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Microkernels have been running the world behind the scenes for a while now, but most people don't seem to have gotten the memo and are still stuck with associat

Microkernels have been running the world behind the scenes for a while now, but most people don't seem to have gotten the memo and are still stuck with associating the Mach server as representative of u-kernels in general.

pjmlp 11y ago
Yeah, for example each Symbian phone has one. Also Mach OS X and Windows are hybrid in design and not the monolithic traditional UNIX way.
JoshTriplett 11y ago
There have been wildly successful microkernels. One of Xen's greatest successes was demonstrating that to encourage widespread adoption of a microkernel, you rebrand it as a hypervisor. More recently, some people have started running software directly under Xen without a full OS, including language runtimes, all without ever calling it a microkernel.
- cbd1984 11y ago
  Microkernels and hypervisors are not the same thing.
  - 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? ;)

pjmlp 11y ago

Yeah, for example each Symbian phone has one. Also Mach OS X and Windows are hybrid in design and not the monolithic traditional UNIX way.

JoshTriplett 11y ago

There have been wildly successful microkernels. One of Xen's greatest successes was demonstrating that to encourage widespread adoption of a microkernel, you rebrand it as a hypervisor. More recently, some people have started running software directly under Xen without a full OS, including language runtimes, all without ever calling it a microkernel.

cbd1984 11y ago
Microkernels and hypervisors are not the same thing.
- 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? ;)