Re: Kernel 2.6 with X (xorg) 4.4 (eats more CPU power)

[Arjan van de Ven <arjan@infradead.org>]

On Wed, 2004-12-01 at 18:21 +0800, Joe Hsu wrote:
> Dear All:
>     I've tried libXv to open an Video Overlay port and
> XvShmPutImage for 60 frames per second. Each frame is
> at a size of 800x600 using format YUYV (YUV2). Before
> each XvShmPutImage, I copy 800x600x2 bytes of non-constant 
> data to XvImage->data. (No user interactive UI)
> 
>     And I found something interisting happened. In pentium 4
> 3.0G machine and linux kernel 2.6, X and my program total 
> consumes 5% of cpu resource.
> 
>     But in pentium 4 2.xG or below, it would consume 10% or 
> more of CPU resource. (If you try this with XFree86 4.2 and 
> pentium 1.xG machine, it would consume 30% or more of cpu 
> resource at a peak.)
> 
>     In contrast, I've tried Kernel 2.4 with same X, same 
> program, and same machine. It consumes almost zero of CPU 
> resource( no matter it runs on a P4 1.xG or P4 3.0G and no
> matter it runs on 4.4 or 4.2 X-server).


reported resource usage is an estimate based on sampling. With HZ=1000 you do get a more accurate
sampling of reality.....

In addition, do check if your code (or X) doesn't do timeouts of < 10 msec; in HZ=100 kernels those always 
delay 10 or 20 msec, while with HZ=1000 kernels the delay becomes far more accurate.