porting iperf2 to the QNX OS

Pavlo Kleymonov — Fri, 06 Mar 2026 12:53:59 -0000

Hello,

I am currently porting iperf2 to the QNX OS.

This effort has a long history. In the past, some of the work was merged into version 2.0.13.

Due to the event-driven architecture of QNX, QNX team has extended the existing functionality for UDP transfers by implementing burst send/receive support using the sendmmsg() and recvmmsg() system calls.
This reduces per-packet overhead and can improve UDP throughput by up to 4× in some cases.
I believe this approach could also improve performance on Linux.

These changes have already been merged into version 2.2.1 in the QNX ports repository:
https://github.com/qnx-ports/iperf2

Build instructions are available in a separate repository:
https://github.com/qnx-ports/build-files

Specifically here:
https://github.com/qnx-ports/build-files/blob/main/conan/recipes/iperf2/README.md

At the moment, this optimization is only enabled for QNX, but it could potentially be adapted for Linux builds as well.

I would like to upstream these changes to the original repository on sourceforge.net
and wanted to first ask whether this would make sense and whether such contributions might be accepted.

Thank you for your time, and I would be happy to discuss the details if there is interest.

Best regards

Using bounceback to detect unsynchronized clocks

Steve Shearer — Thu, 29 May 2025 00:07:38 -0000

Thanks Bob

Using bounceback to detect unsynchronized clocks

Robert McMahon — Wed, 28 May 2025 18:04:17 -0000

These are directional one way delays. They're shown on the client for convenience (vs requiring one to look at the server for OWD-TX and the client of OWD-RX.)

The RTT equivalent is the BB8 PDF.

Using bounceback to detect unsynchronized clocks

Steve Shearer — Wed, 28 May 2025 17:24:32 -0000

Thanks for the clarification. So am i correct to think that OWD-TX-PDF is effectively a PDF of RTT - but perhaps without the return trip? Could I make use of OWD-RX-PDF to factor in the return trip?

Using bounceback to detect unsynchronized clocks

Robert McMahon — Wed, 28 May 2025 00:34:30 -0000

See the man page. PDF or histograms with binning.

--bounceback-period of 0 means just bb as fast as possible and don't do any bursting.

[ 1] 0.00-5.10 sec BB8-PDF:
bin(w=100us):cnt(50)=35:1,37:1,39:1,40:3,41:4,42:1,43:1,52:1,57:1,65:1,68:1,69:1,70:1,72:2,74:1,75:5,78:1,79:2,80:4,81:3,82:1,83:1,88:2,90:2,92:1,94:1,117:1,126:1,369:1,1000:1,1922:1,3710:1 (5.00/95.00/99.7%=39/1000/3710,Outliers=4,obl/obu=0/0)

where,
[ 1] The traffic thread number
0.00-5.10 sec The time interval of the histogram
BB8-PDF BB8 is the histogram name and the PDF indicates a histogram raw output
bin(w=100us) provides the bin width. The bin width of this histogram is 100 microseconds
cnt(50) provides the total number of samples in the histogram. There are 50 samples in this histogram
35:1 provides the bin no then the number of samples in that bin. Bin 35 with bin width 100us is 3.4 ms - 3.5 ms and there was one sample that landed there
5.00/95.00/99.7%=39/1000/3710 provides the bin confidence intervals (per the integrated cumulative distribution function.) 5% landed in 3.9 ms or better (recall bin number multiplies by bin width.) 95% landed in 10 ms or better. 99.7% or 3 standards of deviation landed in 37.1 ms or better
Outliers=4 provides the outlier count, similar to 3IQR (3 times the inter quartile range) but uses 10% and 90% for inner & outer fence post, then 3 times that for outlier detection.
obl/obu=0/0 out of bounds lower and out of bands upper, provides the number of samples that could not be binned because the value landed outside of all possible bins

Using bounceback to detect unsynchronized clocks

Steve Shearer — Tue, 27 May 2025 20:06:50 -0000

I am trying to get something like a histogram of TCP RTT and I've been poking around at various things. Could someone point me to a description of OWD-TX-PDF and OWD-RX-PDF please, I cant seem to find a reference to what it is a PDF of exactly.
Also I see in the above, --bounceback-period 0, - what does this do?

