duke@435: /*
xdono@1014:  * Copyright 2001-2009 Sun Microsystems, Inc.  All Rights Reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
duke@435:  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435:  * CA 95054 USA or visit www.sun.com if you need additional information or
duke@435:  * have any questions.
duke@435:  *
duke@435:  */
duke@435: 
ysr@976: #ifdef LP64
ysr@976: typedef juint TAG_TYPE;
ysr@976: // for a taskqueue size of 4M
ysr@976: #define LOG_TASKQ_SIZE 22
ysr@976: #else
ysr@976: typedef jushort TAG_TYPE;
ysr@976: // for a taskqueue size of 16K
ysr@976: #define LOG_TASKQ_SIZE 14
ysr@976: #endif
ysr@976: 
duke@435: class TaskQueueSuper: public CHeapObj {
duke@435: protected:
duke@435:   // The first free element after the last one pushed (mod _n).
ysr@976:   volatile uint _bottom;
duke@435: 
duke@435:   // log2 of the size of the queue.
duke@435:   enum SomeProtectedConstants {
ysr@976:     Log_n = LOG_TASKQ_SIZE
duke@435:   };
ysr@976: #undef LOG_TASKQ_SIZE
duke@435: 
duke@435:   // Size of the queue.
ysr@976:   uint n() { return (1 << Log_n); }
duke@435:   // For computing "x mod n" efficiently.
ysr@976:   uint n_mod_mask() { return n() - 1; }
duke@435: 
duke@435:   struct Age {
ysr@976:     TAG_TYPE _top;
ysr@976:     TAG_TYPE _tag;
duke@435: 
ysr@976:     TAG_TYPE tag() const { return _tag; }
ysr@976:     TAG_TYPE top() const { return _top; }
duke@435: 
duke@435:     Age() { _tag = 0; _top = 0; }
duke@435: 
duke@435:     friend bool operator ==(const Age& a1, const Age& a2) {
duke@435:       return a1.tag() == a2.tag() && a1.top() == a2.top();
duke@435:     }
duke@435:   };
duke@435:   Age _age;
duke@435:   // These make sure we do single atomic reads and writes.
duke@435:   Age get_age() {
ysr@976:     uint res = *(volatile uint*)(&_age);
duke@435:     return *(Age*)(&res);
duke@435:   }
duke@435:   void set_age(Age a) {
ysr@976:     *(volatile uint*)(&_age) = *(uint*)(&a);
duke@435:   }
duke@435: 
ysr@976:   TAG_TYPE get_top() {
duke@435:     return get_age().top();
duke@435:   }
duke@435: 
duke@435:   // These both operate mod _n.
ysr@976:   uint increment_index(uint ind) {
duke@435:     return (ind + 1) & n_mod_mask();
duke@435:   }
ysr@976:   uint decrement_index(uint ind) {
duke@435:     return (ind - 1) & n_mod_mask();
duke@435:   }
duke@435: 
duke@435:   // Returns a number in the range [0.._n).  If the result is "n-1", it
duke@435:   // should be interpreted as 0.
ysr@976:   uint dirty_size(uint bot, uint top) {
ysr@976:     return ((int)bot - (int)top) & n_mod_mask();
duke@435:   }
duke@435: 
duke@435:   // Returns the size corresponding to the given "bot" and "top".
ysr@976:   uint size(uint bot, uint top) {
ysr@976:     uint sz = dirty_size(bot, top);
duke@435:     // Has the queue "wrapped", so that bottom is less than top?
duke@435:     // There's a complicated special case here.  A pair of threads could
duke@435:     // perform pop_local and pop_global operations concurrently, starting
duke@435:     // from a state in which _bottom == _top+1.  The pop_local could
duke@435:     // succeed in decrementing _bottom, and the pop_global in incrementing
duke@435:     // _top (in which case the pop_global will be awarded the contested
duke@435:     // queue element.)  The resulting state must be interpreted as an empty
duke@435:     // queue.  (We only need to worry about one such event: only the queue
duke@435:     // owner performs pop_local's, and several concurrent threads
duke@435:     // attempting to perform the pop_global will all perform the same CAS,
duke@435:     // and only one can succeed.  Any stealing thread that reads after
ysr@976:     // either the increment or decrement will see an empty queue, and will
duke@435:     // not join the competitors.  The "sz == -1 || sz == _n-1" state will
duke@435:     // not be modified  by concurrent queues, so the owner thread can reset
duke@435:     // the state to _bottom == top so subsequent pushes will be performed
duke@435:     // normally.
