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=-2.3 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 5B82AC11D2F for ; Mon, 24 Feb 2020 15:57:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 239C020828 for ; Mon, 24 Feb 2020 15:57:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="jT3YwVVg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727874AbgBXP5f (ORCPT ); Mon, 24 Feb 2020 10:57:35 -0500 Received: from mail-wm1-f53.google.com ([209.85.128.53]:53061 "EHLO mail-wm1-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727693AbgBXP5f (ORCPT ); Mon, 24 Feb 2020 10:57:35 -0500 Received: by mail-wm1-f53.google.com with SMTP id p9so9493054wmc.2 for ; Mon, 24 Feb 2020 07:57:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:autocrypt:message-id:date:user-agent :mime-version:in-reply-to; bh=uh7zQa/YMj/IN90JAfIqS4qXW/WXnBw7ej8pdpWyY10=; b=jT3YwVVgOEG1tDEYERbW0YcaQv2hqXK7hlYJ//CJ+xTyhaVgsiczzizFqSofjLlm2c +uLRlwUeF6WJWwLuT1Up1CqLssV6mmqYrVVcSYjizXLrkUJEjGLxG7hvV8BKcO9q8BT8 +3jVylsZVBIG+xZlIX7JYBosKpfTdE/1ulE74/qu405dvpHC8JsKB8XpscylmuHYAV/n 8DA9buvQAGY7AxD0YA8EHdnvgkMGEz5Ucr6gvf0p16ictWenG3B8gmw0zkBgNnM2U06E 7pvPo83F/e1L961KqLROZhcET6DzAokcPlW7optI7diZ1SaZRMLN7ibCY3jLKwML1Nqi FVMA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:autocrypt :message-id:date:user-agent:mime-version:in-reply-to; bh=uh7zQa/YMj/IN90JAfIqS4qXW/WXnBw7ej8pdpWyY10=; b=BjX31WbmdkCIKDislEHmgFpN9E/ldQwd+qP7IYUUztsu2g6fFT83R94qEHBvaNVEOf CCYNGZo6SesrKlPvJSwAWf3XmzkLdhPYqT3Rx6O+KsoPlNQz1HRaaWnGV2tDva0VENOk gIpA3Z9Gw/a24JkWoiEwgWB1xfm1jhXrM9WSm8Km4fqnofgMgXb9QHFNCRR3gGV8qLiP MkM7XD/5wcLZIdtJ9YXI4kYYAAxWM7/CRbeG9olmMiZK5B4P9EcLNK7332+qwabB6QJj 3FoZXRnTwgulksgt8/JhE1jOdP+oL48CwXQG0kvvt+slIm9rnfIcBMCv9de+2pyOYgBw fRNQ== X-Gm-Message-State: APjAAAUwQG3VXVnnwdrqLBK1HroXKu8r6BuWiDm8gxYVc/2IfeQbKw9q y1B/hOV1NhIhDQyw8BBbG+XaxU8i X-Google-Smtp-Source: APXvYqwgPTxQGeKRX6PVia6urXcl0eTV3AtJSFX9nKXtIzriknQ9we04Y/4xsUwKCZFz3cOeWXGvZQ== X-Received: by 2002:a7b:ca47:: with SMTP id m7mr22765660wml.4.1582559852468; Mon, 24 Feb 2020 07:57:32 -0800 (PST) Received: from [192.168.43.177] ([109.126.137.65]) by smtp.gmail.com with ESMTPSA id e1sm18896363wrt.84.2020.02.24.07.57.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Feb 2020 07:57:31 -0800 (PST) Subject: Re: Deduplicate io_*_prep calls? To: Jens Axboe , Andres Freund Cc: io-uring@vger.kernel.org References: <20200224010754.h7sr7xxspcbddcsj@alap3.anarazel.de> <20200224033352.j6bsyrncd7z7eefq@alap3.anarazel.de> <90097a02-ade0-bc9a-bc00-54867f3c24bc@kernel.dk> <20200224071211.bar3aqgo76sznqd5@alap3.anarazel.de> <933f2211-d395-fa84-59ae-0b2e725df613@kernel.dk> <23a49bca-26a6-ddbd-480b-d7f3caa16c29@gmail.com> <065ee992-7eaf-051a-e8c5-9e0e8731b3f1@kernel.dk> <746b93f0-d0b5-558a-28c7-a614b2367d91@gmail.com> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Message-ID: Date: Mon, 24 Feb 2020 18:56:41 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="cPG4IVSUowUrAHJL5uYJYoJO09P1apBr8" Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --cPG4IVSUowUrAHJL5uYJYoJO09P1apBr8 Content-Type: multipart/mixed; boundary="7KhBISCoFt8dSU1XA2vI0H42WTML1mi8Q"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , Andres