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At least 127 records · Page 7Linked to original sources

arXiv2012

LNOS - Live Network Operating System

Operating Systems exists since existence of computers, and have been evolving continuously from time to time. In this paper we have reviewed a relatively new or unexplored topic of Live OS. From networking perspective, Live OS is used for establishing Clusters, Firewalls and as Network security assessment tool etc. Our proposed concept is that a Live OS can be established or configured for an organizations specific network requirements with respect to their servers. An important server failure due to hardware or software could take time for remedy of the problem, so for that situation a preconfigured server in the form of Live OS on CD/DVD/USB can be used as an immediate solution. In a network of ten nodes, we stopped the server machine and with necessary adjustments, Live OS replaced the server in less than five minutes. Live OS in a network environment is a quick replacement of the services that are failed due to server failure (hardware or software). It is a cost effective solution for low budget networks. The life of Live OS starts when we boot it from CD/DVD/USB and remains in action for that session. As soon as the machine is rebooted, any work done for that session is gone, (in case we do not store any information on permanent storage media). Live CD/DVD/USB is normally used on systems where we do not have Operating Systems installed. A Live OS can also be used on systems where we already have an installed OS. On the basis of functionality a Live OS can be used for many purposes and has some typical advantages that are not available on other operating systems. Vendors are releasing different distributions of Live OS and is becoming their sole identity in a particular domain like Networks, Security, Education or Entertainment etc. There can be many aspects of Live OS, but Linux based Live OS and their use in the field of networks is the main focus of this paper.

cs.NI↗

arXiv2013

RevDedup: A Reverse Deduplication Storage System Optimized for Reads to Latest Backups

Scaling up the backup storage for an ever-increasing volume of virtual machine (VM) images is a critical issue in virtualization environments. While deduplication is known to effectively eliminate duplicates for VM image storage, it also introduces fragmentation that will degrade read performance. We propose RevDedup, a deduplication system that optimizes reads to latest VM image backups using an idea called reverse deduplication. In contrast with conventional deduplication that removes duplicates from new data, RevDedup removes duplicates from old data, thereby shifting fragmentation to old data while keeping the layout of new data as sequential as possible. We evaluate our RevDedup prototype using microbenchmark and real-world workloads. For a 12-week span of real-world VM images from 160 users, RevDedup achieves high deduplication efficiency with around 97% of saving, and high backup and read throughput on the order of 1GB/s. RevDedup also incurs small metadata overhead in backup/read operations.

cs.DC↗

arXiv2013

Parametric Schedulability Analysis of Fixed Priority Real-Time Distributed Systems

Parametric analysis is a powerful tool for designing modern embedded systems, because it permits to explore the space of design parameters, and to check the robustness of the system with respect to variations of some uncontrollable variable. In this paper, we address the problem of parametric schedulability analysis of distributed real-time systems scheduled by fixed priority. In particular, we propose two different approaches to parametric analysis: the first one is a novel technique based on classical schedulability analysis, whereas the second approach is based on model checking of Parametric Timed Automata (PTA). The proposed analytic method extends existing sensitivity analysis for single processors to the case of a distributed system, supporting preemptive and non-preemptive scheduling, jitters and unconstrained deadlines. Parametric Timed Automata are used to model all possible behaviours of a distributed system, and therefore it is a necessary and sufficient analysis. Both techniques have been implemented in two software tools, and they have been compared with classical holistic analysis on two meaningful test cases. The results show that the analytic method provides results similar to classical holistic analysis in a very efficient way, whereas the PTA approach is slower but covers the entire space of solutions.

cs.DC↗

arXiv2013

Energy Minimization for Parallel Real-Time Systems with Malleable Jobs and Homogeneous Frequencies

In this work, we investigate the potential utility of parallelization for meeting real-time constraints and minimizing energy. We consider malleable Gang scheduling of implicit-deadline sporadic tasks upon multiprocessors. We first show the non-necessity of dynamic voltage/frequency regarding optimality of our scheduling problem. We adapt the canonical schedule for DVFS multiprocessor platforms and propose a polynomial-time optimal processor/frequency-selection algorithm. We evaluate the performance of our algorithm via simulations using parameters obtained from a hardware testbed implementation. Our algorithm has up to a 60 watt decrease in power consumption over the optimal non-parallel approach.

