3 files changed, 34 insertions, 0 deletions
diff --git a/cli/js/40_testing.js b/cli/js/40_testing.js
index 3058fcee3..740e950a3 100644
--- a/cli/js/40_testing.js
+++ b/cli/js/40_testing.js
@@ -685,6 +685,8 @@ function test(
   });
 }
 
+let registeredWarmupBench = false;
+
 // Main bench function provided by Deno.
 function bench(
   nameOrFnOrOptions,
@@ -695,6 +697,25 @@ function bench(
     return;
   }
 
+  if (!registeredWarmupBench) {
+    registeredWarmupBench = true;
+    const warmupBenchDesc = {
+      name: "<warmup>",
+      fn: function warmup() {},
+      async: false,
+      ignore: false,
+      baseline: false,
+      only: false,
+      sanitizeExit: true,
+      permissions: null,
+      warmup: true,
+    };
+    warmupBenchDesc.fn = wrapBenchmark(warmupBenchDesc);
+    const { id, origin } = ops.op_register_bench(warmupBenchDesc);
+    warmupBenchDesc.id = id;
+    warmupBenchDesc.origin = origin;
+  }
+
   let benchDesc;
   const defaults = {
     ignore: false,
@@ -777,6 +798,7 @@ function bench(
   const AsyncFunction = (async () => {}).constructor;
   benchDesc.async = AsyncFunction === benchDesc.fn.constructor;
   benchDesc.fn = wrapBenchmark(benchDesc);
+  benchDesc.warmup = false;
 
   const { id, origin } = ops.op_register_bench(benchDesc);
   benchDesc.id = id;
diff --git a/cli/ops/bench.rs b/cli/ops/bench.rs
index f569a8cbb..0f7509751 100644
--- a/cli/ops/bench.rs
+++ b/cli/ops/bench.rs
@@ -101,6 +101,8 @@ struct BenchInfo<'s> {
   group: Option<String>,
   ignore: bool,
   only: bool,
+  #[serde(default)]
+  warmup: bool,
 }
 
 #[derive(Debug, Serialize)]
@@ -128,6 +130,7 @@ fn op_register_bench<'a>(
     group: info.group,
     ignore: info.ignore,
     only: info.only,
+    warmup: info.warmup,
   };
   let function: v8::Local<v8::Function> = info.function.v8_value.try_into()?;
   let function = v8::Global::new(scope, function);
diff --git a/cli/tools/bench.rs b/cli/tools/bench.rs
index f926cec5a..fd686a938 100644
--- a/cli/tools/bench.rs
+++ b/cli/tools/bench.rs
@@ -95,6 +95,7 @@ pub struct BenchDescription {
   pub group: Option<String>,
   pub ignore: bool,
   pub only: bool,
+  pub warmup: bool,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -194,6 +195,10 @@ impl BenchReporter for JsonReporter {
   fn report_output(&mut self, _output: &str) {}
 
   fn report_result(&mut self, desc: &BenchDescription, result: &BenchResult) {
+    if desc.warmup {
+      return;
+    }
+
     let maybe_bench = self.0.benches.iter_mut().find(|bench| {
       bench.origin == desc.origin
         && bench.group == desc.group
@@ -326,6 +331,10 @@ impl BenchReporter for ConsoleReporter {
   }
 
   fn report_result(&mut self, desc: &BenchDescription, result: &BenchResult) {
+    if desc.warmup {
+      return;
+    }
+
     let options = self.options.as_ref().unwrap();
 
     match result {