1 /* 2 * Copyright (c) 2018, 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 package sun.jvm.hotspot.gc.z; 26 27 import sun.jvm.hotspot.debugger.Address; 28 import sun.jvm.hotspot.runtime.VM; 29 import sun.jvm.hotspot.runtime.VMObject; 30 import sun.jvm.hotspot.types.AddressField; 31 import sun.jvm.hotspot.types.CIntegerField; 32 import sun.jvm.hotspot.types.Type; 33 import sun.jvm.hotspot.types.TypeDataBase; 34 35 public class ZForwardingTable extends VMObject { 36 private static AddressField tableField; 37 private static CIntegerField sizeField; 38 39 static { 40 VM.registerVMInitializedObserver((o, d) -> initialize(VM.getVM().getTypeDataBase())); 41 } 42 43 static private synchronized void initialize(TypeDataBase db) { 44 Type type = db.lookupType("ZForwardingTable"); 45 46 tableField = type.getAddressField("_table"); 47 sizeField = type.getCIntegerField("_size"); 48 } 49 50 public ZForwardingTable(Address addr) { 51 super(addr); 52 } 53 54 Address table() { 55 return tableField.getAddress(addr); 56 } 57 58 long size() { 59 return sizeField.getJLong(addr); 60 } 61 62 ZForwardingTableEntry at(ZForwardingTableCursor cursor) { 63 return new ZForwardingTableEntry(table().getAddressAt(cursor._value * VM.getVM().getBytesPerLong())); 64 } 65 66 ZForwardingTableEntry first(long from_index, ZForwardingTableCursor cursor) { 67 long mask = size() - 1; 68 long hash = ZHash.uint32_to_uint32(from_index); 69 cursor._value = hash & mask; 70 return at(cursor); 71 } 72 73 ZForwardingTableEntry next(ZForwardingTableCursor cursor) { 74 long mask = size() - 1; 75 cursor._value = (cursor._value + 1) & mask; 76 return at(cursor); 77 } 78 79 ZForwardingTableEntry find(long from_index, ZForwardingTableCursor cursor) { 80 // Reading entries in the table races with the atomic cas done for 81 // insertion into the table. This is safe because each entry is at 82 // most updated once (from -1 to something else). 83 ZForwardingTableEntry entry = first(from_index, cursor); 84 while (!entry.is_empty()) { 85 if (entry.from_index() == from_index) { 86 // Match found, return matching entry 87 return entry; 88 } 89 90 entry = next(cursor); 91 } 92 93 // Match not found, return empty entry 94 return entry; 95 } 96 97 ZForwardingTableEntry find(long from_index) { 98 ZForwardingTableCursor dummy = new ZForwardingTableCursor(); 99 return find(from_index, dummy); 100 } 101 102 void dump() { 103 long s = size(); 104 long count = 0; 105 System.out.println("Dumping ZForwardingTable[" + s + "]:"); 106 ZForwardingTableCursor cursor = new ZForwardingTableCursor(); 107 for (long i = 0; i < s; i++) { 108 cursor._value = i; 109 ZForwardingTableEntry entry = at(cursor); 110 if (!entry.is_empty()) { 111 long hash = ZHash.uint32_to_uint32(entry.from_index()); 112 System.out.println(i + " " + count + " " + entry + " hash: " + hash + " masked_hash: " + (hash & (s - 1))); 113 count++; 114 } 115 } 116 } 117 }