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SubjectRe: fbcon + scrolling = irq timeouts?
On Mon, Nov 29, 1999 at 02:05:56PM +0100, Benno Senoner wrote:
> > In redraw mode there is NO any BIOS call after mode intialization AFAIK with
> > vesa frame buffer as well. The only thing : redrawing the screen takes
> > too much time in kernel time without process scheduling etc ... That's
> > why I suggested a kernel thread to do this instead. But I think this problem
> > is present with other non-vesa frame buffers as well if screen redrawing
> > is not fast enough (however latency would be definitly better with kernel
> > thread based frame buffer redrawing etc). This letter is strongly afaik and
> > imho however :)
>
> As long as there is no nasty recursive code, I think it's easier to shorten the
> execution paths of the framebuffer code by inserting rescheduling hookups
> (checking if rescheduling is needed then call schedule() ).
> An update kernel thread could work as well, but it might be more complicated to
> implement this, plus you get async updates instead of sync updates which is not
> really desired.

Yes, I see. But many-many framebuffer code (and will) exists for various cards
and you can't know their exact speed so you don't know how often should be
schedule() inserted. (accelerated framebuffer code may not need but some old
video cards require it much often). But a kernel thread introduces problems
you mentioned ...

However if framebuffer become a true standard with accelerated functions and
like, some cards/drivers will have got the some problem : locking the
kernel too long ... A general solution would be wonderful ...

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