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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 AC990C33CB3 for ; Thu, 16 Jan 2020 06:05:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 83EDE20748 for ; Thu, 16 Jan 2020 06:05:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=intel-com.20150623.gappssmtp.com header.i=@intel-com.20150623.gappssmtp.com header.b="fsNlBtGF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729966AbgAPGFM (ORCPT ); Thu, 16 Jan 2020 01:05:12 -0500 Received: from mail-ot1-f68.google.com ([209.85.210.68]:45325 "EHLO mail-ot1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729841AbgAPGFM (ORCPT ); Thu, 16 Jan 2020 01:05:12 -0500 Received: by mail-ot1-f68.google.com with SMTP id 59so18337070otp.12 for ; Wed, 15 Jan 2020 22:05:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=vKEanVLYKixbIE4jpjng52Wg/z0Mh1eAfP4hJSdIQE0=; b=fsNlBtGFziQY0A8zQejjqkkTuvqiwdIiAM7NACeEOxrAaoxzDd4fUjk9pwpqAIUvXJ cdDCKjUTJGaZHkHv0G5ee/JsbwsslnTNyPu9bqoswts39/75GIb/59yCbwuO1xPlgi3c f+VW6u6TSpKsnTkYP5lrw9eMUS+qyf9nS8llrLCzHtqnC0A8+9WP1s1jpoFVC48zw4nR NVsWjZ5qsu9jZPsaq387+XdtKQjAobHkTTamKsz9df6VShLY/jSMaIKhT//gj04wSyQB dgjbIZWVcmuv6zDtMtLARK6RBcjdJGnJuT7/m4Mi0K92sfnfQrOSyoSUt8DpH3L7o5oD 9Oyw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=vKEanVLYKixbIE4jpjng52Wg/z0Mh1eAfP4hJSdIQE0=; b=NG/dHOygWBbyY5hZwo6KXnUxSa9pULznSDaFf1T1YrZ1Hfr8na96wr1gbkyBMMNv8L 6vg+sOD8Yx0DtPdKuEgkjN6nFsjvtH+JOE0lhhq/5a7B0Pzu3Tbj0nW91uwmunsFelkJ R+SFiOj3ZamiB7I7mcT/KnbcxWrR/Xy3FXgSnjbRIvsPifuTM+v8ZsaZ8yWVDh+k/dUj ybSFvP8tH5mndLTl9lOEvnNJJRtuDfkR0ttNzwCpR96daBvSHp5jHO4zK2AljY9Q1PVp zErhIiUxbTQydE7vKQMxz30L9dNDhib+AtB8F5NcrJzNnMdl3oMiwQj2hCaImM/ApM/c llKQ== X-Gm-Message-State: APjAAAWfR6vuLTOdXazKGIDyZjc1DXciTdAtO4nBqBic+aOTGIts8e0F cvPIJCf5RO/BEFtN9hfk5RZkPytwTNnVMmTzXmG4+w== X-Google-Smtp-Source: APXvYqzEy+pngv/HMRf0P3fZnf1I8EeAbKVY4SqM8e/rzz5VxvD8FVTh6UXXEgSv+bh5N1RhUnQGLNyaWJI9Xe8L7mc= X-Received: by 2002:a9d:68d3:: with SMTP id i19mr740541oto.71.1579154711112; Wed, 15 Jan 2020 22:05:11 -0800 (PST) MIME-Version: 1.0 References: <20200110192942.25021-1-ira.weiny@intel.com> <20200110192942.25021-2-ira.weiny@intel.com> <20200115113715.GB2595@quack2.suse.cz> <20200115173834.GD8247@magnolia> <20200115194512.GF23311@iweiny-DESK2.sc.intel.com> <20200115223821.GG23311@iweiny-DESK2.sc.intel.com> <20200116053935.GB8235@magnolia> In-Reply-To: <20200116053935.GB8235@magnolia> From: Dan Williams Date: Wed, 15 Jan 2020 22:05:00 -0800 Message-ID: Subject: Re: [RFC PATCH V2 01/12] fs/stat: Define DAX statx attribute To: "Darrick J. Wong" Cc: Ira Weiny , Jan Kara , Linux Kernel Mailing List , Alexander Viro , Dave Chinner , Christoph Hellwig , "Theodore Y. Ts'o" , linux-ext4 , linux-xfs , linux-fsdevel Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 15, 2020 at 9:39 PM Darrick J. Wong wrote: [..] > > attempts to minimize software cache effects for both I/O and > > memory mappings of this file. It requires a file system which > > has been configured to support DAX. > > > > DAX generally assumes all accesses are via cpu load / store > > instructions which can minimize overhead for small accesses, but > > may adversely affect cpu utilization for large transfers. > > > > File I/O is done directly to/from user-space buffers and memory > > mapped I/O may be performed with direct memory mappings that > > bypass kernel page cache. > > > > While the DAX property tends to result in data being transferred > > synchronously, it does not give the same guarantees of > > synchronous I/O where data and the necessary metadata are > > transferred together. > > (I'm frankly not sure that synchronous I/O actually guarantees that the > metadata has hit stable storage...) Oh? That text was motivated by the open(2) man page description of O_SYNC.