Troubles with 'em' driver and UDP packets

[Vaidas Damoševičius]

Hello,

I have 2 boxes with FreeBSD 10.1-RELEASE/amd64 and "Intel(R) PRO/1000 Network Connection 7.4.2" NIC's directly connected to each other. I noticed strange problem - I'm loosing small UDP packets under high load. I've tried to test it with iperf and got the following:

---

vd at v0s4:~ % iperf3 -u -c 1.2.3.4
Connecting to host 1.2.3.4, port 5201
[  4] local 1.2.3.3 port 64254 connected to 1.2.3.4 port 5201
[ ID] Interval           Transfer     Bandwidth       Total Datagrams
[  4]   0.00-1.01   sec   120 KBytes   976 Kbits/sec  15  
[  4]   1.01-2.01   sec   128 KBytes  1.05 Mbits/sec  16  
[  4]   2.01-3.01   sec   128 KBytes  1.05 Mbits/sec  16  
[  4]   3.01-4.01   sec   128 KBytes  1.05 Mbits/sec  16  
[  4]   4.01-5.01   sec   128 KBytes  1.05 Mbits/sec  16  
[  4]   5.01-6.01   sec   128 KBytes  1.05 Mbits/sec  16  
[  4]   6.01-7.01   sec   128 KBytes  1.05 Mbits/sec  16  
[  4]   7.01-8.00   sec   128 KBytes  1.05 Mbits/sec  16  
[  4]   8.00-9.01   sec   128 KBytes  1.05 Mbits/sec  16  
[  4]   9.01-10.01  sec   128 KBytes  1.05 Mbits/sec  16  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Jitter    Lost/Total Datagrams
[  4]   0.00-10.01  sec  1.24 MBytes  1.04 Mbits/sec  0.325 ms  0/159 (0%)  
[  4] Sent 159 datagrams

Any advice how to solve it ?

Thank you.