[CentOS] Not seeing all memory in CentOS 5.1 x86_64

Ruslan Sivak wrote:
> John R Pierce wrote:
>>
>> whats cat /proc/meminfo   say?
>>
> # cat /proc/meminfo
> MemTotal:      6104064 kB
> ...
> HighTotal:           0 kB
> HighFree:            0 kB
> LowTotal:      6104064 kB
> LowFree:       1992580 kB
> ...

> Linux version 2.6.18-53.1.21.el5xen (mockbuild at builder10.centos.org) 
> (gcc version 4.1.2 20070626 (Red Hat 4.1.2-14)) #1 SMP Tue May 20 
> 10:03:27 EDT 2008
> BIOS-provided physical RAM map:
> Xen: 0000000000000000 - 00000001ef8fb000 (usable)
that range is about 7.9 GiBytes, so the rest is getting lost somewhere. 

I'm unfamiliar with Xens innards..