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[23.128.96.18]) by mx.google.com with ESMTP id o18si2781252eje.528.2020.12.10.06.51.44; Thu, 10 Dec 2020 06:52:07 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389736AbgLJNzh (ORCPT + 99 others); Thu, 10 Dec 2020 08:55:37 -0500 Received: from szxga01-in.huawei.com ([45.249.212.187]:2088 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389696AbgLJNzc (ORCPT ); Thu, 10 Dec 2020 08:55:32 -0500 Received: from dggeme753-chm.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4CsFkf40FfzVnSn; Thu, 10 Dec 2020 21:53:46 +0800 (CST) Received: from [10.174.184.120] (10.174.184.120) by dggeme753-chm.china.huawei.com (10.3.19.99) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1913.5; Thu, 10 Dec 2020 21:54:41 +0800 Subject: Re: [PATCH v2] vfio iommu type1: Improve vfio_iommu_type1_pin_pages performance To: Cornelia Huck , Eric Farman CC: , , Alex Williamson , , , , , , , Zhenyu Wang , Zhi Wang References: <60d22fc6-88d6-c7c2-90bd-1e8eccb1fdcc@huawei.com> <4d58b74d-72bb-6473-9523-aeaa392a470e@huawei.com> <20201209125450.3f5834ab.cohuck@redhat.com> From: "xuxiaoyang (C)" Message-ID: Date: Thu, 10 Dec 2020 21:54:41 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.3.2 MIME-Version: 1.0 In-Reply-To: <20201209125450.3f5834ab.cohuck@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-GB Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.184.120] X-ClientProxiedBy: dggeme710-chm.china.huawei.com (10.1.199.106) To dggeme753-chm.china.huawei.com (10.3.19.99) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/12/9 19:54, Cornelia Huck wrote: > On Tue, 8 Dec 2020 21:55:53 +0800 > "xuxiaoyang (C)" wrote: > >> On 2020/11/21 15:58, xuxiaoyang (C) wrote: >>> vfio_pin_pages() accepts an array of unrelated iova pfns and processes >>> each to return the physical pfn. When dealing with large arrays of >>> contiguous iovas, vfio_iommu_type1_pin_pages is very inefficient because >>> it is processed page by page.In this case, we can divide the iova pfn >>> array into multiple continuous ranges and optimize them. For example, >>> when the iova pfn array is {1,5,6,7,9}, it will be divided into three >>> groups {1}, {5,6,7}, {9} for processing. When processing {5,6,7}, the >>> number of calls to pin_user_pages_remote is reduced from 3 times to once. >>> For single page or large array of discontinuous iovas, we still use >>> vfio_pin_page_external to deal with it to reduce the performance loss >>> caused by refactoring. >>> >>> Signed-off-by: Xiaoyang Xu > > (...) > >> >> hi Cornelia Huck, Eric Farman, Zhenyu Wang, Zhi Wang >> >> vfio_pin_pages() accepts an array of unrelated iova pfns and processes >> each to return the physical pfn. When dealing with large arrays of >> contiguous iovas, vfio_iommu_type1_pin_pages is very inefficient because >> it is processed page by page. In this case, we can divide the iova pfn >> array into multiple continuous ranges and optimize them. I have a set >> of performance test data for reference. >> >> The patch was not applied >> 1 page 512 pages >> no huge pages: 1638ns 223651ns >> THP: 1668ns 222330ns >> HugeTLB: 1526ns 208151ns >> >> The patch was applied >> 1 page 512 pages >> no huge pages 1735ns 167286ns >> THP: 1934ns 126900ns >> HugeTLB: 1713ns 102188ns >> >> As Alex Williamson said, this patch lacks proof that it works in the >> real world. I think you will have some valuable opinions. > > Looking at this from the vfio-ccw angle, I'm not sure how much this > would buy us, as we deal with IDAWs, which are designed so that they > can be non-contiguous. I guess this depends a lot on what the guest > does. > > Eric, any opinion? Do you maybe also happen to have a test setup that > mimics workloads actually seen in the real world? > > . > Thank you for your reply. The iova array constructed using pfn_array_alloc is continuous, and I think there will be some performance improvements here. Regards, Xu