Speaker Details

The session will start with a quick introduction to the theory of profiling discussing the motivations, explaining the different types of profiling and visualization format while listing the tools available for this purpose. This also includes some tooling for reliably emulating the load generation and validating the improvements.
Then we will guide the attendees through the profiling tools that we want to use throughout the session:

• Java VisualVM: https://visualvm.github.io/download.html
• Async-profiler: https://github.com/jvm-profiling-tools/async-profiler
• JDK Mission Control: https://www.oracle.com/java/technologies/jdk-mission-control.html
• JMH: https://github.com/openjdk/jmh
• Hyperfoil: https://hyperfoil.io/ (for load generation)

Then we will put these tools at work in a practical real-world scenario. We will provide a sample Quarkus-based Java webapp, using a simple but realistic technology stack, having different performance issues involving excessive memory allocation, CPU consumption, slow blocking I/O, locks contention and cache misses. We will demonstrate how to use the before mentioned profiling tools to discover, investigate, fix and verify these issues.

Virtual threads finally exited their development and preview phases and with JVM 21 are available as a stable and supported Java feature. During the latest Devoxx edition I started exploring the characteristics of virtual threads and their performance implications putting them at work, with a funny but practical example, using a Conway's Game of Life implementation based on Project Loom. Starting from the same playground this time we will explore more in depth the internal implementation details of virtual threads, trying to answer to some interesting questions. What does it mean in practice that virtual threads aren't preemptive? Are scoped values enough to replace ThreadLocals in all possible scenarios? What does it happen if you try to replace the fork/join pool, used as default carrier thread pool, with something different? At the end we will conclude this exploration trying to experience the multithreaded programming equivalent of the sound of one hand clapping or how virtual threads make it possible to cause a deadlock using one single lock.