https://jvq.net/tags/explainers/ Recent content in Explainers on JVQ.net Hugo en-us Sun, 18 Oct 2026 00:00:00 +0000 https://jvq.net/performance-budgets-in-ci-only-work-when-base-and-head-run-side-by-side/ Sun, 18 Oct 2026 00:00:00 +0000 https://jvq.net/performance-budgets-in-ci-only-work-when-base-and-head-run-side-by-side/ <p>A performance budget is a promise written into the pipeline: this change may make the code at most 5% slower, and if it&rsquo;s worse, the build fails. Tests already guard what the code does. A budget guards how fast it does it.</p> <p>The idea is old and simple. Making it work on ordinary CI machines is the hard part, because those machines are noisy. On the shared two-core cloud machine where jvq was tested, the very same benchmark binary, run 40 times in a row, spread by 8.9% from one run to the next. A budget of 5% sits well inside that noise, so a naive check can&rsquo;t tell a real slowdown from the runner having a bad minute.</p>