cs.OS↗

arXiv2013

Capturing Information Flows inside Android and Qemu Environments

The smartphone market has grown so wide that it assumed a strategic relevance. Today the most common smartphone OSs are Google's Android and Apple's iOS. The former is particularly interesting due to its open source nature, that allows everyone to deeply inspect every aspect of the OS. Android source code is also bundled with an hardware emulator, based on the open source software Qemu, that allows the user to run the Android OS without the need of a physical device. We first present a procedure to extract information flows from a generic system. We then focus on Android and Qemu architectures and their logging infrastructures. Finally, we detail what happens inside an Android device in a particular scenario: the system boot.

cs.OS↗

arXiv2013

LFTL: A multi-threaded FTL for a Parallel IO Flash Card under Linux

New PCI-e flash cards and SSDs supporting over 100,000 IOPs are now available, with several usecases in the design of a high performance storage system. By using an array of flash chips, arranged in multiple banks, large capacities are achieved. Such multi-banked architecture allow parallel read, write and erase operations. In a raw PCI-e flash card, such parallelism is directly available to the software layer. In addition, the devices have restrictions such as, pages within a block can only be written sequentially. The devices also have larger minimum write sizes (greater than 4KB). Current flash translation layers (FTLs) in Linux are not well suited for such devices due to the high device speeds, architectural restrictions as well as other factors such as high lock contention. We present a FTL for Linux that takes into account the hardware restrictions, that also exploits the parallelism to achieve high speeds. We also consider leveraging the parallelism for garbage collection by scheduling the garbage collection activities on idle banks. We propose and evaluate an adaptive method to vary the amount of garbage collection according to the current I/O load on the device.

cs.OS↗

arXiv2013

Towards Python-based Domain-specific Languages for Self-reconfigurable Modular Robotics Research

This paper explores the role of operating system and high-level languages in the development of software and domain-specific languages (DSLs) for self-reconfigurable robotics. We review some of the current trends in self-reconfigurable robotics and describe the development of a software system for ATRON II which utilizes Linux and Python to significantly improve software abstraction and portability while providing some basic features which could prove useful when using Python, either stand-alone or via a DSL, on a self-reconfigurable robot system. These features include transparent socket communication, module identification, easy software transfer and reliable module-to-module communication. The end result is a software platform for modular robots that where appropriate builds on existing work in operating systems, virtual machines, middleware and high-level languages.

cs.RO↗

arXiv2013

Survey of Server Virtualization

Virtualization is a term that refers to the abstraction of computer resources. The purpose of virtual computing environment is to improve resource utilization by providing a unified integrated operating platform for users and applications based on aggregation of heterogeneous and autonomous resources. More recently, virtualization at all levels (system, storage, and network) became important again as a way to improve system security, reliability and availability, reduce costs, and provide greater flexibility. Virtualization has rapidly become a go-to technology for increasing efficiency in the data center. With virtualization technologies providing tremendous flexibility, even disparate architectures may be deployed on a single machine without interference This paper explains the basics of server virtualization and addresses pros and cons of virtualization

cs.OS↗

arXiv2013

Making I/O Virtualization Easy with Device Files

Personal computers have diverse and fast-evolving I/O devices, making their I/O virtualization different from that of servers and data centers. In this paper, we present our recent endeavors in simplifying I/O virtualization for personal computers. Our key insight is that many operating systems, including Unix-like ones, abstract I/O devices as device files. There is a small and stable set of operations on device files, therefore, I/O virtualization at the device file boundary requires a one-time effort to support various I/O devices. We present devirtualization, our design of I/O virtualization at the device file boundary and its implementation for Linux/x86 systems. We are able to virtualize various GPUs, input devices, cameras, and audio devices with fewer than 4900 LoC, of which only about 300 are specific to I/O device classes. Our measurements show that devirtualized devices achieve interactive performance indistinguishable from native ones by human users, even when running 3D HD games.

