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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 6AA31C433ED for ; Thu, 15 Apr 2021 10:44:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 40DFB61249 for ; Thu, 15 Apr 2021 10:44:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230260AbhDOKoy (ORCPT ); Thu, 15 Apr 2021 06:44:54 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:2866 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230056AbhDOKox (ORCPT ); Thu, 15 Apr 2021 06:44:53 -0400 Received: from fraeml741-chm.china.huawei.com (unknown [172.18.147.226]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4FLbRx1gVfz68BSk; Thu, 15 Apr 2021 18:39:09 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml741-chm.china.huawei.com (10.206.15.222) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2106.2; Thu, 15 Apr 2021 12:44:27 +0200 Received: from [10.47.83.117] (10.47.83.117) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2106.2; Thu, 15 Apr 2021 11:44:26 +0100 Subject: Re: [bug report] shared tags causes IO hang and performance drop To: Ming Lei CC: Kashyap Desai , , , "Martin K. Petersen" , Jens Axboe , Douglas Gilbert References: <9a6145a5-e6ac-3d33-b52a-0823bfc3b864@huawei.com> <87ceccf2-287b-9bd1-899a-f15026c9e65b@huawei.com> From: John Garry Message-ID: <3e76ffc7-1d71-83b6-ef5b-3986e947e372@huawei.com> Date: Thu, 15 Apr 2021 11:41:52 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.83.117] X-ClientProxiedBy: lhreml721-chm.china.huawei.com (10.201.108.72) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi Ming, I'll have a look. BTW, are you intentionally using scsi_debug over null_blk? null_blk supports shared sbitmap as well, and performance figures there are generally higher than scsi_debug for similar fio settings. Thanks, john EOM >> IOPs >> mq-deadline usr=21.72%, sys=44.18%, 423K >> none usr=23.15%, sys=74.01% 450K > Today I re-run the scsi_debug test on two server hardwares(32cores, dual > numa nodes), and the CPU utilization issue can be reproduced, follow > the test result: > > 1) randread test on ibm-x3850x6[*] with deadline > > |IOPS | FIO CPU util > ------------------------------------------------ > hosttags | 94k | usr=1.13%, sys=14.75% > ------------------------------------------------ > non hosttags | 124k | usr=1.12%, sys=10.65%, > > > 2) randread test on ibm-x3850x6[*] with none > |IOPS | FIO CPU util > ------------------------------------------------ > hosttags | 120k | usr=0.89%, sys=6.55% > ------------------------------------------------ > non hosttags | 121k | usr=1.07%, sys=7.35% > ------------------------------------------------ > > *: > - that is the machine Yanhui reported VM cpu utilization increased by 20% > - kernel: latest linus tree(v5.12-rc7, commit: 7f75285ca57) > - also run same test on another 32cores machine, IOPS drop isn't > observed, but CPU utilization is increased obviously > > 3) test script > #/bin/bash > > run_fio() { > RTIME=$1 > JOBS=$2 > DEVS=$3 > BS=$4 > > QD=64 > BATCH=16 > > fio --bs=$BS --ioengine=libaio \ > --iodepth=$QD \ > --iodepth_batch_submit=$BATCH \ > --iodepth_batch_complete_min=$BATCH \ > --filename=$DEVS \ > --direct=1 --runtime=$RTIME --numjobs=$JOBS --rw=randread \ > --name=test --group_reporting > } > > SCHED=$1 > > NRQS=`getconf _NPROCESSORS_ONLN` > > rmmod scsi_debug > modprobe scsi_debug host_max_queue=128 submit_queues=$NRQS virtual_gb=256 > sleep 2 > DEV=`lsscsi | grep scsi_debug | awk '{print $6}'` > echo $SCHED >/sys/block/`basename $DEV`/queue/scheduler > echo 128 >/sys/block/`basename $DEV`/device/queue_depth > run_fio 20 16 $DEV 8K > > > rmmod scsi_debug > modprobe scsi_debug max_queue=128 submit_queues=1 virtual_gb=256 > sleep 2 > DEV=`lsscsi | grep scsi_debug | awk '{print $6}'` > echo $SCHED >/sys/block/`basename $DEV`/queue/scheduler > echo 128 >/sys/block/`basename $DEV`/device/queue_depth > run_fio 20 16 $DEV 8k