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SubjectRe: Minimal jitter = good desktop.
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This is really simple, and I don`t care about top posting, down posting,  
in the middle comments or whatever. Do whatehver you like, and have no
other rule that what is in your soul. That is what drives ultimately
society. Look up Aristotle natural-law. Which actually is based in divine
nature.

Now jitter, is really easy. Jitter-sensitive OpenGL applications will show
visible jitter. Doom 3 is extremely sensitive. I have tried to make it run
well many times, but it wasn`t until I became aware of more unintuitive
behaviour not according to theory with some settings, and I started trying
reversing them. And then I found 90hz to be optimal, and giving a
perfectly running doom 3. Someone actually suggested I try 10000hz BFS
patch, because "it would reduce latency." Which I did. But then I also
tried 20hz, and there was little difference on BFS. Ultimately I arrived
at 90hz with CFS, and tweaking it`s granularity a bit, and it worked well.
(Better than BFS). So in that case, JITTER is solved. Also a lot of
low-jitter configs use low hz. So that seems to back it up. And everything
on my computer seems to be running better. Smoother, more responsive. Even
the ads in my browser ;(

I also appreciate those who can measure small jitter in the uS range, and
mitigate it. But I would also like for those, to check if a simple
hold-logic would be better. For the 10ms filter I mentioned. Say hold for
1ms at 0, and then to regular peak values. It seems that would be a better
filter. This just me being a perfectionist ofcourse.

So yes, according to the general definition of "os-jitter" it seems highly
reduced.

I don`t know at all why you are mentioning opengl calls. Obviously games,
do run quite well. Atleast now. It is also going to be great to test new
games coming, and keep iterating knowledge and tuning. Also ofcourse
OpenGL is a great part of Wayland, and I hear more h/w is used there, and
hopefully it doesn`t stop performance in games, so one can have an
effectful desktop, without worrying about game-performance. Some of the
GUI in doom3, running completely smooth, shows some great potential for
GUI-ideas aswell :)

Peace Be With You.

On Sat, 06 Oct 2012 16:53:16 +0200, el_es <el.es.cr@gmail.com> wrote:

> Uwaysi Bin Kareem <uwaysi.bin.kareem <at> paradoxuncreated.com> writes:
>
> [sorry for cutting out the context], but it's been topposted]
>
> But the problem is, we cannot measure 'jitter' directly.
> There is no reliable benchmark that produces results adherent
> to what someones' definition of 'jitter' is.
>
> At software level we only have a notion of latency, and that
> leads to jitter as david said, but as the kernel is not real-time,
> you cannot guarantee every opengl command/fb transfer will be finished
> in time for next frame to be drawn.
>
> Maybe if someone could get the information of % finished frames
> (or % dropped frames) within one slice of userspace, that would
> be something to build on, but it's still a derivative and with
> unknown bias level.
>
> Lukasz
>
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