Wed, 24 Feb 2010 07:00:33 -0800
6928081: G1: rename parameters common with CMS
Summary: Rename marking stack sizing flags to be common between G1 and CMS
Reviewed-by: ysr, tonyp
1 /*
2 * Copyright 2001-2009 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 */
25 class TaskQueueSuper: public CHeapObj {
26 protected:
27 // Internal type for indexing the queue; also used for the tag.
28 typedef NOT_LP64(uint16_t) LP64_ONLY(uint32_t) idx_t;
30 // The first free element after the last one pushed (mod N).
31 volatile uint _bottom;
33 enum {
34 N = 1 << NOT_LP64(14) LP64_ONLY(17), // Queue size: 16K or 128K
35 MOD_N_MASK = N - 1 // To compute x mod N efficiently.
36 };
38 class Age {
39 public:
40 Age(size_t data = 0) { _data = data; }
41 Age(const Age& age) { _data = age._data; }
42 Age(idx_t top, idx_t tag) { _fields._top = top; _fields._tag = tag; }
44 Age get() const volatile { return _data; }
45 void set(Age age) volatile { _data = age._data; }
47 idx_t top() const volatile { return _fields._top; }
48 idx_t tag() const volatile { return _fields._tag; }
50 // Increment top; if it wraps, increment tag also.
51 void increment() {
52 _fields._top = increment_index(_fields._top);
53 if (_fields._top == 0) ++_fields._tag;
54 }
56 Age cmpxchg(const Age new_age, const Age old_age) volatile {
57 return (size_t) Atomic::cmpxchg_ptr((intptr_t)new_age._data,
58 (volatile intptr_t *)&_data,
59 (intptr_t)old_age._data);
60 }
62 bool operator ==(const Age& other) const { return _data == other._data; }
64 private:
65 struct fields {
66 idx_t _top;
67 idx_t _tag;
68 };
69 union {
70 size_t _data;
71 fields _fields;
72 };
73 };
75 volatile Age _age;
77 // These both operate mod N.
78 static uint increment_index(uint ind) {
79 return (ind + 1) & MOD_N_MASK;
80 }
81 static uint decrement_index(uint ind) {
82 return (ind - 1) & MOD_N_MASK;
83 }
85 // Returns a number in the range [0..N). If the result is "N-1", it should be
86 // interpreted as 0.
87 uint dirty_size(uint bot, uint top) {
88 return (bot - top) & MOD_N_MASK;
89 }
91 // Returns the size corresponding to the given "bot" and "top".
92 uint size(uint bot, uint top) {
93 uint sz = dirty_size(bot, top);
94 // Has the queue "wrapped", so that bottom is less than top? There's a
95 // complicated special case here. A pair of threads could perform pop_local
96 // and pop_global operations concurrently, starting from a state in which
97 // _bottom == _top+1. The pop_local could succeed in decrementing _bottom,
98 // and the pop_global in incrementing _top (in which case the pop_global
99 // will be awarded the contested queue element.) The resulting state must
100 // be interpreted as an empty queue. (We only need to worry about one such
101 // event: only the queue owner performs pop_local's, and several concurrent
102 // threads attempting to perform the pop_global will all perform the same
103 // CAS, and only one can succeed.) Any stealing thread that reads after
104 // either the increment or decrement will see an empty queue, and will not
105 // join the competitors. The "sz == -1 || sz == N-1" state will not be
106 // modified by concurrent queues, so the owner thread can reset the state to
107 // _bottom == top so subsequent pushes will be performed normally.
108 return (sz == N - 1) ? 0 : sz;
109 }
111 public:
112 TaskQueueSuper() : _bottom(0), _age() {}
114 // Return "true" if the TaskQueue contains any tasks.
115 bool peek();
117 // Return an estimate of the number of elements in the queue.
118 // The "careful" version admits the possibility of pop_local/pop_global
119 // races.
120 uint size() {
121 return size(_bottom, _age.top());
122 }
124 uint dirty_size() {
125 return dirty_size(_bottom, _age.top());
126 }
128 void set_empty() {
129 _bottom = 0;
130 _age.set(0);
131 }
133 // Maximum number of elements allowed in the queue. This is two less
134 // than the actual queue size, for somewhat complicated reasons.
