This kernel works as expected with one exception. The exception has been a nagging problem, but I have not reported it because 1) we are using a research OS in DomU and 2) we are not clear if the problem is in our code, Linux or Xen. But, here are the symptoms:
Occasionally (this seems to correlate to network activity between Dom0 and DomU), the system becomes unresponsive. I am running the Michael Young kernel at runlevel 3 within Dom0 (very little memory used by applications). Our OS runs in DomU and is constrained to 128MB of memory. When the system is unresponsive, typing a character into a Dom0 console take 2-5 seconds to appear on the screen. Likewise, other activity is extremely slow. As I mentioned, we have not been able to isolate where the problem is. Running, for example, an OpenWrt Linux build in DomU does not have this problem.
I have seen something similar, though I don't know where the fault lies either.
That is somewhat good to hear. I have today solved this problem by running "xm vcpu-set Domain-0 1." By default, Xen assigned Dom0 all of my cores (two). Reducing this to one solves the problem for me. I am working on a better write up that I'll send to fedora-xen and possibly the upstream Xen mailing list. I have not decided if this is a bug and am having some discussions locally that may help me formulate a better inquiry.