CPU limit test

Go to Project 9 from the git repository root:

cd projects/p09

Project structure:

.
└── Dockerfile

Files

Dockerfile

# Based on "Petar Maric outdated image"
# https://github.com/petarmaric/docker.cpu_stress_test

FROM ubuntu:20.04

# Update the Ubuntu package index and install the required Ubuntu packages
RUN apt-get update \
 && apt-get install -y --no-install-recommends stress

# Parameterize this Dockerfile, by storing the app configuration within environment variables 
ENV STRESS_TIMEOUT 120
ENV STRESS_MAX_CPU_CORES 1

CMD stress --cpu $STRESS_MAX_CPU_CORES --timeout $STRESS_TIMEOUT

We test the CPU limit in this example using an image based on petermaric/docker.cpu-stress-test. Since that image is outdated, we create a new image similar to Peter Maric’s work.

docker build -t localhost/stress .

Execute the following command to test a whole CPU core:

docker run -it --rm \
  -e STRESS_MAX_CPU_CORES=1 \
  -e STRESS_TIMEOUT=30 \
  --cpus=1 \
  localhost/stress

Run “top” in an other terminal to see that the “stress” process uses 100% of one CPU. To see the same result on any host operating system, we will run top in an Ubuntu container using the process namespace of the host.

docker run --rm -it --pid host ubuntu:20.04 top

Press Ctrl-C and execute the following command to test two CPU core and allow the container to use only 1 and a half CPU.

docker run -it --rm \
  -e STRESS_MAX_CPU_CORES=2 \
  -e STRESS_TIMEOUT=30 \
  --cpus=1.5 \
  localhost/stress

Use “top” again to see that the “stress” process uses 75% of two CPU.

You can test on one CPU core again and allow the container to use 50% of a specific CPU core by setting the core index.

docker run -it --rm \
  -e STRESS_MAX_CPU_CORES=1 \
  -e STRESS_TIMEOUT=60 \
  --cpus=0.5 \
  --cpuset-cpus=0 \
  localhost/stress

You can use top again, but do not forget to add the index column to the list:

  • run docker run --rm -it --pid host ubuntu:20.04 top

  • press “f”

  • Select column “P” by navigating with the arrow keys

  • Press “SPACE” to select “P”

  • Press “ESC”

Now you can see the indexes in the column “P”.

Press “1” to list all the CPU-s at the top of the terminal so you can see the usage of all the CPU-s.