From mboxrd@z Thu Jan 1 00:00:00 1970 From: swise@opengridcomputing.com (Steve Wise) Date: Wed, 8 Feb 2017 09:41:03 -0600 Subject: [PATCH] nvme-rdma: Support 2 inline data SGEs for write commands. In-Reply-To: References: <1486507170-23285-1-git-send-email-parav@mellanox.com> <20170208082743.GB7629@lst.de> Message-ID: <030701d28221$c115d1d0$43417570$@opengridcomputing.com> > > > > This looks fine to me in general, but I'm a little curious how your arrived at > > that 2 number. Why not 4 or 8? > > Some adapters doesn't support more than 5 sges. So increasing it to 4 or 8 would > fail them. > Chuck reported 1 out of 3 adapters only support 3. Its likely due to min(send_sge, > recv_sge). > With total of 3 SGEs (64B cmd sge + data sges), WQE fits in 64 bytes size at the > provider driver level. So to strike balance between cache line usage and > performance, and to be nice to those adapters which has low SGE (either due to > min(send_sge, recv) or other otherwise, I picked 2 data sges. > > Side note: I have split out send and recv sge in other unrelated patch which is in > review internally from linux-rdma tree. I'm looking forward to this patch since cxgb4 has max_recv_sge of 4 and max_send_sge of 17! Steve.