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 E2ED4C433EF for ; Thu, 9 Jun 2022 08:01:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238417AbiFIIBB (ORCPT ); Thu, 9 Jun 2022 04:01:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55418 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240415AbiFIIBA (ORCPT ); Thu, 9 Jun 2022 04:01:00 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3ED075FDB; Thu, 9 Jun 2022 01:00:54 -0700 (PDT) Received: from fraeml743-chm.china.huawei.com (unknown [172.18.147.207]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4LJbxw3Jf7z6881w; Thu, 9 Jun 2022 15:56:04 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml743-chm.china.huawei.com (10.206.15.224) 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 10:00:52 +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 09:00:51 +0100 Message-ID: <5b214e95-dd95-551a-496e-a2139a74e8eb@huawei.com> Date: Thu, 9 Jun 2022 09:00:50 +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> 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 08/06/2022 22:07, Bart Van Assche wrote: > On 6/8/22 10:50, John Garry wrote: >> Please note that this limit only applies if we have an IOMMU enabled >> for the scsi host dma device. Otherwise we are limited by dma direct >> or swiotlb max mapping size, as before. > > 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)? Thanks, John