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47 lines
2.2 KiB
Markdown
47 lines
2.2 KiB
Markdown
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# scx_bpfland
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This is a single user-defined scheduler used within [sched_ext](https://github.com/sched-ext/scx/tree/main), which is a Linux kernel feature which enables implementing kernel thread schedulers in BPF and dynamically loading them. [Read more about sched_ext](https://github.com/sched-ext/scx/tree/main).
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## Overview
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scx_bpfland: a vruntime-based sched_ext scheduler that prioritizes interactive
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workloads.
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This scheduler is derived from scx_rustland, but it is fully implemented in BPF
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with minimal user-space Rust part to process command line options, collect
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metrics and logs out scheduling statistics. The BPF part makes all the
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scheduling decisions.
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Tasks are categorized as either interactive or regular based on their average
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rate of voluntary context switches per second. Tasks that exceed a specific
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voluntary context switch threshold are classified as interactive. Interactive
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tasks are prioritized in a higher-priority queue, while regular tasks are
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placed in a lower-priority queue. Within each queue, tasks are sorted based on
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their weighted runtime: tasks that have higher weight (priority) or use the CPU
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for less time (smaller runtime) are scheduled sooner, due to their a higher
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position in the queue.
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Moreover, each task gets a time slice budget. When a task is dispatched, it
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receives a time slice equivalent to the remaining unused portion of its
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previously allocated time slice (with a minimum threshold applied). This gives
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latency-sensitive workloads more chances to exceed their time slice when needed
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to perform short bursts of CPU activity without being interrupted (i.e.,
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real-time audio encoding / decoding workloads).
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## Typical Use Case
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Interactive workloads, such as gaming, live streaming, multimedia, real-time
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audio encoding/decoding, especially when these workloads are running alongside
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CPU-intensive background tasks.
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In this scenario scx_bpfland ensures that interactive workloads maintain a high
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level of responsiveness.
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## Production Ready?
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The scheduler is based on scx_rustland, implementing nearly the same scheduling
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algorithm with minor changes and optimizations to be fully implemented in BPF.
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Given that the scx_rustland scheduling algorithm has been extensively tested,
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this scheduler can be considered ready for production use.
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