Why is .NET 5 HttpClient performance better than .NET6?

[suchoss]

Why is .NET 5 HttpClient performance better than .NET6?

Or is it?

In this solution I tried to find out why is .NET 5 working "correctly" when using NEST library, while .NET 6 is failing quite quickly when running more requests/s. What I found out is that .NET 5 HttpClientFactory behaves differently from .NET 6 HttpClientFactory.

It seems that the HttpClientFactory for .NET 6 is less performant than the one for .NET 5

.NET5

• it can handle over 100 requests/s without creating new threads
• only about 40 requests are really outgoing
• more requests created mean that less requests are really sent

.NET6

• it can not handle more than 100 requests/s without creating new threads
• after more than 100 requests/s the app starts creating new threads locked in waiting until it ultimately fails
• only about 40 requests are really outgoing
• more requests created mean that less requests are really sent

Am I doing something wrong?

Is .NET 5 more performant, or does that mean it swallows some errors and we don't know about them?
Why .NET 6 is so quickly depleting TCP connections leading to rapid grow of threads?

Below is my original issue created on Elasticsearch Github project

Picture from elastic/elasticsearch-net#6342 (comment)