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=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 2E5B4C433B4 for ; Wed, 14 Apr 2021 10:39:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E4687613C3 for ; Wed, 14 Apr 2021 10:39:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233726AbhDNKjl (ORCPT ); Wed, 14 Apr 2021 06:39:41 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:54496 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233871AbhDNKj3 (ORCPT ); Wed, 14 Apr 2021 06:39:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618396743; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=7mtxNf9G7ZE9nH07cAbuCxEu8T2eiRwRRG1NfOPrUKo=; b=CfZ0NeAAHXOUzMnoiSocHLcFM8U3dW0xJG/6Wi85sCNyGkpxbHrY1l3otbyo5hLw3r/aEn /6AU2zIZjOo/bfaqlQyVARItzSkNIcTAlI1dQuh2MezKM/EhuFxUHbQvHWbV4Ga6BUHSAP whbyU4ftbaXm5PUL1hEmuxd7iVdH99o= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-540-x6jvojrPPW6xCf0lyYg1Bw-1; Wed, 14 Apr 2021 06:38:59 -0400 X-MC-Unique: x6jvojrPPW6xCf0lyYg1Bw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DAD8783DD22; Wed, 14 Apr 2021 10:38:57 +0000 (UTC) Received: from T590 (ovpn-12-91.pek2.redhat.com [10.72.12.91]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 595A25D76F; Wed, 14 Apr 2021 10:38:53 +0000 (UTC) Date: Wed, 14 Apr 2021 18:38:49 +0800 From: Ming Lei To: John Garry Cc: linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, Kashyap Desai , "Martin K. Petersen" , Jens Axboe , Douglas Gilbert Subject: Re: [bug report] shared tags causes IO hang and performance drop Message-ID: References: <9a6145a5-e6ac-3d33-b52a-0823bfc3b864@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9a6145a5-e6ac-3d33-b52a-0823bfc3b864@huawei.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Apr 14, 2021 at 11:10:39AM +0100, John Garry wrote: > Hi Ming, > > > > > It is reported inside RH that CPU utilization is increased ~20% when > > running simple FIO test inside VM which disk is built on image stored > > on XFS/megaraid_sas. > > > > When I try to investigate by reproducing the issue via scsi_debug, I found > > IO hang when running randread IO(8k, direct IO, libaio) on scsi_debug disk > > created by the following command: > > > > modprobe scsi_debug host_max_queue=128 submit_queues=$NR_CPUS virtual_gb=256 > > > > So I can recreate this hang for using mq-deadline IO sched for scsi debug, > in that fio does not exit. I'm using v5.12-rc7. > > Do you have any idea of what changed to cause this, as we would have tested > this before? Or maybe only none IO sched on scsi_debug. And normally 4k > block size and only rw=read (for me, anyway). Just run a quick test with none on scsi_debug, looks the issue can't be reproduced, but very worse performance is observed with none(20% IOPS drops, and 50% CPU utilization increased). > > Note that host_max_queue=128 will cap submit queue depth at 128, while would > be 192 by default. I take 128 because the reported megaraid_sas's host queue depth is 128. Thanks, Ming