Problem with SIS660 video card, Xorg 1.6.5 - slow XVideo output

[Arseniy Lartsev]

Hi,

I have a trouble with XVideo on a laptop with SIS chipset when running
xorg-server 1.6.5 (xf86-video-sis 0.10.2, Linux 2.6.31.3).

When I play video in any video player with XVideo output, X server uses up to 
50% CPU time depending on resolution of the picture.

Xorg version 1.5.2 works fine on the same machine with the same kernel. I'm 
attaching lspci -v and Xorg.0.log from both 1.6.5 and 1.5.2. The most notable 
difference is the following:

1.5.2:
(II) SIS(0): Benchmarking system RAM to video RAM memory transfer methods:
(--) SIS(0):     Checked libc memcpy()...     116.8 MiB/s
(--) SIS(0):     Checked built-in-1 memcpy()...     116.9 MiB/s
(--) SIS(0):     Checked built-in-2 memcpy()...     56.6 MiB/s
(--) SIS(0):     Checked MMX memcpy()...     130.3 MiB/s
(--) SIS(0):     Checked MMX2 memcpy()...     162.0 MiB/s

1.6.5:
(II) SIS(0): Benchmarking system RAM to video RAM memory transfer methods:
(--) SIS(0):     Checked libc memcpy()...     20.0 MiB/s
(--) SIS(0):     Checked built-in-1 memcpy()...     20.0 MiB/s
(--) SIS(0):     Checked built-in-2 memcpy()...     16.6 MiB/s
(--) SIS(0):     Checked MMX memcpy()...     39.7 MiB/s
(--) SIS(0):     Checked MMX2 memcpy()...     39.9 MiB/s

Copying to video RAM appears to be surprisingly slow (and apparently CPU 
consuming).

Could you help me finding out the reason? I'd like to have this problem solved 
in my distribution.
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VGA compatible controller: Silicon Integrated Systems [SiS] 661/741/760 PCI/AGP or 662/761Gx PCIE VGA Display Adapter (prog-if 00 [VGA controller])
        Subsystem: Acer Incorporated [ALI] Device 0082
        Flags: 66MHz, medium devsel, IRQ 7
        BIST result: 00
        Memory at e8000000 (32-bit, prefetchable) [size=128M]
        Memory at e2100000 (32-bit, non-prefetchable) [size=128K]
        I/O ports at 9000 [size=128]
        Expansion ROM at <unassigned> [disabled]
        Capabilities: [40] Power Management version 2
        Capabilities: [50] AGP version 3.0