/* * This file is part of the Jikes RVM project (http://jikesrvm.org). * * This file is licensed to You under the Common Public License (CPL); * 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/cpl1.0.php * * See the COPYRIGHT.txt file distributed with this work for information * regarding copyright ownership. */ package org.mmtk.plan.generational; import org.mmtk.plan.*; import org.mmtk.policy.CopyLocal; import org.mmtk.policy.Space; import org.mmtk.utility.deque.*; import org.mmtk.utility.alloc.Allocator; import org.mmtk.utility.statistics.Stats; import org.mmtk.vm.VM; import org.vmmagic.pragma.*; import org.vmmagic.unboxed.*; /** * This abstract class implements <i>per-mutator thread</i> behavior * and state for <i>generational copying collectors</i>.<p> * * Specifically, this class defines mutator-time allocation into the nursery; * write barrier semantics, and per-mutator thread collection semantics * (flushing and restoring per-mutator allocator and remset state). * * @see Gen * @see GenCollector * @see StopTheWorldMutator * @see MutatorContext */ @Uninterruptible public class GenMutator extends StopTheWorldMutator { /***************************************************************************** * * Instance fields */ protected final CopyLocal nursery = new CopyLocal(Gen.nurserySpace); protected final WriteBuffer remset; protected final AddressPairDeque arrayRemset; /**************************************************************************** * * Initialization */ /** * Constructor * * Note that each mutator is a producer of remsets, while each * collector is a consumer. The <code>GenCollector</code> class * is responsible for construction of the consumer. * @see GenCollector */ public GenMutator() { remset = new WriteBuffer(global().remsetPool); arrayRemset = new AddressPairDeque(global().arrayRemsetPool); } /**************************************************************************** * * Mutator-time allocation */ /** * Allocate memory for an object. * * @param bytes The number of bytes required for the object. * @param align Required alignment for the object. * @param offset Offset associated with the alignment. * @param allocator The allocator associated with this request. * @param site Allocation site * @return The low address of the allocated memory. */ @Inline public Address alloc(int bytes, int align, int offset, int allocator, int site) { if (allocator == Gen.ALLOC_NURSERY) { if (Stats.GATHER_MARK_CONS_STATS) Gen.nurseryCons.inc(bytes); return nursery.alloc(bytes, align, offset); } return super.alloc(bytes, align, offset, allocator, site); } /** * Perform post-allocation actions. For many allocators none are * required. * * @param ref The newly allocated object * @param typeRef the type reference for the instance being created * @param bytes The size of the space to be allocated (in bytes) * @param allocator The allocator number to be used for this allocation */ @Inline public void postAlloc(ObjectReference ref, ObjectReference typeRef, int bytes, int allocator) { if (allocator != Gen.ALLOC_NURSERY) { super.postAlloc(ref, typeRef, bytes, allocator); } } /** * Return the space into which an allocator is allocating. This * particular method will match against those spaces defined at this * level of the class hierarchy. Subclasses must deal with spaces * they define and refer to superclasses appropriately. * * @param a An allocator * @return The space into which <code>a</code> is allocating, or * <code>null</code> if there is no space associated with * <code>a</code>. */ public Space getSpaceFromAllocator(Allocator a) { if (a == nursery) return Gen.nurserySpace; // a does not belong to this plan instance return super.getSpaceFromAllocator(a); } /** * Return the allocator instance associated with a space * <code>space</code>, for this plan instance. * * @param space The space for which the allocator instance is desired. * @return The allocator instance associated with this plan instance * which is allocating into <code>space</code>, or <code>null</code> * if no appropriate allocator can be established. */ public Allocator getAllocatorFromSpace(Space space) { if (space == Gen.nurserySpace) return nursery; return super.getAllocatorFromSpace(space); } /**************************************************************************** * * Barriers */ /** * A new reference is about to be created. Take appropriate write * barrier actions.