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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 65181C43603 for ; Fri, 6 Dec 2019 16:19:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 32915206DF for ; Fri, 6 Dec 2019 16:19:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="kDgU7N/F" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726403AbfLFQTK (ORCPT ); Fri, 6 Dec 2019 11:19:10 -0500 Received: from mail-pj1-f47.google.com ([209.85.216.47]:34220 "EHLO mail-pj1-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726284AbfLFQTJ (ORCPT ); Fri, 6 Dec 2019 11:19:09 -0500 Received: by mail-pj1-f47.google.com with SMTP id j11so1817064pjs.1; Fri, 06 Dec 2019 08:19:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=41QvHatHr0g3uZPwHbiixW/aEz8FiwJ4DRuDN3ZTAZU=; b=kDgU7N/FqrEaiBPUK3AQSShoOnDpdLUi6+T3Dv9758TdJM2N+yVEtJUwPnP1GSb0n6 rMHgB0VGs98mnoNW9NaSuWAYvL8bRPDc9JI9cx5HrvxojjckmbBiflAlsB8wP0XVPh1Q GcqLi6HqEyxzTyMilAkmWUNAXUYVdsmJjrVkJn2zS18WlZFuAikif/gEGsUCsNCHcHBh Dc0c51GCkZu66l673y4us9LPrn3GkE+Kd/FN/7QiZWNIfRxepmIedBdah+hE4WW3KDb2 Iqjkjxxj6WYH2NFHKV/ngt9/G1hI2ONc3vz90tEpX9twhfPbM2X7UaK0pmCSKYjZ/vzF rEKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=41QvHatHr0g3uZPwHbiixW/aEz8FiwJ4DRuDN3ZTAZU=; b=cnZ4QgpPlU71Xt4PaTw9akOtBrLf6QX9xZsc0RJv9YBPBiKhY+aJEv7xCUUELICxnp Yxiw4Ea/m7BqlXwVfCp/zgQtqaJVt0IBMYGaS1/VmXofC1EknZWfszGHK2WYduoQJ496 0q91JmZMZxyZf3tpHWy/YLuwG51zsCgyyPtWYbFXlaf1u0mLiwkepLOZi27DFO8SQWPM za3pCMD2MQLHhXFjmoQxXyUGXjbv5vZFQdrThrrn2Ta1LSR3tkDc82fdxPn2AfhEsEoz wzSt+LUXn1AOu8YY2weTEAEKBRmGHLa1uSOzuNKnLHH0PKztv+CeH065itsNblC0ULFO EXBA== X-Gm-Message-State: APjAAAXSlZCo8zfZYAYKl3McihEUqOx6lbUywwF9TV5dwQH6kgXOBN8d daGS63KQBCdqXvqF6+4IvoUN4ZO8 X-Google-Smtp-Source: APXvYqwP7ciMTfz113hONKdgvFWnVcg5bk56SmmrYXxIlvQPh6h6eSbqeAGJ8qI3xCJCnyWSnBnXBQ== X-Received: by 2002:a17:90a:c790:: with SMTP id gn16mr16647645pjb.76.1575649149075; Fri, 06 Dec 2019 08:19:09 -0800 (PST) Received: from [192.168.84.65] (8.100.247.35.bc.googleusercontent.com. [35.247.100.8]) by smtp.gmail.com with ESMTPSA id s2sm17531268pfb.109.2019.12.06.08.19.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 06 Dec 2019 08:19:08 -0800 (PST) Subject: Re: recvfrom/recvmsg performance and CONFIG_HARDENED_USERCOPY To: Paolo Abeni , Eric Dumazet , David Laight , network dev , "x86@kernel.org" , "linux-kernel@vger.kernel.org" References: <23db23416d3148fa86e54dccc6152266@AcuMS.aculab.com> <8b8a3cc1c3341912e0db5c55cd0e504dd4371588.camel@redhat.com> From: Eric Dumazet Message-ID: Date: Fri, 6 Dec 2019 08:19:03 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <8b8a3cc1c3341912e0db5c55cd0e504dd4371588.camel@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/6/19 8:09 AM, Paolo Abeni wrote: > Oh, nice! I though the compiler was smart enough to avoid the indirect > call with the current code, but it looks like that least gcc 9.2.1 is > not. > > Thanks for pointing that out! > > In this specific scenario I think the code you propose above is better > than INDIRECT_CALL. > > Would you submit the patch formally? Certainly, although I am not sure this will be enough to close the gap between recvmsg() and recvfrom() :) Also I was wondering if a likely() or unlikely() clause would make sense. This could prevent an over zealous compiler optimizer to put back the indirect call that we tried to avoid.