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Add docs/PERFORMANCE.md documenting the post-Phase-4 startup slowdown: the ~290ms increase is entirely Fyne 2.5.3->2.6.3's w.Show() cost, not the Service/domain/UI refactor. Includes the GOSENTRY_TIMING method and warm-run results table so it can be reproduced. Wire the startup re-measurement into the existing Fyne 2.6.3->2.7.x upgrade task in ROADMAP.md so 2.7's effect on w.Show() gets checked. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
58 lines
2.8 KiB
Markdown
58 lines
2.8 KiB
Markdown
# Performance Notes
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Measured performance findings for GoSentry. Each entry records the method so the
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numbers can be reproduced and re-checked after relevant changes.
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## Startup Time
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### Finding (2026-06-22)
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After the Phase 4 refactor, cold startup time (the History "Window shown in …"
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metric) increased by **~290 ms**. The increase is caused entirely by the
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**Fyne v2.5.3 → v2.6.3 upgrade** (task T4.1), **not** by the Service / domain /
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UI restructuring.
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### Method
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Env-gated phase timers (`GOSENTRY_TIMING`) were added across the startup path
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(`Run` in `src/ui/run.go` and `newMainView` in `src/ui/mainwindow.go`) and the
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equivalent points in the pre-refactor entry point (`src/gui/app.go` at commit
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`c5e0ef9`, the last commit before T4.1). Both were built with the CGO / MSYS2
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UCRT64 toolchain and run 5× each; the first run of each is a cold-disk outlier
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and is excluded. The timed span (`started` → `w.Show()`) is identical in both
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builds, so the comparison is fair.
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### Results (warm-run averages)
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| Phase (cumulative from start) | Old (Fyne 2.5.3) | New (Fyne 2.6.3) | Δ |
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|-------------------------------|------------------|------------------|--------|
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| after single-instance check | ~0.5 ms | ~0.6 ms | — |
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| after Fyne app + window + tray | ~277 ms | ~285 ms | +8 ms |
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| `app.Open()` done | +3 ms | +3 ms | 0 |
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| views built + `svc.Start()` | +42 ms | +43 ms | ~0 |
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| after `SetContent` | ~348 ms | ~353 ms | +5 ms |
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| **after `w.Show()` (TOTAL)** | **~348 ms** | **~644 ms** | **+~290 ms** |
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### Interpretation
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- Everything up to and including `SetContent` costs the same in both versions
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(~350 ms). The refactor-specific code — `app.Open()` (~3 ms) and the new
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`app.Service` plus view construction (~42 ms) — is unchanged, so the
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restructuring added no measurable startup cost.
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- The entire regression lands in **`w.Show()`**: ~0 ms under Fyne 2.5.3,
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~290 ms under 2.6.3. Fyne 2.6 reworked main-thread marshaling (the change that
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introduced `fyne.Do`) and front-loads first-window GL/driver realization into
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the `Show()` call.
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- The cost is a fixed, one-time Fyne expense, not a leak in GoSentry code, and
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the upgrade cannot be reverted because `fyne.Do` requires Fyne ≥ 2.6.
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- The tray / autostart path (`--start-in-tray`) skips `w.Show()` until the user
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opens the window, so it is unaffected.
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### Next check
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Re-measure with the same method after the planned **Fyne 2.6.3 → 2.7.x upgrade**
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(see [ROADMAP.md](ROADMAP.md) → Tray Interaction). The goal is to learn whether
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2.7's driver/threading changes recover any of the ~290 ms `w.Show()` cost or
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hold it steady. Reuse the `GOSENTRY_TIMING` instrumentation pattern above; do not
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commit the temporary timers.
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