1 /*
2 * Copyright 2001-2008 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact 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 }
107
108 // process our set of indices (include header in first chunk)
109 // should make sure end is even (aligned to HeapWord in case of compressed oops)
110 if ((HeapWord *)obj < young_old_boundary()) {
111 // object is in to_space
112 obj->oop_iterate_range(&_to_space_closure, start, end);
113 } else {
114 // object is in old generation
115 obj->oop_iterate_range(&_old_gen_closure, start, end);
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 {
204 SharedHeap::fill_region_with_object(MemRegion(obj, word_sz));
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
329 void ParScanWithBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, true, false); }
330 void ParScanWithBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, false); }
331
332 void ParScanWithoutBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, false, false); }
333 void ParScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, false); }
334
335 void ParRootScanWithBarrierTwoGensClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, true, true); }
336 void ParRootScanWithBarrierTwoGensClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, true); }
337
338 void ParRootScanWithoutBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, false, true); }
339 void ParRootScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, true); }
340
341 ParScanWeakRefClosure::ParScanWeakRefClosure(ParNewGeneration* g,
342 ParScanThreadState* par_scan_state)
343 : ScanWeakRefClosure(g), _par_scan_state(par_scan_state)
344 {}
345
346 void ParScanWeakRefClosure::do_oop(oop* p) { ParScanWeakRefClosure::do_oop_work(p); }
347 void ParScanWeakRefClosure::do_oop(narrowOop* p) { ParScanWeakRefClosure::do_oop_work(p); }
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 }
407 // Finish the last termination pause.
408 par_scan_state()->end_term_time();
409 }
410
411 ParNewGenTask::ParNewGenTask(ParNewGeneration* gen, Generation* next_gen,
412 HeapWord* young_old_boundary, ParScanThreadStateSet* state_set) :
413 AbstractGangTask("ParNewGeneration collection"),
414 _gen(gen), _next_gen(next_gen),
415 _young_old_boundary(young_old_boundary),
416 _state_set(state_set)
417 {}
418
419 void ParNewGenTask::work(int i) {
420 GenCollectedHeap* gch = GenCollectedHeap::heap();
421 // Since this is being done in a separate thread, need new resource
422 // and handle marks.
423 ResourceMark rm;
424 HandleMark hm;
425 // We would need multiple old-gen queues otherwise.
426 guarantee(gch->n_gens() == 2,
427 "Par young collection currently only works with one older gen.");
428
429 Generation* old_gen = gch->next_gen(_gen);
430
431 ParScanThreadState& par_scan_state = _state_set->thread_sate(i);
432 par_scan_state.set_young_old_boundary(_young_old_boundary);
433
434 par_scan_state.start_strong_roots();
435 gch->gen_process_strong_roots(_gen->level(),
436 true, // Process younger gens, if any,
437 // as strong roots.
438 false,// not collecting perm generation.
439 SharedHeap::SO_AllClasses,
440 &par_scan_state.older_gen_closure(),
441 &par_scan_state.to_space_root_closure());
442 par_scan_state.end_strong_roots();
443
444 // "evacuate followers".
445 par_scan_state.evacuate_followers_closure().do_void();
446 }
447
448 #ifdef _MSC_VER
449 #pragma warning( push )
450 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
451 #endif
452 ParNewGeneration::
453 ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level)
454 : DefNewGeneration(rs, initial_byte_size, level, "PCopy"),
455 _overflow_list(NULL),
456 _is_alive_closure(this),
457 _plab_stats(YoungPLABSize, PLABWeight)
458 {
459 _task_queues = new ObjToScanQueueSet(ParallelGCThreads);
460 guarantee(_task_queues != NULL, "task_queues allocation failure.");
461
462 for (uint i1 = 0; i1 < ParallelGCThreads; i1++) {
463 ObjToScanQueuePadded *q_padded = new ObjToScanQueuePadded();
464 guarantee(q_padded != NULL, "work_queue Allocation failure.");
465
466 _task_queues->register_queue(i1, &q_padded->work_queue);
467 }
468
469 for (uint i2 = 0; i2 < ParallelGCThreads; i2++)
470 _task_queues->queue(i2)->initialize();
471
472 if (UsePerfData) {
473 EXCEPTION_MARK;
474 ResourceMark rm;
475
476 const char* cname =
477 PerfDataManager::counter_name(_gen_counters->name_space(), "threads");
478 PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_None,
479 ParallelGCThreads, CHECK);
480 }
481 }
482 #ifdef _MSC_VER
483 #pragma warning( pop )
484 #endif
485
486 // ParNewGeneration::
487 ParKeepAliveClosure::ParKeepAliveClosure(ParScanWeakRefClosure* cl) :
488 DefNewGeneration::KeepAliveClosure(cl), _par_cl(cl) {}
489
490 template <class T>
491 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop_work(T* p) {
492 #ifdef ASSERT
493 {
494 assert(!oopDesc::is_null(*p), "expected non-null ref");
495 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
496 // We never expect to see a null reference being processed
497 // as a weak reference.
