From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dario Faggioli Subject: Re: [RFC v2][PATCH 1/3] docs: design and intended usage for NUMA-aware ballooning Date: Sat, 17 Aug 2013 01:30:52 +0200 Message-ID: <1376695852.2757.44.camel@Abyss> References: <1376626416-12901-1-git-send-email-lccycc123@gmail.com> <520E085A02000078000EC810@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============3957570907124961504==" Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1VATTu-0004fQ-FD for xen-devel@lists.xenproject.org; Fri, 16 Aug 2013 23:30:58 +0000 In-Reply-To: <520E085A02000078000EC810@nat28.tlf.novell.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: Jan Beulich Cc: Ian.Campbell@eu.citrix.com, xen-devel , Ian.Jackson@eu.citrix.com, ufimtseva@gmail.com, Yechen Li List-Id: xen-devel@lists.xenproject.org --===============3957570907124961504== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-bhL9Kin1fKKjKVgj3m7e" --=-bhL9Kin1fKKjKVgj3m7e Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On ven, 2013-08-16 at 10:09 +0100, Jan Beulich wrote: > >>> On 16.08.13 at 06:13, Yechen Li wrote: > > +The biggest difference between current and NUMA-aware ballooning is th= at the > > +latter needs to keep multiple lists of the ballooned pages in an array= , with > > +one element for each virtual node. This way, it is always evident, at = any > > +given time, what ballooned pages belong to what vnode. >=20 > That's wrong afaict: ballooned out pages aren't associated with any > memory, and hence can't be associated with any vNID. Once they > get re-populated, which vNID the memory belongs to is an attribute > of the memory coming in, not the control structure that it's to be > associated with. >=20 I may be wrong (I'm sorry, I had very few chance to look at the ballooning code, and won't be able to do so for a while), but I think what we want here is the other way around, i.e., having a way to make sure that the memory that will come in will also end up --in the guest-- within a specific v-node. I don't know if the only/best way to do this is the array of lists in Yechen's patches, and I agree (as per the other e-mail) that this more an implementation detail than anything else, but I think the point here is: do we want to support that operational mode (again, perhaps not as the default node, even in a virtual NUMA enabled guest) ? > I believe this thinking of yours stems from the fact that in Linux the > page control structures are associated with nodes by way of the > physical memory map being split into larger pieces, each coming from > a particular node. But other OSes don't need to follow this model, > and what you propose would also exclude extending the spanned > nodes set if memory gets ballooned in that's not associated with > any node the domain so far was "knowing" of. >=20 I agree on the first part of this comment... Too much Linux-ism in the description of what should be a generic model. The second part (the one about what happens if memory comes from an "unknown" node), I'm not sure I get what you mean. Suppose we have guest G with 2 v-nodes and with pages in v-node 0 (say, page 0,1,2..N-1) are backed by frames on p-node 2, while pages in v-node 1 (say, N,N+1,N+2..2N-1) are backed by frames on p-node 4, and that is because, at creation time, either the user or the toolstack decided this was the way to go. So, if page 2 was ballooned down, when ballooning it up, we would like to retain the fact that it is backed by a frame in p-node 2, and we could ask Xen to try make that happen. On failure (e.g., no free frames on p-node 2), we could either fail or have Xen allocate the memory somewhere else, i.e., not on p-node 2 or p-node 4, and live with it (i.e., map G's page 2 there), which I think is what you mean with <>, isn't it? Or was it something different that you were asking? Thanks and Regards, Dario --=20 <> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) --=-bhL9Kin1fKKjKVgj3m7e 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 v1.4.14 (GNU/Linux) iEYEABECAAYFAlIOtiwACgkQk4XaBE3IOsRbEACeL7rnqvO0J3hbqgOBIpb/DwyK d6wAnRnVOCqb0Vjq8WY6EQM6+CfOjqwE =QCu4 -----END PGP SIGNATURE----- --=-bhL9Kin1fKKjKVgj3m7e-- --===============3957570907124961504== 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 --===============3957570907124961504==--