Hi all,
I am trying to understand iperf3.7 performance using small UDP packets. I have two systems
running iperf 3.7+ (cJSON 1.5.2) that were complied on each system from the latest github
release. One system is an Intel Core i5-8500 (6 cores) running Ubuntu 18.04.3 LTS. The other is
an Intel Pentium N4200 (4 cores) running Linux Mint 19.1 (Debian based). Running iperf3 server
on the Pentium machine. The two systems are connected via a 1 Gbps Ethernet switch.
I'm trying to understand the difference in behavior between a normal run (iperf3 client sending)
and -R (iperf3 server sending).
When traffic flows from client to server, throughput is close to what is set in -b and there is
packet loss.
But for traffic server to client, throughput appears to be adjusted closer to actual 1 Gigabit
link capacity and no packet loss is
reported.
Why?
Thanks for any insight/advice you can provide.
Outputs from both runs are below.
Traffic client to server (normal)
=======================
$ iperf3 -c 10.168.3.246 -V -u -l 128 -b 400M --get-server-output
--udp-counters-64bit
iperf 3.7+
Linux bbf-testbed 4.15.0-70-generic #79-Ubuntu SMP Tue Nov 12 10:36:11 UTC 2019
x86_64
Control connection MSS 1448
Time: Tue, 10 Dec 2019 17:13:18 GMT
Connecting to host 10.168.3.246, port 5201
Cookie: zlqtq4axmfrtvtvb6ynuqstiuxv2uewfurcb
Target Bitrate: 400000000
[ 5] local 10.168.3.176 port 36267 connected to 10.168.3.246 port 5201
Starting Test: protocol: UDP, 1 streams, 128 byte blocks, omitting 0 seconds,
10 second test, tos 0
[ ID] Interval Transfer Bitrate Total Datagrams
[ 5] 0.00-1.00 sec 43.4 MBytes 364 Mbits/sec 355660
[ 5] 1.00-2.00 sec 43.6 MBytes 366 Mbits/sec 357373
[ 5] 2.00-3.00 sec 43.6 MBytes 366 Mbits/sec 357033
[ 5] 3.00-4.00 sec 43.7 MBytes 367 Mbits/sec 358194
[ 5] 4.00-5.00 sec 43.9 MBytes 368 Mbits/sec 359560
[ 5] 5.00-6.00 sec 43.6 MBytes 366 Mbits/sec 357470
[ 5] 6.00-7.00 sec 43.7 MBytes 366 Mbits/sec 357695
[ 5] 7.00-8.00 sec 43.5 MBytes 365 Mbits/sec 356415
[ 5] 8.00-9.00 sec 43.8 MBytes 367 Mbits/sec 358502
[ 5] 9.00-10.00 sec 43.7 MBytes 367 Mbits/sec 358241
- - - - - - - - - - - - - - - - - - - - - - - - -
Test Complete. Summary Results:
[ ID] Interval Transfer Bitrate Jitter Lost/Total
Datagrams
[ 5] 0.00-10.00 sec 437 MBytes 366 Mbits/sec 0.000 ms 0/3576143 (0%)
sender
[ 5] 0.00-10.05 sec 402 MBytes 336 Mbits/sec 0.001 ms 282418/3576080
(7.9%) receiver
CPU Utilization: local/sender 99.9% (26.4%u/73.6%s), remote/receiver 69.3%
(9.1%u/60.2%s)
Server output:
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Accepted connection from 10.168.3.176, port 55472
[ 5] local 10.168.3.246 port 5201 connected to 10.168.3.176 port 36267
[ ID] Interval Transfer Bitrate Jitter Lost/Total
Datagrams
[ 5] 0.00-1.00 sec 8.22 MBytes 69.0 Mbits/sec 0.020 ms 270794/338157
(80%)
[ 5] 1.00-2.00 sec 43.3 MBytes 363 Mbits/sec 0.001 ms 3396/358336
(0.95%)
[ 5] 2.00-3.00 sec 43.6 MBytes 366 Mbits/sec 0.001 ms 174/357139
(0.049%)
[ 5] 3.00-4.00 sec 43.7 MBytes 366 Mbits/sec 0.001 ms 167/357972
(0.047%)
[ 5] 4.00-5.00 sec 44.0 MBytes 369 Mbits/sec 0.001 ms 137/360199
(0.038%)
[ 5] 5.00-6.00 sec 43.6 MBytes 366 Mbits/sec 0.001 ms 175/357313
(0.049%)
