On Tue, 18 Dec 2001, Vladimir Dergachev wrote:
> On Tue, 18 Dec 2001, Mark Vojkovich wrote:
>
> > On Tue, 18 Dec 2001, Peter Surda wrote:
> >
> > > On Tue, Dec 18, 2001 at 03:07:29PM +0100, Andre Werthmann wrote:
> > > > I have a laptop with a SiS630 chipset and use XFree86 4.1 (sis driver
> > > with
> > > > the vesafb hack).
> > > > When I play a dvd in windowed mode (720x576) with xine and I use
> > > XVideo
> > > > the cpu(1.1Ghz P3) is utilized at 66% while playing with XShm the cpu
> > > is
> > > > utilized only at 31% !
> > > > (the same with mplayer)
> > > >
> > > > This effect is the same at all colordepths (16bpp and 24bpp).
> > > >
> > > > I thought Xv should take the strain off the cpu a bit...
> > > >
> > > >
> > > > Anyone has an idea what may cause the problem ?
> > > It is because the driver uses memcpy for transferring of the data. The
> > > correct
> > > way to solve this is to add dma support. In current cvs XF86 r128 does
> > > this so
> > > it can be used as a reference implementation.
> > >
> >
> > That's silly. Plenty of other drivers do this without DMA
> > and have large performance increases over XShmPutImage - typically a
> > factor of two savings with scaling for free. In the worst case
> > XvShmPutImage should be comparable to XShmPutImage. Absense of
> > DMA capability is not the problem.
>
> Note that the author said "for the images of the same type". I.e. no
> scaling is going on. What I think happens is that XShmPutImage with sis
> is done using DMA (as DRM driver exists), but XvShmPutImage is not. Hence
> the difference in cpu consumption.
>
> Vladimir Dergachev
I don't see any Image acceleration at all in the sis driver
in CVS. I do see while loops polling registers in the Xv code
paths, however. The code would imply that you can only program
the overlay during the retrace, hence polling until the retrace
for every XvShmPutImage request.
Mark.
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