From 85470dbc2e9792a9c7bb6eadd540b99b36189b44 Mon Sep 17 00:00:00 2001
From: Fabrice Vaillant <fa.vaillant+github@gmail.com>
Date: Wed, 26 Jun 2024 11:40:55 +0200
Subject: [PATCH] Reduces allocation in attributes

---
 CHANGELOG.md                         |  1 +
 internal/attribute/attribute.go      | 24 ++++++++---------
 internal/attribute/attribute_test.go | 39 ++++++++++++++++++++++++++++
 3 files changed, 52 insertions(+), 12 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 41609fae5f5a..57b7288fe98d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -32,6 +32,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Fixed
 
+- Improved performance in all `{Bool,Int64,Float64,String}SliceValue` function of `go.opentelemetry.io/attributes` by reducing the number of allocations. (#5549)
 - Retry trace and span ID generation if it generated an invalid one in `go.opentelemetry.io/otel/sdk/trace`. (#5514)
 - Log a warning to the OpenTelemetry internal logger when a `Record` in `go.opentelemetry.io/otel/sdk/log` drops an attribute due to a limit being reached. (#5376)
 - Identify the `Tracer` returned from the global `TracerProvider` in `go.opentelemetry.io/otel/global` with its schema URL. (#5426)
diff --git a/internal/attribute/attribute.go b/internal/attribute/attribute.go
index f32766e57f66..822d84794741 100644
--- a/internal/attribute/attribute.go
+++ b/internal/attribute/attribute.go
@@ -14,33 +14,33 @@ import (
 // BoolSliceValue converts a bool slice into an array with same elements as slice.
 func BoolSliceValue(v []bool) interface{} {
 	var zero bool
-	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero)))
-	copy(cp.Elem().Slice(0, len(v)).Interface().([]bool), v)
-	return cp.Elem().Interface()
+	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero))).Elem()
+	reflect.Copy(cp, reflect.ValueOf(v))
+	return cp.Interface()
 }
 
 // Int64SliceValue converts an int64 slice into an array with same elements as slice.
 func Int64SliceValue(v []int64) interface{} {
 	var zero int64
-	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero)))
-	copy(cp.Elem().Slice(0, len(v)).Interface().([]int64), v)
-	return cp.Elem().Interface()
+	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero))).Elem()
+	reflect.Copy(cp, reflect.ValueOf(v))
+	return cp.Interface()
 }
 
 // Float64SliceValue converts a float64 slice into an array with same elements as slice.
 func Float64SliceValue(v []float64) interface{} {
 	var zero float64
-	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero)))
-	copy(cp.Elem().Slice(0, len(v)).Interface().([]float64), v)
-	return cp.Elem().Interface()
+	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero))).Elem()
+	reflect.Copy(cp, reflect.ValueOf(v))
+	return cp.Interface()
 }
 
 // StringSliceValue converts a string slice into an array with same elements as slice.
 func StringSliceValue(v []string) interface{} {
 	var zero string
-	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero)))
-	copy(cp.Elem().Slice(0, len(v)).Interface().([]string), v)
-	return cp.Elem().Interface()
+	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero))).Elem()
+	reflect.Copy(cp, reflect.ValueOf(v))
+	return cp.Interface()
 }
 
 // AsBoolSlice converts a bool array into a slice into with same elements as array.
diff --git a/internal/attribute/attribute_test.go b/internal/attribute/attribute_test.go
index 7202700cac15..113b644c80e1 100644
--- a/internal/attribute/attribute_test.go
+++ b/internal/attribute/attribute_test.go
@@ -94,3 +94,42 @@ func TestSliceValue(t *testing.T) {
 		})
 	}
 }
+
+// sync is a global used to ensure the benchmark are not optimized away.
+var sync any
+
+func BenchmarkBoolSliceValue(b *testing.B) {
+	b.ReportAllocs()
+	s := []bool{true, false, true, false}
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		sync = BoolSliceValue(s)
+	}
+}
+
+func BenchmarkInt64SliceValue(b *testing.B) {
+	b.ReportAllocs()
+	s := []int64{1, 2, 3, 4}
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		sync = Int64SliceValue(s)
+	}
+}
+
+func BenchmarkFloat64SliceValue(b *testing.B) {
+	b.ReportAllocs()
+	s := []float64{1.2, 3.4, 5.6, 7.8}
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		sync = Float64SliceValue(s)
+	}
+}
+
+func BenchmarkStringSliceValue(b *testing.B) {
+	b.ReportAllocs()
+	s := []string{"a", "b", "c", "d"}
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		sync = StringSliceValue(s)
+	}
+}