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=-5.6 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 53499C433E1 for ; Sun, 19 Jul 2020 11:17:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2C6542073A for ; Sun, 19 Jul 2020 11:17:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="HDU5WjfK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725988AbgGSLRO (ORCPT ); Sun, 19 Jul 2020 07:17:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60030 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725836AbgGSLRO (ORCPT ); Sun, 19 Jul 2020 07:17:14 -0400 Received: from mail-wm1-x341.google.com (mail-wm1-x341.google.com [IPv6:2a00:1450:4864:20::341]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BF129C0619D2; Sun, 19 Jul 2020 04:17:13 -0700 (PDT) Received: by mail-wm1-x341.google.com with SMTP id 17so22463602wmo.1; Sun, 19 Jul 2020 04:17:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=to:references:from:autocrypt:subject:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=YV6aWfSNIZGkcvE4CuOe8cgC1NWSfoopwY+bhDebPSU=; b=HDU5WjfKAJt7VWQ0ijGLE4JHFJU6Zk2TZO3CJ/J+baoVskBjRvxKP3T7u7ihUW+IXV 3ud8iNgEqZHd+ue1JDYkqB5ThUTDX+ES4LRjj7PY/eOVA4M8ouYnHaphGFbGO/I+J4fB eFkBh4Y6we9UlPJlBElAXyFscUmyd3EM7orE82L1a2k/XBquqB4yyLcgmlSYcIHtytZm LpxuHqPrhUAKL2LHAleSOTg3SUcjIzP6N7MJUKKS1HO1DSfWGvRelCFRYG3kTp8tnxiK 8xXmiR3KVA6m9VOh7GbtIKQE0iJAwS3LOXroPNg3bAbnnp5cdvqAz5cezv41EkZLk0P1 UhLQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:references:from:autocrypt:subject:message-id :date:user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=YV6aWfSNIZGkcvE4CuOe8cgC1NWSfoopwY+bhDebPSU=; b=HeKWjnFBOQWZ8efyzyhm0E6rPIEubySZSCMYsTNyjDOCNC063XnK+qF4+LOfQDv3/c HRs88d2dmLU1OVch4nzDOd91go6z7bMxL50Rn7ergwxvTGzeAnBcO+uxsAsQxXBL5N9F jep0zV/a8ghx5UCp1ARGt4xkgM9HGk67puzx5tdZSmK+AIKsdEfHD6pqmiMccZ/lNvRn XhO7mCKv+on0TNAAsDZ2SwqCkkPyiVclpO6pZfaU+c57u27yVA6p20LEQ3hHtnHl0uYG z8f01ccgXpGlrmvBlrNcbTnIjkD0r8B6umuk+aNe9i95zZ5OVfufi7Luo656rx3vUtCT Ue3w== X-Gm-Message-State: AOAM530g0GRsVNUrRXwJXMeRVv0gUozrpNd2B8tKVi8RPxn7sB0QsM3F TSljYbJNYFGpvcdj2WPQHaXv64pQ X-Google-Smtp-Source: ABdhPJzKMj/R0LDr0WKCYTl2kSsfEcYY4T2K6tjj2zM7h49lks2k6J1K3T28Ik4mIkUrQzA2efFXCw== X-Received: by 2002:a1c:2392:: with SMTP id j140mr16847369wmj.6.1595157432062; Sun, 19 Jul 2020 04:17:12 -0700 (PDT) Received: from [192.168.43.23] ([5.100.193.69]) by smtp.gmail.com with ESMTPSA id t141sm26724688wmt.26.2020.07.19.04.17.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 19 Jul 2020 04:17:11 -0700 (PDT) To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: 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 0/2] task_put batching Message-ID: Date: Sun, 19 Jul 2020 14:15:21 +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: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 18/07/2020 17:37, Jens Axboe wrote: > On 7/18/20 2:32 AM, Pavel Begunkov wrote: >> For my a bit exaggerated test case perf continues to show high CPU >> cosumption by io_dismantle(), and so calling it io_iopoll_complete(). >> Even though the patch doesn't yield throughput increase for my setup, >> probably because the effect is hidden behind polling, but it definitely >> improves relative percentage. And the difference should only grow with >> increasing number of CPUs. Another reason to have this is that atomics >> may affect other parallel tasks (e.g. which doesn't use io_uring) >> >> before: >> io_iopoll_complete: 5.29% >> io_dismantle_req: 2.16% >> >> after: >> io_iopoll_complete: 3.39% >> io_dismantle_req: 0.465% > > Still not seeing a win here, but it's clean and it _should_ work. For Well, if this thing is useful, it'd be hard to quantify, because active polling would hide it. I think, it'd need to apply a lot of isolated pressure on cache synchronisation (e.g. spam with barriers), or try to create and measure an atomic heavy task pinned to another core. Don't worth the effort IMHO. ` Just out of curiosity, let me ask how do you test it? - is it a VM? - how many cores and threads do you use? - how many io_uring instances you have? Per thread? - Is it all goes to a single NVMe SSD? > some reason I end up getting the offset in task ref put growing the > fput_many(). Which doesn't (on the surface) make a lot of sense, but > may just mean that we have some weird side effects. I'll take a look whether I can reproduce. -- Pavel Begunkov