Mercurial > hg > graal-compiler
annotate src/share/vm/gc_implementation/parNew/parNewGeneration.cpp @ 6:73e96e5c30df
6624765: Guarantee failure "Unexpected dirty card found"
Summary: In verification take into account partial coverage of a region by a card and expansion of the card table.
Reviewed-by: ysr, apetrusenko
| author | jmasa |
|---|---|
| date | Fri, 15 Feb 2008 07:01:10 -0800 |
| parents | a61af66fc99e |
| children | ba764ed4b6f2 |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 2 * Copyright 2001-2007 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 // process our set of indices (include header in first chunk) | |
| 108 oop* start_addr = start == 0 ? (oop*)obj : obj->obj_at_addr(start); | |
| 109 oop* end_addr = obj->base() + end; // obj_at_addr(end) asserts end < length | |
| 110 MemRegion mr((HeapWord*)start_addr, (HeapWord*)end_addr); | |
| 111 if ((HeapWord *)obj < young_old_boundary()) { | |
| 112 // object is in to_space | |
| 113 obj->oop_iterate(&_to_space_closure, mr); | |
| 114 } else { | |
| 115 // object is in old generation | |
| 116 obj->oop_iterate(&_old_gen_closure, mr); | |
| 117 } | |
| 118 } | |
| 119 | |
| 120 | |
| 121 void ParScanThreadState::trim_queues(int max_size) { | |
| 122 ObjToScanQueue* queue = work_queue(); | |
| 123 while (queue->size() > (juint)max_size) { | |
| 124 oop obj_to_scan; | |
| 125 if (queue->pop_local(obj_to_scan)) { | |
| 126 note_pop(); | |
| 127 | |
| 128 if ((HeapWord *)obj_to_scan < young_old_boundary()) { | |
| 129 if (obj_to_scan->is_objArray() && | |
| 130 obj_to_scan->is_forwarded() && | |
| 131 obj_to_scan->forwardee() != obj_to_scan) { | |
| 132 scan_partial_array_and_push_remainder(obj_to_scan); | |
| 133 } else { | |
| 134 // object is in to_space | |
| 135 obj_to_scan->oop_iterate(&_to_space_closure); | |
| 136 } | |
| 137 } else { | |
| 138 // object is in old generation | |
| 139 obj_to_scan->oop_iterate(&_old_gen_closure); | |
| 140 } | |
| 141 } | |
| 142 } | |
| 143 } | |
| 144 | |
| 145 HeapWord* ParScanThreadState::alloc_in_to_space_slow(size_t word_sz) { | |
| 146 | |
| 147 // Otherwise, if the object is small enough, try to reallocate the | |
| 148 // buffer. | |
| 149 HeapWord* obj = NULL; | |
| 150 if (!_to_space_full) { | |
| 151 ParGCAllocBuffer* const plab = to_space_alloc_buffer(); | |
| 152 Space* const sp = to_space(); | |
| 153 if (word_sz * 100 < | |
| 154 ParallelGCBufferWastePct * plab->word_sz()) { | |
| 155 // Is small enough; abandon this buffer and start a new one. | |
| 156 plab->retire(false, false); | |
| 157 size_t buf_size = plab->word_sz(); | |
| 158 HeapWord* buf_space = sp->par_allocate(buf_size); | |
| 159 if (buf_space == NULL) { | |
| 160 const size_t min_bytes = | |
| 161 ParGCAllocBuffer::min_size() << LogHeapWordSize; | |
| 162 size_t free_bytes = sp->free(); | |
| 163 while(buf_space == NULL && free_bytes >= min_bytes) { | |
| 164 buf_size = free_bytes >> LogHeapWordSize; | |
| 165 assert(buf_size == (size_t)align_object_size(buf_size), | |
| 166 "Invariant"); | |
| 167 buf_space = sp->par_allocate(buf_size); | |
| 168 free_bytes = sp->free(); | |
| 169 } | |
| 170 } | |
| 171 if (buf_space != NULL) { | |
| 172 plab->set_word_size(buf_size); | |
| 173 plab->set_buf(buf_space); | |
| 174 record_survivor_plab(buf_space, buf_size); | |
| 175 obj = plab->allocate(word_sz); | |
| 176 // Note that we cannot compare buf_size < word_sz below | |
| 177 // because of AlignmentReserve (see ParGCAllocBuffer::allocate()). | |
| 178 assert(obj != NULL || plab->words_remaining() < word_sz, | |
| 179 "Else should have been able to allocate"); | |
| 180 // It's conceivable that we may be able to use the | |
| 181 // buffer we just grabbed for subsequent small requests | |
| 182 // even if not for this one. | |
| 183 } else { | |
| 184 // We're used up. | |
| 185 _to_space_full = true; | |
| 186 } | |
| 187 | |
| 188 } else { | |
| 189 // Too large; allocate the object individually. | |
| 190 obj = sp->par_allocate(word_sz); | |
| 191 } | |
| 192 } | |
| 193 return obj; | |
| 194 } | |
| 195 | |
| 196 | |
| 197 void ParScanThreadState::undo_alloc_in_to_space(HeapWord* obj, | |
| 198 size_t word_sz) { | |
| 199 // Is the alloc in the current alloc buffer? | |
| 200 if (to_space_alloc_buffer()->contains(obj)) { | |
| 201 assert(to_space_alloc_buffer()->contains(obj + word_sz - 1), | |
| 202 "Should contain whole object."); | |
| 203 to_space_alloc_buffer()->undo_allocation(obj, word_sz); | |
| 204 } else { | |
| 205 SharedHeap::fill_region_with_object(MemRegion(obj, word_sz)); | |
| 206 } | |
| 207 } | |
| 208 | |
| 209 class ParScanThreadStateSet: private ResourceArray { | |
| 210 public: | |
| 211 // Initializes states for the specified number of threads; | |
| 212 ParScanThreadStateSet(int num_threads, | |
| 213 Space& to_space, | |
| 214 ParNewGeneration& gen, | |
| 215 Generation& old_gen, | |
| 216 ObjToScanQueueSet& queue_set, | |
| 217 size_t desired_plab_sz, | |
| 218 ParallelTaskTerminator& term); | |
| 219 inline ParScanThreadState& thread_sate(int i); | |
| 220 int pushes() { return _pushes; } | |
| 221 int pops() { return _pops; } | |
| 222 int steals() { return _steals; } | |
| 223 void reset(); | |
| 224 void flush(); | |
| 225 private: | |
| 226 ParallelTaskTerminator& _term; | |
| 227 ParNewGeneration& _gen; | |
| 228 Generation& _next_gen; | |
| 229 // staticstics | |
| 230 int _pushes; | |
| 231 int _pops; | |
| 232 int _steals; | |
| 233 }; | |
| 234 | |
| 235 | |
| 236 ParScanThreadStateSet::ParScanThreadStateSet( | |
| 237 int num_threads, Space& to_space, ParNewGeneration& gen, | |
