From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH RFC 1/3] virtio infrastructure Date: Mon, 04 Jun 2007 14:25:32 +0300 Message-ID: <4663F6AC.7070100@qumranet.com> References: <1180613947.11133.58.camel@localhost.localdomain> <46610E8D.10706@qumranet.com> <1180777836.9228.44.camel@localhost.localdomain> <46625192.5020108@qumranet.com> <1180866540.17442.74.camel@localhost.localdomain> <4662A86A.7010706@qumranet.com> <1180914836.17442.104.camel@localhost.localdomain> <4663E18D.4030007@qumranet.com> <1180955964.25878.27.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Jimi Xenidis , Stephen Rothwell , Xen Mailing List , "jmk-zzFmDc4TPjtKvsKVC3L/VUEOCMrvLtNR@public.gmane.org" , Herbert Xu , kvm-devel , virtualization , Christian Borntraeger , Suzanne McIntosh , Martin Schwidefsky To: Rusty Russell Return-path: In-Reply-To: <1180955964.25878.27.camel-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Rusty Russell wrote: > >> Networking hardware generally services descriptors in a FIFO manner. >> > > Well, ethernet guarantees order. Not sure about others tho... > > OT: Does that hold for bonded interfaces too? >> virtio may not (for example, it may offload copies of larger packets to >> a dma engine such as I/OAT, resulting in a delay, but copy smaller >> packets immediately). that means that there will be some mismatch >> between virtio drivers and real hardware drivers. >> > > I think your point is that the completion bitmap (or indeed, the current > approach) does not maintain order? Hmm, this is more convincing to me > than cache arguments, since some devices might want ordering and want > more than a single io in flight. > Well, it wasn't really; sorry for being unclear. My point was that virtio interfaces will not match hardware exactly. My objection is to "scan all slots, occupied or not, for completion". I think virtio should present completed descriptors without the need for scanning, even if it means looking a bit different from a typical ethernet driver. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/