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 7B0ACC433DF for ; Wed, 8 Jul 2020 13:02:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5130120774 for ; Wed, 8 Jul 2020 13:02:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729316AbgGHNCi (ORCPT ); Wed, 8 Jul 2020 09:02:38 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:2442 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728918AbgGHNCh (ORCPT ); Wed, 8 Jul 2020 09:02:37 -0400 Received: from lhreml724-chm.china.huawei.com (unknown [172.18.7.106]) by Forcepoint Email with ESMTP id 6303BD8543793A5CD515; Wed, 8 Jul 2020 14:02:36 +0100 (IST) Received: from [127.0.0.1] (10.210.171.111) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.1913.5; Wed, 8 Jul 2020 14:02:35 +0100 From: John Garry Subject: Re: [PATCH 0/4] iommu/arm-smmu-v3: Improve cmdq lock efficiency To: , CC: , , , , , , References: <1592846920-45338-1-git-send-email-john.garry@huawei.com> Message-ID: Date: Wed, 8 Jul 2020 14:00:54 +0100 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: <1592846920-45338-1-git-send-email-john.garry@huawei.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.210.171.111] X-ClientProxiedBy: lhreml709-chm.china.huawei.com (10.201.108.58) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/06/2020 18:28, John Garry wrote: Hi, Can you guys let me know if this is on the radar at all? I have been talking about this performance issue since Jan, and not getting anything really. thanks > As mentioned in [0], the CPU may consume many cycles processing > arm_smmu_cmdq_issue_cmdlist(). One issue we find is the cmpxchg() loop to > get space on the queue takes approx 25% of the cycles for this function. > > This series removes that cmpxchg(). > > For my NVMe test with 3x NVMe SSDs, I'm getting a ~24% throughput > increase: > Before: 1310 IOPs > After: 1630 IOPs > > I also have a test harness to check the rate of DMA map+unmaps we can > achieve: > > CPU count 32 64 128 > Before: 63187 19418 10169 > After: 93287 44789 15862 > > (unit is map+unmaps per CPU per second) > > [0] https://lore.kernel.org/linux-iommu/B926444035E5E2439431908E3842AFD24B86DB@DGGEMI525-MBS.china.huawei.com/T/#ma02e301c38c3e94b7725e685757c27e39c7cbde3 > > John Garry (4): > iommu/arm-smmu-v3: Fix trivial typo > iommu/arm-smmu-v3: Calculate bits for prod and owner > iommu/arm-smmu-v3: Always issue a CMD_SYNC per batch > iommu/arm-smmu-v3: Remove cmpxchg() in arm_smmu_cmdq_issue_cmdlist() > > drivers/iommu/arm-smmu-v3.c | 233 +++++++++++++++++++++++------------- > 1 file changed, 151 insertions(+), 82 deletions(-) >