Hi,
I see very high network latency between domUs running on the same
dom0.
dom0 is SLES 11 SP1 + xen 4.0.2, domUs are SLES 10 SP1 or SLES 10 SP4.
Problem does not occur between dom0 and domUs, or between domUs running
on different servers.
There's also no problem when dom0 is running with SLES 10 SP4.

ping between 2 domUs:

# ping -c10 -s1000 10.1.74.30
PING 10.1.74.30 (10.1.74.30) 1000(1028) bytes of data.
1008 bytes from 10.1.74.30: icmp_seq=1 ttl=64 time=7.82 ms
1008 bytes from 10.1.74.30: icmp_seq=2 ttl=64 time=1.92 ms
1008 bytes from 10.1.74.30: icmp_seq=3 ttl=64 time=5.34 ms
1008 bytes from 10.1.74.30: icmp_seq=4 ttl=64 time=5.32 ms
1008 bytes from 10.1.74.30: icmp_seq=5 ttl=64 time=5.33 ms
1008 bytes from 10.1.74.30: icmp_seq=6 ttl=64 time=1.38 ms
1008 bytes from 10.1.74.30: icmp_seq=7 ttl=64 time=0.143 ms
1008 bytes from 10.1.74.30: icmp_seq=8 ttl=64 time=1.39 ms
1008 bytes from 10.1.74.30: icmp_seq=9 ttl=64 time=1.40 ms
1008 bytes from 10.1.74.30: icmp_seq=10 ttl=64 time=1.40 ms

--- 10.1.74.30 ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 9034ms
rtt min/avg/max/mdev = 0.143/3.150/7.824/2.429 ms


ping between domU and dom0:

# ping -c10 -s1000 10.1.74.84
PING 10.1.74.84 (10.1.74.84) 1000(1028) bytes of data.
1008 bytes from 10.1.74.84: icmp_seq=1 ttl=64 time=0.075 ms
1008 bytes from 10.1.74.84: icmp_seq=2 ttl=64 time=0.081 ms
1008 bytes from 10.1.74.84: icmp_seq=3 ttl=64 time=0.079 ms
1008 bytes from 10.1.74.84: icmp_seq=4 ttl=64 time=0.078 ms
1008 bytes from 10.1.74.84: icmp_seq=5 ttl=64 time=0.092 ms
1008 bytes from 10.1.74.84: icmp_seq=6 ttl=64 time=0.090 ms
1008 bytes from 10.1.74.84: icmp_seq=7 ttl=64 time=0.088 ms
1008 bytes from 10.1.74.84: icmp_seq=8 ttl=64 time=0.076 ms
1008 bytes from 10.1.74.84: icmp_seq=9 ttl=64 time=0.077 ms
1008 bytes from 10.1.74.84: icmp_seq=10 ttl=64 time=0.072 ms



The latency also seems to depend on the package size:

# ping -c10 -s96 10.1.74.30
PING 10.1.74.30 (10.1.74.30) 96(124) bytes of data.
104 bytes from 10.1.74.30: icmp_seq=1 ttl=64 time=0.101 ms
104 bytes from 10.1.74.30: icmp_seq=2 ttl=64 time=0.133 ms
104 bytes from 10.1.74.30: icmp_seq=3 ttl=64 time=0.138 ms
104 bytes from 10.1.74.30: icmp_seq=4 ttl=64 time=0.132 ms
104 bytes from 10.1.74.30: icmp_seq=5 ttl=64 time=0.131 ms
104 bytes from 10.1.74.30: icmp_seq=6 ttl=64 time=0.140 ms
104 bytes from 10.1.74.30: icmp_seq=7 ttl=64 time=0.145 ms
104 bytes from 10.1.74.30: icmp_seq=8 ttl=64 time=0.146 ms
104 bytes from 10.1.74.30: icmp_seq=9 ttl=64 time=0.147 ms
104 bytes from 10.1.74.30: icmp_seq=10 ttl=64 time=0.145 ms

--- 10.1.74.30 ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 8998ms
rtt min/avg/max/mdev = 0.101/0.135/0.147/0.019 ms


# ping -c10 -s97 10.1.74.30
PING 10.1.74.30 (10.1.74.30) 97(125) bytes of data.
105 bytes from 10.1.74.30: icmp_seq=1 ttl=64 time=7.79 ms
105 bytes from 10.1.74.30: icmp_seq=2 ttl=64 time=5.31 ms
105 bytes from 10.1.74.30: icmp_seq=3 ttl=64 time=1.34 ms
105 bytes from 10.1.74.30: icmp_seq=4 ttl=64 time=5.34 ms
105 bytes from 10.1.74.30: icmp_seq=5 ttl=64 time=5.33 ms
105 bytes from 10.1.74.30: icmp_seq=6 ttl=64 time=5.34 ms
105 bytes from 10.1.74.30: icmp_seq=7 ttl=64 time=2.95 ms
105 bytes from 10.1.74.30: icmp_seq=8 ttl=64 time=1.34 ms
105 bytes from 10.1.74.30: icmp_seq=9 ttl=64 time=5.34 ms
105 bytes from 10.1.74.30: icmp_seq=10 ttl=64 time=1.28 ms

--- 10.1.74.30 ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 9034ms
rtt min/avg/max/mdev = 1.288/4.141/7.791/2.136 ms


Is this a bug? Or a (mis)configuration issue? Did anyone else
experienced the same problem?


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