CPU Constraints

#### CPU Constraints

You can limit CPU, either using a percentage of all CPUs, or by using specific cores.  

For example, you can tell the [`cpu-shares`](https://docs.docker.com/engine/reference/run/#/cpu-share-constraint) setting.  The setting is a bit strange -- 1024 means 100% of the CPU, so if you want the container to take 50% of all CPU cores, you should specify 512.  See <https://goldmann.pl/blog/2014/09/11/resource-management-in-docker/#_cpu> for more:

```
docker run -it -c 512 agileek/cpuset-test
```

You can also only use some CPU cores using [`cpuset-cpus`](https://docs.docker.com/engine/reference/run/#/cpuset-constraint).  See <https://agileek.github.io/docker/2014/08/06/docker-cpuset/> for details and some nice videos:

```
docker run -it --cpuset-cpus=0,4,6 agileek/cpuset-test
```

Note that Docker can still **see** all of the CPUs inside the container -- it just isn't using all of them.  See <https://github.com/docker/docker/issues/20770> for more details.