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

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Date:	Fri, 21 Aug 2009 04:14:47 -0400 (EDT)
From:	Miroslav Rezanina <mrezanin@...hat.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
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


----- Original Message -----
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>
Sent: Thursday, August 20, 2009 6:39:02 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
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

I agree. However, I'm not sure if xen supports such a precise handling.
  
-- 
Miroslav Rezanina
Software Engineer - Virtualization Team - XEN kernel

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