1 /* 2 * Copyright (c) 2001, 2011, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_UTILITIES_TASKQUEUE_HPP 26 #define SHARE_VM_UTILITIES_TASKQUEUE_HPP 27 28 #include "memory/allocation.hpp" 29 #include "memory/allocation.inline.hpp" 30 #include "runtime/mutex.hpp" 31 #include "utilities/stack.hpp" 32 #ifdef TARGET_OS_ARCH_linux_x86 33 # include "orderAccess_linux_x86.inline.hpp" 34 #endif 35 #ifdef TARGET_OS_ARCH_linux_sparc 36 # include "orderAccess_linux_sparc.inline.hpp" 37 #endif 38 #ifdef TARGET_OS_ARCH_linux_zero 39 # include "orderAccess_linux_zero.inline.hpp" 40 #endif 41 #ifdef TARGET_OS_ARCH_solaris_x86 42 # include "orderAccess_solaris_x86.inline.hpp" 43 #endif 44 #ifdef TARGET_OS_ARCH_solaris_sparc 45 # include "orderAccess_solaris_sparc.inline.hpp" 46 #endif 47 #ifdef TARGET_OS_ARCH_windows_x86 48 # include "orderAccess_windows_x86.inline.hpp" 49 #endif 50 #ifdef TARGET_OS_ARCH_linux_arm 51 # include "orderAccess_linux_arm.inline.hpp" 52 #endif 53 #ifdef TARGET_OS_ARCH_linux_ppc 54 # include "orderAccess_linux_ppc.inline.hpp" 55 #endif 56 57 // Simple TaskQueue stats that are collected by default in debug builds. 58 59 #if !defined(TASKQUEUE_STATS) && defined(ASSERT) 60 #define TASKQUEUE_STATS 1 61 #elif !defined(TASKQUEUE_STATS) 62 #define TASKQUEUE_STATS 0 63 #endif 64 65 #if TASKQUEUE_STATS 66 #define TASKQUEUE_STATS_ONLY(code) code 67 #else 68 #define TASKQUEUE_STATS_ONLY(code) 69 #endif // TASKQUEUE_STATS 70 71 #if TASKQUEUE_STATS 72 class TaskQueueStats { 73 public: 74 enum StatId { 75 push, // number of taskqueue pushes 76 pop, // number of taskqueue pops 77 pop_slow, // subset of taskqueue pops that were done slow-path 78 steal_attempt, // number of taskqueue steal attempts 79 steal, // number of taskqueue steals 80 overflow, // number of overflow pushes 81 overflow_max_len, // max length of overflow stack 82 last_stat_id 83 }; 84 85 public: 86 inline TaskQueueStats() { reset(); } 87 88 inline void record_push() { ++_stats[push]; } 89 inline void record_pop() { ++_stats[pop]; } 90 inline void record_pop_slow() { record_pop(); ++_stats[pop_slow]; } 91 inline void record_steal(bool success); 92 inline void record_overflow(size_t new_length); 93 94 TaskQueueStats & operator +=(const TaskQueueStats & addend); 95 96 inline size_t get(StatId id) const { return _stats[id]; } 97 inline const size_t* get() const { return _stats; } 98 99 inline void reset(); 100 101 // Print the specified line of the header (does not include a line separator). 102 static void print_header(unsigned int line, outputStream* const stream = tty, 103 unsigned int width = 10); 104 // Print the statistics (does not include a line separator). 105 void print(outputStream* const stream = tty, unsigned int width = 10) const; 106 107 DEBUG_ONLY(void verify() const;) 108 109 private: 110 size_t _stats[last_stat_id]; 111 static const char * const _names[last_stat_id]; 112 }; 113 114 void TaskQueueStats::record_steal(bool success) { 115 ++_stats[steal_attempt]; 116 if (success) ++_stats[steal]; 117 } 118 119 void TaskQueueStats::record_overflow(size_t new_len) { 120 ++_stats[overflow]; 121 if (new_len > _stats[overflow_max_len]) _stats[overflow_max_len] = new_len; 122 } 123 124 void TaskQueueStats::reset() { 125 memset(_stats, 0, sizeof(_stats)); 126 } 127 #endif // TASKQUEUE_STATS 128 129 template <unsigned int N> 130 class TaskQueueSuper: public CHeapObj { 131 protected: 132 // Internal type for indexing the queue; also used for the tag. 133 typedef NOT_LP64(uint16_t) LP64_ONLY(uint32_t) idx_t; 134 135 // The first free element after the last one pushed (mod N). 