How to measure UDP one-way latency?

Yunha Choi — Fri, 16 May 2025 06:30:34 -0000

Oh, I can check this in the server header output.

Server listening on UDP port 5001 with pid 43577
Read buffer size: 1.44 KByte (Dist bin width= 183 Byte)
Enabled receive histograms bin-width=0.100 ms, bins=10000 (clients should use --trip-times)
UDP buffer size:  208 KByte (default)

How to measure UDP one-way latency?

Yunha Choi — Fri, 16 May 2025 06:26:16 -0000

Thanks for your reply.
When I run iperf -s -u -e --histograms, and iperf -u --trip-times -e the result shows:

[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-15.00 sec   562 MBytes   315 Mbits/sec   0.030 ms 51/401246 (0.013%) 0.236/0.174/1.132/0.066 ms -0 pps 401195/6(0) pkts 401196/0/0 166335
[  1] 0.00-15.00 sec T8(f)-PDF: bin(w=100us):cnt(401194)=2:81670,3:307775,4:5088,5:1025,6:1039,7:1775,8:1690,9:942,10:167,11:20,12:3 (5.00/95.00/99.7%u=0/0) (1.132 ms/1747374314.450849)

I noticed that the bin width is shown as 100 μs, but according to the manual, the default bin width is supposed to be 1 ms. Which one is correct?
Also, why is the PPS value shown as -0?

How to measure UDP one-way latency?

Robert McMahon — Sun, 20 Apr 2025 21:51:43 -0000

Use --trip-times if the clocks are synchronized.

rjmcmahon@rpi5-34:~ $ iperf -s -i 1 -e -u
------------------------------------------------------------
Server listening on UDP port 5001 with pid 43853
Read buffer size: 1470 Byte 
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.34%eth0 port 5001 connected with 192.168.1.35 port 51657 (trip-times) (peer 2.2.2-master) on 2025-04-20 14:47:46.856 (PDT)
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.123/0.122/0.162/0.004 ms 91 pps 90/0(0) pkts 90/0/0 1077
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.123/0.129/0.001 ms 45 pps 89/0(0) pkts 89/0/0 1069
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1073
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec   0.000 ms 0/89 (0%) 0.122/0.122/0.126/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1075
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.129/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1075
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1071
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.122/0.122/0.128/0.001 ms 90 pps 90/0(0) pkts 90/0/0 1080
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1069
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.119/0.129/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1070
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1070
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec   0.001 ms 0/894 (0%) 0.122/0.119/0.162/0.002 ms 81 pps 894/0(0) pkts 895/0/0 1075

rjmcmahon@rpi5-35:~ $ iperf -c 192.168.1.34 -i 1 -e --trip-times -u
------------------------------------------------------------
Client connecting to 192.168.1.34, UDP port 5001 with pid 24142 (1/0 flows/load)
TOS defaults to 0x0 (dscp=0,ecn=0) (Nagle on)
Sending 1470 byte datagrams, IPG target: 0.00 us (kalman adjust)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.35%eth0 port 51657 connected with 192.168.1.34 port 5001 (trip-times) on 2025-04-20 14:47:46.855 (PDT)
[ ID] Interval        Transfer     Bandwidth      Write/Err/Timeo  PPS
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec  894/0/0      81 pps
[  1] Sent 895 datagrams
[  1] Server Report:
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec   0.000 ms 0/894 (0%) 0.122/0.119/0.162/0.002 ms 89 pps 89/0(0) pkts 0/0/0 1075

