Mercurial > hg > graal-compiler
view src/share/vm/utilities/taskqueue.hpp @ 1141:b1f619d38249
6914002: unsigned compare problem after 5057818
Reviewed-by: kvn, twisti
author | never |
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date | Tue, 05 Jan 2010 16:12:26 -0800 |
parents | 1ee412f7fec9 |
children | 5f1f51edaff6 |
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/* * Copyright 2001-2009 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: // Internal type for indexing the queue; also used for the tag. typedef NOT_LP64(uint16_t) LP64_ONLY(uint32_t) idx_t; // The first free element after the last one pushed (mod N). volatile uint _bottom; enum { N = 1 << NOT_LP64(14) LP64_ONLY(17), // Queue size: 16K or 128K MOD_N_MASK = N - 1 // To compute x mod N efficiently. }; class Age { public: Age(size_t data = 0) { _data = data; } Age(const Age& age) { _data = age._data; } Age(idx_t top, idx_t tag) { _fields._top = top; _fields._tag = tag; } Age get() const volatile { return _data; } void set(Age age) volatile { _data = age._data; } idx_t top() const volatile { return _fields._top; } idx_t tag() const volatile { return _fields._tag; } // Increment top; if it wraps, increment tag also. void increment() { _fields._top = increment_index(_fields._top); if (_fields._top == 0) ++_fields._tag; } Age cmpxchg(const Age new_age, const Age old_age) volatile { return (size_t) Atomic::cmpxchg_ptr((intptr_t)new_age._data, (volatile intptr_t *)&_data, (intptr_t)old_age._data); } bool operator ==(const Age& other) const { return _data == other._data; } private: struct fields { idx_t _top; idx_t _tag; }; union { size_t _data; fields _fields; }; }; volatile Age _age; // These both operate mod N. static uint increment_index(uint ind) { return (ind + 1) & MOD_N_MASK; } static uint decrement_index(uint ind) { return (ind - 1) & MOD_N_MASK; } // Returns a number in the range [0..N). If the result is "N-1", it should be // interpreted as 0. uint dirty_size(uint bot, uint top) { return (bot - top) & MOD_N_MASK; } // Returns the size corresponding to the given "bot" and "top". uint size(uint bot, uint top) { uint 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 see 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. return (sz == N - 1) ? 0 : 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. uint size() { return size(_bottom, _age.top()); } uint dirty_size() { return dirty_size(_bottom, _age.top()); } void set_empty() { _bottom = 0; _age.set(0); } // Maximum number of elements allowed in the queue. This is two less // than the actual queue size, for somewhat complicated reasons. uint 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, uint dirty_n_elems); bool pop_local_slow(uint 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(); // apply the closure to all elements in the task queue void oops_do(OopClosure* f); private: // Element array. volatile E* _elems; }; template<class E> GenericTaskQueue<E>::GenericTaskQueue():TaskQueueSuper() { assert(sizeof(Age) == sizeof(size_t), "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> void GenericTaskQueue<E>::oops_do(OopClosure* f) { // tty->print_cr("START OopTaskQueue::oops_do"); uint iters = size(); uint index = _bottom; for (uint i = 0; i < iters; ++i) { index = decrement_index(index); // tty->print_cr(" doing entry %d," INTPTR_T " -> " INTPTR_T, // index, &_elems[index], _elems[index]); E* t = (E*)&_elems[index]; // cast away volatility oop* p = (oop*)t; assert((*t)->is_oop_or_null(), "Not an oop or null"); f->do_oop(p); } // tty->print_cr("END OopTaskQueue::oops_do"); } template<class E> bool GenericTaskQueue<E>::push_slow(E t, uint dirty_n_elems) { if (dirty_n_elems == N - 1) { // Actually means 0, so do the push. uint localBot = _bottom; _elems[localBot] = t; OrderAccess::release_store(&_bottom, increment_index(localBot)); return true; } return false; } template<class E> bool GenericTaskQueue<E>:: pop_local_slow(uint 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((idx_t)localBot, oldAge.tag() + 1); // Perhaps a competing pop_global has already incremented "top", in which // case it wins the element. if (localBot == oldAge.top()) { // No competing pop_global has yet incremented "top"; we'll try to // install new_age, thus claiming the element. Age tempAge = _age.cmpxchg(newAge, oldAge); if (tempAge == oldAge) { // We win. assert(dirty_size(localBot, _age.top()) != N - 1, "sanity"); return true; } } // We lose; 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. _age.set(newAge); assert(dirty_size(localBot, _age.top()) != N - 1, "sanity"); return false; } template<class E> bool GenericTaskQueue<E>::pop_global(E& t) { Age oldAge = _age.get(); uint localBot = _bottom; uint n_elems = size(localBot, oldAge.top()); if (n_elems == 0) { return false; } t = _elems[oldAge.top()]; Age newAge(oldAge); newAge.increment(); Age resAge = _age.cmpxchg(newAge, oldAge); // Note that using "_bottom" here might fail, since a pop_local might // have decremented it. assert(dirty_size(localBot, newAge.top()) != N - 1, "sanity"); 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: uint _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(uint queue_num, int* seed, E& t); bool steal_best_of_2(uint queue_num, int* seed, E& t); bool steal_best_of_all(uint queue_num, int* seed, E& t); void register_queue(uint i, GenericTaskQueue<E>* q); GenericTaskQueue<E>* queue(uint 