javax.realtime

Class AperiodicParameters

java.lang.Object

javax.realtime.ReleaseParameters<AperiodicParameters>

javax.realtime.AperiodicParameters

All Implemented Interfaces:

Serializable, Cloneable

Direct Known Subclasses:

SporadicParameters

public class AperiodicParameters
extends ReleaseParameters<AperiodicParameters>
implements Cloneable

Jamaica Real-Time Specification for Java class AperiodicParameters

This class characterizes the release of schedulable objects that can be released at any time. Note that the presence of AperiodicParameters typically makes the feasibility analysis of any set of schedulable objects impossible, unless the total execution time required by aperiodic tasks are restricted by adequate ProcessingGroupParameters.

Note that any changes to RelativeTime arguments of this object do not propagate to the schedulable object until the corresponding setter method of AperiodicParameters is called to notify this object about the change.

NOTE: the methods in this class are not synchronized. They cannot be used by several threads simultaneously without proper explicit synchronization.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static String	arrivalTimeQueueOverflowExcept The "EXCEPT" policy for dealing with arrival time queue overflow.
static String	arrivalTimeQueueOverflowIgnore The "IGNORE" policy for dealing with arrival time queue overflow.
static String	arrivalTimeQueueOverflowReplace The "REPLACE" policy for dealing with arrival time queue overflow.
static String	arrivalTimeQueueOverflowSave The "SAVE" policy for dealing with arrival time queue overflow.

Fields inherited from class javax.realtime.ReleaseParameters

DISABLE_MONITORING

Constructor Summary

Constructors

Constructor and Description
AperiodicParameters() Create an AperiodicParameters object.
AperiodicParameters(RelativeTime deadline) Equivalent to AperiodicParameters(RelativeTime, RelativeTime, AsyncEventHandler, AsyncEventHandler, boolean) with the argument list (null, deadline, null, null, false).
AperiodicParameters(RelativeTime deadline, AsyncEventHandler missHandler, boolean rousable) Equivalent to AperiodicParameters(RelativeTime, RelativeTime, AsyncEventHandler, AsyncEventHandler, boolean) with the argument list (null, deadline, null, missHandler, rousable).
AperiodicParameters(RelativeTime cost, RelativeTime deadline, AsyncEventHandler overrunHandler, AsyncEventHandler missHandler) Constructor of AperiodicParameters to be used as ReleaseParameters for AsyncEventHandler if the event handler will be scheduled aperiodically.
AperiodicParameters(RelativeTime cost, RelativeTime deadline, AsyncEventHandler overrunHandler, AsyncEventHandler missHandler, boolean rousable) Creates an AperiodicParameters object.

Method Summary

Modifier and Type	Method and Description
Object	clone() clone creates a clone of this object with the same parameters but without association to any schedulable object.
String	getArrivalTimeQueueOverflowBehavior() getArrivalTimeQueueOverflowBehavior returns the current arrival time queue overflow behavior.
int	getInitialArrivalTimeQueueLength() getInitialArrivalTimeQueueLength returns the initial length of the arrival time queue.
void	setArrivalTimeQueueOverflowBehavior(String behavior) setArrivalTimeQueueOverflowBehavior sets the behavior for the case of an overflow in the arrival time queue.
boolean	setIfFeasible(RelativeTime cost, RelativeTime deadline) This method first performs a feasibility analysis using the new cost and deadline as replacements for the matching attributes of this.
void	setInitialArrivalTimeQueueLength(int initial) setInitialArrivalTimeQueueLength sets the initial number of elements in the arrival time queue for the schedulable object that receives this AperiodicParameters in its constructor.

Methods inherited from class javax.realtime.ReleaseParameters

getCost, getCost, getCostOverrunHandler, getDeadline, getDeadline, getDeadlineMissHandler, getEventQueueOverflowPolicy, getInitialQueueLength, isRousable, setCost, setCostOverrunHandler, setDeadline, setDeadlineMissHandler, setEventQueueOverflowPolicy, setInitialQueueLength, setRousable

Methods inherited from class java.lang.Object

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

Field Detail

arrivalTimeQueueOverflowExcept

public static final String arrivalTimeQueueOverflowExcept

The "EXCEPT" policy for dealing with arrival time queue overflow. Throws an ArrivalTimeQueueOverflowException on a call to fire() when the arrival time queue would otherwise overflow.

