Linux limit cpu usage

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2 Ways to Limit CPU Usage of a Process in Linux
1) cpulimit
2) cputool
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Limit CPU Usage of a Process in Linux with CPULimit Tool
Install CPULimit to Limit CPU Usage Of a Process in Linux
Limiting Process CPU Usage With CUPLimit
If You Appreciate What We Do Here On TecMint, You Should Consider:
Linux Limit CPU Usage Per Process
Install cpulimit
A note about Debian / Ubuntu Linux users
How do I use cpulimit?
Root vs Normal User Account
A Note About SMP (Multicore / MultiCpu) Systems
Related Throttling Utilities
Recommended Readings:
How to Limit CPU Usage of a Process on Linux
Limiting CPU Usage with nice and renice:
Limiting CPU Usage with CGROUPS:

2 Ways to Limit CPU Usage of a Process in Linux

While administering your Linux system you need to limit the CPU usage of a process because it can consume more CPU usage and affects the performance of the whole system. This tutorial I will show how you can control CPU time of a process on Centos 7 and Ubuntu 16.

1) cpulimit

cpulimit is a nice command-line tool written in C programming language for limiting the CPU usage of a process. It is not present by default so we need to install it.

To install cpulimit on Ubuntu 16.04, do as below

Install on centos 7

We limit the CPU usage by using the —limit or -l option to set a usage percentage for a process. Before limiting the CPU usage, you need to find the process or the command that is using all your CPU time. There are three ways to use cpulimit, by acting

on the executable program with the —executable or -e option

on the absolute path name of the file with the —path or -P option

on the PID of the process with the —pid or -p option

So, we will first check the process/program which consumes the CPU time

Then you can use the following command with the name of the program.

You can see the tool has detected automatically the process id of the program. You can limit the cpu usage with the process id as below

And you can see the result below

You can run cpulimit in background by using the —background or -b option

2) cputool

You can use cputool which also uses cpulimit to reduce CPU usage.This can be also done by using the load limit. cputool is not present by default so you need to install it on Ubuntu 16

To use cputool, you need to respect the syntax below

With the same example, you can use the cputool as below

The command will take the control of your terminal so you can use it in background as below:

You can see the result as below

With these tools, you can easily control the CPU usage of a process when it is already running. You don’t need to kill the processes to reduce the usage but you can simply assign a percentage to not exceed.

Limit CPU Usage of a Process in Linux with CPULimit Tool

In an earlier post, we’ve explained CPUTool for limiting and controlling CPU utilization of any process in Linux. It allows a system administrator to interrupt execution of a process (or process group) if the CPU/system load goes beyond a defined threshold. Here, we will learn how to use a similar tool called cpulimit.

Cpulimit is used to restrict the CPU usage of a process in the same way as CPUTool, however, it offers more usage options compared to its counterpart. One important difference is that cpulimit doesn’t manage system load unlike cputool.

Install CPULimit to Limit CPU Usage Of a Process in Linux

CPULimit is available to install from default software repositories of Debian/Ubuntu and its derivatives using a package management tool.

In RHEL/CentOS and Fedora, you need to first enable EPEL repository and then install cpulimit as shown.

# yum install epel-release
# yum install cpulimit

Limiting Process CPU Usage With CUPLimit

In this sub section, we’ll explain how cpulimit works. First, let’s run a command (same dd command we looked at while covering cputool) which should result into a high CPU percentage, in the background (note that the process PID is printed out after running the command).

Next, we can use the top or glances tools which output the actual frequently updated state of a running Linux system, to watch the CPU usage of the command above.

Monitor CPU Usage in Linux

Looking at the output above, we can see that the dd process is utilizing the highest percentage of CPU time 100.0%.

But we can limit this using cputlimit as follows. The —pid or -p option is used to specify the PID and —limit or -l is used to set a usage percentage for a process.

The command below will limit the dd command (PID 17918) to 50% use of one CPU core.

