Scott Trent

A study of Java's non-Java memory

A Java application sometimes raises an out-of-memory ex-ception. This is usually because it has exhausted the Java heap. However, a Java application can raise an out-of-memory exception when it exhausts the memory used by Java that is not in the Java heap. We call this area non-Java memory. For example, an out-of-memory exception in the non-Java memory can happen when the JVM attempts to load too many classes. Although it is relatively rare to ex-haust the non-Java memory compared to exhausting the Java heap, a Java application can consume a considerable amount of non-Java memory. This paper presents a quantitative analysis of non-Java memory. To the best of our knowledge, this is the first in-depth analysis of the non-Java memory. To do this we cre-ated a tool called Memory Analyzer for Redundant, Unused, and String Areas (MARUSA), which gathers memory statis-tics from both the OS and the Java virtual machine, break-ing down and visualizing the non-Java memory usage. We studied the use of non-Java memory for a wide range of Java applications, including the DaCapo benchmarks and Apache DayTrader. Our study is based on the IBM J9 Java Virtual Machine for Linux. Although some of our results may be specific to this combination, we believe that most of our observations are applicable to other platforms as well.

Evaluation of a just-in-time compiler retrofitted for PHP

Programmers who develop Web applications often use dynamic scripting languages such as Perl, PHP, Python, and Ruby. For general purpose scripting language usage, interpreter-based implementations are efficient and popular but the server-side usage for Web application development implies an opportunity to significantly enhance Web server throughput. This paper summarizes a study of the optimization of PHP script processing. We developed a PHP processor, P9, by adapting an existing production-quality just-in-time (JIT) compiler for a Java virtual machine, for which optimization technologies have been well-established, especially for server-side application. This paper describes and contrasts microbenchmarks and SPECweb2005 benchmark results for a well-tuned configuration of a traditional PHP interpreter and our JIT compiler-based implementation, P9. Experimental results with the microbenchmarks show 2.5-9.5x advantage with P9, and the SPECweb2005 measurements show about 20-30% improvements. These results show that the acceleration of dynamic scripting language processing does matter in a realistic Web application server environment. CPU usage profiling shows our simple JIT compiler introduction reduces the PHP core runtime overhead from 45% to 13% for a SPECweb2005 scenario, implying that further improvements of dynamic compilers would provide little additional return unless other major overheads such as heavy memory copy between the language runtime and Web server frontend are reduced.

Highly scalable web applications with zero-copy data transfer

The performance of server-side applications is becoming increasingly important as more applications exploit the Web application model. Extensive work has been done to improve the performance of individual software components such as Web servers and programming language runtimes. This paper describes a novel approach to boost Web application performance by improving inter-process communication between a programming language runtime and Web server runtime. The approach reduces redundant processing for memory copying and the context switch overhead between user space and kernel space by exploiting the zero-copy data transfer methodology, such as the sendfile system call. In order to transparently utilize this optimization feature with existing Web applications, we propose enhancements of the PHP runtime, FastCGI protocol, and Web server. Our proposed approach achieves a 126% performance improvement with micro-benchmarks and a 44% performance improvement for a standard Web benchmark, SPECweb2005.

COOL: A Model-Driven and Automated System for Guided and Verifiable Cloud Solution Design

In this paper, we present COOL (ClOud sOlution design tooL), which is a model-driven cloud solution design tool for automatic solution generation, and solution verification. It offers a guided solutioning and customization method starting from complex client business and IT requirements, and enables verification of solution correctness by leveraging constraint satisfaction solvers.