在用iperf3单线程测速时，经常遇到速率不稳，跑不满，这有可能是网卡设置导致的性能低下。
例如如果开启了中断裁决(中断调控 interrupt moderation)，那么网卡不会第一时间中断，而是有一个超时时间，这会导致性能低下，一般网卡驱动默认都是启用这个的，关闭后，测速性能大幅度提高
再就是可能开启了节能模式，会导致性能低。
我这边测试情况是，当开启了interrupt moderation后，千兆网卡 RTL8111E，很垃圾的那种淘宝16块钱买的，测速不到900Mbps，甚至有时候是 600~700Mbps。关闭interrupt moderation
Connecting to host 20.0.0.2, port 5201
[ 4] local 20.0.0.1 port 53869 connected to 20.0.0.2 port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 112 MBytes 939 Mbits/sec
[ 4] 1.00-2.00 sec 112 MBytes 939 Mbits/sec
[ 4] 2.00-3.00 sec 112 MBytes 940 Mbits/sec
[ 4] 3.00-4.00 sec 112 MBytes 941 Mbits/sec
[ 4] 4.00-5.00 sec 112 MBytes 940 Mbits/sec
[ 4] 5.00-6.00 sec 112 MBytes 938 Mbits/sec
[ 4] 6.00-7.00 sec 111 MBytes 928 Mbits/sec
[ 4] 7.00-8.00 sec 112 MBytes 940 Mbits/sec
[ 4] 8.00-9.00 sec 112 MBytes 937 Mbits/sec
[ 4] 9.00-10.00 sec 112 MBytes 941 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.00 sec 1.09 GBytes 938 Mbits/sec sender
[ 4] 0.00-10.00 sec 1.09 GBytes 938 Mbits/sec receiver千兆已经跑满了 940Mbps
另外就是手上有两块 MCX353A-FCBT，链路速度是56Gbps，单线程跑iperf3，只有4Gbps，开8线程跑也才只有21Gbps的样子。但是关闭interrupt moderation之后，单线程就能跑17Gbps
C:\iperf>iperf3.exe -c 20.20.20.2
Connecting to host 20.20.20.2, port 5201
[ 4] local 20.20.20.1 port 50686 connected to 20.20.20.2 port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 2.02 GBytes 17.3 Gbits/sec
[ 4] 1.00-2.00 sec 1.95 GBytes 16.8 Gbits/sec
[ 4] 2.00-3.00 sec 1.98 GBytes 17.0 Gbits/sec
[ 4] 3.00-4.00 sec 2.01 GBytes 17.3 Gbits/sec
[ 4] 4.00-5.00 sec 1.94 GBytes 16.6 Gbits/sec
[ 4] 5.00-6.00 sec 2.02 GBytes 17.4 Gbits/sec
[ 4] 6.00-7.00 sec 2.01 GBytes 17.3 Gbits/sec
[ 4] 7.00-8.00 sec 2.02 GBytes 17.4 Gbits/sec
[ 4] 8.00-9.00 sec 2.02 GBytes 17.3 Gbits/sec
[ 4] 9.00-10.00 sec 2.01 GBytes 17.2 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.00 sec 20.0 GBytes 17.2 Gbits/sec sender
[ 4] 0.00-10.00 sec 20.0 GBytes 17.2 Gbits/sec receiver