org.mmtk.policy

Class MarkSweepLocal

java.lang.Object

org.mmtk.utility.alloc.Allocator

org.mmtk.utility.alloc.SegregatedFreeList<S>

org.mmtk.utility.alloc.SegregatedFreeListLocal<MarkSweepSpace>

org.mmtk.policy.MarkSweepLocal

public final class MarkSweepLocal
extends SegregatedFreeListLocal<MarkSweepSpace>

This class implements unsynchronized (local) elements of a mark-sweep collector. Allocation is via the segregated free list (@see SegregatedFreeList). Marking is done using both a bit in each header's object word, and a mark bitmap. Sweeping is performed lazily.

A free list block is a contiguous region of memory containing cells of a single size class, and is a construct of the SegregatedFreeList. This class extends the block to include a mark bitmap. During the mark phase, if an object is encountered with the mark bit in its header unset, it is set and the mark bit in the block header corresponding to that object is set. The rationale behind this approach is that testing (and setting) the mark bit in the object header is cheap, while using a bitmap makes sweeping more efficient. This approach maximizes the speed of the common case when marking, while also allowing for fast sweeping, with minimal space overhead (2 bits per object).

See Also:

SegregatedFreeList, MarkSweepSpace

Field Summary

Fields inherited from class org.mmtk.utility.alloc.SegregatedFreeListLocal

currentBlock

Fields inherited from class org.mmtk.utility.alloc.SegregatedFreeList

freeList, space

Constructor Summary

Constructors

Constructor and Description
MarkSweepLocal(MarkSweepSpace space) Constructor

Method Summary

Modifier and Type	Method and Description
void	prepare() Prepare for a collection.
void	release() Finish up after a collection.

Methods inherited from class org.mmtk.utility.alloc.SegregatedFreeListLocal

allocSlowOnce, flush

Methods inherited from class org.mmtk.utility.alloc.SegregatedFreeList

alloc, getSpace

Methods inherited from class org.mmtk.utility.alloc.Allocator

alignAllocation, alignAllocation, alignAllocationNoFill, allocSlow, allocSlowInline, determineCollectionAttempts, fillAlignmentGap, getMaximumAlignedSize, getMaximumAlignedSize

Methods inherited from class java.lang.Object

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

Constructor Detail

MarkSweepLocal

public MarkSweepLocal(MarkSweepSpace space)

Constructor

Parameters:

space - The mark-sweep space to which this allocator instances is bound.

Method Detail

prepare

public void prepare()

Prepare for a collection. If paranoid, perform a sanity check.

release

public void release()

Finish up after a collection.