Marcus Hirt

There really should be an official JVM Appreciation Day, where we give our JVMs some tea and a massage.

I am finally at zero unhandled emails in my (non-work) inboxes: github.com/thegreystone/m… Claude + @graalvm FTW! ;)

@headius You need many teams. :)

Too many projects I wish I had time for. * A (new) impl of Python, Go, or Rust-like language for JVM. * Ruby library for emitting Project Babylon CUDA code. * Ruby LSP plug-in for JRuby Java integration. * New JRuby SSL library based on JDK crypto support. I need a team.

The Virtual @OpenJDK Serviceability Meetup 2025 will be the 17th of December: mail.openjdk.org/pipermail/serv…

WOW 🤩 The OpenJDK Vector API improvements to the JRuby JSON lib now improve encoding perf by better than 2X on real-world benchmarks, all without writing a line of assembly code! The potential of JRuby to accelerate Ruby apps grows with every JVM release. buff.ly/yKE2nfq

@java JavaOne 2025 was awesome! :) Can't wait to attend the 2026 edition.

JavaOne 2025 was such a hit that we just have to run it back. 😎 Save the date for our next #JavaOne event, coming to you March 17-19, 2026! social.ora.cl/6011fdkbH

Full tournament results 👇

Oooh! @OpenJDK @javamissionctrl won the tools category! x.com/java/status/19… JMC 10 will have a lot of exciting features - including support for the new (proper) CPU profiler in openjdk.org/jeps/509. On behalf of the project - thanks for all the votes! :)

Curious about open source? Join us in Switzerland on the 22nd of November for Hack-Commit-Push - a full day of hands-on OSS fun, no prior experience needed! Great chance to contribute, learn & connect. switzerland2025.hack-commit-pu.sh @Hackergarten @OpenJDK @javamissionctrl

The Eclipse Mission Control binary distribution of JMC 9.1.1 is available here: adoptium.net/en-GB/jmc/

The @OpenJDK Mission Control 9.1.1 source release is now tagged. A small, but oh-so important, release for @javamissionctrl users on Windows: hirt.se/blog/?p=1566 github.com/openjdk/jmc/re…

@headius I've been thinking the same. Job security for observability vendors though. ;)

I'm starting to become genuinely curious who is going to managed and maintain all this AI-generated code once companies have fired most of their developers. There's going to be a lucrative opportunity for humans to contract at insane rates to add features and fix critical bugs.

Hej @kstefanj! Regarding what we talked about at @JavaOne, this might help: github.com/openjdk/jmc/pu…

@AichaLaafia Nice! :)

Oooh, good thing I found this tweet, or maybe it found me👀 , I am about to prepare a demo using JMC for my next talk 💚

The @OpenJDK @javamissionctrl 9.1.0 source release is now available: github.com/openjdk/jmc/re… Here is what's new: hirt.se/blog/?p=1561

@headius That context could, for example, be provided by a tracer (that's what we do at Datadog). There is an ongoing discussion on how to best get "profiling labels" support for JFR. This would be an amazing tooling enabler, and support for it could then be added to JMC.

@headius The best way to do this is normally to have context labelling the events/samples, so that you can easier make sense of it. That context, could for example be provided by a tracer. For now you could emit contextual events.

@hirt Excuse me for going straight to the top, but I feel like I’m not getting the best results out of JFR/JMC and I want to understand why. Most recently, a performance problem was almost entirely due to synchronized methods that didn’t need to be synchronized. How to see that?

@headius Hi! Sorry for the late reply, I'm really not checking my social network stuff anymore. All information is a bit dated. You could try github.com/thegreystone/j….

More generally, what is the best source for learning how to get the most out of JFR? There’s such a hodge-podge of articles and howtos out there these days and they don’t seem to answer my questions well.

Congrats to Hendrik Schick on his first @OpenJDK @javamissionctrl contribution: github.com/openjdk/jmc/pu… Also thanks to the excellent @hackcommitpush initiative that enabled it: switzerland2024.hack-commit-pu.sh