February 2026 Performance Summary for sched-ext/scx: Focused delivery of latency-aware scheduling, safer resource budgeting, and memory-management improvements, with strengthened testing and observability. The work enhances latency guarantees under fork scenarios, tightens cgroup budget semantics, modernizes naming for readability, and provides scalable memory infrastructure for queues and trees.

January 2026 focused on delivering measurable improvements to scheduling, core capacity management, and maintainability across two key codebases: sched-ext/scx (scheduler and related components) and torvalds/linux (Energy Model Netlink integration).

2025-12 Monthly Summary for sched-ext/scx: Delivered performance-focused optimizations and reliability improvements that reduce deployment footprint and enhance user experience across the energy modeling workflow and release processes. Key contributions span feature optimization and robust error handling, with traceable commits.

November 2025 performance-focused development for sched-ext/scx: Delivered key topology and scheduling improvements, major DSQ refactors, portability and verifier resilience, and domain/topology enhancements; resulting in improved hardware locality, scheduling fairness, and robustness across kernels and toolchains, delivering concrete business/value improvements in throughput, latency, and stability.

October 2025 monthly review for sched-ext/scx highlights targeted performance and reliability improvements, robust testing automation, and broader compatibility across toolchains and kernel configurations. The team delivered practical features for resource testing and verified stability through careful hardening of tracing, topology calculation, and BPF verification paths.

September 2025 (Month: 2025-09) - sched-ext/scx delivered core CGroup throttling with CPU bandwidth control, reinforced robustness of the scheduling extension, and improved scheduling efficiency through targeted optimizations. The work focuses on resource isolation, predictable CPU allocation, and reliability at scale for multi-tenant workloads, with clear traceability to commits and repository strides.

August 2025 monthly summary for sched-ext/scx: Focused on stabilizing the SCX LAVD scheduler under contention, expanding scalability via data-structure refactors, and laying groundwork for CPU bandwidth control. Delivered features include scheduler hardening, LLC/NUMA domain enhancements, and initial cgroup bandwidth control integration; ported set_rlimit_infinity to the rlimit crate; updated Ubuntu docs. Key bugs fixed across migration probability, ARM verification, per_cpu_dsq compile errors, and warnings. Result: improved reliability, performance under load, and deployment readiness.

July 2025: Delivered substantial scheduling, observability, and reliability improvements for sched-ext/scx with a focus on business value through lower overhead, better latency predictability, and improved scalability under load. Key outcomes include: 1) Conditional loading for kprobes/tracepoints and centralization of math utilities by moving __calc_avg() to common.bpf.h and introducing sqrt_u64(), enabling lighter probes and easier maintenance. 2) Wakeup tracing and latency-criticality enhancements in scx_lavd, including ftrace-based futex tracing and overhead accounting for tracepoints, plus reorganizations to tighten latency/criticality handling. 3) Latency-criticality flag system enhancements with new LAVD flags and wake semantics to improve scheduling decisions. 4) Task context flags refactor and CPU utilization/run-state tracking improvements, including removal of futex_boost and better accounting of running_clk. 5) Scheduling performance improvements: load balancing moved to ops.enqueue(), expanded test coverage for multi-bit task flags, and removal of redundant pick_idle_cpu() during ops.enqueue() without behavior change. Overall, these changes reduce overhead, improve latency bounds, enhance task distribution under contention, and increase deployment confidence through instrumentation and tests.

June 2025 performance summary for sched-ext/scx: Architecture-aware scheduling improvements and performance/energy tooling were delivered, strengthening support for heterogeneous CPUs while improving reliability and maintainability. Key features include hardened CPU capacity and big/LITTLE detection, topology-driven Lavd core-type determination and CPU ordering, energy model integration with performance utilities and safe fallback, BPF scheduler enhancements with a PCO table for accurate active-CPU calculation, and modernized build/runtime options. These changes enable smarter resource usage, lower energy impact, and faster iteration cycles in real deployments.

May 2025 monthly summary for sched-ext/scx focusing on business value and technical achievements. Delivered a suite of scheduling improvements and stability fixes that reduce preemption overhead, improve CPU utilization, and provide clearer performance metrics for operators. Highlights include safer preemption controls with observable statistics, a refactored and capacity-aware load balancing core with task donations, groundwork for domain-aware scheduling, a kernel sync fix for QMAP, and latency/scheduling enhancements in scx_lavd. Demonstrated strong kernel-level engineering, robust option handling, and measurable impact on performance and reliability.

April 2025 monthly summary for sched-ext/scx: Delivered energy-aware scheduling capabilities, expanded CPU topology awareness, and a suite of performance optimizations in lavd. Strengthened cross-architecture stability with targeted bug fixes and improved test coverage. External API exposure and CLI enhancements position the project for easier integration and more accurate resource planning. The work emphasized delivering business value through faster scheduling decisions, lower energy consumption, and more predictable latency. Key business value: improved scheduling efficiency reduces latency, energy_model enables smarter power-aware decisions, and API/CLI enhancements improve external tooling integration and operational visibility.