Freund Cc: io-uring@vger.kernel.org Message-ID: Subject: Re: Deduplicate io_*_prep calls? References: <20200224010754.h7sr7xxspcbddcsj@alap3.anarazel.de> <20200224033352.j6bsyrncd7z7eefq@alap3.anarazel.de> <90097a02-ade0-bc9a-bc00-54867f3c24bc@kernel.dk> <20200224071211.bar3aqgo76sznqd5@alap3.anarazel.de> <933f2211-d395-fa84-59ae-0b2e725df613@kernel.dk> <23a49bca-26a6-ddbd-480b-d7f3caa16c29@gmail.com> <065ee992-7eaf-051a-e8c5-9e0e8731b3f1@kernel.dk> <746b93f0-d0b5-558a-28c7-a614b2367d91@gmail.com> In-Reply-To: --7KhBISCoFt8dSU1XA2vI0H42WTML1mi8Q Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 24/02/2020 18:53, Jens Axboe wrote: > On 2/24/20 8:50 AM, Pavel Begunkov wrote: >> On 24/02/2020 18:46, Jens Axboe wrote: >>> On 2/24/20 8:44 AM, Pavel Begunkov wrote: >>>>> Fine like this, though easier if you inline the patches so it's eas= ier >>>>> to comment on them. >>>>> >>>>> Agree that the first patch looks fine, though I don't quite see why= >>>>> you want to pass in opcode as a separate argument as it's always >>>>> req->opcode. Seeing it separate makes me a bit nervous, thinking th= at >>>>> someone is reading it again from the sqe, or maybe not passing in >>>>> the right opcode for the given request. So that seems fragile and i= t >>>>> should go away. >>>> >>>> I suppose it's to hint a compiler, that opcode haven't been changed >>>> inside the first switch. And any compiler I used breaks analysis the= re >>>> pretty easy. Optimising C is such a pain... >>> >>> But if the choice is between confusion/fragility/performance vs obvio= us >>> and safe, then I'll go with the latter every time. We should definite= ly >>> not pass in req and opcode separately. >> >> Yep, and even better to go with the latter, and somehow hint, that it = won't >> change. Though, never found a way to do that. Have any tricks in a sle= eve? >=20 > We could make it const and just make the assignment a bit hackier... Ap= art > from that, don't have any tricks up my sleeve. Usually doesn't work because of such possible "hackier assignments". Ok, I have to go and experiment a bit. Anyway, it probably generates a lo= t of useless stuff, e.g. for req->ctx --=20 Pavel Begunkov --7KhBISCoFt8dSU1XA2vI0H42WTML1mi8Q-- --cPG4IVSUowUrAHJL5uYJYoJO09P1apBr8 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl5T8jkACgkQWt5b1Glr +6V6tQ/+Ki+5zbVAw/0FcK/E4G5GLqlPK1wP/9WZigG1NiFd+B4WsAKtx/dg3OEJ 1myu5zm48DIfBZ8uNO5Z7WFTvN6zqAknryJjg8nA65SmqT3Swl9J8mjm94jBX+xM xMFXjF9LKEPXkabVZa5Hw7jjqypgb9vCR0IgOVfPflpDnYueeeHL0ubff0aBKnM9 5BxoO0Diky8RK811VoNUnghgSDAHCCZ2udrX42f7ojmKnKt1HLh4SJn/UbQuJX+B 02E2aKT+1/mewR8mQm41fXdJ3cauSSJ4sTQOTGm0YQBvzQ/oIidX1iHI9ex3tWem saLempajqNPSqwfcWpz2s2qZMWngNUkXUj3Nfo4T8ZyWkFJtSRZOkJMC7gqalHC5 9KgSyVC0pH7OWVPHRiN7j23aNBPobgqGk8JwOzZh1S1zv4WFJthXWsRznlnMg4V2 HWwEuH9HWWgGrwcEjTAwlDmCieeMWVYJf0Y0dKRzvXZVqcnEqD21fjk7uagUUqbt gak7bIbuORiltS07iQxYcUrp7PqvMZfBiyd1qEhzHzcEgJOVrKq33LkPs8jmREDY IoOTYa83FT5o9/qR5JGYsua8QiU74486LtbTievrVzHwGErQn1rWE5Xag5lgEBw2 71EDxuFCK+yvXHiUmSnAXmsAGh5JGuAfdQN83z8MbPQ5k3PrOB4= =aIwS -----END PGP SIGNATURE----- --cPG4IVSUowUrAHJL5uYJYoJO09P1apBr8--