Tue, 23 Nov 2010 13:22:55 -0800
6989984: Use standard include model for Hospot
Summary: Replaced MakeDeps and the includeDB files with more standardized solutions.
Reviewed-by: coleenp, kvn, kamg
1 /*
2 * Copyright (c) 2001, 2010, 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 */
25 #ifndef SHARE_VM_UTILITIES_TASKQUEUE_HPP
26 #define SHARE_VM_UTILITIES_TASKQUEUE_HPP
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
51 // Simple TaskQueue stats that are collected by default in debug builds.
53 #if !defined(TASKQUEUE_STATS) && defined(ASSERT)
54 #define TASKQUEUE_STATS 1
55 #elif !defined(TASKQUEUE_STATS)
56 #define TASKQUEUE_STATS 0
57 #endif
59 #if TASKQUEUE_STATS
60 #define TASKQUEUE_STATS_ONLY(code) code
61 #else
62 #define TASKQUEUE_STATS_ONLY(code)
63 #endif // TASKQUEUE_STATS
65 #if TASKQUEUE_STATS
66 class TaskQueueStats {
67 public:
68 enum StatId {
69 push, // number of taskqueue pushes
70 pop, // number of taskqueue pops
71 pop_slow, // subset of taskqueue pops that were done slow-path
72 steal_attempt, // number of taskqueue steal attempts
73 steal, // number of taskqueue steals
74 overflow, // number of overflow pushes
75 overflow_max_len, // max length of overflow stack
76 last_stat_id
77 };
79 public:
80 inline TaskQueueStats() { reset(); }
82 inline void record_push() { ++_stats[push]; }
83 inline void record_pop() { ++_stats[pop]; }
84 inline void record_pop_slow() { record_pop(); ++_stats[pop_slow]; }
85 inline void record_steal(bool success);
86 inline void record_overflow(size_t new_length);
88 TaskQueueStats & operator +=(const TaskQueueStats & addend);
90 inline size_t get(StatId id) const { return _stats[id]; }
91 inline const size_t* get() const { return _stats; }
93 inline void reset();
95 // Print the specified line of the header (does not include a line separator).
96 static void print_header(unsigned int line, outputStream* const stream = tty,
97 unsigned int width = 10);
98 // Print the statistics (does not include a line separator).
99 void print(outputStream* const stream = tty, unsigned int width = 10) const;
101 DEBUG_ONLY(void verify() const;)
103 private:
104 size_t _stats[last_stat_id];
105 static const char * const _names[last_stat_id];
106 };
108 void TaskQueueStats::record_steal(bool success) {
109 ++_stats[steal_attempt];
110 if (success) ++_stats[steal];
111 }
113 void TaskQueueStats::record_overflow(size_t new_len) {
114 ++_stats[overflow];
115 if (new_len > _stats[overflow_max_len]) _stats[overflow_max_len] = new_len;
116 }
118 void TaskQueueStats::reset() {
119 memset(_stats, 0, sizeof(_stats));
120 }
121 #endif // TASKQUEUE_STATS
123 template <unsigned int N>
124 class TaskQueueSuper: public CHeapObj {
125 protected:
126 // Internal type for indexing the queue; also used for the tag.
127 typedef NOT_LP64(uint16_t) LP64_ONLY(uint32_t) idx_t;
129 // The first free element after the last one pushed (mod N).
130 volatile uint _bottom;
132 enum { MOD_N_MASK = N - 1 };
134 class Age {
135 public:
136 Age(size_t data = 0) { _data = data; }
137 Age(const Age& age) { _data = age._data; }
138 Age(idx_t top, idx_t tag) { _fields._top = top; _fields._tag = tag; }
140 Age get() const volatile { return _data; }
141 void set(Age age) volatile { _data = age._data; }
143 idx_t top() const volatile { return _fields._top; }
144 idx_t tag() const volatile { return _fields._tag; }
146 // Increment top; if it wraps, increment tag also.
