Replicating real‐time garbage collector

Kalibera, Tomas

doi:10.1002/cpe.1669

Cited by 2 publications

(2 citation statements)

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“…We have verified that with GCC 4.1, which we used earlier [Kalibera et al 2009b], arraylets do incur a slowdown even on the current platform: the joint overhead is 50%, the independent overhead of arraylets is 12%, and of defragmentation 46%. In our later work [Kalibera 2011], we identified the cause of the speed-up of arraylets when added to defragmentation with GCC 4.4 -this version of the compiler did not inline many dereferences of Brooks forwarding pointers used for defragmentation, but it always inlined all dereferences to arraylets. Hence, with defragmentation, array accesses were faster with arraylets than without.…”

Section: Relative Gc Overheadsmentioning

confidence: 99%

“…Hence, with defragmentation, array accesses were faster with arraylets than without. We fixed the problem in [Kalibera 2011] by enforcing inlining of dereferences of Brooks forwarding pointers. With the fix, we obtained 8% independent overhead of arraylets, 10% independent overhead of defragmentation, and 16% joint overhead of arraylets and defragmentation (measured on another platform, but with the same compiler).…”

Section: Relative Gc Overheadsmentioning

confidence: 99%

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Scheduling real-time garbage collection on uniprocessors

Kalibera

Pizlo

Hosking

et al. 2011

ACM Trans. Comput. Syst.

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Managed languages such as Java and C# are increasingly being considered for hard real-time applications because of their productivity and software engineering advantages. Automatic memory management, or garbage collection, is a key enabler for robust, reusable libraries, yet remains a challenge for analysis and implementation of real-time execution environments. This paper comprehensively compares leading approaches to hard real-time garbage collection. There are many design decisions involved in selecting a real-time garbage collection algorithm. For time-based garbage collectors on uni-processors one must choose whether to use periodic, slack-based or hybrid scheduling. A significant impediment to valid experimental comparison of such choices is that commercial implementations use completely different proprietary infrastructures. We present Minuteman, a framework for experimenting with real-time collection algorithms in the context of a high-performance execution environment for real-time Java. We provide the first comparison of the approaches, both experimentally using realistic workloads, and analytically in terms of schedulability.

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Section: Relative Gc Overheadsmentioning

confidence: 99%

Section: Relative Gc Overheadsmentioning

confidence: 99%

Scheduling real-time garbage collection on uniprocessors

Kalibera

Pizlo

Hosking

et al. 2011

ACM Trans. Comput. Syst.

Self Cite

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Introduction to the Special Issue: JTRES 2009

Schoeberl

Higuera-Toledano

2011

Concurrency and Computation

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Java is a very successful language for several application domains: be it desktop applications, large enterprise server applications, web services, or applets for mobile phones. With the Real-Time Specification for Java (RTSJ) and the upcoming definition of a Safety-Critical Java profile, Java enters the domain of soft and hard real-time systems.The The RTSJ is the main standard for real-time systems implemented in Java. Several commercial and research implementations of the RTSJ are available today. However, the optimal implementation of some features of the RTSJ is still an open research questions. The primary goal for asynchronous event handlers (AEH) in the RTSJ is to have a lightweight concurrency mechanism. In the article, Applying Fixed-Priority Preemptive Scheduling with Preemption Threshold to Asynchronous EventHandling in the RTSJ [1], Kim and Wellings propose a scheduling scheme for AEH that minimizes the number of server threads needed. In the article they first define the worst-case scenario that demands the least upper bound of servers for self-suspending and non-self-suspending handlers. Based on the worst-case scenarios, it is proved that the number of servers required to execute a given number of non-self-suspending handlers depends on the number of priority levels, not on the number of handlers. It is also shown that each self-suspending handler is required to have its own server to prevent unbounded priority inversion.The RTSJ supports two kinds of real-time threads: one that can operate on the garbage collected heap and another one that avoids influence by garbage collection by using a region-based memory management. Basanta-Val et al. present in their article, Extending the concurrency model of the Real-Time Specification for Java [2], a more flexible thread model, where the thread can switch between a heap and a non-heap mode. The authors propose a simple extension to the current threading model named RealtimeThread++, in an attempt to introduce more flexibility in the RTSJ concurrency model. The article describes the extension from several points of view: (i) the programmer, identifying scenarios that may benefit from it significantly; (ii) the real-time Java technology perspective, identifying changes required in the current real-time virtual machine to support it; and (iii) the accumulated experience, relating empirical results obtained from a software prototype that supports the extension.The current practice for soft real-time systems in Java is to avoid the cumbersome programming model of scoped memories and, instead, use a real-time garbage collector. Kalibera presents in his article, Replicating , an incremental garbage collector. The realtime collector has to relocate objects in the heap to avoid fragmentation. This is usually achieved via an indirection that has to be followed on every read and write to the heap. Kalibera presents an alternative solution, based on object replication, which does not need any special handling for memory reads, but writes are more expensive: every va...

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Replicating real‐time garbage collector

Cited by 2 publications

References 40 publications

Scheduling real-time garbage collection on uniprocessors

Scheduling real-time garbage collection on uniprocessors

Introduction to the Special Issue: JTRES 2009

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