nexoniarz/SchOS
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Filename Latest commit message Latest commit date
Nexoniarz a2d987db5f sched: fair share by virtual runtime, with nice 
The scheduler was xv6's round-robin: run everything RUNNABLE in slot
order and yield on every timer tick. Slot order is not fairness, a
process alone on a CPU paid a full context switch a hundred times a
second to be handed straight back to itself, and there was no way to
say that one thing mattered more than another.

Every process now carries vruntime, the CPU time it has used divided
by its weight, and the scheduler runs the runnable process with the
smallest. Fairness and interactivity both fall out of that one rule;
nice is a weight, 1.25x per level as UNIX has always had it. A slice
is 20 ms shared among the runnable processes, never below 2 ms, and
the timer tick preempts only once it is spent. A process waking from
a long sleep is brought up to min_vruntime less one period, so it is
scheduled promptly without being owed everything it slept through;
fork inherits vruntime, so forking does not reset a debt.

getpriority/setpriority are real, with Linux's offset of 20 on the
return; /proc/<pid>/schedstat and the ctxt_switches lines of status
report what the scheduler did. docs/architecture/scheduler.md has the
reasoning, including why the run queue is still a scan of ptable.

This was written in an earlier session and left uncommitted. Finished
here: a signal waking a sleeper goes through the same vruntime floor
as wakeup() does, and sched_yield() yields -- it returned 0 doing
nothing, harmless while every tick was a yield and a spin of a whole
slice once ticks stopped being one.

