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

From: Arjan van de Ven
Date: Wed Dec 01 2004 - 05:30:11 EST


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.

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