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 _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
