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=-10.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, 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 6BD78C7619D for ; Thu, 20 Feb 2020 02:17:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 385422465D for ; Thu, 20 Feb 2020 02:17:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="hv1SpOye" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727370AbgBTCRb (ORCPT ); Wed, 19 Feb 2020 21:17:31 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:42974 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727280AbgBTCRb (ORCPT ); Wed, 19 Feb 2020 21:17:31 -0500 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 01K2HHWY183381; Thu, 20 Feb 2020 02:17:17 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=0/2OyJF84m0LWo1yBUvro4SLyt9gGN7kRN0u9YFoIiE=; b=hv1SpOyegSH10dg/t/Q/BQFMtxEMWb5wxJoOhXoWbgmpxrptAVPUeV2n5FodARP4lPgu xZojYGReZmMPYJYKSb9EJv0Ern6tdMGFLVgkUIX/7OtKxQS3ZVgjXWl6aIwbz53joD2g TWKY78tQuoFwR+niQaVVQR43o+DD9e/6XLS7CRQCxe/ph+GLV5N4E5sow5NQVgJXXI9b 2yL3iya5yEGxOLTP7i/TqvnozKLExQqZbBmoJocDwiUmj1uYdy6iLGTLqSD/84fVEUKW 7BR8Mj/giHaTGUfb9jzC+31bcBDSHvYc31s3OPtlvEeAMbmAByc7rz6ACokkt/eeBWTU Sw== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by aserp2120.oracle.com with ESMTP id 2y8udkevwn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 20 Feb 2020 02:17:11 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 01K28CZA097435; Thu, 20 Feb 2020 02:15:11 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3020.oracle.com with ESMTP id 2y8ud9bv9g-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 20 Feb 2020 02:15:11 +0000 Received: from abhmp0011.oracle.com (abhmp0011.oracle.com [141.146.116.17]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 01K2F8dr011498; Thu, 20 Feb 2020 02:15:08 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 19 Feb 2020 18:15:08 -0800 Date: Wed, 19 Feb 2020 18:15:07 -0800 From: "Darrick J. Wong" To: Eric Sandeen Cc: Luis Chamberlain , Richard Wareing , linux-xfs@vger.kernel.org, Anthony Iliopoulos , Yong Sun Subject: Re: Modern uses of CONFIG_XFS_RT Message-ID: <20200220021507.GS9506@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> <20200219220104.GE9504@magnolia> <20200220001729.GT11244@42.do-not-panic.com> <86c1597a-3681-be41-a838-d32e22c0c363@sandeen.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <86c1597a-3681-be41-a838-d32e22c0c363@sandeen.net> 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 spamscore=0 mlxlogscore=999 phishscore=0 suspectscore=0 mlxscore=0 malwarescore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002200015 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9536 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 lowpriorityscore=0 suspectscore=0 spamscore=0 priorityscore=1501 adultscore=0 mlxscore=0 clxscore=1015 malwarescore=0 mlxlogscore=999 phishscore=0 impostorscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002200016 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 08:12:23PM -0600, Eric Sandeen wrote: > > > On 2/19/20 6:17 PM, Luis Chamberlain wrote: > > On Wed, Feb 19, 2020 at 02:01:04PM -0800, Darrick J. Wong wrote: > >> 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. > > > > Ah great to know, thanks! > > > >>>> 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? > > > > They share the same problem with fstests when using an alternative log > > device, which I pointed out on [0] and [1]. > > > > [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 > > > >>> 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. > > > > That goes to show that the fstests assumption on a shared data/log device was > > not only a thing of the past, its still present, and unless we address > > soon, the gap will only get bigger. > > > > OK thanks for the feedback. The situation in terms of testing rtdev or > > external logs seems actually worse than I expected given the outlook for > > the future and no one seeming to really care too much right now. If the > > dax folks didn't care, then the code will likely just bit rot even more. > > Is it too nutty for us to consider removing it as a future goal? > > Less nutty would be to analyze the failures and fix the tests. > > Here's a start, I'll send this one to fstests. > > diff --git a/common/repair b/common/repair > index 5a9097f4..cf69dde9 100644 > --- a/common/repair > +++ b/common/repair > @@ -9,8 +9,12 @@ _zero_position() > value=$1 > struct="$2" > > + SCRATCH_OPTIONS="" > + [ "$USE_EXTERNAL" = yes -a ! -z "$SCRATCH_LOGDEV" ] && \ > + SCRATCH_OPTIONS="-l$SCRATCH_LOGDEV" > + > # set values for off/len variables provided by db > - eval `xfs_db -r -c "$struct" -c stack $SCRATCH_DEV | perl -ne ' > + eval `xfs_db -r -c "$struct" -c stack $SCRATCH_OPTIONS $SCRATCH_DEV | perl -ne ' > if (/byte offset (\d+), length (\d+)/) { > print "offset=$1\nlength=$2\n"; exit > }'` > diff --git a/tests/xfs/030 b/tests/xfs/030 > index efdb6a18..e1cc32ef 100755 > --- a/tests/xfs/030 > +++ b/tests/xfs/030 > @@ -77,7 +77,10 @@ else > _scratch_unmount > fi > clear="" > -eval `xfs_db -r -c "sb 1" -c stack $SCRATCH_DEV | perl -ne ' > +SCRATCH_OPTIONS="" > +[ "$USE_EXTERNAL" = yes -a ! -z "$SCRATCH_LOGDEV" ] && \ > + SCRATCH_OPTIONS="-l$SCRATCH_LOGDEV" > +eval `xfs_db -r -c "sb 1" -c stack $SCRATCH_OPTIONS $SCRATCH_DEV | perl -ne ' _scratch_xfs_db --D > if (/byte offset (\d+), length (\d+)/) { > print "clear=", $1 / 512, "\n"; exit > }'` > > >