E2E Latency Benchmarks

The script viiper/_testing/e2e/scripts/lat_bench.go runs (or parses) end‑to‑end input latency benchmarks and produces enriched output (table, markdown, or JSON).

It groups repeated cycles when -count > 1 and uses the single press E2E measurement (E2E-InputDelay) as the 100% baseline.

Output

Column	Meaning
Benchmark	Name of the sub benchmark
Count	Iterations performed (from Go bench output; affected by -benchtime)
ns/op	Nanoseconds per operation (direct Go benchmark figure)
% of Full	Relative to E2E-InputDelay (single press baseline)
Client Share %	Portion attributed to the (go) client write phase (for E2E rows)
Latency Share %	Remainder attributed to transport + virtual device/host stack + tight device polling loop

E2E-PressAndRelease includes both press and release cycles, so it is expected to be ~2× the single press and thus can exceed 100% in % of Full.

Scope / Methodology

• All benchmarks included here are executed against a VIIPER server on the same host (localhost).
  They therefore measure in-process client emission plus local USBIP stack + emulated device processing only.
  Remote/network USBIP attachment will add network RTT and jitter which is intentionally excluded from these baseline figures.
• Benchmarks use a single emulated Xbox360 controller device.
  Other devices might produce slightly different results depending on USB report size and VIIPER-InputState size.
• Benchmarks use a single button press, which is enough as clients/VIIPER always produce a full report of the devices state.

Benchtime Mode

Runs use a fixed-iteration benchtime (e.g. -benchtime=1000x, -benchtime=10000x) rather than time-based (e.g. 2s).

Running

From repository root:

cd testing/e2e
# Single run, 1000 fixed iterations per sub benchmark
go run ./scripts/lat_bench.go -benchtime=1000x -count=1 -format markdown

Results (Arch Linux / SteamDeck Kernel / Steam Deck LCD / Go 1.25+, 10k iterations):

Benchmark	Count	ns/op	% of Full	Client Share %	Latency Share %
1_Go-Client-Write	10000	10668	11.98	100.00	0.00
2_InputDelay-Without-Client	10000	74154	83.25	0.00	100.00
3_E2E-InputDelay	10000	89078	100.00	11.98	88.02
4_E2E-PressAndRelease	10000	184870	207.54	11.54	88.46

Example output (Windows / AMD Ryzen 9 3900X / Go 1.25+, 10k iterations):

Benchmark	Count	ns/op	% of Full	Client Share %	Latency Share %
1_Go-Client-Write	10000	27933	16.60	100.00	0.00
2_InputDelay-Without-Client	10000	133724	79.45	0.00	100.00
3_E2E-InputDelay	10000	168307	100.00	16.60	83.40
4_E2E-PressAndRelease	10000	331439	196.93	16.86	83.14

Variability across repeated measurement runs has been negligible.
Use a larger -count if you want to increase the number of runs.

Notes

• Memory statistics from Go benchmarks are intentionally omitted.
• % of Full falls back to the largest ns/op if the baseline row is missing.
• All benchmarking must run with parallelism 1 in underlying benches.
• Benchmarks use a tight polling loop using SDL3 to detect input state changes on the emulated device.
• Benchmarks must be run without an already running VIIPER server instance.