147 void increment() {
148 _fields._top = increment_index(_fields._top);
149 if (_fields._top == 0) ++_fields._tag;
150 }
152 Age cmpxchg(const Age new_age, const Age old_age) volatile {
153 return (size_t) Atomic::cmpxchg_ptr((intptr_t)new_age._data,
154 (volatile intptr_t *)&_data,
155 (intptr_t)old_age._data);
156 }
158 bool operator ==(const Age& other) const { return _data == other._data; }
160 private:
161 struct fields {
162 idx_t _top;
163 idx_t _tag;
164 };
165 union {
166 size_t _data;
167 fields _fields;
168 };
169 };
171 volatile Age _age;
173 // These both operate mod N.
174 static uint increment_index(uint ind) {
175 return (ind + 1) & MOD_N_MASK;
176 }
177 static uint decrement_index(uint ind) {
178 return (ind - 1) & MOD_N_MASK;
179 }
181 // Returns a number in the range [0..N). If the result is "N-1", it should be
182 // interpreted as 0.
183 uint dirty_size(uint bot, uint top) const {
184 return (bot - top) & MOD_N_MASK;
185 }
187 // Returns the size corresponding to the given "bot" and "top".
188 uint size(uint bot, uint top) const {
189 uint sz = dirty_size(bot, top);
190 // Has the queue "wrapped", so that bottom is less than top? There's a
191 // complicated special case here. A pair of threads could perform pop_local
192 // and pop_global operations concurrently, starting from a state in which
193 // _bottom == _top+1. The pop_local could succeed in decrementing _bottom,
194 // and the pop_global in incrementing _top (in which case the pop_global
195 // will be awarded the contested queue element.) The resulting state must
196 // be interpreted as an empty queue. (We only need to worry about one such
197 // event: only the queue owner performs pop_local's, and several concurrent
198 // threads attempting to perform the pop_global will all perform the same
199 // CAS, and only one can succeed.) Any stealing thread that reads after
200 // either the increment or decrement will see an empty queue, and will not
201 // join the competitors. The "sz == -1 || sz == N-1" state will not be
202 // modified by concurrent queues, so the owner thread can reset the state to
203 // _bottom == top so subsequent pushes will be performed normally.
204 return (sz == N - 1) ? 0 : sz;
205 }
207 public:
208 TaskQueueSuper() : _bottom(0), _age() {}
210 // Return true if the TaskQueue contains/does not contain any tasks.
211 bool peek() const { return _bottom != _age.top(); }
212 bool is_empty() const { return size() == 0; }
214 // Return an estimate of the number of elements in the queue.
215 // The "careful" version admits the possibility of pop_local/pop_global
216 // races.
217 uint size() const {
218 return size(_bottom, _age.top());
219 }
221 uint dirty_size() const {
222 return dirty_size(_bottom, _age.top());
223 }
225 void set_empty() {
226 _bottom = 0;
227 _age.set(0);
228 }
230 // Maximum number of elements allowed in the queue. This is two less
231 // than the actual queue size, for somewhat complicated reasons.
232 uint max_elems() const { return N - 2; }
234 // Total size of queue.
235 static const uint total_size() { return N; }
237 TASKQUEUE_STATS_ONLY(TaskQueueStats stats;)
238 };
240 template<class E, unsigned int N = TASKQUEUE_SIZE>
241 class GenericTaskQueue: public TaskQueueSuper<N> {
242 protected:
243 typedef typename TaskQueueSuper<N>::Age Age;
244 typedef typename TaskQueueSuper<N>::idx_t idx_t;
246 using TaskQueueSuper<N>::_bottom;
247 using TaskQueueSuper<N>::_age;
248 using TaskQueueSuper<N>::increment_index;
249 using TaskQueueSuper<N>::decrement_index;
250 using TaskQueueSuper<N>::dirty_size;
252 public:
253 using TaskQueueSuper<N>::max_elems;
254 using TaskQueueSuper<N>::size;
255 TASKQUEUE_STATS_ONLY(using TaskQueueSuper<N>::stats;)
257 private:
258 // Slow paths for push, pop_local. (pop_global has no fast path.)
