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SubjectRe: [PATCH v2 0/4] Optimise 64-bit IOVA allocations
Hi Robin.

On Fri, Jul 21, 2017 at 12:41:57PM +0100, Robin Murphy wrote:
> Hi all,
> In the wake of the ARM SMMU optimisation efforts, it seems that certain
> workloads (e.g. storage I/O with large scatterlists) probably remain quite
> heavily influenced by IOVA allocation performance. Separately, Ard also
> reported massive performance drops for a graphical desktop on AMD Seattle
> when enabling SMMUs via IORT, which we traced to dma_32bit_pfn in the DMA
> ops domain getting initialised differently for ACPI vs. DT, and exposing
> the overhead of the rbtree slow path. Whilst we could go around trying to
> close up all the little gaps that lead to hitting the slowest case, it
> seems a much better idea to simply make said slowest case a lot less slow.

Do you have some numbers here? How big was the impact before these
patches and how is it with the patches?


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