kern.sched.quantum: Creepy, sadistic scheduler

Kevin Oberman rkoberman at
Tue Apr 17 15:49:34 UTC 2018

On Mon, Apr 16, 2018 at 11:56 PM, Eivind Nicolay Evensen <
eivinde at> wrote:

> 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)
> --
> Eivind

My experience has long been that 4BSD works far better for interactive, X
based systems than ULE. Even on 10 I saw long, annoying pauses with ULE and
I don't se those with 4BSD. I'd really like to see it better known that
this is often the case. BTW, my system is 2 core/4 thread Sandybridge.
Kevin Oberman, Part time kid herder and retired Network Engineer
E-mail: rkoberman at
PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683

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