While benchmarks are a very difficult exercixe and as such the results must be considered carefully, they are still interesting to compare the respective performance between the solutions for different workloads.

This page will try to keep an eye on the relative performances of Xen and KVM. Until virtio is not part of the mainstream linux kernel, the tests will concentrate on performance on HVM systems, so the guest system will be an "unmodified OS".

= 13 Feb 2008 =

Tests on an AMD based system with an AMD X2 4400+ and 4GB RAM. The test VM for both Xen and KVM is the same image: an unmodified Debian Lenny kernel amd64 w/512 MB RAM

The test is still the "make clean && make allnoconfig && time make" of a 2.6.24 kernel

 * Host is an opensource Xen-3.2 (from xen.org) with a Dom0 running a kernel-2.6.18-xen, Dom0 userspace is a 64bits Ubuntu Gutsy

|| '''run''' || '''1''' || '''2''' || '''3''' ||
|| '''real''' || 2m28.261s || 2m17.069s || 2m16.441s ||
|| '''user'''  || 1m27.213s || 1m27.137s || 1m27.189s ||
|| '''sys''' || 0m51.111s || 0m49.231s || 0m48.751s ||

 * Host in Ubuntu gutsy amd64 kernel 2.6.22-14-generic

|| '''run''' || '''1''' || '''2''' || '''3''' ||
|| '''real''' || 2m30.767s ||  2m28.551s || 2m28.852s ||
|| '''user'''  || 1m35.882s || 1m35.866s || 1m36.410s ||
|| '''sys''' || 0m52.179s ||  0m53.283s || 0m52.239s ||

= 12 Feb 2008 =

Thanks for Dan Berrange who pointed me on xen.org instead of xensource.com as a source of download for the latest Xen.

The tests consists of the compilation of a linux kernel 2.6.24 with allnoconfig (make allnoconfig && time make). The host hardware is a 1.86Ghz Intel Core2duo.

== unmodified VM: 64bits Debian Etch ==

The first two tests run the same Virtual Machine with an unmodified 64bits Debian Etch.

 * Host is an opensource Xen-3.2 (from xen.org) with a Dom0 running a kernel-2.6.18-xen, Dom0 userspace is a 64bits Debian Lenny

|| '''run''' || '''1''' || '''2''' || '''3''' ||
|| '''real''' || 2m26 || 2m19 || 2m20 ||
|| '''user''' ||1m21 || 1m22 || 1m21 ||
|| '''sys''' || 1m02 || 0m58 || 1m00 ||

 * Host is a 64bits Debian Lenny with a 2.6.24 kernel and KVM-60

|| '''run''' || '''1''' || '''2''' || '''3''' ||
|| '''real''' || 2m11 || 2m07 || 2m07 ||
|| '''user''' || 1m26 || 1m26 || 1m26 ||
|| '''sys''' || 0m45 || 0m40 || 0m40 ||

== paravirtualised VM: 64bits Debian Etch with xenified kernel ==

The following test runs on the same hardware than the previous one. The kernel used in the DomU is the same as in Dom0:

 * Host is an opensource Xen 3.2 (from xen.org) with a Dom0 running a kernel-2.6.18-xen, Dom0 userspace is a 64bits Debian Lenny

|| '''run''' || '''1''' || '''2''' || '''3''' ||
|| '''real''' || 1m34 || 1m33 || 1m33 ||
|| '''user''' || 1m17 || 1m18 || 1m18 ||
|| '''sys''' || 0m15 || 0m15 || 0m15 ||

= 11 Feb 2008 =

For the following 2 tests, the system is an Intel core 2 duo 2.4Ghz w/ 2GB RAM running the latest available versions:

 * for Xen: opensource Xen 3.1.0 (from xen.xensource.com) + Dom0 kernel based on kernel.org 2.6.18
 * for KVM: kvm-60 on a 2.6.23

The guest used in both case is the exact same VM (non-paravirtualised 64 bit Debian etch with 256 MB RAM).

== Guest system boot-up time ==

|| '''plateform'''||'''time in seconds'''||
|| '''Xen''' || 23 ||
|| '''KVM''' || 20 ||

== Kernel compilation benchmark ==

Time to compile a  2.6.24 allnoconfig

 * first try - cold cache

|| '''plateform'''||'''real time'''||'''user time'''||'''sys time'''||
|| '''Xen''' || 1m53 || 1m06 || 0m43 ||
|| '''KVM''' || 1m03 || 1m06 || 0m33 ||

 * second try - w/ cache

|| '''plateform'''||'''real time'''||'''user time'''||'''sys time'''||
|| '''Xen''' || 1m52 || 1m07 || 0m43 ||
|| '''KVM''' || 0m56 || 1m07 || 0m31 ||