FD maximum and limit

The number of FD determines the maximum value of FD.

 

In Linux, the total number of FD enabled by the system is:

/Proc/sys/fs/file-Max, depending on the memory

The file-Max file/proc/sys/fs/file-Max sets the maximum number of file-handles that the Linux kernel will allocate. we generally tune this file to improve the number of open files by increasing the value of/proc/sys/fs/file-Max to something reasonable like 256 for every 4 m of ram we have: i. e. for a machine with 128 MB of RAM, set it to 8192-128/4 = 32 32*256 = 8192.

/Proc/sys/fs/file-Nr records the usage of FD in the system, and the number of allocated file handles
Number of file handles used
Maximum number of file handles,

The maximum number of FD opened by a single process is ulimit-N. You can use sysconf (_ SC _open_max) to obtain the default number of FD opened processes.

To modify the FD limit, you can first modify the shell's ulimit-N,

You can also use the setrlimit function to modify the settings:

Void modifyfdlimit ()
{
Rlimit fdlimit;

Fdlimit. rlim_cur= 30000;
Fdlimit. rlim_max = 30000;

If (-1 = setrlimit (rlimit_nofile, & fdlimit ))
{
Printf ("Set max FD open count Fai./nl ");

Char cmdbuffer [64];
Sprintf (cmdbuffer, "ulimit-N % d", 30000 );

If (-1 = System (cmdbuffer ))
{
Printf ("% s failed./N", cmdbuffer );

Exit (0 );
}

If (-1 = getrlimit (rlimit_nofile, & fdlimit ))
{
Printf ("ulimit FD number failed .");

Exit (0 );
}
}

// Printf ("Hard limit: % d. Soft limit: % d", fdlimit. rlim_max, fdlimit. rlim_cur );
}