6957084: simplify TaskQueue overflow handling

Reviewed-by: ysr, jmasa

hotspot/src/share/vm/utilities/taskqueue.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2009, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2010, Oracle and/or its affiliates. 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
@@ -109,8 +109,9 @@ protected:
 public:
   TaskQueueSuper() : _bottom(0), _age() {}
 
-  // Return true if the TaskQueue contains any tasks.
-  bool peek() { return _bottom != _age.top(); }
+  // Return true if the TaskQueue contains/does not contain any tasks.
+  bool peek()     const { return _bottom != _age.top(); }
+  bool is_empty() const { return size() == 0; }
 
   // Return an estimate of the number of elements in the queue.
   // The "careful" version admits the possibility of pop_local/pop_global
@@ -165,18 +166,16 @@ public:
 
   void initialize();
 
-  // Push the task "t" on the queue.  Returns "false" iff the queue is
-  // full.
+  // 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.
+  // Attempts to claim a task from the "local" end of the queue (the most
+  // recently pushed).  If successful, returns true and sets t to the task;
+  // otherwise, returns false (the queue is empty).
   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.
+  // Like pop_local(), but uses the "global" end of the queue (the least
+  // recently pushed).
   bool pop_global(E& t);
 
   // Delete any resource associated with the queue.
@@ -198,7 +197,6 @@ GenericTaskQueue<E, N>::GenericTaskQueue() {
 template<class E, unsigned int N>
 void GenericTaskQueue<E, N>::initialize() {
   _elems = NEW_C_HEAP_ARRAY(E, N);
-  guarantee(_elems != NULL, "Allocation failed.");
 }
 
 template<class E, unsigned int N>
@@ -289,7 +287,87 @@ GenericTaskQueue<E, N>::~GenericTaskQueue() {
   FREE_C_HEAP_ARRAY(E, _elems);
 }
 
-// Inherits the typedef of "Task" from above.
+// OverflowTaskQueue is a TaskQueue that also includes an overflow stack for
+// elements that do not fit in the TaskQueue.
+//
+// Three methods from super classes are overridden:
+//
+// initialize() - initialize the super classes and create the overflow stack
+// push() - push onto the task queue or, if that fails, onto the overflow stack
+// is_empty() - return true if both the TaskQueue and overflow stack are empty
+//
+// Note that size() is not overridden--it returns the number of elements in the
+// TaskQueue, and does not include the size of the overflow stack.  This
+// simplifies replacement of GenericTaskQueues with OverflowTaskQueues.
+template<class E, unsigned int N = TASKQUEUE_SIZE>
+class OverflowTaskQueue: public GenericTaskQueue<E, N>
+{
+public:
+  typedef GrowableArray<E>       overflow_t;
+  typedef GenericTaskQueue<E, N> taskqueue_t;
+
+  OverflowTaskQueue();
+  ~OverflowTaskQueue();
+  void initialize();
+
+  inline overflow_t* overflow_stack() const { return _overflow_stack; }
+
+  // Push task t onto the queue or onto the overflow stack.  Return true.
+  inline bool push(E t);
+
+  // Attempt to pop from the overflow stack; return true if anything was popped.
+  inline bool pop_overflow(E& t);
+
+  inline bool taskqueue_empty() const { return taskqueue_t::is_empty(); }
+  inline bool overflow_empty()  const { return overflow_stack()->is_empty(); }
+  inline bool is_empty()        const {
+    return taskqueue_empty() && overflow_empty();
+  }
+
+private:
+  overflow_t* _overflow_stack;
+};
+
+template <class E, unsigned int N>
+OverflowTaskQueue<E, N>::OverflowTaskQueue()
+{
+  _overflow_stack = NULL;
+}
+
+template <class E, unsigned int N>
+OverflowTaskQueue<E, N>::~OverflowTaskQueue()
+{
+  if (_overflow_stack != NULL) {
+    delete _overflow_stack;
+    _overflow_stack = NULL;
+  }
+}
+
+template <class E, unsigned int N>
+void OverflowTaskQueue<E, N>::initialize()
+{
+  taskqueue_t::initialize();
+  assert(_overflow_stack == NULL, "memory leak");
+  _overflow_stack = new (ResourceObj::C_HEAP) GrowableArray<E>(10, true);
+}
+
+template <class E, unsigned int N>
+bool OverflowTaskQueue<E, N>::push(E t)
+{
+  if (!taskqueue_t::push(t)) {
+    overflow_stack()->push(t);
+  }
+  return true;
+}
+
+template <class E, unsigned int N>
+bool OverflowTaskQueue<E, N>::pop_overflow(E& t)
+{
+  if (overflow_empty()) return false;
+  t = overflow_stack()->pop();
+  return true;
+}
+
 class TaskQueueSetSuper: public CHeapObj {
 protected:
   static int randomParkAndMiller(int* seed0);
@@ -323,11 +401,11 @@ public:
 
   T* 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.
+  // 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" to the stolen task, otherwise returns
+  // false.
   bool steal(uint queue_num, int* seed, E& t);
 
   bool peek();
@@ -507,7 +585,7 @@ GenericTaskQueue<E, N>::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,
+  // 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...");
@@ -533,8 +611,7 @@ GenericTaskQueue<E, N>::pop_local(E& t) {
   }
 }
 
-typedef oop Task;
-typedef GenericTaskQueue<Task>            OopTaskQueue;
+typedef GenericTaskQueue<oop>             OopTaskQueue;
 typedef GenericTaskQueueSet<OopTaskQueue> OopTaskQueueSet;
 
 #ifdef _MSC_VER
@@ -615,35 +692,8 @@ private:
 #pragma warning(pop)
 #endif
 
-typedef GenericTaskQueue<StarTask>            OopStarTaskQueue;
+typedef OverflowTaskQueue<StarTask>           OopStarTaskQueue;
 typedef GenericTaskQueueSet<OopStarTaskQueue> OopStarTaskQueueSet;
 
-typedef size_t RegionTask;  // index for region
-typedef GenericTaskQueue<RegionTask>         RegionTaskQueue;
-typedef GenericTaskQueueSet<RegionTaskQueue> 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
+typedef OverflowTaskQueue<size_t>             RegionTaskQueue;
+typedef GenericTaskQueueSet<RegionTaskQueue>  RegionTaskQueueSet;