On 2012-05-22 07:04, Stefan Hajnoczi wrote:
On Mon, May 21, 2012 at 5:54 PM, Erik Rull<address@hidden> wrote:
is there a summary existing that shows up the rough or actual differences
between qemu --enable-kvm and qemu-kvm? I tested both versions with the same
compile and start options, the CPU performance results are identical, only
the bootup time of my guest system with qemu-kvm seemed to be a bit faster
(not measured, it just feeled so).
Current upstream does not enable the in-kernel irqchip of KVM by
default. This should explain the difference in boot-up times. Try
"-machine accel=kvm,kernel_irqchip=on". But the default will be on, just
like in qemu-kvm, once [1] is merged.
For production KVM instances I think it still makes sense to use
qemu-kvm packages from your distro or qemu-kvm upstream source.
Jan Kiszka has reduced the delta between qemu.git and qemu-kvm.git to
the point where I think the list of differences is rather small -
maybe PCI passthrough stuff, irqfd for vhost-net (which is now also
being upstreamed into qemu.git), and a few other things I don't know
of.
Right, the list of differences is dramatically shrinking. As stated in
[2], soon only PCI passthrough and legacy interface dependencies on
qemu-kvm will be the remaining reasons to use it. If we are lucky, PCI
passthrough will also make it into upstream for QEMU 1.2, we are working
on this.
For development most patches should be against qemu.git unless they
have a dependency on qemu-kvm.git code.
Yes, unless you are working on the upstream merge itself, there is
practically no reason anymore to develop against qemu-kvm directly.
Jan
[1] http://thread.gmane.org/gmane.comp.emulators.kvm.devel/91171
[2] http://thread.gmane.org/gmane.comp.emulators.kvm.devel/91026