On Thu, 2004-07-22 at 18:39, Philippe Gerum wrote:
> On Thu, 2004-07-22 at 17:56, Eric Valette wrote:
> > Philippe Gerum wrote:
> >
> > > Never put X in the loop; results cannot be reliable with it and it makes
> > > no sense to interpret them since the user-space X driver can do whatever
> > > it wants to with your hadware, especially when switching back and forth
> > > vt7. So I cannot comment these figures.
> >
> > May I make the same comment again, publicly this time : for me, one
> > reason of using a RTAI implementation is having the normal linux
> > environment including sophisticated X11/KDE, apps. Otherwyse, I would go
> > for RTEMS or eCos.
> >
> > So I think making benchmarks with X app running, is relevant (not
> > obviously the vt switch). Also, for embeded application, using the
> > framebuffer makes the X server behaves almost like any other linux
> > driver. Furthermore, the X server indeed performs IO but do not handle
> > interrupts directly. And if you use this argument, any user space
> > drivers would also be removed and this includes USB drivers, ...
>
> To summarize my views here:
>
> o Yes, RTAI might work with X if your X driver does not fiddle with the
> same stuff that RTAI does, basically: on-boad/on-cpu timer or interrupt
> mask at CPU level (and a few other bus-related things I guess). Wrt to
> the latter, I guess that we both know why iopl() was implemented in the
> first place...
> o Indeed, I've experimented many crashes while transitioning back and
> forth X and non-X displays while a RTAI app was running.
> o Yes, frame buffer might help, but depending on your X-driver code, it
-- fb-driver code
> might or might not be sufficient to have it enabled for the whole thing
> to work reliably. It's a matter of experimentation.
> o No, I cannot recommend using X blindly with RTAI, because I would have
> to know about the implementation of all pre-compiled drivers (which
> makes your USB argument irrelevant since USB support is compiled from
> kernel sources in any case, so it cannot remain in our way wrt interrupt
> handling). Any source for the NVidia ones btw?
>
> The above has nothing to do with the usefulness of RTAI as a RTOS, it's
> only a matter of tested configurations.
--
Philippe.