498 assert(obj->is_oop(), "expected an oop while scanning weak refs");
499 }
500 #endif // ASSERT
501
502 _par_cl->do_oop_nv(p);
503
504 if (Universe::heap()->is_in_reserved(p)) {
505 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
506 _rs->write_ref_field_gc_par(p, obj);
507 }
508 }
509
510 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(oop* p) { ParKeepAliveClosure::do_oop_work(p); }
511 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(narrowOop* p) { ParKeepAliveClosure::do_oop_work(p); }
512
513 // ParNewGeneration::
514 KeepAliveClosure::KeepAliveClosure(ScanWeakRefClosure* cl) :
515 DefNewGeneration::KeepAliveClosure(cl) {}
516
517 template <class T>
518 void /*ParNewGeneration::*/KeepAliveClosure::do_oop_work(T* p) {
519 #ifdef ASSERT
520 {
521 assert(!oopDesc::is_null(*p), "expected non-null ref");
522 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
523 // We never expect to see a null reference being processed
524 // as a weak reference.
525 assert(obj->is_oop(), "expected an oop while scanning weak refs");
526 }
527 #endif // ASSERT
528
529 _cl->do_oop_nv(p);
530
531 if (Universe::heap()->is_in_reserved(p)) {
532 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
533 _rs->write_ref_field_gc_par(p, obj);
534 }
535 }
536
537 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(oop* p) { KeepAliveClosure::do_oop_work(p); }
538 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(narrowOop* p) { KeepAliveClosure::do_oop_work(p); }
539
540 template <class T> void ScanClosureWithParBarrier::do_oop_work(T* p) {
541 T heap_oop = oopDesc::load_heap_oop(p);
542 if (!oopDesc::is_null(heap_oop)) {
543 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
544 if ((HeapWord*)obj < _boundary) {
545 assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?");
546 oop new_obj = obj->is_forwarded()
547 ? obj->forwardee()
548 : _g->DefNewGeneration::copy_to_survivor_space(obj);
549 oopDesc::encode_store_heap_oop_not_null(p, new_obj);
550 }
551 if (_gc_barrier) {
552 // If p points to a younger generation, mark the card.
553 if ((HeapWord*)obj < _gen_boundary) {
554 _rs->write_ref_field_gc_par(p, obj);
555 }
556 }
557 }
558 }
559
560 void ScanClosureWithParBarrier::do_oop(oop* p) { ScanClosureWithParBarrier::do_oop_work(p); }
561 void ScanClosureWithParBarrier::do_oop(narrowOop* p) { ScanClosureWithParBarrier::do_oop_work(p); }
562
563 class ParNewRefProcTaskProxy: public AbstractGangTask {
564 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
565 public:
566 ParNewRefProcTaskProxy(ProcessTask& task, ParNewGeneration& gen,
567 Generation& next_gen,
568 HeapWord* young_old_boundary,
569 ParScanThreadStateSet& state_set);
570
571 private:
572 virtual void work(int i);
573
574 private:
575 ParNewGeneration& _gen;
576 ProcessTask& _task;
577 Generation& _next_gen;
578 HeapWord* _young_old_boundary;
579 ParScanThreadStateSet& _state_set;
580 };
581
582 ParNewRefProcTaskProxy::ParNewRefProcTaskProxy(
583 ProcessTask& task, ParNewGeneration& gen,
584 Generation& next_gen,
585 HeapWord* young_old_boundary,
586 ParScanThreadStateSet& state_set)
587 : AbstractGangTask("ParNewGeneration parallel reference processing"),
588 _gen(gen),
589 _task(task),
590 _next_gen(next_gen),
591 _young_old_boundary(young_old_boundary),
592 _state_set(state_set)
593 {
594 }
595
596 void ParNewRefProcTaskProxy::work(int i)
597 {
598 ResourceMark rm;
599 HandleMark hm;
