Limiting CPU and RAM Usage for Processes on Ubuntu VPS

In this article, we will explore different methods to limit CPU and RAM usage for processes on an Ubuntu Virtual Private Server (VPS). This is an essential task for system administrators who want to ensure that no single process consumes all available resources, potentially slowing down or crashing the system.

Understanding the Need for Resource Limiting

Before we dive into the methods, it’s important to understand why we need to limit resource usage. In a multi-user environment or a server running multiple processes, it’s possible for a single process to consume an excessive amount of resources, leading to a system slowdown or even a crash. By limiting the CPU and RAM usage for each process, we can ensure that the system runs smoothly and efficiently.

Method 1: Using the nice Command

The nice command in Linux is used to manipulate the priority of a process. The priority level ranges from -20 (highest priority) to 19 (lowest priority). By default, all processes are started with a nice value of 0.

Here’s an example of how to use the nice command:

nice -n 10 {command}

In this example, {command} is the command you want to run with the specified nice value. The -n parameter specifies the nice value. A higher nice value (closer to 19) means lower CPU priority.

Method 2: Using the cpulimit Tool

The cpulimit tool allows you to limit the CPU usage of a process to a specific percentage. To use cpulimit, you first need to install it:

sudo apt-get install cpulimit

Then, you can limit the CPU usage of a process using its process name, absolute path, or PID. For example:

sudo cpulimit -e foo -l 60

In this command, -e specifies the executable program name and -l specifies the CPU usage limit in percentage. So, this command limits the CPU usage of the process named “foo” to 60%.

Method 3: Using Control Groups (Cgroups)

Control groups (Cgroups) provide a more flexible way to control resource allocation for a group of processes. You can limit CPU, memory, and other resources using Cgroups.

To use Cgroups, you first need to install the necessary tools:

sudo apt-get install cgroup-tools

Then, create a control group:

sudo cgcreate -g cpu,mem:/mygroup

In this command, -g specifies the subsystems (cpu and mem) and /mygroup is the name of the control group.

Next, set the CPU and memory limits for the group:

sudo cgset -r cpu.cfs_quota_us=60000 -r mem.limit_in_bytes=2048000000 mygroup

In this command, cpu.cfs_quota_us=60000 sets the CPU limit to 60% (60000 microseconds out of every 100000 microseconds), and mem.limit_in_bytes=2048000000 sets the memory limit to 2048 MB.

Finally, move the desired process to the control group:

sudo cgexec -g cpu,mem:mygroup {command}

Replace {command} with the command you want to run within the control group.

Conclusion

Limiting CPU and RAM usage for processes on an Ubuntu VPS is an essential task for system administrators. It ensures that system resources are shared fairly among processes, preventing any single process from hogging all the resources. While the nice command and cpulimit tool are easy to use, Cgroups provide more flexibility and control over resource allocation. Choose the method that best suits your requirements.