Mercurial > hg > graal-jvmci-8
diff src/share/vm/utilities/taskqueue.hpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
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children | ba764ed4b6f2 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/utilities/taskqueue.hpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,525 @@ +/* + * Copyright 2001-2006 Sun Microsystems, Inc. All Rights Reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +class TaskQueueSuper: public CHeapObj { +protected: + // The first free element after the last one pushed (mod _n). + // (For now we'll assume only 32-bit CAS). + volatile juint _bottom; + + // log2 of the size of the queue. + enum SomeProtectedConstants { + Log_n = 14 + }; + + // Size of the queue. + juint n() { return (1 << Log_n); } + // For computing "x mod n" efficiently. + juint n_mod_mask() { return n() - 1; } + + struct Age { + jushort _top; + jushort _tag; + + jushort tag() const { return _tag; } + jushort top() const { return _top; } + + Age() { _tag = 0; _top = 0; } + + friend bool operator ==(const Age& a1, const Age& a2) { + return a1.tag() == a2.tag() && a1.top() == a2.top(); + } + + }; + Age _age; + // These make sure we do single atomic reads and writes. + Age get_age() { + jint res = *(volatile jint*)(&_age); + return *(Age*)(&res); + } + void set_age(Age a) { + *(volatile jint*)(&_age) = *(int*)(&a); + } + + jushort get_top() { + return get_age().top(); + } + + // These both operate mod _n. + juint increment_index(juint ind) { + return (ind + 1) & n_mod_mask(); + } + juint decrement_index(juint ind) { + return (ind - 1) & n_mod_mask(); + } + + // Returns a number in the range [0.._n). If the result is "n-1", it + // should be interpreted as 0. + juint dirty_size(juint bot, juint top) { + return ((jint)bot - (jint)top) & n_mod_mask(); + } + + // Returns the size corresponding to the given "bot" and "top". + juint size(juint bot, juint top) { + juint sz = dirty_size(bot, top); + // Has the queue "wrapped", so that bottom is less than top? + // There's a complicated special case here. A pair of threads could + // perform pop_local and pop_global operations concurrently, starting + // from a state in which _bottom == _top+1. The pop_local could + // succeed in decrementing _bottom, and the pop_global in incrementing + // _top (in which case the pop_global will be awarded the contested + // queue element.) The resulting state must be interpreted as an empty + // queue. (We only need to worry about one such event: only the queue + // owner performs pop_local's, and several concurrent threads + // attempting to perform the pop_global will all perform the same CAS, + // and only one can succeed. Any stealing thread that reads after + // either the increment or decrement will seen an empty queue, and will + // not join the competitors. The "sz == -1 || sz == _n-1" state will + // not be modified by concurrent queues, so the owner thread can reset + // the state to _bottom == top so subsequent pushes will be performed + // normally. + if (sz == (n()-1)) return 0; + else return sz; + } + +public: + TaskQueueSuper() : _bottom(0), _age() {} + + // Return "true" if the TaskQueue contains any tasks. + bool peek(); + + // Return an estimate of the number of elements in the queue. + // The "careful" version admits the possibility of pop_local/pop_global + // races. + juint size() { + return size(_bottom, get_top()); + } + + juint dirty_size() { + return dirty_size(_bottom, get_top()); + } + + // Maximum number of elements allowed in the queue. This is two less + // than the actual queue size, for somewhat complicated reasons. + juint max_elems() { return n() - 2; } + +}; + +template<class E> class GenericTaskQueue: public TaskQueueSuper { +private: + // Slow paths for push, pop_local. (pop_global has no fast path.) + bool push_slow(E t, juint dirty_n_elems); + bool pop_local_slow(juint localBot, Age oldAge); + +public: + // Initializes the queue to empty. + GenericTaskQueue(); + + void