1 files changed, 160 insertions, 0 deletions
diff --git a/benches/shared.rs b/benches/shared.rs
new file mode 100644
index 0000000..56508c4
--- /dev/null
+++ b/benches/shared.rs
@@ -0,0 +1,160 @@
+#![allow(dead_code)]
+use criterion::{black_box, measurement::WallTime, Bencher};
+use tracing::{field, span, Event, Id, Metadata};
+
+use std::{
+    fmt::{self, Write},
+    sync::{Mutex, MutexGuard},
+};
+
+pub fn for_all_recording(
+    group: &mut criterion::BenchmarkGroup<'_, WallTime>,
+    mut iter: impl FnMut(&mut Bencher<'_, WallTime>),
+) {
+    // first, run benchmarks with no subscriber
+    group.bench_function("none", &mut iter);
+
+    // then, run benchmarks with a scoped default subscriber
+    tracing::subscriber::with_default(EnabledSubscriber, || {
+        group.bench_function("scoped", &mut iter)
+    });
+
+    let subscriber = VisitingSubscriber(Mutex::new(String::from("")));
+    tracing::subscriber::with_default(subscriber, || {
+        group.bench_function("scoped_recording", &mut iter);
+    });
+
+    // finally, set a global default subscriber, and run the benchmarks again.
+    tracing::subscriber::set_global_default(EnabledSubscriber)
+        .expect("global default should not have already been set!");
+    let _ = log::set_logger(&NOP_LOGGER);
+    log::set_max_level(log::LevelFilter::Trace);
+    group.bench_function("global", &mut iter);
+}
+
+pub fn for_all_dispatches(
+    group: &mut criterion::BenchmarkGroup<'_, WallTime>,
+    mut iter: impl FnMut(&mut Bencher<'_, WallTime>),
+) {
+    // first, run benchmarks with no subscriber
+    group.bench_function("none", &mut iter);
+
+    // then, run benchmarks with a scoped default subscriber
+    tracing::subscriber::with_default(EnabledSubscriber, || {
+        group.bench_function("scoped", &mut iter)
+    });
+
+    // finally, set a global default subscriber, and run the benchmarks again.
+    tracing::subscriber::set_global_default(EnabledSubscriber)
+        .expect("global default should not have already been set!");
+    let _ = log::set_logger(&NOP_LOGGER);
+    log::set_max_level(log::LevelFilter::Trace);
+    group.bench_function("global", &mut iter);
+}
+
+const NOP_LOGGER: NopLogger = NopLogger;
+
+struct NopLogger;
+
+impl log::Log for NopLogger {
+    fn enabled(&self, _metadata: &log::Metadata) -> bool {
+        true
+    }
+
+    fn log(&self, record: &log::Record) {
+        if self.enabled(record.metadata()) {
+            let mut this = self;
+            let _ = write!(this, "{}", record.args());
+        }
+    }
+
+    fn flush(&self) {}
+}
+
+impl Write for &NopLogger {
+    fn write_str(&mut self, s: &str) -> std::fmt::Result {
+        black_box(s);
+        Ok(())
+    }
+}
+
+/// Simulates a subscriber that records span data.
+struct VisitingSubscriber(Mutex<String>);
+
+struct Visitor<'a>(MutexGuard<'a, String>);
+
+impl<'a> field::Visit for Visitor<'a> {
+    fn record_debug(&mut self, _field: &field::Field, value: &dyn fmt::Debug) {
+        let _ = write!(&mut *self.0, "{:?}", value);
+    }
+}
+
+impl tracing::Subscriber for VisitingSubscriber {
+    fn new_span(&self, span: &span::Attributes<'_>) -> Id {
+        let mut visitor = Visitor(self.0.lock().unwrap());
+        span.record(&mut visitor);
+        Id::from_u64(0xDEAD_FACE)
+    }
+
+    fn record(&self, _span: &Id, values: &span::Record<'_>) {
+        let mut visitor = Visitor(self.0.lock().unwrap());
+        values.record(&mut visitor);
+    }
+
+    fn event(&self, event: &Event<'_>) {
+        let mut visitor = Visitor(self.0.lock().unwrap());
+        event.record(&mut visitor);
+    }
+
+    fn record_follows_from(&self, span: &Id, follows: &Id) {
+        let _ = (span, follows);
+    }
+
+    fn enabled(&self, metadata: &Metadata<'_>) -> bool {
+        let _ = metadata;
+        true
+    }
+
+    fn enter(&self, span: &Id) {
+        let _ = span;
+    }
+
+    fn exit(&self, span: &Id) {
+        let _ = span;
+    }
+}
+
+/// A subscriber that is enabled but otherwise does nothing.
+struct EnabledSubscriber;
+
+impl tracing::Subscriber for EnabledSubscriber {
+    fn new_span(&self, span: &span::Attributes<'_>) -> Id {
+        let _ = span;
+        Id::from_u64(0xDEAD_FACE)
+    }
+
+    fn event(&self, event: &Event<'_>) {
+        let _ = event;
+    }
+
+    fn record(&self, span: &Id, values: &span::Record<'_>) {
+        let _ = (span, values);
+    }
+
+    fn record_follows_from(&self, span: &Id, follows: &Id) {
+        let _ = (span, follows);
+    }
+
+    fn enabled(&self, metadata: &Metadata<'_>) -> bool {
+        let _ = metadata;
+        true
+    }
+
+    fn enter(&self, span: &Id) {
+        let _ = span;
+    }
+
+    fn exit(&self, span: &Id) {
+        let _ = span;
+    }
+}