Since:

RTSJ V1.0.1

See Also:

Constant Field Values

arrivalTimeQueueOverflowIgnore

public static final String arrivalTimeQueueOverflowIgnore

The "IGNORE" policy for dealing with arrival time queue overflow. Ignores a call to fire() when the arrival time queue would otherwise overflow.

Since:

RTSJ V1.0.1

See Also:

Constant Field Values

arrivalTimeQueueOverflowReplace

public static final String arrivalTimeQueueOverflowReplace

The "REPLACE" policy for dealing with arrival time queue overflow. Replaces an entry in the arrival time queue when the arrival time queue would otherwise overflow.

Since:

RTSJ V1.0.1

See Also:

Constant Field Values

arrivalTimeQueueOverflowSave

public static final String arrivalTimeQueueOverflowSave

The "SAVE" policy for dealing with arrival time queue overflow. Extends the queue length when the arrival time queue would otherwise overflow. The initial queue length is not affected by this extension.

Since:

RTSJ V1.0.1

See Also:

Constant Field Values

Constructor Detail

AperiodicParameters

public AperiodicParameters()

Create an AperiodicParameters object. This constructor is equivalent to AperiodicParameters(null, null, null, null).

AperiodicParameters

public AperiodicParameters(RelativeTime deadline,
                           AsyncEventHandler missHandler,
                           boolean rousable)

Equivalent to AperiodicParameters(RelativeTime, RelativeTime, AsyncEventHandler, AsyncEventHandler, boolean) with the argument list (null, deadline, null, missHandler, rousable).

Since:

RTSJ 2.0

AperiodicParameters

public AperiodicParameters(RelativeTime deadline)

Equivalent to AperiodicParameters(RelativeTime, RelativeTime, AsyncEventHandler, AsyncEventHandler, boolean) with the argument list (null, deadline, null, null, false).

Since:

RTSJ 2.0

AperiodicParameters

public AperiodicParameters(RelativeTime cost,
                           RelativeTime deadline,
                           AsyncEventHandler overrunHandler,
                           AsyncEventHandler missHandler)

Constructor of AperiodicParameters to be used as ReleaseParameters for AsyncEventHandler if the event handler will be scheduled aperiodically.

Throws:

StaticIllegalArgumentException - if cost is negative or deadline is negative or zero.

Parameters:

cost - The CPU time required for each release. If cost monitoring is performed, this gives the maximum amount of CPU time that will be allowed for each release. In any case, this may be used by the feasibility analysis. If null, the default value will be new RelativeTime(0, 0). Note that on a system with cost monitoring, this default value will allow no execution time for the associated schedulable object.

deadline - The deadline for the completion of one release, relative to the release time of that release. If null, the default value is a new instance of RealtiveTime(Long.MAX_VALUE, 999999).

overrunHandler - This handler will be invoked if the cost of one invocation exceeds the cost parameter. If null, there will be no overrunHandler.

For JamaicaVM, cost overrun checking is enabled if CpuTime.CPU_TIME_SUPPORTED is true. The accuracy of the cost enforcement can be specified in nanoseconds via the property jamaica.cost_monitoring_accuracy. The default value is 5000000, i.e., 5milliseconds.

missHandler - This handler will be invoked if the deadline of one release is missed. If null, there will be no deadline.

AperiodicParameters

public AperiodicParameters(RelativeTime cost,
                           RelativeTime deadline,
                           AsyncEventHandler overrunHandler,
                           AsyncEventHandler missHandler,
                           boolean rousable)

Creates an AperiodicParameters object.

Throws:

StaticIllegalArgumentException - when the time value of cost is less than zero, or the time value of deadline is less than or equal to zero.

IllegalAssignmentError - when cost, deadline, overrunHandler or missHandler cannot be stored in this.