| 238 Generation& old_gen, ObjToScanQueueSet& queue_set, | |
| 239 size_t desired_plab_sz, ParallelTaskTerminator& term) | |
| 240 : ResourceArray(sizeof(ParScanThreadState), num_threads), | |
| 241 _gen(gen), _next_gen(old_gen), _term(term), | |
| 242 _pushes(0), _pops(0), _steals(0) | |
| 243 { | |
| 244 assert(num_threads > 0, "sanity check!"); | |
| 245 // Initialize states. | |
| 246 for (int i = 0; i < num_threads; ++i) { | |
| 247 new ((ParScanThreadState*)_data + i) | |
| 248 ParScanThreadState(&to_space, &gen, &old_gen, i, &queue_set, | |
| 249 desired_plab_sz, term); | |
| 250 } | |
| 251 } | |
| 252 | |
| 253 inline ParScanThreadState& ParScanThreadStateSet::thread_sate(int i) | |
| 254 { | |
| 255 assert(i >= 0 && i < length(), "sanity check!"); | |
| 256 return ((ParScanThreadState*)_data)[i]; | |
| 257 } | |
| 258 | |
| 259 | |
| 260 void ParScanThreadStateSet::reset() | |
| 261 { | |
| 262 _term.reset_for_reuse(); | |
| 263 } | |
| 264 | |
| 265 void ParScanThreadStateSet::flush() | |
| 266 { | |
| 267 for (int i = 0; i < length(); ++i) { | |
| 268 ParScanThreadState& par_scan_state = thread_sate(i); | |
| 269 | |
| 270 // Flush stats related to To-space PLAB activity and | |
| 271 // retire the last buffer. | |
| 272 par_scan_state.to_space_alloc_buffer()-> | |
| 273 flush_stats_and_retire(_gen.plab_stats(), | |
| 274 false /* !retain */); | |
| 275 | |
| 276 // Every thread has its own age table. We need to merge | |
| 277 // them all into one. | |
| 278 ageTable *local_table = par_scan_state.age_table(); | |
| 279 _gen.age_table()->merge(local_table); | |
| 280 | |
| 281 // Inform old gen that we're done. | |
| 282 _next_gen.par_promote_alloc_done(i); | |
| 283 _next_gen.par_oop_since_save_marks_iterate_done(i); | |
| 284 | |
| 285 // Flush stats related to work queue activity (push/pop/steal) | |
| 286 // This could conceivably become a bottleneck; if so, we'll put the | |
| 287 // stat's gathering under the flag. | |
| 288 if (PAR_STATS_ENABLED) { | |
| 289 _pushes += par_scan_state.pushes(); | |
| 290 _pops += par_scan_state.pops(); | |
| 291 _steals += par_scan_state.steals(); | |
| 292 if (ParallelGCVerbose) { | |
| 293 gclog_or_tty->print("Thread %d complete:\n" | |
| 294 " Pushes: %7d Pops: %7d Steals %7d (in %d attempts)\n", | |
| 295 i, par_scan_state.pushes(), par_scan_state.pops(), | |
| 296 par_scan_state.steals(), par_scan_state.steal_attempts()); | |
| 297 if (par_scan_state.overflow_pushes() > 0 || | |
| 298 par_scan_state.overflow_refills() > 0) { | |
| 299 gclog_or_tty->print(" Overflow pushes: %7d " | |
| 300 "Overflow refills: %7d for %d objs.\n", | |
| 301 par_scan_state.overflow_pushes(), | |
| 302 par_scan_state.overflow_refills(), | |
| 303 par_scan_state.overflow_refill_objs()); | |
| 304 } | |
| 305 | |
| 306 double elapsed = par_scan_state.elapsed(); | |
| 307 double strong_roots = par_scan_state.strong_roots_time(); | |
| 308 double term = par_scan_state.term_time(); | |
| 309 gclog_or_tty->print( | |
| 310 " Elapsed: %7.2f ms.\n" | |
| 311 " Strong roots: %7.2f ms (%6.2f%%)\n" | |
| 312 " Termination: %7.2f ms (%6.2f%%) (in %d entries)\n", | |
| 313 elapsed * 1000.0, | |
| 314 strong_roots * 1000.0, (strong_roots*100.0/elapsed), | |
| 315 term * 1000.0, (term*100.0/elapsed), | |
| 316 par_scan_state.term_attempts()); | |
| 317 } | |
| 318 } | |
| 319 } | |
| 320 } | |
| 321 | |
| 322 | |
| 323 ParScanClosure::ParScanClosure(ParNewGeneration* g, | |
| 324 ParScanThreadState* par_scan_state) : | |
| 325 OopsInGenClosure(g), _par_scan_state(par_scan_state), _g(g) | |
| 326 { | |
| 327 assert(_g->level() == 0, "Optimized for youngest generation"); | |
| 328 _boundary = _g->reserved().end(); | |
| 329 } | |
| 330 | |
| 331 ParScanWeakRefClosure::ParScanWeakRefClosure(ParNewGeneration* g, | |
| 332 ParScanThreadState* par_scan_state) | |
| 333 : ScanWeakRefClosure(g), _par_scan_state(par_scan_state) | |
| 334 { | |
| 335 } | |
| 336 | |
| 337 #ifdef WIN32 | |
| 338 #pragma warning(disable: 4786) /* identifier was truncated to '255' characters in the browser information */ | |
| 339 #endif | |
| 340 | |
| 341 ParEvacuateFollowersClosure::ParEvacuateFollowersClosure( | |
| 342 ParScanThreadState* par_scan_state_, | |
| 343 ParScanWithoutBarrierClosure* to_space_closure_, | |
| 344 ParScanWithBarrierClosure* old_gen_closure_, | |
| 345 ParRootScanWithoutBarrierClosure* to_space_root_closure_, | |
| 346 ParNewGeneration* par_gen_, | |
| 347 ParRootScanWithBarrierTwoGensClosure* old_gen_root_closure_, | |
| 348 ObjToScanQueueSet* task_queues_, | |
| 349 ParallelTaskTerminator* terminator_) : | |
| 350 | |
| 351 _par_scan_state(par_scan_state_), | |
| 352 _to_space_closure(to_space_closure_), | |
| 353 _old_gen_closure(old_gen_closure_), | |
| 354 _to_space_root_closure(to_space_root_closure_), | |
| 355 _old_gen_root_closure(old_gen_root_closure_), | |
| 356 _par_gen(par_gen_), | |
| 357 _task_queues(task_queues_), | |
| 358 _terminator(terminator_) | |
| 359 {} | |
| 360 | |
| 361 void ParEvacuateFollowersClosure::do_void() { | |
| 362 ObjToScanQueue* work_q = par_scan_state()->work_queue(); | |
| 363 | |
| 364 while (true) { | |
| 365 | |
| 366 // Scan to-space and old-gen objs until we run out of both. | |
| 367 oop obj_to_scan; | |
| 368 par_scan_state()->trim_queues(0); | |
| 369 | |
| 370 // We have no local work, attempt to steal from other threads. | |
| 371 | |
| 372 // attempt to steal work from promoted. | |
| 373 par_scan_state()->note_steal_attempt(); | |
| 374 if (task_queues()->steal(par_scan_state()->thread_num(), | |
| 375 par_scan_state()->hash_seed(), | |
