The story of one latency spike

This post details the investigation and resolution of rare, significant latency spikes experienced by a customer. It showcases the use of advanced debugging tools like System Tap and flame graphs to pinpoint the root cause within the Linux kernel's `tcp_collapse` function, which was exacerbated by large TCP receive buffer sizes. The post demonstrates how tuning the `net.ipv4.tcp_rmem` sysctl parameter significantly improved network performance and stability, highlighting Cloudflare's commitment to deep system-level performance optimization.