On 2012-05-22 07:04, Stefan Hajnoczi wrote: > On Mon, May 21, 2012 at 5:54 PM, Erik Rull <webmas...@rdsoftware.de> 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 -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux