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=-3.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 CAA78C43215 for ; Sun, 17 Nov 2019 09:52:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A264720727 for ; Sun, 17 Nov 2019 09:52:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=dlink.ru header.i=@dlink.ru header.b="CYTJS3OP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726089AbfKQJwk (ORCPT ); Sun, 17 Nov 2019 04:52:40 -0500 Received: from mail.dlink.ru ([178.170.168.18]:37258 "EHLO fd.dlink.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725953AbfKQJwk (ORCPT ); Sun, 17 Nov 2019 04:52:40 -0500 Received: by fd.dlink.ru (Postfix, from userid 5000) id 44A741B20C5D; Sun, 17 Nov 2019 12:52:35 +0300 (MSK) DKIM-Filter: OpenDKIM Filter v2.11.0 fd.dlink.ru 44A741B20C5D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=dlink.ru; s=mail; t=1573984355; bh=kb0YVBramWtjA/Ad8wxxFedgfyiwwLDzdL9qmwmkwJo=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=CYTJS3OPFdbnqAqD6h9NnT5GP96M+sKXbB5l2quB1ODwLZ2oRj8lF8SMe3fQnKBrx eGlDMkBsi6YPE0BtsF4dpyMVNNE4XzANSawajT2/yphkVDHVOtp5uoTfmfHy90cZhg LXfVWQAU8GF+SLSwmSAA6dBrnKKYolIuygqq/w5c= Received: from mail.rzn.dlink.ru (mail.rzn.dlink.ru [178.170.168.13]) by fd.dlink.ru (Postfix) with ESMTP id 903E41B202CB; Sun, 17 Nov 2019 12:52:24 +0300 (MSK) DKIM-Filter: OpenDKIM Filter v2.11.0 fd.dlink.ru 903E41B202CB Received: from mail.rzn.dlink.ru (localhost [127.0.0.1]) by mail.rzn.dlink.ru (Postfix) with ESMTP id 57C4B1B2022F; Sun, 17 Nov 2019 12:52:24 +0300 (MSK) Received: from mail.rzn.dlink.ru (localhost [127.0.0.1]) by mail.rzn.dlink.ru (Postfix) with ESMTPA; Sun, 17 Nov 2019 12:52:24 +0300 (MSK) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Sun, 17 Nov 2019 12:52:24 +0300 From: Alexander Lobakin To: David Miller Cc: ecree@solarflare.com, jiri@mellanox.com, edumazet@google.com, idosch@mellanox.com, pabeni@redhat.com, petrm@mellanox.com, sd@queasysnail.net, f.fainelli@gmail.com, jaswinder.singh@linaro.org, manishc@marvell.com, GR-Linux-NIC-Dev@marvell.com, johannes.berg@intel.com, emmanuel.grumbach@intel.com, luciano.coelho@intel.com, linuxwifi@intel.com, kvalo@codeaurora.org, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 net-next] net: core: allow fast GRO for skbs with Ethernet header in head In-Reply-To: <20191116.130101.268806870571558138.davem@davemloft.net> References: <20191115091135.13487-1-alobakin@dlink.ru> <20191116.130101.268806870571558138.davem@davemloft.net> User-Agent: Roundcube Webmail/1.4.0 Message-ID: <5622418d39ce3ebc3d526d3e16c8546b@dlink.ru> X-Sender: alobakin@dlink.ru Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org David Miller wrote 17.11.2019 00:01: > From: Alexander Lobakin > Date: Fri, 15 Nov 2019 12:11:35 +0300 > >> Commit 78d3fd0b7de8 ("gro: Only use skb_gro_header for completely >> non-linear packets") back in May'09 (v2.6.31-rc1) has changed the >> original condition '!skb_headlen(skb)' to >> 'skb->mac_header == skb->tail' in gro_reset_offset() saying: "Since >> the drivers that need this optimisation all provide completely >> non-linear packets" (note that this condition has become the current >> 'skb_mac_header(skb) == skb_tail_pointer(skb)' later with commmit >> ced14f6804a9 ("net: Correct comparisons and calculations using >> skb->tail and skb-transport_header") without any functional changes). >> >> For now, we have the following rough statistics for v5.4-rc7: >> 1) napi_gro_frags: 14 >> 2) napi_gro_receive with skb->head containing (most of) payload: 83 >> 3) napi_gro_receive with skb->head containing all the headers: 20 >> 4) napi_gro_receive with skb->head containing only Ethernet header: 2 >> >> With the current condition, fast GRO with the usage of >> NAPI_GRO_CB(skb)->frag0 is available only in the [1] case. >> Packets pushed by [2] and [3] go through the 'slow' path, but >> it's not a problem for them as they already contain all the needed >> headers in skb->head, so pskb_may_pull() only moves skb->data. >> >> The layout of skbs in the fourth [4] case at the moment of >> dev_gro_receive() is identical to skbs that have come through [1], >> as napi_frags_skb() pulls Ethernet header to skb->head. The only >> difference is that the mentioned condition is always false for them, >> because skb_put() and friends irreversibly alter the tail pointer. >> They also go through the 'slow' path, but now every single >> pskb_may_pull() in every single .gro_receive() will call the *really* >> slow __pskb_pull_tail() to pull headers to head. This significantly >> decreases the overall performance for no visible reasons. > ... >> Signed-off-by: Alexander Lobakin > > Applied to net-next, thanks. Thank you! Regards, ᚷ ᛖ ᚢ ᚦ ᚠ ᚱ