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hotspot/src/share/vm/gc_implementation/parallelScavenge/prefetchQueue.hpp

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+/*
+ * Copyright 2002-2003 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.
+ *
+ */
+
+//
+// PrefetchQueue is a FIFO queue of variable length (currently 8).
+//
+// We need to examine the performance penalty of variable lengths.
+// We may also want to split this into cpu dependant bits.
+//
+
+const int PREFETCH_QUEUE_SIZE  = 8;
+
+class PrefetchQueue : public CHeapObj {
+ private:
+  oop*                         _prefetch_queue[PREFETCH_QUEUE_SIZE];
+  unsigned int                 _prefetch_index;
+
+ public:
+  int length() { return PREFETCH_QUEUE_SIZE; }
+
+  inline void clear() {
+    for(int i=0; i<PREFETCH_QUEUE_SIZE; i++) {
+      _prefetch_queue[i] = NULL;
+    }
+    _prefetch_index = 0;
+  }
+
+  inline oop* push_and_pop(oop* p) {
+    Prefetch::write((*p)->mark_addr(), 0);
+    // This prefetch is intended to make sure the size field of array
+    // oops is in cache. It assumes the the object layout is
+    // mark -> klass -> size, and that mark and klass are heapword
+    // sized. If this should change, this prefetch will need updating!
+    Prefetch::write((*p)->mark_addr() + (HeapWordSize*2), 0);
+    _prefetch_queue[_prefetch_index++] = p;
+    _prefetch_index &= (PREFETCH_QUEUE_SIZE-1);
+    return _prefetch_queue[_prefetch_index];
+  }
+
+  // Stores a NULL pointer in the pop'd location.
+  inline oop* pop() {
+    _prefetch_queue[_prefetch_index++] = NULL;
+    _prefetch_index &= (PREFETCH_QUEUE_SIZE-1);
+    return _prefetch_queue[_prefetch_index];
+  }
+};