Phoronix: VirtualBox Is Still Running Slower Than QEMU-KVM
Recently I ran some benchmarks looking at the performance of the Ubuntu 14.04 LTS development code and from there I tested the bare metal system, the same system with a Linux KVM instance of Ubuntu 14.04 itself, and then afterwards another VM with the same settings and software but using Oracle VM VirtualBox. Here are those early Ubuntu 14.04 Linux virtualization benchmarks.
I used virtualbox in the past until i starrted to build my kernels and find that it didnt work with the latest ones (around 3.8 or something).
So i replaced it with qemu (i use libvirt+virtmanager for ease of management), converted my hdd images to raw then the VMs. This libvirt thingie is mightily handy, you can supervize your VMs that run in separated processes independent from X + you can connect to the supervizor via ssh, tunnel spice connections to it (inluding the attaching of REMOTE usb devices), a feature that virtualbox lacked.
Linux guests are like fish in the water with qemu/kvm since the virtio drivers are built in the kernel, absolutely no intervention required.
For Windows guests you just have to go to http://www.spice-space.org/download.html , download+install the windows guest tools, reboot and you will have all virtio+qxl drivers installed along with the vdagent (that passes through clipboard, seamless mouse and USB redirection).
Note - for optimal operation, you have to use the virtio devices (virtual network card and virtual hdd controller), qxl virtual video device, spice connection and set up a spice channel for USB redirection.
All in all using this setup (=qemo/kvm + libvirt/virt-manager) greatly reduced management related issues and introduced previously lacking full remote control features. What was lost is some 3d support in Windows guests (doesnt really bother me since i dont need it).
Performance wise qemu/kvm seems to perform just like vbox, never bothered with specifics as long as it doesnt hog my computer needlessly when idle.
Originally Posted by Calinou
You can in some cases (I think, Intel only, on AMD, the IGP is disabled if a dedicated card is plugged).
I have an AMD integrated (A8-5500/A8-6500) and i played around a bit with vga pass through and i could attach the dedicated card (i had some old cards laying around) to the VM, install the driver but it couldnt initialize in the guest. I didnt pursue this farther and maybe the issue was that at that time i used fglrx (someone said that fglrx doesnt play nice here). BTW you have to use a mobo that supports iommu for this AFAIK which usually is available in certain higher(ish) end chipsets and mobos.