Optimal static WCET-aware scratchpad allocation of program code

• Published in: 2009 46th ACM/IEEE Design Automation Conference pp. 732 - 737
• Main Authors: Falk, Heiko, Kleinsorge, Jan C.
• Format: Conference Proceeding
• Language: English
• Published: New York, NY, USA ACM 26.07.2009; IEEE
• Series: ACM Conferences
• Subjects: Computer science; Computer systems organization > Embedded and cyber-physical systems; Computer systems organization > Real-time systems; Costs; Design optimization; Embedded system; Energy efficiency; Optimizing compilers; Product design; Real time systems; Safety; Scanning probe microscopy; Scratchpad Allocation; Software and its engineering > Software notations and tools > Compilers; WCET; scratchpad allocation; WCET
• ISBN: 9781605584973; 1605584975
• ISSN: 0738-100X
• DOI: 10.1145/1629911.1630101

Caches are notorious for their unpredictability. It is difficult or even impossible to predict if a memory access will result in a definite cache hit or miss. This unpredictability is highly undesired especially when designing real-time systems where the worst-case execution time (WCET) is one of the key metrics. Scratchpad memories (SPMs) have proven to be a fully predictable alternative to caches. In contrast to caches, however, SPMs require dedicated compiler support. This paper presents an optimal static SPM allocation algorithm for program code. It minimizes WCETs by placing the most beneficial parts of a program's code in an SPM. Our results underline the effectiveness of the proposed techniques. For a total of 73 realistic benchmarks, we reduced WCETs on average by 7.4% up to 40%. Additionally, the run times of our ILP-based SPM allocator are negligible.