| 376 obj_to_scan)) { | |
| 377 par_scan_state()->note_steal(); | |
| 378 bool res = work_q->push(obj_to_scan); | |
| 379 assert(res, "Empty queue should have room for a push."); | |
| 380 | |
| 381 par_scan_state()->note_push(); | |
| 382 // if successful, goto Start. | |
| 383 continue; | |
| 384 | |
| 385 // try global overflow list. | |
| 386 } else if (par_gen()->take_from_overflow_list(par_scan_state())) { | |
| 387 continue; | |
| 388 } | |
| 389 | |
| 390 // Otherwise, offer termination. | |
| 391 par_scan_state()->start_term_time(); | |
| 392 if (terminator()->offer_termination()) break; | |
| 393 par_scan_state()->end_term_time(); | |
| 394 } | |
| 395 // Finish the last termination pause. | |
| 396 par_scan_state()->end_term_time(); | |
| 397 } | |
| 398 | |
| 399 ParNewGenTask::ParNewGenTask(ParNewGeneration* gen, Generation* next_gen, | |
| 400 HeapWord* young_old_boundary, ParScanThreadStateSet* state_set) : | |
| 401 AbstractGangTask("ParNewGeneration collection"), | |
| 402 _gen(gen), _next_gen(next_gen), | |
| 403 _young_old_boundary(young_old_boundary), | |
| 404 _state_set(state_set) | |
| 405 {} | |
| 406 | |
| 407 void ParNewGenTask::work(int i) { | |
| 408 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 409 // Since this is being done in a separate thread, need new resource | |
| 410 // and handle marks. | |
| 411 ResourceMark rm; | |
| 412 HandleMark hm; | |
| 413 // We would need multiple old-gen queues otherwise. | |
| 414 guarantee(gch->n_gens() == 2, | |
| 415 "Par young collection currently only works with one older gen."); | |
| 416 | |
| 417 Generation* old_gen = gch->next_gen(_gen); | |
| 418 | |
| 419 ParScanThreadState& par_scan_state = _state_set->thread_sate(i); | |
| 420 par_scan_state.set_young_old_boundary(_young_old_boundary); | |
| 421 | |
| 422 par_scan_state.start_strong_roots(); | |
| 423 gch->gen_process_strong_roots(_gen->level(), | |
| 424 true, // Process younger gens, if any, | |
| 425 // as strong roots. | |
| 426 false,// not collecting perm generation. | |
| 427 SharedHeap::SO_AllClasses, | |
| 428 &par_scan_state.older_gen_closure(), | |
| 429 &par_scan_state.to_space_root_closure()); | |
| 430 par_scan_state.end_strong_roots(); | |
| 431 | |
| 432 // "evacuate followers". | |
| 433 par_scan_state.evacuate_followers_closure().do_void(); | |
| 434 } | |
| 435 | |
| 436 #ifdef _MSC_VER | |
| 437 #pragma warning( push ) | |
| 438 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list | |
| 439 #endif | |
| 440 ParNewGeneration:: | |
| 441 ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level) | |
| 442 : DefNewGeneration(rs, initial_byte_size, level, "PCopy"), | |
| 443 _overflow_list(NULL), | |
| 444 _is_alive_closure(this), | |
| 445 _plab_stats(YoungPLABSize, PLABWeight) | |
| 446 { | |
| 447 _task_queues = new ObjToScanQueueSet(ParallelGCThreads); | |
| 448 guarantee(_task_queues != NULL, "task_queues allocation failure."); | |
| 449 | |
| 450 for (uint i1 = 0; i1 < ParallelGCThreads; i1++) { | |
| 451 ObjToScanQueuePadded *q_padded = new ObjToScanQueuePadded(); | |
| 452 guarantee(q_padded != NULL, "work_queue Allocation failure."); | |
| 453 | |
| 454 _task_queues->register_queue(i1, &q_padded->work_queue); | |
| 455 } | |
| 456 | |
| 457 for (uint i2 = 0; i2 < ParallelGCThreads; i2++) | |
| 458 _task_queues->queue(i2)->initialize(); | |
| 459 | |
| 460 if (UsePerfData) { | |
| 461 EXCEPTION_MARK; | |
| 462 ResourceMark rm; | |
| 463 | |
| 464 const char* cname = | |
| 465 PerfDataManager::counter_name(_gen_counters->name_space(), "threads"); | |
| 466 PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_None, | |
| 467 ParallelGCThreads, CHECK); | |
| 468 } | |
| 469 } | |
| 470 #ifdef _MSC_VER | |
| 471 #pragma warning( pop ) | |
| 472 #endif | |
| 473 | |
| 474 // ParNewGeneration:: | |
| 475 ParKeepAliveClosure::ParKeepAliveClosure(ParScanWeakRefClosure* cl) : | |
| 476 DefNewGeneration::KeepAliveClosure(cl), _par_cl(cl) {} | |
| 477 | |
| 478 void | |
| 479 // ParNewGeneration:: | |
| 480 ParKeepAliveClosure::do_oop(oop* p) { | |
| 481 // We never expect to see a null reference being processed | |
| 482 // as a weak reference. | |
| 483 assert (*p != NULL, "expected non-null ref"); | |
| 484 assert ((*p)->is_oop(), "expected an oop while scanning weak refs"); | |
| 485 | |
| 486 _par_cl->do_oop_nv(p); | |
| 487 | |
| 488 if (Universe::heap()->is_in_reserved(p)) { | |
| 489 _rs->write_ref_field_gc_par(p, *p); | |
| 490 } | |
| 491 } | |
| 492 | |
| 493 // ParNewGeneration:: | |
| 494 KeepAliveClosure::KeepAliveClosure(ScanWeakRefClosure* cl) : | |
| 495 DefNewGeneration::KeepAliveClosure(cl) {} | |
| 496 | |
| 497 void | |
| 498 // ParNewGeneration:: | |
| 499 KeepAliveClosure::do_oop(oop* p) { | |
| 500 // We never expect to see a null reference being processed | |
| 501 // as a weak reference. | |
| 502 assert (*p != NULL, "expected non-null ref"); | |
| 503 assert ((*p)->is_oop(), "expected an oop while scanning weak refs"); | |
| 504 | |
| 505 _cl->do_oop_nv(p); | |
| 506 | |
| 507 if (Universe::heap()->is_in_reserved(p)) { | |
| 508 _rs->write_ref_field_gc_par(p, *p); | |
| 509 } | |
| 510 } | |
| 511 | |
| 512 void ScanClosureWithParBarrier::do_oop(oop* p) { | |
| 513 oop obj = *p; | |
| 514 // Should we copy the obj? | |
| 515 if (obj != NULL) { | |
| 516 if ((HeapWord*)obj < _boundary) { | |
| 517 assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?"); | |
| 518 if (obj->is_forwarded()) { | |
| 519 *p = obj->forwardee(); | |
| 520 } else { | |
| 521 *p = _g->DefNewGeneration::copy_to_survivor_space(obj, p); | |
