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=-0.9 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 A898DC352A4 for ; Thu, 13 Feb 2020 03:02:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7FC7A20873 for ; Thu, 13 Feb 2020 03:02:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="uQ+dyeDm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729488AbgBMDCY (ORCPT ); Wed, 12 Feb 2020 22:02:24 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:32922 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729432AbgBMDCX (ORCPT ); Wed, 12 Feb 2020 22:02:23 -0500 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 01D32AML195412; Thu, 13 Feb 2020 03:02:15 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-2020-01-29; bh=LLzhfUkTLcL96RVaoKPShnmZ7NANy0fpYjkZKVROifY=; b=uQ+dyeDmJ6wPB5pK3LGgE+pkKrektaFXz12MHSbeXZ1YNpX7gdnisgU37ThSWTodnpNc RJofHafsz1l3FnDPvIhVsC8w8g2R8yirzlFyjOcBEAe6dHDrg+QGI7pHV1qqBQmBNWlK 19ZwNHRjJOk7X3p/xxEJ/eDXh3v5ntp7sN8qztebQTTXlV86hi/wBUDvf8U3XqEwHEaS +gp4SHKAx/SNv9OvkOIS0WvZYZzp6S1SBGaVmwA+YziNs0buIiUtcvFn2j3wyVb1kq4U lQyo05Glgk3nXPbxDeHJ6TKOFLIGA3nvma6Bc1FiV9dw9pGxAb9ewfRdfqyvnTT0ud33 MA== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by userp2120.oracle.com with ESMTP id 2y2p3spnhg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 13 Feb 2020 03:02:15 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 01D2vIjw131601; Thu, 13 Feb 2020 03:02:15 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3020.oracle.com with ESMTP id 2y4k9gxatq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 13 Feb 2020 03:02:15 +0000 Received: from abhmp0009.oracle.com (abhmp0009.oracle.com [141.146.116.15]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 01D32CWN010378; Thu, 13 Feb 2020 03:02:13 GMT Received: from ca-mkp.ca.oracle.com (/10.159.214.123) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 12 Feb 2020 19:02:11 -0800 To: Damien Le Moal Cc: Tim Walker , Ming Lei , "linux-block\@vger.kernel.org" , linux-scsi , "linux-nvme\@lists.infradead.org" Subject: Re: [LSF/MM/BPF TOPIC] NVMe HDD From: "Martin K. Petersen" Organization: Oracle Corporation References: <20200211122821.GA29811@ming.t460p> Date: Wed, 12 Feb 2020 22:02:08 -0500 In-Reply-To: (Damien Le Moal's message of "Wed, 12 Feb 2020 01:47:53 +0000") 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=9529 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 suspectscore=0 spamscore=0 adultscore=0 bulkscore=0 phishscore=0 malwarescore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002130023 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9529 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxscore=0 malwarescore=0 suspectscore=0 mlxlogscore=999 priorityscore=1501 clxscore=1011 impostorscore=0 lowpriorityscore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002130023 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Damien, > Exposing an HDD through multiple-queues each with a high queue depth > is simply asking for troubles. Commands will end up spending so much > time sitting in the queues that they will timeout. Yep! > This can already be observed with the smartpqi SAS HBA which exposes > single drives as multiqueue block devices with high queue depth. > Exercising these drives heavily leads to thousands of commands being > queued and to timeouts. It is fairly easy to trigger this without a > manual change to the QD. This is on my to-do list of fixes for some > time now (lacking time to do it). Controllers that queue internally are very susceptible to application or filesystem timeouts when drives are struggling to keep up. > NVMe HDDs need to have an interface setup that match their speed, that > is, something like a SAS interface: *single* queue pair with a max QD > of 256 or less depending on what the drive can take. Their is no > TASK_SET_FULL notification on NVMe, so throttling has to come from the > max QD of the SQ, which the drive will advertise to the host. At the very minimum we'll need low queue depths. But I have my doubts whether we can make this work well enough without some kind of TASK SET FULL style AER to throttle the I/O. > NVMe specs will need an update to have a "NONROT" (non-rotational) bit in > the identify data for all this to fit well in the current stack. Absolutely. -- Martin K. Petersen Oracle Linux Engineering