操作系统实验（一）—— 使用动态优先权的进程调度算法模拟

本文最后更新于：2019年11月14日 晚上

概览：动态优先权的进程调度算法模拟，主要使用单链表完成。

实验内容

用C语言来实现对N个进程采用动态优先权优先算法的进程调度。

每个用来标识进程的进程控制块PCB用结构来描述，包括以下字段：

  • 进程标识数 ID。
  • 进程优先数 PRIORITY，并规定优先数越大的进程，其优先权越高。
  • 进程已占用的CPU时间CPUTIME。
  • 进程还需占用的CPU时间ALLTIME。当进程运行完毕时，ALLTIME变为0。
  • 进程的阻塞时间STARTBLOCK，表示当进程再运行STARTBLOCK个时间片后，将进入阻塞状态。
  • 进程被阻塞的时间BLOCKTIME，表示已足赛的进程再等待BLOCKTIME个时间片后，将转换成就绪状态。
  • 进程状态START。
  • 队列指针NEXT，用来将PCB排成队列。

优先数改变的原则：

进程在就绪队列中呆一个时间片，优先数加1。

进程每运行一个时间片，优先数减3。

假设在调度前，系统中有5个进程，它们的初始状态如下：

ID 0 1 2 3 4
PRIORITY 9 38 30 29 0
CPUTIME 0 0 0 0 0
ALLTIME 3 3 6 3 4
STARTBLOCK 2 -1 -1 -1 -1
BLOCKTIME 3 0 0 0 0
STATE READY READY READY READY READY

为了清楚的观察各进程的调度过程，程序应将每个时间片内的情况显示出来

代码思想

头一次做这个实验的时候，总是想的太多，导致写的代码十分混乱，重写多次都还是给自己挖了很多坑，于是上CSDN找了一份代码，仔细抄录了一遍。理解了思想之后，修改其中部分代码，结果如下。

过了几天找不到原作者的文章和链接了，就不放参考链接了，见谅……

整个代码使用了单链表，构建了两个链：就绪队列链和阻塞队列链。同时使用的链表时带头节点的链表。

然后链表构造的时候按照了优先级的大小来排序。这样从就绪队列中找到优先级最高的进程时非常的方便。

代码

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#include <iostream>
#include <vector>
#include <algorithm>
#include <conio.h>

using namespace std;

struct PCB {
	int id;
	int priority;/*进程优先数*/
	int cputime;/*已经占用的cpu时间*/
	int alltime;/*还需占用的cpu时间*/
	int startblock;/*进程的阻塞时间*/
	int blocktime;/*进程被阻塞的时间*/
	int state;/*进程状态,0表示就绪，1表示运行,2表示阻塞,3表示完成*/
	PCB *next;//指向下一个进程

    //结构体的构造函数
	PCB(int a1, int a2, int a3, int a4, int a5, int a6, int a7)
	{
		id = a1;
		priority = a2;
		cputime = a3;
		alltime = a4;
		startblock = a5;
		blocktime = a6;
		state = a7;
		next = NULL;
	}
};

PCB *Ready_Queue_Head = NULL;
PCB *Block_Queue_Head = NULL;
PCB *Finish_Queue_Head = NULL; //实际上基本没用到
//创建了就绪队列和阻塞队列，均包含头结点，以后的节点插入均采取插入排序

void InitQueue()
{
	Ready_Queue_Head = (PCB*)malloc(sizeof(PCB));
	Ready_Queue_Head->priority = 99999;
	Ready_Queue_Head->next = NULL;

	Block_Queue_Head = (PCB*)malloc(sizeof(PCB));
	Block_Queue_Head->priority = 99999;
	Block_Queue_Head->next = NULL;

	Finish_Queue_Head = (PCB*)malloc(sizeof(PCB));
	Finish_Queue_Head->priority = 99999;
	Finish_Queue_Head->next = NULL;
}

void FreeQueue()
{
	free(Ready_Queue_Head);
	free(Block_Queue_Head);
	free(Finish_Queue_Head);
}

void InsertProcess(PCB *InsertProcess, PCB *InsertProcessHead)
{
	PCB *p = InsertProcessHead->next;
	PCB *p_before = InsertProcessHead;
	while (p != NULL && p->priority > InsertProcess->priority)
	{
		p_before = p;
		p = p->next;
	}
	InsertProcess->next = p;
	p_before->next = InsertProcess;

