silicera_lab/
calm.rs

1//! Soft environment calm / noise probe (single machine).
2//!
3//! Detects unstable measurement conditions (background load, migration noise)
4//! without privileged counters. Advisory only — never modifies OS power policy.
5
6use serde::{Deserialize, Serialize};
7use silicera::hardware::HardwareInfo;
8use silicera::measure::{MeasurementConfig, MeasurementEngine, Stability};
9use silicera::Result;
10
11/// Calm-check report.
12#[derive(Debug, Clone, Serialize, Deserialize)]
13pub struct CalmCheckReport {
14    /// Host brand.
15    pub host_brand: String,
16    /// Fingerprint.
17    pub fingerprint: Option<String>,
18    /// First campaign stability.
19    pub pass_a: String,
20    /// Second campaign stability.
21    pub pass_b: String,
22    /// Median ns pass A (constant work).
23    pub median_a_ns: f64,
24    /// Median ns pass B.
25    pub median_b_ns: f64,
26    /// Relative drift |A-B|/max(A,B).
27    pub relative_drift: f64,
28    /// Whether the host looks calm enough for specialization.
29    pub calm: bool,
30    /// Recommendation.
31    pub recommendation: String,
32}
33
34/// Run two back-to-back constant workloads; flag drift / instability.
35pub fn run_calm_check(info: &HardwareInfo, iterations: usize) -> Result<CalmCheckReport> {
36    let eng = MeasurementEngine::new(MeasurementConfig {
37        warmup: 5,
38        iterations: iterations.max(20),
39        ..Default::default()
40    });
41    let a = eng.measure(|| {
42        let mut x = 1u64;
43        for i in 0..50_000u64 {
44            x = x.wrapping_mul(1664525).wrapping_add(1013904223).wrapping_add(i);
45        }
46        std::hint::black_box(x);
47    })?;
48    // Brief yield so scheduler noise can appear between passes.
49    std::thread::sleep(std::time::Duration::from_millis(50));
50    let b = eng.measure(|| {
51        let mut x = 1u64;
52        for i in 0..50_000u64 {
53            x = x.wrapping_mul(1664525).wrapping_add(1013904223).wrapping_add(i);
54        }
55        std::hint::black_box(x);
56    })?;
57    let denom = a.median_ns.max(b.median_ns).max(1.0);
58    let relative_drift = (a.median_ns - b.median_ns).abs() / denom;
59    let calm = a.stability != Stability::Unstable
60        && b.stability != Stability::Unstable
61        && relative_drift < 0.15;
62    let recommendation = if calm {
63        "Host looks calm enough for specialization under this soft probe.".into()
64    } else {
65        "MEASUREMENT ENVIRONMENT MAY BE NOISY — close background load, re-run calm-check, \
66         then retrain. Do not trust razor-thin specialization margins."
67            .into()
68    };
69    Ok(CalmCheckReport {
70        host_brand: info.brand.clone(),
71        fingerprint: info.fingerprint.as_ref().map(|f| f.value.clone()),
72        pass_a: a.stability.label().into(),
73        pass_b: b.stability.label().into(),
74        median_a_ns: a.median_ns,
75        median_b_ns: b.median_ns,
76        relative_drift,
77        calm,
78        recommendation,
79    })
80}
silicera_lab/calm.rs

silicera_lab/
calm.rs
