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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 D750FC6783C for ; Fri, 12 Oct 2018 10:47:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 693F32086A for ; Fri, 12 Oct 2018 10:47:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 693F32086A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728071AbeJLSTJ (ORCPT ); Fri, 12 Oct 2018 14:19:09 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:13626 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726665AbeJLSTI (ORCPT ); Fri, 12 Oct 2018 14:19:08 -0400 Received: from DGGEMS408-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 6906FFBBEE3F2; Fri, 12 Oct 2018 18:47:15 +0800 (CST) Received: from [127.0.0.1] (10.202.226.41) by DGGEMS408-HUB.china.huawei.com (10.3.19.208) with Microsoft SMTP Server id 14.3.399.0; Fri, 12 Oct 2018 18:47:10 +0800 From: John Garry Subject: Re: [PATCH 0/7] hisi_sas: Misc bugfixes and an optimisation patch To: "Martin K. Petersen" References: <1537801594-207139-1-git-send-email-john.garry@huawei.com> CC: , , , Message-ID: Date: Fri, 12 Oct 2018 11:47:05 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.226.41] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/10/2018 02:58, Martin K. Petersen wrote: > > John, > Hi Martin, >> However it does block us in future from enabling SCSI MQ in the driver. > > We're going to remove the legacy I/O path so I'm not particularly keen > on merging something that's going in the opposite direction. What I really meant was that we cannot expose multiple queues to upper layer, and nothing related to legacy IO path. > >> This is because the IPTT index must be a unique value per HBA. However, >> if we switched to SCSI MQ, the block layer tag becomes unique per queue, >> and not per HBA. > > That doesn't sound right. > Again, my wording my probably was not accurate. I meant that rq tag is not unqiue across all hw queues. As I mentioned in the thread that spawned from this, we actually can't expose multiple hw queues at the moment. And, if we did, we find a performance drop due to having to go back to manage this IPTT internally. So how to handle? We're going to continue to work towards exposing multiple queues to upper layer, but for the moment I think patch 6/7 is a good change. Please let me know. Thanks, John