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 9D282C33CA9 for ; Mon, 13 Jan 2020 18:09:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 705E6207FD for ; Mon, 13 Jan 2020 18:09:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="fpIgpHDc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726985AbgAMSJp (ORCPT ); Mon, 13 Jan 2020 13:09:45 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:43766 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726435AbgAMSJo (ORCPT ); Mon, 13 Jan 2020 13:09:44 -0500 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 00DI89MU155402; Mon, 13 Jan 2020 18:09:41 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=8CXIBTkMZKDmkj+GcKbThC8AhZgD4xXngtzKEVDhMGk=; b=fpIgpHDc2wdcD+fS6+lhXVOYNN+YcSmorA1sIaWT0m2DVHmdGKEk/31VJf+sTrkvj0GS mu+8oFuux60739PQBD98VM38W/MzzjAHwPChkfIReYh/WjNseMn/yOIYKQb5KnBXXrUn k4rbcdZBCTJlKF+ABpR0N8a2oawsz/nMQ1X3gk/8RnHEiNCIVG/CpWsz0yXkOemfkV/1 GDpjIhE0GG1BycJbn21HlthkDm8U709KVeGGG8+5HKYE5ZZihbp3jwSFAjjb6SIFCZd1 DoBwNSot3l6y/ikc6N6xQD75o1GJ8YxhIe3WFn7iKLyRDYmCu9ESaEV1FW9J6YXuGay3 LA== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by userp2120.oracle.com with ESMTP id 2xf73y8nrg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 13 Jan 2020 18:09:41 +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 00DI9K1v167096; Mon, 13 Jan 2020 18:09:41 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3030.oracle.com with ESMTP id 2xfqu4xv5u-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 13 Jan 2020 18:09:36 +0000 Received: from abhmp0018.oracle.com (abhmp0018.oracle.com [141.146.116.24]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 00DI9FOU007514; Mon, 13 Jan 2020 18:09:15 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 13 Jan 2020 10:09:15 -0800 Date: Mon, 13 Jan 2020 10:09:14 -0800 From: "Darrick J. Wong" To: Gionatan Danti Cc: linux-xfs@vger.kernel.org Subject: Re: XFS reflink vs ThinLVM Message-ID: <20200113180914.GI8247@magnolia> References: <20200113111025.liaargk3sf4wbngr@orion> <703a6c17-cc02-2c2c-31ce-6cd12a888743@assyoma.it> <20200113114356.midcgudwxpze3xfw@orion> <627cb07f-9433-ddfd-37d7-27efedd89727@assyoma.it> <39b50e2c-cb78-3bcd-0130-defa9c573b71@assyoma.it> <20200113165341.GE8247@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=9499 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=943 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001130146 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9499 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-2001130146 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Mon, Jan 13, 2020 at 06:00:15PM +0100, Gionatan Danti wrote: > On 13/01/20 17:53, Darrick J. Wong wrote: > > mkfs.xfs -d extszinherit=NNN is what you want here. > > Hi Darrik, thank you, I missed that option. > > > Right. > > Ok > > > xfs_bmap -c, but only if you have xfs debugging enabled. > > [root@neutron xfs]# xfs_bmap -c test.img > /usr/sbin/xfs_bmap: illegal option -- c > Usage: xfs_bmap [-adelpvV] [-n nx] file... > > Maybe my xfs_bmap version is too old: Doh, sorry, thinko on my part. -c is exposed in the raw xfs_io command but not in the xfs_bmap wrapper. xfs_io -c 'bmap -c -e -l -p -v ' test.img > > If you happen to have rmap enabled, you can use the xfs_io fsmap command > > to look for 'cow reservation' blocks, since that 124k is (according to > > ondisk metadata, anyway) owned by the refcount btree until it gets > > remapped into the file on writeback. > > I see. By default, on RHEL at least, rmapbt is disabled. As a side note, do > you suggest enabling it when creating a new fs? If you are interested in online scrub, then I'd say yes because it's the secret sauce that gives online metadata checking most of its power. I confess, I haven't done a lot of performance analysis of rmap lately, the metadata ops overhead might still be in the ~10% range. The two issues preventing rmap from being turned on by default (at least in my head) are (1) scrub itself is still EXPERIMENTAL and (2) it's not 100% clear that online fsck is such a killer app that everyone will want it, since you always pay the performance overhead of enabling rmap regardless of whether you use xfs_scrub. (If your workload is easily restored from backup/Docker and you need all the performance you can squeeze then perhaps don't enable this.) Note that I've been running with rmap=1 and scrub=1 on all systems since 2016, and frankly I've noticed the system stumbling over broken writeback throttling much more than whatever the tracing tools attribute to rmap. --D > Thanks. > > -- > Danti Gionatan > Supporto Tecnico > Assyoma S.r.l. - www.assyoma.it > email: g.danti@assyoma.it - info@assyoma.it > GPG public key ID: FF5F32A8