org.mmtk.utility.heap

Class HeapGrowthManager

java.lang.Object

org.mmtk.utility.heap.HeapGrowthManager

public abstract class HeapGrowthManager
extends Object

This class is responsible for growing and shrinking the heap size by observing heap utilization and GC load.

Field Summary

Fields

Modifier and Type	Field and Description
private static double	accumulatedGCTime
private static Extent	currentHeapSize The current heap size in bytes
private static long	endLastMajorGC
private static double[][]	function An encoding of the function used to manage heap size.
private static double[][]	generationalFunction
private static Extent	initialHeapSize The initial heap size (-Xms) in bytes
private static Extent	maxHeapSize The maximum heap size (-Xms) in bytes
private static double[][]	nongenerationalFunction

Constructor Summary

Constructors

Constructor and Description
HeapGrowthManager()

Method Summary

Modifier and Type	Method and Description
static void	boot(Extent initial, Extent max) Initialize heap size parameters and the mechanisms used to adaptively change heap size.
private static double	computeHeapChangeRatio(double liveRatio)
static boolean	considerHeapSize() Decide how to grow/shrink the heap to respond to application's memory usage.
static Extent	getCurrentHeapSize()
static Extent	getInitialHeapSize() Return the initial heap size in bytes (as set by -Xms).
static Extent	getMaxHeapSize() Return the max heap size in bytes (as set by -Xmx).
static void	overrideGrowHeapSize(Extent size) Forcibly grow the heap by the given number of bytes.
static void	recordGCTime(double time) Record the time taken by the current GC; used to compute gc load, one of the inputs into the heap size management function
static void	reset() Reset timers used to compute gc load
private static void	sanityCheck() Check that function satisfies the invariants

Methods inherited from class java.lang.Object

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

Field Detail

initialHeapSize

private static Extent initialHeapSize

The initial heap size (-Xms) in bytes

maxHeapSize

private static Extent maxHeapSize

The maximum heap size (-Xms) in bytes

currentHeapSize

private static Extent currentHeapSize

The current heap size in bytes

generationalFunction

private static final double[][] generationalFunction

nongenerationalFunction

private static final double[][] nongenerationalFunction

function

private static final double[][] function

An encoding of the function used to manage heap size. The xaxis represents the live ratio at the end of a major collection. The yaxis represents the GC load (GC time/total time). The interior of the matrix represents a ratio to shrink or grow the heap for a given pair of live ratio and GC load. The constraints on the matrix are:

• function[0][0] is ignored.
• All numbers in the first row must monotonically increase and must be in the range from 0 to 1 inclusive.
• All numbers in the first column must monotonically increase and must be in the range from 0 to 1 inclusive.
• There must be 0 and 1 values specified in both dimensions.
• For all interior points in the matrix, the value must be greater than the liveRatio for that column.

endLastMajorGC

private static long endLastMajorGC

accumulatedGCTime

private static double accumulatedGCTime

Constructor Detail

HeapGrowthManager

public HeapGrowthManager()

Method Detail

boot

public static void boot(Extent initial,
                        Extent max)

Initialize heap size parameters and the mechanisms used to adaptively change heap size.

Parameters:

initial - the initial heap size

max - the maximum heap size

getCurrentHeapSize

public static Extent getCurrentHeapSize()

Returns:

the current heap size in bytes

getMaxHeapSize

public static Extent getMaxHeapSize()

Return the max heap size in bytes (as set by -Xmx).

Returns:

The max heap size in bytes (as set by -Xmx).

getInitialHeapSize

public static Extent getInitialHeapSize()

Return the initial heap size in bytes (as set by -Xms).

Returns:

The initial heap size in bytes (as set by -Xms).

overrideGrowHeapSize

public static void overrideGrowHeapSize(Extent size)

Forcibly grow the heap by the given number of bytes. Used to provide headroom when handling an OutOfMemory situation.

Parameters:

size - number of bytes to grow the heap

recordGCTime

public static void recordGCTime(double time)

Record the time taken by the current GC; used to compute gc load, one of the inputs into the heap size management function

Parameters:

time - number of time taking for current GC, in milliseconds

reset

public static void reset()

Reset timers used to compute gc load

considerHeapSize

public static boolean considerHeapSize()

Decide how to grow/shrink the heap to respond to application's memory usage.

Returns:

true if heap size was changed, false otherwise

computeHeapChangeRatio

private static double computeHeapChangeRatio(double liveRatio)

sanityCheck

private static void sanityCheck()

Check that function satisfies the invariants