Compiler and Runtime Optimizations for Fine-Grained Distributed Shared Memory Systems

Bal, H.E. [Promotor

High-performance all-software distributed shared memory

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (p. 165-172).by Kirk Lauritz Johnson.Ph.D

OctopusDB : flexible and scalable storage management for arbitrary database engines

We live in a dynamic age with the economy, the technology, and the people around us changing faster than ever before. Consequently, the data management needs in our modern world are much different than those envisioned by the early database inventors in the 70s. Today, enterprises face the challenge of managing ever-growing dataset sizes with dynamically changing query workloads. As a result, modern data managing systems, including relational as well as big data management systems, can no longer afford to be carved-in-stone solutions. Instead, data managing systems must inherently provide flexible data management techniques in order to cope with the constantly changing business needs. The current practice to deal with changing query workloads is to have a different specialized product for each workload type, e.g. row stores for OLTP workload, column stores for OLAP workload, streaming systems for streaming workload, and scan-oriented systems for shared query processing. However, this means that the enterprises have to now glue different data managing products together and copy data from one product to another, in order to support several query workloads. This has the additional penalty of managing a zoo of data managing systems in the first place, which is tedious, expensive, as well as counter-productive for modern enterprises. This thesis presents an alternative approach to supporting several query workloads in a data managing system. We observe that each specialized database product has a different data store, indicating that different query workloads work well with different data layouts. Therefore, a key requirement for supporting several query workloads is to support several data layouts. Therefore, in this thesis, we study ways to inject different data layouts into existing (and familiar) data managing systems. The goal is to develop a flexible storage layer which can support several query workloads in a single data managing system. We present a set of non-invasive techniques, coined Trojan Techniques, to inject different data layouts into a data managing system. The core idea of Trojan Techniques is to drop the assumption of having one fixed data store per data managing system. Trojan Techniques are non-invasive in the sense that they do not make heavy untenable changes to the system. Rather, they affect the data managing system from inside, almost at the core. As a result, Trojan Techniques bring significant improvements in query performance. It is interesting to note that in our approach we follow a design pattern that has been used in other non-invasive research works as well, such as PAX, fractal prefetching B+-trees, and RowCol. We propose four Trojan Techniques. First, Trojan Indexes add an additional index access path in Hadoop MapReduce. Second, Trojan Joins allow for co-partitioned joins in Hadoop MapReduce. Third, Trojan Layouts allow for row, column, or column-grouped layouts in Hadoop MapReduce. Together, these three techniques provide a highly flexible data storage layer for Hadoop MapReduce. Our final proposal, Trojan Columns, introduces columnar functionality in row-oriented relational databases, including closed source commercial databases, thus bridging the gap between row and column oriented databases. Our experimental results show that Trojan Techniques can improve the performance of Hadoop MapReduce by a factor of up to 18, and that of a top-notch commercial database product by a factor of up to 17.Wir leben in einer dynamischen Zeit, in der sich Wirtschaft, Technologie und Gesellschaft schneller verändern als jemals zuvor. Folglich unterscheiden sich die Anforderungen an Datenverarbeitung heute sehr von dem, was sich die Pioniere dieses Forschungsgebiets in den 70er Jahren ursprünglich ausgemalt hatten. Heutzutage sehen sich Firmen mit der Herausforderung konfrontiert, stark fluktuierende Anfragelasten über einer stetig wachsender Datenmengen zu bewältigen. Daher können es sich moderne Datenbanksysteme, sowohl relationale als auch Big Data Systeme, nicht mehr leisten, wie starre, in Stein gemeißelte Lösungen zu funktionieren. Stattdessen sollten moderne Datenbanksysteme von Grunde auf für flexible Datenverwaltung konzipiert werden, um mit sich ständig ändernden Anforderungen Schritt halten zu können. Die gegenwärtige Praxis im Umgang mit häufig wechselnden Anfragemustern besteht allerdings noch darin, jeweils unterschiedliche, spezialisierte Lösungen für die verschiedenen Anfragetypen zu nutzen - zum Beispiel zeilenorientierte Systeme für OLTP Anfragen, spaltenorientierte Systeme für OLAP Anfragen, Data Stream Management Systeme für kontinuierliche Datenströme und Scan-basierte Systeme für die Bearbeitung von vielen gleichzeitigen Anfragen. Leider setzt dieses Vorgehen aber voraus, dass die Unternehmen es schaffen die verschiedensten Systeme irgendwie miteinander zu verknüpfen und einen Datenaustausch zwischen ihnen zu gewährleisten. Ein zusätzlicher Nachteil ist, dass hierbei oft ein ganzes Sortiment von Datenbankprodukten eingerichtet und gepflegt werden muss, was sowohl zeit- als auch kostenintensiv und damit letztlich aufwendig ist. Diese Dissertation präsentiert eine alternative Lösung, um wechselnde Anfragemuster effizient mit einem einzigen Datenverwaltungssystem zu unterstützen. Aus der Beobachtung, dass jedes spezielle Datenbankprodukt unterschiedliche Ansätze zur Datenspeicherung nutzt, folgern wir, dass verschiedene Anfragen jeweils auf bestimmten Datenlayouts effizienter beantwortet werden können als auf anderen. Deshalb ist eine zentrale Anforderung zur effizienten Verarbeitung unterschiedlicher Anfragetypen mit nur einem System, dass dieses System verschiedene Datenlayouts unterstützen muss. Dazu untersuchen wir in dieser Arbeit Möglichkeiten, um verschiedene Datenlayouts nachträglich in bestehende (und bekannte) Datenbanksysteme einzuschleusen. Das Ziel hierbei ist die Entwicklung einer flexiblen Speicherschicht, die verschiedenste Anfragen in einem einzigen Datenbanksystem unterstützen kann. Wir haben hierzu eine Reihe von nichtinvasiven Techniken, auch Trojanische Techniken genannt, entwickelt, mit denen sich verschiedene Datenlayouts nachträglich in existierende Systeme einschleusen lassen. Die Grundidee hinter diesen Trojanischen Techniken ist es, die Annahme, dass jedes Datenbanksystem nur eine festgelegte Art der Datenspeicherung haben kann, fallen zu lassen. Die Trojanischen Techniken erfordern nur minimale Änderungen am ursprünglichen Datenbanksystem, sondern beeinflussen dessen Verhalten von innen heraus. Der Einsatz Trojanischen Techniken kann die Anfragegeschwindigkeit erheblich steigern. Wir folgen mit diesem Ansatz einem Entwurfsmuster, das auch in anderen nichtinvasiven Forschungsprojekten wie PAX, fpB+-Bäume und RowCol verwendet wurde. Wir stellen in dieser Arbeit vier verschiedene Trojanische Techniken vor. Als erstes zeigen wir, wie Trojanische Indexe die Integration eines Index in Hadoop MapReduce ermöglichen. Ergänzt wird dies durch Trojanische Joins, welche kopartitionierte Joins in Hadoop MapReduce ermöglichen. Danach zeigen wir, wie Trojanische Layouts Hadoop MapReduce um zeilen-, spalten- und gruppierte spaltenorientierte Datenlayouts erweitern. Zusammen bilden diese Techniken eine flexible Speicherschicht für das Hadoop MapReduce Framework. Unsere vierte Technik, Trojanische Spalten, erlaubt es uns, spaltenorientierte Datenverarbeitung nachträglich in zeilenbasierten Datenbanksysteme einzuführen und lässt sich sogar auf kommerzielle closed-source Produkten anwenden. Wir schließen damit die Lücke zwischen zeilen- und spaltenorientierten Datenbanksystemen. In unseren Experimenten zeigen wir, dass die Trojanischen Techniken die Leistung des Hadoop MapReduce Frameworks um das bis zu 18fache und die Geschwindigkeit einer aktuellen kommerziellen Datenbank um das 17fache erhöhen können

