Re: [Xen-devel] can not use all available memory

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

This question belongs on xen-users.

On Fri, 2012-11-23 at 11:35 +0000, Alexander Bienzeisler wrote:
> Hello,
> 
> i just tried to add a domU with 16 gigs of ram (maxmem = 16384, memory = 
> 16384) with free_memory : 28969 but got an error:
> 
> libxl: error: libxl.c:3433:libxl_set_memory_target: new target 0 for 
> dom0 is below the minimum threshold

The clue is in this message -- you cannot safely balloon down a guest
(including dom0) to an arbitrarily small value relative to its initial
size. The kernel will have certain fixed datastructures etc which are
sized according to the maximum amount of RAM at start of day.

If you were to balloon down too low then you would run out of RAM and
the OOM killer would step in and start killing stuff, so xl includes a
safety catch which prevents this.

If you have a huge host and want a small dom0 use the dom0_mem option
and disable xl's autoballoon option or whatever the equivalent xend
option is.

Ian.


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