From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:43936) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h1pvk-0003ze-DY for qemu-devel@nongnu.org; Thu, 07 Mar 2019 05:07:13 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h1pvj-0007Rs-Iq for qemu-devel@nongnu.org; Thu, 07 Mar 2019 05:07:12 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58342) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1h1pvj-0007RX-9d for qemu-devel@nongnu.org; Thu, 07 Mar 2019 05:07:11 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 908B2307E07A for ; Thu, 7 Mar 2019 10:07:10 +0000 (UTC) Date: Thu, 7 Mar 2019 10:07:05 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20190307100705.GH32268@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <1551893605-236413-1-git-send-email-imammedo@redhat.com> <20190306181608.GL20806@redhat.com> <20190306195417.02ea9a4c@Igors-MacBook-Pro.local> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190306195417.02ea9a4c@Igors-MacBook-Pro.local> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v2] numa: warn if numa 'mem' option or default RAM splitting between nodes is used. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Igor Mammedov Cc: qemu-devel@nongnu.org, ehabkost@redhat.com, libvir-list@redhat.com, eblake@redhat.com, Markus Armbruster On Wed, Mar 06, 2019 at 07:54:17PM +0100, Igor Mammedov wrote: > On Wed, 6 Mar 2019 18:16:08 +0000 > Daniel P. Berrang=C3=A9 wrote: >=20 > > On Wed, Mar 06, 2019 at 06:33:25PM +0100, Igor Mammedov wrote: > > > Amend -numa option docs and print warnings if 'mem' option or defau= lt RAM > > > splitting between nodes is used. It's intended to discourage users = from using > > > configuration that allows only to fake NUMA on guest side while lea= ding > > > to reduced performance of the guest due to inability to properly co= nfigure > > > VM's RAM on the host. > > >=20 > > > In NUMA case, it's recommended to always explicitly configure guest= RAM > > > using -numa node,memdev=3D{backend-id} option. > > >=20 > > > Signed-off-by: Igor Mammedov > > > --- > > > numa.c | 5 +++++ > > > qemu-options.hx | 12 ++++++++---- > > > 2 files changed, 13 insertions(+), 4 deletions(-) > > >=20 > > > diff --git a/numa.c b/numa.c > > > index 3875e1e..42838f9 100644 > > > --- a/numa.c > > > +++ b/numa.c > > > @@ -121,6 +121,8 @@ static void parse_numa_node(MachineState *ms, N= umaNodeOptions *node, > > > =20 > > > if (node->has_mem) { > > > numa_info[nodenr].node_mem =3D node->mem; > > > + warn_report("Parameter -numa node,mem is obsolete," > > > + " use -numa node,memdev instead"); > >=20 > > My comments from v1 still apply. We must not do this as long as > > libvirt has no choice but to continue using this feature. > It has a choice to use 'memdev' whenever creating a new VM and continue > using 'mem' with exiting VMs. Unfortunately we don't have such a choice. Libvirt has no concept of the distinction between an 'existing' and 'new' VM. It just receives an XML file from the mgmt application and with transient guests, we have no persistent configuration record of the VM. So we've no way of knowing whether this VM was previously running on this same host, or another host, or is completely new. Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberran= ge :| |: https://libvirt.org -o- https://fstop138.berrange.c= om :| |: https://entangle-photo.org -o- https://www.instagram.com/dberran= ge :|