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=-9.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 09A2AC433FE for ; Thu, 10 Dec 2020 14:02:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B93F123B85 for ; Thu, 10 Dec 2020 14:02:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389870AbgLJOCR (ORCPT ); Thu, 10 Dec 2020 09:02:17 -0500 Received: from szxga01-in.huawei.com ([45.249.212.187]:2089 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389750AbgLJN4o (ORCPT ); Thu, 10 Dec 2020 08:56:44 -0500 Received: from dggeme753-chm.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4CsFm91zPlzVmqm; Thu, 10 Dec 2020 21:55:05 +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 21:56:00 +0800 Subject: Re: [PATCH v2] vfio iommu type1: Improve vfio_iommu_type1_pin_pages performance To: Eric Farman , Cornelia Huck 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> <9e37b8d9-3654-5b89-e3b4-5e6ede736320@linux.ibm.com> From: "xuxiaoyang (C)" Message-ID: Date: Thu, 10 Dec 2020 21:56:00 +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: <9e37b8d9-3654-5b89-e3b4-5e6ede736320@linux.ibm.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 22:42, Eric Farman wrote: > > > On 12/9/20 6:54 AM, 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. > > This would be my concern too, but I don't have data off the top of my head to say one way or another... > >> >> Eric, any opinion? Do you maybe also happen to have a test setup that >> mimics workloads actually seen in the real world? >> > > ...I do have some test setups, which I will try to get some data from in a couple days. At the moment I've broken most of those setups trying to implement some other stuff, and can't revert back at the moment. Will get back to this. > > Eric > . Thank you for your reply. Looking forward to your test data. Regards, Xu