Tommaso Cucinotta Home Page

Filed patents

Tommaso Cucinotta. "Scheduling," Filed European Patent EP13305397. March 2013.

Tommaso Cucinotta. "System Security," Filed European Patent EP13305396. March 2013.

I. Bedini, Tommaso Cucinotta, Alessandra Sala, Bart Theeten. "Systems And Methods For Self-Adaptive Distributed Systems," Filed US Patent 13/853533. March 2013.

Tommaso Cucinotta, Davide Cherubini, Eric Jul. "Collaborative Uses of a Cloud Computing Confidential Domain of Execution," Filed US Patent 13/622007. September 2012.

Tommaso Cucinotta, Davide Cherubini. "System Control," Filed European Patent EP12360068. September 2012.

Tommaso Cucinotta, Davide Cherubini, Eric Jul. "Secure Data Processing," Filed European Patent EP12360045. June 2012.

Tommaso Cucinotta, Davide Cherubini, Eric Jul. "Secure Data Processing," Filed European Patent EP12360044. June 2012.

Tommaso Cucinotta. "Task Scheduling," Filed European Patent EP12360037. May 2012

Publications on international conference and workshop proceedings

Tommaso Cucinotta, Nilo Redini. "Access Control for the Pepys Internet-Wide File-System," in Proceedings of the 7th International Workshop on Plan 9 (IWP9 2012), November 14-16 2012, Dublin, Ireland. Abstract

This paper describes the Access Control Model realized for the novel Pepys distributed, Internet-wide, file-system. The model design has been widely inspired to various existing standards and best practices about access control and security in file-system access, but it also echoes peculiar basic principles characterizing the design of Pepys, as well as the πP protocol, over which Pepys itself relies. The paper also provides technical details about how the model has been realized on a Linux port of Pepys.

Kleopatra Konstanteli, Tommaso Cucinotta, Konstantinos Psychas, Theodora Varvarigou. "Admission Control for Elastic Cloud Services," in Proceedings of the 5th IEEE International Conference on Cloud Computing (IEEE CLOUD 2012), June 24-29 2012, Honolulu, Hawaii, USA. Abstract

This paper presents an admission control test for deciding whether or not it is worth to admit a set of services into a Cloud, and in case of acceptance, obtain the optimum allocation for each of the components that comprise the services. In the proposed model, the focus is on hosting elastic services the resource requirements of which may dynamically grow and shrink, depending on the dynamically varying number of users and patterns of requests. In finding the optimum allocation, the presented admission control test uses an optimization model, which incorporates business rules in terms of trust, eco-efficiency and cost, and also takes into account affinity rules the components that comprise the service may have. The proposed approach also allows for partial acceptance of a service and possible federation with other Cloud providers. By incorporating a probabilistic approach that relies on the actual probabilities of requiring extra elastic computing and networking capacity for the services at runtime, the model reduces the physical resources that need to be booked for elasticity reasons by promoting the allocation of more services on already used physical hosts. The output of the admission control test is the set of accepted services, and the allocated computing and networking capacity for the components that comprise them on the selected physical hosts and subnets. The problem was modeled on the General Algebraic Modeling System (GAMS) and solved under realistic provider’s settings that demostrate the efficiency of the proposed method.

Kleopatra Konstanteli, Tommaso Cucinotta, Theodora Varvarigou. "Probabilistic Admission Control for Elastic Cloud Computing," in Proceedings of the IEEE International Conference on Service-Oriented Computing and Applications (SOCA 2011), December 12-14 2011, Irvine, CA. Abstract

Focusing on elasticity, this paper tackles the problem of optimum allocation of elastic services on virtualized physical resources by incorporating a probabilistic approach in terms of availability guarantees. The proposed approach relies on the actual probabilities of needing extra computational requirements during runtime, which are incorporated into the admission control test, allowing for reducing the number of physical computational resources that need to be booked for elasticity reasons. The output of the optimization problem is the set of the admitted services, as well as the allocated computing capacity for each service component that comprise them on the physical hosts that have been selected in the optimal allocation pattern. The resulting optimization problem constitutes a probabilistic admission control test that also allows for proper trade-offs among business level objectives in terms of trust, eco-efficiency and cost, depending on their relative sensitivity as considered by the Cloud provider. The problem was modeled on the General Algebraic Modeling System (GAMS) and solved under realistic provider’s settings that demostrate the efficiency of the proposed method.

Tommaso Cucinotta, Gaetano Anastasi. "A Heuristic for Optimum Allocation of Real-Time Service Workflows," in Proceedings of the IEEE International Conference on Service-Oriented Computing and Applications (SOCA 2011), December 12-14 2011, Irvine, CA. Abstract

In this paper, the problem of optimum allocation of real-time service workflows over a set of heterogeneous resources is tackled. In previous works, this problem was formally stated in terms of a Mixed-Integer Non-Linear Programming optimization program, that could be solved by recurring to commercial solvers. However, due to the big dimension of the solution space to be searched, finding the absolutely optimum solution: might take too much time in order to be concretely useful; it may preclude the use of these techniques in large-scale infrastructures; it makes the technique hardly usable adaptively in response to corrective actions that may be needed when some bad event occurs while the services are running (e.g., hardware-level failures). Therefore, in this paper a heuristic algorithm based on graph-matching is introduced that may find very efficiently a reasonably good, albeit non-necessarily optimum, solution. The algorithm is described, and its performance assessed by a set of synthetic experiments.

Luca Abeni and Tommaso Cucinotta, "Efficient Virtualisation of Real-Time Activities," in Proceedings of the IEEE International Workshop on Real-Time Service-Oriented Architecture and Applications (RTSOAA 2011), December 12-14 2011, Irvine, CA. Abstract

Reservation-based scheduling has been proved to be an effective solution for serving virtual machines when some kind of real-time guarantees are required. However, the virtualisation mechanism and the algorithm used for implementing CPU reservations might have a large impact on the guarantees provided to tasks running inside the VMs. This paper presents an experimental evaluation of some different solutions, showing the different trade-offs and the advantages of using more advanced scheduling algorithms.

Gaetano F. Anastasi, Tommaso Cucinotta, Giuseppe Lipari, Marisol Garcia-Valls, "A QoS Registry for Adaptive Real-Time Service-Oriented Applications," in Proceedings of the IEEE International Workshop on Real-Time Service-Oriented Architecture and Applications (RTSOAA 2011), December 12-14 2011, Irvine, CA. Abstract

Real-time service-oriented applications are charac- terized by Quality of Service (QoS) requirements that cannot be properly managed by using classical real-time systems methodologies. In dynamic environments the QoS management can effectively leverage adaptive techniques, that provide flexibility and do not require a complex offline analysis. In turn, such techniques make a massive use of on-line collected data regarding the application performance and the resource requirements. Moreover, a common issue for adaptive systems is the one of deciding the initial configuration of the application and/or the run-time environment at the time of service instantiation. In this paper, we propose a QoS registry for coping with these issues and supporting the configuration of proper scheduling parameters in real-time Service Oriented Architectures (SOAs). The registry permits to gather QoS data related to different functional behaviors of applications, to predict the future trend based on data already collected and to permanently store such data for an effective reuse at the time of future re-instantiations. We have also built an implementation of such registry, computed its overhead costs and performed some experiments for showing the effectiveness in auto-tuning resource allocations for providing QoS guarantees in a real-time SOA.