136 volatile uint _bottom; 137 138 enum { MOD_N_MASK = N - 1 }; 139 140 class Age { 141 public: 142 Age(size_t data = 0) { _data = data; } 143 Age(const Age& age) { _data = age._data; } 144 Age(idx_t top, idx_t tag) { _fields._top = top; _fields._tag = tag; } 145 146 Age get() const volatile { return _data; } 147 void set(Age age) volatile { _data = age._data; } 148 149 idx_t top() const volatile { return _fields._top; } 150 idx_t tag() const volatile { return _fields._tag; } 151 152 // Increment top; if it wraps, increment tag also. 153 void increment() { 154 _fields._top = increment_index(_fields._top); 155 if (_fields._top == 0) ++_fields._tag; 156 } 157 158 Age cmpxchg(const Age new_age, const Age old_age) volatile { 159 return (size_t) Atomic::cmpxchg_ptr((intptr_t)new_age._data, 160 (volatile intptr_t *)&_data, 161 (intptr_t)old_age._data); 162 } 163 164 bool operator ==(const Age& other) const { return _data == other._data; } 165 166 private: 167 struct fields { 168 idx_t _top; 169 idx_t _tag; 170 }; 171 union { 172 size_t _data; 173 fields _fields; 174 }; 175 }; 176 177 volatile Age _age; 178 179 // These both operate mod N. 180 static uint increment_index(uint ind) { 181 return (ind + 1) & MOD_N_MASK; 182 } 183 static uint decrement_index(uint ind) { 184 return (ind - 1) & MOD_N_MASK; 185 } 186 187 // Returns a number in the range [0..N). If the result is "N-1", it should be 188 // interpreted as 0. 189 uint dirty_size(uint bot, uint top) const { 190 return (bot - top) & MOD_N_MASK; 191 } 192 193 // Returns the size corresponding to the given "bot" and "top". 194 uint size(uint bot, uint top) const { 195 uint sz = dirty_size(bot, top); 196 // Has the queue "wrapped", so that bottom is less than top? There's a 197 // complicated special case here. A pair of threads could perform pop_local 198 // and pop_global operations concurrently, starting from a state in which 199 // _bottom == _top+1. The pop_local could succeed in decrementing _bottom, 200 // and the pop_global in incrementing _top (in which case the pop_global 201 // will be awarded the contested queue element.) The resulting state must 202 // be interpreted as an empty queue. (We only need to worry about one such 203 // event: only the queue owner performs pop_local's, and several concurrent 204 // threads attempting to perform the pop_global will all perform the same 205 // CAS, and only one can succeed.) Any stealing thread that reads after 206 // either the increment or decrement will see an empty queue, and will not 207 // join the competitors. The "sz == -1 || sz == N-1" state will not be 208 // modified by concurrent queues, so the owner thread can reset the state to 209 // _bottom == top so subsequent pushes will be performed normally. 210 return (sz == N - 1) ? 0 : sz; 211 } 212 213 public: 214 TaskQueueSuper() : _bottom(0), _age() {} 215 216 // Return true if the TaskQueue contains/does not contain any tasks. 217 bool peek() const { return _bottom != _age.top(); } 218 bool is_empty() const { return size() == 0; } 219 220 // Return an estimate of the number of elements in the queue. 221 // The "careful" version admits the possibility of pop_local/pop_global 222 // races. 223 uint size() const { 224 return size(_bottom, _age.top()); 225 } 226 227 uint dirty_size() const { 228 return dirty_size(_bottom, _age.top()); 229 } 230 231 void set_empty() { 232 _bottom = 0; 233 _age.set(0); 234 } 235 236 // Maximum number of elements allowed in the queue. This is two less 237 // than the actual queue size, for somewhat complicated reasons. 238 uint max_elems() const { return N - 2; } 239 240 // Total size of queue. 