From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752725AbeDPPI7 (ORCPT ); Mon, 16 Apr 2018 11:08:59 -0400 Received: from shards.monkeyblade.net ([184.105.139.130]:42380 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751135AbeDPPI5 (ORCPT ); Mon, 16 Apr 2018 11:08:57 -0400 Date: Mon, 16 Apr 2018 11:08:55 -0400 (EDT) Message-Id: <20180416.110855.61732218036810337.davem@davemloft.net> To: rafalo@cadence.com Cc: nicolas.ferre@microchip.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/3] Receive Side Coalescing for macb driver From: David Miller In-Reply-To: <1523739187-20077-1-git-send-email-rafalo@cadence.com> References: <1523739187-20077-1-git-send-email-rafalo@cadence.com> X-Mailer: Mew version 6.7 on Emacs 25.3 / Mule 6.0 (HANACHIRUSATO) 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 From: Rafal Ozieblo Date: Sat, 14 Apr 2018 21:53:07 +0100 > This patch series adds support for receive side coalescing > for Cadence GEM driver. Receive segmentation coalescing > is a mechanism to reduce CPU overhead. This is done by > coalescing received TCP message segments together into > a single large message. This means that when the message > is complete the CPU only has to process the single header > and act upon the one data payload. You're going to have to think more deeply about enabling this feature. If you can't adjust the receive buffer offset, then the various packet header fields will be unaligned. On certain architectures this will result in unaligned traps all over the networking stack as the packet is being processed. So enabling this by default will hurt performance on such systems a lot. The whole "skb_reserve(skb, NET_IP_ALIGN)" is not just for fun, it is absolutely essential.