From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58448) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dLsyP-0003Qa-Os for qemu-devel@nongnu.org; Fri, 16 Jun 2017 11:15:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dLsyK-0007fk-Rv for qemu-devel@nongnu.org; Fri, 16 Jun 2017 11:15:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51176) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dLsyK-0007ep-I0 for qemu-devel@nongnu.org; Fri, 16 Jun 2017 11:15:40 -0400 Date: Fri, 16 Jun 2017 18:15:37 +0300 From: "Michael S. Tsirkin" Message-ID: <20170616181040-mutt-send-email-mst@kernel.org> References: <9f196d71-f06b-7520-ca03-e94bf3b5a986@redhat.com> <593FB550.6090903@intel.com> <26250da7-b394-4964-8842-5c45bbe85e09@redhat.com> <6547dfcf-ea3a-f5f6-222d-40ff274654df@redhat.com> <20170614180459-mutt-send-email-mst@kernel.org> <59422E91.7080407@intel.com> <20170616061949-mutt-send-email-mst@kernel.org> <40a12829-6e84-e63e-ac47-6f09cc85c3cc@redhat.com> <5943AE93.7020502@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <5943AE93.7020502@intel.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [virtio-dev] Re: [virtio-dev] Re: [virtio-dev] Re: [PATCH v1] virtio-net: enable configurable tx queue size List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Wei Wang Cc: Jason Wang , "virtio-dev@lists.oasis-open.org" , "stefanha@gmail.com" , "qemu-devel@nongnu.org" , "jan.scheurich@ericsson.com" , "armbru@redhat.com" , "marcandre.lureau@gmail.com" , "pbonzini@redhat.com" On Fri, Jun 16, 2017 at 06:10:27PM +0800, Wei Wang wrote: > On 06/16/2017 04:57 PM, Jason Wang wrote: > >=20 > >=20 > > On 2017=E5=B9=B406=E6=9C=8816=E6=97=A5 11:22, Michael S. Tsirkin wrot= e: > > > > I think the issues can be solved by VIRTIO_F_MAX_CHAIN_SIZE. > > > >=20 > > > > For now, how about splitting it into two series of patches: > > > > 1) enable 1024 tx queue size for vhost-user, to let the users of > > > > vhost-user > > > > to easily use 1024 queue size. > > > Fine with me. 1) will get property from user but override it on > > > !vhost-user. Do we need a protocol flag? It seems prudent but we ge= t > > > back to cross-version migration issues that are still pending solut= ion. > What do you have in mind about the protocol flag? Merely this: older clients might be confused if they get a s/g with 1024 entries. > Btw, I just tested the patch of 1), and it works fine with migration fr= om > the > patched to non-patched version of QEMU. I'll send it out. Please have a > check. >=20 >=20 > > > Marc Andre, what's the status of that work? > > >=20 > > > > 2) enable VIRTIO_F_MAX_CHAIN_SIZE, to enhance robustness. > > > Rather, to support it for more backends. > >=20 > > Ok, if we want to support different values of max chain size in the > > future. It would be problematic for migration of cross backends, > > consider the case when migrating from 2048 (vhost-user) to 1024 > > (qemu/vhost-kernel). > >=20 >=20 > I think that wouldn't be a problem. If there is a possibility to change= the > backend resulting in a change of config.max_change_size, a configuratio= n > change notification can be injected to the guest, then guest will read = and > get the new value. >=20 > Best, > Wei This might not be supportable by all guests. E.g. some requests might already be in the queue. I'm not against reconfiguring devices across migration but I think it's a big project. As a 1st step I would focus on keeping configuration consistent across migrations. --=20 MST