Runtime & Environment Factors Attention to the runtime environment can make a critical difference to message latency statistics. Save Cycles & Reduce Process Switching Run low-latency applications on computers that are not encumbered by other processes. Competing processes could monopolize CPU or I/O resources at a critical moment. Process-switching can increase latency—whether the other processes are similar applications, cooperating applications, operating system daemons or utilities. • Run instances of similar applications on separate host computers. • Whenever possible, disable unneeded operating system daemons, such as UNIX cron and smtp. Clear the Network Crowded networks increase message latency. To speed delivery, ensure focused usage of network bandwidth. • Provision networks for high bandwidth availability. Avoid congestion. Network congestion can result in missed packets and retransmission, which slows message delivery. • Run low-latency applications on dedicated networks. • Limit the total message volume on the network. • Limit the number of sending applications on the network. • Reduce the sorting load on network interface cards by dividing traffic among multicast groups, targeting specific host computers. • Configure network routing hardware (rather than rvrd) for multicast transfer among subnets. Limit Duplication When several programs that include IPM run on the same host computer, then this duplication of IPM may be less efficient and more resource intensive than if those programs all connected to a single external daemon. Several factors (including the number of processor cores) can affect actual performance. Use empirical testing for each deployment.
