Thomas Stuefe
Principal Software Engineer at IBM
Mainz, Rhineland-Palatinate, Germany
Summary
🤩
Rockstar🎓
Top SchoolThomas Stuefe is a Principal Software Engineer with over two decades of systems and JVM-focused experience and 11 years in senior engineering roles, currently at IBM after a recent tenure at Red Hat. He is a hands-on OpenJDK contributor and reviewer, with notable commits improving the HotSpot runtime—thread management, C1 codegen, Metaspace sizing, and JNI—helping stabilize and optimize Java's core. His background spans platform porting and low-level C++ work for large enterprise JVMs (SAP JVM) and legacy systems on IBM platforms, giving him deep expertise in memory management, runtime compilers, and observability. Colleagues rely on him for tricky runtime diagnostics and performance tuning that few engineers undertake, and he regularly bridges the gap between product-grade enterprise requirements and upstream OpenJDK development. Based in Mainz, Germany, he combines academic grounding in information technology with pragmatic engineering that improves both tooling and production JVM behavior.
11 years of coding experience
27 years of employment as a software developer
Master's degree, Information Technology, Master's degree, Information Technology at Hochschule Stralsund
English
Github Skills (18)
c-language10
jvm10
memory-management10
virtual-machine10
java10
javas10
openjdk10
performance-optimization10
hotspot10
cprogramming-language10
multithreading9
concurrency9
g8
operating-system8
garbage-collection8
Programming languages (10)
Github contributions (5)
openjdk/jdk
May 2021 - Jan 2023
JDK main-line development https://openjdk.org/projects/jdk
Role in this project:
Back-end Developer
Back-end DeveloperContributions:2522 reviews, 16 commits, 425 PRs in 1 year 9 months
Contributions summary:Thomas contributed to the development of the OpenJDK, with a focus on low-level system optimizations and core Java Virtual Machine improvements. The commits involve modifications to the core runtime, including changes to thread management, code generation (C1), memory management (Metaspace), and the Java Native Interface (JNI). The contributions cover debugging, improving performance, and extending the overall stability of the Java platform.
openjdkjavajvmjdk
openjdk/jdk17u
Jan 2023 - Feb 2023
https://wiki.openjdk.org/display/JDKUpdates/JDK+17u
Role in this project:Back-end Developer
Back-end DeveloperContributions:2 reviews, 8 commits, 10 PRs in 10 days
Contributions summary:Thomas contributed to the OpenJDK 17u repository by modifying the hotspot code. They focused on removing and deprecating features related to the NMT shutdown command and also contributed to showing the signal block state within signal handler printouts. Further contributions include ignoring non-modifying sigaction calls and increasing metaspace mappings and size. The user's work primarily involved C++ code and Java-related testing.
openjdkjavawikijdk
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