On Monday 05 March 2007, Drew Weaver wrote:

Fedora has a PAE kernel which is useful in instances like this, what would be the CentOS alternative to that?

That would be not using PAE since the OP is on x86_64.

/Peter

While I too believe that it is a BIOS setting that is giving you troubles, as another suggestion and data point, whenever I install new memory, I run memtest (via the install CD boot: prompt) and let memory tests run overnight [if it finds all the memory installed on the box.]. If it doesn't find all the memory, you want to start looking at the memory sticks, are they seated correctly, etc. Finally, I check timing.

Then, if Linux doesn't see the memory, it is usually the BIOS that is the problem (at least for me where my memory is less than 8 GB). Also, I go over the first couple of pages of dmesg (at boot-up) with a fine tooth comb and understand all the messages, their implications, etc.

If all else fails, I use the* Linux*-ready *Firmware* Developer Kit at:

http://www.linuxfirmwarekit.org/

While it doesn't do a lot with memory, it might find some "issues" with your BIOS .....

Hope this helps ...

Rich

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Correction: largesmp kernel, nor hugemem.

[]s

On Mon, Mar 05, 2007 at 02:04:06PM -0300, Rodrigo Barbosa wrote:

Maybe the hugemem kernel ?

[]s

On Mon, Mar 05, 2007 at 11:51:15AM -0500, Drew Weaver wrote:

...

Fedora has a PAE kernel which is useful in instances like this, what would be the CentOS alternative to that?

-Drew

-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Kanwar Ranbir Sandhu Sent: Monday, March 05, 2007 11:47 AM To: CentOS mailing list Subject: [CentOS] CentOS 4.4 not seeing all RAM

Hi Everyone,

My server is only seeing 4.8 GB out of 6 GB available. I don't know why.

I have a CentOS 4.4 x86_64 server running on a Tyan s2895 with 6 GB of RAM (two 1 GB sticks and 2 2 GB sticks). I upgraded the RAM, powered up the server, and when CentOS was finished booting, checked the available RAM with free. This is what it's reporting:

             total           used            free     shared

buffers cached Mem: 4809064 4769492 39572 0 197156 3127704 -/+ buffers/cache: 1444632 3364432 Swap: 2064376 176 2064200

The BIOS sees all of the RAM. In fact, it looks to me like the kernel knows 6 GB is available. But, it is only using 4.8 GB because I see this in dmesg:

Memory: 4808464k/6291456k available (2106k kernel code, 0k reserved, 1299k data, 196k init)

What happened to the other 1 GB+ of RAM?

BTW, the server isn't running all the newest updates, but it is running the latest CentOS 4 kernel (2.6.9-42.0.10.ELsmp).

Regards,

Ranbir

Kanwar Ranbir Sandhu Linux 2.6.19-1.2911.fc6 i686 GNU/Linux 11:39:08 up 2 days, 10:28, 2 users, load average: 1.18, 0.64, 0.60

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-- Rodrigo Barbosa "Quid quid Latine dictum sit, altum viditur" "Be excellent to each other ..." - Bill & Ted (Wyld Stallyns)

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- -- Rodrigo Barbosa "Quid quid Latine dictum sit, altum viditur" "Be excellent to each other ..." - Bill & Ted (Wyld Stallyns)

On Mon, 2007-03-05 at 17:08 +0000, James Pearson wrote:

It's probably a memory hole mapping setting ... you probably need to enable it - have a look under 'Advanced Hammer Configuration' (or similar) in the BIOS

Hmmm...I see this too in dmesg:

No AGP bridge found Your BIOS doesn't leave a aperture memory hole Please enable the IOMMU option in the BIOS setup This costs you 64 MB of RAM Mapping aperture over 65536 KB of RAM @ 4000000

I guess I'll try enabling it and see what happens.

Regards,

Ranbir