Open Source .NET – 2 years later

A little over 2 years ago Microsoft announced that they were open sourcing large parts of the .NET framework and as Scott Hanselman said in his recent Connect keynote, the community has been contributing in a significant way:

How does the 'fixed' keyword work?

Well it turns out that it’s a really nice example of collaboration between the main parts of the .NET runtime, here’s a list of all the components involved:

Adding a verb to the dotnet CLI tooling

The dotnet CLI tooling comes with several built-in cmds such as build, run and test, but it turns out it’s possible to add your own verb to that list.

Optimising LINQ

What’s the problem with LINQ? As outlined by Joe Duffy, LINQ introduces inefficiencies in the form of hidden allocations, from The ‘premature optimization is evil’ myth:

Compact strings in the CLR

In the CLR strings are stored as a sequence of UTF-16 code units, i.e. an array of char items. So if we have the string ‘testing’, in memory it looks like this:

Subverting .NET Type Safety with 'System.Runtime.CompilerServices.Unsafe'

In which we use System.Runtime.CompilerServices.Unsafe a generic API (“type-safe” but still “unsafe”) and mess with the C# Type System!

Analysing .NET Memory Dumps with CLR MD

If you’ve ever spent time debugging .NET memory dumps in WinDBG you will be familiar with the commands shown below, which aren’t always the most straight-forward to work with!

Analysing Optimisations in the Wire Serialiser

Recently Roger Johansson wrote a post titled Wire – Writing one of the fastest .NET serializers, describing the optimisation that were implemented to make Wire as fast as possible. He also followed up that post with a set of benchmarks, showing how Wire compared to other .NET serialisers:

Preventing .NET Garbage Collections with the TryStartNoGCRegion API

Pauses are a known problem in runtimes that have a Garbage Collector (GC), such as Java or .NET. GC Pauses can last several milliseconds, during which your application is blocked or suspended. One way you can alleviate the pauses is to modify your code so that it doesn’t allocate, i.e. so the GC has nothing to do. But this can require lots of work and you really have to understand the runtime as many allocation are hidden.

GC Pauses and Safe Points

GC pauses are a popular topic, if you do a google search, you’ll see lots of articles explaining how to measure and more importantly how to reduce them. This issue is that in most runtimes that have a GC, allocating objects is a quick operation, but at some point in time the GC will need to clean up all the garbage and to do this is has to pause the entire runtime (except if you happen to be using Azul’s pauseless GC for Java).