Tommaso Cucinotta and Vivek Subramanian. "Characterization and analysis of pipelined applications on the Intel SCC," in Proceedings of the 4th Symposium of the Many-core Applications Research Community (MARC 2011), Potsdam, Germany, December 2011. Abstract

Many-core computing platforms can be used to parallelize computations by dividing the data to be processed into smaller chunks and processing them simultaneously on different cores. One possible approach in such parallelization is to set up a pipeline such that each smaller chunk of data passes in turn through all the processors involved. In this paper we examine some approaches to set up such a pipeline on the Intel SCC. We use a combination of the message passing and the shared memory capability of the SCC hardware through the interfaces provided by the RCCE library for our implementation. We build a model to analyze and compare the performance of such pipelines by measuring the total time for computation. This model is used to illustrate the effects of type of memory scheme used, ordering of cores in the pipeline and caching.

Tommaso Cucinotta. "Optimum Scalability Point for Parallelisable Real-Time Components," in Proceedings of the International Workshop on Synthesis and Optimization Methods for Real-time and Embedded Systems (SOMRES 2011), co-located with the 32nd IEEE Real-Time Systems Symposium (RTSS 2011), Vienna, Austria, November 29 - December 2, 2011. Abstract

Distributing the workload of computationally intensive software components across a set of homogeneous computing resources (nodes, hosts, processors, cores), for the purpose of allowing them to meet precise timing (response-time) constraints, is often a pain due to the difficulties in understanding how the software will actually scale. Often, such a problem is faced by recurring to a trial-and-error process. In this paper, a methodology is introduced to tackle the problem of finding the optimum number of processors for deploying parallelisable real-time software components. Basic building blocks of the methodology are: a generic performance model for the response-time of a parallel software component; a concrete procedure for tuning optimally the parameters of the model; the application of optimisation techniques that allow to compute what is the minimum allocation needed to meet precise deadline constraints, as well as the one that minimises the response-time; the consideration of multiple real-time (independent) components to be deployed on the same multi/many-core hardware.

Tommaso Cucinotta, Spyridon Gogouvitis, Kleopatra Konstanteli. "SLAs in Virtualized Cloud Computing Infrastructures with QoS Assurance," in Proceedings of the International Workshop on eContracting in the Clouds, co-located with the eChallenges 2011 Conference, Florence, Italy, October 27th 2011. Abstract

Cloud Computing is gaining momentum as one of the technologies that promises to subvert our own idea of computing. With an increasing usage of cloud applications and their consequent dependency from connectivity, the nowadays Personal Computer is becoming merely a mobile device acting as a front-end to on-line applications and services. This huge paradigm shift in computing is witnessed for example by big market players who announced the imminent launch of innovative products and Operating Systems (like Chrome notebooks and the accompanying Chrome OS2. by Google), which are capable of projecting the user into the network in a few seconds by booting and starting immediately a web browser and (mostly) nothing else. In such a challenging scenario, more and more of the applications that we traditionally used locally on our PC are being hosted on cloud infrastructures and operated remotely through the Internet. This includes not only batch tasks, but also interactive applications which need to operate inherently with good levels of responsiveness. In this paper, the challenging problem is discussed of how to ensure predictable levels of Quality of Service (QoS) to cloud applications across the multiple layers of a typical cloud infrastructure, and how a reasonable Service Level Agreement (SLA) management and enforcement policy might look like. The scope of this paper represents a hands-on experience that was gained by the authors realising the IRMOS real-time cloud-computing infrastructure in the context of the IRMOS European Project.

Tommaso Cucinotta, Fabio Checconi, Dhaval Giani. "Improving Responsiveness for Virtualized Networking Under Intensive Computing Workloads," in Proceedings of the 13th Real-Time Linux Workshop (RTLWS 2011), Prague, Czech Republic, October 2011. Abstract

In this paper the problem of providing network response guarantees to multiple Virtual Machines (VMs) co-scheduled on the same set of CPUs is tackled, where the VMs may have to host both responsive real-time applications and batch compute-intensive workloads. When trying to use a real-time reservation- based CPU scheduler for providing stable performance guarantees to such a VM, the compute-intensive workload would be scheduled better with high time granularities, to increase performance and reduce system overheads, whilst the real-time workload would need lower time granularities in order to keep the response-time under acceptable levels. The mechanism that is proposed in this paper mixes both concepts, allowing the scheduler to dynamically switch between fine-grain and coarse-grain scheduling intervals depending on whether the VM is performing network operations or not. A prototype implementation of the proposed mechanism has been realized for the KVM hypervisor when running on Linux, modifying a deadline-based real-time scheduling strategy for the Linux kernel developed previously. The gathered experimental results show that the proposed technique is effective in controlling the response-times of the real-time workload inside a VM while at the same time it allows for an efficient execution of the batch compute-intensive workload.

Juri Lelli, Giuseppe Lipari, Dario Faggioli, Tommaso Cucinotta, "An efficient and scalable implementation of global EDF in Linux," Proceedings of the 7th International Workshop on Operating Systems Platforms for Embedded Real-Time Applications (OSPERT 2011), Porto, Portugal, July 2011. Abstract

The increasing popularity of multi-core architectures is pushing researchers and developers to consider multi-cores for executing soft and hard real-time applications. Real-Time schedulers for multi processor systems can be roughly categorized into partitioned and global schedulers. The first ones are more adequate for hard real-time embedded systems, in which applications are statically loaded at start-up and rarely change at run-time. Thanks to automatic load balancing, global schedulers may be useful in open systems, where applications can join and leave the system at any time, and for applications with highly varying workloads.
Linux supports global and partitioned scheduling through its real-time scheduling class, which provides SCHED_FIFO and SCHED_RR fixed priority policies. Recently, the SCHED_DEADLINE policy was proposed that provides Earliest Deadline First scheduling with budget control. In this paper we propose a new implementation for global EDF scheduling which uses a heap global data structure to speed-up scheduling decisions. We also compare the execution time of the main scheduling functions in the kernel for four different implementations of global scheduling, showing that our implementation is as scalable and efficient as SCHED_FIFO.

Tommaso Cucinotta, Dario Faggioli, Giacomo Bagnoli, "Low-Latency Audio on Linux by Means of Real-Time Scheduling," Proceedings of the Linux Audio Conference (LAC 2011), Maynooth, Ireland, May 2011. Abstract

In this paper, we propose to use resource reservations scheduling and feedback-based allocation techniques for the provisioning of proper timeliness guarantees to audio processing applications. This al- lows real-time audio tasks to meet the tight timing constraints characterizing them, even if other in- teractive activities are present in the system. The JACK sound infrastructure has been modified, leveraging the real-time scheduler present in the Adaptive Quality of Service Architecture (AQuoSA). The effectiveness of the proposed approach, which does not require any modifiction to existing JACK clients, is validated through extensive experiments under different load conditions.

Sunil Kumar, Tommaso Cucinotta, Giuseppe Lipari, "A Latency Simulator for Many-core Systems," in Proceedings of the 44th Annual Simulation Symposium (ANSS 2011), part of the Spring Simulation Multiconference (SpringSim'11). Abstract

In this paper we present MCoreSim, an open-source simulation framework for massively parallel and many-core com- puting systems based on OMNeT++. The simulator supports tile-based architectures with distributed memory and mesh-based interconnects. Its primary purpose is to allow for in- vestigations on the impact of the heterogeneous in-chip communication latencies, as arising due to the network-on-a-chip structure of future and emerging many-core processors, on the performance of the hosted applications. We plan to use MCoreSim to study the variety of possible choices in realizing a suitable software stack for these systems, especially in terms of the choices at the kernel design level.

