[CentOS] "near native" performance with xen?

Just wondering if there was a howto or other URL that explains what is needed to achieve "near native" performance on a xen domU -- for this purpose, I am thinking about a single domU running on a physical server, in comparison to that same physical server running the same kernel but non-xenified.

For instance, using a physical partition for VBD v. using a file-backed one is one of the more obvious ones. Assigning all the VCPUs. And as much RAM as you can get away with (maybe leaving the dom0 with 512MB).

But are there others? Since I'm doing paravirtualization, I assume I don't need to turn on VT in the BIOS? What about 32-bit v. 64-bit OS, for the dom0 and for the domU? (I'll be using CentOS-5.) Anything else?

johnn