WCET analysis of multi-level set-associative instruction caches

With the advent of increasingly complex hardware in real-time embedded systems (processors with performance enhancing features such as pipelines, cache hierarchy, multiple cores), many processors now have a set-associative L2 cache. Thus, there is a need for considering cache hierarchies when validating the temporal behavior of real-time systems, in particular when estimating tasks' worst-case execution times (WCETs). To the best of our knowledge, there is only one approach for WCET estimation for systems with cache hierarchies [Mueller, 1997], which turns out to be unsafe for set-associative caches. In this paper, we highlight the conditions under which the approach described in [Mueller, 1997] is unsafe. A safe static instruction cache analysis method is then presented. Contrary to [Mueller, 1997] our method supports set-associative and fully associative caches. The proposed method is experimented on medium-size and large programs. We show that the method is most of the time tight. We further show that in all cases WCET estimations are much tighter when considering the cache hierarchy than when considering only the L1 cache. An evaluation of the analysis time is conducted, demonstrating that analysing the cache hierarchy has a reasonable computation time

The Heptane Static Worst-Case Execution Time Estimation Tool

Estimation of worst-case execution times (WCETs) is required to validate the temporal behavior of hard real time systems. Heptane is an open-source software program that estimates upper bounds of execution times on MIPS and ARM v7 architectures, offered to the WCET estimation community to experiment new WCET estimation techniques. The software architecture of Heptane was designed to be as modular and extensible as possible to facilitate the integration of new approaches. This paper is devoted to a description of Heptane, and includes information on the analyses it implements, how to use it and extend it

Changing Expectations, Same Perspective: Pre-service Teachers’ Judgments of Professional Efficacy

This two-part study tracks and measures the professional self-efficacy judgements of two cohorts of pre-service teachers (PST). In Part One, the GTCE’s Code of Conduct and Practice (GTCE, 2009) was used to help form an instrument which tracked changes in the professional self-efficacy judgements of 211 PST through a one-year graduate program. Judgements were sought from PST both about themselves, and importantly, also about practicing teachers in the profession. In Part Two, statements making up the new DfE Teaching Standards (DfE, 2011) were similarly used to form an instrument and used with a subsequent cohort of 416 PST. Outcomes showed that PST’s judgement of professional self-efficacy were extremely high on both occasions, and in nearly all cases, significantly more positive than their ratings for current serving teachers. Tracked through their one-year program, the self-judgements barely changed, although views of the practicing teaching increased markedly, although never quite reaching the levels of self-judgements. The detail and significance of these findings is analysed and discussed

Cache-Conscious Offline Real-Time Task Scheduling for Multi-Core Processors

Most schedulability analysis techniques for multi-core architectures assume a single Worst-Case Execution Time (WCET) per task, which is valid in all execution conditions. This assumption is too pessimistic for parallel applications running on multi-core architectures with local instruction or data caches, for which the WCET of a task depends on the cache contents at the beginning of its execution, itself depending on the task that was executed before the task under study. In this paper, we propose two scheduling techniques for multi-core architectures equipped with local instruction and data caches. The two techniques schedule a parallel application modeled as a task graph, and generate a static partitioned non-preemptive schedule. We propose an optimal method, using an Integer Linear Programming (ILP) formulation, as well as a heuristic method based on list scheduling. Experimental results show that by taking into account the effect of private caches on tasks\u27 WCETs, the length of generated schedules is significantly reduced as compared to schedules generated by cache-unaware scheduling methods. The observed schedule length reduction on streaming applications is 11% on average for the optimal method and 9% on average for the heuristic method

Sex, Gender, Sexuality and the Law: social and legal issues facing individuals, couples and families

In the past decade, people whose bodies, genders or sexualities differ from socially expected norms have become more visible and have been granted greater recognition within the law. Yet despite this, many service providers do not have a strong understanding of the social and legal issues that continue to have a significant impact on these diverse groups of people and their relationships and families. In order to address this knowledge gap, this book brings together research findings from often disparate disciplines into an accessible and useful form for practitioners, as well as for researchers, academics, students, and the general public. Part one defines key terms, and addresses the psychosocial and legal issues faced by trans or gender diverse, intersex, and/or non-heterosexual individuals. Part two looks at the psychosocial and legal aspects of couple relationships. Part three considers parenting and families. Part four discusses practical tips for professionals working with this client group, including specific content for lawyers and mediators. As a whole, this book both questions the presumed neutrality of the law, yet insists that it is possible for the law to play a key role in challenging cisgenderism and heterosexism

