Fedora DL380G3 not seeing all memory

[John Horne_1]

Hello,

We have bought two DL380 G3 servers which have 5GB of physical memory - 4x1GB and 2x512MB. The BIOS sees all the memory, but Fedora core 2 using 'top' only shows 4GB. I have also tried 'cat /proc/meminfo' and again only 4GB is seen. Fedora runs the SMP kernel on these servers, and as such there should be a 64GB memory limit. They are running the latest 2.6.6 kernel from fedora updates.

Anyone know why they are only seeing 4GB of memory, and how we can get them to see the full 5GB?


Thanks,

John.

[Steven E. Protter]

The system comes with a diagnostic CD. You can boot off of it.

Do so and run the memory tests.

If all memory passes you may have to adjust a kernel parameter or run into some kind of bug.

Its unclear to me if you have any otehr Fedora Core 2 servers with this much memory. If so, that would help with further recommended action.

I doubt bad memory because usually that causes a kernel panic.

SEP

[Mark Grant]

I know you are saying that the SMP kernel is supposed to have support for 64GB or RAM and maybe it does, I don't have much recent experience of Red Hat SMP kernels.

However, 4GB is the default Linux maximum and therefore it looks a lot like this might be how your kernel s set.

If you have your kernel sources to hand do a "grep CONFIG_HIGHMEM64G .config" in the source directory and confirm that this is set. If not, you'll need to configure support for this and rebuild the kernel.

One other possibility is that with the 64GB set, the kernel is supposed to auto-detect how much RAM you actually have. However, it might not be doing that properly and perhaps you need to pass a kernel parameter "mem=6144M" from lilo or grub

[John Horne_1]

Yes I have run the diagnostics CD memory check, and it passes that fine (seeing all 5GB). There is also a mmeory tester available when the system starts up (pressing F10 I think) and it passes that too.

No, we don't have any other HP systems with this much memory. We have bought in total 4 such systems (with 5GB) though, but I have only just started on two of them.

Yes the SMP kernel supports 64GB, the CONFIG_HIGHMEM64G is set ('y'). You can see that it is not set for the 'up' kernel (some other 4GB option is set instead).

Booting the system with 'mem=5120' (5GB) does nothing - it still only sees 4GB; no messages or errors logged. It sees the command line option but the kernel still only sees 4GB.


John.

[John Horne_1]

Okay, I think you can forget about this. Looking closely at the numbers I can see what I have been doing now.

Fedora *is* seeing the 5GB of memory but running 'top' shows what *looked* like 4GB. In fact it was 4934884KB - which is 5GB minus about 300MB. I was just seeing the leading '4' and thinking it was only 4GB, in fact it's nearer 5GB. Looking at the bios memory map and picking out the useable areas gives 4979747KB (44MB more than what top shows).

So, allowing for some system resources, etc, 'top' is showing the correct amount of memory available.

Sorry about that - user error I'm afraid :-)


John.

[Steven E. Protter]

If the posts made to this question were useful, please assign points. Even if there was no solution. Its how itrc works.

SEP

[David Gatz]

John, you will need to turn on the /PAE option for systems with over 4 gigs of memory. Here is a link for more information.

http://www.microsoft.com/whdc/system/platform/server/PAE/PAEdrv.mspx

David