Docker In Action: performance?

[Will Myers]

Does using Docker impact performance? Is there an extra 'hop' when using a Docker image?

[Liutauras Vilda]

Maybe author would find it easier to answer the question if you'd specify "comparing to what?".

[Stephen Kuenzli]

The general answer to that question is that a program running inside a container on a Linux container host will observe:

* no cpu and memory access overhead
* potentially measurable, but low networking overhead on the order of 1% or lower for throughput heavy applications
* significant storage write throughput performance impact if using an overlay filesystem... but you probably shouldn't do that because it sounds like you're storing data inside an ephemeral container filesystem; you should probably take a look at Chapter 4 and bind-mount a directory from the host or use a volume instead

[Tim Holloway]

It's not whether or not there's an impact. Yes, a Docker container is a virtual environment and it has virtualization overhead. But then, any general-purpose OS has overhead. If 100% hardware efficiency was that important, you'd custom-craft your own system.

But hardware these days is cheap enough that you could literally hand out small systems as party favors, and custom OS design is not, since it requires a great deal of work by specialized developers.

Suffice it to say that I found it more effective in the long run to move my stand-alone OS apps into Docker containers than to leave them free of the Docker overhead.