259 bool push_slow(E t, uint dirty_n_elems);
260 bool pop_local_slow(uint localBot, Age oldAge);
262 public:
263 typedef E element_type;
265 // Initializes the queue to empty.
266 GenericTaskQueue();
268 void initialize();
270 // Push the task "t" on the queue. Returns "false" iff the queue is full.
271 inline bool push(E t);
273 // Attempts to claim a task from the "local" end of the queue (the most
274 // recently pushed). If successful, returns true and sets t to the task;
275 // otherwise, returns false (the queue is empty).
276 inline bool pop_local(E& t);
278 // Like pop_local(), but uses the "global" end of the queue (the least
279 // recently pushed).
280 bool pop_global(E& t);
282 // Delete any resource associated with the queue.
283 ~GenericTaskQueue();
285 // apply the closure to all elements in the task queue
286 void oops_do(OopClosure* f);
288 private:
289 // Element array.
290 volatile E* _elems;
291 };
293 template<class E, unsigned int N>
294 GenericTaskQueue<E, N>::GenericTaskQueue() {
295 assert(sizeof(Age) == sizeof(size_t), "Depends on this.");
296 }
298 template<class E, unsigned int N>
299 void GenericTaskQueue<E, N>::initialize() {
300 _elems = NEW_C_HEAP_ARRAY(E, N);
301 }
303 template<class E, unsigned int N>
304 void GenericTaskQueue<E, N>::oops_do(OopClosure* f) {
305 // tty->print_cr("START OopTaskQueue::oops_do");
306 uint iters = size();
307 uint index = _bottom;
308 for (uint i = 0; i < iters; ++i) {
309 index = decrement_index(index);
310 // tty->print_cr(" doing entry %d," INTPTR_T " -> " INTPTR_T,
311 // index, &_elems[index], _elems[index]);
312 E* t = (E*)&_elems[index]; // cast away volatility
313 oop* p = (oop*)t;
314 assert((*t)->is_oop_or_null(), "Not an oop or null");
315 f->do_oop(p);
316 }
317 // tty->print_cr("END OopTaskQueue::oops_do");
318 }
320 template<class E, unsigned int N>
321 bool GenericTaskQueue<E, N>::push_slow(E t, uint dirty_n_elems) {
322 if (dirty_n_elems == N - 1) {
323 // Actually means 0, so do the push.
324 uint localBot = _bottom;
325 // g++ complains if the volatile result of the assignment is unused.
326 const_cast<E&>(_elems[localBot] = t);
327 OrderAccess::release_store(&_bottom, increment_index(localBot));
328 TASKQUEUE_STATS_ONLY(stats.record_push());
329 return true;
330 }
331 return false;
332 }
334 // pop_local_slow() is done by the owning thread and is trying to
335 // get the last task in the queue. It will compete with pop_global()
336 // that will be used by other threads. The tag age is incremented
337 // whenever the queue goes empty which it will do here if this thread
338 // gets the last task or in pop_global() if the queue wraps (top == 0
339 // and pop_global() succeeds, see pop_global()).
340 template<class E, unsigned int N>
341 bool GenericTaskQueue<E, N>::pop_local_slow(uint localBot, Age oldAge) {
342 // This queue was observed to contain exactly one element; either this
343 // thread will claim it, or a competing "pop_global". In either case,
344 // the queue will be logically empty afterwards. Create a new Age value
345 // that represents the empty queue for the given value of "_bottom". (We
346 // must also increment "tag" because of the case where "bottom == 1",
347 // "top == 0". A pop_global could read the queue element in that case,
348 // then have the owner thread do a pop followed by another push. Without
349 // the incrementing of "tag", the pop_global's CAS could succeed,
350 // allowing it to believe it has claimed the stale element.)
351 Age newAge((idx_t)localBot, oldAge.tag() + 1);
352 // Perhaps a competing pop_global has already incremented "top", in which
353 // case it wins the element.