| 522 } | |
| 523 } | |
| 524 if (_gc_barrier) { | |
| 525 // If p points to a younger generation, mark the card. | |
| 526 if ((HeapWord*)obj < _gen_boundary) { | |
| 527 _rs->write_ref_field_gc_par(p, obj); | |
| 528 } | |
| 529 } | |
| 530 } | |
| 531 } | |
| 532 | |
| 533 class ParNewRefProcTaskProxy: public AbstractGangTask { | |
| 534 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; | |
| 535 public: | |
| 536 ParNewRefProcTaskProxy(ProcessTask& task, ParNewGeneration& gen, | |
| 537 Generation& next_gen, | |
| 538 HeapWord* young_old_boundary, | |
| 539 ParScanThreadStateSet& state_set); | |
| 540 | |
| 541 private: | |
| 542 virtual void work(int i); | |
| 543 | |
| 544 private: | |
| 545 ParNewGeneration& _gen; | |
| 546 ProcessTask& _task; | |
| 547 Generation& _next_gen; | |
| 548 HeapWord* _young_old_boundary; | |
| 549 ParScanThreadStateSet& _state_set; | |
| 550 }; | |
| 551 | |
| 552 ParNewRefProcTaskProxy::ParNewRefProcTaskProxy( | |
| 553 ProcessTask& task, ParNewGeneration& gen, | |
| 554 Generation& next_gen, | |
| 555 HeapWord* young_old_boundary, | |
| 556 ParScanThreadStateSet& state_set) | |
| 557 : AbstractGangTask("ParNewGeneration parallel reference processing"), | |
| 558 _gen(gen), | |
| 559 _task(task), | |
| 560 _next_gen(next_gen), | |
| 561 _young_old_boundary(young_old_boundary), | |
| 562 _state_set(state_set) | |
| 563 { | |
| 564 } | |
| 565 | |
| 566 void ParNewRefProcTaskProxy::work(int i) | |
| 567 { | |
| 568 ResourceMark rm; | |
| 569 HandleMark hm; | |
| 570 ParScanThreadState& par_scan_state = _state_set.thread_sate(i); | |
| 571 par_scan_state.set_young_old_boundary(_young_old_boundary); | |
| 572 _task.work(i, par_scan_state.is_alive_closure(), | |
| 573 par_scan_state.keep_alive_closure(), | |
| 574 par_scan_state.evacuate_followers_closure()); | |
| 575 } | |
| 576 | |
| 577 class ParNewRefEnqueueTaskProxy: public AbstractGangTask { | |
| 578 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; | |
| 579 EnqueueTask& _task; | |
| 580 | |
| 581 public: | |
| 582 ParNewRefEnqueueTaskProxy(EnqueueTask& task) | |
| 583 : AbstractGangTask("ParNewGeneration parallel reference enqueue"), | |
| 584 _task(task) | |
| 585 { } | |
| 586 | |
| 587 virtual void work(int i) | |
| 588 { | |
| 589 _task.work(i); | |
| 590 } | |
| 591 }; | |
| 592 | |
| 593 | |
| 594 void ParNewRefProcTaskExecutor::execute(ProcessTask& task) | |
| 595 { | |
| 596 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 597 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 598 "not a generational heap"); | |
| 599 WorkGang* workers = gch->workers(); | |
| 600 assert(workers != NULL, "Need parallel worker threads."); | |
| 601 ParNewRefProcTaskProxy rp_task(task, _generation, *_generation.next_gen(), | |
| 602 _generation.reserved().end(), _state_set); | |
| 603 workers->run_task(&rp_task); | |
| 604 _state_set.reset(); | |
| 605 } | |
| 606 | |
| 607 void ParNewRefProcTaskExecutor::execute(EnqueueTask& task) | |
| 608 { | |
| 609 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 610 WorkGang* workers = gch->workers(); | |
| 611 assert(workers != NULL, "Need parallel worker threads."); | |
| 612 ParNewRefEnqueueTaskProxy enq_task(task); | |
| 613 workers->run_task(&enq_task); | |
| 614 } | |
| 615 | |
| 616 void ParNewRefProcTaskExecutor::set_single_threaded_mode() | |
| 617 { | |
| 618 _state_set.flush(); | |
| 619 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 620 gch->set_par_threads(0); // 0 ==> non-parallel. | |
| 621 gch->save_marks(); | |
| 622 } | |
| 623 | |
| 624 ScanClosureWithParBarrier:: | |
| 625 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier) : | |
| 626 ScanClosure(g, gc_barrier) {} | |
| 627 | |
| 628 EvacuateFollowersClosureGeneral:: | |
| 629 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level, | |
| 630 OopsInGenClosure* cur, | |
| 631 OopsInGenClosure* older) : | |
| 632 _gch(gch), _level(level), | |
| 633 _scan_cur_or_nonheap(cur), _scan_older(older) | |
| 634 {} | |
| 635 | |
| 636 void EvacuateFollowersClosureGeneral::do_void() { | |
| 637 do { | |
| 638 // Beware: this call will lead to closure applications via virtual | |
| 639 // calls. | |
| 640 _gch->oop_since_save_marks_iterate(_level, | |
| 641 _scan_cur_or_nonheap, | |
| 642 _scan_older); | |
| 643 } while (!_gch->no_allocs_since_save_marks(_level)); | |
| 644 } | |
| 645 | |
| 646 | |
| 647 bool ParNewGeneration::_avoid_promotion_undo = false; | |
| 648 | |
| 649 void ParNewGeneration::adjust_desired_tenuring_threshold() { | |
| 650 // Set the desired survivor size to half the real survivor space | |
| 651 _tenuring_threshold = | |
| 652 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize); | |
| 653 } | |
| 654 | |
| 655 // A Generation that does parallel young-gen collection. | |
| 656 | |
| 657 void ParNewGeneration::collect(bool full, | |
| 658 bool clear_all_soft_refs, | |
| 659 size_t size, | |
| 660 bool is_tlab) { | |
| 661 assert(full || size > 0, "otherwise we don't want to collect"); | |
| 662 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 663 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 664 "not a CMS generational heap"); | |
| 665 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); | |
| 666 WorkGang* workers = gch->workers(); | |
| 667 _next_gen = gch->next_gen(this); | |
| 668 assert(_next_gen != NULL, | |
| 669 "This must be the youngest gen, and not the only gen"); | |
| 670 assert(gch->n_gens() == 2, | |
| 671 "Par collection currently only works with single older gen."); | |
| 672 // Do we have to avoid promotion_undo? | |
