Adaptive Resource Relocation in Virtualized Heterogeneous Clusters

Cluster computing has recently gone through an evolution from single processor systems to multicore/multi-socket systems. This has resulted in lowering the cost/performance ratio of the compute machines. Compute farms that host these machines tend to become heterogeneous over time due to incremental extensions, hardware upgrades and/or nodes being purchased for users with particular needs. This heterogeneity is not surprising given the wide range of processor, memory and network technologies that become available and the relatively small price difference between these various options. Different CPU architectures, memory capacities, communication and I/O interfaces of the participating compute nodes present many challenges to job scheduling and often result in under or over utilization of the compute resources. In general, it is not feasible for the application programmers to specifically optimize their programs for such a set of differing compute n odes, due to the difficulty and time-intensiveness of such a task. The trend of heterogeneous compute farms has coincided with resurgence in the virtualization technology. Virtualization technology is receiving widespread adoption, mainly due to the benefits of server consolidation and isolation, load balancing, security and fault tolerance. Virtualization has also generated considerable interest in the High Performance Computing (HPC) community, due to the resulting high availability, fault tolerance, cluster partitioning and accommodation of conflicting user requirements. However, the HPC community is still wary of the potential overheads associated with‘ virtualization, as it results in slower network communications and disk I/O, which need to be addressed. The live migration feature, available to most virtualization technologies, can be leveraged to improve the throughput of a heterogeneous compute farm (HC) used for HPC applications. For this we mitigated the slow network communication in Xen; an open source virtual machine monitor. We present a detailed analysis of the communication framework of Xen and propose communication configurations that give 50% improvement over the conventional Xen network configuration. From a detailed study of the migration facility in Xen, we propose an improvement in the live migration facility specifically targeting HPC applications. This optimization gives around 50% improvement over the default migration facility of Xen. In this thesis, we also investigate resource scheduling in heterogeneous compute farm with the perspective of dynamic resource re-mapping. Our approach is to profile each job in the compute farm at runtime, and propose a better resource mapping compared to the initial allocation. We then migrate the job(s) to the best-suited homogeneous sub-cluster to improve overall throughput of the HC. For this, we develop a novel heterogeneity and virtualization-aware profiling framework, which is able to predict the CPU and communication characteristics of high performance scientific applications. The prediction accuracy of our performance estimation model is over 80%. The framework implementation is lightweight, with an overhead of 3%. Our experiments show that we are able to improve the throughput of the compute farm by 25% and the time saved by the HC with our framework is over 30%. The framework can be readily extended to HCs supporting a cloud computing environment

ADEPT Runtime/Scalability Predictor in support of Adaptive Scheduling

A job scheduler determines the order and duration of the allocation of resources, e.g. CPU, to the tasks waiting to run on a computer. Round-Robin and First-Come-First-Serve are examples of algorithms for making such resource allocation decisions. Parallel job schedulers make resource allocation decisions for applications that need multiple CPU cores, on computers consisting of many CPU cores connected by different interconnects. An adaptive parallel scheduler is a parallel scheduler that is capable of adjusting its resource allocation decisions based on the current resource usage and demand. Adaptive parallel schedulers that decide the numbers of CPU cores to allocate to a parallel job provide more flexibility and potentially improve performance significantly for both local and grid job scheduling compared to non-adaptive schedulers. A major reason why adaptive schedulers are not yet used practically is due to lack of knowledge of the scalability curves of the applications, and high cost of existing white-box approaches for scalability prediction. We show that a runtime and scalability prediction tool can be developed with 3 requirements: accuracy comparable to white-box methods, applicability, and robustness. Applicability depends only on knowledge feasible to gain in a production environment. Robustness addresses anomalous behaviour and unreliable predictions. We present ADEPT, a speedup and runtime prediction tool that satisfies all criteria for both single problem size and across different problem sizes of a parallel application. ADEPT is also capable of handling anomalies and judging reliability of its predictions. We demonstrate these using experiments with MPI and OpenMP implementations of NAS benchmarks and seven real applications