600 ParScanThreadState& par_scan_state = _state_set.thread_sate(i);
601 par_scan_state.set_young_old_boundary(_young_old_boundary);
602 _task.work(i, par_scan_state.is_alive_closure(),
603 par_scan_state.keep_alive_closure(),
604 par_scan_state.evacuate_followers_closure());
605 }
606
607 class ParNewRefEnqueueTaskProxy: public AbstractGangTask {
608 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
609 EnqueueTask& _task;
610
611 public:
612 ParNewRefEnqueueTaskProxy(EnqueueTask& task)
613 : AbstractGangTask("ParNewGeneration parallel reference enqueue"),
614 _task(task)
615 { }
616
617 virtual void work(int i)
618 {
619 _task.work(i);
620 }
621 };
622
623
624 void ParNewRefProcTaskExecutor::execute(ProcessTask& task)
625 {
626 GenCollectedHeap* gch = GenCollectedHeap::heap();
627 assert(gch->kind() == CollectedHeap::GenCollectedHeap,
628 "not a generational heap");
629 WorkGang* workers = gch->workers();
630 assert(workers != NULL, "Need parallel worker threads.");
631 ParNewRefProcTaskProxy rp_task(task, _generation, *_generation.next_gen(),
632 _generation.reserved().end(), _state_set);
633 workers->run_task(&rp_task);
634 _state_set.reset();
635 }
636
637 void ParNewRefProcTaskExecutor::execute(EnqueueTask& task)
638 {
639 GenCollectedHeap* gch = GenCollectedHeap::heap();
640 WorkGang* workers = gch->workers();
641 assert(workers != NULL, "Need parallel worker threads.");
642 ParNewRefEnqueueTaskProxy enq_task(task);
643 workers->run_task(&enq_task);
644 }
645
646 void ParNewRefProcTaskExecutor::set_single_threaded_mode()
647 {
648 _state_set.flush();
649 GenCollectedHeap* gch = GenCollectedHeap::heap();
650 gch->set_par_threads(0); // 0 ==> non-parallel.
651 gch->save_marks();
652 }
653
654 ScanClosureWithParBarrier::
655 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier) :
656 ScanClosure(g, gc_barrier) {}
657
658 EvacuateFollowersClosureGeneral::
659 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level,
660 OopsInGenClosure* cur,
661 OopsInGenClosure* older) :
662 _gch(gch), _level(level),
663 _scan_cur_or_nonheap(cur), _scan_older(older)
664 {}
665
666 void EvacuateFollowersClosureGeneral::do_void() {
667 do {
668 // Beware: this call will lead to closure applications via virtual
669 // calls.
670 _gch->oop_since_save_marks_iterate(_level,
671 _scan_cur_or_nonheap,
672 _scan_older);
673 } while (!_gch->no_allocs_since_save_marks(_level));
674 }
675
676
677 bool ParNewGeneration::_avoid_promotion_undo = false;
678
679 void ParNewGeneration::adjust_desired_tenuring_threshold() {
680 // Set the desired survivor size to half the real survivor space
681 _tenuring_threshold =
682 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
683 }
684
685 // A Generation that does parallel young-gen collection.
686
687 void ParNewGeneration::collect(bool full,
688 bool clear_all_soft_refs,
689 size_t size,
690 bool is_tlab) {
691 assert(full || size > 0, "otherwise we don't want to collect");
692 GenCollectedHeap* gch = GenCollectedHeap::heap();
693 assert(gch->kind() == CollectedHeap::GenCollectedHeap,
694 "not a CMS generational heap");
695 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
696 WorkGang* workers = gch->workers();
697 _next_gen = gch->next_gen(this);
698 assert(_next_gen != NULL,
699 "This must be the youngest gen, and not the only gen");
700 assert(gch->n_gens() == 2,
701 "Par collection currently only works with single older gen.");
702 // Do we have to avoid promotion_undo?
