实验四存储器管理.doc

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。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，存放内存中已经存在的作业。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 2.0C语言4实验提示一、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Next 前向指针，指向下一个空区Back 反向指针，指向上一个空区Adderss 本空区首地址2、内存分配表JOBMAT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，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（高地址部分），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coalesce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*You can select one of the following:(1)Require to be allocate. 请分配内存(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*1Enter your job name:JOB1Enter your job length:1000name length(b) addreJOB1 1000 2000The total left is 4000 bytes6实验程序#include #include #include #include #include #include string.h#define TOTALSPACE 5000 /*起始空闲空间大小#define INITADDRESS 2000 /*起始地址#define MINSPACE 100#define MAXJOBCNT 10 /* 内存中作业数量最大值struct JobMat char name10; int address; int length; struct JobMat * next; struct JobMat * back;struct FreeArea int address; int size; struct FreeArea * next; struct FreeArea * back;struct JobMat *p_JobMat;struct FreeArea *p_FreeArea;int UnusedSpace; /*未分配的空闲空间大小int CurrentJobCnt; /*目前内存中的作业数量int JobSize; /*目前要分配的作业的大小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=NULL; 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 (UnusedSpacesize) 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-address;if (p_JobMat=NULL)jp2-next=NULL;jp2-back=NULL;p_JobMat=jp2;elsejp=p_JobMat;while(jp!=NULL)&(jp2-addressaddress)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-next=jp2; else p_JobMat=jp2; jp-back=jp2; if (fp-size-JobSizenext!=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;/*exit(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 (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;elsefp=p_FreeArea;while(fp!=NULL)&(fp-addressaddress)fp1=fp;fp=fp-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 *)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-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!=NULL) jp-next-back=jp-back;if (jp-back!=NULL) jp-back-next=jp-next;free(jp);void showyou()struct JobMat *jp;/*clrscr();*/if (CurrentJobCntname, jp-length,jp-address);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 (CurrentJobCnt0)jp=p_JobMat;bottom=TOTALSPACE+INITADDRESS;while (jp!=NULL)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;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(4)Quit.n);printf(*n);scanf(%d,&select);switch(select)case 1:if( CurrentJobCnt=MAXJOBCNT)printf(The job is too many);elseprintf(Enter your job name:);scanf(%s,JobName);printf(Enter your job length:);scanf(%d,&JobSize);ffallocation();switch (JobAddress)case -1:printf(the memory is full);break;cas