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=-0.8 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,UNPARSEABLE_RELAY 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 EECC7C43215 for ; Fri, 22 Nov 2019 02:25:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C7A74206DA for ; Fri, 22 Nov 2019 02:25:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="sTVu9Csq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726573AbfKVCZp (ORCPT ); Thu, 21 Nov 2019 21:25:45 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:59328 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726335AbfKVCZo (ORCPT ); Thu, 21 Nov 2019 21:25:44 -0500 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id xAM2O45X129595; Fri, 22 Nov 2019 02:25:32 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=to : cc : subject : from : references : date : in-reply-to : message-id : mime-version : content-type; s=corp-2019-08-05; bh=+IcW1brC9RRuMP8eAOD+qcqBkj+fn9n/g8hILFx4gso=; b=sTVu9CsqSD1I+39pMRFypx5e6502JPrLE4TiNzEu7KUZ1OnpHeftqKZ+ES6TXjP6e8sy fAQjpLHXhLaFA/92zdrrG7DXGSXedCbFOSswFH21JxlIYQ5x91ILVJ6wtqZ66Nz/JoGC IDcv3kmx1xCKRuPWiZfMwnkVS6ljIdOWM3KXrdPPCCjRnwUNoVhLA7jZ31Hf29XePPpH kkpj4SGOyk1DkIiLXrZZ7jtNtIp4v2Nv1+MfXuYnPhOZ6CKLlswuEMIa7rnBNIndXst0 teSFhcFyMZjTe0+xEoyV1dUW3YCYQsHCANRSXL+FoIlR/vmHaLN2SyHz1JPr3U+Iytnu lg== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by userp2120.oracle.com with ESMTP id 2wa9rqyuyp-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 22 Nov 2019 02:25:32 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id xAM2NHNN142965; Fri, 22 Nov 2019 02:25:31 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserp3020.oracle.com with ESMTP id 2wdfrwexjj-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 22 Nov 2019 02:25:31 +0000 Received: from abhmp0002.oracle.com (abhmp0002.oracle.com [141.146.116.8]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id xAM2PTqd005753; Fri, 22 Nov 2019 02:25:29 GMT Received: from ca-mkp.ca.oracle.com (/10.159.214.123) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 21 Nov 2019 18:25:29 -0800 To: "Ewan D. Milne" Cc: Bart Van Assche , Hannes Reinecke , Ming Lei , Jens Axboe , linux-block@vger.kernel.org, "James E . J . Bottomley" , "Martin K . Petersen" , linux-scsi@vger.kernel.org, Sathya Prakash , Chaitra P B , Suganath Prabu Subramani , Kashyap Desai , Sumit Saxena , Shivasharan S , Christoph Hellwig , Bart Van Assche Subject: Re: [PATCH 4/4] scsi: core: don't limit per-LUN queue depth for SSD From: "Martin K. Petersen" Organization: Oracle Corporation References: <20191118103117.978-1-ming.lei@redhat.com> <20191118103117.978-5-ming.lei@redhat.com> <1081145f-3e17-9bc1-2332-50a4b5621ef7@suse.de> <9bbcbbb42b659c323c9e0d74aa9b062a3f517d1f.camel@redhat.com> <44644664-f7b6-facd-d1bb-f7cfc9524379@acm.org> Date: Thu, 21 Nov 2019 21:25:25 -0500 In-Reply-To: (Ewan D. Milne's message of "Wed, 20 Nov 2019 16:36:41 -0500") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1.92 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9448 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=986 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-1911220020 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9448 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-1911220020 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org Ewan, > Delaying the queue re-run vs. a ramp down might negatively affect > performance. I'm not sure how accurate the ramp is at discovering the > optimum though. The optimum - as well as the actual limit - might change over time in a multi-initiator setup as other hosts grab resources on the device. I do think that the only way forward here, if we want to avoid counting outstanding commands for performance reasons, is to ensure that the BUSY/QUEUE_FULL/TASK_SET_FULL handling is relatively fast path and not something deep in the bowels of error handling. Which it actually isn't. But I do think we'll need to take a closer look. -- Martin K. Petersen Oracle Linux Engineering