loom VS loomylin

It's more accurate to say Loom is [a particular type of] continuations in the JVM, which can be used to implement green threads / fibers.

You can see the implementation of VirtualThread here: https://github.com/openjdk/loom/blob/fibers/src/java.base/sh...

This uses the internal 'one-shot delimited continuation': https://github.com/openjdk/loom/blob/fibers/src/java.base/sh...

So, at least in principle, there is scope for other styles of concurrency to be implemented over this.

Loom is actively developed https://github.com/openjdk/loom

Currently the Thread public constructor defaults to platform threads to be fully backwards compatible. So all libraries must be updated to support the new model.

I've been casually following the repo ( https://github.com/openjdk/loom ) and the mailing list ( https://mail.openjdk.java.net/mailman/listinfo/loom-dev ) over the last 18 months or so, and it definitely appears that things are ramping up as of late. The implication (as I see it) is that they are relatively happy with the general design are and are at the point where they want help from experts in the various areas of the JDK (GC, Debugging, etc) to make sure that their pieces play well with Loom.

https://github.com/openjdk/loom/blob/fibers/src/java.base/share/classes/sun/nio/ch/NioSocketImpl.java#L177

[1] https://github.com/openjdk/loom/blob/fibers/src/java.base/share/classes/java/lang/VirtualThread.java#L933

The performance benefit is close to be the same as writing reactive code. It grows with number of concurrent connections. In my final project for university I did some perf tests on kinda advanced business logic (jetty server with rest api, calling external web services, cassandra, redis) and got such results. Its not public, neither finished but checkout this one: https://github.com/tipsy/loomylin - tests made here are with small number of connections but when you go 10k difference is getting bigger (just remember to configure your host file limits and port ranges)