[Xen-users] Dropped packets from DomU

["- Tethys" <tethys@xxxxxxxxx>]

I'm having performance problems when accessing certain web sites from
a DomU machine. After a bit of digging, I noticed that mtr[1] was
showing packet loss at virtually every hop from the DomU machine, but
none when run on the Dom0 machine, tracing to the same destination. It
seems that they're being dropped as they hit the vifX.Y interface in
Dom0:

springfield:~# netstat -i
Kernel Interface table
Iface       MTU Met    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR
TX-DRP TX-OVR Flg
eth0       1500   0   379875      0      0      0     2676      0
0      0 BMRU
eth1       1500   0 18152761      0      0      0 15507998     35
0      0 BMRU
lo        16436   0     1545      0      0      0     1545      0
0      0 LRU
peth0      1500   0 99293632      0      0      0 82455003      0
0      0 BORU
vif0.0     1500   0     2676      0      0      0   379875      0
0      0 BORU
vif2.0     1500   0  8167576      0      0      0 10080429      0
58      0 BORU
vif3.0     1500   0 78502165      0      0      0 91983028      0
316747      0 BORU
vif4.0     1500   0   674403      0      0      0  1192724      0
478      0 BORU
vif5.0     1500   0  4097341      0      0      0  6305952      0
884      0 BORU
xenbr0     1500   0   374121      0      0      0        0      0
0      0 BORU

vif3.0 is my busiest DomU, and as you can see, there are an abnormally
high number of dropped packets. Plotting a graph of them, they'r
ebeing dropped consistently over a long period of time, and aren't
confined to DomU startup, or any other abnormal conditions that I can
see.

Any ideas on what might be going on, and what I can do to fix it?

I'm using Xen-3.0.3 on amd64 Linux.

Thanks,

Tet

[1] http://www.bitwizard.nl/mtr/

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