An alternative optimization technique for JavaScript engines

ABSTRACT Thread Level Speculation at function level has been suggested as a method to automatically (or semi-automatically) extract parallelism from sequential programs. While there have been multiple implementations in both hardware and software, little work has been done in the context of dynamic programming languages such as JavaScript. In this paper we evaluate the effects of a simple Thread Level Speculation approach, implemented on top of the Rhino1 7R2 JavaScript engine. The evalauation is done using the wellknown JavaScript benchmark suite V8. More specifically, we have measured the effects of our null return value prediction approach for function calls, conflicts with variables in a global scope, and the effects on the execution time. The results show that our strategy to speculate on return values is successful, that conflicts with global variables occur, and for several applications are the execution time improved, while the performance decrease for some applications due to speculation overhead

Introducing concurrency in sequential Java via laws

AbstractNowadays multi-core processors can be found everywhere. It is well known that one way of improving performance is by parallelization. In this paper we propose a parallelization strategy for Java using algebraic laws. We perform an experiment with two benchmarks and show that our strategy produces a gain similar to a specialized parallel version provided by the Java Grande Benchmark (JGB)

POWER: Parallel Optimizations With Executable Rewriting

The hardware industry's rapid development of multicore and many core hardware has outpaced the software industry's transition from sequential to parallel programs. Most applications are still sequential, and many cores on parallel machines remain unused. We propose a tool that uses data-dependence profiling and binary rewriting to parallelize executables without access to source code. Our technique uses Bernstein's conditions to identify independent sets of basic blocks that can be executed in parallel, introducing a level of granularity between fine-grained instruction level and coarse grained task level parallelism. We analyze dynamically generated control and data dependence graphs to find independent sets of basic blocks which can be parallelized. We then propose to parallelize these candidates using binary rewriting techniques. Our technique aims to demonstrate the parallelism that remains in serial application by exposing concrete opportunities for parallelism

A Survey on Thread-Level Speculation Techniques

Producción CientíficaThread-Level Speculation (TLS) is a promising technique that allows the parallel execution of sequential code without relying on a prior, compile-time-dependence analysis. In this work, we introduce the technique, present a taxonomy of TLS solutions, and summarize and put into perspective the most relevant advances in this field.MICINN (Spain) and ERDF program of the European Union: HomProg-HetSys project (TIN2014-58876-P), CAPAP-H5 network (TIN2014-53522-REDT), and COST Program Action IC1305: Network for Sustainable Ultrascale Computing (NESUS)

Dynamic web worker pool management for highly parallel javascript web applications

JavaScript web applications are improving performance mainly thanks to the inclusion of new standards by HTML5. Among others, web workers API allows multithreaded JavaScript web apps to exploit parallel processors. However, developers have difficulties to determine the minimum number of web workers that provide the highest performance. But even if developers found out this optimal number, it is a static value configured at the beginning of the execution. Because users tend to execute other applications in background, the estimated number of web workers could be non-optimal, because it may overload or underutilize the system. In this paper, we propose a solution for highly parallel web apps to dynamically adapt the number of running web workers to the actual available resources, avoiding the hassle to estimate a static optimal number of threads. The solution consists in the inclusion of a web worker pool and a simple management algorithm in the web app. Even though there are co-running applications, the results show our approach dynamically enables a number of web workers close to the optimal. Our proposal, which is independent of the web browser, overcomes the lack of knowledge of the underlying processor architecture as well as dynamic resources availability changes.Peer ReviewedPostprint (author's final draft

Computational Caches

Caching is a well-known technique for speeding up computation. We cache data from file systems and databases; we cache dynamically generated code blocks; we cache page translations in TLBs. We propose to cache the act of computation, so that we can apply it later and in different contexts. We use a state-space model of computation to support such caching, involving two interrelated parts: speculatively memoized predicted/resultant state pairs that we use to accelerate sequential computation, and trained probabilistic models that we use to generate predicted states from which to speculatively execute. The key techniques that make this approach feasible are designing probabilistic models that automatically focus on regions of program execution state space in which prediction is tractable and identifying state space equivalence classes so that predictions need not be exact.Engineering and Applied Science