cs.OS↗

arXiv2013

Paging with dynamic memory capacity

We study a generalization of the classic paging problem that allows the amount of available memory to vary over time - capturing a fundamental property of many modern computing realities, from cloud computing to multi-core and energy-optimized processors. It turns out that good performance in the "classic" case provides no performance guarantees when memory capacity fluctuates: roughly speaking, moving from static to dynamic capacity can mean the difference between optimality within a factor 2 in space and time, and suboptimality by an arbitrarily large factor. More precisely, adopting the competitive analysis framework, we show that some online paging algorithms, despite having an optimal (h,k)-competitive ratio when capacity remains constant, are not (3,k)-competitive for any arbitrarily large k in the presence of minimal capacity fluctuations. In this light it is surprising that several classic paging algorithms perform remarkably well even if memory capacity changes adversarially - even without taking those changes into explicit account! In particular, we prove that LFD still achieves the minimum number of faults, and that several classic online algorithms such as LRU have a "dynamic" (h,k)-competitive ratio that is the best one can achieve without knowledge of future page requests, even if one had perfect knowledge of future capacity fluctuations (an exact characterization of this ratio shows it is almost, albeit not quite, equal to the "classic" ratio k/(k-h+1)). In other words, with careful management, knowing/predicting future memory resources appears far less crucial to performance than knowing/predicting future data accesses.

cs.DS↗

arXiv2013

Invasive Computing - Common Terms and Granularity of Invasion

Future MPSoCs with 1000 or more processor cores on a chip require new means for resource-aware programming in order to deal with increasing imperfections such as process variation, fault rates, aging effects, and power as well as thermal problems. On the other hand, predictable program executions are threatened if not impossible if no proper means of resource isolation and exclusive use may be established on demand. In view of these problems and menaces, invasive computing enables an application programmer to claim for processing resources and spread computations to claimed processors dynamically at certain points of the program execution. Such decisions may be depending on the degree of application parallelism and the state of the underlying resources such as utilization, load, and temperature, but also with the goal to provide predictable program execution on MPSoCs by claiming processing resources exclusively as the default and thus eliminating interferences and creating the necessary isolation between multiple concurrently running applications. For achieving this goal, invasive computing introduces new programming constructs for resource-aware programming that meanwhile, for testing purpose, have been embedded into the parallel computing language X10 as developed by IBM using a library-based approach. This paper presents major ideas and common terms of invasive computing as investigated by the DFG Transregional Collaborative Research Centre TR89. Moreoever, a reflection is given on the granularity of resources that may be requested by invasive programs.

cs.OS↗

arXiv2013

Network Control Systems RTAI framework A Review

With the advancement in the automation industry, to perform complex remote operations is required. Advancements in the networking technology has led to the development of different architectures to implement control from a large distance. In various control applications of the modern industry, the agents, such as sensors, actuators, and controllers are basically geographically distributed. For efficient working of a control application, all of the agents have to exchange information through a communication media. At present, an increasing number of distributed control systems are based on platforms made up of conventional PCs running open-source real-time operating systems. Often, these systems needed to have networked devices supporting synchronized operations with respect to each node. A framework is studied that relies on standard software and protocol as RTAI, EtherCAT, RTnet and IEEE 1588. RTAI and its various protocols are studied in network control systems environment.

cs.OS↗

arXiv2013

Practical Fine-grained Privilege Separation in Multithreaded Applications

An inherent security limitation with the classic multithreaded programming model is that all the threads share the same address space and, therefore, are implicitly assumed to be mutually trusted. This assumption, however, does not take into consideration of many modern multithreaded applications that involve multiple principals which do not fully trust each other. It remains challenging to retrofit the classic multithreaded programming model so that the security and privilege separation in multi-principal applications can be resolved. This paper proposes ARBITER, a run-time system and a set of security primitives, aimed at fine-grained and data-centric privilege separation in multithreaded applications. While enforcing effective isolation among principals, ARBITER still allows flexible sharing and communication between threads so that the multithreaded programming paradigm can be preserved. To realize controlled sharing in a fine-grained manner, we created a novel abstraction named ARBITER Secure Memory Segment (ASMS) and corresponding OS support. Programmers express security policies by labeling data and principals via ARBITER's API following a unified model. We ported a widely-used, in-memory database application (memcached) to ARBITER system, changing only around 100 LOC. Experiments indicate that only an average runtime overhead of 5.6% is induced to this security enhanced version of application.