duke@435:     if (sz == (n()-1)) return 0;
duke@435:     else return sz;
duke@435:   }
duke@435: 
duke@435: public:
duke@435:   TaskQueueSuper() : _bottom(0), _age() {}
duke@435: 
duke@435:   // Return "true" if the TaskQueue contains any tasks.
duke@435:   bool peek();
duke@435: 
duke@435:   // Return an estimate of the number of elements in the queue.
duke@435:   // The "careful" version admits the possibility of pop_local/pop_global
duke@435:   // races.
ysr@976:   uint size() {
duke@435:     return size(_bottom, get_top());
duke@435:   }
duke@435: 
ysr@976:   uint dirty_size() {
duke@435:     return dirty_size(_bottom, get_top());
duke@435:   }
duke@435: 
ysr@777:   void set_empty() {
ysr@777:     _bottom = 0;
ysr@777:     _age = Age();
ysr@777:   }
ysr@777: 
duke@435:   // Maximum number of elements allowed in the queue.  This is two less
duke@435:   // than the actual queue size, for somewhat complicated reasons.
ysr@976:   uint max_elems() { return n() - 2; }
duke@435: 
duke@435: };
duke@435: 
duke@435: template<class E> class GenericTaskQueue: public TaskQueueSuper {
duke@435: private:
duke@435:   // Slow paths for push, pop_local.  (pop_global has no fast path.)
ysr@976:   bool push_slow(E t, uint dirty_n_elems);
ysr@976:   bool pop_local_slow(uint localBot, Age oldAge);
duke@435: 
duke@435: public:
duke@435:   // Initializes the queue to empty.
duke@435:   GenericTaskQueue();
duke@435: 
duke@435:   void initialize();
duke@435: 
duke@435:   // Push the task "t" on the queue.  Returns "false" iff the queue is
duke@435:   // full.
duke@435:   inline bool push(E t);
duke@435: 
duke@435:   // If succeeds in claiming a task (from the 'local' end, that is, the
duke@435:   // most recently pushed task), returns "true" and sets "t" to that task.
duke@435:   // Otherwise, the queue is empty and returns false.
duke@435:   inline bool pop_local(E& t);
duke@435: 
duke@435:   // If succeeds in claiming a task (from the 'global' end, that is, the
duke@435:   // least recently pushed task), returns "true" and sets "t" to that task.
duke@435:   // Otherwise, the queue is empty and returns false.
duke@435:   bool pop_global(E& t);
duke@435: 
duke@435:   // Delete any resource associated with the queue.
duke@435:   ~GenericTaskQueue();
duke@435: 
ysr@777:   // apply the closure to all elements in the task queue
ysr@777:   void oops_do(OopClosure* f);
ysr@777: 
duke@435: private:
duke@435:   // Element array.
duke@435:   volatile E* _elems;
duke@435: };
duke@435: 
duke@435: template<class E>
duke@435: GenericTaskQueue<E>::GenericTaskQueue():TaskQueueSuper() {
ysr@976:   assert(sizeof(Age) == sizeof(int), "Depends on this.");
duke@435: }
duke@435: 
duke@435: template<class E>
duke@435: void GenericTaskQueue<E>::initialize() {
duke@435:   _elems = NEW_C_HEAP_ARRAY(E, n());
duke@435:   guarantee(_elems != NULL, "Allocation failed.");
duke@435: }
duke@435: 
duke@435: template<class E>
ysr@777: void GenericTaskQueue<E>::oops_do(OopClosure* f) {
ysr@777:   // tty->print_cr("START OopTaskQueue::oops_do");
ysr@976:   uint iters = size();
ysr@976:   uint index = _bottom;
ysr@976:   for (uint i = 0; i < iters; ++i) {
ysr@777:     index = decrement_index(index);
ysr@777:     // tty->print_cr("  doing entry %d," INTPTR_T " -> " INTPTR_T,
ysr@777:     //            index, &_elems[index], _elems[index]);
ysr@777:     E* t = (E*)&_elems[index];      // cast away volatility
ysr@777:     oop* p = (oop*)t;
ysr@777:     assert((*t)->is_oop_or_null(), "Not an oop or null");
ysr@777:     f->do_oop(p);
ysr@777:   }
ysr@777:   // tty->print_cr("END OopTaskQueue::oops_do");
ysr@777: }
ysr@777: 
ysr@777: 
ysr@777: template<class E>
ysr@976: bool GenericTaskQueue<E>::push_slow(E t, uint dirty_n_elems) {
duke@435:   if (dirty_n_elems == n() - 1) {
duke@435:     // Actually means 0, so do the push.
