June 2026: Delivered foundational advancements for SCX workload characterization and LLC-aware scheduling in sched-ext/scx. Focus areas included consolidating the workload toolchain, enabling end-to-end performance profiling, adding robust data extraction capabilities, and hardening scheduling/drain paths for stability and measurable impact.

March 2026 Monthly Summary for sched-ext/scx Key features delivered: - Cpumask Handling Refactor and API Stabilization: Consolidated cpumask handling into a common header (cell_cpumask.bpf.h), introduced documented APIs for error handling, and prepared the groundwork for subcell cpumask support. Commits: 44211b0f71879932322830c249c030e490545430. Outcome: reduced duplication, clearer error semantics, and scalable design for future patches. - Code Style Standardization to Kernel clang-format: Migrated scx_mitosis C code to kernel clang-format for improved readability and maintainability. Commit: 78b77506ba43e9b9e6f929738544ce07bba26001. Outcome: consistent coding style and reduced lint warnings across sched-ext components. Major bugs fixed: - None explicitly reported this month; focus was on refactoring and style alignment to reduce defect surfaces and improve reliability. Where applicable, improved fatal vs non-fatal error handling paths to prevent silent failures and ensure safer recovery. Overall impact and accomplishments: - Increased maintainability, scalability, and developer productivity through API-stabilized cpumask handling and standardized coding style. Prepared groundwork for subcell cpumask support, enabling smoother future enhancements with lower risk. Technologies/skills demonstrated: - C/kernel-level development, BPF interactions, cpumask management, API design and documentation, and adherence to kernel clang-format standards.

November 2025 monthly summary: Targeted stability and performance improvements in sched-ext/scx focused on the StickyDynamic growth algorithm. Implemented a core allocation bug fix that computes precise core add/free sets and updates layer cpumasks directly, preventing fragmentation and enabling proper CPU allocation/free when layers are emptied. The change is scoped to StickyDynamic to avoid regressions in other growth algorithms, and it enhances production workload stability and CPU utilization under saturation. Also ensured HintEquals modifiers function correctly with empty layers.

October 2025 (2025-10) monthly summary for sched-ext/scx: Delivered high-frequency admission control enhancements in the SCX Layered scheduler, introduced two new matchers with EWMA-based gating, and enhanced observability and documentation. Implemented SystemCpuUtilBelow and DsqInsertBelow high-frequency matchers, each enabling more robust gatekeeping for task admission under varying load. Exposed EWMA metrics in stats (global for SystemCpuUtilBelow and per-layer for DsqInsertBelow) to improve visibility into admission decisions. Added comprehensive docs for the new matchers to guide usage and expectations. Major stability and code quality improvements included fixing a race condition where a task layer refresh could be processed twice, and cleaning up whitespace in BPF C source to reduce diffs and improve maintainability. These changes reduce crash risk and improve long-term stability. Business impact: with tighter, data-driven admission control and improved observability, the system experiences more predictable latency, fewer oscillations under load, and easier debugging and maintenance. Demonstrated capabilities in C development, EWMA-based throttling, per-layer statistics, and thorough documentation.

September 2025 performance summary: Across linux-riscv/linux and sched-ext/scx, delivered key features and bug fixes that improve reliability, security, and observability. Implemented rqspinlock NMI fallback with deadlock checks and stress tests to prevent system lockups; broadened BPF cgroup access across namespaces and added non-root namespace testing; reinforced RCU safety for KF_RCU_PROTECTED BPF functions with enhanced error feedback; extended BPF JIT with signed loads in arena memory; added task hint monitoring in scxcash to trace task-local hints via a ring buffer.

August 2025 (2025-08) monthly summary for sched-ext/scx: Focused on delivering high-impact kernel scheduler improvements and a robust performance monitoring stack. Key outcomes include retiring the homegrown RCU in scx_mitosis, enabling kernel-supported queued wakeups for faster, more reliable wakeups; hardening scheduling robustness to avoid uninitialized min_vtime_dsq and improving dispatch safety; advancing hint-based dynamic scheduling with safety checks and layer matching; and laying down a scalable performance monitoring foundation for scxcash with cache usage analysis groundwork, perf sampling backend, AMD address capture, and unified event formats.

Concise monthly summary for 2025-06 focused on sched-ext/scx development, emphasizing business value, stability, and observability improvements.

May 2025 monthly summary for sched-ext/scx. Key feature delivered: Scx_layered Scheduler with Task Hint Framework and Dynamic Vruntime Scaling. Implemented a pinned BPF map scx_layered_task_hint_map to enable system tasks to publish hints and allow broad read/write access; this enables the scheduler to dynamically adjust vruntime advancement based on hints rather than a fixed weight. No major bugs fixed this month. Business impact: more flexible and responsive scheduling for system tasks, reducing manual tuning and enabling adaptive behavior under varying workload patterns. Technologies/skills demonstrated: BPF pinned maps, dynamic scheduling, VRUNTIME-based scheduling, kernel-user-space integration. Traceability: commits 0dc1276248393278a3aa8f146897f8407cb65451 and 8e252f674e8e88ca143c60d5e7110fba87072955 in sched-ext/scx.

March 2025 focused on delivering a new StickyDynamic Growth CPU Allocation algorithm for the scx_layered system within the sched-ext/scx repository, paired with a refactor of the core order generation to reflect dynamic layer size changes. The solution dynamically allocates CPU across layers based on their size while preserving stickiness to LLCs, enabling more responsive and efficient resource distribution under shifting workloads. The work is anchored by a single primary commit that introduces the StickyDynamic growth algorithm.

February 2025: Implemented a critical bug fix in bpftrace to ensure accurate feature detection for dpath and skboutput. The patch fixes 64-bit vs 32-bit loads when forming the tracing program pointer, resolving a feature-detection failure. Committed as bpffeature: Fix detection for tracing programs (commit 4618ba460933df6d10e1b676358a97a7b4e6a531). This improvement reduces false negatives in feature reporting, enhancing reliability for users and downstream tooling.