[Xen-users] Question regarding dropped packets

[Jeff Fisher <jeff@xxxxxx>]

Hi,

I've got a machine that's hosting a number of virtual machines (58 + the 
dom0) and I'm having some weird issues with packet loss and high latency 
that happens when ksoftirqd spikes in CPU usage.
The machine itself is CentOS 5 x86_64 running the stock Xen packages 
(3.1.2). It's a dual quad-core w/ hyperthreading, 48 gigs of ram, and 
using Adaptec hardware raid w/ SAS drives.
Almost every 2 minutes, I'll lose between 2 and 4 packets (while running 
ping) to the domUs and see a couple of packets with very high latency. I 
see the packets coming in on eth0, the bridge, and sometimes on the vif 
device but the domU itself doesn't see these packets.
Has anyone seen this type of behaviour before? I've tried all the 
following with little success:
    - increasing txqueuelen
    - changing the smp_affinity settings for our network devces
    - dedicating the first 2 cores to dom0 and letting the domUs use 
the remaining 14.
If anyone has any ideas or additional things I can try, I would be most 
grateful :)
Thanks,
Jeff

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