performance.yml

name: Performance

on:
  push:
    branches: [main]
  # On pull requests too. This only ran on main, so when a benchmark stopped
  # compiling the branch went green, merged, and main went red: eight commits
  # in a row before anyone looked at the commit list.
  pull_request:
  schedule:
    - cron: '0 6 * * 1'
  workflow_dispatch:

concurrency:
  group: performance-ratchet-${{ github.ref }}
  cancel-in-progress: false

permissions:
  contents: read

jobs:
  ratchet:
    name: edit-loop and runtime ratchet
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v7

      - uses: dtolnay/rust-toolchain@stable

      - uses: Swatinem/rust-cache@v2

      - name: cargo test --release performance ratchet
        id: measure
        env:
          # Absolute: cargo runs the test binary from the package directory, not the workspace root.
          DEED_PERF_RESULTS: ${{ github.workspace }}/performance-results.json
        run: >
          cargo test --release -p deed-driver --test performance_regression
          existing_bench_slopes_stay_inside_the_ratchet
          -- --ignored --exact --nocapture --test-threads=1

      - name: summarize the measured slopes
        if: always()
        env:
          MEASURE_OUTCOME: ${{ steps.measure.outcome }}
        run: |
          python3 - <<'PY'
          import json
          import os
          from pathlib import Path

          path = Path("performance-results.json")
          if not path.exists():
              # The test writes this before it asserts, so a step that passed wrote one.
              if os.environ["MEASURE_OUTCOME"] == "success":
                  raise SystemExit(f"{path} is missing after the ratchet passed")
              raise SystemExit(0)

          data = json.loads(path.read_text())
          edit = data["edit_loop"]
          passes = edit["passes_us_per_file"]
          logs = data["logs_report"]

          rows = [
              (
                  "edit loop total",
                  f"{edit['total_us_per_file']:.2f} us/file",
                  f"{edit['total_segment_ratio']:.2f}x",
              )
          ]
          rows += [
              (f"edit loop {name}", f"{passes[name]:.2f} us/file", "")
              for name in ("lex", "parse", "resolve", "typeck", "effects")
          ]
          rows.append(
              (
                  "logs report",
                  f"{logs['us_per_line']:.2f} us/line",
                  f"{logs['segment_ratio']:.2f}x",
              )
          )

          with open(os.environ["GITHUB_STEP_SUMMARY"], "a", encoding="utf-8") as out:
              out.write("## Performance ratchet\n\n")
              out.write("| measurement | slope | segment ratio |\n")
              out.write("| --- | ---: | ---: |\n")
              for measurement, slope, ratio in rows:
                  out.write(f"| {measurement} | {slope} | {ratio} |\n")
          PY

      - uses: actions/upload-artifact@v7
        if: always()
        with:
          name: performance-results
          path: performance-results.json
          if-no-files-found: warn