From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dario Faggioli Subject: Re: [PATCH for-4.5] xen: vnuma: expose vnode_to_pnode to guest Date: Mon, 10 Nov 2014 11:51:28 +0100 Message-ID: <1415616688.3717.16.camel@Abyss> References: <1415475807-8699-1-git-send-email-wei.liu2@citrix.com> <546091A40200007800045E86@mail.emea.novell.com> <20141110100016.GA17065@zion.uk.xensource.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============8046174122477965082==" Return-path: In-Reply-To: <20141110100016.GA17065@zion.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Wei Liu Cc: Elena Ufimtseva , Jan Beulich , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org --===============8046174122477965082== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-BhSIc3fjd5+i1PeDaLSk" --=-BhSIc3fjd5+i1PeDaLSk Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2014-11-10 at 10:00 +0000, Wei Liu wrote: > On Mon, Nov 10, 2014 at 09:21:24AM +0000, Jan Beulich wrote: > > >>> On 08.11.14 at 20:43, wrote: > > > This information is passed in in domctl hypercall but the guest > > > interface doesn't expose it to guest. PV NUMA-aware ballooning relies= on > > > this piece of information to function properly. > >=20 > > Considering that exposing this mapping is wrong from a conceptual > > pov (as was discussed during the review of Elena's original series), > > the desire to nevertheless expose it would need to be explained > > much better than what you did above. > >=20 >=20 > My thought was that if a PV guest needs to do NUMA-aware ballooning, it > would be easier to have the mapping at hand to let the guest request > explicitly from what physical node it wants the page. It was based > on my vague memory of early version of Elena's series. >=20 Some discussion on this happened while talking about some early work on NUMA-aware ballooning. This is a message from that thread: http://lists.xenproject.org/archives/html/xen-devel/2013-08/msg01986.html > However, if this is conceptually wrong and has been discussed before, > (as I said in the other email) please just ignore this patch. I can try > to modify the hypervisor instead to make NUMA-aware ballooning happen > under the hood without guest knowing anything. That is, to make use of > the vmemrange structure to identify the vnode of a particular gpfn, then > with vnode_to_pnode map to identify the physical node of that gpfn, then > do NUMA-aware ballooning. >=20 I'm all for *not* exposing such information to the guest. However, a quote from George, from that thread, with which I *totally* agree with, is this one: <> If this can be done without exposing the mapping, as Wei suggests, then I agree we should go for it. If not, we'll have to introduce something like this (along with proper documentation of how it should be used) at some point. I'm 100% ok to re-start that discussion here and now... however, how stable should this interface be? Can't we deal with this when actually implementing NUMA aware ballooning and add stuff at than point, if necessary? Regards, Dario --=20 <> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) --=-BhSIc3fjd5+i1PeDaLSk Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iEYEABECAAYFAlRgmLAACgkQk4XaBE3IOsStUwCcCcHQGzN0yM2xTXdiFlRaoQ0M TCIAnjaL+d6LzEj59TlkKiMB7RNWTEsn =IFy0 -----END PGP SIGNATURE----- --=-BhSIc3fjd5+i1PeDaLSk-- --===============8046174122477965082== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel --===============8046174122477965082==--