| 673 if (gch->collector_policy()->is_concurrent_mark_sweep_policy()) { | |
| 674 set_avoid_promotion_undo(true); | |
| 675 } | |
| 676 | |
| 677 // If the next generation is too full to accomodate worst-case promotion | |
| 678 // from this generation, pass on collection; let the next generation | |
| 679 // do it. | |
| 680 if (!collection_attempt_is_safe()) { | |
| 681 gch->set_incremental_collection_will_fail(); | |
| 682 return; | |
| 683 } | |
| 684 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); | |
| 685 | |
| 686 init_assuming_no_promotion_failure(); | |
| 687 | |
| 688 if (UseAdaptiveSizePolicy) { | |
| 689 set_survivor_overflow(false); | |
| 690 size_policy->minor_collection_begin(); | |
| 691 } | |
| 692 | |
| 693 TraceTime t1("GC", PrintGC && !PrintGCDetails, true, gclog_or_tty); | |
| 694 // Capture heap used before collection (for printing). | |
| 695 size_t gch_prev_used = gch->used(); | |
| 696 | |
| 697 SpecializationStats::clear(); | |
| 698 | |
| 699 age_table()->clear(); | |
| 700 to()->clear(); | |
| 701 | |
| 702 gch->save_marks(); | |
| 703 assert(workers != NULL, "Need parallel worker threads."); | |
| 704 ParallelTaskTerminator _term(workers->total_workers(), task_queues()); | |
| 705 ParScanThreadStateSet thread_state_set(workers->total_workers(), | |
| 706 *to(), *this, *_next_gen, *task_queues(), | |
| 707 desired_plab_sz(), _term); | |
| 708 | |
| 709 ParNewGenTask tsk(this, _next_gen, reserved().end(), &thread_state_set); | |
| 710 int n_workers = workers->total_workers(); | |
| 711 gch->set_par_threads(n_workers); | |
| 712 gch->change_strong_roots_parity(); | |
| 713 gch->rem_set()->prepare_for_younger_refs_iterate(true); | |
| 714 // It turns out that even when we're using 1 thread, doing the work in a | |
| 715 // separate thread causes wide variance in run times. We can't help this | |
| 716 // in the multi-threaded case, but we special-case n=1 here to get | |
| 717 // repeatable measurements of the 1-thread overhead of the parallel code. | |
| 718 if (n_workers > 1) { | |
| 719 workers->run_task(&tsk); | |
| 720 } else { | |
| 721 tsk.work(0); | |
| 722 } | |
| 723 thread_state_set.reset(); | |
| 724 | |
| 725 if (PAR_STATS_ENABLED && ParallelGCVerbose) { | |
| 726 gclog_or_tty->print("Thread totals:\n" | |
| 727 " Pushes: %7d Pops: %7d Steals %7d (sum = %7d).\n", | |
| 728 thread_state_set.pushes(), thread_state_set.pops(), | |
| 729 thread_state_set.steals(), | |
| 730 thread_state_set.pops()+thread_state_set.steals()); | |
| 731 } | |
| 732 assert(thread_state_set.pushes() == thread_state_set.pops() + thread_state_set.steals(), | |
| 733 "Or else the queues are leaky."); | |
| 734 | |
| 735 // For now, process discovered weak refs sequentially. | |
| 736 #ifdef COMPILER2 | |
| 737 ReferencePolicy *soft_ref_policy = new LRUMaxHeapPolicy(); | |
| 738 #else | |
| 739 ReferencePolicy *soft_ref_policy = new LRUCurrentHeapPolicy(); | |
| 740 #endif // COMPILER2 | |
| 741 | |
| 742 // Process (weak) reference objects found during scavenge. | |
| 743 IsAliveClosure is_alive(this); | |
| 744 ScanWeakRefClosure scan_weak_ref(this); | |
| 745 KeepAliveClosure keep_alive(&scan_weak_ref); | |
| 746 ScanClosure scan_without_gc_barrier(this, false); | |
| 747 ScanClosureWithParBarrier scan_with_gc_barrier(this, true); | |
| 748 set_promo_failure_scan_stack_closure(&scan_without_gc_barrier); | |
| 749 EvacuateFollowersClosureGeneral evacuate_followers(gch, _level, | |
| 750 &scan_without_gc_barrier, &scan_with_gc_barrier); | |
| 751 if (ref_processor()->processing_is_mt()) { | |
| 752 ParNewRefProcTaskExecutor task_executor(*this, thread_state_set); | |
| 753 ref_processor()->process_discovered_references( | |
| 754 soft_ref_policy, &is_alive, &keep_alive, &evacuate_followers, | |
| 755 &task_executor); | |
| 756 } else { | |
| 757 thread_state_set.flush(); | |
| 758 gch->set_par_threads(0); // 0 ==> non-parallel. | |
| 759 gch->save_marks(); | |
| 760 ref_processor()->process_discovered_references( | |
| 761 soft_ref_policy, &is_alive, &keep_alive, &evacuate_followers, | |
| 762 NULL); | |
| 763 } | |
| 764 if (!promotion_failed()) { | |
| 765 // Swap the survivor spaces. | |
| 766 eden()->clear(); | |
| 767 from()->clear(); | |
| 768 swap_spaces(); | |
| 769 | |
| 770 assert(to()->is_empty(), "to space should be empty now"); | |
| 771 } else { | |
| 772 assert(HandlePromotionFailure, | |
| 773 "Should only be here if promotion failure handling is on"); | |
| 774 if (_promo_failure_scan_stack != NULL) { | |
| 775 // Can be non-null because of reference processing. | |
| 776 // Free stack with its elements. | |
| 777 delete _promo_failure_scan_stack; | |
| 778 _promo_failure_scan_stack = NULL; | |
| 779 } | |
| 780 remove_forwarding_pointers(); | |
| 781 if (PrintGCDetails) { | |
| 782 gclog_or_tty->print(" (promotion failed)"); | |
| 783 } | |
| 784 // All the spaces are in play for mark-sweep. | |
| 785 swap_spaces(); // Make life simpler for CMS || rescan; see 6483690. | |
| 786 from()->set_next_compaction_space(to()); | |
| 787 gch->set_incremental_collection_will_fail(); | |
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788 |
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789 // Reset the PromotionFailureALot counters. |
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790 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();) |
| 0 | 791 } |
| 792 // set new iteration safe limit for the survivor spaces | |
| 793 from()->set_concurrent_iteration_safe_limit(from()->top()); | |
| 794 to()->set_concurrent_iteration_safe_limit(to()->top()); | |
