On 1/3/25 8:04 PM, Luis Chamberlain wrote:
Try aiming high for a single 2 MiB for a single IO on x86_64 on NVMe, that is currently not possible. At the max 128 NVMe number of DMA segments, and we have 4 KiB per DMA segment, for a 512 KiB IO limit. Should multi-page bvec enable to lift this?
4 KiB per DMA segment for NVMe? I think that the DMA segment size limit for PRP and SGL modes is much larger than 4 KiB. See also the
description of the CC.MPS parameter and PRP Lists in the NVMe base specification. From a system with an NVMe controller: $ cat /sys/block/nvme0n1/queue/max_segment_size 4294967295 Thanks, Bart.
