Non-blocking garbage collection for real-time Android

Abstract

The Android platform is an open source operating system for mobile devices developed by the Open Handset Alliance. Due to its usability and rich set of functionalities, Android is an attractive platform for both, developers and end-users. RTAndroid is a modified version of the Android 2.2 platform extended with a real-time capable scheduler [11]. This modification aims to enable the domain of industrial applications. But unfortunately, the predictability and deterministic behavior of RTAndroid in its current version highly depend on its memory management components. For instance, explicit memory management cannot be used to free objects that were allocated without the knowledge of the developer. Further, invocations of the native garbage collection result in non-deterministic process suspensions during runtime. This paper presents a concept for a real-time capable, automatic memory management mechanism in order to improve the timing and predictability of the process behavior in RTAndroid. The introduced memory management respects the execution cycles and deadlines of running real-time processes. Empirical evaluations highlight the improvements resulting from the applied system modifications.

Predictable Broadcasting of Parallel Intents in Real-Time Android

“…By applying a real-time patch to the underlying Linux kernel, the system was enabled to predictably schedule real-time processes based on their priorities. To avoid undesired suspensions by the native stop-the-world markand-sweep garbage collector, Gerlitz et al further extended RTAndroid with a soft real-time capable, non-blocking garbage collection algorithm [5]. Neither of both publications refers to the topic of inter-process communication or any kind of information passing between real-time processes.…”

“…Additionally, RTAndroid is modified to avoid non-deterministic process suspensions caused by invocations of the native mark-and-sweep garbage collection [5]. A real-time capable, concurrent reference counting algorithm is implemented instead of the stop-the-world garbage collection used in the original Android platform.…”

“…RTAndroid was presented by Kalkov et al as an extension of the original Android platform [5,7]. It introduces a realtime capable scheduler and a non-blocking garbage collection to achieve a predictable process behavior and reduce maximal scheduling latencies for real-time applications to just a few milliseconds.…”

“…Hereby, we focus on the fundamentals of Android's unique message broadcasting system for intra-and inter-process communication. The second part summarizes the main real-time extensions of the Android platform as presented in the work of Kalkov et al [7] and Gerlitz et al [5].…”

Development and execution of PLC programs on real-time capable mobile devices

“…Additionally, RTAndroid provides a solution for nondeterministic process suspensions due to invocations of the native mark-and-sweep garbage collection [9]. The stop-theworld garbage collection algorithm used in the original Android distribution is replaced by a real-time capable, concurrent reference counting algorithm.…”