Tommaso Cucinotta, Fabio Checconi, George Kousiouris, Dimosthenis Kyriazis, Theodora Varvarigou, Alessandro Mazzetti, Zlatko Zlatev, Jury Papay, Michael Boniface, Sören Berger, Dominik Lamp, Thomas Voith, Manuel Stein, "Virtualised e-Learning with Real-Time Guarantees on the IRMOS Platform," in Proceedings of the IEEE International Conference on Service-Oriented Computing and Applications (SOCA 2010), Perth, Australia, December 2010. Best Paper Award! Abstract

In this paper we focus on how Quality of Service guarantees are provided to virtualised applications in the Cloud Computing infrastructure that is being developed in the context of the IRMOS European Project. Provisioning of proper timeliness guarantees to distributed real-time applications involves the careful use of real-time scheduling mechanisms at the virtual-machine hypervisor level, of QoS-aware networking protocols and of proper design methodologies and tools for stochastic modelling of the application. The paper focuses on how we applied these techniques to a case-study involving a real e- Learning mobile content delivery application that has been integrated into the IRMOS platform and its achieved performance.

Dimosthenis Kyriazis, Andreas Menychtas, George Kousiouris, Karsten Oberle, Thomas Voith, Michael Boniface, Eduardo Oliveros, Tommaso Cucinotta, Soren Berger, "A Real-time Service Oriented Infrastructure," in Proceedings of the Annual International Conference on Real-Time and Embedded Systems (RTES 2010), Singapore, November 2010. Abstract

The advancements in distributed computing have driven the emergence of service-based infrastructures that allow for on-demand provision of ICT assets. Taking into consideration the complexity of distributed environments, significant challenges exist in providing and managing the offered on-demand resources with the required level of Quality of Service (QoS), especially for real-time interactive and streaming applications. In this paper we propose an approach for providing real-time QoS guarantees by enhancing service oriented infrastructures with coherent and consistent real-time attributes at various levels (application, network, storage, processing). The approach considers the full lifecycle of service-based systems including service engineering, Service Level Agreement (SLA) negotiation and management, service provisioning and monitoring. QoS parameters at application, platform and infrastructure levels are given specific attention as the basis for provisioning policies in the context of temporal constraints.

Tommaso Cucinotta, Dhaval Giani, Dario Faggioli, Fabio Checconi, "Effective Real-Time Computing on Linux," in Proceedings of the 12th Real-Time Linux Workshop (RTLWS 2010), Nairobi, Kenya, October 2010. Abstract

In this paper we present an architecture design for supporting real time computing on Linux. This architecture focuses on improving the usability of real time capabilities for applications by providing a unified Application Programming Interface. Applications can therefore use it without having to know exactly what the underlying scheduling algorithm is. Still, the real-time computing capabilities of the platform may be exploited to the maximum extent. The main aim of the paper is to gather feedback from the community about the design and directions for development.

Tommaso Cucinotta, Dhaval Giani, Dario Faggioli and Fabio Checconi, "Providing Performance Guarantees to Virtual Machines using Real-Time Scheduling," in Proceedings of the 5^th Workshop on Virtualization and High-Performance Cloud Computing (VHPC 2010), Ischia (Naples), Italy, August 2010. Abstract

In this paper we tackle the problem of providing Quality of Service guarantees to virtualized applications, focusing on computing and networking guarantees. We propose a mechanism for providing temporal isolation based on a CPU real time scheduling strategy. This allows not only to have control over the individual virtual machine throughput, but also on the activation latency and response-time by which virtualized software components react to external events. We show experimental results gathered on a real system validating the approach.

Tommaso Cucinotta, Dario Faggioli, "An Exception Based Approach to Timing Constraints Violations in Real-Time and Multimedia Applications," in Proceedings of the IEEE Symposium on Industrial Embedded Systems (SIES 2010), Trento, Italy, July 2010. Abstract

Dario Faggioli, Giuseppe Lipari, Tommaso Cucinotta, "The Multiprocessor BandWidth Inheritance Protocol," in Proceedings of the 22^nd Euromicro Conference on Real-Time Systems (ECRTS 2010), Bruxelles, Belgium, July 2010. Abstract

In this paper we present the Multiprocessor Bandwidth Inheritance (M-BWI) protocol, an extension of the Bandwidth Inheritance (BWI) protocol to symmetric multiprocessor and multicore systems. Similarly to priority inheritance, M-BWI reduces priority inversion in reservation-based scheduling systems; it allows the coexistence of hard, soft and non-real-time tasks; it does not require any information on the temporal parameters of the tasks; hence, it is particularly suitable to open systems, where tasks can dynamically arrive and leave, and their temporal parameters are unknown or only partially known. Moreover, if it is possible to estimate such parameters as the worst-case execution time and the critical sections length, then it is possible to compute an upper bound to the task blocking time. Finally, the M-BWI protocol is neutral to the underlying scheduling scheme, since it can be implemented both in global and partitioned scheduling schemes.

Tommaso Cucinotta, Fabio Checconi, Luca Abeni, Luigi Palopoli, "Self-tuning Schedulers for Legacy Real-Time Applications," in Proceedings of the 5^th ACM European Conference on Computer Systems (EuroSys 2010), Paris, France, April 2010. Abstract

We present an approach for adaptive scheduling of soft realtime legacy applications (for which no timing information is exposed to the system). Our strategy is based on the combination of two techniques: 1) a real-time monitor that observes the sequence of events generated by the application to infer its activation period, 2) a feedback mechanism that adapts the scheduling parameters to ensure a timely execution of the application. By a thorough experimental evaluation of an implementation of our approach, we show its performance and its efficiency.

Tommaso Cucinotta, Kleopatra Konstanteli, Theodora Varvarigou, "Advance Reservations for Distributed Real-Time Workflows with Probabilistic Service Guarantees," in Proceedings of the IEEE International Conference on Service-Oriented Computing and Applications (SOCA 2009), Taipei, Taiwan, December 2009. Abstract

This paper addresses the problem of optimum allocation of distributed real-time workflows with probabilistic service guarantees over a Grid of physical resources made available by a provider. The discussion focuses on how such a problem may be mathematically formalised, both in terms of constraints and objective function to be optimized, which also accounts for possible business rules for regulating the deployment of the workflows. The presented formal problem constitutes a probabilistic admission control test that may be run by a provider in order to decide whether or not it is worth to admit new workflows into the system, and to decide what the optimum allocation of the workflow to the available resources is. Various options are presented which may be plugged into the formal problem description, depending on the specific needs of individual workflows.