Predictable Code and Data Paging for Real Time Systems

There is a need for using virtual memory in real-time ap-plications: using virtual addressing provides isolation between concurrent processes; in addition, paging allows the execution of applications whose size is larger than main memory capac-ity, which is useful in embedded systems where main memory is expensive and thus scarce. However, virtual memory is gen-erally avoided when developing real-time and embedded appli-cations due to predictability issues. In this paper we propose a predictable paging system in which the page loading and page eviction points are selected at compile-time. The contents of main memory is selected using an Integer Linear Programming (ILP) formulation. Our approach is applied to code, static data and stack regions of individual tasks. We show that the time re-quired for selecting memory contents is reasonable for all ap-plications including the largest ones, demonstrating the scala-bility of our approach. Experimental results compare our ap-proach with a previous one, based on graph coloring. It shows that quality of page allocation is generally improved, with an average improvement of 30 % over the previous approach. An-other comparison with a state-of-the-art demand-paging sys-tem shows that predictability does not come at the price of per-formance loss. 1

Estimation of Cache Related Migration Delays for Multi-Core Processors with Shared Instruction Caches

International audienceMulti-core architectures, which have multiple processors on a single chip, have been adopted by most chip manufacturers. In most such architectures, the different cores have private caches and also shared on-chip caches. For real-time systems to exploit multi-core architectures, it is required to obtain both tight and safe estimations of a number of metrics required to validate the system temporal behaviour in all situations, including the worst-case: tasks worst-case execution times (WCET), preemption delays and migration delays. Estimating such metrics is very challenging because of the possible interferences between cores due to shared hardware resources such as shared caches, memory bus, etc. In this paper, we propose a new method to estimate worst-case cache reload cost due to a task migration between cores. Safe estimations of the so-called Cache- Related Migration Delay (CRMD) are obtained through static code analysis. Experimental results demonstrate the practicality of our approach by comparing predicted worstcase CRMDs with those obtained by a naive approach. To the best of our knowledge, our method is the first one to provide safe upper bounds of cache-related migration delays in multi-core architectures with shared instruction cache

Comets 12^{12}CO+^+ and 13^{13}CO+^+ fluorescence models for measuring the 12^{12}C/13^{13}C isotopic ratio in CO+^+

Context: CO is an abundant species in comets, creating CO$^+$ ion with emission lines that can be observed in the optical spectral range. A good modeling of its fluorescence spectrum is important for a better measurement of the CO$^+$ abundance. Such a species, if abundant enough, can also be used to measure the $^{12}$C/$^{13}$C isotopic ratio. Aims: This study uses the opportunity of a high CO content observed in the comet C/2016 R2 (PanSTARRS), that created bright CO$^{+}$ emission lines in the optical range, to build and test a new fluorescence model of this species and to measure for the first time the $^{12}$C/$^{13}$C isotopic ratio in this chemical species with ground-based observations. Methods: Thanks to laboratory data and theoretical works available in the scientific literature we developed a new fluorescence model both for $^{12}$CO$^+$ and $^{13}$CO$^+$ ions. The $^{13}$CO$^+$ model can be used for coadding faint emission lines and obtain a sufficient signal-to-noise ratio to detect this isotopologue. Results: Our fluorescence model provides a good modeling of the $^{12}$CO$^+$ emission lines, allowing to publish revised fluorescence efficiencies. Based on similar transition probabilities for $^{12}$CO$^+$ and $^{13}$CO$^+$ we derive a $^{12}$C/$^{13}$C isotopic ratio of 73$\pm$20 for CO$^+$ in comet C/2016 R2. This value is in agreement with the solar system ratio of 89$\pm$2 within the error bars, making the possibility that this comet was an interstellar object unlikely.Comment: 11 pages, 8 figure

Field dependence of the electronic phase separation in Pr0.67Ca0.33MnO3 by small angle magnetic neutron scattering

We have studied by small angle neutron scattering the evolution induced by the application of magnetic field of the coexistence of ferromagnetism (F) and antiferromagnetism (AF) in a crystal of Pr$_{0.67}$Ca$_{0.33}$MnO$_3$. The results are compared to magnetic measurements which provide the evolution of the ferromagnetic fraction. These results show that the growth of the ferromagnetic phase corresponds to an increase of the thickness of the ferromagnetic ''cabbage'' sheets

Socio-Technological Characterization of Goat Industry at Tamarugal Province in Atacama Desert

The following article displays a study carried over the goat producers in the northern Tamarugal province in Chile, including the analysis of a survey that characterizes the technical capability of the industry mainly constituted by altiplanean natives communities, exposing the needs that the innovation system requires to be improved in order to boost the generation of added value products useful for project sustainability of these communities. As well, sensitization of the main social breakthroughs is made in order to develop an effective technology transfer to the communities to accomplish this aimed sustainability, through innovative use of the resources