kern.sched.quantum: Creepy, sadistic scheduler

[George Mitchell]

On 04/17/18 19:01, George Mitchell wrote:
> On 04/17/18 17:20, EBFE via freebsd-stable wrote:
>> [...]
>> 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
> 
I've now done SCHED_ULE runs with preempt_thresh set to 0, 1, 5, 80,
and 224.  The wall clock time is uniformly in the vicinity of 10 hours.
The "time" output is consistent with SCHED_4BSD, but the wall clock
time is really what I care about.

Now I have set kern.sched.preempt_thresh back to the default of 80 and
I am experimenting with kern.sched.interact.  I'm pretty sure that
setting kern.sched.preempt_thresh is not the answer to my problem.
-- George

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