Varta v0.1.0 — Bench Harness Results

Per-metric measurements captured by the dependency-free varta-bench harness (Session 06). Each row corresponds to one acceptance contract assertion in docs/acceptance/varta-v0-1-0.md.

Host

Field	Value
OS	Darwin 25.4.0 (xnu-12377.101.15) arm64
Hardware	Apple Silicon (Mac, T6050 series)
Rust toolchain	rustc 1.93.1 (01f6ddf75 2026-02-11) — pinned via `rust-toolchain.toml`
Working tree	`epic/varta-v0-1-0--s06-integration-and-bench` clean at run time

Results

Metric	Threshold	Measured	Status	Command
`latency`	p99 < 1 µs	p99 = 916 ns	PASS	`cargo run -p varta-bench --release -- latency`
`cpu-50-agents`	< 0.1 %	0.0552 %	PASS	`cargo run -p varta-bench --release -- cpu-50-agents`
`binary-size`	Δ < 20 KB	Δ = 3 872 B	PASS	`cargo run -p varta-bench --release -- binary-size`

Auxiliary latency metrics (same run): p50 = 584 ns, p99.9 = 1042 ns.

Reproducibility

# Build the workspace once so varta-watch is in target/release.
cargo build --workspace --release

cargo run -p varta-bench --release -- latency
cargo run -p varta-bench --release -- cpu-50-agents       # ~35 s wall
cargo run -p varta-bench --release -- binary-size         # ~5 s wall

cpu-50-agents waits for the daemon to self-exit via --shutdown-after-secs 35 before snapshotting getrusage(RUSAGE_CHILDREN), so the measurement covers the full wall window over which the 50 agent threads emit at 1 Hz. The wall is therefore the dominant cost.

Threshold notes

latency: thresholds are tagged HOST-DEPENDENT in crates/varta-bench/src/main.rs. Apple Silicon laptops show p99 ≈ 900 ns idle. Virtualised CI runners with noisy neighbours can spike — if the bench reports STATUS: WARN with a measured value above 1 µs, the harness is doing its job and a CI gate should classify it as a soft failure (warning, not red).
cpu-50-agents: the daemon is mostly blocked in recvfrom(2) with the 100 ms read timeout. CPU usage scales sublinearly with agent count because the kernel batches wakeups. 0.0552 % of a 35 s wall is ~19 ms of daemon CPU.
binary-size: link-time pulls in Varta::connect, the Frame codec, and the BeatOutcome enum. The diff is dominated by Rust’s standard- library boilerplate for UnixDatagram plus a few KB of generated code for the encoder. The fixture crates use lto = false, codegen-units = 1, opt-level = 3 so size comparisons are stable across runs.

Status

All three contract assertions PASS on the host above. No WARN or FAIL deviations to record for this session.