Kai Schaetzl wrote: > S.Tindall wrote on Sun, 3 Aug 2008 21:47:06 -0400: > >> The cpuspeed changelog may be relevant: >> >> [quote] >> * Thu Mar 06 2008 Jarod Wilson <jwilson at redhat.com> >> >> - Disable freq scaling by default on AMD rev F and earlier cpus >> when running xen, due to clock instability (#435321) >> [/quote] > > Thanks, it didn't occur to me that cpuspeed may also be relevant to this. > However, I don't think it's relevant for the wrong cpu frequency reading > on the 3.2 Xen kernels (which in turn is responsible for the missing > scalability). Cpuspeed is not part of the kernel and did not change during > all my tests. See below for possible explanation. > >> I didn't look up your cpu, but I think it's a revision F. > > Hm, /proc/cpuinfo doesn't show any revision number. A bit googling tells > me that the CPUs, at least the second one, are more likely to be rev. H or > above. The older one is a 3800+ EE and the newer one is a 4850e which I > bought right after it became available. Unless rev. G and up are only quad > core CPUs at least the latter 45nm one should be rev G or up, too. But I > can't find a definitive list, shouldn't there be one on the AMD site? > Maybe this is relevant to you: http://www.centos.org/modules/newbb/viewtopic.php?topic_id=15328&forum=41 quote # Frequency scaling on AMD rev F CPUs under Xen can result in # timekeeping problems for fully virtualized guests, so we disable # it by default. if [ -d /proc/xen ] && [ "$cpu_vendor" == AuthenticAMD ] \ && [ "$cpu_family" -le 15 ]; then default_governor=performance fi /quote