initialize(); + + // Push the task "t" on the queue. Returns "false" iff the queue is + // full. + inline bool push(E t); + + // If succeeds in claiming a task (from the 'local' end, that is, the + // most recently pushed task), returns "true" and sets "t" to that task. + // Otherwise, the queue is empty and returns false. + inline bool pop_local(E& t); + + // If succeeds in claiming a task (from the 'global' end, that is, the + // least recently pushed task), returns "true" and sets "t" to that task. + // Otherwise, the queue is empty and returns false. + bool pop_global(E& t); + + // Delete any resource associated with the queue. + ~GenericTaskQueue(); + +private: + // Element array. + volatile E* _elems; +}; + +template<class E> +GenericTaskQueue<E>::GenericTaskQueue():TaskQueueSuper() { + assert(sizeof(Age) == sizeof(jint), "Depends on this."); +} + +template<class E> +void GenericTaskQueue<E>::initialize() { + _elems = NEW_C_HEAP_ARRAY(E, n()); + guarantee(_elems != NULL, "Allocation failed."); +} + +template<class E> +bool GenericTaskQueue<E>::push_slow(E t, juint dirty_n_elems) { + if (dirty_n_elems == n() - 1) { + // Actually means 0, so do the push. + juint localBot = _bottom; + _elems[localBot] = t; + _bottom = increment_index(localBot); + return true; + } else + return false; +} + +template<class E> +bool GenericTaskQueue<E>:: +pop_local_slow(juint localBot, Age oldAge) { + // This queue was observed to contain exactly one element; either this + // thread will claim it, or a competing "pop_global". In either case, + // the queue will be logically empty afterwards. Create a new Age value + // that represents the empty queue for the given value of "_bottom". (We + // must also increment "tag" because of the case where "bottom == 1", + // "top == 0". A pop_global could read the queue element in that case, + // then have the owner thread do a pop followed by another push. Without + // the incrementing of "tag", the pop_global's CAS could succeed, + // allowing it to believe it has claimed the stale element.) + Age newAge; + newAge._top = localBot; + newAge._tag = oldAge.tag() + 1; + // Perhaps a competing pop_global has already incremented "top", in which + // case it wins the element. + if (localBot == oldAge.top()) { + Age tempAge; + // No competing pop_global has yet incremented "top"; we'll try to + // install new_age, thus claiming the element. + assert(sizeof(Age) == sizeof(jint) && sizeof(jint) == sizeof(juint), + "Assumption about CAS unit."); + *(jint*)&tempAge = Atomic::cmpxchg(*(jint*)&newAge, (volatile jint*)&_age, *(jint*)&oldAge); + if (tempAge == oldAge) { + // We win. + assert(dirty_size(localBot, get_top()) != n() - 1, + "Shouldn't be possible..."); + return true; + } + } + // We fail; a completing pop_global gets the element. But the queue is + // empty (and top is greater than bottom.) Fix this representation of + // the empty queue to become the canonical one. + set_age(newAge); + assert(dirty_size(localBot, get_top()) != n() - 1, + "Shouldn't be possible..."); + return false; +} + +template<class E> +bool GenericTaskQueue<E>::pop_global(E& t) { + Age newAge; + Age oldAge = get_age(); + juint localBot = _bottom; + juint n_elems = size(localBot, oldAge.top()); + if (n_elems == 0) { + return false; + } + t = _elems[oldAge.top()]; + newAge = oldAge; + newAge._top = increment_index(newAge.top()); + if ( newAge._top == 0 ) newAge._tag++; + Age resAge; + *(jint*)&resAge = Atomic::cmpxchg(*(jint*)&newAge, (volatile jint*)&_age, *(jint*)&oldAge); + // Note that using "_bottom" here might fail, since a pop_local might + // have decremented it. + assert(dirty_size(localBot, newAge._top) != n() - 1, + "Shouldn't be possible..."); + return (resAge == oldAge); +} + +template<class E> +GenericTaskQueue<E>::~GenericTaskQueue() { + FREE_C_HEAP_ARRAY(E, _elems); +} + +// Inherits the typedef of "Task" from above. +class TaskQueueSetSuper: public CHeapObj { +protected: + static int randomParkAndMiller(int* seed0); +public: + // Returns "true" if