Exponential histogram benchmarks (#4332)

test/Benchmarks/Metrics/ExponentialHistogramBenchmarks.cs

@@ -0,0 +1,90 @@
+// <copyright file="ExponentialHistogramBenchmarks.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.Diagnostics.Metrics;
+using BenchmarkDotNet.Attributes;
+using OpenTelemetry;
+using OpenTelemetry.Metrics;
+using OpenTelemetry.Tests;
+
+/*
+BenchmarkDotNet=v0.13.5, OS=macOS Ventura 13.4 (22F66) [Darwin 22.5.0]
+Apple M1 Max, 1 CPU, 10 logical and 10 physical cores
+.NET SDK=7.0.101
+  [Host]     : .NET 7.0.1 (7.0.122.56804), Arm64 RyuJIT AdvSIMD
+  DefaultJob : .NET 7.0.1 (7.0.122.56804), Arm64 RyuJIT AdvSIMD
+
+
+|           Method | Scale |     Mean |    Error |   StdDev | Allocated |
+|----------------- |------ |---------:|---------:|---------:|----------:|
+| HistogramHotPath |   -11 | 29.79 ns | 0.054 ns | 0.042 ns |         - |
+| HistogramHotPath |     3 | 32.10 ns | 0.086 ns | 0.080 ns |         - |
+| HistogramHotPath |    20 | 32.08 ns | 0.076 ns | 0.063 ns |         - |
+*/
+
+namespace Benchmarks.Metrics;
+
+public class ExponentialHistogramBenchmarks
+{
+    private const int MaxValue = 10000;
+    private readonly Random random = new();
+    private Histogram<long> histogram;
+    private MeterProvider provider;
+    private Meter meter;
+
+    // This is a simple benchmark that records values in the range [0, 10000].
+    // The reason the following scales are benchmarked are as follows:
+    //
+    // -11: Non-positive scales should perform better than positive scales.
+    //      The algorithm to map values to buckets for non-positive scales is more efficient.
+    //   3: The benchmark records values in the range [0, 10000] and uses the default max number of buckets (160).
+    //      Scale 3 is the maximum scale that will fit this range of values given the number of buckets.
+    //      That is, no scale down will occur.
+    //  20: Scale 20 should perform the same as scale 3. During warmup the histogram should scale down to 3.
+    [Params(-11, 3, 20)]
+    public int Scale { get; set; }
+
+    [GlobalSetup]
+    public void Setup()
+    {
+        this.meter = new Meter(Utils.GetCurrentMethodName());
+        this.histogram = this.meter.CreateHistogram<long>("histogram");
+
+        var exportedItems = new List<Metric>();
+
+        this.provider = Sdk.CreateMeterProviderBuilder()
+            .AddMeter(this.meter.Name)
+            .AddInMemoryExporter(exportedItems, metricReaderOptions =>
+            {
+                metricReaderOptions.PeriodicExportingMetricReaderOptions.ExportIntervalMilliseconds = 1000;
+            })
+            .AddView("histogram", new Base2ExponentialBucketHistogramConfiguration() { MaxScale = this.Scale, MaxSize = Metric.DefaultExponentialHistogramMaxBuckets })
+            .Build();
+    }
+
+    [GlobalCleanup]
+    public void Cleanup()
+    {
+        this.meter?.Dispose();
+        this.provider?.Dispose();
+    }
+
+    [Benchmark]
+    public void HistogramHotPath()
+    {
+        this.histogram.Record(this.random.Next(MaxValue));
+    }
+}

test/Benchmarks/Metrics/ExponentialHistogramMapToIndexBenchmarks.cs

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+// <copyright file="ExponentialHistogramMapToIndexBenchmarks.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 BenchmarkDotNet.Attributes;
+using OpenTelemetry.Metrics;
+
+/*
+BenchmarkDotNet=v0.13.5, OS=macOS Ventura 13.4 (22F66) [Darwin 22.5.0]
+Apple M1 Max, 1 CPU, 10 logical and 10 physical cores
+.NET SDK=7.0.101
+  [Host]     : .NET 7.0.1 (7.0.122.56804), Arm64 RyuJIT AdvSIMD
+  DefaultJob : .NET 7.0.1 (7.0.122.56804), Arm64 RyuJIT AdvSIMD
+
+
+|     Method | Scale |     Mean |    Error |   StdDev | Allocated |
+|----------- |------ |---------:|---------:|---------:|----------:|
+| MapToIndex |   -11 | 11.60 ns | 0.057 ns | 0.053 ns |         - |
+| MapToIndex |     3 | 14.63 ns | 0.135 ns | 0.126 ns |         - |
+| MapToIndex |    20 | 14.40 ns | 0.026 ns | 0.024 ns |         - |
+*/
+
+namespace Benchmarks.Metrics;
+
+public class ExponentialHistogramMapToIndexBenchmarks
+{
+    private const int MaxValue = 10000;
+    private readonly Random random = new();
+    private Base2ExponentialBucketHistogram exponentialHistogram;
+
+    [Params(-11, 3, 20)]
+    public int Scale { get; set; }
+
+    [GlobalSetup]
+    public void Setup()
+    {
+        this.exponentialHistogram = new Base2ExponentialBucketHistogram(scale: this.Scale);
+    }
+
+    [Benchmark]
+    public void MapToIndex()
+    {
+        this.exponentialHistogram.MapToIndex(this.random.Next(MaxValue));
+    }
+}