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regression detector (2026)

regression detector replays a codebase's benchmarks across its git history, each commit built and run in its own locked-down Docker container, and flags the commits that made it slower.

Instead of a fixed "10% slower" rule, it measures how noisy each benchmark is on its own and only flags changes bigger than that noise. It caught a real regression in Pebble, CockroachDB's storage engine: commit ae0e76fcc4 added a heap allocation when iterators are set up. The timing barely moved, but the allocation count did.

Pebble dashboard
S2 compression dashboard