Rust-Written Linux Scheduler Showing Promising Results for Gaming Performance
A prototype Linux scheduler written in Rust and plugged in via eBPF reportedly improves game performance under heavy system load, such as compiling a kernel in the background. Commenters note that the gains come from a workload-specialized scheduling algorithm and the new sched_ext infrastructure, not from Rust being inherently faster than C, while still seeing it as a meaningful proof that Rust can handle core, performance‑sensitive tasks. The thread also highlights how hot‑swappable, user‑space schedulers enable rapid experimentation, alongside recurring debates over Rust hype, ergonomics, and its role in replacing or complementing C in low‑level systems.
Rust vs C and Performance
- Many argue the performance win comes from the scheduling algorithm and workload specialization, not from Rust itself.
- Others note Rust can still matter indirectly: stronger safety and ergonomics may make it easier to attempt more complex or risky algorithms correctly.
- It’s emphasized that any such scheduler could be written in C (or other languages) and that C can implement arbitrarily complex algorithms.
Rust in the Kernel and sched_ext/eBPF
- Several comments stress the real story is that a core kernel component can be built via sched_ext and eBPF, and that the user-space part was written in Rust mostly incidentally.
- The kernel-side part of this scheduler is in C; Rust is used for the user-space logic.
- There are already other sched_ext schedulers, some fully in-kernel C, some with user-space C, that outperform the default scheduler for certain production workloads.
Scheduler Behavior and Benchmarks
- The showcased gain is for gaming with a heavy background task (e.g., kernel compile) and is explicitly workload-specific.
- Some see the result as impressive for something hacked together over a holiday; others warn that toy or specialized schedulers often omit edge cases and can underperform more general ones elsewhere.
- There is debate over whether kernel compiles are typically CPU- vs IO-/memory-bound; consensus is “it depends on the system.”
Interactivity and “Active Window” Priority
- Multiple commenters highlight that desktop responsiveness under load is the interesting metric.
- Some are surprised Linux doesn’t more aggressively prioritize the foreground/interactive process; others note the kernel has no inherent concept of “active window” and only heuristics are possible.
- Past and out-of-tree schedulers targeting interactivity are mentioned as prior art.
Hype, Language Wars, and Community Dynamics
- Several criticize headlines and third-party coverage as overhyping a hobby experiment and fueling “rewrite it in Rust” culture.
- Others counter that experimentation is healthy, Rust’s kernel use is newsworthy, and every language community goes through a hype phase.
- There’s concern that aggressive advocacy and moral framing around “unsafe languages” can be off-putting.
Safety and Failure Modes
- Questions are raised about deadlocks and ensuring the user-space scheduler itself gets CPU time.
- Responses describe a watchdog that unloads a misbehaving scheduler and reverts to the default, plus logic to ensure the scheduler task is run when needed.
- Offloading scheduling to user space is acknowledged to have overhead and risk, so other schedulers may be better for production.