1 #ifdef USE_PRAGMA_IDENT_HDR 2 #pragma ident "@(#)parNewGeneration.hpp 1.48 07/05/17 15:52:44 JVM" 3 #endif 4 /* 5 * Copyright 2001-2008 Sun Microsystems, Inc. All Rights Reserved. 6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 7 * 8 * This code is free software; you can redistribute it and/or modify it 9 * under the terms of the GNU General Public License version 2 only, as 10 * published by the Free Software Foundation. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 23 * CA 95054 USA or visit www.sun.com if you need additional information or 24 * have any questions. 25 * 26 */ 27 28 class ChunkArray; 29 class ParScanWithoutBarrierClosure; 30 class ParScanWithBarrierClosure; 31 class ParRootScanWithoutBarrierClosure; 32 class ParRootScanWithBarrierTwoGensClosure; 33 class ParEvacuateFollowersClosure; 34 35 // It would be better if these types could be kept local to the .cpp file, 36 // but they must be here to allow ParScanClosure::do_oop_work to be defined 37 // in genOopClosures.inline.hpp. 38 39 typedef OopTaskQueue ObjToScanQueue; 40 typedef OopTaskQueueSet ObjToScanQueueSet; 41 42 // Enable this to get push/pop/steal stats. 43 const int PAR_STATS_ENABLED = 0; 44 45 class ParKeepAliveClosure: public DefNewGeneration::KeepAliveClosure { 46 private: 47 ParScanWeakRefClosure* _par_cl; 48 protected: 49 template <class T> void do_oop_work(T* p); 50 public: 51 ParKeepAliveClosure(ParScanWeakRefClosure* cl); 52 virtual void do_oop(oop* p); 53 virtual void do_oop(narrowOop* p); 54 }; 55 56 // The state needed by thread performing parallel young-gen collection. 57 class ParScanThreadState { 58 friend class ParScanThreadStateSet; 59 private: 60 ObjToScanQueue *_work_queue; 61 GrowableArray<oop>* _overflow_stack; 62 63 ParGCAllocBuffer _to_space_alloc_buffer; 64 65 ParScanWithoutBarrierClosure _to_space_closure; // scan_without_gc_barrier 66 ParScanWithBarrierClosure _old_gen_closure; // scan_with_gc_barrier 67 ParRootScanWithoutBarrierClosure _to_space_root_closure; // scan_root_without_gc_barrier 68 // One of these two will be passed to process_strong_roots, which will 69 // set its generation. The first is for two-gen configs where the 70 // old gen collects the perm gen; the second is for arbitrary configs. 71 // The second isn't used right now (it used to be used for the train, an 72 // incremental collector) but the declaration has been left as a reminder. 73 ParRootScanWithBarrierTwoGensClosure _older_gen_closure; 74 // This closure will always be bound to the old gen; it will be used 75 // in evacuate_followers. 76 ParRootScanWithBarrierTwoGensClosure _old_gen_root_closure; // scan_old_root_with_gc_barrier 77 ParEvacuateFollowersClosure _evacuate_followers; 78 DefNewGeneration::IsAliveClosure _is_alive_closure; 79 ParScanWeakRefClosure _scan_weak_ref_closure; 80 ParKeepAliveClosure _keep_alive_closure; 81 82 83 Space* _to_space; 84 Space* to_space() { return _to_space; } 85 86 ParNewGeneration* _young_gen; 87 ParNewGeneration* young_gen() const { return _young_gen; } 88 89 Generation* _old_gen; 90 Generation* old_gen() { return _old_gen; } 91 92 HeapWord *_young_old_boundary; 93 94 int _hash_seed; 95 int _thread_num; 96 ageTable _ageTable; 97 98 bool _to_space_full; 99 100 int _pushes, _pops, _steals, _steal_attempts, _term_attempts; 101 int _overflow_pushes, _overflow_refills, _overflow_refill_objs; 102 103 // Timing numbers. 104 double _start; 105 double _start_strong_roots; 106 double _strong_roots_time; 107 double _start_term; 108 double _term_time; 109 110 // Helper for trim_queues. Scans subset of an array and makes 111 // remainder available for work stealing. 