[CentOS] 4gb ram shows as 3.3gb

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


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:
>=20
> [root at ubercore1 ~]# free
>              total       used       free     shared    buffers=20=20=20=
=20
> cached
> Mem:       3369544    2549668     819876          0      29008=20=20=20
> 2382360
> -/+ buffers/cache:     138300    3231244
> Swap:      6291448          0    6291448
>=20
> 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=3D/dev/sys/root rhgb quiet)
Linux version 2.6.18-8.1.8.el5xen (mockbuild at builder6.centos.org) (gcc vers=
ion 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, 1=
312k=20
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 versi=
on 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, 76=
1k 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 mem=
ory,=20
with both CentOS4 and CentOS5 64bits, I had SLES9-x86_64 on that machine an=
d it=20
used all 4GB. And on the SuperMicro with 32bits OS I'm using all 4GB, but d=
idn't=20
try CentOS5 on it yet.
=20
   Hope this data helps someone on this issue :)
=20=20
   Antonio

--=20
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| Antonio S. Martins Jr. - Support Analist | "Only The Shadow Knows     |
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--=20
Esta mensagem foi verificada pelo sistema de antiv=EDrus e
 acredita-se estar livre de perigo.




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