some TaskQueue in the set contains a task. + virtual bool peek() = 0; +}; + +template<class E> class GenericTaskQueueSet: public TaskQueueSetSuper { +private: + int _n; + GenericTaskQueue<E>** _queues; + +public: + GenericTaskQueueSet(int n) : _n(n) { + typedef GenericTaskQueue<E>* GenericTaskQueuePtr; + _queues = NEW_C_HEAP_ARRAY(GenericTaskQueuePtr, n); + guarantee(_queues != NULL, "Allocation failure."); + for (int i = 0; i < n; i++) { + _queues[i] = NULL; + } + } + + bool steal_1_random(int queue_num, int* seed, E& t); + bool steal_best_of_2(int queue_num, int* seed, E& t); + bool steal_best_of_all(int queue_num, int* seed, E& t); + + void register_queue(int i, GenericTaskQueue<E>* q); + + GenericTaskQueue<E>* queue(int n); + + // The thread with queue number "queue_num" (and whose random number seed + // is at "seed") is trying to steal a task from some other queue. (It + // may try several queues, according to some configuration parameter.) + // If some steal succeeds, returns "true" and sets "t" the stolen task, + // otherwise returns false. + bool steal(int queue_num, int* seed, E& t); + + bool peek(); +}; + +template<class E> +void GenericTaskQueueSet<E>::register_queue(int i, GenericTaskQueue<E>* q) { + assert(0 <= i && i < _n, "index out of range."); + _queues[i] = q; +} + +template<class E> +GenericTaskQueue<E>* GenericTaskQueueSet<E>::queue(int i) { + return _queues[i]; +} + +template<class E> +bool GenericTaskQueueSet<E>::steal(int queue_num, int* seed, E& t) { + for (int i = 0; i < 2 * _n; i++) + if (steal_best_of_2(queue_num, seed, t)) + return true; + return false; +} + +template<class E> +bool GenericTaskQueueSet<E>::steal_best_of_all(int queue_num, int* seed, E& t) { + if (_n > 2) { + int best_k; + jint best_sz = 0; + for (int k = 0; k < _n; k++) { + if (k == queue_num) continue; + jint sz = _queues[k]->size(); + if (sz > best_sz) { + best_sz = sz; + best_k = k; + } + } + return best_sz > 0 && _queues[best_k]->pop_global(t); + } else if (_n == 2) { + // Just try the other one. + int k = (queue_num + 1) % 2; + return _queues[k]->pop_global(t); + } else { + assert(_n == 1, "can't be zero."); + return false; + } +} + +template<class E> +bool GenericTaskQueueSet<E>::steal_1_random(int queue_num, int* seed, E& t) { + if (_n > 2) { + int k = queue_num; + while (k == queue_num) k = randomParkAndMiller(seed) % _n; + return _queues[2]->pop_global(t); + } else if (_n == 2) { + // Just try the other one. + int k = (queue_num + 1) % 2; + return _queues[k]->pop_global(t); + } else { + assert(_n == 1, "can't be zero."); + return false; + } +} + +template<class E> +bool GenericTaskQueueSet<E>::steal_best_of_2(int queue_num, int* seed, E& t) { + if (_n > 2) { + int k1 = queue_num; + while (k1 == queue_num) k1 = randomParkAndMiller(seed) % _n; + int k2 = queue_num; + while (k2 == queue_num || k2 == k1) k2 = randomParkAndMiller(seed) % _n; + // Sample both and try the larger. + juint sz1 = _queues[k1]->size(); + juint sz2 = _queues[k2]->size(); + if (sz2 > sz1) return _queues[k2]->pop_global(t); + else return _queues[k1]->pop_global(t); + } else if (_n == 2) { + // Just try the other one. + int k = (queue_num + 1) % 2; + return _queues[k]->pop_global(t); + } else { + assert(_n == 1, "can't be zero."); + return false; + } +} + +template<class E> +bool GenericTaskQueueSet<E>::peek() { + // Try all the queues. + for (int j = 0; j < _n; j++) { + if (_queues[j]->peek()) + return true; + } + return false; +} + +// A class to aid in the termination of a set of parallel tasks using +// TaskQueueSet's for work stealing. + +class ParallelTaskTerminator: public StackObj { +private: + int _n_threads; + TaskQueueSetSuper* _queue_set; + jint _offered_termination; + + bool peek_in_queue_set(); +protected: + virtual void yield(); + void sleep(uint millis); + +public: + + // "n_threads" is the number of threads to be terminated. "queue_set" is a + // queue sets of work queues of other threads. + ParallelTaskTerminator(int n_threads, TaskQueueSetSuper* queue_set); + + // The