jdk8-mips64-public/hotspot: comparison src/share/vm/utilities/taskqueue.hpp

--1:000000000000
+:a61af66fc99e
+/*
+* 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

Mercurial > jdk8-mips64-public > hotspot / file comparison

comparison: src/share/vm/utilities/taskqueue.hpp

src/share/vm/utilities/taskqueue.hpp