atagen

monolith

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Commit 53111dd60132

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atagen <boss@atagen.co>2026-10-17 03:48 UTC

2 files changed+22-6
monolith: make the slow span threshold configurable

A 3.4 ms CPU-bound render had no single span over 1 ms, so the existing threshold could not say where the time went. MONOLITH_SLOW_SPAN_US lowers it for a run.
crates/monolith/src/main.rs+6−3
@@ -117,13 +117,16 @@ fn main() -> ExitCode {
117117 .with_ansi(std::io::IsTerminal::is_terminal(&std::io::stderr()))
118118 .with_filter(filter);
119119 #[cfg(feature = "spans")]
120- let spans =
121- Some(slow_spans::SlowSpans.with_filter(tracing_subscriber::filter::LevelFilter::TRACE));
120+ let slow = slow_spans::SlowSpans::from_env();
121+ #[cfg(feature = "spans")]
122+ let threshold_us = slow.threshold_us;
123+ #[cfg(feature = "spans")]
124+ let spans = Some(slow.with_filter(tracing_subscriber::filter::LevelFilter::TRACE));
122125 #[cfg(not(feature = "spans"))]
123126 let spans: Option<tracing_subscriber::layer::Identity> = None;
124127 tracing_subscriber::registry().with(fmt).with(spans).init();
125128 #[cfg(feature = "spans")]
126- tracing::info!("logging spans slower than 1 ms");
129+ tracing::info!("logging spans slower than {threshold_us} us");
127130 let backend = match backend {
128131 Backend::Auto if std::env::var_os("WAYLAND_DISPLAY").is_some() => Backend::Nested,
129132 Backend::Auto => Backend::Drm,
crates/monolith/src/slow_spans.rs+16−3
@@ -1,5 +1,6 @@
11 //! Prints every span that runs for a millisecond or more, for finding what
2-//! makes a frame late. Built only with the `spans` feature.
2+//! makes a frame late. `MONOLITH_SLOW_SPAN_US` lowers the bar when the slow
3+//! part is many small spans. Built only with the `spans` feature.
34
45 use std::time::Instant;
56 use tracing::span;
@@ -7,7 +8,19 @@ use tracing_subscriber::Layer;
78 use tracing_subscriber::layer::Context;
89 use tracing_subscriber::registry::LookupSpan;
910
10-pub struct SlowSpans;
11+pub struct SlowSpans {
12+ pub threshold_us: u128,
13+}
14+
15+impl SlowSpans {
16+ pub fn from_env() -> Self {
17+ let threshold_us = std::env::var("MONOLITH_SLOW_SPAN_US")
18+ .ok()
19+ .and_then(|v| v.parse().ok())
20+ .unwrap_or(1000);
21+ Self { threshold_us }
22+ }
23+}
1124
1225 struct Entered(Instant);
1326
@@ -27,7 +40,7 @@ where
2740 return;
2841 };
2942 let took = at.elapsed();
30- if took.as_micros() >= 1000 {
43+ if took.as_micros() >= self.threshold_us {
3144 let path: Vec<&str> = span.scope().from_root().map(|s| s.name()).collect();
3245 eprintln!("slow span {} took_us={}", path.join(">"), took.as_micros());
3346 }