sched: fix kern.sched.{4bsd,ule}.slice

[mchoo]

Summary

Fix three problems with kern.sched.{4bsd,ule}.slice:

• Guarantee minimum slice is 1.
• Recalculate hogticks on sysctl write.
• For ULE, recalculate sched_slice_min on sysctl write.

MFC after: 2 weeks
MFC to: stable/14, stable/15
Sponsored by: FreeBSD Foundation

[olce]

sys/kern/sched_4bsd.c

215

It's an internal function, no need to have 4bsd_ in the name.

Additionally, I'm planning to rename back all implementations of the current interface (to the rest of the kernel) to their prior names, that is, with ule_ or 4bsd_ removed, relatively soon (but there is EuroBSDCon next week).

225

Not necessary given the previous test. Replace by an assertion?

226–227

Could you please factor out the hogticks computation and setting in a separate function, and use it throughout the file (preferably as a separate commit)?

sys/kern/sched_ule.c

3490–3502

Same comments as for 4BSD.

[mchoo]

Remove unnecessary imax()

[mchoo]

sys/kern/sched_4bsd.c

215

Since sysctl_kern_4bsd_quantum already has the namespace, I'll keep it for now. It can be renamed when the cleanup is done across 4BSD and ULE.

225

I think assertion is unnecessary here.

sys/kern/sched_ule.c

3499

D59408 adds imax() check for quantum sysctl.

[olce]

sys/kern/sched_4bsd.c

215

Let's go right now in the intended direction. Additionally, having 4bsd_ here and no ule_ below is inconsistent. So please remove it.

[mchoo]

Remove namespacing

[mchoo]

sys/kern/sched_4bsd.c

226–227

Done in D59471