112 void scan_partial_array_and_push_remainder(oop obj); 113 114 // In support of CMS' parallel rescan of survivor space. 115 ChunkArray* _survivor_chunk_array; 116 ChunkArray* survivor_chunk_array() { return _survivor_chunk_array; } 117 118 void record_survivor_plab(HeapWord* plab_start, size_t plab_word_size); 119 120 ParScanThreadState(Space* to_space_, ParNewGeneration* gen_, 121 Generation* old_gen_, int thread_num_, 122 ObjToScanQueueSet* work_queue_set_, 123 GrowableArray<oop>** overflow_stack_set_, 124 size_t desired_plab_sz_, 125 ParallelTaskTerminator& term_); 126 127 public: 128 ageTable* age_table() {return &_ageTable;} 129 130 ObjToScanQueue* work_queue() { return _work_queue; } 131 132 ParGCAllocBuffer* to_space_alloc_buffer() { 133 return &_to_space_alloc_buffer; 134 } 135 136 ParEvacuateFollowersClosure& evacuate_followers_closure() { return _evacuate_followers; } 137 DefNewGeneration::IsAliveClosure& is_alive_closure() { return _is_alive_closure; } 138 ParScanWeakRefClosure& scan_weak_ref_closure() { return _scan_weak_ref_closure; } 139 ParKeepAliveClosure& keep_alive_closure() { return _keep_alive_closure; } 140 ParScanClosure& older_gen_closure() { return _older_gen_closure; } 141 ParRootScanWithoutBarrierClosure& to_space_root_closure() { return _to_space_root_closure; }; 142 143 // Decrease queue size below "max_size". 144 void trim_queues(int max_size); 145 146 // Private overflow stack usage 147 GrowableArray<oop>* overflow_stack() { return _overflow_stack; } 148 bool take_from_overflow_stack(); 149 void push_on_overflow_stack(oop p); 150 151 // Is new_obj a candidate for scan_partial_array_and_push_remainder method. 152 inline bool should_be_partially_scanned(oop new_obj, oop old_obj) const; 153 154 int* hash_seed() { return &_hash_seed; } 155 int thread_num() { return _thread_num; } 156 157 // Allocate a to-space block of size "sz", or else return NULL. 158 HeapWord* alloc_in_to_space_slow(size_t word_sz); 159 160 HeapWord* alloc_in_to_space(size_t word_sz) { 161 HeapWord* obj = to_space_alloc_buffer()->allocate(word_sz); 162 if (obj != NULL) return obj; 163 else return alloc_in_to_space_slow(word_sz); 164 } 165 166 HeapWord* young_old_boundary() { return _young_old_boundary; } 167 168 void set_young_old_boundary(HeapWord *boundary) { 169 _young_old_boundary = boundary; 170 } 171 172 // Undo the most recent allocation ("obj", of "word_sz"). 173 void undo_alloc_in_to_space(HeapWord* obj, size_t word_sz); 174 175 int pushes() { return _pushes; } 176 int pops() { return _pops; } 177 int steals() { return _steals; } 178 int steal_attempts() { return _steal_attempts; } 179 int term_attempts() { return _term_attempts; } 180 int overflow_pushes() { return _overflow_pushes; } 181 int overflow_refills() { return _overflow_refills; } 182 int overflow_refill_objs() { return _overflow_refill_objs; } 183 184 void note_push() { if (PAR_STATS_ENABLED) _pushes++; } 185 void note_pop() { if (PAR_STATS_ENABLED) _pops++; } 186 void note_steal() { if (PAR_STATS_ENABLED) _steals++; } 187 void note_steal_attempt() { if (PAR_STATS_ENABLED) _steal_attempts++; } 188 void note_term_attempt() { if (PAR_STATS_ENABLED) _term_attempts++; } 189 void note_overflow_push() { if (PAR_STATS_ENABLED) _overflow_pushes++; } 190 void note_overflow_refill(int objs) { 191 if (PAR_STATS_ENABLED) { 192 _overflow_refills++; 193 _overflow_refill_objs += objs; 194 } 195 } 196 197 void start_strong_roots() { 198 _start_strong_roots = os::elapsedTime(); 199 } 200 void end_strong_roots() { 201 _strong_roots_time += (os::elapsedTime() - _start_strong_roots); 