[LU-14803] Activate relaxed ordering optimization on MOFED cards

• Type: Improvement
• Resolution: Unresolved
• Priority: Minor
• Assignee: Etienne Aujames
• Reporter: Etienne Aujames

Description

IB access flags "IB_ACCESS_RELAXED_ORDERING/IBV_ACCESS_RELAXED_ORDERING" was added in 5.6 (commit 2233c6609c11146ed1a26eec2e4335131077a608: "RDMA/uverbs: Add new relaxed ordering memory region access flag") and in MOFED-5.0-1.

Since MOFED 5.1-0.6.6.0, "relaxed ordering" PCI feature is supported for ConnectX-4 and above:

Relaxed ordering is a PCIe feature which allows flexibility in the transaction order over the PCIe. This reduces the number of retransmissions on the lane, and increases performance up to 4 times.
[...]

ref: https://docs.mellanox.com/display/MLNXOFEDv531050/Release+Notes+Change+Log+History

The following patch add the flag IB_ACCESS_RELAXED_ORDERING to ib access flags and add ko2iblnd parameter "ib_relaxed_ordering" to deactivate/activate the feature (if the driver or kernel have buggy implementation).