BPI-M2+ Packet drops UDP

Hello,

I test my M2+ boards (several) with iperf (ver. 2.0.1) and iperf3 (ver. 3.6 with cJSON 1.5.2) and I noticed strange packet losses reported by iperfs (regardless of version). Perhaps someone has experienced similar problems? I’m not sure if these are the iperf problem or the BananaPi boards are faulty.

The results below are collected with the iperf3 server running with default settings (iperf3 -s -i 1). (results from iperf confirm these findings, so I will skip them). For really low loads below 30mbps iperf3 reports no drops, later we have an increasing number of drops - note 50% (!!!) for 500mbps and then we are back at 3% drop for 1000mbps.

if I test my interface with netstat (netstat -i), no drops are reported on the interface:

Kernel Interface table
Iface      MTU    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0      1500   609836      0      0 0           804      0      0      0 BMRU
lo       65536        3      0      0 0             3      0      0      0 LRU
wlan0     1500        0      0      0 0             0      0      0      0 BMU

my kernel version Linux bpi2 5.1.1-BPI-Kernel #1 SMP Thu Aug 22 13:53:49 CST 2019 armv7l GNU/Linux

pi@bpi2:~$  lsb_release -a
No LSB modules are available.
Distributor ID:	Debian
Description:	Debian GNU/Linux 10 (buster)
Release:	10
Codename:	buster

Thanks in advance for any help!

============================ iperf3 results

iperf3 -c 192.168.1.11 -u -b 1000m -t 3
[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-3.00   sec   339 MBytes   949 Mbits/sec  0.000 ms  0/245798 (0%)  sender
[  5]   0.00-3.00   sec   329 MBytes   920 Mbits/sec  0.011 ms  7301/245683 (3%)  receiver

iperf3 -c 192.168.1.11 -u -b 500m -t 3
[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-3.00   sec   179 MBytes   500 Mbits/sec  0.000 ms  0/129456 (0%)  sender
[  5]   0.00-3.00   sec   100 MBytes   281 Mbits/sec  0.015 ms  56743/129456 (44%)  receiver


for iperf3 -c 192.168.1.11 -u -b 100m -t 3
[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-3.00   sec  35.8 MBytes   100 Mbits/sec  0.000 ms  0/25892 (0%)  sender
[  5]   0.00-3.00   sec  33.0 MBytes  92.3 Mbits/sec  0.033 ms  1975/25892 (7.6%)  receiver

for iperf3 -c 192.168.1.11 -u -b 50m -t 3
[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-3.00   sec  17.9 MBytes  50.0 Mbits/sec  0.000 ms  0/12946 (0%)  sender
[  5]   0.00-3.02   sec  17.7 MBytes  49.1 Mbits/sec  0.400 ms  98/12911 (0.76%)  receiver