| 795 | |
| 796 adjust_desired_tenuring_threshold(); | |
| 797 if (ResizePLAB) { | |
| 798 plab_stats()->adjust_desired_plab_sz(); | |
| 799 } | |
| 800 | |
| 801 if (PrintGC && !PrintGCDetails) { | |
| 802 gch->print_heap_change(gch_prev_used); | |
| 803 } | |
| 804 | |
| 805 if (UseAdaptiveSizePolicy) { | |
| 806 size_policy->minor_collection_end(gch->gc_cause()); | |
| 807 size_policy->avg_survived()->sample(from()->used()); | |
| 808 } | |
| 809 | |
| 810 update_time_of_last_gc(os::javaTimeMillis()); | |
| 811 | |
| 812 SpecializationStats::print(); | |
| 813 | |
| 814 ref_processor()->set_enqueuing_is_done(true); | |
| 815 if (ref_processor()->processing_is_mt()) { | |
| 816 ParNewRefProcTaskExecutor task_executor(*this, thread_state_set); | |
| 817 ref_processor()->enqueue_discovered_references(&task_executor); | |
| 818 } else { | |
| 819 ref_processor()->enqueue_discovered_references(NULL); | |
| 820 } | |
| 821 ref_processor()->verify_no_references_recorded(); | |
| 822 } | |
| 823 | |
| 824 static int sum; | |
| 825 void ParNewGeneration::waste_some_time() { | |
| 826 for (int i = 0; i < 100; i++) { | |
| 827 sum += i; | |
| 828 } | |
| 829 } | |
| 830 | |
| 831 static const oop ClaimedForwardPtr = oop(0x4); | |
| 832 | |
| 833 // Because of concurrency, there are times where an object for which | |
| 834 // "is_forwarded()" is true contains an "interim" forwarding pointer | |
| 835 // value. Such a value will soon be overwritten with a real value. | |
| 836 // This method requires "obj" to have a forwarding pointer, and waits, if | |
| 837 // necessary for a real one to be inserted, and returns it. | |
| 838 | |
| 839 oop ParNewGeneration::real_forwardee(oop obj) { | |
| 840 oop forward_ptr = obj->forwardee(); | |
| 841 if (forward_ptr != ClaimedForwardPtr) { | |
| 842 return forward_ptr; | |
| 843 } else { | |
| 844 return real_forwardee_slow(obj); | |
| 845 } | |
| 846 } | |
| 847 | |
| 848 oop ParNewGeneration::real_forwardee_slow(oop obj) { | |
| 849 // Spin-read if it is claimed but not yet written by another thread. | |
| 850 oop forward_ptr = obj->forwardee(); | |
| 851 while (forward_ptr == ClaimedForwardPtr) { | |
| 852 waste_some_time(); | |
| 853 assert(obj->is_forwarded(), "precondition"); | |
| 854 forward_ptr = obj->forwardee(); | |
| 855 } | |
| 856 return forward_ptr; | |
| 857 } | |
| 858 | |
| 859 #ifdef ASSERT | |
| 860 bool ParNewGeneration::is_legal_forward_ptr(oop p) { | |
| 861 return | |
| 862 (_avoid_promotion_undo && p == ClaimedForwardPtr) | |
| 863 || Universe::heap()->is_in_reserved(p); | |
| 864 } | |
| 865 #endif | |
| 866 | |
| 867 void ParNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { | |
| 868 if ((m != markOopDesc::prototype()) && | |
| 869 (!UseBiasedLocking || (m != markOopDesc::biased_locking_prototype()))) { | |
| 870 MutexLocker ml(ParGCRareEvent_lock); | |
| 871 DefNewGeneration::preserve_mark_if_necessary(obj, m); | |
| 872 } | |
| 873 } | |
| 874 | |
| 875 // Multiple GC threads may try to promote an object. If the object | |
| 876 // is successfully promoted, a forwarding pointer will be installed in | |
| 877 // the object in the young generation. This method claims the right | |
| 878 // to install the forwarding pointer before it copies the object, | |
| 879 // thus avoiding the need to undo the copy as in | |
| 880 // copy_to_survivor_space_avoiding_with_undo. | |
| 881 | |
| 882 oop ParNewGeneration::copy_to_survivor_space_avoiding_promotion_undo( | |
| 883 ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) { | |
| 884 // In the sequential version, this assert also says that the object is | |
| 885 // not forwarded. That might not be the case here. It is the case that | |
| 886 // the caller observed it to be not forwarded at some time in the past. | |
| 887 assert(is_in_reserved(old), "shouldn't be scavenging this oop"); | |
| 888 | |
| 889 // The sequential code read "old->age()" below. That doesn't work here, | |
| 890 // since the age is in the mark word, and that might be overwritten with | |
| 891 // a forwarding pointer by a parallel thread. So we must save the mark | |
| 892 // word in a local and then analyze it. | |
| 893 oopDesc dummyOld; | |
| 894 dummyOld.set_mark(m); | |
| 895 assert(!dummyOld.is_forwarded(), | |
| 896 "should not be called with forwarding pointer mark word."); | |
| 897 | |
| 898 oop new_obj = NULL; | |
| 899 oop forward_ptr; | |
| 900 | |
| 901 // Try allocating obj in to-space (unless too old) | |
| 902 if (dummyOld.age() < tenuring_threshold()) { | |
| 903 new_obj = (oop)par_scan_state->alloc_in_to_space(sz); | |
| 904 if (new_obj == NULL) { | |
| 905 set_survivor_overflow(true); | |
| 906 } | |
| 907 } | |
| 908 | |
| 909 if (new_obj == NULL) { | |
| 910 // Either to-space is full or we decided to promote | |
| 911 // try allocating obj tenured | |
| 912 | |
| 913 // Attempt to install a null forwarding pointer (atomically), | |
| 914 // to claim the right to install the real forwarding pointer. | |
| 915 forward_ptr = old->forward_to_atomic(ClaimedForwardPtr); | |
| 916 if (forward_ptr != NULL) { | |
| 917 // someone else beat us to it. | |
| 918 return real_forwardee(old); | |
| 919 } | |
| 920 | |
| 921 new_obj = _next_gen->par_promote(par_scan_state->thread_num(), | |
| 922 old, m, sz); | |
| 923 | |
| 924 if (new_obj == NULL) { | |
| 925 if (!HandlePromotionFailure) { | |
| 926 // A failed promotion likely means the MaxLiveObjectEvacuationRatio flag | |
| 927 // is incorrectly set. In any case, its seriously wrong to be here! | |
| 928 vm_exit_out_of_memory(sz*wordSize, "promotion"); | |
