As I found out recently, memory hotplug is disabled in f17 and f18 kernels (but not in f16). Can anybody please recall the reason for that? The commit doing that is not particularly enlightening: commit 2ee9f1482920f6d831eb6d70458bd0988394982b Author: Dave Jones <davej(a)redhat.com&gt; Date: Fri Jan 13 17:33:51 2012 -0500 Disable memory hotplug on x86-64 I'd like to propose to re-enable it but I'm trying to figure out why it was disabled in the first place. Thanks, Roman.