Estimation of object lifetime using static analysis

Abstract

A computer implemented technique for the static evaluation of the lifetime of objects allocated in memory is presented, which find application in reducing the overhead of generational garbage collection. The method combines pointer alias analysis with static object size determination, from which accurate generational assignment of newly created objects can be accomplished.

Description

BACKGROUND OF THE INVENTION[0001] 1. Field of the Invention[0002] This invention relates to computational methods. More particularly this invention relates to the static analysis of the lifetimes of heap-allocated objects in functioning computer programs and the application of this analysis to generational garbage collection of heap memory.[0003] 2. Description of the Related Art[0004] Current generational schemes of garbage collection allocate newly created objects on the heap to the youngest generation. If such an object survives a certain number of collections of that generation, it is promoted to an older generation. Older generations are collected less often. Promotion overhead continues to be paid until the object is either collected or it resides in the oldest generation. Generational garbage collection can be combined with various collection schemes, e.g., copying collection, mark-sweep collection, and the amount of overhead depends on the specific scheme.[0005] For example,...

AI Technical Summary

Benefits of technology

[0019] Preferred embodiments of the present invention teach an improved technique of data flow analysis using pointer analysis, which can be applied to improve the performance of generational garbage collection of heap memory.

[0024] An advantage of some aspects of the invention is the improved estimation of object lifetimes. It is known that the age distribution of objects exceeding about 50 kb is nearly flat. This, and the fact that more copying of such large objects takes place are further reasons to be aware of object lifetimes.

[0025] The application of some aspects of the invention result in a significant improvement in the static analysis of object lifetime to reduce garbage collection overhead.

[0026] These and other advantages of the present invention are attained by a technique for efficiently identifying objects that will persist for long periods of time. In an environment in which generational garbage collection is employed, exploitation of the knowledge of object lifetimes reduces the cost of repeatedly promoting the objects to older generations.

Problems solved by technology

Such lower bound estimations might be too conservative and can result in insufficient reduction in the garbage collection overhead.

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