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=-4.0 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,URIBL_BLOCKED,USER_AGENT_GIT 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 C905EC2BA19 for ; Mon, 6 Apr 2020 11:53:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9215B2072A for ; Mon, 6 Apr 2020 11:53:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="qDP0Sb+0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727512AbgDFLxc (ORCPT ); Mon, 6 Apr 2020 07:53:32 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:34214 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727376AbgDFLxc (ORCPT ); Mon, 6 Apr 2020 07:53:32 -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 036Blfvv078926 for ; Mon, 6 Apr 2020 11:53:31 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : subject : date : message-id; s=corp-2020-01-29; bh=0rtjslhY8mSKNkHG4Rj96Lp2huNXxcgmDcxkfnMn39Q=; b=qDP0Sb+02M2yyZn/3CSUcutPCtNMWSPyZ7yNfeQskAp2bDOSMq3/44hkrU9jrIYoQnyW nc5mGZy+ATzvzyFJX3UYVfu8liR7S7ExaGORFEFxSagg+jDNNrUuiyCH8iNyUmUncMF5 fKRoHkERyOxNZFtcMNyxezXCSb5+V6trGSXermMW2RSPZRbtWgJf2XDmpylWnV2Gtyjd hWV9dqbKe/5RLf4LMTicaPqW/xsbZjfw4PMFv4Npzl3CxnQf3tlWZjMrLJlBpFOk+ZMy JhnI+aaNtmKqSLoVQbGBATqnH5HPi5p4OZKU8Z4iGBrGGXEtNhaGDvJtlpC4OYofaf5v jg== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by aserp2120.oracle.com with ESMTP id 306j6m6b0u-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Mon, 06 Apr 2020 11:53:30 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 036BlDxK064678 for ; Mon, 6 Apr 2020 11:51:30 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3030.oracle.com with ESMTP id 3073qcw4qw-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Mon, 06 Apr 2020 11:51:30 +0000 Received: from abhmp0008.oracle.com (abhmp0008.oracle.com [141.146.116.14]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 036BpTlT009203 for ; Mon, 6 Apr 2020 11:51:29 GMT Received: from tp.localdomain (/39.109.145.141) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 06 Apr 2020 04:51:28 -0700 From: Anand Jain To: linux-btrfs@vger.kernel.org Subject: [PATCH v7 rebased 0/5] readmirror feature (sysfs and in-memory only approach; with new read_policy device) Date: Mon, 6 Apr 2020 19:51:06 +0800 Message-Id: <1586173871-5559-1-git-send-email-anand.jain@oracle.com> X-Mailer: git-send-email 1.8.3.1 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9582 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 mlxscore=0 mlxlogscore=999 spamscore=0 bulkscore=0 adultscore=0 malwarescore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004060104 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9582 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 mlxlogscore=999 spamscore=0 priorityscore=1501 suspectscore=0 lowpriorityscore=0 malwarescore=0 impostorscore=0 mlxscore=0 phishscore=0 adultscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004060104 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org v7: Fix switch's fall through warning. Changle logs updates where necessary. v6: Patch 4/5 - If there is no change in device's read prefer then don't log Patch 4/5 - Add pid to the logs Patch 5/5 - If there isn't read preferred device in the chunk don't reset read policy to default, instead just use stripe 0. As this is in the read path it avoids going through the device list to find read preferred device. So inline to this drop to check if there is read preferred device before setting read policy to device. __ Original email: __ v5: Worked on review comments as received in its previous version. Please refer to individual patches for the specific changes. Introduces the new read_policy 'device'. v4: Rename readmirror attribute to read_policy. Drop separate kobj for readmirror instead create read_policy attribute in fsid kobj. merge v2:2/3 and v2:3/3 into v4:2/2. Patch titles have changed. v3: v2: Mainly fixes the fs_devices::readmirror declaration type from atomic_t to u8. (Thanks Josef). v1: As of now we use only %pid method to read stripped mirrored data. So application's process id determines the stripe id to be read. This type of routing typically helps in a system with many small independent applications tying to read random data. On the other hand the %pid based read IO distribution policy is inefficient if there is a single application trying to read large data as because the overall disk bandwidth would remains under utilized. One type of readmirror policy isn't good enough and other choices are routing the IO based on device's waitqueue or manual when we have a read-preferred device or a readmirror policy based on the target storage caching. So this patch-set introduces a framework where we could add more readmirror policies. This policy is a filesystem wide policy as of now, and though the readmirror policy at the subvolume level is a novel approach as it provides maximum flexibility in the data center, but as of now its not practical to implement such a granularity as you can't really ensure reflinked extents will be read from the stripe of its desire and so there will be more limitations and it can be assessed separately. The approach in this patch-set is sys interface with in-memory policy. And does not add any new readmirror type in this set, which can be add once we are ok with the framework. Also the default policy remains %pid. Previous works: ---------------------------------------------------------------------- There were few RFCs [1] before, mainly to figure out storage (or in memory only) for the readmirror policy and the interface needed. [1] https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg86368.html https://lore.kernel.org/linux-btrfs/20190826090438.7044-1-anand.jain@oracle.com/ https://lore.kernel.org/linux-btrfs/5fcf9c23-89b5-b167-1f80-a0f4ac107d0b@oracle.com/ https://patchwork.kernel.org/cover/10859213/ Mount -o: In the first trial it was attempted to use the mount -o option to carry the readmirror policy, this is good for debugging which can make sure even the mount thread metadata tree blocks are read from the disk desired. It was very effective in testing radi1/raid10 write-holes. Extended attribute: As extended attribute is associated with the inode, to implement this there is bit of extended attribute abuse or else makes it mandatory to mount the rootid 5. Its messy unless readmirror policy is applied at the subvol level which is not possible as of now. An item type: The proposed patch was to create an item to hold the readmirror policy, it makes sense when compared to the abusive extended attribute approach but introduces a new item and so no backward compatibility. ----------------------------------------------------------------------- Anand Jain (5): btrfs: add btrfs_strmatch helper btrfs: create read policy framework btrfs: create read policy sysfs attribute, pid btrfs: introduce new device-state read_preferred btrfs: introduce new read_policy device fs/btrfs/sysfs.c | 128 +++++++++++++++++++++++++++++++++++++++++++++ fs/btrfs/volumes.c | 39 +++++++++++++- fs/btrfs/volumes.h | 16 ++++++ 3 files changed, 182 insertions(+), 1 deletion(-) -- 2.23.0