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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 35557C2BA83 for ; Thu, 13 Feb 2020 10:07:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1323520873 for ; Thu, 13 Feb 2020 10:07:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729531AbgBMKHf (ORCPT ); Thu, 13 Feb 2020 05:07:35 -0500 Received: from lhrrgout.huawei.com ([185.176.76.210]:2419 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729428AbgBMKHf (ORCPT ); Thu, 13 Feb 2020 05:07:35 -0500 Received: from LHREML710-CAH.china.huawei.com (unknown [172.18.7.107]) by Forcepoint Email with ESMTP id 084F856825ACC3C28FFE; Thu, 13 Feb 2020 10:07:33 +0000 (GMT) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by LHREML710-CAH.china.huawei.com (10.201.108.33) with Microsoft SMTP Server (TLS) id 14.3.408.0; Thu, 13 Feb 2020 10:07:32 +0000 Received: from [127.0.0.1] (10.202.226.45) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Thu, 13 Feb 2020 10:07:32 +0000 Subject: Re: [PATCH 09/11] megaraid_sas: switch fusion adapters to MQ To: Sumit Saxena CC: Hannes Reinecke , "Martin K. Petersen" , Jens Axboe , Christoph Hellwig , James Bottomley , "Ming Lei" , Linux SCSI List , "linux-block@vger.kernel.org" , Hannes Reinecke References: <20191202153914.84722-1-hare@suse.de> <20191202153914.84722-10-hare@suse.de> <11034edd-732a-3dd5-0bdc-891b9de05e56@huawei.com> From: John Garry Message-ID: Date: Thu, 13 Feb 2020 10:07:31 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.226.45] X-ClientProxiedBy: lhreml720-chm.china.huawei.com (10.201.108.71) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 17/01/2020 11:18, Sumit Saxena wrote: >>>> or doing a performance test here. >>> Hi Hannes, >>> Hi Sumit, >>> Sorry for the delay in replying, I observed a few issues with this patchset: >>> >>> 1. "blk_mq_unique_tag_to_hwq(tag)" does not return MSI-x vector to >>> which IO submitter CPU is affined with. Due to this IO submission and >>> completion CPUs are different which causes performance drop for low >>> latency workloads. >> Hi Sumit, >> >> So the new code has: >> >> megasas_build_ldio_fusion() >> { >> >> cmd->request_desc->SCSIIO.MSIxIndex = >> blk_mq_unique_tag_to_hwq(tag); >> >> } >> >> So the value here is hw queue index from blk-mq point of view, and not >> megaraid_sas msix index, as you alluded to. > Yes John, value filled in "cmd->request_desc->SCSIIO.MSIxIndex" is HW > queue index. > >> So we get 80 msix, 8 are reserved for low_latency_index_start (that's >> how it seems to me), and we report other 72 as #hw queues = 72 to SCSI >> midlayer. >> >> So I think that this should be: >> >> cmd->request_desc->SCSIIO.MSIxIndex = >> blk_mq_unique_tag_to_hwq(tag) + low_latency_index_start; Can you possibly test performance again with this local change, or would you rather an updated patchset be sent? > Agreed, this should return correct HW queue index. >> Thanks, John