[CentOS-virt] Xen network problem

Christopher G. Stach II cgs at ldsys.net
Fri Oct 30 20:48:47 UTC 2009

----- "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.

Christopher G. Stach II

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