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Thread: Memory Upgrade- Memory Not Being Used?

  1. #1
    Join Date
    Mar 2010
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    25
    Distro
    Ubuntu 9.10 Karmic Koala

    Memory Upgrade- Memory Not Being Used?

    Hi:
    I just upgraded my memory from 1GB to 4GB. For some reason the system is only reporting 2.8GB total:

    noleks-ub:~> free -m
    total used free shared buffers cached
    Mem: 2770 1321 1448 0 169 571
    -/+ buffers/cache: 580 2190
    Swap: 2557 0 2557


    Has anyone else seen this? I read something about reconfiguring the kernel to use more memory, but I'm not sure whether the Update Manager can adapt to the new physical memory available, or whether I need to tweak and rebuild the kernel myself?
    If the latter is the case, I then would have a couple additional questions:
    1) What is the working directory for a kernel build, for instance I don't know the difference here in /usr/src:
    drwxr-xr-x 24 root root 4096 2011-03-30 23:25 linux-headers-2.6.32-30
    drwxr-xr-x 7 root root 4096 2011-03-30 23:26 linux-headers-2.6.32-30-generic
    2) If I run make menuconfig or whatever, will the settings used for the previous kernel build be maintained (ie I can tweak just what I need to tweak)?

    Thanks!

  2. #2
    Join Date
    Jun 2007
    Beans
    12,579

    Re: Memory Upgrade- Memory Not Being Used?

    This is expected behavior for a 32-bit system (also looks like you have some memory going to onboard video). Install 64-bit distro or use PAE: https://help.ubuntu.com/community/EnablingPAE
    What would happen if your hard disk died right now?

  3. #3
    Join Date
    Mar 2010
    Beans
    25
    Distro
    Ubuntu 9.10 Karmic Koala

    Re: Memory Upgrade- Memory Not Being Used?

    Uh-oh...
    Well it looked like everything was going swimmingly until I rebooted. I installed pae headers and it looks like it rebuilt the kernel. But now I get this:

    Ubuntu 10.04.2 LTS noleks-ub tty1

    noleks-ub login: [ 24.540101 cx25840 2-0044: 0x0000 is not a valid video input!
    [ 135.328566] cx25840 2-0044: 0x0000 is not a valid video input!


    I can login so hopefully I can back out or repair what happened at the command line?

    HELP!!

    P.S. "free -m" now reports 3764MB total, so pretty sure pae IS working!
    Last edited by noleks; March 31st, 2011 at 03:57 PM. Reason: More info

  4. #4
    Join Date
    Jun 2007
    Beans
    12,579

    Re: Memory Upgrade- Memory Not Being Used?

    It looks like your video tuner card is not liking the PAE kernel. Just boot into the old kernel.
    What would happen if your hard disk died right now?

  5. #5
    Join Date
    Mar 2010
    Beans
    25
    Distro
    Ubuntu 9.10 Karmic Koala

    Re: Memory Upgrade- Memory Not Being Used?

    Hi:
    Looking at the undo procedure in the "Enabling PAE" howto I noticed I was missing one package:

    linux-headers-generic-pae 2.6.32.30.36

    This seems to have fixed things.

    Thanks!!

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