Messages in this thread | | | Date | Fri, 21 Aug 2009 12:51:06 +0100 | From | Gianluca Guida <> | Subject | Re: [PATCH][v2.6.29][XEN] Return unused memory to hypervisor |
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Miroslav Rezanina writes: > ----- Original Message ----- > From: "Jeremy Fitzhardinge" <jeremy@goop.org> > To: "Miroslav Rezanina" <mrezanin@redhat.com> > Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, "Gianluca Guida" <gianluca.guida@citrix.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.
Xen will just get a list of mfn to remove from the domain. That is precise enough. The scenario Jeremy is describing does happen, especially in dom0 kernels.
G.
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