[CentOS] 4gb ram shows as 3.3gb

Thu Jul 26 14:04:46 UTC 2007
Antonio da Silva Martins Junior <asmartins at uem.br>

Hi Nick,

----- "Nick" <list at everywhereinternet.com> escreveu:
> Running Centos 5 (32bit)... running a server with 4gb of RAM and it's
> shows up as:
> 
> [root at ubercore1 ~]# free
>              total       used       free     shared    buffers    
> cached
> Mem:       3369544    2549668     819876          0      29008   
> 2382360
> -/+ buffers/cache:     138300    3231244
> Swap:      6291448          0    6291448
> 
> I know 4gb is the limit for a 32bit OS but i thought it would be able
> to use all of it? Is there another kernel i was supposed to install?

  I have almost the same issue here :) what I can advice is to take a look
on the reserved memory on boot (using dmesg), but I didn't know what can
be done to change it. Take a look:

---> CentOS-5.0 (x86_64) on HP-DL380G4 (4GB)

[root at Suzuka ~]# dmesg |more
Bootdata ok (command line is ro root=/dev/sys/root rhgb quiet)
Linux version 2.6.18-8.1.8.el5xen (mockbuild at builder6.centos.org) (gcc version 4
.1.1 20070105 (Red Hat 4.1.1-52)) #1 SMP Tue Jul 10 07:06:45 EDT 2007
<... cut ...>
Memory: 3772028k/3933628k available (2321k kernel code, 152780k reserved, 1312k 
data, 168k init)

   The "free" command on this machine reports less memory because of Xen.
[root at Suzuka ~]# free
             total       used       free     shared    buffers     cached
Mem:       3032064    3024120       7944          0      15472     313564
-/+ buffers/cache:    2695084     336980
Swap:      4194296    1280636    2913660

   But "xentop" reports aprox. 4GB:
xentop - 11:02:21   Xen 3.0.3-rc5-8.1.8.el
3 domains: 3 running, 0 blocked, 0 paused, 0 crashed, 0 dying, 0 shutdown
Mem: 4128324k total, 4127496k used, 828k free    CPUs: 4 @ 3400MHz


---> CentOS-4.5 (i386) on SuperMicro MoBo

[root at Sakhir ~]# dmesg |more
Linux version 2.6.9-55.0.2.ELsmp (mockbuild at builder4.centos.org) (gcc version 3.
4.6 20060404 (Red Hat 3.4.6-8)) #1 SMP Tue Jun 26 14:30:58 EDT 2007
<... cut ...>
Memory: 4149888k/4587520k available (1883k kernel code, 42852k reserved, 761k da
ta, 188k init, 3276224k highmem)

[root at Sakhir ~]# free
             total       used       free     shared    buffers     cached
Mem:       4151980    4100544      51436          0     233316    1579404
-/+ buffers/cache:    2287824    1864156
Swap:      2104504        192    2104312


   I don't know why, but on my HP machine CentOS always recognized less memory, 
with both CentOS4 and CentOS5 64bits, I had SLES9-x86_64 on that machine and it 
used all 4GB. And on the SuperMicro with 32bits OS I'm using all 4GB, but didn't 
try CentOS5 on it yet.
 
   Hope this data helps someone on this issue :)
  
   Antonio

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| Antonio S. Martins Jr. - Support Analist | "Only The Shadow Knows     |
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-- 
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