Not trying to take this off-topic, I think it is relevant. Christopher: When I booted up with dom0-cpus 1, Windows 2008 could not "find" its second cpu. However, once up, I can "xm or virt-manager" it down to 1 cpu on cup 0 and everything is fine. Is this a unique issue or do you have a tweak or hack to force smp with dom0 on one cpu? Christopher G. Stach II wrote: > ----- "Ken Bass" <kbass at kenbass.com> wrote: > >> It sounds like the domU is impacting the overall Xen performance. Is >> there anything I can do to tune this? It kinda defeats the whole Xen >> virtualization concept if a single CPU messes up the network. I am >> going >> to try to add a 'nice' to the crontab for the 4am job, but still, >> something doesn't seem correct. Any suggestions would be much >> appreciated. Thanks! > > In high I/O environments or ones with a lot of unpredictable guests, it's a good idea to pin dom0's CPU(s) to physical cores and exclude those cores from the guests. I find that dom0 usually only needs one CPU (pinned to one core) in almost every environment. For example, on an 8 core box, dom0 gets CPU 0 (dom0-cpus 1) and all of the guests use 1-7. The occasional firewall/load balancer/something else high-I/O guest would also gets its own core, also excluded from use by the other guests, but you should avoid that until you find that it's necessary. >