Add spawn bench

Cargo.toml

@@ -49,9 +49,14 @@ wepoll-binding = "2.0.0"
 [dev-dependencies]
 num_cpus = "1.13.0"
 tempfile = "3.1.0"
+criterion = "0.3"
 
 [workspace]
 members = [
   ".",
   "examples",
 ]
+
+[[bench]]
+name = "spawn"
+harness = false

benches/spawn.rs

@@ -0,0 +1,21 @@
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use futures::future;
+use smol::Task;
+
+pub fn spawn_benchmark(c: &mut Criterion) {
+    std::thread::spawn(|| smol::run(future::pending::<()>()));
+    c.bench_function("spawn time", |b| {
+        b.iter(|| {
+            let x = black_box(5);
+            smol::block_on(async {
+                Task::spawn(async move {
+                    let _ = x + 1;
+                })
+                .await;
+            });
+        })
+    });
+}
+
+criterion_group!(benches, spawn_benchmark);
+criterion_main!(benches);