InfiniBand Network Architecture

RDMA Read Relaxed Ordering Rules

Writes Can Complete Faster Than Reads

For the following reasons, a QP can often complete a write to its local memory faster than it can read requested read data from its local memory:

• Inbound memory writes (e.g., a Send or an RDMA Write operation) to local memory are frequently handled by posting the memory write data into a fast posted memory write buffer. The fast-access buffer absorbs the data and the addresses it is to be written to, thereby accepting responsibility to write the data to memory at a later time. From the perspective of the device requesting the memory write (e.g., a local QP), the memory write thereby appears to complete very rapidly and the QP can move on to another operation.

• Memory reads