135 uint max_elems() { return N - 2; }
137 // Total size of queue.
138 static const uint total_size() { return N; }
139 };
141 template<class E> class GenericTaskQueue: public TaskQueueSuper {
142 private:
143 // Slow paths for push, pop_local. (pop_global has no fast path.)
144 bool push_slow(E t, uint dirty_n_elems);
145 bool pop_local_slow(uint localBot, Age oldAge);
147 public:
148 // Initializes the queue to empty.
149 GenericTaskQueue();
151 void initialize();
153 // Push the task "t" on the queue. Returns "false" iff the queue is
154 // full.
155 inline bool push(E t);
157 // If succeeds in claiming a task (from the 'local' end, that is, the
158 // most recently pushed task), returns "true" and sets "t" to that task.
159 // Otherwise, the queue is empty and returns false.
160 inline bool pop_local(E& t);
162 // If succeeds in claiming a task (from the 'global' end, that is, the
163 // least recently pushed task), returns "true" and sets "t" to that task.
164 // Otherwise, the queue is empty and returns false.
165 bool pop_global(E& t);
167 // Delete any resource associated with the queue.
168 ~GenericTaskQueue();
170 // apply the closure to all elements in the task queue
171 void oops_do(OopClosure* f);
173 private:
174 // Element array.
175 volatile E* _elems;
176 };
178 template<class E>
179 GenericTaskQueue<E>::GenericTaskQueue():TaskQueueSuper() {
180 assert(sizeof(Age) == sizeof(size_t), "Depends on this.");
181 }
183 template<class E>
184 void GenericTaskQueue<E>::initialize() {
185 _elems = NEW_C_HEAP_ARRAY(E, N);
186 guarantee(_elems != NULL, "Allocation failed.");
187 }
189 template<class E>
190 void GenericTaskQueue<E>::oops_do(OopClosure* f) {
191 // tty->print_cr("START OopTaskQueue::oops_do");
192 uint iters = size();
193 uint index = _bottom;
194 for (uint i = 0; i < iters; ++i) {
195 index = decrement_index(index);
196 // tty->print_cr(" doing entry %d," INTPTR_T " -> " INTPTR_T,
197 // index, &_elems[index], _elems[index]);
198 E* t = (E*)&_elems[index]; // cast away volatility
199 oop* p = (oop*)t;
200 assert((*t)->is_oop_or_null(), "Not an oop or null");
201 f->do_oop(p);
202 }
203 // tty->print_cr("END OopTaskQueue::oops_do");
204 }
207 template<class E>
208 bool GenericTaskQueue<E>::push_slow(E t, uint dirty_n_elems) {
209 if (dirty_n_elems == N - 1) {
210 // Actually means 0, so do the push.
211 uint localBot = _bottom;
212 _elems[localBot] = t;
213 OrderAccess::release_store(&_bottom, increment_index(localBot));
214 return true;
215 }
216 return false;
217 }
219 template<class E>
220 bool GenericTaskQueue<E>::
221 pop_local_slow(uint localBot, Age oldAge) {
222 // This queue was observed to contain exactly one element; either this
223 // thread will claim it, or a competing "pop_global". In either case,
224 // the queue will be logically empty afterwards. Create a new Age value
225 // that represents the empty queue for the given value of "_bottom". (We
226 // must also increment "tag" because of the case where "bottom == 1",
227 // "top == 0". A pop_global could read the queue element in that case,
228 // then have the owner thread do a pop followed by another push. Without
229 // the incrementing of "tag", the pop_global's CAS could succeed,
230 // allowing it to believe it has claimed the stale element.)
231 Age newAge((idx_t)localBot, oldAge.tag() + 1);
232 // Perhaps a competing pop_global has already incremented "top", in which
233 // case it wins the element.
234 if (localBot == oldAge.top()) {
235 // No competing pop_global has yet incremented "top"; we'll try to
236 // install new_age, thus claiming the element.
237 Age tempAge = _age.cmpxchg(newAge, oldAge);
238 if (tempAge == oldAge) {
239 // We win.
