Dissecting the new() constraint in C#: a perfect example of a leaky abstraction

Most likely you’ve heard about The Law of Leaky Abstractions coined by Joel Spolsky. Even if you never heard of it, you definitely faced it in your day-to-day job. The “law” is pretty simple: “All non-trivial abstractions, to some degree, are leaky”. And this is 100% true. But sometimes even not that complicated abstractions can…

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Dissecting the local functions in C# 7

The Local functions is a new feature in C# 7 that allows defining a function inside another function. When to use a local function? The main idea of local functions is very similar to anonymous methods: in some cases creating a named function is too expensive in terms of cognitive load on a reader. Sometimes…

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Dissecting the pattern matching in C# 7

C# 7 finally introduced a long-awaited feature called “pattern matching”. If you’re familiar with functional languages like F# you may be slightly disappointed with this feature in its current state, but even today it can simplify your code in a variety of different scenarios. Every new feature is fraught with danger for a developer working…

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Dissecting the async methods in C#

The async series Dissecting the async methods in C#. Extending the async methods in C#. The performance characteristics of the async methods in C#. One user scenario to rule them all. The C# language is great for developer’s productivity and I’m glad for the recent push towards making it more suitable for high-performance applications. Here…

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A common execution path optimization

Today I want to talk about one interesting optimization pattern that you may face in framework code or in high-performance libraries. The idea is simple: suppose you have a commonly used method that has two execution paths – one is very common and simple, and the second one takes longer to execute, has more steps…

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Understanding different GC modes with Concurrency Visualizer

In this post I’m going to visualize what exactly happens during Garbage Collection (GC) and how different GC modes can significantly affect application performance. I assume that the reader is familiar with garbage collection basics. If this isn’t the case I encourage you to spend 15 minutes to fill this gap, for instance from the…

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Dissecting the tuples in C# 7

System.Tuple types were introduced in .NET 4.0 with two significant drawbacks: (1) tuple types are classes and (2) there was no language support for constructing/deconstructing them. To solve these issues, C# 7 introduces new language feature as well as a new family of types (*). Today, if you need to glue together two values to…

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Managed object internals, Part 2. Object header layout and the cost of locking

Working on my current project I’ve faced a very interesting situation. For each object of a given type, I had to create a monotonically growing identifier with few caveats: 1) the solution should work in multithreaded environment 2) the number of objects is fairly large, up to 10 million instances and 3) identity should be…

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Managed object internals, Part 1. The layout

The layout of a managed object is pretty simple: a managed object contains instance data, a pointer to a meta-data (a.k.a. method table pointer) and a bag of internal information also known as an object header. The first time I’ve read about it, I’ve got a question: why the layout of an object is so…

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To box or not to Box? That is the question!

Discussions on reddit, hacker news. Recently I’ve noticed that the Equal method from our ValueTuple (*) struct generates significant memory traffic (~1Gb). That was a bit of a surprise to me. This struct is well designed and was used pretty heavily in many performance critical scenarios. Here how the struct looks like: public struct ValueTuple<TItem1, TItem2> :…

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