ASC: Automatically Scalable Computation

We present an architecture designed to transparently and automatically scale the performance of sequential programs as a function of the hardware resources available. The architecture is predicated on a model of computation that views program execution as a walk through the enormous state space composed of the memory and registers of a single-threaded processor. Each instruction execution in this model moves the system from its current point in state space to a deterministic subsequent point. We can parallelize such execution by predictively partitioning the complete path and speculatively executing each partition in parallel. Accurately partitioning the path is a challenging prediction problem. We have implemented our system using a functional simulator that emulates the x86 instruction set, including a collection of state predictors and a mechanism for speculatively executing threads that explore potential states along the execution path. While the overhead of our simulation makes it impractical to measure speedup relative to native x86 execution, experiments on three benchmarks show scalability of up to a factor of 256 on a 1024 core machine when executing unmodified sequential programs.Engineering and Applied Science

Runtime-adaptive generalized task parallelism

Multi core systems are ubiquitous nowadays and their number is ever increasing. And while, limited by physical constraints, the computational power of the individual cores has been stagnating or even declining for years, a solution to effectively utilize the computational power that comes with the additional cores is yet to be found. Existing approaches to automatic parallelization are often highly specialized to exploit the parallelism of specific program patterns, and thus to parallelize a small subset of programs only. In addition, frequently used invasive runtime systems prohibit the combination of different approaches, which impedes the practicality of automatic parallelization. In the following thesis, we show that specializing to narrowly defined program patterns is not necessary to efficiently parallelize applications coming from different domains. We develop a generalizing approach to parallelization, which, driven by an underlying mathematical optimization problem, is able to make qualified parallelization decisions taking into account the involved runtime overhead. In combination with a specializing, adaptive runtime system the approach is able to match and even exceed the performance results achieved by specialized approaches.Mehrkernsysteme sind heutzutage allgegenwärtig und finden täglich weitere Verbreitung. Und während, limitiert durch die Grenzen des physikalisch Machbaren, die Rechenkraft der einzelnen Kerne bereits seit Jahren stagniert oder gar sinkt, existiert bis heute keine zufriedenstellende Lösung zur effektiven Ausnutzung der gebotenen Rechenkraft, die mit der steigenden Anzahl an Kernen einhergeht. Existierende Ansätze der automatischen Parallelisierung sind häufig hoch spezialisiert auf die Ausnutzung bestimmter Programm-Muster, und somit auf die Parallelisierung weniger Programmteile. Hinzu kommt, dass häufig verwendete invasive Laufzeitsysteme die Kombination mehrerer Parallelisierungs-Ansätze verhindern, was der Praxistauglichkeit und Reichweite automatischer Ansätze im Wege steht. In der Ihnen vorliegenden Arbeit zeigen wir, dass die Spezialisierung auf eng definierte Programmuster nicht notwendig ist, um Parallelität in Programmen verschiedener Domänen effizient auszunutzen. Wir entwickeln einen generalisierenden Ansatz der Parallelisierung, der, getrieben von einem mathematischen Optimierungsproblem, in der Lage ist, fundierte Parallelisierungsentscheidungen unter Berücksichtigung relevanter Kosten zu treffen. In Kombination mit einem spezialisierenden und adaptiven Laufzeitsystem ist der entwickelte Ansatz in der Lage, mit den Ergebnissen spezialisierter Ansätze mitzuhalten, oder diese gar zu übertreffen.Part of the work presented in this thesis was performed in the context of the SoftwareCluster project EMERGENT (http://www.software-cluster.org). It was funded by the German Federal Ministry of Education and Research (BMBF) under grant no. “01IC10S01”. Later work has been supported, also by the German Federal Ministry of Education and Research (BMBF), through funding for the Center for IT-Security, Privacy and Accountability (CISPA) under grant no. “16KIS0344”