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Overview ======== This scheduler is derived from scx_rustland, but it is fully implemented in BFP with minimal user-space Rust part to process command line options, collect metrics and logs out scheduling statistics. Unlike scx_rustland, all scheduling decisions are made by the BPF component. Motivation ========== The primary goal of this scheduler is to act as a performance baseline for comparison with scx_rustland, allowing for a better assessment of the overhead caused by kernel/user-space interactions. It can also be used to deploy prototypes initially tested in the scx_rustland scheduler. In fact, this scheduler is expected to outperform scx_rustland, due to the elimitation of the kernel/user-space overhead. Scheduling policy ================= scx_bpfland is a vruntime-based sched_ext scheduler that prioritizes interactive workloads. Its scheduling policy closely mirrors scx_rustland, but it has been re-implemented in BPF with some small adjustments. Tasks are categorized as either interactive or regular based on their average rate of voluntary context switches per second: tasks that exceed a specific voluntary context switch threshold are classified as interactive. Interactive tasks are prioritized in a higher-priority DSQ, while regular tasks are placed in a lower-priority DSQ. Within each queue, tasks are sorted based on their weighted runtime, using the built-in scx vtime ordering capabilities (scx_bpf_dispatch_vtime()). Moreover, each task gets a time slice budget. When a task is dispatched, it receives a time slice equivalent to the remaining unused portion of its previously allocated time slice (with a minimum threshold applied). This gives latency-sensitive workloads more chances to exceed their time slice when needed to perform short bursts of CPU activity without being interrupted (i.e., real-time audio encoding / decoding workloads). Results ======= According to the initial test results, using the same benchmark "playing a videogame while recompiling the kernel", this scheduler seems to provide a +5% improvement in the frames-per-second (fps) compared to scx_rustland, with video games such as Cyberpunk 2077, Counter-Strike 2 and Baldur's Gate 3. Initial test results indicate that this scheduler offers around a +5% improvement in frames-per-second (fps) compared to scx_rustland when using the benchmark "playing a video game while recompiling the kernel". This improvement was observed in games such as Cyberpunk 2077, Counter-Strike 2, and Baldur's Gate 3. Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
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RUST SCHEDULERS
Introduction
This directory contains schedulers with user space rust components.
The README in each scheduler directory provides some background and describes the types of workloads or scenarios they're designed to accommodate. For more details on any of these schedulers, please see the header comment in their main.rs or *.bpf.c files.