How can I test that NBD Swap is working?

[Jim Kronebusch]

On Mon, 03 Sep 2007 17:35:52 -0500, Zackary Boarman wrote
> When the client's boot using LTSP it uses the RAM OF THE SERVER, so the
> ram on the client won't have any effect unless it is the video ram,
> which is more than likely not it, because webpages don't wouldn't even
> use 2mb of vram. So is there any other kids using the server when the
> freezes, then the server may be running out of ram, goto System >
> Administration > System Monitor & go to the webpage another time & see
> if the ram usage goes up, or if swap usage goes up.

This post was also on the edubuntu-users list.  I forgot to follow up on this list I
guess.  Firefox caches pixmaps to X11 so a webpage with a ton of graphics quickly chews
up client RAM and swap.  Once full the client freezes.  Increasing nbd-swap will help
but has other tradeoffs such as increased network traffic and server drive space.  If
you look at the edubuntu-users thread you can also see details on implementing a ldm
hack that will never allow X to use more than a certain percentage of client memory
(provided by Scott Balneaves).  Both of these are bandaids and the only real fix would
be to disable pixmap caching in firefox (which it doesn't look like anyone has figured
out yet).  Quick fix for me was to install Opera which does not have this problem and
still seems to work fairly well and is also fast.  However this is not "free" software
either so not a great permanent solution either, but will buy me time.  

If anyone knows of how to patch firefox it would be very appreciated.

Jim

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