Understanding RuntimeHelpers.IsKnownConstant Method

In this post my goal is to gain understanding of the RuntimeHelpers.IsKnownConstant method. I have come across it in the Performance Improvements in .NET 7 blog post. There are two examples presented in the post:

  • bool StartsWith(char value)

  • Math.Round with MidpointRounding mode is specified

I will learn about JIT optimization including RuntimeHelpers.IsKnownConstant through a simple and slightly artificial example. A bool IsPalindromePosition(int position) method is part of a type which has a static property ReadOnlySpan<char> Text. The method returns true when the given position from the beginning of the string returns the same character as one from the end. For the sake of simplicity this method omits all input validation.

public static ReadOnlySpan<char> Text => "hellobolleh";

[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
public bool IsPalindromePosition(int position)
    if (int.IsOddInteger(Text.Length) && position == Text.Length / 2 + 1)
        return true;

    return Text[position] == Text[Text.Length - position - 1];

[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
public bool Work()
    var result = IsPalindromePosition(0);
    return result;

Find out more

Kestrel Serving Requests

In this post I review the way Kestrel serves HTTP requests. Please note, that the architecture described here may change from release to release of ASP.NET Core. At the time of writing .NET 7 and the corresponding ASP.NET Core is a month away from release.

Accepting connection on HTTP2 and HTTP3

ASP.NET Core's Kestrel opens IConnectionListener<T>s upon startup. For each ASPNETCORE_URLS set, a connection listener is instantiated. A base IConnectionListener implementation is a SocketConnectionListener. Connection listeners implement the decorator pattern. For example, GenericConnectionListener expects another connection listener as a constructor parameter.Connection listeners provide basic functionality to bind/unbind to a given port and to accept new connection requests.

ConnectionDispatcher also initiated during startup. It starts to run an infinite while loop in AcceptConnectionsAsync() method to accept new connections on a given listener. When a client sends a request, a new connection in initialized. In this case a KestrelConnection<T>, that also implements IThreadPoolWorkItem.Execute().

Find out more

Streams, Pipes and gRPC

.NET 7 introduces new methods for Stream type: ReadExactly(...), ReadAtLeast(...) and their async counterparts allow the developers to await 'enough' data to be present for further processing input streams.

At the time of writing this post .NET 7 is still in preview bits. Which means there is still a chance that these methods will not be released.

Why do we have it?

At first these methods may seem a surplus, as developers have been using streams for many years, so why would we need them? There are several workloads in software stack that fits perfectly with this concept. Or rather say payloads instead of workloads.

Find out more

Palindrome as an Interview Question

Palindrome often comes up as an interview question. In this post I will investigate 3 implementations and their relative performance.

What is a palindrome? Wikipedia says A palindrome is a word, number, phrase, or other sequence of characters which reads the same backward as forward, such as madam or racecar.

It is quite common to ask an interview candidate to implement a function to check if a given string is a palindrome. In this blog post I will show 4 different implementations. While these implementations might not handle all use cases identically, they satisfy a set of testcases to make sure they all work correctly based on a common interpretation.


Find out more

Rate Limiting Streaming gRPC Calls

In this post I investigate implementing rate limiting with .NET 7 for gRPC streaming messages. In my previous post I looked into how to apply rate limiting on gRPC requests (unary or streaming).

When we apply the ASP.NET Core rate limiting middleware to gRPC services, we can limit the rate of incoming requests. However, if the request is a long running (client stream, server streaming or duplex) we cannot limit the rate of messages sent.

In this post I create a sample rate limiter for ASP.NET Core gRPC streaming services. The limiter is built on top of .NET 7's rate limiting API.

When would I need to rate limit the incoming messages? For example clients sending long running requests with streaming data can rate limited per endpoint or per resource accessed.

Find out more