r/java • u/jaccomoc • 22h ago

Vert.x Event-Loop vs Virtual Threads: Jactl Suspend/Resume Benchmark

https://jactl.io/blog/2026/09/02/jactl-virtual-threads-benchmark

The article benchmarks Jactl script execution with differing number of blocking operations comparing throughput with Jactl built-in suspend/resume on Vert.x Event-Loops and throughput with Jactl on Virtual Threads. The benchmarks are run on both Java 21 and Java 25 with some surprising (to me at least) results.

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u/s0ftware-dev 21h ago

TLDR virtual threads are better. 

-5

u/jaccomoc 21h ago

But only on Java 25 and not by as much as I thought they would be.

I was frankly surprised at the difference between Java 21 and Java 25.

14

u/Neful34 21h ago

Nah if you follow a bit the java youtube channel they explained a lot about the optimizations and the issues they had with virtual threads in java 21, and the optimization they did in java 25. I also recall a recent talk from netflix discussing about it too

5

u/jaccomoc 20h ago

I know that they fixed the OS thread pinning issues and that there are always some performance improvements but the the improvement for scripts with multiple blocking operations was a lot more significant than I expected. Or maybe what I should say is that the performance on Java 21 when a script does multiple blocking operations with virtual threads was a lot worse than I expected.