实验四存储器管理

1、实验四 存储器管理1、目的与要求本实验的目的是让学生熟悉存储器管理的方法， 加深对所学各种存储器管理方案的了 解；要求采用一些常用的存储器分配算法， 设计一个存储器管理模拟系统， 模拟内存空间的 分配和释放。存放内存中已经存在的作业。2、实验内容 设计一个存放空闲块的自由链和一个内存作业分配表， 编制一个按照首次适应法分配内存的算法，进行内存分配。 同时设计内存的回收以及内存清理(如果要分配的作业块大于任何一个空闲块，但 小于总的空闲分区，则需要进行内存的清理，空出大块的空闲分区)的算法。3实验环境 PC兼容机 Windows 、 DOS 系统、 Turbo c 2.0 C 语言4实验提示一、

2、数据结构1、自由链 内存空区采用自由链结构，链首由指针 freep 指向，链中各空区按地址递增次序排列。初启动时整个用户内存区为一个大空区，每个空区首部设置一个区头(freearea)结构，区头信息包括：Size空区大小NextBackAdderss前向指针，指向下一个空区 反向指针，指向上一个空区 本空区首地址32、内存分配表 JOBMA T系统设置一个 MAT，每个运行的作业都在 MAT中占有一个表目，回收分区时清除相应表目，表目信息包括：Name用户作业名Length作业区大小Addr作业区首地址二、算法存储分配算法采用首次适应法， 根据指针 freep 查找自由链， 当找到第一块可满足

3、分配 请求的空区便分配，当某空区被分配后的剩余空闲空间大于所规定的碎片最小量mini 时，则形成一个较小的空区留在自由链中。回收时, 根据 MAT 将制定分区链入自由链, 若该分区有前邻或后邻分区, 则将他们拼 成一个较大的空区。当某个分配请求不能被满足，但此时系统中所有碎片总容量满足分配请求的容量时，高地系统立即进行内存搬家, 消除碎片。 即将各作业占用区集中下移到用户内存区的下部 址部分），形成一片连续的作业区，而在用户内存区的上部形成一块较大的空闲，然后再进 行分配。本系统的主要程序模块包括：分配模块 ffallocation ,回收模块 ffcollection ,搬家模块coales

4、ce及命令处理模块 menu, menu用以模拟系统的输入，通过键盘命令选择进行分配模 块、回收模块、内存查询以及退出的操作。程序运行的流程如下图：5实验运行情况*MENU*请分配内存You can select one of the following:(1) Require to be allocate.(2) Require to collecte the size. 将分配的内存回收(3) Check the memory.检查当前的内存情况(4) Quit. 退出*Enter your job name:JOB1Enter your job length:1000name lengt

5、h(b) addreJOB110002000The total left is 4000 bytes6实验程序#include <stdio.h> #include <dos.h>#include <stdlib.h>#include <conio.h> #include <io.h>#include "string.h"#define TOTALSPACE 5000 #define INITADDRESS 2000#define MINSPACE 100#define MAXJOBCNT 10/* 起始空闲空间大

6、小/*起始地址 /* 内存中作业数量最大值struct JobMatchar name10; int address;int length;struct JobMat * next; struct JobMat * back;struct FreeAreaint address;int size;struct FreeArea * next;struct FreeArea * back; ;/*未分配的空闲空间大小 /*目前内存中的作业数量struct JobMat *p_JobMat; struct FreeArea *p_FreeArea; int UnusedSpace; int Cur

7、rentJobCnt;/*目前要分配的作业的大小int JobSize; char JobName10; int JobAddress;void initiation() p_FreeArea=(struct FreeArea *)malloc(sizeof(struct FreeArea); p_FreeArea->size=TOTALSPACE; p_FreeArea->address=INITADDRESS; p_FreeArea->next=NULL;p_FreeArea->back=NULL; UnusedSpace=TOTALSPACE;p_JobMat=N

8、ULL; CurrentJobCnt=0;JobSize=0; memset(JobName, 0, 10); JobAddress=0;void ffallocation()struct FreeArea * fp; struct JobMat *jp;struct JobMat *jp1;struct JobMat *jp2; JobAddress=-1;if (UnusedSpace<JobSize)/*prin tf("Sorry, you input job len gth is too big 人_人 n");*/ return;JobAddress=0;

9、 fp=p_FreeArea; while (fp!=NULL)if(fp->size) < JobSize)fp=fp->next; elseCurrentJobCnt=CurrentJobCnt+1; UnusedSpace=UnusedSpace-JobSize; jp2=(struct JobMat *)malloc(sizeof(struct JobMat); strcpy(jp2->name,JobName); jp2->length=JobSize;jp2->address=fp->address;JobAddress=jp2->a

10、ddress;if (p_JobMat=NULL)jp2->next=NULL; jp2->back=NULL; p_JobMat=jp2; elsejp=p_JobMat;while(jp!=NULL)&&(jp2->address<jp->address) jp1=jp; jp=jp->next;jp2->next=jp;if (jp=NULL) jp2->back=jp1;jp1->next=jp2; elsejp2->back=jp->back;if (jp->back!=NULL) jp1->

