openjdk/leyden
Nov 2025 – Jan 2026
3 Months active
Languages Used
C++JavaC
Technical Skills
Concurrency ManagementGarbage Collection ManagementJavaLinux developmentPerformance OptimizationTesting
Jonas Norlinder
PROFILE
Jonas Norlinder
Worked on the openjdk/leyden repository to enhance cross-platform thread CPU time reporting and garbage collection telemetry, focusing on both Windows and Linux environments. Used C++, Java, and Linux system programming to overhaul thread CPU time measurement, replacing /proc-based reads with clock_gettime and introducing benchmarking for validation. Improved file I/O performance by eliminating unnecessary fstat calls and modernized code paths for compatibility with recent Linux kernels. Addressed G1 garbage collector stability under high processor counts by capping concurrent threads, and introduced total CPU time counters for unsupported garbage collectors, enabling more accurate performance monitoring and reducing maintenance complexity across the codebase.
Overall Statistics
Feature vs Bugs
86%Features
Repository Contributions
11Total
Bugs
1
Commits
11
Features
6
Lines of code
391
Activity Months3
Your Network
642 peopleSame Organization
@openjdk.org340
Anton ArtemovMember
Alexey BakhtinMember
Artur BarashevMember
Anass BayaMember
Abhishek KumarMember
Aggelos BiboudisMember
Axel Boldt-ChristmasMember
Alisen ChungMember
Archie CobbsMember
Work History
January 2026
5 Commits • 2 Features
Jan 1, 2026January 2026 performance summary for openjdk/leyden. Delivered targeted performance improvements, stability fixes, and modernization cleanup across file I/O and OS-level code. Key outcomes include: (1) improved file opening paths by eliminating unnecessary fstat calls, (2) enhanced G1 GC stability under high processor counts, and (3) modernization cleanup to align with modern Linux kernels and ZGC.
5 Commits • 2 Features
Jan 1, 2026January 2026 performance summary for openjdk/leyden. Delivered targeted performance improvements, stability fixes, and modernization cleanup across file I/O and OS-level code. Key outcomes include: (1) improved file opening paths by eliminating unnecessary fstat calls, (2) enhanced G1 GC stability under high processor counts, and (3) modernization cleanup to align with modern Linux kernels and ZGC.
January 2026
December 2025
3 Commits • 3 Features
Dec 1, 2025December 2025 performance summary for openjdk/leyden focusing on CPU time measurement, code quality, and GC telemetry. Delivered three main capabilities: (1) Thread CPU time measurement overhaul using clock_gettime instead of /proc, with a new method to retrieve thread clock IDs and a benchmarking suite to validate performance; (2) Linux OS implementation code cleanup to improve clarity and maintainability by removing stale comments; (3) Garbage collection CPU time tracking enhancement adding a total counter for CPU time in unsupported garbage collectors to enable better monitoring and analysis.
December 2025
3 Commits • 3 Features
Dec 1, 2025December 2025 performance summary for openjdk/leyden focusing on CPU time measurement, code quality, and GC telemetry. Delivered three main capabilities: (1) Thread CPU time measurement overhaul using clock_gettime instead of /proc, with a new method to retrieve thread clock IDs and a benchmarking suite to validate performance; (2) Linux OS implementation code cleanup to improve clarity and maintainability by removing stale comments; (3) Garbage collection CPU time tracking enhancement adding a total counter for CPU time in unsupported garbage collectors to enable better monitoring and analysis.
November 2025
3 Commits • 1 Features
Nov 1, 2025November 2025: Delivered cross-platform thread CPU time reporting enhancements for openjdk/leyden, improving the accuracy and reliability of CPU time metrics across Windows and Linux. Implemented Windows GC CPU time tracing, refined ThreadMXBean.getThreadUserTime for accurate user CPU time reporting, and simplified Linux CPU time retrieval by removing obsolete fast_thread_clock_init logic. These changes enhance observability for performance tuning and GC analysis, while reducing maintenance risk.
3 Commits • 1 Features
Nov 1, 2025November 2025: Delivered cross-platform thread CPU time reporting enhancements for openjdk/leyden, improving the accuracy and reliability of CPU time metrics across Windows and Linux. Implemented Windows GC CPU time tracing, refined ThreadMXBean.getThreadUserTime for accurate user CPU time reporting, and simplified Linux CPU time retrieval by removing obsolete fast_thread_clock_init logic. These changes enhance observability for performance tuning and GC analysis, while reducing maintenance risk.
November 2025
Activity
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Quality Metrics
Correctness96.4%
Maintainability89.0%
Architecture89.0%
Performance94.6%
AI Usage20.0%
Skills & Technologies
Programming Languages
CC++Java
Technical Skills
C++C++ developmentConcurrency ManagementGarbage Collection ManagementJavaJava I/OJava managementLinux OSLinux developmentPerformance OptimizationTestingbenchmarkingcode maintenancegarbage collectionmemory management
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