Performance Improvements in .NET 6

Four years ago, around the time .NET Core 2.0 was being released, I wrote Performance Improvements in .NET Core to highlight the quantity and quality of performance improvements finding their way into .NET. With its very positive reception, I did so again a year later with Performance Improvements in .NET Core 2.1, and an annual tradition was born. Then came Performance Improvements in .NET Core 3.0, followed by Performance Improvements in .NET 5. Which brings us to today.

The dotnet/runtime repository is the home of .NET’s runtimes, runtime hosts, and core libraries. Since its main branch forked a year or so ago to be for .NET 6, there have been over 6500 merged PRs (pull requests) into the branch for the release, and that’s excluding automated PRs from bots that do things like flow dependency version updates between repos (not to discount the bots’ contributions; after all, they’ve actually received interview offers by email from recruiters who just possibly weren’t being particularly discerning with their candidate pool). I at least peruse if not review in depth the vast majority of all those PRs, and every time I see a PR that is likely to impact performance, I make a note of it in a running log, giving me a long list of improvements I can revisit when it’s blog time. That made this August a little daunting, as I sat down to write this post and was faced with the list I’d curated of almost 550 PRs. Don’t worry, I don’t cover all of them here, but grab a large mug of your favorite hot beverage, and settle in: this post takes a rip-roarin’ tour through ~400 PRs that, all together, significantly improve .NET performance for .NET 6.

As in previous posts, I’m using BenchmarkDotNet for the majority of the examples throughout. To get started, I created a new console application:

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