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=-2.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, 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 E990CC2D0DB for ; Wed, 22 Jan 2020 15:12:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC5C12467C for ; Wed, 22 Jan 2020 15:12:55 +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="0BiBfmf/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725928AbgAVPMz (ORCPT ); Wed, 22 Jan 2020 10:12:55 -0500 Received: from mail-io1-f47.google.com ([209.85.166.47]:44229 "EHLO mail-io1-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725911AbgAVPMy (ORCPT ); Wed, 22 Jan 2020 10:12:54 -0500 Received: by mail-io1-f47.google.com with SMTP id e7so2290391iof.11 for ; Wed, 22 Jan 2020 07:12:54 -0800 (PST) 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=rdkEhUHMXVV4uMlw6eSjH7IdEMBOKL36dN/RS3uVdVw=; b=0BiBfmf/zzqW+wrXuf0+LW17/QUqOfDpfTA7tHCn2W0DFE8rOP5jQczViPkU3FU84f /QOPrE273+e78m+9iWgWWrwMTDMClNtGcIwZBklILgTI0ZOM11lUb+6SoGXDN/1VvxTX UHQ6NKQl6B8o4K2CN45TJhUoTxkZHs80ajEguUsIVCtLv8itUD0O6dx8YB/0eJaAvJMC /iwawKEfoms3tMtQ5Aj6t0UIAyHp61PJJbPwWBxENWpFt9s5uIm4CJ4eC09y8zI/3HVZ lyUJb4SKY+wvSpBfJ2hcBIPKIxBG1OaEu2nbnNaRjAk5Dt4vy6KpIWYkwrL0lX5CB5/N UHyA== 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=rdkEhUHMXVV4uMlw6eSjH7IdEMBOKL36dN/RS3uVdVw=; b=QbIw9uaWi6oJSRG1hpoCsI+S6UB9FTSEQMIOH9gaacINIINJHn3JJ28dab8Z+swGXW uZZjT7Xe4KS2ALaqlW/gMuJbVYb8jOKRaFu0SIDWEYe03gq0mVff401/E88uEILlW6cM Uhd6gpctGo9UHB/eB+TuUZ3nmw6yJyxDDXxheqim45brYNC3q6J0na7TNtIUJqXDHhKZ KeKzerv9vj9Helobb0M3U5Uniz7mIk5oJ9kLblBWgbfASWuOdZpTqI670baX+6ZBNqac 2EanGbtz/BvzlW79lEC2AS6M01LbMooRDNGeG8yQGg+ZwL3INKqRh3Oky3N1H9NcY5AL BLWw== X-Gm-Message-State: APjAAAViTfpyhw2ew/iWq7TbTJn6rq20JeGr7EvmtE0XAbU7nn6vGlGF sq7u9utHBm10wjRqGNTZOJVF9Q== X-Google-Smtp-Source: APXvYqxVmB1KS10FdBSJoV91Nr0VcOYKOZim6vIUbNnIFWnKsjB7OdIJ9GOshLGPoK3wn713Gy1UAA== X-Received: by 2002:a6b:e90b:: with SMTP id u11mr7028106iof.14.1579705974024; Wed, 22 Jan 2020 07:12:54 -0800 (PST) Received: from [192.168.1.159] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id t16sm14462195ilh.75.2020.01.22.07.12.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Jan 2020 07:12:53 -0800 (PST) Subject: Re: [LSF/MM/BPF TOPIC] Do not pin pages for various direct-io scheme To: Michal Hocko , Jerome Glisse Cc: lsf-pc@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Benjamin LaHaise References: <20200122023100.75226-1-jglisse@redhat.com> <20200122045723.GC76712@redhat.com> <20200122115926.GW29276@dhcp22.suse.cz> From: Jens Axboe Message-ID: <015647b0-360c-c9ac-ac20-405ae0ec4512@kernel.dk> Date: Wed, 22 Jan 2020 08:12:51 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200122115926.GW29276@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 1/22/20 4:59 AM, Michal Hocko wrote: > On Tue 21-01-20 20:57:23, Jerome Glisse wrote: >> We can also discuss what kind of knobs we want to expose so that >> people can decide to choose the tradeof themself (ie from i want low >> latency io-uring and i don't care wether mm can not do its business; to >> i want mm to never be impeded in its business and i accept the extra >> latency burst i might face in io operations). > > I do not think it is a good idea to make this configurable. How can > people sensibly choose between the two without deep understanding of > internals? Fully agree, we can't just punt this to a knob and call it good, that's a typical fallacy of core changes. And there is only one mode for io_uring, and that's consistent low latency. If this change introduces weird reclaim, compaction or migration latencies, then that's a non-starter as far as I'm concerned. And what do those two settings even mean? I don't even know, and a user sure as hell doesn't either. io_uring pins two types of pages - registered buffers, these are used for actual IO, and the rings themselves. The rings are not used for IO, just used to communicate between the application and the kernel. -- Jens Axboe