User Manual

Rev 4.70
Mellanox Technologies
148
14.4.8 ibv_read_lat
This is a more advanced version of ib_read_lat ,and contains more flags and features than the
older version and also improved algorithms. ibv_read_lat calculates the latency of RDMA read
operation of message_size between a pair of machines. One acts as a server and the other as a cli-
ent. They perform a ping pong benchmark on which one side RDMA reads the memory of the
other side only after the other side have read his memory. Each of the sides samples the CPU
clock each time they read the other side memory, to calculate latency. Read is available only in
RC connection mode (as specified in InfiniBand spec).
14.4.8.1
ibv_read_lat Synopsis
ibv_read_lat [-i(b_port) ib_port] [-m(tu) mtu_size] [-s(ize) message_size] [-t(x-
depth) tx_size] [-I(nline_size) inline size] [-u qp timeout] [-S(L) sl type] [-d
ib_device name] [-x gid index] [-n iteration_num] [-o(uts)
outstanding reads] [-e(vents) use events] [-
p(ort) PDT_port] [-a(ll)] [-V(ersion)] [-C report cycles] [-H
report histogram] [-U report unsorted] [-F CPU freq fail]
14.4.8.2 ibv_read_lat Options
The table below lists the various flags of the command.
-Q, --cq-mod Generate Cqe only after <--cq-mod> completion
-N, --no peak-bw Cancel peak-bw calculation (default with peak)
Table 43 - ibv_read_lat Flags and Options
Flag Description
-p, --port=<port> Listens on/connect to port <port> (default 18515)
-d, --ib-dev=<dev> Uses IB device <device guid> (default first device found)
-i, --ib-port=<port> Uses port <port> of IB device (default 1)
-m, --mtu=<mtu> The mtu size (default 1024)
-o, --outs=<num> The number of outstanding read/atom(default for ConnectX 16 (oth-
ers 4)
-s, --size=<size> The size of message to exchange (default 65536)
-a, --all Runs sizes from 2 till 2^23
-t, --tx-depth=<dep> The size of tx queue (default 100)
-n, --iters=<iters> The number of exchanges (at least 2, default 1000)
-u, --qp-timeout=<timeout> QP timeout. The timeout value is 4 usec * 2 ^(timeout), default 14
-S, --sl=<sl> The service level (default 0)
Table 42 - ibv_read_bw Flags and Options
Flag Description