随机IO读取 [英] Random IO Read

问题描述

大家好


以下代码生成文件。你知道如何为多用户访问编写一个随机的文件代码吗？


我们想要测试FileSystem IO性能。


#include< fcntl.h>

#include< stdio.h>

#include< unistd.h>


#define FAIL -1

#define BSIZE 8192

#define FSIZE 5000


int writeit（int）;

int main（void）

{

if（-1 == writeit（FSIZE））printf（" ;文件操作失败\ nn）;

}


int writeit（int blocks）

{

char buf [BSIZE];

int fdes;

int i;

int written;

if（（fdes = open（&.;。/ testfile.bm"，O_WRONLY | O_CREAT，0777））< 0）

返回FAIL;

for（i = 0; i< blocks; i ++）

{

if（write = write（fdes，buf，BSIZE）！= BSIZE）return FAIL;

}

返回0;

}

解决方案

moonhkt写道：

大家好


以下代码生成文件。你知道如何为多用户访问编写一个随机的文件代码吗？


我们想要测试FileSystem IO性能。


#include< fcntl.h>

#include< stdio.h>

#include< unistd.h>


#define FAIL -1

#define BSIZE 8192

#define FSIZE 5000


int writeit（int）;

int main（void）

{

if（-1 == writeit（FSIZE））printf（" ;文件操作失败\ nn）;

}


int writeit（int blocks）

{

char buf [BSIZE];

int fdes;

int i;

int written;

if（（fdes = open（&.;。/ testfile.bm"，O_WRONLY | O_CREAT，0777））< 0）

返回FAIL;

for（i = 0; i< blocks; i ++）

{

if（write = write（fdes，buf，BSIZE）！= BSIZE）return FAIL;

}

返回0;

}


你将在comp.unix.programmer中得到更好的服务，因为你的代码是UNIX

具体且几乎不是标准C.

2008年4月24日星期四14:35:35 +0530，santosh< sa ********* @ gmail.com>

写道：

> moonhkt写道：

>大家好

忽略你的非标准函数和标题，你的问题好像是如何用BSIZE随机字符填充buf 。一种方法是：

将buf更改为unsigned char。

调用srand来播放rand函数。

在一个循环中，调用rand并存储它返回的int的某些部分

current buf的元素。

>>
我们要测试FileSystem IO的性能。

合理的担心IO性能会受到涉及位模式的影响吗？如果buf

与0xa5一起提交，结果会有什么不同吗？如果存在差异，那么5000个字符足够

是否会被注意到（或测量）？

>>
#include< fcntl.h>
#include< stdio.h>
#include< unistd.h>

#define FAIL -1
#define BSIZE 8192
#define FSIZE 5000
int writeit（int）;
int main（void）
{
if（-1 == writeit（FSIZE））printf（FILE OPERATION FAILED\ n）;
}
int writeit（int blocks）
{
char buf [BSIZE];
int fdes;
int i;
int written;
if（（fdes = open（&.;。/ testfile.bm" ;，O_WRONLY | O_CREAT，0777））< 0）
返回FAIL;
for（i = 0; i< blocks; i ++）
{
if（written = write （fdes，buf，BSIZE）！= BSIZE）返回失败;
}
返回0;
}

你会得到更好的服务在comp.unix.programmer中，因为你的代码是UNIX特定的，几乎不是标准的C 。

删除电子邮件的del

moonhkt写道：

大家好


以下代码生成文件。你知道如何为多用户访问编写一个随机的文件代码吗？


我们想要测试FileSystem IO性能。

如果你想这样做，可以使用为此任务设计的许多工具之一。


-

Ian Collins。

Hi All

Below coding for generate a file. Do you know how to write a code for
random a a file for multi-user access ?

We want testing FileSystem IO performance.

#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

#define FAIL -1
#define BSIZE 8192
#define FSIZE 5000

int writeit(int);
int main(void)
{
if ( -1 == writeit(FSIZE)) printf("FILE OPERATION FAILED\n");
}

int writeit(int blocks)
{
char buf[BSIZE];
int fdes;
int i;
int written;
if ( (fdes = open("./testfile.bm",O_WRONLY|O_CREAT,0777)) < 0)
return FAIL;
for (i=0;i< blocks ; i++)
{
if (written = write(fdes,buf,BSIZE) != BSIZE) return FAIL;
}
return 0;
}

解决方案

moonhkt wrote:

Hi All

Below coding for generate a file. Do you know how to write a code for
random a a file for multi-user access ?

We want testing FileSystem IO performance.

#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

#define FAIL -1
#define BSIZE 8192
#define FSIZE 5000

int writeit(int);
int main(void)
{
if ( -1 == writeit(FSIZE)) printf("FILE OPERATION FAILED\n");
}

int writeit(int blocks)
{
char buf[BSIZE];
int fdes;
int i;
int written;
if ( (fdes = open("./testfile.bm",O_WRONLY|O_CREAT,0777)) < 0)
return FAIL;
for (i=0;i< blocks ; i++)
{
if (written = write(fdes,buf,BSIZE) != BSIZE) return FAIL;
}
return 0;
}

You''ll be better served in comp.unix.programmer as your code is UNIX
specific and hardly standard C.

On Thu, 24 Apr 2008 14:35:35 +0530, santosh <sa*********@gmail.com>
wrote:

>moonhkt wrote:

>Hi All

Below coding for generate a file. Do you know how to write a code for
random a a file for multi-user access ?

Ignoring your non-standard functions and headers, your problem seems
to be how to fill buf with BSIZE random char. One method would be to:
Change buf to unsigned char.
Call srand to seed the rand function.
In a loop, call rand and store some part of the int it returns in
the "current" element of buf.

>>
We want testing FileSystem IO performance.

Is it a reasonable concern that IO performance would be affected by
the bit patterns involved? Would the results be any different if buf
were filed with 0xa5? If there is a difference, is 5000 char enough
for it to be noticed (or measured)?

>>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

#define FAIL -1
#define BSIZE 8192
#define FSIZE 5000

int writeit(int);
int main(void)
{
if ( -1 == writeit(FSIZE)) printf("FILE OPERATION FAILED\n");
}

int writeit(int blocks)
{
char buf[BSIZE];
int fdes;
int i;
int written;
if ( (fdes = open("./testfile.bm",O_WRONLY|O_CREAT,0777)) < 0)
return FAIL;
for (i=0;i< blocks ; i++)
{
if (written = write(fdes,buf,BSIZE) != BSIZE) return FAIL;
}
return 0;
}

You''ll be better served in comp.unix.programmer as your code is UNIX
specific and hardly standard C.

Remove del for email

moonhkt wrote:

Hi All

Below coding for generate a file. Do you know how to write a code for
random a a file for multi-user access ?

We want testing FileSystem IO performance.

If you want to do that, use one of the many tools that have been
designed for this task.

--
Ian Collins.

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