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=-7.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, USER_AGENT_SANE_1 autolearn=ham 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 7FF95C5ACC4 for ; Wed, 19 Feb 2020 22:01:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5120B24670 for ; Wed, 19 Feb 2020 22:01:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="pvHTGM5z" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726760AbgBSWBX (ORCPT ); Wed, 19 Feb 2020 17:01:23 -0500 Received: from userp2130.oracle.com ([156.151.31.86]:33598 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726703AbgBSWBW (ORCPT ); Wed, 19 Feb 2020 17:01:22 -0500 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 01JM107i040771; Wed, 19 Feb 2020 22:01:07 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=0kuFK854nQQye3G1yeMWluWNHU6Ca0QKGKTvXcx1+Mk=; b=pvHTGM5zeEpKMASBIFayCNMfUTVItpj4r0wpdFLFydZ0Z2H+GBA2gz6oztzPZARS9xZI PwstxDVx36O0Fs42d6wHoDkU49gZQ4gd4gdVOESF5ZFoM8NaemOvRkou8LMhjorFXzs6 4Q/NnEALsGD7AJaPCljwjR9IyYFJbmvfG/g7yq33ZyCgxrm9cBLRiWEulhORsDRNnMPS fHpRSTPahVo1Z1nFhRuaJv+Yuw70852SEIhZmwWNsFG3yFjsNiW+LzhnMlL2cYN9qdwl shqrh8RmNxr/qi0r5PK+PmDbG2TxFIjufD/A8FyX5S7IV2lqgTkC03mjV1SDrw/9zpft Lw== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by userp2130.oracle.com with ESMTP id 2y8udd64p6-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 19 Feb 2020 22:01:06 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 01JLvmQJ195005; Wed, 19 Feb 2020 22:01:06 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 2y8ud23f5x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 19 Feb 2020 22:01:06 +0000 Received: from abhmp0001.oracle.com (abhmp0001.oracle.com [141.146.116.7]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 01JM15E2017457; Wed, 19 Feb 2020 22:01:05 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 19 Feb 2020 14:01:05 -0800 Date: Wed, 19 Feb 2020 14:01:04 -0800 From: "Darrick J. Wong" To: Luis Chamberlain Cc: Richard Wareing , linux-xfs@vger.kernel.org, Anthony Iliopoulos , Yong Sun Subject: Re: Modern uses of CONFIG_XFS_RT Message-ID: <20200219220104.GE9504@magnolia> References: <20200219135715.GZ30113@42.do-not-panic.com> <20200219143227.aavgzkbuazttpwky@andromeda> <20200219143824.GR11244@42.do-not-panic.com> <20200219170945.GN9506@magnolia> <20200219175502.GS11244@42.do-not-panic.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200219175502.GS11244@42.do-not-panic.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9536 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 malwarescore=0 mlxlogscore=999 suspectscore=0 adultscore=0 spamscore=0 mlxscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002190161 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9536 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 impostorscore=0 mlxlogscore=999 malwarescore=0 mlxscore=0 suspectscore=0 priorityscore=1501 bulkscore=0 adultscore=0 spamscore=0 lowpriorityscore=0 clxscore=1011 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002190163 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Wed, Feb 19, 2020 at 05:55:02PM +0000, Luis Chamberlain wrote: > On Wed, Feb 19, 2020 at 09:09:45AM -0800, Darrick J. Wong wrote: > > On Wed, Feb 19, 2020 at 02:38:24PM +0000, Luis Chamberlain wrote: > > > On Wed, Feb 19, 2020 at 03:32:27PM +0100, Carlos Maiolino wrote: > > > > On Wed, Feb 19, 2020 at 01:57:15PM +0000, Luis Chamberlain wrote: > > > > > I hear some folks still use CONFIG_XFS_RT, I was curious what was the > > > > > actual modern typical use case for it. I thought this was somewhat > > > > > realted to DAX use but upon a quick code inspection I see direct > > > > > realtionship. > > > > > > > > Hm, not sure if there is any other use other than it's original purpose of > > > > reducing latency jitters. Also XFS_RT dates way back from the day DAX was even a > > > > thing. But anyway, I don't have much experience using XFS_RT by myself, and I > > > > probably raised more questions than answers to yours :P > > > > > > What about another question, this would certainly drive the users out of > > > the corners: can we remove it upstream? > > > > My DVR and TV still use it to record video data. > > Is anyone productizing on that though? > > I was curious since most distros are disabling CONFIG_XFS_RT so I was > curious who was actually testing this stuff or caring about it. Most != All. We enabled it here, for development of future products. > > I've also been pushing the realtime volume for persistent memory devices > > because you can guarantee that all the expensive pmem gets used for data > > storage, that the extents will always be perfectly aligned to large page > > sizes, and that fs metadata will never defeat that alignment guarantee. > > For those that *are* using XFS in production with realtime volume with dax... > I wonder whatcha doing about all these tests on fstests which we don't > have a proper way to know if the test succeeded / failed [0] when an > external logdev is used, this then applies to regular external log dev > users as well [1]. Huh? How did we jump from realtime devices to external log files? > Which makes me also wonder then, what are the typical big users of the > regular external log device? > > Reviewing a way to address this on fstests has been on my TODO for > a while, but it begs the question of how much do we really care first. > And that's what I was really trying to figure out. > > Can / should we phase out external logdev / realtime dev? Who really is > caring about this code these days? Not many, I guess. :/ There seem to be a lot more tests these days that use dmflakey on the data device to simulate a temporary disk failure... but those aren't going to work for external log devices because they seem to assume that what we call the data device is also the log device. --D > [0] https://github.com/mcgrof/oscheck/blob/master/expunges/linux-next-xfs/xfs/unassigned/xfs_realtimedev.txt > [1] https://github.com/mcgrof/oscheck/blob/master/expunges/linux-next-xfs/xfs/unassigned/xfs_logdev.txt > > Luis