Beyond the usual new wired/wireless network hardware support and the other routine churn in the big Linux networking subsystem, the Linux 6.8 kernel is bringing some key improvements to the core networking code that can yield up to a ~40% improvement for TCP performance when encountering many concurrent network connections.
First up, there's been an analysis and reorganization of core networking structures. This effort has been around optimizing cacheline consumption and adding safeguards to ensure future changes don't regress. In turn this optimizing of core networking structures is causing TCP performance with many concurrent connections to increase by as much as 40% or more!