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| 1 | +# Performance benchmarking |
| 2 | + |
| 3 | +The S36 perf-pass ships a small in-repo benchmark harness so perf |
| 4 | +regressions are visible in PR review, not discovered in production. |
| 5 | + |
| 6 | +## Targets (warm cache, MVP hardware) |
| 7 | + |
| 8 | +The S36 spec defines: |
| 9 | + |
| 10 | +- Tree of root on 100k-file repo: < 200ms p95 |
| 11 | +- Blame on 10k-line file: < 500ms p95 |
| 12 | +- Commits list page on 1M-commit repo: < 250ms p95 |
| 13 | +- Issue list (state filter) on 100k issues: < 200ms p95 |
| 14 | +- Notifications inbox first page: < 150ms p95 |
| 15 | + |
| 16 | +These targets assume the big-fixture generators land. Until they |
| 17 | +do, `make bench-small` runs against the dev seed and serves as a |
| 18 | +floor regression detector for the harness itself + handler latency |
| 19 | +on the small dataset. |
| 20 | + |
| 21 | +## Running |
| 22 | + |
| 23 | +```sh |
| 24 | +# Defaults: target=http://localhost:8080, iters=20. |
| 25 | +make bench-small |
| 26 | + |
| 27 | +# Pin a different target / iteration count. |
| 28 | +BENCH_TARGET=http://staging.shithub.example BENCH_ITERS=100 make bench-small |
| 29 | +``` |
| 30 | + |
| 31 | +Output is one JSON line per scenario: |
| 32 | + |
| 33 | +```json |
| 34 | +{"scenario":"home","iters":20,"ok_count":20,"p50_us":432,"p95_us":5692,"p99_us":5692,"max_us":5692,"mean_us":693.15} |
| 35 | +``` |
| 36 | + |
| 37 | +`ok_count == 0` for a scenario means every probe missed the |
| 38 | +expected status (typically: the dev seed doesn't have the repo the |
| 39 | +scenario targets). The harness keeps running and reports zeros so |
| 40 | +the suite doesn't bail mid-run. |
| 41 | + |
| 42 | +## Adding scenarios |
| 43 | + |
| 44 | +Append to `bench/run.go::main`'s `scenarios` slice: |
| 45 | + |
| 46 | +```go |
| 47 | +{"my-scenario", "GET", "/some/path", 200}, |
| 48 | +``` |
| 49 | + |
| 50 | +Scenarios are intentionally URL-shape probes, not deep state |
| 51 | +manipulators. If a scenario needs a logged-in user or a specific |
| 52 | +repo state, prefer staging via `make seed` over making the |
| 53 | +harness write its own state. |
| 54 | + |
| 55 | +## N+1 query auditing |
| 56 | + |
| 57 | +Wire a route's integration test to assert max-queries: |
| 58 | + |
| 59 | +```go |
| 60 | +import "github.com/tenseleyFlow/shithub/internal/web/middleware" |
| 61 | + |
| 62 | +r.Use(middleware.CountQueries()) |
| 63 | +// ... drive a request through r ... |
| 64 | +if got := middleware.QueriesFor(req); got > 8 { |
| 65 | + t.Fatalf("issuesList ran %d queries; threshold 8", got) |
| 66 | +} |
| 67 | +``` |
| 68 | + |
| 69 | +The pgx tracer (`internal/infra/db.QueryCounter`) increments a |
| 70 | +per-context counter on every Query/QueryRow/Exec; the middleware |
| 71 | +opts the request context in. Production paths pay one |
| 72 | +context.WithValue per request — cheap, but the assertion only |
| 73 | +fires in tests. |
| 74 | + |
| 75 | +## Big-fixture plan (deferred) |
| 76 | + |
| 77 | +`bench/fixtures/README.md` documents the planned generators for |
| 78 | +the 1M-commit / 100k-file / 100k-issue / 5k-member-org fixtures. |
| 79 | +They aren't generated yet — the seed cost is non-trivial and the |
| 80 | +small dev seed is sufficient as a floor regression detector while |
| 81 | +the perf surface is still settling. When the generators land, |
| 82 | +`make bench-full` (currently a stub) hooks them up. |
| 83 | + |
| 84 | +## Profile dumps |
| 85 | + |
| 86 | +`bench/profiles/` is the canonical home for `pprof` captures |
| 87 | +referenced by the perf docs. The S36 spec asks for profile dumps |
| 88 | +for the slowest scenarios; until the big fixtures land, the |
| 89 | +captures are dev-machine pprof of `make bench-small` and aren't |
| 90 | +checked in by default. |
