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Taskset

The taskset command is used to set or retrieve the CPU affinity of a running process given its pid, or to launch a new command with a given CPU affinity.

#Getting Started

#Usage

The default behavior is to run a new command with a given affinity mask

$ taskset [mask] [command] [arguments]

#Usage #2

$ taskset -p [pid]

$ taskset -p [mask] [pid]

You can also retrieve the CPU affinity of an existing task

#Common Options

Command Alternavite Meaning
-a --all-tasks Set or retrieve the CPU affinity of all the task (threads) for a given PID.
-c --cpu-list Interpret mask as numerical list of processors instead of a bitmask.
Numbers are separated by commas and may include ranges. For example: 0,5,8-11
-p --pid Operate on an existing PID and do not launch a new task.
-h --help Display help text and exit.
-v --version Print version and exit.

#Example

#View CPU Affinity

$ taskset -cp 29523
pid 29523's current affinity list: 0-15

That mean process with PID 29523 is active on CPU range from [0,1,...,15] which means 16 total.

PID: Process Identifier - is a unique numerical identifier given to each running process, you can view PID of processes in top or htop tools

If you run the above command but get the message bad usage, try with PID = 1

$ taskset -cp 1

#Set CPU Affinity

Now let's try to set process in to a specify CPU. For example, we have a process has PID = 14846

Let's see the CPU affinity list of this process first:

$ taskset -cp 14846
pid 14846's current affinity list: 0-15

#Change CPU affinity to 1:

$ taskset -cp 1 14846
pid 14846's current affinity list: 0-15
pid 14846's new affinity list: 1

As we see, CPU affinity was changed

#Set CPU Affinity with muliple value

That mean new CPU affinity list is [0,1,2,3]

$ taskset -cp 0-3 14846
pid 14846's current affinity list: 1
pid 14846's new affinity list: 0-3

You can set single CPU with the following command:

$ taskset -cp 5,8,12 14846
pid 14846's current affinity list: 0-3
pid 14846's new affinity list: 5,8,12

That mean new CPU affinity list is [5,8,12]

#Other

You can set affinity by range with other like a specify CPU

$ taskset -cp 1-3,12 14846

Or

$ taskset -cp 1-6:2 14846

The suffix ":N" specifies stride in the range, for example 0-10:3 is interpreted as 0,3,6,9 list.

#Also see

taskset — Linux manual page (man7.org)