The most interesting piece of this puzzle to me is initiatives like MirageOS, which let you run your application very close to the metal—you give up a lot of convenience when you dump the traditional OS, but you give up a lot of inefficiency, too.

Or you could keep the convenience while dumping the overhead by using Docker. As a bonus you also get to be cool.

Docker is still a full Linux kernel. The point of MirageOS is that your app is the kernel.

For MirageOS, Xen is the kernel.

But Xen is smaller than Linux.

My impression is that typical docker deployments have them sitting on VMs anyway— so it's the worst of both worlds in that scenario.

What do you mean "again"?

It doesn't seem to be important now.

http://en.wikipedia.org/wiki/Wirth's_law

Even if you make particularly efficient code, the giant tower of abstractions we all operate on top of make running your code dozens of times slower than it could possibly be running on bare metal.