1 /* 2 * Copyright (c) 2000, 2012, 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. 8 * 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 16 * 2 along with this work; if not, write to the Free Software Foundation, 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 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 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<mtGC> { 33 public: 34 virtual bool should_clear_reference(oop p, jlong timestamp_clock) { 35 ShouldNotReachHere(); 36 return true; 37 } 38 39 // Capture state (of-the-VM) information needed to evaluate the policy 40 virtual void setup() { /* do nothing */ } 41 }; 42 43 class NeverClearPolicy : public ReferencePolicy { 44 public: 45 virtual bool should_clear_reference(oop p, jlong timestamp_clock) { 46 return false; 47 } 48 }; 49 50 class AlwaysClearPolicy : public ReferencePolicy { 51 public: 52 virtual bool should_clear_reference(oop p, jlong timestamp_clock) { 53 return true; 54 } 55 }; 56 57 class LRUCurrentHeapPolicy : public ReferencePolicy { 58 private: 59 jlong _max_interval; 60 61 public: 62 LRUCurrentHeapPolicy(); 63 64 // Capture state (of-the-VM) information needed to evaluate the policy 65 void setup(); 66 virtual bool should_clear_reference(oop p, jlong timestamp_clock); 67 }; 68 69 class LRUMaxHeapPolicy : public ReferencePolicy { 70 private: 71 jlong _max_interval; 72 73 public: 74 LRUMaxHeapPolicy(); 75 76 // Capture state (of-the-VM) information needed to evaluate the policy 77 void setup(); 78 virtual bool should_clear_reference(oop p, jlong timestamp_clock); 79 }; 80 81 #endif // SHARE_VM_MEMORY_REFERENCEPOLICY_HPP