354 if (localBot == oldAge.top()) {
355 // No competing pop_global has yet incremented "top"; we'll try to
356 // install new_age, thus claiming the element.
357 Age tempAge = _age.cmpxchg(newAge, oldAge);
358 if (tempAge == oldAge) {
359 // We win.
360 assert(dirty_size(localBot, _age.top()) != N - 1, "sanity");
361 TASKQUEUE_STATS_ONLY(stats.record_pop_slow());
362 return true;
363 }
364 }
365 // We lose; a completing pop_global gets the element. But the queue is empty
366 // and top is greater than bottom. Fix this representation of the empty queue
367 // to become the canonical one.
368 _age.set(newAge);
369 assert(dirty_size(localBot, _age.top()) != N - 1, "sanity");
370 return false;
371 }
373 template<class E, unsigned int N>
374 bool GenericTaskQueue<E, N>::pop_global(E& t) {
375 Age oldAge = _age.get();
376 uint localBot = _bottom;
377 uint n_elems = size(localBot, oldAge.top());
378 if (n_elems == 0) {
379 return false;
380 }
382 const_cast<E&>(t = _elems[oldAge.top()]);
383 Age newAge(oldAge);
384 newAge.increment();
385 Age resAge = _age.cmpxchg(newAge, oldAge);
387 // Note that using "_bottom" here might fail, since a pop_local might
388 // have decremented it.
389 assert(dirty_size(localBot, newAge.top()) != N - 1, "sanity");
390 return resAge == oldAge;
391 }
393 template<class E, unsigned int N>
394 GenericTaskQueue<E, N>::~GenericTaskQueue() {
395 FREE_C_HEAP_ARRAY(E, _elems);
396 }
398 // OverflowTaskQueue is a TaskQueue that also includes an overflow stack for
399 // elements that do not fit in the TaskQueue.
400 //
401 // This class hides two methods from super classes:
402 //
403 // push() - push onto the task queue or, if that fails, onto the overflow stack
404 // is_empty() - return true if both the TaskQueue and overflow stack are empty
405 //
406 // Note that size() is not hidden--it returns the number of elements in the
407 // TaskQueue, and does not include the size of the overflow stack. This
408 // simplifies replacement of GenericTaskQueues with OverflowTaskQueues.
409 template<class E, unsigned int N = TASKQUEUE_SIZE>
410 class OverflowTaskQueue: public GenericTaskQueue<E, N>
411 {
412 public:
413 typedef Stack<E> overflow_t;
414 typedef GenericTaskQueue<E, N> taskqueue_t;
416 TASKQUEUE_STATS_ONLY(using taskqueue_t::stats;)
418 // Push task t onto the queue or onto the overflow stack. Return true.
419 inline bool push(E t);
421 // Attempt to pop from the overflow stack; return true if anything was popped.
422 inline bool pop_overflow(E& t);
424 inline overflow_t* overflow_stack() { return &_overflow_stack; }
426 inline bool taskqueue_empty() const { return taskqueue_t::is_empty(); }
427 inline bool overflow_empty() const { return _overflow_stack.is_empty(); }
428 inline bool is_empty() const {
429 return taskqueue_empty() && overflow_empty();
430 }
432 private:
433 overflow_t _overflow_stack;
434 };
436 template <class E, unsigned int N>
437 bool OverflowTaskQueue<E, N>::push(E t)
438 {
439 if (!taskqueue_t::push(t)) {
440 overflow_stack()->push(t);
441 TASKQUEUE_STATS_ONLY(stats.record_overflow(overflow_stack()->size()));
442 }
443 return true;
444 }
446 template <class E, unsigned int N>
447 bool OverflowTaskQueue<E, N>::pop_overflow(E& t)
448 {
449 if (overflow_empty()) return false;
450 t = overflow_stack()->pop();
451 return true;
452 }
454 class TaskQueueSetSuper: public CHeapObj {
455 protected:
456 static int randomParkAndMiller(int* seed0);
457 public:
458 // Returns "true" if some TaskQueue in the set contains a task.
