kern.sched.quantum: Creepy, sadistic scheduler

[George Mitchell]

On 04/17/18 17:20, EBFE via freebsd-stable wrote:
> On Tue, 17 Apr 2018 09:05:48 -0700
> Freddie Cash <fjwcash at gmail.com> wrote:
> 
>> # Tune for desktop usage
>> kern.sched.preempt_thresh=224
>>
>> ​Works quite nicely on a 4-core AMD Phenom-II X4 960T Processor
>> (3010.09-MHz K8-class CPU) running KDE4 using an Nvidia 210 GPU.
> 
> For interactive tasks, there is a "special" tunable:
> % sysctl kern.sched.interact
> kern.sched.interact: 10 # default is 30
> % sysctl -d kern.sched.interact
> kern.sched.interact: Interactivity score threshold
> 
> reducing the value from 30 to 10-15 keeps your gui/system responsive,
> even under high load.
> [...]

I suspect my case (make buildworld while running misc/dnetc) doesn't
qualify.  However, I just completed a SCHED_ULE run with
preempt_thresh set to 5, and "time make buildworld" reports:
7336.748u 677.085s 9:25:19.86 23.6%     27482+473k 42147+431581io 38010pf+0w
Much closer to SCHED_4BSD!  I'll try preempt_thresh=0 next, and I
guess I'll at least try preempt_thresh=224 to see how that works
for me.                                                 -- George

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