[ 5] 6.00-7.00 sec 43.6 MBytes 366 Mbits/sec 0.001 ms 302/357366
(0.085%)
[ 5] 7.00-8.00 sec 43.5 MBytes 365 Mbits/sec 0.001 ms 111/356347
(0.031%)
[ 5] 8.00-9.00 sec 42.9 MBytes 360 Mbits/sec 0.001 ms 6993/358445 (2%)
[ 5] 9.00-10.00 sec 43.7 MBytes 367 Mbits/sec 0.001 ms 169/358259
(0.047%)
[ 5] 10.00-10.05 sec 2.02 MBytes 366 Mbits/sec 0.001 ms 0/16547 (0%)
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Jitter Lost/Total
Datagrams
[ 5] 0.00-10.05 sec 402 MBytes 336 Mbits/sec 0.001 ms 282418/3576080
(7.9%) receiver
Traffic server to client (-R)
$ iperf3 -c 10.168.3.246 -V -u -l 128 -b 400M --get-server-output
--udp-counters-64bit -R
iperf 3.7+
Linux bbf-testbed 4.15.0-70-generic #79-Ubuntu SMP Tue Nov 12 10:36:11 UTC 2019
x86_64
Control connection MSS 1448
Time: Tue, 10 Dec 2019 17:14:22 GMT
Connecting to host 10.168.3.246, port 5201
Reverse mode, remote host 10.168.3.246 is sending
Cookie: u3ss45wjb3ih6nmzwozuqk66zb2nvxnq2gsc
Target Bitrate: 400000000
[ 5] local 10.168.3.176 port 56182 connected to 10.168.3.246 port 5201
Starting Test: protocol: UDP, 1 streams, 128 byte blocks, omitting 0 seconds,
10 second test, tos 0
[ ID] Interval Transfer Bitrate Jitter Lost/Total
Datagrams
[ 5] 0.00-1.00 sec 17.5 MBytes 147 Mbits/sec 0.013 ms 5628/149164
(3.8%)
[ 5] 1.00-2.00 sec 14.5 MBytes 121 Mbits/sec 0.011 ms 0/118430 (0%)
[ 5] 2.00-3.00 sec 14.5 MBytes 122 Mbits/sec 0.013 ms 0/118741 (0%)
[ 5] 3.00-4.00 sec 14.5 MBytes 122 Mbits/sec 0.013 ms 0/118753 (0%)
[ 5] 4.00-5.00 sec 14.5 MBytes 121 Mbits/sec 0.012 ms 0/118620 (0%)
[ 5] 5.00-6.00 sec 14.7 MBytes 123 Mbits/sec 0.013 ms 0/120057 (0%)
[ 5] 6.00-7.00 sec 14.7 MBytes 123 Mbits/sec 0.012 ms 0/120211 (0%)
[ 5] 7.00-8.00 sec 14.6 MBytes 122 Mbits/sec 0.013 ms 0/119591 (0%)
[ 5] 8.00-9.00 sec 14.6 MBytes 122 Mbits/sec 0.013 ms 0/119378 (0%)
[ 5] 9.00-10.00 sec 14.7 MBytes 123 Mbits/sec 0.013 ms 0/120160 (0%)
- - - - - - - - - - - - - - - - - - - - - - - - -
Test Complete. Summary Results:
[ ID] Interval Transfer Bitrate Jitter Lost/Total
Datagrams
[ 5] 0.00-10.04 sec 149 MBytes 125 Mbits/sec 0.000 ms 0/1223121 (0%)
sender
[ 5] 0.00-10.00 sec 149 MBytes 125 Mbits/sec 0.013 ms 5628/1223105
(0.46%) receiver
Server output:
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Accepted connection from 10.168.3.176, port 55538
[ 5] local 10.168.3.246 port 5201 connected to 10.168.3.176 port 56182
[ ID] Interval Transfer Bitrate Total Datagrams
[ 5] 0.00-1.00 sec 17.6 MBytes 148 Mbits/sec 144440
[ 5] 1.00-2.00 sec 14.4 MBytes 121 Mbits/sec 118318
[ 5] 2.00-3.00 sec 14.5 MBytes 122 Mbits/sec 118816
[ 5] 3.00-4.00 sec 14.5 MBytes 121 Mbits/sec 118536
[ 5] 4.00-5.00 sec 14.5 MBytes 122 Mbits/sec 118782
[ 5] 5.00-6.00 sec 14.6 MBytes 123 Mbits/sec 119940
[ 5] 6.00-7.00 sec 14.7 MBytes 123 Mbits/sec 120248
[ 5] 7.00-8.00 sec 14.6 MBytes 122 Mbits/sec 119586
[ 5] 8.00-9.00 sec 14.6 MBytes 122 Mbits/sec 119473
[ 5] 9.00-10.00 sec 14.7 MBytes 123 Mbits/sec 120069
[ 5] 10.00-10.04 sec 614 KBytes 116 Mbits/sec 4913
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Jitter Lost/Total
Datagrams
[ 5] 0.00-10.04 sec 149 MBytes 125 Mbits/sec 0.000 ms 0/1223121 (0%)
sender
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