703 if (gch->collector_policy()->is_concurrent_mark_sweep_policy()) {
704 set_avoid_promotion_undo(true);
705 }
706
707 // If the next generation is too full to accomodate worst-case promotion
708 // from this generation, pass on collection; let the next generation
709 // do it.
710 if (!collection_attempt_is_safe()) {
711 gch->set_incremental_collection_will_fail();
712 return;
713 }
714 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
715
716 init_assuming_no_promotion_failure();
717
718 if (UseAdaptiveSizePolicy) {
719 set_survivor_overflow(false);
720 size_policy->minor_collection_begin();
721 }
722
723 TraceTime t1("GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);
724 // Capture heap used before collection (for printing).
725 size_t gch_prev_used = gch->used();
726
727 SpecializationStats::clear();
728
729 age_table()->clear();
730 to()->clear(SpaceDecorator::Mangle);
731
732 gch->save_marks();
733 assert(workers != NULL, "Need parallel worker threads.");
734 ParallelTaskTerminator _term(workers->total_workers(), task_queues());
735 ParScanThreadStateSet thread_state_set(workers->total_workers(),
736 *to(), *this, *_next_gen, *task_queues(),
737 desired_plab_sz(), _term);
738
739 ParNewGenTask tsk(this, _next_gen, reserved().end(), &thread_state_set);
740 int n_workers = workers->total_workers();
741 gch->set_par_threads(n_workers);
742 gch->change_strong_roots_parity();
743 gch->rem_set()->prepare_for_younger_refs_iterate(true);
744 // It turns out that even when we're using 1 thread, doing the work in a
745 // separate thread causes wide variance in run times. We can't help this
746 // in the multi-threaded case, but we special-case n=1 here to get
747 // repeatable measurements of the 1-thread overhead of the parallel code.
748 if (n_workers > 1) {
749 workers->run_task(&tsk);
750 } else {
751 tsk.work(0);
752 }
753 thread_state_set.reset();
754
755 if (PAR_STATS_ENABLED && ParallelGCVerbose) {
756 gclog_or_tty->print("Thread totals:\n"
757 " Pushes: %7d Pops: %7d Steals %7d (sum = %7d).\n",
758 thread_state_set.pushes(), thread_state_set.pops(),
759 thread_state_set.steals(),
760 thread_state_set.pops()+thread_state_set.steals());
761 }
762 assert(thread_state_set.pushes() == thread_state_set.pops() + thread_state_set.steals(),
763 "Or else the queues are leaky.");
764
765 // For now, process discovered weak refs sequentially.
766 #ifdef COMPILER2
767 ReferencePolicy *soft_ref_policy = new LRUMaxHeapPolicy();
768 #else
769 ReferencePolicy *soft_ref_policy = new LRUCurrentHeapPolicy();
770 #endif // COMPILER2
771
772 // Process (weak) reference objects found during scavenge.
773 IsAliveClosure is_alive(this);
774 ScanWeakRefClosure scan_weak_ref(this);
775 KeepAliveClosure keep_alive(&scan_weak_ref);
776 ScanClosure scan_without_gc_barrier(this, false);
777 ScanClosureWithParBarrier scan_with_gc_barrier(this, true);
778 set_promo_failure_scan_stack_closure(&scan_without_gc_barrier);
779 EvacuateFollowersClosureGeneral evacuate_followers(gch, _level,
780 &scan_without_gc_barrier, &scan_with_gc_barrier);
781 if (ref_processor()->processing_is_mt()) {
782 ParNewRefProcTaskExecutor task_executor(*this, thread_state_set);
783 ref_processor()->process_discovered_references(
784 soft_ref_policy, &is_alive, &keep_alive, &evacuate_followers,
785 &task_executor);
786 } else {
787 thread_state_set.flush();
788 gch->set_par_threads(0); // 0 ==> non-parallel.
789 gch->save_marks();
790 ref_processor()->process_discovered_references(
791 soft_ref_policy, &is_alive, &keep_alive, &evacuate_followers,
792 NULL);
793 }
794 if (!promotion_failed()) {
795 // Swap the survivor spaces.
796 eden()->clear(SpaceDecorator::Mangle);
797 from()->clear(SpaceDecorator::Mangle);
798 if (ZapUnusedHeapArea) {
799 // This is now done here because of the piece-meal mangling which
800 // can check for valid mangling at intermediate points in the
801 // collection(s). When a minor collection fails to collect
802 // sufficient space resizing of the young generation can occur
803 // an redistribute the spaces in the young generation. Mangle
804 // here so that unzapped regions don't get distributed to
805 // other spaces.
