The command taskset is used to set or get a process’s CPU affinity. CPU affinity is a feature that allows you to bind or unbind processes to a particular central processing unit, or a range of CPUs.

Installation

aptitude install util-linux

Usage

How To Get 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 easy 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, when starting a new process manually or via a scheduler one should know and understand how to pin a process to certain CPUs.

taskset 0xf0 long-running-command

It is of course also possible to run a process on a range of CPUs with the -cp option, but that usually makes only sense if the task switching has no penalty involved. Usually it is better to pin a process to one core unless the task is a wrapper that pins it sub process by itself to dedicated cores.

History

Version	Date	Notes
0.1.1	2022-06-15	History, shell->bash
0.1.0	2020-05-01	Initial release