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Hello!
I'm having a problem, archlinux isn't identifying all my memory. I'm using a Lenovo Thinkpad W500 with 4GB ram. Before arch I had Lubuntu and it showed correctly my 4GB of RAM. I did some research and found that Linux uses your memory for disk cashing, it seems that this is usually a source of confusion for newbies like myself, but I think my problem is not related.
Here is some useful information:
Output of free -t from archlinux:
total used free shared buffers cached
Mem: 2545944 696732 1849212 0 22620 277104
-/+ buffers/cache: 397008 2148936
Swap: 975868 0 975868
Total: 3521812 696732 2825080
Output of free -t from lubuntu:
total used free shared buffers cached
Mem: 4008660 738232 3270428 0 85884 450348
-/+ buffers/cache: 202000 3806660
Swap: 0 0 0
Total: 4008660 738232 3270428
Both arch and lubuntu are on the same disk. I have lubuntu as a backup.
Thanks in advance!
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64bit lubuntu vs. 32bit Arch?
Edit:
Maybe lubuntu uses a bigmem kernel. If I am not mistaken, Debian made the bigmem kernel the default 32bit kernel a year ago (I might be wrong on this). Since turds roll down hill and Debian → Ubuntu → Lubuntu, you might have a bigmem kernel. Try 64bit Arch, if your CPU supports it.
Last edited by Awebb (2012-06-05 12:42:54)
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I see. I will try with 64bit arch then.
However, I find it strange that arch 32bit doesn't support 4GB of RAM by default. After all you can correctly index that amount of memory with a 32bit data bus.
Thank you for your reply Awebb!
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It's because with only 4GB of address space, it must assign some of that to other hardware devices.
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You can't even properly support over 1GiB of RAM on 32bit without hacks -- see CONFIG_HIGH_MEMORY. Even with that enabled, the PCI bus will not be able to access memory above the 1GiB mark. Still, because of MMIO, address remapping, and sometimes hardware restrictions, a 32 bit OS generally won't be able to address over 3.2GB. To go beyond this requires PAE, which Ubuntu enables. Arch won't do this (search the bug tracker). Use 64 bit.
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However, I find it strange that arch 32bit doesn't support 4GB of RAM by default. After all you can correctly index that amount of memory with a 32bit data bus.
I'm beyond my level of incompetence here, but I think it depends on the hardware. I've seen different machines (with 4+GB) running XP which reported different amounts of RAM.
But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist.
-Lysander Spooner
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falconindy, yes, I think I remember seeing some messages about PAE at boot.
Thank you for your replies guys. It appears that installing 64bit arch is the only sensible choice. Unfortunately I will have to reconfigure my system and reinstall all my apps . Is there any way to avoid this, at least partially?
Edit: I just found some useful wiki entries that answer my previous question, I will leave them here for future reference:
Arch64 wiki
https://wiki.archlinux.org/index.php/Arch64_FAQ
Migrating between architectures without reinstalling
https://wiki.archlinux.org/index.php/Mi … installing
Last edited by iseedeadpeople (2012-06-05 14:09:12)
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This may help.
https://wiki.archlinux.org/index.php/Ar … talling.3F
Edit:
MIssed it by that much. This is what I get for getting coffee in between,
Last edited by doug piston (2012-06-05 14:11:19)
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You can back up a list of your installed packages to easily reinstall if the above methods don't work (probably a good idea to generate the list anyways though):
https://wiki.archlinux.org/index.php/Pa … d_packages
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I just finished installing arch 64bits and my RAM went up by a substantial amount. However, I still don't have as much as I had with Lubuntu . I guess this is because of how Archlinux works?
Output of free -t:
total used free shared buffers cached
Mem: 3945540 786636 3158904 0 21608 305024
-/+ buffers/cache: 460004 3485536
Swap: 0 0 0
Total: 3945540 786636 3158904
Last edited by iseedeadpeople (2012-06-05 23:08:42)
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