[Xen-users] Xen/Gentoo/NFS=really slow & nfs timeout

[Adam Carheden <adam.carheden@xxxxxxxxx>]

I've got Gentoo Linux running as both DOM0 and DOMU on a few Xen
boxes, but the NFS client with this configuration is really slow
because it keeps timeing out. The following is true:

Gentoo (No Xen) = FAST
SuSE (No Xen) = FAST
Gentoo (DOM0) = SLOW
Gentoo (DOMU) = SLOW (Gentoo is DOM0)
SuSE (DOMU) = FAST (Gentoo is DOM0)

I've tried all configurations with both a Gentoo and SuSE NFS server
(No XEN) with the same results. I can speed things up by setting rsize
and wsize to 16384, but it's still much slower than SuSE DOMU or
non-xen (Gentoo or SuSE).

Gentoo (No Xen): 231.7 MB/s (95 MB file)
SuSE DOMU (Gentoo DOM0): 339 MB/s (95 MB file)
Gentoo DOM0: .035 MB/s (1MB file, rsize/wsize=16384)

What's more, I get slower speeds on SuSE DOMU when Gentoo DOM0 is
accessing NFS, so I'm guessing it's generating network traffic to slow
stuff down.

And the answers to the obvious questions...
- I can duplicate the problem on two differen Gentoo/Xen boxes (one is
pentium$, the other is AMD64).
- Other other network operations work about the same on various
configurations, though SCP only gives me about 10MB/s on SuSE or
Gentoo uner Xen while it gives me about 22MB/s on Gentoo without Xen.
- I'm using bridging to share the network connection.
- I get "nfs: server <my-nfs-server> not responding, timed out" in
dmesg in Gentoo under Xen, but not on SuSE/Xen or Gentoo/No Xen.

Any ideas why nfs is timeing out under xen and/or how to fix it?

Thanks
--
Adam Carheden

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