| /* |
| * 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.stickyms; |
| |
| import org.mmtk.plan.TransitiveClosure; |
| import org.mmtk.plan.marksweep.MS; |
| import org.mmtk.policy.Space; |
| import org.mmtk.utility.Log; |
| import org.mmtk.utility.deque.SharedDeque; |
| import org.mmtk.utility.options.Options; |
| import org.mmtk.utility.sanitychecker.SanityChecker; |
| import org.mmtk.vm.VM; |
| |
| import org.vmmagic.pragma.*; |
| import org.vmmagic.unboxed.ObjectReference; |
| |
| /** |
| * This class implements the global state of a simple sticky mark bits collector, |
| * based a simple on mark-sweep collector. The sticky mark bits algorithm is |
| * due to Demmers et al. (http://doi.acm.org/10.1145/96709.96735), and allows |
| * generational collection to be performed in a non-moving heap by overloading |
| * the role of mark bits to also indicate whether an object is new (nursery) or |
| * not. Thus nursery objects are identified by a bit in their header, not by |
| * where they lie within the address space. While Demmers et al. did their work |
| * in a conservative collector, here we have an exact collector, so we can use |
| * a regular write barrier, and don't need to use page protection etc. |
| * |
| * All plans make a clear distinction between <i>global</i> and |
| * <i>thread-local</i> activities, and divides global and local state |
| * into separate class hierarchies. Global activities must be |
| * synchronized, whereas no synchronization is required for |
| * thread-local activities. There is a single instance of Plan (or the |
| * appropriate sub-class), and a 1:1 mapping of PlanLocal to "kernel |
| * threads" (aka CPUs or in Jikes RVM, Processors). Thus instance |
| * methods of PlanLocal allow fast, unsychronized access to functions such as |
| * allocation and collection. |
| * |
| * The global instance defines and manages static resources |
| * (such as memory and virtual memory resources). This mapping of threads to |
| * instances is crucial to understanding the correctness and |
| * performance properties of MMTk plans. |
| */ |
| @Uninterruptible |
| public class StickyMS extends MS { |
| |
| /**************************************************************************** |
| * Constants |
| */ |
| /** If true, then new PLOS objects are collected at each nursery GC */ |
| static final boolean NURSERY_COLLECT_PLOS = true; |
| /** If true then we only do full heap GCs---so we're like MarkSweep (+ write barrier) */ |
| static final boolean MAJOR_GC_ONLY = false; |
| |
| /**************************************************************************** |
| * Class variables |
| */ |
| |
| public static int SCAN_NURSERY = 1; |
| |
| /**************************************************************************** |
| * Instance variables |
| */ |
| /* status fields */ |
| /** will the next collection collect the whole heap? */ |
| public boolean nextGCWholeHeap = false; |
| /** will this collection collect the whole heap */ |
| public boolean collectWholeHeap = nextGCWholeHeap; |
| |
| /* Remset pool */ |
| public final SharedDeque modPool = new SharedDeque("msgen mod objects", metaDataSpace, 1); |
| |
| /**************************************************************************** |
| * Static initialization |
| */ |
| { |
| msSpace.makeAgeSegregatedSpace(); /* this space is to be collected generationally */ |
| } |
| |
| /***************************************************************************** |
| * |
| * Collection |
| */ |
| |
| /** |
| * A user-triggered GC has been initiated. |
| */ |
| public void userTriggeredGC() { |
| nextGCWholeHeap |= Options.fullHeapSystemGC.getValue(); |
| } |
| |
| /** |
| * Force the next collection to be full heap. |
| */ |
| @Override |
| public void forceFullHeapCollection() { |
| nextGCWholeHeap = true; |
| } |
| |
| /** |
| * Perform a (global) collection phase. |
| * |
| * @param phaseId Collection phase to execute. |
| */ |
| @Inline |
| @Override |
| public final void collectionPhase(short phaseId) { |
| |
| if (phaseId == INITIATE) { |
| collectWholeHeap = MAJOR_GC_ONLY || emergencyCollection || nextGCWholeHeap; |
| nextGCWholeHeap = false; |
| super.collectionPhase(phaseId); |
| return; |
| } |
| |
| if (!collectWholeHeap) { |
| if (phaseId == PREPARE) { |
| msTrace.prepare(); |
| msSpace.prepare(false); |
| return; |
| } |
| |
| if (phaseId == RELEASE) { |
| msTrace.release(); |
| msSpace.release(); |
| modPool.reset(); |
| nextGCWholeHeap = (getPagesAvail() < Options.nurserySize.getMinNursery()); |
| return; |
| } |
| } |
| |
| super.collectionPhase(phaseId); |
| } |
| |
| /***************************************************************************** |
| * |
| * Accounting |
| */ |
| |
| /** |
| * Print pre-collection statistics. In this class we prefix the output |
| * indicating whether the collection was full heap or not. |
| */ |
| @Override |
| public void printPreStats() { |
| if ((Options.verbose.getValue() >= 1) && (collectWholeHeap)) |
| Log.write("[Full heap]"); |
| super.printPreStats(); |
| } |
| |
| /** |
| * @return Is current GC only collecting objects allocated since last GC. |
| */ |
| public final boolean isCurrentGCNursery() { |
| return !collectWholeHeap; |
| } |
| |
| /** |
| * @return Is last GC a full collection? |
| */ |
| public final boolean isLastGCFull() { |
| return collectWholeHeap; |
| } |
| |
| /** |
| * Return the expected reference count. For non-reference counting |
| * collectors this becomes a true/false relationship. |
| * @param object The object to check. |
| * @param sanityRootRC The number of root references to the object. |
| * |
| * @return The expected (root excluded) reference count. |
| */ |
| public int sanityExpectedRC(ObjectReference object, int sanityRootRC) { |
| Space space = Space.getSpaceForObject(object); |
| |
| // Immortal spaces |
| if (space == StickyMS.immortalSpace || space == StickyMS.vmSpace) { |
| return space.isReachable(object) ? SanityChecker.ALIVE : SanityChecker.DEAD; |
| } |
| |
| // Mature space (nursery collection) |
| if (VM.activePlan.global().isCurrentGCNursery() && space != StickyMS.msSpace) { |
| return SanityChecker.UNSURE; |
| } |
| |
| return super.sanityExpectedRC(object, sanityRootRC); |
| } |
| |
| /** |
| * Register specialized methods. |
| */ |
| @Interruptible |
| protected void registerSpecializedMethods() { |
| TransitiveClosure.registerSpecializedScan(SCAN_NURSERY, StickyMSNurseryTraceLocal.class); |
| super.registerSpecializedMethods(); |
| } |
| } |