Handling timing constraints violations in soft real-time applications as exceptions

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

Management of Application Quality of Service

This paper proposes a new language for the development of distributed multimedia applications: Quality Assurance Language (QuAL). QuAL abstractions allow the specification of Quality of Service (QoS) constraints expected from the underlying computing and communication environment. QuAL specifications are compiled into run time components that monitor the actual QoS delivered. Upon QoS violations, application provided exception handlers are signaled to act upon the faulty events. Language level abstractions of QoS shelter programs from the heterogeneity of underlying infrastructures. This simplifies the development and maintenance of multimedia applications and promotes their portability and reuse. QuAL generates Management Information Bases (MIBs) that contain QoS statistics per application. Such MIBs may be used to integrate application level QoS management into standard network management frameworks

Script-Based QOS Specifications for Multimedia Presentations

Multimedia presentations can convey information not only by the sequence of events but by their timing. The correctness of such presentations thus depends on the timing of events as well as their sequence and content. This paper introduces a formal specification language for playback of real-time presentations. The main contribution of this language is a quality of service (QOS) specification that relaxes resolution and synchronization requirements for playback. Our definitions give a precise meaning to the correctness of a presentation. This specification language will form the basis for a QOS interface for reservation of operating system resources

Efficient Memory-Protected Integration of Add-On Software Subsystems in Small Embedded Automotive Applications

Current innovations in the automotive industry evolve mainly in the electronics and software domain. This leads to an increasing integration of additional software subsystems into already existing electronic control units (ECUs) to cope with the raised amount and complexity of present ECUs in modern high-end vehicles. This paper discusses different approaches which are required to integrate such add-on software subsystems in an isolated memory domain, and considers particularly the special needs of small embedded systems—including the limited hardware support. Special focus is brought to the efficient detection of malicious memory accesses, as well as the benefits of a thereupon possible and adaptable failure-handling strategy. All investigations are based on a developed memory-protection framework which has been tailored to the special needs of a sample vehicle dynamics control system. Its usage allows the combination of. integrating additional subsystems without reducing the main application’s availability

QoSME: QoS Management Environment

Distributed multimedia applications are sensitive to the Quality of Service (QoS) delivered by underlying communication networks. For example, a video conference exchange can be very sensitive to the effective network throughput. Network jitter can greatly disrupt a speech stream. The main question this thesis addresses is how to adapt multimedia applications to the QoS delivered by the network and vice versa. Such adaptation is especially important because current networks are unable to assure the QoS required by applications and the latter is usually unprepared for periods of QoS degradation. This work introduces the QoS Management Environment (QoSME) that provides mechanisms for such adaptation. The main contributions of this thesis are: Language level abstractions for QoS management. The Quality Assurance Language (QuAL) in QoSME enables the specification of how to allocate, monitor, analyze, and adapt to delivered QoS. Applications can express in QuAL their QoS needs and how to handle potential violations. Automatic QoS monitoring. QoSME automatically generates the instrumentation to monitor QoS when applications use QuAL constructs. The QoSME runtime scrutinizes interactions among applications, transport protocols, and Operating Systems (OS) and collects in QoS Management Information Bases (MIBs) statistics on the QoS delivered. Integration of QoS and standard network management. A Simple Network Management Protocol (SNMP) agent embedded in QoSME provides QoS MIB access to SNMP managers. The latter can use this feature to monitor end-to-end QoS delivery and adapt network resource allocation and operations accordingly. A partial prototype of QoSME has been released for public access. It runs on SunOS 4.3 and Solaris 2.3 and supports communication on ATM adaptation layer, ST-II, UDP/IP, TCP/IP, and Unix internal protocols

Vector processing-aware advanced clock-gating techniques for low-power fused multiply-add