cs.OS↗

arXiv2013

Augmenting Operating Systems With the GPU

The most popular heterogeneous many-core platform, the CPU+GPU combination, has received relatively little attention in operating systems research. This platform is already widely deployed: GPUs can be found, in some form, in most desktop and laptop PCs. Used for more than just graphics processing, modern GPUs have proved themselves versatile enough to be adapted to other applications as well. Though GPUs have strengths that can be exploited in systems software, this remains a largely untapped resource. We argue that augmenting the OS kernel with GPU computing power opens the door to a number of new opportunities. GPUs can be used to speed up some kernel functions, make other scale better, and make it feasible to bring some computation-heavy functionality into the kernel. We present our framework for using the GPU as a co-processor from an OS kernel, and demonstrate a prototype in Linux.

cs.OS↗

arXiv2013

On the periodic behavior of real-time schedulers on identical multiprocessor platforms

This paper is proposing a general periodicity result concerning any deterministic and memoryless scheduling algorithm (including non-work-conserving algorithms), for any context, on identical multiprocessor platforms. By context we mean the hardware architecture (uniprocessor, multicore), as well as task constraints like critical sections, precedence constraints, self-suspension, etc. Since the result is based only on the releases and deadlines, it is independent from any other parameter. Note that we do not claim that the given interval is minimal, but it is an upper bound for any cycle of any feasible schedule provided by any deterministic and memoryless scheduler.

cs.OS↗

arXiv2013

Partitioned scheduling of multimode multiprocessor real-time systems with temporal isolation

We consider the partitioned scheduling problem of multimode real-time systems upon identical multiprocessor platforms. During the execution of a multimode system, the system can change from one mode to another such that the current task set is replaced with a new one. In this paper, we consider a synchronous transition protocol in order to take into account mode-independent tasks, i.e., tasks of which the execution pattern must not be jeopardized by the mode changes. We propose two methods for handling mode changes in partitioned scheduling. The first method is offline/optimal and computes a static allocation of tasks schedulable and respecting both tasks and transition deadlines (if any). The second approach is subject to a sufficient condition in order to ensure online First Fit based allocation to satisfy the timing constraints.

cs.OS↗

arXiv2013

A Comparative Study of CPU Scheduling Algorithms

Developing CPU scheduling algorithms and understanding their impact in practice can be difficult and time consuming due to the need to modify and test operating system kernel code and measure the resulting performance on a consistent workload of real applications. As processor is the important resource, CPU scheduling becomes very important in accomplishing the operating system (OS) design goals. The intention should be allowed as many as possible running processes at all time in order to make best use of CPU. This paper presents a state diagram that depicts the comparative study of various scheduling algorithms for a single CPU and shows which algorithm is best for the particular situation. Using this representation, it becomes much easier to understand what is going on inside the system and why a different set of processes is a candidate for the allocation of the CPU at different time. The objective of the study is to analyze the high efficient CPU scheduler on design of the high quality scheduling algorithms which suits the scheduling goals. Key Words:-Scheduler, State Diagrams, CPU-Scheduling, Performance

cs.OS↗

arXiv2013

An Optimum Multilevel Dynamic Round Robin Scheduling Algorithm

The main objective of this paper is to improve the Round Robin scheduling algorithm using the dynamic time slice concept. CPU scheduling becomes very important in accomplishing the operating system (OS) design goals. The intention should be allowed as many as possible running processes at all time in order to make best use of CPU. CPU scheduling has strong effect on resource utilization as well as overall performance of the system. Round Robin algorithm performs optimally in time-shared systems, but it is not suitable for soft real time systems, because it gives more number of context switches, larger waiting time and larger response time. In this paper, a new CPU scheduling algorithm called An Optimum Multilevel Dynamic Round Robin Scheduling Algorithm is proposed, which calculates intelligent time slice and changes after every round of execution. The suggested algorithm was evaluated on some CPU scheduling objectives and it was observed that this algorithm gave good performance as compared to the other existing CPU scheduling algorithms.

cs.OS↗