[interfacekit] Re: :) Again - BBitmap

On Tue, 29 Jul 2003 17:18:51 +0300 "Adi Oanca" <adioanca@xxxxxxxxxxxxx>
 wrote:
> > >     So, if understood corectly, drawing on application side, by
> > > acquring the
> > > lock that the graphic card driver holds, involves a lot of 
> > > context
> > > switching
> > > at that low level, and, as I see the things, that is not quite so
> > > good as
> > > letting only one context switch for the app_server to draw in the
> > > name of
> > > all threads.
> > >     Don't you?
> >
> > No, all I'm saying is, that drawing into non-off-screen bitmaps
> > application side results in a lower latency, since doing it in the 
> > app
> > server requires context switches (and mode changes for the
> > communication).
> 
>     non-off-screen bitmaps? that means... on screen, and that under 
> no
> circumstance I agree. Maybe you wanted to say: drawing into off-
> screen
> bitmaps application side ?

I mean by non-off-screen bitmaps those, that don't have the 
B_BITMAP_IS_OFFSCREEN flag set, i.e. those whose bits reside in main 
memory. Sorry, if that caused confusion.

>     And... to reformulate my earlier question: Is it equal good to 
> have
> context switching at server side or at driver side? Isn't the one at 
> driver
> side more costly?

I actually don't get what you mean by context switching on driver side. 
If a thread from another team is scheduled, then a context switch is 
done. For a syscall (including driver calls through ioctl()) only a 
mode change is done.

CU, Ingo

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