set_, &term_), | |
49 _is_alive_closure(gen_), _scan_weak_ref_closure(gen_, this), | |
50 _keep_alive_closure(&_scan_weak_ref_closure), | |
51 _pushes(0), _pops(0), _steals(0), _steal_attempts(0), _term_attempts(0), | |
52 _strong_roots_time(0.0), _term_time(0.0) | |
53 { | |
54 _survivor_chunk_array = | |
55 (ChunkArray*) old_gen()->get_data_recorder(thread_num()); | |
56 _hash_seed = 17; // Might want to take time-based random value. | |
57 _start = os::elapsedTime(); | |
58 _old_gen_closure.set_generation(old_gen_); | |
59 _old_gen_root_closure.set_generation(old_gen_); | |
60 } | |
61 #ifdef _MSC_VER | |
62 #pragma warning( pop ) | |
63 #endif | |
64 | |
65 void ParScanThreadState::record_survivor_plab(HeapWord* plab_start, | |
66 size_t plab_word_size) { | |
67 ChunkArray* sca = survivor_chunk_array(); | |
68 if (sca != NULL) { | |
69 // A non-null SCA implies that we want the PLAB data recorded. | |
70 sca->record_sample(plab_start, plab_word_size); | |
71 } | |
72 } | |
73 | |
74 bool ParScanThreadState::should_be_partially_scanned(oop new_obj, oop old_obj) const { | |
75 return new_obj->is_objArray() && | |
76 arrayOop(new_obj)->length() > ParGCArrayScanChunk && | |
77 new_obj != old_obj; | |
78 } | |
79 | |
80 void ParScanThreadState::scan_partial_array_and_push_remainder(oop old) { | |
81 assert(old->is_objArray(), "must be obj array"); | |
82 assert(old->is_forwarded(), "must be forwarded"); | |
83 assert(Universe::heap()->is_in_reserved(old), "must be in heap."); | |
84 assert(!_old_gen->is_in(old), "must be in young generation."); | |
85 | |
86 objArrayOop obj = objArrayOop(old->forwardee()); | |
87 // Process ParGCArrayScanChunk elements now | |
88 // and push the remainder back onto queue | |
89 int start = arrayOop(old)->length(); | |
90 int end = obj->length(); | |
91 int remainder = end - start; | |
92 assert(start <= end, "just checking"); | |
93 if (remainder > 2 * ParGCArrayScanChunk) { | |
94 // Test above combines last partial chunk with a full chunk | |
95 end = start + ParGCArrayScanChunk; | |
96 arrayOop(old)->set_length(end); | |
97 // Push remainder. | |
98 bool ok = work_queue()->push(old); | |
99 assert(ok, "just popped, push must be okay"); | |
100 note_push(); | |
101 } else { | |
102 // Restore length so that it can be used if there | |
103 // is a promotion failure and forwarding pointers | |
104 // must be removed. | |
105 arrayOop(old)->set_length(end); | |
106 } | |
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107 |
0 | 108 // process our set of indices (include header in first chunk) |
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109 // should make sure end is even (aligned to HeapWord in case of compressed oops) |
0 | 110 if ((HeapWord *)obj < young_old_boundary()) { |
111 // object is in to_space | |
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112 obj->oop_iterate_range(&_to_space_closure, start, end); |
0 | 113 } else { |
114 // object is in old generation | |
113
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115 obj->oop_iterate_range(&_old_gen_closure, start, end); |
0 | 116 } |
117 } | |
118 | |
119 | |
120 void ParScanThreadState::trim_queues(int max_size) { | |
121 ObjToScanQueue* queue = work_queue(); | |
122 while (queue->size() > (juint)max_size) { | |
123 oop obj_to_scan; | |
124 if (queue->pop_local(obj_to_scan)) { | |
125 note_pop(); | |
126 | |
127 if ((HeapWord *)obj_to_scan < young_old_boundary()) { | |
128 if (obj_to_scan->is_objArray() && | |
129 obj_to_scan->is_forwarded() && | |
130 obj_to_scan->forwardee() != obj_to_scan) { | |
131 scan_partial_array_and_push_remainder(obj_to_scan); | |
132 } else { | |
133 // object is in to_space | |
134 obj_to_scan->oop_iterate(&_to_space_closure); | |
135 } | |
136 } else { | |
137 // object is in old generation | |
138 obj_to_scan->oop_iterate(&_old_gen_closure); | |
139 } | |
140 } | |
141 } | |
142 } | |
143 | |
144 HeapWord* ParScanThreadState::alloc_in_to_space_slow(size_t word_sz) { | |
145 | |
146 // Otherwise, if the object is small enough, try to reallocate the | |
147 // buffer. | |
148 HeapWord* obj = NULL; | |
149 if (!_to_space_full) { | |
150 ParGCAllocBuffer* const plab = to_space_alloc_buffer(); | |
151 Space* const sp = to_space(); | |
152 if (word_sz * 100 < | |
153 ParallelGCBufferWastePct * plab->word_sz()) { | |
154 // Is small enough; abandon this buffer and start a new one. | |
155 plab->retire(false, false); | |
156 size_t buf_size = plab->word_sz(); | |
157 HeapWord* buf_space = sp->par_allocate(buf_size); | |
158 if (buf_space == NULL) { | |
159 const size_t min_bytes = | |
160 ParGCAllocBuffer::min_size() << LogHeapWordSize; | |
161 size_t free_bytes = sp->free(); | |
162 while(buf_space == NULL && free_bytes >= min_bytes) { | |
163 buf_size = free_bytes >> LogHeapWordSize; | |
164 assert(buf_size == (size_t)align_object_size(buf_size), | |
165 "Invariant"); | |
166 buf_space = sp->par_allocate(buf_size); | |
167 free_bytes = sp->free(); | |
168 } | |
169 } | |
170 if (buf_space != NULL) { | |
171 plab->set_word_size(buf_size); | |
172 plab->set_buf(buf_space); | |
173 record_survivor_plab(buf_space, buf_size); | |
174 obj = plab->allocate(word_sz); | |
175 // Note that we cannot compare buf_size < word_sz below | |
176 // because of AlignmentReserve (see ParGCAllocBuffer::allocate()). | |
177 assert(obj != NULL || plab->words_remaining() < word_sz, | |
178 "Else should have been able to allocate"); | |
179 // It's conceivable that we may be able to use the | |
180 // buffer we just grabbed for subsequent small requests | |
181 // even if not for this one. | |
182 } else { | |
183 // We're used up. | |
184 _to_space_full = true; | |
185 } | |
186 | |
187 } else { | |
188 // Too large; allocate the object individually. | |
189 obj = sp->par_allocate(word_sz); | |
190 } | |
191 } | |
192 return obj; | |
193 } | |
194 | |
195 | |
196 void ParScanThreadState::undo_alloc_in_to_space(HeapWord* obj, | |
197 size_t word_sz) { | |
198 // Is the alloc in the current alloc buffer? | |
199 if (to_space_alloc_buffer()->contains(obj)) { | |
200 assert(to_space_alloc_buffer()->contains(obj + word_sz - 1), | |
201 "Should contain whole object."); | |
202 to_space_alloc_buffer()->undo_allocation(obj, word_sz); | |
203 } else { | |
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204 CollectedHeap::fill_with_object(obj, word_sz); |
0 | 205 } |
206 } | |
207 | |
208 class ParScanThreadStateSet: private ResourceArray { | |
209 public: | |
210 // Initializes states for the specified number of threads; | |
211 ParScanThreadStateSet(int num_threads, | |
212 Space& to_space, | |
213 ParNewGeneration& gen, | |
214 Generation& old_gen, | |
215 ObjToScanQueueSet& queue_set, | |
216 size_t desired_plab_sz, | |
217 ParallelTaskTerminator& term); | |
218 inline ParScanThreadState& thread_sate(int i); | |
219 int pushes() { return _pushes; } | |
220 int pops() { return _pops; } | |
221 int steals() { return _steals; } | |
222 void reset(); | |
223 void flush(); | |
224 private: | |
225 ParallelTaskTerminator& _term; | |
226 ParNewGeneration& _gen; | |
227 Generation& _next_gen; | |
228 // staticstics | |
229 int _pushes; | |
230 int _pops; | |