Also supported are full histograms

rjmcmahon@rpi5-34:~ $ iperf -s -i 1 -e -u --histograms=10u
------------------------------------------------------------
Server listening on UDP port 5001 with pid 43866
Read buffer size: 1470 Byte 
Enabled receive histograms bin-width=0.010 ms, bins=0 (clients should use --trip-times)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.34%eth0 port 5001 connected with 192.168.1.35 port 52920 (trip-times) (peer 2.2.2-master) on 2025-04-20 14:50:18.179 (PDT)
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.122/0.122/0.161/0.004 ms 91 pps 90/0(0) pkts 90/0/0 1082
[  1] 0.00-1.00 sec T8-PDF: bin(w=10us):cnt(90)=13:89,17:1 (5.00/95.00/99.7%=13/13/17,Outliers=0,obl/obu=0/0) (0.161 ms/1745185818.179112)
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 45 pps 89/0(0) pkts 89/0/0 1075
[  1] 1.00-2.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.128 ms/1745185820.007306)
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.126/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1075
[  1] 2.00-3.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.126 ms/1745185820.455915)
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.126/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1076
[  1] 3.00-4.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.126 ms/1745185821.913893)
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1071
[  1] 4.00-5.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185822.441008)
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1068
[  1] 5.00-6.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185823.416732)
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.123/0.122/0.127/0.001 ms 90 pps 90/0(0) pkts 90/0/0 1080
[  1] 6.00-7.00 sec T8-PDF: bin(w=10us):cnt(90)=13:90 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185824.459744)
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.123/0.123/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1066
[  1] 7.00-8.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185825.424256)
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.123/0.123/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1064
[  1] 8.00-9.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185826.422409)
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.123/0.123/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1066
[  1] 9.00-10.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185827.431782)
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec   0.001 ms 0/894 (0%) 0.122/0.122/0.161/0.002 ms 81 pps 894/0(0) pkts 895/0/0 1074
[  1] 0.00-10.02 sec T8(f)-PDF: bin(w=10us):cnt(894)=13:893,17:1 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.161 ms/1745185818.179112)

rjmcmahon@rpi5-35:~ $ iperf -c 192.168.1.34 -i 1 -e --trip-times -u
------------------------------------------------------------
Client connecting to 192.168.1.34, UDP port 5001 with pid 24152 (1/0 flows/load)
TOS defaults to 0x0 (dscp=0,ecn=0) (Nagle on)
Sending 1470 byte datagrams, IPG target: 0.00 us (kalman adjust)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.35%eth0 port 52920 connected with 192.168.1.34 port 5001 (trip-times) on 2025-04-20 14:50:18.178 (PDT)
[ ID] Interval        Transfer     Bandwidth      Write/Err/Timeo  PPS
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec  894/0/0      81 pps
[  1] Sent 895 datagrams
[  1] Server Report:
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc

PS. I'd recommend 2.2.1.

How to measure UDP one-way latency?

Robert McMahon — Sun, 20 Apr 2025 21:51:38 -0000

Use --trip-times if the clocks are synchronized.

rjmcmahon@rpi5-34:~ $ iperf -s -i 1 -e -u
------------------------------------------------------------
Server listening on UDP port 5001 with pid 43853
Read buffer size: 1470 Byte 
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.34%eth0 port 5001 connected with 192.168.1.35 port 51657 (trip-times) (peer 2.2.2-master) on 2025-04-20 14:47:46.856 (PDT)
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.123/0.122/0.162/0.004 ms 91 pps 90/0(0) pkts 90/0/0 1077
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.123/0.129/0.001 ms 45 pps 89/0(0) pkts 89/0/0 1069
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1073
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec   0.000 ms 0/89 (0%) 0.122/0.122/0.126/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1075
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.129/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1075
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1071
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.122/0.122/0.128/0.001 ms 90 pps 90/0(0) pkts 90/0/0 1080
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1069
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.119/0.129/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1070
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1070
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec   0.001 ms 0/894 (0%) 0.122/0.119/0.162/0.002 ms 81 pps 894/0(0) pkts 895/0/0 1075

