| /* |
| * This file is part of the Jikes RVM project (http://jikesrvm.org). |
| * |
| * This file is licensed to You under the Eclipse Public License (EPL); |
| * You may not use this file except in compliance with the License. You |
| * may obtain a copy of the License at |
| * |
| * http://www.opensource.org/licenses/eclipse-1.0.php |
| * |
| * See the COPYRIGHT.txt file distributed with this work for information |
| * regarding copyright ownership. |
| */ |
| package org.mmtk.plan.semispace.gctrace; |
| |
| import org.mmtk.plan.Trace; |
| import org.mmtk.plan.semispace.*; |
| import org.mmtk.policy.Space; |
| import org.mmtk.utility.TraceGenerator; |
| |
| import org.vmmagic.unboxed.*; |
| import org.vmmagic.pragma.*; |
| |
| /** |
| * This plan has been modified slightly to perform the processing necessary |
| * for GC trace generation. To maximize performance, it attempts to remain |
| * as faithful as possible to semiSpace/Plan.java. |
| * |
| * The generated trace format is as follows: |
| * B 345678 12 |
| * (Object 345678 was created in the boot image with a size of 12 bytes) |
| * U 59843 234 47298 |
| * (Update object 59843 at the slot at offset 234 to refer to 47298) |
| * S 1233 12345 |
| * (Update static slot 1233 to refer to 12345) |
| * T 4567 78924 |
| * (The TIB of 4567 is set to refer to 78924) |
| * D 342789 |
| * (Object 342789 became unreachable) |
| * A 6860 24 346648 3 |
| * (Object 6860 was allocated, requiring 24 bytes, with fp 346648 on |
| * thread 3; this allocation has perfect knowledge) |
| * a 6884 24 346640 5 |
| * (Object 6864 was allocated, requiring 24 bytes, with fp 346640 on |
| * thread 5; this allocation DOES NOT have perfect knowledge) |
| * I 6860 24 346648 3 |
| * (Object 6860 was allocated into immortal space, requiring 24 bytes, |
| * with fp 346648 on thread 3; this allocation has perfect knowledge) |
| * i 6884 24 346640 5 |
| * (Object 6864 was allocated into immortal space, requiring 24 bytes, |
| * with fp 346640 on thread 5; this allocation DOES NOT have perfect |
| * knowledge) |
| * 48954->[345]LObject;:blah()V:23 Ljava/lang/Foo; |
| * (Citation for: a) where the was allocated, fp of 48954, |
| * at the method with ID 345 -- or void Object.blah() -- and bytecode |
| * with offset 23; b) the object allocated is of type java.lang.Foo) |
| * D 342789 361460 |
| * (Object 342789 became unreachable after 361460 was allocated) |
| * |
| * This class implements a simple semi-space collector. See the Jones |
| * & Lins GC book, section 2.2 for an overview of the basic |
| * algorithm. This implementation also includes a large object space |
| * (LOS), and an uncollected "immortal" space.<p> |
| * |
| * All plans make a clear distinction between <i>global</i> and |
| * <i>thread-local</i> activities. Global activities must be |
| * synchronized, whereas no synchronization is required for |
| * thread-local activities. Instances of Plan map 1:1 to "kernel |
| * threads" (aka CPUs). Thus instance |
| * methods allow fast, unsychronized access to Plan utilities such as |
| * allocation and collection. Each instance rests on static resources |
| * (such as memory and virtual memory resources) which are "global" |
| * and therefore "static" members of Plan. This mapping of threads to |
| * instances is crucial to understanding the correctness and |
| * performance proprties of this plan. |
| */ |
| @Uninterruptible |
| public final class GCTraceTraceLocal extends SSTraceLocal { |
| |
| /** |
| * Constructor |
| * |
| * @param trace The global trace to use. |
| */ |
| public GCTraceTraceLocal(Trace trace) { |
| super(trace, false); |
| } |
| |
| /**************************************************************************** |
| * |
| * Object processing and tracing |
| */ |
| |
| /** |
| * Trace a reference during GC. This involves determining which |
| * collection policy applies (such as those needed for trace generation) |
| * and taking the appropriate actions. |
| * |
| * @param object The object reference to be traced. In certain |
| * cases, this should <i>NOT</i> be an interior pointer. |
| * @return The possibly moved reference. |
| */ |
| @Inline |
| public ObjectReference traceObject(ObjectReference object) { |
| if (object.isNull()) return object; |
| if (GCTrace.traceInducedGC) { |
| /* We are performing a root scan following an allocation. */ |
| TraceGenerator.rootEnumerate(object); |
| return object; |
| } else if (GCTrace.deathScan) { |
| /* We are performing the last scan before program termination. */ |
| TraceGenerator.propagateDeathTime(object); |
| return object; |
| } else { |
| /* *gasp* We are actually performing garbage collection */ |
| return super.traceObject(object); |
| } |
| } |
| |
| /** |
| * Ensure that the referenced object will not move during a collection |
| * by 'precopying' it at the beginning. |
| * |
| * @param object The object to ensure will not move. |
| */ |
| @Inline |
| public ObjectReference precopyObject(ObjectReference object) { |
| if (object.isNull()) return object; |
| if (GCTrace.traceInducedGC) { |
| /* We are performing a root scan following an allocation. */ |
| TraceGenerator.rootEnumerate(object); |
| return object; |
| } else if (GCTrace.deathScan) { |
| /* We are performing the last scan before program termination. */ |
| TraceGenerator.propagateDeathTime(object); |
| return object; |
| } else { |
| return super.precopyObject(object); |
| } |
| } |
| |
| |
| /** |
| * If the referenced object has moved, return the new location. |
| * |
| * Some copying collectors will need to override this method. |
| * |
| * @param object The object which may have been forwarded. |
| * @return The new location of <code>object</code>. |
| */ |
| @Inline |
| public ObjectReference getForwardedReference(ObjectReference object) { |
| if (object.isNull()) return object; |
| if (SS.hi && Space.isInSpace(SS.SS0, object)) { |
| return SS.copySpace0.traceObject(this, object, GCTrace.ALLOC_SS); |
| } else if (!SS.hi && Space.isInSpace(SS.SS1, object)) { |
| return SS.copySpace1.traceObject(this, object, GCTrace.ALLOC_SS); |
| } |
| return object; |
| } |
| |
| /** |
| * Return true if <code>obj</code> is a live object. |
| * |
| * @param object The object in question |
| * @return True if <code>obj</code> is a live object. |
| */ |
| public boolean isLive(ObjectReference object) { |
| if (object.isNull()) return false; |
| else if (GCTrace.traceInducedGC) return true; |
| else return super.isLive(object); |
| } |
| |
| /** |
| * Return true if <code>obj</code> is a reachable object. |
| * |
| * @param object The object in question |
| * @return True if <code>obj</code> is a reachable object; |
| * unreachable objects may still be live, however |
| */ |
| public boolean isReachable(ObjectReference object) { |
| if (GCTrace.finalDead) return false; |
| else if (object.isNull()) return false; |
| else { |
| Space space = Space.getSpaceForObject(object); |
| return space.isReachable(object); |
| } |
| } |
| |
| /** |
| * Is this object guaranteed not to move during the collection. |
| * |
| * @param object The object to check. |
| * @return True if the object is guaranteed not to move. |
| */ |
| public boolean willNotMoveInCurrentCollection(ObjectReference object) { |
| if (GCTrace.traceInducedGC) return true; |
| else return super.willNotMoveInCurrentCollection(object); |
| } |
| } |