459 virtual bool peek() = 0;
460 };
462 template<class T>
463 class GenericTaskQueueSet: public TaskQueueSetSuper {
464 private:
465 uint _n;
466 T** _queues;
468 public:
469 typedef typename T::element_type E;
471 GenericTaskQueueSet(int n) : _n(n) {
472 typedef T* GenericTaskQueuePtr;
473 _queues = NEW_C_HEAP_ARRAY(GenericTaskQueuePtr, n);
474 for (int i = 0; i < n; i++) {
475 _queues[i] = NULL;
476 }
477 }
479 bool steal_1_random(uint queue_num, int* seed, E& t);
480 bool steal_best_of_2(uint queue_num, int* seed, E& t);
481 bool steal_best_of_all(uint queue_num, int* seed, E& t);
483 void register_queue(uint i, T* q);
485 T* queue(uint n);
487 // The thread with queue number "queue_num" (and whose random number seed is
488 // at "seed") is trying to steal a task from some other queue. (It may try
489 // several queues, according to some configuration parameter.) If some steal
490 // succeeds, returns "true" and sets "t" to the stolen task, otherwise returns
491 // false.
492 bool steal(uint queue_num, int* seed, E& t);
494 bool peek();
495 };
497 template<class T> void
498 GenericTaskQueueSet<T>::register_queue(uint i, T* q) {
499 assert(i < _n, "index out of range.");
500 _queues[i] = q;
501 }
503 template<class T> T*
504 GenericTaskQueueSet<T>::queue(uint i) {
505 return _queues[i];
506 }
508 template<class T> bool
509 GenericTaskQueueSet<T>::steal(uint queue_num, int* seed, E& t) {
510 for (uint i = 0; i < 2 * _n; i++) {
511 if (steal_best_of_2(queue_num, seed, t)) {
512 TASKQUEUE_STATS_ONLY(queue(queue_num)->stats.record_steal(true));
513 return true;
514 }
515 }
516 TASKQUEUE_STATS_ONLY(queue(queue_num)->stats.record_steal(false));
517 return false;
518 }
520 template<class T> bool
521 GenericTaskQueueSet<T>::steal_best_of_all(uint queue_num, int* seed, E& t) {
522 if (_n > 2) {
523 int best_k;
524 uint best_sz = 0;
525 for (uint k = 0; k < _n; k++) {
526 if (k == queue_num) continue;
527 uint sz = _queues[k]->size();
528 if (sz > best_sz) {
529 best_sz = sz;
530 best_k = k;
531 }
532 }
533 return best_sz > 0 && _queues[best_k]->pop_global(t);
534 } else if (_n == 2) {
535 // Just try the other one.
536 int k = (queue_num + 1) % 2;
537 return _queues[k]->pop_global(t);
538 } else {
539 assert(_n == 1, "can't be zero.");
540 return false;
541 }
542 }
544 template<class T> bool
545 GenericTaskQueueSet<T>::steal_1_random(uint queue_num, int* seed, E& t) {
546 if (_n > 2) {
547 uint k = queue_num;
548 while (k == queue_num) k = randomParkAndMiller(seed) % _n;
549 return _queues[2]->pop_global(t);
550 } else if (_n == 2) {
551 // Just try the other one.
552 int k = (queue_num + 1) % 2;
553 return _queues[k]->pop_global(t);
554 } else {
555 assert(_n == 1, "can't be zero.");
556 return false;
557 }
558 }
560 template<class T> bool
561 GenericTaskQueueSet<T>::steal_best_of_2(uint queue_num, int* seed, E& t) {
562 if (_n > 2) {
563 uint k1 = queue_num;
564 while (k1 == queue_num) k1 = randomParkAndMiller(seed) % _n;
565 uint k2 = queue_num;
566 while (k2 == queue_num || k2 == k1) k2 = randomParkAndMiller(seed) % _n;
567 // Sample both and try the larger.
568 uint sz1 = _queues[k1]->size();
569 uint sz2 = _queues[k2]->size();
570 if (sz2 > sz1) return _queues[k2]->pop_global(t);
571 else return _queues[k1]->pop_global(t);
572 } else if (_n == 2) {
573 // Just try the other one.
