/*
* 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.generational;
import org.mmtk.plan.*;
import org.mmtk.policy.CopyLocal;
import org.mmtk.policy.Space;
import org.mmtk.utility.HeaderByte;
import org.mmtk.utility.deque.*;
import org.mmtk.utility.alloc.Allocator;
import org.mmtk.utility.statistics.Stats;
import org.mmtk.vm.VM;
import static org.mmtk.plan.generational.Gen.USE_OBJECT_BARRIER_FOR_AASTORE;
import static org.mmtk.plan.generational.Gen.USE_OBJECT_BARRIER_FOR_PUTFIELD;
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);
private final ObjectReferenceDeque modbuf; /* remember modified scalars */
protected final WriteBuffer remset; /* remember modified array fields */
protected final AddressPairDeque arrayRemset; /* remember modified array ranges */
/****************************************************************************
*
* 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() {
modbuf = new ObjectReferenceDeque("modbuf", global().modbufPool);
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 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
*/
/**
* Perform the write barrier fast path, which may involve remembering
* a reference if necessary.
*
* @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 mode The mode of the store (eg putfield, putstatic etc)
*/
@Inline
private void fastPath(ObjectReference src, Address slot, ObjectReference tgt, int mode) {
if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbFast.inc();
if ((mode == ARRAY_ELEMENT && USE_OBJECT_BARRIER_FOR_AASTORE) ||
(mode == INSTANCE_FIELD && USE_OBJECT_BARRIER_FOR_PUTFIELD)) {
if (HeaderByte.isUnlogged(src)) {
if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbSlow.inc();
HeaderByte.markAsLogged(src);
modbuf.insert(src);
}
} else {
if (!Gen.inNursery(slot) && Gen.inNursery(tgt)) {
if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbSlow.inc();
remset.insert(slot);
}
}
}
/**
* 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 value that assists the host VM in creating a store
* @param metaDataB A value that assists the host VM in creating a store
* @param mode The mode of the store (eg putfield, putstatic etc)
*/
@Inline
public final void objectReferenceWrite(ObjectReference src, Address slot,
ObjectReference tgt, Word metaDataA,
Word metaDataB, int mode) {
fastPath(src, slot, tgt, mode);
VM.barriers.objectReferenceWrite(src, tgt, metaDataA, metaDataB, mode);
}
/**
* Perform the root write barrier fast path, which may involve remembering
* a reference if necessary.
*
* @param slot The address into which the new reference will be
* stored.
* @param tgt The target of the new reference
* @param mode The mode of the store (eg putfield, putstatic etc)
*/
@Inline
private void fastPath(Address slot, ObjectReference tgt) {
if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbFast.inc();
if (Gen.inNursery(tgt)) {
if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbSlow.inc();
remset.insert(slot);
}
}
/**
* A new reference is about to be created in a location that is not
* a regular heap object. 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 slot The address into which the new reference will be
* stored.
* @param tgt The target of the new reference
* @param metaDataA A value that assists the host VM in creating a store
* @param metaDataB A value that assists the host VM in creating a store
*/
@Inline
public final void objectReferenceNonHeapWrite(Address slot, ObjectReference tgt,
Word metaDataA, Word metaDataB) {
fastPath(slot, tgt);
VM.barriers.objectReferenceNonHeapWrite(slot, tgt, metaDataA, metaDataB);
}
/**
* 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 A value that assists the host VM in creating a store
* @param metaDataB A value 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 objectReferenceTryCompareAndSwap(ObjectReference src, Address slot, ObjectReference old, ObjectReference tgt,
Word metaDataA, Word metaDataB, int mode) {
boolean result = VM.barriers.objectReferenceTryCompareAndSwap(src, old, tgt, metaDataA, metaDataB, mode);
if (result)
fastPath(src, slot, tgt, mode);
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 be copied
* @param srcIdx The starting source index
* @param dst The mutated object, i.e. the destination of the copy.
* @param srcIdx The starting source index
* @param len The number of array elements to be copied
* @return True if the update was performed by the barrier, false if
* left to the caller (always false in this case).
*/
@Inline
@Override
public final boolean objectReferenceBulkCopy(ObjectReference src, Offset srcOffset, ObjectReference dst, Offset dstOffset, int bytes) {
if (!Gen.inNursery(dst)) {
Address start = dst.toAddress().plus(dstOffset);
arrayRemset.insert(start, start.plus(bytes));
}
return false;
}
/**
* Flush per-mutator remembered sets into the global remset pool.
*/
public final void flushRememberedSets() {
modbuf.flushLocal();
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(modbuf.isFlushed());
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.reset();
if (global().traceFullHeap()) {
super.collectionPhase(phaseId, primary);
modbuf.flushLocal();
remset.resetLocal();
arrayRemset.resetLocal();
} else {
flushRememberedSets();
}
return;
}
if (phaseId == Gen.RELEASE) {
if (global().traceFullHeap()) {
super.collectionPhase(phaseId, primary);
}
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();
}
}