Checked under QEMU on 1 and 4 CPUs: a nice 10 loop beside a nice 0
one gets about a tenth of a shared CPU, and a command typed meanwhile
answers in 26 ms.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
2026-10-23 15:01:27 +02:00
..
acpi.h acpi: uACPI, for interrupt routing, the power button and power-off 2026-10-22 16:12:28 +02:00
asm.h Initial commit: Schunix as it stands before the SchOS rename 2026-08-09 13:47:01 +02:00
audio.h audio: /dev/dsp, AudioEngine, and an AC'97 under it 2026-09-24 14:23:13 +02:00
blkdev.h vfs: room for 32 disks and partitions, 32 mounts, 16 SchFS volumes 2026-10-23 12:19:50 +02:00
buf.h bio: a buffer cache that grows to 1/32 of RAM, looked up by hash 2026-10-23 13:28:12 +02:00
config_sinit.h Initial commit: Schunix as it stands before the SchOS rename 2026-08-09 13:47:01 +02:00
date.h Initial commit: Schunix as it stands before the SchOS rename 2026-08-09 13:47:01 +02:00
dbg.h debugger: D5, the network transport -- and the plan closes 2026-09-14 15:33:53 +02:00
defs.h sched: fair share by virtual runtime, with nice 2026-10-23 15:01:27 +02:00
device.h limits: 256 PCI functions, 128 sockets and devices, 64 USB interfaces 2026-10-23 13:54:37 +02:00
display.h gfx: the second head shows the boot, not just what comes after it 2026-09-22 21:47:35 +02:00
dma.h dma: the 4 MB cap was the refusal, not the arena 2026-09-14 22:52:20 +02:00
elf.h Initial commit: Schunix as it stands before the SchOS rename 2026-08-09 13:47:01 +02:00
errno.h schfs: a format version policy, and refusing is not falling back 2026-09-12 17:13:59 +02:00
fat.h vfs: room for 32 disks and partitions, 32 mounts, 16 SchFS volumes 2026-10-23 12:19:50 +02:00
fb.h Rename Schunix to SchOS; the kernel becomes SchIFT 2026-08-09 14:09:59 +02:00
fcntl.h Rename Schunix to SchOS; the kernel becomes SchIFT 2026-08-09 14:09:59 +02:00
file.h smp: 64 processors, and say how many there are 2026-10-23 13:50:08 +02:00
font.h Rename Schunix to SchOS; the kernel becomes SchIFT 2026-08-09 14:09:59 +02:00
fs.h init survives stray signals; commands are 4-34x faster 2026-08-09 15:54:05 +02:00
fsstat.h licence: SchOS is GPL-2.0-or-later, no longer Apache-2.0 2026-10-22 08:48:45 +02:00
gfx.h gfx: draw the console in RAM, and write it to the card write-combined 2026-10-22 23:46:58 +02:00
hwinfo.h hwreport: describe a machine onto a USB stick, from a Linux-style /sys 2026-10-23 12:54:11 +02:00
input.h usb-hid: bind an absolute pointer, and plumb EV_ABS through 2026-08-10 18:27:01 +02:00
ioperm.h ldls: a second driver, and everything it found 2026-09-14 15:20:07 +02:00
irq.h acpi: uACPI, for interrupt routing, the power button and power-off 2026-10-22 16:12:28 +02:00
kbd.h kbd: three layouts, and the arrow keys were sitting on top of UTF-8 2026-09-20 01:09:32 +02:00
keymap.h kbd: three layouts, and the arrow keys were sitting on top of UTF-8 2026-09-20 01:09:32 +02:00
klog.h debugger: D5, the network transport -- and the plan closes 2026-09-14 15:33:53 +02:00
kmem.h kmem: a slab allocator, and what the fixed tables actually cost 2026-09-22 09:32:06 +02:00
logo.h docs: a branding folder, and the three marks are not interchangeable 2026-09-12 18:19:09 +02:00
memlayout.h kalloc: never-used memory stays a range; 256 GB; free is a counter 2026-10-23 14:05:40 +02:00
mmu.h Initial commit: Schunix as it stands before the SchOS rename 2026-08-09 13:47:01 +02:00
mp.h boot: stop assuming the machine is an emulator 2026-10-22 10:29:12 +02:00
netdev.h net: a frame wakes the stack, instead of waiting for the clock 2026-09-12 17:23:46 +02:00
netuser.h ldls: L4 was free after all, and the plan closes 2026-09-14 13:37:04 +02:00
param.h limits: 256 PCI functions, 128 sockets and devices, 64 USB interfaces 2026-10-23 13:54:37 +02:00
pci.h limits: 256 PCI functions, 128 sockets and devices, 64 USB interfaces 2026-10-23 13:54:37 +02:00
pciuser.h licence: SchOS is GPL-2.0-or-later, no longer Apache-2.0 2026-10-22 08:48:45 +02:00
posix.h licence: SchOS is GPL-2.0-or-later, no longer Apache-2.0 2026-10-22 08:48:45 +02:00
proc.h sched: fair share by virtual runtime, with nice 2026-10-23 15:01:27 +02:00
qr.h docs: four directories, and a rule for when a thing leaves the roadmap 2026-09-12 17:13:35 +02:00
sbuf.h debugger: D5, the network transport -- and the plan closes 2026-09-14 15:33:53 +02:00
schboot.h hwreport: describe a machine onto a USB stick, from a Linux-style /sys 2026-10-23 12:54:11 +02:00
schfs.h unix: a bound socket is a file 2026-09-22 10:06:10 +02:00
schinit.h licence: SchOS is GPL-2.0-or-later, no longer Apache-2.0 2026-10-22 08:48:45 +02:00
sleeplock.h Initial commit: Schunix as it stands before the SchOS rename 2026-08-09 13:47:01 +02:00
socket.h limits: 256 PCI functions, 128 sockets and devices, 64 USB interfaces 2026-10-23 13:54:37 +02:00
spinlock.h Initial commit: Schunix as it stands before the SchOS rename 2026-08-09 13:47:01 +02:00
stat.h unix: a bound socket is a file 2026-09-22 10:06:10 +02:00
syscall.h Initial commit: Schunix as it stands before the SchOS rename 2026-08-09 13:47:01 +02:00
text.h gfx: one glyph blitter, and a terminal cell is a surface 2026-09-23 17:57:16 +02:00
theme.h gfx: the console and the crash screen stop drawing on a driver by name 2026-08-15 17:04:10 +02:00
traps.h irq: MSI first, and poll the INTx lines that never arrive 2026-10-22 10:29:24 +02:00
ttf.h Initial commit: Schunix as it stands before the SchOS rename 2026-08-09 13:47:01 +02:00
types.h Initial commit: Schunix as it stands before the SchOS rename 2026-08-09 13:47:01 +02:00
uaccess.h exec: Linux's 2 MB of arguments; mmap: merge neighbouring mappings 2026-10-23 13:20:29 +02:00
usb.h usb: plug and play -- hot-plug, unplug, every interface, real mice 2026-10-22 11:38:13 +02:00
user.h hwreport: describe a machine onto a USB stick, from a Linux-style /sys 2026-10-23 12:54:11 +02:00
virtio.h hybrid: a modeset, from a process 2026-09-14 01:36:05 +02:00
vmap.h gfx: draw the console in RAM, and write it to the card write-combined 2026-10-22 23:46:58 +02:00
vt.h licence: SchOS is GPL-2.0-or-later, no longer Apache-2.0 2026-10-22 08:48:45 +02:00
x86.h audio: /dev/dsp, AudioEngine, and an AC'97 under it 2026-09-24 14:23:13 +02:00