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.
While Ubuntu 14.04 is still months away from its debut, I decided to run some early virtualization benchmarks since this release will be very important for such use-cases due to its Long-Term Support focus that makes it prime for usage in data-centers, etc. All the testing today was from an Intel Core i7 4960X Ivy Bridge Extreme system running Ubuntu 14.04 with the Linux 3.12 kernel, Unity 7.1.2, GCC 4.8.2, and an EXT4 file-system. The same packages were used both on the base operating system and for the two VMs.
The Linux-KVM packages in conjunction with virt-manager were obtained from the Ubuntu "Trusty Tahr" archive in December while the VirtualBox virtualization software was obtained from the Oracle web-site at the same time with their latest version being 4.3.4.
A wide range of open-source Linux benchmarks were run on the system "bare metal" and then when under the KVM and VirtualBox environments. During the VM testing, each VM was allowed access to 6GB of the system's 8GB of RAM. Additionally, each VM had a 88GB virtualized disk from the Seagate 1TB SATA 3.0 SSHD. The VMs were able to access all 12 threads of the i7-4960X: six physical cores plus Hyper Threading.
All of this Linux virtualization benchmarking was done via the open-source Phoronix Test Suite software with OpenBenchmarking.org. When the official release of Ubuntu 14.04 LTS nears in April, there will be more benchmarks on Phoronix along with other hypervisors like Xen.