iMac (Retina 5K, 27-inch, 2020) 插 2.5G USB 网卡速度上不去

This topic created in 1437 days ago, the information mentioned may be changed or developed.

刚把相关设备升级到了 2.5G ，目前其他一切正常，唯独一台 iMac 下载速率不正常。

下载速率：

 iperf3 -c 192.168.11.11 Connecting to host 192.168.11.11, port 5201 [ 5] local 192.168.11.129 port 50249 connected to 192.168.11.11 port 5201 [ ID] Interval Transfer Bitrate [ 5] 0.00-1.00 sec 131 MBytes 1.10 Gbits/sec [ 5] 1.00-2.00 sec 131 MBytes 1.10 Gbits/sec [ 5] 2.00-3.00 sec 131 MBytes 1.10 Gbits/sec [ 5] 3.00-4.00 sec 131 MBytes 1.10 Gbits/sec [ 5] 4.00-5.00 sec 134 MBytes 1.12 Gbits/sec [ 5] 5.00-6.00 sec 129 MBytes 1.08 Gbits/sec [ 5] 6.00-7.00 sec 130 MBytes 1.09 Gbits/sec [ 5] 7.00-8.00 sec 129 MBytes 1.09 Gbits/sec [ 5] 8.00-9.00 sec 133 MBytes 1.12 Gbits/sec [ 5] 9.00-10.00 sec 128 MBytes 1.08 Gbits/sec - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate [ 5] 0.00-10.00 sec 1.28 GBytes 1.10 Gbits/sec sender [ 5] 0.00-10.00 sec 1.28 GBytes 1.10 Gbits/sec receiver

上传速率：

 iperf3 -c 192.168.11.11 -R Connecting to host 192.168.11.11, port 5201 Reverse mode, remote host 192.168.11.11 is sending [ 5] local 192.168.11.129 port 51966 connected to 192.168.11.11 port 5201 [ ID] Interval Transfer Bitrate [ 5] 0.00-1.00 sec 279 MBytes 2.34 Gbits/sec [ 5] 1.00-2.00 sec 280 MBytes 2.35 Gbits/sec [ 5] 2.00-3.00 sec 280 MBytes 2.35 Gbits/sec [ 5] 3.00-4.00 sec 280 MBytes 2.35 Gbits/sec [ 5] 4.00-5.00 sec 281 MBytes 2.35 Gbits/sec [ 5] 5.00-6.00 sec 280 MBytes 2.35 Gbits/sec [ 5] 6.00-7.00 sec 281 MBytes 2.35 Gbits/sec [ 5] 7.00-8.00 sec 280 MBytes 2.35 Gbits/sec [ 5] 8.00-9.00 sec 280 MBytes 2.35 Gbits/sec [ 5] 9.00-10.00 sec 280 MBytes 2.35 Gbits/sec - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Ret [ 5] 0.00-10.00 sec 2.74 GBytes 2.35 Gbits/sec 0 sender [ 5] 0.00-10.00 sec 2.74 GBytes 2.35 Gbits/sec receiver

已经排查的点：

同一个端口同一个 USB 网卡，一台 Linux 是正常的，一台 M1 Mac Mini 是正常的。说明网线和 USB 网卡没问题，交换机没问题，iperf server 也没问题
手动下载 RTL8156 驱动并安装，并没有任何区别
关闭 iMac 上的 Surge 、iStat 等可能影响性能的软件，然而并没有用

请教一下大神，还有哪里可能有问题？我还可以怎么排查？

2.5G USB 网卡地址： https://item.jd.com/100023635636.html
驱动地址： https://www.realtek.com/en/component/zoo/category/network-interface-controllers-10-100-1000m-gigabit-ethernet-usb-3-0-software

