On 2/10/23 11:18?AM, Bart Van Assche wrote: > On 2/10/23 10:00, Kanchan Joshi wrote: >> 3. DMA cost: is high in presence of IOMMU. Keith posted the work[1], >> with block IO path, last year. I imagine plumbing to get a bit simpler >> with passthrough-only support. But what are the other things that must >> be sorted out to have progress on moving DMA cost out of the fast path? > > Are performance numbers available? > > Isn't IOMMU cost something that has already been solved? From https://www.usenix.org/system/files/conference/atc15/atc15-paper-peleg.pdf: "Evaluation of our designs under Linux shows that (1) > they achieve 88.5%?100% of the performance obtained > without an IOMMU". Sorry no, IOMMU cost is definitely not a solved problem, it adds considerable overhead. Caveat that I didn't read that paper, but speaking from practical experience. Let's not be naive here. -- Jens Axboe
