Implementing time-predictable load and store operations

Scratchpads have been widely proposed as an alternative to caches for embedded systems. Advantages of scratchpads include reduced energy consumption in comparison to a cache and access latencies that are independent of the preceding memory access pattern. The latter property makes memory accesses time-predictable, which is useful for hard real-time tasks as the worst-case execution time (WCET) must be safely estimated in order to check that the system will meet timing requirements. However, data must be explicitly moved between scratchpad and external memory as a task executes in order to make best use of the limited scratchpad space. When dynamic data is moved, issues such as pointer aliasing and pointer invalidation become problematic. Previous work has proposed solutions that are not suitable for hard real-time tasks because memory accesses are not time-predictable. This paper proposes the scratchpad memory management unit (SMMU) as an enhancement to scratchpad technology. The SMMU...

• Type: Conference
• Year: 2009
• Where: EMSOFT
• Authors: Jack Whitham, Neil C. Audsley
• Keywords: EMSOFT 2009, Hard Real-time Tasks, Pointer Invalidation, Scratchpad, Software Engineering