From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966838AbeCAJQO (ORCPT ); Thu, 1 Mar 2018 04:16:14 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:58280 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S966601AbeCAJQB (ORCPT ); Thu, 1 Mar 2018 04:16:01 -0500 Date: Thu, 1 Mar 2018 10:15:53 +0100 From: Jesper Dangaard Brouer To: Jason Wang Cc: mst@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, john.fastabend@gmail.com, brouer@redhat.com Subject: Re: [PATCH net-next 2/2] virtio-net: simplify XDP handling in small buffer Message-ID: <20180301101553.55c4c6bd@redhat.com> In-Reply-To: References: <1519874345-10235-1-git-send-email-jasowang@redhat.com> <1519874345-10235-3-git-send-email-jasowang@redhat.com> <20180301090206.04e13a71@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 1 Mar 2018 16:49:24 +0800 Jason Wang wrote: > > 2. This can easily cause out-of-order packets. > > I may miss something, but it looks to me packets were still delivered > in order? Or you mean the packets that was dropped by cpumap? No. Packets can now travel two code paths to the egress device. (1) XDP native via ndp_xdp_xmit via direct delivery into a lockfree/dedicated TX queue, (2) via normal network stack which can involve being queue in a qdisc. Do you see the possibility of the reorder now? -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer