One of the most exciting aspects of .NET Core is performance. Microsoft has found ways to improve that performance even further. Check out this elaborate post for a tour through just a selection of the performance improvements you’ll find in .NET Core, and in particular in .NET Core 2.0, focusing on a few examples from a variety of the core libraries.
https://blogs.msdn.microsoft.com/dotnet/2017/06/07/performance-improvements-in-net-core/