ysr@976:     uint localBot = _bottom;
duke@435:     _elems[localBot] = t;
duke@435:     _bottom = increment_index(localBot);
duke@435:     return true;
duke@435:   } else
duke@435:     return false;
duke@435: }
duke@435: 
duke@435: template<class E>
duke@435: bool GenericTaskQueue<E>::
ysr@976: pop_local_slow(uint localBot, Age oldAge) {
duke@435:   // This queue was observed to contain exactly one element; either this
duke@435:   // thread will claim it, or a competing "pop_global".  In either case,
duke@435:   // the queue will be logically empty afterwards.  Create a new Age value
duke@435:   // that represents the empty queue for the given value of "_bottom".  (We
duke@435:   // must also increment "tag" because of the case where "bottom == 1",
duke@435:   // "top == 0".  A pop_global could read the queue element in that case,
duke@435:   // then have the owner thread do a pop followed by another push.  Without
duke@435:   // the incrementing of "tag", the pop_global's CAS could succeed,
duke@435:   // allowing it to believe it has claimed the stale element.)
duke@435:   Age newAge;
duke@435:   newAge._top = localBot;
duke@435:   newAge._tag = oldAge.tag() + 1;
duke@435:   // Perhaps a competing pop_global has already incremented "top", in which
duke@435:   // case it wins the element.
duke@435:   if (localBot == oldAge.top()) {
duke@435:     Age tempAge;
duke@435:     // No competing pop_global has yet incremented "top"; we'll try to
duke@435:     // install new_age, thus claiming the element.
ysr@976:     assert(sizeof(Age) == sizeof(int), "Assumption about CAS unit.");
ysr@976:     *(uint*)&tempAge = Atomic::cmpxchg(*(uint*)&newAge, (volatile uint*)&_age, *(uint*)&oldAge);
duke@435:     if (tempAge == oldAge) {
duke@435:       // We win.
duke@435:       assert(dirty_size(localBot, get_top()) != n() - 1,
duke@435:              "Shouldn't be possible...");
duke@435:       return true;
duke@435:     }
duke@435:   }
duke@435:   // We fail; a completing pop_global gets the element.  But the queue is
duke@435:   // empty (and top is greater than bottom.)  Fix this representation of
duke@435:   // the empty queue to become the canonical one.
duke@435:   set_age(newAge);
duke@435:   assert(dirty_size(localBot, get_top()) != n() - 1,
duke@435:          "Shouldn't be possible...");
duke@435:   return false;
duke@435: }
duke@435: 
duke@435: template<class E>
duke@435: bool GenericTaskQueue<E>::pop_global(E& t) {
duke@435:   Age newAge;
duke@435:   Age oldAge = get_age();
ysr@976:   uint localBot = _bottom;
ysr@976:   uint n_elems = size(localBot, oldAge.top());
duke@435:   if (n_elems == 0) {
duke@435:     return false;
duke@435:   }
duke@435:   t = _elems[oldAge.top()];
duke@435:   newAge = oldAge;
duke@435:   newAge._top = increment_index(newAge.top());
duke@435:   if ( newAge._top == 0 ) newAge._tag++;
duke@435:   Age resAge;
ysr@976:   *(uint*)&resAge = Atomic::cmpxchg(*(uint*)&newAge, (volatile uint*)&_age, *(uint*)&oldAge);
duke@435:   // Note that using "_bottom" here might fail, since a pop_local might
duke@435:   // have decremented it.