241 static const uint total_size() { return N; } 242 243 TASKQUEUE_STATS_ONLY(TaskQueueStats stats;) 244 }; 245 246 template<class E, unsigned int N = TASKQUEUE_SIZE> 247 class GenericTaskQueue: public TaskQueueSuper<N> { 248 protected: 249 typedef typename TaskQueueSuper<N>::Age Age; 250 typedef typename TaskQueueSuper<N>::idx_t idx_t; 251 252 using TaskQueueSuper<N>::_bottom; 253 using TaskQueueSuper<N>::_age; 254 using TaskQueueSuper<N>::increment_index; 255 using TaskQueueSuper<N>::decrement_index; 256 using TaskQueueSuper<N>::dirty_size; 257 258 public: 259 using TaskQueueSuper<N>::max_elems; 260 using TaskQueueSuper<N>::size; 261 TASKQUEUE_STATS_ONLY(using TaskQueueSuper<N>::stats;) 262 263 private: 264 // Slow paths for push, pop_local. (pop_global has no fast path.) 265 bool push_slow(E t, uint dirty_n_elems); 266 bool pop_local_slow(uint localBot, Age oldAge); 267 268 public: 269 typedef E element_type; 270 271 // Initializes the queue to empty. 272 GenericTaskQueue(); 273 274 void initialize(); 275 276 // Push the task "t" on the queue. Returns "false" iff the queue is full. 277 inline bool push(E t); 278 279 // Attempts to claim a task from the "local" end of the queue (the most 280 // recently pushed). If successful, returns true and sets t to the task; 281 // otherwise, returns false (the queue is empty). 282 inline bool pop_local(E& t); 283 284 // Like pop_local(), but uses the "global" end of the queue (the least 285 // recently pushed). 286 bool pop_global(E& t); 287 288 // Delete any resource associated with the queue. 289 ~GenericTaskQueue(); 290 291 // apply the closure to all elements in the task queue 292 void oops_do(OopClosure* f); 293 294 private: 295 // Element array. 296 volatile E* _elems; 297 }; 298 299 template<class E, unsigned int N> 300 GenericTaskQueue<E, N>::GenericTaskQueue() { 301 assert(sizeof(Age) == sizeof(size_t), "Depends on this."); 302 } 303 304 template<class E, unsigned int N> 305 void GenericTaskQueue<E, N>::initialize() { 306 _elems = NEW_C_HEAP_ARRAY(E, N); 307 } 308 309 template<class E, unsigned int N> 310 void GenericTaskQueue<E, N>::oops_do(OopClosure* f) { 311 // tty->print_cr("START OopTaskQueue::oops_do"); 312 uint iters = size(); 313 uint index = _bottom; 314 for (uint i = 0; i < iters; ++i) { 315 index = decrement_index(index); 316 // tty->print_cr(" doing entry %d," INTPTR_T " -> " INTPTR_T, 317 // index, &_elems[index], _elems[index]); 318 E* t = (E*)&_elems[index]; // cast away volatility 319 oop* p = (oop*)t; 320 assert((*t)->is_oop_or_null(), "Not an oop or null"); 321 f->do_oop(p); 322 } 323 // tty->print_cr("END OopTaskQueue::oops_do"); 324 } 325 326 template<class E, unsigned int N> 327 bool GenericTaskQueue<E, N>::push_slow(E t, uint dirty_n_elems) { 328 if (dirty_n_elems == N - 1) { 329 // Actually means 0, so do the push. 330 uint localBot = _bottom; 331 // g++ complains if the volatile result of the assignment is unused. 332 const_cast<E&>(_elems[localBot] = t); 333 OrderAccess::release_store(&_bottom, increment_index(localBot)); 334 TASKQUEUE_STATS_ONLY(stats.record_push()); 335 return true; 336 } 337 return false; 338 } 339 340 // pop_local_slow() is done by the owning thread and is trying to 341 // get the last task in the queue. It will compete with pop_global() 342 // that will be used by other threads. The tag age is incremented 343 // whenever the queue goes empty which it will do here if this thread 344 // gets the last task or in pop_global() if the queue wraps (top == 0 345 // and pop_global() succeeds, see pop_global()). 