202 } 203 double strong_roots_time() { return _strong_roots_time; } 204 void start_term_time() { 205 note_term_attempt(); 206 _start_term = os::elapsedTime(); 207 } 208 void end_term_time() { 209 _term_time += (os::elapsedTime() - _start_term); 210 } 211 double term_time() { return _term_time; } 212 213 double elapsed() { 214 return os::elapsedTime() - _start; 215 } 216 }; 217 218 class ParNewGenTask: public AbstractGangTask { 219 private: 220 ParNewGeneration* _gen; 221 Generation* _next_gen; 222 HeapWord* _young_old_boundary; 223 class ParScanThreadStateSet* _state_set; 224 225 public: 226 ParNewGenTask(ParNewGeneration* gen, 227 Generation* next_gen, 228 HeapWord* young_old_boundary, 229 ParScanThreadStateSet* state_set); 230 231 HeapWord* young_old_boundary() { return _young_old_boundary; } 232 233 void work(int i); 234 }; 235 236 class KeepAliveClosure: public DefNewGeneration::KeepAliveClosure { 237 protected: 238 template <class T> void do_oop_work(T* p); 239 public: 240 KeepAliveClosure(ScanWeakRefClosure* cl); 241 virtual void do_oop(oop* p); 242 virtual void do_oop(narrowOop* p); 243 }; 244 245 class EvacuateFollowersClosureGeneral: public VoidClosure { 246 private: 247 GenCollectedHeap* _gch; 248 int _level; 249 OopsInGenClosure* _scan_cur_or_nonheap; 250 OopsInGenClosure* _scan_older; 251 public: 252 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level, 253 OopsInGenClosure* cur, 254 OopsInGenClosure* older); 255 virtual void do_void(); 256 }; 257 258 // Closure for scanning ParNewGeneration. 259 // Same as ScanClosure, except does parallel GC barrier. 260 class ScanClosureWithParBarrier: public ScanClosure { 261 protected: 262 template <class T> void do_oop_work(T* p); 263 public: 264 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier); 265 virtual void do_oop(oop* p); 266 virtual void do_oop(narrowOop* p); 267 }; 268 269 // Implements AbstractRefProcTaskExecutor for ParNew. 270 class ParNewRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 271 private: 272 ParNewGeneration& _generation; 273 ParScanThreadStateSet& _state_set; 274 public: 275 ParNewRefProcTaskExecutor(ParNewGeneration& generation, 276 ParScanThreadStateSet& state_set) 277 : _generation(generation), _state_set(state_set) 278 { } 279 280 // Executes a task using worker threads. 281 virtual void execute(ProcessTask& task); 282 virtual void execute(EnqueueTask& task); 283 // Switch to single threaded mode. 284 virtual void set_single_threaded_mode(); 285 }; 286 287 288 // A Generation that does parallel young-gen collection. 289 290 class ParNewGeneration: public DefNewGeneration { 291 friend class ParNewGenTask; 292 friend class ParNewRefProcTask; 293 friend class ParNewRefProcTaskExecutor; 294 friend class ParScanThreadStateSet; 295 296 private: 297 // XXX use a global constant instead of 64! 298 struct ObjToScanQueuePadded { 299 ObjToScanQueue work_queue; 300 char pad[64 - sizeof(ObjToScanQueue)]; // prevent false sharing 301 }; 302 303 // The per-worker-thread work queues 304 ObjToScanQueueSet* _task_queues; 305 306 // Per-worker-thread local overflow stacks 307 GrowableArray<oop>** _overflow_stacks; 308 309 // Desired size of survivor space plab's 310 PLABStats _plab_stats; 311 312 // A list of from-space images of to-be-scanned objects, threaded through 313 // klass-pointers (klass information already copied to the forwarded 314 // image.) Manipulated with CAS. 315 oop _overflow_list; 316 317 // If true, older generation does not support promotion undo, so avoid. 318 static bool _avoid_promotion_undo; 319 320 // This closure is used by the reference processor to filter out 321 // references to live referent. 