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annotate agent/src/share/classes/sun/jvm/hotspot/utilities/LivenessAnalysis.java @ 2042:0a8e0d4345b3 hs20-b05 jdk7-b124
7010068: Update all 2010 Oracle-changed OpenJDK files to have the proper copyright dates - first pass
Summary: Update the copyright to be 2010 on all changed files in OpenJDK
Reviewed-by: jcoomes
| author | trims |
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| date | Mon, 03 Jan 2011 15:30:05 -0800 |
| parents | c18cbe5936b8 |
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| 0 | 1 /* |
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2 * Copyright (c) 2001, 2006, Oracle and/or its affiliates. All rights reserved. |
| 0 | 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 * | |
|
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
| 0 | 22 * |
| 23 */ | |
| 24 | |
| 25 package sun.jvm.hotspot.utilities; | |
| 26 | |
| 27 import java.io.*; | |
| 28 import java.util.*; | |
| 29 import sun.jvm.hotspot.debugger.*; | |
| 30 import sun.jvm.hotspot.gc_interface.*; | |
| 31 import sun.jvm.hotspot.memory.*; | |
| 32 import sun.jvm.hotspot.oops.*; | |
| 33 import sun.jvm.hotspot.runtime.*; | |
| 34 | |
| 35 /** Finds all paths from roots to the specified set of objects. NOTE: | |
| 36 currently only a subset of the roots known to the VM is exposed to | |
| 37 the SA: objects on the stack, static fields in classes, and JNI | |
| 38 handles. These should be most of the user-level roots keeping | |
| 39 objects alive. */ | |
| 40 | |
| 41 public class LivenessAnalysis { | |
| 42 // Used for debugging this code | |
| 43 private static final boolean DEBUG = false; | |
| 44 | |
| 45 private LivenessAnalysis() {} | |
| 46 | |
| 47 public static LivenessPathList computeAllLivenessPaths(Oop target) { | |
| 48 LivenessPathList list = computeAllLivenessPaths(target, true); | |
| 49 if ((list == null) || (list.size() == 0)) { | |
| 50 // Dead object | |
| 51 return null; | |
| 52 } | |
| 53 return list; | |
| 54 } | |
| 55 | |
| 56 //--------------------------------------------------------------------------- | |
| 57 // Internals only below this point | |
| 58 // | |
| 59 | |
| 60 // Returns true if a new path was completed, otherwise false | |
| 61 // indicating there were no more paths to complete. | |
| 62 // | |
| 63 // The trimPathsThroughPopularObjects flag alters the behavior of | |
| 64 // the returned results. If true, then if multiple paths to | |
| 65 // different roots all go through a particular popular object, those | |
| 66 // paths will be truncated and only one (arbitrary one) will be be | |
| 67 // returned. On the other hand, if the target object itself is | |
| 68 // popular and there are multiple distinct paths to it (indicating | |
| 69 // that there are multiple objects pointing directly to it) then all | |
| 70 // of those paths will be reported. | |
| 71 private static LivenessPathList computeAllLivenessPaths(Oop target, boolean trimPathsThroughPopularObjects) { | |
| 72 ReversePtrs rev = VM.getVM().getRevPtrs(); | |
| 73 if (rev == null) { | |
| 74 throw new RuntimeException("LivenessAnalysis requires ReversePtrs to have been computed"); | |
| 75 } | |
| 76 | |
| 77 // Currently the reverse pointer analysis returns non-null results | |
| 78 // only for live objects | |
| 79 if (rev.get(target) == null) { | |
| 80 // Object is dead | |
| 81 return null; | |
| 82 } | |
| 83 | |
| 84 // HashSet of Oops acting as a bit mask indicating which ones have | |
| 85 // already been traversed | |
| 86 Set/*<Oop>*/ visitedOops = new HashSet/*<Oop>*/(); | |
| 87 | |
| 88 // IdentityHashMap of LivenessElements acting as a bit mask | |
| 89 // indicating which roots have already been traversed | |
| 90 Map/*<LivenessElement, LivenessElement>*/ visitedRoots = | |