240 assert(dirty_size(localBot, _age.top()) != N - 1, "sanity");
241 return true;
242 }
243 }
244 // We lose; a completing pop_global gets the element. But the queue is empty
245 // and top is greater than bottom. Fix this representation of the empty queue
246 // to become the canonical one.
247 _age.set(newAge);
248 assert(dirty_size(localBot, _age.top()) != N - 1, "sanity");
249 return false;
250 }
252 template<class E>
253 bool GenericTaskQueue<E>::pop_global(E& t) {
254 Age oldAge = _age.get();
255 uint localBot = _bottom;
256 uint n_elems = size(localBot, oldAge.top());
257 if (n_elems == 0) {
258 return false;
259 }
261 t = _elems[oldAge.top()];
262 Age newAge(oldAge);
263 newAge.increment();
264 Age resAge = _age.cmpxchg(newAge, oldAge);
266 // Note that using "_bottom" here might fail, since a pop_local might
267 // have decremented it.
268 assert(dirty_size(localBot, newAge.top()) != N - 1, "sanity");
269 return resAge == oldAge;
270 }
272 template<class E>
273 GenericTaskQueue<E>::~GenericTaskQueue() {
274 FREE_C_HEAP_ARRAY(E, _elems);
275 }
277 // Inherits the typedef of "Task" from above.
278 class TaskQueueSetSuper: public CHeapObj {
279 protected:
280 static int randomParkAndMiller(int* seed0);
281 public:
282 // Returns "true" if some TaskQueue in the set contains a task.
283 virtual bool peek() = 0;
284 };
286 template<class E> class GenericTaskQueueSet: public TaskQueueSetSuper {
287 private:
288 uint _n;
289 GenericTaskQueue<E>** _queues;
291 public:
292 GenericTaskQueueSet(int n) : _n(n) {
293 typedef GenericTaskQueue<E>* GenericTaskQueuePtr;
294 _queues = NEW_C_HEAP_ARRAY(GenericTaskQueuePtr, n);
295 guarantee(_queues != NULL, "Allocation failure.");
296 for (int i = 0; i < n; i++) {
297 _queues[i] = NULL;
298 }
299 }
301 bool steal_1_random(uint queue_num, int* seed, E& t);
302 bool steal_best_of_2(uint queue_num, int* seed, E& t);
303 bool steal_best_of_all(uint queue_num, int* seed, E& t);
305 void register_queue(uint i, GenericTaskQueue<E>* q);
307 GenericTaskQueue<E>* queue(uint n);
309 // The thread with queue number "queue_num" (and whose random number seed
310 // is at "seed") is trying to steal a task from some other queue. (It
311 // may try several queues, according to some configuration parameter.)
312 // If some steal succeeds, returns "true" and sets "t" the stolen task,
313 // otherwise returns false.
314 bool steal(uint queue_num, int* seed, E& t);
316 bool peek();
317 };
319 template<class E>
320 void GenericTaskQueueSet<E>::register_queue(uint i, GenericTaskQueue<E>* q) {
321 assert(i < _n, "index out of range.");
322 _queues[i] = q;
323 }
325 template<class E>
326 GenericTaskQueue<E>* GenericTaskQueueSet<E>::queue(uint i) {
327 return _queues[i];
328 }
330 template<class E>
331 bool GenericTaskQueueSet<E>::steal(uint queue_num, int* seed, E& t) {
332 for (uint i = 0; i < 2 * _n; i++)
333 if (steal_best_of_2(queue_num, seed, t))
334 return true;
335 return false;
336 }
338 template<class E>
339 bool GenericTaskQueueSet<E>::steal_best_of_all(uint queue_num, int* seed, E& t) {
340 if (_n > 2) {
341 int best_k;
342 uint best_sz = 0;
343 for (uint k = 0; k < _n; k++) {
344 if (k == queue_num) continue;
345 uint sz = _queues[k]->size();
346 if (sz > best_sz) {
347 best_sz = sz;
348 best_k = k;
349 }
350 }
351 return best_sz > 0 && _queues[best_k]->pop_global(t);
352 } else if (_n == 2) {
353 // Just try the other one.
