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 E5275C433DF for ; Tue, 19 May 2020 10:02:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B14A92065F for ; Tue, 19 May 2020 10:02:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="k+mY+Tx8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726508AbgESKCo (ORCPT ); Tue, 19 May 2020 06:02:44 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:41284 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726121AbgESKCn (ORCPT ); Tue, 19 May 2020 06:02:43 -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 04JA1hcD038047; Tue, 19 May 2020 10:02:37 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2020-01-29; bh=CrMNP7uTiyM+3erDd6enSk9WDSnH7i6Ecsz3fiQHQbE=; b=k+mY+Tx8FNYOFDQnbNskCKtfhlwkE+9h7T+TkF2Fm1yx81EKa4meg2n+AbxPqMwmsdyf 2VMkBOqrOVzEiSiQZHdVC63N3XjQ2jtjY6Gku0XbeDXTsYDrz85bcispl5fmqGE5k1uH he1Ir3Jr5zBP17VqFJX//lwJC3srAuRSyalnq+f5x6ahx5KaCTQJxPa2593O5uPPNOQn cOa7mf7JDmAy7qgi3F0FB9B6d8kvFzs3yNRwzXr21R1lF0ULa8Vjz+EB8bzCJy0LsdBK rQyKaL9CRAdjwONP5OjDt0hbDS8pPpPExbunaFy3tBb87wuBCyVliQRhvpT3DVdf0+lm eA== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by aserp2120.oracle.com with ESMTP id 31284kvg19-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 19 May 2020 10:02:37 +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 04J9xBVM040935; Tue, 19 May 2020 10:02:36 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 312sxsd1ae-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 19 May 2020 10:02:36 +0000 Received: from abhmp0006.oracle.com (abhmp0006.oracle.com [141.146.116.12]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 04JA2ZJr026916; Tue, 19 May 2020 10:02:36 GMT Received: from [192.168.1.102] (/39.109.177.87) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 19 May 2020 03:02:35 -0700 Subject: Re: [PATCH v7 rebased 0/5] readmirror feature (sysfs and in-memory only approach; with new read_policy device) To: dsterba@suse.cz, dsterba@suse.com, linux-btrfs@vger.kernel.org References: <1586173871-5559-1-git-send-email-anand.jain@oracle.com> <20200515195858.GS18421@twin.jikos.cz> From: Anand Jain Message-ID: Date: Tue, 19 May 2020 18:02:32 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200515195858.GS18421@twin.jikos.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9625 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 phishscore=0 malwarescore=0 mlxlogscore=999 bulkscore=0 mlxscore=0 suspectscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005190090 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9625 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 mlxscore=0 cotscore=-2147483648 impostorscore=0 malwarescore=0 mlxlogscore=999 lowpriorityscore=0 phishscore=0 spamscore=0 bulkscore=0 adultscore=0 priorityscore=1501 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005190090 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 16/5/20 3:58 am, David Sterba wrote: > On Thu, Apr 30, 2020 at 05:02:27PM +0800, Anand Jain wrote: >> I am not sure if this will be integrated in 5.8 and worth the time to >> rebase. Kindly suggest. > > The preparatory work is ok, but the actual mirror selection policy > addresses a usecase that I think is not the one most users are > interested in. Devices of vastly different performance capabilities like > rotational disks vs nvme vs ssd vs network block devices in one > filesystem are not something commonly found. > > What we really need is a saner balancing mechanism than pid-based, that > is also going to be used any time there are more devices from the same > speed class for the fast devices too. > There are two things here, the read_policy framework in the preparatory patches and a new balancing or read_policy, device. > So, no the patchset is not on track for a merge without the improved > default balancing. It can be worked on top of the preparatory read_policy framework? This patchset does not change any default read_policy (or balancing) which is pid as of now. Working on a default read_policy/balancing was out of the scope of this patchset. > The preferred device for reads can be one of the > policies, I understand the usecase and have not problem with that > although wouldn't probably have use for it. For us, read_policy:device helps to reproduce raid1 data corruption https://patchwork.kernel.org/patch/11475417/ And xfstests btrfs/14[0-3] can be improved so that the reads directly go the device of the choice, instead of waiting for the odd/even pid. Common configuration won't need this, advance configurations assembled with heterogeneous devices where read performance is more critical than write will find read_policy:device useful. Thanks, Anand