The Role of Virtual Time in Real-time Scheduling
Report ID: TR-611-99Author: Peterson, Larry / Bavier, Andy
Date: 1999-12-00
Pages: 12
Download Formats: |PDF| |Postscript|
Abstract:
The BERT scheduler is designed to schedule a mix of best effort and real-time processes. BERT is based on manipulating how tasks run in the fair queueing fluid model and tracking the changes using virtual time. This paper makes two contributions. First, it builds on results in real-time scheduling to show two properties of BERT: (1) important real-time tasks are schedulable with regard to their finish times in the fluid model and (2) unimportant tasks have bounded workahead. BERT relies on these two properties when making scheduling decisions. Second, it draws attention to the thread that connects the fluid model and the BERT implementation: virtual time. Virtual time is multifaceted and powerful abstraction and we use our results for BERT to argue that it can form the basis for designing, implementing, and analyzing new real-time scheduling algorithms.