kern.sched.quantum: Creepy, sadistic scheduler

Peter pmc at
Wed Apr 18 18:13:20 UTC 2018

EBFE via freebsd-stable wrote:
> On Tue, 17 Apr 2018 09:05:48 -0700
> Freddie Cash <fjwcash at> 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.

Yes, this may improve the "irresponsive-desktop" problem. Because 
threads that are scored interactive, are run as realtime threads, ahead 
of all regular workload queues.
But it will likely not solve the problem described by George, having two 
competing batch jobs. And for my problem as described at the beginning
of the thread, I could probably tune so far that my "worker" thread 
would be considered interactive, but then it would just toggle between
realtime and timesharing queues - and while this may make things better, 
it will probably not lead to a smooth system behaviour.


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