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rblampain 01-19-2008 09:41 AM

slow scrolling on one machine, fast scrolling of same files on another
I have a web site I am testing on local machines on a lan and on an internet site. It renders properly when scrolling, on my secondary machine, whether displaying the files from the Internet site or from a CD backup made from my main machine, but the scrolling is extremely slow on my main machine, regardless of where the files are coming from, Internet site or the main machine itself.

It is so slow that I often get a message saying that the window is not responding when I try to close it although it often closes after issuing the message.

My main machine:
Debian Etch, Iceweasel and a Samsung SyncMaster 940N LCD monitor.
1G memory, 32MB video card, AMD Sempron 2000 or 2400 (not sure)

My secondary machine:
Debian Sarge, Mozilla and a 15" CRT monitor.
512MB memory, 32MB video card, AMD sempron 2400 or 2000 (not sure)

Both are used with the software coming with the distro.
The scrolling is slow even with files that contain only a few words. The apparent culprit been an animated gif image of 2 images that contain a white background and a few gray pixels which are repositioned in the second image to imitate the rain. I don't think that should take too much CPU time. It doesn't on the other machine.

My questions:
Is the LCD monitor the cause of the slow scrolling? I have been using it for only a few months.

I just turned off the machine, unplugged the CRT, plugged the LCD and rebooted, should I have made the change differently.

If it is, what could I do to solve this problem for visitors who use LCD monitors?

If not, what should I be looking for?

Thank you for your help.

budword 01-20-2008 09:48 PM

On the slow machine, does the top command show any program taking up more than 50% of cpu or ram ?


rblampain 01-21-2008 01:02 AM

Thank you for your reply.

I did not know the "top" command, it is very useful.

Yes, Xorg takes more than 99% of cpu time on the slow machine (Debian Etch) when I display HTML files from this site but less than 5% when I display some HTML from the Internet.

In comparison, the faster machine (Debian Sarge), which uses Xfree86, uses about 32%, 42% or 52% of cpu time on the same files downloaded from the Internet, depending which file is displayed and 52% is the result of rendering one of the smaller file.

Do I have 2 problems? One problem with the HTML code and another problem with Xorg?

All the files have been meticulously checked with the W3C validators but it is a "frame" environment, if this could make such a difference.

budword 01-21-2008 05:28 PM

Do you have a friend who could try your html code on other machines and other operating systems ? That would tell you if it was a linux problem or some ineffiecent html code. I'm not sure I'd want to use any html that would bring a decent box to it's knees like that. It's just a web page. How big are those .gifs ? I think the problem is with those animations. One other thing you could try is updated video drivers, if they are nvidia based, the latest nvidia driver might help. Some people won't use them because they aren't open source, but to each their own.

I don't think frames would make that much of a difference, but the fact it's a simple animation might. Web animations are annoying to anyone who uses the net everyday, and personally, I would rather do without them. I don't know of anyone who likes them. They are a neat trick, and maybe a cool toy, but not for long, then they just annoy.

Best of luck with that.....


rblampain 01-21-2008 11:40 PM

Thank you again.

I was beginning to think it's partly due to the size of the monitor on my main machine, a 19" LCD compared to a 15" CRT on the faster machine. On the faster machine, I get cpu usage of 30 to 50% when these HTML are displaying, including the image.

I opened another post about the image, which does not show and does not annoy the visitor because it is a faint background image imitating the rain, it is only subconsciously visible. Here is what I said about it:
The image is 16 bytes by 32 bytes (100 ms), it contains 2 colors (white and gray), 2 diagonal rows of 3 pixels and 1 diagonal row of 2 pixels are gray on a white background. On the second image, the location of these rows of gray pixel is changed to simulate the rain. The .gif file is 146 bytes.

Perhaps I should try it with a bigger image so that it does not "tile" anymore. The files are viewed by other participants on the Internet but nobody has mentioned anything, I cannot expect them to investigate any further as this is all done by volunteers having different skills.

I would be very happy if you could tell me what your views are about this image because it is an important part of the site, not just a useless decoration or distraction.

budword 01-22-2008 03:20 AM

Well, a web developer has to make choices I guess. The size of the monitor wouldn't make any difference. I think the problem is that the browser is constantly loading and reloading those images. A real web developer might have some ideas on how to implement your idea's without making the browser choke. You might want to try a forum aimed at web professionals. People here are linux gurus. If you find an html expert here its just luck. Sorry, I don't know enough to help you further.

Good luck....


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