SCHED_4BSD(4)

🎀 SCHED_4BSD(4) 🎀

okay bestie, this is the Kernel Interfaces Manual page for sched_4bsd — she’s the 4.4BSD scheduler and the vibe is very OG-but-still-slaying. 💅

🌸 NAME 🌸

sched_4bsd — the 4.4BSD scheduler. periodt.

✨ SYNOPSIS ✨

# 💖 DESCRIPTION 💖

okay so `sched_4bsd` is the traditional system scheduler, and she’s literally serving both <hotpink>high throughput</hotpink> and <purple>solid interactive response</purple> even when the system is under load. no cap.

these sysctls are the relevant ones for how `sched_4bsd` operates, bestie:

- **`kern.sched.name`** — this read-only sysctl reports the name of the active scheduler. slay.
- **`kern.sched.quantum`** — this read-write sysctl reports or sets the length of the quantum (in micro-seconds) granted to a thread. that’s the quantum, bestie ✨
- **`kern.sched.ipiwakeup.enabled`** — this read-write sysctl sets whether or not the scheduler will generate an inter-processor interrupt (IPI) to an idle CPU when a thread is woken up. otherwise, idle CPUs will wait until the next clock tick before looking for new work. 🫶
- **`kern.sched.preemption`** — this read-only sysctl reports whether or not the kernel is configured to support preemption, which reduces the latency to run lower priority threads on wakeup. 👑

> 🦋 heads-up: some sysctls will be available only on systems supporting SMP.

# 🌈 SEE ALSO 🌈

- `sched_ule(4)`
- `sysctl(8)`

# 🧚 HISTORY 🧚

the `sched_4bsd` scheduler has been present, in various forms, since the inception of BSD. old money, no cap. 👑

# 💀 BUGS 💀

while she’s a highly robust and time-tested scheduler, `sched_4bsd` lacks specific knowledge of how to schedule advantageously in non-symmetric processor configurations, such as hyper-threading. so like, solid icon — but the hyper-threading caveat is real, bestie. 💀

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mwah 💋 — this page’s source/version footer says **Debian**, dated **January 21, 2008**. iconic.