Unpacking Cloudflare Workers CPU Performance Benchmarks

What this post added

This post details the investigation and resolution of performance disparities observed in CPU-intensive benchmarks between Cloudflare Workers and Vercel. Key contributions include: 1. Identifying and fixing a scheduling issue related to sharding and warm isolate routing that caused requests to be blocked, impacting perceived performance without affecting billed CPU time. 2. Tuning the V8 garbage collector by adjusting the young generation size, which was previously set too rigidly based on outdated recommendations, leading to a ~25% performance boost. 3. Identifying and fixing unnecessary allocations and buffer copies within the OpenNext adapter and related frameworks (Next.js, React) that were contributing to high garbage collection overhead.