Something I found out when writing:

https://cowtowncoder.medium.com/jackson-2-18-fast-vector-reads-writes-6c2cf99c4594

is that while with JDKs 8 and 17 optimized floating-point writes (with StreamWriteFeature.USE_FAST_DOUBLE_WRITER) is about 2x as fast as JDK one, with JDK 21, JDK version is now slightly faster.

Code Jackson uses is from https://github.com/c4f7fcce9cb06515/Schubfach (as per notes on 3 classes in com.fasterxml.jackson.core.io.schubfach).

So it'd be good to consider what to do, if anything:

1. Could there be newer version of "Schubfach" code implementation to use?
2. Is there an explanation of why/how JDK 21 (and later presumably, could try) is so much faster than earlier versions (link would be nice to add)
3. Should we document feature, suggesting it probably should not be enabled for JDKs 21 and above)