org.mmtk.plan.generational

Class GenMutator

java.lang.Object

org.mmtk.plan.MutatorContext

org.mmtk.plan.SimpleMutator

org.mmtk.plan.StopTheWorldMutator

org.mmtk.plan.generational.GenMutator

Direct Known Subclasses:

GenCopyMutator, GenImmixMutator, GenMSMutator

public class GenMutator
extends StopTheWorldMutator

This abstract class implements per-mutator thread behavior and state for generational copying collectors.

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 Also:

Gen, GenCollector, StopTheWorldMutator, MutatorContext

Field Summary

Fields

Modifier and Type	Field and Description
protected AddressPairDeque	arrayRemset
private ObjectReferenceDeque	modbuf
protected CopyLocal	nursery
protected WriteBuffer	remset

Fields inherited from class org.mmtk.plan.MutatorContext

immortal, lgcode, log, los, nonmove, smcode

Constructor Summary

Constructors

Constructor and Description
GenMutator() Constructor Note that each mutator is a producer of remsets, while each collector is a consumer.

Method Summary

Modifier and Type	Method and Description
Address	alloc(int bytes, int align, int offset, int allocator, int site) Allocate memory for an object.
void	assertRemsetsFlushed() Assert that the remsets have been flushed.
void	collectionPhase(short phaseId, boolean primary) Perform a per-mutator collection phase.
private void	fastPath(Address slot, ObjectReference tgt) Perform the root write barrier fast path, which may involve remembering a reference if necessary.
private void	fastPath(ObjectReference src, Address slot, ObjectReference tgt, int mode) Perform the write barrier fast path, which may involve remembering a reference if necessary.
void	flushRememberedSets() Flush per-mutator remembered sets into the global remset pool.
Allocator	getAllocatorFromSpace(Space space) Return the allocator instance associated with a space space, for this plan instance.
private static Gen	global()
boolean	objectReferenceBulkCopy(ObjectReference src, Offset srcOffset, ObjectReference dst, Offset dstOffset, int bytes) A number of references are about to be copied from object src to object dst (as in an array copy).
void	objectReferenceNonHeapWrite(Address slot, ObjectReference tgt, Word metaDataA, Word metaDataB) A new reference is about to be created in a location that is not a regular heap object.
boolean	objectReferenceTryCompareAndSwap(ObjectReference src, Address slot, ObjectReference old, ObjectReference tgt, Word metaDataA, Word metaDataB, int mode) Attempt to atomically exchange the value in the given slot with the passed replacement value.
void	objectReferenceWrite(ObjectReference src, Address slot, ObjectReference tgt, Word metaDataA, Word metaDataB, int mode) Write an object reference.
void	postAlloc(ObjectReference ref, ObjectReference typeRef, int bytes, int allocator) Perform post-allocation actions.

Methods inherited from class org.mmtk.plan.MutatorContext

addressBulkCopy, addressRead, addressTryCompareAndSwap, addressWrite, booleanBulkCopy, booleanRead, booleanWrite, byteBulkCopy, byteRead, byteWrite, charBulkCopy, charRead, charWrite, checkAllocator, deinitMutator, doubleBulkCopy, doubleRead, doubleWrite, extentBulkCopy, extentRead, extentWrite, floatBulkCopy, floatRead, floatWrite, flush, getId, getLog, initMutator, intBulkCopy, intRead, intTryCompareAndSwap, intWrite, javaLangReferenceReadBarrier, longBulkCopy, longRead, longTryCompareAndSwap, longWrite, objectReferenceNonHeapRead, objectReferenceRead, offsetBulkCopy, offsetRead, offsetWrite, shortBulkCopy, shortRead, shortWrite, wordBulkCopy, wordRead, wordTryCompareAndSwap, wordWrite

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

nursery

protected final CopyLocal nursery

modbuf

private final ObjectReferenceDeque modbuf

remset

protected final WriteBuffer remset

arrayRemset

protected final AddressPairDeque arrayRemset

Constructor Detail

GenMutator

public GenMutator()

Constructor

Note that each mutator is a producer of remsets, while each collector is a consumer. The GenCollector class is responsible for construction of the consumer.

See Also:

GenCollector

Method Detail

alloc

public Address alloc(int bytes,
                     int align,
                     int offset,
                     int allocator,
                     int site)

Allocate memory for an object.

Overrides:

alloc in class MutatorContext

Parameters:

bytes - The number of bytes required for the object.

align - Required alignment for the object.

offset - Offset associated with the alignment.

allocator - The allocator associated with this request.

site - Allocation site

Returns:

The low address of the allocated chunk.

postAlloc

public void postAlloc(ObjectReference ref,
                      ObjectReference typeRef,
                      int bytes,
                      int allocator)

Description copied from class: MutatorContext

Perform post-allocation actions. For many allocators none are required.

