From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCHv3 net-next 0/8] enable/disable zero copy tx dynamically Date: Fri, 02 Nov 2012 21:31:10 -0400 (EDT) Message-ID: <20121102.213110.2070365320544608145.davem@davemloft.net> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: mst@redhat.com Cc: vyasevic@redhat.com, alexander.h.duyck@intel.com, Ian.Campbell@citrix.com, kvm@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, edumazet@google.com, akpm@linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org From: "Michael S. Tsirkin" Date: Thu, 1 Nov 2012 21:16:17 +0200 > > tun supports zero copy transmit since 0690899b4d4501b3505be069b9a687e68ccbe15b, > however you can only enable this mode if you know your workload does not > trigger heavy guest to host/host to guest traffic - otherwise you > get a (minor) performance regression. > This patchset addresses this problem by notifying the owner > device when callback is invoked because of a data copy. > This makes it possible to detect whether zero copy is appropriate > dynamically: we start in zero copy mode, when we detect > data copied we disable zero copy for a while. > > With this patch applied, I get the same performance for > guest to host and guest to guest both with and without zero copy tx. Series applied, thanks Michael.