arXiv subjects

Nectarios Koziris

Publications and source records attributed to Nectarios Koziris.

22 records · Page 2Linked to original sources

arXiv2017

A Decision Tree Based Approach Towards Adaptive Profiling of Distributed Applications

The adoption of the distributed paradigm has allowed applications to increase their scalability, robustness and fault tolerance, but it has also complicated their structure, leading to an exponential growth of the applications' configuration space and increased difficulty in predicting their performance. In this work, we describe a novel, automated profiling methodology that makes no assumptions on application structure. Our approach utilizes oblique Decision Trees in order to recursively partition an application's configuration space in disjoint regions, choose a set of representative samples from each subregion according to a defined policy and return a model for the entire space as a composition of linear models over each subregion. An extensive evaluation over real-life applications and synthetic performance functions showcases that our scheme outperforms other state-of-the-art profiling methodologies. It particularly excels at reflecting abnormalities and discontinuities of the performance function, allowing the user to influence the sampling policy based on the modeling accuracy and the space coverage.

cs.DC↗

arXiv2017

Elastic Resource Management with Adaptive State Space Partitioning of Markov Decision Processes

Modern large-scale computing deployments consist of complex applications running over machine clusters. An important issue in these is the offering of elasticity, i.e., the dynamic allocation of resources to applications to meet fluctuating workload demands. Threshold based approaches are typically employed, yet they are difficult to configure and optimize. Approaches based on reinforcement learning have been proposed, but they require a large number of states in order to model complex application behavior. Methods that adaptively partition the state space have been proposed, but their partitioning criteria and strategies are sub-optimal. In this work we present MDP_DT, a novel full-model based reinforcement learning algorithm for elastic resource management that employs adaptive state space partitioning. We propose two novel statistical criteria and three strategies and we experimentally prove that they correctly decide both where and when to partition, outperforming existing approaches. We experimentally evaluate MDP_DT in a real large scale cluster over variable not-encountered workloads and we show that it takes more informed decisions compared to static and model-free approaches, while requiring a minimal amount of training data.

cs.DC↗

arXiv2016

Improving virtual host efficiency through resource and interference aware scheduling

Modern Infrastructure-as-a-Service Clouds operate in a competitive environment that caters to any user's requirements for computing resources. The sharing of the various types of resources by diverse applications poses a series of challenges in order to optimize resource utilization while avoiding performance degradation caused by application interference. In this paper, we present two scheduling methodologies enforcing consolidation techniques on multicore physical machines. Our resource-aware and interference-aware scheduling schemes aim at improving physical host efficiency while preserving the application performance by taking into account host oversubscription and the resulting workload interference. We validate our fully operational framework through a set of real-life workloads representing a wide class of modern cloud applications. The experimental results prove the efficiency of our system in optimizing resource utilization and thus energy consumption even in the presence of oversubscription. Both methodologies achieve significant reductions of the CPU time consumed, reaching up to 50%, while at the same time maintaining workload performance compared to widely used scheduling schemes under a variety of representative cloud platform scenarios.

cs.DC↗

arXiv2016

A lightweight optimization selection method for Sparse Matrix-Vector Multiplication

In this paper, we propose an optimization selection methodology for the ubiquitous sparse matrix-vector multiplication (SpMV) kernel. We propose two models that attempt to identify the major performance bottleneck of the kernel for every instance of the problem and then select an appropriate optimization to tackle it. Our first model requires online profiling of the input matrix in order to detect its most prevailing performance issue, while our second model only uses comprehensive structural features of the sparse matrix. Our method delivers high performance stability for SpMV across different platforms and sparse matrices, due to its application and architecture awareness. Our experimental results demonstrate that a) our approach is able to distinguish and appropriately optimize special matrices in multicore platforms that fall out of the standard class of memory bandwidth bound matrices, and b) lead to a significant performance gain of 29% in a manycore platform compared to an architecture-centric optimization, as a result of the successful selection of the appropriate optimization for the great majority of the matrices. With a runtime overhead equivalent to a couple dozen SpMV operations, our approach is practical for use in iterative numerical solvers of real-life applications.

cs.PF↗