Focusing on the Rust Unwrap in the CloudFlare outage is really the scalability equivalent of "When a sage points to the moon, all the fool sees is the finger". At that scale, failures *will* happen. Programming error are unavoidable. What's interesting is why it took down the entire system.

Fun fact: you can't use print screen to capture a screenshot of a crash of SnippingTool

#UCP25 | Kevin Gosse - The Hidden Life of Method Calls Kevin reveals in his session what really happens when your code runs: ➡️ calling conventions ➡️ stack frames ➡️ JIT compilation ➡️ virtual dispatch ➡️ CPU-level mechanics ➡️ prague.updateconf.net #DotNet #Performance @kevingosse.net @woodruff.dev

I had a ton of fun at Techorama NL. It's not everyday that you get a chance to debug variadic .NET functions on a giant movie theater screen.

We are getting closer to the release of Resharper 2025.3 , so I ran some performance tests to see how much we improved compared to 2025.2. For this iteration, I focused my effort mainly on the huge Datadog.Trace solution, available on the DataDog/dd-trace-dotnet repository. Results below 👇

I just published a new article: Using profiler function hooks in .NET with Silhouette. In the process, we also learn how to use static linking with NativeAOT. minidump.net/using-functi...

New blog post: In 2021 I found an invisible memory leak in a tool (VS Code) that I have never used. Impossible? Easy: randomascii.wordpress.com/2025/10/09/f...

There's an even more adverse effect to the way closures are allocated: sharplab.io#v2:EYLgxg9gT... Because the same closure is reused for different calls, you can end up extending the lifetime of some of your objects without realizing it.

Top thing I wish I had known earlier as a software engineer: before leaving a company, make sure to download your favorite slack emojis, so you don't have to frenetically look for them on the web when you realize they're missing from the new slack.

Worked at Datadog, encountered crashes because of mysterious race-conditions in .NET writeable metadata: github.com/dotnet/runti... Moved to JetBrains, encountered crashes because of mysterious race-conditions in .NET writeable metadata: github.com/dotnet/runti... I think I'm cursed.

As requested, I published an article about how the UI profiler works: minidump.net/measuring-ui... It allows me to measure the responsiveness of Visual Studio when running with ReSharper, in various conditions. I also made the source code available on github: github.com/kevingosse/U...

Congrats to Microsoft on this new release, I've been using it for a few weeks now and it really feels great. Note that Resharper is already compatible, if you want to try it!

Not entirely sure what I'm going to do with all that money.

I just discovered that whenever you create a closure in a generic C# method, the closure is also generic even when it's not needed. This is very frustrating to me because generics cause performance issues in Resharper (see bsky.app/profile/kevi...) sharplab.io#v2:EYLgxg9gT...

Monday

I can't recommend strongly enough to use an unlimited online backup service (I use @backblaze.bsky.social). Backup your whole disk and forget about it. Just today, I realized I lost some code I wrote months ago (~2 days of work). Painlessly restored it from the automatic backup.

To help reduce the number of UI freezes caused by Resharper, I built an internal tool to measure UI responsiveness. Here, you can see the improvement between the current 2025.1 version (on the left) and the upcoming 2025.2 version (on the right) with out-of-process enabled.

As I work on Resharper performance, I learn about limitations of .NET (at least, .NET Framework) that I wasn't aware of. Here, I shaved 1 second of CPU time on startup by... removing a call to Array.Empty<T>.

Working on performance, it's a lot of time wasted on dead-ends and getting the impression of making no progress, and then suddenly managing to shave 10 seconds of CPU time off R# startup.

One thing I like about working on a new codebase is finding all those low-hanging fruits, optimizations that have a significant impact for a relatively low effort. Here, before/after, squashing ~140 MB of heap allocations from Resharper licensing code.

I really enjoyed participating to the last 2codeOrNot2code, so I'm happy to repeat the experience. This time, we will have some fun with functions, unveiling interesting details about what happens when you call them. If you like to understand how things work, don't miss it!

I'm experimenting with interfacing dnlib with my Silhouette library. The .NET profiling API provides almost no helper at all to manipulate IL, it just exposes the method body as a binary blob. Having access to dnlib greatly simplifies IL rewriting. github.com/kevingosse/S...

I released v2.0.0 of Silhouette, my library to write .NET profilers in C#. The main change is the addition of IMetadataImport2. There are a few small breaking changes, so I'm embracing semver and bumping the major version number. github.com/kevingosse/S...

sourceof.net now redirects to github.com/microsoft/re.... I really hope Microsoft will reconsider this change, code navigation on Github isn't even remotely as good as what we had before (basically source.dot.net but for .NET Framework)

I've been playing with "Next edit suggestions" in Visual Studio (devblogs.microsoft.com/visualstudio...) and in my opinion it crosses the fine line between "useful AI" and "noisy AI". Too many irrelevant suggestions, and hard to ignore without pressing esc. I hope they can tone it down.

