Replacing a sort algorithm in the FreeBSD kernel has improved its boot speed by a factor of 100 or more… and although it’s aimed at a micro-VM, the gains should benefit everyone. From a report: MicroVMs are a hot area of technology R&D in the last half decade or so. The core idea is a re-invention of some of concepts and technology that IBM invented along with the hypervisor in the 1960s: designing OSes specifically to run as guests under another OS. This means building the OS specifically to run inside a VM, and to talk to resources provided by a specific hypervisor rather than to fake hardware.
This means that the guest OS needs next to no support for real hardware, just VirtIO drivers which talk directly to facilities provided by the host hypervisor. In turn, the hypervisor doesn’t have to provide an emulated PCI bus, emulated power management, emulated graphics card, emulated network interface cards, and so on. The result is that the hypervisor itself can be much smaller and simpler. The result of ruthlessly chopping down both the hypervisor, and the OS that runs inside it, is that both ends can be much smaller and simpler. That means that VMs can use much fewer resources, and start up much quicker.
