8.04 i386 -generic kernel seeing 3GB RAM on 64-bit 8GB RAM system

[Michael Blinn]

i386 Ubuntu Desktop -generic kernel (updated as of 2008-04-14) sees only 3GB RAM in my 64-bit 8GB computer.

Booting using an i386 Hardy Beta LiveCD finds all 8GB - also a Gutsy 64-bit LiveCD finds all 8GB.

I've booted using mem=8192M and this does not help.

I've tried both 2.6.24-16-generic and 2.6.24-12-generic and they both only see 3GB.

ppi@ws1-249:~$ uname -a
Linux ws1-249 2.6.24-16-generic #1 SNMP Thu Apr 10 13:23:42 UTC 2008 i686 GNU/Linux

ppi@ws1-249:~$ cat /proc/mtrr
reg00: base=0x00000000 ( 0MB), size=2048MB: write-back, count=1
reg01: base=0x80000000 (2048MB), size=1024MB: write-back, count=1
reg02: base=0xc0000000 (3072MB), size= 256MB: write-back, count=1
reg03: base=0x100000000 (4096MB), size=4096MB: write-back, count=1
reg04: base=0x200000000 (8192MB), size=1024MB: write-back, count=1
reg05: base=0xcfc00000 (3324MB), size= 4MB: uncachable, count=1
reg06: base=0xd8000000 (3456MB), size= 16MB: write-combining, count=1

ppi@ws1-249:~$ cat /proc/meminfo
MemTotal: 3365072 kB
MemFree: 2558552 kB
Buffers: 13800 kB
Cached: 306848 kB
SwapCached: 0 kB
Active: 529352 kB
Inactive: 230964 kB
HighTotal: 2485568 kB
HighFree: 1728764 kB
LowTotal: 879504 kB
LowFree: 829788 kB
SwapTotal: 6008300 kB
SwapFree: 6008300 kB
Dirty: 88 kB
Writeback: 0 kB
AnonPages: 439856 kB
Mapped: 36212 kB
Slab: 22324 kB
SReclaimable: 12744 kB
SUnreclaim: 9580 kB
PageTables: 1824 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
CommitLimit: 7690836 kB
Committed_AS: 1081764 kB
VmallocTotal: 114680 kB
VmallocUsed: 6284 kB
VmallocChunk: 108156 kB

[Amit Kucheria (amitk)]

Aah.. so it is detected correctly by the LiveCDs.

In that case it is a simple case of the Desktop version of kernel (-generic) not being configured to handle more than 4Gb memory. You have two options:

1. Use the precompiled -server kernel that is configured to use upto 64Gb of memory

OR

2. Compile your own -generic kernel with CONFIG_HIGHMEM64G set