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Re: [Xen-users] RAM disapeared?

To: "Simon Hobson" <linux@xxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] RAM disapeared?
From: Heiko <rupertt@xxxxxxxxx>
Date: Wed, 7 Jan 2009 12:50:36 +0100
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
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On Wed, Jan 7, 2009 at 12:44 PM, Simon Hobson <linux@xxxxxxxxxxxxxxxx> wrote:
> Heiko wrote:
>
>> I have some dom0 which have 8GB RAM, but when I look with xm list, it
>> just shows me 6GB,
>> I need to setup some new VM, each with 1GB, so I should have with 3VM
>> still 5GB free,
>> but im only seeing 3GB.
>> Can I just create 2 new VM with each 1GB and still have 3GB for the dom0?
>>
>> #xm top
>> xentop - 11:31:17   Xen 3.1.0-53.1.14.el5
>> 4 domains: 1 running, 3 blocked, 0 paused, 0 crashed, 0 dying, 0 shutdown
>> Mem: 8386888k total, 6336300k used, 2050588k free    CPUs: 8 @ 2327MHz
>>
>> #xm list:
>> Name                                      ID Mem(MiB) VCPUs State
>> Time(s)
>> Domain-0                                   0     3057     8 r-----
>> 1265671.8
>> xxx-vm2                              12      999     2 r-----   4074.0
>> xxxx-vm2                 11      999     2 -b----    620.2
>> xxxxxx-vm2                           7      999     2 -b---- 238229.7
>
> It could be that the combination of OS & hardware limits the host to "under
> 4G" for itself, and so that's all that shows up. The rest of the ram could
> well be available to be divvied up between guests though.
>
> You can also explicitly limit host ram usage, and I believe this is
> recommended for two reasons :
> 1) Some kernel tables are sized according to memory at boot time - so when
> the memory is ballooned down, the kernel tables are bigger than they need to
> be.
> 2) When I upgraded Xen at home over Christmas, I came up with an error
> (can't recall what) which was specific to running Dom0 without a memory
> limit.
>
> You limit Dom0 memory by adding "dom0_mem=<some value>" to your Xen kernel
> line, like this :
>>
>>  kernel      /xen-3.2-1-amd64.gz dom0_mem=512M
>
Hello,
i dont have any of these entry on my servers.
xm info gives me something different on each server.

total_memory           : 8190
free_memory            : 0


total_memory           : 8190
free_memory            : 1000

total_memory           : 8190
free_memory            : 2002

total_memory           : 8190
free_memory            : 1000

does it mean in the last case, that when xm list gives me 3GB for dom0,
that I can create 2 1GB VMs and still have 2GB for the dom0 Server?

greetings


>
>
> --
> Simon Hobson
>
> Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
> author Gladys Hobson. Novels - poetry - short stories - ideal as
> Christmas stocking fillers. Some available as e-books.
>
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