TechTalks from event: IEEE IPDPS 2011

Note 1: Only plenary sessions (keynotes, panels, and best papers) are accessible without requiring log-in. For other talks, you will need to log-in using the email you registered for IPDPS 2011. Note 2: Many of the talks (those without a thumbnail next to the their description below) are yet to be uploaded. Some of them were not recorded because of technical problems. We are working with the corresponding authors to upload the self-recorded versions here. We sincerely thank all authors for their efforts in making their videos available.

SESSION 20: Operating Systems and Resource Management

  • Reducing fragmentation on torus-connected supercomputers Authors: Wei Tang (Illinois Institute of Technology, USA); Zhiling Lan (Illinois Institute of Technology, USA); Narayan Desai (Argonne N
    Torus-based networks are prevalent on leadership-class petascale systems, providing a good balance between network cost and performance. The major disadvantage of this network architecture is its susceptibility to fragmentation. Many studies have attempted to reduce resource fragmentation in this architecture. Although the approaches suggested can make good allocation decisions reducing fragmentation at job start time, none of them considers a job’s walltime, which can cause resource fragmentation when neighboring jobs do not complete closely. In this paper, we propose a walltime-aware job allocation strategy, which adjacently packs jobs that ?nish around the same time, in order to minimize resource fragmentation caused by job length, discrepancy. Event-driven simulations using real job traces from a production Blue Gene/P system at Argonne National Laboratory demonstrate that our walltime-aware strategy can effectively reduce system fragmentation and improve overall system performance.
  • Co-Analysis of RAS Log and Job Log on Blue Gene/P Authors: Ziming Zheng (Illinois Institute of Technology, USA); Li Yu (Illinois Institute of Technology, USA); Wei Tang (Illinois Institu
    With the growth of system size and complexity, reliability has become of paramount importance for petascale systems. Reliability, Availability, and Serviceability (RAS) logs have been commonly used for failure analysis. However, analysis based on just the RAS logs has proved to be insuf?cient in understanding failures and system behaviors. To overcome the limitation of this existing methodologies, we analyze the Blue Gene/P RAS logs and the Blue Gene/P job logs in a cooperative manner. From our co-analysis effort, we have identi?ed a dozen important observations about failure characteristics and job interruption characteristics on the Blue Gene/P systems. These observations can signi?cantly facilitate the research in fault resilience of large-scale systems.
  • Decal: Transparent Checkpointing and Process Migration of OpenCL Applications Authors: Hiroyuki Takizawa (Tohoku University, Japan); Kentaro Koyama (Tohoku University, Japan); Katsuto Sato (Tohoku University, Japan
    In this paper, we propose a new transparent checkpoint/restart (CPR) tool, named CheCL, for high-performance and dependable GPU computing. CheCL can perform CPR on an OpenCL application program without any modi?cation and recompilation of its code. A conventional checkpointing system fails to checkpoint a process if the process uses OpenCL. Therefore, in CheCL, every API call is forwarded to another process called an API proxy, and the API proxy invokes the API function; two processes, an application process and an API proxy, are launched for an OpenCL application. In this case, as the application process is not an OpenCL process but a standard process, it can be safely checkpointed. While CheCL intercepts all API calls, it records the information necessary for restoring OpenCL objects. The application process does not hold any OpenCL handles, but CheCL handles to keep such information. Those handles are automatically converted to OpenCL handles and then passed to API functions. Upon restart, OpenCL objects are automatically restored based on the recorded information. This paper demonstrates the feasibility of transparent checkpointing of OpenCL programs including MPI applications, and quantitatively evaluates the runtime overheads. It is also discussed that CheCL can enable process migration of OpenCL applications among distinct nodes, and among different kinds of compute devices such as a CPU and a GPU.

SESSION 5: Routing and Communication

  • On Nonblocking Folded-Clos Networks in Computer Communication Environments Authors: Xin Yuan (Florida State University, USA)
    Folded-Clos networks, also referred to as fat-trees, have been widely used as interconnects in large scale high performance computing clusters. The switching capability of such interconnects in computer communication environments, however, is not well understood. In particular, the concept of nonblocking interconnects, which is often used by system vendors, has only been studied in the telephone communication environment with the assumption of a centralized controller. Such “nonblocking”networks do not support nonblocking communications in computer communication environments where the network control is distributed. This paper theoretically analyzes the conditions for folded-Clos networks to achieve nonblocking communications in computer communication environments with various routing schemes including deterministic routing and adaptive routing, and establishes nonblocking conditions.
  • vFtree - A Fat-tree Routing Algorithm using Virtual Lanes to Alleviate Congestion Authors: Wei Lin Guay (Simula Research Laboratory, Norway); Bartosz Bogdanski (Simula Research Laboratory, Norway); Sven-Arne Reinemo (S
    It is a well known fact that multiple virtual lanes can improve performance in interconnection networks, but this knowledge has had little impact on real clusters. Currently, a large number of clusters using In?niBand is based on fat-tree topologies that can be routed deadlock-free using only one virtual lane. Consequently, all the remaining virtual lanes are left unused. In this paper we suggest an enhancement to the fat-tree algorithm that utilizes virtual lanes to improve performance when hot-spots are present. Even though the bisection bandwidth in a fat-tree is constant, hot-spots are still possible and they will degrade performance for ?ows not contributing to them due to head-of-line blocking. Such a situation may be alleviated through adaptive routing or congestion control, however, these methods are not yet readily available in In?niBand technology. To remedy this problem, we have implemented an enhanced fat-tree algorithm in OpenSM that distributes traf?c across all available virtual lanes without any con?guration needed. We evaluated the performance of the algorithm on a small cluster and did a large-scale evaluation through simulations. In a congested environment, results show that we are able to achieve throughput increases up to 38% on a small cluster and from 221% to 757% depending on the hot-spot scenario for a 648-port simulated cluster.
  • Measuring Temporal Lags in Delay-Tolerant Networks Authors: Arnaud Casteigts (University of Ottawa, Canada); Paola Flocchini (University of Ottawa, Canada); Bernard Mans (Macquarie Univer
    Delay-tolerant networks (DTNs) are characterized by a possible absence of end-to-end communication routes at any instant. In most cases, however, a form of connectivity can be established over time and space. This particularity leads to consider the relevance of a given route not only in terms of hops (topological length), but also in terms of time (temporal length). The problem of measuring temporal distances between individuals in a social network was recently addressed, based on a posteriori analysis of interaction traces. This paper focuses on the distributed version of this problem, asking whether every node in a network can know precisely and in real time how out-of-date it is with respect to every other. Answering af?rmatively is simple when contacts between the nodes are punctual, using the temporal adaptation of vector clocks provided in (Kossinets et al., 2008). It becomes more dif?cult when contacts have a duration and can overlap in time with each other. We demonstrate that the problem remains solvable with arbitrarily long contacts and non-instantaneous (though invariant and known) propagation delays on edges. This is done constructively by extending the temporal adaptation of vector clocks to non-punctual causality. The second part of the paper discusses how the knowledge of temporal lags could be used as a building block to solve more concrete problems, such as the construction of foremost broadcast trees or network backbones in periodically-varying DTNs.

