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 0CFA4C2BB1D for ; Tue, 14 Apr 2020 21:05:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB0AD2076A for ; Tue, 14 Apr 2020 21:05:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="oHEweahb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2633671AbgDNVFb (ORCPT ); Tue, 14 Apr 2020 17:05:31 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:51622 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2633645AbgDNVEv (ORCPT ); Tue, 14 Apr 2020 17:04:51 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 03EL469C133804; Tue, 14 Apr 2020 21:04:38 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-2020-01-29; bh=7AGgMb1PjME7s9rPiVWSDRYMFiGgWwtSji2SOveCIpQ=; b=oHEweahbVZSQKWrSswPx90EP9moF7zB9bjp6JQQucufuN6b+Rety1PhjeHPPRquASDZL cmOUhclzlGH7t2NwbSXgDZGYrPnKsdHSBPBLMg8knLjukbfT01J4rET+KJx6VdvhmQDf iKY+MVjUWqE6AvT3Q99zjMPEvLPZXU3pJKdBahvzUmtu8hCdR1SB9MG+AuW4YeyBNDFl ksY08SpjHKti9NWYT9EJnO4KMkZc5+q+zTvbGLOdNjMIpJLGdcLTN7hwFYuGza58AFDx RFhrP5Jdl6jvrwdnxh7lNuZDQG0nt18/mIOHuwzKvXfZG9x1JqFljGKi8kebw3yyEtb/ fQ== Received: from aserp3030.oracle.com (aserp3030.oracle.com [141.146.126.71]) by aserp2120.oracle.com with ESMTP id 30b5um7db5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 14 Apr 2020 21:04:38 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 03EKv9dO108124; Tue, 14 Apr 2020 21:02:38 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3030.oracle.com with ESMTP id 30ctab5maj-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 14 Apr 2020 21:02:37 +0000 Received: from abhmp0008.oracle.com (abhmp0008.oracle.com [141.146.116.14]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 03EL2XOc020543; Tue, 14 Apr 2020 21:02:34 GMT Received: from localhost (/10.159.239.16) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 14 Apr 2020 14:02:33 -0700 Date: Tue, 14 Apr 2020 14:02:31 -0700 From: "Darrick J. Wong" To: Ira Weiny Cc: Dan Williams , Linux Kernel Mailing List , Dave Chinner , Christoph Hellwig , "Theodore Y. Ts'o" , Jan Kara , Jeff Moyer , linux-ext4 , linux-xfs , linux-fsdevel Subject: Re: [PATCH V7 9/9] Documentation/dax: Update Usage section Message-ID: <20200414210231.GJ6742@magnolia> References: <20200413054046.1560106-1-ira.weiny@intel.com> <20200413054046.1560106-10-ira.weiny@intel.com> <20200414161509.GF6742@magnolia> <20200414195754.GH6742@magnolia> <20200414200015.GF1853609@iweiny-DESK2.sc.intel.com> <20200414201808.GI6742@magnolia> <20200414205443.GC1982089@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200414205443.GC1982089@iweiny-DESK2.sc.intel.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9591 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 suspectscore=0 spamscore=0 adultscore=0 mlxscore=0 phishscore=0 mlxlogscore=999 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004140149 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9591 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 clxscore=1015 bulkscore=0 mlxscore=0 mlxlogscore=999 lowpriorityscore=0 impostorscore=0 adultscore=0 phishscore=0 spamscore=0 suspectscore=0 malwarescore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004140150 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 14, 2020 at 01:54:44PM -0700, Ira Weiny wrote: > On Tue, Apr 14, 2020 at 01:18:08PM -0700, Darrick J. Wong wrote: > > On Tue, Apr 14, 2020 at 01:00:15PM -0700, Ira Weiny wrote: > > > On Tue, Apr 14, 2020 at 12:57:54PM -0700, Darrick J. Wong wrote: > > > > On Tue, Apr 14, 2020 at 12:04:57PM -0700, Dan Williams wrote: > > > > > On Tue, Apr 14, 2020 at 9:15 AM Darrick J. Wong wrote: > > > > > > [snip] > > > > > > > > > > > + > > > > > > > > +Enabling DAX on xfs > > > > > > > > +------------------- > > > > > > > > + > > > > > > > > +Summary > > > > > > > > +------- > > > > > > > > + > > > > > > > > + 1. There exists an in-kernel access mode flag S_DAX that is set when > > > > > > > > + file accesses go directly to persistent memory, bypassing the page > > > > > > > > + cache. > > > > > > > > > > > > > > I had reserved some quibbling with this wording, but now that this is > > > > > > > being proposed as documentation I'll let my quibbling fly. "dax" may > > > > > > > imply, but does not require persistent memory nor does it necessarily > > > > > > > "bypass page cache". For example on configurations that support dax, > > > > > > > but turn off MAP_SYNC (like virtio-pmem), a software flush is > > > > > > > required. Instead, if we're going to define "dax" here I'd prefer it > > > > > > > be a #include of the man page definition that is careful (IIRC) to > > > > > > > only talk about semantics and not backend implementation details. In > > > > > > > other words, dax is to page-cache as direct-io is to page cache, > > > > > > > effectively not there, but dig a bit deeper and you may find it. > > > > > > > > > > > > Uh, which manpage? Are you talking about the MAP_SYNC documentation? > > > > > > > > > > No, I was referring to the proposed wording for STATX_ATTR_DAX. > > > > > There's no reason for this description to say anything divergent from > > > > > that description. > > > > > > > > Ahh, ok. Something like this, then: > > > > > > > > 1. There exists an in-kernel access mode flag S_DAX. When set, the > > > > file is in the DAX (cpu direct access) state. DAX state attempts to > > > > minimize software cache effects for both I/O and memory mappings of > > > > this file. The S_DAX state is exposed to userspace via the > > > > STATX_ATTR_DAX statx flag. > > > > > > > > See the STATX_ATTR_DAX in the statx(2) manpage for more information. > > > > > > We crossed in the ether!!! I propose even less details here... Leave all the > > > details to the man page. > > > > > > > > > 1. There exists an in-kernel access mode flag S_DAX that is set when file > > > accesses is enabled for 'DAX'. Applications must call statx to discover > > > the current S_DAX state (STATX_ATTR_DAX). See the man page for statx for > > > more details. > > > > > > > Why stop cutting there? :) > > > > 1. There exists an in-kernel file access mode flag S_DAX that > > corresponds to the statx flag STATX_ATTR_DIRECT_LOAD_STORE. See the > > manpage for statx(2) for details about this access mode. > > Sure! But I'm holding to STATX_ATTR_DAX... I don't like introducing another > alias for this stuff. Why have '-o dax=x' and then have some other term here? Ok, STATX_ATTR_DAX then. > Keep the name the same for consistency. > > Searching for 'DAX Linux'[*] results in 'About 877,000 results' on Google. > > While "'direct load store' Linux" results in 'About 2,630 results'. > > I'll update the rest of the text though! :-D > > Ira > > [*] Because 'DAX' is some company index and or a rapper... Don't forget Jadzia and Ezri. ;) --D