I think that the --cgroup-parent flag, which has been released with docker 1.6, is one of the most underrated feature.
If done correctly could make docker a full class citizen of commercial deployments.
Cgroups allow for a very fine control of resource usage: cpu, memory, IOPS, bandwidth, etc…
They are the best way to manage resources as they are both effective (wide range of resources to control, with several options) and efficient (almost zero overhead), thanks to the fact that they are implemented directly in the kernel.
Another plus is that they offer an unified way to control resources, instead of relying on several different flags.
I see from git commits that features are progressing nicely, with more control groups added recently. Does this flag support hierarchical cgroups? Is it possible to assign multiple cgroups to a container? (i.e. control IOPS AND bandwidth)
Anyone using them in the wild?