Tommaso Cucinotta, Luca Abeni, Luigi Palopoli, Fabio Checconi, "The Wizard of OS: a Heartbeat for Legacy Multimedia Applications," in Proceedings of the 7^th IEEE Workshop on Embedded Systems for Real-Time Multimedia (ESTImedia 2009), Grenoble, France, October 2009. Abstract

Multimedia applications are often characterised by implicit temporal constraints but, in many cases, they are not programmed using any specialised real-time API. These Legacy applications have no way to communicate their temporal constraints to the OS kernel, and their quality of service (QoS), being necessarily linked to the temporal behaviour, fails to satisfy acceptable standards. In this paper we propose an innovative way for dealing with these applications, based on the combination of an on-line identification mechanism (which extracts from high-level observations such important parameters as the execution rate) and an adaptive scheduler (specialised for legacy applications) that identifies the correct amount of CPU needed by each application. Preliminary experimental results are reported, proving the effectiveness of the proposed idea in providing a widely used multimedia player on Linux with appropriate QoS guarantees, through an appropriate choice of the scheduling parameters. Finally, a detailed road-map is presented with the possible extensions to the approach.

Tommaso Cucinotta, Giuseppe Lipari, Luigi Palopoli, Luca Abeni, Rodrigo Santos, "Multi-level feedback control for Quality of Service Management," in Proceedings of the 14^th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA 2009), Palma de Mallorca, Spain, September 2009. Abstract

We consider the problem of power-aware Quality of Service (QoS) control for soft real-time embedded systems. Applications can have time-varying and scarcely known resource requirements, and can be activated and terminated at any time. However, they have the capability to switch among a discrete set of operation modes with different QoS levels and resource requirements. In addition, the platform provides resources with power-scaling capabilities and may be subject to power constraints. We present a QoS control architecture achieving optimum trade-offs between overall QoS and power consumption of the system, based on two nested control loops. The external one decides dynamically the optimum configuration for the system, in terms of application QoS modes and resource power modes, while the internal one modulates the resource allocations on a job by job basis, so as to respect timing constraints. We demonstrate the effectiveness of the approach by extensive simulations with trace data of real multimedia applications.

Fabio Checconi, Tommaso Cucinotta, Manuel Stein, "Real-Time Issues in Live Migration of Virtual Machines," in Proceedings of the 4^th Workshop on Virtualization and High-Performance Cloud Computing (VHPC 2009), Delft, The Netherlands, August 2009. Abstract

This paper addresses the issue of how to meet the strict timing constraints of (soft) real-time virtualized applications while the Virtual Machine (VM) hosting them is undergoing a live migration. To this purpose, it is essential that the resource requirements of a migration are identified in advance, that appropriate resources are reserved to the process, and that multiple VMs sharing the same resources are temporally isolated from each other. The first issue is dealt with by introducing a stochastic model for the migration process. The other ones by introducing a methodology making use of proper scheduling algorithms (for both CPU and network) that allow for reserving resource shares to individual VMs. Also, an extensive set of simulations have been done by using traces of a VLC video server virtualized by using KVM on Linux. The traces have been obtained by patching KVM at the kernel level, and the same patch constitutes an important step towards the complete implementation of the proposed technique. The obtained results highlight the benefits of the proposed approach.

Tommaso Cucinotta, Gaetano Anastasi, Luca Abeni "Respecting temporal constraints in virtualised services," in Proceedings of the 2^nd IEEE International Workshop on Real-Time Service-Oriented Architecture and Applications (RTSOAA 2009), Seattle, Washington, July 2009. Abstract

This paper reports some experiences in providing service guarantees to real-time (RT) applications running in a Virtual Machine (VM), showing how proper scheduling is a necessary condition for a predictable execution. In particular, resource reservation techniques allow to cope with some of the overhead and unpredictabilities experienced when executing multiple VMs on the same host.

Kleopatra Konstanteli, Dimosthenis Kyriazis, Theodora Varvarigou, Tommaso Cucinotta, Gaetano Anastasi, "Real-time guarantees in flexible advance reservations," in Proceedings of the 2^nd IEEE International Workshop on Real-Time Service-Oriented Architecture and Applications (RTSOAA 2009), Seattle, Washington, July 2009. Abstract

This paper deals with the problem of scheduling workflow applications with Quality of Service (QoS) constraints, comprising real-time and interactivity constraints, over a serviceoriented Grid network. A novel approach is proposed, in which high-level Advance Reservations, supporting flexible start and end time, are combined with low-level soft real-time scheduling, allowing for the concurrent deployment of multiple services on the same host while fulfilling their QoS requirements. By undertaking a stochastic approach, in which a-priori knowledge is leveraged about the probability of activation of the application workflows within the reserved time-frame, the proposed methodology allows for the achievement of various trade-offs between the need for respecting QoS constraints (user perspective) and the need for having good resource saturation levels (service provider perspective).

Fabio Checconi, Tommaso Cucinotta, Dario Faggioli, Giuseppe Lipari, "Hierarchical Multiprocessor CPU Reservations for the Linux Kernel," in Proceedings of the 5^th International Workshop on Operating Systems Platforms for Embedded Real-Time Applications (OSPERT 2009), Dublin, Ireland, June 2009. Abstract

This paper presents ongoing work in the development of a scheduling framework that will improve the service guarantees for soft real-time applications deployed on Linux. The scheduler has been designed around the current kernel infrastructure, trying to keep the changes minimal, and basing the scheduling policy on strong theoretical results. The main goal is to achieve hierarchical distribution of the available computing power on multiprocessor platforms, avoiding alterations to the existing user interfaces. The proposed framework exploits the hierarchical arrangement of tasks within groups and subgroups that is already possible within the Linux kernel. However, it adds the capability for each group to be assigned a precise fraction of the computing power available on all the processors, using existing uni-processor resource reservation techniques. Tasks are scheduled globally within each single group, and the partitions assigned to each group need not to be static, but can be dynamically balanced. Furthermore, the proposed mechanism can be used to support a variety of possible partitioning schemes using processor affinities.

Tommaso Cucinotta, Dario Faggioli, Alessandro Evangelista, "Exception-Based Management of Timing Constraints Violations for Soft Real-Time Applications," in Proceedings of the 5^th International Workshop on Operating Systems Platforms for Embedded Real-Time Applications (OSPERT 2009), Dublin, Ireland, June 2009. Abstract

This paper presents an open-source library for the C language supporting the specification and management of timing constraints within embedded soft real-time applications. The library provides a set of well-designed C macros that allow developers to associate timing constraints to code segments, and to deal with their violations through the wellestablished practise of exception-based management. After a brief overview of the requirements motivating the work, the exceptions library is presented. Then, the paper focuses on the specific macros that deal with the specification of deadline and execution-time constraints, with a few notes on how the library has been implemented. Finally, a few experimental results are shown in order to discuss the features and limitations of this approach, with the current implementation (on Linux) that relies almost completely on POSIX-compliant system calls.

Tommaso Cucinotta, Gaetano Anastasi, Luca Abeni, "Real-Time Virtual Machines," in Proceedings of the 29^th Real-Time System Symposium (RTSS 2008) -- Work in Progress Session, Barcelona, December 2008. Abstract

This paper tackles the problem of guaranteeing appropriate timeliness guarantees to real-time applications running in a virtualised Operating System. Preliminary experimental results are presented, highlighting how the appropriate use of well-established real-time scheduling strategies may be effective in facing with this challenging issue.

Tommaso Cucinotta, Luca Abeni, Sanjoy K. Baruah, Giuseppe Lipari, Luigi Palopoli, "Weighted Feedback Reclaiming for Multimedia Applications," in Proceedings of the 6^th IEEE Workshop on Embedded Systems for Real-Time Multimedia (ESTImedia 2008), Atlanta, Georgia, United States, October 2008. Abstract

Resource reservations are a very popular choice to schedule multimedia tasks. However, the high variability of the resource requirements hinders a static choice of the scheduling parameters. In this paper we address this problem by a combination of two strategies: adaptive reservations and resource reclaiming. The first one operates "locally" (using the information of a single task), the second one operates "globally" distributing unused bandwidth between the tasks. In this paper, we show by analytical results and by extensive simulations that the two techniques can be safely and usefully combined.