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(uint queue_num, int* seed, E& t); bool peek(); }; template<class E> void GenericTaskQueueSet<E>::register_queue(uint i, GenericTaskQueue<E>* q) { assert(i < _n, "index out of range."); _queues[i] = q; } template<class E> GenericTaskQueue<E>* GenericTaskQueueSet<E>::queue(uint i) { return _queues[i]; } template<class E> bool GenericTaskQueueSet<E>::steal(uint queue_num, int* seed, E& t) { for (uint 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(uint queue_num, int* seed, E& t) { if (_n > 2) { int best_k; uint best_sz = 0; for (uint k = 0; k < _n; k++) { if (k == queue_num) continue; uint 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(uint queue_num, int* seed, E& t) { if (_n > 2) { uint 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(uint queue_num, int* seed, E& t) { if (_n > 2) { uint k1 = queue_num; while (k1 == queue_num) k1 = randomParkAndMiller(seed) % _n; uint k2 = queue_num; while (k2 == queue_num || k2 == k1) k2 = randomParkAndMiller(seed) % _n; // Sample both and try the larger. uint sz1 = _queues[k1]->size(); uint 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. uint 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 (uint j = 0; j < _n; j++) { if (_queues[j]->peek()) return true; } return false; } // When to terminate from the termination protocol. class TerminatorTerminator: public CHeapObj { public: virtual bool should_exit_termination() = 0; }; // A class to aid in the termination of a set of parallel tasks using // TaskQueueSet's for work stealing. #undef TRACESPINNING class ParallelTaskTerminator: public StackObj { private: int _n_threads; TaskQueueSetSuper* _queue_set; int _offered_termination; #ifdef TRACESPINNING static uint _total_yields; static uint _total_spins; static uint _total_peeks; #endif 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() { return offer_termination(NULL); } // As above, but it also terminates if the should_exit_termination() // method of the terminator parameter returns true. If terminator is // NULL, then it is ignored. bool offer_termination(TerminatorTerminator* terminator); // 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(); #ifdef TRACESPINNING static uint total_yields() { return _total_yields; } static uint total_spins() { return _total_spins; } static uint total_peeks() { return _total_peeks; } static void print_termination_counts(); #endif }; template<class E> inline bool GenericTaskQueue<E>::push(E t) { uint localBot = _bottom; assert((localBot >= 0) && (localBot < N), "_bottom out of range."); idx_t top = _age.top(); uint 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; OrderAccess::release_store(&_bottom, increment_index(localBot)); return true; } else { return push_slow(t, dirty_n_elems); } } template<class E> inline bool GenericTaskQueue<E>::pop_local(E& t) { uint 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.) uint dirty_n_elems = dirty_size(localBot, _age.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. idx_t tp = _age.top(); // XXX if (size(localBot, tp) > 0) { assert(dirty_size(localBot, tp) != N - 1, "sanity"); return true; } else { // Otherwise, the queue contained exactly one element; we take the slow // path. return pop_local_slow(localBot, _age.get()); } } typedef oop Task; typedef GenericTaskQueue<Task> OopTaskQueue; typedef GenericTaskQueueSet<Task> OopTaskQueueSet; #define COMPRESSED_OOP_MASK 1 // This is a container class for either an oop* or a narrowOop*. // Both are pushed onto a task queue and the consumer will test is_narrow() // to determine which should be processed. class StarTask { void* _holder; // either union oop* or narrowOop* public: StarTask(narrowOop* p) { assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!"); _holder = (void *)((uintptr_t)p | COMPRESSED_OOP_MASK); } StarTask(oop* p) { assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!"); _holder = (void*)p; } StarTask() { _holder = NULL; } operator oop*() { return (oop*)_holder; } operator narrowOop*() { return (narrowOop*)((uintptr_t)_holder & ~COMPRESSED_OOP_MASK); } // Operators to preserve const/volatile in assignments required by gcc void operator=(const volatile StarTask& t) volatile { _holder = t._holder; } bool is_narrow() const { return (((uintptr_t)_holder & COMPRESSED_OOP_MASK) != 0); } }; typedef GenericTaskQueue<StarTask> OopStarTaskQueue; typedef GenericTaskQueueSet<StarTask> OopStarTaskQueueSet; typedef size_t RegionTask; // index for region typedef GenericTaskQueue<RegionTask> RegionTaskQueue; typedef GenericTaskQueueSet<RegionTask> RegionTaskQueueSet; class RegionTaskQueueWithOverflow: public CHeapObj { protected: RegionTaskQueue _region_queue; GrowableArray<RegionTask>* _overflow_stack; public: RegionTaskQueueWithOverflow() : _overflow_stack(NULL) {} // Initialize both stealable queue and overflow void initialize(); // Save first to stealable queue and then to overflow void save(RegionTask t); // Retrieve first from overflow and then from stealable queue bool retrieve(RegionTask& region_index); // Retrieve from stealable queue bool retrieve_from_stealable_queue(RegionTask& region_index); // Retrieve from overflow bool retrieve_from_overflow(RegionTask& region_index); bool is_empty(); bool stealable_is_empty(); bool overflow_is_empty(); uint stealable_size() { return _region_queue.size(); } RegionTaskQueue* task_queue() { return &_region_queue; } }; #define USE_RegionTaskQueueWithOverflow