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[Xen-devel] Re: [PATCH][v2.6.29][XEN] Return unused memory to hypervisor

To: Miroslav Rezanina <mrezanin@xxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH][v2.6.29][XEN] Return unused memory to hypervisor
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Thu, 20 Aug 2009 09:39:02 -0700
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Gianluca Guida <gianluca.guida@xxxxxxxxxx>
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On 08/20/09 00:47, Miroslav Rezanina wrote:
> there is handled e820 map in guest. However, this patch informs 
> hypervisor, that guest uses less memory than was assigned to it. 
> If hypervisor is not informed, memory is reserved for guest that
> do not need it. If hypervisor is informed, he decrease memory
> reservation for guest and unused memory is marked as free 
> for use by other guests.

Yes.  But the guest will modify its own e820 map for a number of
reasons; for example: reducing its own memory, or clearing a space for
the PCI hole.  In general we want to free any underlying pages which
don't correspond to E820_RAM regions.


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