BERT: A Scheduler for Best Effort and Realtime Tasks - revised
Report ID: TR-602-99Author: Peterson, Larry / Bavier, Andy / Mosberger, David
Date: 1999-03-00
Pages: 12
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Abstract:
We describe a new scheduler, called BERT, that runs both best effort and realtime tasks on a multimedia workstation. BERT exploits two innovations. First, it extends the proportional share scheduling algorithm to allow one task to dynamically steal cycles from another. This mechanism allows BERT to address a main drawback of scheduling MPEG video decoding using proportional share: the difficulty of making the right reservation. Second, BERT combines the stealing mechanism with task importance to maintain QoS guarantees in overload. In BERT, important realtime tasks can steal to make deadlines and important best effort tasks can be made immune from stealing. The result is a graceful degradation of performance under heavy load. We have implemented BERT in the Scout operating system and we present our experiences using it to schedule multimedia workloads.