| 929 } | |
| 930 // promotion failed, forward to self | |
| 931 _promotion_failed = true; | |
| 932 new_obj = old; | |
| 933 | |
| 934 preserve_mark_if_necessary(old, m); | |
| 935 } | |
| 936 | |
| 937 old->forward_to(new_obj); | |
| 938 forward_ptr = NULL; | |
| 939 } else { | |
| 940 // Is in to-space; do copying ourselves. | |
| 941 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz); | |
| 942 forward_ptr = old->forward_to_atomic(new_obj); | |
| 943 // Restore the mark word copied above. | |
| 944 new_obj->set_mark(m); | |
| 945 // Increment age if obj still in new generation | |
| 946 new_obj->incr_age(); | |
| 947 par_scan_state->age_table()->add(new_obj, sz); | |
| 948 } | |
| 949 assert(new_obj != NULL, "just checking"); | |
| 950 | |
| 951 if (forward_ptr == NULL) { | |
| 952 oop obj_to_push = new_obj; | |
| 953 if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) { | |
| 954 // Length field used as index of next element to be scanned. | |
| 955 // Real length can be obtained from real_forwardee() | |
| 956 arrayOop(old)->set_length(0); | |
| 957 obj_to_push = old; | |
| 958 assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push, | |
| 959 "push forwarded object"); | |
| 960 } | |
| 961 // Push it on one of the queues of to-be-scanned objects. | |
| 962 if (!par_scan_state->work_queue()->push(obj_to_push)) { | |
| 963 // Add stats for overflow pushes. | |
| 964 if (Verbose && PrintGCDetails) { | |
| 965 gclog_or_tty->print("queue overflow!\n"); | |
| 966 } | |
| 967 push_on_overflow_list(old); | |
| 968 par_scan_state->note_overflow_push(); | |
| 969 } | |
| 970 par_scan_state->note_push(); | |
| 971 | |
| 972 return new_obj; | |
| 973 } | |
| 974 | |
| 975 // Oops. Someone beat us to it. Undo the allocation. Where did we | |
| 976 // allocate it? | |
| 977 if (is_in_reserved(new_obj)) { | |
| 978 // Must be in to_space. | |
| 979 assert(to()->is_in_reserved(new_obj), "Checking"); | |
| 980 if (forward_ptr == ClaimedForwardPtr) { | |
| 981 // Wait to get the real forwarding pointer value. | |
| 982 forward_ptr = real_forwardee(old); | |
| 983 } | |
| 984 par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz); | |
| 985 } | |
| 986 | |
| 987 return forward_ptr; | |
| 988 } | |
| 989 | |
| 990 | |
| 991 // Multiple GC threads may try to promote the same object. If two | |
| 992 // or more GC threads copy the object, only one wins the race to install | |
| 993 // the forwarding pointer. The other threads have to undo their copy. | |
| 994 | |
| 995 oop ParNewGeneration::copy_to_survivor_space_with_undo( | |
| 996 ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) { | |
| 997 | |
| 998 // In the sequential version, this assert also says that the object is | |
| 999 // not forwarded. That might not be the case here. It is the case that | |
| 1000 // the caller observed it to be not forwarded at some time in the past. | |
| 1001 assert(is_in_reserved(old), "shouldn't be scavenging this oop"); | |
| 1002 | |
| 1003 // The sequential code read "old->age()" below. That doesn't work here, | |
| 1004 // since the age is in the mark word, and that might be overwritten with | |
| 1005 // a forwarding pointer by a parallel thread. So we must save the mark | |
| 1006 // word here, install it in a local oopDesc, and then analyze it. | |
| 1007 oopDesc dummyOld; | |
| 1008 dummyOld.set_mark(m); | |
| 1009 assert(!dummyOld.is_forwarded(), | |
| 1010 "should not be called with forwarding pointer mark word."); | |
| 1011 | |
| 1012 bool failed_to_promote = false; | |
| 1013 oop new_obj = NULL; | |
| 1014 oop forward_ptr; | |
| 1015 | |
| 1016 // Try allocating obj in to-space (unless too old) | |
| 1017 if (dummyOld.age() < tenuring_threshold()) { | |
| 1018 new_obj = (oop)par_scan_state->alloc_in_to_space(sz); | |
| 1019 if (new_obj == NULL) { | |
| 1020 set_survivor_overflow(true); | |
| 1021 } | |
| 1022 } | |
| 1023 | |
| 1024 if (new_obj == NULL) { | |
| 1025 // Either to-space is full or we decided to promote | |
| 1026 // try allocating obj tenured | |
| 1027 new_obj = _next_gen->par_promote(par_scan_state->thread_num(), | |
| 1028 old, m, sz); | |
| 1029 | |
| 1030 if (new_obj == NULL) { | |
| 1031 if (!HandlePromotionFailure) { | |
| 1032 // A failed promotion likely means the MaxLiveObjectEvacuationRatio | |
| 1033 // flag is incorrectly set. In any case, its seriously wrong to be | |
| 1034 // here! | |
| 1035 vm_exit_out_of_memory(sz*wordSize, "promotion"); | |
| 1036 } | |
| 1037 // promotion failed, forward to self | |
| 1038 forward_ptr = old->forward_to_atomic(old); | |
| 1039 new_obj = old; | |
| 1040 | |
| 1041 if (forward_ptr != NULL) { | |
| 1042 return forward_ptr; // someone else succeeded | |
| 1043 } | |
| 1044 | |
| 1045 _promotion_failed = true; | |
| 1046 failed_to_promote = true; | |
| 1047 | |
| 1048 preserve_mark_if_necessary(old, m); | |
| 1049 } | |
| 1050 } else { | |
| 1051 // Is in to-space; do copying ourselves. | |
| 1052 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz); | |
| 1053 // Restore the mark word copied above. | |
| 1054 new_obj->set_mark(m); | |
| 1055 // Increment age if new_obj still in new generation | |
| 1056 new_obj->incr_age(); | |
| 1057 par_scan_state->age_table()->add(new_obj, sz); | |
| 1058 } | |
| 1059 assert(new_obj != NULL, "just checking"); | |
| 1060 | |
| 1061 // Now attempt to install the forwarding pointer (atomically). | |
| 1062 // We have to copy the mark word before overwriting with forwarding | |
| 1063 // ptr, so we can restore it below in the copy. | |
| 1064 if (!failed_to_promote) { | |