Parameters:

cost - Processing time per invocation. On implementations which can measure the amount of time a schedulable object is executed, this value is the maximum amount of time a schedulable receives. On implementations which cannot measure execution time, it is not possible to determine when any particular object exceeds cost. When null, the default value is a new instance of RelativeTime(0,0).

deadline - The latest permissible completion time measured from the release time of the associated invocation of the schedulable. When null, the default value is a new instance of RelativeTime(Long.MAX_VALUE, 999999).

overrunHandler - This handler is invoked when an invocation of the schedulable exceeds cost. Not required for minimum implementation. When null, the default value is no overrun handler.

missHandler - This handler is invoked when the run() method of the schedulable object is still executing after the deadline has passed. When null, the default value is no miss handler.

rousable - determines whether or not an instance of Schedulable can be prematurely released by a thread interrupt.

Since:

RTSJ 2.0

Method Detail

setIfFeasible

public boolean setIfFeasible(RelativeTime cost,
                             RelativeTime deadline)

This method first performs a feasibility analysis using the new cost and deadline as replacements for the matching attributes of this. When the resulting system is feasible, the method replaces the current scheduling characteristics of this with the new scheduling characteristics.

Overrides:

setIfFeasible in class ReleaseParameters<AperiodicParameters>

Throws:

StaticIllegalArgumentException - when the time value of cost is less than zero, or the time value of deadline is less than or equal to zero, or the values are incompatible with the scheduler for any of the schedulables which are presently using this parameter object.

IllegalAssignmentError - when cost or deadline cannot be stored in this.

Parameters:

cost - The proposed cost used to determine when any particular object exceeds cost. When null, the default value is a new instance of RelativeTime(0,0).

deadline - The proposed deadline. When null, the default value is a new instance of RelativeTime(Long.MAX_VALUE, 999999).

Returns:

false. Aperiodic parameters never yield a feasible system. (Subclasses of AperiodicParameters, such as SporadicParameters, need not return false.)

getInitialArrivalTimeQueueLength

public int getInitialArrivalTimeQueueLength()

getInitialArrivalTimeQueueLength returns the initial length of the arrival time queue. This value may be different from the actual queue length if the length has been extended due to the use of the arrivalTimeQueueOverflowSave behavior or the length was changed by a call to setInitialArrivalTimeQueueLength after the schedulable object was constructed.

Returns:

the current value for the initial arrival time queue length.

Since:

RTSJ V1.0.1

setInitialArrivalTimeQueueLength

public void setInitialArrivalTimeQueueLength(int initial)

setInitialArrivalTimeQueueLength sets the initial number of elements in the arrival time queue for the schedulable object that receives this AperiodicParameters in its constructor.

Throws:

StaticIllegalArgumentException - if initial is less than zero.

Parameters:

initial - the initial arrival time queue length.

Since:

RTSJ V1.0.1

setArrivalTimeQueueOverflowBehavior

public void setArrivalTimeQueueOverflowBehavior(String behavior)

setArrivalTimeQueueOverflowBehavior sets the behavior for the case of an overflow in the arrival time queue.

Throws:

StaticIllegalArgumentException - if behavior is not one of the constants arrivalTimeQueueOverflowExcept, arrivalTimeQueueOverflowIgnore, arrivalTimeQueueOverflowReplace, arrivalTimeQueueOverflowSave.

Parameters:

behavior - the behavior, must be one of arrivalTimeQueueOverflowExcept, arrivalTimeQueueOverflowIgnore, arrivalTimeQueueOverflowReplace, arrivalTimeQueueOverflowSave.

Since:

RTSJ V1.0.1

getArrivalTimeQueueOverflowBehavior

public String getArrivalTimeQueueOverflowBehavior()

getArrivalTimeQueueOverflowBehavior returns the current arrival time queue overflow behavior.

Returns:

the current behavior, one of arrivalTimeQueueOverflowExcept, arrivalTimeQueueOverflowIgnore, arrivalTimeQueueOverflowReplace, arrivalTimeQueueOverflowSave.

Since:

RTSJ V1.0.1

clone

public Object clone()

clone creates a clone of this object with the same parameters but without association to any schedulable object. According to RTSJ 1.0.2, the cost and deadline attributes are deep-copied, whereas the missHandler, overrunHandler, and the overflow behavior attributes are only shallow-copied.

Overrides:

clone in class ReleaseParameters<AperiodicParameters>

Returns:

a new instance of AperiodicParameters with equal cost and deadline attributes, and copied references of the overrunHandler, missHandler, and overflow behavior attributes.

Since:

RTSJ V1.0.1

See Also:

Cloneable