346 template<class E, unsigned int N> 347 bool GenericTaskQueue<E, N>::pop_local_slow(uint localBot, Age oldAge) { 348 // This queue was observed to contain exactly one element; either this 349 // thread will claim it, or a competing "pop_global". In either case, 350 // the queue will be logically empty afterwards. Create a new Age value 351 // that represents the empty queue for the given value of "_bottom". (We 352 // must also increment "tag" because of the case where "bottom == 1", 353 // "top == 0". A pop_global could read the queue element in that case, 354 // then have the owner thread do a pop followed by another push. Without 355 // the incrementing of "tag", the pop_global's CAS could succeed, 356 // allowing it to believe it has claimed the stale element.) 357 Age newAge((idx_t)localBot, oldAge.tag() + 1); 358 // Perhaps a competing pop_global has already incremented "top", in which 359 // case it wins the element. 360 if (localBot == oldAge.top()) { 361 // No competing pop_global has yet incremented "top"; we'll try to 362 // install new_age, thus claiming the element. 363 Age tempAge = _age.cmpxchg(newAge, oldAge); 364 if (tempAge == oldAge) { 365 // We win. 366 assert(dirty_size(localBot, _age.top()) != N - 1, "sanity"); 367 TASKQUEUE_STATS_ONLY(stats.record_pop_slow()); 368 return true; 369 } 370 } 371 // We lose; a completing pop_global gets the element. But the queue is empty 372 // and top is greater than bottom. Fix this representation of the empty queue 373 // to become the canonical one. 374 _age.set(newAge); 375 assert(dirty_size(localBot, _age.top()) != N - 1, "sanity"); 376 return false; 377 } 378 379 template<class E, unsigned int N> 380 bool GenericTaskQueue<E, N>::pop_global(E& t) { 381 Age oldAge = _age.get(); 382 uint localBot = _bottom; 383 uint n_elems = size(localBot, oldAge.top()); 384 if (n_elems == 0) { 385 return false; 386 } 387 388 const_cast<E&>(t = _elems[oldAge.top()]); 389 Age newAge(oldAge); 390 newAge.increment(); 391 Age resAge = _age.cmpxchg(newAge, oldAge); 392 393 // Note that using "_bottom" here might fail, since a pop_local might 394 // have decremented it. 395 assert(dirty_size(localBot, newAge.top()) != N - 1, "sanity"); 396 return resAge == oldAge; 397 } 398 399 template<class E, unsigned int N> 400 GenericTaskQueue<E, N>::~GenericTaskQueue() { 401 FREE_C_HEAP_ARRAY(E, _elems); 402 } 403 404 // OverflowTaskQueue is a TaskQueue that also includes an overflow stack for 405 // elements that do not fit in the TaskQueue. 406 // 407 // This class hides two methods from super classes: 408 // 409 // push() - push onto the task queue or, if that fails, onto the overflow stack 410 // is_empty() - return true if both the TaskQueue and overflow stack are empty 411 // 412 // Note that size() is not hidden--it returns the number of elements in the 413 // TaskQueue, and does not include the size of the overflow stack. This 414 // simplifies replacement of GenericTaskQueues with OverflowTaskQueues. 415 template<class E, unsigned int N = TASKQUEUE_SIZE> 416 class OverflowTaskQueue: public GenericTaskQueue<E, N> 417 { 418 public: 419 typedef Stack<E> overflow_t; 420 typedef GenericTaskQueue<E, N> taskqueue_t; 421 422 TASKQUEUE_STATS_ONLY(using taskqueue_t::stats;) 423 424 // Push task t onto the queue or onto the overflow stack. Return true. 425 inline bool push(E t); 426 427 // Attempt to pop from the overflow stack; return true if anything was popped. 