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MicroPhase: An approach to proactively invoking garbage collection for improved performance

acm sigplan NOTICES 2007年第10期42卷 77-96页

作者： Xian, Feng Srisa-an, Witawas Jiang, Hong Univ Nebraska Dept Comp Sci & Engn Lincoln NE 68588 USA

To date, the most commonly used criterion for invoking garbage collection (GC) is based on heap usage;that is, garbage collection is invoked when the heap or an area inside the heap is full. This approach can suffer from two performance shortcomings: untimely garbage collection invocations and large volumes of surviving objects. In this work, we explore a newGC triggering approach called MicroPhase that exploits two observations: (i) allocation requests occur in phases and (ii) phase boundaries coincide with times when most objects also die. Thus, proactively invoking garbage collection at these phase boundaries can yield high efficiency. We extended the HotSpot virtual machine from Sun Microsystems to support MicroPhase and conducted experiments using 20 benchmarks. The experimental results indicate that our technique can reduce the GC times in 19 applications. The differences in GC overhead range from an increase of 1% to a decrease of 26% when the heap is set to twice the maximum live-size. As a result, MicroPhase can improve the overall performance of 13 benchmarks. The performance differences range from a degradation of 2.5% to an improvement of 14%.

关键词： experimentation languages performance

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MOP: An efficient and generic runtime verification framework

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acm sigplan NOTICES 2007年第10期42卷 569-588页

作者： Chen, Feng Rosu, Grigore Univ Illinois Urbana IL 61801 USA

Monitoring-oriented programming (MOP1) [21, 18, 22, 19] is a formal framework for software development and analysis, in which the developer specifies desired properties using definable specification formalisms, along with code to execute when properties are violated or validated. The MOP framework automatically generates monitors from the specified properties and then integrates them together with the user-defined code into the original system. The previous design of MOP only allowed specifications without parameters, so it could not be used to state and monitor safety properties referring to two or more related objects. In this paper we propose a parametric specification-formalism-independent extension of MOP, together with an implementation of JavaMOP that supports parameters. In our current implementation, parametric specifications are translated into AspectJ code and then weaved into the application using off-the-shelf AspectJ compilers;hence, MOP specifications can be seen as formal or logical aspects. Our JavaMOP implementation was extensively evaluated on two benchmarks, Dacapo [14] and Tracematches [8], showing that runtime verification in general and MOP in particular are feasible. In some of the examples, millions of monitor instances are generated, each observing a set of related objects. To keep the runtime overhead of monitoring and event observation low, we devised and implemented a decentralized indexing optimization. Less than 8% of the experiments showed more than 10% runtime overhead;in most cases our tool generates monitoring code as efficient as the hand-optimized code. Despite its genericity, JavaMOP is empirically shown to be more efficient than runtime verification systems specialized and optimized for particular specification formalisms. Many property violations were detected during our experiments;some of them are benign, others indicate defects in programs. Many of these are subtle and hard to find by ordinary testing.

关键词： runtime verification aspect-oriented programming monitoring-oriented programming

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Probabilistic calling context

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acm sigplan NOTICES 2007年第10期42卷 97-111页

作者： Bond, Michael D. McKinley, Kathryn S. Univ Texas Austin Dept Comp Sci Austin TX 78712 USA

Calling context enhances program understanding and dynamic analyses by providing a rich representation of program location. Compared to imperative programs, object-oriented programs use more interprocedural and less intraprocedural control flow, increasing the importance of context sensitivity for analysis. However, prior online methods for computing calling context, such as stack-walking or maintaining the current location in a calling context tree, are expensive in time and space. This paper introduces a new online approach called probabilistic calling context (PCC) that continuously maintains a probabilistically unique value representing the current calling context. For millions of unique contexts, a 32-bit PCC value has few conflicts. Computing the PCC value adds 3% average overhead to a Java virtual machine. PCC is well-suited to clients that detect new or anomalous behavior since PCC values from training and production runs can be compared easily to detect new context-sensitive behavior;clients that query the PCC value at every system call, Java utility call, and Java API call add 0-9% overhead on average. PCC adds space overhead proportional to the distinct contexts stored by the client (one word per context). Our results indicate PCC is efficient and accurate enough to use in deployed software for residual testing, bug detection, and intrusion detection.

