NGINX structural enhancements for HTTP/2 performance

The Cloudflare PROTOCOLS team has made significant changes to the internal structure of NGINX while implementing Enhanced HTTP/2 Prioritization product. These changes were aimed at improving performance and addressing shortcomings in the original NGINX, particularly concerning data flow within the system. Changes included HTTP/2 frame write queue reclamation, HTTP/2 frame write event re-ordering, upstream buffer partial re-use, and TLS layer buffering adjustments. The team plans to continue testing and refining these changes for future releases and apply their newfound skills to other technologies such as QUIC and HTTP/3.