Class Job

java.lang.Object
  |
  +--Job

class Job

extends java.lang.Object

A Job represents one customer of services. It records the job's current state as well as statistics about its lifetime. It generally spends its lifetime moving form Server to Server.

One Job is created from each line of the input trace file.

The resources required by a Job are characterized by an amount `cpuNeeded' of CPU time (all times are in milliseconds) and a number `ioNeeded' of I/O operations, each representing one disk transfer of Sim.BLOCKSIZE bytes of data. The CPU time is assumed to be distributed as evenly as possible into ioNeeded "bursts" of cpu time, each followed by an I/O operation (unless the job does no I/O at all).

Note the terminology: A "burst" is the amount of computing a Job wants to do before choosing to do I/O. Depending on the CPU scheduing algorithm in force, these bursts may be divided into "quanta" (plural of "quantum").

Field Summary

(package private) int	arrivalTime Arrival time in ms from start of simulation
static int	BLOCKED Job needs to do an I/O operation next
int	burst size of current burst
private int	burstRemaining amount in current burst (until next I/O op) remaining
int	burstStart time when current burst started (job "arrived" at the cpu queue)
private int	cpuNeeded Total CPU time (ms) required by this job
private int	cpuRemaining total amount of CPU time (in ms) left to consume
static int	DONE Job has completed
private int	ioNeeded Total number of I/O operations required by this job
private int	ioRemaining number of I/O operations left to do
private static int	lastSerial Counter used for assigning serial numbers to Jobs (for debugging output).
private int	lastStart time when this Jobs last started using the CPU
private java.lang.String	name Name of this job (for debugging)
(package private) Job	next Link for linking into queues
private java.util.Random	rand random number generator used by newBurst
static int	READY Job is ready to run
private int	serial Serial number of this job (for debugging)
private java.util.Vector	trace Trace of significant events in this job's lifetime (only if Sim.traceFlag)

Constructor Summary

Job(java.io.BufferedReader traceFile)
Create a Job from a line of the trace file.

Method Summary

void	doIO() Called when this Job does an I/O operation
JobStats	finish() This job is finished.
private void	newBurst() Recaculate the amount of CPU to be used by this job before the next I/O operation: the amount of cpu time remaining divided by the number of I/O operations remaining, rounded up.
int	nextBurst() Return the amount of CPU time remaining for this job until it next does I/O, or completes.
void	start() Called when this Job is started running on the CPU
int	state() What is the current state of this Job?
void	stop() Called when this Job is removed from the CPU
java.lang.String	toString() For debugging, information about this device.

Methods inherited from class java.lang.Object

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

Field Detail

name

private java.lang.String name

Name of this job (for debugging)

serial

private int serial

Serial number of this job (for debugging)

trace

private java.util.Vector trace

Trace of significant events in this job's lifetime (only if Sim.traceFlag)

next

Job next

Link for linking into queues

arrivalTime

int arrivalTime

Arrival time in ms from start of simulation

cpuNeeded

private int cpuNeeded

Total CPU time (ms) required by this job

ioNeeded

private int ioNeeded

Total number of I/O operations required by this job

ioRemaining

private int ioRemaining

number of I/O operations left to do

cpuRemaining

private int cpuRemaining

total amount of CPU time (in ms) left to consume

burst

public int burst

size of current burst

burstRemaining

private int burstRemaining

amount in current burst (until next I/O op) remaining

burstStart

public int burstStart

time when current burst started (job "arrived" at the cpu queue)

lastStart

private int lastStart

time when this Jobs last started using the CPU

rand

private java.util.Random rand

random number generator used by newBurst

lastSerial

private static int lastSerial

Counter used for assigning serial numbers to Jobs (for debugging output).

DONE

public static final int DONE

Job has completed

BLOCKED

public static final int BLOCKED

Job needs to do an I/O operation next

READY

public static final int READY

Job is ready to run

Constructor Detail

Job

public Job(java.io.BufferedReader traceFile)
    throws java.io.EOFException

Create a Job from a line of the trace file.

Parameters:

traceFile - the file to read from.

Method Detail

toString

public java.lang.String toString()

For debugging, information about this device.

Overrides:

toString in class java.lang.Object

Returns:

information about the device: If verbosity > 2,
name:jobnumber[arrival-time; cpu; io]
where cpu = total/remaining/burst-remaining
and io = total/remaining
otherwise, just the name and serial number (like a prisoner of war).

state

public int state()

What is the current state of this Job?

Returns:

READY, BLOCKED, or DONE

start

public void start()

Called when this Job is started running on the CPU

stop

public void stop()

Called when this Job is removed from the CPU

nextBurst

public int nextBurst()

Return the amount of CPU time remaining for this job until it next does I/O, or completes.

Returns:

the remaining time (in milliseconds)

doIO

public void doIO()

Called when this Job does an I/O operation

finish

public JobStats finish()

This job is finished. Return some summary statistics.

Returns:

summary statistics.

newBurst

private void newBurst()

Recaculate the amount of CPU to be used by this job before the next I/O operation: the amount of cpu time remaining divided by the number of I/O operations remaining, rounded up. This spreads the cpu time as even as possible in to bursts, each preceding one I/O. The case ioRemaining==0 only arises if the job does no I/O at all. To give a little variety, we occasionally create an unusual burst that is x*b in length, where b is the "normal" burst length (as just described) and x is a random number uniformly distributed between 0 and 2. In any case, the result is limited by the amount of CPU time remaining.