ysmoradi / MicroOptimizationBenchmark

How much really slow is the code which uses reflection and some other parts of the C# .NET which are known to be slow.

We've a slow code which is known to be very slow! We've provided 1 benchmark + 1 load test to see how slow is that.

public async Task<int> SlowCode()
{
    int finalResult = 0;

    for (int i = 0; i < 100; i++)
    {
        var result1 = (ResultClass)typeof(Tests).GetMethod("Sum1")/*Reflection*/.Invoke(this, new object[] { 1, 2 /*Boxing*/ })/*Dynamic Dispath*/;
        var result2 = await ((Task<ResultClass>)typeof(Tests).GetMethod("Sum1Async")/*Reflection*/.Invoke(this, new object[] { 1, 2 /*Boxing*/ }))/*Dynamic Dispath*/;
        // await without configure await false (I know console apps have no sync context!)
        finalResult += result1.Sum + result2.Sum;

        try
        {
            throw new DivideByZeroException(); // exception
        }
        catch { }
    }

    return finalResult;
}

SlowCode SlowCode performs reflection and other bad codes 100 times. It also throws an exception 100 times! Every 100 iterations only took 551.600 us!

I'm going to compare its performance with FastCode which uses struct instead of class, it uses direct method call instead of reflection and it uses ValueTask instead of Task and it doesn't throw an exception at all.

BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19041.388 (2004/?/20H1)
Intel Core i7-7700K CPU 4.20GHz (Kaby Lake), 1 CPU, 8 logical and 4 physical cores
.NET Core SDK=5.0.100-preview.6.20318.15
  [Host]     : .NET Core 5.0.0 (CoreCLR 5.0.20.30506, CoreFX 5.0.20.30506), X64 RyuJIT
  Job-JWLQUD : .NET Core 5.0.0 (CoreCLR 5.0.20.30506, CoreFX 5.0.20.30506), X64 RyuJIT

RunStrategy=Throughput

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
SlowCode	565.852 us	11.1719 us	12.8655 us	13.6719	-	-	57675 B
FastCode	1.447 us	0.0101 us	0.0095 us	-	-	-	-

We also have fast api & slow api In slow api, we throws ResourceNotFoundException which gets mapped to 404 status code later in a middleware. There's also a fast api which simply returns Not found. It also has the same middleware but for unknown exceptions. Developers are not intended to throw an exception in that aspnetcore app!

Using https://github.com/rogerwelin/cassowary we achieved following results:

cassowary.exe run -u http://localhost:5000/weatherforecast/ -c 100 -n 150000

Fast: 30299.31 req/s Slow: 30150.26 req/s

Note that in real world, api throws exceptions rarely, and api logic is more complicated than a simple return! For example api needs authorization, authenticatin, database and cache access etc. So, this load test is testing worse case!

Note that I've tested these on Windows. Results might be different on Linux!