Dario Faggioli, Giuseppe Lipari, Tommaso Cucinotta, "An Efficient Implementation of the BandWidth Inheritance Protocol for Handling Hard and Soft Real-Time Applications in the Linux Kernel," in Proceedings of the 4^th International Workshop on Operating Systems Platforms for Embedded Real-Time Applications (OSPERT 2008), Prague, Czech Republic, July 2008. Abstract

This paper presents an improvement of the Bandwidth Inheritance Protocol, the natural extension of the well-known Priority Inheritance Protocol to resource reservation schedulers. The modified protocol allows for a better management of nested critical section, removes unneeded overheads in the management of task block and unblock events, and introduces a run-time deadlock detection mechanism at no cost. Also, an implementation of the new protocol on the Linux kernel is presented, along with experimental results gathered while running a synthetic application load. We show the introduced overhead is low and negligible for the applications of interest.

Tommaso Cucinotta "Access Control for Adaptive Reservations on Multi-User Systems," in Proceedings of the 14^th IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS 2008), St. Louis, MO, United States, April 2008. Abstract

This paper tackles the problem of defining an appropriate access control model for multi-user systems providing adaptive resource reservations to unprivileged users. Security requirements that need to be met by the system are identified, and an access control model satisfying them is proposed that also does not degrade the flexibility available on such systems due to the adaptive reservations framework. Also, the implementation of the proposed model within the AQuoSA architecture for Linux is briefly discussed.

Tommaso Cucinotta, Luigi Palopoli, "Feedback scheduling for pipelines of tasks," in Proceedings of the 10^th International Conference on Hybrid Systems: Computation and Control (HSCC 2007), Pisa, Italy, April 2007. Abstract

The problem analysed in this paper is how to effectively share a pool of resources amongst software applications consisting of pipelines of communicating tasks. The goal is to guarantee that specified Quality of Service (QoS) requirements are met. To this end, we advocate the use of a scheduling mechanism able to reserve fraction of the different resources to the competing tasks. Our work is focused on a feedback controlled adaptation of these fractions based on measurements of the QoS experienced by the application.

Tommaso Cucinotta, Luigi Palopoli, Luca Marzario, Antonio Mancina, Paolo Valente, "A unified framework for managing different resources with QoS guarantees," in Proceedings of the 1^st International Workshop on Operating System Platforms for Embedded Real-Time Applications (OSPERT 2005), Palma de Mallorca, Balearic Islands, Spain, July 2005. Abstract

This paper describes ongoing research activities aimed at developing a unified framework by which a general purpose operative system is able to support applications with Quality of Service requirements. The work is focused on a feedback based dynamic management of the resources required by an application, where each resource is handled through the use of a Resource Reservation paradigm. This allows applications to share the access to a resource by specifying the fraction of usage, where such fractions are dynamically adapted by the system on the basis of observations made on the hosted activities. Research in this area comprises development of both a theoretical framework for modelling applications and analysing the impact of control theoretic feedback strategies to the QoS experienced by applications, and a prototype implementation of an architecture with the ability of providing the needed functionality on a Linux Operative System.

Tommaso Cucinotta, Di Marco Di Natale, David Corcoran, "Breaking down architectural gaps in smart-card middleware design," in Proceedings of the 1^st International Conference on Trust and Privacy in Digital Business (TrustBus 2004), Zaragoza (Spain), September 2004, Springer-Verlag Lecture Notes in Computer Science (LNCS) 3184

Tommaso Cucinotta, Riccardo Brigo, Marco Di Natale, "Hybrid fingerprint matching on programmable smart cards," in Proceedings of the 1^st International Conference on Trust and Privacy in Digital Business (TrustBus 2004), Zaragoza (Spain), September 2004, Springer-Verlag Lecture Notes in Computer Science (LNCS) 3184

Tommaso Cucinotta, Luigi Palopoli, Luca Marzario, Giuseppe Lipari, Luca Abeni, "Adaptive reservations in a Linux environment," Proceedings of the 10^th IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS 2004), Toronto, Canada, May 2004

Tommaso Cucinotta, David Corcoran, Marco Di Natale, "A protocol for programmable smart cards," Trust and Privacy in Digital Business Workshop, Prague, Czech Republic, September 2003. In proceedings of the 14^th International Workshop on Database and Expert Systems Applications (DEXA 2003), IEEE Computer Society

Tommaso Cucinotta, Marco Di Natale, Shiva Kolachalam, "A Modular Open Source Architecture for ICT Services in the Public Administration," in Proceedings of the 2^nd EGOV Conference, Prague, Czech Republic, September 2003, Lecture Notes in Computer Science Serires, Vol. 2739

Tommaso Cucinotta, Gabriele Cecchetti, Gianluca Ferraro, "Adopting redundancy techniques for multicast stream authentication," in Proceedings of the 9^th IEEE Workshop on Future Trends of Distributed Computing Systems (FTDCS 2003), Puerto Rico, May 2003, IEEE Computer Society

Tommaso Cucinotta, Luigi Palopoli, Luca Marzario, "Stochastic feedback-based control of QoS in soft real-time systems," in Proceedings of the 43^rd IEEE Conference on Decision and Control (CDC 2004), Bahamas, December 2004. Abstract

This paper investigates application of feedback based control mechanisms to the problem of scheduling soft real-time tasks on a shared CPU. Each task has an execution time stochastically varying in time and it has to be provided with a specified level of Quality of Service (QoS). The problem of feedback control is formalised in the stochastic domain, by expressing QoS requirements in terms of properties to be satisfied by the stochastic process describing the evolution of the system state. We present several control schemes and address the fundamental problem of stochastic stability. Experimental results collected by a modified version of the Linux operating system show the effectiveness of the approach and its practical feasibility.

Luigi Palopoli, Tommaso Cucinotta, Antonio Bicchi, "Quality of service control for soft real-time applications," in Proceedings of the 42^nd IEEE Conference on Decision and Control (CDC 2003), Hawaii, USA, December 2003. Abstract

In this paper we present results obtained in the context of Quality of Service (QoS) control for soft real-time applications. The discussion addresses the issue of dynamically adjusting the bandwidth for a set of periodic tasks, when a reservation-based (RB) CPU scheduling policy is used. RB techniques are particularly suitable for this kind of applications since they allow an accurate mathematical modelling of the dynamic evolution of the QoS experienced by tasks. Based on this model, a control policy guaranteeing specified QoS levels for different tasks is illustrated, along with necessary and sufficient conditions for its existence. Moreover, the problem of steering a task QoS back into its nominal level is tackled, in response to deviations due to temporary overload conditions. Simulation results are reported, for the purpose of validating the approach.

Publications on international journals

Tommaso Cucinotta, Fabio Checconi, Luca Abeni, Luigi Palopoli, "Adaptive Real-Time Scheduling for Legacy Multimedia Applications," ACM Transactions on Embedded Computing Systems, Special Section on Embedded Systems for Real-Time Multimedia, Vol.11, No.4, December 2012. Abstract

Multimedia applications are often executed on standard Personal Computers. The absence of established standards has hindered the adoption of real-time scheduling solutions in this class of applications. Developers have adopted a wide range of heuristic approaches to achieve an acceptable timing behaviour but the result is often unreliable. We propose a mechanism to extend the benefits of real-time scheduling to legacy applications based on the combination of two techniques: 1) a real-time monitor that observes and infers the activation period of the application, and 2) a feedback mechanism that adapts the scheduling parameters to improve its real-time performance.

