cpulimit

cpulimit is a handy tool that helps you manage how much CPU power a process can use. Instead of just counting time, it looks at the actual percentage of CPU usage. This is super useful for keeping batch jobs from hogging all your resources.

How cpulimit Works

The cool thing about cpulimit is that it doesn’t mess with nice values or other scheduling things. It focuses solely on real CPU usage and adjusts itself based on what’s happening with the system load. That means it can react quickly to changes!

Requirements for Using cpulimit

Requirements:

• Runs on any Linux version 2.2 or greater.


• Users have reported success even on SMP hardware, but remember that CPU usage might mean different things in those cases.


• If you can tweak the source code to work on non-Linux systems, let me know! I’d love to publish your version.

Getting Started with cpulimit

You can download cpulimit here. It comes under the GPL license. Once you've got it, unzip and compile it like this:

$ tar zxf cpulimit-1.0.tar.gz

  $ cd cpulimit-1.0

  $ make

Your executable will be named cpulimit.

How to Use cpulimit

If you want to limit a program called 'bigloop' to 40% CPU, you can run:

$ ./cpulimit --exe bigloop --limit 40

You can also use the full path:

$ ./cpulimit --path /usr/local/bin/bigloop --limit 40

Limiting by PID

If you're going by PID, here's how you'd limit it to 55%:

$ ./cpulimit --pid 2960 --limit 55

Your Options Explained

• -l, --limit=N: Set the CPU percentage from 0-100 (this part is required).


• -v, --verbose: Show control stats.


• -z, --lazy: Exit if no suitable process is found or if it dies.


• -h, --help: Get help and exit.

If you've got just one processor, it's straightforward—set your limit from 0% to 100%. But if you're running four processors? Well then your limits go from 0% up to 400%. So limiting at 200% means using half of what’s available!

You should run cpulimit as the same user who runs the controlled process for best results; however, running as root gives you more precision.

A little heads up: right now cpulimit does not control children processes or threads of the original process. I know this is a limitation and I'm working on adding that feature!