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Message-ID: <YOhcOv1oOwm6fco+@T590>
Date: Fri, 9 Jul 2021 22:24:58 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Robin Murphy <robin.murphy@....com>
Cc: linux-nvme@...ts.infradead.org, Will Deacon <will@...nel.org>,
linux-arm-kernel@...ts.infradead.org,
iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [bug report] iommu_dma_unmap_sg() is very slow then running IO
from remote numa node
On Fri, Jul 09, 2021 at 11:26:53AM +0100, Robin Murphy wrote:
> On 2021-07-09 09:38, Ming Lei wrote:
> > Hello,
> >
> > I observed that NVMe performance is very bad when running fio on one
> > CPU(aarch64) in remote numa node compared with the nvme pci numa node.
> >
> > Please see the test result[1] 327K vs. 34.9K.
> >
> > Latency trace shows that one big difference is in iommu_dma_unmap_sg(),
> > 1111 nsecs vs 25437 nsecs.
>
> Are you able to dig down further into that? iommu_dma_unmap_sg() itself
> doesn't do anything particularly special, so whatever makes a difference is
> probably happening at a lower level, and I suspect there's probably an SMMU
> involved. If for instance it turns out to go all the way down to
> __arm_smmu_cmdq_poll_until_consumed() because polling MMIO from the wrong
> node is slow, there's unlikely to be much you can do about that other than
> the global "go faster" knobs (iommu.strict and iommu.passthrough) with their
> associated compromises.
Follows the log of 'perf report'
1) good(run fio from cpus in the nvme's numa node)
- 34.86% 1.73% fio [nvme] [k] nvme_process_cq ▒
- 33.13% nvme_process_cq ▒
- 32.93% nvme_pci_complete_rq ▒
- 24.92% nvme_unmap_data ▒
- 20.08% dma_unmap_sg_attrs ▒
- 19.79% iommu_dma_unmap_sg ▒
- 19.55% __iommu_dma_unmap ▒
- 16.86% arm_smmu_iotlb_sync ▒
- 16.81% arm_smmu_tlb_inv_range_domain ▒
- 14.73% __arm_smmu_tlb_inv_range ▒
14.44% arm_smmu_cmdq_issue_cmdlist ▒
0.89% __pi_memset ▒
0.75% arm_smmu_atc_inv_domain ▒
+ 1.58% iommu_unmap_fast ▒
+ 0.71% iommu_dma_free_iova ▒
- 3.25% dma_unmap_page_attrs ▒
- 3.21% iommu_dma_unmap_page ▒
- 3.14% __iommu_dma_unmap_swiotlb ▒
- 2.86% __iommu_dma_unmap ▒
- 2.48% arm_smmu_iotlb_sync ▒
- 2.47% arm_smmu_tlb_inv_range_domain ▒
- 2.19% __arm_smmu_tlb_inv_range ▒
2.16% arm_smmu_cmdq_issue_cmdlist ▒
+ 1.34% mempool_free ▒
+ 7.68% nvme_complete_rq ▒
+ 1.73% _start
2) bad(run fio from cpus not in the nvme's numa node)
- 49.25% 3.03% fio [nvme] [k] nvme_process_cq ▒
- 46.22% nvme_process_cq ▒
- 46.07% nvme_pci_complete_rq ▒
- 41.02% nvme_unmap_data ▒
- 34.92% dma_unmap_sg_attrs ▒
- 34.75% iommu_dma_unmap_sg ▒
- 34.58% __iommu_dma_unmap ▒
- 33.04% arm_smmu_iotlb_sync ▒
- 33.00% arm_smmu_tlb_inv_range_domain ▒
- 31.86% __arm_smmu_tlb_inv_range ▒
31.71% arm_smmu_cmdq_issue_cmdlist ▒
+ 0.90% iommu_unmap_fast ▒
- 5.17% dma_unmap_page_attrs ▒
- 5.15% iommu_dma_unmap_page ▒
- 5.12% __iommu_dma_unmap_swiotlb ▒
- 5.05% __iommu_dma_unmap ▒
- 4.86% arm_smmu_iotlb_sync ▒
- 4.85% arm_smmu_tlb_inv_range_domain ▒
- 4.70% __arm_smmu_tlb_inv_range ▒
4.67% arm_smmu_cmdq_issue_cmdlist ▒
+ 0.74% mempool_free ▒
+ 4.83% nvme_complete_rq ▒
+ 3.03% _start
Thanks,
Ming
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