kern.sched.quantum: Creepy, sadistic scheduler

Eivind Nicolay Evensen eivinde at
Tue Apr 17 07:10:28 UTC 2018

On Wed, Apr 04, 2018 at 09:32:58AM -0400, George Mitchell wrote:
> On 04/04/18 06:39, Alban Hertroys wrote:
> > [...]
> > That said, SCHED_ULE (the default scheduler for quite a while now) was designed with multi-CPU configurations in mind and there are claims that SCHED_4BSD works better for single-CPU configurations. You may give that a try, if you're not already on SCHED_4BSD.
> > [...]
> A small, disgruntled community of FreeBSD users who have never seen
> proof that SCHED_ULE is better than SCHED_4BSD in any environment
> continue to regularly recompile with SCHED_4BSD.  I dread the day when
> that becomes impossible, but at least it isn't here yet.      -- George

Indeed 4bsd is better in my case aswell. While for some unknown to me reason
ule performed a bit better in the 10.x series than before, in 11.x
it again is in my case not usable.

Mouse freezes for around half a second with even frequency by just moving
it around in x11. Using 4bsd instead makes the problem go away.
I'm actually very happy that ule became worse again because going
back to 4bsd yet again also gave improved performance from other
dreadfully slow but (to me) still useful programs, like darktable.

With 4bsd, when adjusting shadows and highlights it is possible to see what I
do when moving sliders. With ule it has never been better than waiting
10-20-30 seconds to see where it was able to read a slider position
and update display, when working on images around 10500x10500 greyscale.

It's not single cpu/single core either:
CPU: AMD FX(tm)-6300 Six-Core Processor              (3817.45-MHz K8-class CPU)


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