最短剩余时间优先：Java多线程

Question

我试图用java模拟CPU调度算法，并使用多线程。我成功地实现了FCFS（先到先得）和SJF（最短工作优先）。但问题是当我开始考虑SRTF（最短剩余时间优先）时，它是一种先发制人的SJF形式。 我使用的是以下模型：

• CPU的一个线程，它有一个CLOCK变量，该变量每100ms一次都在滴答作响（一个简单的时钟增量）。我有一个boolean isAvailable;标志，让进程在开始执行之前检查CPU是否可用
• 用于长期调度程序（LTS）的线程，它将进程从进程列表推送到就绪队列
• 短期调度程序（STS）的线程，它从ReadyQueue中获取一个进程并将其分配给CPU
• 一旦进程被STS从ReadyQueue中移除以执行，该进程将检查CPU的isAvailable标志。如果true，它会将标志设置为false并开始执行（我只是让线程睡眠(100 * burstTime) ms，因为这只是一个模拟）。否则，进程就会一直忙着等待：while(CPU.isAvailable != true);

我手头有进程列表，以及它们的到达时间和突发时间。 在我模拟非抢占式调度（FCFS和SJF）之前，一切都没问题。但是当我尝试SRTF时，我无法找到一种方法来抢占当前正在运行的进程线程

对于SRTF，我知道如何从ReadyQueue中选择下一个流程。一旦我从队列中选择了一个进程，我可以尝试将isAvailable标志设置为false，但那我怎么知道最初执行的是哪个线程呢？由于我没有使用太多的同步b/w线程，我将有多个进程使用CPU线程。有点乱了。请帮忙。谢谢

以下是流程的代码：

enum State {ARRIVED, WAITING, READY, RUNNING, EXECUTED}
public class Process implements Runnable
{
    int pid;
    int arrTime;
int burstTime;
int priority;
long startTime;
long endTime;
State procState = null;

Process(int pid, int arrTime, int burstTime, int priority)
{
    this.pid = pid;
    this.arrTime = arrTime;
    this.burstTime = burstTime;
    this.priority = priority;
    this.procState = State.ARRIVED;
    this.startTime = 0;


    this.endTime = 0;    /* I also considered adding a timeElapsedUnderExecution
 attribute to the process. So I can check after every cycle if the CPU is still available
 and keep incrementing the time elapsed. Once the timeElapsed becomes same as burstTime, i
 stop the process. Or if after a cycle, the CPU is not available, i know from where to
 resume my Process. Is this the way to go ? */

    }

boolean isReady()
{
    if((this.arrTime <= CPU.CLOCK) && (this.procState == State.ARRIVED))
        return true;
    else return false;
}

@Override
public void run() {
    // TODO Auto-generated method stub
    if(this.procState == State.READY)
        this.procState = State.WAITING;

    while(!CPU.isAvailable());

    try 
    {
        this.procState = State.RUNNING;
        System.out.println("Process " + pid + " executing...");
        this.startTime = CPU.CLOCK;
        System.out.println("Process " + this.pid + ": Begins at " + this.startTime);
        Thread.sleep(this.burstTime * 100);
        this.endTime = CPU.CLOCK;
        System.out.println("Process " + this.pid + ": Ends at " + this.endTime);
        this.procState = State.EXECUTED;

    }
    catch (InterruptedException e) 
    {
        // TODO Auto-generated catch block
        System.out.println("Interrupted: " + pid);
        e.printStackTrace();
    }
    }
}

CPU的代码：

    import java.util.LinkedList;
    import java.util.Queue;

    public class CPU implements Runnable

{
    static Long CLOCK = new Long(0);
    static LinkedList<Process> ReadyQ = new LinkedList<Process>();
private static boolean isAvailable = true;
static boolean done = false;

public static boolean isAvailable() {
    return isAvailable;
}

public static void setAvailable(boolean isAvailable) {
    CPU.isAvailable = isAvailable;
}

static void incrementCLOCK()
{
    LTS.checkArrival();
    CPU.CLOCK++;
    try {
        Thread.sleep(100);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    System.out.println("Clock Tick: " + CPU.CLOCK);
}

@Override
public void run() {
    // TODO Auto-generated method stub
    System.out.println("CPU starts.!!!");
    while(CPU.done != true)
        synchronized(CPU.CLOCK)
        {
            incrementCLOCK();
            }
    }
}

LTS的代码：

public class LTS implements Runnable 
{
    private static Process[] pList = null;
    private final int NUM;
    static Integer procStarted;
    static Integer procFinished;
    static boolean STSDone = false;


LTS(Process[] pList, int num)
{
    this.NUM = num;
    LTS.pList = pList;
}

static void checkArrival()
{
    if(pList == null) return;
    for(int i = 0; i < pList.length; i++)
        if(pList[i].isReady())
        {
            pList[i].procState = State.READY;
            System.out.println("Process " + pList[i].pid + " is now ready.");
            CPU.ReadyQ.add(pList[i]);
        }
}

@Override
public void run() {
    // TODO Auto-generated method stub
    System.out.println("Long Term Scheduler starts.!!!");
    while(LTS.STSDone != true)
    {
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    System.out.println(LTS.STSDone);
    System.out.println("LTS ends.!!!");
        CPU.done = true;
    }
}