Tobias Hartmann
Software Development Manager at Oracle
Basel Metropolitan Area Switzerland
Summary
🤩
Rockstar🎓
Top SchoolTobias Hartmann is a Software Development Manager and compiler engineer with 12 years of deep expertise across the full Java execution stack, from low-level assembly on x86, SPARC and ARM to high-level Java libraries and runtime internals. He leads the Swiss JVM Compiler Team at Oracle and has been a principal contributor and go-to expert on HotSpot JIT compilers, driving major efforts like Valhalla (value types) and Compact Strings while triaging critical compiler bugs. His contributions to flagship OpenJDK projects (jdk and valhalla) include fixes that improved JVM stability and C2 support for flattened value types, reflecting both broad and highly specialized impact on the Java ecosystem. Tobias combines hands-on C/C++ and assembly development with mentoring and technical leadership, and his academic work includes papers on multi-tiered compilation and code-cache management. Based in the Basel region, he blends production-grade systems thinking with research-grade rigor—evident from supervising theses and presenting technical talks to the OpenJDK community.
12 years of coding experience
9 years of employment as a software developer
Australian National UniversityBachelor's Degree, Computer Science, 5.19 - good, Bachelor's Degree, Computer Science, 5.19 - good at Eidgenössische Technische Hochschule Zürich
German, English
Github Skills (17)
c-language10
jvm10
datatypes10
java10
javas10
cprogramming-language10
primitive-types10
collector9
garbage9
performance-optimization9
garbage-collection9
g9
compiler9
multithreading8
debug8
Programming languages (4)
Github contributions (5)
openjdk/valhalla
Sep 2017 - Oct 2022
https://openjdk.org/projects/valhalla
Role in this project:
Back-end Developer
Back-end DeveloperContributions:164 reviews, 413 commits, 253 PRs in 5 years 1 month
Contributions summary:Tobias primarily worked on the C2 compiler support for flattened value types within the OpenJDK/Valhalla project. Their contributions focused on implementing features for the C2 compiler to handle non-flattened value type fields and ensuring the correct handling of these types at runtime. They addressed critical issues such as crashes caused by the compiler and improved the efficiency of accessing value type fields by ensuring proper scalarization.
openjdkjavavalhalla
openjdk/jdk
Jan 2023 - Jan 2023
JDK main-line development https://openjdk.org/projects/jdk
Role in this project:Back-end Developer
Back-end DeveloperContributions:1926 reviews, 10 commits, 139 PRs in 21 days
Contributions summary:Tobias contributed to the JDK main-line development, primarily focusing on the Java Virtual Machine (JVM) and its internals. Their commits addressed issues related to time-related C1 intrinsics, incorporating crucial pinning to ensure consistent results. They also fixed bugs related to memory access, such as missing null pointer checks in interpreter runtime code, and addressing issues with string concatenation, improving the stability of Java. The contributions involved code changes in core JVM files and test classes.
openjdkjavajvmjdk
Find and Hire Top DevelopersWe’ve analyzed the programming source code of over 60 million software developers on GitHub and scored them by 50,000 skills. Sign-up on Prog,AI to search for software developers.