Overrides:

postAlloc in class MutatorContext

Parameters:

ref - The newly allocated object

typeRef - the type reference for the instance being created

bytes - The size of the space to be allocated (in bytes)

allocator - The allocator number to be used for this allocation

getAllocatorFromSpace

public Allocator getAllocatorFromSpace(Space space)

Description copied from class: MutatorContext

Return the allocator instance associated with a space space, for this plan instance.

Overrides:

getAllocatorFromSpace in class MutatorContext

Parameters:

space - The space for which the allocator instance is desired.

Returns:

The allocator instance associated with this plan instance which is allocating into space, or null if no appropriate allocator can be established.

fastPath

private void fastPath(ObjectReference src,
                      Address slot,
                      ObjectReference tgt,
                      int mode)

Perform the write barrier fast path, which may involve remembering a reference if necessary.

Parameters:

src - The object into which the new reference will be stored

slot - The address into which the new reference will be stored.

tgt - The target of the new reference

mode - The mode of the store (eg putfield, putstatic etc)

objectReferenceWrite

public final void objectReferenceWrite(ObjectReference src,
                                       Address slot,
                                       ObjectReference tgt,
                                       Word metaDataA,
                                       Word metaDataB,
                                       int mode)

Write an object reference. Take appropriate write barrier actions.

By default do nothing, override if appropriate.

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.

Overrides:

objectReferenceWrite in class MutatorContext

Parameters:

src - The object into which the new reference will be stored

slot - The address into which the new reference will be stored.

tgt - The value of the new reference

metaDataA - A value that assists the host VM in creating a store

metaDataB - A value that assists the host VM in creating a store

mode - The context in which the store occurred

fastPath

private void fastPath(Address slot,
                      ObjectReference tgt)

Perform the root write barrier fast path, which may involve remembering a reference if necessary.

Parameters:

slot - The address into which the new reference will be stored.

tgt - The target of the new reference

objectReferenceNonHeapWrite

public final void objectReferenceNonHeapWrite(Address slot,
                                              ObjectReference tgt,
                                              Word metaDataA,
                                              Word metaDataB)

A new reference is about to be created in a location that is not a regular heap object. Take appropriate write barrier actions.

By default do nothing, override if appropriate.

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.

Overrides:

objectReferenceNonHeapWrite in class MutatorContext

Parameters:

slot - The address into which the new reference will be stored.

tgt - The target of the new reference

metaDataA - A value that assists the host VM in creating a store

metaDataB - A value that assists the host VM in creating a store

objectReferenceTryCompareAndSwap

public boolean objectReferenceTryCompareAndSwap(ObjectReference src,
                                                Address slot,
                                                ObjectReference old,
                                                ObjectReference tgt,
                                                Word metaDataA,
                                                Word metaDataB,
                                                int 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.

By default do nothing, override if appropriate.

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.

Overrides:

objectReferenceTryCompareAndSwap in class MutatorContext

Parameters:

src - The object into which the new reference will be stored

slot - The address into which the new reference will be stored.

old - The old reference to be swapped out

tgt - The target of the new reference

metaDataA - A value that assists the host VM in creating a store

metaDataB - A value that assists the host VM in creating a store

mode - The context in which the store occurred

Returns:

True if the swap was successful.

objectReferenceBulkCopy

public final boolean objectReferenceBulkCopy(ObjectReference src,
                                             Offset srcOffset,
                                             ObjectReference dst,
                                             Offset dstOffset,
                                             int bytes)

A number of references are about to be copied from object src to object dst (as in an array copy). Thus, dst is the mutated object. Take appropriate write barrier actions.

In this case, we remember the mutated source address range and will scan that address range at GC time.

Overrides:

objectReferenceBulkCopy in class MutatorContext

Parameters:

src - The source array

srcOffset - The starting source offset

dst - The destination array

dstOffset - The starting destination offset

bytes - The number of bytes to be copied

Returns:

true if the update was performed by the barrier, false if left to the caller (always false in this case).

flushRememberedSets

public final void flushRememberedSets()

Description copied from class: MutatorContext

Flush per-mutator remembered sets into the global remset pool.

Overrides:

flushRememberedSets in class MutatorContext

assertRemsetsFlushed

public final void assertRemsetsFlushed()

Description copied from class: MutatorContext

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 entries it is its own responsibility to ensure that they are flushed before returning to MMTk.

Overrides:

assertRemsetsFlushed in class MutatorContext

collectionPhase

public void collectionPhase(short phaseId,
                            boolean primary)

Perform a per-mutator collection phase. This is executed by one collector thread on behalf of a mutator thread.

Overrides:

collectionPhase in class SimpleMutator

Parameters:

phaseId - The unique phase identifier

primary - Should this thread be used to execute any single-threaded local operations?

global

private static Gen global()

Returns:

The active global plan as a Gen instance.