231 int _steals; | |
232 }; | |
233 | |
234 | |
235 ParScanThreadStateSet::ParScanThreadStateSet( | |
236 int num_threads, Space& to_space, ParNewGeneration& gen, | |
237 Generation& old_gen, ObjToScanQueueSet& queue_set, | |
238 size_t desired_plab_sz, ParallelTaskTerminator& term) | |
239 : ResourceArray(sizeof(ParScanThreadState), num_threads), | |
240 _gen(gen), _next_gen(old_gen), _term(term), | |
241 _pushes(0), _pops(0), _steals(0) | |
242 { | |
243 assert(num_threads > 0, "sanity check!"); | |
244 // Initialize states. | |
245 for (int i = 0; i < num_threads; ++i) { | |
246 new ((ParScanThreadState*)_data + i) | |
247 ParScanThreadState(&to_space, &gen, &old_gen, i, &queue_set, | |
248 desired_plab_sz, term); | |
249 } | |
250 } | |
251 | |
252 inline ParScanThreadState& ParScanThreadStateSet::thread_sate(int i) | |
253 { | |
254 assert(i >= 0 && i < length(), "sanity check!"); | |
255 return ((ParScanThreadState*)_data)[i]; | |
256 } | |
257 | |
258 | |
259 void ParScanThreadStateSet::reset() | |
260 { | |
261 _term.reset_for_reuse(); | |
262 } | |
263 | |
264 void ParScanThreadStateSet::flush() | |
265 { | |
266 for (int i = 0; i < length(); ++i) { | |
267 ParScanThreadState& par_scan_state = thread_sate(i); | |
268 | |
269 // Flush stats related to To-space PLAB activity and | |
270 // retire the last buffer. | |
271 par_scan_state.to_space_alloc_buffer()-> | |
272 flush_stats_and_retire(_gen.plab_stats(), | |
273 false /* !retain */); | |
274 | |
275 // Every thread has its own age table. We need to merge | |
276 // them all into one. | |
277 ageTable *local_table = par_scan_state.age_table(); | |
278 _gen.age_table()->merge(local_table); | |
279 | |
280 // Inform old gen that we're done. | |
281 _next_gen.par_promote_alloc_done(i); | |
282 _next_gen.par_oop_since_save_marks_iterate_done(i); | |
283 | |
284 // Flush stats related to work queue activity (push/pop/steal) | |
285 // This could conceivably become a bottleneck; if so, we'll put the | |
286 // stat's gathering under the flag. | |
287 if (PAR_STATS_ENABLED) { | |
288 _pushes += par_scan_state.pushes(); | |
289 _pops += par_scan_state.pops(); | |
290 _steals += par_scan_state.steals(); | |
291 if (ParallelGCVerbose) { | |
292 gclog_or_tty->print("Thread %d complete:\n" | |
293 " Pushes: %7d Pops: %7d Steals %7d (in %d attempts)\n", | |
294 i, par_scan_state.pushes(), par_scan_state.pops(), | |
295 par_scan_state.steals(), par_scan_state.steal_attempts()); | |
296 if (par_scan_state.overflow_pushes() > 0 || | |
297 par_scan_state.overflow_refills() > 0) { | |
298 gclog_or_tty->print(" Overflow pushes: %7d " | |
299 "Overflow refills: %7d for %d objs.\n", | |
300 par_scan_state.overflow_pushes(), | |
301 par_scan_state.overflow_refills(), | |
302 par_scan_state.overflow_refill_objs()); | |
303 } | |
304 | |
305 double elapsed = par_scan_state.elapsed(); | |
306 double strong_roots = par_scan_state.strong_roots_time(); | |
307 double term = par_scan_state.term_time(); | |
308 gclog_or_tty->print( | |
309 " Elapsed: %7.2f ms.\n" | |
310 " Strong roots: %7.2f ms (%6.2f%%)\n" | |
311 " Termination: %7.2f ms (%6.2f%%) (in %d entries)\n", | |
312 elapsed * 1000.0, | |
313 strong_roots * 1000.0, (strong_roots*100.0/elapsed), | |
314 term * 1000.0, (term*100.0/elapsed), | |
315 par_scan_state.term_attempts()); | |
316 } | |
317 } | |
318 } | |
319 } | |
320 | |
321 ParScanClosure::ParScanClosure(ParNewGeneration* g, | |
322 ParScanThreadState* par_scan_state) : | |
323 OopsInGenClosure(g), _par_scan_state(par_scan_state), _g(g) | |
324 { | |
325 assert(_g->level() == 0, "Optimized for youngest generation"); | |
326 _boundary = _g->reserved().end(); | |
327 } | |
328 | |
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329 void ParScanWithBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, true, false); } |
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330 void ParScanWithBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, false); } |
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331 |
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332 void ParScanWithoutBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, false, false); } |
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333 void ParScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, false); } |
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334 |
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335 void ParRootScanWithBarrierTwoGensClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, true, true); } |
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336 void ParRootScanWithBarrierTwoGensClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, true); } |
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337 |
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338 void ParRootScanWithoutBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, false, true); } |
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339 void ParRootScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, true); } |
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340 |
0 | 341 ParScanWeakRefClosure::ParScanWeakRefClosure(ParNewGeneration* g, |
342 ParScanThreadState* par_scan_state) | |
343 : ScanWeakRefClosure(g), _par_scan_state(par_scan_state) | |
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344 {} |
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345 |
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346 void ParScanWeakRefClosure::do_oop(oop* p) { ParScanWeakRefClosure::do_oop_work(p); } |
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347 void ParScanWeakRefClosure::do_oop(narrowOop* p) { ParScanWeakRefClosure::do_oop_work(p); } |
0 | 348 |
349 #ifdef WIN32 | |
350 #pragma warning(disable: 4786) /* identifier was truncated to '255' characters in the browser information */ | |
351 #endif | |
352 | |
353 ParEvacuateFollowersClosure::ParEvacuateFollowersClosure( | |
354 ParScanThreadState* par_scan_state_, | |
355 ParScanWithoutBarrierClosure* to_space_closure_, | |
356 ParScanWithBarrierClosure* old_gen_closure_, | |
357 ParRootScanWithoutBarrierClosure* to_space_root_closure_, | |
358 ParNewGeneration* par_gen_, | |
359 ParRootScanWithBarrierTwoGensClosure* old_gen_root_closure_, | |
360 ObjToScanQueueSet* task_queues_, | |
361 ParallelTaskTerminator* terminator_) : | |
362 | |
363 _par_scan_state(par_scan_state_), | |
364 _to_space_closure(to_space_closure_), | |
365 _old_gen_closure(old_gen_closure_), | |
366 _to_space_root_closure(to_space_root_closure_), | |
367 _old_gen_root_closure(old_gen_root_closure_), | |
368 _par_gen(par_gen_), | |
369 _task_queues(task_queues_), | |
370 _terminator(terminator_) | |
371 {} | |
372 | |
373 void ParEvacuateFollowersClosure::do_void() { | |
374 ObjToScanQueue* work_q = par_scan_state()->work_queue(); | |
375 | |
376 while (true) { | |
377 | |
378 // Scan to-space and old-gen objs until we run out of both. | |
379 oop obj_to_scan; | |
380 par_scan_state()->trim_queues(0); | |
381 | |
382 // We have no local work, attempt to steal from other threads. | |
383 | |
384 // attempt to steal work from promoted. | |
