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Wed, 28 Jul 2021 11:38:41 +0100 From: John Garry Subject: Re: [bug report] iommu_dma_unmap_sg() is very slow then running IO from remote numa node To: Ming Lei References: <74537f9c-af5f-cd84-60ab-49ca6220310e@huawei.com> <9c929985-4fcb-e65d-0265-34c820b770ea@huawei.com> <0adbe03b-ce26-e4d3-3425-d967bc436ef5@arm.com> <6ceab844-465f-3bf3-1809-5df1f1dbbc5c@huawei.com> Message-ID: Date: Wed, 28 Jul 2021 11:38:18 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Originating-IP: [10.47.27.80] X-ClientProxiedBy: lhreml706-chm.china.huawei.com (10.201.108.55) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Cc: Robin Murphy , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, iommu@lists.linux-foundation.org, Will Deacon , linux-arm-kernel@lists.infradead.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 28/07/2021 02:32, Ming Lei wrote: > On Mon, Jul 26, 2021 at 3:51 PM John Garry wrote: >> On 23/07/2021 11:21, Ming Lei wrote: >>>> Thanks, I was also going to suggest the latter, since it's what >>>> arm_smmu_cmdq_issue_cmdlist() does with IRQs masked that should be most >>>> indicative of where the slowness most likely stems from. >>> The improvement from 'iommu.strict=0' is very small: >>> >> Have you tried turning off the IOMMU to ensure that this is really just >> an IOMMU problem? >> >> You can try setting CONFIG_ARM_SMMU_V3=n in the defconfig or passing >> cmdline param iommu.passthrough=1 to bypass the the SMMU (equivalent to >> disabling for kernel drivers). > Bypassing SMMU via iommu.passthrough=1 basically doesn't make a difference > on this issue. A ~90% throughput drop still seems to me to be too high to be a software issue. More so since I don't see similar on my system. And that throughput drop does not lead to a total CPU usage drop, from the fio log. Do you know if anyone has run memory benchmark tests on this board to find out NUMA effect? I think lmbench or stream could be used for this. Testing network performance in an equivalent fashion to storage could also be an idea. Thanks, John > > And from fio log, submission latency is good, but completion latency > is pretty bad, > and maybe it is something that writing to PCI memory isn't committed to HW in > time? _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu