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=-5.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 7FDBFC11D2F for ; Mon, 24 Feb 2020 16:19:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 470702084E for ; Mon, 24 Feb 2020 16:19:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="W+sgGT1f" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727090AbgBXQTV (ORCPT ); Mon, 24 Feb 2020 11:19:21 -0500 Received: from mail-wr1-f46.google.com ([209.85.221.46]:46845 "EHLO mail-wr1-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727299AbgBXQTU (ORCPT ); Mon, 24 Feb 2020 11:19:20 -0500 Received: by mail-wr1-f46.google.com with SMTP id g4so4736702wro.13 for ; Mon, 24 Feb 2020 08:19:18 -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=R8y8uGTnzd8mVgtP5d2WdraCSUe4sNTM+mlwoyGa4f0=; b=W+sgGT1fbIkGHw5XjcotOcUs2tmrfSzlm5n6WHx3yL75eJI47Qu53H96GqDsDkzAZ/ BdLSmzwTw53lnwTP4CYP1sy0mn8MOeb+RzpgvK9kSiAn16i4UkORrbD/7egfhHiyEd+u 5KRhMzzEFqui5gsAaKRvE1Ipf+kjDbEVse05eiZJi/RSVTCMPArHnvzqH3JyZi8+xCa8 Ofu1DfB19UR1JKBpUI+Hu7/BshCecNtlwGqYIZ80CWjrmKFe8p0V4q6tYR2rA/1DLz/I ziEv5793Br3hCcAXab8Z5qRy0wFRYSrDeS+ks8IUnQImqovYgm+DhpeC8YB/SDV+NsiE canQ== 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=R8y8uGTnzd8mVgtP5d2WdraCSUe4sNTM+mlwoyGa4f0=; b=lf2ztX3thMeQHaqtrGQgFl9lSiSDK+nByydkWi/LndrZ+76OKlMgG1iZb9s9TphfLL td0bS+Twi7Vfp57EHkjIpBxYSCFGl5NtkBR1Fb4thBIkg+zvLp/EvVhh+UNvXRlK5YEX wkCaN3vjb/zDozf1665AP65ORGqBV+EiQ4hgZfdxUr7Y9yy+k7YRbUYA/JlZzkyvj759 6/BAg/Pd5Y3JoDS1zO/l50PDsRmBHAl4ENUdJ8MGyIK18reAtisfqOdKIFPLu8Gxya/c QpsXauRHMYsHv2J0updkQiMpJigIlNRCDH620JmuwQxg1iUaj4BUX79QMmUycusSQVG3 h3zA== X-Gm-Message-State: APjAAAVcnrtvXJTwH/BkKdTn4nhl2tyHdacEWZKvRF7+kks30k0C2qPf rX8DBzlHyjLdtlgn76TmtUGoIl9+ X-Google-Smtp-Source: APXvYqxNl5ZrITggirP07B2YJzamyMTBJzxylxZb2b6+VNrMELKwZwRweVjwO5wsL1Iw/DmbgnEzqg== X-Received: by 2002:adf:f7c6:: with SMTP id a6mr70681519wrq.164.1582561157671; Mon, 24 Feb 2020 08:19:17 -0800 (PST) Received: from [192.168.43.177] ([109.126.137.65]) by smtp.gmail.com with ESMTPSA id t3sm4373200wrx.38.2020.02.24.08.19.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Feb 2020 08:19:16 -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 19:18:26 +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="gvx6oMzitEfTJzkmbk6w4OujWhNYX7qpg" 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) --gvx6oMzitEfTJzkmbk6w4OujWhNYX7qpg Content-Type: multipart/mixed; boundary="6ZpSjsKScup28emj7QmVxwAyXdrMULCCM"; 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: --6ZpSjsKScup28emj7QmVxwAyXdrMULCCM Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 