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,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 66047C76190 for ; Mon, 22 Jul 2019 23:31:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3349721951 for ; Mon, 22 Jul 2019 23:31:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="2y5dCRqN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730693AbfGVXbM (ORCPT ); Mon, 22 Jul 2019 19:31:12 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:48956 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727157AbfGVXbL (ORCPT ); Mon, 22 Jul 2019 19:31:11 -0400 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x6MNTCdL104363; Mon, 22 Jul 2019 23:30:47 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=ZOinQjjkfv+8JYlsnjKtWVora/RDCEJ06rc6HsclIrg=; b=2y5dCRqNbyDeHDW0jO++e2I1na2Hzhb0IYMqCXazV73vVweZ4OOd8KSFXiqhSyPL/eem iXesaIm/WdS+KhEKF6eZ68fZEQTJoluEaEKrd7STPFx+IQffTHYYhJ543/d0UaYk+pmf MGTEO88kQsEaOzcNiR5TXyYkL1k4AwSs7+1do0/FOkeAymeiVs6+Im8IHK6XodjXW6Rr dM5lAOwvQUdebQviltw1VTHfLR2jpc1Z/PVcidXg9ld9vlb78FoECgHwBnwhfyGHfj3f eDEefmgyPeKhTIPH4C3fUOM934zI2/pGn0ZQuNNo018pzFMzr1uxRWmAxyh7uPY5VdJd 5Q== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by userp2130.oracle.com with ESMTP id 2tutctaeaa-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 22 Jul 2019 23:30:47 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x6MNRu3t087843; Mon, 22 Jul 2019 23:30:46 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 2tut9mkw89-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 22 Jul 2019 23:30:46 +0000 Received: from abhmp0008.oracle.com (abhmp0008.oracle.com [141.146.116.14]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x6MNUjZ1000912; Mon, 22 Jul 2019 23:30:45 GMT Received: from [192.168.1.14] (/180.165.87.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 22 Jul 2019 16:30:44 -0700 Subject: Re: [RFC PATCH 0/3] md: export internal stats through debugfs To: Hou Tao , linux-raid@vger.kernel.org, songliubraving@fb.com Cc: neilb@suse.com, linux-block@vger.kernel.org, snitzer@redhat.com, agk@redhat.com, dm-devel@redhat.com, linux-kernel@vger.kernel.org References: <20190702132918.114818-1-houtao1@huawei.com> From: Bob Liu Message-ID: <1ebcf2e8-f3ce-7417-4060-b9264a5a4e51@oracle.com> Date: Tue, 23 Jul 2019 07:30:38 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190702132918.114818-1-houtao1@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9326 signatures=668684 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=8.0.1-1810050000 definitions=main-1907220248 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9326 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1907220248 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/2/19 9:29 PM, Hou Tao wrote: > Hi, > > There are so many io counters, stats and flags in md, so I think > export these info to userspace will be helpful for online-debugging, For online-debugging, I'd suggest you have a try eBPF which can be very helpful. -Bob > especially when the vmlinux file and the crash utility are not > available. And these info can also be utilized during code > understanding. > > MD has already exported some stats through sysfs files under > /sys/block/mdX/md, but using sysfs file to export more internal > stats are not a good choice, because we need to create a single > sysfs file for each internal stat according to the use convention > of sysfs and there are too many internal stats. Further, the > newly-created sysfs files would become APIs for userspace tools, > but that is not we wanted, because these files are related with > internal stats and internal stats may change from time to time. > > And I think debugfs is a better choice. Because we can show multiple > related stats in a debugfs file, and the debugfs file will never be > used as an userspace API. > > Two debugfs files are created to expose these internal stats: > * iostat: io counters and io related stats (e.g., mddev->active_io, > r1conf->nr_pending, or r1confi->retry_list) > * stat: normal stats/flags (e.g., mddev->recovery, conf->array_frozen) > > Because internal stats are spreaded all over md-core and md-personality, > so both md-core and md-personality will create these two debugfs files > under different debugfs directory. > > Patch 1 factors out the debugfs files creation routine for md-core and > md-personality, patch 2 creates two debugfs files: iostat & stat under > /sys/kernel/debug/block/mdX for md-core, and patch 3 creates two debugfs > files: iostat & stat under /sys/kernel/debug/block/mdX/raid1 for md-raid1. > > The following lines show the hierarchy and the content of these debugfs > files for a RAID1 device: > > $ pwd > /sys/kernel/debug/block/md0 > $ tree > . > ├── iostat > ├── raid1 > │   ├── iostat > │   └── stat > └── stat > > $ cat iostat > active_io 0 > sb_wait 0 pending_writes 0 > recovery_active 0 > bitmap pending_writes 0 > > $ cat stat > flags 0x20 > sb_flags 0x0 > recovery 0x0 > > $ cat raid1/iostat > retry_list active 0 > bio_end_io_list active 0 > pending_bio_list active 0 cnt 0 > sync_pending 0 > nr_pending 0 > nr_waiting 0 > nr_queued 0 > barrier 0 > > $ cat raid1/stat > array_frozen 0 > > I'm not sure whether the division of internal stats is appropriate and > whether the internal stats in debugfs files are sufficient, so questions > and comments are weclome. > > Regards, > Tao > > Hou Tao (3): > md-debugfs: add md_debugfs_create_files() > md: export inflight io counters and internal stats in debugfs > raid1: export inflight io counters and internal stats in debugfs > > drivers/md/Makefile | 2 +- > drivers/md/md-debugfs.c | 35 ++++++++++++++++++ > drivers/md/md-debugfs.h | 16 +++++++++ > drivers/md/md.c | 65 ++++++++++++++++++++++++++++++++++ > drivers/md/md.h | 1 + > drivers/md/raid1.c | 78 +++++++++++++++++++++++++++++++++++++++++ > drivers/md/raid1.h | 1 + > 7 files changed, 197 insertions(+), 1 deletion(-) > create mode 100644 drivers/md/md-debugfs.c > create mode 100644 drivers/md/md-debugfs.h >