6711316: Open source the Garbage-First garbage collector

First mercurial integration of the code for the Garbage-First garbage collector.

Reviewed-by: apetrusenko, iveresov, jmasa, sgoldman, tonyp, ysr

hotspot/src/share/vm/gc_implementation/g1/ptrQueue.hpp

@@ -0,0 +1,229 @@
+/*
+ * Copyright 2001-2007 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.
+ *
+ */
+
+// There are various techniques that require threads to be able to log
+// addresses.  For example, a generational write barrier might log
+// the addresses of modified old-generation objects.  This type supports
+// this operation.
+
+class PtrQueueSet;
+
+class PtrQueue: public CHeapObj {
+
+protected:
+  // The ptr queue set to which this queue belongs.
+  PtrQueueSet* _qset;
+
+  // Whether updates should be logged.
+  bool _active;
+
+  // The buffer.
+  void** _buf;
+  // The index at which an object was last enqueued.  Starts at "_sz"
+  // (indicating an empty buffer) and goes towards zero.
+  size_t _index;
+
+  // The size of the buffer.
+  size_t _sz;
+
+  // If true, the queue is permanent, and doesn't need to deallocate
+  // its buffer in the destructor (since that obtains a lock which may not
+  // be legally locked by then.
+  bool _perm;
+
+  // If there is a lock associated with this buffer, this is that lock.
+  Mutex* _lock;
+
+  PtrQueueSet* qset() { return _qset; }
+
+public:
+  // Initialize this queue to contain a null buffer, and be part of the
+  // given PtrQueueSet.
+  PtrQueue(PtrQueueSet*, bool perm = false);
+  // Release any contained resources.
+  ~PtrQueue();
+
+  // Associate a lock with a ptr queue.
+  void set_lock(Mutex* lock) { _lock = lock; }
+
+  void reset() { if (_buf != NULL) _index = _sz; }
+
+  // Enqueues the given "obj".
+  void enqueue(void* ptr) {
+    if (!_active) return;
+    else enqueue_known_active(ptr);
+  }
+
+  inline void handle_zero_index();
+  void locking_enqueue_completed_buffer(void** buf);
+
+  void enqueue_known_active(void* ptr);
+
+  size_t size() {
+    assert(_sz >= _index, "Invariant.");
+    return _buf == NULL ? 0 : _sz - _index;
+  }
+
+  // Set the "active" property of the queue to "b".  An enqueue to an
+  // inactive thread is a no-op.  Setting a queue to inactive resets its
+  // log to the empty state.
+  void set_active(bool b) {
+    _active = b;
+    if (!b && _buf != NULL) {
+      _index = _sz;
+    } else if (b && _buf != NULL) {
+      assert(_index == _sz, "invariant: queues are empty when activated.");
+    }
+  }
+
+  static int byte_index_to_index(int ind) {
+    assert((ind % oopSize) == 0, "Invariant.");
+    return ind / oopSize;
+  }
+
+  static int index_to_byte_index(int byte_ind) {
+    return byte_ind * oopSize;
+  }
+
+  // To support compiler.
+  static ByteSize byte_offset_of_index() {
+    return byte_offset_of(PtrQueue, _index);
+  }
+  static ByteSize byte_width_of_index() { return in_ByteSize(sizeof(size_t)); }
+
+  static ByteSize byte_offset_of_buf() {
+    return byte_offset_of(PtrQueue, _buf);
+  }
+  static ByteSize byte_width_of_buf() { return in_ByteSize(sizeof(void*)); }
+
+  static ByteSize byte_offset_of_active() {
+    return byte_offset_of(PtrQueue, _active);
+  }
+  static ByteSize byte_width_of_active() { return in_ByteSize(sizeof(bool)); }
+
+};
+
+// A PtrQueueSet represents resources common to a set of pointer queues.
+// In particular, the individual queues allocate buffers from this shared
+// set, and return completed buffers to the set.
+// All these variables are are protected by the TLOQ_CBL_mon. XXX ???
+class PtrQueueSet: public CHeapObj {
+
+protected:
+
+  class CompletedBufferNode: public CHeapObj {
+  public:
+    void** buf;
+    size_t index;
+    CompletedBufferNode* next;
+    CompletedBufferNode() : buf(NULL),
+      index(0), next(NULL){ }
+  };
+
+  Monitor* _cbl_mon;  // Protects the fields below.
+  CompletedBufferNode* _completed_buffers_head;
+  CompletedBufferNode* _completed_buffers_tail;
+  size_t _n_completed_buffers;
+  size_t _process_completed_threshold;
+  volatile bool _process_completed;
+
+  // This (and the interpretation of the first element as a "next"
+  // pointer) are protected by the TLOQ_FL_lock.
+  Mutex* _fl_lock;
+  void** _buf_free_list;
+  size_t _buf_free_list_sz;
+
+  // The size of all buffers in the set.
+  size_t _sz;
+
+  bool _all_active;
+
+  // If true, notify_all on _cbl_mon when the threshold is reached.
+  bool _notify_when_complete;
+
+  // Maximum number of elements allowed on completed queue: after that,
+  // enqueuer does the work itself.  Zero indicates no maximum.
+  int _max_completed_queue;
+
+  int completed_buffers_list_length();
+  void assert_completed_buffer_list_len_correct_locked();
+  void assert_completed_buffer_list_len_correct();
+
+protected:
+  // A mutator thread does the the work of processing a buffer.
+  // Returns "true" iff the work is complete (and the buffer may be
+  // deallocated).
+  virtual bool mut_process_buffer(void** buf) {
+    ShouldNotReachHere();
+    return false;
+  }
+
+public:
+  // Create an empty ptr queue set.
+  PtrQueueSet(bool notify_when_complete = false);
+
+  // Because of init-order concerns, we can't pass these as constructor
+  // arguments.
+  void initialize(Monitor* cbl_mon, Mutex* fl_lock,
+                  int max_completed_queue = 0) {
+    _max_completed_queue = max_completed_queue;
+    assert(cbl_mon != NULL && fl_lock != NULL, "Init order issue?");
+    _cbl_mon = cbl_mon; _fl_lock = fl_lock;
+  }
+
+  // Return an empty oop array of size _sz (required to be non-zero).
+  void** allocate_buffer();
+
+  // Return an empty buffer to the free list.  The "buf" argument is
+  // required to be a pointer to the head of an array of length "_sz".
+  void deallocate_buffer(void** buf);
+
+  // Declares that "buf" is a complete buffer.
+  void enqueue_complete_buffer(void** buf, size_t index = 0,
+                               bool ignore_max_completed = false);
+
+  bool completed_buffers_exist_dirty() {
+    return _n_completed_buffers > 0;
+  }
+
+  bool process_completed_buffers() { return _process_completed; }
+
+  bool active() { return _all_active; }
+
+  // Set the buffer size.  Should be called before any "enqueue" operation
+  // can be called.  And should only be called once.
+  void set_buffer_size(size_t sz);
+
+  // Get the buffer size.
+  size_t buffer_size() { return _sz; }
+
+  // Set the number of completed buffers that triggers log processing.
+  void set_process_completed_threshold(size_t sz);
+
+  // Must only be called at a safe point.  Indicates that the buffer free
+  // list size may be reduced, if that is deemed desirable.
+  void reduce_free_list();
+
+  size_t completed_buffers_num() { return _n_completed_buffers; }
+};