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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,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 78E4EC3F68F for ; Thu, 16 Jan 2020 06:18:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4E37620728 for ; Thu, 16 Jan 2020 06:18:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="gbaHBSoU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730470AbgAPGSU (ORCPT ); Thu, 16 Jan 2020 01:18:20 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:44390 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725768AbgAPGSU (ORCPT ); Thu, 16 Jan 2020 01:18:20 -0500 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 00G6Df5J006639; Thu, 16 Jan 2020 06:18:08 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2019-08-05; bh=thM1DU+ci72geM1S8as2qtc2X97JclnuS2KhKwDxVtM=; b=gbaHBSoUq9DJ0mkHpuVLRvItOlqO/0ixqhK7g0BIV5DtMWrLd0FBvD2AWyggbML1zx/s 0/z5qydhFCw1y5nBlNLXx/5zy9ofMSb0MC5MVSvRHK0/34x9CtJTmbUwxyxuxqqG2+Fo JeAEKnd/nTvY5uGY5vYQNRI6yP9Dl42jo4X4Owgl+x5+G1LjsRjAlRet8eCkRUH4ubrC guvKTJrwjYBSGn2Jj7Jz8fUNWFCAPFiIPj1a3Z5JZlyUHxM4M+RwuSpQ94fe6iXJvfH2 coalhiFLT9w8AjtlIeSDWK6+xN4+Eg2DOnnBGPbZRXISjcL/tcocRw4O9eTHHolbpaC8 3g== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by aserp2120.oracle.com with ESMTP id 2xf73u0d6f-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 16 Jan 2020 06:18:08 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 00G6DdfK038228; Thu, 16 Jan 2020 06:18:07 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3030.oracle.com with ESMTP id 2xhy22qh0u-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 16 Jan 2020 06:18:07 +0000 Received: from abhmp0014.oracle.com (abhmp0014.oracle.com [141.146.116.20]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 00G6I62l027636; Thu, 16 Jan 2020 06:18:06 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 15 Jan 2020 22:18:06 -0800 Date: Wed, 15 Jan 2020 22:18:04 -0800 From: "Darrick J. Wong" To: Dan Williams 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 Subject: Re: [RFC PATCH V2 01/12] fs/stat: Define DAX statx attribute Message-ID: <20200116061804.GI8257@magnolia> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9501 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001160052 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9501 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001160052 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 10:05:00PM -0800, Dan Williams wrote: > 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. Eh, that's just me being cynical about software. Yes, the O_SYNC docs say that data+metadata are supposed to happen; that's good enough for another section in the man pages. :) --D