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How to obtain system open file table value in Linux
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nfile(5) File Formats Manual nfile(5) NAME
nfile - maximum number of open files (system-wide) VALUES
Failsafe Default The default value for is (zero). The value of zero means that the system limit usually enforced by will be disabled (that is, the number of system-wide open files is limited only by available memory). Allowed values The allowed values for are either (zero) or values between the minimum and maximum (inclusive). The minimum value is The maximum value is the maximum 32-bit signed integer value that can be represented in the system. The value is further constrained in that it must be greater than or equal to two times the per-process open file hard limit (that is, Specify a positive integer value. DESCRIPTION
This tunable is now private and deprecated. It should no longer be used. The system open file table was restructured in 11iV3 to remove the architectural limitations on this value, and, therefore, is no longer needed. The recommended way to regulate the maximum number of open files on the system is to set the values of and appropriately; the theoretical system maximum can be assumed to be * The tunable defines the maximum number of slots in the system open file table. This number limits the cumulative number of open files by all processes in the system. In addition to named files (regular files, directories, links, device files, and so on), other objects that consume slots in the system open file table include pipes, FIFOs, sockets, and streams. Be aware that the and system calls consume entries in the per-process file tables but do not consume new slots in the system open file table. Who Is Expected to Change This Tunable? This tunable is not expected to be changed. Restrictions on Changing This tunable is dynamic; tuning will take effect immediately on the running system. When the value of is dynamically tuned it cannot be set to a value lower than the number of current open files in the running kernel. To allow an unlimited number of system-wide open files, the value should be set to the default. When Should the Value of This Tunable Be Raised? This tunable should only be set to a non-zero value to enforce a limit on the number of open files. What Are the Side Effects of Raising the Value? By setting this tunable to a positive, non-zero value, the system wide limit will be enforced. By requiring the system to enforce a global limit, performance of the system call and other related system calls may be impaired. When Should the Value of This Tunable Be Lowered? The value of rarely needs to be lowered. The value may be lowered to limit the number of open files on a system, and this may reduce mem- ory consumption. What Are the Side Effects of Lowering the Value? A lower limit may restrict an application's ability to allocate a new file descriptor or open a named file. What Other Tunable Values Should Be Changed at the Same Time? must be equal to or greater than two times the value of Kernel checks during tunable setting ensure this. WARNINGS
This tunable is obsolete and will be removed in a future release of HP-UX. All HP-UX kernel tunable parameters are release specific. This parameter may be removed or have its meaning changed in future releases of HP-UX. Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parameter values. After installation, some tunable parameters may no longer be at the default or recommended values. For information about the effects of installation on tun- able values, consult the documentation for the kernel software being installed. For information about optional kernel software that was factory installed on your system, see at AUTHOR
was developed by HP. SEE ALSO
kctune(1M), sam(1M), dup(2), dup2(2), gettune(2), open(2), settune(2), maxfiles(5), maxfiles_lim(5), nproc(5). OBSOLETE
Tunable Kernel Parameters nfile(5)