385 par_scan_state()->note_steal_attempt(); | |
386 if (task_queues()->steal(par_scan_state()->thread_num(), | |
387 par_scan_state()->hash_seed(), | |
388 obj_to_scan)) { | |
389 par_scan_state()->note_steal(); | |
390 bool res = work_q->push(obj_to_scan); | |
391 assert(res, "Empty queue should have room for a push."); | |
392 | |
393 par_scan_state()->note_push(); | |
394 // if successful, goto Start. | |
395 continue; | |
396 | |
397 // try global overflow list. | |
398 } else if (par_gen()->take_from_overflow_list(par_scan_state())) { | |
399 continue; | |
400 } | |
401 | |
402 // Otherwise, offer termination. | |
403 par_scan_state()->start_term_time(); | |
404 if (terminator()->offer_termination()) break; | |
405 par_scan_state()->end_term_time(); | |
406 } | |
534 | 407 assert(par_gen()->_overflow_list == NULL && par_gen()->_num_par_pushes == 0, |
408 "Broken overflow list?"); | |
0 | 409 // Finish the last termination pause. |
410 par_scan_state()->end_term_time(); | |
411 } | |
412 | |
413 ParNewGenTask::ParNewGenTask(ParNewGeneration* gen, Generation* next_gen, | |
414 HeapWord* young_old_boundary, ParScanThreadStateSet* state_set) : | |
415 AbstractGangTask("ParNewGeneration collection"), | |
416 _gen(gen), _next_gen(next_gen), | |
417 _young_old_boundary(young_old_boundary), | |
418 _state_set(state_set) | |
419 {} | |
420 | |
421 void ParNewGenTask::work(int i) { | |
422 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
423 // Since this is being done in a separate thread, need new resource | |
424 // and handle marks. | |
425 ResourceMark rm; | |
426 HandleMark hm; | |
427 // We would need multiple old-gen queues otherwise. | |
428 guarantee(gch->n_gens() == 2, | |
429 "Par young collection currently only works with one older gen."); | |
430 | |
431 Generation* old_gen = gch->next_gen(_gen); | |
432 | |
433 ParScanThreadState& par_scan_state = _state_set->thread_sate(i); | |
434 par_scan_state.set_young_old_boundary(_young_old_boundary); | |
435 | |
436 par_scan_state.start_strong_roots(); | |
437 gch->gen_process_strong_roots(_gen->level(), | |
438 true, // Process younger gens, if any, | |
439 // as strong roots. | |
440 false,// not collecting perm generation. | |
441 SharedHeap::SO_AllClasses, | |
442 &par_scan_state.older_gen_closure(), | |
443 &par_scan_state.to_space_root_closure()); | |
444 par_scan_state.end_strong_roots(); | |
445 | |
446 // "evacuate followers". | |
447 par_scan_state.evacuate_followers_closure().do_void(); | |
448 } | |
449 | |
450 #ifdef _MSC_VER | |
451 #pragma warning( push ) | |
452 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list | |
453 #endif | |
454 ParNewGeneration:: | |
455 ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level) | |
456 : DefNewGeneration(rs, initial_byte_size, level, "PCopy"), | |
457 _overflow_list(NULL), | |
458 _is_alive_closure(this), | |
459 _plab_stats(YoungPLABSize, PLABWeight) | |
460 { | |
534 | 461 NOT_PRODUCT(_overflow_counter = ParGCWorkQueueOverflowInterval;) |
462 NOT_PRODUCT(_num_par_pushes = 0;) | |
0 | 463 _task_queues = new ObjToScanQueueSet(ParallelGCThreads); |
464 guarantee(_task_queues != NULL, "task_queues allocation failure."); | |
465 | |
466 for (uint i1 = 0; i1 < ParallelGCThreads; i1++) { | |
467 ObjToScanQueuePadded *q_padded = new ObjToScanQueuePadded(); | |
468 guarantee(q_padded != NULL, "work_queue Allocation failure."); | |
469 | |
470 _task_queues->register_queue(i1, &q_padded->work_queue); | |
471 } | |
472 | |
473 for (uint i2 = 0; i2 < ParallelGCThreads; i2++) | |
474 _task_queues->queue(i2)->initialize(); | |
475 | |
476 if (UsePerfData) { | |
477 EXCEPTION_MARK; | |
478 ResourceMark rm; | |
479 | |
480 const char* cname = | |
481 PerfDataManager::counter_name(_gen_counters->name_space(), "threads"); | |
482 PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_None, | |
483 ParallelGCThreads, CHECK); | |
484 } | |
485 } | |
486 #ifdef _MSC_VER | |
487 #pragma warning( pop ) | |
488 #endif | |
489 | |
490 // ParNewGeneration:: | |
491 ParKeepAliveClosure::ParKeepAliveClosure(ParScanWeakRefClosure* cl) : | |
492 DefNewGeneration::KeepAliveClosure(cl), _par_cl(cl) {} | |
493 | |
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494 template <class T> |
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495 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop_work(T* p) { |
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496 #ifdef ASSERT |
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497 { |
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498 assert(!oopDesc::is_null(*p), "expected non-null ref"); |
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499 oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
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500 // We never expect to see a null reference being processed |
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501 // as a weak reference. |
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502 assert(obj->is_oop(), "expected an oop while scanning weak refs"); |
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503 } |
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504 #endif // ASSERT |
0 | 505 |
506 _par_cl->do_oop_nv(p); | |
507 | |
508 if (Universe::heap()->is_in_reserved(p)) { | |
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509 oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
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510 _rs->write_ref_field_gc_par(p, obj); |
0 | 511 } |
512 } | |
513 | |
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514 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(oop* p) { ParKeepAliveClosure::do_oop_work(p); } |
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515 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(narrowOop* p) { ParKeepAliveClosure::do_oop_work(p); } |
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516 |
0 | 517 // ParNewGeneration:: |
518 KeepAliveClosure::KeepAliveClosure(ScanWeakRefClosure* cl) : | |
519 DefNewGeneration::KeepAliveClosure(cl) {} | |
520 | |
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521 template <class T> |
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522 void /*ParNewGeneration::*/KeepAliveClosure::do_oop_work(T* p) { |
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523 #ifdef ASSERT |
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524 { |
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525 assert(!oopDesc::is_null(*p), "expected non-null ref"); |
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526 oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
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527 // We never expect to see a null reference being processed |
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528 // as a weak reference. |
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529 assert(obj->is_oop(), "expected an oop while scanning weak refs"); |
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530 } |
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531 #endif // ASSERT |
0 | 532 |
533 _cl->do_oop_nv(p); | |
534 | |
535 if (Universe::heap()->is_in_reserved(p)) { | |
