[Xen-users] how much memory does the hypervisor need

[Philipp Schmid <lists@xxxxxxxxxxx>]

Hi,

I wonder how much memory the hypervisor needs. I have the following  
vms running:

xen26:~# xm list
Name                                        ID   Mem VCPUs       
State   Time(s)
Domain-0                                     0   725     1      
r-----   2064.7
g-hlsan9ib                                   1  4096     4     - 
b----    160.9
g-lp549ugs                                  19  1024     4     - 
b----     83.0
g-lpjj78e9                                   2  1024     2     - 
b----    156.1
g-nt731fct                                  17  2048     2     - 
b----    116.5
g-resl3iqi                                   4  2048     4     - 
b----    326.7
g-rujbc3il                                   5  2048     4     - 
b----    192.6
g-v72lkt0b                                   6  1024     2     - 
b----    197.5
725+4096+1024+1024+2048+2048+2048+1024 = 14037mb


dom0 has fixed 725mb of memory, the server has 16gb of memory.

if try to launch another 2048mb vm i get the following:

xen26:~# xm create /etc/xen/g-ida7k5fo.cfg
Using config file "/etc/xen/g-ida7k5fo.cfg".
Error: Not enough free memory and enable-dom0-ballooning is False, so  
I cannot release any more.  I need 2138112 KiB but only have 1930744.

so if i take the 16384mb of ram minus the used space and the space xen  
sys it still has i get:
16384 - 14037 - 1930744/1024 ~= 461.5mb

does the hypervisor really need 460mb of memory?
is there a way to calculate how much memory the hypervisior needs?

lg philipp



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