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Safety-critical systems depend on the temporal guarantees provided by schedulability analysis of hard real-time systems. Worst-case execution time analysis (WCET) is a necessary component in schedulability analysis of hard real-time systems. A central goal of WCET analysis is to produce a tight bound, since tighter bounds (generally) increase the schedulability of a system. Cache memory is an impediment to tight WCET analysis due to the variability it introduces into task systems. However, static modification of memory access patterns within mutable objects may increase cache-hits and reduce WCET. Herein, a mechanism for modifying and analyzing hard real-time tasks is proposed. The proposed mechanism leverages existing persistence analysis to identify sets of blocks to retain in cache during execution. Retention guarantees persistence, resulting in tighter WCET analysis.
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Handling write backs in multi-level cache analysis for WCET estimation
In this paper, we investigate how to soundly analyze multi-level caches that employ write-back policy at each level for worst-case execution time (WCET) estimation. To the best of our knowledge, there is only one existing approach for dealing with write backs in multi-level cache analysis. However, as shown in the paper, this existing approach is not sound. In order to soundly handle write backs, at a cache level, we need to consider whether a memory block is potentially dirty and when such a potentially dirty block may be evicted from the cache. To this end, we introduce a dirty attribute into persistence analysis for tracking dirty blocks, and over-approximate a write back window for each possible write back. Based on the overestimated write back occurring times, we propose an approach that can soundly deal with write backs in analysis of multi-level (unified) caches for WCET estimation. Possible write back costs are also integrated into path analysis. We evaluate the proposed approach on a set of benchmarks to demonstrate its effectiveness.
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- Award ID(s):
- 1739328
- PAR ID:
- 10069248
- Date Published:
- Journal Name:
- RTNS '17 Proceedings of the 25th International Conference on Real-Time Networks and Systems
- Page Range / eLocation ID:
- 208 to 217
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1145/3139258.3139269
