The SPLASH-2 suite of parallel applications has recently been released to facilitate the study of centralized and distributed shared-address-space multiprocessors. In this context, this paper has two goals. One is to quantitatively characterize the SPLASH-2 programs in terms of fundamental properties and architectural interactions that are important to understand them well. The properties we study include the computational load balance, communication to computation ratio and traffic needs, important working set sizes, and issues related to spatial locality, as well as how these properties scale with problem size and the number of processors. The other, related goal is methodological: to assist people who will use the programs in architectural evaluations to prune the space of application and machine parameters in an informed and meaningful way. For example, by characterizing the working sets of the applications, we describe which operating points in terms of cache size and problem size are representative of realistic situations, which are not, and which re redundant. Using SPLASH-2 as an example, we hope to convey the importance of understanding the interplay of problem size, number of processors, and working sets in designing experiments and interpreting their results.

/pdf/the-splash-2-programs-characterization-and-methodological-14b6i8va45.pdf

The SPLASH-2 programs: characterization and methodological considerations

Mobile computing continuously evolve through the sustained effort of many researchers. It seamlessly augments users' cognitive abilities via compute-intensive capabilities such as speech recognition, natural language processing, etc. By thus empowering mobile users, we could transform many areas of human activity. This article discusses the technical obstacles to these transformations and proposes a new architecture for overcoming them. In this architecture, a mobile user exploits virtual machine (VM) technology to rapidly instantiate customized service software on a nearby cloudlet and then uses that service over a wireless LAN; the mobile device typically functions as a thin client with respect to the service. A cloudlet is a trusted, resource-rich computer or cluster of computers that's well-connected to the Internet and available for use by nearby mobile devices. Our strategy of leveraging transiently customized proximate infrastructure as a mobile device moves with its user through the physical world is called cloudlet-based, resource-rich, mobile computing. Crisp interactive response, which is essential for seamless augmentation of human cognition, is easily achieved in this architecture because of the cloudlet's physical proximity and one-hop network latency. Using a cloudlet also simplifies the challenge of meeting the peak bandwidth demand of multiple users interactively generating and receiving media such as high-definition video and high-resolution images. Rapid customization of infrastructure for diverse applications emerges as a critical requirement, and our results from a proof-of-concept prototype suggest that VM technology can indeed help meet this requirement.

/pdf/the-case-for-vm-based-cloudlets-in-mobile-computing-1rofse2vmh.pdf

The Case for VM-Based Cloudlets in Mobile Computing

Cloud computing has recently emerged as a new paradigm for hosting and delivering services over the Internet. Cloud computing is attractive to business owners as it eliminates the requirement for users to plan ahead for provisioning, and allows enterprises to start from the small and increase resources only when there is a rise in service demand. However, despite the fact that cloud computing offers huge opportunities to the IT industry, the development of cloud computing technology is currently at its infancy, with many issues still to be addressed. In this paper, we present a survey of cloud computing, highlighting its key concepts, architectural principles, state-of-the-art implementation as well as research challenges. The aim of this paper is to provide a better understanding of the design challenges of cloud computing and identify important research directions in this increasingly important area.

/pdf/cloud-computing-state-of-the-art-and-research-challenges-49ws7tdgj3.pdf

Cloud computing: state-of-the-art and research challenges

Migrating operating system instances across distinct physical hosts is a useful tool for administrators of data centers and clusters: It allows a clean separation between hard-ware and software, and facilitates fault management, load balancing, and low-level system maintenance.By carrying out the majority of migration while OSes continue to run, we achieve impressive performance with minimal service downtimes; we demonstrate the migration of entire OS instances on a commodity cluster, recording service downtimes as low as 60ms. We show that that our performance is sufficient to make live migration a practical tool even for servers running interactive loads.In this paper we consider the design options for migrating OSes running services with liveness constraints, focusing on data center and cluster environments. We introduce and analyze the concept of writable working set, and present the design, implementation and evaluation of high-performance OS migration built on top of the Xen VMM.

/pdf/live-migration-of-virtual-machines-o3cs0reg9z.pdf

Live migration of virtual machines

This paper presents MAUI, a system that enables fine-grained energy-aware offload of mobile code to the infrastructure. Previous approaches to these problems either relied heavily on programmer support to partition an application, or they were coarse-grained requiring full process (or full VM) migration. MAUI uses the benefits of a managed code environment to offer the best of both worlds: it supports fine-grained code offload to maximize energy savings with minimal burden on the programmer. MAUI decides at run-time which methods should be remotely executed, driven by an optimization engine that achieves the best energy savings possible under the mobile device's current connectivity constrains. In our evaluation, we show that MAUI enables: 1) a resource-intensive face recognition application that consumes an order of magnitude less energy, 2) a latency-sensitive arcade game application that doubles its refresh rate, and 3) a voice-based language translation application that bypasses the limitations of the smartphone environment by executing unsupported components remotely.

