From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:44155) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h1ZZM-0000cg-Cy for qemu-devel@nongnu.org; Wed, 06 Mar 2019 11:39:01 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h1ZZI-0007Nv-7w for qemu-devel@nongnu.org; Wed, 06 Mar 2019 11:38:57 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42262) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1h1ZZF-0007Kg-Mj for qemu-devel@nongnu.org; Wed, 06 Mar 2019 11:38:54 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A76A980472 for ; Wed, 6 Mar 2019 16:38:48 +0000 (UTC) References: <1551889825-227155-1-git-send-email-imammedo@redhat.com> From: Eric Blake Message-ID: Date: Wed, 6 Mar 2019 10:38:40 -0600 MIME-Version: 1.0 In-Reply-To: <1551889825-227155-1-git-send-email-imammedo@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="BbPLAWspBDriGXf4m7GKG2ro7Itr1QsuL" Subject: Re: [Qemu-devel] [PATCH] 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 , qemu-devel@nongnu.org Cc: ehabkost@redhat.com, libvir-list@redhat.com, berrange@redhat.com This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --BbPLAWspBDriGXf4m7GKG2ro7Itr1QsuL From: Eric Blake To: Igor Mammedov , qemu-devel@nongnu.org Cc: ehabkost@redhat.com, libvir-list@redhat.com, berrange@redhat.com Message-ID: Subject: Re: [PATCH] numa: warn if numa 'mem' option or default RAM splitting between nodes is used. References: <1551889825-227155-1-git-send-email-imammedo@redhat.com> In-Reply-To: <1551889825-227155-1-git-send-email-imammedo@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 3/6/19 10:30 AM, Igor Mammedov wrote: > Ammend -numa option docs and print warnings if 'mem' option or default = RAM s/Ammend/Amend/ > splitting between nodes is used. It's intended to discourage users from= using > configuration that allows only to fake NUMA on guest side while leading= > to reduced performance of the guest due to inability to properly config= ure > 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 > @@ -407,6 +409,9 @@ void numa_complete_configuration(MachineState *ms) > if (i =3D=3D nb_numa_nodes) { > assert(mc->numa_auto_assign_ram); > mc->numa_auto_assign_ram(mc, numa_info, nb_numa_nodes, ram= _size); > + warn_report("Default splitting of RAM between nodes is obs= olete," > + " Use '-numa node,memdev' to explictly define = RAM" s/explictly/explicitly/ > +++ b/qemu-options.hx > @@ -206,10 +206,14 @@ For example: > -numa cpu,node-id=3D0,socket-id=3D0 -numa cpu,node-id=3D1,socket-id=3D= 1 > @end example > =20 > -@samp{mem} assigns a given RAM amount to a node. @samp{memdev} > -assigns RAM from a given memory backend device to a node. If > -@samp{mem} and @samp{memdev} are omitted in all nodes, RAM is > -split equally between them. > +@samp{memdev} assigns RAM from a given memory backend device to a node= =2E > + > +Legacy options/behaviour: @samp{mem} assigns a given RAM amount to a n= ode. > +If @samp{mem} and @samp{memdev} are omitted in all nodes, RAM is split= equally > +between them. Option @samp{mem} and default RAM splitting are obsolete= as they > +do not provide means to manage RAM on host side and only allow QEMU to= fake s/on host/on the host/ > +NUMA support which in practice could degrade VM performance. > +It's advised to always explicitly configure NUMA RAM using @samp{memde= v} option. s/using/by using the/ --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org --BbPLAWspBDriGXf4m7GKG2ro7Itr1QsuL Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAlx/95EACgkQp6FrSiUn Q2o17ggAgGh9FO4lf/XMjvhMbXu+5IWvrzwWoLGrV3xqsE4PeSC5f3KaweviKkA0 F+9PDwRr06L4ITnLMYtitkakAd5kkNex+qpxTwzSaSqAvYmPSOLSl3MZVhkrubkX 7c0jluKBx6A7P3k1cyrprsnbpmIDZPBiC+8uUCadbZUJtjSxU19KR/0HS1KshaGN GCuzCiIVeAhwgRhMgHLb5Ins35wa/986U1uoBNKvmPUodw5eanskhaPV5ORBqsTS 8VTqOf3ndJpvMQBXpquZv3grsIIiu5WrmKX62yUHinfwy1uY+nZTk5xxEs9eGgiy 06byJbKCbaiSwMrsYMbgbAze/N/CBg== =Phhu -----END PGP SIGNATURE----- --BbPLAWspBDriGXf4m7GKG2ro7Itr1QsuL--