org.mmtk.plan.generational.copying
Class GenCopy

java.lang.Object
  org.mmtk.plan.Plan
      org.mmtk.plan.Simple
          org.mmtk.plan.StopTheWorld
              org.mmtk.plan.generational.Gen
                  org.mmtk.plan.generational.copying.GenCopy

All Implemented Interfaces:

Constants

public class GenCopy
extends Gen

This class implements the functionality of a standard two-generation copying collector. Nursery collections occur when either the heap is full or the nursery is full. The nursery size is determined by an optional command line argument. If undefined, the nursery size is "infinite", so nursery collections only occur when the heap is full (this is known as a flexible-sized nursery collector). Thus both fixed and flexible nursery sizes are supported. Full heap collections occur when the nursery size has dropped to a statically defined threshold, NURSERY_THRESHOLD

See the Jones & Lins GC book, chapter 7 for a detailed discussion of generational collection and section 7.3 for an overview of the flexible nursery behavior ("The Standard ML of New Jersey collector"), or go to Appel's paper "Simple generational garbage collection and fast allocation." SP&E 19(2):171--183, 1989.

All plans make a clear distinction between global and thread-local activities. Global activities must be synchronized, whereas no synchronization is required for thread-local activities. Instances of Plan map 1:1 to "kernel threads" (aka CPUs). Thus instance methods allow fast, unsychronized access to Plan utilities such as allocation and collection. Each instance rests on static resources (such as memory and virtual memory resources) which are "global" and therefore "static" members of Plan. This mapping of threads to instances is crucial to understanding the correctness and performance properties of this plan.

hi

static boolean hi

true if copying to "higher" semispace

matureSpace0

static CopySpace matureSpace0

The low half of the copying mature space. We allocate into this space when hi is false.

MS0

static final int MS0

matureSpace1

static CopySpace matureSpace1

The high half of the copying mature space. We allocate into this space when hi is true.

MS1

static final int MS1

matureTrace

final Trace matureTrace

GenCopy

public GenCopy()

Constructor

copyMature

protected boolean copyMature()

Overrides:

copyMature in class Gen

Returns:

Does the mature space do copying ?

toSpace

static CopySpace toSpace()

Returns:

The semispace we are currently allocating into

toSpaceDesc

static int toSpaceDesc()

Returns:

Space descriptor for to-space.

fromSpace

static CopySpace fromSpace()

Returns:

The semispace we are currently copying from (or copied from at last major GC)

fromSpaceDesc

static int fromSpaceDesc()

Returns:

Space descriptor for from-space

collectionPhase

public void collectionPhase(short phaseId)

Perform a (global) collection phase.

Overrides:

collectionPhase in class Gen

Parameters:

phaseId - The unique id of the phase to perform.

getPagesUsed

public int getPagesUsed()

Return the number of pages reserved for use given the pending allocation.

Overrides:

getPagesUsed in class Gen

Returns:

The number of pages reserved given the pending allocation, excluding space reserved for copying.

getCollectionReserve

public final int getCollectionReserve()

Return the number of pages reserved for copying.

Overrides:

getCollectionReserve in class Gen

Returns:

the number of pages reserved for copying.

getMaturePhysicalPagesAvail

public int getMaturePhysicalPagesAvail()

Description copied from class: Gen

Return the number of pages available for allocation into the mature space.

Specified by:

getMaturePhysicalPagesAvail in class Gen

Returns:

The number of pages available for allocation into the mature space.

activeMatureSpace

public Space activeMatureSpace()

Description copied from class: Gen

Accessor method to allow the generic generational code in Gen.java to access the mature space.

Specified by:

activeMatureSpace in class Gen

Returns:

The mature space we are currently allocating into

registerSpecializedMethods

protected void registerSpecializedMethods()

Description copied from class: Plan

Register specialized methods.

Overrides:

registerSpecializedMethods in class Gen