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[Xen-users] Memory missing

I've got a strange memory problem...

I installed debian testing with the debian testing version of xen (4.1)
and am using the xm/xend toolstack.

I have 16G RAM installed in the machine, but the dom0 dmesg command
produces the following:
             total       used       free     shared    buffers     cached
Mem:       3485856    1026140    2459716          0      87408     751056
-/+ buffers/cache:     187676    3298180
Swap:      1632252          0    1632252

ie, only 3.5G total RAM, which seems to come from this line in the dom0
[    0.000000] Memory: 15498248k/17268736k available (3418k kernel code,
525336k absent, 1245152k reserved, 3319k data, 576k init)

I realise there is the dom0_mem xen kernel option, but that doesn't seem
to be used:
xm dmesg shows:
(XEN) Command line: placeholder dom0_max_vcpus=1 dom0_vcpus_pin=1

also, dmesg shows:
[    0.000000] Command line: placeholder
root=UUID=8a8dd516-0d4d-4080-af43-d2efffb738a2 ro quiet
which matches /proc/cmdline.

So, I just can't find where or why the dom0 has less than the full
amount of memory.
xm list
Name                                        ID   Mem VCPUs      State  
Domain-0                                     0  3751     1     r-----  

There are no domU's currently running, xm info shows:
total_memory           : 16351
free_memory            : 12417

I have a Windows 2003 domU that I want to run, and I'd like to create a
4G ramdisk, allocate that to the domU, and then get windows to use the
ramdisk for the pagefile (which should provide windows an effective 8G
RAM, and reduce IO to the physical disks).

Of course, the downside I've seen to this is that I won't be able to do
a live migration anymore (since the pagefile won't exist on the
destination host), but I can deal with that by simply shutdown on old
machine, and startup on new machine. Also, I will need to pre-populate
the NTFS and pagefile on the ramdisk before windows bootup each time I
reboot the dom0.

Any suggestions on how to get more RAM allocated to the dom0?


Adam Goryachev
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