}

//获取进程列表的第一个进程
PCB * GetFirstProcess(PCB *ProcessQueue)
{
	PCB * p = ProcessQueue->next;
	ProcessQueue->next = p->next;
	return p;
}

bool EmptyProcessQueue(PCB *ProcessQueue)
{
	if (ProcessQueue->next == NULL)
		return true;
	else
		return false;
}

void ShowProcess(PCB *p)
{
	cout << "\tId: " << p->id << " Priority: " << p->priority << " Cputime: " << p->cputime << " Alltime:" << p->alltime
		<< " Startblock: " << p->startblock << " Blocktime: " << p->blocktime << " State: " << p->state << endl;
}

void ShowProcessQueue(PCB *ProcessQueue)
{
	PCB *p = ProcessQueue->next;
	while (p != NULL)
	{
		cout << "\tId: " << p->id << " Priority: " << p->priority << " Cputime: " << p->cputime << " Alltime:" << p->alltime
			<< " Startblock: " << p->startblock << " Blocktime: " << p->blocktime << " State: " << p->state << endl;
		p = p->next;
	}
}

//就绪队列
void UpdateReadyQueue()
{
	PCB *p = Ready_Queue_Head->next;
	while (p != NULL)
	{
		p->priority += 1;
		p = p->next;
	}
}

//阻塞队列
void UpdateBlockQueue()
{
	PCB *p = Block_Queue_Head->next;
	PCB *p_before = Block_Queue_Head;
	while (p != NULL)
	{
		p->blocktime -= 1;
		if (p->blocktime == 0)
		{
			p_before->next = p->next;
			p->state = 0;
			InsertProcess(p, Ready_Queue_Head);
			p = p_before->next;
		}
		else
		{
			p_before = p;
			p = p->next;
		}
	}
}

int main()
{
	InitQueue();
	PCB p1(0, 9, 0, 3, 2, 3, 0);
	InsertProcess(&p1, Ready_Queue_Head);
	PCB p2(1, 38, 0, 3, -1, 0, 0);
	InsertProcess(&p2, Ready_Queue_Head);
	PCB p3(2, 30, 0, 6, -1, 0, 0);
	InsertProcess(&p3, Ready_Queue_Head);
	PCB p4(3, 29, 0, 3, -1, 0, 0);
	InsertProcess(&p4, Ready_Queue_Head);
	PCB p5(4, 0, 0, 4, -1, 0, 0);
	InsertProcess(&p5, Ready_Queue_Head);
    
	cout << "Init" << endl;
    
	cout << "Ready Process:" << endl;
	ShowProcessQueue(Ready_Queue_Head);
    
	cout << "Block Process:" << endl;
	ShowProcessQueue(Block_Queue_Head);
    
	cout << "========================" << endl;
    
	PCB *NowRunProcess = NULL;
	bool Is_CPU_Busy = false;

	int time = 1; //表示时间片

	while (1)
	{
		if (EmptyProcessQueue(Ready_Queue_Head) && EmptyProcessQueue(Block_Queue_Head))
			break; //如果就绪队列和阻塞对列都为空，结束

		//获取要运行的程序
		if (!Is_CPU_Busy)
		{
			NowRunProcess = GetFirstProcess(Ready_Queue_Head);
			NowRunProcess->state = 1;
		}
		else
		{
			//不忙
			if (!EmptyProcessQueue(Ready_Queue_Head) && NowRunProcess->priority < Ready_Queue_Head->next->priority)
			{
				//如果现在运行的程序小于就绪队列中第一个程序的优先级
				NowRunProcess->state = 0;
				InsertProcess(NowRunProcess, Ready_Queue_Head);
				NowRunProcess = GetFirstProcess(Ready_Queue_Head);
				NowRunProcess->state = 1;
			}
		}

		//运行进程
		Is_CPU_Busy = true;

		cout << "第" << time << "个时间片：" << endl;
		cout << "Running Process: Id" << NowRunProcess->id << endl;
		ShowProcess(NowRunProcess);

		//就绪队列
		UpdateReadyQueue();
		cout << "Ready Process:" << endl;
		ShowProcessQueue(Ready_Queue_Head);

		//阻塞队列
		UpdateBlockQueue();
		cout << "Block Process:" << endl;
		ShowProcessQueue(Block_Queue_Head);


		//运行进程
		NowRunProcess->priority -= 3;
		NowRunProcess->cputime += 1;
		NowRunProcess->alltime -= 1;
		NowRunProcess->startblock -= 1;
		if (NowRunProcess->alltime == 0)
		{
			Is_CPU_Busy = false;
			NowRunProcess->state = 3;
			InsertProcess(NowRunProcess, Finish_Queue_Head);
		}
		else
		{
			if (NowRunProcess->startblock == 0)
			{
				Is_CPU_Busy = false;
				NowRunProcess->state = 2;
				InsertProcess(NowRunProcess, Block_Queue_Head);
			}
		}
		time++;

		cout << "Runned Process:" << endl;
		ShowProcess(NowRunProcess);

		cout << "========================" << endl;
	}
    
	FreeQueue();

