sched-ext/scx
Feb 2026 – Apr 2026
3 Months active
Languages Used
CRustPythonShell
Technical Skills
BPFBPF programmingC programmingCPU schedulingData SerializationJSON
Tejun Heo
PROFILE
Tejun Heo
Worked on the sched-ext/scx repository to advance NUMA-aware CPU scheduling and kernel extensibility. Over three months, delivered a unified per-node allocation framework, enhanced per-node state management, and introduced BPF scheduling extensions with compatibility wrappers for multiple kernel versions. Leveraged C, Rust, and BPF programming to optimize performance, improve scalability for high-node-count systems, and ensure robust error handling. Upgraded the scx_pandemonium package to version 5.6.0, validated through targeted testing and CI/CD pipelines. Documented upgrade impacts and usage for downstream teams, supporting reliable adoption. The work emphasized maintainability, kernel compatibility, and efficient resource management in complex system environments.
Overall Statistics
Feature vs Bugs
85%Features
Repository Contributions
65Total
Bugs
3
Commits
65
Features
17
Lines of code
2,043,423
Activity Months3
Work History
April 2026
1 Commits • 1 Features
Apr 1, 2026Month: 2026-04 focused on delivering a critical package upgrade for sched-ext/scx and maintaining system stability. No major bugs fixed this month; significant business value delivered through feature upgrade and performance improvements.
1 Commits • 1 Features
Apr 1, 2026Month: 2026-04 focused on delivering a critical package upgrade for sched-ext/scx and maintaining system stability. No major bugs fixed this month; significant business value delivered through feature upgrade and performance improvements.
April 2026
March 2026
20 Commits • 2 Features
Mar 1, 20262026-03 sched-ext/scx monthly summary. Key features delivered: - BPF Scheduling Extensions and Compatibility Wrappers: Adds BPF scheduling extensions, wrappers, and compatibility shims for multiple kernel versions, including new argument wrapper structures, new BPF symbols, compatibility wrappers for DSQ operations, guarded API compatibility, and task slice/virtual time wrappers; updated symbols and enums to extend scheduling capabilities. - NUMA Hardware Scalability Enhancements: Increased MAX_NUMA_NODES from 8 to 32 and consolidated per-node statistics into a single line for readability and efficiency on high-node-count systems (AMD EPYC). Major bugs fixed: - Hotplug: Fix errno and endptr checks in scx_hotplug_seq to validate error conditions correctly; align with upstream behavior. - Fix ksym name: scx_bpf_rq_locked -> scx_bpf_locked_rq naming correction to ensure proper symbol resolution across kernel versions. Overall impact and accomplishments: - Improved kernel-version compatibility, stability, and scalability for large NUMA systems; reduced runtime risk due to symbol resolution and API changes; streamlined per-node reporting for operators; supports adoption on newer kernel lines with minimal changes. Technologies/skills demonstrated: - BPF and libbpf development, kernel symbol management, compatibility wrappers, kfuncs, and verifications; NUMA-aware performance considerations; code hygiene and alignment with upstream practices.
March 2026
20 Commits • 2 Features
Mar 1, 20262026-03 sched-ext/scx monthly summary. Key features delivered: - BPF Scheduling Extensions and Compatibility Wrappers: Adds BPF scheduling extensions, wrappers, and compatibility shims for multiple kernel versions, including new argument wrapper structures, new BPF symbols, compatibility wrappers for DSQ operations, guarded API compatibility, and task slice/virtual time wrappers; updated symbols and enums to extend scheduling capabilities. - NUMA Hardware Scalability Enhancements: Increased MAX_NUMA_NODES from 8 to 32 and consolidated per-node statistics into a single line for readability and efficiency on high-node-count systems (AMD EPYC). Major bugs fixed: - Hotplug: Fix errno and endptr checks in scx_hotplug_seq to validate error conditions correctly; align with upstream behavior. - Fix ksym name: scx_bpf_rq_locked -> scx_bpf_locked_rq naming correction to ensure proper symbol resolution across kernel versions. Overall impact and accomplishments: - Improved kernel-version compatibility, stability, and scalability for large NUMA systems; reduced runtime risk due to symbol resolution and API changes; streamlined per-node reporting for operators; supports adoption on newer kernel lines with minimal changes. Technologies/skills demonstrated: - BPF and libbpf development, kernel symbol management, compatibility wrappers, kfuncs, and verifications; NUMA-aware performance considerations; code hygiene and alignment with upstream practices.
February 2026
44 Commits • 14 Features
Feb 1, 2026February 2026 (2026-02) delivered a major leap in NUMA-aware scheduling for sched-ext/scx by introducing a unified per-node allocation framework, enhanced per-node state, and extensive testing. The work lays the groundwork for true NUMA-aware CPU allocation, reduces cross-node traffic, and improves predictability in multi-node environments.
44 Commits • 14 Features
Feb 1, 2026February 2026 (2026-02) delivered a major leap in NUMA-aware scheduling for sched-ext/scx by introducing a unified per-node allocation framework, enhanced per-node state, and extensive testing. The work lays the groundwork for true NUMA-aware CPU allocation, reduces cross-node traffic, and improves predictability in multi-node environments.
February 2026
Activity
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Quality Metrics
Correctness98.4%
Maintainability88.6%
Architecture95.8%
Performance89.2%
AI Usage21.6%
Skills & Technologies
Programming Languages
CPythonRustShell
Technical Skills
API designBPFBPF programmingC programmingCI/CDCPU schedulingData SerializationJSONKernel DevelopmentKernel developmentNUMA architecturePython scriptingRustRust programmingSoftware Development
Repositories Contributed To
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