Now that we’ve looked at the performance of several lower-level subsystems, the CPU, memory, and the I/O subsystem, it’s time to put the parts together to build high-performance user interfaces. That means both drawing those user interfaces quickly, and also putting everything together so the application reacts quickly to user requests.
When we speak of a high-performance user interface, we usually mean one that is responsive, meaning it responds quickly to a user action. How quickly? Well, in general as quickly as possible, but there are actually specific perceptual thresholds that delineate qualitative differences in user perception. These limits are shown in Table 14.1.