jdk8-mips64-public/hotspot: src/share/vm/utilities/taskqueue.hpp@a61af66fc99e (annotated)

src/share/vm/utilities/taskqueue.hpp@a61af66fc99e (annotated)

src/share/vm/utilities/taskqueue.hpp

Sat, 01 Dec 2007 00:00:00 +0000

author: duke
date: Sat, 01 Dec 2007 00:00:00 +0000
changeset 435: a61af66fc99e
child 548: ba764ed4b6f2
permissions: -rw-r--r--

Initial load

 /*
  * 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 / annotate

src/share/vm/utilities/taskqueue.hpp@a61af66fc99e (annotated)

src/share/vm/utilities/taskqueue.hpp