Automatic Generation of Efficient Predictable Memory Patterns

Verifying firm real-time requirements gets increasingly complex, as the number of applications in embedded systems grows. Predictable systems reduce the complexity by enabling formal verification. However, these systems require predictable software and hardware components, which is problematic for resources with highly variable execution times, such as SDRAM controllers. A predictable SDRAM controller has been proposed that addresses this problem using predictable memory patterns, which are precomputed sequences of SDRAM commands. However, the memory patterns are derived manually, which is a time-consuming and error-prone process that must be repeated for every memory device, and may result in inefficient use of scarce and expensive bandwidth. This paper addresses this issue by proposing three algorithms for automatic generation of efficient memory patterns that provide different trade-offs between run-time of the algorithm and the bandwidth guaranteed by the controller. We experimentally evaluate the algorithms for a number of DDR2/DDR3 memories and show that an appropriate choice of algorithm reduces run-time to less than a second and increases the guaranteed bandwidth by up to 10.2%.