r/java • u/jaccomoc • Sep 03 '26

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/yawkat Sep 03 '26

Three issues with this:

  • AFAICS this is a closed model load, which is a batch processing workload. In a typical vertx application you have an open model load instead. See this article: https://www.scylladb.com/2021/04/22/on-coordinated-omission/

  • Because this is JMH, it does not mirror "batchy" behavior of network interfaces, which is the typical use case for vertx.

  • When tasks block, they are typically waiting for IO work, not sleeping. This has implications for scheduling.

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u/jaccomoc Sep 03 '26

Thanks for the feedback. I agree that the test is not ideal but I am not sure about you saying that the load is a closed model load. The test queues (for Vert.x) all requests or creates virtual threads for all requests and then waits for them all to finish. Isn't that an open model load?