Today I needed some information about method jitting in R#, but ETW was missing some bits. It was a nice opportunity to test Silhouette, and it only took me a few hours to write a profiler to retrieve everything I needed. (and yes, it's XML, I'm old 👴)

Time to make it official: starting Monday, I'll be leaving Datadog and joining JetBrains as principal engineer 🎉 I'll be working on various topics, but one of my first responsibilities will be to improve the performance of Resharper, which is a thrilling but frightening challenge.

Pro .NET Memory Management The co-authors of the 2nd edition - Konrad Kokosa, @chrisnas.bsky.social, @kevingosse.net - talk about the content and the book per se. Join with your curiosity and your questions to the trio. 2025-03-25 18:00 UTC #dotnet #CSharp #Memory www.youtube.com/watch?v=DboS...

I'm starting to prepare my talk for @updateconference.bsky.social in Krakow next May. krakow.updateconference.net/en/2025/sche... First (and most important step), using AI to build a concept for the illustration (with cats), then commissioning a pixel-art artist for the final drawing.

This episode explains how to monitor the startup of a .NET application and get insights about its lock and wait contentions duration. Feel free to install the corresponding "dotnet wait" CLI tool :^)

I published the fifth part of my series of articles about writing a .NET garbage collector in C#. This time, we learn about GCDesc, a runtime structure that indicates where to find the references of a given object. minidump.net/writing-a-ne... #dotnet

I wrote an article to explain why FastDoom is fast: fabiensanglard.net/fastdoom/ind....

In case you missed it, Pro .NET Memory Management 2nd edition is out! A discussion on reddit convinced me to do a bit of self promotion and address one very negative review that was posted about the book. minidump.net/pro-net-memo... #dotnet

It's hard to focus on your work when @andrewlock.bsky.social knows your weakness

This is a fascinating read. Learn how to do seriously unsafe shit with the NonGC (née Frozen Object) Heap in #dotnet 8 and later.

The fourth part of my series of articles about writing a .NET garbage collector in C# is available. This time, we learn how to walk the heap, and we start using segments to manage our allocation contexts. minidump.net/writing-a-ne... #dotnet

I've published the third part of my series of articles about writing a .NET garbage collector in C#. In this one, we add a helper method to inspect the objects in memory, learning about thread modes and the DAC. minidump.net/writing-a-ne... #dotnet

Can you help me investigate some weird behavior I'm facing on Windows with cscript? I'm running this script: gist.github.com/kevingosse/2... cscript.exe script.js

I published the second part of my series of article about writing a .NET garbage collector in C#. This time, we build the simplest possible GC, capable of running basic .NET apps without ever freeing memory. minidump.net/writing-a-ne... #dotnet

After writing a profiler in C#, I've now published the first of a series of articles about how use C# to... write a .NET Garbage Collector. #dotnet minidump.net/2025-28-01-w...

If you are interested in measuring the latency impact of lock, mutex, semaphore, events in your .NET apps, this article is for you :^) chnasarre.medium.com/measuring-th...

I published part 5 of my "Writing a .NET profiler in C#" series. All the foundations built in the previous articles have been moved to a library named Silhouette. In this new article, we finally have everything we need to write an actual profiler. minidump.net/writing-a-ne... #dotnet

Finally had time over the holidays to realize a long-standing dream of mine: a hex editor that knows about the PE file and .NET metadata format. You can click any byte and it will show you which data structure it is in the tree. Every byte is covered. The parser is at github.com/KirillOsenko...

I migrated ClipPing from WPF to @avaloniaui.net + NativeAOT. Commit size is still surprising to me, but the overall memory usage has been massively reduced.

Since many people are asking for it, I published a first (early) version: github.com/kevingosse/C... Keep in mind that it's really barebone, and there is no "launch at startup" feature yet. In the coming days I'm going to look at how to integrate it into the Powertoys.

I finally got so annoyed with ctrl+c randomly failing that I built a tool for it. It monitors the content of the clipboard, and highlights the active window when a change is detected. It acts as a visual confirmation that you properly copied stuff.

If you noticed in Visual Studio that the execution randomly resumes while stepping through a .NET 9 program, it's not just you. github.com/dotnet/runti... The fix can't come soon enough, the bug is incredibly annoying.

If you're annoyed at Github not showing the files in the build folders when using "Go to file", you can actually customize that behavior by adding the proper lines in your .gitattributes file. docs.github.com/en/search-gi...

The one downside of having a proven track record of debugging crazy issues is that people start assuming you're some kind of magician. Support just sent me a random memory dump and all the information I have is "the customer is having some kind of performance issue, figure it out"

Did you know that you can define a DebuggerDisplayAttribute for a type from another assembly? Just add an assembly-level attribute to your code and specify the Target type: [assembly: DebuggerDisplay(@"\{Color = {Color}}", Target = typeof(Pen))]