Dario Faggioli, Giuseppe Lipari, Tommaso Cucinotta. "Analysis and implementation of the multiprocessor bandwidth inheritance protocol," Springer Real-Time Systems Journal. September 2012. Abstract

The Multiprocessor Bandwidth Inheritance (M-BWI) protocol is an extension of the Bandwidth Inheritance (BWI) protocol for symmetric multiprocessor systems. Similar to Priority Inheritance, M-BWI lets a task that has locked a resource execute in the resource reservations of the blocked tasks, thus reducing their blocking time. The protocol is particularly suitable for open systems where different kinds of tasks dynamically arrive and leave, because it guarantees temporal isolation among independent subsets of tasks without requiring any information on their temporal parameters. Additionally, if the temporal parameters of the interacting tasks are known, it is possible to compute an upper bound to the interference suffered by a task due to other interacting tasks. Thus, it is possible to provide timing guarantees for a subset of interacting hard real-time tasks. Finally, the M-BWI protocol is neutral to the underlying scheduling policy: it can be implemented in global, clustered and semi-partitioned scheduling. After introducing the M-BWI protocol, in this paper we formally prove its isolation properties, and propose an algorithm to compute an upper bound to the interference suffered by a task. Then, we describe our implementation of the protocol for the LITMUS RT real-time testbed, and measure its overhead. Finally, we compare M-BWI against FMLP and OMLP, two other protocols for resource sharing in multiprocessor systems.

Rodrigo Santos, Giuseppe Lipari, Enrico Bini, Tommaso Cucinotta. "On-line schedulability tests for adaptive reservations in fixed priority scheduling," Springer Real-Time Systems Journal, Vol. 48, Issue 5, pp. 601-634. September 2012. Abstract

Adaptive reservation is a real-time scheduling technique in which each application is associated a fraction of the computational resource (a reservation) that can be dynamically adapted to the varying requirements of the application by using appropriate feedback control algorithms. An adaptive reservation is typically implemented by using an aperiodic server (e.g. sporadic server) algorithm with fixed period and variable budget. When the feedback law demands an increase of the reservation budget, the system must run a schedulability test to check if there is enough spare bandwidth to accommodate such increase. The schedulability test must be very fast, as it may be performed at each budget update, i.e. potentially at each instance of a task; yet, it must be as efficient as possible, to maximize resource usage. In this paper, we tackle the problem of performing an efficient on-line schedulability test for adaptive resource reservations in fixed priority schedulers. In the literature, a number of algorithms have been proposed for on-line admission control in fixed priority systems. We describe four of these tests, with increasing complexity and performance. In addition, we propose a novel on-line test, called Spare-Pot algorithm, which has been specifically designed for the problem at hand, and which shows a good cost/performance ratio compared to the other tests.

Juri Lelli, Dario Faggioli, Tommaso Cucinotta, Giuseppe Lipari. "An Experimental Comparison of Different Real-Time Schedulers on Multicore Systems," Elsevier Journal of Systems and Software (JSS), Vol. 85, Issue 10, pp. 2405-2416. October 2012. Abstract

In this work, an experimental comparison among the Rate Monotonic (RM) and Earliest Deadline First (EDF) multi-processor real-time schedulers is performed, with a focus on soft real-time systems. We generated random workloads of synthetic periodic task sets and executed them on a big multi-core machine, using Linux as Operating System, gathering an extensive amount of data related to their exhibited performance under various real-time scheduling strategies. The comparison involves the fixed-priority scheduler for multiprocessors as available in the Linux kernel (with priorities set so as to achieve RM), and on our own implementation of EDF, both configured in global, partitioned and clustered mode. The impact of the various scheduling strategies on the performance of the applications, as well as the generated scheduling overheads, are compared presenting an extensive set of experimental results. These provide a comprehensive view of the performance achievable by the different schedulers under various workload conditions.

Tommaso Cucinotta et al. "The IRMOS/ISONI Real-Time Cloud Infrastructure: a Virtualised e-Learning Case-Study," IEEE Communications Society Multimedia Communications Technical Committee (COMSOC MMTC) E-Letter, Special Issue On Multimedia Sensor Networks In Sustainable Systems, Vol. 6, No. 12, December 2011. Abstract

Nowadays, applications are increasingly developed and made available in distributed infrastructures, where users access their services from remote. In the Cloud Computing model, applications are developed by Software-as-a- Service (SaaS) providers, by means of tools made available by Platform-as-a-Service (PaaS) providers, for being deployed over the resources made available by Infrastructure-as-a-Service (IaaS) providers. The viability of IaaS is dependent on the use of virtualisation technologies, which allow for deploying multiple virtual machines (VMs), hosting multiple Operating Systems and services, over the same physical hosts, achieving an increased server consolidation level. In this evolving scenario, more and more distributed applications with tight interactivity and timing requirements are being deployed over virtualised IaaS infrastructures. Unfortunately, when multiple VMs are deployed over the same physical resources (e.g., links and CPUs), the level of performance experienced by each VM is not stable any more, but it depends heavily on the overall workload imposed by the other VMs competing for the shared resources. However, using proper scheduling technologies and performance modelling techniques, it is possible to deploy virtualised distributed applications with a stable performance level, as being experimented with the virtualised Cloud Computing infrastructure developed in the IRMOS EU Project (http://www.irmosproject.eu/) In this paper, we show how these concepts have been practically applied to a real e-Learning application. A more extended discussion can be found in the original article appeared at the IEEE SOCA 2010 Conference.

Tommaso Cucinotta and Dario Faggioli. "Handling Timing Constraints Violations in Soft Real-Time Applications as Exceptions," Elsevier Journal of Systems and Software (JSS), December 2011. Abstract

In this paper, an exception-based programming paradigm is envisioned to deal with timing constraints violations occurring in soft real-time and multimedia applications written in the C language. In order to prove viability of the approach, a mechanism allowing to use such paradigm has been designed and implemented as an open-source library of C macros making use of the standard POSIX API (a few Linux-specific optimizations are also briefly discussed). The proposed approach has been validated by modifying mplayer, one of the most widely used multimedia player for Linux, so as to use the introduced library. An extensive experimental evaluation has been made, both when running the player alone and when mixing it with a workload of other synthetic real-time applications. In the latter case, different scheduling policies have been used, including both standard priority-based ones as available on the mainline Linux, and an experimental deadline-based one available as a separate patch. The shown results demonstrate how the exception-based paradigm is effective in improving the audio/video delay exhibited by the player achieving a superior performance and a dramatically better Quality of Experience as compared to the original heuristic frame-dropping mechanism of the player.

