我在我的MacBook上使用Java打开文件时,发现最多只能打开10223个文件,而且我已经通过sysctl、launchd和ulimit设置了文件打开限制为65535,但是用C程序可以打开62282个文件。您知道Java是否遇到了额外的限制,以及如何更改它吗?
我用于测试的Java代码是:
import java.io.*;
import java.util.*;
class OpenFilesTest {
private static List<InputStream> streams = new ArrayList<InputStream>();
public static void main(String[] args) {
for (int i = 0; true; i++) {
FileInputStream f = null;
try {
f = new FileInputStream("/dev/null");
} catch (Throwable e) {
System.err.println(e.getMessage());
e.printStackTrace();
System.exit(1);
}
streams.add(f);
System.out.println("We have " + (i + 1) + " InputStream's for /dev/null");
}
}
}
这将输出:
We have 1 InputStream's for /dev/null
We have 2 InputStream's for /dev/null
We have 3 InputStream's for /dev/null
...
We have 10221 InputStream's for /dev/null
We have 10222 InputStream's for /dev/null
We have 10223 InputStream's for /dev/null
/dev/null (Too many open files)
java.io.FileNotFoundException: /dev/null (Too many open files)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:138)
at java.io.FileInputStream.<init>(FileInputStream.java:97)
at OpenFilesTest.main(test.java:11)
我使用的C代码进行测试:
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
int main(void)
{
for (int i = 0; 1; i++)
{
int fd = open("/dev/null", O_RDONLY);
if (fd == -1)
{
perror("Couldn't open /dev/null one more time");
exit(EXIT_FAILURE);
} else {
printf("Opened /dev/null %d times\n", i + 1);
}
}
}
以及它的输出:
Opened /dev/null 1 times
Opened /dev/null 2 times
Opened /dev/null 3 times
...
Opened /dev/null 62287 times
Opened /dev/null 62288 times
Opened /dev/null 62289 times
Couldn't open /dev/null one more time: Too many open files in system
关于该系统的更多相关信息:
$ uname -a
Darwin hostname.local 13.1.0 Darwin Kernel Version 13.1.0: Thu Jan 16 19:40:37 PST 2014; root:xnu-2422.90.20~2/RELEASE_X86_64 x86_64
$ java -version
java version "1.7.0_25"
Java(TM) SE Runtime Environment (build 1.7.0_25-b15)
Java HotSpot(TM) 64-Bit Server VM (build 23.25-b01, mixed mode)
我也在Linux(Debian Wheezy 7.4)上尝试过这个方法,在那里我可以使用这个Java程序打开大约65535个文件句柄。 这么多打开的文件句柄的基本用例是Scala中的服务器负载测试应用程序。
for (int i = 0; true; i++)
真的很丑陋。如果你喜欢的话,为什么不只用while(true)
或者for(;;)
呢? - halex