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536 oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
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537 _rs->write_ref_field_gc_par(p, obj); |
0 | 538 } |
539 } | |
540 | |
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541 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(oop* p) { KeepAliveClosure::do_oop_work(p); } |
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542 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(narrowOop* p) { KeepAliveClosure::do_oop_work(p); } |
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543 |
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544 template <class T> void ScanClosureWithParBarrier::do_oop_work(T* p) { |
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545 T heap_oop = oopDesc::load_heap_oop(p); |
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546 if (!oopDesc::is_null(heap_oop)) { |
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547 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); |
0 | 548 if ((HeapWord*)obj < _boundary) { |
549 assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?"); | |
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550 oop new_obj = obj->is_forwarded() |
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551 ? obj->forwardee() |
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552 : _g->DefNewGeneration::copy_to_survivor_space(obj); |
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553 oopDesc::encode_store_heap_oop_not_null(p, new_obj); |
0 | 554 } |
555 if (_gc_barrier) { | |
556 // If p points to a younger generation, mark the card. | |
557 if ((HeapWord*)obj < _gen_boundary) { | |
558 _rs->write_ref_field_gc_par(p, obj); | |
559 } | |
560 } | |
561 } | |
562 } | |
563 | |
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564 void ScanClosureWithParBarrier::do_oop(oop* p) { ScanClosureWithParBarrier::do_oop_work(p); } |
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565 void ScanClosureWithParBarrier::do_oop(narrowOop* p) { ScanClosureWithParBarrier::do_oop_work(p); } |
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566 |
0 | 567 class ParNewRefProcTaskProxy: public AbstractGangTask { |
568 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; | |
569 public: | |
570 ParNewRefProcTaskProxy(ProcessTask& task, ParNewGeneration& gen, | |
571 Generation& next_gen, | |
572 HeapWord* young_old_boundary, | |
573 ParScanThreadStateSet& state_set); | |
574 | |
575 private: | |
576 virtual void work(int i); | |
577 | |
578 private: | |
579 ParNewGeneration& _gen; | |
580 ProcessTask& _task; | |
581 Generation& _next_gen; | |
582 HeapWord* _young_old_boundary; | |
583 ParScanThreadStateSet& _state_set; | |
584 }; | |
585 | |
586 ParNewRefProcTaskProxy::ParNewRefProcTaskProxy( | |
587 ProcessTask& task, ParNewGeneration& gen, | |
588 Generation& next_gen, | |
589 HeapWord* young_old_boundary, | |
590 ParScanThreadStateSet& state_set) | |
591 : AbstractGangTask("ParNewGeneration parallel reference processing"), | |
592 _gen(gen), | |
593 _task(task), | |
594 _next_gen(next_gen), | |
595 _young_old_boundary(young_old_boundary), | |
596 _state_set(state_set) | |
597 { | |
598 } | |
599 | |
600 void ParNewRefProcTaskProxy::work(int i) | |
601 { | |
602 ResourceMark rm; | |
603 HandleMark hm; | |
604 ParScanThreadState& par_scan_state = _state_set.thread_sate(i); | |
605 par_scan_state.set_young_old_boundary(_young_old_boundary); | |
606 _task.work(i, par_scan_state.is_alive_closure(), | |
607 par_scan_state.keep_alive_closure(), | |
608 par_scan_state.evacuate_followers_closure()); | |
609 } | |
610 | |
611 class ParNewRefEnqueueTaskProxy: public AbstractGangTask { | |
612 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; | |
613 EnqueueTask& _task; | |
614 | |
615 public: | |
616 ParNewRefEnqueueTaskProxy(EnqueueTask& task) | |
617 : AbstractGangTask("ParNewGeneration parallel reference enqueue"), | |
618 _task(task) | |
619 { } | |
620 | |
621 virtual void work(int i) | |
622 { | |
623 _task.work(i); | |
624 } | |
625 }; | |
626 | |
627 | |
628 void ParNewRefProcTaskExecutor::execute(ProcessTask& task) | |
629 { | |
630 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
631 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
632 "not a generational heap"); | |
633 WorkGang* workers = gch->workers(); | |
634 assert(workers != NULL, "Need parallel worker threads."); | |
635 ParNewRefProcTaskProxy rp_task(task, _generation, *_generation.next_gen(), | |
636 _generation.reserved().end(), _state_set); | |
637 workers->run_task(&rp_task); | |
638 _state_set.reset(); | |
639 } | |
640 | |
641 void ParNewRefProcTaskExecutor::execute(EnqueueTask& task) | |
642 { | |
643 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
644 WorkGang* workers = gch->workers(); | |
645 assert(workers != NULL, "Need parallel worker threads."); | |
646 ParNewRefEnqueueTaskProxy enq_task(task); | |
647 workers->run_task(&enq_task); | |
648 } | |
649 | |
650 void ParNewRefProcTaskExecutor::set_single_threaded_mode() | |
651 { | |
652 _state_set.flush(); | |
653 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
654 gch->set_par_threads(0); // 0 ==> non-parallel. | |
655 gch->save_marks(); | |
656 } | |
657 | |
658 ScanClosureWithParBarrier:: | |
659 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier) : | |
660 ScanClosure(g, gc_barrier) {} | |
661 | |
662 EvacuateFollowersClosureGeneral:: | |
663 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level, | |
664 OopsInGenClosure* cur, | |
665 OopsInGenClosure* older) : | |
666 _gch(gch), _level(level), | |
667 _scan_cur_or_nonheap(cur), _scan_older(older) | |
668 {} | |
669 | |
670 void EvacuateFollowersClosureGeneral::do_void() { | |
671 do { | |
672 // Beware: this call will lead to closure applications via virtual | |
673 // calls. | |
674 _gch->oop_since_save_marks_iterate(_level, | |
675 _scan_cur_or_nonheap, | |
676 _scan_older); | |
677 } while (!_gch->no_allocs_since_save_marks(_level)); | |
678 } | |
679 | |
680 | |
681 bool ParNewGeneration::_avoid_promotion_undo = false; | |
682 | |
683 void ParNewGeneration::adjust_desired_tenuring_threshold() { | |
684 // Set the desired survivor size to half the real survivor space | |
685 _tenuring_threshold = | |
686 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize); | |
687 } | |
688 | |
689 // A Generation that does parallel young-gen collection. | |
690 | |
691 void ParNewGeneration::collect(bool full, | |
692 bool clear_all_soft_refs, | |
693 size_t size, | |
694 bool is_tlab) { | |
695 assert(full || size > 0, "otherwise we don't want to collect"); | |
696 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
697 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
698 "not a CMS generational heap"); | |
699 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); | |
700 WorkGang* workers = gch->workers(); | |
701 _next_gen = gch->next_gen(this); | |
702 assert(_next_gen != NULL, | |
703 "This must be the youngest gen, and not the only gen"); | |
704 assert(gch->n_gens() == 2, | |
705 "Par collection currently only works with single older gen."); | |
