[9fans] qemu, kvm, xen

["ron minnich" <rminnich@gmail.com>]

I decided to try out the new kvm hypervisor. It is built into the
linux 2.6.20 kernel, and is far simpler to run and setup than xen. In
fact, it is quite nice: if you know how to run qemu, you know how to
run kvm: they have modified qemu so that you use the same command
line, tools, etc. If kvm is not present, qemu runs as always; if kvm
is present, the modified qemu starts up kvm with the target system as
a guest.

First problem I hit with kvm was an emulation problem, so you do need
to modify your plan9.ini to set
*norealmode=1
The far jump in again16bit causes kvm to crash and burn (look for the
"EA", etc. at the end of again16bit).

Well, never mind that, the numbers will show it does not (yet) really
matter. The test system here is a Thinkpad T60 with Core Duo (NOT Core
2). 1 GB memory. It's fast.

The plan 9 systems I booted were, for qemu and kvm, a terminal; and
for xen, a cpu server. I.e. the xen Plan 9 system is doing a bit more
work, as it starts up more servers, but does not start up rio.

boot:
qemu, 60 seconds
kvm, 100 seconds (yes, indeed, kvm did indeed boot more slowly than
plain old qemu)
xen, 6 seconds (it's nice)

build a pccpuf kernel:
qemu, 100 seconds
kvm, 80 seconds
xen, 12 seconds

So, the choice for speed is still xen. THX will remain xen-based for now.

thanks

ron