topic Re: RHEL 5.2 not recognizing memory beyond 4GB in Operating System - Linux

RHEL 5.2 not recognizing memory beyond 4GB

arkie — Tue, 23 Feb 2010 13:11:15 GMT

Hi,

A rx2660 has 8GB of Physical memory installed, but RHEL 5.2 is showing only 4GB.

Can anyone pls help?

Thanks in advance

Re: RHEL 5.2 not recognizing memory beyond 4GB

Goran Koruga — Tue, 23 Feb 2010 13:17:25 GMT

Does the kernel you're using have CONFIG_HIGHMEM64G enabled?

Goran

Re: RHEL 5.2 not recognizing memory beyond 4GB

arkie — Tue, 23 Feb 2010 13:18:57 GMT

Hi Goran,

Pls guide me on how to check this & confirm

Re: RHEL 5.2 not recognizing memory beyond 4GB

Goran Koruga — Tue, 23 Feb 2010 13:53:21 GMT

Hello.

Well I suppose you're using the kernel from RH so grep for it in its config file in /boot.

Perhaps you just need proper kernel package installed, i.e. something similar to "bigmem" kernels in Debian.

Regards,
Goran

Re: RHEL 5.2 not recognizing memory beyond 4GB

Steven E. Protter — Tue, 23 Feb 2010 14:38:12 GMT

Shalom,

The only version of Red Hat that works on an Itanium Server is RHEL for IA-64.

It should without any modification, being pure 64 bit, memory beyond 4 GB.

There is no hugemem or special kernel settings for IA-64 Red Hat.

Please post the following output for further diagnosis:

free

vmstat

Please confirm on the hardware side that all 8 GB of ram are working.

SEP

Re: RHEL 5.2 not recognizing memory beyond 4GB

Goran Koruga — Wed, 24 Feb 2010 08:46:17 GMT

Doh, so much for knowing what rx2660 is ;)

Re: RHEL 5.2 not recognizing memory beyond 4GB

arkie — Thu, 25 Feb 2010 06:16:42 GMT

The issue is resolved. We were using the xen kernel. Actually, during the installation, we did not deselect "Virtualization" and that had left our the ia64 kernel.

The ia64 kernel is showing 8GB memory now.

One more unique thing was observed - the xen kernel does not show the service startups during booting, and, we couldn't get into the Single-user mode with the xen kernel.

Thanks all.

Re: RHEL 5.2 not recognizing memory beyond 4GB

arkie — Thu, 25 Feb 2010 06:23:35 GMT

Can anyone lend me the procedure to enable CONFIG_HIGHMEM64G in a kernel (where it is not enabled)?

Thanks again!

Re: RHEL 5.2 not recognizing memory beyond 4GB

Goran Koruga — Thu, 25 Feb 2010 07:24:11 GMT

Hi.

I have mislead you with CONFIG_HIGHMEM64G option because I had no idea this is an Itanium machine. Sorry about that.

This option is only relevant for 32bit kernels running on x86.

Regards,
Goran

Re: RHEL 5.2 not recognizing memory beyond 4GB

arkie — Thu, 25 Feb 2010 08:06:57 GMT

Hi Goran,

It was not clear on my part about the architecture.

But, it very important to know how to configure the CONFIG_HIGHMEM64G option even in case of 32bit kernels running on x86. Can you provide me some leads with that.

Thanks!

Re: RHEL 5.2 not recognizing memory beyond 4GB

Goran Koruga — Thu, 25 Feb 2010 08:28:53 GMT

Hi.

This is only relevant if you compile your own kernels - it's part of the kernel config phase.

There you simply find the option and enable it. It's under "Processor type and features" and then "High Memory Support".

Regards,
Goran