测试 RAM 盘和 DISK 盘的文件读写速度

一、目的

1.熟悉类 UNIX 系统的 I/O 设备管理
2.熟悉 MINIX 块设备驱动
3.熟悉 MINIX RAM 盘

二、内容与设计思想

测试 RAM 盘和 DISK 盘的文件读写速度，分析其读写速度差异原因（可用图表形式体现在实验报告中）。

三、使用环境

Minix，Moba

四、实验过程

1、增加 RAM 盘：修改/usr/src/minix/drivers/storage/memory/memory.c ，增加默认的用户 RAM 盘数： RAMDISKS=7。重新编译内核，reboot。

2、创建设备 mknod /dev/myram b 1 13，查看设备是否创建成功输入 ls /dev/ | grep ram。实现 buildmyram 初始化工具（用于分配容量）。

3、参考/usr/src/minix/commands/ramdisk/ramdisk.c，实现 buildmyram.c，但是需要将 KB 单位修改成 MB。

4、编译 buildmyram.c 文件，然后执行命令： buildmyram /dev/myram。创建一个 RAM 盘。

5、在 ram 盘上创建内存文件系统，mkfs.mfs /dev/myram。将 ram 盘挂载到用户目录下，mount /dev/myram /root/myram,查看是否挂在成功：输入 df。

注：重启后用户自定义的ram盘内容会丢失，需要重新设置大小，创建文件系统，并挂载。
6、出现write error错误，应该是因为空间太小了，可以考虑缩小读写次数或者增大磁盘容量，我这里将128MB设置成1GB，这个问题就消失了。

五、总结

刚开始，因为追求块大小的最大值将其设为65536，导致重复的次数减少设为500，最终得出了disk性能优于ram的结论，与假设矛盾。所以之后将块大小调成4096，而增加重复次数为10000，并且删除myram文件夹里的缓存文件，结论恢复正常，但读操作仍然还有改进空间。