Once we run cpulimit, we can view the current CPU usage for the dd command with top or glances. From the output, the value ranges from (51.5%-55.0% or slightly beyond).

Limit CPU Usage of Process in Linux

We can throttle its CPU usage for a second time as follows, this time lowering the percentage further as follows:

As we did before, we can run top or glances to view the new CPU usage for the process, which will range from 20%-25.0% or slightly beyond this.

Throttle CPU Usage in Linux

Note: The shell becomes un-interactive – doesn’t expect any user input when cpulimit is running. To kill it (which should stop the CPU usage limitation operation), press [Ctrl + C] .

To run cpulimit as a background process, use the —background or -b switch, freeing up the terminal.

To specify the number of CPU cores present on the system, use the —cpu or -c flag (this is normally detected automatically).

Rather than limit a process’s CPU usage, we can kill it with the —kill or -k option. The default is signal sent to the process is SIGCONT, but to send a different signal, use the —signal or -s flag.

To exit if there is no suitable target process, or in case it dies, include the -z or —lazy like this.

For additional information and usage options, view the cpulimit man page.

Do check out the following useful guides for finding CPU info and CPU/system performance monitoring.

In comparison, after testing CPUTool and CPULimit, we noticed that the former offers a more effective and reliable “process CPU usage limitation” functionality.

This is according to the percentage range of CPU usage observed after running both tools against a given process. Try out both tools and add your thoughts to this article using the feedback form below.

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Linux Limit CPU Usage Per Process

I don’t want background process to eat all my CPU. I know how to find out CPU utilization but how do I limit the cpu usage of a process under Linux operating system? How do I force a process to limit itself to 25% only?

You can use cpulimit program that attempts to limit the cpu usage of a process. Limits are expressed in percentage and not in cpu time. cpulimit does not act on the nice value or other scheduling priority stuff, but on the real cpu usage. Also, it is able to adapt itself to the overall system load, dynamically and quickly.

Install cpulimit

Type the following commands to install latest stable release:
# cd /tmp
# wget ‘http://downloads.sourceforge.net/cpulimit/cpulimit-1.1.tar.gz’
# tar -zxvf cpulimit-1.1.tar.gz
# cd cpulimit-1.1
# make
# cp cpulimit /usr/local/sbin/
# rm -rf cpulimit*

A note about Debian / Ubuntu Linux users

Type the following command to install cpulimit:
$ sudo apt-get update
$ sudo apt-get install cpulimit

How do I use cpulimit?

To limit CPU usage of the process called firefox to 30%, enter:
# cpulimit -e firefox -l 30
To limit CPU usage of the process to 30% by using its PID, enter:
# cpulimit -p 1313 -l 30
To find out PID of the process use any of the following:
# ps aux | less
# ps aux | grep firefox
# pgrep -u vivek php-cgi
# pgrep lighttpd
You can also use absolute path name of the executable, enter:
# cpulimit -P /opt/firefox/firebox -l 30
Where,

-p : Process PID.
-e : Process name.
-l : percentage of CPU allowed from 0 to 100.
-P: absolute path name of the executable program file.

Root vs Normal User Account

From the project webpage:

cpulimit should run at least with the same user running the controlled process. But it is much better if you run cpulimit as root, in order to have a higher priority and a more precise control.

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A Note About SMP (Multicore / MultiCpu) Systems

Again quoting from the project webpage:

If your machine has one processor you can limit the percentage from 0% to 100%, which means that if you set for example 50%, your process cannot use more than 500 ms of cpu time for each second. But if your machine has four processors, percentage may vary from 0% to 400%, so setting the limit to 200% means to use no more than half of the available power. In any case, the percentage is the same of what you see when you run top.

ionice utility – Avoid sudden outburst of backup shell script / program disk I/O.
Limit disk I/O for rsync tool.
Linux nice command: Run Process With Modified Scheduling Priority ( nicenesses )
renice command: Change the Priority of a Already Running Process

How to Limit CPU Usage of a Process on Linux

You can set how much CPU a single process is allowed to have. If the process really needs a lot of CPU power, you can run a few commands to give it all the idle CPU cycles (CPU cycles that you don’t need). That way, you will never have to sit and stare at your unresponsive computer for long.

