[Solved] 16GB RAM missing

ArthurBorsboom · 2014-09-15 19:10:07

My server has 32GB of memory and the kernel reports in dmesg 32GB memory:

[arthur@orion1695 tmp]$ dmesg | grep Memory
[    0.000000] Memory: 32053016K/33290424K available (5334K kernel code, 887K rwdata, 1688K rodata, 1128K init, 1164K bss, 1237408K reserved)

I have a normal 64-bit Arch kernel.

[arthur@orion1695 tmp]$ uname -a
Linux orion1695 3.16.1-1-ARCH #1 SMP PREEMPT Thu Aug 14 07:40:19 CEST 2014 x86_64 GNU/Linux

dmidecode reports 4 modules of 8 GB.

[arthur@orion1695 tmp]$ sudo dmidecode --type memory
# dmidecode 2.12
SMBIOS 2.5 present.

Handle 0x0026, DMI type 16, 15 bytes
Physical Memory Array
	Location: System Board Or Motherboard
	Use: System Memory
	Error Correction Type: None
	Maximum Capacity: 16 GB
	Error Information Handle: Not Provided
	Number Of Devices: 4

Handle 0x0028, DMI type 17, 27 bytes
Memory Device
	Array Handle: 0x0026
	Error Information Handle: Not Provided
	Total Width: 64 bits
	Data Width: 72 bits
	Size: 8192 MB
	Form Factor: DIMM
	Set: None
	Locator: DIMM1
	Bank Locator: BANK0
	Type: SDRAM
	Type Detail: Synchronous
	Speed: 800 MHz
	Manufacturer: Manufacturer00
	Serial Number: SerNum00
	Asset Tag: AssetTagNum0
	Part Number: ModulePartNumber00

Handle 0x002A, DMI type 17, 27 bytes
Memory Device
	Array Handle: 0x0026
	Error Information Handle: Not Provided
	Total Width: 64 bits
	Data Width: 72 bits
	Size: 8192 MB
	Form Factor: DIMM
	Set: None
	Locator: DIMM2
	Bank Locator: BANK1
	Type: SDRAM
	Type Detail: Synchronous
	Speed: 800 MHz
	Manufacturer: Manufacturer01
	Serial Number: SerNum01
	Asset Tag: AssetTagNum1
	Part Number: ModulePartNumber01

Handle 0x002C, DMI type 17, 27 bytes
Memory Device
	Array Handle: 0x0026
	Error Information Handle: Not Provided
	Total Width: 64 bits
	Data Width: 72 bits
	Size: 8192 MB
	Form Factor: DIMM
	Set: None
	Locator: DIMM3
	Bank Locator: BANK2
	Type: SDRAM
	Type Detail: Synchronous
	Speed: 800 MHz
	Manufacturer: Manufacturer02
	Serial Number: SerNum02
	Asset Tag: AssetTagNum2
	Part Number: ModulePartNumber02

Handle 0x002E, DMI type 17, 27 bytes
Memory Device
	Array Handle: 0x0026
	Error Information Handle: Not Provided
	Total Width: 64 bits
	Data Width: 72 bits
	Size: 8192 MB
	Form Factor: DIMM
	Set: None
	Locator: DIMM4
	Bank Locator: BANK3
	Type: SDRAM
	Type Detail: Synchronous
	Speed: 800 MHz
	Manufacturer: Manufacturer03
	Serial Number: SerNum03
	Asset Tag: AssetTagNum3
	Part Number: ModulePartNumber03

However, when I query with free, I see only 13GB available.

[arthur@orion1695 tmp]$ free -h
                    total       used       free     shared    buffers     cached
Mem:                  13G       7.9G       5.5G       1.1G       136M       7.0G
-/+ buffers/cache:              741M        12G
Swap:                7.6G         0B       7.6G

For now, I can't explain why.
Maybe important to share is that the xen package has been installed for virtualization.

What can be the reason for the missing memory?
And even better, does anyone know how to make it available?

Last edited by ArthurBorsboom (2014-09-16 16:38:05)

nomorewindows · 2014-09-15 22:58:06

DMIdecode shows a limit of 16GB, but that's still short of 13GB available. I know I had one machine that I had the machine past its' limit, and it took it anyway. Not all machines behave the same. Was this 16 the original memory before you added more? Maybe memtest gives us a clue. 1G went into reserve memory. That's only 15GB. Is this a stock OEM box or a custom build?

Roberth · 2014-09-15 23:27:10

Maybe your motherboard doesn't support more than 16 GB of ram, try update the bios.

ArthurBorsboom · 2014-09-16 07:01:32

Honestly I don't know much about the hardware, since it is a hosted machine somewhere in Germany (I live in The Netherlands).
It is a machine which I have never seen or touched. A previous employee has ordered this machine.

The motherboard is a MSI 760GM-E51 (FX), which has the latest BIOS v3.6.
The specification states that it should support 32 GB of memory, as reported initially by the Linux kernel.

I do know that before when Windows 2008 was installed, at least 24 GB was recognized.
Now running Arch, there is only 13 GB available.

