協同加速器系統之即時程序同步機制

Abstract

增進程式潛在加速之議題已帶動在電子工業上混合通用處理器與加 速器的設計,不過這樣的設計也在共享資源時導致嚴重的同步問題。 這篇論文同時探討在即時系統下之工作同步機制與加速器分配,其目 的在於減少每個工作於最糟情況下存取資源與加速器之總阻塞時間, 以便滿足所有工作的即時限制。在加速器分配下,我們發展一套加速 器使用權繼承之機制,可以使低優先權工作在阻擋高優先權工作執行 時,以高優先權工作之優先權去使用加速器。我們的同步機制協同所 提出之加速器分配機制能夠有效率地限制住每個即時工作被阻擋次數 在兩次以內。藉由目前信號器之使用與配置於加速器之執行工作之優 先權,我們的機制可以預防工作形成阻擋鍊,此問題存在於大多數現 存未考慮加速器之同步機制裡。

The potential speedup of applications has motivated the hybrid design of general purpose processors and dedicated accelerators in electronics industry, but such a design also leads to a serious synchronization problem when shared resources are considered. This paper explores the joint consideration of task synchronization and accelerator allocation for real-time systems, and the ob- jective is to minimize the worst-case total blocking time for accessing share resources and accelerators of each task so as to meet all real-time require- ments. For accelerator allocation, we develop an inheritance mechanism of accelerator privilege, which allows low-priority task to use an accelerator at the priority of the high-priority task when the high-priority task is blocked by the low-priority task. Co-working with the proposed accelerator alloca- tion mechanism, our synchronization protocol efficiently bounds the times of blocking to 2 for each real-time task. By looking into the currently used semaphores and the priorities of all tasks offloaded on accelerators, our pro- tocol is developed to prevent chained blocking among tasks, which could be caused by most of the existing synchronization protocols that are not aware of accelerators.