事情是这样的
我这边有一个 freescale 的开发板。要用 iperf 指令来测试他的 throughput
板子和笔电之间对连，两边都有安装 iperf。
我笔电当 server: iperf.exe -s -w 256K -i 1 -M 64
板子当 client: iperf -c 10.10.10.1 -i 1 -w 256K -M 64
MTU 为 64
结果: 效能接近官方文件的 400Mbps
[ 3] 0.0- 1.0 sec 41.8 MBytes 350 Mbits/sec
[ 3] 1.0- 2.0 sec 38.5 MBytes 323 Mbits/sec
[ 3] 2.0- 3.0 sec 42.4 MBytes 355 Mbits/sec
[ 3] 3.0- 4.0 sec 49.0 MBytes 411 Mbits/sec
[ 3] 4.0- 5.0 sec 49.4 MBytes 414 Mbits/sec
[ 3] 5.0- 6.0 sec 50.2 MBytes 422 Mbits/sec
[ 3] 6.0- 7.0 sec 50.4 MBytes 423 Mbits/sec
[ 3] 7.0- 8.0 sec 44.1 MBytes 370 Mbits/sec
[ 3] 8.0- 9.0 sec 44.5 MBytes 373 Mbits/sec
[ 3] 9.0-10.0 sec 47.1 MBytes 395 Mbits/sec
[ 3] 0.0-10.0 sec 458 MBytes 384 Mbits/sec
===========================================================================
如果我改为
iperf.exe -s -w 256K -i 1 -M 128 (笔电)
iperf -c 10.10.10.1 -i 1 -w 256K -M 128 (板子)
效能其差无比:
[ 3] 0.0- 1.0 sec 5.88 MBytes 49.3 Mbits/sec
[ 3] 1.0- 2.0 sec 6.38 MBytes 53.5 Mbits/sec
[ 3] 2.0- 3.0 sec 6.25 MBytes 52.4 Mbits/sec
[ 3] 3.0- 4.0 sec 6.38 MBytes 53.5 Mbits/sec
[ 3] 4.0- 5.0 sec 6.25 MBytes 52.4 Mbits/sec
[ 3] 5.0- 6.0 sec 6.25 MBytes 52.4 Mbits/sec
[ 3] 6.0- 7.0 sec 6.38 MBytes 53.5 Mbits/sec
[ 3] 7.0- 8.0 sec 6.25 MBytes 52.4 Mbits/sec
[ 3] 8.0- 9.0 sec 6.25 MBytes 52.4 Mbits/sec
[ 3] 9.0-10.0 sec 6.25 MBytes 52.4 Mbits/sec
[ 3] 0.0-10.0 sec 62.6 MBytes 52.5 Mbits/sec
=============================================================================
如果我将 MTU 改成 -M 256 512 1024 1280 1518 ，会慢慢趋近于400，且从 -M 128
开始，throughput 大约是两倍增加，也就是上面的数值x2，这样似乎 MTU 成了
关键，有没有高手能够为我解惑这种行为?
我单独用笔电做测试 ping wwww.google.com -f -l xxxx
去算他的 MTU，发现用 128 也是会卡卡的，最后xxxx数值为 1468 才比较顺，总而言之
上面笔电和板子对连结果，我不知道为何从 -M 64 变成 -128 效能会差那么多.....
恳请指教，谢谢。