iperf，linux調度報告的可變數量的失去UDP數據包？

我正在測試與在 Bananpi M2+ 單板電腦（Debian，5.1.1-BPI-Kernel #1 SM）上執行的 iperf 伺服器（iperf 版本 2.0.13（2019 年 1 月 21 日）pthreads）的連接。對於不同的目標頻寬，我觀察到不同的丟包率。對於非常低和非常高的目標頻寬設置（低於 1%），丟棄的數據包數量很少。然而，對於中等值，失去的數據包數量非常高（例如，29% 的數據包在 400 Mbps 時失去）。什麼可能導致這種行為？（詳細結果見下文）。這是在測試網路中發生的唯一通信（因此必須在目標端發生丟棄）。

我已經嘗試調整 UDP 套接字的大小，但這並沒有改善結果。

------------------------------------------------------------
Server listening on UDP port 5001
Receiving 1470 byte datagrams
UDP buffer size: 3.81 MByte (WARNING: requested 1.91 MByte)
------------------------------------------------------------
[  3] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 37950
[ ID] Interval       Transfer     Bandwidth        Jitter   Lost/Total Datagrams
[  3]  0.0-10.0 sec  11.9 MBytes  10.0 Mbits/sec   0.195 ms    0/ 8504 (0%)
[  4] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 32833
[  4]  0.0-10.0 sec   118 MBytes  98.9 Mbits/sec   0.306 ms  571/85034 (0.67%)
[  3] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 56833
[  3]  0.0-10.0 sec   344 MBytes   288 Mbits/sec   0.053 ms 9951/255103 (3.9%)
[  4] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 51751
[  4]  0.0-10.0 sec   337 MBytes   283 Mbits/sec   0.026 ms 99684/340136 (29%)
[  3] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 53331
[  3]  0.0-10.0 sec   512 MBytes   429 Mbits/sec   0.018 ms 60157/425171 (14%)
[  4] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 35110
[  4]  0.0-10.0 sec   832 MBytes   698 Mbits/sec   0.014 ms 1860/595239 (0.31%)
[  3] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 52002
[  3]  0.0-10.0 sec  1.04 GBytes   897 Mbits/sec   0.013 ms 2895/765308 (0.38%)

當我將 iperf 作為具有預設優先級的程序執行時，更新為 400 Mbps，我得到以下結果：

pi@bpi2:~$ iperf -s -u 
------------------------------------------------------------
Server listening on UDP port 5001
Receiving 1470 byte datagrams
UDP buffer size: 25.0 MByte (default)
------------------------------------------------------------
[  3] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 44269
[ ID] Interval       Transfer     Bandwidth        Jitter   Lost/Total Datagrams
[  3]  0.0-10.0 sec   379 MBytes   318 Mbits/sec   0.030 ms 69509/340136 (20%)
[  4] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 53115
[  4]  0.0-10.0 sec   463 MBytes   389 Mbits/sec   0.022 ms 9715/340137 (2.9%)
[  3] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 39077
[  3]  0.0-10.0 sec   431 MBytes   362 Mbits/sec   0.031 ms 32537/340136 (9.6%)
[  4] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 47676
[  4]  0.0-10.0 sec   363 MBytes   305 Mbits/sec   0.029 ms 81019/340136 (24%)
[  3] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 52106
[  3]  0.0-10.0 sec   407 MBytes   341 Mbits/sec   0.030 ms 49872/340136 (15%)

當我設置最高優先級時：

pi@bpi2:~$ sudo ionice -c 1 -n 0 nice -n -20 iperf -s -u       
------------------------------------------------------------
Server listening on UDP port 5001
Receiving 1470 byte datagrams
UDP buffer size: 25.0 MByte (default)
------------------------------------------------------------
[  3] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 59056
[ ID] Interval       Transfer     Bandwidth        Jitter   Lost/Total Datagrams
[  3]  0.0-10.0 sec   460 MBytes   386 Mbits/sec   0.022 ms 11665/340137 (3.4%)
[  4] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 54558
[  4]  0.0-10.0 sec   450 MBytes   378 Mbits/sec   0.039 ms 18941/340137 (5.6%)
[  3] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 34361
[  3]  0.0-10.0 sec   437 MBytes   366 Mbits/sec   0.029 ms 28662/340137 (8.4%)
[  4] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 47201
[  4]  0.0-10.0 sec   474 MBytes   398 Mbits/sec   0.033 ms 1953/340136 (0.57%)
[  3] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 34809
[  3]  0.0-10.0 sec   442 MBytes   371 Mbits/sec   0.030 ms 24886/340136 (7.3%)
[  4] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 54412
[  4]  0.0-10.0 sec   429 MBytes   360 Mbits/sec   0.037 ms 34388/340138 (10%)
[  3] local 192.168.1.11 port 5001 connected with 192.168.1.201 port 55946
[  3]  0.0-10.0 sec   446 MBytes   374 Mbits/sec   0.034 ms 22341/340136 (6.6%)

與此同時，我自己設法找到了解決方案。iperf 出現這種奇怪行為的原因不是應用程序本身，而是 NIC 的驅動程序有問題（很可能與正確設置 GbE 延遲有關）。

幫助的是完全重新安裝作業系統並切換到具有正確驅動程序集的 Armbian 4.19。我設法在 armbian 論壇中找到了解決方案，該論壇為所有對 allwinner h3 SoC 感興趣的人（我的 BananaPi M2+ 以及許多其他產品中使用的那個）提供了非常廣泛的資訊。

引用自：https://serverfault.com/questions/990793