Allow users to hide Gen X columns (#1764)

* don't display Gen X collumn if there were no collections for X generation

* add MemoryDiagnoserConfig, allow users to customize MemoryDiagnoser

Author: adamsitnik

src/BenchmarkDotNet/Attributes/MemoryDiagnoserAttribute.cs

@@ -9,9 +9,10 @@ public class MemoryDiagnoserAttribute : Attribute, IConfigSource
     {
         public IConfig Config { get; }
 
-        public MemoryDiagnoserAttribute()
+        /// <param name="displayGenColumns">Display Garbage Collections per Generation columns (Gen 0, Gen 1, Gen 2). True by default.</param>
+        public MemoryDiagnoserAttribute(bool displayGenColumns = true)
         {
-            Config = ManualConfig.CreateEmpty().AddDiagnoser(MemoryDiagnoser.Default);
+            Config = ManualConfig.CreateEmpty().AddDiagnoser(new MemoryDiagnoser(new MemoryDiagnoserConfig(displayGenColumns)));
         }
     }
 }

src/BenchmarkDotNet/Columns/MetricColumn.cs

@@ -16,7 +16,7 @@ public class MetricColumn : IColumn
         public string Legend => descriptor.Legend;
         public bool AlwaysShow => true;
         public ColumnCategory Category => ColumnCategory.Metric;
-        public int PriorityInCategory => 0;
+        public int PriorityInCategory => descriptor.PriorityInCategory;
         public bool IsNumeric => true;
         public UnitType UnitType => descriptor.UnitType;
 

src/BenchmarkDotNet/Configs/ImmutableConfig.cs

@@ -92,7 +92,7 @@ internal ImmutableConfig(
         public IAnalyser GetCompositeAnalyser() => new CompositeAnalyser(analysers);
         public IDiagnoser GetCompositeDiagnoser() => new CompositeDiagnoser(diagnosers);
 
-        public bool HasMemoryDiagnoser() => diagnosers.Contains(MemoryDiagnoser.Default);
+        public bool HasMemoryDiagnoser() => diagnosers.OfType<MemoryDiagnoser>().Any();
 
         public bool HasThreadingDiagnoser() => diagnosers.Contains(ThreadingDiagnoser.Default);
 

src/BenchmarkDotNet/Diagnosers/AllocatedNativeMemoryDescriptor.cs

@@ -12,6 +12,7 @@ internal class AllocatedNativeMemoryDescriptor : IMetricDescriptor
         public UnitType UnitType => UnitType.Size;
         public string Unit => SizeUnit.B.Name;
         public bool TheGreaterTheBetter => false;
+        public int PriorityInCategory => 0;
     }
 
     internal class NativeMemoryLeakDescriptor : IMetricDescriptor
@@ -23,5 +24,6 @@ internal class NativeMemoryLeakDescriptor : IMetricDescriptor
         public UnitType UnitType => UnitType.Size;
         public string Unit => SizeUnit.B.Name;
         public bool TheGreaterTheBetter => false;
+        public int PriorityInCategory => 0;
     }
 }

src/BenchmarkDotNet/Diagnosers/MemoryDiagnoser.cs

@@ -15,9 +15,11 @@ public class MemoryDiagnoser : IDiagnoser
     {
         private const string DiagnoserId = nameof(MemoryDiagnoser);
 
-        public static readonly MemoryDiagnoser Default = new MemoryDiagnoser();
+        public static readonly MemoryDiagnoser Default = new MemoryDiagnoser(new MemoryDiagnoserConfig(displayGenColumns: true));
 
-        private MemoryDiagnoser() { } // we want to have only a single instance of MemoryDiagnoser
+        public MemoryDiagnoser(MemoryDiagnoserConfig config) => Config = config;
+
+        public MemoryDiagnoserConfig Config { get; }
 
         public RunMode GetRunMode(BenchmarkCase benchmarkCase) => RunMode.NoOverhead;
 
@@ -33,9 +35,13 @@ public void Handle(HostSignal signal, DiagnoserActionParameters parameters) { }
 
