/*
* 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();
}
}