SESSION 6: Self Stabilization and Security

  • A Lightweight Method for Automated Design of Convergence Authors: Ali Ebnenasir (Michigan Technological University, USA); Aly Farahat (Michigan Technological University, USA)
    Design and veri?cation of Self-Stabilizing (SS) network protocols are dif?cult tasks in part because of the requirement that a SS protocol must recover to a set of legitimate states from any state in its state space (when perturbed by transient faults). Moreover, distribution issues exacerbate the design complexity of SS protocols as processes should take local actions that result in global recovery/convergence of a network protocol. As such, most existing design techniques focus on protocols that are locally-correctable. To facilitate the design of ?nite-state SS protocols (that may not necessarily be locally-correctable), this paper presents a lightweight formal method supported by a software tool that automatically adds convergence to nonstabilizing protocols. We have used our method/tool to automatically generate several SS protocols with up to 40 processes (and 3 40 states) in a few minutes on a regular PC. Surprisingly, our tool has automatically synthesized both protocols that are the same as their manually-designed versions as well as new solutions for well-known problems in the literature (e.g., Dijkstra’s token ring [?]). Moreover, the proposed method has helped us reveal ?aws in a manually designed SS protocol.
  • Snap-Stabilizing Committee Coordination Authors: Borzoo Bonakdarpour (University of Waterloo, Canada); Stéphane Devismes (Université Joseph Fourier, France); Fran
    In this paper, we propose two snap-stabilizing distributed algorithms for the committee coordination problem. In this problem, a committee consists of a set of processes and committee meetings are synchronized, so that each process participates in at most one committee meeting at a time. Snap-stabilization is a versatile technique allowing to design algorithms that ef?ciently tolerate transient faults. Indeed, after a ?nite number of such faults (e.g. memory corruptions, message losses, etc), a snapstabilizing algorithm immediately operates correctly, without any external intervention. We design snap-stabilizing committee coordination algorithms enriched with some desirable properties related to concurrency, (weak) fairness, and a stronger synchronization mechanism called 2-Phase Discussion Time. From previous papers, we know that (1) in the general case, (weak) fairness cannot be achieved in the committee coordination, and (2) it becomes feasible provided that each process waits for meetings in?nitely often. Nevertheless, we show that even under this latter assumption, it is impossible to implement a fair solution that allows maximal concurrency. Hence, we propose two orthogonal snap-stabilizing algorithms, each satisfying 2-phase discussion time, and either maximal concurrency or fairness. The algorithm implementing fairness requires that every process waits for meetings in?nitely often. Moreover, for this algorithm, we introduce and evaluate a new ef?ciency criterion called the degree of fair concurrency. This criterion shows that even if it does not satisfy maximal concurrency, our snap-stabilizing fair algorithm still allows a high level of concurrency
  • SC-OA: A Secure and Efficient Scheme for Origin Authentication of Interdomain Routing in Cloud Computing Networks, Authors: Z. Le (Jiangxi University of Finance and Economics, China), N. Xiong (Georgia State University, USA), B. Yang (Jiangxi Universit
    IP pre?x hijacking is one of the top threats in the cloud computing Internets. Based on cryptography, many schemes for preventing pre?x hijacks have been proposed. Securing binding between IP pre?x and its owner underlies these schemes. We believe that a scheme for securing this binding should try to satisfy these seven critical requirements: no key escrow, no other secure channel, defending against Malicious Key Issuer (MKI) in the phase of pre?x announcement, defending against MKI in the phase of key issuing, no certi?cate, in-band delegation attestation, and in-band public key witness. In this paper, we propose a new scheme, Origin Authentication based on Self-Certi?ed public keys (SC-OA), using self-certi?ed public keys to authenticate origin autonomous systems. To the best of our knowledge, it is the ?rst work for securing pre?x ownership using self-certi?ed public keys to achieve an ef?cient and secure scheme that satis?es all seven requirements. The analyses show that SC-OA can defend against regular pre?x, subpre?x, unassigned pre?x, interception-based, and MKI hijacking, and improve performance in many aspects. It will be pushed ahead to practical deployment for preventing pre?x hijacks.