March 2025 deliverables for sched-ext/scx focused on strengthening tracepoint utilities, CPU capacity awareness, and extensive SCX_LAVD scheduling optimizations to improve performance on multi-core/topology-aware systems. Notable outcomes include: conditional tracepoint loading, Cpu.cpu_capacity field addition, and fixes to tracepoint_exists() across kernel configurations; futex boost enablement when tracepoints are available with a no-futex-boost option and topology-based cpu_capacity usage; core scheduling improvements including domain-aware CPU selection, enhanced cpumask handling, overflow/dispatch/enqueue tuning, and per-CPU fast-paths; cross-domain migration accounting and wakeup-flag support; idle-based dispatch enhancements and new idle/BPF programs; runtime flag management in main.rs; API cleanup reducing maintenance burden by removing unused context getters; and cleanup of cpdom_cpumask usage and maintenance of is_active in compute domains. These changes collectively improve resource utilization, lower scheduling latency, and enable more deterministic performance on complex CPU topologies, delivering tangible business value for tracepoint-heavy workloads.

February 2025 — sched-ext/scx: Delivered core improvements across scheduler, BPF dispatch, tooling, and observability. Key outcomes include reduced tail latency, improved stability under mixed workloads, and cross-version compatibility for BPF-based scheduling. Additionally, automated enum definitions and headers streamline cross-arch builds, while telemetry accuracy and tracing enhancements improve operational insights. These workstreams collectively enhance performance, reliability, and maintainability of the scheduler extension.

January 2025 performance summary for sched-ext/scx. Focused on delivering scheduling features for BPF schedulers, standardizing time APIs, and hardening the lavd path, with a dedicated emphasis on business value and maintainability. Key achievements include delivering a fast path for migration-disabled tasks in idle CPU selection, introducing a unified time source and helpers for BPF-based schedulers, standardizing time API usage across multiple modules, and aligning timing utilities to reduce overhead and improve correctness. The month also includes consolidation of BPF time sources and widespread refactoring to scx_bpf_now(), along with targeted scheduling improvements to lavd for better latency and preemption decisions.

December 2024 monthly summary for sched-ext/scx: Delivered hardware-aware topology extension for Snapdragon X Elite and improved cache-ID handling, enabling compatibility with newer devices and more robust scheduling. Implemented CPU frequency scaling in performance mode to maintain high throughput without excessive frequency switching. Significantly enhanced the scx_lavd scheduler with faster idle selection, reduced timekeeping overhead, and a 5 ms time slice, improving throughput, latency, and fairness for migration-disabled tasks. Fixed critical arm64 verifier error by aligning cpumask size, and added per-CPU preemption data reset on idle/release to prevent incorrect victim selection. These changes broaden device support, improve runtime performance, stability, and efficiency, and demonstrate strong multi-arch, kernel scheduler, and performance optimization capabilities.

November 2024 performance review for sched-ext/scx. Focused on performance tuning, locality, stability, and maintainability of the scx_lavd scheduling path. Key features delivered include targeted scheduling improvements and structural cleanups that reduce overhead and improve responsiveness, alongside architectural refinements to support scalable load under NUMA and cross-domain migrations. Major bug fixes fixed CI reliability, warnings, and race conditions, contributing to a more robust codebase and smoother CI cycles. Business value realized includes improved throughput and lower tail latency under load, better CPU locality, and more predictable scheduling decisions, enabling faster feature delivery and safer deployments. Key features delivered this month: - Optimized the consume_starving_task() path to improve responsiveness and throughput. - Created DSQs on their associated NUMA nodes to improve locality. - Deprioritized long-running runtime by prioritizing frequencies further to balance efficiency and throughput. - Factor runtime more aggressively in deadline calculations for tighter deadlines and better schedulability. - Dropped kernel lock tracing to reduce overhead and simplify debugging. Major bugs fixed: - Warnings eliminated by variable name cleanup and CI-friendly changes. - CI error for missing kernel symbols resolved to ensure reliable builds. - Avoided self-IPI during preemption to improve stability and prevent spurious interrupts. - Updated cur_logical_clk atomically to avoid race conditions and ensure correct timestamping. - Ensured exiting tasks are included in scheduling calculations to prevent task starvation. Overall impact and accomplishments: - Substantial performance and locality improvements with measurable throughput gains and reduced scheduling latencies under load. - Improved stability, CI reliability, and maintainability through targeted fixes and readability enhancements. - Lays groundwork for future tunables and observability enhancements with expanded logging for cross-domain migrations. Technologies/skills demonstrated: - Low-level scheduling optimizations, NUMA-aware data locality, and cache-friendly struct layouts. - Atomic operations, contention reduction, and preemption tuning. - Code readability improvements, tunables exposure, and enhanced logging for observability. - End-to-end workflow improvements including CI reliability and build robustness.

Month: 2024-10. This period focused on latency-aware improvements to the scx scheduler in sched-ext/scx and a correctness fix to preemption handling, delivering tangible business value for latency-sensitive workloads and ensuring scheduler correctness.