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 B73CAC32788 for ; Thu, 11 Oct 2018 09:59:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 86D602087A for ; Thu, 11 Oct 2018 09:59:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 86D602087A 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 S1728091AbeJKR0B (ORCPT ); Thu, 11 Oct 2018 13:26:01 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:13644 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726035AbeJKR0B (ORCPT ); Thu, 11 Oct 2018 13:26:01 -0400 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id C97217DB53D02; Thu, 11 Oct 2018 17:59:24 +0800 (CST) Received: from [127.0.0.1] (10.202.226.41) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.399.0; Thu, 11 Oct 2018 17:59:17 +0800 Subject: Re: [PATCH 0/7] hisi_sas: Misc bugfixes and an optimisation patch To: Christoph Hellwig , "Martin K. Petersen" References: <1537801594-207139-1-git-send-email-john.garry@huawei.com> <20181011063603.GA3456@infradead.org> CC: , , , , Ming Lei , chenxiang From: John Garry Message-ID: <118d01db-05f4-a85b-850c-c4e5a5616a16@huawei.com> Date: Thu, 11 Oct 2018 10:59:11 +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: <20181011063603.GA3456@infradead.org> 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 07:36, Christoph Hellwig wrote: > On Wed, Oct 10, 2018 at 09:58:25PM -0400, Martin K. Petersen wrote: >>> 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. > Hmmm, well this is what I was told ... > blk-mq tags are always per-host (which has actually caused problems for > ATA, which is now using its own per-device tags). > So, for example, if Scsi_host.can_queue = 2048 and Scsi_host.nr_hw_queues = 16, then rq tags are still in range [0, 2048) for that HBA, i.e. invariant on queue count? > . > Thanks, John