Managed object internals, Part 4. Fields layout

In the recent blog posts we’ve discussed invisible part of the object layout in the CLR: Managed object internals, Part 1. The Layout Managed object internals, Part 2. Object header layout and the cost of locking Managed object internals, Part 3. The layout of a managed array This time we’re going to focus on the…


Managed object internals, Part 3. The layout of a managed array

Arrays are one of the basic building blocks of every applications. Even if you do not use arrays directly every day you definitely use them indirectly as part of almost any library. C# has arrays from the very beginning and back in the day that was the only “generic”-like and type safe data structure available….


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…


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…


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> :…


Garbage collection and variable lifetime tracking

Here is a seemingly simple question for you: Is it possible that the CLR will call a finalizer for an instance when an instance method is still running? In other words, is it possible in the following case to see ‘Finalizing instance.’ before ‘Finished doing something.’? internal class GcIsWeird{    ~GcIsWeird()    {        Console.WriteLine(“Finalizing instance.”);    }     public int data = 42;    …


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…


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…


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…


Dissecting the ActionBlock: a Short Story About a Nasty Deadlock

I think almost every project in the real world uses some form of producer-consumer queue. The idea behind this problem is very simple. Application needs to decouple consumers of some data from the logic that processes it. Consider, for instance, the thread pool from the CLR: application can schedule some work using ThreadPool.QueueUserWorkItem and the…