> On Dec 11, 2018, at 9:02 AM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > On Mon, Dec 10, 2018 at 11:29:45AM -0500, Chuck Lever wrote: >> Some devices advertise a large max_fast_reg_page_list_len >> capability, but perform optimally when MRs are significantly smaller >> than that depth -- probably when the MR itself is no larger than a >> page. >> >> By default, the RDMA R/W core API uses max_sge_rd as the maximum >> page depth for MRs. For some devices, the value of max_sge_rd is >> 1, which is also not optimal. Thus, when max_sge_rd is larger than >> 1, use that value. Otherwise use the value of the >> max_fast_reg_page_list_len attribute. >> >> I've tested this with a couple of devices, and it reproducibly >> improves the throughput of large I/Os by several percent. > > Can you list which devices for reference in the changelog? I have only three devices here. I can't make an exhaustive list. Besides, this is exactly how rdma_rw works. I thought this was common knowledge. -- Chuck Lever
