Memory Size doubt

karlochacon · 03-18-2010, 02:12 PM

hi

I have some Red Hat Ent 5.0 Servers which have 4GB of RAM
2.6.18-8.el5 #1 SMP Fri Jan 26 14:15:21 EST 2007 i686 i686 i386

Code:

[root@~]# dmidecode | grep Size
        Runtime Size: 57104 bytes
        ROM Size: 4096 kB
        Installed Size: 32 KB
        Maximum Size: 32 KB
        Installed Size: 12288 KB
        Maximum Size: 12288 KB
        Size: 2048 MB
        Size: 2048 MB

but when I run top it shows

Code:

Mem:   3369744k total,  3126036k used,   243708k free,

same thing when I run

Code:

# free -m
            total       used       free     shared    buffers     cached
Mem:        3290       3052        237          0        359       1905

any idea why is not reporting the 4 GB?

thanks a lot

karlochacon · 03-18-2010, 02:15 PM

is this why is not reporting the 4GB? or something else?
http://www.cyberciti.biz/tips/redhat...m-support.html

jamescondron · 03-18-2010, 06:43 PM

What happens if you install the package?

chrism01 · 03-18-2010, 06:55 PM

Fundamentally, the system reserves some mem for the kernel+drivers, see eg http://kbase.redhat.com/faq/docs/DOC-6571, http://kbase.redhat.com/faq/docs/DOC-7064. Have a search http://www.redhat.com/search .

Quakeboy02 · 03-18-2010, 07:31 PM

Quote:

Originally Posted by karlochacon

is this why is not reporting the 4GB? or something else?
http://www.cyberciti.biz/tips/redhat...m-support.html

More than likely, at least that's the usual issue.

nodopro · 03-19-2010, 02:59 AM

Well actually it's 4GB. When you dmidecode will list each slot (bank). In your case, it list 2 banks that having 2GB memory each and you grep 'size' that's why it show size two times. To add it up, you have 4GB total (2 DIMMS and 2GB each).

johnsfine · 03-19-2010, 07:27 AM

Quote:

Originally Posted by karlochacon

is this why is not reporting the 4GB? or something else?
http://www.cyberciti.biz/tips/redhat...m-support.html

The topic of that link (install the PAE kernel) is almost certainly what you need.

But in that link there is some very careless phrasing

The non-PAE kernel can only address up to 4GB of memory. Install the kernel-PAE package if your machine has more than 4GB of memory

That part is misleading (and contradicted by other phrases on the same page).

The correct information is:

The non-PAE kernel can address up to 4GB of physical address space. 4GB of physical address space can contain only 3 and a fraction GB of actual memory (the exact amount is determined by the BIOS, not by Linux).

Install the kernel-PAE package if your machine has more than the 3 and a fraction GB of memory that fits in 4GB of physical address space.

i92guboj · 03-19-2010, 08:46 AM

To sum up. you need a PAE-enabled kernel *or* a 64 bits OS, in case your cpu supports x86_64 at all.