Thin Clients freezing in Firefox

Jim Kronebusch jim at
Sat Sep 1 05:24:43 BST 2007

The client has 128MB RAM which must be shared with video.  It looks like by default the
client is allocating 32MB to video (as seen when running free at a shell on the client).
 It is only leaving 2MB free out of 128MB.  I assume this explains the crashes.  I tried
running xrestop but it appears to freeze almost immediately when I hit the page in
question, the last update says firefox is using just over 2MB.  Is there any way I can
put in a setting to force the client to not use so much?  I can't find any place to
change the settings in the bios.

I just added X_COLOR_DEPTH = 16 to lts.conf, we'll see if that helps.

Thanks for your help.  Things are not looking good for the school year if I can't get
this solved.

> That's not something that can be controlled via software.
> IF it's possible to change the amount of video memory, it would be in 
> the bios of the thin client.
> But, I'd be pretty surprised if you are running out of video ram.  If 
> anything, you've probably got too much video ram allocated.  If you 
> could reduce it to something reasonable, like 4mb, that would leave more 
> for the system.
> When calculating the amount of video ram needed, as long as you aren't 
> running any GL stuff.  The general formula is:
>      horizontal resolution * vertical resolution * color-depth-in-bytes 
> = ram-needed.
> If you are running 16-bit color (2-bytes) and 1024x768 resolution, then 
> it's:
>     1024 * 768 * 2 = 1,572,864  (a bit more than 1.5mb).
> with 4mb of video ram, you could easily do 1600x1200 with 16-bit color.
> I'm not sure what the default color depth is for Ubuntu/LTSP.  If it's 
> 24-bits, try reducing it to 16-bits.  That might help.
> Almost always, if you are browsing the web and the terminal locks up, 
> it's because the firefox has asked the Xserver to allocate some memory 
> to hold bitmaps or fonts, but the thin client doesn't have enough free 
> memory to accommodate the request.  The Xserver then locks up and that's 
> the end.
> If the T150 lasts longer before locking up than the Devon, then it 
> probably indicates that the T150 has more usable memory than the Devon.
> Enabling swap *should* help.
> Adding more physical ram should help even more.
> Also, there's a cool program called 'xrestop'.  You can apt-get install 
> that and run it.  It's an X app, so you can run it on the server and 
> it'll monitor your Xserver on your client.
> It is sort of like the 'top' utility, but rather than showing process 
> status, it shows resource status within the Xserver.  Of particular 
> interest is the column called 'Pxm mem'.  that's the amount of memory 
> the Xserver has allocated for pixmaps per X client app.  The total 
> pixmap memory is also displayed in the top section.
> Try running that AND firefox at the same time, if you can see them both 
> on the screen simultaneously, after you've been browsing for a bit and 
> the terminal locks up, you should be able to see the last snapshot of 
> the resources.  Might tell you exactly what's going on.
> Jim McQuillan
> jam at
> -- 
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Jim Kronebusch
Cotter Tech Department

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