Supplement 1 Jun 9, 2022

已经在恢复模式测试过了：

提升了不少，但是依然不稳定。
```
Connecting to host 192.168.11.11, port 5201
[ 4] local 192.168.11.129 port 49224 connected to 192.168.11.11 port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 225 MBytes 1.89 Gbits/sec
[ 4] 1.00-2.00 sec 201 MBytes 1.69 Gbits/sec
[ 4] 2.00-3.00 sec 7.83 MBytes 65.4 Mbits/sec
[ 4] 3.00-4.00 sec 75.1 MBytes 632 Mbits/sec
[ 4] 4.00-5.00 sec 281 MBytes 2.36 Gbits/sec
[ 4] 5.00-6.00 sec 280 MBytes 2.35 Gbits/sec
[ 4] 6.00-7.00 sec 277 MBytes 2.33 Gbits/sec
[ 4] 7.00-8.00 sec 253 MBytes 2.12 Gbits/sec
[ 4] 8.00-9.00 sec 240 MBytes 2.02 Gbits/sec
[ 4] 9.00-10.00 sec 198 MBytes 1.66 Gbits/sec

```

另外，我平时用内置千兆网口测速也会不稳定。
```
Connecting to host 192.168.11.11, port 5201
[ 4] local 192.168.11.145 port 49867 connected to 192.168.11.11 port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 113 MBytes 946 Mbits/sec
[ 4] 1.00-2.00 sec 108 MBytes 905 Mbits/sec
[ 4] 2.00-3.00 sec 111 MBytes 930 Mbits/sec
[ 4] 3.00-4.00 sec 111 MBytes 929 Mbits/sec
[ 4] 4.00-5.00 sec 105 MBytes 881 Mbits/sec
[ 4] 5.00-6.00 sec 108 MBytes 906 Mbits/sec
[ 4] 6.00-7.00 sec 112 MBytes 940 Mbits/sec
[ 4] 7.00-8.00 sec 112 MBytes 940 Mbits/sec
[ 4] 8.00-9.00 sec 112 MBytes 940 Mbits/sec
[ 4] 9.00-10.00 sec 112 MBytes 940 Mbits/sec

```

Supplement 2 Jun 9, 2022

我拿 2 台电脑直连，也是一样的现象，应该不是交换机或网线的问题了。

Supplement 3 Jun 9, 2022

网上搜了一下，找到了这样一个案例：
https://www.reddit.com/r/MacOS/comments/l2uxo5/slow_download_with_plugable_25gbit_ethernet/

他的交换机有下行流控，导致下载速度不如上传。

我怀疑我的 Intel macOS 是不是哪里也有流控？

我用文章里的教程，并发跑 iperf3 ，速度可以上去 50%，但是还是不能跑满。

Supplement 4 Jun 9, 2022

再更一个，我用磁盘测速工具（目的地选 NAS ），结果速度是正常的。。。

https://imgur.com/8wbmuXp

感觉就是 iperf3 不知为何触发了流控。

Supplement 5 Jun 10, 2022

再更一版：

https://share.cleanshot.com/6qXY3r

我抓包发现这里 Window 一开始是 65535 ，后面就一直是 2058 ，非常奇怪。

还不够 2 个 MTU ，那按道理发送端就会控制发送速率。

iperf3 里有一个参数： -w, --window #[KMG] set send/receive socket buffer sizes

尝试这么跑就正常了。

```
iperf3 -c 192.168.11.11 -w 200K
Connecting to host 192.168.11.11, port 5201
[ 5] local 192.168.11.137 port 52617 connected to 192.168.11.11 port 5201
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 278 MBytes 2.34 Gbits/sec
[ 5] 1.00-2.00 sec 279 MBytes 2.34 Gbits/sec
[ 5] 2.00-3.00 sec 277 MBytes 2.33 Gbits/sec
[ 5] 3.00-4.00 sec 279 MBytes 2.34 Gbits/sec
[ 5] 4.00-5.00 sec 276 MBytes 2.31 Gbits/sec
[ 5] 5.00-6.00 sec 279 MBytes 2.34 Gbits/sec
[ 5] 6.00-7.00 sec 279 MBytes 2.34 Gbits/sec
[ 5] 7.00-8.00 sec 279 MBytes 2.34 Gbits/sec
[ 5] 8.00-9.00 sec 279 MBytes 2.34 Gbits/sec
[ 5] 9.00-10.00 sec 275 MBytes 2.31 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-10.00 sec 2.72 GBytes 2.33 Gbits/sec sender
[ 5] 0.00-10.00 sec 2.72 GBytes 2.33 Gbits/sec receiver

iperf Done.
```

接下来就要去看看我这电脑默认的缓冲区为什么太小了。

9 replies 2022-06-10 12:33:30 +08:00