354 int k = (queue_num + 1) % 2;
355 return _queues[k]->pop_global(t);
356 } else {
357 assert(_n == 1, "can't be zero.");
358 return false;
359 }
360 }
362 template<class E>
363 bool GenericTaskQueueSet<E>::steal_1_random(uint queue_num, int* seed, E& t) {
364 if (_n > 2) {
365 uint k = queue_num;
366 while (k == queue_num) k = randomParkAndMiller(seed) % _n;
367 return _queues[2]->pop_global(t);
368 } else if (_n == 2) {
369 // Just try the other one.
370 int k = (queue_num + 1) % 2;
371 return _queues[k]->pop_global(t);
372 } else {
373 assert(_n == 1, "can't be zero.");
374 return false;
375 }
376 }
378 template<class E>
379 bool GenericTaskQueueSet<E>::steal_best_of_2(uint queue_num, int* seed, E& t) {
380 if (_n > 2) {
381 uint k1 = queue_num;
382 while (k1 == queue_num) k1 = randomParkAndMiller(seed) % _n;
383 uint k2 = queue_num;
384 while (k2 == queue_num || k2 == k1) k2 = randomParkAndMiller(seed) % _n;
385 // Sample both and try the larger.
386 uint sz1 = _queues[k1]->size();
387 uint sz2 = _queues[k2]->size();
388 if (sz2 > sz1) return _queues[k2]->pop_global(t);
389 else return _queues[k1]->pop_global(t);
390 } else if (_n == 2) {
391 // Just try the other one.
392 uint k = (queue_num + 1) % 2;
393 return _queues[k]->pop_global(t);
394 } else {
395 assert(_n == 1, "can't be zero.");
396 return false;
397 }
398 }
400 template<class E>
401 bool GenericTaskQueueSet<E>::peek() {
402 // Try all the queues.
403 for (uint j = 0; j < _n; j++) {
404 if (_queues[j]->peek())
405 return true;
406 }
407 return false;
408 }
410 // When to terminate from the termination protocol.
411 class TerminatorTerminator: public CHeapObj {
412 public:
413 virtual bool should_exit_termination() = 0;
414 };
416 // A class to aid in the termination of a set of parallel tasks using
417 // TaskQueueSet's for work stealing.
419 #undef TRACESPINNING
421 class ParallelTaskTerminator: public StackObj {
422 private:
423 int _n_threads;
424 TaskQueueSetSuper* _queue_set;
425 int _offered_termination;
427 #ifdef TRACESPINNING
428 static uint _total_yields;
429 static uint _total_spins;
430 static uint _total_peeks;
431 #endif
433 bool peek_in_queue_set();
434 protected:
435 virtual void yield();
436 void sleep(uint millis);
438 public:
440 // "n_threads" is the number of threads to be terminated. "queue_set" is a
441 // queue sets of work queues of other threads.
442 ParallelTaskTerminator(int n_threads, TaskQueueSetSuper* queue_set);
444 // The current thread has no work, and is ready to terminate if everyone
445 // else is. If returns "true", all threads are terminated. If returns
446 // "false", available work has been observed in one of the task queues,
447 // so the global task is not complete.
448 bool offer_termination() {
449 return offer_termination(NULL);
450 }
452 // As above, but it also terminates if the should_exit_termination()
453 // method of the terminator parameter returns true. If terminator is
454 // NULL, then it is ignored.
455 bool offer_termination(TerminatorTerminator* terminator);
457 // Reset the terminator, so that it may be reused again.
458 // The caller is responsible for ensuring that this is done
459 // in an MT-safe manner, once the previous round of use of
460 // the terminator is finished.
461 void reset_for_reuse();
463 #ifdef TRACESPINNING
464 static uint total_yields() { return _total_yields; }
465 static uint total_spins() { return _total_spins; }
466 static uint total_peeks() { return _total_peeks; }
467 static void print_termination_counts();
468 #endif
469 };
471 template<class E> inline bool GenericTaskQueue<E>::push(E t) {
472 uint localBot = _bottom;
473 assert((localBot >= 0) && (localBot < N), "_bottom out of range.");
474 idx_t top = _age.top();
475 uint dirty_n_elems = dirty_size(localBot, top);
476 assert((dirty_n_elems >= 0) && (dirty_n_elems < N), "n_elems out of range.");
477 if (dirty_n_elems < max_elems()) {
478 _elems[localBot] = t;
479 OrderAccess::release_store(&_bottom, increment_index(localBot));
480 return true;
481 } else {
482 return push_slow(t, dirty_n_elems);
483 }
484 }
486 template<class E> inline bool GenericTaskQueue<E>::pop_local(E& t) {
487 uint localBot = _bottom;
488 // This value cannot be N-1. That can only occur as a result of
489 // the assignment to bottom in this method. If it does, this method
490 // resets the size( to 0 before the next call (which is sequential,
491 // since this is pop_local.)