In this article, I will show you how to Limit CPU usage of a process on Linux. I am going to use CentOS 7 in this article. But any modern Linux distribution should work. So, Let’s get started.

Limiting CPU Usage with nice and renice:

On Linux, the priorities of each running processes can be changed. You can set higher priorities to the process which is more important to you than a process that is hogging your CPU for no good reason.

Every process on Linux has a nice value. The value of nice determines which process has higher priorities and which has lower. Nice value can be between -20 to 19. A process with the nice value of -20 will have the highest priority and will use the most CPU cycles. A process with the nice value 19 will have the lowest priority and will use the CPU when no other processes are using it only.

There are two ways to set the nice value of a process. You can either start a process with the nice command to set a nice value while starting the process. Or you can use the renice command to set a nice value after a process has started.

To set a nice value when you start a process, run the process as follows:

NOTE: Here NICE_VALUE can be anything from -20 to 19 and COMMAND_TO_RUN is any command that you want to run with the nice value of NICE_VALUE.

For example, let’s say, you want to run the sleep command with the nice value of 14. Run the command as follows:

Now you can verify whether the nice value is set correctly using the top command. You can list all the processes that you started (as your login user) with the following command:

As you can see, the nice value of the process is set to 14.

Now if you wish to change the nice value of your existing processes, then all you need is the process ID (PID) of the process of which you want to change the nice value. You can use the ps aux command or the top command to find the process ID or PID.

Then you can run renice command as follows to change the nice value of an existing process:

As you can see, the nice value of the process with PID 6422 is changed.

Limiting CPU Usage with CGROUPS:

The full form of CGROUPS is Control Groups. It is a Linux kernel features used to limit resources to process groups such as (CPU, memory, permissions and many more) on Linux.

All you have to do is, create a new process group and add your processes that you want to limit resources to, to that group. Simple!

CGROUPS management tools are not installed on CentOS 7 by default. But it is available in the official package repository of CentOS 7.

First update the YUM package repository cache with the following command:

Now install CGROUPS management tools with the following command:

Now press y and then press .

It should be installed.

You can limit CPU usage of a single group. For example, you can use CGROUPS to tell a process within a CGROUP to use let’s say 100ms out of every 1000ms (or .1s out of every 1s) of CPU time.

First create a CGROUP with the following command:

NOTE: Here, cpulimit is the group name that controls the cpu usage.

Now, you have to set cpu.cfs_period_us and cpu.cfs_quota_us property on the cpulimit group.

For this example, 1000ms (milliseconds) or 1000000us (microseconds) should be set to cpu.cfs_period_us property and 100ms or 100000us should be set to the cpu.cfs_quota_us property.

Run the following commands to set these properties to the cpulimit group:

Now you can run the following command to check whether all the properties are correctly set:

NOTE: Here, cpulimit is the name of the CGROUP and cpu is the resource that I am limiting.

As you can see, cpu.cfs_period_us and cpu.cfs_quota_us are correctly set.

Now whatever process you add to cpulimit CGROUP will use 1/10 th (100000/1000000 = 1/10 = 0.1 = 10%) of the total CPU cycles.

Now to limit CPU of a process, start the program or command with cgexec as follows:

NOTE: Here, YOUR_COMMAND can be any valid Linux commands.

To prove that it actually works, first I am going to run the following command without CGROUPS and then with CGROUPS and show you the results.

As you can see, without CGROUPS, the command uses 90% of the total CPU.

Then, I ran the same command with CGROUPS as follows:

As you can see, the CPU usage is 10% at maximum. The process is not using more than that.

So that’s how you use CGROUPS to limit CPU usage of a process on Linux. Thanks for reading this article.