574 uint k = (queue_num + 1) % 2;
575 return _queues[k]->pop_global(t);
576 } else {
577 assert(_n == 1, "can't be zero.");
578 return false;
579 }
580 }
582 template<class T>
583 bool GenericTaskQueueSet<T>::peek() {
584 // Try all the queues.
585 for (uint j = 0; j < _n; j++) {
586 if (_queues[j]->peek())
587 return true;
588 }
589 return false;
590 }
592 // When to terminate from the termination protocol.
593 class TerminatorTerminator: public CHeapObj {
594 public:
595 virtual bool should_exit_termination() = 0;
596 };
598 // A class to aid in the termination of a set of parallel tasks using
599 // TaskQueueSet's for work stealing.
601 #undef TRACESPINNING
603 class ParallelTaskTerminator: public StackObj {
604 private:
605 int _n_threads;
606 TaskQueueSetSuper* _queue_set;
607 int _offered_termination;
609 #ifdef TRACESPINNING
610 static uint _total_yields;
611 static uint _total_spins;
612 static uint _total_peeks;
613 #endif
615 bool peek_in_queue_set();
616 protected:
617 virtual void yield();
618 void sleep(uint millis);
620 public:
622 // "n_threads" is the number of threads to be terminated. "queue_set" is a
623 // queue sets of work queues of other threads.
624 ParallelTaskTerminator(int n_threads, TaskQueueSetSuper* queue_set);
626 // The current thread has no work, and is ready to terminate if everyone
627 // else is. If returns "true", all threads are terminated. If returns
628 // "false", available work has been observed in one of the task queues,
629 // so the global task is not complete.
630 bool offer_termination() {
631 return offer_termination(NULL);
632 }
634 // As above, but it also terminates if the should_exit_termination()
635 // method of the terminator parameter returns true. If terminator is
636 // NULL, then it is ignored.
637 bool offer_termination(TerminatorTerminator* terminator);
639 // Reset the terminator, so that it may be reused again.
640 // The caller is responsible for ensuring that this is done
641 // in an MT-safe manner, once the previous round of use of
642 // the terminator is finished.
643 void reset_for_reuse();
644 // Same as above but the number of parallel threads is set to the
645 // given number.
646 void reset_for_reuse(int n_threads);
648 #ifdef TRACESPINNING
649 static uint total_yields() { return _total_yields; }
650 static uint total_spins() { return _total_spins; }
651 static uint total_peeks() { return _total_peeks; }
652 static void print_termination_counts();
653 #endif
654 };
656 template<class E, unsigned int N> inline bool
657 GenericTaskQueue<E, N>::push(E t) {
658 uint localBot = _bottom;
659 assert((localBot >= 0) && (localBot < N), "_bottom out of range.");
660 idx_t top = _age.top();
661 uint dirty_n_elems = dirty_size(localBot, top);
662 assert(dirty_n_elems < N, "n_elems out of range.");
663 if (dirty_n_elems < max_elems()) {
664 // g++ complains if the volatile result of the assignment is unused.
665 const_cast<E&>(_elems[localBot] = t);
666 OrderAccess::release_store(&_bottom, increment_index(localBot));
667 TASKQUEUE_STATS_ONLY(stats.record_push());
668 return true;
669 } else {
670 return push_slow(t, dirty_n_elems);
671 }
672 }
674 template<class E, unsigned int N> inline bool
675 GenericTaskQueue<E, N>::pop_local(E& t) {
676 uint localBot = _bottom;
677 // This value cannot be N-1. That can only occur as a result of
678 // the assignment to bottom in this method. If it does, this method
679 // resets the size to 0 before the next call (which is sequential,
680 // since this is pop_local.)
681 uint dirty_n_elems = dirty_size(localBot, _age.top());
682 assert(dirty_n_elems != N - 1, "Shouldn't be possible...");
683 if (dirty_n_elems == 0) return false;
684 localBot = decrement_index(localBot);
685 _bottom = localBot;
686 // This is necessary to prevent any read below from being reordered
687 // before the store just above.
