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=-4.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 75971C433DB for ; Sat, 9 Jan 2021 21:30:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C33323A82 for ; Sat, 9 Jan 2021 21:30:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726377AbhAIVaI (ORCPT ); Sat, 9 Jan 2021 16:30:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50338 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726006AbhAIVaH (ORCPT ); Sat, 9 Jan 2021 16:30:07 -0500 Received: from mail-wm1-x329.google.com (mail-wm1-x329.google.com [IPv6:2a00:1450:4864:20::329]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F2012C061786; Sat, 9 Jan 2021 13:29:26 -0800 (PST) Received: by mail-wm1-x329.google.com with SMTP id g185so11412068wmf.3; Sat, 09 Jan 2021 13:29:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=to:cc:references:from:autocrypt:subject:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=qGJGJxCcHriRua+XWavSyBDVkT64GdF8AXVlo22Bpoc=; b=HzoLYVKJykBK/r8Nqeb1VA3oF2zL5u7kEBe8f4VAJYrRrADprAOzfJZPdnL7zS5quL LJh7Oa72OLdGEkfWHt7X12pBrUYGvzDHy73UpNgaRi1aF17kzFebEWFbYmHe5Uxy3++K un9h3t2NUU6j2v7zunEaBiztXfCMx0+PiFF4LQOwqFuPvbNOro4/dANXpx2ZpCALgVbQ Ho4yzw0cXaSKKCCfU6jxhJuqC6FamNJJvavVx/XpwYXmAJMeXt+uWl6vNhOM5gYFDflj KPuwDUMU676ptv4bgL7yT8/HgXsAQ8iDyHoJ47zv1lQA7MZNumRHnhQeK6vyr7bG5PBE ua4Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:cc:references:from:autocrypt:subject :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=qGJGJxCcHriRua+XWavSyBDVkT64GdF8AXVlo22Bpoc=; b=kqd49liPD112yGV9qQ17SNQ30/Q4uebU+HwS87eN3ajplf+iJF9mS0nlOvDQQBs64b xg/ktBxZsJpp6atsLJLnNFdIwr0e2mxhsywAmJGnTInhuJyi3/LPS/ewXlL9CedvIi5B qpTqLdTzTTCwKAWcAw/HCF3gxj8xK4hxTtQjHp01tNgnOEKDyUenWhAd1W1eDn/qhJo4 /ZEBZXiY03tJUJcU6txLgCjEL6+P9lOu/RACiAz9JF5Xo7dYwk4jOcjygujV3S0/RbuI 3c4NxQeUW/Bl+FzJu4WYvgPAern3LgReWd3NTqAgH6889CIKQ9DrLNzOQqefKI/PPTTQ cvtw== X-Gm-Message-State: AOAM530FgternqcOvnzP6Z697dAymMHs/qn7aH+mtWyGuz4Ai5gFQdzm Rtitxr0Vt2t45TkFpfK2WNjdDIXLDC0lk0+a X-Google-Smtp-Source: ABdhPJwLbLb8fhue53UQ885oIKJSPpazUlX1KOawxhZTzuXO87vhOJt2poDrXdB5/QcggEN9MlFgew== X-Received: by 2002:a1c:24c4:: with SMTP id k187mr8731041wmk.14.1610227765480; Sat, 09 Jan 2021 13:29:25 -0800 (PST) Received: from [192.168.8.114] ([85.255.237.6]) by smtp.gmail.com with ESMTPSA id y2sm16252726wma.6.2021.01.09.13.29.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 09 Jan 2021 13:29:25 -0800 (PST) To: Chaitanya Kulkarni , "Martin K . Petersen" Cc: "linux-scsi@vger.kernel.org" , "target-devel@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <34cd22d6cec046e3adf402accb1453cc255b9042.1610207523.git.asml.silence@gmail.com> <4d063dde-c710-44e3-31b9-8fb6b7e1d952@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== Subject: Re: [PATCH] target/file: don't zero iter before iov_iter_bvec Message-ID: Date: Sat, 9 Jan 2021 21:25:53 +0000 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: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/01/2021 20:52, Chaitanya Kulkarni wrote: > On 1/9/21 12:40, Pavel Begunkov wrote: >> I expect you won't find any, but such little things can pile up >> into a not-easy-to-spot overhead over time. > > That is what I suspected with the resulting assembly. The commit log > needs to document that there is no direct impact on the performance It's obvious that 3-4 extra mov $0 off(%reg) won't change performance but still hasn't been formally confirmed ... > which can be seen with this patch, but this is nice to have ... so if you don't mind, I won't be resending just for that. -- Pavel Begunkov