On Tuesday 20 March 2001 21:48, Wilken Boie wrote:
> David Olofson schrieb:
> > On Tuesday 20 March 2001 10:37, Erwin Rol wrote:
> > > The low latency ppl also warm against using the linux framebuffer
> > > drivers, although they
> > > don't have hardrealtime so this warning might not be of importance for
> > > RTAI.
> >
> > Right; Linux/lowlatency relies on the Linux scheduler, and the
> > framebuffer problem (possibly about to be fixed) is that the fb drivers
> > stay in kernel space for extended amounts of time. A fully preemptive RT
> > kernel that bypasses Linux (such as RTL or RTAI) wouldn't be affected by
> > that.
>
> Is there anybody who could be a bit more specific about this? E.g. I
> remember I heard this occurs when _scrolling_ the fb. Does this in turn
> mean we're fine without scrolling?
Happens when switching as well. (Another big copy operation that's done in
kernel context.) There are complete DDT (Don't Do That) list for the
Linux/lowlatency patches - I just can't seem to find the right URL...
> I would appreciate, if somebody could point me to the right resources for
> this issue (mailing list, fixing status etc.).
Linux Audio Dev:
http://www.linuxdj.com/audio/lad/index.php3
(Site and list; many Linux/lowlatency users here.
Links to various resources on the site.)
Linux Audio-Quality-HOWTO:
http://www.linuxdj.com/audio/quality/
(Info on low latency solutions + some links.)
Article on Mstation:
http://www.mstation.org/lowlatency.html
(And THERE's the URL I was thinking about: )
Andrew Morton's site w/ patches & info:
http://www.uow.edu.au/~andrewm/linux/schedlat.html
...and in particular:
http://www.uow.edu.au/~andrewm/linux/schedlat.html#ddt
Note: Virtually none of the above has anything to do with RTL or RTAI;
it's related to the lowlatency patches.
> The reason is, that there is
> in deed a world beside X and to a good part that's based on fb (e.g. QT
> embedded), and I would like to use that under low latency conditions.
So would I. (Although I have a great deal of other work to do before I really
need it...)
//David
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