Ruslan Asaula, Tommaso Cucinotta, Gianluca Dini, Luigi Palopoli. "Trading security for control performance in distributed robotic applications," International Transactions on Systems Science and Applications (ITSSA), Vol. 7, No. 1/2, November 2011, pp. 26-39. Abstract

Networked embedded and control systems are largely used in factory automation for production and logistics tasks. In this application domain, security has become a prominent issue due to the critical consequences a cyber attack may have in terms of safety and financial losses. Unfortunately security solutions compete against control applications for the often scarce resources of embedded platforms. In this paper, we show how security can be dealt with as one of different Quality of Service dimensions and traded for control performance in an adaptive QoS management scheme. The system is able to respond to increased resource requirements or to changes in the risk level by reconfiguring the application modes and the security modes. We offer an explanatory case study to show how this idea is implemented.

Tommaso Cucinotta, Fabio Checconi, George Kousiouris, Kleopatra Konstanteli, Spyridon Gogouvitis, Dimosthenis Kyriazis, Theodora Varvarigou, Alessandro Mazzetti, Zlatko Zlatev, Juri Papay, Michael Boniface, Sören Berger, Dominik Lamp, Thomas Voith, Manuel Stein. "Virtualised e-Learning on the IRMOS Real-time Cloud," Springer Service Oriented Computing and Applications, 2011. DOI 10.1007/s11761-011-0089-4. Abstract

This paper presents the real-time virtualized Cloud infrastructure that was developed in the context of the IRMOS European Project. The paper shows how different concepts, such as real-time scheduling, QoS-aware network protocols, and methodologies for stochastic modelling and run-time provisioning, were practically combined to provide strong performance guarantees to soft real-time interactive applications in a virtualized environment.The efficiency of the IRMOS Cloud is demonstrated by two real interactive e-Learning applications, an e-Learning mobile content delivery application and a virtual world e-Learning application.

Tommaso Cucinotta, Luca Abeni, Luigi Palopoli, Giuseppe Lipari, "A robust mechanism for adaptive scheduling of multimedia applications," ACM Transactions on Embedded Computing Systems, Vol. 10, No. 4, November 2011. Abstract

We propose an adaptive scheduling technique to schedule highly dynamic multimedia tasks on a CPU. We use a combination of two techniques: the first one is a feedback mechanism to track the resource requirements of the tasks based on local observations. The second one is a mechanism that operates with a global visibility, reclaiming unused bandwidth. The combination proves very effective: resource reclaiming increases the robustness of the feedback, while the identification of the correct bandwidth made by the feedback increases the effectiveness of the reclamation. We offer both theoretical results and an extensive experimental validation of the approach.

George Kousiouris, Tommaso Cucinotta, Theodora Varvarigou. "The Effects of Scheduling, Workload Type and Consolidation Scenarios on Virtual Machine Performance and their Prediction through Optimized Artificial Neural Networks," Elsevier Journal of Systems & Software (JSS). DOI 10.1016/j.jss.2011.04.013, 2011. Abstract

The aim of this paper is to study and predict the effect of a number of critical parameters on the performance of Virtual Machines (VMs). These parameters include allocation percentages, real-time scheduling decisions and co-placement of VMs when these are deployed concurrently on the same physical node, as dictated by the server consolidation trend and the recent advances in the Cloud computing systems. Different combinations of VM workload types are investigated in relation to the aforementioned factors in order to find the optimal allocation strategies. What is more, different levels of memory sharing are applied, based on the coupling of VMs to cores on a multi-core architecture. For all the aforementioned cases, the effect on the score of specific benchmarks running inside the VMs is measured. Finally, a black box method based on genetically optimized Artificial Neural Networks is inserted in order to investigate the degradation prediction ability a priori of the execution and is compared to the linear regression method.

Michal Sojka, Pavel Pisa, Dario Faggioli, Tommaso Cucinotta, Fabio Checconi, Zdenek Hanzalek, Giuseppe Lipari, "Modular Software Architecture for Flexible Reservation Mechanisms on Heterogeneous Resources," Elsevier Journal of Systems Architecture (JSA), Vol. 57, Issue 4, pp. 366-382, April 2011. Abstract

Management, allocation and scheduling of heterogeneous resources for complex distributed real-time applications is a chal- lenging problem. Timing constraints of applications may be fulfilled by the proper use of real-time scheduling policies, admission control and enforcement of timing constraints. However, it is not easy to design basic infrastructure services that allow for easy access to the allocation of multiple heterogeneous resources in a distributed environment. In this paper, we present a middleware for providing distributed soft real-time applications with a uniform API for reserving heterogeneous resources with real-time scheduling capabilities in a distributed environment. The architecture relies on standard POSIX OS facilities, such as time management and standard TCP/IP networking services, and it is designed around CORBA, in order to facilitate modularity, flexibility and portability of the applications using it. However, real-time scheduling is supported by proper extensions at the kernel-level, plugged within the framework by means of dedicated resource managers. Our current implementation on Linux supports the reservation of the CPU, disk and network bandwidth. However, additional resource managers supporting alternative real-time schedulers for these resources, as well as additional types of resources, may be easily added. We present experimental results gathered on both synthetic applications and a real multimedia video streaming case study, showing the advantages deriving from the use of the proposed middleware. Finally, overhead figures are reported, showing the sustainability of the approach for a wide class of complex, distributed, soft real-time applications.

Dimosthenis Kyriazis, Andreas Menychtas, George Kousiouris, Karsten Oberle, Thomas Voith, Michael Boniface, Eduardo Oliveros, Tommaso Cucinotta, Soren Berger, "A Real-time Service Oriented Infrastructure," GSTF International Journal on Computing, Vol. 1, No. 2, ISSN 2010-2283, February 2011. Abstract

Kleopatra Konstanteli, Tommaso Cucinotta, Theodora Varvarigou, "Optimum Allocation of Distributed Service Workflows with Probabilistic Real-Time Guarantees," Springer Service Oriented Computing and Applications, Vol. 4, No. 4, December 2010. Abstract

This paper addresses the problem of optimum allocation of distributed real- time workflows with probabilistic service guarantees over a set of physical resources. The discussion focuses on how such a problem may be mathematically formalised, both in terms of constraints and objective function to be optimized, which also accounts for possible business rules for regulating the deployment of the workflows. The presented formal problem constitutes a probabilistic admission control test that may be run by a provider in order to decide whether or not it is worth to admit new workflows into the system, and to decide what the optimum allocation of the workflow to the available resources is. Various options are presented which may be plugged into the formal problem description, depending on the specific needs of individual workflows. The presented problem has been implemented using GAMS and has been tested under various solvers. An illustrative numerical example and an analysis of the results of the implemented model under realistic settings are presented.

Tommaso Cucinotta, Luigi Palopoli, Luca Abeni, Dario Faggioli, Giuseppe Lipari, "On the integration of application level and resource level QoS control for real-time applications," IEEE Transactions on Industrial Informatics, Vol. 6, No. 4, November 2010. Abstract

We consider a dynamic set of soft real-time applications using a set of shared resources. Each application can execute in different modes, each one associated with a level of Quality of Service (QoS). Resources, in their turn, have different modes, each one with a speed and a power consumption, and are managed by a Reservation Based scheduler enabling a dynamic allocation of the fraction of resources (bandwidth) assigned to each application. To cope with dynamic changes of the application, we advocate an adaptive resource allocation policy organised in two nested feedback loops. The internal loop operates on the scheduling parameter to obtain a resource allocation that meets the temporal constraints of the applications. The external loop operates on the QoS level of the applications and on the power level of the resources to strike a good trade-off between the global QoS and the energy consumption. This loop comes into play whenever the workload of the application exceeds the bounds that permit the internal loop to operate correctly, or whenever it decreases below a level that permit more aggressive choices for the QoS or substantial energy saving.