I don't have a console access to this machine (only SSH), so I am not sure if I can run a memtest.

HiImTye · 2014-09-16 07:19:15

ArthurBorsboom wrote:

[arthur@orion1695 tmp]$ sudo dmidecode --type memory
# dmidecode 2.12
SMBIOS 2.5 present.

Handle 0x0026, DMI type 16, 15 bytes
Physical Memory Array
...
	Maximum Capacity: 16 GB
...

for some reason, it's indicated that your maximum capacity is only 16GiB, which is only a few hundred megabytes more than what is indicated by the free command

Last edited by HiImTye (2014-09-16 07:20:00)

ArthurBorsboom · 2014-09-16 08:44:36

Yes, I have noticed that too.

However, the Linux kernel reports 32GB and in Windows I recall (hopefully correct) that it had 24GB available.

R00KIE · 2014-09-16 08:56:48

I know you don't have physical access but I would look into the bios configuration, maybe something needs to be enabled/disabled. Maybe the full dmesg output will provide some clues.

You should also double check that the board has the latest bios version and also check the full manual for the supported memory combinations.

Lone_Wolf · 2014-09-16 12:27:25

ArthurBorsboom,

it's a longshot, but maybe you're ssh'ing into a virtual machine instead of a physical one ?
the output of lspci might help to verify that.

ArthurBorsboom · 2014-09-16 13:21:47

I am sure I am logging in into the host instead of a guest, but yes, thanks for thinking along.
Simple mistakes like that are common.

I am sure about the latest BIOS version.

Dmesg output can be found here: http://pastebin.com/cQ4vG4Pk

The answer might be found in the difference between these two motherboards.

MSI 760GM-E51 (supports 16 GB)
MSI 760GM-E51 (FX) (supports 32 GB)

The Linux kernel states 760GM-E51, but I am not sure if the optional FX would be visible here.
I will try to contact the hosting company for a clear answer.

nomorewindows · 2014-09-16 14:11:47

I would think it is the FX since it would take the 24GB with windows. Seems like a problem with the chipset. I don't think it'll make any difference, but kernel 3.16.1-1 isn't the newest kernel.

Last edited by nomorewindows (2014-09-16 14:36:05)

ArthurBorsboom · 2014-09-16 16:36:35

I have found the cause.

The hardware and OS function correctly.
The tool free shows the information different than usual due to the Xen kernel / addition.

The free command shows the free space available to dom0 (for other virtual machines).
The missing memory is being taken by the Xen hypervisor and the 4 running VM's.

The command xl info shows the total amount of memory correct.

host                   : orion1695
release                : 3.16.2-1-ARCH
version                : #1 SMP PREEMPT Sat Sep 6 13:12:51 CEST 2014
machine                : x86_64
nr_cpus                : 8
max_cpu_id             : 23
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 2
cpu_mhz                : 2300
hw_caps                : 178bf3ff:2fd3fbff:00000000:00001700:36983203:00000000:01ebbfff:00000008
virt_caps              : hvm
total_memory           : 32510
free_memory            : 743
sharing_freed_memory   : 0
sharing_used_memory    : 0
outstanding_claims     : 0
free_cpus              : 0
xen_major              : 4
xen_minor              : 4
xen_extra              : .0
xen_version            : 4.4.0
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64 
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : 
xen_commandline        : /boot/xen-4.4.0.gz xsave=1
cc_compiler            : gcc (GCC) 4.9.1
cc_compile_by          : arthur
cc_compile_domain      : 
cc_compile_date        : Fri Aug 22 16:25:44 CEST 2014
xend_config_format     : 4

So there is nothing wrong with the server.
Everything works as it should work.

Thanks for the help.

ArthurBorsboom · 2014-09-16 16:37:32

And a small thanks to my hosting company server4you for the quick response and professional help for testing the hardware.

nomorewindows · 2014-09-16 16:48:32

If there was a problem with the hardware, they'd have to fix it, obviously.

Arch Linux

#1 2014-09-15 19:10:07

[Solved] 16GB RAM missing

#2 2014-09-15 22:58:06

Re: [Solved] 16GB RAM missing

#3 2014-09-15 23:27:10

Re: [Solved] 16GB RAM missing

#4 2014-09-16 07:01:32

Re: [Solved] 16GB RAM missing

#5 2014-09-16 07:19:15

Re: [Solved] 16GB RAM missing

#6 2014-09-16 08:44:36

Re: [Solved] 16GB RAM missing

#7 2014-09-16 08:56:48

Re: [Solved] 16GB RAM missing

#8 2014-09-16 12:27:25

Re: [Solved] 16GB RAM missing

#9 2014-09-16 13:21:47

Re: [Solved] 16GB RAM missing

#10 2014-09-16 14:11:47

Re: [Solved] 16GB RAM missing

#11 2014-09-16 16:36:35

Re: [Solved] 16GB RAM missing

#12 2014-09-16 16:37:32

Re: [Solved] 16GB RAM missing

#13 2014-09-16 16:48:32

Re: [Solved] 16GB RAM missing

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