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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BF243C433EF for ; Thu, 9 Jun 2022 17:54:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238465AbiFIRyK (ORCPT ); Thu, 9 Jun 2022 13:54:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47404 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343666AbiFIRyI (ORCPT ); Thu, 9 Jun 2022 13:54:08 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DFFB231E53F; Thu, 9 Jun 2022 10:54:06 -0700 (PDT) Received: from fraeml715-chm.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4LJs7n4GZKz67xjL; Fri, 10 Jun 2022 01:50:29 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml715-chm.china.huawei.com (10.206.15.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 9 Jun 2022 19:54:03 +0200 Received: from [10.47.88.201] (10.47.88.201) 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 15.1.2375.24; Thu, 9 Jun 2022 18:54:02 +0100 Message-ID: <9b1d155e-28cc-08dc-5a5a-8580132575e7@huawei.com> Date: Thu, 9 Jun 2022 18:54:01 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH v3 3/4] scsi: core: Cap shost max_sectors according to DMA optimum mapping limits To: Bart Van Assche , , , , , , , , CC: , , , , , , , References: <1654507822-168026-1-git-send-email-john.garry@huawei.com> <1654507822-168026-4-git-send-email-john.garry@huawei.com> <31417477-953d-283e-808e-cf8701e820a8@huawei.com> <5b214e95-dd95-551a-496e-a2139a74e8eb@huawei.com> From: John Garry In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.88.201] X-ClientProxiedBy: lhreml727-chm.china.huawei.com (10.201.108.78) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-ide@vger.kernel.org On 09/06/2022 18:18, Bart Van Assche wrote: >>> >>> SCSI host bus adapters that support 64-bit DMA may support much >>> larger transfer sizes than 128 KiB. >> >> Indeed, and that is my problem today, as my storage controller is >> generating DMA mapping lengths which exceeds 128K and they slow >> everything down. >> >> If you say that SRP enjoys best peformance with larger transfers then >> can you please test this with an IOMMU enabled (iommu group type DMA >> or DMA-FQ)? > > Hmm ... what exactly do you want me to test? Do you perhaps want me to > measure how much performance drops with an IOMMU enabled? Yes, I would like to know of any performance change with an IOMMU enabled and then with an IOMMU enabled and including my series. > I don't have > access anymore to the SRP setup I referred to in my previous email. But > I do have access to devices that boot from UFS storage. For these > devices we need to transfer 2 MiB per request to achieve full bandwidth. ok, but do you have a system where the UFS host controller is behind an IOMMU? I had the impression that UFS controllers would be mostly found in embedded systems and IOMMUs are not as common on there. Thanks, John