On Fri, Apr 13, 2018 at 10:12:41AM -0700, Tushar Dave wrote:
> I guess there is nothing we need to do!
> On x86, in case of no intel iommu or iommu is disabled, you end up in
> swiotlb for DMA API calls when system has 4G memory.
> However, AFAICT, for 64bit DMA capable devices swiotlb DMA APIs do not
> use bounce buffer until and unless you have swiotlb=force specified in
> kernel commandline.

Sure.  But that means very sync_*_to_device and sync_*_to_cpu now
involves an indirect call to do exactly nothing, which in the workload
Jesper is looking at is causing a huge performance degradation due to

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