11、;next=jp2; else p_JobMat=jp2;jp->back=jp2;if (fp->size-JobSize<MINSPACE)if (fp->next!=NULL) fp->next->back=fp->back; if (fp->back!=NULL) fp->back->next=fp->next; else p_FreeArea=fp->next;elsefp->size=fp->size-JobSize;fp->address=fp->address+JobSize;/*e

12、xit(1);*/ return;void ffcollection()struct FreeArea *fp;struct FreeArea *fp1;struct FreeArea *fp2;struct JobMat *jp;int f;jp=p_JobMat;f=0;while(jp!=NULL) && strcmp(jp->name, JobName) != 0) jp=jp->next;if (jp!=NULL)CurrentJobCnt=CurrentJobCnt-1;UnusedSpace=UnusedSpace+jp->length;if (

13、p_FreeArea=NULL)p_FreeArea=(struct FreeArea *)malloc(sizeof(struct FreeArea); p_FreeArea->address=jp->address; p_FreeArea->size=jp->length;p_FreeArea->next=NULL;p_FreeArea->back=NULL; else fp=p_FreeArea; while(fp!=NULL)&&(fp->address<jp->address) fp1=fp; fp=fp->

14、next; if (fp!=NULL)if (fp->next!=NULL)&&(fp->next->address=jp->address+jp->length) f=f+1;if (fp->back!=NULL)&&(jp->address=fp1->address+fp1->size)f=f+2;else if (jp->address) = (fp1->address+(fp1->size) f=f+2;switch (f)case 0:fp2=(struct FreeArea *)

15、malloc(sizeof(struct FreeArea);fp2->address=jp->address;fp2->size=jp->length;fp2->next=fp;if (fp!=NULL)fp2->back=fp->back;if (fp->back!=NULL) fp1->next=fp2;else p_FreeArea=fp2;fp->back=fp2;elsefp2->back=fp1;fp1->next=fp2;break;case 1:fp->size=fp->size+jp->

16、;length;fp->address=jp->address;break;case 2:fp1->size=fp1->size+jp->length;break;case 3:fp1->size=fp1->size+jp->length+fp->size; fp1->next=fp->next;if (fp->next!=NULL)fp->next->back=fp2;free (fp);break;if (jp=p_JobMat) p_JobMat=jp->next;if (jp->next!=

17、NULL) jp->next->back=jp->back;if (jp->back!=NULL) jp->back->next=jp->next; free(jp);void showyou() struct JobMat *jp; /*clrscr();*/ if (CurrentJobCnt<=0) printf("No job.n"); elseprintf("name length(b) addren"); jp=p_JobMat;5while (jp!=NULL)%d%dn", jp-

18、>name, jp->length,jp->address);printf("%s jp=jp->next;printf("The total left is %d bytesn",UnusedSpace);void coalesce()struct FreeArea *fp;struct FreeArea *fp1;struct JobMat *jp;int bottom;if (CurrentJobCnt>0) jp=p_JobMat; bottom=TOTALSPACE+INITADDRESS; while (jp!=NULL)

19、 jp->address=bottom-jp->length; bottom=bottom-jp->length; jp=jp->next;fp=p_FreeArea;while(fp!=NULL) fp1=fp; fp=fp->next; free(fp1);p_FreeArea=(struct FreeArea *)malloc(sizeof(struct FreeArea); p_FreeArea->size=UnusedSpace; p_FreeArea->address=INITADDRESS;p_FreeArea->next=NULL

20、; p_FreeArea->back=NULL;void menu()int select; printf("nnn*MENU*n"); printf("You can select one of the following:n"); printf("(1)Require to be allocate.n"); printf("(2)Require to collecte the size.n"); printf("(3)Check the memory.n"); printf("

21、;(4)Quit.n"); printf("*n"); scanf("%d",&select);switch(select)case 1:if( CurrentJobCnt>=MAXJOBCNT)printf("The job is too many");else printf("Enter your job name:"); scanf("%s",JobName); printf("Enter your job length:"); scanf(&q

22、uot;%d",&JobSize); ffallocation();switch (JobAddress)case -1:printf("the memory is full"); break;case 0:coalesce(); ffallocation(); break;default:break;break;case 2:printf("Enter the name of job:"); scanf("%s",JobName); ffcollection();break;case 3:break;case 4:

23、exit(1); break;default:printf("You input a wrong number!n"); break;void main()initiation();while (1) menu(); showyou();*MENU*You can select one of the following:(1) Require to be allocate.(2) Require to collecte the size.(3) Check the memory.(4) Quit.幵*卄*卄*卄*卄*卄*卄*卄*卄*幵*Enter your job name

24、:AEnter your job length:1000 name length(b) addre 1000 2000The total left is 4000 bytes*MENU* You can select one of the following: (1)Require to be allocate.15(2)Require to collecte the size.(3)Check the memory.(4)Quit.幵*卄*卄*卄*卄*卄*卄*卄*卄*幵*1Enter your job name:BEnter your job length:3000 nameBlength(

25、b)3000addre3000AThe total left is 1000 bytes10002000*MENU* You can select one of the following: (1)Require to be allocate. (2)Require to collecte the size. (3)Check the memory.(4)Quit.幵*卄*卄*卄*卄*卄*卄*卄*卄*幵*1Enter your job name:CEnter your job length:500namelength(b)addreC5006000B30003000A10002000The total