         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);
+            if (diagnoserResults.GcStats.Gen0Collections > 0 && Config.DisplayGenColumns)
+                yield return new Metric(GarbageCollectionsMetricDescriptor.Gen0, diagnoserResults.GcStats.Gen0Collections / (double)diagnoserResults.GcStats.TotalOperations * 1000);
+            if (diagnoserResults.GcStats.Gen1Collections > 0 && Config.DisplayGenColumns)
+                yield return new Metric(GarbageCollectionsMetricDescriptor.Gen1, diagnoserResults.GcStats.Gen1Collections / (double)diagnoserResults.GcStats.TotalOperations * 1000);
+            if (diagnoserResults.GcStats.Gen2Collections > 0 && Config.DisplayGenColumns)
+                yield return new Metric(GarbageCollectionsMetricDescriptor.Gen2, diagnoserResults.GcStats.Gen2Collections / (double)diagnoserResults.GcStats.TotalOperations * 1000);
+
             yield return new Metric(AllocatedMemoryMetricDescriptor.Instance, diagnoserResults.GcStats.GetBytesAllocatedPerOperation(diagnoserResults.BenchmarkCase));
         }
 
@@ -50,6 +56,7 @@ private class AllocatedMemoryMetricDescriptor : IMetricDescriptor
             public UnitType UnitType => UnitType.Size;
             public string Unit => SizeUnit.B.Name;
             public bool TheGreaterTheBetter => false;
+            public int PriorityInCategory => GC.MaxGeneration + 1;
         }
 
         private class GarbageCollectionsMetricDescriptor : IMetricDescriptor
@@ -63,6 +70,7 @@ private GarbageCollectionsMetricDescriptor(int generationId)
                 Id = $"Gen{generationId}Collects";
                 DisplayName = $"Gen {generationId}";
                 Legend = $"GC Generation {generationId} collects per 1000 operations";
+                PriorityInCategory = generationId;
             }
 
             public string Id { get; }
@@ -72,6 +80,7 @@ private GarbageCollectionsMetricDescriptor(int generationId)
             public UnitType UnitType => UnitType.Dimensionless;
             public string Unit => "Count";
             public bool TheGreaterTheBetter => false;
+            public int PriorityInCategory { get; }
         }
     }
 }

src/BenchmarkDotNet/Diagnosers/MemoryDiagnoserConfig.cs

@@ -0,0 +1,16 @@
+using JetBrains.Annotations;
+
+namespace BenchmarkDotNet.Diagnosers
+{
+    public class MemoryDiagnoserConfig
+    {
+        /// <param name="displayGenColumns">Display Garbage Collections per Generation columns (Gen 0, Gen 1, Gen 2). True by default.</param>
+        [PublicAPI]
+        public MemoryDiagnoserConfig(bool displayGenColumns = true)
+        {
+            DisplayGenColumns = displayGenColumns;
+        }
+
+        public bool DisplayGenColumns { get; }
+    }
+}

src/BenchmarkDotNet/Diagnosers/PmcMetricDescriptor.cs

@@ -20,5 +20,6 @@ internal PmcMetricDescriptor(PreciseMachineCounter counter)
         public string NumberFormat => "N0";
         public UnitType UnitType => UnitType.Dimensionless;
         public string Unit => "Count";
+        public int PriorityInCategory => 0;
     }
 }

src/BenchmarkDotNet/Diagnosers/ThreadingDiagnoser.cs

@@ -61,6 +61,7 @@ private class CompletedWorkItemCountMetricDescriptor : IMetricDescriptor
             public UnitType UnitType => UnitType.Dimensionless;
             public string Unit => "Count";
             public bool TheGreaterTheBetter => false;
+            public int PriorityInCategory => 0;
         }
 
         private class LockContentionCountMetricDescriptor : IMetricDescriptor
@@ -74,6 +75,7 @@ private class LockContentionCountMetricDescriptor : IMetricDescriptor
             public UnitType UnitType => UnitType.Dimensionless;
             public string Unit => "Count";
             public bool TheGreaterTheBetter => false;
+            public int PriorityInCategory => 0;
         }
     }
 }

src/BenchmarkDotNet/Disassemblers/DisassemblyDiagnoser.cs

@@ -169,6 +169,7 @@ private class NativeCodeSizeMetricDescriptor : IMetricDescriptor
             public UnitType UnitType => UnitType.Size;
             public string Unit => SizeUnit.B.Name;
             public bool TheGreaterTheBetter => false;
+            public int PriorityInCategory => 0;
         }
     }
 }

src/BenchmarkDotNet/Reports/Metric.cs

@@ -32,6 +32,8 @@ public interface IMetricDescriptor
         [PublicAPI] string Unit { get; }
 
         [PublicAPI] bool TheGreaterTheBetter { get; }
+
+        [PublicAPI] int PriorityInCategory { get; }
     }
 
     public class MetricDescriptorEqualityComparer : EqualityComparer<IMetricDescriptor>