706 // Do we have to avoid promotion_undo? | |
707 if (gch->collector_policy()->is_concurrent_mark_sweep_policy()) { | |
708 set_avoid_promotion_undo(true); | |
709 } | |
710 | |
711 // If the next generation is too full to accomodate worst-case promotion | |
712 // from this generation, pass on collection; let the next generation | |
713 // do it. | |
714 if (!collection_attempt_is_safe()) { | |
715 gch->set_incremental_collection_will_fail(); | |
716 return; | |
717 } | |
718 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); | |
719 | |
720 init_assuming_no_promotion_failure(); | |
721 | |
722 if (UseAdaptiveSizePolicy) { | |
723 set_survivor_overflow(false); | |
724 size_policy->minor_collection_begin(); | |
725 } | |
726 | |
727 TraceTime t1("GC", PrintGC && !PrintGCDetails, true, gclog_or_tty); | |
728 // Capture heap used before collection (for printing). | |
729 size_t gch_prev_used = gch->used(); | |
730 | |
731 SpecializationStats::clear(); | |
732 | |
733 age_table()->clear(); | |
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734 to()->clear(SpaceDecorator::Mangle); |
0 | 735 |
736 gch->save_marks(); | |
737 assert(workers != NULL, "Need parallel worker threads."); | |
738 ParallelTaskTerminator _term(workers->total_workers(), task_queues()); | |
739 ParScanThreadStateSet thread_state_set(workers->total_workers(), | |
740 *to(), *this, *_next_gen, *task_queues(), | |
741 desired_plab_sz(), _term); | |
742 | |
743 ParNewGenTask tsk(this, _next_gen, reserved().end(), &thread_state_set); | |
744 int n_workers = workers->total_workers(); | |
745 gch->set_par_threads(n_workers); | |
746 gch->change_strong_roots_parity(); | |
747 gch->rem_set()->prepare_for_younger_refs_iterate(true); | |
748 // It turns out that even when we're using 1 thread, doing the work in a | |
749 // separate thread causes wide variance in run times. We can't help this | |
750 // in the multi-threaded case, but we special-case n=1 here to get | |
751 // repeatable measurements of the 1-thread overhead of the parallel code. | |
752 if (n_workers > 1) { | |
753 workers->run_task(&tsk); | |
754 } else { | |
755 tsk.work(0); | |
756 } | |
757 thread_state_set.reset(); | |
758 | |
759 if (PAR_STATS_ENABLED && ParallelGCVerbose) { | |
760 gclog_or_tty->print("Thread totals:\n" | |
761 " Pushes: %7d Pops: %7d Steals %7d (sum = %7d).\n", | |
762 thread_state_set.pushes(), thread_state_set.pops(), | |
763 thread_state_set.steals(), | |
764 thread_state_set.pops()+thread_state_set.steals()); | |
765 } | |
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766 assert(thread_state_set.pushes() == thread_state_set.pops() |
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767 + thread_state_set.steals(), |
0 | 768 "Or else the queues are leaky."); |
769 | |
770 // Process (weak) reference objects found during scavenge. | |
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771 ReferenceProcessor* rp = ref_processor(); |
0 | 772 IsAliveClosure is_alive(this); |
773 ScanWeakRefClosure scan_weak_ref(this); | |
774 KeepAliveClosure keep_alive(&scan_weak_ref); | |
775 ScanClosure scan_without_gc_barrier(this, false); | |
776 ScanClosureWithParBarrier scan_with_gc_barrier(this, true); | |
777 set_promo_failure_scan_stack_closure(&scan_without_gc_barrier); | |
778 EvacuateFollowersClosureGeneral evacuate_followers(gch, _level, | |
779 &scan_without_gc_barrier, &scan_with_gc_barrier); | |
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780 rp->setup_policy(clear_all_soft_refs); |
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781 if (rp->processing_is_mt()) { |
0 | 782 ParNewRefProcTaskExecutor task_executor(*this, thread_state_set); |
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783 rp->process_discovered_references(&is_alive, &keep_alive, |
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784 &evacuate_followers, &task_executor); |
0 | 785 } else { |
786 thread_state_set.flush(); | |
787 gch->set_par_threads(0); // 0 ==> non-parallel. | |
788 gch->save_marks(); | |
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789 rp->process_discovered_references(&is_alive, &keep_alive, |
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790 &evacuate_followers, NULL); |
0 | 791 } |
792 if (!promotion_failed()) { | |
793 // Swap the survivor spaces. | |
263
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794 eden()->clear(SpaceDecorator::Mangle); |
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795 from()->clear(SpaceDecorator::Mangle); |
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796 if (ZapUnusedHeapArea) { |
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797 // This is now done here because of the piece-meal mangling which |
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798 // can check for valid mangling at intermediate points in the |
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799 // collection(s). When a minor collection fails to collect |
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800 // sufficient space resizing of the young generation can occur |
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801 // an redistribute the spaces in the young generation. Mangle |
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802 // here so that unzapped regions don't get distributed to |
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803 // other spaces. |
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804 to()->mangle_unused_area(); |
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805 } |
0 | 806 swap_spaces(); |
807 | |
808 assert(to()->is_empty(), "to space should be empty now"); | |
809 } else { | |
810 assert(HandlePromotionFailure, | |
811 "Should only be here if promotion failure handling is on"); | |
812 if (_promo_failure_scan_stack != NULL) { | |
813 // Can be non-null because of reference processing. | |
814 // Free stack with its elements. | |
815 delete _promo_failure_scan_stack; | |
816 _promo_failure_scan_stack = NULL; | |
817 } | |
818 remove_forwarding_pointers(); | |
819 if (PrintGCDetails) { | |
820 gclog_or_tty->print(" (promotion failed)"); | |
821 } | |
822 // All the spaces are in play for mark-sweep. | |
823 swap_spaces(); // Make life simpler for CMS || rescan; see 6483690. | |
824 from()->set_next_compaction_space(to()); | |
825 gch->set_incremental_collection_will_fail(); | |
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826 |
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827 // Reset the PromotionFailureALot counters. |
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828 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();) |
0 | 829 } |
830 // set new iteration safe limit for the survivor spaces | |
831 from()->set_concurrent_iteration_safe_limit(from()->top()); | |
832 to()->set_concurrent_iteration_safe_limit(to()->top()); | |
833 | |
834 adjust_desired_tenuring_threshold(); | |
835 if (ResizePLAB) { | |
836 plab_stats()->adjust_desired_plab_sz(); | |
837 } | |
838 | |
839 if (PrintGC && !PrintGCDetails) { | |
840 gch->print_heap_change(gch_prev_used); | |
841 } | |
842 | |
843 if (UseAdaptiveSizePolicy) { | |
844 size_policy->minor_collection_end(gch->gc_cause()); | |
