2 Search Results for "Hernández, Carles"

Document
DOI: 10.4230/LIPIcs.ECRTS.2018.3
HWP: Hardware Support to Reconcile Cache Energy, Complexity, Performance and WCET Estimates in Multicore Real-Time Systems

Authors: Pedro Benedicte, Carles Hernandez, Jaume Abella, and Francisco J. Cazorla

Published in: LIPIcs, Volume 106, 30th Euromicro Conference on Real-Time Systems (ECRTS 2018)

Abstract
High-performance processors have deployed multilevel cache (MLC) systems for decades. In the embedded real-time market, the use of MLC is also on the rise, with processors for future systems in space, railway, avionics and automotive already featuring two or more cache levels. One of the most critical elements for MLC is the write policy that not only affects several key metrics such as performance, WCET estimates, energy/power, and reliability, but also the design of complexity-prone cache coherence protocol and cache reliability solutions. In this paper we make an extensive analysis of existing write policies, namely write-through (WT) and write-back (WB). In the context of the real-time domain, we show that no write policy is superior for all metrics: WT simplifies the design of the coherence and reliability solutions at the cost of performance, WCET, and energy; while WB improves performance and energy results, but complicates cache design. To take the best of each policy, we propose Hybrid Write Policy (HWP) a low-complexity hardware mechanism that reconciles the benefits of WT in terms of simplifying the cache design (e.g. coherence solution) and the benefits of WB in improved average performance and WCET estimates as the pressure on the interconnection network increases. Guaranteed performance results show that HWP scales with core count similar to WB. Likewise, HWP reduces cache energy usage of WT, to levels similar to those of WB. These benefits are obtained while retaining the reduced coherence complexity of WT, in contrast to high coherence costs under WB.
Cite as

Pedro Benedicte, Carles Hernandez, Jaume Abella, and Francisco J. Cazorla. HWP: Hardware Support to Reconcile Cache Energy, Complexity, Performance and WCET Estimates in Multicore Real-Time Systems. In 30th Euromicro Conference on Real-Time Systems (ECRTS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 106, pp. 3:1-3:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{benedicte_et_al:LIPIcs.ECRTS.2018.3,
  author =	{Benedicte, Pedro and Hernandez, Carles and Abella, Jaume and Cazorla, Francisco J.},
  title =	{{HWP: Hardware Support to Reconcile Cache Energy, Complexity, Performance and WCET Estimates in Multicore Real-Time Systems}},
  booktitle =	{30th Euromicro Conference on Real-Time Systems (ECRTS 2018)},
  pages =	{3:1--3:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-075-0},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{106},
  editor =	{Altmeyer, Sebastian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2018.3},
  URN =		{urn:nbn:de:0030-drops-90005},
  doi =		{10.4230/LIPIcs.ECRTS.2018.3},
  annote =	{Keywords: multilevel caches, real-time systems, multicores, WCET}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2017.16
Design and Implementation of a Time Predictable Processor: Evaluation With a Space Case Study

Authors: Carles Hernández, Jaume Abella, Francisco J. Cazorla, Alen Bardizbanyan, Jan Andersson, Fabrice Cros, and Franck Wartel

Published in: LIPIcs, Volume 76, 29th Euromicro Conference on Real-Time Systems (ECRTS 2017)

Abstract
Embedded real-time systems like those found in automotive, rail and aerospace, steadily require higher levels of guaranteed computing performance (and hence time predictability) motivated by the increasing number of functionalities provided by software. However, high-performance processor design is driven by the average-performance needs of mainstream market. To make things worse, changing those designs is hard since the embedded real-time market is comparatively a small market. A path to address this mismatch is designing low-complexity hardware features that favor time predictability and can be enabled/disabled not to affect average performance when performance guarantees are not required. In this line, we present the lessons learned designing and implementing LEOPARD, a four-core processor facilitating measurement-based timing analysis (widely used in most domains). LEOPARD has been designed adding low-overhead hardware mechanisms to a LEON3 processor baseline that allow capturing the impact of jittery resources (i.e. with variable latency) in the measurements performed at analysis time. In particular, at core level we handle the jitter of caches, TLBs and variable-latency floating point units; and at the chip level, we deal with contention so that time-composable timing guarantees can be obtained. The result of our applied study with a Space application shows how per-resource jitter is controlled facilitating the computation of high-quality WCET estimates.
Cite as

Carles Hernández, Jaume Abella, Francisco J. Cazorla, Alen Bardizbanyan, Jan Andersson, Fabrice Cros, and Franck Wartel. Design and Implementation of a Time Predictable Processor: Evaluation With a Space Case Study. In 29th Euromicro Conference on Real-Time Systems (ECRTS 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 76, pp. 16:1-16:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{hernandez_et_al:LIPIcs.ECRTS.2017.16,
  author =	{Hern\'{a}ndez, Carles and Abella, Jaume and Cazorla, Francisco J. and Bardizbanyan, Alen and Andersson, Jan and Cros, Fabrice and Wartel, Franck},
  title =	{{Design and Implementation of a Time Predictable Processor: Evaluation With a Space Case Study}},
  booktitle =	{29th Euromicro Conference on Real-Time Systems (ECRTS 2017)},
  pages =	{16:1--16:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-037-8},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{76},
  editor =	{Bertogna, Marko},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2017.16},
  URN =		{urn:nbn:de:0030-drops-71737},
  doi =		{10.4230/LIPIcs.ECRTS.2017.16},
  annote =	{Keywords: Processor design, performance guarantees, multicore, Industrial case studies, Application of real-time technology in realistic systems}
}
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