	_getch();
	return 0;
}

运行结果

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Init
Ready Process:
        Id: 1 Priority: 38 Cputime: 0 Alltime:3 Startblock: -1 Blocktime: 0 State: 0
        Id: 2 Priority: 30 Cputime: 0 Alltime:6 Startblock: -1 Blocktime: 0 State: 0
        Id: 3 Priority: 29 Cputime: 0 Alltime:3 Startblock: -1 Blocktime: 0 State: 0
        Id: 0 Priority: 9 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 0 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
========================
第1个时间片：
Running Process: Id1
        Id: 1 Priority: 38 Cputime: 0 Alltime:3 Startblock: -1 Blocktime: 0 State: 1
Ready Process:
        Id: 2 Priority: 31 Cputime: 0 Alltime:6 Startblock: -1 Blocktime: 0 State: 0
        Id: 3 Priority: 30 Cputime: 0 Alltime:3 Startblock: -1 Blocktime: 0 State: 0
        Id: 0 Priority: 10 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 1 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 1 Priority: 35 Cputime: 1 Alltime:2 Startblock: -2 Blocktime: 0 State: 1
========================
第2个时间片：
Running Process: Id1
        Id: 1 Priority: 35 Cputime: 1 Alltime:2 Startblock: -2 Blocktime: 0 State: 1
Ready Process:
        Id: 2 Priority: 32 Cputime: 0 Alltime:6 Startblock: -1 Blocktime: 0 State: 0
        Id: 3 Priority: 31 Cputime: 0 Alltime:3 Startblock: -1 Blocktime: 0 State: 0
        Id: 0 Priority: 11 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 2 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 1 Priority: 32 Cputime: 2 Alltime:1 Startblock: -3 Blocktime: 0 State: 1
========================
第3个时间片：
Running Process: Id1
        Id: 1 Priority: 32 Cputime: 2 Alltime:1 Startblock: -3 Blocktime: 0 State: 1
Ready Process:
        Id: 2 Priority: 33 Cputime: 0 Alltime:6 Startblock: -1 Blocktime: 0 State: 0
        Id: 3 Priority: 32 Cputime: 0 Alltime:3 Startblock: -1 Blocktime: 0 State: 0
        Id: 0 Priority: 12 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 3 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 1 Priority: 29 Cputime: 3 Alltime:0 Startblock: -4 Blocktime: 0 State: 3
========================
第4个时间片：
Running Process: Id2
        Id: 2 Priority: 33 Cputime: 0 Alltime:6 Startblock: -1 Blocktime: 0 State: 1
Ready Process:
        Id: 3 Priority: 33 Cputime: 0 Alltime:3 Startblock: -1 Blocktime: 0 State: 0
        Id: 0 Priority: 13 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 4 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 2 Priority: 30 Cputime: 1 Alltime:5 Startblock: -2 Blocktime: 0 State: 1
========================
第5个时间片：
Running Process: Id3
        Id: 3 Priority: 33 Cputime: 0 Alltime:3 Startblock: -1 Blocktime: 0 State: 1
Ready Process:
        Id: 2 Priority: 31 Cputime: 1 Alltime:5 Startblock: -2 Blocktime: 0 State: 0
        Id: 0 Priority: 14 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 5 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 3 Priority: 30 Cputime: 1 Alltime:2 Startblock: -2 Blocktime: 0 State: 1
========================
第6个时间片：
Running Process: Id2
        Id: 2 Priority: 31 Cputime: 1 Alltime:5 Startblock: -2 Blocktime: 0 State: 1
Ready Process:
        Id: 3 Priority: 31 Cputime: 1 Alltime:2 Startblock: -2 Blocktime: 0 State: 0
        Id: 0 Priority: 15 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 6 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 2 Priority: 28 Cputime: 2 Alltime:4 Startblock: -3 Blocktime: 0 State: 1
========================
第7个时间片：
Running Process: Id3
        Id: 3 Priority: 31 Cputime: 1 Alltime:2 Startblock: -2 Blocktime: 0 State: 1
Ready Process:
        Id: 2 Priority: 29 Cputime: 2 Alltime:4 Startblock: -3 Blocktime: 0 State: 0
        Id: 0 Priority: 16 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 7 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 3 Priority: 28 Cputime: 2 Alltime:1 Startblock: -3 Blocktime: 0 State: 1
========================
第8个时间片：
Running Process: Id2
        Id: 2 Priority: 29 Cputime: 2 Alltime:4 Startblock: -3 Blocktime: 0 State: 1
Ready Process:
        Id: 3 Priority: 29 Cputime: 2 Alltime:1 Startblock: -3 Blocktime: 0 State: 0
