[bug report] iommu_dma_unmap_sg() is very slow then running IO from remote numa node

[John Garry]

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).

Thanks,
John