duke@435:   assert(dirty_size(localBot, newAge._top) != n() - 1,
duke@435:          "Shouldn't be possible...");
duke@435:   return (resAge == oldAge);
duke@435: }
duke@435: 
duke@435: template<class E>
duke@435: GenericTaskQueue<E>::~GenericTaskQueue() {
duke@435:   FREE_C_HEAP_ARRAY(E, _elems);
duke@435: }
duke@435: 
duke@435: // Inherits the typedef of "Task" from above.
duke@435: class TaskQueueSetSuper: public CHeapObj {
duke@435: protected:
duke@435:   static int randomParkAndMiller(int* seed0);
duke@435: public:
duke@435:   // Returns "true" if some TaskQueue in the set contains a task.
duke@435:   virtual bool peek() = 0;
duke@435: };
duke@435: 
duke@435: template<class E> class GenericTaskQueueSet: public TaskQueueSetSuper {
duke@435: private:
ysr@976:   uint _n;
duke@435:   GenericTaskQueue<E>** _queues;
duke@435: 
duke@435: public:
duke@435:   GenericTaskQueueSet(int n) : _n(n) {
duke@435:     typedef GenericTaskQueue<E>* GenericTaskQueuePtr;
duke@435:     _queues = NEW_C_HEAP_ARRAY(GenericTaskQueuePtr, n);
duke@435:     guarantee(_queues != NULL, "Allocation failure.");
duke@435:     for (int i = 0; i < n; i++) {
duke@435:       _queues[i] = NULL;
duke@435:     }
duke@435:   }
duke@435: 
ysr@976:   bool steal_1_random(uint queue_num, int* seed, E& t);
ysr@976:   bool steal_best_of_2(uint queue_num, int* seed, E& t);
ysr@976:   bool steal_best_of_all(uint queue_num, int* seed, E& t);
duke@435: 
ysr@976:   void register_queue(uint i, GenericTaskQueue<E>* q);
duke@435: 
ysr@976:   GenericTaskQueue<E>* queue(uint n);
duke@435: 
duke@435:   // The thread with queue number "queue_num" (and whose random number seed
duke@435:   // is at "seed") is trying to steal a task from some other queue.  (It
duke@435:   // may try several queues, according to some configuration parameter.)
duke@435:   // If some steal succeeds, returns "true" and sets "t" the stolen task,
duke@435:   // otherwise returns false.
ysr@976:   bool steal(uint queue_num, int* seed, E& t);
duke@435: 
duke@435:   bool peek();
duke@435: };
duke@435: 
duke@435: template<class E>
ysr@976: void GenericTaskQueueSet<E>::register_queue(uint i, GenericTaskQueue<E>* q) {
ysr@976:   assert(i < _n, "index out of range.");
duke@435:   _queues[i] = q;
duke@435: }
duke@435: 
duke@435: template<class E>
ysr@976: GenericTaskQueue<E>* GenericTaskQueueSet<E>::queue(uint i) {
duke@435:   return _queues[i];
duke@435: }
duke@435: 
duke@435: template<class E>
ysr@976: bool GenericTaskQueueSet<E>::steal(uint queue_num, int* seed, E& t) {
ysr@976:   for (uint i = 0; i < 2 * _n; i++)
duke@435:     if (steal_best_of_2(queue_num, seed, t))
duke@435:       return true;
duke@435:   return false;
duke@435: }
duke@435: 
duke@435: template<class E>
ysr@976: bool GenericTaskQueueSet<E>::steal_best_of_all(uint queue_num, int* seed, E& t) {
duke@435:   if (_n > 2) {
duke@435:     int best_k;
ysr@976:     uint best_sz = 0;
ysr@976:     for (uint k = 0; k < _n; k++) {
duke@435:       if (k == queue_num) continue;
ysr@976:       uint sz = _queues[k]->size();
duke@435:       if (sz > best_sz) {
duke@435:         best_sz = sz;
duke@435:         best_k = k;
duke@435:       }
duke@435:     }
duke@435:     return best_sz > 0 && _queues[best_k]->pop_global(t);
duke@435:   } else if (_n == 2) {
duke@435:     // Just try the other one.
