Re: [PATCH 7/9] IB/core: generic RDMA READ/WRITE API

Sagi Grimberg
2016-03-01T09:19:47Z

>>>> + if (rdma_rw_use_mr(qp->device, port_num)) {
>>>> + ret = rdma_rw_init_mr_wrs(ctx, qp, port_num, sg, sg_offset,
>>>> + remote_addr, rkey, dir);
>>>
>>> At some point I would like the iWARP IO to do no-mr for WRITE/dma_nents
>>> == 1, and WRITE/dma_nents <= max_send_sge for the device. I think this
>>> will help smaller iSER/NVMEF READ IOPs. I'm testing this out now on the
>>> NVMEF code, which is slightly different. If it proves out to better the
>>> performance, I'll post a follow-on patch...
>>
>> Is this possible given that pd->local_dma_lkey has only local
>> permissions?
>
> I think he means NVMe / SCSI READ commands, which use RDMA WRITE.
> For NVMe / SCSI WRITE commands that use RDMA READ all bets are off
> for iWarp, but at least it supports READ W/ INVALIDATE.

I interpreted "no-mr for WRITE/dma_nents == 1" as either RDMA_WRITE of
RDMA_READ with a single dma entry (and that part I didn't understand).
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