六、测试代码

#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <stdbool.h>
#include <unistd.h>
#include <time.h>
#include <string.h>
#include <sys/wait.h>/* macro */
#define Concurrency 15      // max concurrent process
//#define repeat 500          // repeat times
#define repeat 10000          // repeat times
//#define Blocksize 65536     // max blocksize
#define Blocksize 4096     // max blocksize
#define maxline (50 * 1024) // array size
#define mod 1000000007      // a big prime number/* global variables */
long long writetext[maxline];                     // testing array
long long readbuff[maxline];                      // buff array
struct timeval starttime, endtime, spendtimeSpec; // used to calculate time
char *filepathdisk[19] ={"/usr/disk1.txt", "/usr/disk2.txt", "/usr/disk3.txt", "/usr/disk4.txt","/usr/disk5.txt", "/usr/disk6.txt", "/usr/disk7.txt", "/usr/disk8.txt","/usr/disk9.txt", "/usr/disk10.txt", "/usr/disk11.txt", "/usr/disk12.txt","/usr/disk13.txt", "/usr/disk14.txt", "/usr/disk15.txt", "/usr/disk16.txt","/usr/disk17.txt", "/usr/disk18.txt", "/usr/disk19.txt"};
char *filepathram[19] ={"/root/myram/ram_test1", "/root/myram/ram_test2", "/root/myram/ram_test3", "/root/myram/ram_test4","/root/myram/ram_test5", "/root/myram/ram_test6", "/root/myram/ram_test7", "/root/myram/ram_test8","/root/myram/ram_test9", "/root/myram/ram_test10", "/root/myram/ram_test11", "/root/myram/ram_test12","/root/myram/ram_test13", "/root/myram/ram_test14", "/root/myram/ram_test15", "/root/myram/ram_test16","/root/myram/ram_test17", "/root/myram/ram_test18", "/root/myram/ram_test19"};/* write files */
void write_file(int blocksize, bool isrand, char *filepath)
{int fp = open(filepath, O_RDWR | O_CREAT | O_SYNC, 0755);if (fp > 0){for (int i = 0; i < repeat; i++){int x = write(fp, writetext, blocksize);if (x < 0){printf("write error!");break;}if (!isrand)lseek(fp, (repeat-1)*(rand() % blocksize), SEEK_SET);}}else{printf("open error!");}lseek(fp, 0, SEEK_SET);
}/* read files */
void read_file(int blocksize, bool isrand, char *filepath)
{int fp = open(filepath, O_RDONLY);int i = 0;if (fp > 0){for (; i < repeat; i++){int x = read(fp, readbuff, blocksize);if (x < 0){printf("read error!\n");break;}if (!isrand)lseek(fp, (repeat-1)*(rand() % blocksize), SEEK_SET);}}else{printf("open error!");}lseek(fp, 0, SEEK_SET);
}/* get time left */
long get_time_left(struct timeval starttime, struct timeval endtime)
{long spendtime = 1000000 * (endtime.tv_sec - starttime.tv_sec) + (endtime.tv_usec - starttime.tv_usec); /* us */return spendtime;
}void test1()
{printf("Ram Sequential Write\n");printf("block\tprocess\tlatency\n");double BLOCK=0;double LATENCY=0;for (int block = 64; block <= Blocksize; block *= 2){for (int concurrency = 1; concurrency <= Concurrency; concurrency ++){gettimeofday(&starttime, NULL);for (int i = 0; i < concurrency; i++){if (fork() == 0){write_file(block, true, filepathram[i]); //ram sequential writeexit(1);}}// wait children to terminatewhile (wait(NULL) != -1);gettimeofday(&endtime, NULL);/* calculate the duration, latency, file_MB */long alltime = get_time_left(starttime, endtime);                        // get the duration (us)double latency = (alltime) / (double)repeat / (double)concurrency;       // single file latency (us)double file_MB = (double)block * repeat * concurrency / 1024.0 / 1024.0; // filesize in totalBLOCK+=block;LATENCY+=latency;printf("%d\t%d\t%.2f\n", block, concurrency, latency);}double throughput=BLOCK/LATENCY;printf("%.3f\n",throughput);BLOCK=LATENCY=0;}
}void test2()
{printf("Ram Random Write\n");printf("block\tprocess\tlatency\n");double BLOCK=0;double LATENCY=0;for (int block = 64; block <= Blocksize; block *= 2){for (int concurrency = 1; concurrency <= Concurrency; concurrency ++){gettimeofday(&starttime, NULL);for (int i = 0; i < concurrency; i++){if (fork() == 0){write_file(block, false, filepathram[i]); //ram random writeexit(1);}}// wait children to terminatewhile (wait(NULL) != -1);gettimeofday(&endtime, NULL);/* calculate the duration, latency, file_MB */long alltime = get_time_left(starttime, endtime);                        // get the duration (us)double latency = (alltime) / (double)repeat / (double)concurrency;       // single file latency (us)double file_MB = (double)block * repeat * concurrency / 1024.0 / 1024.0; // filesize in totalBLOCK+=block;LATENCY+=latency;printf("%d\t%d\t%.2f\n", block, concurrency, latency);}double throughput=BLOCK/LATENCY;printf("%.3f\n",throughput);BLOCK=LATENCY=0;}
}void test3()
{printf("Ram Sequential Read\n");printf("block\tprocess\tlatency\n");double BLOCK=0;double LATENCY=0;for (int block = 64; block <= Blocksize; block *= 2){for (int concurrency = 1; concurrency <= Concurrency; concurrency ++){gettimeofday(&starttime, NULL);for (int i = 0; i < concurrency; i++){if (fork() == 0){read_file(block, true, filepathram[i]);  //ram sequential readexit(1);}}// wait children to terminatewhile (wait(NULL) != -1);gettimeofday(&endtime, NULL);/* calculate the duration, latency, file_MB*/long alltime = get_time_left(starttime, endtime);                        // get the duration (us)double latency = (alltime) / (double)repeat / (double)concurrency;       // single file latency (us)double file_MB = (double)block * repeat * concurrency / 1024.0 / 1024.0; // filesize in totalBLOCK+=block;LATENCY+=latency;printf("%d\t%d\t%.2f\n", block, concurrency, latency);}double throughput=BLOCK/LATENCY;printf("%.3f\n",throughput);BLOCK=LATENCY=0;}
