From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Abeni Subject: Re: [PATCH net-next] virtio_net: replace netdev_alloc_skb_ip_align() with napi_alloc_skb() Date: Fri, 18 Mar 2016 09:21:41 +0100 Message-ID: <1458289301.5314.11.camel@redhat.com> 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: Venkatesh Srinivas Cc: netdev@vger.kernel.org, "Michael S. Tsirkin" , Hannes Frederic Sowa , virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org On Thu, 2016-03-17 at 18:01 -0700, Venkatesh Srinivas wrote: > On Thu, Mar 17, 2016 at 7:44 AM, Paolo Abeni wrote: > > > > This gives small but noticeable rx performance improvement (2-3%) > > and will allow exploiting future napi improvement. > > > > Signed-off-by: Paolo Abeni > > --- > > Worked in my tests, though the performance win was in the noise (+0.6% > - +1% bandwidth). > What tests did you see a 2-3% win on? I'm doing net2VM tests (i.e. the traffic generator is on a different host) with guest tuned a bit for performance. i.e. cpu pinning, no iptables, no dhclient (yes, that makes a big difference: http://lists.openwall.net/netdev/2013/10/29/5) > Do you think its worth modifying add_recvbuf_small() to use > napi_alloc_skb() when called from > Rx NAPI (virtnet_receive)? Oops, I missed that invocation. Probably that path is not hit in my test. I think it should be really worthy. I'll send a v2. The important thing, more than the current improvement, is allowing the virtio_net driver to leverage future napi allocation improvement (i.e. bulk alloc: http://www.spinics.net/lists/netdev/msg367568.html) which should be a real win. Paolo