The graph models an ideal system that's perfectly scalable with the exception of garbage collection (GC). It plots the number of processors (x-axis) against throughput (y-axis). It contains six plotted lines labeled 1% GC, 2% GC, 3% GC, 10% GC, 20% GC, and 30% GC. Each line represents the changing throughput for an application that spends the specified percentage of time used for garbage collection on a uniprocessor system versus on a multiprocessor system. The graph is described in the text that precedes it.