use benchmark process runtime, not host process runtime when deciding whether allocation quantum side effects should be excluded

Author: adamsitnik

src/BenchmarkDotNet/Diagnosers/MemoryDiagnoser.cs

@@ -36,7 +36,7 @@ public IEnumerable<Metric> ProcessResults(DiagnoserResults diagnoserResults)
             yield return new Metric(GarbageCollectionsMetricDescriptor.Gen0, diagnoserResults.GcStats.Gen0Collections / (double)diagnoserResults.GcStats.TotalOperations * 1000);
             yield return new Metric(GarbageCollectionsMetricDescriptor.Gen1, diagnoserResults.GcStats.Gen1Collections / (double)diagnoserResults.GcStats.TotalOperations * 1000);
             yield return new Metric(GarbageCollectionsMetricDescriptor.Gen2, diagnoserResults.GcStats.Gen2Collections / (double)diagnoserResults.GcStats.TotalOperations * 1000);
-            yield return new Metric(AllocatedMemoryMetricDescriptor.Instance, diagnoserResults.GcStats.BytesAllocatedPerOperation);
+            yield return new Metric(AllocatedMemoryMetricDescriptor.Instance, diagnoserResults.GcStats.GetBytesAllocatedPerOperation(diagnoserResults.BenchmarkCase));
         }
 
         private class AllocatedMemoryMetricDescriptor : IMetricDescriptor

src/BenchmarkDotNet/Engines/GcStats.cs

@@ -2,6 +2,7 @@
 using System.Reflection;
 using BenchmarkDotNet.Jobs;
 using BenchmarkDotNet.Portability;
+using BenchmarkDotNet.Running;
 using JetBrains.Annotations;
 
 namespace BenchmarkDotNet.Engines
@@ -38,19 +39,15 @@ private GcStats(int gen0Collections, int gen1Collections, int gen2Collections, l
 
         public long TotalOperations { get; }
 
-        public long BytesAllocatedPerOperation
+        public long GetBytesAllocatedPerOperation(BenchmarkCase benchmarkCase)
         {
-            get
-            {
-                bool excludeAllocationQuantumSideEffects = !RuntimeInformation.IsNetCore
-                    || RuntimeInformation.GetCurrentRuntime().RuntimeMoniker == RuntimeMoniker.NetCoreApp20; // the issue got fixed for .NET Core 2.0+ https://github.com/dotnet/coreclr/issues/10207
-
-                return GetTotalAllocatedBytes(excludeAllocationQuantumSideEffects) == 0
-                    ? 0
-                    : (long) Math.Round( // let's round it to reduce the side effects of Allocation quantum
-                        (double) GetTotalAllocatedBytes(excludeAllocationQuantumSideEffects) / TotalOperations,
-                        MidpointRounding.ToEven);
-            }
+            bool excludeAllocationQuantumSideEffects = benchmarkCase.GetRuntime().RuntimeMoniker <= RuntimeMoniker.NetCoreApp20; // the issue got fixed for .NET Core 2.0+ https://github.com/dotnet/coreclr/issues/10207
+
+            return GetTotalAllocatedBytes(excludeAllocationQuantumSideEffects) == 0
+                ? 0
+                : (long) Math.Round( // let's round it to reduce the side effects of Allocation quantum
+                    (double) GetTotalAllocatedBytes(excludeAllocationQuantumSideEffects) / TotalOperations,
+                    MidpointRounding.ToEven);
         }
 
         public static GcStats operator +(GcStats left, GcStats right)

src/BenchmarkDotNet/Exporters/Csv/CsvMeasurementsExporter.cs

@@ -69,7 +69,7 @@ private static MeasurementColumn[] GetColumns(Summary summary)
                 new MeasurementColumn("Gen_0", (_, report, __) => report.GcStats.Gen0Collections.ToString(summary.GetCultureInfo())),
                 new MeasurementColumn("Gen_1", (_, report, __) => report.GcStats.Gen1Collections.ToString(summary.GetCultureInfo())),
                 new MeasurementColumn("Gen_2", (_, report, __) => report.GcStats.Gen2Collections.ToString(summary.GetCultureInfo())),
-                new MeasurementColumn("Allocated_Bytes", (_, report, __) => report.GcStats.BytesAllocatedPerOperation.ToString(summary.GetCultureInfo()))
+                new MeasurementColumn("Allocated_Bytes", (_, report, __) => report.GcStats.GetBytesAllocatedPerOperation(report.BenchmarkCase).ToString(summary.GetCultureInfo()))
             };
 
             return columns.ToArray();

src/BenchmarkDotNet/Reports/SummaryTable.cs

@@ -50,7 +50,7 @@ internal SummaryTable(Summary summary, SummaryStyle style = null)
 
             if (style.SizeUnit == null)
             {
-                style = style.WithSizeUnit(SizeUnit.GetBestSizeUnit(summary.Reports.Select(r => r.GcStats.BytesAllocatedPerOperation).ToArray()));
+                style = style.WithSizeUnit(SizeUnit.GetBestSizeUnit(summary.Reports.Select(r => r.GcStats.GetBytesAllocatedPerOperation(r.BenchmarkCase)).ToArray()));
             }
 
             var columns = summary.GetColumns();

tests/BenchmarkDotNet.IntegrationTests/MemoryDiagnoserTests.cs

@@ -276,7 +276,7 @@ private void AssertAllocations(IToolchain toolchain, Type benchmarkType, Diction
                 {
                     var benchmarkReport = summary.Reports.Single(report => report.BenchmarkCase == benchmark);
 
-                    Assert.Equal(benchmarkAllocationsValidator.Value, benchmarkReport.GcStats.BytesAllocatedPerOperation);
+                    Assert.Equal(benchmarkAllocationsValidator.Value, benchmarkReport.GcStats.GetBytesAllocatedPerOperation(benchmark));
 
                     if (benchmarkAllocationsValidator.Value == 0)
                     {