845 size_policy->avg_survived()->sample(from()->used()); | |
846 } | |
847 | |
848 update_time_of_last_gc(os::javaTimeMillis()); | |
849 | |
850 SpecializationStats::print(); | |
851 | |
453
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852 rp->set_enqueuing_is_done(true); |
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853 if (rp->processing_is_mt()) { |
0 | 854 ParNewRefProcTaskExecutor task_executor(*this, thread_state_set); |
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855 rp->enqueue_discovered_references(&task_executor); |
0 | 856 } else { |
453
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857 rp->enqueue_discovered_references(NULL); |
0 | 858 } |
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859 rp->verify_no_references_recorded(); |
0 | 860 } |
861 | |
862 static int sum; | |
863 void ParNewGeneration::waste_some_time() { | |
864 for (int i = 0; i < 100; i++) { | |
865 sum += i; | |
866 } | |
867 } | |
868 | |
869 static const oop ClaimedForwardPtr = oop(0x4); | |
870 | |
871 // Because of concurrency, there are times where an object for which | |
872 // "is_forwarded()" is true contains an "interim" forwarding pointer | |
873 // value. Such a value will soon be overwritten with a real value. | |
874 // This method requires "obj" to have a forwarding pointer, and waits, if | |
875 // necessary for a real one to be inserted, and returns it. | |
876 | |
877 oop ParNewGeneration::real_forwardee(oop obj) { | |
878 oop forward_ptr = obj->forwardee(); | |
879 if (forward_ptr != ClaimedForwardPtr) { | |
880 return forward_ptr; | |
881 } else { | |
882 return real_forwardee_slow(obj); | |
883 } | |
884 } | |
885 | |
886 oop ParNewGeneration::real_forwardee_slow(oop obj) { | |
887 // Spin-read if it is claimed but not yet written by another thread. | |
888 oop forward_ptr = obj->forwardee(); | |
889 while (forward_ptr == ClaimedForwardPtr) { | |
890 waste_some_time(); | |
891 assert(obj->is_forwarded(), "precondition"); | |
892 forward_ptr = obj->forwardee(); | |
893 } | |
894 return forward_ptr; | |
895 } | |
896 | |
897 #ifdef ASSERT | |
898 bool ParNewGeneration::is_legal_forward_ptr(oop p) { | |
899 return | |
900 (_avoid_promotion_undo && p == ClaimedForwardPtr) | |
901 || Universe::heap()->is_in_reserved(p); | |
902 } | |
903 #endif | |
904 | |
905 void ParNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { | |
906 if ((m != markOopDesc::prototype()) && | |
907 (!UseBiasedLocking || (m != markOopDesc::biased_locking_prototype()))) { | |
908 MutexLocker ml(ParGCRareEvent_lock); | |
909 DefNewGeneration::preserve_mark_if_necessary(obj, m); | |
910 } | |
911 } | |
912 | |
913 // Multiple GC threads may try to promote an object. If the object | |
914 // is successfully promoted, a forwarding pointer will be installed in | |
915 // the object in the young generation. This method claims the right | |
916 // to install the forwarding pointer before it copies the object, | |
917 // thus avoiding the need to undo the copy as in | |
918 // copy_to_survivor_space_avoiding_with_undo. | |
919 | |
920 oop ParNewGeneration::copy_to_survivor_space_avoiding_promotion_undo( | |
921 ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) { | |
922 // In the sequential version, this assert also says that the object is | |
923 // not forwarded. That might not be the case here. It is the case that | |
924 // the caller observed it to be not forwarded at some time in the past. | |
925 assert(is_in_reserved(old), "shouldn't be scavenging this oop"); | |
926 | |
927 // The sequential code read "old->age()" below. That doesn't work here, | |
928 // since the age is in the mark word, and that might be overwritten with | |
929 // a forwarding pointer by a parallel thread. So we must save the mark | |
930 // word in a local and then analyze it. | |
931 oopDesc dummyOld; | |
932 dummyOld.set_mark(m); | |
933 assert(!dummyOld.is_forwarded(), | |
934 "should not be called with forwarding pointer mark word."); | |
935 | |
936 oop new_obj = NULL; | |
937 oop forward_ptr; | |
938 | |
939 // Try allocating obj in to-space (unless too old) | |
940 if (dummyOld.age() < tenuring_threshold()) { | |
941 new_obj = (oop)par_scan_state->alloc_in_to_space(sz); | |
942 if (new_obj == NULL) { | |
943 set_survivor_overflow(true); | |
944 } | |
945 } | |
946 | |
947 if (new_obj == NULL) { | |
948 // Either to-space is full or we decided to promote | |
949 // try allocating obj tenured | |
950 | |
951 // Attempt to install a null forwarding pointer (atomically), | |
952 // to claim the right to install the real forwarding pointer. | |
953 forward_ptr = old->forward_to_atomic(ClaimedForwardPtr); | |
954 if (forward_ptr != NULL) { | |
955 // someone else beat us to it. | |
956 return real_forwardee(old); | |
957 } | |
958 | |
959 new_obj = _next_gen->par_promote(par_scan_state->thread_num(), | |
960 old, m, sz); | |
961 | |
962 if (new_obj == NULL) { | |
963 if (!HandlePromotionFailure) { | |
964 // A failed promotion likely means the MaxLiveObjectEvacuationRatio flag | |
965 // is incorrectly set. In any case, its seriously wrong to be here! | |
966 vm_exit_out_of_memory(sz*wordSize, "promotion"); | |
967 } | |
968 // promotion failed, forward to self | |
969 _promotion_failed = true; | |
970 new_obj = old; | |
971 | |
972 preserve_mark_if_necessary(old, m); | |
973 } | |
974 | |
975 old->forward_to(new_obj); | |
976 forward_ptr = NULL; | |
977 } else { | |
978 // Is in to-space; do copying ourselves. | |
979 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz); | |
980 forward_ptr = old->forward_to_atomic(new_obj); | |
981 // Restore the mark word copied above. | |
982 new_obj->set_mark(m); | |
983 // Increment age if obj still in new generation | |
984 new_obj->incr_age(); | |
985 par_scan_state->age_table()->add(new_obj, sz); | |
986 } | |
987 assert(new_obj != NULL, "just checking"); | |
988 | |
989 if (forward_ptr == NULL) { | |
990 oop obj_to_push = new_obj; | |
991 if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) { | |
992 // Length field used as index of next element to be scanned. | |
993 // Real length can be obtained from real_forwardee() | |
994 arrayOop(old)->set_length(0); | |
995 obj_to_push = old; | |
996 assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push, | |
997 "push forwarded object"); | |
998 } | |
999 // Push it on one of the queues of to-be-scanned objects. | |
534 | 1000 bool simulate_overflow = false; |
1001 NOT_PRODUCT( | |
1002 if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) { | |
1003 // simulate a stack overflow | |
1004 simulate_overflow = true; | |
1005 } | |
1006 ) | |
1007 if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) { | |
0 | 1008 // Add stats for overflow pushes. |
1009 if (Verbose && PrintGCDetails) { | |
1010 gclog_or_tty->print("queue overflow!\n"); | |
1011 } | |
534 | 1012 push_on_overflow_list(old, par_scan_state); |
0 | 1013 par_scan_state->note_overflow_push(); |
1014 } | |
1015 par_scan_state->note_push(); | |
1016 | |
1017 return new_obj; | |
1018 } | |
1019 | |
1020 // Oops. Someone beat us to it. Undo the allocation. Where did we | |
1021 // allocate it? | |
