scx_intent

scx_intent is an intent-aware, multi-tier CPU scheduler for Linux built on sched_ext using in-kernel BPF.

Instead of treating all threads with homogeneous timeslices or relying solely on runtime heuristics, scx_intent assigns tasks into 5 dedicated BPF Dispatch Queues (DSQs) based on their execution profile. Interactive UI, compositor, and audio tasks receive short, low-latency slices, while heavy throughput/batch tasks run on wider slices to minimize cache thrashing and context-switch overhead.

Architecture

Tasks are classified inside BPF at enqueue time (ops.enqueue) and dispatched across 5 priority-ranked DSQs:

Intent Tier	Target Workloads	DSQ ID	Time Slice	Precedence
INTENT_AUDIT	Security logging, auditd, live system monitors	0	10 ms	1 (Highest)
INTENT_INTERACTIVE	Wayland compositors, X11, audio engines (PipeWire), shells	1	4 ms	2
INTENT_IO	Storage I/O workers, database sync/flush operations	2	5 ms	3
INTENT_NETWORK	Socket handlers, network packet ingress/egress workers	3	8 ms	4
INTENT_COMPUTE	Compilers (rustc, gcc), batch computations, rendering	4	20 ms	5 (Lowest)

Dispatching & Multi-Tier Anti-Starvation

1. In-Kernel BPF Routing: Dispatch decisions happen entirely in kernel space via BPF iterator and scx_bpf_dispatch(). No userspace IPC trips in the critical path.
2. Prioritized Drain: Higher-ranked DSQs are evaluated first on dispatch (Audit -> Interactive -> IO -> Network -> Compute).
3. Starvation Prevention: Under sustained compute saturation, lower-priority DSQs track missed dispatch opportunities. Once a tier's starvation counter reaches the configured threshold (default: 32 ticks), it is injected directly into the dispatch queue to guarantee forward progress across all tasks.

Requirements

• Linux Kernel 6.12 or newer with CONFIG_SCHED_CLASS_EXT=y
• Clang / LLVM 17+
• Rust 1.80+ (with Cargo)
• bpftool and libbpf development headers

Building & Running

Clone the repository and build with release optimizations:

git clone https://github.com/Exploidus/scx_intent.git
cd scx_intent

# Run with standard desktop preset
cargo run --release

# Run with gaming / low-latency preset
cargo run --release -- --preset gaming

# Run with custom JSON configuration
cargo run --release -- --config intent.example.json

To inspect runtime parameters and options:

cargo run --release -- --help

Origins

The concept of dedicated intent classification originally stems from design work on the Exploidus kernel, reimagined and natively rewritten for the Linux sched_ext infrastructure.

License

GPL-2.0-only