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i have a KVM linux based virtual machines, as the network performance of the host is running perfect with 1GB/s(in internal network) and using iperf tools it show that the network is running perfect in host , but guests is slow network performance as iperf result was so strange as it is not 100MB/s and is not 1GB/s its range between 350 and 500MB/s maximum, and this is result of using iperf command (iperf -c servername -P 15)

[ ID] Interval       Transfer     Bandwidth
[ 17]  0.0-10.0 sec  68.6 MBytes  57.5 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0-10.0 sec  18.6 MBytes  15.5 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  5]  0.0-10.0 sec  61.9 MBytes  51.9 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 11]  0.0-10.0 sec  16.0 MBytes  13.4 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 10]  0.0-10.0 sec  24.3 MBytes  20.4 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 15]  0.0-10.0 sec  20.2 MBytes  16.9 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 12]  0.0-10.0 sec  30.2 MBytes  25.3 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  36.2 MBytes  30.3 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  8]  0.0-10.0 sec  23.6 MBytes  19.8 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  9]  0.0-10.0 sec  24.2 MBytes  20.3 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 14]  0.0-10.0 sec  31.0 MBytes  25.9 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  7]  0.0-10.0 sec  16.6 MBytes  13.9 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  6]  0.0-10.0 sec  18.8 MBytes  15.7 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 13]  0.0-10.0 sec  13.3 MBytes  11.2 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 16]  0.0-10.0 sec  29.6 MBytes  24.8 Mbits/sec
[SUM]  0.0-10.0 sec    433 MBytes    363 Mbits/sec

i tested different network models and the best result was with the virtio model any one please can help to get the full performance of network and be 1 GB/s

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1 Answer

try and stop iptables and run your test again, I have seen a miss configured "mingle table" can have similar effects on your kvm guests.

/etc/init.d/iptables off
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i did and flushed the iptables in the host , but the result is the same speed of guest machine with the same range between 350 MB/s & 500 MB/s –  Moaz Refat Feb 11 '13 at 14:49
    
what type of network card are you using? Virtio? is not, please try with Virtio Nics –  user1007727 Feb 11 '13 at 20:08
    
physical network card of the Host is Ethernet controller: Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet (rev 20) and i did a test with a guest to use the virtio network card –  Moaz Refat Feb 12 '13 at 10:13
    
i noted that when i moved the virtual machine to another host (redhat 5.3 64 bit) it work with 1 GB/s but i don't know why this happen with current hos which is ubuntu 10.04 64 bit –  Moaz Refat Feb 18 '13 at 12:35
    
Virtio drives version are the same on RHEL? –  user1007727 Feb 20 '13 at 16:19
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