1 /*
   2  * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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  24 
  25 #ifndef SHARE_VM_MEMORY_REFERENCEPOLICY_HPP
  26 #define SHARE_VM_MEMORY_REFERENCEPOLICY_HPP
  27 
  28 // referencePolicy is used to determine when soft reference objects
  29 // should be cleared.
  30 
  31 
  32 class ReferencePolicy : public CHeapObj {
  33  public:
  34   virtual bool should_clear_reference(oop p)       { ShouldNotReachHere(); return true; }
  35   // Capture state (of-the-VM) information needed to evaluate the policy
  36   virtual void setup() { /* do nothing */ }
  37 };
  38 
  39 class NeverClearPolicy : public ReferencePolicy {
  40  public:
  41   bool should_clear_reference(oop p) { return false; }
  42 };
  43 
  44 class AlwaysClearPolicy : public ReferencePolicy {
  45  public:
  46   bool should_clear_reference(oop p) { return true; }
  47 };
  48 
  49 class LRUCurrentHeapPolicy : public ReferencePolicy {
  50  private:
  51   jlong _max_interval;
  52 
  53  public:
  54   LRUCurrentHeapPolicy();
  55 
  56   // Capture state (of-the-VM) information needed to evaluate the policy
  57   void setup();
  58   bool should_clear_reference(oop p);
  59 };
  60 
  61 class LRUMaxHeapPolicy : public ReferencePolicy {
  62  private:
  63   jlong _max_interval;
  64 
  65  public:
  66   LRUMaxHeapPolicy();
  67 
  68   // Capture state (of-the-VM) information needed to evaluate the policy
  69   void setup();
  70   bool should_clear_reference(oop p);
  71 };
  72 
  73 #endif // SHARE_VM_MEMORY_REFERENCEPOLICY_HPP