gosentry/docs/PERFORMANCE.md

Performance Notes

Measured performance findings for GoSentry. Each entry records the method so the numbers can be reproduced and re-checked after relevant changes.

Startup Time

Finding (2026-06-22)

After the Phase 4 refactor, cold startup time (the History "Window shown in …" metric) increased by ~290 ms. The increase is caused entirely by the Fyne v2.5.3 → v2.6.3 upgrade (task T4.1), not by the Service / domain / UI restructuring.

Method

Env-gated phase timers (GOSENTRY_TIMING) were added across the startup path (Run in src/ui/run.go and newMainView in src/ui/mainwindow.go) and the equivalent points in the pre-refactor entry point (src/gui/app.go at commit c5e0ef9, the last commit before T4.1). Both were built with the CGO / MSYS2 UCRT64 toolchain and run 5× each; the first run of each is a cold-disk outlier and is excluded. The timed span (started → w.Show()) is identical in both builds, so the comparison is fair.

Results (warm-run averages)

Phase (cumulative from start)	Old (Fyne 2.5.3)	New (Fyne 2.6.3)	Δ
after single-instance check	~0.5 ms	~0.6 ms	—
after Fyne app + window + tray	~277 ms	~285 ms	+8 ms
app.Open() done	+3 ms	+3 ms	0
views built + svc.Start()	+42 ms	+43 ms	~0
after SetContent	~348 ms	~353 ms	+5 ms
after w.Show() (TOTAL)	~348 ms	~644 ms	+~290 ms

Interpretation

• Everything up to and including SetContent costs the same in both versions (~350 ms). The refactor-specific code — app.Open() (~3 ms) and the new app.Service plus view construction (~42 ms) — is unchanged, so the restructuring added no measurable startup cost.
• The entire regression lands in w.Show(): ~0 ms under Fyne 2.5.3, ~290 ms under 2.6.3. Fyne 2.6 reworked main-thread marshaling (the change that introduced fyne.Do) and front-loads first-window GL/driver realization into the Show() call.
• The cost is a fixed, one-time Fyne expense, not a leak in GoSentry code, and the upgrade cannot be reverted because fyne.Do requires Fyne ≥ 2.6.
• The tray / autostart path (--start-in-tray) skips w.Show() until the user opens the window, so it is unaffected.

Next check

Re-measure with the same method after the planned Fyne 2.6.3 → 2.7.x upgrade (see ROADMAP.md → Tray Interaction). The goal is to learn whether 2.7's driver/threading changes recover any of the ~290 ms w.Show() cost or hold it steady. Reuse the GOSENTRY_TIMING instrumentation pattern above; do not commit the temporary timers.