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World Congress 2026 Europe • Jul 10, 2026 • Session details

Swapping Code, Losing Memory: A JVM Deep Dive

Marco Sussitz

Hot-swapping code is pure magic, until it silently exhausts your off-heap memory. Dive into OpenJDK's C++ core to uncover the hidden metaspace leak crashing your Java applications.

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#1 about 3 min

Introduction to live debugging and code hot swapping

How live debuggers utilize runtime code manipulation to safely expose running application state inside production environments.

#2 about 3 min

Demonstrating code hot swapping in a running application

How intercepting loaded classes and injecting updated logic via embedded decompilers enables real-time application modifications.

#3 about 3 min

Utilizing the JVM tool interface for dynamic code changes

How debuggers avoid costly virtual machine restarts by utilizing native low-level functions to trigger runtime behavior changes.

#4 about 2 min

Implementing class file load hooks and retransformations

How leveraging class file hooks enables continuous monitoring and dynamic reinjection of updated binary arrays.

#5 about 3 min

Translating low-level structures into basic Java agents

How adopting standard class file transformers bypasses the complexity of constructing binary code replacements manually.

#6 about 3 min

Discovering application crashes caused by excessive code hot swapping

How aggressively applying dynamic breakpoints reveals hidden stability limitations underlying fundamental code reloading mechanisms.

#7 about 2 min

Profiling Java memory to uncover metaspace leaks

How standard flight recording utilities identify persistent meta-space memory leaks hidden beneath apparently healthy heap utilizations.

#8 about 4 min

Isolating metaspace memory leaks with a minimal reproducer

How isolating test conditions and analyzing documentation specifications uncovers architectural boundaries restricting native memory deallocation.

#9 about 3 min

Compiling and configuring the OpenJDK for direct debugging

How compiling internal source elements with active debug symbols enables direct observation of underlying code behaviors.

#10 about 4 min

Debugging internal mixed stack traces to inspect variables

How tracing mixed internal native threads exposes fundamental execution flaws triggering uncontrolled constant pool expansions.

#11 about 2 min

Fixing memory leak bugs by removing unused string constants

How dropping unused reference fields from structural configurations successfully halts excessive memory accumulation across back-to-back updates.

#12 about 2 min

Practical takeaways for investigating obscure runtime memory leaks

Why surfacing obscure defect findings via appropriate ticket channels proves more reliable than forcing complicated local modifications.

Matching moments

6:21 min

Exploring JVM crashes and future debugging trends

Johannes Bechberger · LIVE

8:29 min

Discussion on JIT memory parameters and cross-language benchmarking

Daniel Strmečki · LIVE

1:28 min

Exploring the high-level Java platform debugging architecture

Johannes Bechberger · LIVE

4:09 min

Tooling challenges with debugging, logging, and IDEs

Gonzalo Ortiz Jaureguizar Gonzalo Ortiz Jaureguizar · World Congress 2026 Europe

4:02 min

Understanding Java virtualization and just-in-time compiler performance challenges

Eric Deandrea Eric Deandrea · World Congress 2025

10:03 min

Addressing updates on concurrency extensions and code diagnostics

Mohamed Taman · LIVE

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