4 ms·

Microkernels and hypervisors are not the same thing.

by cbd1984 11y ago

JoshTriplett 11y ago
What's the difference between Xen and a microkernel? They both manage memory, do CPU scheduling, provide efficient message-passing, protect "processes" running underneath them from each other, and leave almost everything else to the "processes" running underneath them.
- cbd1984 11y ago
  > What's the difference between Xen and a microkernel? Xen allows full OSes to be guests and run on top of it. Microkernels only allow servers to run on top of it, and those servers have to be purpose-written and cannot meaningfully be ported. Xen doesn't provide hardware abstraction and is fully invisible (except to the extent it advertises itself); microkernels are neither. Paravirtualization (what you did before VT-x and similar) was an oddity, and blurs these lines a tiny bit, but the distinction is fairly clear otherwise.
  - JoshTriplett 11y ago
    > Xen allows full OSes to be guests and run on top of it. Microkernels only allow servers to run on top of it, and those servers have to be purpose-written and cannot meaningfully be ported. L4 is an archetypal microkernel, and people often run full OSes or other ported software under it, including Linux. > Xen doesn't provide hardware abstraction and is fully invisible (except to the extent it advertises itself); microkernels are neither. Microkernels typically don't abstract any hardware other than CPU and memory; any other drivers would run under the microkernel. And Xen is only "invisible" if you run full hardware virtualization and no paravirtualized drivers. > Paravirtualization (what you did before VT-x and similar) People still use "paravirtualization" today; see the "virtio" drivers typically used with KVM.
  - nickpsecurity 11y ago
    Gernot Heiser states it here: https://microkerneldude.wordpress.com/2008/04/03/microkernels-vs-hypervisors/ https://microkerneldude.wordpress.com/2008/04/03/microkernel... Their highly-efficient microkernel has been doing so well that most people using it don't know it's in their smartphones. Do most virtualization solutions have a similar impact on user experience? ;)

Microkernels and hypervisors are not the same thing.

by cbd1984 11y ago

Microkernels and hypervisors are not the same thing.

What's the difference between Xen and a microkernel? They both manage memory, do CPU scheduling, provide efficient message-passing, protect "processes" running underneath them from each other, and leave almost everything else to the "processes" running underneath them.

cbd1984 11y ago
> What's the difference between Xen and a microkernel? Xen allows full OSes to be guests and run on top of it. Microkernels only allow servers to run on top of it, and those servers have to be purpose-written and cannot meaningfully be ported. Xen doesn't provide hardware abstraction and is fully invisible (except to the extent it advertises itself); microkernels are neither. Paravirtualization (what you did before VT-x and similar) was an oddity, and blurs these lines a tiny bit, but the distinction is fairly clear otherwise.
- JoshTriplett 11y ago
  > Xen allows full OSes to be guests and run on top of it. Microkernels only allow servers to run on top of it, and those servers have to be purpose-written and cannot meaningfully be ported. L4 is an archetypal microkernel, and people often run full OSes or other ported software under it, including Linux. > Xen doesn't provide hardware abstraction and is fully invisible (except to the extent it advertises itself); microkernels are neither. Microkernels typically don't abstract any hardware other than CPU and memory; any other drivers would run under the microkernel. And Xen is only "invisible" if you run full hardware virtualization and no paravirtualized drivers. > Paravirtualization (what you did before VT-x and similar) People still use "paravirtualization" today; see the "virtio" drivers typically used with KVM.
- nickpsecurity 11y ago
  Gernot Heiser states it here: https://microkerneldude.wordpress.com/2008/04/03/microkernels-vs-hypervisors/ https://microkerneldude.wordpress.com/2008/04/03/microkernel... Their highly-efficient microkernel has been doing so well that most people using it don't know it's in their smartphones. Do most virtualization solutions have a similar impact on user experience? ;)