Taskset

Christian Külker

0.1.2

2023-03-13

The taskset command is used to set or get the CPU affinity of a process. CPU affinity is a feature that allows you to bind or unbind processes to a particular CPU or range of CPUs.

Installation

aptitude install util-linux

Usage

How Do I Get the CPU Affinity of a Process?

Use the PID with the -p option to get the affinity mask.

taskset -p 32677
pid 32677's current affinity mask: ff

The mask is a bit mask. For this example, the process has the affinity to run on all CPUs hex 0xff = binary 11111111 = decimal 8 cores. That the system has 8 cores can be easily confirmed with numctl.

numactl --hardware
available: 1 nodes (0)
node 0 cpus: 0 1 2 3 4 5 6 7
node 0 size: 11975 MB
node 0 free: 3123 MB
node distances:
node   0
  0:  10

How to Change the CPU Affinity Of a Process?

taskset -p  32677
pid 32677's current affinity mask: ff
taskset -p 0x0f 32677
pid 32677's current affinity mask: ff
pid 32677's new affinity mask: f
taskset -p  32677
pid 32677's current affinity mask: f

How to Start a Process with CPU Affinity?

This task is quite common in HPC, so when starting a new process manually or through a scheduler, you should know and understand how to pin a process to specific CPUs.

taskset 0xf0 long-running-command

Of course, it is also possible to run a process on a range of CPUs with the -cp option, but this usually only makes sense if there is no penalty for switching tasks. It is usually better to pin a process to one core, unless the task is a wrapper that pins its subprocess to dedicated cores by itself.

History

Version Date Notes
0.1.2 2023-03-13 Improve writing, fix version, fix link
0.1.1 2022-06-15 History, shell->bash
0.1.0 2020-05-01 Initial release
  • Taskset