[openib-general] RC v/s UD

[Michael S. Tsirkin]

With RC, you can send larger messages and hardware will perform the
fragmentation.
BTW, ibv_rc_pingpong/ibv_ud_pingpong are pingpong examples - they do not
attempt to measure maximum streaming bandwidth.

Look under the perftests directory for some benchmarks:
e.g. send_bw can measure bandwidth with sends.

Note that with RC, RDMA and SEND bandwidth can also mean different things.


Quoting r. john t <johnt1johnt2 at gmail.com>:
Subject: RC v/s UD

Hi,
 
I ran "ibv_rc_pingpong" and "ibv_ud_pingpong" utilities and found that RC gives
a BW of 4302 Mbit/sec and UD gives a BW of 2133 Mbit/sec on my setup (2 hosts
connected to a switch). So it seems UD is inefficient then RC (gives almost
half the BW as that of RC). Is this expected? Isnt it true that UD involves
less overheads then RC?
 
Are there ways to get maximum BW (close to RC) from UD?
 
Regards,
John T.

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