492 uint dirty_n_elems = dirty_size(localBot, _age.top());
493 assert(dirty_n_elems != N - 1, "Shouldn't be possible...");
494 if (dirty_n_elems == 0) return false;
495 localBot = decrement_index(localBot);
496 _bottom = localBot;
497 // This is necessary to prevent any read below from being reordered
498 // before the store just above.
499 OrderAccess::fence();
500 t = _elems[localBot];
501 // This is a second read of "age"; the "size()" above is the first.
502 // If there's still at least one element in the queue, based on the
503 // "_bottom" and "age" we've read, then there can be no interference with
504 // a "pop_global" operation, and we're done.
505 idx_t tp = _age.top(); // XXX
506 if (size(localBot, tp) > 0) {
507 assert(dirty_size(localBot, tp) != N - 1, "sanity");
508 return true;
509 } else {
510 // Otherwise, the queue contained exactly one element; we take the slow
511 // path.
512 return pop_local_slow(localBot, _age.get());
513 }
514 }
516 typedef oop Task;
517 typedef GenericTaskQueue<Task> OopTaskQueue;
518 typedef GenericTaskQueueSet<Task> OopTaskQueueSet;
521 #define COMPRESSED_OOP_MASK 1
523 // This is a container class for either an oop* or a narrowOop*.
524 // Both are pushed onto a task queue and the consumer will test is_narrow()
525 // to determine which should be processed.
526 class StarTask {
527 void* _holder; // either union oop* or narrowOop*
528 public:
529 StarTask(narrowOop* p) {
530 assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!");
531 _holder = (void *)((uintptr_t)p | COMPRESSED_OOP_MASK);
532 }
533 StarTask(oop* p) {
534 assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!");
535 _holder = (void*)p;
536 }
537 StarTask() { _holder = NULL; }
538 operator oop*() { return (oop*)_holder; }
539 operator narrowOop*() {
540 return (narrowOop*)((uintptr_t)_holder & ~COMPRESSED_OOP_MASK);
541 }
543 // Operators to preserve const/volatile in assignments required by gcc
544 void operator=(const volatile StarTask& t) volatile { _holder = t._holder; }
546 bool is_narrow() const {
547 return (((uintptr_t)_holder & COMPRESSED_OOP_MASK) != 0);
548 }
549 };
551 typedef GenericTaskQueue<StarTask> OopStarTaskQueue;
552 typedef GenericTaskQueueSet<StarTask> OopStarTaskQueueSet;
554 typedef size_t RegionTask; // index for region
555 typedef GenericTaskQueue<RegionTask> RegionTaskQueue;
556 typedef GenericTaskQueueSet<RegionTask> RegionTaskQueueSet;
558 class RegionTaskQueueWithOverflow: public CHeapObj {
559 protected:
560 RegionTaskQueue _region_queue;
561 GrowableArray<RegionTask>* _overflow_stack;
563 public:
564 RegionTaskQueueWithOverflow() : _overflow_stack(NULL) {}
565 // Initialize both stealable queue and overflow
566 void initialize();
567 // Save first to stealable queue and then to overflow
568 void save(RegionTask t);
569 // Retrieve first from overflow and then from stealable queue
570 bool retrieve(RegionTask& region_index);
571 // Retrieve from stealable queue
572 bool retrieve_from_stealable_queue(RegionTask& region_index);
573 // Retrieve from overflow
574 bool retrieve_from_overflow(RegionTask& region_index);
575 bool is_empty();
576 bool stealable_is_empty();
577 bool overflow_is_empty();
578 uint stealable_size() { return _region_queue.size(); }
579 RegionTaskQueue* task_queue() { return &_region_queue; }
580 };
582 #define USE_RegionTaskQueueWithOverflow