[ofa-general] Very high CPU load during RDMA communication

[Bart Van Assche]

A newbie question about  InfiniBand: while running an RDMA bandwidth
test I noticed that the RDMA communication occupied 99% CPU time,
which is much more than I expected for InfiniBand. Is this normal or
should I check my setup ?

How the test was run:
(host 1) ib_rdma_bw -s 104857600
(host 2) time ib_rdma_bw -s 104857600 192.168.64.7
Transfer speed: 934 MB/s.
Elapsed time: 107.613s real, 107.150s user, 0.418s system.

Hardware: eight Intel Xeon CPU's (1.6GHz); 16 GB RAM; Mellanox MT25204
HCA (MemFree).
Software: 2.6.22.12 Linux kernel in 32-bit mode + OFED-1.2.5.4 userspace tools.

Regards,

Bart Van Assche.