duke@435:     int k = (queue_num + 1) % 2;
duke@435:     return _queues[k]->pop_global(t);
duke@435:   } else {
duke@435:     assert(_n == 1, "can't be zero.");
duke@435:     return false;
duke@435:   }
duke@435: }
duke@435: 
duke@435: template<class E>
ysr@976: bool GenericTaskQueueSet<E>::steal_1_random(uint queue_num, int* seed, E& t) {
duke@435:   if (_n > 2) {
ysr@976:     uint k = queue_num;
duke@435:     while (k == queue_num) k = randomParkAndMiller(seed) % _n;
duke@435:     return _queues[2]->pop_global(t);
duke@435:   } else if (_n == 2) {
duke@435:     // Just try the other one.
duke@435:     int k = (queue_num + 1) % 2;
duke@435:     return _queues[k]->pop_global(t);
duke@435:   } else {
duke@435:     assert(_n == 1, "can't be zero.");
duke@435:     return false;
duke@435:   }
duke@435: }
duke@435: 
duke@435: template<class E>
ysr@976: bool GenericTaskQueueSet<E>::steal_best_of_2(uint queue_num, int* seed, E& t) {
duke@435:   if (_n > 2) {
ysr@976:     uint k1 = queue_num;
duke@435:     while (k1 == queue_num) k1 = randomParkAndMiller(seed) % _n;
ysr@976:     uint k2 = queue_num;
duke@435:     while (k2 == queue_num || k2 == k1) k2 = randomParkAndMiller(seed) % _n;
duke@435:     // Sample both and try the larger.
ysr@976:     uint sz1 = _queues[k1]->size();
ysr@976:     uint sz2 = _queues[k2]->size();
duke@435:     if (sz2 > sz1) return _queues[k2]->pop_global(t);
duke@435:     else return _queues[k1]->pop_global(t);
duke@435:   } else if (_n == 2) {
duke@435:     // Just try the other one.
ysr@976:     uint k = (queue_num + 1) % 2;
duke@435:     return _queues[k]->pop_global(t);
duke@435:   } else {
duke@435:     assert(_n == 1, "can't be zero.");
duke@435:     return false;
duke@435:   }
duke@435: }
duke@435: 
duke@435: template<class E>
duke@435: bool GenericTaskQueueSet<E>::peek() {
duke@435:   // Try all the queues.
ysr@976:   for (uint j = 0; j < _n; j++) {
duke@435:     if (_queues[j]->peek())
duke@435:       return true;
duke@435:   }
duke@435:   return false;
duke@435: }
duke@435: 
ysr@777: // When to terminate from the termination protocol.
ysr@777: class TerminatorTerminator: public CHeapObj {
ysr@777: public:
ysr@777:   virtual bool should_exit_termination() = 0;
ysr@777: };
ysr@777: 
duke@435: // A class to aid in the termination of a set of parallel tasks using
duke@435: // TaskQueueSet's for work stealing.
duke@435: 
jmasa@981: #undef TRACESPINNING
jmasa@981: 
duke@435: class ParallelTaskTerminator: public StackObj {
duke@435: private:
duke@435:   int _n_threads;
duke@435:   TaskQueueSetSuper* _queue_set;
ysr@976:   int _offered_termination;
duke@435: 
jmasa@981: #ifdef TRACESPINNING
jmasa@981:   static uint _total_yields;
jmasa@981:   static uint _total_spins;
jmasa@981:   static uint _total_peeks;
jmasa@981: #endif
jmasa@981: 
duke@435:   bool peek_in_queue_set();
duke@435: protected:
duke@435:   virtual void yield();
duke@435:   void sleep(uint millis);
duke@435: 
duke@435: public:
duke@435: 
duke@435:   // "n_threads" is the number of threads to be terminated.  "queue_set" is a
duke@435:   // queue sets of work queues of other threads.
