How we diagnosed and resolved Redis latency spikes with BPF and other tools

This post details the diagnosis and resolution of chronic Redis latency spikes on GitLab.com. It describes the use of BPF and profiling tools (perf, flamescope, funclatency) to identify that eviction bursts were causing CPU saturation on the Redis main thread. The root cause was found to be an interaction effect leading to excessive evictions, and the solution involved a simple fix to break this cycle.