1022 if (is_in_reserved(new_obj)) { | |
1023 // Must be in to_space. | |
1024 assert(to()->is_in_reserved(new_obj), "Checking"); | |
1025 if (forward_ptr == ClaimedForwardPtr) { | |
1026 // Wait to get the real forwarding pointer value. | |
1027 forward_ptr = real_forwardee(old); | |
1028 } | |
1029 par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz); | |
1030 } | |
1031 | |
1032 return forward_ptr; | |
1033 } | |
1034 | |
1035 | |
1036 // Multiple GC threads may try to promote the same object. If two | |
1037 // or more GC threads copy the object, only one wins the race to install | |
1038 // the forwarding pointer. The other threads have to undo their copy. | |
1039 | |
1040 oop ParNewGeneration::copy_to_survivor_space_with_undo( | |
1041 ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) { | |
1042 | |
1043 // In the sequential version, this assert also says that the object is | |
1044 // not forwarded. That might not be the case here. It is the case that | |
1045 // the caller observed it to be not forwarded at some time in the past. | |
1046 assert(is_in_reserved(old), "shouldn't be scavenging this oop"); | |
1047 | |
1048 // The sequential code read "old->age()" below. That doesn't work here, | |
1049 // since the age is in the mark word, and that might be overwritten with | |
1050 // a forwarding pointer by a parallel thread. So we must save the mark | |
1051 // word here, install it in a local oopDesc, and then analyze it. | |
1052 oopDesc dummyOld; | |
1053 dummyOld.set_mark(m); | |
1054 assert(!dummyOld.is_forwarded(), | |
1055 "should not be called with forwarding pointer mark word."); | |
1056 | |
1057 bool failed_to_promote = false; | |
1058 oop new_obj = NULL; | |
1059 oop forward_ptr; | |
1060 | |
1061 // Try allocating obj in to-space (unless too old) | |
1062 if (dummyOld.age() < tenuring_threshold()) { | |
1063 new_obj = (oop)par_scan_state->alloc_in_to_space(sz); | |
1064 if (new_obj == NULL) { | |
1065 set_survivor_overflow(true); | |
1066 } | |
1067 } | |
1068 | |
1069 if (new_obj == NULL) { | |
1070 // Either to-space is full or we decided to promote | |
1071 // try allocating obj tenured | |
1072 new_obj = _next_gen->par_promote(par_scan_state->thread_num(), | |
1073 old, m, sz); | |
1074 | |
1075 if (new_obj == NULL) { | |
1076 if (!HandlePromotionFailure) { | |
1077 // A failed promotion likely means the MaxLiveObjectEvacuationRatio | |
1078 // flag is incorrectly set. In any case, its seriously wrong to be | |
1079 // here! | |
1080 vm_exit_out_of_memory(sz*wordSize, "promotion"); | |
1081 } | |
1082 // promotion failed, forward to self | |
1083 forward_ptr = old->forward_to_atomic(old); | |
1084 new_obj = old; | |
1085 | |
1086 if (forward_ptr != NULL) { | |
1087 return forward_ptr; // someone else succeeded | |
1088 } | |
1089 | |
1090 _promotion_failed = true; | |
1091 failed_to_promote = true; | |
1092 | |
1093 preserve_mark_if_necessary(old, m); | |
1094 } | |
1095 } else { | |
1096 // Is in to-space; do copying ourselves. | |
1097 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz); | |
1098 // Restore the mark word copied above. | |
1099 new_obj->set_mark(m); | |
1100 // Increment age if new_obj still in new generation | |
1101 new_obj->incr_age(); | |
1102 par_scan_state->age_table()->add(new_obj, sz); | |
1103 } | |
1104 assert(new_obj != NULL, "just checking"); | |
1105 | |
1106 // Now attempt to install the forwarding pointer (atomically). | |
1107 // We have to copy the mark word before overwriting with forwarding | |
1108 // ptr, so we can restore it below in the copy. | |
1109 if (!failed_to_promote) { | |
1110 forward_ptr = old->forward_to_atomic(new_obj); | |
1111 } | |
1112 | |
1113 if (forward_ptr == NULL) { | |
1114 oop obj_to_push = new_obj; | |
1115 if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) { | |
1116 // Length field used as index of next element to be scanned. | |
1117 // Real length can be obtained from real_forwardee() | |
1118 arrayOop(old)->set_length(0); | |
1119 obj_to_push = old; | |
1120 assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push, | |
1121 "push forwarded object"); | |
1122 } | |
1123 // Push it on one of the queues of to-be-scanned objects. | |
534 | 1124 bool simulate_overflow = false; |
1125 NOT_PRODUCT( | |
1126 if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) { | |
1127 // simulate a stack overflow | |
1128 simulate_overflow = true; | |
1129 } | |
1130 ) | |
1131 if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) { | |
0 | 1132 // Add stats for overflow pushes. |
534 | 1133 push_on_overflow_list(old, par_scan_state); |
0 | 1134 par_scan_state->note_overflow_push(); |
1135 } | |
1136 par_scan_state->note_push(); | |
1137 | |
1138 return new_obj; | |
1139 } | |
1140 | |
1141 // Oops. Someone beat us to it. Undo the allocation. Where did we | |
1142 // allocate it? | |
1143 if (is_in_reserved(new_obj)) { | |
1144 // Must be in to_space. | |
1145 assert(to()->is_in_reserved(new_obj), "Checking"); | |
1146 par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz); | |
1147 } else { | |
1148 assert(!_avoid_promotion_undo, "Should not be here if avoiding."); | |
1149 _next_gen->par_promote_alloc_undo(par_scan_state->thread_num(), | |
1150 (HeapWord*)new_obj, sz); | |
1151 } | |
1152 | |
1153 return forward_ptr; | |
1154 } | |
1155 | |
534 | 1156 #ifndef PRODUCT |
1157 // It's OK to call this multi-threaded; the worst thing | |
1158 // that can happen is that we'll get a bunch of closely | |
1159 // spaced simulated oveflows, but that's OK, in fact | |
1160 // probably good as it would exercise the overflow code | |
1161 // under contention. | |
1162 bool ParNewGeneration::should_simulate_overflow() { | |
1163 if (_overflow_counter-- <= 0) { // just being defensive | |
1164 _overflow_counter = ParGCWorkQueueOverflowInterval; | |
1165 return true; | |
1166 } else { | |
1167 return false; | |
1168 } | |
1169 } | |
1170 #endif | |
1171 | |
1172 #define BUSY (oop(0x1aff1aff)) | |
1173 void ParNewGeneration::push_on_overflow_list(oop from_space_obj, ParScanThreadState* par_scan_state) { | |
0 | 1174 // if the object has been forwarded to itself, then we cannot |
1175 // use the klass pointer for the linked list. Instead we have | |
1176 // to allocate an oopDesc in the C-Heap and use that for the linked list. | |
534 | 1177 // XXX This is horribly inefficient when a promotion failure occurs |
1178 // and should be fixed. XXX FIX ME !!! | |
1179 #ifndef PRODUCT | |
1180 Atomic::inc_ptr(&_num_par_pushes); | |
1181 assert(_num_par_pushes > 0, "Tautology"); | |
1182 #endif | |
0 | 1183 if (from_space_obj->forwardee() == from_space_obj) { |
1184 oopDesc* listhead = NEW_C_HEAP_ARRAY(oopDesc, 1); | |
1185 listhead->forward_to(from_space_obj); | |
1186 from_space_obj = listhead; | |
1187 } | |
534 | 1188 oop observed_overflow_list = _overflow_list; |
1189 oop cur_overflow_list; | |
1190 do { | |
1191 cur_overflow_list = observed_overflow_list; | |
1192 if (cur_overflow_list != BUSY) { | |
1193 from_space_obj->set_klass_to_list_ptr(cur_overflow_list); | |
1194 } else { | |
1195 from_space_obj->set_klass_to_list_ptr(NULL); | |
1196 } | |
1197 observed_overflow_list = | |
