[arch-general] qemu-kvm vs. qemu upstream

C Anthony Risinger anthony at extof.me
Thu Feb 24 12:43:33 EST 2011

On Thu, Feb 24, 2011 at 11:23 AM, Jelle van der Waa <jelle at vdwaa.nl> wrote:
> On Thu, 2011-02-24 at 11:07 -0600, C Anthony Risinger wrote:
>> hmm, soo qemu doesn't actually use the VT extensions?  wtf is the
>> point then?
> QEMU is an emulator -> so for ARM for example
>> this is what i don't understand; if qemu supports KVM via
>> the `-enable-kvm` switch why does it suck so much -- it seems just as
>> slow to me as no KVM support at all.
> Here it's not, are you using qemu-kvm or some selfcompiled version?

qemu-kvm is always fast.  qemu is never fast -- libvirt uses
`-enable-kvm` when i tell it to, ie. for either package.  i've tried
recompiling the regular `qemu` package with explicit KVM support, and
the speed is still absolutely abysmal.

>> I have a server that runs
>> several KVM/libvirt instances (windows being one of them purely for
>> ... i dont even know) so i'm pretty familiar with it all, but i'm just
>> trying to get solid info why there is such a huge performance gap when
>> the both "use KVM".  i thought KVM itself did all the VT handling.
> Another tip for kvm usage is installing your OS on virtio [1]

already do :-) i use all the virtio drivers -- when i say perf is bad
i mean it's like KVM isnt even working.  i haven't `lsof` yet to make
sure qemu (not qemu-kvm!!) is actually opening the /dev/kvm device.

i read thru the packages of both.  i tried symlinking
`/usr/bin/qemu-kvm -> qemu-system-x86_64` (this is what qemu-kvm
package does) ... no difference.

so my real question is, is anyone using the upstream package `qemu`,
with KVM, and getting proper results?  are good results expected?
what am i missing here.

C Anthony

More information about the arch-general mailing list