428 inline bool pop_overflow(E& t); 429 430 inline overflow_t* overflow_stack() { return &_overflow_stack; } 431 432 inline bool taskqueue_empty() const { return taskqueue_t::is_empty(); } 433 inline bool overflow_empty() const { return _overflow_stack.is_empty(); } 434 inline bool is_empty() const { 435 return taskqueue_empty() && overflow_empty(); 436 } 437 438 private: 439 overflow_t _overflow_stack; 440 }; 441 442 template <class E, unsigned int N> 443 bool OverflowTaskQueue<E, N>::push(E t) 444 { 445 if (!taskqueue_t::push(t)) { 446 overflow_stack()->push(t); 447 TASKQUEUE_STATS_ONLY(stats.record_overflow(overflow_stack()->size())); 448 } 449 return true; 450 } 451 452 template <class E, unsigned int N> 453 bool OverflowTaskQueue<E, N>::pop_overflow(E& t) 454 { 455 if (overflow_empty()) return false; 456 t = overflow_stack()->pop(); 457 return true; 458 } 459 460 class TaskQueueSetSuper: public CHeapObj { 461 protected: 462 static int randomParkAndMiller(int* seed0); 463 public: 464 // Returns "true" if some TaskQueue in the set contains a task. 465 virtual bool peek() = 0; 466 }; 467 468 template<class T> 469 class GenericTaskQueueSet: public TaskQueueSetSuper { 470 private: 471 uint _n; 472 T** _queues; 473 474 public: 475 typedef typename T::element_type E; 476 477 GenericTaskQueueSet(int n) : _n(n) { 478 typedef T* GenericTaskQueuePtr; 479 _queues = NEW_C_HEAP_ARRAY(GenericTaskQueuePtr, n); 480 for (int i = 0; i < n; i++) { 481 _queues[i] = NULL; 482 } 483 } 484 485 bool steal_1_random(uint queue_num, int* seed, E& t); 486 bool steal_best_of_2(uint queue_num, int* seed, E& t); 487 bool steal_best_of_all(uint queue_num, int* seed, E& t); 488 489 void register_queue(uint i, T* q); 490 491 T* queue(uint n); 492 493 // The thread with queue number "queue_num" (and whose random number seed is 494 // at "seed") is trying to steal a task from some other queue. (It may try 495 // several queues, according to some configuration parameter.) If some steal 496 // succeeds, returns "true" and sets "t" to the stolen task, otherwise returns 497 // false. 498 bool steal(uint queue_num, int* seed, E& t); 499 500 bool peek(); 501 }; 502 503 template<class T> void 504 GenericTaskQueueSet<T>::register_queue(uint i, T* q) { 505 assert(i < _n, "index out of range."); 506 _queues[i] = q; 507 } 508 509 template<class T> T* 510 GenericTaskQueueSet<T>::queue(uint i) { 511 return _queues[i]; 512 } 513 514 template<class T> bool 515 GenericTaskQueueSet<T>::steal(uint queue_num, int* seed, E& t) { 516 for (uint i = 0; i < 2 * _n; i++) { 517 if (steal_best_of_2(queue_num, seed, t)) { 518 TASKQUEUE_STATS_ONLY(queue(queue_num)->stats.record_steal(true)); 519 return true; 520 } 521 } 522 TASKQUEUE_STATS_ONLY(queue(queue_num)->stats.record_steal(false)); 523 return false; 524 } 525 526 template<class T> bool 527 GenericTaskQueueSet<T>::steal_best_of_all(uint queue_num, int* seed, E& t) { 528 if (_n > 2) { 529 int best_k; 530 uint best_sz = 0; 531 for (uint k = 0; k < _n; k++) { 532 if (k == queue_num) continue; 533 uint sz = _queues[k]->size(); 534 if (sz > best_sz) { 535 best_sz = sz; 536 best_k = k; 537 } 538 } 539 return best_sz > 0 && _queues[best_k]->pop_global(t); 540 } else if (_n == 2) { 541 // Just try the other one. 542 int k = (queue_num + 1) % 2; 543 return _queues[k]->pop_global(t); 544 } else { 545 assert(_n == 1, "can't be zero."); 546 return false; 547 } 548 } 549 550 template<class T> bool 551 GenericTaskQueueSet<T>::steal_1_random(uint queue_num, int* seed, E& t) { 552 if (_n > 2) { 553 uint k = queue_num; 554 while (k == queue_num) k = randomParkAndMiller(seed) % _n; 555 return _queues[2]->pop_global(t); 556 } else if (_n == 2) { 557 // Just try the other one. 558 int k = (queue_num + 1) % 2; 559 return _queues[k]->pop_global(t); 560 } else { 561 assert(_n == 1, "can't be zero."); 562 return false; 563 } 564 } 565 566 template<class T> bool 567 GenericTaskQueueSet<T>::steal_best_of_2(uint queue_num, int* seed, E& t) { 568 if (_n > 2) { 569 uint k1 = queue_num; 570 while (k1 == queue_num) k1 = randomParkAndMiller(seed) % _n; 571 uint k2 = queue_num; 572 while (k2 == queue_num || k2 == k1) k2 = randomParkAndMiller(seed) % _n; 573 // Sample both and try the larger. 574 uint sz1 = _queues[k1]->size(); 575 uint sz2 = _queues[k2]->size(); 576 if (sz2 > sz1) return _queues[k2]->pop_global(t); 577 else return _queues[k1]->pop_global(t); 578 } else if (_n == 2) { 579 // Just try the other one. 580 uint k = (queue_num + 1) % 2; 581 return _queues[k]->pop_global(t); 582 } else { 583 assert(_n == 1, "can't be zero."); 584 return false; 585 } 586 } 587 588 template<class T> 589 bool GenericTaskQueueSet<T>::peek() { 590 // Try all the queues. 591 for (uint j = 0; j < _n; j++) { 592 if (_queues[j]->peek()) 593 return true; 594 } 595 return false; 596 } 597 598 // When to terminate from the termination protocol. 599 class TerminatorTerminator: public CHeapObj { 600 public: 601 virtual bool should_exit_termination() = 0; 602 }; 603 604 // A class to aid in the termination of a set of parallel tasks using 605 // TaskQueueSet's for work stealing. 606 607 #undef TRACESPINNING 608 609 class ParallelTaskTerminator: public StackObj { 610 private: 611 int _n_threads; 612 TaskQueueSetSuper* _queue_set; 613 int _offered_termination; 614 615 #ifdef TRACESPINNING 616 static uint _total_yields; 617 static uint _total_spins; 618 static uint _total_peeks; 619 #endif 620 621 bool peek_in_queue_set(); 622 protected: 623 virtual void yield(); 624 void sleep(uint millis); 625 626 public: 627 628 // "n_threads" is the number of threads to be terminated. "queue_set" is a 629 // queue sets of work queues of other threads. 630 ParallelTaskTerminator(int n_threads, TaskQueueSetSuper* queue_set); 631 632 // The current thread has no work, and is ready to terminate if everyone 633 // else is. If returns "true", all threads are terminated. If returns 634 // "false", available work has been observed in one of the task queues, 635 // so the global task is not complete. 636 bool offer_termination() { 637 return offer_termination(NULL); 638 } 639 640 // As above, but it also terminates if the should_exit_termination() 641 // method of the terminator parameter returns true. If terminator is 642 // NULL, then it is ignored. 643 bool offer_termination(TerminatorTerminator* terminator); 644 645 // Reset the terminator, so that it may be reused again. 646 // The caller is responsible for ensuring that this is done 647 // in an MT-safe manner, once the previous round of use of 648 // the terminator is finished. 649 void reset_for_reuse(); 650 // Same as above but the number of parallel threads is set to the 651 // given number. 652 void reset_for_reuse(int n_threads); 653 654 #ifdef TRACESPINNING 655 static uint total_yields() { return _total_yields; } 656 static uint total_spins() { return _total_spins; } 657 static uint total_peeks() { return _total_peeks; } 658 static void print_termination_counts(); 659 #endif 660 }; 661 662 template<class E, unsigned int N> inline bool 663 GenericTaskQueue<E, N>::push(E t) { 664 uint localBot = _bottom; 665 assert((localBot >= 0) && (localBot < N), "_bottom out of range."); 666 idx_t top = _age.top(); 667 uint dirty_n_elems = dirty_size(localBot, top); 668 assert(dirty_n_elems < N, "n_elems out of range."); 669 if (dirty_n_elems < max_elems()) { 670 // g++ complains if the volatile result of the assignment is unused. 671 const_cast<E&>(_elems[localBot] = t); 672 OrderAccess::release_store(&_bottom, increment_index(localBot)); 673 TASKQUEUE_STATS_ONLY(stats.record_push()); 674 return true; 675 } else { 676 return push_slow(t, dirty_n_elems); 677 } 678 } 679 680 template<class E, unsigned int N> inline bool 681 GenericTaskQueue<E, N>::pop_local(E& t) { 682 uint localBot = _bottom; 683 // This value cannot be N-1. That can only occur as a result of 684 // the assignment to bottom in this method. If it does, this method 685 // resets the size to 0 before the next call (which is sequential, 686 // since this is pop_local.) 