1. Overview

There are many cases in which we need to limit the usage of resources on the docker host machine.

In this tutorial, we’ll learn how to set the memory and CPU limit for docker containers.

2. Setting Resources Limit With docker run

We can set the resource limits directly using the docker run command. It’s a simple solution. However, the limit will apply only to one specific execution of the image.

2.1. Memory

For instance, let’s limit the memory that the container can use to 512 megabytes. To constrain memory, we need to use the m parameter:

$ docker run -m 512m nginx

We can also set a soft limit called a reservation. It’s activated when docker detects low memory on the host machine:

$ docker run -m 512m --memory-reservation=256m nginx

2.2. CPU

By default, access to the computing power of the host machine is unlimited. **We can set the CPUs limit using the cpus parameter. **For example, let’s constrain our container to use at most two CPUs:

$ docker run --cpus=2 nginx

We can also specify the priority of CPU allocation. The default is 1024, higher numbers are higher priority:

$ docker run --cpus=2 --cpu-shares=2000 nginx

Similarly to the memory reservation, CPU shares play the main role when computing power is scarce and needs to be divided between competing processes.

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