From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752132AbbIORRb (ORCPT ); Tue, 15 Sep 2015 13:17:31 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:32020 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751198AbbIORR3 (ORCPT ); Tue, 15 Sep 2015 13:17:29 -0400 X-IronPort-AV: E=Sophos;i="5.17,536,1437436800"; d="asc'?scan'208";a="303778842" Message-ID: <1442337418.7789.52.camel@citrix.com> Subject: Re: [Xen-devel] [PATCH RFC] xen: if on Xen, "flatten" the scheduling domain hierarchy From: Dario Faggioli To: Juergen Gross CC: Boris Ostrovsky , "xen-devel@lists.xenproject.org" , "Andrew Cooper" , Stefano Stabellini , linux-kernel , George Dunlap , David Vrabel , "Luis R. Rodriguez" Date: Tue, 15 Sep 2015 19:16:58 +0200 In-Reply-To: <55E707E9.6000805@suse.com> References: <1439913332.4239.134.camel@citrix.com> <55D61964.90608@suse.com> <55E47CFE.8020809@oracle.com> <55E6E454.7090503@suse.com> <55E702E7.6070709@oracle.com> <55E707E9.6000805@suse.com> Organization: Citrix Inc. Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-/3EtjyFRrCXx9EeaqhGZ" X-Mailer: Evolution 3.12.11 (3.12.11-1.fc21) MIME-Version: 1.0 X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-/3EtjyFRrCXx9EeaqhGZ Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2015-09-02 at 16:30 +0200, Juergen Gross wrote: > On 09/02/2015 04:08 PM, Boris Ostrovsky wrote: > > On 09/02/2015 07:58 AM, Juergen Gross wrote: > >> On 08/31/2015 06:12 PM, Boris Ostrovsky wrote: > >>> If set_cpu_sibling_map()'s has_mp is false, wouldn't we effectively h= ave > >>> both of your patches? > >> > >> Hmm, sort of. > >> > >> OTOH this would it make hard to make use of some of the topology > >> information in case of e.g. pinned vcpus (as George pointed out). > > > > > > I didn't mean to just set has_mp to zero unconditionally (for Xen, or > > any other, guest). We'd need to have some logic as to when to set it to > > false. >=20 > In case we want to be able to use some of the topology information this > would mean we'd have two different mechanisms to either disable all > topology usage or only parts of it. I'd rather have a way to specify > which levels of the topology information (numa nodes, cache siblings, > core siblings) are to be used. Using none is just one possibility with > all levels disabled. >=20 I agree, indeed, acting on has_mp seems overkill/not ideal to me too (I'm not even sure I fully understand how it's used in set_cpu_sibling_map()... I'll dig more). However... > >> > >>> Also, it seems to me that Xen guests would not be the only ones havin= g > >>> to deal with topology inconsistencies due to migrating VCPUs. Don't K= VM > >>> guests, for example, have the same problem? And if yes, perhaps we > >>> should try solving it in non-Xen-specific way (especially given that > >>> both of those patches look pretty simple and thus are presumably easy= to > >>> integrate into common code). > >> > >> Indeed. I'll have a try. > >> ...yes, this is an interesting point, and it's worth try looking at how to implement things that way. 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) --=-/3EtjyFRrCXx9EeaqhGZ 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 iEYEABECAAYFAlX4UooACgkQk4XaBE3IOsSb6gCfcm/p+w6k1PW8A97mtJXjCKdS H8gAn31gOb8+8Trv2Y9VE+otNPkEkovV =LfKy -----END PGP SIGNATURE----- --=-/3EtjyFRrCXx9EeaqhGZ--