From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753471AbdBVDGo (ORCPT ); Tue, 21 Feb 2017 22:06:44 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53968 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752806AbdBVDGf (ORCPT ); Tue, 21 Feb 2017 22:06:35 -0500 Date: Wed, 22 Feb 2017 05:06:34 +0200 From: "Michael S. Tsirkin" To: Jason Wang Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] virtio-net: switch to use build_skb() for small buffer Message-ID: <20170222050601-mutt-send-email-mst@kernel.org> References: <1487666788-9658-1-git-send-email-jasowang@redhat.com> <20170221162849-mutt-send-email-mst@kernel.org> <35244d06-2d0d-3f2e-0cd1-43137988c869@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <35244d06-2d0d-3f2e-0cd1-43137988c869@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Wed, 22 Feb 2017 03:06:36 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 22, 2017 at 10:58:08AM +0800, Jason Wang wrote: > > > On 2017年02月21日 22:37, Michael S. Tsirkin wrote: > > On Tue, Feb 21, 2017 at 04:46:28PM +0800, Jason Wang wrote: > > > This patch switch to use build_skb() for small buffer which can have > > > better performance for both TCP and XDP (since we can work at page > > > before skb creation). It also remove lots of XDP codes since both > > > mergeable and small buffer use page frag during refill now. > > > > > > Before | After > > > XDP_DROP(xdp1) 64B : 11.1Mpps | 14.4Mpps > > > > > > Tested with xdp1/xdp2/xdp_ip_tx_tunnel and netperf. > > > > > > Signed-off-by: Jason Wang > > Thanks! > > I had a similar patch for mergeable too, though it's trickier there > > as host has a lot of flexibility in sizing buffers. > > Looks like a good intermediate step to me. > > Yes, I think it's more tricky for the case of mergeable buffer: > > 1) we need reserve NET_SKB_PAD + NET_IP_ALIGN for each buffer, this will > break rx frag coalescing > 2) need tailroom for skb_shinfo, so it won't work for all size of packet > > Thanks Have you seen my prototype? It works with qemu in practice, just needs to cover a bunch of corner cases. > > > > > > Acked-by: Michael S. Tsirkin > >