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=-12.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, 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 5A713C433E0 for ; Wed, 20 Jan 2021 03:20:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 13F05207CF for ; Wed, 20 Jan 2021 03:20:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730297AbhATDUR (ORCPT ); Tue, 19 Jan 2021 22:20:17 -0500 Received: from userp2130.oracle.com ([156.151.31.86]:52986 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387599AbhATClU (ORCPT ); Tue, 19 Jan 2021 21:41:20 -0500 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 10K2e235086244; Wed, 20 Jan 2021 02:40:23 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-2020-01-29; bh=PXytxwVzE5VR53HPMta1k/oaIyuKttBLtN1ccsE0Qp4=; b=s4AZug77Uuf1sknpBjVQxzEIlT+mjYZTytKD5p8SZFFMSKJbR8rURBRe5ILZKOPOQsog 8sO+yrKjnFd2LiT6N7wKVTenjDs1qt30jnxBsOBYYLTVcBRKctQXuJQci1kA00nUG29F hOei1e9YXWdYV621nteQ6t20uxzQ15mqR0YYIvNiXwa11I/Psrsx+wQUSVQzc8DX3lxB Lp4dFQWbLRT2935ef1TwuG1s4xiS+mMYrt+iUSt9JCMNG5xtsXPKj8c87FcKM97cQg+9 lGhTFd/5ZtQeja/xa42K4+1bQONcxdMfKtvgeDs18zjAj1mevpesAfDharDMxeaYsp1M jg== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by userp2130.oracle.com with ESMTP id 3668qa8eeh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 20 Jan 2021 02:40:23 +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 10K2dkJH073259; Wed, 20 Jan 2021 02:40:22 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3020.oracle.com with ESMTP id 3668rd77vm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 20 Jan 2021 02:40:22 +0000 Received: from abhmp0016.oracle.com (abhmp0016.oracle.com [141.146.116.22]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 10K2eLUh031064; Wed, 20 Jan 2021 02:40:21 GMT Received: from [192.168.10.137] (/39.109.186.25) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 19 Jan 2021 18:40:21 -0800 Subject: Re: [PATCH RFC 4/4] btrfs: introduce new read_policy round-robin To: Josef Bacik , linux-btrfs@vger.kernel.org Cc: dsterba@suse.com References: <8e0afaa33f33d1a5efbf37fa4465954056ce3f59.1610324448.git.anand.jain@oracle.com> From: Anand Jain Message-ID: <1337063c-1f3c-7d6f-8d0c-49b8a37beda3@oracle.com> Date: Wed, 20 Jan 2021 10:40:17 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9869 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 spamscore=0 suspectscore=0 adultscore=0 mlxlogscore=999 bulkscore=0 malwarescore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101200014 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9869 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 spamscore=0 impostorscore=0 mlxscore=0 priorityscore=1501 phishscore=0 mlxlogscore=999 lowpriorityscore=0 malwarescore=0 adultscore=0 clxscore=1015 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101200014 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 20/1/21 3:41 am, Josef Bacik wrote: > On 1/11/21 4:41 AM, Anand Jain wrote: >> Add round-robin read policy to route the read IO to the next device in >> the >> round-robin order. The chunk allocation and thus the stripe-index follows >> the order of free space available on devices. So to make the round-robin >> effective it shall follow the devid order instead of the stripe-index >> order. >> >> Signed-off-by: Anand Jain >> -- >> RFC because: Provides terrible performance with the fio tests. >> I am not yet sure if there is any io workload or a block layer >> tuning that shall make this policy better. As of now just an >> experimental patch. >> > > Just drop this one, if we can't find a reason to use it then don't > bother adding the code.  The other options have real world valuable > uses, so stick with those.  Thanks, > Yep. I will drop this patch in the next iteration. The low performance is attributed to the low number of read IO mergers in the block layer. The consecutive blocks in my test case (fio random read) were read from the other disk, so the block layer lost the opportunity to merge the IOs. Thanks, Anand > Josef >