linux-kernel - Re: [PATCH][v2.6.29][XEN] Return unused memory to hypervisor

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Message-ID: <4A8D7C26.5020902@goop.org>
Date:	Thu, 20 Aug 2009 09:39:02 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Miroslav Rezanina <mrezanin@...hat.com>
CC:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	Gianluca Guida <gianluca.guida@...rix.com>
Subject: Re: [PATCH][v2.6.29][XEN] Return unused memory to hypervisor

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.

    J
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