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
>
>
> Mark.
>
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