From fe7b917365a7992c3de3702d18fb1079170edee0 Mon Sep 17 00:00:00 2001
From: Michael Maxwell <micmax@microsoft.com>
Date: Thu, 3 Feb 2022 16:06:06 -0800
Subject: [PATCH] Histogram Record Method Benchmark (#2754)

---
 src/OpenTelemetry/CHANGELOG.md                |   2 +-
 .../Benchmarks/Metrics/HistogramBenchmarks.cs | 110 ++++++++++++++++++
 2 files changed, 111 insertions(+), 1 deletion(-)
 create mode 100644 test/Benchmarks/Metrics/HistogramBenchmarks.cs

diff --git a/src/OpenTelemetry/CHANGELOG.md b/src/OpenTelemetry/CHANGELOG.md
index e2c05734c6e..17e717053cb 100644
--- a/src/OpenTelemetry/CHANGELOG.md
+++ b/src/OpenTelemetry/CHANGELOG.md
@@ -26,7 +26,7 @@ Released 2021-Nov-29
 
 * Prevent accessing activity Id before sampler runs in case of legacy
   activities.
-  ([2659](https://github.com/open-telemetry/opentelemetry-dotnet/pull/2659))
+  ([#2659](https://github.com/open-telemetry/opentelemetry-dotnet/pull/2659))
 
 * Added `ReadOnlyTagCollection` and expose `Tags` on `MetricPoint` instead of
   `Keys`+`Values`
diff --git a/test/Benchmarks/Metrics/HistogramBenchmarks.cs b/test/Benchmarks/Metrics/HistogramBenchmarks.cs
new file mode 100644
index 00000000000..aff46b76686
--- /dev/null
+++ b/test/Benchmarks/Metrics/HistogramBenchmarks.cs
@@ -0,0 +1,110 @@
+// <copyright file="HistogramBenchmarks.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.Metrics;
+using System.Threading;
+using BenchmarkDotNet.Attributes;
+using OpenTelemetry;
+using OpenTelemetry.Exporter;
+using OpenTelemetry.Metrics;
+using OpenTelemetry.Tests;
+
+/*
+BenchmarkDotNet=v0.13.1, OS=Windows 10.0.19044.1503 (21H2)
+AMD Ryzen 9 3900X, 1 CPU, 24 logical and 12 physical cores
+.NET SDK=6.0.101
+  [Host]     : .NET 6.0.1 (6.0.121.56705), X64 RyuJIT
+  DefaultJob : .NET 6.0.1 (6.0.121.56705), X64 RyuJIT
+
+
+|                 Method | BoundCount |     Mean |    Error |   StdDev | Allocated |
+|----------------------- |----------- |---------:|---------:|---------:|----------:|
+|   HistogramLongHotPath |         10 | 55.44 ns | 0.211 ns | 0.187 ns |         - |
+| HistogramDoubleHotPath |         10 | 55.69 ns | 0.129 ns | 0.107 ns |         - |
+|   HistogramLongHotPath |         20 | 57.71 ns | 0.297 ns | 0.278 ns |         - |
+| HistogramDoubleHotPath |         20 | 58.10 ns | 0.117 ns | 0.110 ns |         - |
+|   HistogramLongHotPath |         50 | 65.21 ns | 0.356 ns | 0.333 ns |         - |
+| HistogramDoubleHotPath |         50 | 66.34 ns | 0.381 ns | 0.356 ns |         - |
+|   HistogramLongHotPath |        100 | 79.49 ns | 0.804 ns | 0.753 ns |         - |
+| HistogramDoubleHotPath |        100 | 85.77 ns | 0.947 ns | 0.840 ns |         - |
+*/
+
+namespace Benchmarks.Metrics
+{
+    [MemoryDiagnoser]
+    public class HistogramBenchmarks
+    {
+        private const int MaxValue = 1000;
+        private static readonly ThreadLocal<Random> ThreadLocalRandom = new(() => new Random());
+        private Histogram<long> histogramLong;
+        private Histogram<double> histogramDouble;
+        private MeterProvider provider;
+        private Meter meter;
+        private double[] bounds;
+
+        [Params(10, 20, 50, 100)]
+        public int BoundCount { get; set; }
+
+        [GlobalSetup]
+        public void Setup()
+        {
+            this.meter = new Meter(Utils.GetCurrentMethodName());
+
+            this.histogramLong = this.meter.CreateHistogram<long>("histogramLong");
+            this.histogramDouble = this.meter.CreateHistogram<double>("histogramDouble");
+
+            // Evenly distribute the bound values over the range [0, MaxValue)
+            this.bounds = new double[this.BoundCount];
+            for (int i = 0; i < this.bounds.Length; i++)
+            {
+                this.bounds[i] = i * MaxValue / this.bounds.Length;
+            }
+
+            var exportedItems = new List<Metric>();
+            var reader = new PeriodicExportingMetricReader(new InMemoryExporter<Metric>(exportedItems), 1000);
+
+            this.provider = Sdk.CreateMeterProviderBuilder()
+                .AddMeter(this.meter.Name)
+                .AddReader(reader)
+                .AddView(this.histogramLong.Name, new ExplicitBucketHistogramConfiguration() { Boundaries = this.bounds })
+                .AddView(this.histogramDouble.Name, new ExplicitBucketHistogramConfiguration() { Boundaries = this.bounds })
+                .Build();
+        }
+
+        [GlobalCleanup]
+        public void Cleanup()
+        {
+            this.meter?.Dispose();
+            this.provider?.Dispose();
+        }
+
+        [Benchmark]
+        public void HistogramLongHotPath()
+        {
+            var random = ThreadLocalRandom.Value;
+            this.histogramLong?.Record(random.Next(MaxValue));
+        }
+
+        [Benchmark]
+        public void HistogramDoubleHotPath()
+        {
+            var random = ThreadLocalRandom.Value;
+            this.histogramDouble?.Record(random.NextDouble() * MaxValue);
+        }
+    }
+}