Single system image: A survey

Single system image is a computing paradigm where a number of distributed computing resources are aggregated and presented via an interface that maintains the illusion of interaction with a single system. This approach encompasses decades of research using a broad variety of techniques at varying levels of abstraction, from custom hardware and distributed hypervisors to specialized operating system kernels and user-level tools. Existing classification schemes for SSI technologies are reviewed, and an updated classification scheme is proposed. A survey of implementation techniques is provided along with relevant examples. Notable deployments are examined and insights gained from hands-on experience are summarized. Issues affecting the adoption of kernel-level SSI are identified and discussed in the context of technology adoption literature

Designing SSI clusters with hierarchical checkpointing and single I/O space

Adopting a new hierarchical checkpointing architecture, the authors develop a single I/O address space for building highly available clusters of computers. They propose a systematic approach to achieving a single system image by integrating existing middleware support with the newly developed features.published_or_final_versio

Asynchronous Validity Resolution in Sequentially Consistent Shared Virtual Memory

Shared Virtual Memory (SVM) is an effort to provide a mechanism for a distributed system, such as a cluster, to execute shared memory parallel programs. Unfortunately, SVM has performance problems due to its underlying distributed architecture. Recent developments have increased performance of SVM by reducing communication. Unfortunately this performance gain was only possible by increasing programming complexity and by restricting the types of programs allowed to execute in the system. Validity resolution is the process of resolving the validity of a memory object such as a page. Current SVM systems use synchronous or deferred validity resolution techniques in which user processing is blocked during the validity resolution process. This is the case even when resolving validity of false shared variables. False-sharing occurs when two or more processes access unrelated variables stored within the same shared block of memory and at least one of the processes is writing. False sharing unnecessarily reduces overall performance of SVM systems?because user processing is blocked during validity resolution although no actual data dependencies exist. This thesis presents Asynchronous Validity Resolution (AVR), a new approach to SVM which reduces the performance losses associated with false sharing while maintaining the ease of programming found with regular shared memory parallel programming methodology. Asynchronous validity resolution allows concurrent user process execution and data validity resolution. AVR is evaluated by com-paring performance of an application suite using both an AVR sequentially con-sistent SVM system and a traditional sequentially consistent (SC) SVM system. The results show that AVR can increase performance over traditional sequentially consistent SVM for programs which exhibit false sharing. Although AVR outperforms regular SC by as much as 26%, performance of AVR is dependent on the number of false-sharing vs. true-sharing accesses, the number of pages in the program’s working set, the amount of user computation that completes per page request, and the internodal round-trip message time in the system. Overall, the results show that AVR could be an important member of the arsenal of tools available to parallel programmers

Reducing Communication Overhead and Page Faults in SDSM Platforms

Abstract. In this paper we present a new dynamic, cache coherence protocol for Software Distributed Shared Memory (SDSM) systems that adopt the scope-consistency mode

Containers : A Sound Basis For a True Single System Image

Clusters of SMPs are attractive for executing shared memory parallel applications but reconciling high performance and ease of programming remains an open issue. A possible approach is to provide an efficient Single System Image (SSI) operating system giving the illusion of an SMP machine. In this paper, we introduce the concept of container as a mechanism to unify global resource management at the lowest operating system level. Higher level operating system services such as virtual memory system and file cache can be easily implemented based on containers and transparently take benefit of the whole memory resource available in the cluster

Vcluster: A Portable Virtual Computing Library For Cluster Computing

Message passing has been the dominant parallel programming model in cluster computing, and libraries like Message Passing Interface (MPI) and Portable Virtual Machine (PVM) have proven their novelty and efficiency through numerous applications in diverse areas. However, as clusters of Symmetric Multi-Processor (SMP) and heterogeneous machines become popular, conventional message passing models must be adapted accordingly to support this new kind of clusters efficiently. In addition, Java programming language, with its features like object oriented architecture, platform independent bytecode, and native support for multithreading, makes it an alternative language for cluster computing. This research presents a new parallel programming model and a library called VCluster that implements this model on top of a Java Virtual Machine (JVM). The programming model is based on virtual migrating threads to support clusters of heterogeneous SMP machines efficiently. VCluster is implemented in 100% Java, utilizing the portability of Java to address the problems of heterogeneous machines. VCluster virtualizes computational and communication resources such as threads, computation states, and communication channels across multiple separate JVMs, which makes a mobile thread possible. Equipped with virtual migrating thread, it is feasible to balance the load of computing resources dynamically. Several large scale parallel applications have been developed using VCluster to compare the performance and usage of VCluster with other libraries. The results of the experiments show that VCluster makes it easier to develop multithreading parallel applications compared to conventional libraries like MPI. At the same time, the performance of VCluster is comparable to MPICH, a widely used MPI library, combined with popular threading libraries like POSIX Thread and OpenMP. In the next phase of our work, we implemented thread group and thread migration to demonstrate the feasibility of dynamic load balancing in VCluster. We carried out experiments to show that the load can be dynamically balanced in VCluster, resulting in a better performance. Thread group also makes it possible to implement collective communication functions between threads, which have been proved to be useful in process based libraries

Comparing the effectiveness of fine-grain memory caching against page migration/replication in reducing traffic in DSM clusters

In this paper we compare and contrast two techniques to improve capacity/conflict miss traffic in CC-NUMA DSM clusters. Page migration/replication optimizes read-write accesses to a page used by a single processor by migrating the page to that processor and replicates all read-shared pages in the sharers' local memories. R-NUMA optimizes read- write accesses to any page by allowing a processor to cache that page in its main memory. Page migration/replication requires less hardware complexity as compared to R-NUMA, but has limited applicability and incurs much higher overheads even with timed hardware/software support. In this paper, we compare and contrast page migration/replication and R-NUMA on simulated clusters of symmetric multiprocessors executing shared-memory applications. Our results show that: (1) both page migration/replication and R-NUMA significantly improve the system performance over “first-touch” migration in many applications, (2) page migration/replication has limited opportunity and can not eliminate all the capacity/conflict misses even with fast hardware support and unlimited amount of memory, (3) R-NUMA always performs best given a page cache large enough to fit an application's primary working set and subsumes page migration/replication, (4) R-NUMA benefits more from hardware support to accelerate page operations than page migration/replication, and (5) integrating page migration/replication into R- NUMA to help reduce the hardware cost requires sophisticated mechanisms and policies to select candidates for page migration/replicatio