Docker Resource Limits

This Gist serves the purpose of better understanding different aspects of docker.

Based on ideas and code from https://dzone.com/articles/docker-container-resource-management-cpu-ram-and-i

# clean up preparation
docker stop $(docker ps -a -q)
docker rm -f $(docker ps -a -q)

Memory

# run container with memory limit
docker container run -d --memory=20m --memory-swap=20m --name myPython python:3-alpine sleep 3600
# open container shell
docker exec -it myPython /bin/sh
# enter python3 environment
python3

# allocate up to 100mb of memory through string concatenation
longstring = []
for x in range(100):
    len(longstring)
    longstring.append('1' * 10**6)

# this program will get killed, when memory limit reached

# stop and remove container
docker container stop myPython
docker container prune -f

Conclusion:

--memory controls how much memory the container has; without setting --memory-swap, the container has the same amount of swap available (so double of what is configured with --memory)
setting --memory-swap to the same value as --memory disables swap

CPU

docker container run -d --name cputest1 --cpus=1.0 alpine:3.8 /bin/sh -c 'time dd if=/dev/urandom bs=1M count=1000 | md5sum'
docker logs cputest1
docker container run -d --name cputest2 --cpus=0.5 alpine:3.8 /bin/sh -c 'time dd if=/dev/urandom bs=1M count=1000 | md5sum'
docker logs cputest2

# stop and remove container
docker container stop cputest1 cputest2
docker container prune -f

Conclusion:

--cpus is well suited to control cpu performance (in the microbenchmark, 0.5 requires almost exactly twice as long as 1.0)

MoeweX/Docker Resource Limits.md

Docker Resource Limits

Memory

CPU