Tommaso Cucinotta, Luigi Palopoli, "QoS Control for Pipelines of Tasks Using Multiple Resources," IEEE Transactions on Computers, Vol. 53, No. 3, pp. 416--430, March 2010, IEEE Computer Society Digital Library. Abstract

We consider soft real-time applications organised as pipelines of tasks using resources of different type (communication, computation, storage). The applications are assumed to be periodically triggered and the different tasks communicate by unidirectional buffers. The problem we cope with is how to effectively share the resources so that some specified Quality of Service (QoS) requirements are met. The QoS considered here is tightly related to the end-to-end temporal behaviour of the application. To compensate for time-varying resource requirements, we advocate a distributed control approach whereby the scheduling parameters of each task are tuned depending on the temporal behaviour of the application measured by appropriate sensors. The use of real-time scheduling strategies enables a mathematically safe control design, in which the QoS requirements are translated into formal control goals, and formal proofs are provided on the ability of the controller to fulfil these goals. We also offer extensive simulations that validate the approach for multimedia applications.

Tommaso Cucinotta, Antonio Mancina, Gaetano Anastasi, Giuseppe Lipari, Leonardo Mangeruca, Roberto Checcozzo, Fulvio Rusinà, "A Real-time Service-Oriented Architecture for Industrial Automation," IEEE Transactions on Industrial Informatics, Vol. 5, n. 3, August 2009. Abstract

Industrial automation platforms are experiencing a paradigm shift. New technologies are making their way in the area, including embedded real-time systems, standard local area networks like Ethernet, Wi-Fi and ZigBee, standard IP-based communication protocols, standard Service Oriented Architectures (SOA) and Web Services. An automation system will be composed of flexible autonomous components with Plug & Play functionality, self configuration and diagnostic, and autonomic local control that communicate through standard networking technologies. However, the introduction of these new technologies raises many important problems that need to be properly solved, one of these being the need to support real-time and Quality of Service (QoS) for hard and soft real-time applications. This paper describes a Service-Oriented Architecture enhanced with real-time capabilities for Industrial Automation. The proposed architecture allows for negotiation of the QoS requested by clients to web services, and provides temporal encapsulation of individual activities. This way, it is possible to perform an a-priori analysis of the temporal behavior of each service, and to avoid unwanted interferences among components. After describing the architecture, experimental results gathered on a real implementation of the framework (which leverages AQuoSA, a soft real-time scheduler for the Linux kernel) are presented, showing the effectiveness of the proposed solution. The experiments were performed on simple case studies designed in the context of industrial automation applications.

Luigi Palopoli, Tommaso Cucinotta, Luca Marzario, Giuseppe Lipari, "AQuoSA - Adaptive Quality of Service Architecture," Software: Practice and Experience, April 2008, doi 10.1002/spe.883. Abstract

This paper presents an architecture for Quality of Service (QoS) control of time- sensitive applications in multi-programmed embedded systems. In such systems, tasks must receive appropriate timeliness guarantees from the Operating System independently from one another, otherwise the QoS experienced by users may decrease. Moreover, fluctuations in time of the workloads make a static partitioning of the CPU not appropriate nor convenient, whereas an adaptive allocation based on an on-line monitoring of the application behaviour leads to an optimum design. By combining a resource reservation scheduler and a feedback based mechanism, we allow applications to meet their QoS requirements with the minimum possible impact on CPU occupation. We implemented the framework in AQuoSA [8], a software architecture that runs on top of the Linux kernel.We provide extensive experimental validation of our results and offer evaluation of the introduced overhead, which is perfectly sustainable in the class of addressed applications.

Luca Abeni, Tommaso Cucinotta, Giuseppe Lipari, Luca Marzario, Luigi Palopoli, "QoS Management through adaptive reservations," Real-Time Systems Journal, Vol. 29, Issue 2-3, March 2005, ISSN:0922-6443, Kluwer Academic. Abstract

Reservation based (RB) scheduling is a class of scheduling algorithms that is well-suited for a large class of soft real-time applications. They are based on a "bandwidth" abstraction, meaning that a task is given the illusion of executing on a dedicated slower processor. In this context, a crucial design issue is deciding the bandwidth that each task should receive. The point we advocate is that, in presence of large fluctuations on the computation requirements of the tasks, it can be a beneficial choice to dynamically adapt the bandwidth based on QoS measurements and on the subsequent application of feedback control (adaptive reservations). In this paper, we present two novel contributions to this research area. First, we propose three new control algorithms inspired to the ideas of stochastic control. Second, we present a flexible and modular software architecture for adaptive reservations. An important feature of this architecture is that it is realised by means of a minimally invasive set of modifications to the Linux kernel.

Tommaso Cucinotta, Marco Di Natale, David Corcoran, "An open middleware for smart-cards," Computer Science Software Engineering (CSSE) Journal, Vol. 20, No. 6, November 2005. Abstract

This paper presents an open and modular middleware for smart cards, providing a simple abstraction of the device to application developers. The software is interoperable across multiple card devices, and portable across various open platforms. The architectural design is centred around the definition of a new API that allows protected access to the storage and cryptographic facilities of a smart card. In the envisioned architecture, a smart card driver architecture is partitioned into a lower card-dependent component, that formats and exchanges APDUs with the external device, and a higher cardindependent component, that implements more sophisticated services and interfaces, such as the well known PKCS-11 standard. Each layer can focus on a smaller set of functionality, thus reducing the effort required for the development as well as the testing and maintenance of each component. The proposed architecture, along with a set of pilot applications such as secure remote shell, secure web services, local login and digital signature, has been developed and tested on various platforms, including Open BSD, Linux, Solaris and Mac OS X, proving effectiveness of the new approach.

Tommaso Cucinotta, Riccardo Brigo, Marco Di Natale, "A fingerprint matching algorithm for programmable smart cards," Information Security Bulletin Journal, Vol. 10, November 2005. Abstract

This paper presents a hybrid fingerprint matching algorithm for user authentication based on the fusion of heterogeneous schemes, and designed to run on programmable smart cards. The approach is based on the well-known texture vector and minutiae based techniques, where image processing and feature extraction occur on the host, while the card device performs the final match against the on-board template, which is never revealed to the outside world. This increases security of the template itself and of the applications using it. The matching algorithms have been tuned in order to achieve an acceptable performance despite computation and memory constraints. Experimental results, gathered from our implementation on a Java Card device, highlight feasibility of the hybrid approach, and show to what extent it is possible to trade precision for speed in the verification process, with an appropriate tuning of the on-board matching parameters.

Publications on national magazines

Tommaso Cucinotta, "Firma digitale e lavoro cooperativo: aspetti tecnologici", pubblicato su "I nuovi scenari del marketing assicurativo", Franco Angeli Editore, 2004

Tommaso Cucinotta, "Firma digitale e assicurazioni: aspetti tecnologici," pubblicato su "L'economia digitale e il settore assicurativo", DEA Quaderni di Impresa Assicurativa, Giuffrè Editore, 2003

Marco Di Natale, Tommaso Cucinotta, Paolo Ancilotti, "Lo sviluppo di una architettura modulare open-source per i servizi della PA: considerazioni tecniche e organizzative," atti del forum "SALPA: Sapere Aperto e Libero nella Pubblica Amministrazione", Marzo 2004, Pisa