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Documents authored by Betts, Adam

Document
DOI: 10.4230/OASIcs.WCET.2010.54
Hybrid measurement-based WCET analysis at the source level using object-level traces

Authors: Adam Betts, Nicholas Merriam, and Guillem Bernat

Published in: OASIcs, Volume 15, 10th International Workshop on Worst-Case Execution Time Analysis (WCET 2010)

Abstract
Hybrid measurement-based approaches to worst-case execution time (WCET) analysis combine measured execution times of small program segments using static analysis of the larger software structure. In order to make the necessary measurements, instrumentation code is added to generate a timestamped trace from the running program. The intrusive presence of this instrumentation code incurs a timing penalty, widely referred to as the probe effect. However, recent years have seen the emergence of trace capability at the hardware level, effectively opening the door to probe-free analysis. Relying on hardware support forces the WCET analysis to the object-code level, since that is all that is known by the hardware. A major disadvantage of this is that it is expensive for a typical software engineer to interpret the results, since most engineers are familiar with the source code but not the object code. Meaningful WCET analysis involves not just running a tool to obtain an overall WCET value but also understanding which sections of code consume most of the WCET in order that corrective actions, such as optimisation, can be applied if the WCET value is too large. The main contribution of this paper is a mechanism by which hybrid WCET analysis can still be performed at the source level when the timestamped trace has been collected at the object level by state-of-the-art hardware. This allows existing, commercial tools, such as \rapitime{}, to operate without the need for intrusive instrumentation and thus without the probe effect.
Cite as

Adam Betts, Nicholas Merriam, and Guillem Bernat. Hybrid measurement-based WCET analysis at the source level using object-level traces. In 10th International Workshop on Worst-Case Execution Time Analysis (WCET 2010). Open Access Series in Informatics (OASIcs), Volume 15, pp. 54-63, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2010)

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@InProceedings{betts_et_al:OASIcs.WCET.2010.54,
  author =	{Betts, Adam and Merriam, Nicholas and Bernat, Guillem},
  title =	{{Hybrid measurement-based WCET analysis at the source level using object-level traces}},
  booktitle =	{10th International Workshop on Worst-Case Execution Time Analysis (WCET 2010)},
  pages =	{54--63},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-21-7},
  ISSN =	{2190-6807},
  year =	{2010},
  volume =	{15},
  editor =	{Lisper, Bj\"{o}rn},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.WCET.2010.54},
  URN =		{urn:nbn:de:0030-drops-28255},
  doi =		{10.4230/OASIcs.WCET.2010.54},
  annote =	{Keywords: WCET analysis, hybrid analysis, trace}
}
Document
DOI: 10.4230/OASIcs.WCET.2010.136
The Mälardalen WCET Benchmarks: Past, Present And Future

Authors: Jan Gustafsson, Adam Betts, Andreas Ermedahl, and Björn Lisper

Published in: OASIcs, Volume 15, 10th International Workshop on Worst-Case Execution Time Analysis (WCET 2010)

Abstract
Modelling of real-time systems requires accurate and tight estimates of the Worst-Case Execution Time (WCET) of each task scheduled to run. In the past two decades, two main paradigms have emerged within the field of WCET analysis: static analysis and hybrid measurement-based analysis. These techniques have been succesfully implemented in prototype and commercial toolsets. Yet, comparison among the WCET estimates derived by such tools remains somewhat elusive as it requires a common set of benchmarks which serve a multitude of needs. The Maelardalen WCET research group maintains a large number of WCET benchmark programs for this purpose. This paper describes properties of the existing benchmarks, including their relative strengths and weaknesses. We propose extensions to the benchmarks which will allow any type of WCET tool evaluate its results against other state-of-the-art tools, thus setting a high standard for future research and development. We also propose an organization supporting the future work with the benchmarks. We suggest to form a committee with a responsibility for the benchmarks, and that the benchmark web site is transformed to an open wiki, with possibility for the WCET community to easily update the benchmarks.
Cite as

Jan Gustafsson, Adam Betts, Andreas Ermedahl, and Björn Lisper. The Mälardalen WCET Benchmarks: Past, Present And Future. In 10th International Workshop on Worst-Case Execution Time Analysis (WCET 2010). Open Access Series in Informatics (OASIcs), Volume 15, pp. 136-146, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2010)

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@InProceedings{gustafsson_et_al:OASIcs.WCET.2010.136,
  author =	{Gustafsson, Jan and Betts, Adam and Ermedahl, Andreas and Lisper, Bj\"{o}rn},
  title =	{{The M\"{a}lardalen WCET Benchmarks: Past, Present And Future}},
  booktitle =	{10th International Workshop on Worst-Case Execution Time Analysis (WCET 2010)},
  pages =	{136--146},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-21-7},
  ISSN =	{2190-6807},
  year =	{2010},
  volume =	{15},
  editor =	{Lisper, Bj\"{o}rn},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.WCET.2010.136},
  URN =		{urn:nbn:de:0030-drops-28336},
  doi =		{10.4230/OASIcs.WCET.2010.136},
  annote =	{Keywords: WCET analysis, benchmark}
}
Document
DOI: 10.4230/OASIcs.WCET.2005.807
Issues using the Nexus Interface for Measurement-Based WCET Analysis

Authors: Adam Betts and Guillem Berant

Published in: OASIcs, Volume 1, 5th International Workshop on Worst-Case Execution Time Analysis (WCET'05) (2007)

Abstract
Hardware debug interfaces such as Nexus have the power to unleash the full potential of measurement-based WCET approaches due to the passive nature in which timing data are collected from the processor. However, difficulties arise as a result of their restrictive nature, thus disallowing true user freedom in the selection of instrumenta- tion point placement. This paper elaborates on the problems encountered when using the Nexus inter- face in our measurement-based WCET framework, and how some of these issues can be resolved, par- ticularly that of irreducibility.
Cite as

Adam Betts and Guillem Berant. Issues using the Nexus Interface for Measurement-Based WCET Analysis. In 5th International Workshop on Worst-Case Execution Time Analysis (WCET'05). Open Access Series in Informatics (OASIcs), Volume 1, pp. 9-12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2007)

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@InProceedings{betts_et_al:OASIcs.WCET.2005.807,
  author =	{Betts, Adam and Berant, Guillem},
  title =	{{Issues using the Nexus Interface for Measurement-Based WCET Analysis}},
  booktitle =	{5th International Workshop on Worst-Case Execution Time Analysis (WCET'05)},
  pages =	{9--12},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-24-8},
  ISSN =	{2190-6807},
  year =	{2007},
  volume =	{1},
  editor =	{Wilhelm, Reinhard},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.WCET.2005.807},
  URN =		{urn:nbn:de:0030-drops-8076},
  doi =		{10.4230/OASIcs.WCET.2005.807},
  annote =	{Keywords: Nexus interface, Measurememt-Based WCET analysis}
}
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