Hackbench is a benchmark and a stress test for the kernel scheduler that is part of the rt-tests suite. Hackbench also stresses parts of the memory subsystem through repeated setup and teardown of threads. Additionally, it stresses inter-process communication (e.g. local sockets, pipes) to a certain degree.
The purpose of the tool is to help identify bottlenecks in the system that should be eliminated or optimized.
Hackbench can be used to generate a system load while measuring latencies with Cyclictest. However, it cannot be used to accurately simulate the load generated by any given RT application because the program does not test communication with devices.