This benchmark shows the performance of using Structs passed by reference vs using Classes

result.md

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.18363.1500 (1909/November2019Update/19H2) Intel Core i7-8550U CPU 1.80GHz (Kaby Lake R), 1 CPU, 8 logical and 4 physical cores .NET SDK=6.0.202 [Host] : .NET 5.0.16 (5.0.1622.16705), X64 RyuJIT

Method	Size	Mean	Error	StdDev	Median	Gen 0	Allocated
RunClass	10	204.9 ns	3.77 ns	6.81 ns	203.4 ns	0.0899	376 B
RunStructNoRef	10	138.7 ns	2.57 ns	2.28 ns	138.7 ns	0.0229	96 B
RunStructRef	10	149.0 ns	3.30 ns	9.31 ns	146.9 ns	0.0229	96 B
RunClass	100	2,080.2 ns	88.92 ns	255.14 ns	1,977.7 ns	0.7782	3,256 B
RunStructNoRef	100	1,211.4 ns	23.33 ns	31.14 ns	1,205.0 ns	0.1087	456 B
RunStructRef	100	1,237.6 ns	23.71 ns	24.35 ns	1,230.8 ns	0.1087	456 B
RunClass	1000	18,751.2 ns	234.45 ns	207.83 ns	18,753.1 ns	7.6599	32,056 B
RunStructNoRef	1000	11,836.6 ns	228.92 ns	224.83 ns	11,771.1 ns	0.9613	4,056 B
RunStructRef	1000	11,961.8 ns	231.53 ns	193.34 ns	11,898.2 ns	0.9613	4,056 B

// * Legends * Size : Value of the 'Size' parameter Mean : Arithmetic mean of all measurements Error : Half of 99.9% confidence interval StdDev : Standard deviation of all measurements Median : Value separating the higher half of all measurements (50th percentile) Gen 0 : GC Generation 0 collects per 1000 operations Allocated : Allocated memory per single operation (managed only, inclusive, 1KB = 1024B) 1 ns : 1 Nanosecond (0.000000001 sec)

// * Diagnostic Output - MemoryDiagnoser *

// ***** BenchmarkRunner: End ***** // ** Remained 0 benchmark(s) to run ** Run time: 00:05:15 (315.08 sec), executed benchmarks: 9

Global total time: 00:05:15 (315.09 sec), executed benchmarks: 9 // * Artifacts cleanup *

struct-by-ref-vs-class.cs

#LINQPad optimize+
void Main()
{
	var summary = BenchmarkRunner.Run<HashSetPerformance>();
}

[MemoryDiagnoser]
public class HashSetPerformance
{

	[Params(10,100,1000)]

	public int Size;
	Random rd;

	public HashSetPerformance()
	{
		this.rd = new Random();
	}

	[Benchmark]
	public void RunClass()
	{
		List<AsClass> items = new List<AsClass>(Size);

		//create
		for (int i = 0; i < Size; i++)
		{
			items.Add(new AsClass
			{
				MyProperty = rd.Next()
			});
		}

		//access
		for (int i = 0; i < items.Count; i++)
		{
			var element = items[i];
			DoClass(element);
		}

	}

	[Benchmark]
	public void RunStructNoRef()
	{
		List<AsStruct> items = new List<AsStruct>(Size);

		//create
		for (int i = 0; i < Size; i++)
		{
			items.Add(new AsStruct
			{
				MyProperty = rd.Next()
			});
		}

		//access

		for (int i = 0; i < items.Count; i++)
		{
			var element = items[i];
			DoNoRef(element);
		}
	}


	[Benchmark]
	public void RunStructRef()
	{
		List<AsStruct> items = new List<AsStruct>(Size);

		//create
		for (int i = 0; i < Size; i++)
		{
			items.Add(new AsStruct
			{
				MyProperty = rd.Next()
			});
		}

		//access

		for (int i = 0; i < items.Count; i++)
		{
			var element = items[i];
			DoRef(ref element);
		}
	}

	public void DoRef(ref AsStruct s)
	{
		s.MyProperty = 29;
	}

	public void DoNoRef(AsStruct s)
	{
		s.MyProperty = 29;

	}

	public void DoClass(AsClass c)
	{
		c.MyProperty = 29;

	}


	public class AsClass
	{
		public int MyProperty { get; set; }
	}

	public struct AsStruct
	{
		public int MyProperty { get; set; }
	}
}