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
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
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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