关键词： reliability security performance experimentation calling context dynamic context sensitivity probabilistic residual testing anomaly-based bug detection intrusion detection managed languages

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Modular verification of higher-order methods with mandatory calls specified by model programs

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acm sigplan NOTICES 2007年第10期42卷 351-367页

作者： Shaner, Steve M. Leavens, Gary T. Naumann, David A. Iowa State Univ Ames IA 50011 USA Stevens Inst Technol Hoboken NJ 07030 USA

What we call a "higher-order method" (HOM) is a method that makes mandatory calls to other dynamically-dispatched methods. Examples include template methods as in the Template method design pattern and notify methods in the Observer pattern. HOMs are particularly difficult to reason about, because standard pre- and postcondition specifications cannot describe the mandatory calls. For reasoning about such methods, existing approaches use either higher-order logic or traces, but both are complex and verbose. We describe a simple, concise, and modular approach to specifying HOMs We show how to verify calls to HOMs and their code using first-order verification conditions, in a sound and modular way. Verification of client code that calls HOMs can take advantage of the client's knowledge about the mandatory calls to make strong conclusions. Our verification technique validates and explains traditional documentation practice for HOMs, which typically shows their code. However, specifications do not have to expose all of the code to clients, but only enough to determine how the HOM makes its mandatory calls.

关键词： languages verification model program verification specification languages grey-box approach higher order method mandatory call Hoare logic refinement calculus

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ILEA: Inter-language analysis across Java and C

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acm sigplan NOTICES 2007年第10期42卷 39-56页

作者： Tan, Gang Morrisett, Greg Boston Coll Chestnut Hill MA 02467 USA Harvard Univ Cambridge MA 02138 USA

Java bug finders perform static analysis to find implementation mistakes that can lead to exploits and failures;Java compilers perform static analysis for optimization. If Java programs contain foreign function calls to C libraries, however, static analysis is forced to make either optimistic or pessimistic assumptions about the foreign function calls, since models of the C libraries are typically not available. We propose ILEA (stands for Inter-LanguagE Analysis), which is a framework that enables existing Java analyses to understand the behavior of C code. Our framework includes: (1) a novel specification language, which extends the Java Virtual Machine Language (JVML) with a few primitives that approximate the effects that the C code might have;(2) an automatic specification extractor, which builds models of the C code. Comparing to other possible specification languages, our language is expressive, yet facilitates construction of automatic specification extractors. Furthermore, because the specification language is based on the JVML, existing Java analyses can be easily migrated to utilize specifications in the language. We also demonstrate the utility of the specifications generated, by modifying an existing non-null analysis to identify null-related bugs in Java applications that contain C libraries. Our preliminary experiments identified dozens of null-related bugs.

关键词： languages reliability verification inter-language analysis Java native interface JNI JVML specification extraction

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Using early phase termination to eliminate load imbalances at barrier synchronization points

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acm sigplan NOTICES 2007年第10期42卷 369-386页

作者： Rinard, Martin MIT Dept Elect Engn & Comp Sci Comp Sci & Artific Intelligence Lab Cambridge MA 02139 USA

We present a new technique, early phase termination, for eliminating idle processors in parallel computations that use barrier synchronization. This technique simply terminates each parallel phase as soon as there are too few remaining tasks to keep all of the processors busy. Although this technique completely eliminates the idling that would otherwise occur at barrier synchronization points, it may also change the computation and therefore the result that the computation produces. We address this issue by providing probabilistic distortion models that characterize how the use of early phase termination distorts the result that the computation produces. Our experimental results show that for our set of benchmark applications, 1) early phase termination can improve the performance of the parallel computation, 2) the distortion is small (or can be made to be small with the use of an appropriate compensation technique) and 3) the distortion models provide accurate and tight distortion bounds. These bounds can enable users to evaluate the effect of early phase termination and confidently accept results from parallel computations that use this technique if they find the distortion bounds to be acceptable. Finally, we identify a general computational pattern that works well with early phase termination and explain why computations that exhibit this pattern can tolerate the early termination of parallel tasks without producing unacceptable results.