}void test4()
{printf("Ram Random Read\n");printf("block\tprocess\tlatency\n");double BLOCK=0;double LATENCY=0;for (int block = 64; block <= Blocksize; block *= 2){for (int concurrency = 1; concurrency <= Concurrency; concurrency ++){gettimeofday(&starttime, NULL);for (int i = 0; i < concurrency; i++){if (fork() == 0){read_file(block, false, filepathram[i]); //ram random readexit(1);}}// wait children to terminatewhile (wait(NULL) != -1);gettimeofday(&endtime, NULL);/* calculate the duration, latency, file_MB*/long alltime = get_time_left(starttime, endtime);                        // get the duration (us)double latency = (alltime) / (double)repeat / (double)concurrency;       // single file latency (us)double file_MB = (double)block * repeat * concurrency / 1024.0 / 1024.0; // filesize in totalBLOCK+=block;LATENCY+=latency;printf("%d\t%d\t%.2f\n", block, concurrency, latency);}double throughput=BLOCK/LATENCY;printf("%.3f\n",throughput);BLOCK=LATENCY=0;}
}void test5()
{printf("Disk Sequential Write\n");printf("block\tprocess\tlatency\n");double BLOCK=0;double LATENCY=0;for (int block = 64; block <= Blocksize; block *= 2){for (int concurrency = 1; concurrency <= Concurrency; concurrency ++){gettimeofday(&starttime, NULL);for (int i = 0; i < concurrency; i++){if (fork() == 0){write_file(block, true, filepathdisk[i]);  //disk sequential writeexit(1);}}// wait children to terminatewhile (wait(NULL) != -1);gettimeofday(&endtime, NULL);/* calculate the duration, latency, file_MB */long alltime = get_time_left(starttime, endtime);                        // get the duration (us)double latency = (alltime) / (double)repeat / (double)concurrency;       // single file latency (us)double file_MB = (double)block * repeat * concurrency / 1024.0 / 1024.0; // filesize in totalBLOCK+=block;LATENCY+=latency;printf("%d\t%d\t%.2f\n", block, concurrency, latency);}double throughput=BLOCK/LATENCY;printf("%.3f\n",throughput);BLOCK=LATENCY=0;}
}void test6()
{printf("Disk Random Write\n");printf("block\tprocess\tlatency\n");double BLOCK=0;double LATENCY=0;for (int block = 64; block <= Blocksize; block *= 2){for (int concurrency = 1; concurrency <= Concurrency; concurrency ++){gettimeofday(&starttime, NULL);for (int i = 0; i < concurrency; i++){if (fork() == 0){write_file(block, false, filepathdisk[i]); //disk random writeexit(1);}}// wait children to terminatewhile (wait(NULL) != -1);gettimeofday(&endtime, NULL);/* calculate the duration, latency, file_MB */long alltime = get_time_left(starttime, endtime);                        // get the duration (us)double latency = (alltime) / (double)repeat / (double)concurrency;       // single file latency (us)double file_MB = (double)block * repeat * concurrency / 1024.0 / 1024.0; // filesize in totalBLOCK+=block;LATENCY+=latency;printf("%d\t%d\t%.2f\n", block, concurrency, latency);}double throughput=BLOCK/LATENCY;printf("%.3f\n",throughput);BLOCK=LATENCY=0;}
}void test7()
{printf("Disk Sequential Read\n");printf("block\tprocess\tlatency\n");double BLOCK=0;double LATENCY=0;for (int block = 64; block <= Blocksize; block *= 2){for (int concurrency = 1; concurrency <= Concurrency; concurrency ++){gettimeofday(&starttime, NULL);for (int i = 0; i < concurrency; i++){if (fork() == 0){read_file(block, true, filepathdisk[i]);  //disk sequential readexit(1);}}// wait children to terminatewhile (wait(NULL) != -1);gettimeofday(&endtime, NULL);/* calculate the duration, latency, file_MB */long alltime = get_time_left(starttime, endtime);                        // get the duration (us)double latency = (alltime) / (double)repeat / (double)concurrency;       // single file latency (us)double file_MB = (double)block * repeat * concurrency / 1024.0 / 1024.0; // filesize in totalBLOCK+=block;LATENCY+=latency;printf("%d\t%d\t%.2f\n", block, concurrency, latency);}double throughput=BLOCK/LATENCY;printf("%.3f\n",throughput);BLOCK=LATENCY=0;}
}void test8()
{printf("Disk Random Read\n");printf("block\tprocess\tlatency\n");double BLOCK=0;double LATENCY=0;for (int block = 64; block <= Blocksize; block *= 2){for (int concurrency = 1; concurrency <= Concurrency; concurrency ++){gettimeofday(&starttime, NULL);for (int i = 0; i < concurrency; i++){if (fork() == 0){read_file(block, false, filepathdisk[i]); //disk random readexit(1);}}// wait children to terminatewhile (wait(NULL) != -1);gettimeofday(&endtime, NULL);/* calculate the duration, latency, file_MB */long alltime = get_time_left(starttime, endtime);                        // get the duration (us)double latency = (alltime) / (double)repeat / (double)concurrency;       // single file latency (us)double file_MB = (double)block * repeat * concurrency / 1024.0 / 1024.0; // filesize in totalBLOCK+=block;LATENCY+=latency;printf("%d\t%d\t%.2f\n", block, concurrency, latency);}double throughput=BLOCK/LATENCY;printf("%.3f\n",throughput);BLOCK=LATENCY=0;}}int main()
{srand((unsigned)time(NULL));int i = 0;// initial a test arrayfor (int j = 0; j < maxline; j++)writetext[j] = (j * j * j - 3 * Blocksize * j) % mod;test1();printf("\n");test2();printf("\n");test3();printf("\n");test4();printf("\n");test5();printf("\n");test6();printf("\n");test7();printf("\n");test8();printf("\n");return 0;
}