| 1065 forward_ptr = old->forward_to_atomic(new_obj); | |
| 1066 } | |
| 1067 | |
| 1068 if (forward_ptr == NULL) { | |
| 1069 oop obj_to_push = new_obj; | |
| 1070 if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) { | |
| 1071 // Length field used as index of next element to be scanned. | |
| 1072 // Real length can be obtained from real_forwardee() | |
| 1073 arrayOop(old)->set_length(0); | |
| 1074 obj_to_push = old; | |
| 1075 assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push, | |
| 1076 "push forwarded object"); | |
| 1077 } | |
| 1078 // Push it on one of the queues of to-be-scanned objects. | |
| 1079 if (!par_scan_state->work_queue()->push(obj_to_push)) { | |
| 1080 // Add stats for overflow pushes. | |
| 1081 push_on_overflow_list(old); | |
| 1082 par_scan_state->note_overflow_push(); | |
| 1083 } | |
| 1084 par_scan_state->note_push(); | |
| 1085 | |
| 1086 return new_obj; | |
| 1087 } | |
| 1088 | |
| 1089 // Oops. Someone beat us to it. Undo the allocation. Where did we | |
| 1090 // allocate it? | |
| 1091 if (is_in_reserved(new_obj)) { | |
| 1092 // Must be in to_space. | |
| 1093 assert(to()->is_in_reserved(new_obj), "Checking"); | |
| 1094 par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz); | |
| 1095 } else { | |
| 1096 assert(!_avoid_promotion_undo, "Should not be here if avoiding."); | |
| 1097 _next_gen->par_promote_alloc_undo(par_scan_state->thread_num(), | |
| 1098 (HeapWord*)new_obj, sz); | |
| 1099 } | |
| 1100 | |
| 1101 return forward_ptr; | |
| 1102 } | |
| 1103 | |
| 1104 void ParNewGeneration::push_on_overflow_list(oop from_space_obj) { | |
| 1105 oop cur_overflow_list = _overflow_list; | |
| 1106 // if the object has been forwarded to itself, then we cannot | |
| 1107 // use the klass pointer for the linked list. Instead we have | |
| 1108 // to allocate an oopDesc in the C-Heap and use that for the linked list. | |
| 1109 if (from_space_obj->forwardee() == from_space_obj) { | |
| 1110 oopDesc* listhead = NEW_C_HEAP_ARRAY(oopDesc, 1); | |
| 1111 listhead->forward_to(from_space_obj); | |
| 1112 from_space_obj = listhead; | |
| 1113 } | |
| 1114 while (true) { | |
| 1115 from_space_obj->set_klass_to_list_ptr(cur_overflow_list); | |
| 1116 oop observed_overflow_list = | |
| 1117 (oop)Atomic::cmpxchg_ptr(from_space_obj, &_overflow_list, cur_overflow_list); | |
| 1118 if (observed_overflow_list == cur_overflow_list) break; | |
| 1119 // Otherwise... | |
| 1120 cur_overflow_list = observed_overflow_list; | |
| 1121 } | |
| 1122 } | |
| 1123 | |
| 1124 bool | |
| 1125 ParNewGeneration::take_from_overflow_list(ParScanThreadState* par_scan_state) { | |
| 1126 ObjToScanQueue* work_q = par_scan_state->work_queue(); | |
| 1127 // How many to take? | |
| 1128 int objsFromOverflow = MIN2(work_q->max_elems()/4, | |
| 1129 (juint)ParGCDesiredObjsFromOverflowList); | |
| 1130 | |
| 1131 if (_overflow_list == NULL) return false; | |
| 1132 | |
| 1133 // Otherwise, there was something there; try claiming the list. | |
| 1134 oop prefix = (oop)Atomic::xchg_ptr(NULL, &_overflow_list); | |
| 1135 | |
| 1136 if (prefix == NULL) { | |
| 1137 return false; | |
| 1138 } | |
| 1139 // Trim off a prefix of at most objsFromOverflow items | |
| 1140 int i = 1; | |
| 1141 oop cur = prefix; | |
| 1142 while (i < objsFromOverflow && cur->klass() != NULL) { | |
| 1143 i++; cur = oop(cur->klass()); | |
| 1144 } | |
| 1145 | |
| 1146 // Reattach remaining (suffix) to overflow list | |
| 1147 if (cur->klass() != NULL) { | |
| 1148 oop suffix = oop(cur->klass()); | |
| 1149 cur->set_klass_to_list_ptr(NULL); | |
| 1150 | |
| 1151 // Find last item of suffix list | |
| 1152 oop last = suffix; | |
| 1153 while (last->klass() != NULL) { | |
| 1154 last = oop(last->klass()); | |
| 1155 } | |
| 1156 // Atomically prepend suffix to current overflow list | |
| 1157 oop cur_overflow_list = _overflow_list; | |
| 1158 while (true) { | |
| 1159 last->set_klass_to_list_ptr(cur_overflow_list); | |
| 1160 oop observed_overflow_list = | |
| 1161 (oop)Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list); | |
| 1162 if (observed_overflow_list == cur_overflow_list) break; | |
| 1163 // Otherwise... | |
| 1164 cur_overflow_list = observed_overflow_list; | |
| 1165 } | |
| 1166 } | |
| 1167 | |
| 1168 // Push objects on prefix list onto this thread's work queue | |
| 1169 assert(cur != NULL, "program logic"); | |
| 1170 cur = prefix; | |
| 1171 int n = 0; | |
| 1172 while (cur != NULL) { | |
| 1173 oop obj_to_push = cur->forwardee(); | |
| 1174 oop next = oop(cur->klass()); | |
| 1175 cur->set_klass(obj_to_push->klass()); | |
| 1176 if (par_scan_state->should_be_partially_scanned(obj_to_push, cur)) { | |
| 1177 obj_to_push = cur; | |
| 1178 assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned"); | |
| 1179 } | |
| 1180 work_q->push(obj_to_push); | |
| 1181 cur = next; | |
| 1182 n++; | |
| 1183 } | |
| 1184 par_scan_state->note_overflow_refill(n); | |
| 1185 return true; | |
| 1186 } | |
| 1187 | |
| 1188 void ParNewGeneration::ref_processor_init() | |
| 1189 { | |
| 1190 if (_ref_processor == NULL) { | |
| 1191 // Allocate and initialize a reference processor | |
| 1192 _ref_processor = ReferenceProcessor::create_ref_processor( | |
| 1193 _reserved, // span | |
| 1194 refs_discovery_is_atomic(), // atomic_discovery | |
| 1195 refs_discovery_is_mt(), // mt_discovery | |
| 1196 NULL, // is_alive_non_header | |
| 1197 ParallelGCThreads, | |
| 1198 ParallelRefProcEnabled); | |
| 1199 } | |
| 1200 } | |
| 1201 | |
| 1202 const char* ParNewGeneration::name() const { | |
| 1203 return "par new generation"; | |
| 1204 } |