Messages in this thread | | | Date | Wed, 8 Jun 2022 18:39:10 +0100 | Subject | Re: [PATCH v3 2/4] dma-iommu: Add iommu_dma_opt_mapping_size() | From | John Garry <> |
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On 08/06/2022 18:26, Bart Van Assche wrote: > On 6/6/22 02:30, John Garry via iommu wrote: >> +unsigned long iova_rcache_range(void) >> +{ >> + return PAGE_SIZE << (IOVA_RANGE_CACHE_MAX_SIZE - 1); >> +} > > My understanding is that iova cache entries may be smaller than > IOVA_RANGE_CACHE_MAX_SIZE and hence that even if code that uses the DMA > mapping API respects this limit that a cache miss can still happen.
Sure, a cache miss may still happen - however once we have stressed the system for a while then the rcaches fill up and don't fail often, or often enough to be noticeable compared to not having a cached IOVAs at all.
Thanks, john
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