24/02/2020 19:02, Jens Axboe wrote: >> Usually doesn't work because of such possible "hackier assignments". >> Ok, I have to go and experiment a bit. Anyway, it probably generates a= lot of >> useless stuff, e.g. for req->ctx >=20 > Tried this, and it generates the same code... Maybe it wasn't able to optimise in the first place E.g. for the following code any compiler generates 2 reads (thanks godbol= t). extern void foo(int); int bar(const int *v) { foo(*v); return *v; } >=20 > diff --git a/fs/io_uring.c b/fs/io_uring.c > index ba8d4e2d9f99..8de5863aa749 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -598,7 +598,7 @@ struct io_kiocb { > =20 > struct io_async_ctx *io; > bool needs_fixed_file; > - u8 opcode; > + const u8 opcode; > =20 > struct io_ring_ctx *ctx; > struct list_head list; > @@ -5427,6 +5427,8 @@ static bool io_get_sqring(struct io_ring_ctx *ctx= , struct io_kiocb *req, > */ > head =3D READ_ONCE(sq_array[ctx->cached_sq_head & ctx->sq_mask]); > if (likely(head < ctx->sq_entries)) { > + u8 *op; > + > /* > * All io need record the previous position, if LINK vs DARIN, > * it can be used to mark the position of the first IO in the > @@ -5434,7 +5436,8 @@ static bool io_get_sqring(struct io_ring_ctx *ctx= , struct io_kiocb *req, > */ > req->sequence =3D ctx->cached_sq_head; > *sqe_ptr =3D &ctx->sq_sqes[head]; > - req->opcode =3D READ_ONCE((*sqe_ptr)->opcode); > + op =3D (void *) req + offsetof(struct io_kiocb, opcode); > + *op =3D READ_ONCE((*sqe_ptr)->opcode); > req->user_data =3D READ_ONCE((*sqe_ptr)->user_data); > ctx->cached_sq_head++; > return true; >=20 --=20 Pavel Begunkov --6ZpSjsKScup28emj7QmVxwAyXdrMULCCM-- --gvx6oMzitEfTJzkmbk6w4OujWhNYX7qpg Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl5T91IACgkQWt5b1Glr +6Vksw/+NvRvHKEqcPS6FCu/o6sPrB8Irj/0k/6GCkRNiMsaEWnamdky+oCgLpRK LPrqMPu2ljJK58O3/RrVmAGSgZDYG5oQfbJhjexZszGIRhcfQu+TU3Fwte0JW4aG rtXtQV+SZm/oRPjPqMR7/nw5u7tMuSTiIJKqkzYXj7zG69XGXQCnFBM0NQQXq/h3 i2BN8hwNO2O50lsuBFdtVHSQ1LoP9r/h4SwSgsryyPDAA2Fq9LCDJh1MM98FxstU mr8wWIQ64gOV1UIItSgZ9aVq/sabOfql1Xo3ZAq2xGEE2repj0vYbxJ/mt/UZoXC 23U2j1Afq5a18uCyyAZifwUxmbAUmQiDoa4yvIY7IQVuOxQI4XfkBJPW6UKuF3gZ TLkEEsrVRKmlotYNocRsjaljJKptTdwLWpas1wxdsm8ptB0oQY08PPrd8WApFd7c 7eUS51hV9ULhyzDCCSH+vc2ZJ+Dl+OOkrsTG3LPTy740kyYzvoJOdhhr78VnI2Yr ewB5veCEfIoiF1BBK1jKL38j1VA1c+y+qqCtLjmeJgMEPtdFOOP5kqSkpNN0H6Kr cXGO+8FphwFWL4dPnx76V3TRGZNrbAQBkqywT3KfNxQ8xKxEGqM/WPbIPyMZlvEk c/gPLRIIF9b7p55y9KKxMG81OzgMsaQ+0uRfx/9BItoyeGbON20= =S5CF -----END PGP SIGNATURE----- --gvx6oMzitEfTJzkmbk6w4OujWhNYX7qpg--