806 to()->mangle_unused_area();
807 }
808 swap_spaces();
809
810 assert(to()->is_empty(), "to space should be empty now");
811 } else {
812 assert(HandlePromotionFailure,
813 "Should only be here if promotion failure handling is on");
814 if (_promo_failure_scan_stack != NULL) {
815 // Can be non-null because of reference processing.
816 // Free stack with its elements.
817 delete _promo_failure_scan_stack;
818 _promo_failure_scan_stack = NULL;
819 }
820 remove_forwarding_pointers();
821 if (PrintGCDetails) {
822 gclog_or_tty->print(" (promotion failed)");
823 }
824 // All the spaces are in play for mark-sweep.
825 swap_spaces(); // Make life simpler for CMS || rescan; see 6483690.
826 from()->set_next_compaction_space(to());
827 gch->set_incremental_collection_will_fail();
828
829 // Reset the PromotionFailureALot counters.
830 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
831 }
832 // set new iteration safe limit for the survivor spaces
833 from()->set_concurrent_iteration_safe_limit(from()->top());
834 to()->set_concurrent_iteration_safe_limit(to()->top());
835
836 adjust_desired_tenuring_threshold();
837 if (ResizePLAB) {
838 plab_stats()->adjust_desired_plab_sz();
839 }
840
841 if (PrintGC && !PrintGCDetails) {
842 gch->print_heap_change(gch_prev_used);
843 }
844
845 if (UseAdaptiveSizePolicy) {
846 size_policy->minor_collection_end(gch->gc_cause());
847 size_policy->avg_survived()->sample(from()->used());
848 }
849
850 update_time_of_last_gc(os::javaTimeMillis());
851
852 SpecializationStats::print();
853
854 ref_processor()->set_enqueuing_is_done(true);
855 if (ref_processor()->processing_is_mt()) {
856 ParNewRefProcTaskExecutor task_executor(*this, thread_state_set);
857 ref_processor()->enqueue_discovered_references(&task_executor);
858 } else {
859 ref_processor()->enqueue_discovered_references(NULL);
860 }
861 ref_processor()->verify_no_references_recorded();
862 }
863
864 static int sum;
865 void ParNewGeneration::waste_some_time() {
866 for (int i = 0; i < 100; i++) {
867 sum += i;
868 }
869 }
870
871 static const oop ClaimedForwardPtr = oop(0x4);
872
873 // Because of concurrency, there are times where an object for which
874 // "is_forwarded()" is true contains an "interim" forwarding pointer
875 // value. Such a value will soon be overwritten with a real value.
876 // This method requires "obj" to have a forwarding pointer, and waits, if
877 // necessary for a real one to be inserted, and returns it.
878
879 oop ParNewGeneration::real_forwardee(oop obj) {
880 oop forward_ptr = obj->forwardee();
881 if (forward_ptr != ClaimedForwardPtr) {
882 return forward_ptr;
883 } else {
884 return real_forwardee_slow(obj);
885 }
886 }
887
888 oop ParNewGeneration::real_forwardee_slow(oop obj) {
889 // Spin-read if it is claimed but not yet written by another thread.
890 oop forward_ptr = obj->forwardee();
891 while (forward_ptr == ClaimedForwardPtr) {
892 waste_some_time();
893 assert(obj->is_forwarded(), "precondition");
894 forward_ptr = obj->forwardee();
895 }
896 return forward_ptr;
897 }
898
899 #ifdef ASSERT
900 bool ParNewGeneration::is_legal_forward_ptr(oop p) {
901 return
902 (_avoid_promotion_undo && p == ClaimedForwardPtr)
903 || Universe::heap()->is_in_reserved(p);
904 }
905 #endif
906
907 void ParNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
908 if ((m != markOopDesc::prototype()) &&
909 (!UseBiasedLocking || (m != markOopDesc::biased_locking_prototype()))) {
910 MutexLocker ml(ParGCRareEvent_lock);
911 DefNewGeneration::preserve_mark_if_necessary(obj, m);
912 }
913 }
914
915 // Multiple GC threads may try to promote an object. If the object
916 // is successfully promoted, a forwarding pointer will be installed in
917 // the object in the young generation. This method claims the right
918 // to install the forwarding pointer before it copies the object,
919 // thus avoiding the need to undo the copy as in
920 // copy_to_survivor_space_avoiding_with_undo.
