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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C8AD0C433EF for ; Wed, 9 Mar 2022 01:10:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230070AbiCIBLv (ORCPT ); Tue, 8 Mar 2022 20:11:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59692 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229971AbiCIBLm (ORCPT ); Tue, 8 Mar 2022 20:11:42 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id C3CD8113D97 for ; Tue, 8 Mar 2022 16:54:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1646787242; 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=LRdaBa2QKiuG4EBT2/d/M9ZBpb/k6yDqa1K8uu98Rcg=; b=PDvQ4XYGdrAIm+T2majGJLA5thIPwZyDeVGZyXK8BvoPTml6n0zqIHyAZVABZ4gHMRwHds 7RNniUapQcC6AW8wSSvVin1f3KXaf2XlaDeEwEdO+/b4VvPem10q/A1l6ZJMDvVq2pMSns NhTw3tGNk4xdIjG1ZwwTz0GBbT9yWUg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-549-ej1psXdBNDKwIqUSmkko1g-1; Tue, 08 Mar 2022 19:53:59 -0500 X-MC-Unique: ej1psXdBNDKwIqUSmkko1g-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 928E4801DDC; Wed, 9 Mar 2022 00:53:58 +0000 (UTC) Received: from T590 (ovpn-8-34.pek2.redhat.com [10.72.8.34]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F0D384BC45; Wed, 9 Mar 2022 00:53:38 +0000 (UTC) Date: Wed, 9 Mar 2022 08:53:34 +0800 From: Ming Lei To: Mike Christie Cc: bvanassche@acm.org, lduncan@suse.com, cleech@redhat.com, martin.petersen@oracle.com, linux-scsi@vger.kernel.org, james.bottomley@hansenpartnership.com Subject: Re: [RFC PATCH 1/4] scsi: Allow drivers to set BLK_MQ_F_BLOCKING Message-ID: References: <20220308003957.123312-1-michael.christie@oracle.com> <20220308003957.123312-2-michael.christie@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220308003957.123312-2-michael.christie@oracle.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Mon, Mar 07, 2022 at 06:39:54PM -0600, Mike Christie wrote: > The software iscsi driver's queuecommand can block and taking the extra > hop from kblockd to its workqueue results in a performance hit. Allowing > it to set BLK_MQ_F_BLOCKING and transmit from that context directly > results in a 20-30% improvement in IOPs for workloads like: > > fio --filename=/dev/sdb --direct=1 --rw=randrw --bs=4k --ioengine=libaio > --iodepth=128 --numjobs=1 > > and for all write workloads. This single patch shouldn't make any difference for iscsi, so please make it as last one if performance improvement data is provided in commit log. Also is there performance effect for other worloads? such as multiple jobs? iscsi is SQ hardware, so if driver is blocked in ->queuecommand() via BLK_MQ_F_BLOCKING, other contexts can't submit IO to scsi ML any more. thanks, Ming