A real-time garbage collector based on the lifetimes of objects

Lieberman, Henry; Hewitt, Carl

doi:10.1145/358141.358147

Cited by 463 publications

(158 citation statements)

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“…Generational GC [3] segregates objects by ages into two or more generations. Since "most objects die young" [3][4] [5], it is cost-effective to collect the young generation more frequently than the old generation, hence to achieve higher throughout.…”

Section: Related Workmentioning

confidence: 99%

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Improve Google Android User Experience with Regional Garbage Collection

He¹,

Yang²,

Li³

2011

Lecture Notes in Computer Science

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Abstract. Google Android is a popular software stack for smart phone, where the user experience is critical to its success. The pause time of its garbage collection in DalvikVM should not be too long to stutter the game animation or webpage scrolling. Generational collection or concurrent collection can be the effective approaches to reducing GC pause time. As of version 2.2, Android implements a non-generational stop-the-world (STW) mark-sweep algorithm. In this paper we present an enhancement called Regional GC for Android that can effectively improve its user experience. During the system bootup period, Android preloads the common runtime classes and data structures in order to save the user applications' startup time. When Android launches a user application the first time, it starts a new process with a new DalvikVM instance to run the application code. Every application process has its separate managed heap; while the system preloaded data space is shared across all the application processes. The Regional GC we propose is similar to a generational GC but actually partitions the heap according to regions instead of generations. One region (called the class region) is for the preloaded data, and the other region (called the user region) is for runtime dynamic data. A major collection of regional GC is the same as DalvikVM's normal STW collection, while a minor collection only marks and sweeps the user region. In this way, the regional GC effectively improves Android in both application performance and user experience. In the evaluation of an Android workload suite (AWS), 2D graphic workload Album Slideshow is improved by 28%, and its average pause time is reduced by 73%. The average pause time reduction across all the AWS applications is 55%. The regional GC can be combined with a concurrent GC to further reduce the pause time. This paper also describes two alternative write barrier designs in the Regional GC. One uses page fault to catch the reference writes on the fly; the other one scans the page table entries to discover the dirty pages. We evaluate the two approaches with the AWS applications, and discuss their respective pros and cons.

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Section: Related Workmentioning

confidence: 99%

“…Since "most objects die young" [3][4] [5], it is cost-effective to collect the young generation more frequently than the old generation, hence to achieve higher throughout. Variations on generational collection include older-first collection [13] and the Beltway framework [14].…”

Section: Related Workmentioning

confidence: 99%

Improve Google Android User Experience with Regional Garbage Collection

He¹,

Yang²,

Li³

2011

Lecture Notes in Computer Science

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“…Generational garbage collection, a more advanced collection technique based on the assumption that objects tend to die young, is proposed to solve the problems by concentrating garbage collection work on subareas of the heap mainly containing young objects [66,102,5].…”

Section: Generational Garbage Collectionmentioning

confidence: 99%

Garbage Collection for Flexible Hard Real-Time Systems

Chang

Wellings

2010

IEEE Trans. Comput.

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Garbage collection is key to improving the productivity and code quality in virtually every computing system with dynamic memory requirements. It dramatically reduces the software complexity and consequently allows the programmers to concentrate on the real problems rather than struggling with memory management issues, which finally results in higher productivity. The code quality is also improved because the two most common memory related errors -dangling pointers and memory leaks -can be prevented (assuming that the garbage collectors are implemented correctly and the user programs are not malicious).However, real-time systems, particularly those with hard real-time requirements, always choose not to use garbage collection (or even dynamic memory) in order to avoid the unpredictable executions of garbage collectors as well as the chances of being blocked due to the lack of free memory. Much effort has been expended trying to build predictable garbage collectors which can provide both temporal and spatial guarantees. Unfortunately, most existing work leads to systems that cannot easily achieve a balance between temporal and spatial performance, although their worst-case behaviours in both dimensions can be predicted. Moreover, the real-time systems targeted by the existing real-time garbage collectors are not the state-ofthe-art ones. The scheduling of those garbage collectors has not been integrated into the modern real-time scheduling frameworks, which makes the benefits provided by those systems very difficult to obtain. This thesis argues that the aforementioned issues should be tackled by introducing new design criteria for real-time garbage collectors. The existing criteria are not enough to reflect the unique requirements of real-time systems. A new performance indicator is proposed to describe the capability of a real-time garbage collector to achieve better balance between temporal and spatial performance. Moreover, it is argued that new real-time garbage collectors should be integrated with the real-time task model and more advanced scheduling techniques should be adopted as well.A hybrid garbage collection algorithm, which combines both reference counting and mark-sweep, is designed according to the new design criteria. On the one hand, the reference counting component helps reduce the overall memory requirements. On the other hand, the mark-sweep component periodically identifies cyclic garbage, which cannot be found by the reference counting component. Both parts of the collector are executed by segregated tasks, which are released periodically as the hard real-time user tasks. In order to improve the performance of soft-or non-realtime tasks in our system while still guaranteeing the hard real-time requirements, the dual-priority scheduling algorithm is used for all the tasks including the GC tasks. A multi-heap approach is also proposed to bound the impacts of the softor non-real-time tasks on the overall memory usage as well as the executions of the GC tasks. More importantly, static ana...

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“…In the incremental copying garbage collectors [Ste75,LH83] for example, objects are copied from one area in memory to another whilst the system is running. The principal aim is to identify unreferenced objects, but by incrementally copying related objects into a new area of memory dynamic grouping is performed.…”

Section: Grouping Categoriesmentioning

confidence: 99%

Dynamic Grouping in an Object-Oriented Virtual Memory Hierarchy

Williams

Wolczko

Hopkins

1987

ECOOP’ 87 European Conference on Object-Oriented Programming

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Object oriented programming environments frequently suffer serious performance degradation because of a high level of paging activity when implemented using a conventional virtual memory system. Although the fine-grained, persistent nature of objects in such environments is not conducive to efficient paging, the performance degradation can be limited by careful grouping of objects within pages. Such object placement schemes can be classified into four categories -the grouping mechanism may be either static or dynamic and may use information acquired from static or dynamic properties. This paper investigates the effectiveness of a simple dynamic grouping strategy based on dynamic behaviour and compares it with a static grouping scheme based on static properties. These schemes are also compared with near-optimal and random cases.

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A real-time garbage collector based on the lifetimes of objects

Cited by 463 publications

References 10 publications

Improve Google Android User Experience with Regional Garbage Collection

Improve Google Android User Experience with Regional Garbage Collection

Garbage Collection for Flexible Hard Real-Time Systems

Dynamic Grouping in an Object-Oriented Virtual Memory Hierarchy

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