Messages in this thread | | | Date | Thu, 17 Aug 2023 11:36:18 -0700 | From | Nicolin Chen <> | Subject | Re: [PATCH v2] iommu/arm-smmu-v3: Add a user-configurable tlb_invalidate_threshold |
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On Wed, Aug 16, 2023 at 01:43:50PM -0700, Nicolin Chen wrote:
> When receiving an __arm_smmu_tlb_inv_range() call with a large size, there > could be a long latency at this function call: one part is coming from a > large software overhead in the routine of building commands, and the other > part is coming from CMDQ hardware consuming the large number of commands. > This latency could be significantly large on an SMMU that does not support > range invalidation commands, i.e. no ARM_SMMU_FEAT_RANGE_INV. > > One way to optimize this is to replace a large number of VA invalidation > commands with one single per-asid invalidation command, when the requested > size reaches a threshold. This threshold can be configurable depending on > the SMMU implementaion.
I'm rethinking about this size-based threshold, since what really affects the latency is the number of the invalidation commands in the request. So having an npages-based threshold might be optimal, though the idea and implementation would be similar.
Thanks Nicolin
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