        Id: 0 Priority: 17 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 8 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 2 Priority: 26 Cputime: 3 Alltime:3 Startblock: -4 Blocktime: 0 State: 1
========================
第9个时间片：
Running Process: Id3
        Id: 3 Priority: 29 Cputime: 2 Alltime:1 Startblock: -3 Blocktime: 0 State: 1
Ready Process:
        Id: 2 Priority: 27 Cputime: 3 Alltime:3 Startblock: -4 Blocktime: 0 State: 0
        Id: 0 Priority: 18 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 9 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 3 Priority: 26 Cputime: 3 Alltime:0 Startblock: -4 Blocktime: 0 State: 3
========================
第10个时间片：
Running Process: Id2
        Id: 2 Priority: 27 Cputime: 3 Alltime:3 Startblock: -4 Blocktime: 0 State: 1
Ready Process:
        Id: 0 Priority: 19 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 10 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 2 Priority: 24 Cputime: 4 Alltime:2 Startblock: -5 Blocktime: 0 State: 1
========================
第11个时间片：
Running Process: Id2
        Id: 2 Priority: 24 Cputime: 4 Alltime:2 Startblock: -5 Blocktime: 0 State: 1
Ready Process:
        Id: 0 Priority: 20 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 11 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 2 Priority: 21 Cputime: 5 Alltime:1 Startblock: -6 Blocktime: 0 State: 1
========================
第12个时间片：
Running Process: Id2
        Id: 2 Priority: 21 Cputime: 5 Alltime:1 Startblock: -6 Blocktime: 0 State: 1
Ready Process:
        Id: 0 Priority: 21 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 0
        Id: 4 Priority: 12 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 2 Priority: 18 Cputime: 6 Alltime:0 Startblock: -7 Blocktime: 0 State: 3
========================
第13个时间片：
Running Process: Id0
        Id: 0 Priority: 21 Cputime: 0 Alltime:3 Startblock: 2 Blocktime: 3 State: 1
Ready Process:
        Id: 4 Priority: 13 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 0 Priority: 18 Cputime: 1 Alltime:2 Startblock: 1 Blocktime: 3 State: 1
========================
第14个时间片：
Running Process: Id0
        Id: 0 Priority: 18 Cputime: 1 Alltime:2 Startblock: 1 Blocktime: 3 State: 1
Ready Process:
        Id: 4 Priority: 14 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 0 Priority: 15 Cputime: 2 Alltime:1 Startblock: 0 Blocktime: 3 State: 2
========================
第15个时间片：
Running Process: Id4
        Id: 4 Priority: 14 Cputime: 0 Alltime:4 Startblock: -1 Blocktime: 0 State: 1
Ready Process:
Block Process:
        Id: 0 Priority: 15 Cputime: 2 Alltime:1 Startblock: 0 Blocktime: 2 State: 2
Runned Process:
        Id: 4 Priority: 11 Cputime: 1 Alltime:3 Startblock: -2 Blocktime: 0 State: 1
========================
第16个时间片：
Running Process: Id4
        Id: 4 Priority: 11 Cputime: 1 Alltime:3 Startblock: -2 Blocktime: 0 State: 1
Ready Process:
Block Process:
        Id: 0 Priority: 15 Cputime: 2 Alltime:1 Startblock: 0 Blocktime: 1 State: 2
Runned Process:
        Id: 4 Priority: 8 Cputime: 2 Alltime:2 Startblock: -3 Blocktime: 0 State: 1
========================
第17个时间片：
Running Process: Id4
        Id: 4 Priority: 8 Cputime: 2 Alltime:2 Startblock: -3 Blocktime: 0 State: 1
Ready Process:
Block Process:
Runned Process:
        Id: 4 Priority: 5 Cputime: 3 Alltime:1 Startblock: -4 Blocktime: 0 State: 1
========================
第18个时间片：
Running Process: Id0
        Id: 0 Priority: 15 Cputime: 2 Alltime:1 Startblock: 0 Blocktime: 0 State: 1
Ready Process:
        Id: 4 Priority: 6 Cputime: 3 Alltime:1 Startblock: -4 Blocktime: 0 State: 0
Block Process:
Runned Process:
        Id: 0 Priority: 12 Cputime: 3 Alltime:0 Startblock: -1 Blocktime: 0 State: 3
========================
第19个时间片：
Running Process: Id4
        Id: 4 Priority: 6 Cputime: 3 Alltime:1 Startblock: -4 Blocktime: 0 State: 1
Ready Process:
Block Process:
Runned Process:
        Id: 4 Priority: 3 Cputime: 4 Alltime:0 Startblock: -5 Blocktime: 0 State: 3
========================
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