Re: RT patch acceptance

[Con Kolivas <kernel@kolivas.org>]

On Wed, 25 May 2005 17:46, Ingo Molnar wrote:
> * Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> > >i agree in theory, but interestingly, people who use the -RT branch do
> > >report a smoother desktop experience. While it might also be a
> > >psychological effect, under -RT an interactive X process has the same
> > >kind of latency properties as if all of the mouse pointer input and
> > >rendering was done in the kernel (like some other desktop OSs do).
> > >
> > >so in terms of mouse pointer 'smoothness', it might very well be
> > >possible for humans to detect a couple of msec delays visually - even
> > >though they are unable to notice those delays directly. (Isnt there some
> > >existing research on this?)
> >
> > I'm guessing not, just because the monitor probably hasn't even
> > refreshed at that point ;) But...
>
> this reminds me, people very much notice the difference between an LCD
> that has 20 msec refresh rates vs. ones that have 10 msec refresh rates.
>
> i'd say the direct perception limit should be somewhere around 10 msec,
> but there can be indirect effects that add up. (e.g. while we might not
> be able to detect so small delays directly, the human eye can see
> _distance_ anomalies that are caused by small delays. E.g. the feeling
> of how 'smoothly' the mouse moves might be more accurate than direct
> delay perception. But i'm really out on a limb here as this is so hard
> to measure directly.)

Quite a lot outside the computing world has been done on human perception and 
the limit of perception on what would be scheduling jitter is approximately 
7ms if I recall correctly.

Cheers,
Con

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