The Overhead of Docker Run

We use Docker a lot. Like a lot, lot. While we love it for a lot of things, it still has a lot of room for improvement. One of those areas that could use improvement is the startup/teardown time of running a container.

The Test

To test the overhead of running a Docker container, I made a script that compares execution times for various docker run options vs not using Docker at all. The script that I’m running is a simple hello world shell script that consists of the following:

echo "Hello World!"

The base Docker image is the official Alpine linux image plus the script above.

4 Things to Compare

  1. As a baseline, the first measurement is sans Docker. This is just running the hello.sh script directly.
  2. The second measure is just docker run IMAGE.
  3. The third measure adds the “rm” flag to remove the container after execution.
  4. The final one is to use docker start instead of run, so we can see the effect of reusing an already created container.

Docker for Mac

Server Version: 1.12.2-rc1

Running: ./hello.sh
avg: 5.897752ms
Running: docker run treeder/hello:sh
avg: 988.098391ms
Running: docker run — rm treeder/hello:sh
avg: 999.637832ms
Running: docker start -a reuse
avg: 986.875089ms

(Note: looks like using Ubuntu as a base image is slightly faster than Alpine, in the 10–50ms range).

Docker on Ubuntu

Server Version: 1.12.1

Running: ./hello.sh
avg: 2.139666ms
Running: docker run treeder/hello:sh
avg: 391.171656ms
Running: docker run — rm treeder/hello:sh
avg: 396.385453ms
Running: docker start -a reuse
each: 340.793602ms

Results

As you can see from the results above, using Docker adds nearly a full second to the execution time of our script on Mac and ~390ms on Linux (~175x slower than running the script without Docker).

Now this may not be much of an issue if your script/application runs for a long period of time, but it is certainly an issue if you run short lived programs.

Try it yourself

Feel free to try running the script on your system and share the results! You can find everything you need here: https://github.com/treeder/dockers/tree/master/hello

Just clone that repo, cd into the hello directory and run:

go run time.go
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