lockpid(ADM)

lockpid -- lock a process onto a specific processor

Syntax

lockpid -l cpu pid

lockpid -u pid

Description

lockpid is a utility which allows a process to be run entirely on a specified processor. This can be used if performance can be improved by restricting certain applications to specific processors. A process cannot be locked to a processor that has been inactivated using cpuonoff(ADM).

root permission is required to run lockpid.

To assign a process to a processor lockpid requires both the CPU number, the base processor being CPU1, and the process identifier. The process identifier or PID can be found using ps(C) or by running the process in the background.

The options are as follows:

-l cpu pid: locks process pid to the processor given by cpu where both cpu and pid are integer values
-u pid: unlocks the previously locked process pid

The -u option has no effect if a locked process has finished executing or terminates abnormally.

Exit values

lockpid exits with 0 upon successful completion. It exits with 1 if an error occurs.

Diagnostics

Messages may include the following:

pid process_id locked on cpu num: Confirmation that process process_id was locked to processor number num.
pid process_id unlocked: Confirmation that the process process_id has been unlocked from the processor.
lockpid: invalid CPU specified: The argument specifying a processor must be numeric.
lockpid: invalid pid specified: The argument specifying a process id must be numeric.
lockpid: cannot specify negative CPU: The argument specifying a processor must be a positive integer.
lockpid: CPU specified exceeds number of CPUs installed: The specified processor does not exist or has not been serialized.
lockpid: cannot lock pid process_id: The process process_id could not be locked to the specified processor. This can occur if the process has already used floating point different from that used by the processor specified.
lockpid: cannot unlock pid process_id: The process process_id could not be unlocked.
lockpid: can't open device: The required device node device is missing. Run idmknod(ADM) to recreate any missing device nodes.
lockpid: cannot determine number of processors: The kernel cannot determine the number of processors installed and serialized.
lockpid: malloc for procdata failed: lockpid could not malloc required memory for its internal work area.
lockpid: cannot determine processor_data: lockpid could not read the relevant processor data from the kernel

Examples

Using the PID returned as a result of running a process in the background, lockpid is used, in the following example, to lock process 22852 to CPU2:

   $ cpusar -Q -P2 1 1
   $ program &
   [1]     22852
   $ lockpid -l 2 22852
   $ cpusar -Q -P2 1 1
   ...

Warnings

Note the following warnings:

This command numbers processors beginning with 1. The similar pbind(ADM) command number processors beginning with 0. The two commands can be used together, but be aware of the numbering sequence difference.
It is possible to use cpuonoff to inactivate a processor to which processes have been locked. These processes will not be executed until the process is activated or unlocked.
A process can be locked to a processor in two ways:
- by a system administrator using lockpid
- by the system itself.
If a process has been locked by the system, it would be unwise for the system administrator to unlock the process or lock it to an alternative processor; such an action may result in unpredictable system behavior.
Using lockpid to lock a large number of processes to a processor may result in processes not being optimally balanced across processors.

Files

/etc/lockpid: command

Standards conformance

lockpid is not part of any currently supported standard; it is an extension of AT&T System V provided by the Santa Cruz Operation, Inc.