a b s t r a c tMulti-Processor Systems on Chip (MPSoC) run multiple independent applications, often developed by different parties. The applications share the hardware resources, e.g. processors, memories and interconnect. The sharing typically causes interference between the applications, which severely complicates system integration and verification. Even if the applications are verified in isolation, the system designer must verify the combined behaviour, leading to an explosion in design complexity. Composable MPSoCs have no interference between applications, thus allowing independent design and verification. For an MPSoC to be composable, all the hardware resources must offer composability. A particularly challenging resource is the processors, often purchased as off-the-shelf intellectual property.In this work we present the design and implementation of CompOSe, a light-weight (only 1500 lines of code) composable operating system for MPSoCs. CompOSe uses fixed-size time slices, coupled with a composable scheduler, to enable composable processor sharing. Using instances of ARM7, ARM11 and the Xilinx MicroBlaze we experimentally demonstrate the ability to provide temporal composability, even in the presence of dynamic application behaviour and multiple use cases. We do so using a diverse set of processor architectures, without requiring any hardware modifications. We also show how CompOSe allows slack to be distributed within and between applications through a novel two-level scheduler and slack-distribution system.

Abstract-Composability means that the behaviour of an application, including its timing, is not affected by the absence or presence of other applications. It is required to be able to design, test, and verify applications independently. In this paper we define composable dynamic voltage and frequency scaling (DVFS) hardware, and composable power management. We ensure that the functional and temporal behaviours of an application are not affected by other applications, even when they are power managed.For dataflow applications with worst-case execution times per task, our power management is also predictable, i.e. guarantees end-to-end real-time requirements, even when the application is mapped on multiple processors that are power managed independently. Our method can be used with various DVFS architectures, such as on-chip and off-chip VF regulators.Our FPGA implementation models a system with multiple tiles, each containing a processor with local memory running a realtime operating system (RTOS) and power management. Tiles are interconnected by a network on chip, and communicate using shared memories. Experiments indicate energy savings of 68% w.r.t. no power management, and 40% w.r.t. power gating only. We also demonstrate composability and predictability on the platform in the presence of power management. I. INTRODUCTION Low energy consumption is important for systems on chip (SOC). Dynamic voltage and frequency scaling (DVFS) is oftenused to trade a linear processor slowdown for a potentially quadratic decrease in energy consumption. This trade-off has been exhaustively addressed for single processors, and for multi-processor SOCs [1], [2]. We propose an architecture that uses existing DVFS hardware to build composable and predictable SOCs running multiple applications.To deal with the complexity of system design and verification, the concept of composability has been advocated [3]-[6] and practised [7]. Behaviours of different applications are independent, to be able to develop, test, verify, and execute applications in isolation before they are integrated to a system. A composable SOC then ensures that applications already integrated do not affect the newly added application, and vice versa.Embedded systems contain a mix of best-effort applications, and those that have (hard or soft) real-time requirements, such as radio pipes, and video and audio decoding. Predictability, or timeliness, is required to guarantee that each application meets its deadlines, while composability ensures that multiple

In this paper we introduce the concepts of work of tokens (e.g. video frames) in an application, and slack arising from variations in work. Slack is used for dynamic voltage and frequency scaling in combination with a conservative power-management policy that never misses deadlines, for hard real-time applications, and with a nonconservative policy for soft real-time applications. We evaluate both policies for a number of different granularities (frequency of activation of the power manager) on an MPEG4 application, on energy and quality (deadline misses). We conclude that for soft real-time applications, there is a clear optimum in the energy, which depends on the work histogram of the application. The conservative policy has no deadline misses, and is only negligibly more expensive in terms of energy than the non-conservative policy. Finally, the granularity of both policies can be very coarse (128 frames) to reduce the power manager activation frequency, which has an insignificant energy cost.

Background Total arterial revascularization is the most durable and technically the most demanding type of coronary artery bypass grafting procedure. It has proven long-term supremacy in comparison to conventional coronary artery bypass grafting. In our study, we investigated the reliability of EuroSCORE II as a predictor of intrahospital death. We showed its impact on adverse perioperative events. Methods In this nonrandomized prospective study, we analyzed 116 consecutive patients who underwent the total arterial revascularization procedure at our Institute from January 2011 until the present. For myocardial revascularization, the most suitable combinations with left internal mammary artery, right internal mammary artery, and radial artery grafts were used. Main fact in this research was intrahospital mortality value in comparison with the value predicted. Results There were 104 (89.7%) males and 12 (10.3%) females. Mean preoperative EuroSCORE II prediction value was 1.98% and postoperative we obtained 1.72%. Postoperative redo for bleeding was 6%. Positive correlation was proven between the EuoroSCORE II value and intensive care unit stay (0.452; p < 0.001). Among patients who received two internal mammary arteries, the highest EuroSCORE II was among those with presternal wound infection (p = 0.005). Patients with bilateral internal mammary arteries and diabetes showed that they have the highest values of EuroSCORE II and, at the same time, that they are extremely prone to wound problems. Conclusions We achieved a lower intrahospital mortality level than it was predicted with preoperative EuroSCORE II value. This tool is a reliable method for preoperative death risk calculation in this group of patients.

Objectives: There is a paucity of data regarding wound-site complications and patient's satisfaction after harvesting of a radial artery. This study is conducted to evaluate the frequency complications and the level of patient's satisfaction after myocardial revascularization in our setting. Methods: From April 2009 to October 2013, 97 patients had radial artery (RA) used as a graft in myocardial revascularization. The graft was harvested using open technique. This was retrospective study. Telephone questionnaire was used to evaluate: arm pain, swelling, mobility, sensory changes, patient's contentment with a cosmetic result and the general health state. Results: Pain of limited duration was reported by 24 patients (24.7%), none of them reported permanent pain. Some problems in performing everyday's activities were reported by 8 pts (8.2%). Sensory changes were permanently present in 5 pts (5.2%), and frequent arm fatigue was reported by 4 pts (4.1%). Positive opinion regarding the cosmetic result was reported by 95 pts (97.9%). State of the health after surgery, 81 pts (83.5%) described as excellent or good. Patients who had more mobility problems, also had more sensory and neurological discomfort respectively. Patients with better self-reported general health state were also more satisfied with the esthetic effect of the intervention. Conclusions: Using the open technique resulted in excellent cosmetic effect. This gives us credit to point out that exclusive need of the endoscopic as a supreme method might be under the question mark. Our study suggests that individual attitude of the particular patient plays extremely important role in his/her overall satisfaction with the end effect of the procedure.