688 OrderAccess::fence();
689 const_cast<E&>(t = _elems[localBot]);
690 // This is a second read of "age"; the "size()" above is the first.
691 // If there's still at least one element in the queue, based on the
692 // "_bottom" and "age" we've read, then there can be no interference with
693 // a "pop_global" operation, and we're done.
694 idx_t tp = _age.top(); // XXX
695 if (size(localBot, tp) > 0) {
696 assert(dirty_size(localBot, tp) != N - 1, "sanity");
697 TASKQUEUE_STATS_ONLY(stats.record_pop());
698 return true;
699 } else {
700 // Otherwise, the queue contained exactly one element; we take the slow
701 // path.
702 return pop_local_slow(localBot, _age.get());
703 }
704 }
706 typedef GenericTaskQueue<oop> OopTaskQueue;
707 typedef GenericTaskQueueSet<OopTaskQueue> OopTaskQueueSet;
709 #ifdef _MSC_VER
710 #pragma warning(push)
711 // warning C4522: multiple assignment operators specified
712 #pragma warning(disable:4522)
713 #endif
715 // This is a container class for either an oop* or a narrowOop*.
716 // Both are pushed onto a task queue and the consumer will test is_narrow()
717 // to determine which should be processed.
718 class StarTask {
719 void* _holder; // either union oop* or narrowOop*
721 enum { COMPRESSED_OOP_MASK = 1 };
723 public:
724 StarTask(narrowOop* p) {
725 assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!");
726 _holder = (void *)((uintptr_t)p | COMPRESSED_OOP_MASK);
727 }
728 StarTask(oop* p) {
729 assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!");
730 _holder = (void*)p;
731 }
732 StarTask() { _holder = NULL; }
733 operator oop*() { return (oop*)_holder; }
734 operator narrowOop*() {
735 return (narrowOop*)((uintptr_t)_holder & ~COMPRESSED_OOP_MASK);
736 }
738 StarTask& operator=(const StarTask& t) {
739 _holder = t._holder;
740 return *this;
741 }
742 volatile StarTask& operator=(const volatile StarTask& t) volatile {
743 _holder = t._holder;
744 return *this;
745 }
747 bool is_narrow() const {
748 return (((uintptr_t)_holder & COMPRESSED_OOP_MASK) != 0);
749 }
750 };
752 class ObjArrayTask
753 {
754 public:
755 ObjArrayTask(oop o = NULL, int idx = 0): _obj(o), _index(idx) { }
756 ObjArrayTask(oop o, size_t idx): _obj(o), _index(int(idx)) {
757 assert(idx <= size_t(max_jint), "too big");
758 }
759 ObjArrayTask(const ObjArrayTask& t): _obj(t._obj), _index(t._index) { }
761 ObjArrayTask& operator =(const ObjArrayTask& t) {
762 _obj = t._obj;
763 _index = t._index;
764 return *this;
765 }
766 volatile ObjArrayTask&
767 operator =(const volatile ObjArrayTask& t) volatile {
768 _obj = t._obj;
769 _index = t._index;
770 return *this;
771 }
773 inline oop obj() const { return _obj; }
774 inline int index() const { return _index; }
776 DEBUG_ONLY(bool is_valid() const); // Tasks to be pushed/popped must be valid.
778 private:
779 oop _obj;
780 int _index;
781 };
783 #ifdef _MSC_VER
784 #pragma warning(pop)
785 #endif
787 typedef OverflowTaskQueue<StarTask> OopStarTaskQueue;
788 typedef GenericTaskQueueSet<OopStarTaskQueue> OopStarTaskQueueSet;
790 typedef OverflowTaskQueue<size_t> RegionTaskQueue;
791 typedef GenericTaskQueueSet<RegionTaskQueue> RegionTaskQueueSet;
794 #endif // SHARE_VM_UTILITIES_TASKQUEUE_HPP