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 61767C3F2D2 for ; Fri, 28 Feb 2020 20:01:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3D39C24677 for ; Fri, 28 Feb 2020 20:01:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726816AbgB1UBv (ORCPT ); Fri, 28 Feb 2020 15:01:51 -0500 Received: from shards.monkeyblade.net ([23.128.96.9]:55714 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725769AbgB1UBv (ORCPT ); Fri, 28 Feb 2020 15:01:51 -0500 Received: from localhost (unknown [IPv6:2601:601:9f00:477::3d5]) (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 D1274159742F2; Fri, 28 Feb 2020 12:01:50 -0800 (PST) Date: Fri, 28 Feb 2020 12:01:50 -0800 (PST) Message-Id: <20200228.120150.302053489768447737.davem@davemloft.net> To: willemdebruijn.kernel@gmail.com Cc: kyk.segfault@gmail.com, netdev@vger.kernel.org Subject: Re: [PATCH] net: Make skb_segment not to compute checksum if network controller supports checksumming From: David Miller In-Reply-To: References: X-Mailer: Mew version 6.8 on Emacs 26.1 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]); Fri, 28 Feb 2020 12:01:51 -0800 (PST) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Willem de Bruijn Date: Fri, 28 Feb 2020 09:30:56 -0500 > Can you contrast this against a run with your changes? The thought is > that the majority of this cost is due to the memory loads and stores, not > the arithmetic ops to compute the checksum. When enabling checksum > offload, the same stalls will occur, but will simply be attributed to > memcpy instead of to do_csum. Agreed.