From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shirley Ma Subject: Re: [RFC PATCH 2/2] macvtap: TX zero copy between guest and host kernel Date: Wed, 15 Sep 2010 07:52:34 -0700 Message-ID: <1284562354.2573.12.camel@localhost.localdomain> References: <20100914152231.GA13105@redhat.com> <1284480025.13351.49.camel@localhost.localdomain> <20100914162952.GB13560@redhat.com> <1284483745.13351.71.camel@localhost.localdomain> <20100914182707.GB15549@redhat.com> <1284490143.13351.82.camel@localhost.localdomain> <20100914190156.GA16037@redhat.com> <1284492983.13351.95.camel@localhost.localdomain> <20100915051241.GA25340@redhat.com> <1284531675.24603.259.camel@localhost.localdomain> <20100915101000.GB28016@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Arnd Bergmann , Avi Kivity , "Xin, Xiaohui" , David Miller , netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: "Michael S. Tsirkin" Return-path: In-Reply-To: <20100915101000.GB28016@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, 2010-09-15 at 12:10 +0200, Michael S. Tsirkin wrote: > Another issue is that macvtap can be bound to almost > anything, including e.g. a tap device or a bridge, > which might hang on to skb fragments for unlimited time. > Zero copy TX won't easily work there. > I can imagine either somehow triggering a data copy after the > fact (hard), or detecting such devices and avoiding > zero copy (unfortunate for guest to guest, and drivers > will need tuning). So far macvtap zero copy patch is limited to lower devices supports high memory DMA, it doesn't apply to a tap device or a bridge. > > Don't you think once I address vhost_add_used_and_signal update > > issue, it is a simple and complete patch for macvtap TX zero copy? > > > > Thanks > > Shirley > > I like the fact that the patch is simple. Unfortunately > I suspect it'll stop being simple by the time it's complete :) I can make a try. :) Thanks Shirley