Intel added a feature to their processors some years ago (2006) called VT-X (Vanderpool) that allowed for near native execution of virtual machines. Without this, virtualisation is slow. With it, you really cannot tell the difference.
(Want to know both more and less @ the same time? watch the movie!)
Sadly, most BIOS writers have some severe hate on for this technology, and it is disabled by default. If you are playing with virtualisation, you need this on. Reboot and check in your BIOS. I'll wait.
OK, back? well, what if you were a wee bit away from the keyboard and wanted this on? This was the situation I just faced, were a dell server in our lab in Bangalore was recalcitrantly emulating all instructions (TCG mode) rather than running them native (KVM mode).
It turns out Dell has made a slightly arcane but not too complex method to 'fix' this. You can either use their IPMI (remote console/remote serial), or you can use these instructions:
# wget -q -O – http://linux.dell.com/repo/hardware/bootstrap.cgi | bash # yum install syscfg # /opt/dell/toolkit/bin/syscfg --virtualization=enable
and then a quick reboot. And now your VM's run @ native speed rather than glacial speed.