921
922 oop ParNewGeneration::copy_to_survivor_space_avoiding_promotion_undo(
923 ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) {
924 // In the sequential version, this assert also says that the object is
925 // not forwarded. That might not be the case here. It is the case that
926 // the caller observed it to be not forwarded at some time in the past.
927 assert(is_in_reserved(old), "shouldn't be scavenging this oop");
928
929 // The sequential code read "old->age()" below. That doesn't work here,
930 // since the age is in the mark word, and that might be overwritten with
931 // a forwarding pointer by a parallel thread. So we must save the mark
932 // word in a local and then analyze it.
933 oopDesc dummyOld;
934 dummyOld.set_mark(m);
935 assert(!dummyOld.is_forwarded(),
936 "should not be called with forwarding pointer mark word.");
937
938 oop new_obj = NULL;
939 oop forward_ptr;
940
941 // Try allocating obj in to-space (unless too old)
942 if (dummyOld.age() < tenuring_threshold()) {
943 new_obj = (oop)par_scan_state->alloc_in_to_space(sz);
944 if (new_obj == NULL) {
945 set_survivor_overflow(true);
946 }
947 }
948
949 if (new_obj == NULL) {
950 // Either to-space is full or we decided to promote
951 // try allocating obj tenured
952
953 // Attempt to install a null forwarding pointer (atomically),
954 // to claim the right to install the real forwarding pointer.
955 forward_ptr = old->forward_to_atomic(ClaimedForwardPtr);
956 if (forward_ptr != NULL) {
957 // someone else beat us to it.
958 return real_forwardee(old);
959 }
960
961 new_obj = _next_gen->par_promote(par_scan_state->thread_num(),
962 old, m, sz);
963
964 if (new_obj == NULL) {
965 if (!HandlePromotionFailure) {
966 // A failed promotion likely means the MaxLiveObjectEvacuationRatio flag
967 // is incorrectly set. In any case, its seriously wrong to be here!
968 vm_exit_out_of_memory(sz*wordSize, "promotion");
969 }
970 // promotion failed, forward to self
971 _promotion_failed = true;
972 new_obj = old;
973
974 preserve_mark_if_necessary(old, m);
975 }
976
977 old->forward_to(new_obj);
978 forward_ptr = NULL;
979 } else {
980 // Is in to-space; do copying ourselves.
981 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz);
982 forward_ptr = old->forward_to_atomic(new_obj);
983 // Restore the mark word copied above.
984 new_obj->set_mark(m);
985 // Increment age if obj still in new generation
986 new_obj->incr_age();
987 par_scan_state->age_table()->add(new_obj, sz);
988 }
989 assert(new_obj != NULL, "just checking");
990
991 if (forward_ptr == NULL) {
992 oop obj_to_push = new_obj;
993 if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) {
994 // Length field used as index of next element to be scanned.
995 // Real length can be obtained from real_forwardee()
996 arrayOop(old)->set_length(0);
997 obj_to_push = old;
998 assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push,
999 "push forwarded object");
1000 }
1001 // Push it on one of the queues of to-be-scanned objects.
1002 if (!par_scan_state->work_queue()->push(obj_to_push)) {
1003 // Add stats for overflow pushes.
1004 if (Verbose && PrintGCDetails) {
1005 gclog_or_tty->print("queue overflow!\n");
1006 }
1007 push_on_overflow_list(old);
1008 par_scan_state->note_overflow_push();
1009 }
1010 par_scan_state->note_push();
1011
1012 return new_obj;
1013 }
1014
1015 // Oops. Someone beat us to it. Undo the allocation. Where did we
1016 // allocate it?
1017 if (is_in_reserved(new_obj)) {
1018 // Must be in to_space.
1019 assert(to()->is_in_reserved(new_obj), "Checking");
1020 if (forward_ptr == ClaimedForwardPtr) {
1021 // Wait to get the real forwarding pointer value.
