[CentOS] CentOS 4.4 not seeing all RAM

[Gordon McLellan]

Interesting.  I wonder if it has something to do with the chipset the
motherboard is using?

Here's free on a new server of mine, with 16gb, runing x86_64, centos 4.4

[root at vmhost ~]# free -m
             total       used       free     shared    buffers     cached
Mem:         16029      16004         24          0       2144      13002
-/+ buffers/cache:        858      15171
Swap:         1983          0       1983

[root at vmhost ~]# dmesg |grep Memory
Memory: 16413932k/17563648k available (2106k kernel code, 0k reserved,
1299k data, 196k init)

I see the same thing you do, basiclly a gigabyte is "missing"

However, on a machine with only 2g of ram, less ram is 'missing':

[root at incognito ~]# dmesg |grep Memory
Memory: 2054916k/2096896k available (2106k kernel code, 0k reserved,
1299k data, 196k init)

[root at incognito ~]# free -m
             total       used       free     shared    buffers     cached
Mem:          2007       1988         18          0         31       1827
-/+ buffers/cache:        129       1877
Swap:          996          0        995

Both these boxes are brand new Dells, first one's a 2950, the other an 860.

Gordon

On 3/5/07, Kanwar Ranbir Sandhu <m3freak at thesandhufamily.ca> wrote:
> 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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