Automatic feedback-directed object inlining in the java hotspot™ virtual machine
Proceedings of the 3rd international conference on Virtual execution environments
Automatic array inlining in java virtual machines
Proceedings of the 6th annual IEEE/ACM international symposium on Code generation and optimization
Design of the Java HotSpot™ client compiler for Java 6
ACM Transactions on Architecture and Code Optimization (TACO)
Automatic feedback-directed object fusing
ACM Transactions on Architecture and Code Optimization (TACO)
Static detection of loop-invariant data structures
ECOOP'12 Proceedings of the 26th European conference on Object-Oriented Programming
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Object-oriented languages, such as Java, encourage the use of many small objects linked together by field references, instead of a few monolithic structures. While this practice is beneficial from a program design perspective, it can slow down program execution by incurring many pointer indirections. One solution to this problem is object inlining: when the compiler can safely do so, it fuses small objects together, thus removing the reads/writes to the removed field, saving the memory needed to store the field and object header, and reducing the number of object allocations. The objective of this paper is to measure the potential for object inlining by studying the run-time behaviour of a comprehensive set of Java programs. We study the traces of program executions in order to determine which fields behave like inlinable fields. Since we are using dynamic information instead of a static analysis, our results give an upper bound on what could be achieved via a static compiler-based approach. Our experimental results measure the potential improvements attainable with object inlining, including reductions in the numbers of field reads and writes, and reduced memory usage. Our study shows that some Java programs can benefit significantly from object inlining, with close to a 10% speedup. Somewhat to our surprise, our study found one case, the db benchmark, where the most important inlinable field was the result of unusual program design, and fixing this small flaw led to both better performance and clearer program design. However, the opportunities for object inlining are highly dependent on the individual program being considered, and are in many cases very limited. Furthermore, fields that are inlinable also have properties that make them potential candidates for other optimizations such as removing redundant memory accesses. The memory savings possible through object inlining are moderate. Copyright © 2005 John Wiley & Sons, Ltd.