Compute Operations are faster on Rocky Linux than Centos7 on AWS C5 instances

Hello I’m testing compute performance of Rocky Linux vs Centos 7 using various computer aided engineering software (CAE) such as STAR-CCM+ and ANSYS Mechanical. These tests span from 1 node to 4-5 nodes. I tested on a couple different AWS hardware (C5 and C5n)

I noticed that there is performance improvement (faster solve time) on the C5 instances which are just vanilla ethernet communication between nodes. I’m talking about 6-10% faster which is highly considerable. However the results on C5n instances, which have high speed interconnect (much faster than ethernet) were pretty much the same. Maybe Rocky Linux here was 1-2% faster than Centos in average with C5n instances but this doesn’t raise any surpises.

My question is what can we attribute to the performance improvement on C5 instances. Everything is the same except the Rocky Linux image vs the Centos7 image. Does Rocky Linux possibly have faster ethernet software drivers?