duke@435:   ParallelTaskTerminator(int n_threads, TaskQueueSetSuper* queue_set);
duke@435: 
duke@435:   // The current thread has no work, and is ready to terminate if everyone
duke@435:   // else is.  If returns "true", all threads are terminated.  If returns
duke@435:   // "false", available work has been observed in one of the task queues,
duke@435:   // so the global task is not complete.
ysr@777:   bool offer_termination() {
ysr@777:     return offer_termination(NULL);
ysr@777:   }
ysr@777: 
ysr@777:   // As above, but it also terminates of the should_exit_termination()
ysr@777:   // method of the terminator parameter returns true. If terminator is
ysr@777:   // NULL, then it is ignored.
ysr@777:   bool offer_termination(TerminatorTerminator* terminator);
duke@435: 
duke@435:   // Reset the terminator, so that it may be reused again.
duke@435:   // The caller is responsible for ensuring that this is done
duke@435:   // in an MT-safe manner, once the previous round of use of
duke@435:   // the terminator is finished.
duke@435:   void reset_for_reuse();
duke@435: 
jmasa@981: #ifdef TRACESPINNING
jmasa@981:   static uint total_yields() { return _total_yields; }
jmasa@981:   static uint total_spins() { return _total_spins; }
jmasa@981:   static uint total_peeks() { return _total_peeks; }
jmasa@981:   static void print_termination_counts();
jmasa@981: #endif
duke@435: };
duke@435: 
duke@435: #define SIMPLE_STACK 0
duke@435: 
duke@435: template<class E> inline bool GenericTaskQueue<E>::push(E t) {
duke@435: #if SIMPLE_STACK
ysr@976:   uint localBot = _bottom;
duke@435:   if (_bottom < max_elems()) {
duke@435:     _elems[localBot] = t;
duke@435:     _bottom = localBot + 1;
duke@435:     return true;
duke@435:   } else {
duke@435:     return false;
duke@435:   }
duke@435: #else
ysr@976:   uint localBot = _bottom;
duke@435:   assert((localBot >= 0) && (localBot < n()), "_bottom out of range.");
ysr@976:   TAG_TYPE top = get_top();
ysr@976:   uint dirty_n_elems = dirty_size(localBot, top);
duke@435:   assert((dirty_n_elems >= 0) && (dirty_n_elems < n()),
duke@435:          "n_elems out of range.");
duke@435:   if (dirty_n_elems < max_elems()) {
duke@435:     _elems[localBot] = t;
duke@435:     _bottom = increment_index(localBot);
duke@435:     return true;
duke@435:   } else {
duke@435:     return push_slow(t, dirty_n_elems);
duke@435:   }
duke@435: #endif
duke@435: }
duke@435: 
duke@435: template<class E> inline bool GenericTaskQueue<E>::pop_local(E& t) {
duke@435: #if SIMPLE_STACK
ysr@976:   uint localBot = _bottom;
duke@435:   assert(localBot > 0, "precondition.");
duke@435:   localBot--;
duke@435:   t = _elems[localBot];
duke@435:   _bottom = localBot;
duke@435:   return true;
duke@435: #else
ysr@976:   uint localBot = _bottom;
duke@435:   // This value cannot be n-1.  That can only occur as a result of
duke@435:   // the assignment to bottom in this method.  If it does, this method
duke@435:   // resets the size( to 0 before the next call (which is sequential,
duke@435:   // since this is pop_local.)
ysr@976:   uint dirty_n_elems = dirty_size(localBot, get_top());
duke@435:   assert(dirty_n_elems != n() - 1, "Shouldn't be possible...");
duke@435:   if (dirty_n_elems == 0) return false;
duke@435:   localBot = decrement_index(localBot);
duke@435:   _bottom = localBot;
duke@435:   // This is necessary to prevent any read below from being reordered
duke@435:   // before the store just above.
duke@435:   OrderAccess::fence();
duke@435:   t = _elems[localBot];
duke@435:   // This is a second read of "age"; the "size()" above is the first.
duke@435:   // If there's still at least one element in the queue, based on the
duke@435:   // "_bottom" and "age" we've read, then there can be no interference with
duke@435:   // a "pop_global" operation, and we're done.
