我使用 iperf3 版本 3.0.11 测量两台虚拟机之间的 UDP 流吞吐量。虚拟机通过 OpenStack 部署。在物理主机中，一台位于布拉迪斯拉发，另一台位于卢布尔雅那。
网络方面，每个物理主机均配备 1Gbit NIC，虚拟机通过 pci_passthrough 连接，从而可以完全访问 NIC。
iperf 服务器显示以下输出：
root@lju:/home/gts# iperf3 -s -V
iperf 3.0.11
Linux lju 3.13.0-37-generic #64-Ubuntu SMP Mon Sep 22 21:28:38 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Time: Fri, 15 Jan 2016 12:16:20 GMT
Accepted connection from 172.16.0.78, port 40774
Cookie: bra.1452860180.557437.6c142f196ae2a4
[ 5] local 172.16.0.80 port 5201 connected to 172.16.0.78 port 57847
Starting Test: protocol: UDP, 1 streams, 8192 byte blocks, omitting 0 seconds, 10 second test
iperf3: OUT OF ORDER - incoming packet = 70 and received packet = 97 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 71 and received packet = 97 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 72 and received packet = 99 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 14 and received packet = 123 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 15 and received packet = 125 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 78 and received packet = 137 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 79 and received packet = 137 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 80 and received packet = 139 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 82 and received packet = 172 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 83 and received packet = 173 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 65 and received packet = 175 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 66 and received packet = 176 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 67 and received packet = 177 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 84 and received packet = 177 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 86 and received packet = 198 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 18 and received packet = 203 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 19 and received packet = 205 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 22 and received packet = 270 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 23 and received packet = 273 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 38 and received packet = 349 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 39 and received packet = 350 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 40 and received packet = 350 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 41 and received packet = 350 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 47 and received packet = 412 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 48 and received packet = 412 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 49 and received packet = 412 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 50 and received packet = 414 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 55 and received packet = 490 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 56 and received packet = 490 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 57 and received packet = 490 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 60 and received packet = 541 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 61 and received packet = 541 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 62 and received packet = 541 AND SP = 5
iperf3: OUT OF ORDER - incoming packet = 63 and received packet = 541 AND SP = 5
[ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
[ 5] 0.00-1.00 sec 105 MBytes 880 Mbits/sec 0.086 ms 141304/154697 (91%)
[ 5] 1.00-2.00 sec 114 MBytes 956 Mbits/sec 0.142 ms 164060/178642 (92%)
[ 5] 2.00-3.00 sec 114 MBytes 956 Mbits/sec 0.083 ms 165925/180507 (92%)
[ 5] 3.00-4.00 sec 114 MBytes 956 Mbits/sec 0.090 ms 164512/179094 (92%)
[ 5] 4.00-5.00 sec 114 MBytes 956 Mbits/sec 0.107 ms 166389/180972 (92%)
[ 5] 5.00-6.00 sec 114 MBytes 956 Mbits/sec 0.079 ms 159459/174041 (92%)
[ 5] 6.00-7.00 sec 114 MBytes 956 Mbits/sec 0.084 ms 168138/182720 (92%)
[ 5] 7.00-8.00 sec 114 MBytes 956 Mbits/sec 0.098 ms 169098/183680 (92%)
[ 5] 8.00-9.00 sec 114 MBytes 956 Mbits/sec 0.101 ms 166463/181046 (92%)
[ 5] 9.00-10.00 sec 114 MBytes 956 Mbits/sec 0.097 ms 168547/183128 (92%)
[ 5] 10.00-10.15 sec 16.6 MBytes 952 Mbits/sec 0.076 ms 23353/25473 (92%)
- - - - - - - - - - - - - - - - - - - - - - - - -
Test Complete. Summary Results:
[ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
[ 5] 0.00-10.15 sec 13.8 GBytes 11.7 Gbits/sec 0.076 ms 1657248/1804000 (92%)
[SUM] 0.0-10.1 sec 1657248 datagrams received out-of-order
CPU Utilization: local/receiver 11.9% (1.3%u/10.6%s), remote/sender 44.5% (4.0%u/40.5%s)
iperf 3.0.11
Linux lju 3.13.0-37-generic #64-Ubuntu SMP Mon Sep 22 21:28:38 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
客户端显示以下输出：
root@bra:/home/gts# iperf3 -u -c 172.16.0.80 -b 0 -V
iperf 3.0.11
Linux bra 3.13.0-37-generic #64-Ubuntu SMP Mon Sep 22 21:28:38 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
Time: Fri, 15 Jan 2016 12:16:20 GMT
Connecting to host 172.16.0.80, port 5201
Cookie: bra.1452860180.557437.6c142f196ae2a4
[ 4] local 172.16.0.78 port 57847 connected to 172.16.0.80 port 5201
Starting Test: protocol: UDP, 1 streams, 8192 byte blocks, omitting 0 seconds, 10 second test
[ ID] Interval Transfer Bandwidth Total Datagrams
[ 4] 0.00-1.00 sec 1.38 GBytes 11.8 Gbits/sec 180260
[ 4] 1.00-2.00 sec 1.37 GBytes 11.7 Gbits/sec 179180
[ 4] 2.00-3.00 sec 1.37 GBytes 11.8 Gbits/sec 179950
[ 4] 3.00-4.00 sec 1.37 GBytes 11.8 Gbits/sec 180030
[ 4] 4.00-5.00 sec 1.37 GBytes 11.7 Gbits/sec 179240
[ 4] 5.00-6.00 sec 1.33 GBytes 11.5 Gbits/sec 174840
[ 4] 6.00-7.00 sec 1.40 GBytes 12.0 Gbits/sec 183040
[ 4] 7.00-8.00 sec 1.40 GBytes 12.1 Gbits/sec 183970
[ 4] 8.00-9.00 sec 1.38 GBytes 11.9 Gbits/sec 180830
[ 4] 9.00-10.00 sec 1.39 GBytes 12.0 Gbits/sec 182660
- - - - - - - - - - - - - - - - - - - - - - - - -
Test Complete. Summary Results:
[ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
[ 4] 0.00-10.00 sec 13.8 GBytes 11.8 Gbits/sec 0.076 ms 1657248/1804000 (92%)
[ 4] Sent 1804000 datagrams
CPU Utilization: local/sender 44.5% (4.0%u/40.5%s), remote/receiver 11.9% (1.3%u/10.6%s)
第一个不寻常的地方是开始测量时传入服务器的无序数据包数量。此外，摘要显示带宽为 11.7Gbit/s，而 NIC 只能达到 1Gbit/s。中间结果显示服务器端有更多潜力，但在客户端显示相同的异常数字。因此似乎还丢失了 92% 的数据报。
有谁能指出为什么 iperf3 会出现这种行为？