On 6/9/22 01:00, John Garry wrote:
On 08/06/2022 22:07, Bart Van Assche wrote:
On 6/8/22 10:50, John Garry wrote:
Please note that this limit only applies if we have an IOMMU enabled for the scsi host dma device. Otherwise we are limited by dma direct or swiotlb max mapping size, as before.

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? 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.


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