97 Things Every Programmer Should Know

Chapter 41. Interprocess Communication Affects Application Response Time

Randy Stafford

RESPONSE TIME IS CRITICAL TO SOFTWARE USABILITY. Few things are as frustrating as waiting for some software system to respond, especially when our interaction with the software involves repeated cycles of stimulus and response. We feel as if the software is wasting our time and affecting our productivity. However, the causes of poor response time are less well appreciated, especially in modern applications. Much performance management literature still focuses on data structures and algorithms, issues that can make a difference in some cases but are far less likely to dominate performance in modern multitier enterprise applications.

When performance is a problem in such applications, my experience has been that examining data structures and algorithms isn’t the right place to look for improvements. Response time depends most strongly on the number of remote interprocess communications (IPCs) conducted in response to a stimulus. While there can be other local bottlenecks, the number of remote interprocess communications usually dominates. Each remote interprocess communication contributes some nonnegligible latency to the overall response time, and these individual contributions add up, especially when they are incurred in sequence.

A prime example is ripple loading in an application using object-relational ...