<p> * * In this case, we remember the address of the source of the * pointer if the new reference points into the nursery from * non-nursery space. * * @param src The object into which the new reference will be stored * @param slot The address into which the new reference will be * stored. * @param tgt The target of the new reference * @param metaDataA A field used by the VM to create a correct store. * @param metaDataB A field used by the VM to create a correct store. * @param mode The mode of the store (eg putfield, putstatic etc) */ @Inline public final void writeBarrier(ObjectReference src, Address slot, ObjectReference tgt, Offset metaDataA, int metaDataB, int mode) { if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbFast.inc(); if (slot.LT(Gen.NURSERY_START) && tgt.toAddress().GE(Gen.NURSERY_START)) { if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbSlow.inc(); remset.insert(slot); } VM.barriers.performWriteInBarrier(src, slot, tgt, metaDataA, metaDataB, mode); } /** * Attempt to atomically exchange the value in the given slot * with the passed replacement value. If a new reference is * created, we must then take appropriate write barrier actions.<p> * * In this case, we remember the address of the source of the * pointer if the new reference points into the nursery from * non-nursery space. * * @param src The object into which the new reference will be stored * @param slot The address into which the new reference will be * stored. * @param old The old reference to be swapped out * @param tgt The target of the new reference * @param metaDataA An int that assists the host VM in creating a store * @param metaDataB An int that assists the host VM in creating a store * @param mode The context in which the store occured * @return True if the swap was successful. */ @Inline public boolean tryCompareAndSwapWriteBarrier(ObjectReference src, Address slot, ObjectReference old, ObjectReference tgt, Offset metaDataA, int metaDataB, int mode) { boolean result = VM.barriers.tryCompareAndSwapWriteInBarrier(src, slot, old, tgt, metaDataA, metaDataB, mode); if (result) { if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbFast.inc(); if (slot.LT(Gen.NURSERY_START) && tgt.toAddress().GE(Gen.NURSERY_START)) { if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbSlow.inc(); remset.insert(slot); } } return result; } /** * A number of references are about to be copied from object * <code>src</code> to object <code>dst</code> (as in an array * copy). Thus, <code>dst</code> is the mutated object. Take * appropriate write barrier actions.<p> * * In this case, we remember the mutated source address range and * will scan that address range at GC time. * * @param src The source of the values to copied * @param srcOffset The offset of the first source address, in * bytes, relative to <code>src</code> (in principle, this could be * negative). * @param dst The mutated object, i.e. the destination of the copy. * @param dstOffset The offset of the first destination address, in * bytes relative to <code>tgt</code> (in principle, this could be * negative). * @param bytes The size of the region being copied, in bytes. * @return True if the update was performed by the barrier, false if * left to the caller (always false in this case). */ @Inline public final boolean writeBarrier(ObjectReference src, Offset srcOffset, ObjectReference dst, Offset dstOffset, int bytes) { // We can ignore when src is in old space, right? if (dst.toAddress().LT(Gen.NURSERY_START)) arrayRemset.insert(dst.toAddress().plus(dstOffset), dst.toAddress().plus(dstOffset.plus(bytes))); return false; } /** * Flush per-mutator remembered sets into the global remset pool. */ public final void flushRememberedSets() { remset.flushLocal(); arrayRemset.flushLocal(); assertRemsetsFlushed(); } /** * Assert that the remsets have been flushed. This is critical to * correctness. We need to maintain the invariant that remset entries * do not accrue during GC. If the host JVM generates barrier entires * it is its own responsibility to ensure that they are flushed before * returning to MMTk. */ public final void assertRemsetsFlushed() { if (VM.VERIFY_ASSERTIONS) { VM.assertions._assert(remset.isFlushed()); VM.assertions._assert(arrayRemset.isFlushed()); } } /**************************************************************************** * * Collection */ /** * Perform a per-mutator collection phase. */ @NoInline public void collectionPhase(short phaseId, boolean primary) { if (phaseId == Gen.PREPARE) { nursery.rebind(Gen.nurserySpace); if (global().traceFullHeap()) { super.collectionPhase(phaseId, primary); remset.resetLocal(); arrayRemset.resetLocal(); } else { plos.prepare(false); flushRememberedSets(); } return; } if (phaseId == Gen.RELEASE) { if (global().traceFullHeap()) { super.collectionPhase(phaseId, primary); } else { plos.release(false); } assertRemsetsFlushed(); return; } super.collectionPhase(phaseId, primary); } /**************************************************************************** * * Miscellaneous */ /** @return The active global plan as a <code>Gen</code> instance. */ @Inline private static Gen global() { return (Gen) VM.activePlan.global(); } }