diff --git a/benchmark_test.go b/benchmark_test.go
new file mode 100644
index 0000000..131a08d
--- /dev/null
+++ b/benchmark_test.go
@@ -0,0 +1,72 @@
+// Copyright 2019, LightStep Inc.
+//
+// The benchmark results point to a performance drop when the
+// largeHeap starts to be used because of interface conversions in and
+// out of the heap, primarily due to the heap interface.  This
+// suggests room for improvement by avoiding the built-in heap.
+
+/*
+BenchmarkAdd_Norm_100-8       	37540165	        32.1 ns/op	       8 B/op	       0 allocs/op
+BenchmarkAdd_Norm_10000-8     	39850280	        30.6 ns/op	       8 B/op	       0 allocs/op
+BenchmarkAdd_Norm_1000000-8   	 7958835	       183 ns/op	      52 B/op	       0 allocs/op
+BenchmarkAdd_Exp_100-8        	41565934	        28.5 ns/op	       8 B/op	       0 allocs/op
+BenchmarkAdd_Exp_10000-8      	43622184	        29.2 ns/op	       8 B/op	       0 allocs/op
+BenchmarkAdd_Exp_1000000-8    	 8103663	       220 ns/op	      55 B/op	       0 allocs/op
+*/
+
+package varopt_test
+
+import (
+	"math"
+	"math/rand"
+	"testing"
+
+	"github.com/lightstep/varopt"
+)
+
+func normValue(rnd *rand.Rand) float64 {
+	return 1 + math.Abs(rnd.NormFloat64())
+}
+
+func expValue(rnd *rand.Rand) float64 {
+	return rnd.ExpFloat64()
+}
+
+func BenchmarkAdd_Norm_100(b *testing.B) {
+	benchmarkAdd(b, 100, normValue)
+}
+
+func BenchmarkAdd_Norm_10000(b *testing.B) {
+	benchmarkAdd(b, 10000, normValue)
+}
+
+func BenchmarkAdd_Norm_1000000(b *testing.B) {
+	benchmarkAdd(b, 1000000, normValue)
+}
+
+func BenchmarkAdd_Exp_100(b *testing.B) {
+	benchmarkAdd(b, 100, expValue)
+}
+
+func BenchmarkAdd_Exp_10000(b *testing.B) {
+	benchmarkAdd(b, 10000, expValue)
+}
+
+func BenchmarkAdd_Exp_1000000(b *testing.B) {
+	benchmarkAdd(b, 1000000, expValue)
+}
+
+func benchmarkAdd(b *testing.B, size int, f func(rnd *rand.Rand) float64) {
+	b.ReportAllocs()
+	rnd := rand.New(rand.NewSource(3331))
+	v := varopt.New(size, rnd)
+	weights := make([]float64, b.N)
+	for i := 0; i < b.N; i++ {
+		weights[i] = f(rnd)
+	}
+
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		v.Add(nil, weights[i])
+	}
+}