I like the initial idea very much. As I can see this is a wrapper over QEMU and controlled by QMP [1][2], so they are providing a kernel, initrd and a image. It is also configuring a machine profile (memory, vcpu, bus, devices, etc.). There are also interfaces for libvirt, xen and others virtualization technologies.

This also looks similar of what Docker is doing now in Windows with HyperV.

My question here is: from where comes the speed improvement in relation with a classical VM approach?

[1] https://github.com/hyperhq/runv/blob/master/hypervisor/qemu/...

[2] https://github.com/hyperhq/runv/blob/master/hypervisor/qemu/...