我运行一个java代码，该代码产生大量的读写文本文件。程序源代码非常简单，在一个循环中，我在一个测试文件中写入2000行，然后再次读取它们，以便生成大量的读取和写入磁盘。但是当程序运行时我通过“iostat -d -x 1”监控磁盘我发现第二个“r/s”的读取没有变化，但是“w/s”增加了，正如我预期的那样！ 这iostat命令的示例输出：为什么在linux命令(iostat)中每秒读取(r/s)一直为零？

Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util

sda 0.00 913.00 0.00 82.00 0.00 7872.00 96.00 0.58 7.09 7.11 58.30

Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util

sda 0.00 869.00 0.00 79.00 0.00 7584.00 96.00 0.57 7.11 7.18 56.70

Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util

sda 0.00 847.00 0.00 77.00 0.00 7392.00 96.00 0.57 7.42 7.43 57.20

Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util

sda 0.00 1221.00 0.00 113.00 0.00 10760.00 95.22 0.84 7.47 7.32 82.70

由于它被示出，所有的 “R/S” 是零！但在Java程序中，我阅读的内容与我在文件中写入的一样多！当我运行Java代码时，每秒写入次数增加，但“r/s”没有变化！ 这里是我监视磁盘时运行Java代码：

import java.io.*;

public class Test {

public static void main(String [] args) throws IOException{

String fileName = "/scratch/dump_file.txt";

File f = new File(fileName);

// Attempt to delete it

boolean success = f.delete();

int j=0;

while(j<20000)

{

++j;

Writer output = null;

String text = "A test content";

File file = new File(fileName);

output = new BufferedWriter(new FileWriter(file));

int i=1;

while(i<2000)

{

//Here we start writing 2000 lines into file line by line

output.write("j==="+Integer.toString(j)+text+Integer.toString(i)+"\n");

++i;

}

output.close();

System.out.println("Your file has been written");

String line = null;

try {

// FileReader reads text files in the default encoding.

FileReader fileReader = new FileReader(fileName);

BufferedReader bufferedReader =

new BufferedReader(fileReader);

i=1;

while((line = bufferedReader.readLine()) != null) {

//Here we start reading from file line by line and show the result on screen

++i;

System.out.println(line);

}

// Always close file

bufferedReader.close();

}

catch(FileNotFoundException ex) {

System.out.println(

"Unable to open file '" +

fileName + "'");

}

catch(IOException ex) {

System.out.println(

"Error reading file '"

+ fileName + "'");

// Or we could just do this:

// ex.printStackTrace();

}

}

}

}