iperf / iperf3
iperf is a simple tool to let you measure memory-to-memory performance access a network. iperf3 is a new implementation from scratch, with the goal of a smaller, simpler code base, and a library version of the functionality that can be used in other programs. iperf3 is not backwards compatible with iperf2.x. The most recent iperf3 release is always available for both Debianand RHEL-based systems from the perfSONAR repository. We recommend iperf3 over iperf becuase the TCP retransmit and CWND report if very helpful for troubleshooting.
The basic commands are the same for iperf and iperf3:
| Server: | |
| iperf/iperf3 -s | Start server on the default port |
| iperf -s -w 32M -D / iperf3 -s -D | Start server with larger TCP window, and in daemon mode |
| iperf -i1 -u -s -p 5003 / iperf3 -s -p 5003 | Start UDP server on port 5003, and give 1 sec interval reports |
| Client | |
| iperf/iperf3 -c remotehost -i 1 -t 30 | Run a 30 second tests, giving results every 1 second |
| iperff/iperf3 -c remotehost -i 1 -t 20 -r | Run a test from remotehost to localhost |
| iperf/iperf3 -c remotehost -i 1 -t 20 -w 32M -P 4 | Run a test with 4 parallel streams, and with a 32M TCP buffer |
| iperf/iperf3 -c remotehost -u -i 1 -b 200M | Run a 200 Mbps UDP test |
iperf3 adds a number of additional features. For example, the -i mode now reports TCP retransmit info (and is on by default), and the verbose mode now gives a lot of useful information on CPU usage, etc. Other new options include:
| Client: | |
| iperf3 -c remotehost -i.5 -0 2 | Run the test for 2 seconds before collecting results, to allow for TCP slowstart to finish. (Omit mode) |
| iperf3 -Z -c remotehost | Use the sendfile() system call for "Zero Copy" mode. This uses much less CPU. |
| iperf3 -c 192.168.12.12 -T s1 & iperf3 -c 192.168.12.13 -T s2 | Run tests to multiple interfaces at once, and label the lines to indicate which test is which |
| iperf3 -c remotehost -J | Output the results in JSON format for easy parsing. |
| iperf3 -A 4,4 -c remotehost | Set the CPU affinity for the sender,receiver (cores are numbered from 0). This has the same affect as doing 'numactl -C 4 iperf3'. |
iperf3 -c 10.20.1.20 -A2,2 -T "1" & ; iperf3 -c 10.20.1.20 -p 5400 -A3,3 -T "2" &
| Run 2 streams on 2 different cores, and label each using the "-T" flag. |
iperf3 thread model
In order to keep the code as simple and maintainable as possible, iperf3 is single threaded. This means that that you may be CPU-bound on some hosts, or on 40G/100G NICs. To run parallel stream iperf3 on mutiple cores, use the method shown in the table above.
Omit Flag
The "omit" flag (-o) allows a specified number of seconds to be removed from a test result. This was created to remove the ‘slow start’ portion of a TCP test, and focus on the steady state period that occurs. For example, a normal TCP based Iperf3 test via BWCTL looks like the following:
[zurawski@newy-pt1 ~]$ bwctl -T iperf3 -f m -t 10 -i 1 -c ps.ncar.xsede.org bwctl: Using tool: iperf3 bwctl: 27 seconds until test results available SENDER START Connecting to host 128.117.212.249, port 5207 [ 15] local 198.124.238.54 port 44605 connected to 128.117.212.249 port 5207 [ ID] Interval Transfer Bandwidth Retr Cwnd [ 15] 0.00-1.00 sec 6.28 MBytes 52.6 Mbits/sec 0 1.32 MBytes [ 15] 1.00-2.00 sec 456 MBytes 3826 Mbits/sec 0 72.1 MBytes [ 15] 2.00-3.00 sec 1.12 GBytes 9658 Mbits/sec 0 72.1 MBytes [ 15] 3.00-4.00 sec 1.12 GBytes 9658 Mbits/sec 0 72.1 MBytes [ 15] 4.00-5.00 sec 1.12 GBytes 9657 Mbits/sec 0 72.1 MBytes [ 15] 5.00-6.00 sec 1.12 GBytes 9658 Mbits/sec 0 72.1 MBytes [ 15] 6.00-7.00 sec 1.12 GBytes 9655 Mbits/sec 0 72.1 MBytes [ 15] 7.00-8.00 sec 1.12 GBytes 9659 Mbits/sec 0 72.1 MBytes [ 15] 8.00-9.00 sec 1.12 GBytes 9658 Mbits/sec 0 72.1 MBytes [ 15] 9.00-10.00 sec 1.12 GBytes 9657 Mbits/sec 0 72.1 MBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bandwidth Retr [ 15] 0.00-10.00 sec 9.45 GBytes 8114 Mbits/sec 0 sender [ 15] 0.00-10.00 sec 9.43 GBytes 8103 Mbits/sec receiver iperf Done. SENDER END
The average will be reported as 8.1 Gbps, even though the majority of the time was spent at 9.6 Gbps. Using the Omit flag, we see the following happen in the data, and final reported average:
[zurawski@newy-pt1 ~]$ bwctl -T iperf3 -f m -t 10 -i 1 -O 3 -c ps.ncar.xsede.org bwctl: Using tool: iperf3 bwctl: 30 seconds until test results available SENDER START Connecting to host 128.117.212.249, port 5208 [ 15] local 198.124.238.54 port 37535 connected to 128.117.212.249 port 5208 [ ID] Interval Transfer Bandwidth Retr Cwnd [ 15] 0.00-1.00 sec 4.96 MBytes 41.6 Mbits/sec 0 987 KBytes (omitted) [ 15] 1.00-2.00 sec 332 MBytes 2786 Mbits/sec 0 65.4 MBytes (omitted) [ 15] 2.00-3.00 sec 1.12 GBytes 9636 Mbits/sec 0 72.1 MBytes (omitted) [ 15] 0.00-1.00 sec 1.12 GBytes 9657 Mbits/sec 0 72.1 MBytes [ 15] 1.00-2.00 sec 1.12 GBytes 9657 Mbits/sec 0 72.1 MBytes [ 15] 2.00-3.00 sec 1.12 GBytes 9657 Mbits/sec 0 72.1 MBytes [ 15] 3.00-4.00 sec 1.12 GBytes 9657 Mbits/sec 0 72.1 MBytes [ 15] 4.00-5.00 sec 1.12 GBytes 9657 Mbits/sec 0 72.1 MBytes [ 15] 5.00-6.00 sec 1.12 GBytes 9657 Mbits/sec 0 72.1 MBytes [ 15] 6.00-7.00 sec 1.13 GBytes 9666 Mbits/sec 0 72.1 MBytes [ 15] 7.00-8.00 sec 1.12 GBytes 9658 Mbits/sec 0 72.1 MBytes [ 15] 8.00-9.00 sec 1.12 GBytes 9657 Mbits/sec 0 72.1 MBytes [ 15] 9.00-10.00 sec 1.12 GBytes 9660 Mbits/sec 0 72.1 MBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bandwidth Retr [ 15] 0.00-10.00 sec 11.2 GBytes 9659 Mbits/sec 0 sender [ 15] 0.00-10.00 sec 11.3 GBytes 9719 Mbits/sec receiver iperf Done.
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