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From: Vadim Rozenfeld <vrozenfe@redhat.com>
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Date: Tue, 29 Nov 2011 15:46:42 +0200
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Subject: Re: [Qemu-devel] windows guest virtio serial and balloon driver
 test issues
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To: Mark Wu <wudxw@linux.vnet.ibm.com>
Cc: "Cao, Bing Bu" <mars@linux.vnet.ibm.com>, QEMU Developers <qemu-devel@nongnu.org>, "Cao,
	Bing Bu" <caobingbu@gmail.com>

On Tue, 2011-11-29 at 10:43 +0800, Mark Wu wrote:
> > Total physical memory on Windows will always be the same,
> > because we don't hot-plug/unplug physical memory.
> > Balloon driver works with non-paged pool memory instead.
> > So, every time you inflate or deflate balloon in your system,
> > you should see "Available memory" is changing, while physical
> > will always be the same.
> But the behaviour of virtio-balloon is different on Linux guest. It 
> updates the totalram_pages on deflate/inflate. Therefore the total
In Windows MmNumberOfPhysicalPages is almost totally undocumented.
It doesn't mean you can't abuse it. But it will be a hack.
>  
> physical memory will be updated in the system management interface even 
> though it doesn't really hot-plug/unplug any physical memory.  If we 
> just use 'info balloon' to query the balloon status, that should be 
> fine. But if the VM management tool also collects  memory information 
> from guest, it will become confusing.  Actually, I am not sure which one 
> make more sense. I just think that it should have unified behaviour on 
> both Linux and Windows guests.
IMO VM management tools should reference to balloon actual size and
amount of available memory, retrieved from guest.