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=-3.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,UNPARSEABLE_RELAY autolearn=ham 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 DD2BAC43387 for ; Fri, 4 Jan 2019 04:58:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9C29E2087F for ; Fri, 4 Jan 2019 04:58:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="EXQysMYJ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726189AbfADE6D (ORCPT ); Thu, 3 Jan 2019 23:58:03 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:40618 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725919AbfADE6C (ORCPT ); Thu, 3 Jan 2019 23:58:02 -0500 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id x044sRDu077447; Fri, 4 Jan 2019 04:57:46 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-2018-07-02; bh=0mQERALhTrEsrDYr9dcg0ectth3nEciBiWRbWNi54Fc=; b=EXQysMYJhQ48JjOnNMZl73p5NTdhOydgjRzoafRktdtPNm2blbW4VDp2lmw0zhTWY5nx xvHIq4QlJELIltBF+20OGhaHxpcFCR1WjD06K6VJf/vWxWmSttvFO8W16lj7QOsfJ3XK d5ZEL6kx5vSjiLAIKfobhJTD3wTF0Dhcc8nXVfdT8XvUqLcvJ1C4YwiBjfRxagqGuFrq VUIG6klEnumxvPg5ale8+itIM3gZJdVSn19Vb07RnctdFOkgpgWsUJTwSFHBAVmFT1E2 Vvu3S4OWeBWRpm6T6+vsy993TYG0aaXH8OSBT7X8ykasdjMJ1TnpE2axQu6+ePX5VmvE AQ== Received: from aserv0021.oracle.com (aserv0021.oracle.com [141.146.126.233]) by userp2120.oracle.com with ESMTP id 2pp1jra9wr-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 04 Jan 2019 04:57:46 +0000 Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserv0021.oracle.com (8.14.4/8.14.4) with ESMTP id x044vjl6032351 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 4 Jan 2019 04:57:45 GMT Received: from abhmp0002.oracle.com (abhmp0002.oracle.com [141.146.116.8]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x044vf8i030947; Fri, 4 Jan 2019 04:57:41 GMT Received: from ca-mkp.ca.oracle.com (/10.159.214.123) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 03 Jan 2019 20:57:41 -0800 To: "Ewan D. Milne" Cc: dgilbert@interlog.com, Randall Huang , Christoph Hellwig , huangrandall@google.com, jejb@linux.vnet.ibm.com, martin.petersen@oracle.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] scsi: associate bio write hint with WRITE CDB From: "Martin K. Petersen" Organization: Oracle Corporation References: <20181226041504.66283-1-huangrandall@google.com> <20190103075133.GA5141@infradead.org> <20190103094755.GA96532@google.com> <6152b478ea77dacf57eef6f758ba795f756cd3da.camel@redhat.com> Date: Thu, 03 Jan 2019 23:57:38 -0500 In-Reply-To: <6152b478ea77dacf57eef6f758ba795f756cd3da.camel@redhat.com> (Ewan D. Milne's message of "Thu, 03 Jan 2019 16:40:41 -0500") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9125 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=677 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901040043 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ewan, > SBC-5 says that support for the grouping function is indicated by the > GROUP_SUP bit in the Extended Inquiry VPD page (86h). I'm not sure > how many devices actually support that page though. Probably most > don't. Several devices support it, albeit for various different purposes. It's one of these wonderful features whose interpretation was left outside the scope of the spec for a long time. So even though we absolutely and positively need to make setting GROUP NUMBER conditional on GROUP_SUP being reported, we also need additional information from the storage about how the field should be interpreted. The official way to report hinting is for the device to implement the IO Advice Hints Grouping mode page. I wrote some code to support that but no vendors that I know of ended up actually shipping an implementation. A few implemented my older I/O class proposal but didn't ship that either despite really convincing performance results. If Randall has access to a device which implements hinting, I'd love to know more. -- Martin K. Petersen Oracle Linux Engineering