1022 forward_ptr = real_forwardee(old);
1023 }
1024 par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz);
1025 }
1026
1027 return forward_ptr;
1028 }
1029
1030
1031 // Multiple GC threads may try to promote the same object. If two
1032 // or more GC threads copy the object, only one wins the race to install
1033 // the forwarding pointer. The other threads have to undo their copy.
1034
1035 oop ParNewGeneration::copy_to_survivor_space_with_undo(
1036 ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) {
1037
1038 // In the sequential version, this assert also says that the object is
1039 // not forwarded. That might not be the case here. It is the case that
1040 // the caller observed it to be not forwarded at some time in the past.
1041 assert(is_in_reserved(old), "shouldn't be scavenging this oop");
1042
1043 // The sequential code read "old->age()" below. That doesn't work here,
1044 // since the age is in the mark word, and that might be overwritten with
1045 // a forwarding pointer by a parallel thread. So we must save the mark
1046 // word here, install it in a local oopDesc, and then analyze it.
1047 oopDesc dummyOld;
1048 dummyOld.set_mark(m);
1049 assert(!dummyOld.is_forwarded(),
1050 "should not be called with forwarding pointer mark word.");
1051
1052 bool failed_to_promote = false;
1053 oop new_obj = NULL;
1054 oop forward_ptr;
1055
1056 // Try allocating obj in to-space (unless too old)
1057 if (dummyOld.age() < tenuring_threshold()) {
1058 new_obj = (oop)par_scan_state->alloc_in_to_space(sz);
1059 if (new_obj == NULL) {
1060 set_survivor_overflow(true);
1061 }
1062 }
1063
1064 if (new_obj == NULL) {
1065 // Either to-space is full or we decided to promote
1066 // try allocating obj tenured
1067 new_obj = _next_gen->par_promote(par_scan_state->thread_num(),
1068 old, m, sz);
1069
1070 if (new_obj == NULL) {
1071 if (!HandlePromotionFailure) {
1072 // A failed promotion likely means the MaxLiveObjectEvacuationRatio
1073 // flag is incorrectly set. In any case, its seriously wrong to be
1074 // here!
1075 vm_exit_out_of_memory(sz*wordSize, "promotion");
1076 }
1077 // promotion failed, forward to self
1078 forward_ptr = old->forward_to_atomic(old);
1079 new_obj = old;
1080
1081 if (forward_ptr != NULL) {
1082 return forward_ptr; // someone else succeeded
1083 }
1084
1085 _promotion_failed = true;
1086 failed_to_promote = true;
1087
1088 preserve_mark_if_necessary(old, m);
1089 }
1090 } else {
1091 // Is in to-space; do copying ourselves.
1092 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz);
1093 // Restore the mark word copied above.
1094 new_obj->set_mark(m);
1095 // Increment age if new_obj still in new generation
1096 new_obj->incr_age();
1097 par_scan_state->age_table()->add(new_obj, sz);
1098 }
1099 assert(new_obj != NULL, "just checking");
1100
1101 // Now attempt to install the forwarding pointer (atomically).
1102 // We have to copy the mark word before overwriting with forwarding
1103 // ptr, so we can restore it below in the copy.
1104 if (!failed_to_promote) {
1105 forward_ptr = old->forward_to_atomic(new_obj);
1106 }
1107
1108 if (forward_ptr == NULL) {
1109 oop obj_to_push = new_obj;
1110 if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) {
1111 // Length field used as index of next element to be scanned.
1112 // Real length can be obtained from real_forwardee()
1113 arrayOop(old)->set_length(0);
1114 obj_to_push = old;
1115 assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push,
1116 "push forwarded object");
1117 }
1118 // Push it on one of the queues of to-be-scanned objects.
1119 if (!par_scan_state->work_queue()->push(obj_to_push)) {
1120 // Add stats for overflow pushes.
1121 push_on_overflow_list(old);
1122 par_scan_state->note_overflow_push();
1123 }
1124 par_scan_state->note_push();
1125
1126 return new_obj;
1127 }
1128
1129 // Oops. Someone beat us to it. Undo the allocation. Where did we
1130 // allocate it?
1131 if (is_in_reserved(new_obj)) {
1132 // Must be in to_space.