0 | 1198 (oop)Atomic::cmpxchg_ptr(from_space_obj, &_overflow_list, cur_overflow_list); |
534 | 1199 } while (cur_overflow_list != observed_overflow_list); |
0 | 1200 } |
1201 | |
534 | 1202 // *NOTE*: The overflow list manipulation code here and |
1203 // in CMSCollector:: are very similar in shape, | |
1204 // except that in the CMS case we thread the objects | |
1205 // directly into the list via their mark word, and do | |
1206 // not need to deal with special cases below related | |
1207 // to chunking of object arrays and promotion failure | |
1208 // handling. | |
1209 // CR 6797058 has been filed to attempt consolidation of | |
1210 // the common code. | |
1211 // Because of the common code, if you make any changes in | |
1212 // the code below, please check the CMS version to see if | |
1213 // similar changes might be needed. | |
1214 // See CMSCollector::par_take_from_overflow_list() for | |
1215 // more extensive documentation comments. | |
0 | 1216 bool |
1217 ParNewGeneration::take_from_overflow_list(ParScanThreadState* par_scan_state) { | |
1218 ObjToScanQueue* work_q = par_scan_state->work_queue(); | |
534 | 1219 assert(work_q->size() == 0, "Should first empty local work queue"); |
0 | 1220 // How many to take? |
534 | 1221 size_t objsFromOverflow = MIN2((size_t)work_q->max_elems()/4, |
1222 (size_t)ParGCDesiredObjsFromOverflowList); | |
0 | 1223 |
1224 if (_overflow_list == NULL) return false; | |
1225 | |
1226 // Otherwise, there was something there; try claiming the list. | |
534 | 1227 oop prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); |
1228 // Trim off a prefix of at most objsFromOverflow items | |
1229 Thread* tid = Thread::current(); | |
1230 size_t spin_count = (size_t)ParallelGCThreads; | |
1231 size_t sleep_time_millis = MAX2((size_t)1, objsFromOverflow/100); | |
1232 for (size_t spin = 0; prefix == BUSY && spin < spin_count; spin++) { | |
1233 // someone grabbed it before we did ... | |
1234 // ... we spin for a short while... | |
1235 os::sleep(tid, sleep_time_millis, false); | |
1236 if (_overflow_list == NULL) { | |
1237 // nothing left to take | |
1238 return false; | |
1239 } else if (_overflow_list != BUSY) { | |
1240 // try and grab the prefix | |
1241 prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); | |
1242 } | |
0 | 1243 } |
534 | 1244 if (prefix == NULL || prefix == BUSY) { |
1245 // Nothing to take or waited long enough | |
1246 if (prefix == NULL) { | |
1247 // Write back the NULL in case we overwrote it with BUSY above | |
1248 // and it is still the same value. | |
1249 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
1250 } | |
1251 return false; | |
1252 } | |
1253 assert(prefix != NULL && prefix != BUSY, "Error"); | |
1254 size_t i = 1; | |
0 | 1255 oop cur = prefix; |
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1256 while (i < objsFromOverflow && cur->klass_or_null() != NULL) { |
0 | 1257 i++; cur = oop(cur->klass()); |
1258 } | |
1259 | |
1260 // Reattach remaining (suffix) to overflow list | |
534 | 1261 if (cur->klass_or_null() == NULL) { |
1262 // Write back the NULL in lieu of the BUSY we wrote | |
1263 // above and it is still the same value. | |
1264 if (_overflow_list == BUSY) { | |
1265 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
0 | 1266 } |
534 | 1267 } else { |
1268 assert(cur->klass_or_null() != BUSY, "Error"); | |
1269 oop suffix = oop(cur->klass()); // suffix will be put back on global list | |
1270 cur->set_klass_to_list_ptr(NULL); // break off suffix | |
1271 // It's possible that the list is still in the empty(busy) state | |
1272 // we left it in a short while ago; in that case we may be | |
1273 // able to place back the suffix. | |
1274 oop observed_overflow_list = _overflow_list; | |
1275 oop cur_overflow_list = observed_overflow_list; | |
1276 bool attached = false; | |
1277 while (observed_overflow_list == BUSY || observed_overflow_list == NULL) { | |
1278 observed_overflow_list = | |
1279 (oop) Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list); | |
1280 if (cur_overflow_list == observed_overflow_list) { | |
1281 attached = true; | |
1282 break; | |
1283 } else cur_overflow_list = observed_overflow_list; | |
1284 } | |
1285 if (!attached) { | |
1286 // Too bad, someone else got in in between; we'll need to do a splice. | |
1287 // Find the last item of suffix list | |
1288 oop last = suffix; | |
1289 while (last->klass_or_null() != NULL) { | |
1290 last = oop(last->klass()); | |
1291 } | |
1292 // Atomically prepend suffix to current overflow list | |
1293 observed_overflow_list = _overflow_list; | |
1294 do { | |
1295 cur_overflow_list = observed_overflow_list; | |
1296 if (cur_overflow_list != BUSY) { | |
1297 // Do the splice ... | |
1298 last->set_klass_to_list_ptr(cur_overflow_list); | |
1299 } else { // cur_overflow_list == BUSY | |
1300 last->set_klass_to_list_ptr(NULL); | |
1301 } | |
1302 observed_overflow_list = | |
1303 (oop)Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list); | |
1304 } while (cur_overflow_list != observed_overflow_list); | |
0 | 1305 } |
1306 } | |
1307 | |
1308 // Push objects on prefix list onto this thread's work queue | |
534 | 1309 assert(prefix != NULL && prefix != BUSY, "program logic"); |
0 | 1310 cur = prefix; |
534 | 1311 ssize_t n = 0; |
0 | 1312 while (cur != NULL) { |
1313 oop obj_to_push = cur->forwardee(); | |
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1314 oop next = oop(cur->klass_or_null()); |
0 | 1315 cur->set_klass(obj_to_push->klass()); |
534 | 1316 // This may be an array object that is self-forwarded. In that case, the list pointer |
1317 // space, cur, is not in the Java heap, but rather in the C-heap and should be freed. | |
1318 if (!is_in_reserved(cur)) { | |
1319 // This can become a scaling bottleneck when there is work queue overflow coincident | |
1320 // with promotion failure. | |
1321 oopDesc* f = cur; | |
1322 FREE_C_HEAP_ARRAY(oopDesc, f); | |
1323 } else if (par_scan_state->should_be_partially_scanned(obj_to_push, cur)) { | |
0 | 1324 assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned"); |
534 | 1325 obj_to_push = cur; |
0 | 1326 } |
534 | 1327 bool ok = work_q->push(obj_to_push); |
1328 assert(ok, "Should have succeeded"); | |
0 | 1329 cur = next; |
1330 n++; | |
1331 } | |
1332 par_scan_state->note_overflow_refill(n); | |
534 | 1333 #ifndef PRODUCT |
1334 assert(_num_par_pushes >= n, "Too many pops?"); | |
1335 Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes); | |
1336 #endif | |
0 | 1337 return true; |
1338 } | |
534 | 1339 #undef BUSY |
0 | 1340 |
1341 void ParNewGeneration::ref_processor_init() | |
1342 { | |
1343 if (_ref_processor == NULL) { | |
1344 // Allocate and initialize a reference processor | |
1345 _ref_processor = ReferenceProcessor::create_ref_processor( | |
1346 _reserved, // span | |
1347 refs_discovery_is_atomic(), // atomic_discovery | |
1348 refs_discovery_is_mt(), // mt_discovery | |
1349 NULL, // is_alive_non_header | |
1350 ParallelGCThreads, | |
1351 ParallelRefProcEnabled); | |
1352 } | |
1353 } | |
1354 | |
1355 const char* ParNewGeneration::name() const { | |
1356 return "par new generation"; | |
1357 } |