Messages in this thread | | | Date | Thu, 9 Jun 2022 18:54:01 +0100 | Subject | Re: [PATCH v3 3/4] scsi: core: Cap shost max_sectors according to DMA optimum mapping limits | From | John Garry <> |
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On 09/06/2022 18:18, Bart Van Assche wrote: >>> >>> SCSI host bus adapters that support 64-bit DMA may support much >>> larger transfer sizes than 128 KiB. >> >> Indeed, and that is my problem today, as my storage controller is >> generating DMA mapping lengths which exceeds 128K and they slow >> everything down. >> >> If you say that SRP enjoys best peformance with larger transfers then >> can you please test this with an IOMMU enabled (iommu group type DMA >> or DMA-FQ)? > > Hmm ... what exactly do you want me to test? Do you perhaps want me to > measure how much performance drops with an IOMMU enabled?
Yes, I would like to know of any performance change with an IOMMU enabled and then with an IOMMU enabled and including my series.
> I don't have > access anymore to the SRP setup I referred to in my previous email. But > I do have access to devices that boot from UFS storage. For these > devices we need to transfer 2 MiB per request to achieve full bandwidth.
ok, but do you have a system where the UFS host controller is behind an IOMMU? I had the impression that UFS controllers would be mostly found in embedded systems and IOMMUs are not as common on there.
Thanks, John
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