Strange question here. I have a server with 1GB of RAM, however when booted this shows as 768MB. I've discovered the reason for it – and that is that it has an unboard graphics card which shares memory with main RAM. Running Ubuntu Server, it doesn't actually ever use anything graphical – it's all set up to be SSH'd into and therefore there's no need to use the VGA.
I believe there may be a setting to switch off VGA/graphics card in BIOS, but my question to you guys is:
- is this recommended? and
- if I turn it off, then how would I turn it back on again in BIOS (given that with it off, I wouldn't be able to see the option to turn it on as there would be no graphics output!!)?
You won't be able to disable the VGA graphics in the bios unless you have a secondary card pci/agp graphics card installed. You might see the option, but it won't let you do it unless there is some other output. If your bios is fancy it might have a serial output in which case you might be able to disable the VGA, just be ready with a serial console if you ever need a display.
The thing to do is change the maximum shared memory value to be as small as possible. 4M, 8M, whatever it will let you move it down to. Once you turn down that shared memory space it isn't going to take up much on your system. If 32M of ram is going to make a difference in the life of your server, buy another gig and make it really happy!
I'm not sure I'd worry about it. Linux is far better at managing RAM than you are. Let it do it's own thing.
If you have DRAC access (or similar) to the BIOS, then you might be able to disable the memory-sharing, or limit it down to 16MB (or so).
Seriously though, RAM is cheap. If you run out, buy more.
You may find this interesting, using the graphics adapter's RAM as a RAM disk.
http://en.gentoo-wiki.com/wiki/Using_Graphics_Card_Memory_as_Swap
Works great on my PowerEdge 2500.