Moving this discussion to the mailing list from the wiki: https://wiki.ubuntu.com/ThinClientMemoryUsage:
* PhillipSusi: I'm confused by the talk of limiting the video memory. The machine is going to have a fixed amount of video memory in it depending on the video card, telling the X server to not use it all seems rather pointless. * OliverGrawert: Parts of the video memory get shadowed into the main memory, so if you run a low profile client with a high/mid end videocard, it can occur that it cant start the X server because the kernel already occupies to much memory, (the ltsp people and me did a fair amount of testing where problems like these were identified and written down in this spec at the shared ubuntu/ltsp conference in Montreal), see the comment from mdz, the spec is not fully done yet (especially in the videoram area) but we will very likely default to the lowest possible value. * PhillipSusi: Could you elaborate? As far as I know, only the video rom bios gets shadowed into ram. Also cheap integrated video usually slices off a chunk of main ram for the video buffer rather than using dedicated VRAM, but telling the X server not to use it all does not allow the rest to return to the free memory pool, because the bios has already marked it as reserved in the memory maps it passes to the kernel. In order to free up these chunks of ram, you have to fiddle with settings in the bios. + * OliverGrawert: Please assemble a 48MB Thin Client with a 128MB videocard, apply all changes described in this spec to make it boot and test yourself .... might be related to the size of the BIOS or to something else, in no case it will boot cleanly as long as you dont limit the videoram the X server allocates... can we please discuss this not on the spec page as long as i'm working on the spec ? i dont want to clutter it with a long comments thread, feel free to mail me personally or to discuss it on the edubuntu-devel list with me.
Could someone explain to me how telling X to limit the amount of vram it can use could possibly effect the amount of system ram used? As far as I know this should not be possible. If this actually does happen, then it seems to me like it's some kind of bug.
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