322 DefNewGeneration::IsAliveClosure _is_alive_closure; 323 324 static oop real_forwardee_slow(oop obj); 325 static void waste_some_time(); 326 327 // Preserve the mark of "obj", if necessary, in preparation for its mark 328 // word being overwritten with a self-forwarding-pointer. 329 void preserve_mark_if_necessary(oop obj, markOop m); 330 331 protected: 332 333 bool _survivor_overflow; 334 335 bool avoid_promotion_undo() { return _avoid_promotion_undo; } 336 void set_avoid_promotion_undo(bool v) { _avoid_promotion_undo = v; } 337 338 bool survivor_overflow() { return _survivor_overflow; } 339 void set_survivor_overflow(bool v) { _survivor_overflow = v; } 340 341 // Adjust the tenuring threshold. See the implementation for 342 // the details of the policy. 343 virtual void adjust_desired_tenuring_threshold(); 344 345 public: 346 ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level); 347 348 ~ParNewGeneration() { 349 for (uint i = 0; i < ParallelGCThreads; i++) 350 delete _task_queues->queue(i); 351 352 delete _task_queues; 353 } 354 355 virtual void ref_processor_init(); 356 virtual Generation::Name kind() { return Generation::ParNew; } 357 virtual const char* name() const; 358 virtual const char* short_name() const { return "ParNew"; } 359 360 // override 361 virtual bool refs_discovery_is_mt() const { 362 assert(UseParNewGC, "ParNewGeneration only when UseParNewGC"); 363 return ParallelGCThreads > 1; 364 } 365 366 // Make the collection virtual. 367 virtual void collect(bool full, 368 bool clear_all_soft_refs, 369 size_t size, 370 bool is_tlab); 371 372 // This needs to be visible to the closure function. 373 // "obj" is the object to be copied, "m" is a recent value of its mark 374 // that must not contain a forwarding pointer (though one might be 375 // inserted in "obj"s mark word by a parallel thread). 376 inline oop copy_to_survivor_space(ParScanThreadState* par_scan_state, 377 oop obj, size_t obj_sz, markOop m) { 378 if (_avoid_promotion_undo) { 379 return copy_to_survivor_space_avoiding_promotion_undo(par_scan_state, 380 obj, obj_sz, m); 381 } 382 383 return copy_to_survivor_space_with_undo(par_scan_state, obj, obj_sz, m); 384 } 385 386 oop copy_to_survivor_space_avoiding_promotion_undo(ParScanThreadState* par_scan_state, 387 oop obj, size_t obj_sz, markOop m); 388 389 oop copy_to_survivor_space_with_undo(ParScanThreadState* par_scan_state, 390 oop obj, size_t obj_sz, markOop m); 391 392 // in support of testing overflow code 393 NOT_PRODUCT(int _overflow_counter;) 394 NOT_PRODUCT(bool should_simulate_overflow();) 395 396 // Accessor for overflow list 397 oop overflow_list() { return _overflow_list; } 398 399 // Push the given (from-space) object on the global overflow list. 400 void push_on_overflow_list(oop from_space_obj, ParScanThreadState* par_scan_state); 401 402 // If the global overflow list is non-empty, move some tasks from it 403 // onto "work_q" (which must be empty). No more than 1/4 of the 404 // max_elems of "work_q" are moved. 405 bool take_from_overflow_list(ParScanThreadState* par_scan_state); 406 bool take_from_overflow_list_work(ParScanThreadState* par_scan_state); 407 408 // The task queues to be used by parallel GC threads. 409 ObjToScanQueueSet* task_queues() { 410 return _task_queues; 411 } 412 413 PLABStats* plab_stats() { 414 return &_plab_stats; 415 } 416 417 size_t desired_plab_sz() { 418 return _plab_stats.desired_plab_sz(); 419 } 420 421 static oop real_forwardee(oop obj); 422 423 DEBUG_ONLY(static bool is_legal_forward_ptr(oop p);) 424 };