/pdf/maui-making-smartphones-last-longer-with-code-offload-go3o1uwp1u.pdf

MAUI: making smartphones last longer with code offload

As users interact with the world and their peers through their computers, it is becoming important to archive and later search the information that they have viewed. We present DejaView, a personal virtual computer recorder that provides a complete record of a desktop computing experience that a user can playback, browse, search, and revive seamlessly. DejaView records visual output, checkpoints corresponding application and file system state, and captures displayed text with contextual information to index the record. A user can then browse and search the record for any visual information that has been displayed on the desktop, and revive and interact with the desktop computing state corresponding to any point in the record. DejaView combines display, operating system, and file system virtualization to provide its functionality transparently without any modifications to applications, window systems, or operating system kernels. We have implemented DejaView and evaluated its performance on real-world desktop applications. Our results demonstrate that DejaView can provide continuous low-overhead recording without any user noticeable performance degradation, and allows browsing, search and playback of records fast enough for interactive use.

/pdf/dejaview-a-personal-virtual-computer-recorder-2n18zcshmo.pdf

DejaView: a personal virtual computer recorder

Although web applications are gaining popularity on mobile wireless PDAs, web browsers on these systems can be quite slow and often lack adequate functionality to access many web sites. We have developed pTHINC, a PDA thin-client solution that leverages more powerful servers to run full-function web browsers and other application logic, then sends simple screen updates to the PDA for display. pTHINC uses server-side screen scaling to provide high-fidelity display and seamless mobility across a broad range of different clients and screen sizes, including both portrait and landscape viewing modes. pTHINC also leverages existing PDA control buttons to improve system usability and maximize available screen resolution for application display. We have implemented pTHINC on Windows Mobile and evaluated its performance on mobile wireless devices. Our results compared to local PDA web browsers and other thin-client approaches demonstrate that pTHINC provides superior web browsing performance and is the only PDA thin client that effectively supports crucial browser helper applications such as video playback.

/pdf/pthinc-a-thin-client-architecture-for-mobile-wireless-web-4bk191aj38.pdf

pTHINC: a thin-client architecture for mobile wireless web

We present a solution to the denial of service (DoS) problem that does not rely on network infrastructure support, conforming to the end-to-end (e2e) design principle. Our approach is to combine an overlay network, which allows us to treat authorized traffic preferentially, with a lightweight process-migration environment that allows us to move services easily between different parts of a distributed system. Functionality residing on a part of the system that is subjected to a DoS attack migrates to an unaffected location. The overlay network ensures that traffic from legitimate users, who are authenticated before they are allowed to access the service, is routed to the new location. We demonstrate the feasibility and effectiveness of our approach by measuring the performance of an experimental prototype against a series of attacks using PlanetLab, a distributed experimental testbed. Our preliminary results show that the end-toend latency remains at acceptable levels during regular operation, increasing only by a factor of 2 to 3, even for large overlays. When a process migrates due to a DoS attack, the disruption of service for the end user is in the order of a few seconds, depending on the network proximity of the servers involved in the migration.

/pdf/move-an-end-to-end-solution-to-network-denial-of-service-nmusu83r03.pdf

MOVE: An End-to-End Solution To Network Denial of Service

Virtual Network Address Translation (VNAT) is a novel architecture that allows transparent migration of end-to-end live network connections associated with various computation units. Such computation units can be either a single process, or a group of processes, or an entire host. VNAT virtualizes network connections perceived by transport protocols so that identification of network connections is decoupled from stationary hosts. Such virtual connections are then remapped into physical connections to be carried on the physical network using network address translation. VNAT requires no modification to existing applications, operating systems, or protocol stacks. Furthermore, it is fully compatible with the existing communication infrastructure; virtual and normal connections can coexist without interfering each other. VNAT functions entirely within end systems and requires no third party services. We have implemented a VNAT prototype with the Linux 2.4 kernel and demonstrated its functionality on a wide range of popular real-world network applications. Our performance results show that VNAT has essentially no network performance overhead except when connections are migrated, in which case the overhead of our Linux prototype is less than 7 percent over a stock RedHat Linux system.

/pdf/mobile-communication-with-virtual-network-address-39dsx6oqec.pdf

Mobile Communication with Virtual Network Address Translation

The computing landscape is shifting towards mobile devices. To learn about operating systems, it is increasingly important for students to gain hands-on kernel programming experience in these environments, which are quite different from traditional desktops and servers. We present our work at Columbia University to teach operating systems using Android, an open, commercially supported software platform increasingly used on mobile and embedded devices. We introduce a series of five Android kernel programming projects suitable for a one semester introductory operating systems course. Each project teaches a core operating system concept infused with Android or mobile device specific context, such as Android specific process relationships, use of sensors, and design considerations for resource constrained mobile devices. We also introduce an Android virtual laboratory based on virtual appliances, distributed version control, and live demonstrations which gives students hands-on Android experience, with minimal computing infrastructure. We have used these Android kernel programming projects and the Android virtual lab to teach an introductory operating systems course. Although this was our first time teaching the course using Android, over 80% of students surveyed enjoyed using Android and the majority of students preferred Android to traditional desktop development.

http://www.cs.columbia.edu/~nieh/pubs/sigcse2012_android.pdf

Jason Nieh

Papers

DejaView: a personal virtual computer recorder

pTHINC: a thin-client architecture for mobile wireless web

MOVE: An End-to-End Solution To Network Denial of Service

Mobile Communication with Virtual Network Address Translation

Teaching operating systems using android