Re: XF4 on Mach64 and 2.2 kernel?
On Thu, Dec 07, 2000 at 03:47:53PM +0100, Michel Dänzer wrote:
> Sven LUTHER wrote:
>
> > > > I don't know shadowfb enough to know how it works, but i guess you write
> > > > to the shadowfb, which in turn get copied to the true screen every now
> > > > and then.
> > >
> > > Yes. The ShadowFB we are talking about does the copy after each operation.
> > > Keith Packard wrote another shadow framebuffer implementation for Tiny X
> > > which only does it in regular intervals which should further improve
> > > performance at the cost of latency, don't know if it will (or even can) be
> > > integrated into the 'normal' XFree86 server.
> >
> > mmm, ...
> >
> > don't know if this would really help here, especially if you want to retain
> > the visual aspect of it.
>
> What do you mean? AFAIK Keith's code refreshes the display 50 times a second,
Well, yes, but you may have higher screen refresh rates, ...
> maybe it could even be done during vertical retrace at least on some hardware.
Not without help from the kernel, ... Or maybe fbdev is able to do that ?
(that said, there is a glint comand called WaitForVertBlank or something such,
that could be helpfull here, but anyway, it will be no help since it is in the
no-accel case that shadowfb is used).
BTW, ...
did you ever experience any fifo overflow when not using direct fifo writes
(CPUToScreenExpansionFills for example) due to the CPU filling the fifo faster
than the permedia2 is able to empty it ?
> > > GNOME draws stippled rectangles, which leads to the whole area of the
> > > rectangles being copied from the shadow framebuffer to the real one. If it
> > > drew the rectangles using four lines instead, it should be much faster.
> >
> > Or if we have some magic in shadowfb that know whatdid change and what not,
> > but i think this would be expensive, well not in bus cycle, but in memory
> > accesses.
> >
> > So no real way out of this, maybe we should fill a bug against gnome ?
>
> Not a bad idea. AFAIR there was a discussion about this on one of the X
> mailing lists with a GNOME developer so I assumed it had already been fixed.
Maybe they think it is not important. Gnome people seem to think that anything
less than 1600x1200 on a 19" monitor and an accelerated server is not a good
setup, at least they don't use it.
Friendly,
Sven Luther
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