Poor and slow iperf performance

Latest response

Hi.

Recently i got new server hw with 10GBE which i wanted to performance test before sending it into production.
Up to now i was always using gentoo, because it just gives best network performance out of the box, utilizing full gbit speed in recent tests.

Now i'm pretty disappointed why rhel (7.7) is so slow, its just showing around 500 mbit/s maximum in iperf3 using the same ports on the switch, the same cable, and the same client.
It cant be the hardware, because the gentoo server providing full gbit speed is an outdated (consumer) system from around 2013.
Its a pretty out-of-the-box installation of rhel7.7, nothing out of the ordinary.
If it isn't able to utilize gbit, i don't even want to test 10gbit.
I also tried several iperf TCP window sizes with no good results, it always tops out at around 500mbit/s.

Are there magic switches in rhel that release the handbrake?

cpu and ram are nearly idling when doing that iperf3 tests, so that shouldnt be an issue.

Responses

This could be a lot of things, it's a bit difficult to troubleshoot within the scope of a discussion thread.

Most common is a small socket buffer size, try these in /etc/sysctl.conf and apply with sysctl -p:

net.ipv4.tcp_rmem = 4096 262144 16777216
net.ipv4.tcp_wmem = 4096 262144 16777216

Install tuned and set the throughput-performance profile. Make sure irqbalance is running. Make sure your iperf and NIC aren't crossing NUMA nodes.

If you have a support entitlement, feel free to open a support case for further investigation. Attach a sosreport as you open so we can get started looking at the system config.

Hi and thanks for your input. I set the values as you suggested and it works very well. I now get full speed on gbit. But i also had a client problem. Testing with other clients showed that they get full gbit speed using iperf and samba. After the tweaks clientside and the now in place 10gbit network, i can achieve up to 1GB/s read/write speeds to the server.