PiCo: A Domain-Specific Language for Data Analytics Pipelines

In the world of Big Data analytics, there is a series of tools aiming at simplifying programming applications to be executed on clusters. Although each tool claims to provide better programming, data and execution models—for which only informal (and often confusing) semantics is generally provided—all share a common under- lying model, namely, the Dataflow model. Using this model as a starting point, it is possible to categorize and analyze almost all aspects about Big Data analytics tools from a high level perspective. This analysis can be considered as a first step toward a formal model to be exploited in the design of a (new) framework for Big Data analytics. By putting clear separations between all levels of abstraction (i.e., from the runtime to the user API), it is easier for a programmer or software designer to avoid mixing low level with high level aspects, as we are often used to see in state-of-the-art Big Data analytics frameworks. From the user-level perspective, we think that a clearer and simple semantics is preferable, together with a strong separation of concerns. For this reason, we use the Dataflow model as a starting point to build a programming environment with a simplified programming model implemented as a Domain-Specific Language, that is on top of a stack of layers that build a prototypical framework for Big Data analytics. The contribution of this thesis is twofold: first, we show that the proposed model is (at least) as general as existing batch and streaming frameworks (e.g., Spark, Flink, Storm, Google Dataflow), thus making it easier to understand high-level data-processing applications written in such frameworks. As result of this analysis, we provide a layered model that can represent tools and applications following the Dataflow paradigm and we show how the analyzed tools fit in each level. Second, we propose a programming environment based on such layered model in the form of a Domain-Specific Language (DSL) for processing data collections, called PiCo (Pipeline Composition). The main entity of this programming model is the Pipeline, basically a DAG-composition of processing elements. This model is intended to give the user an unique interface for both stream and batch processing, hiding completely data management and focusing only on operations, which are represented by Pipeline stages. Our DSL will be built on top of the FastFlow library, exploiting both shared and distributed parallelism, and implemented in C++11/14 with the aim of porting C++ into the Big Data world

