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Re: [Xen-users] Disable memory balloon in dom0

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Subject: Re: [Xen-users] Disable memory balloon in dom0
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Thu, 8 May 2008 21:20:18 +0100
Cc: Nick Anderson <nick@xxxxxxxxxxxx>
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> So I take that to mean setting dom0-min-mem to 0 disables memory
> ballooning(for dom0). I just want to clarify if that is the way to
> disable memory ballooning from dom0. I had been told in ##xen that
> booting with dom0_mem=X effectively disables ballooning.

I'm not sure that dom0_mem=X will disable ballooning completely on it's own; 
I'd expect that Xend will still autoballoon dom0 in order to make space for 
new domUs, if the dom0-min-mem setting allows it to.  So you should disable 
autoballooning even when using dom0_mem=X if you want it not to happen.

> Or is all of this mute if I never allocate more memory that what I have
> in the physical machine total?

If your domU's memory allocations can be satisfied without ballooning dom0 
then I believe it won't get ballooned.  I'd still advise explicitly disabling 
it if you really want it not to happen (and I've been in the habit of 
recommending this as a good practice for a server, since you don't need 
autoballooning there, typically).  This ensures a "safety catch" that 
prevents dom0 accidentally getting shrunk if you start more domUs than 
expected without thinking about the available memory.


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