ysr@976:   TAG_TYPE tp = get_top();    // XXX
duke@435:   if (size(localBot, tp) > 0) {
duke@435:     assert(dirty_size(localBot, tp) != n() - 1,
duke@435:            "Shouldn't be possible...");
duke@435:     return true;
duke@435:   } else {
duke@435:     // Otherwise, the queue contained exactly one element; we take the slow
duke@435:     // path.
duke@435:     return pop_local_slow(localBot, get_age());
duke@435:   }
duke@435: #endif
duke@435: }
duke@435: 
duke@435: typedef oop Task;
duke@435: typedef GenericTaskQueue<Task>         OopTaskQueue;
duke@435: typedef GenericTaskQueueSet<Task>      OopTaskQueueSet;
duke@435: 
coleenp@548: 
coleenp@548: #define COMPRESSED_OOP_MASK  1
coleenp@548: 
coleenp@548: // This is a container class for either an oop* or a narrowOop*.
coleenp@548: // Both are pushed onto a task queue and the consumer will test is_narrow()
coleenp@548: // to determine which should be processed.
coleenp@548: class StarTask {
coleenp@548:   void*  _holder;        // either union oop* or narrowOop*
coleenp@548:  public:
ysr@1280:   StarTask(narrowOop* p) {
ysr@1280:     assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!");
ysr@1280:     _holder = (void *)((uintptr_t)p | COMPRESSED_OOP_MASK);
ysr@1280:   }
ysr@1280:   StarTask(oop* p)       {
ysr@1280:     assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!");
ysr@1280:     _holder = (void*)p;
ysr@1280:   }
coleenp@548:   StarTask()             { _holder = NULL; }
coleenp@548:   operator oop*()        { return (oop*)_holder; }
coleenp@548:   operator narrowOop*()  {
coleenp@548:     return (narrowOop*)((uintptr_t)_holder & ~COMPRESSED_OOP_MASK);
coleenp@548:   }
coleenp@548: 
coleenp@548:   // Operators to preserve const/volatile in assignments required by gcc
coleenp@548:   void operator=(const volatile StarTask& t) volatile { _holder = t._holder; }
coleenp@548: 
coleenp@548:   bool is_narrow() const {
coleenp@548:     return (((uintptr_t)_holder & COMPRESSED_OOP_MASK) != 0);
coleenp@548:   }
coleenp@548: };
coleenp@548: 
duke@435: typedef GenericTaskQueue<StarTask>     OopStarTaskQueue;
duke@435: typedef GenericTaskQueueSet<StarTask>  OopStarTaskQueueSet;
duke@435: 
jcoomes@810: typedef size_t RegionTask;  // index for region
jcoomes@810: typedef GenericTaskQueue<RegionTask>    RegionTaskQueue;
jcoomes@810: typedef GenericTaskQueueSet<RegionTask> RegionTaskQueueSet;
duke@435: 
jcoomes@810: class RegionTaskQueueWithOverflow: public CHeapObj {
duke@435:  protected:
jcoomes@810:   RegionTaskQueue              _region_queue;
jcoomes@810:   GrowableArray<RegionTask>*   _overflow_stack;
duke@435: 
duke@435:  public:
jcoomes@810:   RegionTaskQueueWithOverflow() : _overflow_stack(NULL) {}
duke@435:   // Initialize both stealable queue and overflow
duke@435:   void initialize();
duke@435:   // Save first to stealable queue and then to overflow
jcoomes@810:   void save(RegionTask t);
duke@435:   // Retrieve first from overflow and then from stealable queue
jcoomes@810:   bool retrieve(RegionTask& region_index);
duke@435:   // Retrieve from stealable queue
jcoomes@810:   bool retrieve_from_stealable_queue(RegionTask& region_index);
duke@435:   // Retrieve from overflow
jcoomes@810:   bool retrieve_from_overflow(RegionTask& region_index);
duke@435:   bool is_empty();
duke@435:   bool stealable_is_empty();
duke@435:   bool overflow_is_empty();
ysr@976:   uint stealable_size() { return _region_queue.size(); }
jcoomes@810:   RegionTaskQueue* task_queue() { return &_region_queue; }
duke@435: };
duke@435: 
jcoomes@810: #define USE_RegionTaskQueueWithOverflow