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=-7.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 20EF7C433E1 for ; Tue, 25 Aug 2020 13:40:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F0D592076C for ; Tue, 25 Aug 2020 13:40:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="w1Rl3nI/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726218AbgHYNkg (ORCPT ); Tue, 25 Aug 2020 09:40:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726551AbgHYNjw (ORCPT ); Tue, 25 Aug 2020 09:39:52 -0400 Received: from mail-io1-xd2e.google.com (mail-io1-xd2e.google.com [IPv6:2607:f8b0:4864:20::d2e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 14A65C0617A9 for ; Tue, 25 Aug 2020 06:39:47 -0700 (PDT) Received: by mail-io1-xd2e.google.com with SMTP id s2so12497463ioo.2 for ; Tue, 25 Aug 2020 06:39:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=sCIyfbyLPajZzm/nkZQjt2emAfD5sYHSpzDHfjMkJC8=; b=w1Rl3nI/cXGdnXWu3alxiw0NJ1wFgTUZalV5QXU64Q2KIRlV/w9lChPZ7ThauC9BkB jCOPhLwKoL5QlQLDmYWmV38PId9QAqwm5PWBOrpcHpVcdf5K25j/T6hS0PMgIB0DAFMv Eex7A1m8o9vV7SiXYeQJrt6XziFJ1y06VS5UF5iKiwkRjPKGsqgupRiAo67gudLtMMy/ a8buIcVe4iSgII7+ZHU5saKlNQ051YlXppdIFWdYgfanGbwSxPahxvCNeVxhjW2MMc73 O62a4QGzievyivHgpZ9GzJ5Qtw+LOqGYaiglpIRPVuyg3XV9ynAtEF0nk/XijvUn5xKh E+0w== 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:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=sCIyfbyLPajZzm/nkZQjt2emAfD5sYHSpzDHfjMkJC8=; b=OUExv/cK19fK8fUjJMrCxoSIvzU6k6hZoc6CNg8dokOy9V3B+h6tMJImxumiNLatiQ pUNkRk/rc7yU43mejXwyFJYXG31McXuNrYP6o/Iy3f94KJrjlpm6TvBs8y/xd7GEJZe8 VPojWozS6gO6qtwHjd+0tx0r0vxjZNmk5AL+MEhZwEzJfGTyIB7O+3k2nx2PoGFNYFvT 2A+et8ggvyOhvwaft2tfuAQ9EEDAvXIyub7ufQP0ofHosy9gQW/toa1M9yF7Ea7MBOoa abadvbre5MOv9S52CKAFyPGqQXmjlaKOrVQDmgqTYCwzJFmzQ1ppMHahridKyfLyU5QA ZBOw== X-Gm-Message-State: AOAM5303I6xI1CJw/+3oXwsiCJdnxZPWQ9kGFu8EKMqmaX/XyHSASglm LCwTCl7G+Ibm2Y0mmWhdjg6d5oOP1hIf39ee X-Google-Smtp-Source: ABdhPJy/ZFiOKpbFt42693LluWDkD1pLd9f8iHGWXTyQphuIgWXqFQLgKT9vMF5qqmAp7H/jflGCpA== X-Received: by 2002:a02:c919:: with SMTP id t25mr10791172jao.38.1598362783717; Tue, 25 Aug 2020 06:39:43 -0700 (PDT) Received: from [192.168.1.58] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id s13sm9132811iln.12.2020.08.25.06.39.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 25 Aug 2020 06:39:41 -0700 (PDT) Subject: Re: Large number of empty reads on 5.9-rc2 under moderate load To: Dmitry Shulyak Cc: io-uring@vger.kernel.org References: <7a148c5e-4403-9c8e-cc08-98cd552a7322@kernel.dk> <06d07d6c-3e91-b2a7-7e03-f6390e787085@kernel.dk> <282f1b86-0cf3-dd8d-911f-813d3db44352@kernel.dk> <42573664-450d-bfe4-aa96-ca1ae0704adb@kernel.dk> From: Jens Axboe Message-ID: <8076e289-2e0b-5676-aaac-eff94245a298@kernel.dk> Date: Tue, 25 Aug 2020 07:39:40 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 8/25/20 2:52 AM, Dmitry Shulyak wrote: > this patch fixes the issue with 0 reads. there seems to be a > regression that is not specific to uring, > regular syscall reads slowed down noticeably. Do you have a test case? Related to specific system calls, or just overall? My initial suspicion would be Yet Another one of the security fixes... -- Jens Axboe