8
Figure 1 Transfer of Data
RDMA reduces demand on the host CPU by enabling applications to directly issue data
transfer request commands to the adapter without having to execute an operating system call
(referred to as "kernel bypass"). The RDMA request is issued from an application running on
one server to the local adapter through its API and that request, along with the application’s
data, is then carried over the network to the remote adapter. The remote adapter then places
the application’s data into the host’s memory without requiring operating system
involvement at either end. Since all of the information pertaining to the remote virtual
memory address is contained in the RDMA message itself, and host and remote memory
protection issues were checked during connection establishment, the operating systems do
not need to be involved in each message.
For each RDMA command, the Ammasso 1100 adapter implements all of the required
RDMA operations as well as the processing of the TCP/IP state machine, thus reducing
demand on the CPU and providing a significant advantage over standard adapters while
maintaining TCP/IP standards and functionality. (see Figure 2).
Server 1
Server 2
Network