687 uint dirty_n_elems = dirty_size(localBot, _age.top()); 688 assert(dirty_n_elems != N - 1, "Shouldn't be possible..."); 689 if (dirty_n_elems == 0) return false; 690 localBot = decrement_index(localBot); 691 _bottom = localBot; 692 // This is necessary to prevent any read below from being reordered 693 // before the store just above. 694 OrderAccess::fence(); 695 const_cast<E&>(t = _elems[localBot]); 696 // This is a second read of "age"; the "size()" above is the first. 697 // If there's still at least one element in the queue, based on the 698 // "_bottom" and "age" we've read, then there can be no interference with 699 // a "pop_global" operation, and we're done. 700 idx_t tp = _age.top(); // XXX 701 if (size(localBot, tp) > 0) { 702 assert(dirty_size(localBot, tp) != N - 1, "sanity"); 703 TASKQUEUE_STATS_ONLY(stats.record_pop()); 704 return true; 705 } else { 706 // Otherwise, the queue contained exactly one element; we take the slow 707 // path. 708 return pop_local_slow(localBot, _age.get()); 709 } 710 } 711 712 typedef GenericTaskQueue<oop> OopTaskQueue; 713 typedef GenericTaskQueueSet<OopTaskQueue> OopTaskQueueSet; 714 715 #ifdef _MSC_VER 716 #pragma warning(push) 717 // warning C4522: multiple assignment operators specified 718 #pragma warning(disable:4522) 719 #endif 720 721 // This is a container class for either an oop* or a narrowOop*. 722 // Both are pushed onto a task queue and the consumer will test is_narrow() 723 // to determine which should be processed. 724 class StarTask { 725 void* _holder; // either union oop* or narrowOop* 726 727 enum { COMPRESSED_OOP_MASK = 1 }; 728 729 public: 730 StarTask(narrowOop* p) { 731 assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!"); 732 _holder = (void *)((uintptr_t)p | COMPRESSED_OOP_MASK); 733 } 734 StarTask(oop* p) { 735 assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!"); 736 _holder = (void*)p; 737 } 738 StarTask() { _holder = NULL; } 739 operator oop*() { return (oop*)_holder; } 740 operator narrowOop*() { 741 return (narrowOop*)((uintptr_t)_holder & ~COMPRESSED_OOP_MASK); 742 } 743 744 StarTask& operator=(const StarTask& t) { 745 _holder = t._holder; 746 return *this; 747 } 748 volatile StarTask& operator=(const volatile StarTask& t) volatile { 749 _holder = t._holder; 750 return *this; 751 } 752 753 bool is_narrow() const { 754 return (((uintptr_t)_holder & COMPRESSED_OOP_MASK) != 0); 755 } 756 }; 757 758 class ObjArrayTask 759 { 760 public: 761 ObjArrayTask(oop o = NULL, int idx = 0): _obj(o), _index(idx) { } 762 ObjArrayTask(oop o, size_t idx): _obj(o), _index(int(idx)) { 763 assert(idx <= size_t(max_jint), "too big"); 764 } 765 ObjArrayTask(const ObjArrayTask& t): _obj(t._obj), _index(t._index) { } 766 767 ObjArrayTask& operator =(const ObjArrayTask& t) { 768 _obj = t._obj; 769 _index = t._index; 770 return *this; 771 } 772 volatile ObjArrayTask& 773 operator =(const volatile ObjArrayTask& t) volatile { 774 _obj = t._obj; 775 _index = t._index; 776 return *this; 777 } 778 779 inline oop obj() const { return _obj; } 780 inline int index() const { return _index; } 781 782 DEBUG_ONLY(bool is_valid() const); // Tasks to be pushed/popped must be valid. 783 784 private: 785 oop _obj; 786 int _index; 787 }; 788 789 #ifdef _MSC_VER 790 #pragma warning(pop) 791 #endif 792 793 typedef OverflowTaskQueue<StarTask> OopStarTaskQueue; 794 typedef GenericTaskQueueSet<OopStarTaskQueue> OopStarTaskQueueSet; 795 796 typedef OverflowTaskQueue<size_t> RegionTaskQueue; 797 typedef GenericTaskQueueSet<RegionTaskQueue> RegionTaskQueueSet; 798 799 800 #endif // SHARE_VM_UTILITIES_TASKQUEUE_HPP