License: Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported license (CC BY-NC-ND 3.0)
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DOI: 10.4230/OASIcs.WCET.2009.2286
URN: urn:nbn:de:0030-drops-22860
URL: http://dagstuhl.sunsite.rwth-aachen.de/volltexte/2009/2286/
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Plazar, Sascha ; Lokuciejewski, Paul ; Marwedel, Peter

WCET-aware Software Based Cache Partitioning for Multi-Task Real-Time Systems

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Abstract

Caches are a source of unpredictability since it is very difficult to predict if a memory access results in a cache hit or miss. In systems running multiple tasks steered by a preempting scheduler, it is even impossible to determine the cache behavior since interrupt-driven schedulers lead to unknown points of time for context switches. Partitioned caches are already used in multi-task environments to increase the cache hit ratio by avoiding mutual eviction of tasks from the cache.

For real-time systems, the upper bound of the execution time is one of the most important metrics, called the Worst-Case Execution Time (WCET). In this paper, we use partitioning of instruction caches as a technique to achieve tighter WCET estimations since tasks can not be evicted from their partition by other tasks. We propose a novel WCET-aware cache partitioning algorithm, which determines the optimal partition size for each task with focus on decreasing the system's WCET for a given set of possible partition sizes. Employing this algorithm, we are able to decrease the WCET depending on the number of tasks in a set by up to 34%. On average, reductions between 12% and 19% can be achieved.

BibTeX - Entry

@InProceedings{plazar_et_al:OASIcs:2009:2286,
  author =	{Sascha Plazar and Paul Lokuciejewski and Peter Marwedel},
  title =	{{WCET-aware Software Based Cache Partitioning for Multi-Task Real-Time Systems}},
  booktitle =	{9th International Workshop on Worst-Case Execution Time Analysis (WCET'09) },
  pages =	{1--11},
  series =	{OpenAccess Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-14-9},
  ISSN =	{2190-6807},
  year =	{2009},
  volume =	{10},
  editor =	{Niklas Holsti},
  publisher =	{Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{http://drops.dagstuhl.de/opus/volltexte/2009/2286},
  URN =		{urn:nbn:de:0030-drops-22860},
  doi =		{10.4230/OASIcs.WCET.2009.2286},
  note =	{also published in print by Austrian Computer Society (OCG) with ISBN 978-3-85403-252-6},
  annote =	{Keywords: WCET analysis, cache partitioning}
}

Keywords: WCET analysis, cache partitioning
Collection: 9th International Workshop on Worst-Case Execution Time Analysis (WCET'09)
Issue Date: 2009
Date of publication: 26.11.2009

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