2023-12-06 22:35:08 +00:00
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RUST SCHEDULERS
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===============
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# Introduction
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This directory contains schedulers with user space rust components.
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2024-01-04 14:55:35 +00:00
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The README in each scheduler directory provides some background and describes
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2023-12-06 22:35:08 +00:00
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the types of workloads or scenarios they're designed to accommodate. For more
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details on any of these schedulers, please see the header comment in their
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main.rs or \*.bpf.c files.
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# Schedulers
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2024-01-04 14:55:35 +00:00
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- [scx_layered](scx_layered/README.md)
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- [scx_rusty](scx_rusty/README.md)
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- [scx_rustland](scx_rustland/README.md)
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2024-02-24 22:04:04 +00:00
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- [scx_rlfifo](scx_rlfifo/README.md)
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2024-03-16 01:31:07 +00:00
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- [scx_lavd](scx_lavd/README.md)
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scheds: introduce scx_bpfland
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>
2024-06-24 06:56:03 +01:00
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- [scx_bpfland](scx_bpfland/README.md)
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