Messages in this thread | | | Subject | Re: [PATCH v3 0/7] iommu: Allow IOVA rcache range be configured | From | Lu Baolu <> | Date | Wed, 2 Jun 2021 12:37:20 +0800 |
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On 6/1/21 10:29 PM, John Garry wrote: > For streaming DMA mappings involving an IOMMU and whose IOVA len regularly > exceeds the IOVA rcache upper limit (meaning that they are not cached), > performance can be reduced. > > This is much more pronounced from commit 4e89dce72521 ("iommu/iova: Retry > from last rb tree node if iova search fails"), as discussed at [0]. > > IOVAs which cannot be cached are highly involved in the IOVA ageing issue, > as discussed at [1]. > > This series allows the IOVA rcache range be configured, so that we may > cache all IOVAs per domain, thus improving performance. > > A new IOMMU group sysfs file is added - max_opt_dma_size - which is used > indirectly to configure the IOVA rcache range: > /sys/kernel/iommu_groups/X/max_opt_dma_size > > This file is updated same as how the IOMMU group default domain type is > updated, i.e. must unbind the only device in the group first.
Could you explain why it requires singleton group and driver unbinding if the user only wants to increase the upper limit? I haven't dived into the details yet, sorry if this is a silly question.
Best regards, baolu
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