Simulation Modelling of Distributed-Shared Memory Multiprocessors

Institute for Computing Systems ArchitectureDistributed shared memory (DSM) systems have been recognised as a compelling platform for parallel computing due to the programming advantages and scalability. DSM systems allow applications to access data in a logically shared address space by abstracting away the distinction of physical memory location. As the location of data is transparent, the sources of overhead caused by accessing the distant memories are difficult to analyse. This memory locality problem has been identified as crucial to DSM performance. Many researchers have investigated the problem using simulation as a tool for conducting experiments resulting in the progressive evolution of DSM systems. Nevertheless, both the diversity of architectural configurations and the rapid advance of DSM implementations impose constraints on simulation model designs in two issues: the limitation of the simulation framework on model extensibility and the lack of verification applicability during a simulation run causing the delay in verification process. This thesis studies simulation modelling techniques for memory locality analysis of various DSM systems implemented on top of a cluster of symmetric multiprocessors. The thesis presents a simulation technique to promote model extensibility and proposes a technique for verification applicability, called a Specification-based Parameter Model Interaction (SPMI). The proposed techniques have been implemented in a new interpretation-driven simulation called DSiMCLUSTER on top of a discrete event simulation (DES) engine known as HASE. Experiments have been conducted to determine which factors are most influential on the degree of locality and to determine the possibility to maximise the stability of performance. DSiMCLUSTER has been validated against a SunFire 15K server and has achieved similarity of cache miss results, an average of +-6% with the worst case less than 15% of difference. These results confirm that the techniques used in developing the DSiMCLUSTER can contribute ways to achieve both (a) a highly extensible simulation framework to keep up with the ongoing innovation of the DSM architecture, and (b) the verification applicability resulting in an efficient framework for memory analysis experiments on DSM architecture

An OS-Based Alternative to Full Hardware Coherence on Tiled Chip-Multiprocessors

Institute for Computing Systems ArchitectureThe interconnect mechanisms (shared bus or crossbar) used in current chip-multiprocessors (CMPs) are expected to become a bottleneck that prevents these architectures from scaling to a larger number of cores. Tiled CMPs offer better scalability by integrating relatively simple cores with a lightweight point-to-point interconnect. However, such interconnects make snooping impractical and, thus, require alternative solutions to cache coherence. This thesis proposes a novel, cost-effective hardware mechanism to support shared-memory parallel applications that forgoes hardware maintained cache coherence. The proposed mech- anism is based on the key ideas that mapping of lines to physical caches is done at the page level with OS support and that hardware supports remote cache accesses. It allows only some controlled migration and replication of data and provides a sufficient degree of flexibility in the mapping through an extra level of indirection between virtual pages and physical tiles. The proposed tiled CMP architecture is evaluated on the SPLASH-2 scientific benchmarks and ALPBench multimedia benchmarks against one with private caches and a distributed direc- tory cache coherence mechanism. Experimental results show that the performance degradation is as little as 0%, and 16% on average, compared to the cache coherent architecture across all benchmarks for 16 and 32 processors

Co-Evolution of Source Code and the Build System: Impact on the Introduction of AOSD in Legacy Systems

Software is omnipresent in our daily lives. As users demand ever more advanced features, software systems have to keep on evolving. In practice, this means that software developers need to adapt the description of a software application. Such a description not only consists of source code written down in a programming language, as a lot of knowledge is hidden in lesser known software development artifacts, like the build system. As its name suggests, the build system is responsible for building an executable program, ready for use, from the source code. There are various indications that the evolution of source code is strongly related to that of the build system. When the source code changes, the build system has to co-evolve to safeguard the ability to build an executable program. A rigid build system on the other hand limits software developers. This phenomenon especially surfaces when drastic changes in the source code are coupled with an inflexible build system, as is the case for the introduction of AOSD technology in legacy systems. AOSD is a young software development approach which enables developers to structure and compose source code in a better way. Legacy systems are old software systems which are still mission-critical, but of which the source code and the build system are no longer fully understood, and which typically make use of old(-fashioned) technology. This PhD dissertation focuses on finding an explanation for this co-evolution of source code and the build system, and on finding developer support to grasp and manage this phenomenon. We postulate four "roots of co-evolution" which represent four different ways in which source code and the build system interact with each other. Based on these roots, we have developed tool and aspect language support to understand and manage co-evolution. The roots and the tool support have been validated in case studies, both in the context of co-evolution in general and of the introduction of AOSD technology in legacy systems. The dissertation experimentally shows that co-evolution indeed is a real problem, but that specific software development and aspect language support enables developers to deal with it

Fundamentals

Volume 1 establishes the foundations of this new field. It goes through all the steps from data collection, their summary and clustering, to different aspects of resource-aware learning, i.e., hardware, memory, energy, and communication awareness. Machine learning methods are inspected with respect to resource requirements and how to enhance scalability on diverse computing architectures ranging from embedded systems to large computing clusters

Fundamentals

Volume 1 establishes the foundations of this new field. It goes through all the steps from data collection, their summary and clustering, to different aspects of resource-aware learning, i.e., hardware, memory, energy, and communication awareness. Machine learning methods are inspected with respect to resource requirements and how to enhance scalability on diverse computing architectures ranging from embedded systems to large computing clusters