The need for power efficiency is driving a rethink of design decisions in processor architectures. While vector processors succeeded in the high-performance market in the past, they need a retailoring for the mobile market that they are entering now. Floating-point (FP) fused multiply-add (FMA), being a functional unit with high power consumption, deserves special attention. Although clock gating is a well-known method to reduce switching power in synchronous designs, there are unexplored opportunities for its application to vector processors, especially when considering active operating mode. In this research, we comprehensively identify, propose, and evaluate the most suitable clock-gating techniques for vector FMA units (VFUs). These techniques ensure power savings without jeopardizing the timing. We evaluate the proposed techniques using both synthetic and “real-world” application-based benchmarking. Using vector masking and vector multilane-aware clock gating, we report power reductions of up to 52%, assuming active VFU operating at the peak performance. Among other findings, we observe that vector instruction-based clock-gating techniques achieve power savings for all vector FP instructions. Finally, when evaluating all techniques together, using “real-world” benchmarking, the power reductions are up to 80%. Additionally, in accordance with processor design trends, we perform this research in a fully parameterizable and automated fashion.The research leading to these results has received funding from the RoMoL ERC Advanced Grant GA 321253 and is supported in part by the European Union (FEDER funds) under contract TTIN2015-65316-P. The work of I. Ratkovic was supported by a FPU research grant from the Spanish MECD.Peer ReviewedPostprint (author's final draft

QuAL: Quality Assurance Language

Distributed multimedia applications are sensitive to the Quality of Services (QoS) provided by their computing and communication environment. For example, scheduling of processing activities or network queueing delays may cause excessive jitter in a speech stream, rendering it difficult to understand. It is thus important to establish effective technologies to ensure delivery of QoS required by distributed multimedia applications. This proposal presents a new language for the development of distributed multimedia applications: Quality Assurance Language (QuAL). QuAL abstractions allow the specification of QoS constraints expected from the underlying computing and communication environment. QuAL specifications are compiled into run time components that monitor the actual QoS delivered. Upon QoS violations, application provided exception handlers are signaled to act upon the faulty events. Language level abstractions of QoS shelter programs from the heterogeneity of underlying infrastructures. This simplifies the development and maintenance of multimedia applications and promotes their portability and reuse. QuAL generates Management Information Bases (MIBs) that contain QoS statistics per application. Such MIBs may be used to integrate application level QoS management into standard network management frameworks

Comment on the Revised Proposed Final Judgement

In these comments, we argue that the Revised Proposed Final Judgement (RPFJ) is not in the "public interest," as that test is applied under the Tunney Act. Accordingly, the RPFJ should either be rejected outright now, or the court should refrain from ruling on the RPFJ until it has completed its further factual inquiry regarding the remedy proposed by the nine states not party to the RPFJ. If, however, the court accepts the RPFJ in the meantime, we strongly urge it to treat the RPFJ as an interim remedy and expressly leave open the possibility of supplementing the RPFJ with the additional remedies discussed in detail in this comment. We also recommend that in conducting its further factual inquiry in the remedy phase of this litigation that the court actively consider a structural remedy that would create some competition in the PC operating system market that, but for Microsoft's unlawful acts, reasonably could have been expected to have emerged by this time.

Managing services quality through admission control and active monitoring

We propose a lightweight traffic admission control scheme based on on-line monitoring which ensures multimedia services quality both intra-domain and end-to-end. The AC strategy is distributed, service-oriented and allows to control QoS and SLS without adding complexity to the network core. For each service class, AC decisions are driven by rate-based SLS control rules and QoS parameters control rules, defined and parameterized according to each service characteristics. These rules are essentially based on systematic on-line measurements of relevant QoS and performance parameters. Thus, from a practical perspective, we discuss and evaluate methodologies and mechanisms for parameter estimation. The AC criteria is evaluated as regards its ability to ensure service commitments while achieving high network utilization. The results show that the proposed model provides a good compromise between simplicity, service level guarantee and network usage, even for services with strict QoS requirements

On the integration of application level and resource level QoS control for real-time applications

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