| 91 new IdentityHashMap/*<LivenessElement, LivenessElement>*/(); | |
| 92 | |
| 93 visitedOops.add(target); | |
| 94 | |
| 95 // Construct the initial LivenessPath | |
| 96 LivenessPathList list = new LivenessPathList(); | |
| 97 { | |
| 98 LivenessPath path = new LivenessPath(); | |
| 99 path.push(new LivenessPathElement(target, null)); | |
| 100 list.add(path); | |
| 101 } | |
| 102 | |
| 103 // Iterate until done | |
| 104 while (true) { | |
| 105 // See if there are any incomplete paths left | |
| 106 LivenessPath path = null; | |
| 107 | |
| 108 for (int i = list.size() - 1; i >= 0; i--) { | |
| 109 LivenessPath tmp = list.get(i); | |
| 110 if (!tmp.isComplete()) { | |
| 111 path = tmp; | |
| 112 break; | |
| 113 } | |
| 114 } | |
| 115 | |
| 116 // If no incomplete paths left, return | |
| 117 if (path == null) { | |
| 118 return list; | |
| 119 } | |
| 120 | |
| 121 // Try to complete this path | |
| 122 | |
| 123 // Remove the path from the list of reported ones in | |
| 124 // anticipation of completing it | |
| 125 list.remove(path); | |
| 126 | |
| 127 try { | |
| 128 // Fetch next set of reverse pointers for the last object on | |
| 129 // the list | |
| 130 ArrayList/*<LivenessPathElement>*/ nextPtrs = | |
| 131 rev.get(path.peek().getObj()); | |
| 132 | |
| 133 // Depending on exactly what the reverse pointers analysis | |
| 134 // yields, these results may be null, although currently they | |
| 135 // won't be | |
| 136 if (nextPtrs != null) { | |
| 137 // Iterate these | |
| 138 for (Iterator iter = nextPtrs.iterator(); iter.hasNext(); ) { | |
| 139 LivenessPathElement nextElement = (LivenessPathElement) iter.next(); | |
| 140 // See whether we've visited this element yet | |
| 141 if ((nextElement.isRoot() && (visitedRoots.get(nextElement) == null)) || | |
| 142 (!nextElement.isRoot() && !visitedOops.contains(nextElement.getObj()))) { | |
| 143 // Show we've visited this one | |
| 144 if (nextElement.isRoot()) { | |
| 145 visitedRoots.put(nextElement, nextElement); | |
| 146 } else { | |
| 147 visitedOops.add(nextElement.getObj()); | |
| 148 } | |
| 149 | |
| 150 // Create a new LivenessPath for each one | |
| 151 LivenessPath nextPath = path.copy(); | |
| 152 nextPath.push(nextElement); | |
| 153 | |
| 154 // Regardless of whether we found a root, put the | |
| 155 // original path back on the list because we're going to | |
| 156 // do depth-first searching rather than breadth-first | |
| 157 list.add(path); | |
| 158 list.add(nextPath); | |
| 159 | |
| 160 // See whether this path is complete (i.e., it | |
| 161 // terminates in a root) | |
| 162 if (trimPathsThroughPopularObjects && nextElement.isRoot()) { | |
| 163 // Go back through the path list and remove all | |
| 164 // incomplete paths ending in any of the intermediate | |
| 165 // (non-root and non-terminal) nodes in this path. | |
| 166 // This has the effect of removing multiple paths | |
| 167 // going through popular objects. | |
| 168 for (int i = 1; i < nextPath.size() - 1; i++) { | |
| 169 LivenessPathElement el = nextPath.get(i); | |
| 170 int j = 0; | |
| 171 while (j < list.size()) { | |
| 172 LivenessPath curPath = list.get(j); | |
| 173 // We can use an object identity since these | |
| 174 // intermediate nodes are canonicalized via the | |
| 175 // ReversePtrsAnalysis | |
| 176 if (curPath.peek() == el) { | |
| 177 list.remove(curPath); | |
| 178 } else { | |
| 179 j++; | |
| 180 } | |
| 181 } | |
| 182 } | |
| 183 } | |
| 184 | |
| 185 // Do depth-first searching, not breadth-first | |
| 186 break; | |
| 187 } | |
| 188 } | |
| 189 } | |
| 190 } catch (Exception e) { | |
| 191 System.err.println("LivenessAnalysis: WARNING: " + e + | |
| 192 " during traversal"); | |
| 193 } | |
| 194 } | |
| 195 } | |
| 196 } |