current thread has no work, and is ready to terminate if everyone + // else is. If returns "true", all threads are terminated. If returns + // "false", available work has been observed in one of the task queues, + // so the global task is not complete. + bool offer_termination(); + + // Reset the terminator, so that it may be reused again. + // The caller is responsible for ensuring that this is done + // in an MT-safe manner, once the previous round of use of + // the terminator is finished. + void reset_for_reuse(); + +}; + +#define SIMPLE_STACK 0 + +template<class E> inline bool GenericTaskQueue<E>::push(E t) { +#if SIMPLE_STACK + juint localBot = _bottom; + if (_bottom < max_elems()) { + _elems[localBot] = t; + _bottom = localBot + 1; + return true; + } else { + return false; + } +#else + juint localBot = _bottom; + assert((localBot >= 0) && (localBot < n()), "_bottom out of range."); + jushort top = get_top(); + juint dirty_n_elems = dirty_size(localBot, top); + assert((dirty_n_elems >= 0) && (dirty_n_elems < n()), + "n_elems out of range."); + if (dirty_n_elems < max_elems()) { + _elems[localBot] = t; + _bottom = increment_index(localBot); + return true; + } else { + return push_slow(t, dirty_n_elems); + } +#endif +} + +template<class E> inline bool GenericTaskQueue<E>::pop_local(E& t) { +#if SIMPLE_STACK + juint localBot = _bottom; + assert(localBot > 0, "precondition."); + localBot--; + t = _elems[localBot]; + _bottom = localBot; + return true; +#else + juint localBot = _bottom; + // This value cannot be n-1. That can only occur as a result of + // the assignment to bottom in this method. If it does, this method + // resets the size( to 0 before the next call (which is sequential, + // since this is pop_local.) + juint dirty_n_elems = dirty_size(localBot, get_top()); + assert(dirty_n_elems != n() - 1, "Shouldn't be possible..."); + if (dirty_n_elems == 0) return false; + localBot = decrement_index(localBot); + _bottom = localBot; + // This is necessary to prevent any read below from being reordered + // before the store just above. + OrderAccess::fence(); + t = _elems[localBot]; + // This is a second read of "age"; the "size()" above is the first. + // If there's still at least one element in the queue, based on the + // "_bottom" and "age" we've read, then there can be no interference with + // a "pop_global" operation, and we're done. + juint tp = get_top(); + if (size(localBot, tp) > 0) { + assert(dirty_size(localBot, tp) != n() - 1, + "Shouldn't be possible..."); + return true; + } else { + // Otherwise, the queue contained exactly one element; we take the slow + // path. + return pop_local_slow(localBot, get_age()); + } +#endif +} + +typedef oop Task; +typedef GenericTaskQueue<Task> OopTaskQueue; +typedef GenericTaskQueueSet<Task> OopTaskQueueSet; + +typedef oop* StarTask; +typedef GenericTaskQueue<StarTask> OopStarTaskQueue; +typedef GenericTaskQueueSet<StarTask> OopStarTaskQueueSet; + +typedef size_t ChunkTask; // index for chunk +typedef GenericTaskQueue<ChunkTask> ChunkTaskQueue; +typedef GenericTaskQueueSet<ChunkTask> ChunkTaskQueueSet; + +class ChunkTaskQueueWithOverflow: public CHeapObj { + protected: + ChunkTaskQueue _chunk_queue; + GrowableArray<ChunkTask>* _overflow_stack; + + public: + ChunkTaskQueueWithOverflow() : _overflow_stack(NULL) {} + // Initialize both stealable queue and overflow + void initialize(); + // Save first to stealable queue and then to overflow + void save(ChunkTask t); + // Retrieve first from overflow and then from stealable queue + bool retrieve(ChunkTask& chunk_index); + // Retrieve from stealable queue + bool retrieve_from_stealable_queue(ChunkTask& chunk_index); + // Retrieve from overflow + bool retrieve_from_overflow(ChunkTask& chunk_index); + bool is_empty(); + bool stealable_is_empty(); + bool overflow_is_empty(); + juint stealable_size() { return _chunk_queue.size(); } + ChunkTaskQueue* task_queue() { return &_chunk_queue; } +}; + +#define USE_ChunkTaskQueueWithOverflow