From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 94076C2D0DB for ; Tue, 21 Jan 2020 10:04:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6B6B720882 for ; Tue, 21 Jan 2020 10:04:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729539AbgAUKE6 (ORCPT ); Tue, 21 Jan 2020 05:04:58 -0500 Received: from shards.monkeyblade.net ([23.128.96.9]:35970 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728741AbgAUKE6 (ORCPT ); Tue, 21 Jan 2020 05:04:58 -0500 Received: from localhost (82-95-191-104.ip.xs4all.nl [82.95.191.104]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id C906E15BD84F7; Tue, 21 Jan 2020 02:04:55 -0800 (PST) Date: Tue, 21 Jan 2020 11:04:54 +0100 (CET) Message-Id: <20200121.110454.2077433904156411260.davem@davemloft.net> To: haiyangz@microsoft.com Cc: sashal@kernel.org, linux-hyperv@vger.kernel.org, netdev@vger.kernel.org, kys@microsoft.com, sthemmin@microsoft.com, olaf@aepfle.de, vkuznets@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH V2,net-next, 1/2] hv_netvsc: Add XDP support From: David Miller In-Reply-To: <1579558957-62496-2-git-send-email-haiyangz@microsoft.com> References: <1579558957-62496-1-git-send-email-haiyangz@microsoft.com> <1579558957-62496-2-git-send-email-haiyangz@microsoft.com> X-Mailer: Mew version 6.8 on Emacs 26.3 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Tue, 21 Jan 2020 02:04:57 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Haiyang Zhang Date: Mon, 20 Jan 2020 14:22:36 -0800 > +u32 netvsc_run_xdp(struct net_device *ndev, struct netvsc_channel *nvchan, > + struct xdp_buff *xdp) > +{ > + struct page *page = NULL; > + void *data = nvchan->rsc.data[0]; > + u32 len = nvchan->rsc.len[0]; > + struct bpf_prog *prog; > + u32 act = XDP_PASS; Please use reverse christmas tree ordering of local variables. > + xdp->data_hard_start = page_address(page); > + xdp->data = xdp->data_hard_start + NETVSC_XDP_HDRM; > + xdp_set_data_meta_invalid(xdp); > + xdp->data_end = xdp->data + len; > + xdp->rxq = &nvchan->xdp_rxq; > + xdp->handle = 0; > + > + memcpy(xdp->data, data, len); Why can't the program run directly on nvchan->rsc.data[0]? This data copy defeats the whole performance gain of using XDP.