linux see 3.5G ram, bios shows 64GB ram

mahmoodn · 06-11-2012, 11:41 PM

Our server motherboard is TYAN 8236 and the bios showed 64GB memory installed. However the linux (AMD64) showed 3.5GB!!
Then in the boot log I saw:

Code:

Jun  9 02:31:32 sv1 kernel: [    0.000000] Your BIOS doesn't leave a aperture memory hole
Jun  9 02:31:32 sv1 kernel: [    0.000000] Please enable the IOMMU option in the BIOS setup
Jun  9 02:31:32 sv1 kernel: [    0.000000] This costs you 64 MB of RAM
Jun  9 02:31:32 sv1 kernel: [    0.000000] Mapping aperture over 65536 KB of RAM @ 20000000

So I entered the BIOS and enabled the IOMMU option. This time, in the boot log, I see:

Code:

Jun 12 12:32:51 sv1 kernel: [    5.742942] pci 0000:00:00.2: irq 56 for MSI/MSI-X
Jun 12 12:32:51 orca kernel: [    5.742960] AMD-Vi: Enabling IOMMU at 0000:00:00.2 cap 0x40
Jun 12 12:32:51 sv1 kernel: [    5.750257] AMD-Vi: device isolation enabled
Jun 12 12:32:51 sv1 kernel: [    5.750397] AMD-Vi: Lazy IO/TLB flushing enabled
Jun 12 12:32:51 sv1 kernel: [    5.753630] Scanning for low memory corruption every 60 seconds
Jun 12 12:32:51 sv1 kernel: [    5.753910] audit: initializing netlink socket (disabled)

However the free command still shows 3.5GB.
Why??

scheidel21 · 06-12-2012, 01:08 AM

What distro are you using and what version?

chrism01 · 06-12-2012, 01:10 AM

As above, we need more info; try these cmds

Code:

uname -a

cat /etc/*release*

cat /proc/cpuinfo

top

rosehosting.com · 06-12-2012, 01:37 AM

Any 32-bit operating system will only see/use 3.5GB of RAM. The solution is to install and use 64-bit OS so that the CPU can access the physical address space above the 4GB boundary.

majalee · 06-12-2012, 02:05 AM

"cat /proc/meminfo" will show the total memory that the your 64-bit OS is able to detect.

For instance, the output of the above command from my desktop is given below :

MemTotal: 3333580 kB (3.4 GB RAM)
MemFree: 406236 kB
Buffers: 318116 kB
Cached: 1531816 kB
SwapCached: 0 kB
Active: 1541272 kB
Inactive: 1077824 kB
Active(anon): 938224 kB
Inactive(anon): 182856 kB
Active(file): 603048 kB
Inactive(file): 894968 kB
Unevictable: 60 kB
Mlocked: 60 kB
SwapTotal: 3903756 kB
SwapFree: 3903756 kB
Dirty: 92 kB
Writeback: 0 kB
AnonPages: 769124 kB
Mapped: 237776 kB
Shmem: 351916 kB
Slab: 208556 kB
SReclaimable: 161472 kB
SUnreclaim: 47084 kB
KernelStack: 3376 kB
PageTables: 33140 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 5570544 kB
Committed_AS: 3623324 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 354964 kB
VmallocChunk: 34359374380 kB
HardwareCorrupted: 0 kB
AnonHugePages: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 38848 kB
DirectMap2M: 3360768 kB

TommyC7 · 06-12-2012, 02:06 AM

Um...I think you can just enable PAE in the kernel instead of reinstalling the entire computer with a 64-bit version of the same distro.

scheidel21 · 06-12-2012, 02:50 AM

He certainly could enable PAE in the kernel to access the RAM, however, if he has any one process that wants to access more than 2GB of RAM I believe it is he will want a 64-bit kernel. The OP is claiming that he is using a 64-bit install, but like you my first reaction is that he's only using a 32-bit install. If he posts the information requested we'll know for sure though.

mahmoodn · 06-12-2012, 04:21 AM

guys
The problem is asked here

However I didn't end up with a solution.
Problem is with amd new processors and old kernels.

Code:

mahmood@n1:~$ uname -a
Linux n1 2.6.32-24-server #39-Ubuntu SMP Wed Jul 28 06:21:40 UTC 2010 x86_64 GNU/Linux

processor model:

Code:

processor	: 31
vendor_id	: AuthenticAMD
cpu family	: 21
model		: 1
model name	: AMD Opteron(TM) Processor 6274

What is the solution then>

scheidel21 · 06-12-2012, 04:35 AM

Try a backport kernel version newer than the one you are using....compile your own new kernel? If you know the issue is a bug with older kernels and newer processors these are really your only options, unless the bug gets fixed.