The segmental phonology of Shangani

This dissertation is an analysis of the segmental phonology of the Shangani language as spoken in the South Eastern parts of Zimbabwe. It starts by presenting the language situation in Zimbabwe and comparing the language’s status in Zimbabwe with that of its sister varieties in South Africa where it is referred to as Tsonga and in Mozambique where it is referred to as XiChangana or Changana. The dissertation is based on data collected from the speakers of Shangani using a variety of research techniques. The dissertation identifies and characterizes the language’s distinctive phonemes using the minimal pair and set tests. It presents the language’s consonants, which include aspirated, breathy-voiced, pre-nasalized, labialized and palatalized consonants. It shows that in Shangani, voiceless consonants cannot be pre-nasalized and that there is an incompatibility between that labio-velar glide /w/ and most labial consonants excpt /m/. The phonemes are analysed using Chomsky and Halle’s (1968) distinctive feature theory. The study uses Clements and Keyser’s (1983) CV phonology of the syllable structure to analyse the language’s syllable structure. The language’s canonical syllable structure is CV. It is also shown that consonant clusters are gaining their way into the language through borrowing from English, Afrikaans and other languages that have consonant clusters in their inventories. Onsetless Vs are marginally attested word-initially. In agent nouns, VV sequences are in most cases retained. These sequences are not analysed as diphthongs since they occupy different V slots on the syllable tier. The second vowel in the sequence is the onsetless syllable. Affricates, NCs, Cws and Cjs are presented as unitary segments that occupy a single C slot of the CV tier. Phonological processes that are attested in the language are also presented. Secondary articulation, vowel deletion, feature spreading, vowel coalescence and nasalization are shown to be the most common phonological process in the language. Since Shangani has the CV syllable typology, most of the phonological processes are there to resolve hiatus that would have been induced by suffixation of vowel commencing stems or suffixes to vowel final prefixes or stems. The notion of domains is shown to be a diagnostic tool for identifying a process in a hiatus situation. The study shows that vowel deletion is the least preferred strategy when secondary articulation, feature spreading, vowel coalescence have been blocked by some constraints like syllable structure processes or the language’s phonotacticsAfrican LanguagesD. Litt. et Phil. (African Languages

A sociological understanding of urban governance and social accountability: the case of Bulawayo, Zimbabwe

This thesis seeks to understand the ways in which urban governance and urban-based civic participation interact with each other in contemporary Zimbabwe, with a particular focus on the factors influencing and shaping social accountability and effective citizen involvement in urban governance processes. This main objective is pursued with specific reference to Bulawayo, which is one of two metropolitan centres in Zimbabwe. The focus is specifically on questions around social accountability, citizen participation and centralised urban governance. In this regard, it is important to recognise that social accountability and urban governance need to be understood in the context of their inherent relationship and how these both shape and determine each other. In this respect, there is need to probe the foundations that shape the lived experiences of communities, through social accountability and urban governance, and how these pattern development and social change. Zimbabwe for over a decade now has gone through a series of economic and political crises which have impacted detrimentally on urban governance. With the economy in free-fall, local authorities have had to pursue a range of strategies to sustain themselves. These socio-economic conditions have forced a change in relations between the state, cities and citizens. Many studies have examined this regarding the politics of contestation between the ruling party (ZANU-PF), the state, and the main opposition party (MDC) in urban governance in Zimbabwe. However, this study zeros in on social accountability and how it is shaped by the prevailing socio-economic and political environment in Zimbabwe. At the same time, the lived experiences of communities vary and this variance influences and affects social accountability interventions and outcomes in cities like Bulawayo. Importantly, the thesis offers a longitudinal study which can map the contextual factors affecting and influencing social accountability in Bulawayo over time. Though recognising the debilitating effects of centralised urban governance on social accountability, the thesis also raises questions about the shifting, and often tenuous, relationship between the city and the central state, on one hand, and the city and its citizens on the other. In doing so, it considers the role of citizens, institutions and actors in responding to the impacts of urban governance and social accountability. In pursuing this thesis, a range of mainly qualitative research methods were used, including key informant interviews, focus group discussions, observation and use of documents. In the end, the thesis offers a nuanced analysis of the everyday complexities and challenges for social accountability in urban Bulawayo, Zimbabwe and thereby contributes to theorising social accountability and urban governance in Africa more broadly