1133 assert(to()->is_in_reserved(new_obj), "Checking");
1134 par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz);
1135 } else {
1136 assert(!_avoid_promotion_undo, "Should not be here if avoiding.");
1137 _next_gen->par_promote_alloc_undo(par_scan_state->thread_num(),
1138 (HeapWord*)new_obj, sz);
1139 }
1140
1141 return forward_ptr;
1142 }
1143
1144 void ParNewGeneration::push_on_overflow_list(oop from_space_obj) {
1145 oop cur_overflow_list = _overflow_list;
1146 // if the object has been forwarded to itself, then we cannot
1147 // use the klass pointer for the linked list. Instead we have
1148 // to allocate an oopDesc in the C-Heap and use that for the linked list.
1149 if (from_space_obj->forwardee() == from_space_obj) {
1150 oopDesc* listhead = NEW_C_HEAP_ARRAY(oopDesc, 1);
1151 listhead->forward_to(from_space_obj);
1152 from_space_obj = listhead;
1153 }
1154 while (true) {
1155 from_space_obj->set_klass_to_list_ptr(cur_overflow_list);
1156 oop observed_overflow_list =
1157 (oop)Atomic::cmpxchg_ptr(from_space_obj, &_overflow_list, cur_overflow_list);
1158 if (observed_overflow_list == cur_overflow_list) break;
1159 // Otherwise...
1160 cur_overflow_list = observed_overflow_list;
1161 }
1162 }
1163
1164 bool
1165 ParNewGeneration::take_from_overflow_list(ParScanThreadState* par_scan_state) {
1166 ObjToScanQueue* work_q = par_scan_state->work_queue();
1167 // How many to take?
1168 int objsFromOverflow = MIN2(work_q->max_elems()/4,
1169 (juint)ParGCDesiredObjsFromOverflowList);
1170
1171 if (_overflow_list == NULL) return false;
1172
1173 // Otherwise, there was something there; try claiming the list.
1174 oop prefix = (oop)Atomic::xchg_ptr(NULL, &_overflow_list);
1175
1176 if (prefix == NULL) {
1177 return false;
1178 }
1179 // Trim off a prefix of at most objsFromOverflow items
1180 int i = 1;
1181 oop cur = prefix;
1182 while (i < objsFromOverflow && cur->klass_or_null() != NULL) {
1183 i++; cur = oop(cur->klass());
1184 }
1185
1186 // Reattach remaining (suffix) to overflow list
1187 if (cur->klass_or_null() != NULL) {
1188 oop suffix = oop(cur->klass());
1189 cur->set_klass_to_list_ptr(NULL);
1190
1191 // Find last item of suffix list
1192 oop last = suffix;
1193 while (last->klass_or_null() != NULL) {
1194 last = oop(last->klass());
1195 }
1196 // Atomically prepend suffix to current overflow list
1197 oop cur_overflow_list = _overflow_list;
1198 while (true) {
1199 last->set_klass_to_list_ptr(cur_overflow_list);
1200 oop observed_overflow_list =
1201 (oop)Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list);
1202 if (observed_overflow_list == cur_overflow_list) break;
1203 // Otherwise...
1204 cur_overflow_list = observed_overflow_list;
1205 }
1206 }
1207
1208 // Push objects on prefix list onto this thread's work queue
1209 assert(cur != NULL, "program logic");
1210 cur = prefix;
1211 int n = 0;
1212 while (cur != NULL) {
1213 oop obj_to_push = cur->forwardee();
1214 oop next = oop(cur->klass());
1215 cur->set_klass(obj_to_push->klass());
1216 if (par_scan_state->should_be_partially_scanned(obj_to_push, cur)) {
1217 obj_to_push = cur;
1218 assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned");
1219 }
1220 work_q->push(obj_to_push);
1221 cur = next;
1222 n++;
1223 }
1224 par_scan_state->note_overflow_refill(n);
1225 return true;
1226 }
1227
1228 void ParNewGeneration::ref_processor_init()
1229 {
1230 if (_ref_processor == NULL) {
1231 // Allocate and initialize a reference processor
1232 _ref_processor = ReferenceProcessor::create_ref_processor(
1233 _reserved, // span
1234 refs_discovery_is_atomic(), // atomic_discovery
1235 refs_discovery_is_mt(), // mt_discovery
1236 NULL, // is_alive_non_header
1237 ParallelGCThreads,
1238 ParallelRefProcEnabled);
1239 }
1240 }
1241
1242 const char* ParNewGeneration::name() const {
1243 return "par new generation";
1244 }