Reordering members can lead to better packing and a smaller memory footprint, due to how alignment works. If you’re iterating a large number of objects, having smaller objects is very favorable in terms of cache locality; you get fewer cache misses, and prefetching is more effective.
For the curious: pahole is a very useful tool for this type of code analysis.
Linux 6.8 TCP Performance Boosts By ~40% For Many Concurrent Connections (www.phoronix.com)