rjmcmahon@rpi5-35:~ $ iperf -c 192.168.1.34 -i 1 -e --trip-times -u
------------------------------------------------------------
Client connecting to 192.168.1.34, UDP port 5001 with pid 24142 (1/0 flows/load)
TOS defaults to 0x0 (dscp=0,ecn=0) (Nagle on)
Sending 1470 byte datagrams, IPG target: 0.00 us (kalman adjust)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.35%eth0 port 51657 connected with 192.168.1.34 port 5001 (trip-times) on 2025-04-20 14:47:46.855 (PDT)
[ ID] Interval        Transfer     Bandwidth      Write/Err/Timeo  PPS
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec  894/0/0      81 pps
[  1] Sent 895 datagrams
[  1] Server Report:
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec   0.000 ms 0/894 (0%) 0.122/0.119/0.162/0.002 ms 89 pps 89/0(0) pkts 0/0/0 1075

Also supported are full histograms

rjmcmahon@rpi5-34:~ $ iperf -s -i 1 -e -u --histograms=10u
------------------------------------------------------------
Server listening on UDP port 5001 with pid 43866
Read buffer size: 1470 Byte 
Enabled receive histograms bin-width=0.010 ms, bins=0 (clients should use --trip-times)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.34%eth0 port 5001 connected with 192.168.1.35 port 52920 (trip-times) (peer 2.2.2-master) on 2025-04-20 14:50:18.179 (PDT)
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.122/0.122/0.161/0.004 ms 91 pps 90/0(0) pkts 90/0/0 1082
[  1] 0.00-1.00 sec T8-PDF: bin(w=10us):cnt(90)=13:89,17:1 (5.00/95.00/99.7%=13/13/17,Outliers=0,obl/obu=0/0) (0.161 ms/1745185818.179112)
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 45 pps 89/0(0) pkts 89/0/0 1075
[  1] 1.00-2.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.128 ms/1745185820.007306)
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.126/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1075
[  1] 2.00-3.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.126 ms/1745185820.455915)
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.126/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1076
[  1] 3.00-4.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.126 ms/1745185821.913893)
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1071
[  1] 4.00-5.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185822.441008)
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1068
[  1] 5.00-6.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185823.416732)
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.123/0.122/0.127/0.001 ms 90 pps 90/0(0) pkts 90/0/0 1080
[  1] 6.00-7.00 sec T8-PDF: bin(w=10us):cnt(90)=13:90 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185824.459744)
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.123/0.123/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1066
[  1] 7.00-8.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185825.424256)
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.123/0.123/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1064
[  1] 8.00-9.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185826.422409)
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.123/0.123/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1066
[  1] 9.00-10.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185827.431782)
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec   0.001 ms 0/894 (0%) 0.122/0.122/0.161/0.002 ms 81 pps 894/0(0) pkts 895/0/0 1074
[  1] 0.00-10.02 sec T8(f)-PDF: bin(w=10us):cnt(894)=13:893,17:1 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.161 ms/1745185818.179112)

rjmcmahon@rpi5-35:~ $ iperf -c 192.168.1.34 -i 1 -e --trip-times -u
------------------------------------------------------------
Client connecting to 192.168.1.34, UDP port 5001 with pid 24152 (1/0 flows/load)
TOS defaults to 0x0 (dscp=0,ecn=0) (Nagle on)
Sending 1470 byte datagrams, IPG target: 0.00 us (kalman adjust)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.35%eth0 port 52920 connected with 192.168.1.34 port 5001 (trip-times) on 2025-04-20 14:50:18.178 (PDT)
[ ID] Interval        Transfer     Bandwidth      Write/Err/Timeo  PPS
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec  894/0/0      81 pps
[  1] Sent 895 datagrams
[  1] Server Report:
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc

PS. I'd recommend 2.2.1.

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