关键词： performance reliability design languages barrier synchronization parallel computing probabilistic distortion models early phase termination

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Tracking bad apples: Reporting the origin of null and undefined value errors

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acm sigplan NOTICES 2007年第10期42卷 405-422页

作者： Bond, Michael D. Nethercote, Nicholas Kent, Stephen W. Guyer, Samuel Z. McKinley, Kathryn S. Univ Texas Austin Dept Comp Sci Austin TX 78712 USA

Programs sometimes crash due to unusable values, for example, when Java and C# programs dereference null pointers and when C and C++ programs use undefined values to affect program behavior. A stack trace produced on such a crash identifies the effect of the unusable value, not its cause, and is often not much help to the programmer. This paper presents efficient origin tracking of unusable values;it shows how to record where these values come into existence, correctly propagate them, and report them if they cause an error. The key idea is value piggybacking: when the original program stores an unusable value, value piggybacking instead stores origin information in the spare bits of the unusable value. Modest compiler support alters the program to propagate these modified values through operations such as assignments and comparisons. We evaluate two implementations: the first tracks null pointer origins in a JVM, and the second tracks undefined value origins in a memory-checking tool built with Valgrind. These implementations show that origin tracking via value piggybacking is fast and often useful, and in the Java case, has low enough overhead for use in a production environment.

关键词： reliability performance experimentation debugging low-overhead run-time support null pointer exceptions undefined values managed languages Java Valgrind

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Type qualifier inference for Java

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acm sigplan NOTICES 2007年第10期42卷 321-336页

作者： Greenfieldboyce, David Foster, Jeffrey S. Univ Maryland College Pk MD 20742 USA

Java's type system provides programmers with strong guarantees of type and memory safety, but there are many important properties not captured by standard Java types. We describe JQual, a tool that adds user-defined type qualifiers to Java, allowing programmers to quickly and easily incorporate extra lightweight, application-specific type checking into their programs. JQual provides type qualifier inference, so that programmers need only add a few key qualifier annotations to their program, and then JQual infers any remaining qualifiers and checks their consistency. We explore two applications of JQual. First, we introduce of opaque and enum qualifiers to track C pointers and enumerations that flow through Java code via the JNI. In our benchmarks we found that these C values are treated correctly, but there are some places where a client could potentially violate safety. Second, we introduce a read only qualifier for annotating references that cannot be used to modify the objects they refer to. We found that JQual is able to automatically infer readonly in many places on method signatures. These results suggest that type qualifiers and type qualifier inference are a useful addition to Java.

关键词： languages verification JQual Java type qualifiers readonly mutable opaque transparent tracked context-sensitivity field-sensitivity context-free language reachability

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SA2: languages for safety-critical software: issues and assessment 07

SA2: languages for safety-critical software: issues and asse...

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Proceedings of the 2007 acm international conference on SIGAda annual international conference

作者： Ben Brosgol AdaCore Inc.

ISBN: (纸本)9781595938763

This intermediate-level tutorial is aimed at people with a technical background in software development. No previous experience with safety-critical standards is required. Some familiarity with one or more of C, C++, Ada, or Java would be ***-critical systems (whose anomalous behavior could cause catastrophic or major failure involving loss of life) are becoming increasingly prevalent. Standards such as DO-178B, originally developed for commercial avionics, are attracting attention in other segments. The requirement to comply with such standards imposes constraints (on quality assurance, traceability, etc. ) much beyond what is typical for Commercial-Off-The-Shelf Software. One of the major decisions that affects safety certification is the choice of programming language(s). Specific language features, either by their presence of absence, may make certification easier or harder. (Practicalities such as tool support and programmer experience are of course also important but are outside the scope of the tutorial).This tutorial first summarizes existing safety standards, with a focus on DO-178B, and explains how they affect the requirements on a programming language. It specifically addresses the challenges imposed by object-oriented Technology and summarizes the work currently underway on DO-178C. The tutorial then assesses three language technologies -- C (including C++), Ada, and Java - with respect to suitability for meeting these requirements through appropriate subsetting. MISRA C, SPARK, and the in-progress Safety-Critical Java Technology are specifically identified and reviewed.

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Using architecture to change code: Studying information needs

Using architecture to change code: Studying information need...

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21st Annual acm sigplan conference on object-oriented programming systems, languages, and Applications, OOPSLA 2006

作者： Latoza, Thomas D. Institute for Software Research International Carnegie Mellon University 5000 Forbes Avenue Pittsburgh PA 15213

While architecture is widely viewed as important, the mechanisms by which understanding architecture helps developers better change code are less clear. We are conducting a laboratory study to gather requirements for ... 详细信息

ISBN: (纸本)159593491X

关键词： Codes (symbols)

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