why did Ubuntu turn off kernel preemption in Edgy?

Toby Smithe toby.smithe at gmail.com
Wed Nov 29 20:31:52 GMT 2006

Whilst very interesting, this is no longer a development issue. Please
continue on sounder.

On Wed, 2006-11-29 at 20:22 +0000, Matthew Garrett wrote:
> On Wed, Nov 29, 2006 at 08:15:19PM +0100, Tobias Wolf wrote:
> > Am Mittwoch, den 29.11.2006, 17:43 +0000 schrieb Matthew Garrett:
> > > If the human eye is unable to distinguish movement at faster than the 
> > > equivalent of 24 frames per second, then you'd see exactly the same 
> > > thing in real life. You don't, which indicates that faster movement is 
> > > still perceivable. In computer games, the difference between 30 frames 
> > > per second and 60 frames per second is quite easy to distinguish.
> > 
> > You do. There is pretty much the same aliasing (wagon wheels) in the
> > visual system. The cinematic industry didn’t choose their FPS
> > arbitrarily, they just underestimated it somewhat.
> Sorry, I should have been clearer. I was only arguing against the 
> idea that the human brain doesn't process visual information faster than 
> 24 frames per second. As you point out, similar effects can be generated 
> in real motion, though I was under the impression that it still wasn't 
> clear what was responsible for that - last time I had anything to do 
> with this stuff, Reichardt detectors were a good model for certain 
> aspects of human vision but hadn't actually been demonstrated to exist 
> in the mammalian visual pathway?
> > Flicker fusion frequency in high contrast regimes like screens is around
> > that but in general depends heavily on the circumstances (luminance,
> > contrast in-/decrement and others).
> > I guess increasing FPS in games amounts to something different than
> > perceptual flicker reduction.
> Absolutely. The point at which flickering vanishes and the point at 
> which an observer stops noticing an increase in fluidity of motion 
> are presumably different phenomena, which is a good indication that 
> different parts of the sensory systems process information at different 
> rates. But this then gets way beyond my field of expertise, which is 
> rather more related to fruitflies...
> -- 
> Matthew Garrett | mjg59 at srcf.ucam.org

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