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Problem with Xen Recognizing Memory

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I mentioned this in the beta release thread, but thought it might be better to start a new topic about this...

 

Xen only seems to see half of the memory I have installed.  Both the BIOS and the unRAID webGUI recognize the full 16GB of memory that is installed in the system.  However, if I run "xl info" or "xl top", Xen only shows that I have a total of 8GB of memory.  Therefore, if I try to allocate 6GB or more to the VM, Xen errors out saying it is out of memory, even though I should have 14GB free after allocating 2GB to unRAID.

 

I tried reformatting my flash drive and starting over from scratch in case I screwed up some settings somewhere, but even with the stock unRAID, it still only shows 8GB.

 

Is anyone else experiencing a similar issue and/or does anyone have any suggestions for me?

screenshots.png.4663c07cacb8148029d09ee85bee304b.png

I just checked, and my Xen install shows 16GB properly.

 

You mentioned 'xl top' shows 8GB. Does just 'top' show the same? Is there any difference between the 'top' results from the Xen boot option vs the non-Xen boot option?

 

'top' is just a Linux command with no Xen, so it would be good to know if it sees anything differently.

 

My first guess would be something funky with the memory itself. If you have other DIMMs to test that may be a good idea. Or even try moving DIMMs around on your motherboard.

xl top should show the total memory available to all the domains in the system

top, run in dom0, should show the memory allocated to dom0 only

 

you can cat /proc/meminfo to see the raw data, memtotal should agree with xl top.

Really? Both commands show me 16GB of total memory.

 

Would xl top work if I had booted into the non-xen config. I don't think I have, but wondering if that would change my results.

 

Really? Both commands show me 16GB of total memory.

 

Would xl top work if I had booted into the non-xen config. I don't think I have, but wondering if that would change my results.

 

have you limited the amount of mem to give dom0 using the dom0_mem kernel option? if not then IIRC that allows dom0 to balloon to all available RAM if required.

 

I have it set like

 

dom0_mem=1024M dom0_max_vpus=1 dom0_vcpus_pin

 

top says

 

KiB Mem:    848868 total,   625956 used,   222912 free,   110556 buffers

 

the missing 100M or so is taken by xen as described in here

 

xl top says

 

Mem: 8043952k total, 5338736k used, 2705216k free    CPUs: 4 @ 3199MHz

      NAME  STATE   CPU(sec) CPU(%)     MEM(k)
  Domain-0 -----r      49957    3.7    1048576
zalaga-lms --b---       3881    3.3    2097152
zalaga-unr --b---       2694    0.0    2097152

 

I have 8G RAM, 1G given to dom0 and 2G to each of the domU's

  • Author

Really? Both commands show me 16GB of total memory.

 

The normal top command within the Xen unraid boot only shows me the 2GB that is allocated to dom0.

 

Unfortunately, I haven't successfully been able to boot into the non-Xen boot option yet.  My network and USB keyboard don't seem to work under that boot option, so I can't test it there. 

 

It is starting to look more like a hardware issue though.  I just started running Memtest86 and while it shows 4 GB in each of the 4 slots, at the top, it is only showing 8GB of total memory.  I will try to mess around with the hardware to try to determine the problem.  Thanks for the help.

I am betting hardware.

 

BTW the 'xl' command is how you 'speak' to xen. So if you're not booted into the xen boot option then xl won't exist. Make sense?

 

Sent from my Nexus 5 using Tapatalk

 

 

  • Author

Thanks guys.  I reseated the memory and everything is working great now! :)

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